Fermentation Technologies for Bioethanol Conversion PDF

Session 01 Fermentation Technologies for Bioethanol Conversion BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Lecture Eng.Prasad Amarasinghe Module Outline Content Lecture Time 1. Fermentation Technologies for 08 Hours Bioethanol Conversion 2. Biodiesel Production Technologies 08 Hours 3. Synthesis of Intermediate Liquid 04 Hours Biofuels from Biorefineries 4. Biofuel Distillation for Initial 04 Hours Separation/Purification 5. Liquid Biofuel Plant Operation and 04 Hours Maintenance 6. Economics of Liquid Biofuel 02 Hours Generation Processes Module Outline Assessment : Continuous Assessment……..40% Final Assessment………60% Practical: Field visit to Bioethanol distillery plant in a Cane sugar processing plant (Incorporated with the field visit for the module: Bioenergy Crop Cultivation and Harvesting Technologies) (12 Hours) Laboratory Sessions: (i) Fermentation laboratory session using the water bath (04 Hours) (ii) Measure the oxidative stability/anti oxidation capacity of Biodiesel using Rancimat (04 Hours) References/Reading Materials: ⮚Singh, L.K. and Chaudhary, G. eds., 2019. Liquid Biofuel Production. John Wiley & Sons, Incorporated. ⮚Riazi, M.R. and Chiaramonti, D. eds., 2017. Biofuels production and processing technology. CRC Press. ⮚Babu, V., Thapliyal, A. and Patel, G.K., 2013. Biofuels production. John Wiley & Sons Learning Outcomes At the completion of this course student will be able to Understand liquid biofuel conversion principles Explain appropriate liquid biofuel production technology based on different feedstocks Apply conversion techniques and produce liquid biofuel up to the required quality Perform operation and maintenance of liquid biofuel production plants Evaluate cost and economic viability of liquid biofuel production First generation feedstocks First generation means bioethanol is primarily derived from food crops like starch, sugars, wheat, and sorghum Problems biodiversity reduction Increasing price of food Limited feedstock Then people has shifted the focus towards next-generation or second generation biofuels. agricultural residue are mainly used as a substrate for production of second-generation biofuels. Although they are cost-effective, the challenges associated with the land and water requirements for the cultivation of second-generation biofuels limits their usage First generation feedstocks First generation means bioethanol is primarily derived from food crops like starch, sugars, wheat, vegetable oil and sorghum. Note that these are all food products It is important to note that the structure of the biofuel itself does not change between generations, But it will change according to the source from which the fuel is derived. First generation feedstocks 1st generation biofuels suffer from the same problems biodiversity reduction threatening the food chain Increasing price of food Limited feedstock Then people has shifted the focus towards next-generation or second generation biofuels. agricultural residue are mainly used as a substrate for production of second- generation biofuels.. First generation feedstocks The use of algae as a source of bioethanol is considered a sustainable approach to deal with the limitations of first- and second-generation biofuels. The cultivation of algae for bioethanol production is more beneficial in terms of yield contrast to cultivation of other feedstocks. Component in biomass CELLULOSE As the most common organic compound on Earth, cellulose comprises 38%–50% of cellulosic biomass. Cellulose is a polymer of 6-carbon sugar molecules (glucose) linked together in a crystal structure In a bioethanol process, cellulose must first be transformed into easily-fermentable monosaccharides (simple sugars, such as glucoses) by physical, chemical, and biological treatments, and then used as a fermentation substrate to produce ethanol through a fermentation process. Component in biomass HEMICELLULOSE It consists of complex polysaccharides from a variety of five- and six-carbon sugars. Hemicellulose is easily hydrolyzed by dilute acid or base, as well as more hemicellulase enzymes LIGNIN It is a complex network polymer with phenyl propane basic units. It fills the spaces in the cell wall between cellulose, hemicellulose. During a bioethanol process, lignin is left as a residue. However, it still has some energy value and can be used to make a variety of value-added products. Component in biomass Conventional route of Liquefaction The different processes are required for the conversion of biomass to energy and these are generally classified into two categories: thermochemical and biochemical conversion. Thermo-Chemical Conversion This category covers the thermal decomposition of organic components into biomass and then fuel products (direct combustion, thermochemical liquefaction, gasification and pyrolysis). Conventional route of Liquefaction Biochemical Conversion There are different biological processes are used for the conversion of biomass into important biofuels (anaerobic digestion, alcoholic fermentation, and biophotolysis). Conventional route of Liquefaction Pyrolysis Fermentation pyrolysis is the process of degradation of organic compounds at high temperatures (above 400 C) Fermentation means extraction of in an inert atmosphere energy from carbohydrates in the (ash, biochar, bio-oil, syngas) absence of Oxygens Out comes are depend on heating rates, and residence time The basic concept of the production of ethanol Pretreatment Saccharification Biomass Milling Fermentation Ethanol Catalytic Gasification Fermentation conversion The basic concept of the production of ethanol Bioethanol mainly produce in three ways Pretreatment Pretreatment is the first step of the cellulosic bioethanol process. In this process make the materials ready for the enzyme hydrolysis step. Break down shield formed by lignin and hemicellulose, Open the fiber structure. Pretreatment does this by partially removing the lignin and hemicellulose, which block the cellulose inside the cell wall The pretreatment step can be done by using acid, alkali, organic solvents, heat treatments, etc. Some options for pretreatment are steam explosion, liquid hot water, lime-ammonia and acid treatment Pretreatment Pretreatment methods may be Physical Chemical Biological Benefit of pretreatment Increase surface area Increase solubilization of cellulose Redistribution of cellulose and lignin Saccharification, and Fermentation Saccharification Saccharification is the process of breaking down complex carbohydrates like corn or sugar cane into glucose, fructose, sucrose and monosaccharide components in the ethanol fuel production process. Enzymes help this saccharification process. Enzyme Monosaccharide/gl Carbohydrates Saccharification ucose/ Fructose/ Sucrose Saccharification, and Fermentation Fermentation fermentation, is a biological process which converts sugars such as glucose, fructose, sucrose, and other monosaccharides into cellular energy, producing ethanol and carbon dioxide as by-products Conventional fermentation is the process that converts the sugars from sugar-rich feedstocks (fruit juices, pomace and grains, such as corn and sweet sorghum) into alcohol in the brewing and beverage alcohol industries Yeast Monosaccharide/gl Fermentation ucose/ Fructose/ Alcohol Sucrose Saccharification Methods Concentrated Acid Hydrolysis The hydrolysis of lignocellulosic materials through concentrated sulphuric acid or hydrochloric acid to produce fermentable sugars. It gives high yields of sugars. Advantage is that it can operate at low temperatures. This method utilizes very high concentrations of acids, which makes it highly corrosive. Hence, expensive alloys or non-metallic materials are required. Saccharification Methods Base Hydrolysis Base pretreatments increase cellulose digestibility and they are more effective for lignin solubilization than cellulose and hemicellulose solubilization by acid or hydrothermal processes. More suitable, alkaline pretreatments are potassium, calcium and ammonium hydroxides. lime pretreatment increases the crystallinity index by removing amorphous substances like lignin. Compared to NaOH or KOH pretreatments, lime required less safety and is cost effective. Saccharification Methods Enzymatic Hydrolysis Enzymatic hydrolysis of biomass are the most commonly used saccharification methods. The utilization of celluloses and hemicelluloses present in the feedstock is enhanced by this method. Amongst the hydrolysis processes, enzymatic hydrolysis gives the highest sugar yield. Saccharification Methods Cellulase Enzymes Hydrolysis Cellulase is a goup of enzymes, produced by bacteria, fungi and protozoans , which work collectively to hydrolyze cellulose. Cellulose enzymes catalyze the reaction in which water is added to glucan chains to release the monomers; glucose molecules. (C6H12O5)n + nH2O → nC6H12O6 In catalyzing cellulolysis, at least three types of cellulases are involved. (endoglucanase, Exoglucanase, B-glucosidase) Saccharification Methods Endoglucanases Cut at random internal sites along the cellulose/hemicellulose chain Exoglucanases Act at reducing and nonreducing ends Beta-glucosidase Break betaglucosidase bond to form glucose Saccharification, and Fermentation Enzyme hydrolysis usually occurs immediately after the pretreatment step. Enzyme hydrolysis is the process used to convert polysaccharides (cellulose and hemicelluloses) into simple sugars which can be fermented by bacteria or yeast. The high cost of enzymes is currently the greatest challenge in this processing step. An important approach to reduce the cost for enzyme hydrolysis is to develop an efficient pretreatment method to reduce the enzyme dosage and enhance the yield of simple sugars. Fermentation Yeast perform this conversion in the absence of oxygen. Alcohol fermentation is consider as anaerobic process. In the developing countries , microbial fermentation processes are the preferred for the production of alcohol. The type of micro organism chosen mostly depend on the nature of the substrate used. Fermentation types Batch fermentation the substrate and producing microorganism are added to the system at time zero and are not removed until the fermentation is complete Continues fermentation Sunstate is added continuously to the fermenter and biomass or products are continuously removed at the same time Fed-batch fermentation Substrate increase as the fermentation progresses. Started as batch wise with a small substrate concentration Fermentation types SHP(Separate hydrolysis and Fermentation ) SHF is a method by which enzymatic hydrolysis and fermentation are performed sequentially. In this process, enzymatic saccharification of starchy biomass or pretreated lignocellulosic biomass is carried out first at the optimal temperature of the saccharifying enzyme. Temperatures of the enzymatic hydrolysis and fermentation can be optimized independently. Bioethanol production process Simultaneous Saccharification and Fermentation (SSF) SSF is a process that saccharification and fermentation will be happened simultaneously in a single steps. both saccharification and fermentation occurs in the same fermentation vessel. Advantage and disadvantages of SHF and SSF method Process Advantages Disadvantages Separate hydrolysis and ❖ Operate at their optimal ❖ Decrease reaction rate fermentation condition ❖ Inhibitory hydrolysis products accumulate ❖ Microbial contamination occurred Simultaneous saccharification and ❖ Higher yield of ethanol ❖ Rate of hydrolysis is slow fermentation ❖ Low potential cost ❖ Difference in optimum ❖ Fewer vessels needed temperature of the hydrolyzing ❖ Prevent significant microbial enzymes and fermentation contamination microorganisms. ❖ A lower amount of enzymes is required ❖ Minimize product inhibition Thank you… Q&A Session 02 Fermentation Technologies for Bioethanol Conversion BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Eng.Prasad Amarasinghe Content …. Simultaneous Liquefaction, Saccharification and Fermentation (SLSF) Second generation feedstocks Third generation feedstocks Fermentation of complex (C6/C5) Sugars Simultaneous Liquefaction, Saccharification and Fermentation (SLSF) Simultaneous Liquefaction, Saccharification, and Fermentation process (SLSF) or no-cook process has been recently introduced to increase ethanol yield and to save energy and investment cost. Alpha-amylase, gluco-amylase are added to the slurry, concomitantly with yeasts. The SLSF is conducted in a unique bioreactor, at a unique pH and at ambient temperature. The presence of yeast along with enzymes minimizes the sugar accumulation in the vessel. Since the sugar is produced slowly during starch breakdown, higher rates, yields and concentrations of ethanol are possible with the use of SLSF Second generation feedstocks Second generation feedstock refers to crops and plants not suitable for human consumption (food) or animal consumption (feed). Second generation feedstock can be either non-food crops (cellulosic feedstock) or waste materials from 1st generation feedstock (e.g. waste vegetable oil, Agricultural waste). Examples of second generation feedstock include: wood, short- rotation crops such as poplar, willow or miscanthus (elephant grass), wheat straw, bagasse, corncobs, palm fruit bunches and switch grass. miscanthus (elephant grass), poplar willow wheat straw bagasse corncobs Products obtained from thermochemical treatment of different second-generation feedstocks Second generation feedstocks Biodiesel usually refers to the products from a chemical reaction of vegetable or waste oil and ethanol and methanol called a Transesterification process. Properties of biodiesel are similar to fossil diesel fuel, which can be used in a standard diesel engine without modification. First generation biodiesel was derived from food bio-feedstocks such as soybeans, palm, canola and rapeseed Promotion of the first generation biodiesel caused interaction problems with human food chains, including supply and demand balancing, land use, water management. Second generation feedstocks Second generation ethanol Comparison of various ethanol types and gasoline feedstocks are mainly from agricultural wastes such as corn waste, sugarcane bagasse and also from wood, grasses or the non-edible parts of plants The second generation ethanol feedstocks overcome the two main bottlenecks for the first generation feedstock: adverse effects on food prices and inability to scale Second generation feedstocks In terms of the environment and GHG mitigation, cellulosic ethanol has the potential to provide significant lifecycle GHG reductions compared to petroleum based gasoline Second generation feedstocks Comparison of first and second generation biofuels Third generation feedstocks Third-generation biofuels is fuels that would be produced from algal biomass, which has a very distinctive growth yield as compared with classical lignocellulosic biomass. Production of biofuels from algae usually depend on the lipid content of the microorganisms. they contain much higher lipid content per biomass There are many challenges associated with algal biomass, some geographical and some technical. large volumes of water are required for industrial scale, The high water content is also a problem when lipids have to be extracted from the algal biomass, which requires dewatering, via either centrifugation or filtration before extracting lipids. Third generation feedstocks The general composition of different algae Third generation feedstocks The diversity of fuel that algae The list of fuels that can be can produce results from two derived from algae includes: characteristics of the Biodiesel microorganism. Butanol First, algae produce an oil that Gasoline can easily be refined into diesel Methane or even certain components of Ethanol gasoline Vegetable Oil It can be genetically manipulated Jet Fuel to produce everything from ethanol and butanol to even gasoline and diesel fuel directly. Third generation feedstocks Algae is also capable of producing outstanding yields, algae have been used to produce up to 9000 gallons of biofuel per acre Cultivation of Third Generation Biofuels Open ponds – These are the simplest systems in which algae is grown in a pond in the open air. They are simple and have low capital costs, but are less efficient than other systems. They are also of concern because other organisms can contaminate the pond and potentially damage or kill the algae Third generation feedstocks Closed-loop systems – These are similar to open ponds, but they are not exposed to the atmosphere and use a sterile source of carbon dioxide. Such systems have potential because they may be able to be directly connected to carbon dioxide sources (such as smokestacks) and thus use the gas before it is every released into the atmosphere. Third generation feedstocks Photobioreactors These are the most advanced and thus most difficult systems to implement, resulting in high capital costs. Their advantages in terms of yield and control, however, are unparalleled. They are closed systems. Third generation feedstocks Algae can be grown in waste water, which means they can offer secondary benefits by helping to digest municipal waste while avoiding taking up any additional land All of the factors above combine to make algae easier to cultivate than traditional biofuels. One of the major benefits of algae is that they can use a diverse array of carbon sources. it has been suggested that algae might be tied directly to carbon emitting sources (power plants, industry, etc.) where they could directly convert emissions into usable fuel. cost of algae-base biofuel is much higher than fuel from other sources. A minor drawback regarding algae is that biofuel produced from them tends to be less stable than biodiesel produced from other sources. Third generation feedstocks Fermentation of complex (C6/C5) Sugars Fermentation is a metabolic process taking place in the absence of oxygen. The process of alcohol fermentation can be divided into two major parts. 1. The first part involves the breaking down of glucose into 2 pyruvate molecules in a process called glycolysis 2. The second part is called fermentation in which 2 pyruvate molecules are converted into 2 molecules of carbon dioxide and 2 ethanol molecules, otherwise known as alcohol. Alcohol fermentation can be represented by the chemical formula as follows C6H12O6 → 2 C2H5OH + 2 CO2 The major purpose of alcohol fermentation is to produce energy in the form of ATP that is used during cellular activities, under anaerobic conditions Fermentation of complex (C6/C5) Sugars The following are the important molecules involved in the process of alcohol fermentation. Pyruvate: Pyruvate or pyruvic acid is a carboxylic acid that is used to make ethanol. 2 pyruvate molecules are formed by breaking down one glucose molecule in the first step. Electron carriers like NADH are also involved in this process Electron Carriers: These are the molecules responsible for capturing the electrons that are released during a chemical reaction NAD is the main electron carrier involved in these reactions. It captures the electrons during the first step of fermentation (glycolysis) and gets reduced to NADH. This reduced form provides electrons during the conversion of pyruvate to ethanol. Fermentation of complex (C6/C5) Sugars The various reactions taking place during alcohol fermentation are as follows Glycolysis The Glycolytic process can be summarized by the following equation: C6H12O6 + 2 ADP + 2 Pi + 2 NAD+ → 2 CH3COCOO− + 2 ATP + 2 NADH + 2 H2O + 2 H+ 2 CH3COCOO− (pyruvate molecules) 2 NADH (acceptor molecule) 2 Pi (inorganic phosphate) The overall products of these reactions are two pyruvate molecules, two NADH and two molecules of ATP. The pyruvate molecules are further processed in the absence of oxygen to form ethanol (alcohol). Fermentation of complex (C6/C5) Sugars Pyruvate to Ethanol Conversion This conversion takes place in two steps: In the first step, the carboxyl group of pyruvate is removed and released in the form of CO2. The product of this reaction is acetaldehyde (a 2 carbon molecule) In the second step, the acetaldehyde molecule is reduced. One molecule of NADH passes its electrons to acetaldehyde, forming ethanol. The NAD molecule is regenerated during this process. Reaction 1: CH3COCOO− + H+ → CH3CHO + CO2 This reaction is catalyzed by (pyruvate decarboxylase) Fermentation of complex (C6/C5) Sugars Reaction 2: CH3CHO + NADH + H+ → C2H5OH + NAD+ This reaction is catalyzed by (alcohol dehydrogenase) CH3CHO (acetaldehyde) CO2 (carbon dioxide) C2H5OH =ethanol (Alcohol) Enzymes The two enzymes that are involved in alcohol fermentation are as follows. Pyruvate decarboxylase: It is an enzyme that catalyzes the decarboxylation of pyruvic acid to carbon dioxide and acetaldehyde. This enzyme plays an important role during the fermentation process in anaerobic conditions Fermentation of complex (C6/C5) Sugars Alcohol dehydrogenase: This enzyme is responsible for converting acetaldehyde to ethanol during alcohol fermentation. Role of Microorganisms The following microbes are involved in ethanol fermentation: Yeast Schizosaccharomyces Saccharomyces cerevisiae Zymomonas mobilis (a bacterium) Fermentation of complex (C6/C5) Sugars Yeast Yeast cells are categorized as unicellular fungi having a diameter in the range of micrometers. The size of these organisms is very small as compared to most of the fungi. They can also vary in size and shape. Yeast is used in several processes like making bread, wine, and alcohol fermentation. Ethanol is also toxic to yeast just like it is to humans. Fermentation of complex (C6/C5) Sugars Ethanol fermentation is depend on following factors Temperature pH Medium composition Plasma membrane modifications Action of some enzymes Thank you… Q&A Session 03 Biodiesel Production Technologies BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Eng.Prasad Amarasinghe Module Outline Content Lecture Time 1. Fermentation Technologies for 08 Hours Bioethanol Conversion 2. Biodiesel Production Technologies 08 Hours 3. Synthesis of Intermediate Liquid 04 Hours Biofuels from Biorefineries 4. Biofuel Distillation for Initial 04 Hours Separation/Purification 5. Liquid Biofuel Plant Operation and 04 Hours Maintenance 6. Economics of Liquid Biofuel 02 Hours Generation Processes Learning Outcomes At the completion of this course student will be able to Understand liquid biofuel conversion principles Explain appropriate liquid biofuel production technology based on different feedstocks Apply conversion techniques and produce liquid biofuel up to the required quality Perform operation and maintenance of liquid biofuel production plants Evaluate cost and economic viability of liquid biofuel production Content …. Acid catalyst esterification Transesterification technology, Acid catalyst esterification Biodiesel is equivalent to fatty acid methyl esters or ethyl esters, produced out of triacylglycerols via transesterification or out of fatty acids via esterification. Esterification is used to convert fatty acids in to biodiesel( fatty acid methyl esters or ethyl esters ) Fatty acid methyl esters(FAME) today are the most commonly used biodiesel species, whereas fatty acid ethyl esters (FAEE) so far have been only produced in laboratory or pilot scale. Acid catalyst esterification Esterification of free fatty acids to corresponding alkyl ester, also called alcoholysis, is one of the reactions used for biodiesel production. In this reaction, fatty acids react with alcohol at atmospheric pressure in the presence of an acid catalyst to form alkyl ester or biodiesel. Methanol is the most common alcohol used for esterification since it is the least expensive alcohol. The temperature of the reaction is lower than the boiling point of alcohol. Water is the by-product of this reaction. Since the esterification reaction is reversible, it can be conducted by reactive distillation to separate and remove water during reaction to increase reaction yield. Acid catalyst esterification Production of fatty acid methyl esters via transesterification Production of fatty acid methyl esters via esterification Acid catalyst esterification Advantages and disadvantages of different types of alcohols used in esterification Acid catalyst esterification vegetable oils or animal fats mainly consist of triacylglycerols (triglycerides) the main reaction for the production of biodiesel is the transesterification. Esterification is only necessary for feedstock with higher content of free fatty acids. Catalysts for transesterification and esterification reactions ▪ Alkaline catalysis ▪ Acid catalysis ▪ Heterogeneous catalysis ▪ Enzymes as catalysts Acid catalyst esterification Acid catalysis Acid catalysis offers the advantage of also esterifying free fatty acids contained in the fats and oils acid-catalyzed transesterifications are usually far slower than alkali catalyzed reactions and require higher temperatures and pressures as well as higher amounts of alcohol. Because of the slow reaction rates and high temperatures needed for transesterification, acid catalysts are only used for esterification reactions. vegetable oils or animal fats with an amount of free fatty acids larger than approx. 3 % Acid catalyst esterification Acid catalysis The free fatty acids can either be removed by alkaline treatment, or they can be esterified under acidic conditions. This so-called pre esterification has the advantage that prior to the transesterification most of the free fatty acids are already converted into FAME, thus the overall yield is very high. these fatty acids are lost in the overall yield unless these fatty acid are esterified in a separate step. The cheapest and best known catalyst for esterification reactions is concentrated sulphuric acid. Acid catalyst esterification The main disadvantage of this catalyst is the possibility of the formation of side products like dark colored oxidized or other decomposition products. The organic compound p-toluene sulphonic acid can also be used, however the high price of the compound so far prevented broader application. Acid catalyst esterification Both heterogeneous and homogeneous catalysts can be used for esterification Advantages and disadvantages of different types of alcohols used in esterification Acid catalyst esterification Esterification of FFA, RCOOH, and alcohol with an acid catalyst Transesterification technology Transesterification is a well-known chemical reaction between an ester(triacylglycerol ) and an alcohol(methanol) to produce a new ester and a new alcohol As vegetable oils or animal fats mainly consist of triacylglycerols (triglycerides) the main reaction for the production of biodiesel is the transesterification. In a transesterification or alcoholysis reaction one mole of triglyceride reacts with three moles of alcohol to form one mole of glycerol and three moles of the respective fatty acid alkyl ester The process is a sequence of three reversible reactions, in which the triglyceride molecule is converted step by step into diglyceride, monoglyceride and glycerol. Transesterification technology Production of fatty acid methyl esters via transesterification In order to shift the equilibrium to the right, methanol is added in an excess over the stoichiometric amount in most commercial biodiesel production plants. the two main products, glycerol and fatty acid methyl esters (FAME), are hardly miscible and thus form separate phases – an upper ester phase and a lower glycerol phase Transesterification technology Ester yields can even be increased - while at the same time minimizing the excess amount of methanol – by conducting methanolysis in two or three steps. the concentration of triglycerides as the starting material decreases and the amount of methyl esters as the desired product increases throughout the reaction, the concentrations of partial glycerides (i.e. mono- and diglycerides) reach a passing maximum Transesterification technology Stepwise transesterification reaction of TAG-based plant oils General transesterification reaction of TAG-based plant oils Transesterification technology Catalysts for transesterification and esterification reactions ▪ Alkaline catalysis ▪ Acid catalysis ▪ Heterogeneous catalysis ▪ Enzymes as catalysts Alkaline catalysis Alkaline or basic catalysis is by far the most commonly used reaction type for biodiesel production alkaline catalysts are less corrosive to industrial equipment, and thus enable the use of less expensive carbon-steel reactor material Therefore alkali-catalyzed transesterifications optimally work with high-quality, low-acidic vegetable oils, which are however more expensive than waste oils. Today most of the commercial biodiesel production plants are utilizing homogeneous, alkaline catalysts. Transesterification technology Alkaline catalysis The advantage of using sodium or potassium methoxide is the fact that no additional water is formed and therefore side reactions can be avoided. The use of the cheaper catalysts sodium or potassium hydroxide leads to the formation of methanolate and water, which can lead to increased amounts of soaps. The amount of alkaline catalyst depends on the quality of the oil, especially on the content of free fatty acids Transesterification technology Transesterification of triglyceride, G(OCOR)3, and alcohol, R′OH, with an alkali catalyst Here, R and R′ represent different kinds of fatty acid residues, while G, G(OH)3, and G(OCOR)2OH represent glycerin residue, glycerin, and a diglyceride, respectively. Transesterification technology Advantages and disadvantages of NaOH & KOH catalyst in esterification Transesterification technology Overview of homogenous alkaline catalysts Transesterification technology Acid catalysis acid-catalyzed transesterifications are usually far slower than alkalicatalyzed reactions and require higher temperatures and pressures as well as higher amounts of alcohol A further disadvantage of acid catalysis – probably prompted by the higher reaction temperatures – is an increased formation of unwanted secondary products, such as dialkylethers or glycerol ethers Because of the slow reaction rates and high temperatures needed for transesterification, acid catalysts are only used for esterification reactions Transesterification technology Transesterification of triglyceride and alcohol with an acid catalyst Transesterification technology Heterogeneous catalysis homogeneous catalysis offers a series of advantages, its major disadvantage is the fact that homogenous catalysts cannot be reused catalyst residues have to be removed from the ester product, usually necessitating several washing steps, which increases production costs there have been various attempts at simplifying product purification by applying heterogeneous catalysts, which can be recovered by decantation or filtration or are alternatively used in a fixed-bed catalyst arrangement. the application of calcium carbonate may seem particularly promising, as it is a readily available, low-cost substance. Moreover, the catalyst showed no decrease in activity even after several weeks of utilization the high reaction temperatures and pressures and the high alcohol volumes required in this technology are likely to prevent its commercial application. Transesterification technology Overview on heterogeneous catalysts Transesterification technology Enzymes as catalysts In addition to the inorganic or metallo-organic catalysts presented so far, also the use of lipases from various microorganisms has become a topic in biodiesel production. Lipases are enzymes which catalyze both the hydrolytic cleavage and the synthesis of ester bonds in glycerol esters As compared to other catalyst types, biocatalysts have several advantages. They enable conversion under mild temperature-, pressure- and pH- conditions. Neither the ester product nor the glycerol phase has to be purified from basic catalyst residues or soaps. Therefore phase separation is easier Transesterification technology high-quality glycerol can be sold as a by-product, and environmental problems due to alkaline wastewater are eliminated both the transesterification of triglycerides and the esterification of free fatty acids occur in one process step However, lipase-catalyzed transesterifications also entail a series of drawbacks. As compared to conventional alkaline catalysis, reaction efficiency tends to be poor, so that biocatalysis usually necessitates far longer reaction times and higher catalyst concentrations The main hurdle to the application of lipases in industrial biodiesel production is their high price, especially if they are used in the form of highly-purified, extra cellular enzyme preparations, which cannot be recovered from the reaction products. Transesterification technology Transesterification without catalysts Basically, transesterification of triglycerides with lower alcohols also proceeds in the absence of a catalyst, provided reaction temperatures and pressures are high enough The advantages of not using a catalyst for transesterification are that high- purity esters and soap-free glycerol are produced. The high excess of methanol which has to be used during supercritical transesterification seems to make the process not economically feasible, however, a two-step process has been described, which in the first step hydrolyzes the glycerides into fatty acid with an excess of water, and in the second step esterification takes place, which requires lower amounts of methanol Transesterification technology Biodiesel production flow sheet. Thank you… Q&A Session 04 Biodiesel Production Technologies BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Eng.Prasad Amarasinghe Module Outline Content Lecture Time 1. Fermentation Technologies for 08 Hours Bioethanol Conversion 2. Biodiesel Production Technologies 08 Hours 3. Synthesis of Intermediate Liquid 04 Hours Biofuels from Biorefineries 4. Biofuel Distillation for Initial 04 Hours Separation/Purification 5. Liquid Biofuel Plant Operation and 04 Hours Maintenance 6. Economics of Liquid Biofuel 02 Hours Generation Processes Content …. catalytic cracking Thermal cracking Bio-oil generation from pyrolysis Catalytic cracking Large hydrocarbons are broken into smaller molecules using catalyst Catalytic cracking is a process used to produce biofuels, such as diesel and gasoline, from edible and nonedible oils by using shape-selective catalysts. Ultra-stable Y zeolites are the catalysts used currently at an industrial level. These are modified Y zeolites selective to gasoline, obtained by a dealumination process. ZSM-5 is commonly used to increase the yields, and thus the gasoline octane number. Catalytic cracking This process typically occurs at 450°C and it is possible to produce high-octane gasoline, lowering the yields of heavy fuel oils and light gases. The main drawback of this technology is coke formation, with related catalyst deactivation because of coke deposits on the catalyst surface The coke is continuously removed by burning it in air, maintaining the catalyst activity catalytic cracking reaction is endothermic, while the coke burning is exothermic, it is possible to recover the heat of combustion by using recirculating fluidized bed reactors. Catalytic cracking To increase the gasoline yield and reduce the coke formation, short residence times are required. This technology, developed for petroleum plants, is applicable also for biorefineries. In particular, triglyceride-based feedstocks are vaporized and placed in contact with the catalyst in a riser reactor. The cracking reaction takes place on cracking catalysts with short residence time. Catalytic cracking Catalytic cracking of vegetable oils over HZSM-5 catalyst reaction path. Catalytic cracking vegetable oil (in this case palm oil) is subjected to catalytic cracking on the external catalyst surface to produce heavy hydrocarbons and oxygenates. They are further cracked into light alkenes and alkanes, water, carbon dioxide, and carbon monoxide. Finally, aromatics can be formed by aromatization, alkylation, and isomerization of heavier olefins and paraffin. Coke is then formed by direct condensation of palm oil and polymerization of aromatics. The catalyst to be adopted must be chosen carefully. Catalytic cracking Two important characteristics must be taken into account, which is the acidity of the catalyst, responsible for the activity in the cracking process, and the morphology. This last is essential because catalysts that present ordered structures provide the selectivity through their pores accessibility. The mesoporous materials, such as MCM-41 and SBA-15, could be used as catalysts for the cracking of crude and used palm oil. Catalytic cracking *, Palm kernel oil; **, used palm oil; ***, palm oil-based waste fatty acid. Catalytic cracking of different feedstocks for the production of liquid biofuel, performed in a microreactor Thermal cracking Breaking of larger hydrocarbons into smaller ones by the application of heat alone is known as thermal cracking. The thermal‐cracking reaction is defined as thermal decomposition of the organic chains by heat in an atmosphere free of oxygen, with or without the aid of a catalyst The reaction will generate always a solid fraction, generally called coke, a liquid product named as bio‐oil, and a gaseous stream known as biogas. This reaction is affected by the feedstock characteristics and the pair temperature‐residence time Thermal cracking The higher the temperature and the residence time, the higher the yield of the gas product. Lower temperatures and higher residence times improve the coke formation. Moderate temperatures with short residence times yield the liquid product. This last operational condition is called fast pyrolysis The solid fraction called coke will appear, and this product will not be easily removed from the reactor. One possibility to remove it is to proceed a controlled burning in the heated reactor through feeding air instead of biomass, for a certain period of time, promoting the combustion of the coke. Thermal cracking Thermal cracking The reaction starts with the decomposition of the triglyceride molecule forming heavy oxygenated hydrocarbons. 1- Initial cracking, thermolysis of triglyceride molecule ester bond; 2- decarboxylation/decarbonylation of long‐chain oxygenated hydrocarbons 3- C‐C bond cleavage of unsaturated oxygenated hydrocarbons 4- decarboxylation/decarbonylation of short‐chain oxygenated hydrocarbons 5- isomerization, polymerization/dehydrogenation, cyclization to form dienes, acetylenes, cycloparaffins, and polyolefins 6- dehydrogenations of cycloparaffins to form cyclo‐olefins Thermal cracking 7- hydrogenations of cyclo‐olefins to form cycloparaffins 8- Diels‐Alder addition of dienes to olefins to form cyclo‐olefins 9- aromatization of cyclo‐olefins to form aromatics and polyaromatics hydrocarbons 10- Coking from polyaromatics 11- coking by polycondensation of oxygenated hydrocarbons 12- coking by polycondensation of triglyceride molecule 13- polymerization of olefins to form coke 14- direct route for C1‐C5 hydrocarbon formation from triglyceride molecule Thermal/catalytic cracking Bio-oil generation from pyrolysis Pyrolysis is a thermochemical conversion process carried out at an elevated temperature and in the absence of oxygen in order to produce condensable organic molecules, noncondensable gases, and char Biomass fast pyrolysis aims to maximize the yield of condensable organic molecules(Bio liquid) The operating conditions for biomass fast pyrolysis differ from those for biomass torrefaction. The first critical operating condition is temperature. Fast pyrolysis is performed at relatively high temperatures, approximately 500°C. Bio-oil generation from pyrolysis Heating of biomass to the desired end temperature is achieved via convection and radiation to the surface of the particles Subsequent heat penetration into the particle is achieved by conduction with thermal decomposition as a result The thermal power introduced in the process allows breaking up the biopolymers and causes the release of volatile components from the biomass The second critical operating condition is vapor residence time The vapors produced during biomass fast pyrolysis consist of condensable and noncondensable organic molecules. Bio-oil generation from pyrolysis Condensable organic components may form smaller, noncondensable molecules through secondary reactions in the gas phase These secondary reactions should be minimized in order to maximize the yield of liquid products, also known as bio-oil or fast pyrolysis oil, produced by condensation of condensable organic molecules. Hence, fast pyrolysis is operated at relatively short gas residence times Bio-oil generation from pyrolysis Reactor Design Several types of reactor configurations have been designed that allow rapid heating of biomass as well as the fast condensation of the produced vapors The three reactor designs are bubbling fluid bed reactor circulating fluid bed reactor rotating cone pyrolysis reactor Each of the presented reactor designs has it specific strengths and flaws Bio-oil generation from pyrolysis bubbling fluid bed reactor Bubbling fluidizing beds have the advantage of being a well- understood technology that is simple in construction and operation, good temperature control, and very efficient heat transfer to the biomass particles Bio-oil generation from pyrolysis Circulating fluid bed reactors Circulating fluid bed reactors are characterized by more complex hydrodynamics, and the product will contain more char. The main advantage of this technology is that higher throughputs are possible. Bio-oil generation from pyrolysis rotating cone pyrolysis reactor It essentially works as a transport bed reactor where the driving force is generated by centrifugal forces. The main advantage is that no carrier gas is required. The main disadvantage is that higher maintenance costs are expected due to moving parts producing the centrifugal forces Bio-oil generation from pyrolysis Overview of fast pyrolysis reactor characteristics for bio-oil production Bio-oil generation from pyrolysis Bio-Oil Characteristics Pyrolysis liquid, known as bio-oil, is a dark red-brown to almost black liquid depending upon its chemical composition and the presence of micro-carbon particles Lignocellulosic biomass fast pyrolysis can be optimized to yield up to 75 wt% of bio-oil. The energy density of bio-oil can be 10 times higher on volumetric basis than that of the original biomass. Bio-oil is a complex mixture of oxygenated organic compounds, including alcohols, esters, aldehydes, phenolic compounds, lignin oligomers, and carboxylic acids. Bio-oil is not miscible with conventional oil fractions Its higher acidity compared to conventional petroleum Pyrolysis oil can be used as an energy carrier Bio-oil generation from pyrolysis Bio-oil generation from pyrolysis Upgrading of Bio-Oil Fast pyrolysis of lignocellulose has high yields of bio-oil Unfortunately, bio-oil has several undesirable characteristics that complicate direct use in combustors and production of renewable chemicals. These undesirable characteristics include high acidity, high water content, high oxygen content, low heating value, high viscosity, poor stability, poor volatility and corrosiveness. A wide variety of bio-oil upgrading methods have been developed that try to reduce/eliminate the above mentioned properties of bio-oil. Bio-oil generation from pyrolysis Upgrading of Bio-Oil The upgrading methods can be physical or chemical Physical methods such as (hot filter, adding solvents, emulsion and vacuum distillation) filtration to reduce ash content and addition of methanol to improve viscosity and reduce aging Chemical methods such as (hydrotreating, catalytic cracking, esterification, and gasification) reduction of oxygen content through hydrotreating These processes reduce the oxygen content of bio-oil. Complete deoxygenation results in a hydrocarbon product that can be readily used in conventional refineries Upgrading of Bio-Oil Hydrotreating Hydrotreating is a catalytic process that removes heteroatoms, such as oxygen, nitrogen, and sulfur through reaction with hydrogen. Oxygen is mainly removed by hydrodeoxygenation(HDO) to form water and hydrocarbons. Other oxygen removal pathways involve decarbonylation and decarboxylation forming CO and CO2, respectively During this process, double bonds and aromatics are saturated by hydrogenation hydrotreating takes place at high pressures (200 bar) and moderate temperatures (400–773 K) over fixed bed reactors The high pressure is necessary to ensure sufficient hydrogen solubility in the liquid phase Upgrading of Bio-Oil (a) Non-catalytic fast hydropyrolysis (b) Catalytic fast hydropyrolysis (c) Non-catalytic fast hydropyrolysis with ex-situ hydrotreating (d) Catalytic fast hydropyrolysis with ex-situ hydrotreating Upgrading of Bio-Oil catalytic cracking In catalytic cracking, the oxygen is removed in the forms of carbon dioxide, carbon monoxide, water and short-chain oxygenates via several reactions such as cracking, decarboxylation, decarbonylation, dehydration and water gas shift. The process is carried out in the presence of a catalyst, mainly zeolites, without hydrogen at atmospheric pressure and a temperature range of 300-600 °C depending on a type of reactor The general reaction where “CH1.2” is an unspecified hydrocarbon product Upgrading of Bio-Oil Zeolite Cracking Bio-oil can be cracked over an acid zeolite catalyst, such as H-ZSM-5. Oxygen is removed through cracking reactions forming CO and CO2. The residual liquid product primarily consists of aromatics, such as benzene, toluene, xylenes, and naphthalene. The formation of aromatics rather than saturated hydrocarbons is a result of the hydrogen deficiency of the bio-oil. Compared to hydrotreating, relatively more carbon atoms are lost through formation of carbon oxides, which results in lower yields of liquid hydrocarbons. The catalytic cracking process can be operated in either liquid or vapor phase. Upgrading of Bio-Oil It can be integrated or coupled in a pyrolysis process or used as a stand-alone process for upgrading Thank you… Q&A Session 05 Synthesis of Intermediate Liquid Biofuels from Biorefineries BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Eng.Prasad Amarasinghe Module Outline Content Lecture Time 1. Fermentation Technologies for 08 Hours Bioethanol Conversion 2. Biodiesel Production Technologies 08 Hours 3. Synthesis of Intermediate Liquid 04 Hours Biofuels from Biorefineries 4. Biofuel Distillation for Initial 04 Hours Separation/Purification 5. Liquid Biofuel Plant Operation and 04 Hours Maintenance 6. Economics of Liquid Biofuel 02 Hours Generation Processes Content …. Bio-based production processes of Methanol Refined Fischer-Tropsch liquids (FTL) Dimethyl ether (DME) Bio-based production processes of Methanol Methanol is one of the most important platform chemicals produced by the chemical industry. methanol is used to make various other chemicals, converted into anti- knocking agents and blended in with fuels, and applied as a solvent and antifreeze. Bio-methanol can be produced from virgin or waste biomass, non-biogenic waste streams, or even CO2 from flue gases. These feedstocks are converted (typically through gasification) into syngas, a mixture of carbon monoxide, hydrogen and other molecules. The syngas is subsequently conditioned through several steps to reach the optimal composition for methanol synthesis, for example by removing CO2 or adding hydrogen Bio-based production processes of Methanol Methanol (CH3OH) is an important basic chemical. It is produced from fossil fuels such as natural gas, coal and oil products. More recently, methanol has also been used for biodiesel production from fats and oils, and it is increasingly investigated as a clean- burning transportation fuel, either directly blended with conventional fuels or after conversion into dimethyl ether (DME). The main processes in a conventional methanol plant are: gasification, gas cleaning, reforming of high hydrocarbons, water-gas shift, hydrogen addition and/or CO2 removal, and methanol synthesis and purification Bio-based production processes of Methanol Overview of major methanol production processes from various carbon sources Bio-based production processes of Methanol Methanol Synthesis and Purification The demand grew, synthetic processes were developed to produce methanol economically and efficiently. Methanol is produced almost exclusively from syngas, using a well- developed commercial catalytic process with high activity and very high selectivity. Methanol from syngas synthesis involves hydrogenation of CO and CO2 reactions and reverse WGS(water gas-shift ) reactions, while catalysts play a crucial role in syngas conversion reactions Bio-based production processes of Methanol After gasification, impurities and contaminants (e.g. tars, dust, and inorganic substances) are removed before the gas is passed through several conditioning steps that optimize its composition for methanol synthesis First, unprocessed syngas can contain small amounts of methane and other light hydrocarbons with high energy content Second, the initial hydrogen concentration in the syngas is usually too low for optimal methanol synthesis To reduce the share of CO and increase the share of H2, a water gas-shift reaction (WGSR) can be used, which converts CO and H2O into CO2 and H2. CO2 can also be removed directly using chemical absorption by amines Bio-based production processes of Methanol Third, hydrogen can be produced separately, and added to the syngas. Industrial hydrogen is produced either by steam reforming of methane or electrolysis of water. While electrolysis is usually expensive, it can offer important synergies if the oxygen produced during electrolysis is used for partial oxidation in the gasification step, thus replacing the need for air or for oxygen production from air separation. the syngas is converted into methanol by a catalytic process based on copper oxide, zinc oxide, or chromium oxide catalysts Distillation is used to remove the water generated during methanol synthesis. Bio-based production processes of Methanol CO + 2H2 ↔ CH3OH ΔH298 = − 90.55 kJ/mol CO2 + 3H2 ↔ CH3OH + H2O ΔH298 = − 49.57 kJ/mol CO2 + H2 ↔ CO + H2O ΔH298 = 41.12 kJ/mol As shown by the heat of reaction, the global process is exothermic, leading to the major challenge associated with methanol synthesis, which is removing the large excess heat produced during the reaction The catalytic activity of methanol synthesis increases at higher temperatures but so does the potential for competing side reactions, which produce CH4, DME, methyl formate, higher alcohols, and acetone Also, the catalysts’ lifetime is reduced by continuous high temperature operation Bio-based production processes of Methanol Methanol synthesis process, In this process, the hotter gas produced (due to the exothermic reaction) is used to preheat the fresh syngas prior to its introduction in the convertor. Side feeds of syngas are also installed in order to mitigate heat escalation along the beds. Raw (crude) methanol produced in the methanol synthesis reactor is usually composed of a mixture of methanol, 8–30 wt% water, up to 0.5 wt% ethanol, and other impurities. The crude methanol is transferred to specially assigned storage tanks where it will become the feed for a purification unit Two distillation columns are used in series Bio-based production processes of Methanol The first column, called the topping column, is designed to remove low boiling impurities (light ends) that boil at a lower temperature than the boiling point of methanol. After the topping process, the crude is transferred to the second column, called the refining column, where the liquid is again constantly boiled until the water (which boils at a higher temperature) separates from methanol. The refining column is a very tall distillation column (total height 60 to 120 plates) as the methanol and water are reluctant to separate. It therefore requires a lot of heat energy (heavy boiling) to achieve the required product purity. Bio-based production processes of Methanol (a) methanol synthesis and (b) purification process Refined Fischer-Tropsch liquids (FTL) Fischer-Tropsch (FT) synthesis is a common process to convert syngas (H2 and CO) to synthetic liquid fuels (i.e. diesel fuel and gasoline) in the presence of catalysts at a temperature range of 220-350 °C and pressure of 10-60 bar. This is a complex process via chain propagation, chain termination and product desorption on the surface of the catalysts. (2n + 1)H2 + nCO CnH(2n+2) + nH2O (paraffin formation) 2nH2 + nCO CnH2n + nH2O (olefin formation) CO + H2O CO2 + H2 (water-gas shift reaction) nCO + 2nH2 CnH(2n + 1) OH + (n – 1) H2O (alcohol formation) Refined Fischer-Tropsch liquids (FTL) Fischer-Tropsch Reactor Four common types of reactors used for FT synthesis Multi-tubular fixed bed Slurry bubble column Bubbling fluidized bed Circulating fluidised bed Refined Fischer-Tropsch liquids (FTL) Fischer-Tropsch schematic Refined Fischer-Tropsch liquids (FTL) Multi-Tubular Fixed Bed The fixed bed reactor is the most common and efficient reactor for FT synthesis, which can be operated at a temperature range of 220-260 °C in a pressure range of 25-45 bar. The products contain a complex mixture of compounds i.e. long chain hydrocarbons (C5+) and waxes (C19+) The major drawbacks of the fixed bed reactors are (i) high pressure drop (ii) short lifetime of catalyst (iii) low heat transfer (iv) diffusion limitations Refined Fischer-Tropsch liquids (FTL) Slurry Bubble Column The slurry reactor is suitable for the synthesis of wax at a temperature range of 250-300 °C The syngas is distributed from the bottom rising through the slurry consisting of a high thermal capacity liquid with fine catalyst particles suspended in it. Hydrocarbon products form the slurry phase while the lighter gaseous products and water diffuse through the gas bubbles This type of reactor enhances heat and mass transfer, and catalyst utilization, resulting in high activity and selectivity the main disadvantage of the slurry reactor is required catalyst/wax separation and cleaning process Refined Fischer-Tropsch liquids (FTL) Fluidized Bed A fluidized bed reactor can be operated in a temperature range of 320-350 °C to produce light alkenes, long chain waxes (C5+) and gasoline The high degree of turbulence in the fluidized bed significantly improves heat and mass transfer. The fluidized bed reactors can be classified into (i) bubbling fluidized bed reactors (ii) circulating fluidized bed reactors Refined Fischer-Tropsch liquids (FTL) Fluidized Bed The bubbling fluidized bed has some advantages over the circulating fluidized bed. i.e. olower catalysts consumption, ogreater isothermal characteristics and temperature control, ogreater conversion capacity, ohigher product selectivity of slightly heavier hydrocarbons oless investment and maintenance costs oeasier construction Refined Fischer-Tropsch liquids (FTL) (a) multi-tubular (b) slurry bubble column (c) bubbling fluidized bed (d) circulating fluidized bed fixed bed Refined Fischer-Tropsch liquids (FTL) Catalyst The common catalysts used in the FT synthesis are Iron (Fe), Nickel (Ni), Cobalt (Co) and Ruthenium (Ru). Fe based catalysts are the most common catalysts for FT due to their low cost and availability compared to other metallic catalysts Fe has activity in the water gas shift reaction, which could help to adjust the ratio of H2/CO. The short chain unsaturated hydrocarbons are selectively produced at high temperatures but methane selectivity is limited when Fe is used as a catalyst Refined Fischer-Tropsch liquids (FTL) Ni catalysts have high selectivity of methane formation Nickel carbonyls (highly toxic) are formed during the process, causing corrosion and a reduction in catalyst activity. Co catalysts have higher activity compared to Ni and Fe, promoting the formation of long chain alkanes (C5+) Co catalysts have a high resistance to deactivation and a low activity in the water gas shift reaction. Co catalysts also have a good selectivity to paraffin but low selectivity to olefins and oxygenates Refined Fischer-Tropsch liquids (FTL) Although, Ru has the highest active catalysts for the FT synthesis, high cost hinders its applications. Therefore, Co and Fe catalysts are the only viable catalysts for the commercial industrial applications. Apart from single metallic catalysts, it has been found that bimetallic catalysts have high potential for FT synthesis The conversion of CO using a bimetallic catalyst can increase by five times compared to a pure metal catalyst The advantages and disadvantages of different types of catalysts in Fischer-Tropsch synthesis Dimethyl ether (DME) DME is an alternative diesel fuel for use in compression ignition (CI) engines and may be produced from a range of waste feedstocks. DME is characterized by low CO2, low NOx and low particulate matter (PM) emissions. Dimethyl ether (typically abbreviated as DME), also known as methoxymethane, wood ether, dimethyl oxide or methyl ether, is the simplest ether. The properties of DME are similar to those of Liquefied Petroleum Gas (LPG). DME is degradable in the atmosphere and is not a greenhouse gas Dimethyl ether (DME) PRODUCTION PROCESS DME is primarily produced by converting natural gas, organic waste or biomass to synthesis gas (syngas) The syngas is then converted into DME via a two-step synthesis, first to methanol in the presence of catalyst , and then by subsequent methanol dehydration in the presence of a different catalyst (for example, silica-alumina) into DME. The following reactions occur: 2H2+ CO CH3OH 2CH3OH CH3OCH3 + H2O CO+H2O CO2+H2 (01). What are the liquid fuels that can be synthesized from biorefineries ? (02).What is the meaning of Refined Fischer-Tropsch liquids (FTL)? (03).What are the different types of catalyst that can be used for refining FTL ? Thank you… Q&A Session 07 Biofuel Distillation for Initial Separation/Purification BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Eng.Prasad Amarasinghe Content …. Use of distillation columns for liquid-liquid separation Azeotropic nature of ethanol/water mixture Basic principles of distillation technology Use of distillation columns for liquid-liquid separation The ethanol obtained after the fermentation reaction is purified using distillation, which is still the most widely used method for ethanol purification Distillation removes water and other impurities from the fermented product thereby purifying the ethanol up to 95% However, some modification in the distillation system is the need of the hour in order to obtain high purity ethanol with less consumption of energy Based on the volatility of components, two phases are formed. The more volatile components will be in vapor rich region and the less volatile in the liquid rich region. Use of distillation columns for liquid-liquid separation Distillation is method of separation of components from a liquid mixture which depends on the differences in boiling points of the individual components and the distributions of the components between a liquid and gas phase in the mixture. The liquid mixture may have different boiling point characteristics depending on the concentrations of the components present in it. Distillation is used to separate liquids from nonvolatile solids, as in the separation of alcoholic liquors from fermented materials, or in the separation of two or more liquids having different boiling points, as in the separation of gasoline, kerosene, and lubricating oil from crude oil. Use of distillation columns for liquid-liquid separation Types of Distillation Columns There are many types of distillation columns, each designed to perform specific types of separations, and each design differs in terms of complexity Batch columns In batch operation, the feed to the column is introduced batch-wise. That is, the column is charged with a 'batch' and then the distillation process is carried out. When the desired task is achieved, a next batch of feed is introduced Use of distillation columns for liquid-liquid separation Types of Distillation Columns Continuous columns continuous columns process a continuous feed stream. No interruptions occur unless there is a problem with the column or surrounding process units. They are capable of handling high throughputs and are the most common of the two types. Use of distillation columns for liquid-liquid separation Types of continuous columns Continuous columns can be further classified according to: The nature of the feed that they are processing binary column - feed contains only two components multi-component column - feed contains more than two components The number of product streams they have multi-product column - column has more than two product streams Where the extra feed exits when it is used to help with the separation extractive distillation - where the extra feed appears in the bottom product stream azeotropic distillation - where the extra feed appears at the top product stream Use of distillation columns for liquid-liquid separation The type of column internals tray column - where trays of various designs are used to hold up the liquid to provide better contact between vapor and liquid, hence better separation packed column - where instead of trays, 'packings' are used to enhance contact between vapor and liquid Use of distillation columns for liquid-liquid separation Main Components of Distillation Columns Distillation columns are made up of several components, each of which is used either to transfer heat energy or enhance material transfer. A typical distillation contains several major components: A vertical shell where the separation of liquid components is carried out column internals such as trays/plates and/or packings which are used to enhance component separations A reboiler to provide the necessary vaporization for the distillation process A condenser to cool and condense the vapor leaving the top of the column A reflux drum to hold the condensed vapour from the top of the column so that liquid (reflux) can be recycled back to the column Use of distillation columns for liquid-liquid separation Basic Operation The liquid mixture that is to be processed is known as the feed and this is introduced usually somewhere near the middle of the column to a tray known as the feed tray. The feed tray divides the column into a top (enriching or rectification) section and a bottom (stripping) section. The feed flows down the column where it is collected at the bottom in the reboiler. Use of distillation columns for liquid-liquid separation Heat is supplied to the reboiler to generate vapor. The source of heat input can be any suitable fluid, although in most chemical plants this is normally steam. In refineries, the heating source may be the output streams of other columns. The vapor raised in the reboiler is re-introduced into the unit at the bottom of the column. The liquid removed from the reboiler is known as the bottoms product or simply, bottoms Use of distillation columns for liquid-liquid separation The vapor moves up the column, and as it exits the top of the unit, it is cooled by a condenser. The condensed liquid is stored in a holding vessel known as the reflux drum. Some of this liquid is recycled back to the top of the column and this is called the reflux The condensed liquid that is removed from the system is known as the distillate or top product. Use of distillation columns for liquid-liquid separation Use of distillation columns for liquid-liquid separation Reflux ratio(R) 𝐿𝑜 R= 𝐷 Overall Material Balance; F = D +W Material balance for the more volatile component; F 𝑋𝑓 = D 𝑋𝐷 +W 𝑋𝑤 Example A feed of 150 kmol/hr containing 45 mol% methanol and 55 mol% water is to be separated in a continuous distillation column to give a distillate containing 98 mol% methanol and a bottom product containing 3 mol% methanol. Determine the liquid and vapor flow rates in the rectifying section and the stripping section of the column. Data : Relative molar masses Methanol : 32 gas density = 1 kg/m3 Water : 18 liquid density = 1000 kg/m F= 150 𝑋𝐹 = 45% =0.45 mol (methanol) 𝑋𝐷 =98%= 0.98 mol (D.M) 𝑋𝑤 =3%= 0.03 mol (B.M) D W Overall Material Balance F = D +W 150 kmol/hr = D +W (01) Material balance for the methanol component F 𝑋𝑓 = D 𝑋𝐷 +W 𝑋𝑤 150 kmol/hr*0.45 = D*0.98 + W*0.03 (02) Example A feed of 140 kmol/hr containing methanol and 60 mol% water is to be separated in a continuous distillation column to give a distillate containing 95 mol% methanol and a bottom product containing 98 mol% water Determine the liquid and vapor flow rates in the rectifying section and the stripping section of the column. Data : Relative molar masses Methanol : 32 gas density = 1 kg/m3 Water : 18 liquid density = 1000 kg/m F=140 𝑋𝐹 = 60%=0.6 (F.W) MF= 40%= 0.4 140*0.4 = D*0.95 + W*0.02 𝑋𝐷 = 5% = 0.05 (D.W) MD= 95%= 0.95 𝑋𝑊 =98% = 0.98 (B.W) MB =2% = 0.02 Overall Material Balance D= 57.2 Kmol/hr W= 82.8 kmol/hr F = D +W 140= D+W (01) Material balance for the water component F 𝑋𝑓 = D 𝑋𝐷 +W 𝑋𝑤 140*0.6 = D *0.05 + W*0.98 (02) Basic principles of distillation technology Separation of components from a liquid mixture via distillation depends on the differences in boiling points of the individual components. Also, depending on the concentrations of the components present, the liquid mixture will have different boiling point characteristics Therefore, distillation processes depends on the vapor pressure characteristics of liquid mixtures. Basic principles of distillation technology Vapor Pressure and Boiling The vapor pressure of a liquid at a particular temperature is the equilibrium pressure exerted by molecules leaving and entering the liquid surface Here are some important points regarding vapor pressure: Energy input raies vapor pressure vapor pressure is related to boiling A liquid is said to ‘boil’ when its vapor pressure equals the surrounding pressure liquid boils depends on its volatility liquids with high vapor pressures (volatile liquids) will boil at lower temperatures the vapor pressure and hence the boiling point of a liquid mixture depends on the relative amounts of the components in the mixture distillation occurs because of the differences in the volatility of the components in the liquid mixture Basic principles of distillation technology The Boiling Point Diagram The boiling point diagram shows how the equilibrium compositions of the components in a liquid mixture vary with temperature at a fixed pressure. Consider an example of a liquid mixture containing 2 components (A and B) - a binary mixture. This has the following boiling point diagram. The boiling point of A is that at which the mole fraction of A is 1. The boiling point of B is that at which the mole fraction of A is 0. In this example, A is the more volatile component and therefore has a lower boiling point than B. Basic principles of distillation technology The upper curve in the diagram is called the dew-point curve while the lower one is called the bubble-point curve. The dew-point is the temperature at which the saturated vapor starts to condense. The bubble-point is the temperature at which the liquid starts to boil. The region above the dew-point curve shows the equilibrium composition of the superheated vapor The region below the bubble-point curve shows the equilibrium composition of the subcooled liquid. Basic principles of distillation technology For example, when a subcooled liquid with mole fraction of A=0.4 (point A) is heated, its concentration remains constant until it reaches the bubble-point (point B),when it starts to boil. The vapors evolved during the boiling has the equilibrium composition given by point C, approximately 0.8 mole fraction A. This is approximately 50% richer in A than the original liquid. This difference between liquid and vapour compositions is the basis for distillation operations. Basic principles of distillation technology Relative Volatility Relative volatility is a measure of the differences in volatility between 2 components, and hence their boiling points. It indicates how easy or difficult a particular separation will be. The relative volatility of component ‘i’ with respect to component ‘j’ is defined as yi = mole fraction of component ‘i’ in the vapor xi = mole fraction of component ‘i’ in the liquid Basic principles of distillation technology Thus if the relative volatility between 2 components is very close to one, it is an indication that they have very similar vapor pressure characteristics. This means that they have very similar boiling points and therefore, it will be difficult to separate the two components via distillation. Azeotropic nature of ethanol/water mixture In the case of mixtures of ethanol and water, this minimum occurs with 95.6% by mass of ethanol in the mixture. The boiling point of this mixture is 78.2°C, compared with the boiling point of pure ethanol at 78.5°C, and water at 100°C. You might think that this 0.3°C doesn't matter much, but it has huge implications for the separation of ethanol / water mixtures. Azeotropic nature of ethanol/water mixture Suppose you are going to distil a mixture of ethanol and water with composition C1 It will boil at a temperature given by the liquid curve and produce a vapor with composition C2. Azeotropic nature of ethanol/water mixture When that vapor condenses it will, of course, still have the composition C 2. If you reboil that, it will produce a new vapor with composition C3 You can see that if you carried on with this boiling-condensing-reboiling sequence, you would eventually end up with a vapor with a composition of 95.6% ethanol. If you condense that you obviously get a liquid with 95.6% ethanol. Azeotropic nature of ethanol/water mixture What happens if you reboil that liquid? The liquid curve and the vapor curve meet at that point. The vapor produced will have that same composition of 95.6% ethanol. If you condense it again, it will still have that same composition. It is impossible to get pure ethanol by distilling any mixture of ethanol and water containing less than 95.6% of ethanol. It has a constant boiling point, and the vapor composition is exactly the same as the liquid. It is known as a constant boiling mixture or an azeotropic mixture or an azeotrope Azeotropic nature of ethanol/water mixture Water and ethanol are known to form an azeotropic mixture. This mixture can be separated via the process of azeotropic distillation In order to achieve this, material separation agents such as benzene, hexane, cyclohexane, pentane, diethyl ether, and acetone are commonly used. Historically, benzene was the most commonly used entrainer for this purpose. the discovery of the carcinogenic nature of benzene is believed to have caused a decline in the use of benzene in the azeotropic distillation of mixtures of water and ethanol. In modern practices, the ethanol-water azeotrope is usually broken with the help of toluene. Thank you… Q&A Session 08 Liquid Biofuel Plant Operation and Maintenance BST 31242-Liquid Biofuel Generation Technology Bachelor of Biosystems Technology Honors (BBST Hons) Degree Program Faculty of Technology Sabaragamuwa university of Srilanka Prepared by: Eng.Prasad Amarasinghe Content …. What is a Fermenter? What is a Bioreactor? Similarities Between Bioreactor and Fermenter Difference Between Bioreactor and Fermenter Continuous stirred tank fermenter Airlift fermenter Bubble column fermenter Fluidized-bed fermenter Packed bed fermenter Parts of the bioreactor and their function What is a Fermenter? Fermenter is a specialized bioreactor. Thus, it only carries out fermentation reactions. Fermentation is the process that produces acids and alcohols from sugar sources under anaerobic conditions. Most industries such as wine industry etc widely use fermentation of sugars to produce lactic acid and ethanol. Thus, fermenters use microbial sources that are capable of fermentation. They include fungi such as Saccharomyces cerevisiae and bacteria such as Acetobacter. What is a Fermenter? Fermentation takes place under anaerobic conditions and the regulation of the temperature and the pH of the system. Hence, fermenter has an inlet and an outlet to add raw materials and to remove the product respectively. Within the fermenters, two main types of fermentations can perform such as submerged fermentation and surface fermentation. Accordingly, submerged fermentation where the cells submerge in the media and surface fermentation where the microbial cultures lie loosely on the surface of the fermenter media. What is a Bioreactor? Bioreactor is a closed vessel that has the ability to process and facilitate all types of biochemical reactions. Thus, these bioreactors are important in various cell culturing techniques to facilitate cellular growth. The cells which grow inside the bioreactors can vary from single-celled microorganisms to multicellular plant and animal cells. At the end of the process, the desired products can be extracted or separated easily. Hence, these bioreactors utilize routinely in industries to produce secondary metabolites such as pharmaceuticals, vitamins and proteins. What is a Bioreactor? There are different types of bioreactors based on the reactions they facilitate. The main types of bioreactors are stirred tank bioreactors, airlift bioreactors, column bioreactors and packed bed bioreactors. Apart from that, there are several kinds of bioreactors based on the types of culturing mechanism used in the bioreactor. If the bioreactors carry out suspension culturing, they are known as suspended growth bioreactors. If the bioreactors form biofilms for producing metabolites, they are termed as biofilm bioreactors. Similarities Between Bioreactor and Fermenter Bioreactor and Fermenter are closed systems They facilitate biochemical reactions. Factors such as temperature, pH, aeration and sterility regulate both systems Furthermore, they are useful in the industry to produce various biological products Both operate in large-scale production of industrially important molecules. Difference Between Bioreactor and Fermenter The key difference between bioreactor and fermenter is the type of reaction that facilitates by each closed system Bioreactor facilitates any type of biochemical reactions while fermenter facilitates fermentation. fermenters are specific bioreactors designed for fermentation reactions that occur under anaerobic conditions. both, the bioreactor and fermenter are industrially important in producing various products. Continuous stirred tank bioreactor A continuous stirred tank bioreactor is made up of a cylindrical vessel with a central shaft controlled by a motor that supports one or more agitators (impellers) The sparger, in combination with impellers (agitators), allows for improved gas distribution throughout the vessel. A stirred tank bioreactor can be operated continuously in the fermenter, temperature control is effortless, construction is cheap, easy to operate, resulting in low labor cost, and it is easy to clean. It is the most common type of bioreactor used in industry. Airlift bioreactor The airlift reactor is generally used for gas-liquid or gas-liquid-solid contact devices. It is also known as a tower reactor. A bioreactor using an airlift system divides the fluid volume into two zones to improve circulation, oxygen transfer, and equalize forces in the reactor In a two-zone system, only one zone is sparged with gas. The zone where the gas is sparged is the riser; the zone in which it is not sparged in the downcomer. Airlift bioreactors are used for aerobic bioprocessing technology so that they can provide a controlled liquid flow in a recycling system using pumps. This equipment has several advantages such as its simplicity of design because it doesn’t contain any moving parts or agitators, its easy sterilization, its low energy requirements, and its low cost. Airlift bioreactor Bubble column bioreactor The bubble column reactor consists of a cylindrical vessel equipped with a gas sparger that pushes gas bubbles into a liquid phase or a liquid-solid suspension. The base of the column air or gas is introduced via perforated pipes or plates, or metal micro porous sparger. The rheological properties of the fluid and the gas flow rate have a significant influence on the mixing of O2 and other performance factors. These reactors are simple in construction, easy maintenance, and have a low operating cost Bubble columns reactors are used in biochemical processes such as fermentation and biological wastewater treatment. It is also used in many chemical, petrochemical, and biochemical industries. Fluidized-bed bioreactor Fluid bed bioreactors constitute packed beds with smaller particles. This prevents problems such as clogging, high liquid pressure drop, channeling, and bed compaction associated with packed bed reactors. Catalyst is laid on the bottom of the reactor and the reactants are pumped into the reactor through a distributor pump to make the bed fluidized. In these reactors, the cells are immobilized small particles which move with the fluid as a result, mass transfer, oxygen transfer, and nutrition to the cells are enhanced. Fluidized-bed bioreactor The bioreactors can be used for reactions involving fluid-suspended biocatalysts, such as immobilized enzymes, immobilized cells, and microbial flocs. Its main advantages include its ability to maintain even temperatures, easy replacement and regeneration of the catalyst, continuity, and automaticity of operation, and reduced contact time between gas and solid, compared to other catalytic reactors. Packed bed bioreactor A packed bed fermenter is a bed of solid particles, having biocatalyst on or within, the matrix of solids. It can either be run in the submerged mode (with or without aeration) or the trickle flow mode. Frequently used in chemical processing processes such as absorption, distillation, stripping, separation process, and catalytic reactions, packed bed reactors are also called fixed bed reactors. In packed-bed bioreactors, the air is introduced through a sieve that supports the substrate. This reactor has many benefits, like a high conversion rate for the catalyst, ease of operation, low construction and operation costs, increased contact between reactant and catalyst, and the ability to work in high temperatures and pressures. Fermenter and its Features A bioreactor is a device in which a substrate of low value is utilized by living cells or enzymes to generate a product of higher value. Bioreactors arc extensively used for food processing, fermentation, waste treatment, etc. On the basis of the agent used, bioreactors are grouped into the following two broad Those based on living cells Those employing enzymes But in terms of process requirements, they are of the following types (i) aerobic, (ii) anaerobic, (iii) solid state, and (iv) immobilized cell bioreactors. Fermenter and its Features A bioreactor should provide for the following (i) Agitation (for mixing of cells and medium) (ii) Aeration (aerobic fermenters; for O2 supply) (iii) Regulation of factors like temperature, pH, pressure, aeration, nutrient feeding, liquid level, etc. (iv) Sterilization and maintenance of sterility (v) withdrawal of cells/medium (for continuous fermenters) Modern fermenters are usually integrated with computers for efficient process monitoring, data acquisition Applications of bioreactor Bioreactors Operation A bioprocess is composed mainly of three stages — upstream processing, bioreaction, and downstream processing — to convert raw material to finished product. The raw material can be of biological or non-biological origin. It is first converted to a more suitable form for processing. This is done in an upstream processing step which involves chemical hydrolysis, preparation of liquid medium, separation of particulate, air purification and many other preparatory operations. After the upstream processing step, the resulting feed is transferred to one or more Bioreaction stages. The Biochemical reactors or bioreactors form the base of the Bioreaction step. This step mainly consists of three operations, namely, production of biomass, metabolite biosynthesis and biotransformation Bioreactors Operation Finally, the material produced in the bioreactor must be further processed in the downstream section to convert it into a more useful form The downstream process mainly consists of physical separation operations which include solid liquid separation, adsorption, liquid- liquid extraction, distillation, drying etc On the basis of mode of operation, a bioreactor may be classified as batch, fed batch or continuous Batch processes In a batch process, all nutrients are provided at the beginning of the cultivation, without adding any more in the subsequent bioprocess. During the entire bioprocess, no additional nutrients are added – just control elements such as gases, acids and bases; it is a closed system The disadvantage of this convenient method is that the biomass and product yields are limited. Batch processes The advantages of a batch culture are: Short duration Less chance of contamination as no nutrients are added Separation of batch material for traceability Easier to manage Some disadvantages include: Product is mixed in with nutrients, reagents, cell debris and toxins Shorter productive time Can involve storage of batches for downstream processing Fed-batch processes One way of keeping nutrients from becoming a limiting factor is to constantly supply them during cultivation. This is called a fed-batch process, which is a partly open system. The advantage of feeding during cultivation is that it allows to overall achieve higher product quantities overall. The substrate is pumped from the supply bottle into the culture vessel through a silicone tube The user can either manually set the feed at any time (linear, exponential, pulse-wise), or add nutrients when specific conditions are met, such as when a certain biomass concentration is reached or when a nutrient is depleted Fed-batch processes The advantages of a fed-batch culture are: Entends a cultures productive duration Can be manipulated for maximum productivity using different feeding strategies Some disadvantages include: Allows build up of inhibitory agents and toxins Provides another point of ingress for contamination Continuous culture After a batch growth phase, an equilibrium is established with respect to a particular component (also called steady state). Under these conditions, as much fresh culture medium is added, as it is removed (chemostat). These bioprocesses are referred to as continuous cultures, and are particularly suitable when an excess of nutrients would result in inhibition due to e.g. toxin build up or excessive heating Other advantages of this method include reduced product inhibition and an improved space-time yield Continuous culture The advantages of a continuous culture are: Allows the maximum productivity Time for cleaning, sterilization and handling of the vessel are all reduced Some disadvantages include difficult to keep a constant population density over prolonged periods The products of a continuous process cannot be neatly separated into batches for traceability Increased risk of contamination and/or genetic changes Parts of the bioreactor and their function These reactors have been designed to maintain certain parameters like flow rates, aeration, temperature, pH, foam control, and agitation rate. The number of parameters that can be monitored and controlled is limited by the number of sensors and control elements incorporated into a given bioreactor Parts of the bioreactor and their function Fermenter Vessel A fermenter is a large cylinder closed at the top and bottom connected with various pipes and valves The vessel is designed in such a way that it allows to work under controlled conditions. Glass and stainless steels are two types of fermenter vessels used. The glass vessel is usually used in small-scale industries. It is non-toxic and corrosion-proof. Stainless steel vessel is used in large scale industries. It can resist pressure and corrosion. Parts of the bioreactor and their function Heating and Cooling Apparatus The fermenter vessel’s exterior is fitted with a cooling jacket that seals the vessel and provides cooling water. Thermostatically controlled baths or internal coils are generally used to provide heat while silicone jackets are used to remove excess heat A cooling jacket is necessary for sterilization of the nutrient medium and removal of the heat generated during fermentation in the fermenter. Parts of the bioreactor and their function Aeration System An aeration system is one of the very important parts of a fermenter. It is important to choose a good aeration system to ensure proper aeration and oxygen availability throughout the culture. It contains two separate aeration devices (sparger and impeller) to ensure proper aeration in a fermenter. The stirring accomplishes two things It helps to mix the gas bubbles through the liquid culture medium It helps to mix the microbial cells through the liquid culture medium which ensures the uniform access of microbial cells to the nutrients Parts of the bioreactor and their function Sealing Assembly The sealing assembly is used for the sealing of the stirrer shaft to offer proper agitation. There are three types of sealing assembly in the fermenter: Packed gland seal Mechanical seal Magnetic drives Baffles The baffles are incorporated into fermenters to prevent a vortex improve aeration in the fermenters. It consists of metal strips attached radially to the wall. Parts of the bioreactor and their function Impeller Impellers are used to provide uniform suspension of microbial cells in different nutrient mediums. They are made up of impeller blades attached to a motor on the lid. Impeller blades play an important role in reducing the size of air bubbles and distribute them uniformly into the fermentation media. Variable impellers are used in the fermenters and are classified as follows Disc turbines Variable pitch open turbine Parts of the bioreactor and their function Sparger A sparger is a system used for introducing sterile air to a fermentation vessel. It helps in providing proper aeration to the vessel. The sparger pipes contain small holes of about 5-10 mm, through which pressurized air is released. Three types of sparger are used Porous sparger Nozzle sparger Combined sparger–agitator Parts of the bioreactor and their function Feed Ports They are used to add nutrients and acid/alkali to the fermenter. Feed ports are tubes made up of silicone. In-situ sterilization is performed before the removal or addition of the products. Foam-Control The level of foam in the vessel must be minimized to avoid contamination, this is an important aspect of the fermenter. Foam is controlled by two units, foam sensing, and a control unit. A foam-controlling device is mounted on top of the fermenter, with an inlet into the fermenter Parts of the bioreactor and their function Valves Valves are used in the fermenter to control the movement of liquid in the vessel. There are around five types of valves are used, that is, globe valve butterfly valve, a ball valve diaphragm valve. A safety valve is built-in in the air and pipe layout to operate under pressure Parts of the bioreactor and their function Controlling Devices for Environmental Factors A variety of devices are utilized to control environmental elements like temperature, oxygen concentration, pH, cell mass, essential nutrient levels, and product concentration. Thank you… Q&A

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