Introduction to Chemical Processes 2024 PDF

Expectation at the end of the course Understand the concept of chemical processes Understand the different major constituents for the manufacture of selected products Carry out different practicals for the manufacture of selected products Roles of a chemist Chemists can find emp...

Expectation at the end of the course Understand the concept of chemical processes Understand the different major constituents for the manufacture of selected products Carry out different practicals for the manufacture of selected products Roles of a chemist Chemists can find employment in government parastatals and department Teaching, research and development institutions Biotechnology Quality control Production and manufacturing industries Water purification and effluent management. Chemists vs Chemical Engineers Chemists Chemical Engineers Design reaction pathways to produce a Design a process to scale the chemist’s chemical from raw materials process to mass produce the product Work in the laboratory setting to produce Work in a chemical plant to produce material on the gram to kilogram scale material in the ton and beyond range Chemical industry Comprises of companies that produce industrial chemicals It converts materials like oil, natural gas, air, water, metals and minerals into more than 70,000 different products Polymers and plastics comprise about 80% of the industry’s output worldwide Chemicals are used in a lot of consumer goods Chemical industries in Nigeria require…… Raw materials Energy Water Machinery Labour Transportation for raw materials and finished products Importance of the chemical industry Supplies farmers pesticides and fertilizers essential for growing crops Produces the fibres and dyes used in the textile industries Provides essential chemical components for the pharmaceutical and health care industry Produces polymers and plastics (e.g. PVC piping, water tanks, wiring, etc.) Chemical products They are essential to modern living standards Almost all aspect of everyday life are supported by chemical products in one way or the other. Chemical products can be divided into three broad classes:  Commodity or bulk chemicals: these are produced in large volumes and purchased on the basis of chemical composition, purity and price. Examples are sulphuric acid, nitrogen, oxygen and chlorine Fine chemicals: these are produced in small volumes and purchase on the basis of chemical composition, purity and price. Examples are dimethyl formamide (used as an intermediate in the manufacture of pharmaceuticals), ion exchange resins Specialty or effect functional chemicals: theses are purchased because of their effect (or function) rather than their chemical composition. These are chemically formulated products manufactured from basic chemicals which are used by industry and domestic consumers for specific purposes. For example: coatings, adhesives, pharmaceutical products, pesticides, cosmetics, disinfectants etc Characteristics of fine versus bulk chemicals Characteristic Fine chemical Bulk chemical e.g. ibuprofen e.g sulphuric acid Scale Small large Price 22 $/kg 0.08 $/kg Process type Batch Continuous Synthesis Multi-step Few steps Characteristic Fine chemical Bulk chemical e.g. ibuprofen e.g sulphuric acid Raw material consumption (kg/kg) High Low Energy consumption (kJ/kg) High Low Uses Specific Diverse Value added High Low Molecular complexity High Low Chemical processes A chemical process is a combination of steps in which staring materials are converted into desire products using systems, equipment and conditions that facilitate that conversion Chemical processes usually have three interrelated steps Transfer of reactants to the reaction zone Chemical reactions involving various unit processes Separation of the products from the reaction zone using various unit operations  Chemical processes A Chemical process is a method of changing one or more chemicals or chemical compounds. Monitoring the purity Preparation Separation of product Synthesis of feedstock of products Handling of by- products and waste All Chemicals are produced using the same steps/processes. Processes may also involve: Homogeneous systems Heterogeneous systems They may also include: Reversible and irreversible reactions Endothermic and exothermic reactions Catalytic and non catalytic reactions  Advanced Plastics, electronic materials, fibres, chemicals, Final products specialties and (ca. 30,000) solvents, detergents, perfumes, insecticides, pharmaceuticals consumer products Acetic acid, formaldehyde, urea, Intermediates ethene oxide, acrylonitrile, (ca. 300) acetaldehyde, terephthalic acid Bulk chemicals Ethene, propene, butene, benzene, Base chemicals synthesis gas, ammonia, methanol, (ca. 20) sulphuric acid, chlorine Fuels (ca. 10) LPG, gasoline, diesel, kersosene Raw materials Oil, natural gas, coal, rock, sulphur, (ca. 10) air, water  Some Important chemical processes Haber Process = Ammonia e.g. fertilisers, cleaning products Some Important chemical processes Contact Process = Sulphuric acid e.g. dyes and pigments, pharmaceuticals, antifreeze  Important chemical processes Electrolysis of brine = Chlorine and hydrogen e.g. disinfecting drinking water, textiles, paper products Some Important chemical processes Fermentation = Ethanol e.g. perfumes  Conditions All reactions need specific conditions in order for them to produce a high yield. A high yield will result in more money for a company and also more chemicals for further production. Variables that affect chemical reactions Temperature Pressure Composition of the reactants Catalyst Rate of heat and mass transfer  The reaction may be carried out in batch, semi- batch or continuous reactor It may isothermal or adiabatic The important factors for chemical processes Basic data : physical and chemical properties of reactants and product Yield: the fraction of raw materials recovered as the main product Conversion: the fraction of material changed to another desired product Kinetics: is the study of reaction rates. Such information is essential for plant design since the reaction rate determines equipment size Catalysts are materials that increase reaction speed Information and requirement for the development of a commercial process 1. Material and energy balances and process flow and piping and instruments diagrams (PFD and P &ID) 2. Raw material and energy consumption per ton of product 3. Batch vs continuous 4. Chemical process selection: design and operation, pilot plant data, equipment required, materials of construction.  Chemical process control and instrumentation Chemical process economics: material and energy cost, labor, overall cost of production Market evaluation: purity and uniformity of products for further processing Plant location Environment protection, health safety and hazardous materials Construction, building and commissioning  Management for productivity and creativity, training of plant personnel Research and development (R &D) Anatomy of a chemical manufacturing process  Stage 1 Raw material storage Feed preparation Stage 2 Recycle of unreacted material Reaction Stage 3 Stage 4 Product separation By products Stage 5 Product purification Waste Stage 6 Product storage Sales Figure: Anatomy of a chemical process Separation and purification processes Why do we need separation and purification processes in the production of chemicals? Separations Exploits Differences of Material Properties Molecular Property Separation Process Boiling Point Distillation Freezing Point Crystallization Filtration Particle size Chromatography Affinity to a stationary Centrifuge Adsorption phase Density Separation process Factors to be considered in choosing a separation/purification process Quantity of material to be separated Rate of separation required Feasibility, selectivity Economics, quality Equipment Mode of operation Mass balance Material balance is a quantitative description of all materials that enter, leave and accumulate in a system with defined boundaries It is based on the Law of conservation of Mass Material balance Rate of Rate of flow Rate of flow Rate of mass accumulation of mass into - of mass out of + generation of mass = the system the system with the within the boundary boundary system system boundary boundary Accumulation = Inflow – Outflow + Generation Input + generation – output – consumption = accumulation  Input: Material that ENTERS the system Output: Materials that LEAVES the system by crossing system boundaries Generation: Material that is GENERATED inside the system Consumption: Material that is USED UP in the system Accumulation: Change in material INSIDE the system  Materials balance applications and uses Mass balances are of fundamental importance in the field of environmental engineering and environmental management To evaluate water and wastewater treatment process performance To study the response of aquatic environment of selected inputs such as the discharge of wastewater Day to day operation of process for monitoring operating efficiency Making calculations for design and development of a process i.e quantities required, sizing equipment, number of items of equipment Some terms: Steady state: No change in process variables with time Non steady state: Process variables changes with time Process variables Flow rate Chemical composition Temperature Concentration Pressure Molar units A mole is the molecular weight of a substance expressed in grams To get the molecular weight of a substance you need its molecular formula and you can then add up the atomic weights of all the atoms in the molecule To convert from moles of a substance to grams multiply by the molecular weight To convert from grams to moles divide by the molecular weight. Mole fraction is moles divided by total moles Mole % is mole fraction multiplied by 100 Simple problem 200 kg of a 40% w/w methanol/water solution is mixed with 100kg of a 70% w/w methanol/water solution in a batch mixer unit. What is the final quantity and composition Solution Total initial mass = total final mass = 300kg Initial methanol mass = final methanol mass 80 + 70 = final methanol mass = 150 kg Therefore the final composition of the batch is (150/300) x 100 = 50% by wt Question Diethyl ether the “ether” used medically as an anesthetic, is prepared commercially by treatment of ethyl alcohol with an acid. How many grams of diethyl ether would you obtain from 40.0 g of ethyl alcohol if the percent yield of the reaction is 87%? 2C2H6O (l) → C4H10O + H2O Types of processes The chemical industry consists of many different sectors (or product groups), each with their own characteristics. For example pharmaceuticals, pesticides, fertilisers, petrochemicals, dyestuffs etc The type of chemical produced will determine the particular characteristics of the process (or processes) used to produce the product. For example compare the processes used to manufacture ammonia and aspirin. Batch process Batch process: the process in not continuous. Operates a batch cycle Materials are added to a vessel in one operation and then process is carried out and the batch cycle repeated.  No mass crosses the system boundaries Rapid reactions in a tank Are economical for small volumes Are flexible in accommodating changes in production formulation Amenable to direct scale up from the laboratory Continuous process This is any process without break, interruption, intervening space or time. The inputs and outputs flow continuously throughout the duration of the process Materials enter and leave the process continuously. Example is pumping of liquids into a distillation column at a constant rate and steadily withdrawing the products from the top and bottom column Synthesis of industrial chemicals Synthetic organic chemicals are produced by the transformation of carbonaceous feedstock into functionalized molecules through one or more chemical reactions The molecules produced find use largely as monomers in polymer synthesis of ubiquitous plastics, or as task specific ingredient for a myriad of applications as divergent as paints leveling agents to food preservatives  Raw materials for the chemical process industries Petroleum and its products Natural gas Biomass conversion More than 90% of organic chemicals are produced from petroleum and natural gas routes Raw materials for industries are classified as Primary raw materials Basic intermediates Primary raw materials are naturally occurring substances that have not been subjected to chemical changes after being recovered Examples Grains Wood Honey Crude oil Secondary intermediates Monomers, caprolactam, terephthalic acid, acrylonitrile for synthesis of fibres, intermediates for dyestuff industry and pesticides Basic intermediates Paraffin Methane propane, and higher hydrocarbons Olefins and derivatives Ethylene, propylene, butadiene, polyvinyl chloride, alcohol Aromatics Benzene, toluene, ethyl benzene, naphthalene Chemical raw materials and feedstock There are five major types of feedstock: Light olefins – ethylene and propylene aromatics – benzene, toluene, xylene C4 hydrocarbons – butane, butene Kerosene derived C9-C17 paraffin Synthesis gas – mixture of carbon monoxide and hydrogen Fermentation History Fermentation is a term coined by Louis Pasteur (1822) for a phenomenon of bubbling of sugar solution Liebig considered it a simple process brought about by complex nitrogenous substances present in the cells of micro organisms In 1896, E. Butchner showed that the production of alcohols from sugar was as a result of the presence of zymase which is present in the cells of yeast It is an enzyme catalyzed metabolic process whereby organisms convert starch or sugar to alcohol or an acid anaerobically  What is fermentation? Chemical transformation of organic substances into simpler compounds by the action of enzymes, complex organic catalysts which are produced by micro organisms such as mold, yeast and bacteria Conversion of sugar to alcohol using yeast Chemical conversion of carbohydrates to alcohols or acids The process is often used to produce wine and beer Also employed in preservation to create lactic acid in sour food such as pickled cucumber and yogurt The science of fermentation is known as zymology Goal is to produce a specific chemical product  Characteristics of enzymes They do not take part in the reaction but act as catalysts A small amount of enzymes can bring about the decomposition of a large substrate Their action is highly specific An enzyme is most reactive at a particular temperature called the optimum temperature usually at 30 – 40oC They are destroyed by ultra-violet light as well as heat They bring about complex reactions such as oxidation, reduction, hydrolysis  Examples of enzymes Diastase – malt or liver Catalase- blood Zymase – yeast Urease – soyabean Lacti – bacilli - curd  Fermentation can make food nutritious, digestible and flavoured. Benefits of consuming fermented food include: It improves digestion and helps maintain intestinal bacteria It has anti-cancer effect It improves immune system Reduces lactose intolerance  Other than the food industry, there are many other areas where the fermentation process is used. Methane is produced by fermentation in sewage treatment plants and freshwater sediments. Conditions favorable for fermentation Temperature Aeration Concentration Presence of other substances Absence of preservatives Examples Some fermentation processes Digestion of food: ptyalin and pepsin Alcohol is produced from the action of zymase enzyme on certain sugar (usually glucose) C6H12O6 zymase 2C2H5OH +2CO2 ALCOHOLIC BEVERAGES An alcoholic beverage is a drink that typically contains 3 – 60 % ethanol/ alcohol They are divided into three classes: beer, wine and spirits (Distilled beverages) Beer This is an alcoholic beverage produced by the saccharification of starch and the fermentation of the resulting sugar Starch and enzyme obtained from malted cereal grains Malt is germinated barley Most beer is flavoured with hops which adds bitterness and acts as a natural preservative. Strength of beer is usually around 4 % to 6% alcohol by volume  INDUSTRIAL PRODUCTION OF BEER  Beer is the alcoholic beverage made by yeast fermentation of grains to ethanol and CO2.  Beer is an example of malt beverage.  The process of manufacturing of beer is called as brewing  Brewing is a complex fermentation process because in this fermentation several factors which do not results from microbial activity (for e.g., Flavor, aroma, clarity, foam formation, foam stability etc.) are considered. Types of beer:-  There are two major types of beer on the basis of fermentation differences. Bottom fermented beer–  are generally called lager beers and utilizes bottom yeast in its manufacture.  As the fermentation subsides, bottom yeast tends to flocculate and settles at the bottom.  Examples of bottom yeast are Saccharomyces uvarum, Saccharomyces carlsbergensis. Top fermented beer- are called ales.  Production of ales utilizes top yeast, which during fermentation rises to the surface and floats on the surface of fermentation broth.  Some strains of Saccharomyces cerevisiae are top yeast. Production process:- The microbial production of beer includes following steps. Microorganism Medium components Preparation of fermentation medium (wort) Fermentation process Maturation, Carbonation and Packaging 1. MICROORGANISM Generally selected strains of the yeast Saccharomyces cerevisiae and Saccharomyces carlsbergensis are used in the beer preparation. 2. MEDIUM COMPONENTS Malt: it is prepared from carefully selected barley grains, which is the chief raw material. Barley grains are first cleaned and then steeped in water for about 2 days. Excess water is then drained off from soaked barley, which is then subjected to germination for about 4-6 days to allow formation of rootlets.  This germination step allows formation of highly active -amylase, β-amylase and proteolytic enzymes as well as various flavor and color components. At the end of 4-6 days, the temperature is just raised to stop germination. It is then dried and ground to a fine powder. Malt contributes amylases, proteases, starch, proteins, growth factors and flavor characteristics to the medium. Hops: Hops are the dried female flowers of hop plant Humulus lupulus. These are added for flavor, colour, aroma, and mild antibacterial activity to prevent spoilage bacteria. 3.PREPARATION OF FERMENTATION MEDIUM (WORT):- The fermentation medium is prepared in four successive operations described below. a)The malt adjuncts are first cooked to gelatinize their starch by heating at 650C for 30 min. b)Cooked malt adjuncts are then added to water along with malt in a ratio of 2/3 malt to 1/3 adjunct. c)This mixture is then subjected to mashing procedure by which various enzymes of malt are allowed to activate over a range of temperature. Mashing process:-  Mashing procedure has a profound influence on the finished beer and thus careful control of mashing process is essential.  Mashing allows malt amylase and protease to degrade their substrate starch and proteins respectively. d)Separation of fermentation medium and boiling with hop.  On completion of mashing procedure, the fermentation medium is separated from undissolved husk and insoluble protein matter by passing into lauter tub.  It is then boiled with hop for 1.5 to 2.5 hrs in brew kettle.  The boiling procedure inactivates the enzymes, which were active during mashing process.  Boiling also extracts certain components (tannin, pectin, and resins) from the hop plant.  After completion of boiling process, insoluble parts off hop and coagulated materials are separated from fermentation medium by passing through hop strainer (filtration unit) and collected in the wort- settling tank.  4. FERMENTATION PROCESS:-  The cooled wort is then placed in a closed fermentation vessel and inoculated with yeast  Within 24 hrs foam begins to appear on the surface of the medium.  After 5 days of fermentation, CO2 evolution is lowered and foam begins to collapse.  Within 7-9 days, the yeast becomes inactive and settles to the bottom.  At this stage medium is cooled to hasten settling.  After fermentation, it is then transferred to storage tank. 5. MATURATION, CARBONATION & PACKAGING:- A) Cold Storage Maturation:-  The fermented medium (beer) is transferred to storage tank and held at 0 – 30C for a period of time. This is called cold storage maturation.  During this process, coagulated nitrogenous substances, resins, insoluble phosphates and yeast cells are sedimented from the beer.  In addition, esters are formed and the beer matures so that it looses its harshness. B) Carbonation (Injection of CO2)  Carbonation is a process of displacing dissolved O2 by injecting CO2 (approximately 0.5 %).  C) Packaging:-  After cold storage maturation, the beer is passed through a diatomaceous earth filter before being packed in bottles, cans, barrels, kegs etc.  Air is removed during packaging to prevent oxidative changes in the beer.  Beer packaged in barrels or kegs is not pasteurized and hence, has a relatively short storage life.  Beer for bottles and cans, however, often is pasteurized after capping of the bottles or closing of the cans.  However, the pasteurization process affects the flavor of beer and hence now a day’s beer is sterilized by passing through bacteriological filter or is sterilized chemically by using n-heptyl – p– hydroxybenzoate at a concentration of 12 ppm.  Finally, sterile beer is packed aseptically and marketed. Recap…….. Exam preparations….. What to expect…………. All the best!!!!!!!!