Food Industrial Waste Engineering FST 4914 PDF

FOOD INDUSTRIAL WASTE ENGINEERING FST 4914 WASTE THERMAL TREATMENT  THERMAL TREATMENT What is Thermal Treatment What is energy? What is required for Thermal Treatment  THERMAL TREATMENT Benefits reduce volume of waste - preserving landfill spa...

FOOD INDUSTRIAL WASTE ENGINEERING FST 4914 WASTE THERMAL TREATMENT  THERMAL TREATMENT What is Thermal Treatment What is energy? What is required for Thermal Treatment  THERMAL TREATMENT Benefits reduce volume of waste - preserving landfill space replace the need for landfills recovery of energy from the solid waste stream. recovery of minerals and chemicals from solid waste stream which can be reused or recycled destroy several contaminants present in the waste stream  THERMAL TREATMENT Thermal treatment technologies can be generally grouped into two main categories: 1) conventional combustion mass burn incineration – majorly used moving grate incineration fluidized bed incineration Rotary kiln incineration 2) advanced thermal treatment gasification pyrolysis plasma gasification  THERMAL TREATMENT 3 main stages of any thermal treatment process: Drying and degassing volatile content released between 100 and 300°C. The process are only dependent on the supplied heat. Pyrolysis and gasification pyrolysis is the further decomposition of organic substances in the absence of added oxygen at 250 – 700°C produce syngas ( gas mixture consisting primarily of H2 and CO), tars (high molecular mass hydrocarbons), and char. gasification - partial thermal degradation of organic substances in presence of oxygen but with insufficient oxygen to oxidize the fuel completely (sub-stoichiometric conditions). gasification occurs between 500 – 1,000°C and results in the in the formation of syngas. this stage results in conversion of solid organic matter to the gaseous phase. Oxidation the combustible gases (i.e., syngas) created in the previous stages are oxidized, depending on the selected thermal treatment method, at temperatures generally between 800 and 1,450°C.  INCINERATION OVERVIEW INCINERATION – single stage combustion/mass burn incineration Combustion of waste in controlled manner to destroy or convert:- Less hazardous Less bulky Controllable constituents Use widely such as for dispose CONVERT WASTE ENERGY Municipal Solid Waste (MSW) Commercial waste Industrial waste Clinical waste Second most preferred management other than landfilling Is currently popular because: Landfilling occupies space - space getting lesser Able to convert waste to energy  INCINERATION BACKGROUND/HISTORY First incinerator – UK 19th century A way to dispose waste neatly and produce energy 1876 - First MSW incinerator – Manchester Using MSW + coal Spread to Hamburg, Germany (1896) then to Brussels, Stockholm, Copenhagen, Zurich (1904) 1920s & 1930s - Basis of moving grate technology by British Babcock and Wilcox introduce grate with rotary kiln 1970 - Electrostatic precipitator – introduce to collect dust 1980s – Air pollution control equipment  INCINERATION WORLD MUNICIPAL WASTE  INCINERATION INCINERATION COUNTRY AREA POPULATION (2016) JAPAN 377,972 km² 127m NORWAY 385,203 km² 5.233m SWITZERLAND 41,285 km² 8.372m FRANCE 643,801 km² 66.9m UK 242,495 km² 65.64m USA 9.834 million km² 325.7m MALAYSIA 330,803 km² 31.19m MALAYSIAN - 0.5-0.8kg waste/person/day INCINERATION Incinerated waste amounts by waste category in the EU-27 in 2008 (http://epp.eurostat.ec.europa.eu)  INCINERATION Normal MSW heating value – general range 10 – 12MJ/kg but allowed 8.5-14.5MJ/kg Broad interval compared to coal and wood chips – single combustion Why broad? Variable type/character of waste Incineration - combustible components reacts with oxygen of combustion air release significant amount of hot combustion gas. Moisture evaporate at initial stage Incombustible material – solid residues (bottom ash/fly ash) Solid constituents undergoes a range of processes due to exposure to heat and combustion air Drying From Li et al., 2004 Gasification (formation of combustible gases) Characterization of solid Ignition and combustion of gases residue from MSW Burnout of solids incinerator  INCINERATION Process and Energy recovery Combustion gas form furnace moves to afterburning chamber To ensure complete burnout of combustion gases Retain gas at least 2 seconds in afterburning chamber Chamber 850 degrees for MSW/ 1100 degrees for certain hazardous waste Waste are not allowed to be fed until the required temperature is reached To produce energy for power generator by expansion in steam turbine Flue gas is cooled in boiler pressurized water heated in high pressure boiler Steam is superheated Heat and power combined plant (co-generation system) 25% steam energy transform to electric power Remaining energy regain through condensation of steam from turbine in heat exchanger generating hot water for heating purposes. EXAMPLE OF INCINERATOR Lets watch to understand more  INCINERATION Waste as Fuel Uses waste as burning medium rather than wood or coal The design is much more unique and complex Design must have general data on amount and composition of waste Design must take into account the byproducts produced Some required segregation and pre-treatment Different types of waste effects (household, clinical etc.) – different process control, different output energy, different byproducts 14%-47% converts into electricity (assuming it changes to electricity)  Key variables in characterizing waste as fuel - moisture content (W) (typically 15-35%, when drying at 105°C) - ash (inorganic) (A) content (typically 10- 25% after ignition at 550°C) - combustible (organic) solids (C) as the difference between the dry solids and the ash content (typically 40-65%) Tanner´s triangle for assessment of combustibility of waste http://www.wtert.eu  INCINERATION qIncineration can be viewed as the flame-initiated, high temperature air oxidation of organic matter. qCurrently practisised to some extend on municipal waste, medical waste and hazardous waste. qCan only destroy the organic compounds, it cannot destroy inorganic (mineral) compounds – which end up as residual ash.  INCINERATION qwaste must be oxidised nearly completely (99.99% destruction and removal capacity is required) so, a large excess of air is used to ensure the sufficient oxygen to do the job. qEmissions from waste incinerators include unburned organic wastes, products of uncomplete combustion or by–products of combustion, heavy metals, acid gas, ash and others. Emissions of these pollutants can be controlled to very low rates by modern air pollution control equipment. qSeveral advantages and disadvantages when compared with other methods of waste treatment, so it is not always the preferred choice.  INCINERATION Advantages Disadvantages Reduction in bulk (save space) Costly Recycle (energy and ash) Protest by locals Destruction of waste and contaminants Generates heat for local population Do not use fossil fuels or other burning Many protocol and agency involves medium To determine suitable technology for Low toxic emissions country Reduce ‘Green House Effect’ Some requires pre-treatment and sorting PEPPERL AND FUCHS INCINERATION PLANT IN BALI  INCINERATION Solid Residue The main part of the ash content of the waste leaves the furnace as a solid residue i.e. bottom ash or slag. The remaining ash leaves the furnace as fly ash. The fly ash is normally separated from the flue gas in the flue gas treatment system in an electrostatic precipitator or bag house filter. There are three types of incinerators: - moving grate incinerator – mostly for municipal waste - rotary kiln incinerator – for industrial waste (liquid, solid and sludge) - fluidised bed incinerator – solid particles mixed with fuel are fluidised by air In the case of grate incinerator, the bottom ash (slag) drops from the end of the grate into the water trap of the slag pusher. The amount of slag is usually 10-20% by weight of the waste feed, depending on the water composition. Fly ash constitute usually 5-10% of the ash content.  INCINERATION Flue Gas ØGas escaped from flue to the atmosphere ØGas produce as byproduct of incineration ØContains nitrogen oxide, sulfur dioxide and particulate matter ØFiltered using bag filter and manage using Air Pollution Control system ØCarbon injection use to absorbs heavy metals and dioxins then caught using bag filter ØIn order to minimise pollutants produced by industrial combustion processes such as energy from waste plants lime used to ‘scrub’ acid pollutants such as HCL and SO2 from the exhaust gases  INCINERATION Refuse derived fuels (RDF) RDF is a result of processing solid waste to separate the combustible fraction from the non-combustibles, such as metals, glass and cinder in municipal solid wastes (MSW). RDF is predominantly composed of paper, plastics, wood and kitchen and yard wastes and has a higher energy content than MSW, typically in the range 12 to 15 000 kJ/kg. Like MSW, RDF can be burned to produce heat or/and electricity. RDF processing is often bound with the recovery of metals, glass and other recyclable materials, thereby improving on paybacks for investment costs. At present time RDF combustion is less common than mass burning of MSW, but it may change in the future as recovery of recyclable materials and environmental concerns over incinerators emissions become more important. The major benefits of RDF are: - It can be shredded into uniformly sized particles or densified into briquets. Easily handled, RDF can be burned or co-fired with another fuel such as wood or coal in an existing facility. - Fewer noncombustibles such as heavy metals are incinerated. The high temperature of MSW furnace can cause metals to partially volatize, resulting in release of toxic fumes and fly ash.  Moving grate incineration Based on a moving grate consists of layered burning of the waste on the grate that transport the waste through the furnace. On the grate the waste is dried and then burn at the high temperature while air is supplied. The ash (including noncombustibile waste fractions) leave the grate via the ash chute as slag (bottom ash). The main advantages of the moving grate are that it is well proven technology, can accomodate large variations in waste composition and in heat values and can be built in the very large units (up to 50 t/h). The main disadvantage is the investment and maintenance cost which are relatively high. The bottom ash (slag) drops from the end of the grate into the water trap of the slag pusher than cooled by contact with cooling water and pass to the conveyor system. The amount of slag is usually 10 - 25 % by weight of the waste feed. Possible designs of moving grate systems http://www.wtert.eu  Fluidised bed incineration Based on a principle where solid particles mixed with the fuel and fluidised by air. By fluidisation the fuel and solids are suspended in an upward air stream, – behaving like a fluid. The reactor usually consists of a vertical refractory lined steel vessel containing a bed of granural material such as silica sand, limestone or a ceramic. The fluidisation is ensured by air injection through a large number of nozzles in the bottom of the incinerator. This causses a vigorous agitation of the bed material in which the incineration of waste takers place in close contact with the bed material and combustion air. This allows for relatively low excess air level, thereby allowing for a high thermal efficiency, up to 90 %. The fluidised bed incinerator is primarily used for homogenous waste type including liquid waste. * Theory of Fluidized bed Watch For Info  Rotary kiln incineration The mass burning incinerator based on a rotary kiln consists of a layered burning of waste in a rotary cilinder. The material transported through the furnace by the rotations of inclined cylinder. The rotary kiln is usually refractory lined. The cylinder diameter may be 1 - 5 m and length 8 - 20 m. The capacity may be as low as 2.4 t/day and is limited to a maximum of approximately 480 t/day. The kiln rotates with a speed of typically 3-5 rotations/h. The excess air ratio is well above the moving grate incinerator and the fluidised bed. The energy efficiency is slightly lower and may not exceed 80 %. Retention time of the flue gas usually is too short for complete reaction to take place in the rotary kiln itself, the cylinder is followed by an after burning chamber, which may be incorporated in the first part of the boiler. * Rotary Kiln incinerator How does it work? Energy conversion technology The energy recovery from a steam producing boiler is known from conventional power plant technology as the Rankine process. The Rankine process allows for energy output in the form of power, steam and various combinations of power, steam and hot water. The energy from hot flue gases is recovered via boiler and passed in the internal circuit of steam. The steam energy may be converted to power by turbine/generator set. The superheated and high-pressured steam from boiler expands via the steam turbine and energy content of the steam is transformed to kinetic (rotation) energy, further transform to electrical energy by the generator. The excess heat of low pressure steam via the heat exchanger (condenser) converted to hot water and passed to district heating network or cooled away.  Energy conversion technology When producing electric power only it is possible to convert an output up to 35 % of the available energy in the waste to power. When producing a combination of heat and power so called co-generation, it is possible to utilise more then 90 % of the energy in the waste (27 % electricity output, 60 - 65 % heat output). Emmissions from waste incinerator – FLUE GAS The most important compounds of emissions from incinerator are: 1. ACIDIC GASES – hydrochloric acid (HCl), hydrofluoric acid (HF), sulphuric acid (H2SO4) 2. PARTICULATES 3. OXIDES OF NITROGEN (NOx) 4. ORGANIC COMPOUNDS such as dioxins and furans 5. CARBON DIOXIDE – not considered as pollutant, however, contributing to the formation of greenhouse effect  Emmissions from waste incinerator – FLUE GAS Controlling emissions to atmosphere Continuous emissions measurement is done on the flue gas at the stack: 1. particulates – measured directly the amount of light reflected by the particulates (Tyndall effect) 2. carbon monoxide 3. hydrogen chloride 4. sulfur dioxide 5. nitrogen dioxide 6. oxygen content  Emmissions from waste incinerator Pollution Control Particulates – electrostatic precipitators, fabric filter (general efficiency more than 99%) Acidic gases – neutralisation with Ca(OH)2 or NaOH in scrubers (wet, semi-dry, dry) Oxides of nitrogen – catalytic or non-catalytic reduction with ammonia or urea resulting in the transformation of NOx to N2. Dioxins and furans – sorption on activated carbon or decomposition by special catalysts simultaneously with NOx removal.  Emmissions from waste incinerator Pollution Control NOx Reduction 1. NOx formation by oxidation of nitrogen in waste by high temperature fixation of nitrogen in combustion air (depends on oxygen availability, temperature, pressure and residence time of gas in combustion unit) 2. NOx removal By catalytic or non-catalytic reduction with ammonia injection or urea. Dioxins and Furans Precursors – products of incomplete combustion Removal – from the gas stream by scrubing the gases and by injection of activated carbon into the gas stream. New approach – catalytic decomposition together with NOx reduction.  Emmissions from waste incinerator Pollution Control Acidic gases (HCl, HF, H2SO4) 1. Formation – by combustion of materials containing these elements 2. Removal – by scrubing and subsequent reaction with bases (Ca(OH)2 or NaOH and using lime Particulates 1. Removal technology depends on the particle size distribution and the removal efficiency required - fabric filters (baghouse) - electrostatic precipitators - carbon injection to remove mercury  Emmissions from waste incinerator Organic micropollutant emissions from waste incinerator *There is no evidence that incineration with proper flue gas purification is the cause of environmental and health damages, but nevertheless it remains an unpopular and controversional waste management option. The main concern – polychlorinated dibenzodioxins and dibenzofurans. Routes by which organic micropollutants can be formed and emitted from incineration processes: 1. As a result of incomplete combustion of organic wastes present in the original waste. If PCB is subjected to a destruction with removal efficiency of 99.9999% than the uncombusted fraction comprising 0.00001% (1 mg for every kilogramme incinerated) will be emitted to the atmosphere. 2. As a result of the synthesis of “new compounds” in the combustion and post-combustion zone of incinerator. Formation of polychlorinated dibenzo-p-dioxins (PCDDs) and Waste treatment methods in Malaysia polychlorinated dibenzofurans (PCDFs) (Fazeli et al., 2017)  DEVELOPMENT IN WASTE INCINERATION In the last years the flue gas cleaning has been improved. The current priority is the optimisation of the thermal process to: - increase the energy efficiency - reduce the flue gas flow - minimize the development of hazardous substances like dioxins, CO and NOx - minimize corrosion - improve the ash management  ADVANCED THERMAL PROCESS Pyrolysis Ø Pyrolysis represents the thermal decomposition of organic molecules in absence of gasification aids such as oxygen, air, CO2, steam, etc. Ø End Product – syngas (CO2, CO, CH4, H2), mixture of solids (char), liquids (oxygenated oils) Ø The pyrolytic oils and syngas can be used directly as boiler fuel or refined for higher quality uses such as engine fuels, chemicals, adhesives, and other products. Ø Thermal energy that is usually applied indirectly by thermal conduction through the walls of a containment reactor Ø In the temperature range between 150 – 900oC volatile compounds are expelled and complex molecules are broken down into simpler ones. Ø Pyrolysis generally takes place at lower temperatures than used for gasification which results in less volatilization of carbon and certain other pollutants, such as heavy metals and dioxin precursors. Ø This process is also called low temperature gasification or destructive distillation. Ø Main product is a gas with heating value 12.5 to 46 MJ/Nm3. Ø The solid residue consists of pyrolysis coke containing varying amount of residual carbon that, unlike gasification, is not converted to gas in this process.  ADVANCED THERMAL PROCESS Pyrolysis Pyrolysis is endothermal transformation, in the absence of oxygen, of biomasses or liquid, solid or gaseous fractions of wastes. Pyrolysis can also be applied in the production of bio-oils with an efficacy reaching 80%. Issues identified in relation to the pyrolysis process include: 1. Low energy outputs 2. The requirement for a properly sealed reaction chamber for safe operation. 3. The pyrolysis process is highly sensitive to the presence of air. Accidental incursions of air can result in process upsets and increase the risk of explosive reactions. 4. The requirement for pre-treatment of the MSW. Pyrolysis  ADVANCED THERMAL PROCESS Gasification v Gasification refers to the conversion of carbon-containing materials at high temperature into gaseous fuels. v Gasification is differentiated from pyrolysis by the addition of reactive gases, which further convert gaseous fuels carbonized residues into additional gaseous products. v Gasification is continuation of pyrolysis process - residual carbon (pyrolysis coke) is oxidized at temperatures above 800°C with a sub-stoichiometric oxygen. v Steam, carbon dioxide, oxygen or air are often used as gasification agents. v Just as pyrolysis, gasification is an independent process, but is still a part of combustion processes. v The necessary reaction energy for the gasification proces is generated by the partial combustion of organic materials in the reactor. v Pyrolysis of organic materials generates several hundred different polycyclic aromatic hydrocarbons (PAH) but only small quantity of dioxins (PCDD) and furans (PCDF) because oxygen is necessary for these to form.  ADVANCED THERMAL PROCESS Gasification Gasification is conversion of waste or biomasses organic fraction into a mixture of combustible gases by partial oxidation at high temperatures (400 – 1500oC). The gas produced mainly a mixture of CO and H2 has calorific potential 4 – 6 MJ/Nm3 and may be used to fuel internal combustion engines or gas turbines. In addition, the gas may be used as raw material for the manufacturing of chemical products (e.g. methanol). Different types of Gasifier Gasification  ADVANCED THERMAL PROCESS Plasma Gasification Plasma gasification technology is a novel method for the treatment of wastes at high temperatures where waste are converted into gas and inert residue. *The term plasma refers to a conductive, electrically ionised gas. Several gases such as argon, helium, methane or steam can be used. The most commonly used gas is air. The air is rendered electrically conductive by subjecting it to marked differences of electric potential, generating a stable electric discharge (arc) between two electrodes. Resistance built by air versus the flow of electrons produces considerably quantities of thermal energy ranging from to 5000 to 10 000°C. Two main technologies: 1. plasma torch 2. system using graphite electrodes  ADVANCED THERMAL PROCESS Plasma Gasification PRINCIPLE Plasma arc gasification uses an electric current that passes through a gas (air) to create plasma which gasifies waste into simple molecules. Plasma is a collection of free-moving electrons and ions that is formed by applying a large voltage across a gas volume at reduced or atmospheric pressure. The high voltage and a low gas pressure, causes electrons in the gas molecules to break away and flow towards the positive side of the applied voltage. When losing one or more electrons, the gas molecules become positively charged ions that transport an electric current and generate heat. When plasma gas passes over waste, it causes rapid decomposition of the waste into syngas. The extreme heat causes the inorganic portion of the waste to become a liquefied slag. The slag is cooled and forms a vitrified solid upon exiting the reaction chamber. This substance is a potentially inert glassy solid. The syngas is generally combusted in a second stage in order to produce heat and electricity for use by local markets.  ADVANCED THERMAL PROCESS Plasma PlasmaGasification technology v Plasma processes suited for treatment of large waste variety having a high inorganic fraction and low heat potential. v This is because heat required for treatment is provided by plasma and not by oxidation process. WHY UNPOPULAR? v Due to the high operational costs, plasma technologies are mainly applied in the treatment of i. to establish a plasma arch and run a plant hazardous or radioactive wastes. is very costly ii. the plasma arch allows only very small v In the future the system may even constitute a amounts to be melted, what makes big promising alternative to the traditional systems of amounts of waste unsuitable to be treated thermovalorisation, leading to the release of gas by this technology emissions with a lower pollutant potential and vitirified solid residue. iii. there are no long-term experiences with this technology v It is clean technology but not well designed currently PLASMA GASIFICATION MALAYSIA WASTE TREATMENT SCENARIO Review by Sovacol and Drupady (2011) MALAYSIA WASTE TREATMENT Review by Sovacol and Drupady (2011) SCENARIO Amount of waste collected per day in Malaysia is enough to bury Petronas Tower in waste for 2 days.  MALAYSIA WASTE TREATMENT SCENARIO Review by Sovacol and Drupady (2011) Malaysia the second fastest growing emitter of Carbon dioxide emission in Malaysia from 1998-2011 greenhouse gases in the world (Fazali et al., 2016) Major contributor is palm oil industry – methane and carbon dioxide release  MALAYSIA WASTE TREATMENT SCENARIO Review by Sovacol and Drupady (2011) Kajang Waste To Energy (WtE) in Malaysia – process 700 t/day Kajang WtE to research on low-grade heat to promote algae growth that can be use as biofuels Malaysia could save $10billion (2011-2020) if adopt MSW WtE 290 landfills in Malaysia only 7 are sanitary (Bukit Tagar – WtE – 2500t/day) Sanitary landfill exude more methane – more economical to capture methane gas Gas captured can be used to produce electricity Government initiative – Small Renewable Energy Program to promote Malaysia’s “Fifth Fuel Policy” “Fifth Fuel Policy” – from conventional coal, oil, gas to biomass, hydroelectricity, solar and MSW MALAYSIA WASTE TREATMENT SCENARIO MALAYSIA WASTE TREATMENT SCENARIO  THE END Disclaimer – all pictures and videos are not owned. 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