Pyrolysis of-biomass

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Biomass pyrolysis is a useful way in recovering biofuels from low value biomass.

Biomass pyrolysis is a useful way in recovering biofuels from low value biomass.

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  • 1. PYROLYSIS OF BIOMASS Thermal decomposition of solid waste (e.g., woody biomass or agroresidue) in an inert atmosphere or with insufficient oxygen to cause partial oxidation (to provide the heat for decomposition) is called pyrolysis. Depending on the rate of heating, final temperature reached, a mixture of gas, liquid and remaining solid are the products. Pyrolysis processes are carried out for (i) to produce char-coal and (ii) To produce pyrolysis-oils (BIO-OIL), which may be processed into liquid fuels. EFFECT OF HEATING BIOMASS IN AN INERT ATM Products: mixture of gas liquid and solid Gas: A fuel about 20-25 % of the input mass. Liquid: Tar + Aqueous solution +Oil Solid: Char Factors which affect amount and quality of products: COMPOSITION OF BIOMASS, RATE OF HEATING & FINAL TEMPERATURE REACHED HIGHER THE HEATING RATE & FINAL TEMP, HIGHER THE CONVERSION TO GAS AND PRODUCTS, HIGHER THE CARBONIZATION OF THE CHAR LIQUID SLOW PYROLYSIS WOOD + HEAT  WOOD CHAR +GAS Thermal decomposition begins at about 100- 150 o C, increases with rising temperature .At about 270 o C, exothermic reactions set in with a rise in temperature (usually held at 400-500 o C) bringing about complete carbonization. The products are charcoal, condensable liquids, and noncondensable gases. 1
  • 2. CHEMICAL REACTIONS: C6n[H2O]5n  6nC +5nH2O Secondary reactions: C+ 2CO C + C + H2O  CO + H2 + 2H2  CH4 + CO2 2H2  CH4 2H2O  CO2 + 2H2 FACTORS AFFECTING CHARCOAL QUALITY AND YIELD: Apart from the moisture content of the wood charge, the type of wood and its chemical composition, the charcoal properties depend significantly upon the carbonization temperature. At lower temperatures the yield is high but carbon content is low. ULTIMATE ANALYSIS OF WOOD AND CHAR: TEMP: 400 o C: (PINE SAW DUST AND BARK CHARCOAL) It is seen that compared to wood the char has higher carbon content, heating value increases and oxygen and hydrogen content decreases. Ash content increases slightly and char is a more reactive fuel free from moisture. Element % C H O N S ASH H H V, KJ/Kg Wood 52.3 5.8 38.8 0.2 0.0 1.4 19.7 Char 75.3 3.8 15.2 0.8 0.0 3.4 27.1 EFFECT OF TEMPERATURE IN PYROLYSIS OF WOOD (on S-LG-- product distribution): With increase in temperature the relative amount of char and condensable liquid fraction keeps decreasing and gas formed increases. 2
  • 3. Temp.oC Char % dry feed 500 29 600 24 700 20 800 17 900 15 1000 14 Lqd. % dry feed 53 52 50 47 40 30 Gas % dry feed 18 24 30 36 45 56 RAPID FLASH PYROLYSIS: 103 – 105 o C/ SEC INTERMEDIATE PYROLYSIS: 10 – 100 o C/ SEC SLOW PYROLYSIS: 0.1 –1 o C/ SEC RAPID PYROLYSIS (FLUIDIZED BED) GAS PRODUCT GIVES OPTIMUM TAR YIELD POTENTIAL AVAILABILITY OF AGRORESIDUE: INDIA (1995-96) MT = Million tons Agro-residue Wheat Straw Rice Husk Maize Cobs Pearl Millet straw Sugar Cane Bagasse Coconut shell Coconut pith Groundnut shells Cotton Stalks Jute Stalks India, MT 83.3 39.8 2.8 9 93.4 3.4 3.4 2.6 27.3 2.7 T.Nadu, MT 9.2 3.3 0.6 0.4 0.6 0.8 3
  • 4. References: 1. „Fast Pyrolysis Processes For Biomass‟, Bridgewater A.V. and Peacocke G.V.C, Renewable and Sustainable Energy Reviews 4(1): 1-73 (2000) 2. Progress in Biomass Conversion, Volume 3 edited by K.V. Sarkanen, D.A. Tillman and E. C. Jahn, Academic Press, „Chapter on Chemistry of Pyrolysis and Combustion of Wood „, pp 51-50. (1982) 3. Pyrolysis Oils from Biomass: Producing, Analyzing and Upgrading - ACS Symposium Series 376, Edited by Ed. J. Soltes and Thomas. A. Milne, American Chemical Society, Washington D.C., 1988. [662.8—76582] Successful production of Bio Oil made from sugar cane bagasse. [Ref: Electrical India 40 (18): 39, 2000] The production run of Bio Oil made from sugarcane bagasse using the patented Bio Oil pyrolysis technology has been successfully completed by Dyna Motive Technologies Corporation in its pilot plant in Vancouver. The patented technology converts low value forest and agricultural wastes into liquid fuel. A commercial Bio Oil production plant processing 100 tonnes of dry bagasse per day will produce approximately 22000tonnes of Bio Oil per annum displacing 10.3 million liters of diesel oil and providing 30000 tons of greenhouse-gas credits. Unlike fossil fuels, Bio Oil is clean burning, low in SOx and NOx emission, is greenhouse gas neutral. It can be produced economically from renewable biomass waste materials. 4
  • 5. Pyrolysis for Pyrolytic oils: Products of pyrolysis of wood are charcoal (25), wood gas (45%), pyroligneous acid (45%), and tar or wood-oil. (15%) excluding the moisture content, the last two liquid products being obtained by condensation of volatiles from the wood. Both liquid and gas product of pyrolysis are combustible and are potential fuel feedstocks. Biomass fast pyrolysis is a thermochemical process that converts feedstock into gaseous, solid, and liquid products through the heating of biomass in the absence of oxygen. To produce transportation biofuels via this thermo-chemical process, fast pyrolysis is followed by bio-oil upgrading. Bio-oil is upgraded to naphtha-range and diesel-range distillation fractions (gasoline blend stock and diesel blend stock, respectively, hereinafter referred to as naphtha and diesel). For modeling, the upgraded pyrolysis oil products are modeled as C8 and C10 hydrocarbons. General processing steps include biomass pretreatment, fast pyrolysis, solids removal, bio-oil collection, char combustion, and bio-oil upgrading. An overall description of the biomass fast pyrolysis process to produce naphtha and diesel is shown in Figure. The hydrogen production scenario 5
  • 6. employs optional equipment to generate requisite hydrogen. Biomass with 25% moisture content is dried to 7% moisture and ground to 3-mm-diameter size prior to being fed into a fluid bed pyrolyzer operating at 480°C and atmospheric pressure. Standard cyclones remove solids consisting mostly of char particles entrained in the vapors exiting the pyrolyzer. Vapors are condensed in indirect contact heat exchangers, yielding liquid bio-oil that can be safely stored at ambient conditions prior to upgrading to transportation fuels. Non-condensable gases are recycled to the pyrolysis reactor after being combusted to provide process heat. This analysis assumes that pyrolysis solid products are sent to a combustor to provide heat for the drying and pyrolysis process. Excess solids consisting of char are sold as a low-heating-value coal substitute. Bio-oil upgrading, which requires hydroprocessing section, generates fuel compatible with existing infrastructure. The upgrading process considered in this study is bio-oil hydrotreating and hydrocracking. Hydrotreating and hydrocracking (hydroprocessing) are commonly employed in the petroleum industry to remove undesired compounds such as sulfur from crude oil and to break large hydrocarbon molecules to produce clean naphtha and diesel. Bio-oil typically contains significant quantities of oxygenated compounds that are undesirable for combustion in vehicle engines. Hydrotreating can convert oxygen found in bio-oil to water and carbon dioxide molecules, leaving hydrocarbons that are suitable for internal combustion engines. Complex hydrocarbon compounds are found in bio-oil, and hydrocracking is a potential method to decompose these heavy compounds into naphtha and diesel. The purpose of the assessed process is to convert biomass into liquid fuels suitable for transportation applications. This is achieved by converting biomass into bio-oil, which is subsequently upgraded to transportation fuels. Design-basis model employs nine distinct sections as described in Table 1. 6
  • 7. 7
  • 8. Biomass pyrolysis generates a large variety of organic and inorganic compounds that make modeling efforts difficult. Hundreds of compounds have been identified in bio-oil— the primary fast pyrolysis product [16]. A common approach is to employ model compounds to represent chemical groups based on their significance and quantity. This model adapts pyrolysis oil and gas composition from research by NREL as described in the “Pyrolysis” section of this report [8]. Two models are developed to study the performance of biomass pyrolysis for different scenarios: a hydrogen production scenario employing bio-oil reforming to generate requisite hydrogen for bio-oil upgrading, and a hydrogen purchase scenario using merchant hydrogen for bio-oil upgrading. Pyrolysis is a flexible process that can be designed with numerous configurations and scaled to various capacities. Hydrogen production fast pyrolysis and oil upgrading employs a portion of the bio-oil produced to generate the required hydrogen for oil hydroprocessing. Additional equipment, including a reformer and gas compressor, are required by the hydrogen production system. The second scenario forgoes the additional investment by purchasing hydrogen from a remote source. Scenarios are based on 2,000 MT/day corn stover input. 8
  • 9. Pyrolysis Fast pyrolysis of biomass is a thermal process that requires temperatures near 500°C, rapid heat transfer, and low residence times. Various reactor designs have been proposed for this process [25]. Because of concerns over the scalability of existing reactor designs, this study assumes that multiple 500 MT/day reactors are employed in parallel. This size is selected based on assumptions from a report by NREL [8]. Commercial units as large as 200 MT/day are currently in operation. Pyrolysis product distribution is adapted from USDA data [14] using the bio-oil and non-condensable gas (NCG) composition shown in Table 6. Bio-oil and NCG composition is modified from a previous NREL analysis [8]. Bio-oil compounds are selected based on available Aspen Plus software compounds and may not share the same properties as compounds selected by NREL. Table 5 shows various pyrolysis yields for corn stover [14, 26]. Table 6 includes the initial pyrolysis product yields employed in this study. The final yield is adjusted to ensure mole and mass balance. 9
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  • 11. COMMERCIAL BIO-OIL PRODUCTION VIA RAPID THERMAL PROCESSING Mr Barry Freel, Dr Robert Graham Ensyn Group Inc. 20 Park Plaza, Suite 434 Boston, MA 02116, USA 11 December, 2000 ABSTRACT: Ensyn has successfully developed a commercial biomass refining business, based on the commercial production of bio-oil and the use of bio-oil for the subsequent production of value-added natural chemical products and fuels. After ten years of commercial operations and with a number of commercial facilities in operation, Ensyn has embarked on a significant expansion of its activities. 1. INTRODUCTION Ensyn's core technology in the biomass sector is the Rapid Thermal Processing or RTP™ process, which consists of a proprietary system for the fast thermal conversion of wood and/or other biomass to high yields of a light, liquid bio-oil, for the subsequent extraction and manufacture of natural chemical products and bio-fuels. Ensyn's RTP™ technology, the world's only commercial fast pyrolysis technology, is the foundation of a new and exciting biomass refining industry. In the biomass refining concept, value-added chemical products are first recovered from bio-oil, and the remaining liquid bio-oil is then used for fuel and power (bio-energy) applications. Ensyn has pioneered the development of the biomass refining industry through the development of a proprietary, commercial, fast pyrolysis technology and, in parallel, the development of a number of value-added natural chemical products and bio-fuels sourced from RTP™ bio-oil and related by-products. Ensyn's RTP™ technology has been under continuous development by Dr Robert Graham and Barry Freel, (Ensyn's President & CEO and VP & Chief 11
  • 12. Technology Officer, respectively) since 1980. The RTP™ name was first established in 1984. The first process patent related to RTP™ issued in 1991, and subsequent process patents issued in 1994 and 1999. A number of additional product patents have issued. The key patents are all held by Ensyn Group Inc. or its 100% controlled subsidiaries. Commercial sales of RTP™ equipment and/or RTP™ bio-oil products were initiated in 1989. The Company's principal design, engineering and R&D operations are located near Ottawa, Ontario. There are presently four (4) RTP™ plants in commercial operation. A new commercial RTP™ plant and a bio-oil refining plant are currently under construction. 2. APPLICATIONS Ensyn's RTP™ technology is based on the biomass refining concept, in which high yields of a consistent quality bio-oil are produced, and value-added chemical products are recovered and/or manufactured from the bio-oil, before the remaining liquid bio-oil is used for fuel and power (bio-energy) applications. Ensyn currently produces approximately 30 chemical products from whole RTP™ bio-oil, and these are sold in commercial applications related to the food, polymer/co-polymer, petrochemical and natural chemical industries. 3. BUSINESS MODEL Ensyn's business model in biomass activities is based on the ownership and operation of production facilities in which value is maximised by optimising multiple product streams available from the pyrolysis of biomass feedstocks. This model is typically based on the extraction of higher-value natural chemical products from RTP™ bio-oil, and the use of remnant bio-oil for lower value 12
  • 13. energy purposes. In addition, the char is a high quality, consistent product which may be consumed for energy in the process itself, sold as is, or activated for higher-value applications. The combustible byproduct gas is normally used internally for RTP™ process heat. In typical biomass applications, Ensyn does not supply its equipment to third parties, nor does it license others to use its technology. 4. NATURAL CHEMICAL PRODUCTS Ensyn has been producing commercial quantities of chemical products from its RTP™ bio-oil since 1991. Early commercial production of chemical products was focused primarily on the food industry. More recently, Ensyn has introduced a range of polymer and co-polymer products. The polymer/copolymer products represent newer markets for Ensyn, but these sectors represent far greater growth potential. Ensyn recently entered into a joint development program with Louisiana Pacific Corp., the leading US wood products manufacturer, for the development of adhesive products from bark wastes; this program was awarded a grant of US$1.4 million from the US Department of Energy. In addition, Ensyn is working with other leading companies in the wood and industrial adhesive markets in the development and application of various adhesive products made from RTP™ bio-oil. The use of these natural products from RTP™ bio-oil presents users with attractive advantages including cost, performance and environmental benefits. The environmental benefits include replacement of fossil-fuel chemicals in adhesive formulations, waste biomass remediation, and possibly CO2 credits. 5. ENERGY APPLICATIONS In addition to natural chemical products, Ensyn has developed a number of actual and potential energy applications for its bio-oil. These include the use of 13
  • 14. RTP™ bio-oil in boilers, stationary drivers (i.e., engines, turbines) and as a fuel component in transport applications. A number of initiatives are under way in these areas which are confidential. As petroleum prices rise and environmental impact costs are accounted for, there are clearly a number of interesting opportunities for Ensyn bio-oil in the energy markets. In particular, reference is made to those energy markets that have fiscal incentives for renewable energy, CO2-neutral fuels, and low sulfur fuels. It is possible that in the future Ensyn will establish RTP™ facilities which are 100% bio-fuel related. Nevertheless, under present market conditions, we believe that the most attractive economics are in adopting a refining approach to this industry, based on the extraction of higher-value natural chemical components first, and the use of remnant bio-oil in lower value applications such as fuels. 6. RAPID THERMAL PROCESSING Ensyn's RTP™ technology has represented a true breakthrough in biomass thermal conversion. It is the world's first and only proven commercial biomass fast pyrolysis technology. In the Ensyn RTP™ process, wood or other biomass material is fed into a heated vessel where it is contacted with a stream of hot sand. There is essentially no combustion occurring in this vessel since air input is minimized. At a temperature of around 500°C, much lower than combustion or gasification, the turbulent hot sand instantly flashes the biomass into a vapor, which is then cooled, condensed and recovered as a liquid product. RTP™ is fast pyrolysis. The processing time, including the time the feedstock is in the reactor and until the product gases and vapors are quenched, is typically under two seconds. The reaction takes place at atmospheric conditions at moderate temperatures. At the heart of the RTP™ technology is the unique ability to produce a consistent, light bio-oil, in high yields, from wood and other biomass in commercial operations. 14
  • 15. 7. BIOMASS FEEDSTOCKS Ensyn processes both hardwoods and softwoods, and both white wood and bark. In addition, Ensyn's RTP™ processes bagasse and various additional (nonpublished) biomass feedstocks for the production of specific natural chemical products. 8. YIELDS Commercial bio-oil yields average 75%. This is the liquid bio-oil yield. The balance is approximately 13% char and 12% combustible gas. These yields are by mass-weight, and are as a percentage of dried wood (approximately 8% moisture content). 9. EXISTING FACILITIES AND EXPANSION PLANS Ensyn has four commercial RTP™ facilities currently in operation, three in Wisconsin and one in Ottawa, Ontario. These are currently the only fast pyrolysis plants in the world operating commercially. The largest of these processes 75 green tons per day of mixed hardwood wastes (i.e., equivalent to around 40 tons of dried wood going to the RTP™ unit). This RTP™ facility was built in Wisconsin by Ensyn in 1996, and has operated with a commercial availability of over 94%. Ensyn produces more than 800 tons of bio-oil per month in Wisconsin. In addition to the commercial facilities, Ensyn currently operates two research RTP™ facilities, both based in Ottawa. 15
  • 16. Ensyn has recently initiated engineering and construction of a new commercial 40 dry ton per day RTP™ unit, in addition to a new bio-oil processing facility. The new RTP™ unit is due to be commissioned by September, 2001 and the processing facility is to be commissioned by February, 2001.These expansions will allow Ensyn to meet commercial delivery commitments of a new polymer compound for a major US chemical company as well as to increase its deliveries of current commercial products for the food industry. This RTP™ facility in Wisconsin processes 70 green tons of wood residues per day. Ensyn's biomass facilities in Wisconsin produce over 800 tons of biooil per month. 16