Thermochemical Conversion of Biomass to Fuels and Feedstocks: An

2 Thermochemical Conversion of Biomass to Fuels and Feedstocks: An Overview of R&D Activities Funded by the Department of Energy

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G. F. SCHIEFELBEIN and L. J. SEALOCK, JR. Pacific Northwest Laboratory1, P.O. Box 999, Richland, WA 99352 S. ERGUN Lawrence Berkeley Laboratory2, Building 77F, Berkeley, CA 94720 This paper is intended to provide an overview of thermochemical conversion technology development activities within the Biomass Energy Systems Branch of the U.S. Department of Energy (DOE). The Biomass Energy Systems Branch (BESB) is a part of DOE's Division of Distributed Solar Technology. The biomass thermochemical conversion technology development activities sponsored by the Biomass Energy Systems Program can be catagorized into four main areas; direct combustion, direct liquefaction, gasification, and indirect liquefaction via synthesis gas. Pacific Northwest Laboratory (PNL) and Lawrence Berkeley Laboratory (LBL) have been selected to provide program management services to the Biomass Energy Systems Program. PNL is responsible for the technical management of development activities directed toward the thermochemical conversion of biomass feedstocks by direct combustion, gasification and indirect liquefaction via synthesis gas. LBL is responsible for the technical management of development activities on the direct liquefaction of biomass feedstocks. Biomass comprises all plant growth, both terrestrial and aquatic and includes renewable resources such as forests and forest residues, agricultural crop residues, animal manures, and crops grown on energy farms specifically for their energy content. Biomass production and conversion is considered a solar technology because living plants absorb solar energy and convert it to biomass through photosynthesis. Program Objective The objective of the thermochemical conversion technology development activities of the Biomass Energy Systems Program is to 'Operated for the U.S. Department of Energy by Battel le Memorial Institute Operated for the U.S. Department of Energy by The University of California

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0-8412-0565-5/80/47-130-013$05.00/0 © 1980 American Chemical Society In Thermal Conversion of Solid Wastes and Biomass; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

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THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

develop cost competative processes for the conversion of biomass feedstocks to fuels and other energy intensive products. This objective can be accomplished by the direct combustion of biomass materials and the substitution of biomass derived fuels and chemical feedstocks for those produced from conventional sources. Thermochemical conversion processes employ elevated temperatures to convert biomass materials to more useful energy forms. Examples include:


• Combustion to produce heat, steam, electricity, or combinations of these; • Pyrolysis to produce gases (low or intermediate BTU), pyrolytic liquids and char; •Gasification to produce low or intermediate BTU fuel gas; •Gasification to produce synthesis gas for the production of synthetic natural gas (SNG), ammonia, methanol, alcohol fuels, or Fischer-Tropsch liquids and gasoline via catalytic processes; and •Direct liquefaction to produce heavy oils, or with upgrading, lighter boiling liquid products such as distillates, light fuel oils and gasoline. Program Organization and Implementation Thermochemical conversion technology development activities sponsored by the Biomass Energy Systems Program can be divided into the following four categories: •Direct Liquefaction • Direct Combustion • Gasification •Indirect Liquefaction Via Synthesis Gas In the remainder of this paper we will briefly discuss individual projects in each of these catagories. Direct Combustion Systems. The direct combustion of biomass feedstocks is already widely practiced by several industries, especially the forest products industry. Many types of direct combustion equipment are commercially available for this purpose. New developments in direct combustion technology are expected to have a near term impact on energy supplies through the utilization

In Thermal Conversion of Solid Wastes and Biomass; Jones, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.


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SCHIEFELBEIN ET AL.

Overview of DOE-Funded R&D

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forest residues and other readily available biomass feedstocks. Therefore, direct combustion technology development projects being funded by the Biomass Energy Systems Program are categorized as near term systems development activities. Two projects are currently being funded by the Biomass Energy Systems Program in the area of direct combustion technology. These projects are shown in the organization chart illustrated in Figure 1. The Aerospace Research Corporation project is developing a wood fueled combustor which can be directly retrofitted to existing oil or gas fired boilers. Direct retrofit requires that heat release rates equivalent to those obtained when firing oil or gas be obtained in the wood fired combustor. Heat release rates on this order have been achieved when firing wood by preheating the combustion air to 800-1000°F. The Wheelabrator Cleanfuel Corporation project is a demonstration of large scale co-generation based on wood feedstock. The scope of this project includes the design of the plant plus additional tasks such as preparation of an environmental impact statement, demonstration of large tree harvesting equipment and determination of feedstock availability for a large facility. The draft final report for this project has been completed and is currently being reviewed. Gasification-Indirect Liquefaction Systems. Development of biomass direct liquefaction, medium BTU gasification and indirect liquefaction technologies are catagorized as mid term development activities because these technologies are not expected to have a substantial impact on U. S. energy supplies for 10 to 20 years. Biomass gasification technologies can be divided into processes which produce a low BTU gas and those which produce a medium BTU gas. Low BTU gasification technology is commercially available for most types of biomass feedstocks and can be expected to have an impact on energy supplies by 1985. Many of these commercial processes are based on low BTU coal gasification technologies and the gas produced can best be used as fuel for supplying process heat, process steam or for electrical power generation. The versatility of low BTU gas is limited and its use is subject to the following limitations: •Substitution of low BTU gas for natural gas as a boiler fuel usually requires boiler derating and/or extensive retrofit modifications. •The low heating value of the gas usually requires that it be consumed on or near the production site in a close coupled process. •The high nitrogen content of low BTU gas precludes its use as a synthesis gas for most chemical commodities which can be produced from synthesis gas.



THERMAL CONVERSION OF SOLID WASTES AND BIOMASS

DOE BIOMASS ENERGY SYSTEMS PROGRAM

PACIFIC N O R T H W E S T L A B S TECHNICAL OPERATIONS

G A S , OIL L A R G E BOILER RETROFIT P R O J E C T

AEROSPACE RESEARCH

Figure 1.

BCL TECHNICAL MANAGEMENT ASSISTANCE

ADVANCED CO-GENERATION SYSTEM D E S I G N E D FOR W O O D

WHEELABRATOR CLEANFUEL CORPORATION

Direct combustion development activities (near term)


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SCHIEFELBEIN ET AL.

Overview of DOE-Funded R&D

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Medium BTU gas (MBG) offers the following advantages over low BTU gas: •Boiler derating is usually less severe when substituting MBG for natural gas than when substituting low BTU gas for natural gas and may not even be required in some cases;


•MBG can be transported moderate distances by pipeline at a reasonable cost; •MBG is required for the synthesis of derived fuels and most chemical feedstocks and commodities which can be produced from synthesis gas. The versatility of MBG is illustrated in Figure 2. The major disadvantage of MBG is that its production by conventional means requires the use of an oxygen blown gasifier which is expensive to operate due to the cost of the oxygen. If the thermochemical conversion of biomass is to achieve its maximum potential for supplementing existing U. S. energy supplies in the mid term, the following two points will have to be addressed. •Barring serious coal production constraints, biomass conversion will have to be economically and environmentally competitive with synthetic fuels produced from coal. •Thermochemical biomass conversion must have an impact on the availability of liquid fuels and chemical feedstock supplies as well as supplementing gas for heating purposes. Biomass has two potential advantages over coal. First, biomass is a renewable resource and coal is not. Second, and more important from a thermochemical conversion standpoint, biomass is more reactive than coal. It has the potential for gasification at lower temperatures, without the addition of oxygen, to produce medium BTU gas. Several of the gasification process development activities sponsored by the Biomass Energy Systems Program are attempting to exploit this advantage. These development activities are also directed toward improving the competitiveness of biomass gasification through the use of catalysts and unique gasification reactors to produce, directly, specific synthesis gases for the production of SNG, methanol or methyl fuels, ammonia and hydrogen. Success in these efforts could eliminate the necessity for external water gas shift or methanation reactors when producing these commodities. The potential elimination of the oxygen requirement and the water gas shift step are indicated by the dashed lines in Figure 2.



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CONVERSION OF SOLID WASTES AND BIOMASS

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Thermochemical Conversion of Biomass to Fuels and Feedstocks: An

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