Thermal Conversion of Biomass to Valuable Fuels, Chemical Feedstocks and Chemicals

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Reactor for High Temperature Thermal Conversion of Biomass to Premium Fuels and Chemical Feedstocks
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Inventors
William Peters
Institute for Soldier Nanotechnologies, MIT
External Link (web.mit.edu)
Professor Jack Howard
Department of Chemical Engineering, MIT, Deceased
External Link (web.mit.edu)
Anthony Modestino
Department of Chemical Engineering, MIT
Frederic Vogel
Paul Scherrer Institute
Carsten Steffin
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Thermal conversion of biomass to valuable fuels, chemical feedstocks and chemicals

US Patent 7,494,637

Technology

This is a high temperature technology to convert virtually any form of biomass e.g. wood, straw, grass, energy crops, municipal solid wastes, agricultural residues and concentrated waste pulping liquors to two major high value products: (a) solid metal carbides readily converted to acetylene or other hydrocarbon gases; and (b) CO + H2 mixtures.  Acetylene and CO + H2 mixtures are both useful as fuels in their own right, and as feedstocks for producing a wide range of high value fuels and chemicals. For pulp and paper manufacture, this technology offers significant environmental and economic benefits, i.e.: recycling pulping chemicals (e.g. Na2CO3) from waste pulping liquors; converting organic residues in the pulping wastes to useful products rather than burning them; and eliminating (or greatly downsizing) high capital cost recovery furnaces that can pose safety hazards. The technology is also of interest for converting mixtures of biomass with fossil feedstocks, e.g. heavy oil, natural gas, coal, and the like, to premium fuels and chemicals.  This can offset the lower energy content of biomass and the fossil carbon emissions of the fossil raw materials. Use of electricity generated only from renewable or nuclear sources further reduces the fossil-carbon footprint of processing such mixtures while processing only biomass results in an essentially zero fossil-carbon process for manufacture of premium fuels and chemicals.

Simplified Process Description

Biomass and a metal oxide, e.g. calcium oxide (CaO) are heated at ≥ 1400oC for short times using a thermal plasma or other suitable means. The reaction products are then rapidly quenched to ≤ 800oC. Reactions of the metal oxide redirect the process chemistry to provide desired products and significantly reduce yields of unwanted substances such as tars and solid carbon.  For example, using CaO, significant amounts of biomass carbon are converted to calcium carbide.  The process also forms mixtures of CO and H2, convertible to various fuels and chemicals, including hydrogen (H2).  When the biomass feedstock consists of concentrated waste pulping liquors, the process also recycles spent pulping chemicals such as Na2CO3.  Heat recovered from the high temperature (biomass-treatment) reactor can be used to pre-heat and remove moisture from the biomass feedstock, e.g. to concentrate waste pulping liquors.

Applications

  • Conversion of diverse forms of biomass to valuable fuels, chemical feedstocks, and chemicals
  • Conversion of mixtures of biomass with heavy oil, natural gas, coal, etc. to valuable fuels and chemicals while reducing the fossil carbon footprint of the process and its products
  • Conversion of lignin and other organic residues of pulping to valuable fuels, chemical feedstocks and chemicals, rather than burning these residues
  • Generation and recycling of pulping chemicals such as Na2CO3 and NaOH from pulping wastes
  • Potential elimination of high capital cost conventional waste liquor recovery boilers in pulp manufacture

Advantages

  • Conversion of diverse forms of biomass as well as mixtures of biomass with other raw materials e.g. heavy oil, natural gas, coal, etc. to premium fuels and chemical feedstocks e.g. CO + H2 mixtures, and metal carbides that can be readily hydrolyzed to valuable fuels and chemical feedstocks.
  • Major products are gases and solids enabling easier products separation and recovery.
  • Chemical solidification of the fuel value of biomass or biomass mixtures in the form of solid metal carbides for economical storage and transport and then up-conversion to valuable gaseous fuels/feedstocks by well known reactions with water.
  • High single-pass conversions of feed at large throughputs with good selectivity to two major high value products using compact reactor vessels
  • Modular reactors to reduce initial capital costs and allow process capacity to be expanded in increments well matched to growth in product demand.
  • Increased electrification of fuels and chemicals manufacture. Here an electrical discharge provides the process energy. When the electricity to power this discharge (plasma) is generated from non-fossil sources, e.g. solar, hydro, geothermal, wind, nuclear, this reduces process fossil carbon emissions.
  • Electricity storage as a solid commodity. By an overall endothermic process chemistry, this technology converts a significant fraction of the biomass carbon to high energy content solids, i.e. metal carbides.  This provides a means to store electricity in the form of solids that can be converted to premium fuel by established hydrolysis reactions, e.g., calcium carbide can be converted to acetylene in high yields.