Transcript Hydrogen from Biomass
Recent Trends in Production of Hydrogen from Biomass
National Seminar ‘Creating Infrastructure for adoption of fuel cell Technology in India
April 15, 2004
Dr. A. K. Gupta INDIAN INSTITUTE OF PETROLEUM DEHRADUN, INDIA
Why Biomass to hydrogen?
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Biomass has the potential to accelerate the realization of hydrogen as a major fuel of the future.
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Biomass is renewable, consumes atmospheric CO 2 during growth and is a CO life cycle.
2 neutral resource in
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It can have a small net CO 2 fossil fuels.
impact compared to
Routes to H
2
From Biomass
Biomass conversion technologies can be divided into two categories.
1. Direct production routes (simplicity of process).
2. Conversion of storable intermediates (additional production steps, distributed production of intermediates, lower transportation costs of biomass, larger-scale H 2 production facilities.)
Both categories involve thermochemical and biological routes.
Pathways From Biomass to
H 2 Biomass Thermochemical
Gasification High Pressure Aqueous Pyrolysis Severe H 2 /CO CH 4 /CO 2 Synthesis CH 4 /CO 2 CH 1.4
O .6
Bio-shift H 2 Shift /CO 2 CH 3 OH/CO 2 Reforming
shift
H Reforming
shift
2 /CO 2 H 2 /CO 2 H 2 /CO 2 H 2 /C Reforming
shift
H 2 /CO 2
Pathways from Biomass to
H 2 Biomass Biological
Anaerobic Digestion Fermentation Metabolic Processing H CH Reforming
shift
2 /CO 2 4 /CO Pyrolysis H 2 2 /C CH 3 CH 2 OH/CO 2 Reforming
shift
Photo biology Bio-shift H 2 /CO 2 H 2 /O 2 H 2 /CO 2
Metabolic Processing of Biomass
H 2 from biomass can also be produced by metabolic processing to split water via photosynthesis or to perform the shift reaction by photo biological organisms. The use of microorganisms to perform the shift reaction is of great relevance to hydrogen production because of the potential to produce CO in the product gas far below than in water gas shift catalysts.
Direct Production of H
2
Biomass From
• •
Gasification coupled with water-gas shift is the most widely practiced process route for biomass to H 2 .
Thermal, steam and partial oxidation gasification technologies are under development around the world.
•
Feedstocks include both dedicated crops and agricultural and forest product residues of hardwood, softwood and herbaceous species.
Oxidative Pyrolysis
By including O 2 in the reaction separate supply of energy is not required Biomass + O 2 CO + H 2 + CO 2 + Energy If air is used to supply O 2 then N 2 is also present.
Examples : GTI high pressure O entrained flow gasifier (Texaco) 2 blown gasifier, CFBD (TPS Termiska), High pressure slurry bed
Direct Solar Gasification
• •
Several investigators have examined the use of solar process heat for gasification or organic solid wastes to produce H 2 .
Studies have shown favourable economic projections for solar gasification of carbonaceous materials such as agricultural waste to produce syn gas for producing H 2 .
Other Direct Processes Explored…..
• • •
Several other heat sources and chemistries have been explored for H materials.
2 from biomass/organic Use of thermo-nuclear device to vaporize waste organic materials in an underground large scale plasma process.
Electrochemical oxidation of solid carbonaceous wastes.
Biomass Derived Synthesis Gas (Syn Gas) Conversion
Sponge Iron and related processes
• • •
Steam Iron processes is one of the oldest processes for producing H 2 from syngas. (developed as early as 1910).
Fe 3 O 4 + 4CO 3Fe + 4CO 2 3Fe + 4H 2 O Fe 3 O 4 + 4H 2 Recently sponge Iron process has been extended to FeO 3FeO + H 2 O H 2 + Fe 3 O 4 Metal hydrides (e.g. LaNi5, and La Ni4.7 Al0.3) has also been investigated for continuous hydrogen recovery from biomass gasification mixtures lean mixtures.
Supercritical Conversion of Biomass
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Aqueous conversion of whole biomass to H 2 under low temperature supercritical conditions in another area of investigation in recent years.
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Corrosion, pumping of biomass slurry, improvement in heating rates, heat transfer, commercial reactor system development are some of the problems need attention.
Pyrolysis to Hydrogen and Carbon or Methanol
This is a high temperature two-step process involving (i) Conversion of biomass to methane (ii) Thermal decomposition of methane to H 2 carbon-black and clean Typical overall stoichiometry is: CH 1.44
O 0.66
C + 0.6 H 2 + 0.66 H 2 O The process is called Hydrocarb process In another process “Carnol Process” methanol is produced with H 2 CH 1.44
O 0.66
+ 0.30 CH 4 0.64 C + 0.66 CH 3 OH
Storable Intermediates
•
Bio-oil reforming
Pyrolysis of biomass produces liquid product called bio-oil or pyrolysis oils which is the basis of several processes for producing H 2 via catalytic steam reforming of bio-oil at 750-850°C.
Bio-oil + H 2 O CO + H 2 O CO CO 2 2 + H + H 2 2
Pyrolysis is endothermic:
Biomass + Energy Bio-oil +Char + Gas Over all stoichiometry gives a maximum yield of 17.2 gH/100 g bio-oil i.e. about 11.2% based on wood.
Typical over all stoichiometry based on wood is: CH 1.9
O 0.7
+ 1.26 H 2 O CO 2 + 2.21 H 2
Storalable Intermediates
• • • •
Regional networks of pyrolysis plants can be established to provide bio-oil to a central steam reforming facility Methanol/Ethanol can also be produced from biomass by a variety of technologies and used for on-board reforming for transportation Methane could be produced by anaerobic digestion which on steam reforming produce H 2 Methane could be pyrolysed to H 2 and carbon, if markets for carbon black are available
.
Co-production of Methanol and Hydrogen
• • • • • •
Both methanol and H 2 vehicles (FCV’s) Methanol and H gasification 2 are well suited for fuel cell can be produced from biomass via Overall efficiencies of around 55% for methanol and around 60% for hydrogen may be obtained.
Using liquid phase methanol synthesis and ceramic membranes for gas separation are crucial to lowering the cost of production.
All larger scales, conversion and power systems (especially the combined cycle) may have higher efficiencies.
R&D is necessary to verify and improve the performance.
KEY PROCESS STEPS IN BIOMASS TO METHANOL AND H 2
Biomass Pretreatment, drying, chipping Gasifier Gas Cleaning Reformer for higher hydrocarbons Shift to adjust CO/H 2 ratio Steam Turbine Methanol Production H 2 Production ) Purge gas Gas Turbine/boiler Hydrogen Methanol Electricity Electricity
Example
Hynol Process: This process produces H 2 and methanol from biomass with reduced CO 2 emissions. Steps involved: a. Hydrogasification of biomass b. Steam reforming c. Methanol synthesis from Syn gas produced.
Areas of Research and Development
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Feed stock preparation
increase accessibility.
: For thermochemical routes, variety and nature of feeds for high temperature and pressure reactors. For biological routes, pretreatment to •
Gasification gas conditioning
in fuel cells.
: Key to utilization of H 2 In Gasification presence of Hydrocarbons, N systems such as PSA.
2 , sulfur, chlorine compounds must be addressed not only for end use applications shift gas reaction catalyst and separation •
System integration
: Integration of several steps, Techno-economics of process alternatives to match the optimum technology with the available feedstocks.
•
Modular systems approach
: There is an opportunity for biomass systems to address small scale and remote applications. These systems will require novel conversion and gas conditioning technologies, designed for the resources available in a particular region.
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Value Co-product integration
: Appropriate systems for conversion of by-product streams from chemical and biological conversion of biomass, are the best prospect for near-term development.
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Larger-scale demonstration
: Most promising technologies will need to be selected at larger scale with successful utilization of H 2 turbine etc.) (i.e. fuel cells, IC engines, • There are other challenges of storage and utilization technologies.
ISSUES
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Since H 2 H 2 content in Biomass is low the yield of is low (Approx. 6% vs. 25% of CH 4 )
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Energy content of biomass is also low due to 40% O 2 content.
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Low energy content of biomass is inherent limitation of the process since over half of H 2 from biomass comes from splitting of water in steam reforming.
continued
…ISSUES
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Even at reasonable high efficiency, production of H 2 from biomass is not presently economically competitive with natural gas steam reforming without the advantage of high-value co-products, very low cost biomass and potential environmental incentives.
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There are no completed technology demonstrations
.