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WO2014063029A1 - Procédé et appareil pour la production de piles photovoltaïques à partir de résidus agricoles - Google Patents

Procédé et appareil pour la production de piles photovoltaïques à partir de résidus agricoles Download PDF

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Publication number
WO2014063029A1
WO2014063029A1 PCT/US2013/065645 US2013065645W WO2014063029A1 WO 2014063029 A1 WO2014063029 A1 WO 2014063029A1 US 2013065645 W US2013065645 W US 2013065645W WO 2014063029 A1 WO2014063029 A1 WO 2014063029A1
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Prior art keywords
metal
silicon
carbon
phosphorus
potassium
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Peter J. Schubert
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Indiana University Research and Technology Corp
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Indiana University Research and Technology Corp
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/10—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of field or garden waste or biomasses
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/40—Carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/023—Preparation by reduction of silica or free silica-containing material
    • C01B33/025—Preparation by reduction of silica or free silica-containing material with carbon or a solid carbonaceous material, i.e. carbo-thermal process
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
    • C10L5/00—Solid fuels
    • C10L5/40—Solid fuels essentially based on materials of non-mineral origin
    • C10L5/44—Solid fuels essentially based on materials of non-mineral origin on vegetable substances
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/02—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment
    • F23G5/027—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment pyrolising or gasifying stage
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H10F71/121—The active layers comprising only Group IV materials
    • H10F71/1221—The active layers comprising only Group IV materials comprising polycrystalline silicon
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
    • C10J2300/0903—Feed preparation
    • C10J2300/0909—Drying
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
    • C10J2300/0913—Carbonaceous raw material
    • C10J2300/0916—Biomass
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
    • C10J2300/0953—Gasifying agents
    • C10J2300/0973—Water
    • C10J2300/0976—Water as steam
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/12—Heating the gasifier
    • C10J2300/1269—Heating the gasifier by radiating device, e.g. radiant tubes
    • C10J2300/1276—Heating the gasifier by radiating device, e.g. radiant tubes by electricity, e.g. resistor heating
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/12—Heating the gasifier
    • C10J2300/1284—Heating the gasifier by renewable energy, e.g. solar energy, photovoltaic cells, wind
    • C10J2300/1292—Heating the gasifier by renewable energy, e.g. solar energy, photovoltaic cells, wind mSolar energy
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/1625—Integration of gasification processes with another plant or parts within the plant with solids treatment
    • C10J2300/1628—Ash post-treatment
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/164—Integration of gasification processes with another plant or parts within the plant with conversion of synthesis gas
    • C10J2300/1643—Conversion of synthesis gas to energy
    • C10J2300/165—Conversion of synthesis gas to energy integrated with a gas turbine or gas motor
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/1671—Integration of gasification processes with another plant or parts within the plant with the production of electricity
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
    • C10J2300/1861—Heat exchange between at least two process streams
    • C10J2300/1884—Heat exchange between at least two process streams with one stream being synthesis gas
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/546—Polycrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/12—Heat utilisation in combustion or incineration of waste
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/10—Biofuels, e.g. bio-diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/141—Feedstock
    • Y02P20/145—Feedstock the feedstock being materials of biological origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to the processing of agricultural residues and, more specifically, to the thermochemical conversion of agricultural residues to high-quality silicon for use in, for example, photovoltaic (PV) devices.
  • PV photovoltaic
  • Agricultural residues are the lignocellulosic plant material remaining after harvest of the cash crop.
  • the seed kernel is the primary output. What remains behind is the stalks, cobs, husks, and leaves, collectively called corn "stover".
  • the hulls also referred to as husks
  • Biomass residues from agricultural operations are often tilled under, burned off, or used as animal bedding. Yet, this biomass has energy value. Less well known is the high mineral content of lignocellulosic biomass, up to 20% in the case of rice hulls. (See http .7/ www.6cn.nl/phyllis/. Energy Research Center of the
  • thermochemical is employed to describe the conversion of lignocellulosic biomass to form (i) a producer gas stream comprising carbon monoxide and hydrogen, and (ii) a quantity of ash comprising silicate material, carbon char and at least one of phosphorus, potassium and a metal.
  • thermophysical could also be employed to describe the conversion of chemical compositions from a solid to a gaseous state by the application of heat, especially since the reduction in the present technique does not require catalysts, reagents, or consumable additives. Nonetheless, the more inclusive term
  • thermochemical will continue to be employed herein as indicative of a conversion of the solid chemical constituents in lignocellulosic biomass to their gaseous counterparts.
  • producer gas an ash that contains silicate minerals, phosphorus, potassium, and carbon char.
  • the moisture content of the lignocellulosic feedstock is monitored and dried as necessary or desirable prior to the thermochemical conversion process.
  • the producer gas is employed to generate electric power and sensible heat, which is used to make the system partially or completely energy self-sufficient.
  • the ash is treated with acidic fluids to remove phosphorus, potassium, and trace metals, then rinsed with water to remove the impurities, some of which are retained for later use.
  • Carbon char content in the ash is controlled by the injection of steam in the thermochemical conversion to be slightly sub-stoichiometric to the silicon in the ash, and optionally by further addition or removal of char.
  • the mixture of carbon char and silicate-rich acid-leached ash is heated in a chemically-inert calcia-stabilized thoria vessel having a reducing environment at 1500-1850°C to produce silicon metal and CO 2 by carbothermal reduction.
  • the molten silicon can be formed into a ribbon, at which point the silicon has one of the following attributes: (1) the silicon melt already is doped n-type or p-type and does not need extra treatment), (2) dopant can be added to the melt to deliberately set the n-type or p-type, and (3) both n-type and p-type dopants are introduced after the extrusion.
  • the n-type or p-type can optionally be obtained from the ash leaching.
  • the dopants Upon application of suitable temperature over a suitable time, the dopants will diffuse into the silicon to form a p-n junction such that, upon application of suitable metal contacts, a PV or solar cell is formed.
  • the silicon ribbon can be cut into manageable pieces and arranged in a solar array for the purpose of producing electric power.
  • a process for producing silicon from lignocellulosic biomass comprises:
  • thermochemically converting a quantity of the lignocellulosic biomass to form (i) a producer gas stream comprising carbon monoxide and hydrogen, and (ii) a quantity of ash comprising silicate material, carbon char and at least one of phosphorus, potassium and a metal;
  • a producer gas stream comprising carbon monoxide and hydrogen
  • a quantity of ash comprising silicate material, carbon char and at least one of phosphorus, potassium and a metal
  • directing the producer gas stream to a generator to generate electric power and heat
  • thermochemically converting step (a) further comprises injecting steam to control the quantity of carbon char.
  • the leaching step (c) further comprises rinsing with water to remove compounds containing the at least one of phosphorus, potassium and a metal from the mixture of the silicate material and carbon char.
  • the leaching step (c) preferably further comprises drying the mixture of the silicate material and carbon char.
  • the leaching step (c) is performed in a counter-current, recirculated acid wash.
  • the heating step (d) is performed at a temperature of about 1500-1850°C.
  • the silicon metal is produced as a ribbon having first and second major planar surfaces.
  • the process preferably further comprises introducing a first dopant to the first major planar surface of the silicon metal ribbon to form one of a p-type or an n-type semiconductor.
  • the first dopant is preferably derived from the at least one of phosphorus, potassium and a metal separated in the leaching step (c).
  • the process preferably further comprises introducing a second dopant to the second major planar surface of the silicon metal ribbon to form the other of a p-type or an n-type semiconductor whereby, upon diffusion of the first and second dopants within the silicon metal ribbon, a p-n junction for a photovoltaic cell is formed.
  • Each of the first and second dopants is preferably derived from the at least one of phosphorus, potassium and a metal separated in the leaching step (c).
  • the heating step (d) is performed in a chemically inert vessel formed from calcia- stabilized thoria.
  • the lignocellulosic biomass comprises rice hulls.
  • the silicon metal produced by the present process can be employed in the fabrication of photovoltaic cells and in the synthesis of hydrogen storage media.
  • the present process can also produce substantially pure, metallurgical grade silicon metal.
  • An apparatus for producing silicon is employable in a photovoltaic cell from lignocellulosic biomass. The apparatus comprises:
  • thermochemically converting a quantity of the lignocellulosic biomass to form (i) a producer gas stream comprising predominantly carbon monoxide and hydrogen, and (ii) a quantity of ash comprising silicate material, carbon char and at least one of phosphorus, potassium and a metal;
  • the silicon metal is a ribbon having first and second major planar surfaces.
  • the apparatus preferably further comprises a first applicator for introducing a first dopant to the first major planar surface of the silicon metal ribbon to form one of a p-type or an n-type semiconductor.
  • the first dopant is preferably derived from the at least one of the phosphorus, potassium and a metal.
  • the apparatus preferably further comprises a second applicator for introducing a second dopant to the second major planar surface of the silicon metal ribbon to form the other of a p-type or an n-type
  • Each of the first and second dopants is preferably derived from the at least one of phosphorus, potassium and a metal.
  • the acid wash is performed in a chemically inert vessel formed from calcia- stabilized thoria.
  • the preferred lignocellulosic biomass comprises rice hulls.
  • the silicon metal produced by the present apparatus can be employed in the fabrication of photovoltaic cells and in the synthesis of hydrogen storage media.
  • the present apparatus can also produce substantially pure, metallurgical grade silicon metal.
  • FIG. 1 is a schematic diagram of a system for extraction of PV-grade silicon from agricultural residues.
  • FIG. 2 is a plot showing the thermodynamic
  • FIG. 3 is a flowchart of the process by which
  • lignocellulosic biomass is converted to solar cells.
  • FIG. 4 is a schematic diagram of an apparatus for producing solar cells from lignocellulosic biomass.
  • the dominant mass of above-ground plant growth is through accumulation of atmospheric carbon dioxide and water, so that most biomass consists of the elements C, O and H in decreasing order of abundance.
  • Smaller quantities of minerals are extracted from the soil and incorporated into the plant matter.
  • Most abundant are silicate materials, which are earth abundant, and when in the ground, include mixtures of silicon, oxygen, and one or more additional metals, such as Al, Mg, Fe and Ti.
  • Phosphorus (P), potassium (K), and nitrogen (N) are plant nutrients also extracted from soil, and present in the plant matter.
  • the lignocellulosic material converts to gases such as water vapor and CO 2 , and leave behind a mineral ash.
  • gases such as water vapor and CO 2
  • ash was leached in water to dissolve the potassium, forming potassium hydroxide, or lye, a key ingredient in the manufacture of soap from animal fat.
  • Additional metals can be removed by acid leaching, typically hydrochloric acid (HC1) or acetic acid (HC 3 HOOH). Further dissolution of the ash can be achieved with hydrofluoric acid (HF) which is known to attack silicates.
  • HC1 hydrochloric acid
  • HC 3 HOOH acetic acid
  • HF hydrofluoric acid
  • Gasification is similar to burning (combustion) with the exception that the fuel (biomass) is restricted in its exposure to air (more specifically the oxygen component of air). After initiating combustion, access to air is restricted by one of several methods, such as covering the fire with dirt or enclosing it within a vessel with adjustable air vents (similar to a home "smoker” cooking apparatus). If less oxygen is available than is needed to convert the lignocellulosic material to water vapor and CO 2 , the heat from partial combustion will cause nearby biomass particles to pyrolyze, or convert to combustible gases such as methane, hydrogen, and carbon monoxide (CO).
  • CO carbon monoxide
  • Producer gas can be used as a fuel in various devices for the purpose of producing electricity, such as an internal combustion engine with a generator (together called a “genset"), or a gas turbine. If suitably cleaned of impurities, producer gas can also be used as a fuel stream for a fuel cell, again generating electric power.
  • a unique form of gasification uses no intentionally introduced air, and supplies external heat in the range of 900 to 1100°C. This method is called Indirectly-Heated Pyrolytic
  • I-HPG Gasification
  • the producer gas from I-HPG is predominantly hydrogen and CO, with very little methane or CO 2 .
  • the ash from I-HPG contains the minerals, but also contains an amount of carbon which depends on how the I-HPG is operated. For example, dry biomass processed by the I-HPG with no introduction of steam will produce a black ash with a great deal of carbon. As another example, wet biomass will produce a light gray ash with little or no carbon, the extra moisture having reacted with the carbon to form H 2 and CO, and thereby increasing the volume of producer gas per unit mass of feedstock.
  • a pending U.S. patent application (Serial No.
  • FIG. 1 A schematic diagram for the production of silicon from agricultural residues is shown in FIG. 1. This is not a
  • FIG. 1 shows the major components of system 10, including a supply of rice hulls 12 and solar panels 14 for powering a biomass gasifier 16.
  • System 10 further includes an acetic acid storage container 18, an acid leach unit 20, a product hydrogen storage container 22, and a genset 24.
  • a carbothermal reactor 26 produces silicon for use in fabricating solar panels in factory 28 and/or for synthesizing hydrogen storage media in factory 30.
  • Hydrogen from storage media synthesized in factory 30, as well as product hydrogen stored in container 22, can be employed as fuel in a fuel cell vehicle 34, a fuel cell tractor 36, a hydrogen-fuelled internal combustion engine vehicle 38, and a hydrogen fuel cell power-assisted electric vehicle 40.
  • the acid to leach the ash is drawn from the capture of dew over a rice paddy.
  • Rice paddy dew contains methyl iodide (CH 3 I), which creates acetic acid on-site.
  • Producer gas can be converted to methanol via high pressure exposure to a Zn-Cr or Cu catalyst.
  • Methanol plus methyl iodide can be converted to acetic acid over a Fe catalyst at moderate pressures, and with some addition of steam.
  • HC1 acid which is a reagent which would need to be purchased from a chemicals distributor.
  • FIG. 3 illustrates a process 110 by which lignocellulosic biomass is converted to solar cells.
  • Process 110 includes a step 112 to determine whether the incoming biomass is too wet. If so, the biomass is directed to step 114, in which the biomass is dried using waste heat. Returning to step 112, if the biomass is not too wet, the biomass is directed in step 116 to a feeder for introduction into an indirectly-heated pyrolytic gasification (I-HPG) unit. Incoming biomass moisture is monitored in step 118.
  • I-HPG indirectly-heated pyrolytic gasification
  • step 120 the carbon contact of the incoming biomass is determined and if too low, the biomass is directed to step 134, in which heat to the dryer is increased. If the carbon content of the biomass in step 120 is too high, the biomass is directed to step 122, in which steam is injected. If the carbon content of the biomass in step 120 is within an acceptable tolerance range (“just right"), step 122 is bypassed and the biomass is directed to step 124, in which thermochemical conversion of the biomass is performed in an I- HPG unit at 900-1100°C to generate producer gas and ash. The producer gas stream is employed in step 136 to generate electricity and heat. The heat from step 136 is directed to biomass drying step 134 and to ash drying step 130.
  • Electric power from step 136 is employed in the operation of I-HPG unit in step 124.
  • the ash produced in step 124 is directed to an acid leach step 126, then to a water rinse step 128, then to a drying step 130, and finally to a transport step 132, in which a hydrogen slip stream is employed as a cover gas.
  • the ash is directed to a carbothermal reduction step 138, in which the ash is reduced at a temperature range of 1500-1850°C.
  • step 138 the reduced ash is formed in step 140 into a ribbon of silicon, and then directed in step 142 to an optional dopant application step 142.
  • step 144 the silicon ribbon with optional dopant is cooled with metallization added to produce solar cells as the output of process 110.
  • the biomass is dried as needed so that the carbon content of the ash is at or above the amount desired for the later step of the carbothermal reduction process.
  • the exact ratio of carbon to silicates is generally determined by experimentation guided by the stoichiometry of the process, and has been estimated to be about 31% carbon. (See Mede et al. reference cited above.)
  • the amount of carbon produced as a function of biomass moisture content will generally depend on the nature of the biomass (rice hulls versus corn stover, for example), and is generally determined by experiment. Once these relationships are established it becomes a simple control problem to adjust the drying of the biomass (using sensible heat from the generation of electric power), and the injection of steam in order to obtain the optimal ratio of carbon to silicate. This ratio will typically allow the carbon to react substantially completely, even at the expense of a slight surfeit of silicates, since carbon is an undesired impurity in the silicon metal.
  • the biomass is fed into the I-HPG, which includes a sensor for monitoring the moisture content of the biomass. This same sensor can be used for the decision block "Biomass too wet?", provided sufficient delay is incorporated into the control protocol to allow for the duration of the material through the drier. Based on the moisture content incoming to the I-HPG reactor, a variable injection of steam (or water, which will vaporize upon contact with hot surfaces) in order to make a final adjustment to the carbon content of the ash.
  • steam or water, which will vaporize upon contact with hot surfaces
  • the producer gas is used for two purposes. Most of the producer gas is used to generate electrical power, a process that also involves the generation of sensible heat. The electric power is used to continue operation of the I-HPG, and can also be used to power the carbothermal reduction process (link not shown in FIG. 3).
  • the heat can be used to dry the incoming lignocellulosic biomass, and can also be used to dry the leached ash in a subsequent step in the process.
  • one or more heat exchangers are used to dry the incoming biomass or to dry the ash.
  • the generator, the heat exchanger(s), or both the generator and the heat exchanger(s) can be used for drying in the system.
  • the hydrogen gas creates a reducing
  • Ash from the I-HPG process will contain carbon plus silicates and a wide variety of elements. Most of the elements other than C, Si and O can be removed by leaching with acetic or hydrochloric acid. This leaching process is generally done in a fluid state, and can be either aqueous or gaseous. The preferred embodiment is a counter-current, recirculated acid wash
  • the reaction proceeds with a duration and temperature (temperature control not shown in FIG. 3) sufficient to reach a final silicon purity of approximately 10 parts per million (ppm) or less of each non-desired element.
  • ppm parts per million
  • the ash is rinsed with water to dissolve and remove salts and byproducts created by reaction with the acid. This water is discarded. The remaining ash is dried, then transported to the carbothermal reduction reactor.
  • the leached silica/carbon mix must generally be heated further to reach the reaction temperatures required (greater than about 1500°C).
  • This power can be, and is preferably, derived from the generator.
  • Molten silicon from the bottom of the carbothermal reaction vessel is drawn into a slab or ribbon. This can be accomplished by one of several methods known to those familiar with the technology involved here. Methods to draw silicon ribbon include, but are not limited to: edge-defined growth, silicon ribbon technology, gravity-fed extrusion from a rectangular orifice. The ribbon can be drawn upward, or applied to a flat, non-reactive surface (such as quartz).
  • molten silicon and hot silicates are extremely aggressive, and will dissolve nearly any material normally used as a vessel. It is therefore important that the proper material selection is employed in connection with the present technique.
  • One choice common in the semiconductor industry is to use a quartz vessel.
  • Another choice, and a preferred embodiment of the present technique is the use of calcia-stabilized thoria, generally having 0.5 to 4.0 percent calcia (CaO) in a matrix of thoria (ThO 2 ).
  • This refractory ceramic has excellent durability when in contact with molten with silicates, and provides the long-duration capability for a cost-effective apparatus.
  • the molten silicon can be doped with either a p-type or n-type dopant.
  • the choice of p-type or n-type is generally based on the effectiveness of removal of native dopants from the mineral ash. For example, if aluminum (Al) remains in the ash, the silicon will tend to be p-type, since Al is a p-type dopant in silicon. If excess phosphorus (P) remains in the ash, the silicon will tend to be n-type. Which of these scenarios exists will generally depend on the type of biomass feedstock, and the choice of leaching acids used, as well as the duration and mixing of the acid with the ash. This information will generally be determined by experimentation, guided by chemistry and analysis, but once determined can be considered to be relatively consistent so that continuous
  • a dopant of the opposite type from that which is dominant in the bulk of the ribbon can be optionally applied to one side of the ribbon.
  • the bulk silicon is p-type from a surplus of aluminum
  • phosphorus-coated silicon can be subjected to a suitable phosphorus-coated silicon
  • FIG. 4 shows a schematic diagram of an apparatus 210 for producing solar cells according to the process of FIG. 3.
  • Apparatus 210 includes a biomass dryer 212, a water storage container 214 and an I-HPG unit 216.
  • Producer gas from I-HPG unit 216 is directed to a heat and power generation unit 218, where power generated in unit 218 is directed back to I-HPG unit 216 and/or directed to carbothermal reactor 240.
  • Producer gas from I- HPG unit is also directed to a hydrogen separation unit 246.
  • Hydrogen from unit 246 is then directed to carbothermal reactor 240.
  • Ash from I-HPG unit 216 is directed to a leach unit 220.
  • Acid from container 224 is directed through a 3-way valved conduit 226 to a pump 222 and introduced to leach unit 220.
  • Effluent from leach unit 220 is dumped via a valved conduit 228.
  • Leached ash from unit 220 is rinsed in step 232 with water from container 230 to produce a rinsed ash stream that is directed to a dryer 236.
  • Effluent from rinse unit 232 is dumped via valved conduit 234.
  • the dried ash from dryer 236 is fed to carbothermal reactor 240, which uses hydrogen from separation unit 246, power from heat and power generation unit 218, and optional dopant from storage container 238, to fabricate silicon ribbon 242. Silicon ribbon 242, optionally treated with dopant, is then processed as described above with respect to FIG. 3 to produce solar cells 244.
  • the biomass enters a dryer using an adjustable amount of heat from the power generation which runs on the producer gas generated by I-HPG of the biomass, which has been mixed with an adjustable amount of steam to control the carbon content in the ash produced.
  • the ash is leached with acid, then rinsed with water, dried using waste heat from the power generation, and then transported to the carbothermal reactor.
  • a hydrogen cover gas is provided via a membrane separation of the producer gas, creating a reducing environment for the
  • An extruded ribbon of silicon is drawn out, after optionally doping the liquid metal prior to extrusion.
  • An opposite type dopant can be optionally added to take advantage of the heat of the ribbon to provide the motive energy for diffusion of the externally-applied dopant to create a p-n junction.
  • the silicon ribbon is then cut into manageable size polygons, preferably rectangles, to form solar cells. With suitable metallization, using methods known to persons familiar with the technology involved here, the solar cells can be contacted on the n-side and p-side, so that power can be generated when the solar cells are exposed to light.

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Abstract

L'objet de la présente invention est de produire le silicium utilisable dans une pile photovoltaïque à partir de résidus agricoles, le procédé comprenant les étapes suivantes : (a) conversion thermochimique de la partie lignocellulosique de résidus agricoles pour former (i) un flux de gaz pauvre de gazogène comprenant du monoxyde de carbone et de l'hydrogène, et ii) une certaine quantité de cendres comprenant une matière silicatée, un produit de carbonisation et au moins un composé parmi le phosphore, le potassium et un métal; (b) acheminement du flux de gaz pauvre de gazogène vers un générateur pour générer du courant électrique et de la chaleur; (c) lixiviation des cendres avec un fluide acide pour séparer le phosphore, le potassium ou le métal et obtenir un mélange de matière silicatée et produit de carbonisation; (d) chauffage du mélange de matière silicatée et produit de carbonisation pour obtenir du silicium métal et du dioxyde de carbone par réduction carbothermique. L'écorce de riz et le résidu agricole préféré entre tous. Un appareil correspondant produit du silicium de qualité photovoltaïque, ledit appareil comprenant un gazogène pyrolytique à chauffage indirect, un générateur, un dispositif de lavage à l'acide et un réacteur carbothermique.
PCT/US2013/065645 2012-10-19 2013-10-18 Procédé et appareil pour la production de piles photovoltaïques à partir de résidus agricoles Ceased WO2014063029A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010017364A2 (fr) * 2008-08-06 2010-02-11 Mayaterials, Inc. Voies économiques d’obtention de silicium de grande pureté et ses dérivés
WO2011014005A2 (fr) * 2009-07-28 2011-02-03 전북대학교산학협력단 Procédé d'élaboration d'un composé de silicium à partir de balle de riz ou de paille de riz

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010017364A2 (fr) * 2008-08-06 2010-02-11 Mayaterials, Inc. Voies économiques d’obtention de silicium de grande pureté et ses dérivés
WO2011014005A2 (fr) * 2009-07-28 2011-02-03 전북대학교산학협력단 Procédé d'élaboration d'un composé de silicium à partir de balle de riz ou de paille de riz

Non-Patent Citations (3)

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Title
EKAPHAN SWATSITANG ET AL.: "Preparation and Characterization of Silicon from Rice Hulls", JOURNAL OF METALS, MATERIALS AND MINERALS, vol. 19, no. 2, 2009, pages 91 - 94 *
S. CHANDRASEKHAR ET AL.: "Review Processing, properties and applications of reactive silica from rice husk-an overview", JOURNAL OF MATERIALS SCIENCE, vol. 38, no. ISSUE, 1 August 2003 (2003-08-01), pages 3159 - 3168 *
SUPAKORN PUKIRD ET AL.: "Synthesis and Characterization of Si02 Nanowires Prepared from Rice Husk Ash", JOURNAL OF METALS, MATERIALS AND MINERALS, vol. 19, no. 2, 2009, pages 33 - 37 *

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