Classifications

• • 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
  • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
  • C10J3/72—Other features
  • C10J3/78—High-pressure apparatus
• • 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
  • C10J2300/0979—Water as supercritical 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
  • C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
  • C10J2300/1807—Recycle loops, e.g. gas, solids, heating medium, water

Definitions

• the invention relates to a method for the hydrothermal gasification of biomass in supercritical water.
• Methods for the hydrothermal gasification of biomass in supercritical water are particularly suitable for the energetic use of wet biomass, since they are characterized by high chemical and energetic efficiencies and good quality and composition of the product gases obtained.
• the gasification takes place at pressures and temperatures above the critical point of the water (22.1 MPa and 374 ° C), whereby organic substances are well dissolved, while inorganic salts precipitate.
• the chemical conversions increase with the reaction temperature and reach almost 100% at temperatures of 700 ° C. At lower reaction temperatures, the chemical conversion is much lower, e.g. 50% at 550 ° C.
• the chemical conversions also increase with the mean residence time in the reactor. The maximum conversion is achieved depending on the temperature within 0.5 - 5 min. However, both a higher temperature and a longer average residence time, which corresponds to the reactor volume at a given material throughput, result in higher costs.
• Wet biomass e.g. Fresh plants or pomace often have a concentration of organic matter in the range of 30% by weight. Such a high concentration is too high for biomass gasification in supercritical water, in particular due to its high viscosity and poor pumpability.
• biomass is usually diluted with water to values in the range of 5 to 20% by weight. Dilution is either at the beginning of the process at ambient conditions or according to the Method according to DE 102 10 178 C1 or the DE 202 20 307 U1 only at high temperatures in the reactor.
• Dilution with water increases both the demand for as low-salt fresh water as possible for carrying out the process and the amount of waste water to be treated by the process, which results in additional costs.
• the DE 100 15 620 A1 discloses a method for generating heat by the combustion of biomass. Dropping salts which do not dissolve in the supercritical water are passed via an outlet into a collecting container. The process wastewater is purified from this separately in a filter unit and returned via a supply line in the combustion vessel. The supply line communicates with a heat exchanger which heats the process waste water with the heat of the supercritical water. In this way, a high heat transfer from the combustion side to the heat exchanger is made possible.
• the organic components of the process wastewater should be gasified as completely as possible in order to achieve the highest possible total carbon gasification conversion.
• the process according to the invention for the hydrothermal gasification of biomass in supercritical water, in which product gases and process wastewater containing inorganic salts and organic residues are formed as reaction products is characterized by the fact that part of the process waste water formed in this process is incorporated into the process is recycled, that with this part of the recirculated process wastewater, the biomass is preferably diluted to a value of 5-20 wt.% Dry substance (TS), but previously the major part of the inorganic salts was separated from the process wastewater.
• TS Dry substance
• the method according to the invention comprises the steps a) to i).
• step a) the major part of the process waste water, which is virtually free from inorganic salts but contains organic reaction residues, is heated to a temperature above 600 ° C, with a pressure higher than 22.1 MPa.
• the biomass is heated to a temperature up to the pseudo-critical temperature, wherein preferably the same pressure as in the process waste water is adjusted.
• the pressure-dependent pseudo-critical temperature of the water is defined as the temperature at which the density drops steeply.
• the pseudo-critical temperature is generally not consistent with the critical temperature of the thermodynamic system. In particular, the pseudo-critical temperature shifts to higher values at higher pressure.
• step c) the two streams, i. the biomass stream heated according to step b) and the process wastewater stream treated in step a) are mixed in the reactor such that the biomass is diluted.
• step d the reaction of the organic matter with the water, wherein as reaction products product gases and process waste water containing inorganic salts and organic residues are formed.
• the inorganic salts are preferably removed from the lower part of the reactor.
• the reactor for this purpose has a bottom outlet or a salt separator, from which the high-salt part stream is separated from the low-salt main stream of product gases and low-salt process wastewater.
• a device for carrying out this method step, for example, a device according to the DE 202 20 307 U1 be used.
• a small salt-rich partial stream is separated from the main stream of material at a suitable point of the reactor, such as, for example, the bottom outlet or the salt separator.
• the liberated from the salt load main stream is low in salt and is for the renewed dilution of biomass directly or as a second reactant stream in the sense of the DE 102 10 178 C1 or the DE 202 20 307 U1 used.
• the process waste water is re-flowed, most of the organic residues are decomposed so that there is no accumulation of carbon compounds.
• step f) the reaction products, i. the product gases and the low-salt product waste water, cooled and the product gas is separated from the effluent according to step g).
• the low-salt product wastewater can subsequently be recycled to the process according to step a) in step h).
• step i) the disposal of the remaining portion of the process wastewater, which has not already been recycled according to step h), takes place.
• the inorganic components are separated from the process and discarded or disposed of.
• process wastewater instead of fresh water as in the DE 102 10 178 C1 or the DE 202 20 307 U1 used. Due to the high temperatures in the preheater, ie before the mixing of the two streams in the reactor, the organic constituents of the process wastewater are completely gasified.
• the inventive method has in particular the following advantages.
• Table 1 shows experimentally determined element quantities in a test with maize silage with the following parameters: throughput 50 kg / h, feed concentration 9.2% by weight, reaction temperature 640 ° C, pressure 28 MPa. The turnover of the carbon gasification was 90%. The majority of the inorganic salts were removed via a bottom draw as a device for salt separation; a smaller proportion has failed before the salt separation in the preheater.
• Tables 2 and 3 show computational examples of mass flows. This is based on a carbon gasification conversion of only 70%. In both cases, the return of a part of the process wastewater achieves a total carbon gasification conversion of almost 90%.
• Table 2 shows a computational example of the mass flow in the conventional process without separation of the salts.
• TS means dry matter.
• Table 3 shows a computational example of the mass flow in the process according to the invention with separation of the salts.
• the salt concentration in the reaction mixture according to Table 2 is about three times higher than the corresponding value of 3.2 kg / h in Table 3 at 9 kg / h. Such a high salt concentration value prevents trouble-free operation and can cause corrosion. Above all, the high salt concentration of 6 kg / h in the recycle stream makes the use of the wastewater stream without salt separation as a substitute for the water flow after the DE 102 10 178 C1 or the DE 202 20 307 U1 impossible.
• a comparison of the amount of process wastewater shows that 300 kg / h (intermediate) wastewater incurred in a process according to Table 2 , but without recirculation of the process wastewater, while in a process according to Table 3 with recycling of waste water only 88 kg / h wastewater for Disposal incurred. This results in a significant saving of about 2/3 of the wastewater.
• the resulting from the salt separation smaller flow of 12 kg / h is disposed of separately.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Processing Of Solid Wastes (AREA)
• Treatment Of Sludge (AREA)

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• 2006
  • 2006-09-20 DE DE200610044116 patent/DE102006044116B3/de active Active
• 2007
  • 2007-09-12 EP EP07017818A patent/EP1903091A1/fr not_active Withdrawn

Patent Citations (9)

Non-Patent Citations (1)

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