EP2895580A1 - A method for processing ash, and an ash processing plant - Google Patents

A method for processing ash, and an ash processing plant

Info

Publication number
EP2895580A1
EP2895580A1 EP13836774.3A EP13836774A EP2895580A1 EP 2895580 A1 EP2895580 A1 EP 2895580A1 EP 13836774 A EP13836774 A EP 13836774A EP 2895580 A1 EP2895580 A1 EP 2895580A1
Authority
EP
European Patent Office
Prior art keywords
ash
combustion
fluidized bed
flue gases
product gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP13836774.3A
Other languages
German (de)
French (fr)
Other versions
EP2895580A4 (en
Inventor
Ville HANKALIN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Valmet Technologies Oy
Original Assignee
Valmet Technologies Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Valmet Technologies Oy filed Critical Valmet Technologies Oy
Publication of EP2895580A1 publication Critical patent/EP2895580A1/en
Publication of EP2895580A4 publication Critical patent/EP2895580A4/en
Withdrawn legal-status Critical Current

Links

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
    • C10J3/46—Gasification of granular or pulverulent flues in suspension
    • C10J3/48—Apparatus; Plants
    • C10J3/52—Ash-removing devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
    • F22B1/1838—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines the hot gas being under a high pressure, e.g. in chemical installations
    • F22B1/1846—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines the hot gas being under a high pressure, e.g. in chemical installations the hot gas being loaded with particles, e.g. waste heat boilers after a coal gasification plant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L15/00—Heating of air supplied for combustion
    • 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
    • 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
    • C10J2300/1687—Integration of gasification processes with another plant or parts within the plant with steam generation
    • 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
    • C10J3/82—Gas withdrawal means
    • C10J3/84—Gas withdrawal means with means for removing dust or tar from the gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2209/00—Specific waste
    • F23G2209/30—Solid combustion residues, e.g. bottom or flyash
    • 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
    • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
    • Y02E20/18—Integrated gasification combined cycle [IGCC], e.g. combined with carbon capture and storage [CCS]
    • 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
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

  • the invention relates to a method for processing ash according to the preamble of claim 1.
  • the invention also relates to an ash processing plant according to the preamble of claim 6.
  • One way of producing fuel is to gasify a carbonaceous raw material, wherein it becomes gas which can be burnt.
  • Particularly popular raw materials include waste materials which are normally organic materials, such as various types of wood waste and package waste (for example, cardboard and paper). The material is also called recovered fuel.
  • the gasification normally takes place in a fluidized bed process at a high temperature under air-deficient conditions.
  • the product gas obtained is suit- able to be burned in, for example, a conventional power plant boiler.
  • fly ash In the gasification of waste, fly ash is produced, which is separated as hot ash, so-called hot filtered ash from the product gas flow from the gasifier.
  • This ash contains, among other things, unreacted carbon (soot), bed material and fuel ash components (including alkali metals, heavy metals and chlorides).
  • the hot filtered ash has a high content of carbon, about 20 to 30 wt-%. However, it is not possible to utilize the hot filtered ash, but it has to be submitted to a waste management company for converting it to a form that is suitable for final disposal. Due to its high carbon content, hot filtered ash is hazardous waste.
  • the caloric value of hot filtered ash is about 8 to 1 1 MJ/kg.
  • processes have been developed for burning the ash.
  • a CFB combustion apparatus has been developed, in which the flue gases from the combustion are conveyed to a point before bag filters in the flue gas duct downstream of the boiler that burns the product gas of gasification, for which reason the flue gases are cooled to a temperature below 200°C.
  • Finnish patent Fl 110266 discloses a method for treating soot-containing solids of the product gas from gasification already at the gasification plant.
  • ash having a high soot content and being separated from the product gas flow is introduced into a fluidized bed reactor acting as an oxi- dizer where it is burnt at a temperature of 800 to 900°C to oxidize the carbon to carbon dioxide.
  • the combustion flue gases are redirected as secondary gasification gas to the gasifier.
  • ash is separated from the flue gases.
  • such a solution to recirculate the flue gases is problematic, because the additional gas flow from the oxidization is rich in oxygen, which makes the control of the gasification process more difficult.
  • the capacity diminishes, because part of the capacity is taken by the flue gas flow which increases the inert flow through the gasifier.
  • Publication WO 03/055962 discloses combustion in a CFB reactor of ash obtained from gasification. Flue gases are conveyed from the CFB reactor to product gas coming from the gasifier, to be carried further via a cooler for the product gas and an ash filter to a boiler for burning the product gas. Accord- ing to the publication, it is an aim to also include ash particles in the flue gas flow issuing from the combustion reactor, for binding tar in the product gas by means of the ash particles so that it would not stick to the cooler for the product gas.
  • the aim of the invention is to present a method for burning carbon-containing hot filtered ashes issuing from a gasification process to reduce the carbon (soot) content and to treat the flue gases obtained from the combustion by a simple solution so that they can be utilized better than before.
  • the method according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 1.
  • the ash separated from the product gas of the gasification process is oxi- dized by fluidized bed combustion, and the flue gases produced by the combustion are introduced into the combustion air of the boiler (main boiler) that burns the product gas of the gasification process.
  • the flue gases which contain CO can be burnt in the main boiler of the gasification plant by first introducing them into the combustion air of the main boiler. Simultaneously, the heat content of the flue gases from the combustion of ash can be utilized for pre-heating the combustion air.
  • the CO is oxidized in the main boiler.
  • the flue gases from the combustion of ash are advantageously filtered before they are introduced into the combustion air of the boiler, wherein a finer ash fraction that is still entrained can be separated from them.
  • the gasification process is known as such, and it will not be described in more detail.
  • the raw material is normally so-called recovered fuel which includes various types of municipal waste and industrial waste, normally car- bonaceous solid fuel suitable for energy production.
  • the fly ash separated from the flow of combustible product gas obtained from the gasification of the fuel is processed in a plant shown in the figure. Normally, such a plant is located in the same power plant as the gasifier itself and the main boiler of the power plant which burns the product gas to produce energy.
  • the gasification process including the supply of ash (hot filtered ash) separated from the process as raw material for the plant, is illustrated with broken lines.
  • This ash, having a high content of unreacted carbon (soot) from the gasified fuel is introduced into a fluidized bed reactor 1 , in which the combustion takes place by means of oxygen-containing combustion air supplied into the reactor (arrow A).
  • the fluidized bed reactor also contains solid bed material (sand, limestone, or the like), which can be added, if necessary.
  • the reactor 1 is a brick-lined, i.e. completely thermally insulated, circulating fluidized bed (CFB) reactor with no heat exchange sur- faces.
  • the combustion temperature in the reactor is below 900°C, and it is adjusted as desired by means of the excess air ratio.
  • the flue gases produced by the combustion process pass through a cyclone 2, in which the solids entrained in the flue gases are separated to the return circulation of the circulating fluidized bed reactor. After the material for the return circulation has been separated, the flue gases pass along a flue gas duct 3 through a heat exchanger 4, in which their temperature is decreased to about 400°C. Filtering is normally advantageous to carry out in the temperature range from 300 to 550°C. Because the flue gases are only cooled to a temperature of about 400°C, a large heat exchanger (cooler) will not be needed.
  • the coarser fraction of ash is removed as bottom ash from below the fluidized bed reactor 1 , and the finer fraction which is not separated in the cyclone 2 to the return circulation of the circulating fluidized bed reactor is carried with the flue gases along the flue gas duct 3 through the heat exchanger 4 to an ash separator 5 in which the ash is separated.
  • the ash separator is a gas filter in which the fine ash fraction is separated by filtering.
  • the ash filter is a so-called hot filter, for example a ceramic fibre filter.
  • the heat exchanger 4 By means of the heat exchanger 4, energy can be recovered from the com- bustion of the carbon in the ash, and at the same time, the temperature of the flue gases can be reduced to a level suitable for filtering.
  • the heat exchange in the heat exchanger 4 takes place by an indirect principle; that is, heat is transferred without a direct contact from the flue gases to the heat transfer medium.
  • the flue gas duct 3 Downstream of the ash separator 5, the flue gas duct 3 is connected to a combustion air duct 6 which introduces combustion air to the main boiler 8 of the gasification plant. In this way, the flue gases coming from the flue gas duct 3 are mixed with the combustion air, simultaneously pre-heating the combustion air.
  • the combustion air duct 6 the flue gases and the combustion air are conveyed to the combustion process of the main boiler 8, which is supplied with product gas as fuel along a channel 7 from the gasification process. Consequently, the heat exchange in the combustion air duct 6 takes place by a direct contact between the gaseous media.
  • the flue gases are combined with the flow of combustion air at such an early stage that they have been mixed with the combustion air and the temperature of the combustion air has been evened out at the time of injecting the combustion air into the main boiler 8.
  • the carbon monoxide contained in the flue gases is oxidized to carbon dioxide in the combustion process of the main boiler 8. Due to the high excess air ratio of the combustion of ash, the flue gases also have a high oxygen content.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Sustainable Development (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Gasification And Melting Of Waste (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Abstract

In a method for processing ash, fly ash is separated from a product gas flow obtained from gasification of fuel, which fly ash is burnt in fluidized bed combustion to reduce the carbon content in the ash, after which the flue gases from the combustion are processed. The ash is burnt by fluidized bed combustion at a temperature below 900°C for reducing the carbon content, and the flue gases produced by the combustion of ash are introduced into combustion air of a boiler (8) that burns the product gas obtained from the gasification.

Description

A method for processing ash, and an ash processing plant
The invention relates to a method for processing ash according to the preamble of claim 1. The invention also relates to an ash processing plant according to the preamble of claim 6.
One way of producing fuel is to gasify a carbonaceous raw material, wherein it becomes gas which can be burnt. Particularly popular raw materials include waste materials which are normally organic materials, such as various types of wood waste and package waste (for example, cardboard and paper). The material is also called recovered fuel.
The gasification normally takes place in a fluidized bed process at a high temperature under air-deficient conditions. The product gas obtained is suit- able to be burned in, for example, a conventional power plant boiler.
In the gasification of waste, fly ash is produced, which is separated as hot ash, so-called hot filtered ash from the product gas flow from the gasifier. This ash contains, among other things, unreacted carbon (soot), bed material and fuel ash components (including alkali metals, heavy metals and chlorides).
The hot filtered ash has a high content of carbon, about 20 to 30 wt-%. However, it is not possible to utilize the hot filtered ash, but it has to be submitted to a waste management company for converting it to a form that is suitable for final disposal. Due to its high carbon content, hot filtered ash is hazardous waste.
The caloric value of hot filtered ash is about 8 to 1 1 MJ/kg. In order to not lose the caloric value of the ash and to reduce the amount of ash disposed as waste, processes have been developed for burning the ash. For example, a CFB combustion apparatus has been developed, in which the flue gases from the combustion are conveyed to a point before bag filters in the flue gas duct downstream of the boiler that burns the product gas of gasification, for which reason the flue gases are cooled to a temperature below 200°C. Finnish patent Fl 110266 discloses a method for treating soot-containing solids of the product gas from gasification already at the gasification plant. In this method, ash having a high soot content and being separated from the product gas flow is introduced into a fluidized bed reactor acting as an oxi- dizer where it is burnt at a temperature of 800 to 900°C to oxidize the carbon to carbon dioxide. The combustion flue gases are redirected as secondary gasification gas to the gasifier. Before this, ash is separated from the flue gases. However, such a solution to recirculate the flue gases is problematic, because the additional gas flow from the oxidization is rich in oxygen, which makes the control of the gasification process more difficult. Also, the capacity diminishes, because part of the capacity is taken by the flue gas flow which increases the inert flow through the gasifier.
Publication WO 03/055962 discloses combustion in a CFB reactor of ash obtained from gasification. Flue gases are conveyed from the CFB reactor to product gas coming from the gasifier, to be carried further via a cooler for the product gas and an ash filter to a boiler for burning the product gas. Accord- ing to the publication, it is an aim to also include ash particles in the flue gas flow issuing from the combustion reactor, for binding tar in the product gas by means of the ash particles so that it would not stick to the cooler for the product gas. The aim of the invention is to present a method for burning carbon-containing hot filtered ashes issuing from a gasification process to reduce the carbon (soot) content and to treat the flue gases obtained from the combustion by a simple solution so that they can be utilized better than before. To achieve this aim, the method according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 1.
The ash separated from the product gas of the gasification process is oxi- dized by fluidized bed combustion, and the flue gases produced by the combustion are introduced into the combustion air of the boiler (main boiler) that burns the product gas of the gasification process. In addition to the possibility of reducing the carbon content of hot filtered ash from the gasification, reducing the mass to be disposed of, and utilizing the heat content of the ash, the flue gases which contain CO can be burnt in the main boiler of the gasification plant by first introducing them into the combustion air of the main boiler. Simultaneously, the heat content of the flue gases from the combustion of ash can be utilized for pre-heating the combustion air. The CO is oxidized in the main boiler. The flue gases from the combustion of ash are advantageously filtered before they are introduced into the combustion air of the boiler, wherein a finer ash fraction that is still entrained can be separated from them.
In the following, the invention will be described in more detail with reference to the appended drawing which is a process chart of an ash processing plant.
The gasification process is known as such, and it will not be described in more detail. The raw material is normally so-called recovered fuel which includes various types of municipal waste and industrial waste, normally car- bonaceous solid fuel suitable for energy production.
The fly ash separated from the flow of combustible product gas obtained from the gasification of the fuel is processed in a plant shown in the figure. Normally, such a plant is located in the same power plant as the gasifier itself and the main boiler of the power plant which burns the product gas to produce energy. The gasification process, including the supply of ash (hot filtered ash) separated from the process as raw material for the plant, is illustrated with broken lines. This ash, having a high content of unreacted carbon (soot) from the gasified fuel, is introduced into a fluidized bed reactor 1 , in which the combustion takes place by means of oxygen-containing combustion air supplied into the reactor (arrow A). The fluidized bed reactor also contains solid bed material (sand, limestone, or the like), which can be added, if necessary. The reactor 1 is a brick-lined, i.e. completely thermally insulated, circulating fluidized bed (CFB) reactor with no heat exchange sur- faces. The combustion temperature in the reactor is below 900°C, and it is adjusted as desired by means of the excess air ratio. The flue gases produced by the combustion process pass through a cyclone 2, in which the solids entrained in the flue gases are separated to the return circulation of the circulating fluidized bed reactor. After the material for the return circulation has been separated, the flue gases pass along a flue gas duct 3 through a heat exchanger 4, in which their temperature is decreased to about 400°C. Filtering is normally advantageous to carry out in the temperature range from 300 to 550°C. Because the flue gases are only cooled to a temperature of about 400°C, a large heat exchanger (cooler) will not be needed.
The coarser fraction of ash is removed as bottom ash from below the fluidized bed reactor 1 , and the finer fraction which is not separated in the cyclone 2 to the return circulation of the circulating fluidized bed reactor is carried with the flue gases along the flue gas duct 3 through the heat exchanger 4 to an ash separator 5 in which the ash is separated. The ash separator is a gas filter in which the fine ash fraction is separated by filtering. The ash filter is a so-called hot filter, for example a ceramic fibre filter.
By means of the heat exchanger 4, energy can be recovered from the com- bustion of the carbon in the ash, and at the same time, the temperature of the flue gases can be reduced to a level suitable for filtering. The heat exchange in the heat exchanger 4 takes place by an indirect principle; that is, heat is transferred without a direct contact from the flue gases to the heat transfer medium.
Downstream of the ash separator 5, the flue gas duct 3 is connected to a combustion air duct 6 which introduces combustion air to the main boiler 8 of the gasification plant. In this way, the flue gases coming from the flue gas duct 3 are mixed with the combustion air, simultaneously pre-heating the combustion air. Along the combustion air duct 6, the flue gases and the combustion air are conveyed to the combustion process of the main boiler 8, which is supplied with product gas as fuel along a channel 7 from the gasification process. Consequently, the heat exchange in the combustion air duct 6 takes place by a direct contact between the gaseous media. Advantageously, the flue gases are combined with the flow of combustion air at such an early stage that they have been mixed with the combustion air and the temperature of the combustion air has been evened out at the time of injecting the combustion air into the main boiler 8. The carbon monoxide contained in the flue gases is oxidized to carbon dioxide in the combustion process of the main boiler 8. Due to the high excess air ratio of the combustion of ash, the flue gases also have a high oxygen content.
From the material balances it can be estimated that the content of flue gases from the ash combustion is not higher than 10% of the combustion air of the main boiler 8 (expressed as mass ratio).

Claims

Claims
1. A method for processing ash, wherein fly ash is separated from a product gas flow obtained from gasification of fuel, which fly ash is burnt in fluidized bed combustion to reduce the carbon content in the ash, after which the flue gases from the combustion are processed, characterized in that
- ash separated from the product gas of the fuel gasification process is introduced as raw material for a fluidized bed reactor into an ash processing plant,
- the ash is burnt by fluidized bed combustion at a temperature below 900°C for reducing the carbon content,
- the flue gases from the combustion of ash are conveyed to a combustion air duct (6), in which they are mixed with the combustion air, and
- the flue gases and the combustion air are conveyed to a separate boiler (8), into which the product gas obtained from the fuel gasification process is introduced as fuel.
2. The method according to claim 1 , characterized in that fine ash material entrained in the flue gases coming from the fluidized bed combustion is separated from the flue gases before they are introduced into the combustion air.
3. The method according to claim 2, characterized in that the separation is performed by filtering, advantageously preceded by cooling of the flue gases by heat exchange.
4. The method according to any of the preceding claims, characterized in that the fluidized bed combustion of the ash takes place in a circulating fluid- ized bed (CFB).
5. An ash processing plant comprising a fluidized bed reactor (1 ) configured to burn fly ash separated from the product gas flow obtained from gasification of fuel, characterized in that the flue gas duct (3) of the fluidized bed reactor (1 ) is connected to a combustion air duct (6) which enters the same boiler (8), to which a channel (7) supplying product gas from gasification of fuel is introduced, for burning the product gas in the boiler (8).
6. The ash processing plant according to claim 5, characterized in that the flue gas duct (3) comprises an ash separator (5) for separating the ash fraction carried with the flue gases.
7. The ash processing plant according to claim 5 or 6, characterized in that the fluidized bed reactor (1 ) is a circulating fluidized bed (CFB) reactor.
8. The ash processing plant according to any of the claims 5 to 7, charac- terized in that the furnace of the fluidized bed reactor (1 ) is fully thermally insulated.
9. The ash processing plant according to any of the claims 5 to 8, characterized in that a heat exchanger (4) is provided in the flue gas duct (3), for cooling the flue gases of the combustion of ash, and an ash separator (5), which is a gas filter, is provided downstream of the heat exchanger (4).
EP13836774.3A 2012-09-13 2013-09-13 PROCESS AND PLANT FOR TREATING ASH Withdrawn EP2895580A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20125949A FI124206B (en) 2012-09-13 2012-09-13 Process for the treatment of ash and plant for the treatment of ash
PCT/FI2013/050891 WO2014041250A1 (en) 2012-09-13 2013-09-13 A method for processing ash, and an ash processing plant

Publications (2)

Publication Number Publication Date
EP2895580A1 true EP2895580A1 (en) 2015-07-22
EP2895580A4 EP2895580A4 (en) 2016-04-20

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EP13836774.3A Withdrawn EP2895580A4 (en) 2012-09-13 2013-09-13 PROCESS AND PLANT FOR TREATING ASH

Country Status (3)

Country Link
EP (1) EP2895580A4 (en)
FI (1) FI124206B (en)
WO (1) WO2014041250A1 (en)

Cited By (1)

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CN118062583A (en) * 2024-04-03 2024-05-24 济民可信(高安)清洁能源有限公司 A clean and environmentally friendly conveying device for gasified carbon residue

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