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WO2014086600A1 - Procédé de mise en œuvre d'un système de pyrolyse - Google Patents

Procédé de mise en œuvre d'un système de pyrolyse Download PDF

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Publication number
WO2014086600A1
WO2014086600A1 PCT/EP2013/074502 EP2013074502W WO2014086600A1 WO 2014086600 A1 WO2014086600 A1 WO 2014086600A1 EP 2013074502 W EP2013074502 W EP 2013074502W WO 2014086600 A1 WO2014086600 A1 WO 2014086600A1
Authority
WO
WIPO (PCT)
Prior art keywords
syngas
burner
pyrolysis
temperature
feedstock
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.)
Ceased
Application number
PCT/EP2013/074502
Other languages
English (en)
Inventor
Philip Michael Beech
Stephen Richard CHURCHILL
Andrew William STAPLETON
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.)
Qinetiq Ltd
Original Assignee
Qinetiq Ltd
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 Qinetiq Ltd filed Critical Qinetiq Ltd
Publication of WO2014086600A1 publication Critical patent/WO2014086600A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • C10J3/723—Controlling or regulating the gasification process
    • 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
    • C10J2300/1215—Heating the gasifier using synthesis gas as fuel
    • 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
    • C10J2300/1223—Heating the gasifier by burners
    • 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
    • C10J2300/1603—Integration of gasification processes with another plant or parts within the plant with gas treatment
    • C10J2300/1606—Combustion processes
    • 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

Definitions

  • the present invention relates to a control method for a thermal processing system.
  • the present invention relates to a control method for a thermal processing system, such as a pyrolysis or gasification system, which comprises the step of using synthesis gas (syngas) produced from (waste) matter to sustain the thermal processing, preferably pyrolysis, step.
  • synthesis gas syngas
  • Pyrolysis is a thermochemical decomposition reaction of organic material (biomass) at elevated temperatures in the absence of oxygen, a thermal processing method. Pyrolysis may occur under a range of pressures and at operating temperatures in the range 400°C to 750°C. Pyrolysis may occur at pressures that are a few mbar (e.g. 5-10mbar) below atmospheric pressure. In general, pyrolysis of organic material produces gas and liquid products and leaves a solid residue richer in carbon content (char). The process may be used in the chemical industry to produce charcoal, activated carbon, methanol, and other chemicals from wood, to convert biomass into syngas and biochar, to turn waste into safely disposable substances, and for transforming medium-weight hydrocarbons from oil into lighter ones like gasoline.
  • waste material containing biomass is pyrolysed in a pyrolysis unit to produce syngas which can then either be combusted (e.g. in a gas turbine engine) to produce energy or which can be further processed to produce synthetic natural gas.
  • FIG. 1 shows a known pyrolysis unit 1 comprising an upright vessel 5 having a chamber 10 and a generally conical lower section 15.
  • the vessel 5 is provided with an inlet 20 into the top of the chamber 10 and an outlet 25 at the base of the chamber 10.
  • a gas outlet 30 is additionally provided at the top of the vessel 5.
  • a process gas conduit 35 is provided at the lower portion of the vessel, which transports hot process gas from a burner (not illustrated) through a biomass 40 to initiate and/or sustain the pyrolysis reaction.
  • biomass 40 is introduced into the chamber 10 through the inlet 20.
  • the biomass pyrolyses upon mixing with the hot process gas and fully pyrolysed biomass (or char) 45 is removed via the outlet 25 at the base of vessel 5/chamber 10.
  • Synthesis gas (syngas) produced by the pyrolysis reaction is removed via the gas outlet 30.
  • the pyrolyser vessel shown in Figure 1 is vertical but the system may be inclined at an angle. In certain embodiments the vessel may be rotated in order to allow the biomass to mix within the chamber in order to increase the exposure of biomass to the heated portion of the vessel.
  • the pyrolysis unit 1 may comprise an auger arrangement to stir the biomass 40 and char 45 within the vessel 5.
  • the pyrolysis unit is typically initiated or primed by burning a fuel such as diesel.
  • a fuel such as diesel.
  • waste is added and the biomass begins to pyrolyse.
  • a portion of the syngas from gas outlet 30 can then be diverted to the burner and used as a fuel.
  • the (diesel) fuel can be switched off and the diverted syngas can be used to provide all of the process energy.
  • the burner may be a dual fuel burner, or separate diesel and syngas burners may be used to provide the process gas.
  • a drawback of the system is that steady state control of the burner and pyrolysis process can be difficult to achieve.
  • Gasification is a thermal process similar to pyrolysis that may be used to convert materials into carbon monoxide, hydrogen, carbon dioxide and methane. Gasification involves reacting the input matter at high temperatures, e.g. above about 700°C, in the presence of controlled amounts of oxygen and water (steam). Known gasification systems experience similar control issues to pyrolysis systems. It is an object of the present invention to provide a control method for a thermal processing system that overcomes or substantially mitigates problems with known systems.
  • a method of operating a pyrolysis system of the type comprising (i) a pyrolysis unit for a feedstock, the pyrolysis unit having an inlet for a hot process gas and an outlet for a synthesis gas produced from the pyrolysed feedstock and (ii) a synthesis gas burner for deriving process gas from at least part of the synthesis gas, the method comprising the step of controlling the syngas burner once pyrolysis of the feedstock has commenced so as to maintain at least one of the inlet temperature T1 and the outlet temperature T2 within pre-determined limits.
  • the "process gas” is usually a combination of hot combustion products created by the combustion of the syngas and optional further fuel (see below); any excess air introduced for combustion; and/or any excess syngas.
  • the composition of the process gas typically depends on the calorific value of the syngas, the target temperature for the process gas and whether the combustion process is running fuel rich (less air than is required for completed combustion) or fuel lean (more air than is required for complete combustion).
  • the feedstock is waste material, more preferably household waste material.
  • the invention is particularly applicable to a small scale waste pyrolysis system.
  • small scale is generally meant a system having a waste capacity of less than around 1000 kg/hour, more preferably less than around 500 kg/hour. Usually, the capacity of the plant is greater than or equal to 50 kg/hour.
  • the preferred mode of operation for a waste pyrolysis system is for the process gas to be delivered to the pyrolysis unit at an optimum temperature (in practice, in an optimum temperature range) for the thermal decomposition (pyrolysis) process to occur.
  • the syngas temperature is generally required to lie in the range 400°C to 450°C.
  • a practical operating temperature for the process gas is 800°C to 825°C, which typically provides a thermal processing temperature in the chamber of about 400°C to 800°C.
  • the feedstock entering a waste pyrolysis unit is generally not homogeneous, and may vary, for example, in chemical composition and/or water content.
  • the syngas leaving the pyrolysis chamber is likely to have variable fuel (calorific) content and/or a variable temperature.
  • the energy required to pyrolyse the feedstock is likely to be variable for the same reason.
  • the invention relates to a control method used to ensure that adequate process energy is delivered for thermal decomposition of the feedstock in the pyrolysis chamber to occur, whilst at the same time maintaining the process gas temperature (T1 ) and the temperature of the syngas leaving the pyrolysis chamber (T2) within desired limits.
  • the invention allows a waste pyrolysis system to be operated in a controlled, near steady state, despite variations in feedstock, thereby improving throughput, reliability and efficiency. It is known to provide pyrolyser process heat using a combination of a syngas burner and a start-up (preferably diesel) burner, the syngas burner being supplied by synthesis gas fed back from the pyrolysis unit.
  • a syngas burner preferably diesel
  • start-up preferably diesel
  • WO 201 1/007125 discloses the use of the syngas produced from the pyrolysis to at least partially produce the heat needed to maintain the pyrolysis process, the syngas preferably being conveyed by a variable speed pump.
  • WO 201 1/007125 discloses that the system may be provided with various temperature, pressure and flow sensors throughout to assist in maintaining and monitoring the system, no specific method is disclosed for ensuring precise control of energy input and syngas temperature.
  • the inventors have found that, in practice, reliable and consistent control of the pyrolysis process can be difficult to achieve, particularly in view of the aforementioned variations in feedstock.
  • the solution offered by the invention is a control method in which the process gas temperature and process energy are controlled independently, thereby enabling the optimum process conditions to be maintained at all times. This is made possible by controlling the syngas burner so as to maintain at least one of the inlet temperature T1 and the outlet temperature T2 within pre-determined limits.
  • temperature T1 is maintained within pre-determined limits by controlling the flow of syngas through the syngas burner. If the calorific content of the syngas remains constant or substantially constant, the flow of syngas is controlled such that it remains constant or substantially constant. If the calorific content of the syngas decreases, the flow of syngas can be increased to maintain T1 within the desired, pre-determined operating range. Conversely, if the calorific content of the syngas increases, the flow of syngas can be decreased to maintain T1 within the pre-determined limits.
  • the flow of syngas can be varied in any suitable way, but it is preferred that the syngas burner comprises a variable speed fan and the flow of the syngas is varied by adjusting the speed of the fan. The fan should preferably be capable of operating at elevated temperatures.
  • the syngas burner may comprise a fixed speed fan and flow valve and the flow of syngas is controlled by the flow valve.
  • Other suitable methods will occur to the skilled person.
  • the pre-determined limits for T1 can be thought of as a set point. If T1 drops below the set point, flow through the syngas burner can increase to introduce more syngas fuel. If T1 increases above the set point, the flow can decrease to introduce less syngas fuel. This allows the control method of the invention to account for variations in the calorific value of the syngas. If T1 drops below the set point and the syngas burner flow rate is already at its maximum, an additional fuel can be used as supplementary heating for the process gas.
  • the syngas burner typically comprises an air inlet valve so as to introduce air for the burner (combustion) process and preferably, temperature T2 is maintained within pre- determined limits by adjusting said valve. Because the inlet temperature T1 preferably remains substantially constant, a decrease in T2 below its set point generally results from feedstock variations (amount, composition, humidity etc of feedstock). Hence, a decrease in temperature T2 generally indicates that more energy needs to be introduced into the pyrolysis unit. In the method of invention, this can be achieved by increasing the setting of (i.e. opening) the air inlet valve, thereby increasing the flow rate of process gas into the pyrolysis unit and delivering more energy to the feedstock. Conversely, decreasing the setting of (i.e.
  • temperature T2 is maintained within pre-determined limits by opening the air inlet valve if the temperature goes below its set point and closing the air inlet valve if the temperature goes above its set point.
  • the syngas burner is controlled such that both T1 and T2 are maintained within pre-determined limits.
  • the pre-determined limits will typically be different limits.
  • Synergistic control of T1 and T2 allows process temperatures to remain within the required limits, whilst also providing an optimum amount of energy delivered to the feedstock.
  • T1 is used to control the process temperature and T2 is used to control the process energy.
  • the syngas burner is operated in lean combustion mode. This means that there is an excess of oxygen available for syngas combustion. As a result, opening the inlet air valve leads to a reduced process gas temperature T1.
  • the method comprises the further step of deriving process gas from burning an additional fuel.
  • the pyrolysis system preferably comprises an additional burner.
  • the syngas burner can be configured to burn an additional fuel.
  • the additional fuel is burnt prior to pyrolysis and/or when the calorific energy of the syngas is insufficient to maintain T1 within the pre-determined limits.
  • the additional fuel is diesel or gas (preferably natural gas).
  • the system may comprise a diesel burner or gas burner.
  • Figure 1 is a prior art pyrolysis unit
  • Figure 2 is a schematic representation of a pyrolysis system capable of implementing the method of the invention.
  • Figure 1 is a prior art pyrolysis unit as described above.
  • FIG 2 is a schematic representation of a pyrolysis system capable of implementing the control method of the invention.
  • the system comprises a pyrolysis unit 50, an optional cyclone 60 to remove particulate material or fly-ash, a syngas burner 90 and an optional further burner 100.
  • the syngas burner comprises a variable speed fan 70 and a variable air inlet valve 80.
  • the pyrolysis unit 50 is of the type illustrated in Figure 1 , but for convenience the detailed structure (including the feedstock inlet and char outlet) are not shown.
  • Temperature sensors are located at positions A and B to measure, respectively, the process gas temperature T1 and the syngas outlet temperature T2. The arrows indicate the direction of gas flows.
  • the optional further burner takes the form of an additional fuel inlet to syngas burner 90.
  • syngas (which consists primarily of carbon monoxide and hydrogen) is drawn from pyrolysis unit 50 to the optional cyclone 60.
  • the majority of the syngas is generally fed to a combustor 1 10 to derive energy from the plant, but at least a portion of the syngas (typically around 5% to 15%) is fed back to the pyrolysis unit via the syngas burner 90.
  • the optional further burner can be used to maintain the temperature of the process gas if the calorific value of the syngas is insufficient to sustain pyrolysis (indicated by T1 decreasing below the set limit when the variable speed fan is at its maximum setting).
  • the control method of the invention maintains temperatures T1 and T2 within predetermined limits, whilst also controlling the thermal energy delivered to the pyrolysis unit 50. This is achieved by varying the following parameters, in the manner described generally above:
  • the target temperature for T2 (i.e. the pre-determined limits) lies in the range 400°C to 450°C. This is achieved by supplying a variable rate of hot process gas at a target temperature T1 in the range 800°C to 825°C. T1 is maintained in its target range by varying the speed of syngas fan 70.
  • the aforementioned method controls the process energy as well as the process gas, leading to good process control.
  • the system can be optimised despite variations in feedstock.
  • the diesel burner is rated at 260kW and when ON operates in the range of 20 to 100% capacity.
  • the diesel burner controls the process gas temperature, T1 , to about 775°C.
  • the process gas temperature is ramped-up from its initial value to 750°C at a rate of 3°C per minute. Once the process gas temperature reaches 750°C and the temperature requirements at the outlet are satisfied the plant control switches to "Process Mode".
  • the syngas burner comprises a hot gas fan operating at between 40 to 100% maximum speed. Typically, in “Start-up Mode” the hot gas fan operates at maximum speed. Once pyrolysis of feedstock has commenced (in “Process Mode”) the hot gas fan is used to control the process gas temperature, T1 , so that it lies in the range 800°C to 825°C, by increasing its speed to increase the gas temperature and reducing the speed to reduce the gas temperature.
  • the combustion air valve has a set-point minimum which is typically around 25 to 40%. The air valve controls syngas outlet gas temperature, T2, to so that it lies in the range 400°C to 450°C by gradually closing to cool gases and opening to increase gas temperature. If T2 increases above the set point, the air valve goes to its minimum setting.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Gasification And Melting Of Waste (AREA)

Abstract

L'invention concerne un procédé de mise en œuvre d'un système de pyrolyse du type comprenant (i) une unité de pyrolyse (50) pour une charge d'alimentation, l'unité de pyrolyse (50) comportant une entrée pour un gaz de procédé chaud et une sortie pour un gaz de synthèse produit à partir de la charge d'alimentation pyrolysée et (ii) un brûleur de gaz de synthèse (90) pour dériver du gaz de procédé d'au moins une partie du gaz de synthèse, qui comprend l'étape de régulation du brûleur de syngaz (90) une fois que la pyrolyse de la charge d'alimentation a commencé de façon à maintenir au moins une parmi la température d'entrée T1 et la température de sortie T2 entre des limites prédéterminées.
PCT/EP2013/074502 2012-12-07 2013-11-22 Procédé de mise en œuvre d'un système de pyrolyse Ceased WO2014086600A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB201222045 2012-12-07
GB1222045.5 2012-12-07

Publications (1)

Publication Number Publication Date
WO2014086600A1 true WO2014086600A1 (fr) 2014-06-12

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PCT/EP2013/074502 Ceased WO2014086600A1 (fr) 2012-12-07 2013-11-22 Procédé de mise en œuvre d'un système de pyrolyse

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6005149A (en) * 1998-08-18 1999-12-21 Engineering, Separation & Recycling, Ltd. Co. Method and apparatus for processing organic materials to produce chemical gases and carbon char
EP1936127A2 (fr) * 2006-09-11 2008-06-25 Hyun Yong Kim Réacteur de gazéification et cycle de turbine à gaz dans un système IGCC
WO2010118513A1 (fr) * 2009-04-17 2010-10-21 Proterrgo Inc. Procédé et appareil pour la gazéification de déchets organiques
WO2011007125A2 (fr) 2009-07-14 2011-01-20 Process Limited Pyrolyseur
US20120085023A1 (en) * 2010-10-08 2012-04-12 Teal William B Biomass torrefaction system and method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6005149A (en) * 1998-08-18 1999-12-21 Engineering, Separation & Recycling, Ltd. Co. Method and apparatus for processing organic materials to produce chemical gases and carbon char
EP1936127A2 (fr) * 2006-09-11 2008-06-25 Hyun Yong Kim Réacteur de gazéification et cycle de turbine à gaz dans un système IGCC
WO2010118513A1 (fr) * 2009-04-17 2010-10-21 Proterrgo Inc. Procédé et appareil pour la gazéification de déchets organiques
WO2011007125A2 (fr) 2009-07-14 2011-01-20 Process Limited Pyrolyseur
US20120085023A1 (en) * 2010-10-08 2012-04-12 Teal William B Biomass torrefaction system and method

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