EP0281569A1 - Procede d'application d'une technique de combustion et appareil destine a etre utilise dans ledit procede - Google Patents

Procede d'application d'une technique de combustion et appareil destine a etre utilise dans ledit procede

Info

Publication number
EP0281569A1
EP0281569A1 EP87902586A EP87902586A EP0281569A1 EP 0281569 A1 EP0281569 A1 EP 0281569A1 EP 87902586 A EP87902586 A EP 87902586A EP 87902586 A EP87902586 A EP 87902586A EP 0281569 A1 EP0281569 A1 EP 0281569A1
Authority
EP
European Patent Office
Prior art keywords
combustion
flowpath
reducing agent
burner
signals
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Withdrawn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
EP87902586A
Other languages
German (de)
English (en)
Inventor
Brian Wills
Gary Johns
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.)
Fives North America Combustion UK Ltd
Original Assignee
Fives North America Combustion UK 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 Fives North America Combustion UK Ltd filed Critical Fives North America Combustion UK Ltd
Publication of EP0281569A1 publication Critical patent/EP0281569A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/56—Nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/235—Heating the glass
    • C03B5/237—Regenerators or recuperators specially adapted for glass-melting furnaces
    • 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
    • F23L15/02—Arrangements of regenerators
    • 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
    • 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
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping

Definitions

  • a method of treating a gaseous mixture resulting from a combustion process and containing free oxygen and oxides of nitrogen in a method in accordance with the first aspect of the invention, a stream of said gaseous mixture is directed along a flowpath, there are obtained first and second signals which are respectively dependant on the concentration of oxygen in the stream at first and second positions along said path, a reducing agent is fed to said stream at a controlled rate to react between said first and second positions with said oxides and with oxygen present in the mixture and wherein said first and second signals are used together in controlling the rate at which the reducing agent is fed to said stream.
  • the method of the invention may be applied to the combustion of fuel using regenerative burners.
  • a regenerative burner has a heat store used to cool products of combustion and, subsequently, to impart heat to air which is to be used for combustion.
  • Regenerative burners are normally used in pairs, the burners of the pair being operated alternately. In a first part of a cycle of operation, air flows through the heat store of one burner and is discharged from the burner with fuel into a combustion space which is common to the pair of burners. Hot products of combustion pass from the combustion space through the heat store associated with the other burner and transfer heat to that heat store.
  • the direction of airflow is reversed and air flows through the hot heat store to the combustion space, being heated by heat exchange with the heat store, so that heat recovered from the products of combustion during the first part of the cycle is returned to the combustion space.
  • This results in efficient operation by which we mean that the products of combustion carry to the atmosphere a relatively small proportion of the heat released by combustion of the fuel.
  • a disadvantageous consequence is that the temperature attained in the combustion space is relatively high. This promotes formation of oxides of nitrogen.
  • the temperature in the heat storage means varies. The variation may be with respect to time, with respect to position or with respect to both of these parameters.
  • the temperature at a selected position along the path will increase during the first part of the cycle and will decrease during the second part of the cycle.
  • the first position is preferably in or immediately adjacent to one of the burners and the second position is downstream of or is at the downstream end of the heat store associated with that burner, considering the direction of gas flow which applies when products of combustion are discharged from the combustion space through that burner and heat store.
  • the reducing agent may be added downstream of the combustion space and is preferably introduced Into the stream of gaseous mixture upstream of the heat store which receives heat from that mixture, preferably within the associated burner.
  • apparatus for the combustion of a fuel in air comprising means defining a combustion space, means defining a flowpath for conducting products of combustion from the combustion space to the atmosphere, first and second signalling means arranged to provide respectively first and second signals which are dependant on the concentration of oxygen in the contents of said flowpath at first and second sensing positions respectively, said sensing positions being spaced apart along the flowpath, means for feeding a reducing agent into said flowpath at a position between said first and second sensing positions and control means for controlling the rate at which reducing agent is fed into the flowpath, the control means being arranged to receive said first and second signals and to vary the rate of feed of reducing agent in a manner dependant on the relation between said first and second signals.
  • the apparatus illustrated in the drawing comprises a pair of burners 10 and 1 1 , each of which is arranged for discharging fuel and air into a common combustion space 12.
  • the combustion space may be the interior of a furnace or the interior of a radiant heating element.
  • the radiant heating element may be disposed in a heating chamber of a furnace.
  • the furnace is of known construction having thermally insulated walls with a refractory lining and will not be further described.
  • the furnace may be arranged for heating workpieces which are fed continuously through the furnace chamber, for heating workpieces which are placed in the chamber for a predetermined period or for heating a fluid contained in a heat exchanger disposed in the furnace chamber or incorporated in the walls thereof.
  • Fuel supply means is provided for supplying fluid fuel to the burners.
  • the fuel supply means includes ducts 13 extending from a supply of fuel, for example a natural gas main, to the burners and appropriate valves 14 and 15 for controlling flow of fuel to the burners.
  • a supply of fuel for example a natural gas main
  • valves 14 and 15 for controlling flow of fuel to the burners.
  • two only valves are shown in the fuel supply means but a larger number of valves would normally be provided, some being intended to exercise control over the fuel flow rate and others intended to prevent the supply of fuel to a burner unless it is appropriate and safe for fuel to be supplied to that burner.
  • a heat store 16 comprising a vessel which contains a bed of refractory elements 17. At one of its ends, the vessel communicates with the burner 10 and at its opposite end the vessel communicates through a duct 18 with a change-over valve 19.
  • a similar vessel 20 containing a bed 21 of refractory elements is associated with the burner 1 1 and connected with the changeover valve by a duct 22.
  • Air supply means of the apparatus comprises a fan 23 arranged for blowing air along one or other of the ducts 18 and 22 through one or other of the heat stores to the corresponding burner.
  • an exhaust fan 24 for drawing products of combustion through one of the burners and the associated heat store and discharging such products of combustion to the atmosphere.
  • the vessels 16 and 20 may be steel vessels and may have thermally Insulated walls.
  • the refractory elements contained in these vessels, or at least some of these refractory elements, are preferably ceramic bodies. The size of each ceramic body is small, as compared with the volume of the vessel in which it is disposed.
  • the parts thus far described may be constructed and arranged in a known manner. Furthermore, there would be provided for each burner a pilot burner which will Ignite fuel discharged from that burner into the combustion space 12.
  • the apparatus includes a control system comprising appropriate sensors, timing devices and valves for operating the burners alternately and checking that the conditions of operation are safe.
  • the control means may comprise a micro-processor.
  • the refractory elements In both of the heat stores may be cold.
  • the valve 1 Is set to direct air from the fan 23 along the duct 18 to the burner 10 and fuel is discharged with air from this burner into the combustion space 12 and is ignited by the associated pilot burner.
  • the valve 19 also directs products of combustion from the combustion space 12, through the burner 1 1 and the heat store 20 to the exhaust fan 24.
  • a period of operation which may be a predetermined period (for example a period within the range 1 to 4 minutes) or which may be such period as Is required to attain a predetermined temperature at a predetermined position in the apparatus, the valve 19 Is operated to bring to an end a first part of the cycle.
  • the valve 19 directs air from the fan 23 through the duct 22 and the heat store 20 to the burner 1 1. Fuel Is discharged with the air from this burner into the combustion space and is ignited by the associated pilot burner. Air which flows through the heat store 20 is heated by contact with the hot, ceramic elements 21 and these elements are cooled.
  • the cycle is brought to an end by operation of the valve 1 when either the predetermined period has elapsed or a predetermined temperature has been attained at a further predetermined position in the apparatus.
  • hot products of combustion pass through the burner 10 to the heat store 16 and impart heat to the refractory elements 17 before passing to the exhaust fan 24.
  • the second part of the cycle also has a duration of at least one minute.
  • air and fuel are fed continuously to the burner 1 1, preferably at rates which are the same as those at which the fuel and air were fed to the burner 10 during the first part of the cycle.
  • the apparatus includes means for reacting at least lower oxides of nitrogen to reduce the concentration thereof in gases discharged to the atmosphere.
  • the apparatus includes feed means 25 for feeding a reducing agent into the hot products of combustion.
  • the feed means includes a bulk supply 26 of the reducing agent and a number of ducts, examples of which are represented at 27, 28, 29 and 30, for discharging the reducing agent into the paths along which products of combustion flow rrom the combustion space 12 to the valve 19 at alternative positions along those paths.
  • Valves are provided for controlling flow along the ducts 27 to 30. These valves are incorporated in the control means and subjected to control by the microprocessor.
  • reducing agents may be discharged into those products of combustion through the duct 28 only at a position upstream of the heat store 20, prefarably into the burner I I , as shown.
  • Flow of the gaseous mixture through the bed of refractory elements 2 ! promotes thorough mixing of the gases so that the reducing agent is distributed throughout the products of combustion.
  • the reducing agent is a gas, at least at the temperatures prevailing in the passage connecting the burner 1 1 with the heat store 20.
  • Oxides of nitrogen are reduced by the reducing agent in the heat store 20 so that the concentration of oxides of nitrogen in the gases passing through the exhaust fan 24 are small, as compared with the concentration present in the combustion space 12.
  • the reducing agent may be admitted through the duct 27 into the bed of refractory elements 21 at a position where the temperature is substantially below that in the combustion space 12. Whilst a single duct for discharging reducing agent Into the bed of elements 21 has been illustrated, a number of alternative ducts for introducing the reducing agent at a selected one of several alternative positions in the bed may be provided. Information received by the microprocessor from temperature sensing devices at appropriate positions may be used to determine the position at which the reducing agent should be introduced into the products of combustion.
  • a suitable reducing agent is ammonia.
  • the bulk supply 26 of ammonia may be liquified ammonia or an aqueous solution of ammonia.
  • the control means Includes first sensing means 31 and second sensing 0 means 32 which are spaced apart along the flowpath defined collectively by the burner 1 1 , the heat store 20 and the duct 22.
  • the sensing means 31 is associated with the burner I I and is arranged to provide an electrical signal representative of the concentration of oxygen in gases flowing through the burner 1 1 , when products of 5 combustion are transferring heat to the heat store 20.
  • the sensing means 32 is arranged adjacent to the downstream end of the heat store 20 to provide an electrical signal representative of the concentration of oxygen in the gaseous mixture leaving the heat store and flowing towards the valve 19.
  • the sensing means 31 and 32 are commercially available oxygen-concentration sensors.
  • signals are fed from the sensing means 31 and 32 to the control means and are compared by the control means.
  • a difference signal Is provided, representing the change in the concentration of oxygen which occurs between the burner 1 1 and the downstream end of the 5 heat store 20.
  • This difference signal Is used to control the rate of flow of reducing agent into the burner 1 1 through the line 28 or into the heat store through the line 27.
  • the products of combustion leaving the combustion chamber contain up to 4,000 parts per million of oxides of nitrogen and up to 2% oxygen.
  • Ammonia is fed into the gaseous mixture at a rate such that reaction of approximately one tenth of the ammonia with the oxides of nitrogen (mainly nitric oxide) will reduce the concentration of oxides of nitrogen by more than 90%, typically leaving 400 parts per million of oxides of nitrogen in the gases which are discharged to atmosphere, almost all of the remainder of the ammonia reacting with oxygen present in the products of combustion to leave the concentration of oxygen downstream of the heat store 20 in the region of 1.5%.
  • sensing means 33 and 34 associated respectively with the burner 10 and duct 18 and corresponding to the sensing means 31 and 32 are used to control the rate of feed of reducing agent into the flowpath defined by the burner 10, heat store 16 and duct 18 in dependence on the change in the concentration of oxygen between the products of combustion leaving the combustion space and the products of combustion flowing to the valve 19.
  • the reducing agent is introduced to the stream of gases being exhausted from the combustion chamber at a position in the burner through which the gases are exhausted.
  • the delay between introduction of the reducing agent and cooling of the gas stream is short, owing to the proximity of the introduction position to the heat exchanger 20.
  • the reducing agent may be introduced at a position upstream of that illustrated in the drawing, for example at a position in the burner near to the combustion chamber, in the combustion chamber rather than in the burner or even in the burner through which fuel and air are supplied.
  • the furnace illustrated in the accompanying drawing may be modified by omission of the burner 1 1 and substitution of a single heat storage means for the separate heat stores 16 and 20 shown in the drawing.
  • the single heat storage means may comprise a rotating body of refractory elements arranged in a known manner so that the combustion air flowing along the duct 18 to the burner 10 is directed through the heat storage means along a first path whilst the hot products of combustion flow from the combustion space 12 to the duct 22 via a second path through the heat storage means.
  • the first and second paths through the heat storage means are separate from each other and each scan the entire heat storage means as the latter rotates. This arrangement is generally called a heat wheel.
  • a single heat storage means there may be provided a single pair of oxygen-concentration sensors, these being disposed one upstream of and one downstream of the heat storage means In the path along which products of combustion are exhausted from the combustion space 12.
  • the reducing agent would be admitted to this path via the duct 28 at a position between the sensors.
  • the duct 29 shown in the drawing for admitting reducing agent to the burner 10 would be omitted from the modified furnace.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Combustion & Propulsion (AREA)

Abstract

Un four à récupération est pourvu d'un organe (25) servant à introduire de l'ammoniaque dans des produits de combustion quittant un espace de combustion (12). La cadence d'addition de l'ammoniaque est régulée en fonction de la différence entre la concentration d'oxygène dans le mélange gazeux s'échappant de l'espace de combustion et la concentration d'oxygène en aval de l'accumulateur de chaleur (20) recevant la chaleur provenant du mélange gazeux.
EP87902586A 1986-09-19 1987-04-01 Procede d'application d'une technique de combustion et appareil destine a etre utilise dans ledit procede Withdrawn EP0281569A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8622593 1986-09-19
GB868622593A GB8622593D0 (en) 1986-09-19 1986-09-19 Carrying out combustion process

Publications (1)

Publication Number Publication Date
EP0281569A1 true EP0281569A1 (fr) 1988-09-14

Family

ID=10604461

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87902586A Withdrawn EP0281569A1 (fr) 1986-09-19 1987-04-01 Procede d'application d'une technique de combustion et appareil destine a etre utilise dans ledit procede

Country Status (3)

Country Link
EP (1) EP0281569A1 (fr)
GB (1) GB8622593D0 (fr)
WO (1) WO1988002088A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4780289A (en) * 1987-05-14 1988-10-25 Fuel Tech, Inc. Process for nitrogen oxides reduction and minimization of the production of other pollutants
JP2594301B2 (ja) * 1988-01-19 1997-03-26 バブコツク日立株式会社 脱硝装置を有する石炭焚きボイラ装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4188190A (en) * 1976-03-23 1980-02-12 Kurashiki Boseki Kabushiki Kaisha Input control method and means for nitrogen oxide removal means
JPS5372773A (en) * 1976-12-10 1978-06-28 Hitachi Ltd Direct reductive denitration method of ammonia
US4328020A (en) * 1980-11-24 1982-05-04 Ppg Industries, Inc. Melting glass with reduced NOx emissions
DE3409859A1 (de) * 1984-03-17 1985-09-19 Brown, Boveri & Cie Ag, 6800 Mannheim Denitrierung von abgasen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8802088A1 *

Also Published As

Publication number Publication date
GB8622593D0 (en) 1986-10-22
WO1988002088A1 (fr) 1988-03-24

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