Classifications

• • 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
  • B01D53/68—Halogens or halogen compounds
  • B01D53/70—Organic halogen compounds
• • 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
  • B01D53/68—Halogens or halogen compounds
• • 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 
  • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
  • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
  • F23C6/045—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/32—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid using a mixture of gaseous fuel and pure oxygen or oxygen-enriched air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/46—Details, e.g. noise reduction means
  • F23D14/70—Baffles or like flow-disturbing devices
• • 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
  • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
  • F23G7/061—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases with supplementary heating
  • F23G7/065—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases with supplementary heating using gaseous or liquid fuel
• • 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 
  • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
  • F23C2900/06041—Staged supply of oxidant
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2215/00—Preventing emissions
  • F23J2215/10—Nitrogen; Compounds thereof

Definitions

• the invention relates to a device for cleaning pollutant-containing exhaust gases in a combustion chamber by means of thermal-chemical conversion.
• pollutant-containing exhaust gases are produced.
• An important group of such exhaust gases contains, in particular, fluorine-containing hydrocarbons or other fluorine compounds.
• most of the exhaust gas contains nitrogen as the carrier gas.
• the pollutants or their reaction products are toxic and polluting and must therefore be removed from the exhaust gas by cleaning them in a suitable facility.
• the pollutants of the exhaust gas are thermochemically converted in a combustion chamber in which a flame acts by burning a fuel gas in pure oxygen or in air (US 5183646). Secondary products of this conversion (e.g. HF), which also have a harmful effect, are subsequently removed from the exhaust gas treated in the combustion chamber by sorption or washing processes.
• a flame acts by burning a fuel gas in pure oxygen or in air (US 5183646).
• Secondary products of this conversion e.g. HF
• HF which also have a harmful effect
• a multi-stage process is usually carried out in facilities for exhaust gas purification.
• Sub-processes take place, such as the thermal-chemical decomposition, the oxidation, the cooling, the sorption, the hydrolysis and the washing out of liquid and solid reaction products.
• the exhaust gas is passed in succession through a combustion chamber and at least one further process device, for example one that works on the washing principle. (EP 89 110 875, DE 43 200 447).
• a device for exhaust gas purification a number of objectives have to be met: The purification must ensure high efficiency, ie for the cleaned exhaust gas, the lowest possible level of primary pollutants can be achieved. It is still possible to effectively remove secondary pollutants in the washing section.
• the combustion chamber is generally designed as a cylindrical body, in one end face of which the burner, most often an annular burner, is inserted.
• This ring burner is fed, mostly centrally, the exhaust gas and, in the simplest case, through a ring gap a fuel gas mixture. After ignition by means of an ignition device, a flame forms over the annular gap, into which the exhaust gas is introduced.
• An increase in the proportion of fuel gas in relation to oxygen compared to the stoichiometric ratio ( ⁇ value ⁇ 1) improves the conversion of pollutants and reduces nitrogen oxide formation, but leads to the emission of harmful carbon monoxide and unburned fuel gas from the gas cleaning device.
• an increase in the proportion of oxygen in the fuel gas-oxygen mixture compared to the stoichiometric ratio ( ⁇ value of the mixture supplied> 1) leads to a critical deterioration in the conversion of pollutants, especially for fluorine-containing exhaust gases, and thus to unacceptably high residual pollutant proportions in the cleaned exhaust gas.
• harmful nitrogen oxides are formed in an oxygen-rich, hot flame.
• an excess of fuel gas ( ⁇ ⁇ l) compared to the stoichiometric ratio to oxygen over the inner ring gap or the inner bores makes a flame area with a reducing effect
• an excess of oxygen ( ⁇ > l) over the outer ring gap or the outer bores makes it an oxidizing one Flame area created (EP 0 735 321 A2).
• reducing reactants such as H atoms and CH X radicals
• pollutant molecules are broken down to a greater extent in the flame region with a 0 2 deficit. The fuel gas supplied is not completely consumed here.
• burners In order to be able to effectively purify larger exhaust gas volumes, burners have therefore been proposed in which two reducing flame areas are realized via two concentric rings or via bores on two concentric circles of holes. Both flame areas are operated with fuel gas-oxygen mixtures with ⁇ values ⁇ 1 in order to increase the volume in which the conditions favorable for the conversion of pollutants arise
• This solution also has the disadvantage that the reducing flame area, which is advantageous for the conversion of pollutants, due to the oxygen absorption on the circumference of the flame is restricted.
• the additional oxygen inlet in the vicinity of the burner in the flame reaches such high temperatures that harmful nitrogen oxides are formed there.
• the separate supply of fuel gas and oxygen to the burner allows extensive variation of the operating conditions with regard to the type of harmful gas and the amount of exhaust gas during operation without structural changes to the burner.
• the adjustment is made by the quantities of fuel gas and oxygen supplied.
• Exhaust gas treatment in a reducing and oxidizing flame area is also possible with separate fuel gas and oxygen feeds to the burner.
• a burner with two concentric slots or bores on two concentric circles of holes is suitable for this.
• An additional supply of oxygen or air from the surroundings of the burner into the jacket of the flame creates an oxidizing flame area in which the reaction of the remaining fuel gas and the oxidation of CO formed in the reducing flame area in CO 2 takes place.
• the object of the invention is to eliminate deficiencies in the prior art in the devices used for this purpose in the purification of exhaust gases by means of thermal-chemical conversion. With a high exhaust gas volume to be cleaned, high efficiency of pollutant removal and a favorable economy with regard to the use of fuel gas must be guaranteed. Soot deposits on the burner should be avoided. A very low proportion of unburned fuel gas, carbon monoxide and especially nitrogen oxide can be achieved in the cleaned exhaust gas.
• the object is achieved by a device according to claims 1 to 13.
• the purification of pollutant-containing exhaust gases in particular those with fluorocarbon and other fluorine-containing compounds and with nitrogen as the carrier gas, by thermo-chemical conversion in a cylindrical combustion chamber with one burner and in a unit with a subsequent one Washing section takes place.
• the burner has a central exhaust gas supply.
• the fuel gas and oxygen are fed separately to the burner up to its outlet nozzles to form a flame.
• the treated hot exhaust gas from the combustion chamber is aftertreated in a washing section with a detergent.
• the hot exhaust gas is cooled and harmful secondary products are also removed from the exhaust gas.
• holes are made in the burner, a ring burner, for the separate supply of fuel gas and oxygen on a single hole circle around the central exhaust gas supply.
• the separate supply is accomplished by alternately admitting fuel gas and oxygen through adjacent holes.
• two ring channels are arranged in the ring burner, which are alternately connected to the holes on the bolt circle.
• a connecting pipe leads out of the burner from each ring channel. Fuel gas is supplied through one connecting pipe, and oxygen is fed into the burner through the second.
• the ring burner ensures the formation of a stable and homogeneous flame with effective energy release for a wide variety of fuel gas and oxygen flows, which is a prerequisite for adaptation to different harmful gases and different exhaust gas flows. Burners with adapted holes do not have to be exchanged for adaptation.
• the burner is not only suitable for fluorocarbons and other fluorine compounds, but also for the disposal of reactive pollutants such as SiH 4 , WF 6 and TEOS.
• said burner is used in a combustion chamber which is closed except for an annular gap between the cylindrical jacket and the end face of the combustion chamber opposite the burner. In this way, no air, ie no oxygen, flows into the surroundings of the burner, for example through slots in the combustion chamber wall.
• the combustion chamber is at least so tight that less than about 3% of the oxygen admitted into the burner can flow in from the environment as air.
• the burner is operated with a separate supply of fuel gas and oxygen with an excess of fuel gas, which corresponds to a mixture with a ⁇ value of, for example, 0.8, not only does a reducing flame area form above the burner, but the entire flame acts reducing the thermal-chemical conversion of the pollutants. Since no air flows in from the surroundings of the burner, so too no oxygen acts on the flame, reducing conditions occur, particularly on the flame's mantle. Ultimately, there are reducing conditions in almost the entire volume of the combustion chamber. In this way, in a larger volume - compared to the volume of a flame with reducing and oxidizing flame areas - there is a high concentration of H atoms and CH 3 radicals as reaction partners for the conversion of the pollutants (e.g.
• the temperature of the device according to the invention can be kept relatively lower (T ⁇ «1200 °) compared to the operation of a device with reducing and oxidizing flame areas.
• the beneficial influence of temperature on the reactions is compensated or overcompensated by the higher concentration of the reducing reactants.
• a high efficiency of the conversion of pollutants is achieved at a relatively lower temperature.
• the hot exhaust gas stream contains at the outlet of the cylindrical jacket of the combustion chamber in the described mode of operation in addition to the reaction products of the combustion and the thermal-chemical conversion, in particular C0 2 , HF, CO and H 2 0, because of the oxygen deficit in the combustion chamber still unburned fuel gas, (CH 4 and Co).
• the hot exhaust gas is not completely oxidized at the end of the combustion chamber.
• the exhaust gas stream is subjected to further oxidation for complete combustion.
• a plurality of, but at least two, pipes distributed around the circumference and directed towards the axis of the combustion chamber for the additional supply of oxygen are placed in the annular gap between the cylindrical jacket of the combustion chamber and the end face of the combustion chamber opposite the burner or air arranged.
• the additional supply of oxygen or air takes place via an annular channel arranged on the end face of the cylindrical jacket of the combustion chamber and evenly distributed over the circumference in the said annular gap.
• a body preferably a plate, made of a heat-resistant material is arranged in a heat-insulated manner, for example via retaining webs, in front of the end face of the combustion chamber.
• the hot exhaust gas stream hits this plate.
• it is first deflected by 90 ° and distributed radially.
• the hot exhaust gas flow is swirled as a result of the deflection and the radial distribution.
• Said plate prevents contact of the hot exhaust gas flow with the end face of the combustion chamber.
• the end face is relatively cold, since at the same time it represents the boundary to the washing section, that is, it is cooled by the washing liquid (T in the range from 20 ° to 90 ° Celsius).
• the heat-insulated plate on the other hand, almost takes on the temperature of the hot exhaust gas flow on the side towards the combustion chamber, ie T> 800 ° Celsius.
• inflowing oxygen or inflowing air
• a ⁇ value> 1, preferably ⁇ 1.2, is established here in the mixture of supplied oxygen (or supplied air) and hot exhaust gas. So much oxygen (or air) is admitted that the oxygen deficit in the combustion chamber is at least compensated.
• the exhaust gas flows into the washing section. It is used to cool the hot exhaust gas flow and neutralize HF as well as wash out solid particles that have arisen as a result of the combustion.
• the cleaned and cooled exhaust gas is then fed into the exhaust air duct of the manufacturing plant.
• Advantages of using the device according to the invention are that a reduction in the required specific amount of fuel gas and thus an improvement in the economy of exhaust gas purification is ensured.
• the reduction in the required amount of fuel gas is achieved by the reduced total throughput (total flow) due to the excluded supply of air or 0 2 into the surroundings of the burner.
• the special solutions ensure a high efficiency of the pollutant conversion in the combustion chamber.
• the solution for the burner also guarantees stable flame formation with a wide variety of ratios of fuel gas to oxygen, with a wide variety of harmful gases in the exhaust gas and for different amounts of harmful gas without any design adjustments to the burner.
• a particularly significant advantage is the drastic reduction in nitrogen oxide discharge with the cleaned exhaust gas. This discharge is about a factor 5 lower than in a device according to the prior art with a ring burner and with the supply of a fuel gas-oxygen mixture and with the supply of additional oxygen into the area of the ring burner, which was operated under comparable conditions ,
• Another advantage of the device according to the invention is that it is structurally unchanged also suitable for cleaning exhaust gases with pollutants, the thermal-chemical conversion of which requires a relatively small amount of energy, e.g. by SiH.
• the bores which are evenly distributed on the bolt circle around the central exhaust gas supply, are made with two different diameters. If the burner is e.g. operated with methane and oxygen and if reducing conditions are to be set in the combustion chamber which correspond to a ⁇ value of 0.8 of the inflowing and mixing gases (fuel gas and oxygen) immediately above the burner surface, then the required gas flow of methane about a factor of 0.6 less than that for oxygen.
• the execution of bores with surfaces which differ by the factor mentioned offers the possibility of adapting the outflow velocities of the two gases in the bores on the burner to one another. This allows e.g. improve the stability of the flame.
• the alternately separate supply of fuel gas and oxygen into adjacent bores on the burner surface is ensured by the fact that two ring channels are made inside the burner and the bores in the burner surface are alternately connected to one of these ring channels.
• the burner has a supply for fuel gas for one of these ring channels and a supply for oxygen for the other ring channel.
• this body in the form of a spherical cap with a depth of Curvature from 15 mm to 60 mm, preferably 20 mm, made of heat-resistant, corrosion-resistant steel with a diameter larger than that of the combustion chamber, but smaller than the diameter of the end face and with the concave side towards the ring burner, to be arranged in a heat-insulating manner.
• this body in the form of a spherical cap with a depth of Curvature from 15 mm to 60 mm, preferably 20 mm, made of heat-resistant, corrosion-resistant steel with a diameter larger than that of the combustion chamber, but smaller than the diameter of the end face and with the concave side towards the ring burner, to be arranged in a heat-insulating manner.
• the said tubes extend approximately 15 mm to 50 mm, preferably 25 mm, over the edge of the end face of the combustion chamber into the gap between and the cylindrical jacket of the combustion chamber and the end face, but not over the edge of the cylindrical jacket. This measure ensures that no detergent gets into pipes for the additional supply of oxygen (or air) and that the ends of said pipes do not overheat and thus corrode.
• a ring channel for the additional supply of oxygen (or air) in the said annular gap
• the ring channel has a width of 1.5 to 2 mm.
• Fig. 1 A device for purifying exhaust gas in a schematic longitudinal section with the supply of additional oxygen via pipes
• FIG. 2 A device for purifying exhaust gas in a schematic longitudinal section with supply of the additional oxygen via a ring channel.
• Fig. 3 The schematic view of a ring burner.
• Fig. 4 The schematic cross section of a ring burner
• the device consists essentially of a cylindrical combustion chamber (1) made of corrosion-resistant material in a housing (2) which is made of corrosion-resistant steel.
• the combustion chamber has a diameter of 100 mm and a height of 400 mm.
• the combustion chamber is sealed off from the outside in the area of the base plate (3) and the cylindrical shell (4).
• the ring burner (5) with an outer diameter of 50 mm is arranged centrally in the base plate (3).
• the ring burner (5) has a central bore (6) with a diameter of 12 mm with the connection (9) for the inlet of the exhaust gas into the combustion chamber (1).
• the ring burner (5) In the surface of the ring burner (5) are evenly distributed on a bolt circle (28) of 30 mm in diameter and alternately in diameter bores (7) of 1 mm in diameter and bores (8) of 1.2 mm in diameter for the separate supply of Fuel gas and oxygen in the ring burner (5).
• the combustion gas is fed to the ring burner via the connection (10) and the oxygen via the connection (11).
• the supplied fuel gas is distributed through the ring channel (29) and the supplied oxygen through the ring channel (30).
• the bores (7) are connected to the ring channel (29) and the bores (8) to the ring channel (30).
• the flame (14) Due to the ⁇ value of the mixture of the separately supplied oxygen and the separately supplied CH, the flame (14) has a reducing effect over its entire cross-section after complete formation. Since no air, that is to say no oxygen, acts on the flame from outside in the area of the ring burner (5), the reducing effect on this is
• Harmful gas is also given in the jacket of the flame and more or less in the entire volume (17) of the combustion chamber (1).
• the conversion of CH 4 , 0 2 , and C 2 F 6 into HF, C0 2) CO and H 2 0 essentially takes place.
• the formation of nitrogen oxide is largely avoided .
• a mixture of hot treated exhaust gas (from N 2 , HF, C0 2 and CO) and still unburned CH 4 flows at a temperature in the range from 800 ° to 1200 ° Celsius in the direction of arrows (18) from the cylindrical part of the combustion chamber (1) towards the hot body (19).
• the cooled end face (16) is also designed as a dome with a dome depth of 40 mm.
• the convex side of the cooled end face (16) points towards the washing section (25). In the gap
• the tubes (21) are connected outside the housing (2) via a ring line (22), to which additional oxygen is supplied via the connection (23). 11 slm of oxygen are blown through the tubes (21) at a speed of approximately 60 ms "1 .
• a double tube (33) is arranged concentrically with the cylindrical combustion chamber (4) in such a way that an annular channel (32) is arranged between the cylindrical combustion chamber and the double tube. is forming. Additional oxygen is introduced into the annular gap (20) approximately uniformly distributed over the circumference via this ring channel. Oxygen (or air) is supplied to the ring channel via a connection (34) at the other end of the ring channel. 20 slm of oxygen (or 100 slm of air) are fed into the ring channel (32).
• the exhaust gas treated in this way flows in the direction of the arrows (24) from the gap (20) in the direction of the washing section (25). This is fed through the connection (26), the washing liquid (27). It cools the hot exhaust gas below 50 ° C.
• the proportion of hydrogen fluoride (HF) in the cooled exhaust gas is hydrolyzed and neutralized in the washing liquid, a 1.0% sodium hydroxide solution.
• the cleaned exhaust gas is discharged into the environment in the direction of arrows (31) via a suction device or via the central exhaust air system of the semiconductor production.
• the proportion of carbon monoxide in the cleaned exhaust gas is 10 ppm.
• the discharge of nitrogen oxides is drastically reduced, it is only «0.1 mol m " in the example of exhaust gas purification. designations
• Combustion chamber volume 18. Arrows

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• 2003
  • 2003-04-04 JP JP2003582467A patent/JP2005522660A/ja active Pending
  • 2003-04-04 WO PCT/EP2003/003517 patent/WO2003085321A1/de active Application Filing

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