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
  • B01D53/74—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
  • B01D53/8631—Processes characterised by a specific device
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/206—Ammonium compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/30—Sulfur compounds

Definitions

• the invention relates to a system for purifying the flue gases of a furnace with at least one selective reduction catalyst for the reduction of nitrogen oxides contained in the flue gas and / or with at least one catalyst for the reduction of carbon monoxide, especially odoriferous, hydrocarbons or ammonia removal, and a Dust separation, and a method for purifying the flue gases of a furnace by selective catalytic reduction of nitrogen oxides with a reducing agent and a reduction catalyst and by dust deposition.
• the flue gas denitration is usually carried out by reductive methods.
• SNCR selective non-catalytic reduction
• SCR selective catalytic reduction
• NO x nitrogen oxides
• a reducing agent - generally ammonia is used as a reducing agent - to elemental nitrogen and water, which subsequently as umweltunbedenkliche substances on the exhaust vent leave the incinerator.
• the selective non-catalytic reduction is usually carried out at temperatures between 900 ° C and 1100 ° C, wherein the reducing agent is fed directly into the furnace.
• the selective catalytic reduction can be carried out at significantly lower temperatures, since the catalyst significantly reduces the activation energies required for the reduction reactions.
• Object of the present invention is to provide a system for denitrification of flue gases after the selective catalytic reduction process (SCR) and a method to provide which (s) in comparison to low-dust concepts a lower energy consumption and compared to high-dust plants has a longer service life of the catalyst.
• SCR selective catalytic reduction process
• This object of the invention is achieved by the aforementioned plant in which the dust is formed by at least a first and a second filter device and the reduction catalyst between the first and the second filter device is arranged, and by the method for cleaning the flue gases of a furnace in the The flue gases before they come into contact with the reduction catalyst are fed to a first dust separation and the fine dust cleaning of the flue gases takes place after the reduction of the nitrogen oxides.
• the circuit of the denitrification catalyst according to the invention has the advantage that the flue gases for the denitration reactions do not have to be additionally heated, but these flue gases still have a sufficient energy content, i. the sufficient temperature to be able to operate the catalyst. It can thus be achieved in comparison to low-dust plants, a reduction of fuels.
• the first filter device can be arranged in the flow direction of the flue gases immediately after the furnace or after a heat exchanger unit, so that the flue gases enter the first filter unit with a very high temperature, whereby the temperature drop in this filter unit - relatively speaking - can be kept low, and the flue gases leave the filter device at a temperature which favors the reduction of the nitrogen oxides on the catalyst.
• high temperature is meant a temperature of at least 250 ° C.
• the first filter device is an electrostatic precipitator.
• this filter can be operated at a high temperature, and on the other hand that this filter technology is already very mature or electrostatic precipitators, for example, are already present in plants for cement production - in the past the dedusting was often carried out with electric motors.
• electrostatic precipitators were largely replaced by cloth filters due to the stricter environmental requirements - and incur no additional investment costs.
• At least one raw material drying plant or raw material drying mill is arranged, so that the residual content of energy of the flue gases for drying of raw materials , which are used, for example, for cement production, can be used.
• this achieves the effect that the flue gases leaving the catalyst bed are cooled even further before being subjected to the second filter device, which is preferably formed by a cloth filter, as a result of which this second filter device is subject to a lower thermal load even without the use of additional cooling devices.
• the dust content of the flue gases in the first dust separation to a dust content of max. 3 g / Nm 3 , in particular max. 2.5 g / Nm 3 , for example, max. 1 g / Nm 3 , or of max. 30 g / Nm 3 , if another pre-separator, so no electrostatic precipitator, is used as the first filter device, reduced because it has been found that the efficiency of the system can be increased at these maximum dust levels of the flue gases.
• the first dust separation is carried out at a temperature of the flue gas which is at least 250 ° C or at most 450 ° C, for example at most 350 ° C, whereby, as stated above, to special measures to reduce the temperature drop in The first filter device can be dispensed with and this can thus be made cheaper.
• FIG. 1 A plant according to the invention in the form of a block diagram.
• Fig. 1 shows a plant 1 for cement clinker production.
• the denitrification plant according to the invention is not limited to use in the cement industry, although this is the preferred embodiment. It can also be equipped with waste incineration plants, caloric power plants, etc.
• the plant 1 has a furnace 2 in the form of a rotary kiln, which is operated by a firing 3, whereby the cement clinker is formed from the known raw materials.
• the flue gases leaving the furnace - arrow 4 - are introduced into a heat exchanger unit 5, which is formed in this embodiment in the form of a cyclone heat exchanger with in 4 cyclones to use the energy content of the flue gases to preheat the raw meal used.
• the heat exchanger unit 5 leaving flue gas - arrow 6 - occurs in the sequence in the gas purification system.
• This gas purification system comprises a first filter device 7, a reduction catalytic converter 8 and a second filter device 9.
• the first filter device 7 is designed as an electrostatic precipitator.
• the flue gas entering the electrostatic precipitator may optionally be preconditioned with water to increase the effectiveness of the electrostatic precipitator.
• a spraying device 11 can be arranged in a supply line 10 to the first filter device 7, is sprayed with the water.
• a mixed gas can be supplied to the flue gas via a mixed gas line 14, for example a gas originating from the furnace 2, a so-called bypass gas which can be withdrawn from the furnace 2 in the region of the heat exchanger unit 5.
• Both in the mixed gas line 14 and in the supply line 10 corresponding conveying devices 15, such as exhaust fan, may be arranged.
• the first filter device 7 may be provided with a thermal insulation which is suitable for these high temperatures, so that the reduction in the Raugastemperatur can be reduced.
• the flue gas enters the reduction catalyst 8, wherein the end nitriding, ie the implementation of the nitrogen oxides to nitrogen and water according to the known reactions takes place.
• a reducing agent is supplied by means of a reducing agent feed 16.
• a reducing agent is usually ammonia used, as is known from the prior art. However, it is also possible to use ammonia-containing compounds or reducing agents which release ammonia at the elevated temperature.
• the reducing agent feed 16 can also be dispensed with if excess ammonia is present in the exhaust gas of the plant 1 or, if the ammonia is too low, only the missing fraction can be supplied via the reducing agent feed 16.
• titanium dioxide or vanadium pentoxide or titanium oxide as a carrier with vanadium pentoxide as the active composition, optionally mixed with tungsten oxide or mixed with other metal oxides.
• these catalysts are known from the prior art, so that at this point a further discussion on its geometry or pore structure, etc. is unnecessary.
• the supply of reducing agent takes place, for example, again via spray nozzles.
• the reducing agent itself can be added to the flue gas before the catalyst, but this reducing agent is preferably fed into or onto the catalyst bed.
• the formation of the catalyst bed per se is also state of the art, so that reference should be made to the relevant literature.
• the reduction catalytic converter it is possible for the reduction catalytic converter to be arranged on a plurality of superimposed planes through which the flue gas flows in succession.
• the de-stoked flue gas - it should be mentioned at this point that with denestered flue gas a flue gas is meant, which corresponds to NO x the emission standards, eg the Austrian emission standards - passes via a line 17 to the second filter device 9.
• This second filter device 9 is a bag filter executed, with filter cloths or filter bags. Also these bag filters are already known and used in the cement industry, so that further discussion is not necessary at this point. With the aid of these filter cloths, the dust content of the flue gas is at least reduced to values which correspond to the exhaust gas standards.
• a spray cooling 18 may be arranged in front of the second filter device 9 to cool the flue gas before entering the second filter device 9 to a temperature, for example a maximum of 250 ° C, which reduces the thermal load of the filter cloth by the flue gases.
• a conveying device 15 can again be arranged between the vent 19 and the second filter device 9.
• the residual energy content of the flue gases leaving the reduction catalytic converter 8 is preferably used for drying the raw materials used for cement production.
• two drying mills 20 are shown in Fig. 1, which are arranged in the flow direction of the flue gases between the reduction catalyst 8 and the second filter device 9.
• these two drying mills 20 are connected in parallel, so that they can be flowed through simultaneously or alternatively by the denitrified flue gases.
• For the corresponding circuit of the flow paths of the flue gas flaps 21 - 24 are shown in Fig. 1.
• drying mills 20 can be connected in parallel to the direct introduction of the flue gases via the line 17 in the second filter device 9, including in this line 17, in turn, a flap 25 is arranged to order between the Flow direction can be switched over the line 17 or at least one of the drying mills 20.
• the drying mills 20 themselves are designed according to the state of the art.
• Dust content of the flue gas leaving the furnace 2 or the heat exchanger 5 60 to 120 g / Nm 3
• Dust content of the flue gas leaving the electrostatic precipitator max. 3 g / Nm 3
• Temperature of the flue gases after the reduction catalyst 8 280 ° C to 320 ° C.
• Dust content of the flue gas entering the bag filter less than 3 g / Nm 3 for direct discharge or approx. 100 g / Nm 3 for "mill operation"
• Dust content of the flue gas when leaving the bag filter max. 10 mg / Nm 3
• the dust content of the flue gases in the reduction catalyst 8 is practically not reduced. If, nevertheless, a dust precipitation takes place in the reduction catalytic converter 8, this can be cleaned periodically, for example by blowing with compressed air.
• the flue gas and carbon monoxide from, in particular, odoriferous, hydrocarbons or ammonia removal from exhaust gases from incinerators, especially the Appendix 1, are used.
• a separate catalyst can be arranged before or after the denitrification catalyst, for example comprising titanium vanadium compounds which can be mixed with palladium and / or platinum.
• Such catalysts are known from the prior art, so reference should be made to the relevant literature.
• the reduction catalyst 8 can be designed as a multilayer catalyst with multiple beds for the individual catalysts, or there is also the possibility of several catalysts separately in the system 1 or a corresponding flue gas cleaning system are arranged, for example, in the flow direction of the flue gases behind each other in their own containers.

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• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)
• Treating Waste Gases (AREA)
• Electrostatic Separation (AREA)

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Cited By (10)

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Citations (11)

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• 2008
  • 2008-01-16 AT AT0003108U patent/AT10369U1/de not_active IP Right Cessation
• 2009
  • 2009-01-15 BR BRPI0907170A patent/BRPI0907170A2/pt not_active IP Right Cessation
  • 2009-01-15 EP EP09702662A patent/EP2237861A1/de not_active Withdrawn
  • 2009-01-15 WO PCT/AT2009/000010 patent/WO2009089559A1/de active Application Filing
  • 2009-01-15 RU RU2010134000/05A patent/RU2484883C2/ru not_active IP Right Cessation
  • 2009-01-15 US US12/863,248 patent/US20100307388A1/en not_active Abandoned
  • 2009-01-15 CN CN2009801092597A patent/CN101977668A/zh active Pending

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