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
  • B01D53/60—Simultaneously removing sulfur oxides and 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
  • B01D53/46—Removing components of defined structure
  • B01D53/68—Halogens or halogen compounds
• • 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
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

• the invention relates to a method for the separation of HC, SO2 and NOx from the flue gases of fossil fuel fired boilers of power plants, waste incineration plants or the like.
• the washing liquid of the first stage contains limestone or hydrated lime and a carboxylic acid which does not prevent the oxidation of CaSO3 to CaSO4, and the washing liquid of the second stage contains sodium hydroxide solution, EDTA and / or NTA and a carboxylic acid which inhibits the oxidation of CaSO3 to CaSO4 and finally also sodium dithionide, sodium sulfite and / or pyrosulfite.
• the SO2 and KCl scrubber is l, with 2 the NOx scrubber, with 3 the gypsum separated from the first washing stage, the z. B. was oxidized in the sump of the first SO2 scrubber.
• the water clarified from the overflow from the EDTA precipitation stage 22, inscribed with 24, is preferably transferred to a biology 25.
• the filler layer height should be 8 - 10 m, however at least 50% of the washing tube volume should be filled with contact surfaces in the execution of fillers.
• washing liquid according to the invention in the washing process is subjected to a subsequent washing liquid treatment for the preparation and recovery of the EDTAs or NTAs.
• the one separated from the first washing stage Plaster shown which was oxidized, for example, in the water sump of the first SO2 scrubber stage;
• 34 shows a sodium hydroxide storage and a sodium sulfite or sodium pyrosulfite mixing container device;
• 35 denotes the EDTA or NTA mixing device, which is mixed at 36 in a mixing ratio appropriate to the task and is transferred to the washing circuit 42 at 37.
• the sodium dithionite, which is transferred at 40, is designated by 39.
• Nit 41 transfers the wastewater to the washing liquid treatment 40a;
• hydrated lime is added at 40b so that the washing solution, which consists of a dilute sodium hydroxide solution, an EDTA complex chelate and has additional reduction and oxidation inhibitors, is converted into calcium sulfate or calcium sulfate in this container 40a via the dewatering station 40c, e.g. Hand over to oxidation level 43 with 20% residual moisture.
• the washing liquid from the dewatering station 40c is returned as 40d to the washing liquid circuit of washing stage 32, so that there is little loss of washing liquid.
• the oxidation air 44 provides a pH of e.g. 3.5 for the formation of gypsum, the pH of e.g. arriving with 7 by sulfuric acid or by acid from the scrubber 31, formed from the chlorine-containing washing stage 31, referred to as HCl scrubber, is used to adjust the pH to e.g. 3.5 - 4 lower.
• the gypsum formed is filtered 45 at 46 with a relatively low humidity of e.g. given less than 8%, and which e.g. Part of the water required for gypsum research is transferred to the iron precipitation stage 47, and the water separated from the filter 45 is also fed to the scrubber 32 as filtrate water 48.
• the water clarified from the overflow from the EDTA precipitation stage 52, designated 54, can, according to the invention, be used in the washing stage 31 as mixing water for limestone and / or hydrated lime or can be transferred to a biology 55 as required.
• Step b) the waste water of step e), the EDTA of step g) and setting a pH of about 6.5, reduction of the iron III chelate to iron II chelate by adding sodium dithionite - to produce a regenerated washing solution for the second stage of flue gas scrubbing.
• the solids 66 thickened in this way are dewatered via a belt filter 64, fed to an oxidation container 65 and diluted again with fresh water 57 to 50% solids per 1 water, and by adding sulfuric acid 68 and air 68a approx. 4 are obtained at a pH value the calcium sulfite antioxidated to calcium sulfate dihydrate.
• the precipitated H4-EDTA is dewatered via a belt filter 73, fed to a mixing container 74 and combined with the iron III sulfate solution.
• nitrate water is fed to the mixing container 74 via line 81 after the band filter 64 with pH II-12 until the pH in the iron III chelate solution has reached pH about 6.5.
• This suspension 101 is filtered by means of a belt filter or centrifuge 102, so that the CaSO4 x 2 H2O 103 is obtained as a salable product.
• the iron sulfate-containing filtrate 104 is not or only partially returned to the SO2 / NOx absorption process, but is provided for a power plant-typical application outside the SO2 / NOx removal system or is worked up separately.
• the filtrate 105 of the pH 12 precipitation 93 contains EDTA according to the concentration used in the washing cycle of the SO2 / NOx absorption and is mixed with fresh Fe (II) SO1 107 to the extent that it forms to form an Fe (II) -EDTA- Chelation complex is required.
• the advantages of this invention are that the Fe (II) / Fe (III) -containing filtrate of the CaSO3 oxidation stage is fed to a separate utilization and that the cheap product Fe2SO4 ⁇ 7H2O is newly added to compensate for this iron removal from the absorption cycle.
• a high Fe (II) concentration is always maintained in the wash water circuit in a simple manner, and the dosage of 17 sodium dithionite can be further reduced or completely set.
• flue gas which is taken in front of the flue gas desulfurization system instead of oxidizing air, creates a reducing phase so that the iron III in the wash water is reduced to iron II.
• the released SO2 is fed back from the container 100 into the flue gas line via a line (not shown further), so that the flue gas quantity is now supplied via the feed 99 instead of air, with the amount of SO2 being controllably released as a function of this flue gas quantity so that the ratio of SO2 to NOx about 1 mg NOX / 4 mg SO2 in the flue gas stream of simultaneous SO2 and NOx washing.
• CaSO3 oxidizes 10 to 90%, preferably 50%, the rest being available for decomposition with the formation of SO2.
• the partial oxidation and decomposition of CaSO3 is controlled by the pH value, with the reactions taking place in a single container or in a container cascade. Air, oxygen-enriched air or oxygen is used as the gaseous oxidizing agent.
• the SO2 is circulated and then introduced into the flue gas stream before the second stage of the flue gas scrubbing.
• the S02 and / or SO2-containing flue gas generated in this stage is circulated.
• a partial flow 121 of the washing cycle of SO2 and NOx removal is combined with Ca (OH) 2 at pH 12 - pH 13
• a short-lived dispersing agent based on polycarboxylic acid is added to the partial flow of the washing liquid, by means of which the precipitation of CaSO3 and CaSO4 as well as iron II and iron III hydroxides is improved without the subsequent reactions of the washing water treatment to disturb.
• the acidic waste water from the EDTA precipitation after stage g) is prepared by decomposing strongly acidified solutions of diathonates and salts of sulfonic acid, such as HON (SO3Na) 2, NH (SO3Na) 2, N (SO3Na) 3, at elevated temperature and possibly increased pressure and converting them into sulfate and sulfite.
• the acidic waste water from the EDTA precipitation after stage g) is evaporated or spray-dried to form Na2SO4, that the Na2SO4 is recycled to the formation of NaOH and CaSO4 in the second stage of the flue gas scrubbing and that Residual product of the evaporation or spray drying is thermally aftertreated, the resulting gaseous products being introduced into the flue gas stream and the remaining Na2SO4 being returned to the second stage of the flue gas scrubbing.
• the process sequence described above is explained in more detail with reference to FIG. 9.
• the Ma2SO4 is returned directly to the washing process 168 and CaSO4 and NaOH are formed in a precipitation stage using Ca (OH) 2.
• the residue 154 of the evaporation is post-treated at 300-600 degrees C, preferably 450-550 degrees C, thermally 165, whereby organic material and S-N compounds escape in gaseous form as CO2, 172, SO2, SO2 and are led into the flue gas path 169.
• the remaining Na2SO4 166 is returned together with the pure Na2SO4 163 from the evaporation to the washing process.
• the gaseous compounds are added to the hot flue gas in the boiler or to the partially cooled flue gas before the 302 wash, which binds the SO2 and SO3 to CaSO4.
• the advantages of this invention are that from Simultaneous SO2-NOx washing process no waste water is released into the receiving water and all salt-like components of the waste water from the H4EDTA precipitation are used for usable products within the overall process.
• a reduction of NOx pollution in flue gases can be carried out electrochemically in such a way that salts are added to the washing liquid which form complexes such as iron nitrosyl complexes with nitrogen monoxide, which, when admixed with formic acid, prevent precipitation of iron III hydroxide on a potentiostatically switched cathode to elemental nitrogen and Water are reduced.
• citric acid and / or tartaric acid should be added to the wash water, preferably between 2 - 5 g / l.
• a corresponding dwell time is provided in the regeneration tank, which is assigned depending on the degree of washout required, the redox potential being negative in relation to calomel with 3-molar KCl solution and from Oxygen content of the flue gas in the reduction phase is not adversely affected.
• the washing section is sprayed with the appropriate washing liquid from the redox tank via a pump via washing water nozzles.
• a predetermined amount of electrolysis water is transferred from the washing system to the SO2 wash.
• the washing liquid is run neutral to alkaline to eliminate the acidic drops from the upstream washing system.
• the reduction takes place in the redox container and is carried out without influencing oxygen from the flue gas.
• 171 the raw gas that comes from a scrubber or from a NOx generator
• 172 the raw gas channel which is designed as a simultaneous washing pipe
• 173 the washing water supplied
• 174 the droplet separator which is arranged in the raw gas channel 175 the electrolysis, which receives the washing water from the washing pipe and the drip catcher, the washing water being passed through a filter 179 beforehand so that it can be used for droplet separation 174 via a pump 180.
• the water can also come from the pump 176 be removed, depending on the redox potential, which is considered necessary for flushing the droplet separator and for washing the gases.
• these substances can be obtained and further processed.
• the sharp acid drops are eliminated by this subsequent connection of a NOx wash in pH control according to the invention, neutral to alkaline. Furthermore, the reductive part is integrated with low oxygen in the guidance of the washing water, ie the reduction is not adversely affected by oxygen from the gas.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Treating Waste Gases (AREA)

Applications Claiming Priority (34)

Publications (1)

Family

ID=27585856

Family Applications (1)

Country Status (2)

Cited By (1)

Families Citing this family (7)

Family Cites Families (4)

• 1986
  • 1986-04-05 WO PCT/EP1986/000207 patent/WO1986005709A1/de not_active Application Discontinuation
  • 1986-04-05 EP EP86902811A patent/EP0217945A1/de not_active Ceased

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events