Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F11/00—Compounds of calcium, strontium, or barium
  • C01F11/46—Sulfates
  • C01F11/464—Sulfates of Ca from gases containing sulfur 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
  • B01D53/48—Sulfur compounds
  • B01D53/50—Sulfur oxides
  • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
  • B03D1/00—Flotation
  • B03D1/02—Froth-flotation processes
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B11/00—Calcium sulfate cements
  • C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
  • C04B11/262—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke waste gypsum other than phosphogypsum
  • C04B11/264—Gypsum from the desulfurisation of flue gases

Definitions

• the present invention concerns a flue-gas purifying procedure conforming to the introductory part of claim 1.
• the object of the invention is to achieve an improvement of the flue gas purifying methods known at present.
• the more detailed object of the invention is to achieve an improvement of the wet washing method presently known.
• the other objects of the invention and the advantages gainable by its aid will became apparent in the disclosure of the invention.
• the procedure of the invention is mainly characterized by that which is stated in the characteristic features part of claim 1.
• the procedure of the invention is simple as to its principle, and a closed design is employed in it.
• flotation of the liquid emerging from the wet washer and of the solid matter therein to became separate partial flows, which are easy to dry, is a simple but thorough insight.
• the washing fluid quantities above all, and also the sizes of the tanks required in the apparatus design are reduced to a fraction of those involved in any presently used procedure. It is possible in an advantageous embodiment of the invention to recover the impurities carried in the whole flue gas quantity, in dry condition and even in chemically bound state without even the slightest aqueous emission.
• FIG. 1 presents an advantageous embodiment of the apparatus design employed in implementing the procedure of the invention, in schematic elevational view.
• the flue gas flow 20 is first conducted, advantageously, into a dry separator 1, which in this embodiment is a conventional cyclone separator. Part of the impurities present in the flue gases depart from the flue gas flow 20 and run down into the lower cone of the cyclone separator 1, whence the dry solid matter may be conducted, with the add of a pressure transmitter 2 located below the cyclone separator 1, as a material flow 13 e.g. to a centralized powdery material storage container (not depicted).
• the flue gases flow to the wet washer 3, where the gaseous components present in the flue gases are washed so that the gas flow 4 emerging from the wet washer 3 will be clean enough.
• the wet washer 3 is known in the art in itself and it may be combined with the cyclone separator, as has been shewn in the figure of the drawing.
• the washing water flows along the line 12 of the wet washer 3.
• the spent washing water flows from the wet washer 3 to a combined mixing and flotation unit 6, in the form of the washing water flow 5.
• Air is conducted to the mixing and flotation unit 6 by the line 14, and the mixing and flotation unit 6 is advantageously provided with a mixing means 21.
• the sulphite in the washing water if any, is oxidized to sulphate, and the flotation process taking place lifts the reaction and washing products that have been formed in the wet washer 3, along with the foam out from the mixing and flotation unit 6.
• Such a foam remover has been indicated with the reference numeral 15 in the figure of the drawing.
• the foam with the solid matter and the liquid held in the foam, is directed to a pressure transmitter 7 which has been disposed to guide the separated foam as a flow 18 to join the flue gas flew 20, the flue gas flow 20 having been arranged to dry out the liquid held in the foam and, as the flue gas temperature usually is in the range of 100 to 240°C, the CaSO 4 loses part of its crystal water.
• the dried solid matter separates and ends up among the solid matter in the lower cone of the cyclone separator 1, in which connection for instance the separated gypsum is in the form of a powder hardening powerfully together with water and thus is a substance well appropriate to be carried to a dump, or to be used otherwise.
• facilities for adding flocculating agent can be provided on the mixing and flotation unit 6, or a flocculation unit alone may be substituted for this unit, depending on what chemicals are used.
• the solid matter which fails to be removed from the mixing and flotation unit 6 runs as an overflow 16 into the tank 8, where advantageously with the aid of centrifugal action the solid matter is directed to settle in the lower cone of the tank 8.
• a pressure transmitter 9 arranged to direct this solid matter in a flow 17 to join the flue gas flow 20, whereby the liquid held by the solid matter evaporates off and the solid matter separates in dry dust form in the lower part of the cyclone separator 1, whence the pressure transmitter 2 sends the dry solid matter as a material flow 13 to the centralized powdery material storage already described.
• the washing liquid flow 12 contains the requisite neutralizing substance, in which capacity Ca(CH) 2 , or so-called milk of lime, serves best.
• the quantity of milk of lime in the washing liquid is advantageously monitored so that the mixing and flotation unit 6 can operate in a pH range of preferably 5 to 9.
• other chemicals may be used instead of milk of lime, for instance NaOH, or caustic liquor, or NaCO 3 , or soda, in which case the sulphur present in the flue gas flow 20 will react without forming any solid products. In that case nothing emerges from the mixing and flotation unit 6 but the quick ash that has passed through the cyclone separator 1.
• the material flews 17 and 18 dried in the incoming flue gas flow 20 are separated in the cyclone separator 1 mainly in granulated form. It should be particularly noted that the size both of the mixing and flotation unit 6 and the tank 8 is comparatively small compared with the liquid tanks in present use. In the procedure of the invention, the requirement of fresh washing water, in terms of weight, is on the order of the coal quantity (the fuel quantity) that is fed in.
• An advantageous way to accomplish such recovery is to arrange for a return flow 11 from the tank 8 to the wet washer 3, e.g. by means of a water circulating pump 10.
• a return flow 11 from the tank 8 to the wet washer 3, e.g. by means of a water circulating pump 10.
• the temperature in the tank varies: for instance in connection with coal firing, between 40 and 60°C.
• the return flow 11 also flushes out impurities from the wet washer 3 because the return flew joins the washing liquid flow 5, which is directed to the mixing and flotation unit 6. It is thus possible in the procedure of the invention to achieve a socalled closed washing liquid circulation.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Ceramic Engineering (AREA)
• Structural Engineering (AREA)
• Inorganic Chemistry (AREA)
• Geology (AREA)
• Materials Engineering (AREA)
• Life Sciences & Earth 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)

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• 1986
  • 1986-03-19 WO PCT/FI1986/000027 patent/WO1987005530A1/en not_active Application Discontinuation
  • 1986-03-19 EP EP19860901880 patent/EP0261110A1/de not_active Withdrawn
• 1987
  • 1987-11-12 DK DK593287A patent/DK593287A/da not_active Application Discontinuation

Non-Patent Citations (1)

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