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WO1992022680A1 - Procede ameliore pour l'elimination du dioxyde de soufre contenu dans des gaz de combustion - Google Patents

Procede ameliore pour l'elimination du dioxyde de soufre contenu dans des gaz de combustion Download PDF

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Publication number
WO1992022680A1
WO1992022680A1 PCT/US1992/004841 US9204841W WO9222680A1 WO 1992022680 A1 WO1992022680 A1 WO 1992022680A1 US 9204841 W US9204841 W US 9204841W WO 9222680 A1 WO9222680 A1 WO 9222680A1
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WIPO (PCT)
Prior art keywords
column
process according
acid
electrode
sulfur dioxide
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Ceased
Application number
PCT/US1992/004841
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English (en)
Inventor
John E. Stauffer
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Individual
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Individual
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Publication date
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Publication of WO1992022680A1 publication Critical patent/WO1992022680A1/fr
Anticipated expiration legal-status Critical
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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
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/507—Sulfur oxides by treating the gases with other liquids
    • 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
    • B01D53/32—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 by electrical effects other than those provided for in group B01D61/00
    • B01D53/326—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 by electrical effects other than those provided for in group B01D61/00 in electrochemical cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/22—Inorganic acids

Definitions

  • the present invention concerns an improved electrolytic process for removing sulfur dioxide (S0 2 ) from a waste gas stream and recovering the sulfur values as sulfuric acid.
  • the sources of said waste gas stream include effluent vent, flue or exhaust gases from power plants, sulfuric acid plants, ore roasters, and solid waste incinerators.
  • the purpose of the process is to achieve economies of operation, provide a useful byproduct, and minimize environmental pollution.
  • the process comprises the steps of scrubbing the gas in a confined scrubbing zone with an aqueous sulfuric acid stream to remove sulfur dioxide from the gas and converting the thus removed sulfur dioxide to sulfurous acid, subjecting the sulfuric acid stream containing the thus produced sulfurous acid to electrolysis in an electrolytic cell to oxidize the sulfurous acid to sulfuric acid, recycling the sulfuric acid stream resulting from the electrolysis step to the scrubbing zone, and maintaining the recycled sulfuric acid within a predetermined range of concentrations by means of make-up water or acid.
  • the scrubbing zone conveniently is a scrubbing column of conventional design or modified design for passage of a stream of effluent gas therethrough.
  • the scrubbing column contains packing material that provides gas-liquid contact surface for the gas stream and the " aqueous acid stream. The design of the packing material is critical in order to minimize channeling and thereby achieve greater scrubbing efficiency.
  • the packing material is electrically conductive, and it serves both as the gas-liquid contact surface for scrubbing and as the electrochemically active surface of the anode of the electrolytic cell.
  • the cathode is located in the electrolytic cell compartment external to the scrubbing column. Electrical contact between the anode and cathode is maintained by the aqueous acid stream flowing through the scrubbing column and the connecting piping leading from the column to the electrolytic cell.
  • Hydrogen gas produced at the cathode is kept isolated form the flue gases by means of the aqueous acid seal in the connecting piping.
  • hydrogen gas cannot intermix with the flue gases forming potentially explosive mixtures.
  • the hydrogen gas formed in the process can be recovered as a useful byproduct for such applications as the production of ammonia.
  • the hydrogen can be burned as a fuel in such general uses as steam generation, or it can be used specifically to reheat the flue gases thereby providing buoyancy to the gases for better dispersibility in the atmosphere.
  • the methods described for removing sulfur dioxide have serious disadvantages. When both electrodes are installed in the electrolytic cell compartment, large quantities of acid must be recycled between the electrolytic cell and the scrubbing column.
  • an object of the present invention to provide a process that overcomes the disadvantages of the conventional methods for removing sulf r dioxide rom waste gases.
  • a further object is to provide a process requiring the minimum investment and offering the lowest operating costs.
  • the invention concerns a process for removing sulfur dioxide from effluent vent or flue gas by scrubbing the gas with an aqueous acid stream in a column 10 comprising a confined scrubbing zone and simultaneously subjecting this acid stream, which contains dissolved sulfur dioxide, to electrolysis.
  • the confined scrubbing zone contains packing material 20a that is electrically conductive. This packing material both provides gas-liquid contact surface for scrubbing and serves as the anode 20 for the electrolysis reaction.
  • the confined scrubbing zone also contains a cathode 30 that is electrically insulated from the packing material but is in intimate contact with the aqueous acid stream.
  • a circulating pump supplies the aqueous acid stream to the scrubbing zone in order to provide effective contact between the gas stream and the liquid phase.
  • the concentration of the aqueous acid stream is maintained within set limits by means of makeup water or acid.
  • Byproduct acid produced by the process is withdrawn from the system.
  • the scrubbing zone consists of a column 10 whose inner walls are manufactured from an electrically conductive material.
  • the walls of the column thus serve the dual purposes of confining the process streams and acting as the cathode 30 for the electrolysis reaction.
  • the inner column walls are insulated from the packing material by insulation means 35 such as webbing, perforated sheet or a porous membrane made from such non-conductive materials as plastics and ceramics. The gaps or holes in the insulation allow effective contact between the aqueous acid stream and the inner column walls 30.
  • the cathode 30 consists of an electrically conductive cylinder that is centered along the vertical axis of the column.
  • This cylinder electrode is insulated from the packing material by insulation means 35 such as described above. It alone may serve as the cathode, or a plurality of spaced apart vertical cylinders may be used.
  • a centrally located electrode may be used together as in Figure 1 with the inner column walls for the cathode.
  • the packing material fills an annular space so that the maximum distance between cathode and anode is one-quarter the diameter of the column.
  • FIGURE 1 is a diagrammatic view of the scrubber/ electrolyzer in which the packing material serves as the anode and the inner column walls as the cathode.
  • a pump is provided to circulate acid through the scrubber.
  • FIGURE 2 is a similar view in which a centrally located electrode serves as the cathode.
  • Electrolysis is an effective and efficient way to convert sulfurous acid to sulfuric acid when sulfurous acid is formed by stripping sulfur dioxide from waste gases that contain relatively low concentrations of sulfur dioxide.
  • the theoretical potential required for this reaction is 0.2 volts, but because of electrode polarization, the applied voltage must be increased to about 0.6 volts before significant reaction takes place. In practice, additional voltage is required in order to overcome the electrical resistance of the acid in the electrolysis cell. At higher potentials, 1.7 volts and above, electrolysis of water commences to form oxygen and hydrogen. Under normal operations, the applied voltage can be adjusted to permit the electrolysis of sulfurous acid but to avoid the electrolysis of water.
  • the hydrogen gas released at the cathode will enter the flue gas stream.
  • the concentration of hydrogen gas resulting from this source will be small.
  • the hydrogen gas concentration in the existing flue gas is limited by the level of sulfur dioxide initially present in the gas.
  • the process is used to scrub flue gases generated by the burning of high sulfur coal or vent gases released from contact sulfuric acid plants, the resulting hydrogen concentration will typically be in the order of 0.2 percent. This value is substantially below the explosive limit for hydrogen in dry air, namely 18 percent.
  • FIG. 1 Flue gas enters at the top of the scrubbing column 10 and flows concurrently with the acid down the column. In this manner, column loadings can be increased over the expected gas flow rates for counter-current operations.
  • a circulating pump supplies sufficient acid to the column 10 to wet the column packing 20a.
  • Standard packing material is designed to prevent channeling in the column. This attribute assures good wetting of the packing so that a good electrical circuit is achieved between the column walls and the packing.
  • a central electrode 30 replaces the column walls at the cathode.
  • Byproduct sulfuric acid is removed from the system during operation of the process.
  • Make-up water or acid is supplied to the acid stream as required to maintain the acid concentration within certain limits.
  • the selected concentration of the acid is a compromise between competing requirements.
  • the electrical conductivities of aqueous sulfuric acid are greatest in the range of 20 weight percent to 40 weight percent. At lower and higher concentrations, the conductivities are reduced but still appreciable within the range of 5 weight percent to 93 weight percent. Balancing the need to maximize the electrical conductivity of the acid is the desire to produce byproduct acid of maximum strength. Concentrated acid has greater utility than weak acid and also is cheaper to ship on an equivalent acid basis. Because the present invention minimizes the spacing between electrodes, acid with higher concentrations can be used in the process for scrubbing without increasing the electrical resistance excessively.

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

Abstract

Procédé permettant d'éliminer par électrolyse le dioxyde de soufre (SO2) contenu dans un flux de gaz de combustion et de récupérer les valeurs soufre sous forme d'acide sulfurique. Les sources dudit flux de gaz de combustion contiennent des gaz résiduaires de décharpage de fumée ou d'évacuation provenant de centrales électriques, d'installations d'acide sulfurique, de fours de grillage de minerais et d'incinérateurs de déchets solides. Le but de ce procédé est de réduire les frais de fonctionnement, d'obtenir un sous-produit utile, et de minimiser la pollution de l'environnement. Le procédé électrolytique est réalisé dans une colonne (10) comportant une zone d'épuration contenant un matériau de garnissage (20a) qui sert également d'anode (20). La zone d'épuration contient aussi une cathode (30) qui est isolée (35) du matériau de garnissage mais est en contact intime avec le flux d'acide aqueux.
PCT/US1992/004841 1991-06-17 1992-06-08 Procede ameliore pour l'elimination du dioxyde de soufre contenu dans des gaz de combustion Ceased WO1992022680A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US71722291A 1991-06-17 1991-06-17
US717,222 1991-06-17
US88653592A 1992-05-20 1992-05-20
US886,535 1992-05-20

Publications (1)

Publication Number Publication Date
WO1992022680A1 true WO1992022680A1 (fr) 1992-12-23

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PCT/US1992/004841 Ceased WO1992022680A1 (fr) 1991-06-17 1992-06-08 Procede ameliore pour l'elimination du dioxyde de soufre contenu dans des gaz de combustion

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Country Link
AU (1) AU2226692A (fr)
WO (1) WO1992022680A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0703995A4 (fr) * 1993-06-15 1996-10-23 John E Stauffer Procede bipolaire d'enlevement de dioxyde de soufre contenu dans des gaz de combustion
US6110426A (en) * 1994-06-17 2000-08-29 The Board Of Trustees Of The Leland Stanford Junior University Methods for fabricating microarrays of biological samples
EP2167423A4 (fr) * 2007-07-23 2011-11-09 Exxonmobile Upstream Res Company Production d'hydrogène gazeux à partir de composés contenant du soufre
US8945368B2 (en) 2012-01-23 2015-02-03 Battelle Memorial Institute Separation and/or sequestration apparatus and methods

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004994A (en) * 1972-07-12 1977-01-25 Stauffer Chemical Company Electrochemical removal of contaminants
US4830718A (en) * 1985-10-21 1989-05-16 John Stauffer Removal of sulfur dioxide (SO2) from waste gases and recovery as sulfuric acid

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004994A (en) * 1972-07-12 1977-01-25 Stauffer Chemical Company Electrochemical removal of contaminants
US4830718A (en) * 1985-10-21 1989-05-16 John Stauffer Removal of sulfur dioxide (SO2) from waste gases and recovery as sulfuric acid

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0703995A4 (fr) * 1993-06-15 1996-10-23 John E Stauffer Procede bipolaire d'enlevement de dioxyde de soufre contenu dans des gaz de combustion
US6110426A (en) * 1994-06-17 2000-08-29 The Board Of Trustees Of The Leland Stanford Junior University Methods for fabricating microarrays of biological samples
EP2167423A4 (fr) * 2007-07-23 2011-11-09 Exxonmobile Upstream Res Company Production d'hydrogène gazeux à partir de composés contenant du soufre
US8945368B2 (en) 2012-01-23 2015-02-03 Battelle Memorial Institute Separation and/or sequestration apparatus and methods

Also Published As

Publication number Publication date
AU2226692A (en) 1993-01-12

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