CA1258441A - Plasma treatment of flue gases - Google Patents
Plasma treatment of flue gasesInfo
- Publication number
- CA1258441A CA1258441A CA000480760A CA480760A CA1258441A CA 1258441 A CA1258441 A CA 1258441A CA 000480760 A CA000480760 A CA 000480760A CA 480760 A CA480760 A CA 480760A CA 1258441 A CA1258441 A CA 1258441A
- Authority
- CA
- Canada
- Prior art keywords
- flue
- flue gases
- steam
- ozone
- gases
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000003546 flue gas Substances 0.000 title claims abstract description 56
- 238000009832 plasma treatment Methods 0.000 title 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000000034 method Methods 0.000 claims abstract description 30
- 239000000779 smoke Substances 0.000 claims abstract description 26
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000007921 spray Substances 0.000 claims abstract description 23
- 230000005855 radiation Effects 0.000 claims abstract description 20
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims abstract description 17
- 235000010269 sulphur dioxide Nutrition 0.000 claims abstract description 8
- 239000004291 sulphur dioxide Substances 0.000 claims abstract description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 33
- 239000001301 oxygen Substances 0.000 claims description 33
- 229910052760 oxygen Inorganic materials 0.000 claims description 33
- 239000002253 acid Substances 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 12
- 150000007513 acids Chemical class 0.000 claims description 10
- 239000012670 alkaline solution Substances 0.000 claims description 10
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 claims description 10
- 239000003518 caustics Substances 0.000 claims description 9
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 claims description 5
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 claims description 5
- 239000000243 solution Substances 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 150000003467 sulfuric acid derivatives Chemical class 0.000 claims description 3
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 2
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 2
- 239000002737 fuel gas Substances 0.000 claims description 2
- 239000004571 lime Substances 0.000 claims description 2
- 230000001590 oxidative effect Effects 0.000 claims 4
- 239000007864 aqueous solution Substances 0.000 claims 3
- 230000003472 neutralizing effect Effects 0.000 claims 2
- 230000035515 penetration Effects 0.000 claims 2
- 238000005507 spraying Methods 0.000 claims 2
- 229910002651 NO3 Inorganic materials 0.000 claims 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims 1
- 239000007788 liquid Substances 0.000 claims 1
- 230000035484 reaction time Effects 0.000 claims 1
- 150000001875 compounds Chemical class 0.000 abstract description 12
- 238000002485 combustion reaction Methods 0.000 abstract description 9
- 238000003916 acid precipitation Methods 0.000 abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 8
- 239000002803 fossil fuel Substances 0.000 abstract description 3
- 206010022000 influenza Diseases 0.000 abstract 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 8
- 238000009434 installation Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000010494 dissociation reaction Methods 0.000 description 2
- 230000005593 dissociations Effects 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 239000000791 photochemical oxidant Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical class OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000012717 electrostatic precipitator Substances 0.000 description 1
- 230000003203 everyday effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- VGQXTTSVLMQFHM-UHFFFAOYSA-N peroxyacetyl nitrate Chemical compound CC(=O)OO[N+]([O-])=O VGQXTTSVLMQFHM-UHFFFAOYSA-N 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
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
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J12/00—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor
- B01J12/002—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor carried out in the plasma state
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J19/12—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electromagnetic waves
- B01J19/122—Incoherent waves
- B01J19/123—Ultraviolet light
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- Toxicology (AREA)
- General Health & Medical Sciences (AREA)
- Electromagnetism (AREA)
- Biomedical Technology (AREA)
- Environmental & Geological Engineering (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Plasma & Fusion (AREA)
- Treating Waste Gases (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
ABSTRACT
A method and apparatus is disclosed for reducing acid rain caused by the combustion of fossil fuels in stationary combustion units, such as power plants, smelters or refineries. Compounds such as nitric oxide and sulphur dioxide are discharged into the atmosphere from smoke stacks of these combustion units and this causes acid rain.
In this invention, these compounds are treated in the smoke stacks or flues of these combustion units by subjecting the flue gases to ozone and ultraviolet radiation produced by a plasma arc burner mounted in the flue. This converts the offending compounds to water soluble oxides and an aqueous alkaline spray is introduced into the flue to dissolve and neutralize these oxides preventing the emission of the acid rain producing compounds from the combustion unit smoke stacks.
A method and apparatus is disclosed for reducing acid rain caused by the combustion of fossil fuels in stationary combustion units, such as power plants, smelters or refineries. Compounds such as nitric oxide and sulphur dioxide are discharged into the atmosphere from smoke stacks of these combustion units and this causes acid rain.
In this invention, these compounds are treated in the smoke stacks or flues of these combustion units by subjecting the flue gases to ozone and ultraviolet radiation produced by a plasma arc burner mounted in the flue. This converts the offending compounds to water soluble oxides and an aqueous alkaline spray is introduced into the flue to dissolve and neutralize these oxides preventing the emission of the acid rain producing compounds from the combustion unit smoke stacks.
Description
- 2 - ~ ~5~
This invention relates to the treatment of flue gases to prevent the emission into the atmosphere of acid rain producing compounds such as nitric oxide and sulphur dioxide. In particular, the invention relates to pollution control equipment to prevent harmful smoke stack emissions from stationary combustion units such as power plants, smelters and refineries.
In the combustion of fossil fuels, harmful compounds such as nitric oxide and sulphur dioxide are produced. These compounds are relatively insoluble in water and are difficult to extract from smoke stack or flue gas by conventional -techniques. As a result, vast quantities of these compounds are discharged into the atmosphere every day. When in the atmosphere, these compounds react with photochemical oxidants, such as ozone and peroxyacetyl nitrate to produce nitrogen dioxide and sulphur trioxide. These new oxides are readily soluble in water and thus produce nitric and sulphuric acids, which then descend to the earth as acid rain or other forms of acid precipitation.
It is an object of the present invention to prevent the emission from smoke stacks of these harmful compounds by causing the co~pounds to react and be rendered harmless right in the flue or smoke stack before they can be emitted to the atmosphere.
~LZ5~
In the present invention, at least one oxygen type plasma arc burner is mounted in the flue to produce ozone and ultraviolet radiation. This causes the oxidizable harmful compounds to react with the ozone and produce water soluble oxides which may be contracted with an aqueous alkaline solution to produce relatively harmless sulphates and nitrates prior to being emitted to the atmosphere. In particular the water soluble oxides may be sprayed with the aqueous alkaline solution.
According to one aspect of the invention there is provided a method of treating flue gases in a flue of the type which includes a smoke stack or the like. The method comprises the steps of injecting an oxygen contalning plasma arc into the flue to produce ozone and ultraviolet radiation in the flue in contact with the flue gases therein. Also, the flue gases are oxidized with the zone to produce oxidized flue gases.
According to another aspect of the invention there is provided apparatus for treating flue gases in a flue having a wall defining a flue passage. The apparatus comprises mounting means defining an opening in the flue wall communicating with the flue passage. A plasma burner is mounted in the mounting means opening to produce a plasma arc extending into the passage. Also oxygen supply means is connected to the plasma burner communicating with the arc for supplying oxygen to the plasma burner :
khereby producing ozone in the flue in contact with the Elue gases.
A preferred embodiment of the invention will now be described, by way of example, wlth reference to -~ 5 the accompanying drawings, in which:
- Figure 1 is a diagrammatic view of a typical : flue gas treatment installation for a plant involved in the combustion of fossil fuels, a preEerred embodiment of the present invention being incorporated in this installation; and Figure 2 is a sectional view taken along lines 2-2 of Figure 1.
Referring to the drawings, a flue gas treatment installation incorporating a preferred embodiment of the present invention is generally indicated by reference numeral 10. Installation 10 includes a smoke stack 12 and a passageway 14 which delivers smoke or flue gases from a source of combustion (not shown) to smoke stack 12. The flue gases enter passageway 14 as indicated by arrow 16 and typically pass throu~h gas cleaning apparatus 1~, such , . ' ~
as an electrostatic precipitator or other equipment to remove solid particulate matter from the flue gases.
The flue gases then continue through a passage or conduit 20 where -they enter a reaction chamber 22 and then proceed on to smoke stack 12. In some cases, the flue gases can be subjected to a second cleaning operation before entering smoke stack 12 and this is indicated in Figure 1 by reference numeral 24, which could be a wet scrubber which is typically used to further clean the flue gases and remove acids therefrom. Figure 1 also shows a spray device 26 mounted in the wall of smoke stack 12. Reaction chamber 22 and spray device 26 are components of the preferred embodiments of the present invention. All of the other components are shown merely by way of example of typical flue gas treatment apparatus, and for the purposes of this invention, all of the passages through which the flue gases pass including smoke stack 12 are considered to be the flue in installation 10.
Referring in particular to Figure 2, reaction chamber 22 is shown having a cylindrical wall 28 which defines an inner chamber or flue passage 30 in communication with conduit 20. This flue passage is lined with a refractory linin~ 31 such as graphite.
Three plasma arc burners 32 are radially mounted in - 6 - 1Z~5~
wall 28, so that in operation, plasma arc burners 32 inject plasma arcs 34 into the flue.
The exact form of the plasma arc burners 32 or their number is not considered to be part of the present invention, but a suitable plasma arc burner is available from Westinghouse Electric Corporation of Pittsburgh, Pennsyalvania, U.S.A. and its construction is substantially like that shown in United States Patent No. 3,832,519 issued on August 27, 1974. In such a plasma arc burner, a gas is introduced through a centrally located inlet 36, and this gas is used to help spin or collimate the arc in the burner. Any gas could be used, but in the present invention, air or oxygen bearing gas is used, and this results in an oxygen containing plasma arc being injected into the flue. Where air is used, the plasma burner arc is referred to as an air plasma arc, and similarly, where oxygen or other oxygen bearing gas is used, it is referred to as an oxygen plasma arc. The air or oxygen in the plasma arc produces ozone in flue passage 30, and arcs 34 produce high intensity ultraviolet radiation, so that the flue gases are brought into contact with this ozone and ultraviolet radiation in the flue.
Plasma burners 32 are also connected -through conduits 38 to suitable sources of cooling water, and of course, the plasma burners are connected through power lines 40 to suitable power supplies to produce the arcs. Once again, the specific structure of the plasma burners and the apparatus required to operate these plasma burners are not part of the present invention, so will not be described in urther detail in this specification. It is part oE the present invention, however, that oxygen bearing gas or air be supplied through conduits 36 so that ozone is produced in the flue.
As seen best in Figure 1, spray device 26 is mounted in the flue wall of smoke stack 12 downstream - of plasma burners 32. Spray device 26 is connected to a supply of alkaline fluid, such as caustic steam, and for the purposes of this specification this is considered to be an aqueous alkaline spray. Although only one spray device 26 is shown in Figure 1, a plurality of spray nozzles would be provided in smoke stack 12.
In operation, flue gases that enter flue passage 30 in reaction chamber 22 are subjected to ozone and ultraviolet radiation. Ozone, being a photochemical oxidant, in conjunction with the ultraviolet radiation of plasma arcs 34, causes the undesirable nitric oxide and sulphur dioxide compounds in the flue gases to be oxidized and converted to - 8 - 1~5~
nitrogen dioxide and sulphur trioxide. It will be appreciated that these forms of ni-trogen and sulphur are soluble in water, so that when -they come into contact with the aqueous alkaline spray in smoke stack 10, acids result which are immediately neutralized.
In fact, the akalinity oE the spray is preferably slightly in excess of the stoichiometric requirement to neutralize the acid gases in the flue. The Einal stack discharge will therefore contain sodium or calcium based sulphates and nitrates and it may be slightly alkaline which may result in basic rain to perhaps reverse some of the existing damage done by acid rain.
Having described preferred embodiments o-f the invention, it will be appreciated that various modifications may be made to the method and apparatus described. For example, it has been mentioned that oxygen or air could be supplied to inlets 36 of the plasma burners, but steam could also be supplied through these inlets, in which case the plasma arc would be referred to as a steam plasma arc. I~ile this would produce the required ozone, it would also produce hydrogen or other fuel gases which would have to be burned oEf.
While three plasma burners 32 are shown in the preferred embodiment, as few as one burner could be 12~
used or more -than three burners could be used. Also, the burners could be mounted in the base of smoke stack 12 or in any other location in the flue upstream of the alkaline spray.
The allcaline spray through device 26 has been described as a caus-tic steam. Of course, it could be a lime steam or any other allcaline steam. Steam is preferred, so that it will not interfere with the buoyant properties of the flue gas in stack 12.
However, if this is not a problem, then any other alkaline spray could be used as well. Further, it will be appreciated that other apparatus could be used for providing the spray than spray nozzles, such as a ]5 spray ring or an atomization device. Finally, it may be desirable to locate the spray device higher up in the smoke stack, such as at mid-height.
Thus in particular, and in accordance with the invention~ nitric oxide and sulphur dioxide in the flue gases are oxidized by the ozone in the presence of the ultraviolet to water soluble nitrogen dioxide and sulphur trioxide, in an arc zone of the flue, the arc zone being a portion of the flue which contains the plasma arc.
- 1o ~2~
SIJPPI.E~1E~TARY DISCLOSUR~
The oxygen-containing plasma arc of the present invention has a temperature in excess oE
5,000C and typically of 5,500 to 27,500. These hiqh temperatures result in the development of ultraviolet radiation of high photon energy, typically of the order of 103 to 104eVr and of short wavelength typically 10A to 1000A, preferably lOA to lOOA.
In accordance with the invention it was Eound that the high photon energy ultraviolet radiation results in the ozone having a relatively long life before dissociation back to oxygen as compared with ozone produced by low photon energy ultraviolet radiation. In addition the short wavelength of the ultraviolet radiation renders it highly penetrating in different media so that the radiation rapidly penetrates the flue gas throughout the plasma arc zone ensuring relatively long life ozone throughout thc flue gas in the arc zone of the flue. In this way the flue gas in the arc zone is quickly and efficiently oxidized in a very short time, less than 1 second. In particular the residence time for oxidation in the arc zone is less than 100 micro-seconds, more usually less than 10 microseconds and most usually less than 1 microsecond.
.. . .
~x~
It was also unexpectedly found that by means of the plasma arc, ozone was produced in high volume, typically a magnitude of 103 times the amount produced in a conventional electrical discharge.
- Thus by means of the invention there is not only produced a high volume of ozone per volume of oxygen but additionally the ozone has a relatively long life sufficient to permit efficient oxidation of the Elue gas components. The ozone is reacted throughout the arc zone with the flue gases in an extremely short time prior to dissociation o the ozone, tllereby maximizing the efficiency of the operation.
In addition the ozidation reations can be carried out under non-agitating, non-mixing conditions in view of the high penetrating nature of the ultra-violet radiation which ensures maintenance o-E
- the relatively long life ozone through the arc zone.
Thus as will be apparent from the foregoing, one aspect of the invention provides a method of treating flue gases in a flue of the type which includes a smoke stack means. The method comprises the steps of injecting an oxygen containing plasma having a temperature in excess of 5000C into the flue to produce ozone and high photon energy ultra-violet radiation in the flue in contact with the flue gases therein. The flue gases are oxidized with the ozone to 5~
produce oxidized flue gases, which may then be contacted downstream of the plasma arc with an a~ueous solution to produce acids, or an alkaline solutlon to neutralize the acids in the flue.
As descrlbed above the oxidized flue gases are suitable sprayed with a spray of the solution, thereby providing a high surface area of contact between the oxidized gases and the solution for the production of acids or the neutralization reaction and dissolution of the water salts formed thereby.
With respect to prior proposals, German Patent No. 1,278,060 issued September l9/68 to Linde AG and Japanese Patent No. 0001-968 issued January 20/75 to Sertetsu Chem. Ind. generally disclose oxidation of nitrogen oxides via a silent electrical discharge or corona discharge. Although it is known that electrical discharge in the presence of oxygen will result in ozone formation, such ozone formation is relatively small as a percentage of the oxygen, and is instable and of short life rapidly dissociating to oxygen.
Furthermore, such ozone is typically formed only in the immediate vicinity of the spart or electrical discharge.
- 13 ~
Such electrical discharges typically have a temperature not exceeding lOOO~C, which is significantly lower than the temperature associatd wi-th oxygen containing p[lasmas, as in the present invention.
U.S. Patent 4,210,503 issued July 1/80 to Confer teaches the use of ultra-violet lamps to provide ultraviolet radiatlon to decompose vinyl chloride as wells as other compounds such as carbon disulphide, hydrogen sulphide and nitric oxide. The ultraviolet radiation is of low energy typically about lOeV and the decomposition reaction requires a residence time of 20 to 50 seconds depending on the intensity of the radition.
From the above it will be appreciated that the present invention is a relatively inexpensive and simple solution to the problem of acid rain caused by the emission of nitric oxide and sulphur dioxide from smoke stacks. Of course, the invention could be used in other applications as will be apparent to those skilled in the art.
This invention relates to the treatment of flue gases to prevent the emission into the atmosphere of acid rain producing compounds such as nitric oxide and sulphur dioxide. In particular, the invention relates to pollution control equipment to prevent harmful smoke stack emissions from stationary combustion units such as power plants, smelters and refineries.
In the combustion of fossil fuels, harmful compounds such as nitric oxide and sulphur dioxide are produced. These compounds are relatively insoluble in water and are difficult to extract from smoke stack or flue gas by conventional -techniques. As a result, vast quantities of these compounds are discharged into the atmosphere every day. When in the atmosphere, these compounds react with photochemical oxidants, such as ozone and peroxyacetyl nitrate to produce nitrogen dioxide and sulphur trioxide. These new oxides are readily soluble in water and thus produce nitric and sulphuric acids, which then descend to the earth as acid rain or other forms of acid precipitation.
It is an object of the present invention to prevent the emission from smoke stacks of these harmful compounds by causing the co~pounds to react and be rendered harmless right in the flue or smoke stack before they can be emitted to the atmosphere.
~LZ5~
In the present invention, at least one oxygen type plasma arc burner is mounted in the flue to produce ozone and ultraviolet radiation. This causes the oxidizable harmful compounds to react with the ozone and produce water soluble oxides which may be contracted with an aqueous alkaline solution to produce relatively harmless sulphates and nitrates prior to being emitted to the atmosphere. In particular the water soluble oxides may be sprayed with the aqueous alkaline solution.
According to one aspect of the invention there is provided a method of treating flue gases in a flue of the type which includes a smoke stack or the like. The method comprises the steps of injecting an oxygen contalning plasma arc into the flue to produce ozone and ultraviolet radiation in the flue in contact with the flue gases therein. Also, the flue gases are oxidized with the zone to produce oxidized flue gases.
According to another aspect of the invention there is provided apparatus for treating flue gases in a flue having a wall defining a flue passage. The apparatus comprises mounting means defining an opening in the flue wall communicating with the flue passage. A plasma burner is mounted in the mounting means opening to produce a plasma arc extending into the passage. Also oxygen supply means is connected to the plasma burner communicating with the arc for supplying oxygen to the plasma burner :
khereby producing ozone in the flue in contact with the Elue gases.
A preferred embodiment of the invention will now be described, by way of example, wlth reference to -~ 5 the accompanying drawings, in which:
- Figure 1 is a diagrammatic view of a typical : flue gas treatment installation for a plant involved in the combustion of fossil fuels, a preEerred embodiment of the present invention being incorporated in this installation; and Figure 2 is a sectional view taken along lines 2-2 of Figure 1.
Referring to the drawings, a flue gas treatment installation incorporating a preferred embodiment of the present invention is generally indicated by reference numeral 10. Installation 10 includes a smoke stack 12 and a passageway 14 which delivers smoke or flue gases from a source of combustion (not shown) to smoke stack 12. The flue gases enter passageway 14 as indicated by arrow 16 and typically pass throu~h gas cleaning apparatus 1~, such , . ' ~
as an electrostatic precipitator or other equipment to remove solid particulate matter from the flue gases.
The flue gases then continue through a passage or conduit 20 where -they enter a reaction chamber 22 and then proceed on to smoke stack 12. In some cases, the flue gases can be subjected to a second cleaning operation before entering smoke stack 12 and this is indicated in Figure 1 by reference numeral 24, which could be a wet scrubber which is typically used to further clean the flue gases and remove acids therefrom. Figure 1 also shows a spray device 26 mounted in the wall of smoke stack 12. Reaction chamber 22 and spray device 26 are components of the preferred embodiments of the present invention. All of the other components are shown merely by way of example of typical flue gas treatment apparatus, and for the purposes of this invention, all of the passages through which the flue gases pass including smoke stack 12 are considered to be the flue in installation 10.
Referring in particular to Figure 2, reaction chamber 22 is shown having a cylindrical wall 28 which defines an inner chamber or flue passage 30 in communication with conduit 20. This flue passage is lined with a refractory linin~ 31 such as graphite.
Three plasma arc burners 32 are radially mounted in - 6 - 1Z~5~
wall 28, so that in operation, plasma arc burners 32 inject plasma arcs 34 into the flue.
The exact form of the plasma arc burners 32 or their number is not considered to be part of the present invention, but a suitable plasma arc burner is available from Westinghouse Electric Corporation of Pittsburgh, Pennsyalvania, U.S.A. and its construction is substantially like that shown in United States Patent No. 3,832,519 issued on August 27, 1974. In such a plasma arc burner, a gas is introduced through a centrally located inlet 36, and this gas is used to help spin or collimate the arc in the burner. Any gas could be used, but in the present invention, air or oxygen bearing gas is used, and this results in an oxygen containing plasma arc being injected into the flue. Where air is used, the plasma burner arc is referred to as an air plasma arc, and similarly, where oxygen or other oxygen bearing gas is used, it is referred to as an oxygen plasma arc. The air or oxygen in the plasma arc produces ozone in flue passage 30, and arcs 34 produce high intensity ultraviolet radiation, so that the flue gases are brought into contact with this ozone and ultraviolet radiation in the flue.
Plasma burners 32 are also connected -through conduits 38 to suitable sources of cooling water, and of course, the plasma burners are connected through power lines 40 to suitable power supplies to produce the arcs. Once again, the specific structure of the plasma burners and the apparatus required to operate these plasma burners are not part of the present invention, so will not be described in urther detail in this specification. It is part oE the present invention, however, that oxygen bearing gas or air be supplied through conduits 36 so that ozone is produced in the flue.
As seen best in Figure 1, spray device 26 is mounted in the flue wall of smoke stack 12 downstream - of plasma burners 32. Spray device 26 is connected to a supply of alkaline fluid, such as caustic steam, and for the purposes of this specification this is considered to be an aqueous alkaline spray. Although only one spray device 26 is shown in Figure 1, a plurality of spray nozzles would be provided in smoke stack 12.
In operation, flue gases that enter flue passage 30 in reaction chamber 22 are subjected to ozone and ultraviolet radiation. Ozone, being a photochemical oxidant, in conjunction with the ultraviolet radiation of plasma arcs 34, causes the undesirable nitric oxide and sulphur dioxide compounds in the flue gases to be oxidized and converted to - 8 - 1~5~
nitrogen dioxide and sulphur trioxide. It will be appreciated that these forms of ni-trogen and sulphur are soluble in water, so that when -they come into contact with the aqueous alkaline spray in smoke stack 10, acids result which are immediately neutralized.
In fact, the akalinity oE the spray is preferably slightly in excess of the stoichiometric requirement to neutralize the acid gases in the flue. The Einal stack discharge will therefore contain sodium or calcium based sulphates and nitrates and it may be slightly alkaline which may result in basic rain to perhaps reverse some of the existing damage done by acid rain.
Having described preferred embodiments o-f the invention, it will be appreciated that various modifications may be made to the method and apparatus described. For example, it has been mentioned that oxygen or air could be supplied to inlets 36 of the plasma burners, but steam could also be supplied through these inlets, in which case the plasma arc would be referred to as a steam plasma arc. I~ile this would produce the required ozone, it would also produce hydrogen or other fuel gases which would have to be burned oEf.
While three plasma burners 32 are shown in the preferred embodiment, as few as one burner could be 12~
used or more -than three burners could be used. Also, the burners could be mounted in the base of smoke stack 12 or in any other location in the flue upstream of the alkaline spray.
The allcaline spray through device 26 has been described as a caus-tic steam. Of course, it could be a lime steam or any other allcaline steam. Steam is preferred, so that it will not interfere with the buoyant properties of the flue gas in stack 12.
However, if this is not a problem, then any other alkaline spray could be used as well. Further, it will be appreciated that other apparatus could be used for providing the spray than spray nozzles, such as a ]5 spray ring or an atomization device. Finally, it may be desirable to locate the spray device higher up in the smoke stack, such as at mid-height.
Thus in particular, and in accordance with the invention~ nitric oxide and sulphur dioxide in the flue gases are oxidized by the ozone in the presence of the ultraviolet to water soluble nitrogen dioxide and sulphur trioxide, in an arc zone of the flue, the arc zone being a portion of the flue which contains the plasma arc.
- 1o ~2~
SIJPPI.E~1E~TARY DISCLOSUR~
The oxygen-containing plasma arc of the present invention has a temperature in excess oE
5,000C and typically of 5,500 to 27,500. These hiqh temperatures result in the development of ultraviolet radiation of high photon energy, typically of the order of 103 to 104eVr and of short wavelength typically 10A to 1000A, preferably lOA to lOOA.
In accordance with the invention it was Eound that the high photon energy ultraviolet radiation results in the ozone having a relatively long life before dissociation back to oxygen as compared with ozone produced by low photon energy ultraviolet radiation. In addition the short wavelength of the ultraviolet radiation renders it highly penetrating in different media so that the radiation rapidly penetrates the flue gas throughout the plasma arc zone ensuring relatively long life ozone throughout thc flue gas in the arc zone of the flue. In this way the flue gas in the arc zone is quickly and efficiently oxidized in a very short time, less than 1 second. In particular the residence time for oxidation in the arc zone is less than 100 micro-seconds, more usually less than 10 microseconds and most usually less than 1 microsecond.
.. . .
~x~
It was also unexpectedly found that by means of the plasma arc, ozone was produced in high volume, typically a magnitude of 103 times the amount produced in a conventional electrical discharge.
- Thus by means of the invention there is not only produced a high volume of ozone per volume of oxygen but additionally the ozone has a relatively long life sufficient to permit efficient oxidation of the Elue gas components. The ozone is reacted throughout the arc zone with the flue gases in an extremely short time prior to dissociation o the ozone, tllereby maximizing the efficiency of the operation.
In addition the ozidation reations can be carried out under non-agitating, non-mixing conditions in view of the high penetrating nature of the ultra-violet radiation which ensures maintenance o-E
- the relatively long life ozone through the arc zone.
Thus as will be apparent from the foregoing, one aspect of the invention provides a method of treating flue gases in a flue of the type which includes a smoke stack means. The method comprises the steps of injecting an oxygen containing plasma having a temperature in excess of 5000C into the flue to produce ozone and high photon energy ultra-violet radiation in the flue in contact with the flue gases therein. The flue gases are oxidized with the ozone to 5~
produce oxidized flue gases, which may then be contacted downstream of the plasma arc with an a~ueous solution to produce acids, or an alkaline solutlon to neutralize the acids in the flue.
As descrlbed above the oxidized flue gases are suitable sprayed with a spray of the solution, thereby providing a high surface area of contact between the oxidized gases and the solution for the production of acids or the neutralization reaction and dissolution of the water salts formed thereby.
With respect to prior proposals, German Patent No. 1,278,060 issued September l9/68 to Linde AG and Japanese Patent No. 0001-968 issued January 20/75 to Sertetsu Chem. Ind. generally disclose oxidation of nitrogen oxides via a silent electrical discharge or corona discharge. Although it is known that electrical discharge in the presence of oxygen will result in ozone formation, such ozone formation is relatively small as a percentage of the oxygen, and is instable and of short life rapidly dissociating to oxygen.
Furthermore, such ozone is typically formed only in the immediate vicinity of the spart or electrical discharge.
- 13 ~
Such electrical discharges typically have a temperature not exceeding lOOO~C, which is significantly lower than the temperature associatd wi-th oxygen containing p[lasmas, as in the present invention.
U.S. Patent 4,210,503 issued July 1/80 to Confer teaches the use of ultra-violet lamps to provide ultraviolet radiatlon to decompose vinyl chloride as wells as other compounds such as carbon disulphide, hydrogen sulphide and nitric oxide. The ultraviolet radiation is of low energy typically about lOeV and the decomposition reaction requires a residence time of 20 to 50 seconds depending on the intensity of the radition.
From the above it will be appreciated that the present invention is a relatively inexpensive and simple solution to the problem of acid rain caused by the emission of nitric oxide and sulphur dioxide from smoke stacks. Of course, the invention could be used in other applications as will be apparent to those skilled in the art.
Claims (29)
1. A method of treating flue gases in a flue of the type which includes a smoke stack , the method comprising: injecting an oxygen containing plasma arc into the flue to produce ozone and ultraviolet radiation in the flue in contact with the flue gases therein; and oxidizing the flue gases with said ozone to produce oxidized flue gases.
2. A method as claimed in claim 1 wherein the oxygen containing plasma arc is an air plasma arc.
3. A method as claimed in claim 1 and further comprising the step of contacting said oxidized flue gases with an aqueous solution to produce acids.
4. A method as claimed in claim 3 wherein said oxidized flue gases are contacted with an aqueous alkaline solution to neutralize said acids.
5. A method as claimed in claim 4 wherein the aqueous alkaline solution is caustic steam.
6. A method as claimed in claim 4 wherein the aqueous alkaline solution is lime steam.
7. A method as claimed in claim 5 or 6 wherein the alkalinity of the steam is slightly in excess of the stoichiometric requirement to neutralize the acids in the flue.
8. A method as claimed in claim 4 wherein the aqueous alkaline solution is caustic steam, and wherein said caustic steam is sprayed into the flue in the flue smoke stack.
9. A method as claimed in claim 1 wherein the oxygen containing plasma arc is a steam plasma arc; and further comprising the step of burning off any fuel gases produced in the flue by the plasma arc.
10. Apparatus for treating flue gases in a flue having a wall defining a flue passage, the apparatus comprising:
mounting means defining an opening in said flue wall communicating with said flue passage; a plasma burner mounted in said mounting means opening to produce a plasma arc extending into the flue passage; and oxygen supply means connected to the plasma burner communicating with the arc for supplying oxygen to the plasma burner thereby producing ozone in the flue in contact with the flue gases.
mounting means defining an opening in said flue wall communicating with said flue passage; a plasma burner mounted in said mounting means opening to produce a plasma arc extending into the flue passage; and oxygen supply means connected to the plasma burner communicating with the arc for supplying oxygen to the plasma burner thereby producing ozone in the flue in contact with the flue gases.
11. Apparatus as claimed in claim 10 and further comprising spray means mounted on the flue wall downstream of the plasma burner for spraying the flue gases therein with an aqueous solution.
12. Apparatus as claimed in claim 10 wherein the oxygen supply means includes an air supply, the air providing the oxygen content to produce the ozone.
13. Apparatus as claimed in claim 10 wherein the oxygen supply means includes a source of steam, the steam providing the oxygen content to produce the ozone.
14. Apparatus as claimed in claim 11 wherein the spray means includes a source of caustic steam, said steam being the aqueous spray.
15. Apparatus as claimed in claim 11, 12 or 14 wherein the plasma burner is a first plasma burner, and further comprising a plurality of additional plasma burners mounted in the flue wall.
16. Apparatus as claimed in claim 11, 12 or 14 wherein the spray means is mounted in the flue downstream of the plasma burners.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
17. A method of treating flue gases in a flue of the type which includes a smoke stack means, the method comprising:
injecting an oxygen containing plasma having a temperature in excess of 5000 degrees C into the flue to produce ozone and high photon energy ultraviolet radiation in the flue in contact with the flue gases therein; and oxidizing said flue gases with said ozone to produce oxidized flue gases.
injecting an oxygen containing plasma having a temperature in excess of 5000 degrees C into the flue to produce ozone and high photon energy ultraviolet radiation in the flue in contact with the flue gases therein; and oxidizing said flue gases with said ozone to produce oxidized flue gases.
18. A method as claimed in claim 17 and further comprising the step of contacting said oxidized flue gases with an aqueous solution to produce acids.
19. A method as claimed in claim 18 wherein said oxidized flue gases are contacted with an aqueous alkaline solution to neutralize said acids.
20. A method as claimed in claim 17, wherein the oxygen containing plasma arc is an air plasma arc.
21. A method as claimed in claim 19, wherein the aqueous alkaline solution is caustic steam.
22. A method as claimed in claim 19, wherein the aqueous alkaline solution is line steam.
23. A method as claimed in claim 19, 21 or 22 wherein the alkalinity of the solution is slightly in excess of the stoichiometric requirement to neutralize the acid gases in the flue.
24. A method as claimed in claim 17, wherein the aqueous alkaline solution is caustic steam, and wherein said caustic steam is sprayed into the flue in the flue smoke stack.
25. A method as claimed in claim 17, wherein the oxygen containing plasma arc is a steam plasma arc; and further comprising the step of burning off any flue gases produced in the flue by the plasma arc.
26. A method of treating flue gases in a flue, comprising:
i) injecting an oxygen component-containing plasma arc having a temperature of 5,500 to 27,750 degrees C into an arc zone of a flue with formation of ozone and high photon energy, high penetration short wave-length ultraviolet radiation;
ii) contacting oxidizable flue gases containing at least one of nitric oxide and sulphur dioxide, with said oxide in said arc zone in the presence of said high photon energy, high penetration, short wavelength ultraviolet radiation;
iii) oxidizing said oxidizable flue gases with said ozone in said arc zone, in a reaction time of less than 100 microseconds to produce oxidized flue gases; and iv) delivering said oxidized flue gases from said arc zone.
i) injecting an oxygen component-containing plasma arc having a temperature of 5,500 to 27,750 degrees C into an arc zone of a flue with formation of ozone and high photon energy, high penetration short wave-length ultraviolet radiation;
ii) contacting oxidizable flue gases containing at least one of nitric oxide and sulphur dioxide, with said oxide in said arc zone in the presence of said high photon energy, high penetration, short wavelength ultraviolet radiation;
iii) oxidizing said oxidizable flue gases with said ozone in said arc zone, in a reaction time of less than 100 microseconds to produce oxidized flue gases; and iv) delivering said oxidized flue gases from said arc zone.
27. A method as claimed in claim 26 and further comprising the step of neutralizing said oxidized flue gases downstream of said arc zone, with an aqueous alkaline liquid.
28. A method according to claim 26, wherein the oxidizable flue gases comprise nitric oxide and sulphur dioxide and wherein the oxidizing step oxidizes nitric oxide to nitrogen dioxide and sulphur dioxide to sulphur trioxide, and said neutralizing step comprises spraying said nitrogen dioxide and sulphur trioxide with an aqueous alkaline spray to form aqueous nitrate and sulphate salts.
29. A process according to claim 26, wherein said ultraviolet radiation in steps i) and ii) has an energy of the order of 103 to 104 eV and a wavelength of 10.ANG. to 100.ANG..
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000480760A CA1258441A (en) | 1985-05-03 | 1985-05-03 | Plasma treatment of flue gases |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000480760A CA1258441A (en) | 1985-05-03 | 1985-05-03 | Plasma treatment of flue gases |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1258441A true CA1258441A (en) | 1989-08-15 |
Family
ID=4130428
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000480760A Expired CA1258441A (en) | 1985-05-03 | 1985-05-03 | Plasma treatment of flue gases |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1258441A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7398643B2 (en) | 2006-05-16 | 2008-07-15 | Dana Canada Corporation | Combined EGR cooler and plasma reactor |
-
1985
- 1985-05-03 CA CA000480760A patent/CA1258441A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7398643B2 (en) | 2006-05-16 | 2008-07-15 | Dana Canada Corporation | Combined EGR cooler and plasma reactor |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7498009B2 (en) | Controlled spectrum ultraviolet radiation pollution control process | |
| EP2462056B1 (en) | Activation of hydrogen peroxide with catalyst | |
| US6676912B1 (en) | Method for removal of nitrogen oxides from stationary combustion sources | |
| KR101902331B1 (en) | NOx reduction system using microwave plasma based on Selective Non-Catalytic Reduction | |
| KR102232920B1 (en) | Exhaust gas treatment method, and exhaust gas treatment device | |
| KR20100121968A (en) | Non-incineration pyrolysis treatment system using steam plasma for pollution materials | |
| CN102160959A (en) | Fume purification system based on advanced oxygenation combining wet scrubbing | |
| US20050019229A1 (en) | High temperature decomposition of hydrogen peroxide | |
| JPH07502332A (en) | How to dispose of liquid waste | |
| CA1258441A (en) | Plasma treatment of flue gases | |
| WO2007061401A2 (en) | Controlled spectrum ultraviolet radiation pollution control process | |
| EP3875167A1 (en) | Improved nox removal method | |
| JP3711490B2 (en) | Method and apparatus for oxidizing SO2 in exhaust gas using HO2 radical as OH generating reactive species in radical chain reaction of SO2 oxidation | |
| JPH08192029A (en) | Denitrifying and desulfurizing method and device therefor | |
| JPH10132241A (en) | Method for disposing of waste liquid or exhaust gas | |
| CN1600409A (en) | Method for removing multipollutant in flue gas by combining free radical showering and absorption of alkali liquor | |
| JPH08197039A (en) | Treatment of ammonia-containing waste water | |
| KR102484219B1 (en) | Flue Gas Denitrification System and Desulfurization System In Wet Oxidation Technology | |
| KR100197287B1 (en) | Reforming reductant for exhaust gas denitrogen and the method of removing nitrogen oxide | |
| KR100335737B1 (en) | Plasma Scrubbing System for Handling Harmful Gas | |
| KR100451285B1 (en) | The reduction method of nitrogen oxides and sulfur oxides using hydrogen peroxide solution and calcium oxide solution | |
| KR19990018050A (en) | Neutralizer injection method and apparatus for flue gas treatment by electron beam irradiation | |
| KR19990071259A (en) | Flue gas recycling method and device | |
| KR200405302Y1 (en) | Burning chamber of a exhausted gas purifying nevice | |
| CN109316912B (en) | Application of wet discharge reactor in removing nitrogen oxides in waste gas |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |