CA1067835A - Increasing the efficiency of electrostatic precipitators - Google Patents
Increasing the efficiency of electrostatic precipitatorsInfo
- Publication number
- CA1067835A CA1067835A CA251,354A CA251354A CA1067835A CA 1067835 A CA1067835 A CA 1067835A CA 251354 A CA251354 A CA 251354A CA 1067835 A CA1067835 A CA 1067835A
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- CA
- Canada
- Prior art keywords
- oxidizing agent
- sulphur
- sulphur dioxide
- flue gas
- air stream
- 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.)
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Abstract
ABSTRACT OF THE DISCLOSURE
A method for improving the performance of electrostatic precipitators by reducing the resistivity of fly ash by the oxidation of sulphur dioxide in the flue gas stream to sulphur trioxide.
A method for improving the performance of electrostatic precipitators by reducing the resistivity of fly ash by the oxidation of sulphur dioxide in the flue gas stream to sulphur trioxide.
Description
~': ~ ~ ( I ~ C)G~783~
INT~ODUCTION
The satisfactory operation of electrostatic pricipitators in collecting fly ash from the flue gases of devices burniny coal is dependent on several factors including the insulating properties of the ash collected on the electrodes of the precipitator. Highly resistant ash can affect precipitator performance in two ways- -1) a layer o~ ash on the dischaxge electrode can suppress the corona current; and 2) a layer of ash on the collecting electroae may prevent the loss of charge from newly arriving fly ash, causing reverse corona discharges and lowering of the flashover voltage.
Resistivity of the fly ash is directly influenced by the formation of trace amounts of sulphur trioxide in the flue ~as.
These trace amounts of sulphur trioxide combine with moisture in the flue gas to form sulphuric acid which is adsorbed onto the surfaces of the fly ash particles as the gas cools, thereby formi~g a conducting film.
Sulphur in coal oxidizes upon combustion to both sulphur dioxide and sulphur trioxide. The volume of sulphur trioxide formed is usually between 1% and 3~ of the volume of sulphur dioxide formed. Therefore, it has been found that i~ the coal burned ha~
a high sulphur content, say above about 2.5~ by weight, it is likely that the sulphur trioxide present in the flue gas wîll be adequate to acilitate efficient precipitation of any fly ash formed. `-Current environmental standards, however, often restrictthe permissible sulphur concentration in the coal to 1%, 0.5% or less. Use of such low sulphur fuels results in a concomitant re-duction in the concentration o sulphur trioxide formed upon combustion o the fuel. Since less sulphur trioxide is available to form sulphuric acid and condense on the fly ash particles, the electrical resistivity of the particles is increased resulting in less efficient electrostatic precipitator operation.
INT~ODUCTION
The satisfactory operation of electrostatic pricipitators in collecting fly ash from the flue gases of devices burniny coal is dependent on several factors including the insulating properties of the ash collected on the electrodes of the precipitator. Highly resistant ash can affect precipitator performance in two ways- -1) a layer o~ ash on the dischaxge electrode can suppress the corona current; and 2) a layer of ash on the collecting electroae may prevent the loss of charge from newly arriving fly ash, causing reverse corona discharges and lowering of the flashover voltage.
Resistivity of the fly ash is directly influenced by the formation of trace amounts of sulphur trioxide in the flue ~as.
These trace amounts of sulphur trioxide combine with moisture in the flue gas to form sulphuric acid which is adsorbed onto the surfaces of the fly ash particles as the gas cools, thereby formi~g a conducting film.
Sulphur in coal oxidizes upon combustion to both sulphur dioxide and sulphur trioxide. The volume of sulphur trioxide formed is usually between 1% and 3~ of the volume of sulphur dioxide formed. Therefore, it has been found that i~ the coal burned ha~
a high sulphur content, say above about 2.5~ by weight, it is likely that the sulphur trioxide present in the flue gas wîll be adequate to acilitate efficient precipitation of any fly ash formed. `-Current environmental standards, however, often restrictthe permissible sulphur concentration in the coal to 1%, 0.5% or less. Use of such low sulphur fuels results in a concomitant re-duction in the concentration o sulphur trioxide formed upon combustion o the fuel. Since less sulphur trioxide is available to form sulphuric acid and condense on the fly ash particles, the electrical resistivity of the particles is increased resulting in less efficient electrostatic precipitator operation.
- 2 -~ ~ ( ~6~335 This problem has, in the past, been remedied by:
1) injecting sluphur trioxide g~s directly into the ilue gas stream, or 2) replacing present electrostatic precipitators which operate in the 300F flue gas temperature range with l'hot" electrostatic precipitators which operate at approximately 600F (fly ash resistivity, which is temperature dependent, alls to acceptable levels at this temperature), or
1) injecting sluphur trioxide g~s directly into the ilue gas stream, or 2) replacing present electrostatic precipitators which operate in the 300F flue gas temperature range with l'hot" electrostatic precipitators which operate at approximately 600F (fly ash resistivity, which is temperature dependent, alls to acceptable levels at this temperature), or
3~ introducing auxiliary mechanical fly ash col-lectors to compensate for the reduction in the efficiency of the electrostatic precipitators.
Each of these remedies has serious draw~acks. Construction o~ -auxiliary me~hanical collectors involves consi~erable short term expense and their efficacy as a solution to this problem is ques-tionable (See: Jacob Katz, "The Effective Collection of Fly Ash _ at Pulverized Coal-Fired Plants," Journal of the Air Pollution Control Association, Volume 15, ~o. 11, November, 1~65~. Replace-_ . ,ment of pr~sent precipitators with new "hot" precipitators is prohibitively expensive and time consuming.
Finally r the direct introduction of sulphur trioxide gas into the flue gas stream is dangerous and therefore, also not a desirable remedy to the resistivit~ problem. Sulphur trioxide is dangerous to handle. It is highly hygroscopic and if dispersed in~o the air, it immediately forms a dense sulphuric acid mist. Sulphur dioxide may ~e oxidized to sulphur trioxide in a catalytic chamber and immediately injected into the ~lue s~stem. However, this reaction is a highly exothermic one re~uiring additional apparatus to maintain the temperature o~ the catalytic chamber.
My invention involves the oxidation of sulphur dioxide already present in the flue gas stream to sulphur trioxide. It , 6~7~35 it more economical and easier to implement than any of the earlier noted remedies.
E INVENTION
Description mis invention involves a method for improving the performance of electrostatic precipitators in the collection of fly ash in flue gas streams containing sulphur dioxide. In implementing this invention, a solution containing an inorganic oxidizing agent is introduced into the flue gas stream prior to treatment by the electrostatic precipitator. Ihe inorganic oxidizing agent oxidizes some of the sulphur dioxide in the flue gas stream to sulphur trioxide, which is necessary for the efficient operation of the electrostatic precipitator.
Thus, according to the broadest aspect of this invention there is provided a method for improving the performance of electrostatic precipitators in the collection of fly ash from flue gas streams containing sulphur dioxide comprising oxidizing at least a portion of the sulphur dioxide present to provide at least 15 ppm sulphur trioxide in the flue gas by means of an amount of an inorganic oxidizing agent introduced into the flue gas and chosen from the group consistlng of chlorine gas, and a~ueous solutions of chlorine, hydrogen peroxide, sodium hypochlorite, sodium chlorite, potassium permanganate, and manganese nitrate.
m e Oxidizing Agents The inorganic oxidizing agent used in the practice of the in~ention may be selected from a large number of inorganic compounds which are capable of oxidizing sulphur dioxide to sulphur trioxide. The preferred inorganic oxidizing agents are water soluble and include such agents as hydrogen peroxide, sodium hypochlorite, sodium chlorite, potassium permanganate, chlorine and manganese nitrate.
~he inorganic oxidizing agents are utilized in the form of solutions, preferably aqueous solutions having concentrations ranging ..... ~
; t -4-~06~33S
between 1% up to the saturation of solubility of the compound in water.
Typical aqueous solutions of these inorganic oxidizing agents used in laboratory tests are set forth in Table I below.
4a-: -:
:
.- ~ ~ .- . .
~................. ~
~ ~ .
., ~-, - .
H U3 ~
p H H c H ~ X ~ X ~ ~ y ~- V j~
r ~ h :~ ~ h 1 ~ U
: ~ , -. , : q~ . . ..
: .~,, -: . . -' ,. ' ~ ' ', ' ' ~: - - . .
-, ' .
'~ , ' . . .
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¦ Dosa~e The amount o~ inorganic oxidizing agent used in the invention may be varied although it may be stated in general terms that the amount of inorganic oxidizing agent should be that amoun~
,which is at least sufficient to oxidize a suficient quantity o~
- ¦ S2 to S03 to produce a total of at least 15 parts per million and preferably 20 parts per million or more of S03 in the system. The lamount of sulphur dioxide sought to be oxidized, therefore, is ¦governed by the amount of S03 that is originally present.
¦ The apparatus used in testing this invention was designed to simulate certain aspects of an electrostatic precipitator, namely the movement of a stream of mixed gases through a cavity operatin~
at a characteristic temperature. It consists of:
l) a hot air blower exhausting into an insulated tube, 2) a port in the insulated tube through which a measured amount of sulphur dioxide is introduced into the heated air stream, 3) an insulated tubulax cavity provided with I several temperature sensing devices along its length,- 4) an injection port located near the blower end of the cavity for introducing a measured amount of an oxidizing agent into the sulphur dioxide rich air stream passing through the insulated cavity, and I 5) a sample poxt located at the other end of the ¦ insulated cavity for extracting samples of the heated ¦ air stream.
¦ At measured time intervals, samples are extracted from the !sample port and analyzed for sulphur dioxide content. Comparison ¦lof the amount of sulphur dioxide initially introduced into the 1067~35 heated air stream with the amount of sulphur dioxide present in the air stream after the introduction of the oxidizing agent and after the passage of the air stream through the insulated cavity shows a si~nificant drop in sulphur dioxide content. ~See Table II). It is believed that this drop is due to oxidation of the sulphur dioxide to sulphur trioxide.
The test results generally suggest a stoichiometric rela-tionship between the amount of oxidizing agent introduced and the amount of sulphur trioxide produced for most of the oxidizing agents tested~ Potassium permanganate and manganese nitrate, however, give greater than stoichiometric results. This is believed to be due to the fact that besides acting directly as oxidi~ing agentsr these compounds also produce decomposition products -- particularly nitrog n and manganese oxides -- which further act as catalyst$ for the convexsion o additional sulphur dioxide to sulphur trioxide_ . .
A measured amount of a 10% aqueous solution of hydrogen peroxide was introduced into the heated air stream at the injectIon port in the form of a mistt using an 8 inch siphon head with a spray nozzle subjected to compxessed air at 20 psi. Samples were con-tinuously extracted at the sample port and sulphur dioxide concentrations at definite time intervals were recorded. The re-sults, shown in tabulated ~orm in Table II, indicate a significant reduction in sulphur dioxide concentration. The chemical reaction occurring is believed to be S02 ~ ~2O2 -~ S03 ~ H~O.
A measured amount of a 5~ aqueous solution of hydrogen peroxide was introduced into the heated air stream at the injec~ion port in the form of a mist, using an 8 inch siphon head with a spray I ~'7~3~
nozzle subjected to compressed air at 20 psi. Samples were continuously extracted at the sample port and sulphur dioxide concentrations at definite time intexvals were recorded. The re-sults, ~hown in tabulated form in Table II, indicate a significant reduction in sulphur dioxide concentration corresponding to a ¦stoichiometric increase in sulphur trioxide concentration.
. .
A measured amount of a 3% aqueous solution of hydrogen per-oxide was introduced into the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spr~y nozzle subjected to compressed air at 20 psi. Samples wexe continu-ously extracted at the sample port and sulphur dioxide concentra-tions at definite time intervals were recorded. The results, shown in tabulated form in Table II, lndicate a significant reduction in sulphur dioxide concentration corresponding to a stoichiometric increase in sulphur trioxide concentration. _ A measured amount of a 5.25~ aqueous solution of sodium hypochlorite was introduced into the heated air 5tream at the in-jection port in the form of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continuously extracted from the air stream at the 5ample port and sulphur dioxide concentrations at definite tlme intervals were jrecorded. The results, as shown in tabulated form in Table II, -¦indicate a significant reduction in sulphur dioxide concentration corresponding to a stoichiometric increase in sulphur trioxide concentration.
. 1, 106~1~135 EXP~LE S
A measured amount of a 10% aqueous solution of sodium chlorite was introduced into the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a s~ray nozzle subjected to compressed air at 20 psi. Samples were continuously extracted from the air stream at the sample port an~
sulphur dioxide concentrations at definite time intervals were recorded. The results, as shown in tabulated form in Table II, indicate a significant reduction in sulphur dioxide concentration corresponding to a stoichiometric increase in sulphur trioxide concentration.
; , ' ,. ,' .
EXAMPLE'6 A measured amount of a 5~ aqueous solution of pota~sium permanganate was introudced into the heated air stream at the in-jection port in the,form of a mist, using an 8 inch siphon head ~ith a spray nozzle subjected to compxessed alr at 20 psi. Samples _ were continuously extracted from,the air stream at the sample por~
and sulphur dioxide concentrations at definite time intervals wére recorded. The results, as shown in tabulated form in ~able II, indicate a significant reduction in sulphur dioxide concentration corresponding to an increase in sulphur trioxide concentration far in excess of what would be expected stoichiometrically. This , excessive change is due to the catalytic effects of decomposition , products of potassium permanganateD , EX~PLE 7 ~
A measured amount of chlorine gas was introduced into the heated air stream at the in~ection port. Samples were continuously extracted at the sample port and sulphur dioxide concentratiOns at definite time 'intervals were recorded. The results, shown in 10~i78~5 j tabulated form in Table II, indicate a significant reduction in sulphur dioxide concentration corresponding to an increase in sul-¦ phur trioxide concentration ar in excess of what would be expected ~stoichiometrically~
A measured amount of chlorine gas and water was introducedinto the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spray nozzle sub~ected ~o ~compressed air at 20 psi~ Samples were continuously extracted a~
the sample port and sulphur dioxide concentrations at definite time intervals were recorded. The results t 5hown in tabulated form i~
Table II indicate a significant reduction in sulphur dioxide con-centràtion corresponding to an increase in sulphur trioxide concen-tration far in excess of what would be expected stoichiometrically.
~XAMPLE 9 ~ _ A measured amount of a 6% aqueous solution of manganese nitrate was introduced into the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continu-ously extracted from the air stream at the sample port and sulphur dioxide concentrations at definite time intervals were recorded. It will be noted that the temperature of the cavit~ has been raised to more nearly simulate flue gas conditions at a point prior to the air ',preheater. It is expected that injectio~ of the oxidiz-¦ing agent at this point will be convenient and effective.
¦l EXAMPLE 10 ¦, A measured amount of a 4% aqueous solution of manganese ~! nitrate was introduced into the he~ted air stream at the injection port in the form of a mist, usin~ an 8 inch siphon head with a sprayj ~ 67~335 nozzle subjected to compressed air at 20 psi. Samples were continuously extracted from the air stream at the sample port and ¦ sulphur dioxide concentrations at definite time intervals were recorded. It will be noted that the temperature of the cavity has been raised to more nearly simulate flue gas conditions at a poin~
prior to the air preheater. It is expected -that injec-tion of the oxidizing agent at this point will be convenient and , effective. The results, as shown in tabulated form in Table II~
indlcate a significant reduction in sulphur dioxide concentxation corresponding to an increase in sulphur trioxide concentration far in excess of what would be expected stoichiometrically. This excess is,believed to be due to the catalytic effects of d~composition products of manganese nitrate.
A measured amount of a 3% aqueous solution of manganese nitrate was introduced into,the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continu-ously extracted from the air stream at the sample port and sulphur dioxide concentrations at definite time intervals were recorded,~ It will be noted that the temperature of the ca~ity has been raised to more nearly simulate flue gas conditions at a point prior to the air preheater. ' It is expected that injection of the oxidiz-ing agent at this point will be convenient and effective. The results, as shown in tabulated form in Table II, indicate a signi-ficant reduction in,sulphur dioxide concentration corresponding t~
an increase in sulphur trioxide concentration far in excess of what would be expected s-toichiometrically. This excess is believed to be d.le to the catalytic effects of decomposition products oE manganese ~nitrat 1067~35 ' EXAMPLE 12 .
A measured amount of a 2P6 aqueous solution of manganese ¦nitrate was introduced into the heated air stream at the injection Ipor~ in the for~ of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continu-¦ously extracted from the air stream at the sample port and sulphurdioxide concentrations at definite time intervals were recorded. It will be noted that the temperature of the cavity has been raiged to .
more nearly simulate flue gas conditions at a point prior to the air ~preheater. It is expected that injection of the oxidiz-¦ing agent at this point will be convenient and effective.
Two test series were run. The results for the first tes~
series, as shown in tabulated form in Table II, indicate a signifi- .
cant reduction in sulphur dioxide concentration corresponding t~ an increase in sulphur trioxide concentration far in excess of what would be expected stoichiometrically. The second test series in which instrumental malfunctions occurred, show results inferior to ~those pre ously obtained.
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CONCLUSION
The invention is not intended to be limited to the . .
treatment of eoal flue gases, but rather may be applied in the treatment of the flue gases of other fossil fuels, such as petro-leum residual fuels. Indeed, the invention may be useful in the treatment of any gas stream containing particulate matter of high electrical resistance which contains sulphur dioxide ~vailable for conversion to sulphur trioxide. In addition, the above examples ..
have been given without intent to limit the extent of this invention.
The method disclosed in this invention can be readily implemented as an e~ficient remedy for electrostatic precipitatox inefficiency resulting from high resistivity fly ash. .
: ~
; I Cla~m: ~
, . ' ' ~:
. . ..
I '- ' . .
I . .
Each of these remedies has serious draw~acks. Construction o~ -auxiliary me~hanical collectors involves consi~erable short term expense and their efficacy as a solution to this problem is ques-tionable (See: Jacob Katz, "The Effective Collection of Fly Ash _ at Pulverized Coal-Fired Plants," Journal of the Air Pollution Control Association, Volume 15, ~o. 11, November, 1~65~. Replace-_ . ,ment of pr~sent precipitators with new "hot" precipitators is prohibitively expensive and time consuming.
Finally r the direct introduction of sulphur trioxide gas into the flue gas stream is dangerous and therefore, also not a desirable remedy to the resistivit~ problem. Sulphur trioxide is dangerous to handle. It is highly hygroscopic and if dispersed in~o the air, it immediately forms a dense sulphuric acid mist. Sulphur dioxide may ~e oxidized to sulphur trioxide in a catalytic chamber and immediately injected into the ~lue s~stem. However, this reaction is a highly exothermic one re~uiring additional apparatus to maintain the temperature o~ the catalytic chamber.
My invention involves the oxidation of sulphur dioxide already present in the flue gas stream to sulphur trioxide. It , 6~7~35 it more economical and easier to implement than any of the earlier noted remedies.
E INVENTION
Description mis invention involves a method for improving the performance of electrostatic precipitators in the collection of fly ash in flue gas streams containing sulphur dioxide. In implementing this invention, a solution containing an inorganic oxidizing agent is introduced into the flue gas stream prior to treatment by the electrostatic precipitator. Ihe inorganic oxidizing agent oxidizes some of the sulphur dioxide in the flue gas stream to sulphur trioxide, which is necessary for the efficient operation of the electrostatic precipitator.
Thus, according to the broadest aspect of this invention there is provided a method for improving the performance of electrostatic precipitators in the collection of fly ash from flue gas streams containing sulphur dioxide comprising oxidizing at least a portion of the sulphur dioxide present to provide at least 15 ppm sulphur trioxide in the flue gas by means of an amount of an inorganic oxidizing agent introduced into the flue gas and chosen from the group consistlng of chlorine gas, and a~ueous solutions of chlorine, hydrogen peroxide, sodium hypochlorite, sodium chlorite, potassium permanganate, and manganese nitrate.
m e Oxidizing Agents The inorganic oxidizing agent used in the practice of the in~ention may be selected from a large number of inorganic compounds which are capable of oxidizing sulphur dioxide to sulphur trioxide. The preferred inorganic oxidizing agents are water soluble and include such agents as hydrogen peroxide, sodium hypochlorite, sodium chlorite, potassium permanganate, chlorine and manganese nitrate.
~he inorganic oxidizing agents are utilized in the form of solutions, preferably aqueous solutions having concentrations ranging ..... ~
; t -4-~06~33S
between 1% up to the saturation of solubility of the compound in water.
Typical aqueous solutions of these inorganic oxidizing agents used in laboratory tests are set forth in Table I below.
4a-: -:
:
.- ~ ~ .- . .
~................. ~
~ ~ .
., ~-, - .
H U3 ~
p H H c H ~ X ~ X ~ ~ y ~- V j~
r ~ h :~ ~ h 1 ~ U
: ~ , -. , : q~ . . ..
: .~,, -: . . -' ,. ' ~ ' ', ' ' ~: - - . .
-, ' .
'~ , ' . . .
' ` j ~0~;7~33~
¦ Dosa~e The amount o~ inorganic oxidizing agent used in the invention may be varied although it may be stated in general terms that the amount of inorganic oxidizing agent should be that amoun~
,which is at least sufficient to oxidize a suficient quantity o~
- ¦ S2 to S03 to produce a total of at least 15 parts per million and preferably 20 parts per million or more of S03 in the system. The lamount of sulphur dioxide sought to be oxidized, therefore, is ¦governed by the amount of S03 that is originally present.
¦ The apparatus used in testing this invention was designed to simulate certain aspects of an electrostatic precipitator, namely the movement of a stream of mixed gases through a cavity operatin~
at a characteristic temperature. It consists of:
l) a hot air blower exhausting into an insulated tube, 2) a port in the insulated tube through which a measured amount of sulphur dioxide is introduced into the heated air stream, 3) an insulated tubulax cavity provided with I several temperature sensing devices along its length,- 4) an injection port located near the blower end of the cavity for introducing a measured amount of an oxidizing agent into the sulphur dioxide rich air stream passing through the insulated cavity, and I 5) a sample poxt located at the other end of the ¦ insulated cavity for extracting samples of the heated ¦ air stream.
¦ At measured time intervals, samples are extracted from the !sample port and analyzed for sulphur dioxide content. Comparison ¦lof the amount of sulphur dioxide initially introduced into the 1067~35 heated air stream with the amount of sulphur dioxide present in the air stream after the introduction of the oxidizing agent and after the passage of the air stream through the insulated cavity shows a si~nificant drop in sulphur dioxide content. ~See Table II). It is believed that this drop is due to oxidation of the sulphur dioxide to sulphur trioxide.
The test results generally suggest a stoichiometric rela-tionship between the amount of oxidizing agent introduced and the amount of sulphur trioxide produced for most of the oxidizing agents tested~ Potassium permanganate and manganese nitrate, however, give greater than stoichiometric results. This is believed to be due to the fact that besides acting directly as oxidi~ing agentsr these compounds also produce decomposition products -- particularly nitrog n and manganese oxides -- which further act as catalyst$ for the convexsion o additional sulphur dioxide to sulphur trioxide_ . .
A measured amount of a 10% aqueous solution of hydrogen peroxide was introduced into the heated air stream at the injectIon port in the form of a mistt using an 8 inch siphon head with a spray nozzle subjected to compxessed air at 20 psi. Samples were con-tinuously extracted at the sample port and sulphur dioxide concentrations at definite time intervals were recorded. The re-sults, shown in tabulated ~orm in Table II, indicate a significant reduction in sulphur dioxide concentration. The chemical reaction occurring is believed to be S02 ~ ~2O2 -~ S03 ~ H~O.
A measured amount of a 5~ aqueous solution of hydrogen peroxide was introduced into the heated air stream at the injec~ion port in the form of a mist, using an 8 inch siphon head with a spray I ~'7~3~
nozzle subjected to compressed air at 20 psi. Samples were continuously extracted at the sample port and sulphur dioxide concentrations at definite time intexvals were recorded. The re-sults, ~hown in tabulated form in Table II, indicate a significant reduction in sulphur dioxide concentration corresponding to a ¦stoichiometric increase in sulphur trioxide concentration.
. .
A measured amount of a 3% aqueous solution of hydrogen per-oxide was introduced into the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spr~y nozzle subjected to compressed air at 20 psi. Samples wexe continu-ously extracted at the sample port and sulphur dioxide concentra-tions at definite time intervals were recorded. The results, shown in tabulated form in Table II, lndicate a significant reduction in sulphur dioxide concentration corresponding to a stoichiometric increase in sulphur trioxide concentration. _ A measured amount of a 5.25~ aqueous solution of sodium hypochlorite was introduced into the heated air 5tream at the in-jection port in the form of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continuously extracted from the air stream at the 5ample port and sulphur dioxide concentrations at definite tlme intervals were jrecorded. The results, as shown in tabulated form in Table II, -¦indicate a significant reduction in sulphur dioxide concentration corresponding to a stoichiometric increase in sulphur trioxide concentration.
. 1, 106~1~135 EXP~LE S
A measured amount of a 10% aqueous solution of sodium chlorite was introduced into the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a s~ray nozzle subjected to compressed air at 20 psi. Samples were continuously extracted from the air stream at the sample port an~
sulphur dioxide concentrations at definite time intervals were recorded. The results, as shown in tabulated form in Table II, indicate a significant reduction in sulphur dioxide concentration corresponding to a stoichiometric increase in sulphur trioxide concentration.
; , ' ,. ,' .
EXAMPLE'6 A measured amount of a 5~ aqueous solution of pota~sium permanganate was introudced into the heated air stream at the in-jection port in the,form of a mist, using an 8 inch siphon head ~ith a spray nozzle subjected to compxessed alr at 20 psi. Samples _ were continuously extracted from,the air stream at the sample por~
and sulphur dioxide concentrations at definite time intervals wére recorded. The results, as shown in tabulated form in ~able II, indicate a significant reduction in sulphur dioxide concentration corresponding to an increase in sulphur trioxide concentration far in excess of what would be expected stoichiometrically. This , excessive change is due to the catalytic effects of decomposition , products of potassium permanganateD , EX~PLE 7 ~
A measured amount of chlorine gas was introduced into the heated air stream at the in~ection port. Samples were continuously extracted at the sample port and sulphur dioxide concentratiOns at definite time 'intervals were recorded. The results, shown in 10~i78~5 j tabulated form in Table II, indicate a significant reduction in sulphur dioxide concentration corresponding to an increase in sul-¦ phur trioxide concentration ar in excess of what would be expected ~stoichiometrically~
A measured amount of chlorine gas and water was introducedinto the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spray nozzle sub~ected ~o ~compressed air at 20 psi~ Samples were continuously extracted a~
the sample port and sulphur dioxide concentrations at definite time intervals were recorded. The results t 5hown in tabulated form i~
Table II indicate a significant reduction in sulphur dioxide con-centràtion corresponding to an increase in sulphur trioxide concen-tration far in excess of what would be expected stoichiometrically.
~XAMPLE 9 ~ _ A measured amount of a 6% aqueous solution of manganese nitrate was introduced into the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continu-ously extracted from the air stream at the sample port and sulphur dioxide concentrations at definite time intervals were recorded. It will be noted that the temperature of the cavit~ has been raised to more nearly simulate flue gas conditions at a point prior to the air ',preheater. It is expected that injectio~ of the oxidiz-¦ing agent at this point will be convenient and effective.
¦l EXAMPLE 10 ¦, A measured amount of a 4% aqueous solution of manganese ~! nitrate was introduced into the he~ted air stream at the injection port in the form of a mist, usin~ an 8 inch siphon head with a sprayj ~ 67~335 nozzle subjected to compressed air at 20 psi. Samples were continuously extracted from the air stream at the sample port and ¦ sulphur dioxide concentrations at definite time intervals were recorded. It will be noted that the temperature of the cavity has been raised to more nearly simulate flue gas conditions at a poin~
prior to the air preheater. It is expected -that injec-tion of the oxidizing agent at this point will be convenient and , effective. The results, as shown in tabulated form in Table II~
indlcate a significant reduction in sulphur dioxide concentxation corresponding to an increase in sulphur trioxide concentration far in excess of what would be expected stoichiometrically. This excess is,believed to be due to the catalytic effects of d~composition products of manganese nitrate.
A measured amount of a 3% aqueous solution of manganese nitrate was introduced into,the heated air stream at the injection port in the form of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continu-ously extracted from the air stream at the sample port and sulphur dioxide concentrations at definite time intervals were recorded,~ It will be noted that the temperature of the ca~ity has been raised to more nearly simulate flue gas conditions at a point prior to the air preheater. ' It is expected that injection of the oxidiz-ing agent at this point will be convenient and effective. The results, as shown in tabulated form in Table II, indicate a signi-ficant reduction in,sulphur dioxide concentration corresponding t~
an increase in sulphur trioxide concentration far in excess of what would be expected s-toichiometrically. This excess is believed to be d.le to the catalytic effects of decomposition products oE manganese ~nitrat 1067~35 ' EXAMPLE 12 .
A measured amount of a 2P6 aqueous solution of manganese ¦nitrate was introduced into the heated air stream at the injection Ipor~ in the for~ of a mist, using an 8 inch siphon head with a spray nozzle subjected to compressed air at 20 psi. Samples were continu-¦ously extracted from the air stream at the sample port and sulphurdioxide concentrations at definite time intervals were recorded. It will be noted that the temperature of the cavity has been raiged to .
more nearly simulate flue gas conditions at a point prior to the air ~preheater. It is expected that injection of the oxidiz-¦ing agent at this point will be convenient and effective.
Two test series were run. The results for the first tes~
series, as shown in tabulated form in Table II, indicate a signifi- .
cant reduction in sulphur dioxide concentration corresponding t~ an increase in sulphur trioxide concentration far in excess of what would be expected stoichiometrically. The second test series in which instrumental malfunctions occurred, show results inferior to ~those pre ously obtained.
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$ ;1 Ll ~ ; I a ~ S:~J;nNIl~
9 6)67B35 1~ ~ ~1 r . . _, ,, . l OD u~ ~ ~ ~ ~ a~
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r c I r j r u u ¦ d r C
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w æ l I~n , ~ ul ~u7 ¦ ~ ~ a~ G ~ N n 1 ~ 3 ', .... ' c 1~ . ,~,''. ' ".
:2 I w . ¦ r i l l l I~ . .
'" I , . . ,~01 , ",', ~jJ ~ I ~ I I I I
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( S:~J;llNIW) :~I;I;
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CONCLUSION
The invention is not intended to be limited to the . .
treatment of eoal flue gases, but rather may be applied in the treatment of the flue gases of other fossil fuels, such as petro-leum residual fuels. Indeed, the invention may be useful in the treatment of any gas stream containing particulate matter of high electrical resistance which contains sulphur dioxide ~vailable for conversion to sulphur trioxide. In addition, the above examples ..
have been given without intent to limit the extent of this invention.
The method disclosed in this invention can be readily implemented as an e~ficient remedy for electrostatic precipitatox inefficiency resulting from high resistivity fly ash. .
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Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for improving the performance of electrostatic precipitators in the collection of fly ash from flue gas streams containing sulphur dioxide comprising oxidizing at least a portion of the sulphur dioxide present to provide at least 15 ppm sulphur trioxide in the flue gas by means of an amount of an inorganic oxidizing agent introduced into the flue gas and chosen from the group consisting of chlorine gas, and aqueous solutions of chlorine, hydrogen peroxide, sodium hypochlorite, sodium chlorite, potassium permanganate, and manganese nitrate.
2. A method according to claim 1 wherein the amount of oxidizing agent introduced is effective to provide at least 20 ppm of sulphur trioxide in the flue gas.
3. The method of claim 1 wherein the oxidizing agent is hydrogen peroxide.
4. The method of claim 1 wherein the oxidizing agent is sodium hypochlorite.
5. The method of claim 1 wherein the oxidizing agent is sodium chlorite.
6. The method of claim 1 wherein the oxidizing agent is potassium permanganate.
7. The method of claim 1 wherein the oxidizing agent is manganese nitrate.
8. The method of claim 1 wherein the oxidizing agent is chlorine gas.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US62468375A | 1975-10-22 | 1975-10-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067835A true CA1067835A (en) | 1979-12-11 |
Family
ID=24502918
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,354A Expired CA1067835A (en) | 1975-10-22 | 1976-04-28 | Increasing the efficiency of electrostatic precipitators |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1067835A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2199374A3 (en) * | 2002-12-18 | 2011-08-17 | Afton Chemical Intangibles LLC | Use of manganese compounds to increase the efficiency of an electrostatic precipitator of a combustion unit |
| US9308493B2 (en) * | 2013-08-16 | 2016-04-12 | ADA-ES, Inc. | Method to reduce mercury, acid gas, and particulate emissions |
| US20160263585A1 (en) * | 2013-08-16 | 2016-09-15 | ADA-ES, Inc. | Method to reduce mercury, acid gas, and particulate emissions |
| US10465137B2 (en) | 2011-05-13 | 2019-11-05 | Ada Es, Inc. | Process to reduce emissions of nitrogen oxides and mercury from coal-fired boilers |
| US10730015B2 (en) | 2010-10-25 | 2020-08-04 | ADA-ES, Inc. | Hot-side method and system |
| US10758863B2 (en) | 2012-04-11 | 2020-09-01 | ADA-ES, Inc. | Control of wet scrubber oxidation inhibitor and byproduct recovery |
| US10767130B2 (en) | 2012-08-10 | 2020-09-08 | ADA-ES, Inc. | Method and additive for controlling nitrogen oxide emissions |
| US11298657B2 (en) | 2010-10-25 | 2022-04-12 | ADA-ES, Inc. | Hot-side method and system |
-
1976
- 1976-04-28 CA CA251,354A patent/CA1067835A/en not_active Expired
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8257450B2 (en) | 2002-12-18 | 2012-09-04 | Afton Chemical Intangibles Llc | Manganese compounds to inhibit both low-and high-temperature corrosion in utility and industrial furnace systems |
| EP2199374A3 (en) * | 2002-12-18 | 2011-08-17 | Afton Chemical Intangibles LLC | Use of manganese compounds to increase the efficiency of an electrostatic precipitator of a combustion unit |
| US11298657B2 (en) | 2010-10-25 | 2022-04-12 | ADA-ES, Inc. | Hot-side method and system |
| US10730015B2 (en) | 2010-10-25 | 2020-08-04 | ADA-ES, Inc. | Hot-side method and system |
| US10465137B2 (en) | 2011-05-13 | 2019-11-05 | Ada Es, Inc. | Process to reduce emissions of nitrogen oxides and mercury from coal-fired boilers |
| US11118127B2 (en) | 2011-05-13 | 2021-09-14 | ADA-ES, Inc. | Process to reduce emissions of nitrogen oxides and mercury from coal-fired boilers |
| US10731095B2 (en) | 2011-05-13 | 2020-08-04 | ADA-ES, Inc. | Process to reduce emissions of nitrogen oxides and mercury from coal-fired boilers |
| US11065578B2 (en) | 2012-04-11 | 2021-07-20 | ADA-ES, Inc. | Control of wet scrubber oxidation inhibitor and byproduct recovery |
| US10758863B2 (en) | 2012-04-11 | 2020-09-01 | ADA-ES, Inc. | Control of wet scrubber oxidation inhibitor and byproduct recovery |
| US11384304B2 (en) | 2012-08-10 | 2022-07-12 | ADA-ES, Inc. | Method and additive for controlling nitrogen oxide emissions |
| US10767130B2 (en) | 2012-08-10 | 2020-09-08 | ADA-ES, Inc. | Method and additive for controlling nitrogen oxide emissions |
| US20160263585A1 (en) * | 2013-08-16 | 2016-09-15 | ADA-ES, Inc. | Method to reduce mercury, acid gas, and particulate emissions |
| US10589292B2 (en) | 2013-08-16 | 2020-03-17 | ADA-ES, Inc. | Method to reduce mercury, acid gas, and particulate emissions |
| US9889451B2 (en) * | 2013-08-16 | 2018-02-13 | ADA-ES, Inc. | Method to reduce mercury, acid gas, and particulate emissions |
| US9308493B2 (en) * | 2013-08-16 | 2016-04-12 | ADA-ES, Inc. | Method to reduce mercury, acid gas, and particulate emissions |
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