CA1311343C - Method for scrubbing pollutants from an exhaust gas stream - Google Patents
Method for scrubbing pollutants from an exhaust gas streamInfo
- Publication number
- CA1311343C CA1311343C CA000577455A CA577455A CA1311343C CA 1311343 C CA1311343 C CA 1311343C CA 000577455 A CA000577455 A CA 000577455A CA 577455 A CA577455 A CA 577455A CA 1311343 C CA1311343 C CA 1311343C
- Authority
- CA
- Canada
- Prior art keywords
- gas stream
- slurry
- ash
- exhaust gas
- alkali
- 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 - Fee Related
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
-
- 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
Abstract
ABSTRACT
A method of scrubbing a boiler exhaust gas stream containing pollutants comprising one or more of the acidic oxides of sulfur, nitrogen and carbon and compounds of any of the halogens while producing useful or benign products, which comprises contacting the stream with a solution derived from dissolving in water the soluble components of ash containing as solids one or more of alkali and alka-line earth metal salts to produce a basic (pH greater than 7) solution. The pollutants react with the water therein to produce acids. The latter react with any oxides, hydroxides and carbonates of alkali and alkaline earth metals therein derived from the ash to yield a solution of alkali and alkaline earth metal salts and anionic salt components, namely, carbonate, sulfate, sulfite, nitrate and nitrite, and compounds of the halogens, along with a precipitate of alkali and alkaline earth metal salts with any insoluble components of the ash.
A method of scrubbing a boiler exhaust gas stream containing pollutants comprising one or more of the acidic oxides of sulfur, nitrogen and carbon and compounds of any of the halogens while producing useful or benign products, which comprises contacting the stream with a solution derived from dissolving in water the soluble components of ash containing as solids one or more of alkali and alka-line earth metal salts to produce a basic (pH greater than 7) solution. The pollutants react with the water therein to produce acids. The latter react with any oxides, hydroxides and carbonates of alkali and alkaline earth metals therein derived from the ash to yield a solution of alkali and alkaline earth metal salts and anionic salt components, namely, carbonate, sulfate, sulfite, nitrate and nitrite, and compounds of the halogens, along with a precipitate of alkali and alkaline earth metal salts with any insoluble components of the ash.
Description
This invention relates to method and apparatus for scrubbing pollutants from an exhaust gas stream whereby the materials reacted with the stream are rendered at least benign and in many cases converted by the reac-tion into useful products.sackground of the Invention Scrubbing of exhaust gas pollutants is generally costly, having significant environmental returns but lit-tle or no economic returns unless it is possible to con-vert by the scrubbing otherwise waste products into usefulproducts. The cost of the initial equipment is high.
Furthermore, the materials for scrubbing, such as the oxides, carbonates, or hydroxldes of alkali and/or alka-line earth metals are a continuing expense. In addition, disposal of the reaction products derived from reaction of the scrubbing materials with the exhaust gas adds to the continuing cost, especially if the products contain toxic components.
There are a growing number of boiler installa-tions which are fueled by combustion of biologic materials(hereinafter collectively i'biomass~ including wood, peat, or crop residue, where there is little or no produc-tion of sulfur oxides and therefore no scrubbing of the gaseous components of the exhaust is needed or done. On the other hand, the ash produced from these operations contains significant alkali and alkaline earth metal salts, occurring commonly as the oxide, or, if wetted and/or reacted with carbon dioxide, as the hydroxide or the carbonate, or perhaps as hydrated salts of these.
I have discovered that the ash from boiler installations, where alkali and alkaline earth metal oxides, hydroxides, and/or carbonates are a significant proportion of the ash, can be used in a process for scrub-bing exhaust gas in place of the usual materials above referred to, thus making use of an otherwise waste product as a substitute for expensive materials which must be purchased.
~ 3 ~
Other materials are also usable for this purpose.
Industrial or municipal waste, incinerator ash or by-products which contaln potassium or sodium or other sol-uble salts which, when dissolved in water yield a basic (high pH) solution and when recovered from the waste or by-product, provide an economic benefit are also suitable.
In the following specification and claims, ash derived from burning biomass material and industrial or municipal wastes or other by-products, usable in the process herein described and claimed, are collectively identified by the generic term, "ash."
Unfortunately, the insoluble portion of reacted ash must usually still be disposed of as waste, for example, in most boiler applications, it will not be lS usable for any other purpose. The waste material, however, will no longer be a caustic material and should, in most cases, be disposable as benlgn common fill or could, in some landfills, be used as cover material. In some cases, where the composltion of the residue and transport costs permit, it may also be used as cement kiln raw feed. In some other situations the insoluble portion of the scrubbing material could be used, as it is now, for production of calcium sulfate or gypsum, or as a mineral filler.
In cases where the facility producing the ash does not itself also have a boiler installation producing an exhaust of high sulfur content in need of scrubbing, the ash could be transported to other boiler installations which have such a problem, or to installations where use of a higher sulfur content fuel would provide an economic benefit. In addition, because ash derived from biomass material generally contains potassium and other alkali and alkaline earth metal salts recoverable by utilization of the exhaust gas heat or other waste heat sources, the resulting alkali and alkaline earth metal salts can be a valuable by-product of the process.
.
Brief Summary of the Invention In accordance with the invention there is provided a novel method of treatment of an exhaust gas stream containing as pollutants, at least one of the acidic oxides of sulphur, nitr~gen, carbon, and halogens and acidic halogen compounds, whose temperature exceeds the dew point of the gas, for producing scrubbed exhaust and useful or benign by-products. The method comprises providing a basic aqueous slurry of ash, the ash containing alkali and alkaline earth metal salts. The exhaust gas stream is contacted with the slurry in a manner to scrub the exhaust gas stream and to cause the pollutants therein to react with the water in the slurry-to produce acids. The acids are allowed to react with any oxides, hydroxides and carbonates of alkali and alkaline metal salts in the slurry, thereby to produce a solution with soluble alkali metal salts and a precipitate of any insoluble alkali and alkaline earth metal salts comprising at least one of halogen compounds, carbonate, sulfate, sulfite, nitrate, and nitrite of calcium, magnesium, potassium and sodium in the slurry.
The precipitate is recovered from the solution and the solution, freed of the precipitate, is evaporated. Any soluble alkali and alkaline earth metal salts present in the solution are recovered in solid form and the scrubbed exhaust gas stream is expelled.
Presently preferred methods include one or more of the following steps: contacting the exhaust gas stream with the slurry by passing the same through said slurry; separating the said solution of alkali and alkaline earth metal salts from the said precipitate and undissolved components; transferring the solution of alkali and alkaline earth metal salts and the precipitate and undissolved components to a separation system wherein the æaid salt solution is separated from the said precipitate and undissolved components; passing the separated salt solution through a heat exchanger wherein r t~.'.i 131 ~343 it extracts heat from the exhaust gas stream before the latter contacts the slurry; cooling the exhaust gas stream to dehumidify it prior to the contacting step;
using the salt solution to cool and dehumidify the exhaust gas stream; using heat from the exhaust gas stream to remove water from the said salt solution and deriving the said heat in part from one or more of (A) the hot exhaust gas of said stream, (B) the latent heat of vaporization of any moisture contained in said exhaust gas stream, (C) the hydration reaction between ash and water, and (D) compressing the said gas prior to the said contacting step.
In another aspect of the invention there is provided a method for treating ash and an exhaust gas stream containing acid forming pollutants whose temperature exceeds the dew point of the gas, to chemically modify the ash and to scrub the exhaust.
Firstly, the gas stream is cooled in a manner to remove and recover heat. Thereafter, an alkali-containing basic scrubbing slurry comprising the ash and water is provided. The cooled gas stream is contacted with the slurry comprising the ash and water to cause pollutants in the gas stream to react with water in the slurry to form acids and allowing the acids to react with the slurry to form a mixture of settleable solids and a liquid solution containing dissolved solids. From the resulting mixture, the settleable solids and liquid solution containing dissolved solids are separated. The liquid solution containing dissolved solids is heated using only recovered heat collected during the cooling of the gas stream. The dissolved solids are recovered in solid form.
Still further objects, features and advantages of the invention will become apparent from the following detailed description of a presently preferred embodiment thereof taken in conjunction with the accompanying drawings.
C
~, ~31 ~343 - 4a -Brief Description of the Drawing In the drawing, the sole figure is a schematic representation of one apparatus for practising the invention.
Detailed Description of Preferred Apparatus and Method A slurry composed of ash and water exiting at 8 from an ash and water mixing tank (not shown), is pumped via pipe 10 into the treatment tank 12, along with additional water through inlet 14 from a suitable source (not shown) to produce a dilute slurry 16. The ash is trucked in from a source such as a generating plant fired by biomass or an incinerator fired by waste material.
Exhaust gas from a cement kiln, incinerator or boiler (not shown) containing one or more of the oxides of sulfur, nitrogen, carbon, and/or compounds of halogens and their oxides, enters heat exchanger 22 through inlet 18 from which it emerges as cooled exhaust. Condensed exhaust gas moisture is collected in the heat exchanger 22 and conveyed to the treatment tank 12 through pipe 44.
The exhaust then travels to compressor 20 through pipe 23 and /-_ ~_ __ ___ ._____ __ __ __ ~ .~
,,"~,..~
131 134'' is delivered via pipe 24 to distribution pipes 26 in the bottom of the treatment tank 12. To prevent settling of t:he sollds to the bottom of treatment tank 12, the slurry may be stirred or recirculated by suitable means, for example by recirculation pump 27.
The exhaust gas bubbles through slurry 16 of ash and water to emerge from the tank top as scrubbed exhaust 28. Slurry 16, as a mixture of treated solid, water, and dissolved materials, is pumped by pump 32 via pipe 30 to the settling tank 34 where the settled solids 36 are pumped out by pump 38 and the water 37 laden with dis-solved salts is pumped to heat exchanger 22 to provide cooling for the input exhaust gas. The water from salt solution 37 is evaporated to a vapor and released via pipe 40 to the atmosphere, or the water is evaporated and then condensed to a liquid to recapture the latent heat for reuse. The æalts from the salt solution 37 are concen-trated and/or preclpitated and collected from the heat exchanger via plpe 42. The cationic components of the collected salts are principally calcium, potassium, magne-sium, and sodlum. The anionlc components of the salts are prlnclpally sulfate, carbonate and nitrate. The actual composition of the salts will depend on the initial compo-sition of the ash to be treated and on the composltion of the exhaust gas.
Ash derived from biomass burning systems may con-tain ~mburned carbon which, in some situations, will float in water. The process illustrated can be modified, if desired, as shown in the Figure to allow removal of the carbon. Water 37 having unburned carbon is pumped from the surface of the settling tank to be filtered or other-wise treated to remove the carbon and is then returned to the process. If necessary, the solution containing dissolved alkali and alkaline earth metal salts may be removed by plping (not shown) to be filtered or otherwise cleansed of particulate matter at a particulate removal 13113~3 component. The solution is then conveyed to the heat exchanger 22.
The heat exchanger 22 is a dual purpose heat exchanger-crystallization unit of a known type which will extract heat from the exhaust gas and use that heat, lncluding latent heat derived from condensation of the exhaust gas moisture to evaporate water.
The Apparatus The whole system is created from well known parts combined by standard methods. For example, typically the treatment tank may have a volume of one million gallons (3,800,000 liters) and be provided with gas distribution and stirring means; the settling tank may have a volume of 100 thousand gallons (380,000 liters), both being con-structed from stainless steel, or other suitablematerials, such as rubber, which can tolerate highly alka-llne or acidic solutions.
Workin~ Principle The basic working prlnciple in this invention ls recomblnation and reactlon of two wastes produced during burning to provide mutual neutralization of the wastes.
One waste stream comprlses the gasses and gaseous oxides which produce acidic solutions in water and the other par-ticulate matter, namely ash from a biomass or lndustrial or municipal waste burning facility, which produces basic solutions in water.
After partial dissolution in water, the two wastes react to neutralize each other. In the case of the ash, the process provides for reaction of or removal of the caustic components, thus rendering what remains as neutral solids suitable for disposal as non-hazardous waste. At the same time, the exhaust gas passing through the slurry in the treatment tank ls cleansed of a slgnlfl-cant portion of the compounds of the halogens and oxldes of sulfur, nitrogen and halogens by forming salts of these components.
cant portion of the compounds of the halogens and oxides of sulfur, nitrogen and halogens by forming salts of these components.
Example S Exhaust gas from, e.g. a boiler, may be fed through duct 18, to heat exchanger 22 at a rate of 200,000 cubic feet (6000 m3) per minute by compressor 20. The exhaust gas is variable in composition, but may contain roughly 10% water, 15% carbon dioxide, 65% nitrogen, 10%
oxygen and 500 to 1000 ppm nitrogen oxides and 100 to 1000 ppm sulfur dioxide. In heat exchanger 22 the exhaust gas is cooled and water is condensed, resulting in a decrease in flow volume. The exhaust gas is then drawn by compres-sor 20 through pipe 23 for delivery through plpe 24 to dlstrlbutlon pipes 26 and allowed to react with slurry 16 where the alogens and the oxides of sulfur, nitrogen, car-bon and halogens are reacted.
Ash may be lntroduced to treatment tank 12, for example, at a rate of elght to twelve tons (7200 to 10,800 kg) per hour dry welght. Water ls added to produce a dllute slurry of up to 95% water content. The slurry water content ls determlned by the initial concentration of alkali and alkallne earth metal salts or other metal salts in the ash and on the desired degree of removal of ~5 these salts from the residue.
After reaction wlth the exhaust gas, the slurry of treated ash ls pumped at a rate of approxlmately 200 gallons (760 llters) per mlnute to settllng tank 34. In thls tank the sollds settle to form a slurry of approxl-mately 35% water and 65% sollds, beneath a solutlon ofwater and soluble salts dlssolved during treatment. The water solution is pumped through outlet 37 to heat exchanger 22 at approximately 200 gallons (760 llters) per minute to provide cooling for the exhaust gas and to evap-orate the water therefrom to produce the by-product salts. Any floatlng carbon can be removed as prevlously 1 31 1 ~3 explained. The by-product salts, removed via pipe 42, are produced at a rate of approximately five to twenty tons (4500 to 18,000 kg) per day. The by-product salts include potassium sulfate, calclum carbonate, and other salts with cationlc components incuding potassium, calcium, magne-sium, and sodium and anionic components including car-bonate, sulfate, and nitrate. A portion of the nitrate oxidizes the sulfite to sulfate.
While there has herein been disclosed and described a presently preferred method and apparatus for practicing the invention, it will nevertheless be under-stood that the same is by way of illustration and not by way of limitation, and it is intended that the scope of the invention be limited only by the proper interpretation to be afforded the appended claims.
Furthermore, the materials for scrubbing, such as the oxides, carbonates, or hydroxldes of alkali and/or alka-line earth metals are a continuing expense. In addition, disposal of the reaction products derived from reaction of the scrubbing materials with the exhaust gas adds to the continuing cost, especially if the products contain toxic components.
There are a growing number of boiler installa-tions which are fueled by combustion of biologic materials(hereinafter collectively i'biomass~ including wood, peat, or crop residue, where there is little or no produc-tion of sulfur oxides and therefore no scrubbing of the gaseous components of the exhaust is needed or done. On the other hand, the ash produced from these operations contains significant alkali and alkaline earth metal salts, occurring commonly as the oxide, or, if wetted and/or reacted with carbon dioxide, as the hydroxide or the carbonate, or perhaps as hydrated salts of these.
I have discovered that the ash from boiler installations, where alkali and alkaline earth metal oxides, hydroxides, and/or carbonates are a significant proportion of the ash, can be used in a process for scrub-bing exhaust gas in place of the usual materials above referred to, thus making use of an otherwise waste product as a substitute for expensive materials which must be purchased.
~ 3 ~
Other materials are also usable for this purpose.
Industrial or municipal waste, incinerator ash or by-products which contaln potassium or sodium or other sol-uble salts which, when dissolved in water yield a basic (high pH) solution and when recovered from the waste or by-product, provide an economic benefit are also suitable.
In the following specification and claims, ash derived from burning biomass material and industrial or municipal wastes or other by-products, usable in the process herein described and claimed, are collectively identified by the generic term, "ash."
Unfortunately, the insoluble portion of reacted ash must usually still be disposed of as waste, for example, in most boiler applications, it will not be lS usable for any other purpose. The waste material, however, will no longer be a caustic material and should, in most cases, be disposable as benlgn common fill or could, in some landfills, be used as cover material. In some cases, where the composltion of the residue and transport costs permit, it may also be used as cement kiln raw feed. In some other situations the insoluble portion of the scrubbing material could be used, as it is now, for production of calcium sulfate or gypsum, or as a mineral filler.
In cases where the facility producing the ash does not itself also have a boiler installation producing an exhaust of high sulfur content in need of scrubbing, the ash could be transported to other boiler installations which have such a problem, or to installations where use of a higher sulfur content fuel would provide an economic benefit. In addition, because ash derived from biomass material generally contains potassium and other alkali and alkaline earth metal salts recoverable by utilization of the exhaust gas heat or other waste heat sources, the resulting alkali and alkaline earth metal salts can be a valuable by-product of the process.
.
Brief Summary of the Invention In accordance with the invention there is provided a novel method of treatment of an exhaust gas stream containing as pollutants, at least one of the acidic oxides of sulphur, nitr~gen, carbon, and halogens and acidic halogen compounds, whose temperature exceeds the dew point of the gas, for producing scrubbed exhaust and useful or benign by-products. The method comprises providing a basic aqueous slurry of ash, the ash containing alkali and alkaline earth metal salts. The exhaust gas stream is contacted with the slurry in a manner to scrub the exhaust gas stream and to cause the pollutants therein to react with the water in the slurry-to produce acids. The acids are allowed to react with any oxides, hydroxides and carbonates of alkali and alkaline metal salts in the slurry, thereby to produce a solution with soluble alkali metal salts and a precipitate of any insoluble alkali and alkaline earth metal salts comprising at least one of halogen compounds, carbonate, sulfate, sulfite, nitrate, and nitrite of calcium, magnesium, potassium and sodium in the slurry.
The precipitate is recovered from the solution and the solution, freed of the precipitate, is evaporated. Any soluble alkali and alkaline earth metal salts present in the solution are recovered in solid form and the scrubbed exhaust gas stream is expelled.
Presently preferred methods include one or more of the following steps: contacting the exhaust gas stream with the slurry by passing the same through said slurry; separating the said solution of alkali and alkaline earth metal salts from the said precipitate and undissolved components; transferring the solution of alkali and alkaline earth metal salts and the precipitate and undissolved components to a separation system wherein the æaid salt solution is separated from the said precipitate and undissolved components; passing the separated salt solution through a heat exchanger wherein r t~.'.i 131 ~343 it extracts heat from the exhaust gas stream before the latter contacts the slurry; cooling the exhaust gas stream to dehumidify it prior to the contacting step;
using the salt solution to cool and dehumidify the exhaust gas stream; using heat from the exhaust gas stream to remove water from the said salt solution and deriving the said heat in part from one or more of (A) the hot exhaust gas of said stream, (B) the latent heat of vaporization of any moisture contained in said exhaust gas stream, (C) the hydration reaction between ash and water, and (D) compressing the said gas prior to the said contacting step.
In another aspect of the invention there is provided a method for treating ash and an exhaust gas stream containing acid forming pollutants whose temperature exceeds the dew point of the gas, to chemically modify the ash and to scrub the exhaust.
Firstly, the gas stream is cooled in a manner to remove and recover heat. Thereafter, an alkali-containing basic scrubbing slurry comprising the ash and water is provided. The cooled gas stream is contacted with the slurry comprising the ash and water to cause pollutants in the gas stream to react with water in the slurry to form acids and allowing the acids to react with the slurry to form a mixture of settleable solids and a liquid solution containing dissolved solids. From the resulting mixture, the settleable solids and liquid solution containing dissolved solids are separated. The liquid solution containing dissolved solids is heated using only recovered heat collected during the cooling of the gas stream. The dissolved solids are recovered in solid form.
Still further objects, features and advantages of the invention will become apparent from the following detailed description of a presently preferred embodiment thereof taken in conjunction with the accompanying drawings.
C
~, ~31 ~343 - 4a -Brief Description of the Drawing In the drawing, the sole figure is a schematic representation of one apparatus for practising the invention.
Detailed Description of Preferred Apparatus and Method A slurry composed of ash and water exiting at 8 from an ash and water mixing tank (not shown), is pumped via pipe 10 into the treatment tank 12, along with additional water through inlet 14 from a suitable source (not shown) to produce a dilute slurry 16. The ash is trucked in from a source such as a generating plant fired by biomass or an incinerator fired by waste material.
Exhaust gas from a cement kiln, incinerator or boiler (not shown) containing one or more of the oxides of sulfur, nitrogen, carbon, and/or compounds of halogens and their oxides, enters heat exchanger 22 through inlet 18 from which it emerges as cooled exhaust. Condensed exhaust gas moisture is collected in the heat exchanger 22 and conveyed to the treatment tank 12 through pipe 44.
The exhaust then travels to compressor 20 through pipe 23 and /-_ ~_ __ ___ ._____ __ __ __ ~ .~
,,"~,..~
131 134'' is delivered via pipe 24 to distribution pipes 26 in the bottom of the treatment tank 12. To prevent settling of t:he sollds to the bottom of treatment tank 12, the slurry may be stirred or recirculated by suitable means, for example by recirculation pump 27.
The exhaust gas bubbles through slurry 16 of ash and water to emerge from the tank top as scrubbed exhaust 28. Slurry 16, as a mixture of treated solid, water, and dissolved materials, is pumped by pump 32 via pipe 30 to the settling tank 34 where the settled solids 36 are pumped out by pump 38 and the water 37 laden with dis-solved salts is pumped to heat exchanger 22 to provide cooling for the input exhaust gas. The water from salt solution 37 is evaporated to a vapor and released via pipe 40 to the atmosphere, or the water is evaporated and then condensed to a liquid to recapture the latent heat for reuse. The æalts from the salt solution 37 are concen-trated and/or preclpitated and collected from the heat exchanger via plpe 42. The cationic components of the collected salts are principally calcium, potassium, magne-sium, and sodlum. The anionlc components of the salts are prlnclpally sulfate, carbonate and nitrate. The actual composition of the salts will depend on the initial compo-sition of the ash to be treated and on the composltion of the exhaust gas.
Ash derived from biomass burning systems may con-tain ~mburned carbon which, in some situations, will float in water. The process illustrated can be modified, if desired, as shown in the Figure to allow removal of the carbon. Water 37 having unburned carbon is pumped from the surface of the settling tank to be filtered or other-wise treated to remove the carbon and is then returned to the process. If necessary, the solution containing dissolved alkali and alkaline earth metal salts may be removed by plping (not shown) to be filtered or otherwise cleansed of particulate matter at a particulate removal 13113~3 component. The solution is then conveyed to the heat exchanger 22.
The heat exchanger 22 is a dual purpose heat exchanger-crystallization unit of a known type which will extract heat from the exhaust gas and use that heat, lncluding latent heat derived from condensation of the exhaust gas moisture to evaporate water.
The Apparatus The whole system is created from well known parts combined by standard methods. For example, typically the treatment tank may have a volume of one million gallons (3,800,000 liters) and be provided with gas distribution and stirring means; the settling tank may have a volume of 100 thousand gallons (380,000 liters), both being con-structed from stainless steel, or other suitablematerials, such as rubber, which can tolerate highly alka-llne or acidic solutions.
Workin~ Principle The basic working prlnciple in this invention ls recomblnation and reactlon of two wastes produced during burning to provide mutual neutralization of the wastes.
One waste stream comprlses the gasses and gaseous oxides which produce acidic solutions in water and the other par-ticulate matter, namely ash from a biomass or lndustrial or municipal waste burning facility, which produces basic solutions in water.
After partial dissolution in water, the two wastes react to neutralize each other. In the case of the ash, the process provides for reaction of or removal of the caustic components, thus rendering what remains as neutral solids suitable for disposal as non-hazardous waste. At the same time, the exhaust gas passing through the slurry in the treatment tank ls cleansed of a slgnlfl-cant portion of the compounds of the halogens and oxldes of sulfur, nitrogen and halogens by forming salts of these components.
cant portion of the compounds of the halogens and oxides of sulfur, nitrogen and halogens by forming salts of these components.
Example S Exhaust gas from, e.g. a boiler, may be fed through duct 18, to heat exchanger 22 at a rate of 200,000 cubic feet (6000 m3) per minute by compressor 20. The exhaust gas is variable in composition, but may contain roughly 10% water, 15% carbon dioxide, 65% nitrogen, 10%
oxygen and 500 to 1000 ppm nitrogen oxides and 100 to 1000 ppm sulfur dioxide. In heat exchanger 22 the exhaust gas is cooled and water is condensed, resulting in a decrease in flow volume. The exhaust gas is then drawn by compres-sor 20 through pipe 23 for delivery through plpe 24 to dlstrlbutlon pipes 26 and allowed to react with slurry 16 where the alogens and the oxides of sulfur, nitrogen, car-bon and halogens are reacted.
Ash may be lntroduced to treatment tank 12, for example, at a rate of elght to twelve tons (7200 to 10,800 kg) per hour dry welght. Water ls added to produce a dllute slurry of up to 95% water content. The slurry water content ls determlned by the initial concentration of alkali and alkallne earth metal salts or other metal salts in the ash and on the desired degree of removal of ~5 these salts from the residue.
After reaction wlth the exhaust gas, the slurry of treated ash ls pumped at a rate of approxlmately 200 gallons (760 llters) per mlnute to settllng tank 34. In thls tank the sollds settle to form a slurry of approxl-mately 35% water and 65% sollds, beneath a solutlon ofwater and soluble salts dlssolved during treatment. The water solution is pumped through outlet 37 to heat exchanger 22 at approximately 200 gallons (760 llters) per minute to provide cooling for the exhaust gas and to evap-orate the water therefrom to produce the by-product salts. Any floatlng carbon can be removed as prevlously 1 31 1 ~3 explained. The by-product salts, removed via pipe 42, are produced at a rate of approximately five to twenty tons (4500 to 18,000 kg) per day. The by-product salts include potassium sulfate, calclum carbonate, and other salts with cationlc components incuding potassium, calcium, magne-sium, and sodium and anionic components including car-bonate, sulfate, and nitrate. A portion of the nitrate oxidizes the sulfite to sulfate.
While there has herein been disclosed and described a presently preferred method and apparatus for practicing the invention, it will nevertheless be under-stood that the same is by way of illustration and not by way of limitation, and it is intended that the scope of the invention be limited only by the proper interpretation to be afforded the appended claims.
Claims (10)
1. A method of treatment of an exhaust gas stream containing as pollutants at least one of the acidic oxides of sulfur, nitrogen, carbon, and halogens and acidic halogen compounds, whose temperature exceeds the dew point of the gas, for producing scrubbed exhaust and useful or benign by-products, said method comprising:
providing a basic aqueous slurry of ash, said ash containing alkali and alkaline earth metal salts, contacting the exhaust gas stream with the slurry in a manner to scrub said exhaust gas stream and to cause the pollutants therein to react with the water in the slurry to produce acids, allowing said acids to react with any oxides, hydroxides and carbonates of alkali and alkaline metal salts in said slurry, thereby to produce a solution with soluble alkali metal salts and a precipitate of any insoluble alkali and alkaline earth metal salts comprising at least one of halogen compounds, carbonate, sulfate, sulfite, nitrate, and nitrite of calcium, magnesium, potassium and sodium in said slurry, recovering said precipitate from said solution, evaporating said solution freed of said precipitate, recovering in solid form any soluble alkali and alkaline earth metal salts present in said solution, and expelling the scrubbed exhaust gas stream.
providing a basic aqueous slurry of ash, said ash containing alkali and alkaline earth metal salts, contacting the exhaust gas stream with the slurry in a manner to scrub said exhaust gas stream and to cause the pollutants therein to react with the water in the slurry to produce acids, allowing said acids to react with any oxides, hydroxides and carbonates of alkali and alkaline metal salts in said slurry, thereby to produce a solution with soluble alkali metal salts and a precipitate of any insoluble alkali and alkaline earth metal salts comprising at least one of halogen compounds, carbonate, sulfate, sulfite, nitrate, and nitrite of calcium, magnesium, potassium and sodium in said slurry, recovering said precipitate from said solution, evaporating said solution freed of said precipitate, recovering in solid form any soluble alkali and alkaline earth metal salts present in said solution, and expelling the scrubbed exhaust gas stream.
2. A method according to claim 1 wherein potassium and sodium are the prime reactants in said ash that combine with sulfur compounds in the flue gas to produce a solution containing alkali metal sulfates, and a precipitate comprising alkaline earth carbonates is formed from carbon dioxide scrubbed from the flue gas.
3. A method according to claim 1 wherein said acids react to neutralize said oxides, hydroxides and carbonates.
4. A method according to claim 1 wherein said soluble alkali and alkaline earth metal salts are recovered by crystallization.
5. A method according to claim 1 wherein water vapor obtained from evaporating said solution is condensed to form distilled water which is returned as needed for use in said method.
6. A method according to claim 1 wherein the heat for evaporating said solution is derived in part from each of the exhaust gas stream, the latent heat of moisture condensed upon cooling said gas stream, the hydration reaction between ash and water, and from compressing said gas stream prior to reacting it with said slurry.
7. A method according to claim 1 wherein said contacting of said basic slurry and said exhaust gas stream is effected by bubbling said gas stream through said slurry.
8. A method of treating ash and an exhaust gas stream containing acid forming pollutants whose temperature exceeds the dew point of the gas, to chemically modify the ash and to scrub the exhaust, the method comprising:
cooling said gas stream in a manner to remove and recover heat therefrom, thereafter providing an alkali-containing basic scrubbing slurry comprising the ash and water, contacting the cooled gas stream with said slurry comprising the ash and water to cause pollutants in the gas stream to react with water in the slurry to form acids and allowing the acids to react with said slurry to form a mixture of settleable solids and a liquid solution containing dissolved solids, separating from the resulting mixture said settleable solids and said liquid solution containing dissolved solids, heating the liquid solution containing dissolved solids using only recovered heat collected during said cooling of said gas stream, and recovering in solid form said dissolved solids.
cooling said gas stream in a manner to remove and recover heat therefrom, thereafter providing an alkali-containing basic scrubbing slurry comprising the ash and water, contacting the cooled gas stream with said slurry comprising the ash and water to cause pollutants in the gas stream to react with water in the slurry to form acids and allowing the acids to react with said slurry to form a mixture of settleable solids and a liquid solution containing dissolved solids, separating from the resulting mixture said settleable solids and said liquid solution containing dissolved solids, heating the liquid solution containing dissolved solids using only recovered heat collected during said cooling of said gas stream, and recovering in solid form said dissolved solids.
9. The method according to claim 8 wherein said dissolved solids are recovered by crystallization.
10. The method according to claim 8 further comprising evaporating liquid from the liquid solution containing dissolved solids and recondensing the evaporated liquid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9763987A | 1987-09-16 | 1987-09-16 | |
| US097,639 | 1987-09-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1311343C true CA1311343C (en) | 1992-12-15 |
Family
ID=22264412
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000577455A Expired - Fee Related CA1311343C (en) | 1987-09-16 | 1988-09-15 | Method for scrubbing pollutants from an exhaust gas stream |
Country Status (28)
| Country | Link |
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| JP (1) | JPH01148330A (en) |
| KR (1) | KR890004760A (en) |
| CN (1) | CN1013642B (en) |
| AT (1) | AT395543B (en) |
| AU (1) | AU611478B2 (en) |
| BE (1) | BE1001118A5 (en) |
| BG (1) | BG49822A3 (en) |
| BR (1) | BR8804771A (en) |
| CA (1) | CA1311343C (en) |
| CH (1) | CH676437A5 (en) |
| DD (1) | DD273386A5 (en) |
| DE (1) | DE3830812A1 (en) |
| DK (1) | DK170605B1 (en) |
| ES (1) | ES2020810A6 (en) |
| FI (1) | FI884278A (en) |
| FR (1) | FR2620351B1 (en) |
| GB (1) | GB2210035B (en) |
| GR (1) | GR1000575B (en) |
| HU (1) | HU206642B (en) |
| IT (1) | IT1223827B (en) |
| NL (1) | NL8802265A (en) |
| NO (1) | NO884101L (en) |
| NZ (1) | NZ225964A (en) |
| PL (1) | PL274651A1 (en) |
| RO (1) | RO103174B1 (en) |
| SE (1) | SE8803286L (en) |
| YU (1) | YU175288A (en) |
| ZA (1) | ZA886879B (en) |
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| JP2004261658A (en) * | 2003-02-26 | 2004-09-24 | Tokyo Electric Power Co Inc:The | Method for absorbing/fixing carbon dioxide in combustion exhaust gas |
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| EP2535314A1 (en) * | 2006-08-29 | 2012-12-19 | Yeda Research & Development Company, Ltd. | Methods and apparatuses for decreasing the co2 concentration of a fluid |
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| US7753618B2 (en) | 2007-06-28 | 2010-07-13 | Calera Corporation | Rocks and aggregate, and methods of making and using the same |
| JP2012513944A (en) | 2007-12-28 | 2012-06-21 | カレラ コーポレイション | How to capture CO2 |
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| EP2212033A4 (en) | 2008-07-16 | 2013-04-24 | Calera Corp | Low-energy 4-cell electrochemical system with carbon dioxide gas |
| KR20110038691A (en) | 2008-07-16 | 2011-04-14 | 칼레라 코포레이션 | Co2 utilization in electrochemical systems |
| US7815880B2 (en) | 2008-09-30 | 2010-10-19 | Calera Corporation | Reduced-carbon footprint concrete compositions |
| US8869477B2 (en) | 2008-09-30 | 2014-10-28 | Calera Corporation | Formed building materials |
| US7939336B2 (en) | 2008-09-30 | 2011-05-10 | Calera Corporation | Compositions and methods using substances containing carbon |
| WO2010039903A1 (en) | 2008-09-30 | 2010-04-08 | Calera Corporation | Co2-sequestering formed building materials |
| US9133581B2 (en) | 2008-10-31 | 2015-09-15 | Calera Corporation | Non-cementitious compositions comprising vaterite and methods thereof |
| WO2010093716A1 (en) | 2009-02-10 | 2010-08-19 | Calera Corporation | Low-voltage alkaline production using hydrogen and electrocatlytic electrodes |
| CA2694959A1 (en) | 2009-03-02 | 2010-09-02 | Calera Corporation | Gas stream multi-pollutants control systems and methods |
| WO2010104989A1 (en) | 2009-03-10 | 2010-09-16 | Calera Corporation | Systems and methods for processing co2 |
| US7993511B2 (en) | 2009-07-15 | 2011-08-09 | Calera Corporation | Electrochemical production of an alkaline solution using CO2 |
| US8864901B2 (en) | 2011-11-30 | 2014-10-21 | Boral Ip Holdings (Australia) Pty Limited | Calcium sulfoaluminate cement-containing inorganic polymer compositions and methods of making same |
| CN105903326A (en) * | 2016-06-14 | 2016-08-31 | 广东龙正节能环保科技有限公司 | Biomass ash desulfurization technology |
| CN106076106A (en) * | 2016-08-02 | 2016-11-09 | 山东大学 | A kind of semi-dry desulfurization and denitrification system and method based on biomass ash |
| CN111545031A (en) * | 2019-02-12 | 2020-08-18 | 源洁科技股份有限公司 | Fossil fuel pollutant control system |
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| JP7356251B2 (en) * | 2019-04-01 | 2023-10-04 | 三菱重工業株式会社 | Apparatus and method related to gas purification treatment and/or combustion ash neutralization treatment |
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| FR2205354A2 (en) * | 1972-11-03 | 1974-05-31 | Rhone Progil | Hydrogen chloride removal from gaseous incinerator emissions - by reacting with alkaline flue dust |
| JPS5210659B2 (en) * | 1973-04-09 | 1977-03-25 | ||
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| DE2642326A1 (en) * | 1976-09-21 | 1978-03-23 | Saarbergwerke Ag | Removal of sulphur di:oxide from flue gases - by water scrubbing with neutralisation using alkaline fly ash |
| US4164547A (en) * | 1977-05-06 | 1979-08-14 | American Air Filter Company, Inc. | Process for removing sulfur dioxide in a wet scrubber |
| SU738645A1 (en) * | 1977-06-01 | 1980-06-05 | Московский Ордена Ленина И Трудового Красного Знамени Химико-Технологический Институт Им.Д.И. Менделеева | Method of purifying off-gases from acid components |
| DE2802018A1 (en) * | 1978-01-18 | 1979-07-19 | Fink Gerdinand | Refuse incinerator flue gas scrubber - with horizontal revolving drum and combustion residue pulp for washing |
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| DE3325140A1 (en) * | 1983-07-12 | 1985-01-31 | KABE Ingenierbüro GmbH, 2000 Hamburg | Process for the purification of dust- and aerosol-containing gases and/or vapours and unit for carrying out the process |
| DD247587A3 (en) * | 1983-11-03 | 1987-07-15 | Zittau Ing Hochschule | BINDING OF POLLUTANTS FROM EXHAUST GASOLATED COMBUSTION PLANTS BY MEANS OF ASH |
| DE3538231A1 (en) * | 1985-10-24 | 1987-04-30 | Mannesmann Ag | Process for reprocessing waste solutions |
| FR2590805B1 (en) * | 1985-12-02 | 1990-02-09 | Propiorga | PROCESS AND PLANT FOR THE NEUTRALIZATION OF ACID FUMES, ESPECIALLY FROM THE COMBUSTION OF RESIDUES |
-
1988
- 1988-08-29 NZ NZ225964A patent/NZ225964A/en unknown
- 1988-09-04 RO RO135160A patent/RO103174B1/en unknown
- 1988-09-09 DE DE3830812A patent/DE3830812A1/en not_active Ceased
- 1988-09-13 JP JP63227647A patent/JPH01148330A/en active Pending
- 1988-09-13 PL PL27465188A patent/PL274651A1/en unknown
- 1988-09-14 DD DD88319781A patent/DD273386A5/en not_active IP Right Cessation
- 1988-09-14 NL NL8802265A patent/NL8802265A/en not_active Application Discontinuation
- 1988-09-14 KR KR1019880011833A patent/KR890004760A/en not_active Application Discontinuation
- 1988-09-15 CA CA000577455A patent/CA1311343C/en not_active Expired - Fee Related
- 1988-09-15 NO NO88884101A patent/NO884101L/en unknown
- 1988-09-15 BR BR8804771A patent/BR8804771A/en not_active Application Discontinuation
- 1988-09-15 ZA ZA886879A patent/ZA886879B/en unknown
- 1988-09-15 ES ES8802825A patent/ES2020810A6/en not_active Expired - Fee Related
- 1988-09-15 DK DK513988A patent/DK170605B1/en not_active IP Right Cessation
- 1988-09-15 CH CH3440/88A patent/CH676437A5/de not_active IP Right Cessation
- 1988-09-15 AU AU22302/88A patent/AU611478B2/en not_active Ceased
- 1988-09-15 IT IT67822/88A patent/IT1223827B/en active
- 1988-09-15 AT AT0226888A patent/AT395543B/en not_active IP Right Cessation
- 1988-09-16 CN CN88107168A patent/CN1013642B/en not_active Expired
- 1988-09-16 BG BG85445A patent/BG49822A3/en unknown
- 1988-09-16 BE BE8801061A patent/BE1001118A5/en not_active IP Right Cessation
- 1988-09-16 GR GR880100612A patent/GR1000575B/en unknown
- 1988-09-16 FR FR888812145A patent/FR2620351B1/en not_active Expired - Lifetime
- 1988-09-16 YU YU01752/88A patent/YU175288A/en unknown
- 1988-09-16 GB GB8821734A patent/GB2210035B/en not_active Expired - Fee Related
- 1988-09-16 HU HU884890A patent/HU206642B/en not_active IP Right Cessation
- 1988-09-16 FI FI884278A patent/FI884278A/en not_active Application Discontinuation
- 1988-09-16 SE SE8803286A patent/SE8803286L/en not_active Application Discontinuation
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