CA2037839A1 - Process of purifying exhaust gas - Google Patents
Process of purifying exhaust gasInfo
- Publication number
- CA2037839A1 CA2037839A1 CA002037839A CA2037839A CA2037839A1 CA 2037839 A1 CA2037839 A1 CA 2037839A1 CA 002037839 A CA002037839 A CA 002037839A CA 2037839 A CA2037839 A CA 2037839A CA 2037839 A1 CA2037839 A1 CA 2037839A1
- Authority
- CA
- Canada
- Prior art keywords
- scrubbing
- stage
- scrubbing liquid
- residual
- liquid
- 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.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000005201 scrubbing Methods 0.000 claims abstract description 41
- 239000007788 liquid Substances 0.000 claims abstract description 29
- 239000003513 alkali Substances 0.000 claims abstract description 12
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 7
- 238000000926 separation method Methods 0.000 claims abstract description 5
- 239000002253 acid Substances 0.000 claims abstract description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 3
- 150000003841 chloride salts Chemical class 0.000 claims abstract description 3
- 150000002222 fluorine compounds Chemical class 0.000 claims abstract description 3
- 239000010802 sludge Substances 0.000 claims abstract description 3
- 239000007787 solid Substances 0.000 claims abstract 2
- 239000007789 gas Substances 0.000 claims description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 7
- 239000003344 environmental pollutant Substances 0.000 claims description 7
- 231100000719 pollutant Toxicity 0.000 claims description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 6
- 239000002585 base Substances 0.000 claims description 5
- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 4
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 150000002731 mercury compounds Chemical class 0.000 claims description 3
- 239000010881 fly ash Substances 0.000 claims description 2
- 238000000746 purification Methods 0.000 abstract description 5
- 241000196324 Embryophyta Species 0.000 description 12
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 241000511343 Chondrostoma nasus Species 0.000 description 1
- VXLCNTLWWUDBSO-UHFFFAOYSA-N Ethiazide Chemical compound ClC1=C(S(N)(=O)=O)C=C2S(=O)(=O)NC(CC)NC2=C1 VXLCNTLWWUDBSO-UHFFFAOYSA-N 0.000 description 1
- 244000228957 Ferula foetida Species 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 241001275899 Salta Species 0.000 description 1
- 240000004543 Vicia ervilia Species 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 241000894007 species Species 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
- B01D53/48—Sulfur compounds
- B01D53/50—Sulfur oxides
- B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- 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
- B01D53/68—Halogens or halogen compounds
-
- 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
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/75—Multi-step processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/048—Purification of waste water by evaporation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
- C02F2101/14—Fluorine or fluorine-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Water Supply & Treatment (AREA)
- Hydrology & Water Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
Abstract
ABSTRACT
In order to improve the economy of the purification of exhaust gas in a process which comprises a dry separation of solids and a scrubbing of gas in two stages succeeding in the direction of flow, it is proposed to operate the first and second scrubbing stages with acid and weakly basic scrubbing liquids, respectively, and to subject those quantities of scrubbing liquid which have been withdrawn from the two scrubbing cycles to separate further processing.
As a result, (a) a sludge which contains the heavy metals and fluorine compounds and constitutes the first residual product to be dumped, (b) a re-usable alkali chloride salt, and (c) condensate and residual solutions both of which can be recycled in the process are obtained from the scrubbing liquid used in the first scrubbing stage and (a) a second residual product which is to be dumped and essentially contains alkali sulfate, and (b) condensate and a residual solution, both of which can also be recycled in the process, are obtained from the scrubbing liquid used in the second scrubbing stage.
In order to improve the economy of the purification of exhaust gas in a process which comprises a dry separation of solids and a scrubbing of gas in two stages succeeding in the direction of flow, it is proposed to operate the first and second scrubbing stages with acid and weakly basic scrubbing liquids, respectively, and to subject those quantities of scrubbing liquid which have been withdrawn from the two scrubbing cycles to separate further processing.
As a result, (a) a sludge which contains the heavy metals and fluorine compounds and constitutes the first residual product to be dumped, (b) a re-usable alkali chloride salt, and (c) condensate and residual solutions both of which can be recycled in the process are obtained from the scrubbing liquid used in the first scrubbing stage and (a) a second residual product which is to be dumped and essentially contains alkali sulfate, and (b) condensate and a residual solution, both of which can also be recycled in the process, are obtained from the scrubbing liquid used in the second scrubbing stage.
Description
~etallge~ellschaft AG ~prll 177 1991 Reutsr~eg t4 6000 F~anX~urt-on-~ai~ 1 Case No. 890061 ` . .
Proces~ o~ Puri~ying Exhaust Ga~
D~SCRIPTION
Thi9 inventio~ relate~ to a proces~ of purifying e~hau~t ga~es, which in addition to fly ash contain gaaeous pollutantsv such as S02, HCl and HF, as well a~ volat~le heavy matal~, particularly mercury compounds, by a dr~ separation of ~olids and a scrubbing with a circulated ~crubbing liquid in two stages.
Such processss are used, inter alia, for the purification of the exhaust ga3e~ which are formed in garbage-incinerating pla~ts (~IP) and ~hich in addition to varyin~ rates of fly dust may contain up to 10,000 mg HCl, up to 2,000 mg S02, up to 1,000 mg HF and up to 100 mg heavy metals per ~m3 (sm3 = standard cubic meter). Said exhaust ga~e~ mu3t be purified in accordance with the regulation3 ~hioh ar~ applicable in any giv~n case. In Germany the limits for GIP in accordance with the TA-Lu~t (teohnical in3truction for air pollution control) of 198~ are: HCl ~ 50, S2 ~ 100~ HF ~ 2.0, heavy metal9 (of Clas~e~ Ig II~ III) ' 0.1/1.0/5.0~ in mg/~m3).
.
On pri~ciple a wet purification adopted to avoid a pollution by exhau~t gas wqll always involve a pollution by waste nater. For thi~ rea~on a pollution by exhaust ga~ ca~not be avoided unle88 the pollution by waste ~ater can ~atisfactorily be avoided and a ~ati3fac-tory disposal of the re~idual materials which are inevitably obtained i~ a3sured.
With th~ exception of tho~e case~ in which a dry purification of exhau~t ga~ may be and i~ adopted as an alternative~ relatively complicated plant~ and proces~es will be required ~or a wet puri~ication o~
exhaust ga~ and the chemical reactio~s involved therein will not fully be understood by ma~y operators. In addition to the gsneral desire to ~olve the problem in a manner which can be under~tood as clearly as po3~ible, it has alwa~ been e~deavored~ for the rea~ons stated, to purify exhau~t gase~ to speci~ied pollutant contents and prescribed pure ga~ compo~itions in a m~oner which is a# simple as pos~ible.
From the aspect of the safety o~ operation~ -the availability o~ the equipment ~or puri~yin~ exhaust ga~ must primarily be taken into account because in the case of a de~ect it will be nece~ary to interrupt the "production of exhaust gas" ~o that the powar plant, the garbage-incineratin~ plant or the chenacal production plant must be shut down until the exhaust gas purifying ,.; ~ ., .
:
; , ,1 ~; , ,: , - '' plant is operable agai~ To ensure the ~afety of operation it i~ al90 neccssary that the exhau~t ga~-purifying equipment can respond in such a ma~ner to widely changing operating cQnditions, ~uch as may ari~e owing to the changing quality o~ fuel, particularly in garbage_i~cinerating plant3, that a pure gas haYing a permissible compo~ition will alway~ be ac~ieved and that this will not give ri~e to a ne~ ~ewage di~posal or dumping problem.
It will al~o be understood that the exhau t gas must be purified with the highest possible economy as far a~ the overall concept i9 concerned. A si~ple plant involving a low capital expenditure ~ill not be economical if it invol~ss relatively high C08t9 for reactants and power and ~or the disposal o~ re~idual substances during the total operating life o~ ~uch plant. On the other hand, a highly effective plant will not be very u~eful i$ its capital expenditure is extremely high or i~ it i~ 90 complicated that it has only a low availability.
The invention i9 ba~ed on a proce~s which i9 0~ the ~ind described fir~t hereinbe~ore and i~
which the lo~ partial pre~ure of the gaseous pollutant~
over th~ scrubbing liquid, which lo~ partial pres~ure i~
required ~or a separation of ~uch pollutant~ to a hi~h degree, is maintained i~ that the scrubbing liquid i~
withdra~n at a high rate. In other word~, the pollutant concentrations in the ~orubbing liquid mu~t not exceed certain upper limits because other~i~e the partial pre~sure of ~uch pollutants ~ill ri~e exee~ively and the degree of ~eparation will e~hibit ~n over- .
proportional decrease. For this rea~on a high degree of ~eparation cannot be achieved in ~uch proce~s unles~
the waste water i~ treated and evaporated in a plant which is designed for a withdra~al of ~aste water at a high rate and uch pla~t will in~olve a correspondin41y high expenditure for supplie~. For this rea~on thc requirement for high degrees of separation in processes of that kind will necessarily result in high capital expenditures and operating costs. Besides, the nece~sary reconditioning of the scrubbing liquid wqll re~ult in a production o~ unusable residual ~aterial~ at relatively high rates and their final dumpi~g will also involve high co~ts.
It is an object of the invention to avoid in the known proce~s the disadvantages ~hich have bee~
pointed out, i . e ., to propo~e a proce~ by which the purification of axhaust gases i~ its entirety can be carried out more economically without a need for a more complicated plant and proce~ing and without a decrease of the safety of operation.
' ` ! i ' ~ i ~, . ~.' , `i Ta accn~nl'sh that obJect it is nrooase~ that the orocess .Aescriberl first hereinheForP shDulr! be carrie~
~ut in such a ~anner that a) the exhaust nases are treate~ l~ith an aci~
scrubbin~ liouid in a first scrubbinn St3Qe, aarticularlv to Aecrease the concentr3tion af HCl, ~F an~ ~ea~/v r~eta1r, an~
ta a~ust a te~perature of :~2 to 700r, an~ in which c o~
alue of l~ tn ~ i5 n"ai:.lain2~ oy a controllen 3~ition of ~!3t~r and bases an~ ~V o~ ith~ral~al of scru~inn lioui~j ~) the ~xhau~t oases 2re tre2te~ with e basi,_ scrub~inn liquid in a secDn~ scrubbinra st3ae, Illhich oar-~icularlv ~erves to ~ecre3se the ~G? concentr2tirn an~
in ~hioh the ~a~ temP2r~ture is maintaine~ _s in the firret ,cruahinn st3a3 anr! in mnich a nH \/alu2 of - to 5 i3 ~ justeo 3v cantroll2~ arlr!itiDr ~ ater ~n~ b~ses an~ b~ e l~!ith-Ara~Jal ~F scrub]ino lio~ A an~ a nurifia~ exh3ust naS i3 obtaine~, o) the scruohinn liqui~ ith~rsl-~n from the first scrllobinn stano is troete~ ~ith a orr.cioitant an~ a F
13nt an~ ub,iecte~ to 3 senar3tinn orocess, in mhich (1) a slu~Fe that contains heevv ~et31s an~ fluorine com-noun~s an~ con9titutes 2 first rr~si~lli21 oro~uct to be r~u~ne~ an~
.
. .
: : :
. -- 6 --(2~ a solution which contain~ alkali chloride are obtained, and (3) ~aid solution i9 evaporated and dewatered to recover alkali chloride ~lts, which ca~ be re-u~ed, as well as a residual solution and conden~ate~ whi~h can be recycled in the process 9 snd d) the ~crubbing liquid which ha~ been withdrawn from the second ~crubbing ~tage i~ treated in that it i9 evaporated and dewatered to provide (1) another residual product ~hich i9 to b~ dumped, which essentiall~ contain~ alkali sulfate 9 and (2) a residual solution and conde~ate, which can be recycled in the process.
A pH value of about 2 i8 preferably adjusted in the fir~t ~crubbing stage and a pH value of about 7~5 in the second scrubbing ~tage~ The ba3e employed suitably consi~t~ of an alkali hydroxide ? particularly sodium hydroxide. It may ba desirablc to add the precipitant and the flocculant to the scrubbing liquid which ha~ been withdrawn rather than into the circulation system ss~ociated with the ~irst scrubbing ~tage.
In the process in accordance with the invention the acid pollutant gases HCl and HF ~hich hav~ been removsd ~rom the exhaust gas in the fir~t scrubbing stage are substantially converted to their salts in ,;
.~
that ba~e~ are admixed in less thPn stoichiometric amounts. ~hi~ will corre~pondingly decrease the partial pres~ures o~ such gases 90 that not only an effective removal o~ heavy metals but al~o a highly e~fec~ive removal o~ HCl and HF can be achieved in that ~ir~t scrubbing ~tage7 in which acid condition~ are maintained~
whereas it i9 not necessary to continuously withdraw ~crubbing liquid ~rom circulation at a high rate. A~
a result, the plant for regenerati~g the scrubbing liquid may be distinctly s~aller than in conventional processes 90 that the capital expe~dit~re will be reduc~d. Another great adva~tage i~ afforded by the ~act that the scrubbing liquids which have been withdra~n from circula~ion are separately reconditioned ~o that the chloride-containing salts formed in the first scrubbing stage can separately be recovered and can bs re-u~ed `
whereas in conventional proceases they must be finally dumped tog~ther with the residual pFoducts. ~he economic advantages which are offered by the process in accordance with the invention can be summarized a~ follows:
(1) ~he capital inve~tment required for the recondition ing ~nd evaporation of the scrubbing liquid is decrea~ed by about 15%;
~2) the steam requirement for the evaporation i~
decreased by about 30~0;
,'' ' ' ~ "
.
. .
. , ~
Proces~ o~ Puri~ying Exhaust Ga~
D~SCRIPTION
Thi9 inventio~ relate~ to a proces~ of purifying e~hau~t ga~es, which in addition to fly ash contain gaaeous pollutantsv such as S02, HCl and HF, as well a~ volat~le heavy matal~, particularly mercury compounds, by a dr~ separation of ~olids and a scrubbing with a circulated ~crubbing liquid in two stages.
Such processss are used, inter alia, for the purification of the exhaust ga3e~ which are formed in garbage-incinerating pla~ts (~IP) and ~hich in addition to varyin~ rates of fly dust may contain up to 10,000 mg HCl, up to 2,000 mg S02, up to 1,000 mg HF and up to 100 mg heavy metals per ~m3 (sm3 = standard cubic meter). Said exhaust ga~e~ mu3t be purified in accordance with the regulation3 ~hioh ar~ applicable in any giv~n case. In Germany the limits for GIP in accordance with the TA-Lu~t (teohnical in3truction for air pollution control) of 198~ are: HCl ~ 50, S2 ~ 100~ HF ~ 2.0, heavy metal9 (of Clas~e~ Ig II~ III) ' 0.1/1.0/5.0~ in mg/~m3).
.
On pri~ciple a wet purification adopted to avoid a pollution by exhau~t gas wqll always involve a pollution by waste nater. For thi~ rea~on a pollution by exhaust ga~ ca~not be avoided unle88 the pollution by waste ~ater can ~atisfactorily be avoided and a ~ati3fac-tory disposal of the re~idual materials which are inevitably obtained i~ a3sured.
With th~ exception of tho~e case~ in which a dry purification of exhau~t ga~ may be and i~ adopted as an alternative~ relatively complicated plant~ and proces~es will be required ~or a wet puri~ication o~
exhaust ga~ and the chemical reactio~s involved therein will not fully be understood by ma~y operators. In addition to the gsneral desire to ~olve the problem in a manner which can be under~tood as clearly as po3~ible, it has alwa~ been e~deavored~ for the rea~ons stated, to purify exhau~t gase~ to speci~ied pollutant contents and prescribed pure ga~ compo~itions in a m~oner which is a# simple as pos~ible.
From the aspect of the safety o~ operation~ -the availability o~ the equipment ~or puri~yin~ exhaust ga~ must primarily be taken into account because in the case of a de~ect it will be nece~ary to interrupt the "production of exhaust gas" ~o that the powar plant, the garbage-incineratin~ plant or the chenacal production plant must be shut down until the exhaust gas purifying ,.; ~ ., .
:
; , ,1 ~; , ,: , - '' plant is operable agai~ To ensure the ~afety of operation it i~ al90 neccssary that the exhau~t ga~-purifying equipment can respond in such a ma~ner to widely changing operating cQnditions, ~uch as may ari~e owing to the changing quality o~ fuel, particularly in garbage_i~cinerating plant3, that a pure gas haYing a permissible compo~ition will alway~ be ac~ieved and that this will not give ri~e to a ne~ ~ewage di~posal or dumping problem.
It will al~o be understood that the exhau t gas must be purified with the highest possible economy as far a~ the overall concept i9 concerned. A si~ple plant involving a low capital expenditure ~ill not be economical if it invol~ss relatively high C08t9 for reactants and power and ~or the disposal o~ re~idual substances during the total operating life o~ ~uch plant. On the other hand, a highly effective plant will not be very u~eful i$ its capital expenditure is extremely high or i~ it i~ 90 complicated that it has only a low availability.
The invention i9 ba~ed on a proce~s which i9 0~ the ~ind described fir~t hereinbe~ore and i~
which the lo~ partial pre~ure of the gaseous pollutant~
over th~ scrubbing liquid, which lo~ partial pres~ure i~
required ~or a separation of ~uch pollutant~ to a hi~h degree, is maintained i~ that the scrubbing liquid i~
withdra~n at a high rate. In other word~, the pollutant concentrations in the ~orubbing liquid mu~t not exceed certain upper limits because other~i~e the partial pre~sure of ~uch pollutants ~ill ri~e exee~ively and the degree of ~eparation will e~hibit ~n over- .
proportional decrease. For this rea~on a high degree of ~eparation cannot be achieved in ~uch proce~s unles~
the waste water i~ treated and evaporated in a plant which is designed for a withdra~al of ~aste water at a high rate and uch pla~t will in~olve a correspondin41y high expenditure for supplie~. For this rea~on thc requirement for high degrees of separation in processes of that kind will necessarily result in high capital expenditures and operating costs. Besides, the nece~sary reconditioning of the scrubbing liquid wqll re~ult in a production o~ unusable residual ~aterial~ at relatively high rates and their final dumpi~g will also involve high co~ts.
It is an object of the invention to avoid in the known proce~s the disadvantages ~hich have bee~
pointed out, i . e ., to propo~e a proce~ by which the purification of axhaust gases i~ its entirety can be carried out more economically without a need for a more complicated plant and proce~ing and without a decrease of the safety of operation.
' ` ! i ' ~ i ~, . ~.' , `i Ta accn~nl'sh that obJect it is nrooase~ that the orocess .Aescriberl first hereinheForP shDulr! be carrie~
~ut in such a ~anner that a) the exhaust nases are treate~ l~ith an aci~
scrubbin~ liouid in a first scrubbinn St3Qe, aarticularlv to Aecrease the concentr3tion af HCl, ~F an~ ~ea~/v r~eta1r, an~
ta a~ust a te~perature of :~2 to 700r, an~ in which c o~
alue of l~ tn ~ i5 n"ai:.lain2~ oy a controllen 3~ition of ~!3t~r and bases an~ ~V o~ ith~ral~al of scru~inn lioui~j ~) the ~xhau~t oases 2re tre2te~ with e basi,_ scrub~inn liquid in a secDn~ scrubbinra st3ae, Illhich oar-~icularlv ~erves to ~ecre3se the ~G? concentr2tirn an~
in ~hioh the ~a~ temP2r~ture is maintaine~ _s in the firret ,cruahinn st3a3 anr! in mnich a nH \/alu2 of - to 5 i3 ~ justeo 3v cantroll2~ arlr!itiDr ~ ater ~n~ b~ses an~ b~ e l~!ith-Ara~Jal ~F scrub]ino lio~ A an~ a nurifia~ exh3ust naS i3 obtaine~, o) the scruohinn liqui~ ith~rsl-~n from the first scrllobinn stano is troete~ ~ith a orr.cioitant an~ a F
13nt an~ ub,iecte~ to 3 senar3tinn orocess, in mhich (1) a slu~Fe that contains heevv ~et31s an~ fluorine com-noun~s an~ con9titutes 2 first rr~si~lli21 oro~uct to be r~u~ne~ an~
.
. .
: : :
. -- 6 --(2~ a solution which contain~ alkali chloride are obtained, and (3) ~aid solution i9 evaporated and dewatered to recover alkali chloride ~lts, which ca~ be re-u~ed, as well as a residual solution and conden~ate~ whi~h can be recycled in the process 9 snd d) the ~crubbing liquid which ha~ been withdrawn from the second ~crubbing ~tage i~ treated in that it i9 evaporated and dewatered to provide (1) another residual product ~hich i9 to b~ dumped, which essentiall~ contain~ alkali sulfate 9 and (2) a residual solution and conde~ate, which can be recycled in the process.
A pH value of about 2 i8 preferably adjusted in the fir~t ~crubbing stage and a pH value of about 7~5 in the second scrubbing ~tage~ The ba3e employed suitably consi~t~ of an alkali hydroxide ? particularly sodium hydroxide. It may ba desirablc to add the precipitant and the flocculant to the scrubbing liquid which ha~ been withdrawn rather than into the circulation system ss~ociated with the ~irst scrubbing ~tage.
In the process in accordance with the invention the acid pollutant gases HCl and HF ~hich hav~ been removsd ~rom the exhaust gas in the fir~t scrubbing stage are substantially converted to their salts in ,;
.~
that ba~e~ are admixed in less thPn stoichiometric amounts. ~hi~ will corre~pondingly decrease the partial pres~ures o~ such gases 90 that not only an effective removal o~ heavy metals but al~o a highly e~fec~ive removal o~ HCl and HF can be achieved in that ~ir~t scrubbing ~tage7 in which acid condition~ are maintained~
whereas it i9 not necessary to continuously withdraw ~crubbing liquid ~rom circulation at a high rate. A~
a result, the plant for regenerati~g the scrubbing liquid may be distinctly s~aller than in conventional processes 90 that the capital expe~dit~re will be reduc~d. Another great adva~tage i~ afforded by the ~act that the scrubbing liquids which have been withdra~n from circula~ion are separately reconditioned ~o that the chloride-containing salts formed in the first scrubbing stage can separately be recovered and can bs re-u~ed `
whereas in conventional proceases they must be finally dumped tog~ther with the residual pFoducts. ~he economic advantages which are offered by the process in accordance with the invention can be summarized a~ follows:
(1) ~he capital inve~tment required for the recondition ing ~nd evaporation of the scrubbing liquid is decrea~ed by about 15%;
~2) the steam requirement for the evaporation i~
decreased by about 30~0;
,'' ' ' ~ "
.
. .
. , ~
(3) the electric po~er required ~or the reconditioning ~nd evaporation i9 decreased by about 15~;
(4) the total amount o~ re~idual sub~tances obtained i8 decreased by about 30% and the chloride-contai~ing ~alt~ ca~ be re used and ne~d not be dumped;
(5~ the amount of re~idual ~ub~tance~ to b~ dumped i9 decrea~ed by 30 to 50 ~.
~ he improvement o~ the known proces~ in accordance with the teachi~g o~ the invention doe~
not render the plant concept or it~ mode of operation more complicated. ~here are al~o no disadvant3ges involved as regard~ the availability and the ~a~sty o~ operation of a plant concaived for carrying out the proce~s in accordance with the invention. ~or this reason a puri~ication of e~hau~t gase~ which in addition to ~ly ash contain gaseous pollutan~s9 such a~ S02, HCl, and H~ and volatile heavy metals, particularly mercury compounds, can be ef~ected much more economically.
Further detail~ of t~e invention will be explained more specifically with reference to the diagram o~ connection~ sho~n in Figure 1.
~ he exhaust gas i8 ~ir~t ~upplied through line 11 to a unit 3 for ~eparating ~olid~9 i.~., fly dust and the like, which are removed from the ~y~tem through line 21. ~he exhaust ga~ i~ then pa~sed through - :~ : ..
.
' :,. .
the consecutive scrubbers 1 and 2 and in a purified ~tate is discharged into the environment through line 12. The t~o scrubbers 1 and 2 are supplied with circulated scrubbing liquid, which i9 handled by the pump~ 7 and 8. The scrubbing cirouit~ are supplied with fresh ~ bases) water and fresh reactan~ through lines 9 and 10.
Part of the scrubbing liquid i8 withdrawn from the circuit a~sociated with the ~irst scrubber 1 and after an addition o~ precipitant and ~locculant through line 13 i9 supplied to a unit 4, in which a 31udge which contain3 the heavy metal~ and fluorine compounds is ~eparated. ~he separated sludge is dewatered and i~ then withdrawn from the proces~ through line 16 a~
the first residual product that i~ to be dumped. After that removal of slud~e ~rom the ~crubbing liquid, whioh consists of a solution that contai~s alkali chloride, that liquid i9 evaporated in a unit 5 so that re~usable alkali chloride salts and a re~idual ~olu~ion and condensate are obtained. ~he alkali chloride salta are withdrawn through line 17. The residual ~olution i9 removed through line 18 and the conden~ate thro~gh line 14. The residual solution ~nd the conden~ate may be recycled in the proces~ to a de~irable point ~o that there is no need for a ~eparat2 di~po~al of waste water.
Part of the wa~hing liquid is al~o withdrawn from the circuit a~sociated with the ~econd ~crubber 2 .
- 10 _ and is evaporated in a unit 6, in which a second residual product is obtained9 which substantially comprises sodium sulfate and i~ withdrawn ~rom the proce~ through line 19. Residual 901utio~ and condensate are also obtained in the unit 6 and flow off through lines 20 and 15 and can be recycled in the proce~.
If the condensate and residual solutions obtained in the evaporator.q 5 and 6 are entirely recyclsd in the proceE~s there Yvill be no need for a disposal of waste water, and in that case thc "product~
of the process of purifying exhau~t gas in accordance with the invention will con~iQt only of puri~ied exhaust gas (in line 12), o~ a sludg~ (in line 16) which contain~
the h~avy metal~ and ~luorine compound~ and con3titutes thc first residual produot that i~ to be dumped, o~
re-usable alkali chloride ~alts ~in line 17¦~ and of a second residual product to be dumped, which e~entially contains sodium sulfate (in line 19~.
, . ;.
..
" . ,, ' ,
(5~ the amount of re~idual ~ub~tance~ to b~ dumped i9 decrea~ed by 30 to 50 ~.
~ he improvement o~ the known proces~ in accordance with the teachi~g o~ the invention doe~
not render the plant concept or it~ mode of operation more complicated. ~here are al~o no disadvant3ges involved as regard~ the availability and the ~a~sty o~ operation of a plant concaived for carrying out the proce~s in accordance with the invention. ~or this reason a puri~ication of e~hau~t gase~ which in addition to ~ly ash contain gaseous pollutan~s9 such a~ S02, HCl, and H~ and volatile heavy metals, particularly mercury compounds, can be ef~ected much more economically.
Further detail~ of t~e invention will be explained more specifically with reference to the diagram o~ connection~ sho~n in Figure 1.
~ he exhaust gas i8 ~ir~t ~upplied through line 11 to a unit 3 for ~eparating ~olid~9 i.~., fly dust and the like, which are removed from the ~y~tem through line 21. ~he exhaust ga~ i~ then pa~sed through - :~ : ..
.
' :,. .
the consecutive scrubbers 1 and 2 and in a purified ~tate is discharged into the environment through line 12. The t~o scrubbers 1 and 2 are supplied with circulated scrubbing liquid, which i9 handled by the pump~ 7 and 8. The scrubbing cirouit~ are supplied with fresh ~ bases) water and fresh reactan~ through lines 9 and 10.
Part of the scrubbing liquid i8 withdrawn from the circuit a~sociated with the ~irst scrubber 1 and after an addition o~ precipitant and ~locculant through line 13 i9 supplied to a unit 4, in which a 31udge which contain3 the heavy metal~ and fluorine compounds is ~eparated. ~he separated sludge is dewatered and i~ then withdrawn from the proces~ through line 16 a~
the first residual product that i~ to be dumped. After that removal of slud~e ~rom the ~crubbing liquid, whioh consists of a solution that contai~s alkali chloride, that liquid i9 evaporated in a unit 5 so that re~usable alkali chloride salts and a re~idual ~olu~ion and condensate are obtained. ~he alkali chloride salta are withdrawn through line 17. The residual ~olution i9 removed through line 18 and the conden~ate thro~gh line 14. The residual solution ~nd the conden~ate may be recycled in the proces~ to a de~irable point ~o that there is no need for a ~eparat2 di~po~al of waste water.
Part of the wa~hing liquid is al~o withdrawn from the circuit a~sociated with the ~econd ~crubber 2 .
- 10 _ and is evaporated in a unit 6, in which a second residual product is obtained9 which substantially comprises sodium sulfate and i~ withdrawn ~rom the proce~ through line 19. Residual 901utio~ and condensate are also obtained in the unit 6 and flow off through lines 20 and 15 and can be recycled in the proce~.
If the condensate and residual solutions obtained in the evaporator.q 5 and 6 are entirely recyclsd in the proceE~s there Yvill be no need for a disposal of waste water, and in that case thc "product~
of the process of purifying exhau~t gas in accordance with the invention will con~iQt only of puri~ied exhaust gas (in line 12), o~ a sludg~ (in line 16) which contain~
the h~avy metal~ and ~luorine compound~ and con3titutes thc first residual produot that i~ to be dumped, o~
re-usable alkali chloride ~alts ~in line 17¦~ and of a second residual product to be dumped, which e~entially contains sodium sulfate (in line 19~.
, . ;.
..
" . ,, ' ,
Claims (6)
1. A process of purifying exhaust gases, which in addition to fly ash contain gaseous pollutants, such as SO2, HCl and HF, as well as volatile heavy metals, particularly mercury compounds, by a dry separation of solids and a scrubbing with a circulated scrubbing liquid in two stages, characterized in that a) the exhaust gases are treated with an acid scrubbing liquid at an adjusted temperature of 50 to 70°C in a first scrubbing stage, in which a pH value of 0 to 3 is maintained by a controller addition of water and bases and by a withdrawal of scrubbing liquid, b) the exhaust gases are treated with a basic scrubbing liquid, which contains alkali hydroxide, in a second scrubbing stage, in which the same temperature is maintained as in the first scrubbing stage and in which a pH value of 6 to 9 is adjusted by a controlled addition of water and bases and by a withdrawal of scrubbing liquid and a purified exhaust gas is obtained, c) the scrubbing liquid withdrawn from the first scrubbing stage is treated with a precipitant and a flocculant and is subjected to a separating process, in which (1) a sludge that contains heavy metals and fluorine compounds and constitutes a first residual product to be dumped and (2) a solution which contains alkali chloride are obtained, and (3) said solution is evaporated and dewatered to recover alkali chloride salts, which can be re-used, as well as a residual solution and condensate, which can be recycled in the process, and d) the scrubbing liquid which has been withdrawn from the second scrubbing stage is treated in that it is evaporated and dewatered to provide (1) another residual product which is to be dumped, which essentially contains alkali sulfate, and (2) a residual solution and condensate, which can be recycled in the process.
2. A process according to claim 1, characterized in that a pH value of about 2 is adjusted in the first scrubbing stage.
3. A process according to claim 1, characterized in that a pH value of about 7.5 is adjusted in the second scrubbing stage.
4. A process according to claim 1, 2 or 3, characterized in that an alkali hydroxide is used as a base.
5. A process according to claim 4, characterized in that sodium hydroxide is used as an alkali hydroxide.
6. A process according to claim 1, characterized in that, as an alternative to feature c), the precipitant and flocculant are supplied to the circulated scrubbing liquid for the first stage.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4012320.0 | 1990-04-18 | ||
| DE4012320A DE4012320C1 (en) | 1990-04-18 | 1990-04-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2037839A1 true CA2037839A1 (en) | 1991-10-19 |
Family
ID=6404564
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002037839A Abandoned CA2037839A1 (en) | 1990-04-18 | 1991-03-08 | Process of purifying exhaust gas |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0453005B1 (en) |
| JP (1) | JPH04227818A (en) |
| KR (1) | KR910018065A (en) |
| AU (1) | AU637686B2 (en) |
| CA (1) | CA2037839A1 (en) |
| DE (2) | DE4012320C1 (en) |
| ES (1) | ES2067135T3 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4206965C2 (en) * | 1992-03-05 | 1996-08-01 | Steinmueller Gmbh L & C | Process for working up an inorganic contaminated waste hydrochloric acid from the scrubbing of an exhaust gas |
| DE4228471A1 (en) * | 1992-08-27 | 1994-03-03 | Henkel Kgaa | Flue gas desulfurization |
| JP2592760B2 (en) * | 1993-02-22 | 1997-03-19 | 呉羽環境株式会社 | How to treat incinerator waste gas |
| SE501346C2 (en) * | 1993-06-08 | 1995-01-23 | Flaekt Ab | Methods and apparatus for purifying sulfur dioxide-containing gas |
| DE4406460C2 (en) * | 1994-02-28 | 2001-05-31 | Linde Ag | Process for the purification of a gasification gas from the gasification of waste and residues |
| JP3711229B2 (en) | 2000-06-30 | 2005-11-02 | 株式会社日本触媒 | Waste liquid treatment method |
| JP4794070B2 (en) * | 2001-06-26 | 2011-10-12 | 小名浜製錬株式会社 | Method for removing mercury contained in exhaust gas |
| JP4794071B2 (en) * | 2001-06-26 | 2011-10-12 | 小名浜製錬株式会社 | Method for removing mercury contained in exhaust gas |
| SG183495A1 (en) | 2010-02-25 | 2012-10-30 | Alfa Laval Corp Ab | Exhaust gas and gas scrubber fluid cleaning equipment and method |
| DK2402288T3 (en) * | 2010-07-02 | 2017-02-06 | Alfa Laval Corp Ab | GAS SCRUBBER FLUID CLEANING EQUIPMENT |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5065052A (en) * | 1973-10-16 | 1975-06-02 | ||
| US4147756A (en) * | 1976-04-09 | 1979-04-03 | Envirotech Corporation | Combustion gas scrubbing system |
| DE2735566A1 (en) * | 1977-08-06 | 1979-02-22 | Metallgesellschaft Ag | METHOD FOR REMOVING FLUOROUS COMPOUNDS AND SULFUR DIOXIDE FROM EXHAUST GASES |
| DE3320466C2 (en) * | 1983-06-07 | 1987-04-30 | Kernforschungszentrum Karlsruhe Gmbh, 7500 Karlsruhe | Process for cleaning flue gas |
| DE3521205A1 (en) * | 1985-06-13 | 1986-12-18 | Gottfried Bischoff Bau kompl. Gasreinigungs- und Wasserrückkühlanlagen GmbH & Co KG, 4300 Essen | Plant for purifying industrial exhaust gases |
| DE3529270A1 (en) * | 1985-06-13 | 1987-02-19 | Bischoff Gasreinigung | Plant for purifying industrial exhaust gases |
| SE455767B (en) * | 1986-06-02 | 1988-08-08 | Erik Lindahl | PROCEDURE AND DEVICE FOR SEPARATION OF MERCURY SILVER FROM COOKING OR PROCESS GASES CONTAINING WATER STEAM |
| AT389238B (en) * | 1987-08-18 | 1989-11-10 | Simmering Graz Pauker Ag | METHOD FOR TREATING THE SMOKE GASES AND COMBUSTION RESIDUES OF A COMBUSTION PLANT, IN PARTICULAR WASTE COMBUSTION PLANT |
| DE3800881A1 (en) * | 1988-01-14 | 1989-07-27 | Siemens Ag | Process and apparatus for purifying flue gases |
| DE3827831A1 (en) * | 1988-08-17 | 1990-02-22 | Thyssen Industrie | METHOD AND SYSTEM FOR THE TREATMENT OF WASTEWATER, IN PARTICULAR FROM THE FLUE GAS DESULFURATION |
-
1990
- 1990-04-18 DE DE4012320A patent/DE4012320C1/de not_active Expired - Lifetime
-
1991
- 1991-03-07 ES ES91200499T patent/ES2067135T3/en not_active Expired - Lifetime
- 1991-03-07 DE DE59104357T patent/DE59104357D1/en not_active Expired - Lifetime
- 1991-03-07 EP EP91200499A patent/EP0453005B1/en not_active Revoked
- 1991-03-08 CA CA002037839A patent/CA2037839A1/en not_active Abandoned
- 1991-04-09 JP JP3103771A patent/JPH04227818A/en active Pending
- 1991-04-17 KR KR1019910006158A patent/KR910018065A/en not_active Withdrawn
- 1991-04-17 AU AU75044/91A patent/AU637686B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| DE4012320C1 (en) | 1991-07-11 |
| DE59104357D1 (en) | 1995-03-09 |
| EP0453005A1 (en) | 1991-10-23 |
| KR910018065A (en) | 1991-11-30 |
| AU7504491A (en) | 1991-10-24 |
| EP0453005B1 (en) | 1995-01-25 |
| ES2067135T3 (en) | 1995-03-16 |
| JPH04227818A (en) | 1992-08-17 |
| AU637686B2 (en) | 1993-06-03 |
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