CA1326755C - Process for concentrating sulphuric acid - Google Patents
Process for concentrating sulphuric acidInfo
- Publication number
- CA1326755C CA1326755C CA000547576A CA547576A CA1326755C CA 1326755 C CA1326755 C CA 1326755C CA 000547576 A CA000547576 A CA 000547576A CA 547576 A CA547576 A CA 547576A CA 1326755 C CA1326755 C CA 1326755C
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- Prior art keywords
- sulphuric acid
- evaporator
- evaporation
- acid
- heated
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/88—Concentration of sulfuric acid
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
Process for concentrating sulphuric acid ABSTRACT OF THE DISCLOSURE
Sulphuric acid is concentrated to concentrations of up to about 80% H2SO4 by multistage evaporation in which the evaporation to concentrations of 40 to 65%
H25O4 is carried out at reduced pressure in circulation or falling film evaporators in which one stage of the evaporator is heated by the vapors from a subsequent horizontal evaporator in which the sulphuric acid is evaporated to concentrations of 66 to 80% H2SO4 at slightly reduced or normal or excess pressure.
Sulphuric acid is concentrated to concentrations of up to about 80% H2SO4 by multistage evaporation in which the evaporation to concentrations of 40 to 65%
H25O4 is carried out at reduced pressure in circulation or falling film evaporators in which one stage of the evaporator is heated by the vapors from a subsequent horizontal evaporator in which the sulphuric acid is evaporated to concentrations of 66 to 80% H2SO4 at slightly reduced or normal or excess pressure.
Description
Process for cDncentrating ~ulphuric acid This invention relate~ to a proce6s for CencQn-trating sulphuric acid to concentrations of up to about 80% H2S04 by multistage evaporation.
BACKG~OUND OF THE INVENTION
Dilute 5ulphuric acid with concentration~ sometime~
below 107/. H2S04 is obtained from many processes for the production of inorganic and organic compounds and the purification of exhau6t ga~ec containing S02. If this - . acid is to ~e used again, it i~ generally necessary to evaporate it to concentrations above 60X. H2S04 and remove or de~troy the impurities.
For concentrating the0e ~ulphuric acids by evapora-tion under energy Baving condition~ it has been propo~ed to employ multistage proce~ses in which the vaporc obtsin~d from one ~tage of evaporationare u~ed as fuel for the next ~tage. The co~t of the apparatus required `. for the eYaporation of sulphuric acid i~, however, rælati~ely high owing to the corrosivene6~ of the acid.
It i~ for this raa~on and due to ~he fact ~hat the boiling point Df the acid rise~ ~harply with increa~ing H2504 concentra~ion, in other words the H20 partial prussur~ Falls ~harply with in rea~ing H2SO~ concentra-tio~ at the maximum evbporation temperature th~t can be allGWed fDr the given material of the apparatu~, that multi~tage proce~ses ha~e hitherto only bean employe~
~$
Le A 24 623 for ra;sing ~oncantration~ to about 70% H2S04 (so-called preconcantration)~ For reasons of co~t, the ~vaporators and pipes used for the~ processes are preferably made of rubberized steel or plaEticfi and thc heat exchanger~ are made of graphite. The operating temperatures are therefore limited to a maximum of 100 to 1~0C ~o that the maximum final concentration that can be obtained at an acceptable cost with thi6 method of vapor condensation ;~ g0nerally 60 to 70% H~SC4, depending on the temperaturez that can be reached.
Enamelled apparatu~ and heat exchanger~ made of tantalum are so expen~ive that they are only usQd when le~s expensive cunstructional material~ can no longer be u~ed. This i~ the case when sulphuric acid at a concentration of about 60 to 70% H2504 i~ evaporated to - . a concantration of 80 ~o 92% H2S04. At this stage of evaporation, temperat~res of 120 to 195C are required owing to the low H20 partial pressure~ and the maximum temperaSure require~ the use of tantalum as construc-tional material for the heat exchanger on ac~ount of it re~i~tance. Gla6s, anamel, cast ferro~ilicon and Teflon are preferred material~ for apparatus, pipec and pumps, Owing to thR high co t of the tantalum heat ex-changer, heating i~ supplied ~y ~team at 5 to 15 bar~
i.e. the e~aporation of water is carr;ed out in one ~tage (~ea Winnacker, Kuchler, Chemi~che Tech~ologie~
30 Vol, 2~ 4th Ed., 1982, Carl-Hanser-Verlag Munchen Wien, page~ 65-72).
Le A 24 623 ~ 3~6755 THE INVENTION
I~ is an object of the present invention to provide an economical process for the concentrating dilute sulphuric acid to concentrations of up to about 80% without the disadvantages of the process described above.
It has now surprisingly been found -that these requirements can be fulfilled by a process in which the dilute sulphuric acid is concentrated in a combination of circulation or falling film evaporators and a horizontal evaporator.
According to the present invention there is provided a process ~or increasing the concentra-tion of sulphuric acid to about 80~ H2SO~ by multistage evaporation, wherein the evaporation to concentrations of 40 to 65% H2SO4 is carried out in one or more stages at reduced pressure and temperatures of not more than 120C
in circulation or falling film evaporators with graphite or Teflon heat exchangers, and one evaporator stage is heate~ by the vapors from a subsequent horizontal evaporator having a heat exchanger in the form of a bundle of tantalum tubes in which the sulphuric acid is evaporated to concentrations of 66 to 80% H2SO4 by evaporation at a slightly reduced pressure, normal pressure or excess pressure.
In the process according to the invention, evaporation of the sulphuric acid is carried out in several stages.
Evaporation to 40 to 65~ H2SO4 is carried out in one or more s~ages at reduced pressure and temperatures of not more than 120C
in circulation or falling film evaporators with graphite or Teflon heat exchangers.
J~
Sub~equent evaporation of the 40 to 65% sulphuric acid to about 66 to 80% H2504 is carried out at slightly reduced prassure or normal pres6ure or exce6s pre~ure in a horizontal evaporator having[a heat exchanger in the form of a bundle nf tantalum tubec~, In thc proces~ according to the invention, evapora-tion of the sulphuric acid in the horizontal evaporatori~ prefQrably carried out under cuch conditions that aulphuric acid at a cQncentration of 66 to 80% ic di~char~ed from thifi evaporator at temperatures of 160 to 195~C.
Th~ preferred constructional material for the hori-zontal evaporator i6 glas~ or enamalled steel with PTFE, The hea~ ~xchan~ar of the horizontal a~aporator is - preferably heated with ~team at 8 to 20 bar, The vapors from the horizontal evaporator are prefsrably used as fuel for a stage of evaporation in a circulation or falli~g film evaporator, and the vapor~ from thi~ 4tage ~3y in turn be u~ed a~ fuel for a subsequent ~ta~e. The optimum number of stage~ of circulation or falling film evaporator~ i~ determined by economical con~iderations taking intn account the overall performance of th~
plant, ths energy co~t~ and available cooling water.
Brief d ecri~t_on of the drawinq The Fi0ure show~ a multistage avaporation unit for concentrating sulphuric acid.
Le A 24 623 ~ - 5 _ t32~755 Detailcd dascriptisn o~_the drawing Th~ proce~ according to th~ invention will now be explainQd with reference the ~igure. Dilut~ ~ulphuric acid is fed into ~vapor~tor stage (1). The drawing ~hows a forced circulation evaporator consisting of ~he evaporator (la~, the circulation pump (lb) and th2 heat exchanger (lc). Dilute acid (11~ is fed into the circulating acid (12~ and heated together with this ~cid in the heat exchangRr tlc) by maans o~ the vapor~ (18) from evaporator stage (2j. In the evaporator (la) water is ~vapora~d from the heated circulsting acid S1~
according to the level to which ~he pre~sure is reducedO
The vapors (14) ars condensed in a conden6er (4) by baing coolcd with water or ~ome oth~r cooling medium - . (15~ and are then di~chsrged into the immer~ion ves~el (5~. Condensation of ~he vapors may al~o be carried out by direct con~ac~ with the cooling madium. Gases (16) which ca~not be condensed are removed from the sy~tam by a vacuum pump, Partially evaporaLed ~ulphuric acit (17) flows from evaporator ~tage ~) into evaporator sta~e (2) which operates at a h;~her temperature and a highar pressure _ tharl ~tage 11). The vapor~ tl9) from the horizon~al evaporator (3a) of evaporator stage (3) are used as ~uel in thQ hea~ exchangQr (2c). Th~ 40 to 65% sulphuric acid t20) ~hich is discharg~d from evaporator atage ~2) into ~aga l~ pre~rably preheated in a gla~s or PTFE
h0at exchanger ~3b) by the 66 to 80% ~ulphuric acid (22) L~ A 24 62 - 6 - 1 ~267 55 which is discharged from e~apora~or (3a) at a tempera-ture of 160 to 195C. Since ~he acid (21) is ~hen fed in~o the horizontal evapora~or (3a) a~ approximately boiling point, ~he ~urface of the ~an~alum h~at QX-changer can be kep~ quite small. The preferred featur~
of installing vertical parti~ions (3c) along the length of the hea~ exchanger ~ubes serve6 the sa~e purpose as it subdividas the op2ration of this evaporator into ~ev2ral stages. The acid (23) cooled to 60 - lZ0C in the heat exchang~r (3b~ may b~ further cooled by ~he dilute acid (11) fed in~o the system or by cooling water. Tha tantalum hea~ exchanger of ~he hDrizontal evaporator (~a) i~ heated wi~h Gteam at 8 - 20 bar (24).
The energy conten~ o~ ~he steam condensate t25~ may ad-vantageously by u~ilized for tha evaporation of sul-_ phuric acid carried out by means of a flash e~aporation in the fuel space of ~h~ heat exchanger (2c).
The advantage~ o~ tha process according to thainvention lie not only in th~ comparatively low C05t of - ~he apparatus bu~ especially also in ~he fact tha~ owing to the high dQw point of the vapors from the horizontal svaporator, i~ is possible ~n carry out one more ~tage of evaporation ~han in known preconcentration processes under otharw;se identicsl condi~ions (in particular iden~ical temperature of cooling water). The ~pecific energy requirem~nt i~ th~reby reduced by 20 to ~0%. On8 particular advantage o~er known proce~a~ is that where-Bi in the known prncesses th~ sooling water ~empara~uresmay b8 too high to enable multistage preconcentration : 35 Le A 24 623 _ 7 ~ 6755 with utilization of the heat from the vapor~ to be carried out economically unless the temperature of the cooling water is lowered by special cooling apparatus, which involves extra cost, in the process according to this invention, the increase in the concentration of the acid from 40 - 65% H2S04 to 66 - 80% H2504 in an evapo-rator stage using a tantalum heat exchanger enables evaporation to be carried out in at least two stageseven if the cooling water temperatures are extremely high, say 30 to 35C. Due to the use of the multistage horizontal evaporator at the stage of the highest sul-phuric acid concentration in the process according to ~he invention, the amount of heating surface requîredat this stage is about 20 to 35% less than that required in forced circulation evaporators so that the use of ~ high quality materials, in particular tantalum, is economicall~ justified.
The advantages of th6 process accordin~ to the in-vention compared with the known processes will now be illustrated by the followin~ Examples which do not limit the scope of the invention.
3~
~.
Sulphuric acid i~ to be concentr~ted from 30% H2S0 to 70% H2504 by evaporation. A comparison i6 made between the characteristics of tha plants and their energy requirements for evaporating 1 t H20/h by a known proces~ (la) and by tha proces~ accordiny to the inven-~ tion (lb).
1 a) Thz concen~ra~ion of sulphuric acid by evaporation can only be carried out economically if limited tu two stages. The ~aporator plant used is a two-stage forc~d circulation ~acuum ~vaporator plant. ~0% sulphuric acid is fed into 6tage 1 and concantrated tn 42% H2S04 by evaporation at llQCo It flows into ~tage 2 where it i conc~ntrated to 70% H2S04 by evaporation at 80C. The hea~ exchanger of graphite tubes used in ~tage 1 is - h~ated with ~team at 3.6 bar and the heat exchanger of stage 2 is heated with the ~apors from 6tage 1. The vapors from stage 2 are directly condensed with cooling water. The 30% sulphuric acid fed in is prehsat~d from ~5C to 38C by tha 70% sulphuric a~id discharg~d frDm t,h~ plant and the 70% acid i5 thereby cooled to 30C.
1 b) Concentration of the ~ulphuric acid by evaporation i3 carried out in a three stage plant a~ shown in Figure 1, The acid t213 fed into tha horizontal evaporator ~3a) has bean heated to 120C in the heat 0xchan~er t~b) ~y tha ac;d ~22) dircharged from the horizontal ~vaporator ~0 and the acid ~22) i~ at the ~ame time soolad to 80 C.
The 70% sulphuric acicl ~2~ t,hen furthar cooled to 30C by the dil~te acid ~113 which iB thereb~ heated to 45C befora ~eing fed into stage (1). The vapors from evaporator (1~) are rondensed by direct contact with cooling water.
Le A 24 623 ~ 9 ~ 1 32h755 The ~6% sulphuric acid from ~aga 1 is fed in~o S stage 2 and discharged as 46% sulphuri~ acid into the horizon~al evapora~or by way of the hea~ e~changar (~b), When the ~wo processe~ (la) and (lb) are compared (Table 1), the process accordin~ to the inven~ion is found to have the following advantages:
1. The energy consump~ion i5 only 77% in th~ process lb a~cording to ~he invention compared wi~h the known process la. ~hen ~he stQam condensate is usad for the ganeration of 6team i~ is only 67%, 2. Owing to the higher daw point of ~he vapors ~o be condensed ~la: 27C, lb: 31C) and the smaller quanti~y o~ steam, the amount of cooling water re-~- . quired when ths water ~emperature is ~he same is only 42%.
BACKG~OUND OF THE INVENTION
Dilute 5ulphuric acid with concentration~ sometime~
below 107/. H2S04 is obtained from many processes for the production of inorganic and organic compounds and the purification of exhau6t ga~ec containing S02. If this - . acid is to ~e used again, it i~ generally necessary to evaporate it to concentrations above 60X. H2S04 and remove or de~troy the impurities.
For concentrating the0e ~ulphuric acids by evapora-tion under energy Baving condition~ it has been propo~ed to employ multistage proce~ses in which the vaporc obtsin~d from one ~tage of evaporationare u~ed as fuel for the next ~tage. The co~t of the apparatus required `. for the eYaporation of sulphuric acid i~, however, rælati~ely high owing to the corrosivene6~ of the acid.
It i~ for this raa~on and due to ~he fact ~hat the boiling point Df the acid rise~ ~harply with increa~ing H2504 concentra~ion, in other words the H20 partial prussur~ Falls ~harply with in rea~ing H2SO~ concentra-tio~ at the maximum evbporation temperature th~t can be allGWed fDr the given material of the apparatu~, that multi~tage proce~ses ha~e hitherto only bean employe~
~$
Le A 24 623 for ra;sing ~oncantration~ to about 70% H2S04 (so-called preconcantration)~ For reasons of co~t, the ~vaporators and pipes used for the~ processes are preferably made of rubberized steel or plaEticfi and thc heat exchanger~ are made of graphite. The operating temperatures are therefore limited to a maximum of 100 to 1~0C ~o that the maximum final concentration that can be obtained at an acceptable cost with thi6 method of vapor condensation ;~ g0nerally 60 to 70% H~SC4, depending on the temperaturez that can be reached.
Enamelled apparatu~ and heat exchanger~ made of tantalum are so expen~ive that they are only usQd when le~s expensive cunstructional material~ can no longer be u~ed. This i~ the case when sulphuric acid at a concentration of about 60 to 70% H2504 i~ evaporated to - . a concantration of 80 ~o 92% H2S04. At this stage of evaporation, temperat~res of 120 to 195C are required owing to the low H20 partial pressure~ and the maximum temperaSure require~ the use of tantalum as construc-tional material for the heat exchanger on ac~ount of it re~i~tance. Gla6s, anamel, cast ferro~ilicon and Teflon are preferred material~ for apparatus, pipec and pumps, Owing to thR high co t of the tantalum heat ex-changer, heating i~ supplied ~y ~team at 5 to 15 bar~
i.e. the e~aporation of water is carr;ed out in one ~tage (~ea Winnacker, Kuchler, Chemi~che Tech~ologie~
30 Vol, 2~ 4th Ed., 1982, Carl-Hanser-Verlag Munchen Wien, page~ 65-72).
Le A 24 623 ~ 3~6755 THE INVENTION
I~ is an object of the present invention to provide an economical process for the concentrating dilute sulphuric acid to concentrations of up to about 80% without the disadvantages of the process described above.
It has now surprisingly been found -that these requirements can be fulfilled by a process in which the dilute sulphuric acid is concentrated in a combination of circulation or falling film evaporators and a horizontal evaporator.
According to the present invention there is provided a process ~or increasing the concentra-tion of sulphuric acid to about 80~ H2SO~ by multistage evaporation, wherein the evaporation to concentrations of 40 to 65% H2SO4 is carried out in one or more stages at reduced pressure and temperatures of not more than 120C
in circulation or falling film evaporators with graphite or Teflon heat exchangers, and one evaporator stage is heate~ by the vapors from a subsequent horizontal evaporator having a heat exchanger in the form of a bundle of tantalum tubes in which the sulphuric acid is evaporated to concentrations of 66 to 80% H2SO4 by evaporation at a slightly reduced pressure, normal pressure or excess pressure.
In the process according to the invention, evaporation of the sulphuric acid is carried out in several stages.
Evaporation to 40 to 65~ H2SO4 is carried out in one or more s~ages at reduced pressure and temperatures of not more than 120C
in circulation or falling film evaporators with graphite or Teflon heat exchangers.
J~
Sub~equent evaporation of the 40 to 65% sulphuric acid to about 66 to 80% H2504 is carried out at slightly reduced prassure or normal pres6ure or exce6s pre~ure in a horizontal evaporator having[a heat exchanger in the form of a bundle nf tantalum tubec~, In thc proces~ according to the invention, evapora-tion of the sulphuric acid in the horizontal evaporatori~ prefQrably carried out under cuch conditions that aulphuric acid at a cQncentration of 66 to 80% ic di~char~ed from thifi evaporator at temperatures of 160 to 195~C.
Th~ preferred constructional material for the hori-zontal evaporator i6 glas~ or enamalled steel with PTFE, The hea~ ~xchan~ar of the horizontal a~aporator is - preferably heated with ~team at 8 to 20 bar, The vapors from the horizontal evaporator are prefsrably used as fuel for a stage of evaporation in a circulation or falli~g film evaporator, and the vapor~ from thi~ 4tage ~3y in turn be u~ed a~ fuel for a subsequent ~ta~e. The optimum number of stage~ of circulation or falling film evaporator~ i~ determined by economical con~iderations taking intn account the overall performance of th~
plant, ths energy co~t~ and available cooling water.
Brief d ecri~t_on of the drawinq The Fi0ure show~ a multistage avaporation unit for concentrating sulphuric acid.
Le A 24 623 ~ - 5 _ t32~755 Detailcd dascriptisn o~_the drawing Th~ proce~ according to th~ invention will now be explainQd with reference the ~igure. Dilut~ ~ulphuric acid is fed into ~vapor~tor stage (1). The drawing ~hows a forced circulation evaporator consisting of ~he evaporator (la~, the circulation pump (lb) and th2 heat exchanger (lc). Dilute acid (11~ is fed into the circulating acid (12~ and heated together with this ~cid in the heat exchangRr tlc) by maans o~ the vapor~ (18) from evaporator stage (2j. In the evaporator (la) water is ~vapora~d from the heated circulsting acid S1~
according to the level to which ~he pre~sure is reducedO
The vapors (14) ars condensed in a conden6er (4) by baing coolcd with water or ~ome oth~r cooling medium - . (15~ and are then di~chsrged into the immer~ion ves~el (5~. Condensation of ~he vapors may al~o be carried out by direct con~ac~ with the cooling madium. Gases (16) which ca~not be condensed are removed from the sy~tam by a vacuum pump, Partially evaporaLed ~ulphuric acit (17) flows from evaporator ~tage ~) into evaporator sta~e (2) which operates at a h;~her temperature and a highar pressure _ tharl ~tage 11). The vapor~ tl9) from the horizon~al evaporator (3a) of evaporator stage (3) are used as ~uel in thQ hea~ exchangQr (2c). Th~ 40 to 65% sulphuric acid t20) ~hich is discharg~d from evaporator atage ~2) into ~aga l~ pre~rably preheated in a gla~s or PTFE
h0at exchanger ~3b) by the 66 to 80% ~ulphuric acid (22) L~ A 24 62 - 6 - 1 ~267 55 which is discharged from e~apora~or (3a) at a tempera-ture of 160 to 195C. Since ~he acid (21) is ~hen fed in~o the horizontal evapora~or (3a) a~ approximately boiling point, ~he ~urface of the ~an~alum h~at QX-changer can be kep~ quite small. The preferred featur~
of installing vertical parti~ions (3c) along the length of the hea~ exchanger ~ubes serve6 the sa~e purpose as it subdividas the op2ration of this evaporator into ~ev2ral stages. The acid (23) cooled to 60 - lZ0C in the heat exchang~r (3b~ may b~ further cooled by ~he dilute acid (11) fed in~o the system or by cooling water. Tha tantalum hea~ exchanger of ~he hDrizontal evaporator (~a) i~ heated wi~h Gteam at 8 - 20 bar (24).
The energy conten~ o~ ~he steam condensate t25~ may ad-vantageously by u~ilized for tha evaporation of sul-_ phuric acid carried out by means of a flash e~aporation in the fuel space of ~h~ heat exchanger (2c).
The advantage~ o~ tha process according to thainvention lie not only in th~ comparatively low C05t of - ~he apparatus bu~ especially also in ~he fact tha~ owing to the high dQw point of the vapors from the horizontal svaporator, i~ is possible ~n carry out one more ~tage of evaporation ~han in known preconcentration processes under otharw;se identicsl condi~ions (in particular iden~ical temperature of cooling water). The ~pecific energy requirem~nt i~ th~reby reduced by 20 to ~0%. On8 particular advantage o~er known proce~a~ is that where-Bi in the known prncesses th~ sooling water ~empara~uresmay b8 too high to enable multistage preconcentration : 35 Le A 24 623 _ 7 ~ 6755 with utilization of the heat from the vapor~ to be carried out economically unless the temperature of the cooling water is lowered by special cooling apparatus, which involves extra cost, in the process according to this invention, the increase in the concentration of the acid from 40 - 65% H2S04 to 66 - 80% H2504 in an evapo-rator stage using a tantalum heat exchanger enables evaporation to be carried out in at least two stageseven if the cooling water temperatures are extremely high, say 30 to 35C. Due to the use of the multistage horizontal evaporator at the stage of the highest sul-phuric acid concentration in the process according to ~he invention, the amount of heating surface requîredat this stage is about 20 to 35% less than that required in forced circulation evaporators so that the use of ~ high quality materials, in particular tantalum, is economicall~ justified.
The advantages of th6 process accordin~ to the in-vention compared with the known processes will now be illustrated by the followin~ Examples which do not limit the scope of the invention.
3~
~.
Sulphuric acid i~ to be concentr~ted from 30% H2S0 to 70% H2504 by evaporation. A comparison i6 made between the characteristics of tha plants and their energy requirements for evaporating 1 t H20/h by a known proces~ (la) and by tha proces~ accordiny to the inven-~ tion (lb).
1 a) Thz concen~ra~ion of sulphuric acid by evaporation can only be carried out economically if limited tu two stages. The ~aporator plant used is a two-stage forc~d circulation ~acuum ~vaporator plant. ~0% sulphuric acid is fed into 6tage 1 and concantrated tn 42% H2S04 by evaporation at llQCo It flows into ~tage 2 where it i conc~ntrated to 70% H2S04 by evaporation at 80C. The hea~ exchanger of graphite tubes used in ~tage 1 is - h~ated with ~team at 3.6 bar and the heat exchanger of stage 2 is heated with the ~apors from 6tage 1. The vapors from stage 2 are directly condensed with cooling water. The 30% sulphuric acid fed in is prehsat~d from ~5C to 38C by tha 70% sulphuric a~id discharg~d frDm t,h~ plant and the 70% acid i5 thereby cooled to 30C.
1 b) Concentration of the ~ulphuric acid by evaporation i3 carried out in a three stage plant a~ shown in Figure 1, The acid t213 fed into tha horizontal evaporator ~3a) has bean heated to 120C in the heat 0xchan~er t~b) ~y tha ac;d ~22) dircharged from the horizontal ~vaporator ~0 and the acid ~22) i~ at the ~ame time soolad to 80 C.
The 70% sulphuric acicl ~2~ t,hen furthar cooled to 30C by the dil~te acid ~113 which iB thereb~ heated to 45C befora ~eing fed into stage (1). The vapors from evaporator (1~) are rondensed by direct contact with cooling water.
Le A 24 623 ~ 9 ~ 1 32h755 The ~6% sulphuric acid from ~aga 1 is fed in~o S stage 2 and discharged as 46% sulphuri~ acid into the horizon~al evapora~or by way of the hea~ e~changar (~b), When the ~wo processe~ (la) and (lb) are compared (Table 1), the process accordin~ to the inven~ion is found to have the following advantages:
1. The energy consump~ion i5 only 77% in th~ process lb a~cording to ~he invention compared wi~h the known process la. ~hen ~he stQam condensate is usad for the ganeration of 6team i~ is only 67%, 2. Owing to the higher daw point of ~he vapors ~o be condensed ~la: 27C, lb: 31C) and the smaller quanti~y o~ steam, the amount of cooling water re-~- . quired when ths water ~emperature is ~he same is only 42%.
3. The hea~ ex~hanga sur~aca and circulation of acid ara Ie55 in (lb~, thereby par~ly compens~ting for the ini~ial costs of ~he appara~u~ ~or stage ~.
The~e are in any cas~ low owing to the simplici~y of construction and high specific evapor3~ion rate of ~he hori~ontal evaporator u~ed ac~ording to ~he invan~ion, 4. In the conv~ntional procas~ (la~, an evaporation ~omperature of up ~o 110C is raquired in ~he cir-c~lation evaporator ~tage 1~ if tha cond~nsation of vapor~ with ordinary cooling wa~er i3 ~o be c~rried out economically. This eliminates many Le A 24 623 inexpen iva matsrials for the construction of the pipas and eYaporator. In ~he proce ~ accord~ng to the invention, a tamperature of only 85C i8 r~-quired for a comparable acid concentration (~tage 2).
Example 2 6 t/h of 30% Sulphuric acid is to be concentrated by evaporation to 96% H2504 and the organic impurities are to be destroyed by oxida~ion with HN03 at about 330C. The vapor~ ~re to be condensed by indirect cooling. The temperature of the available cooling water i~ ~0C.
2a) Solution of problem ~ccording to the ~tate of the art:
The sulphuric acid i5 concentrated to 70% H250~ by _ evaporation at 100C in a ~ingle sta~e ~orced circula-tion evaporator with a he~t exchanger compo~ed of graphite tu~es. The 30% acid fed into the apparatu~ i8 preheated from ~0C to 46C b~ the 70% acid di6charged from the apparatus. The 70% acid, which is thereby cooled ~o 40C, i~ tran~Serred to the stage of high grade concentration and oxidative purification by the Pauling/Plinke method ~6ee Bodenbrenn~r fft al, DECHEMA-Monogr. 86 ~1980) 1~7). ~efore the ~cid i~ fed into the dephlegmator it is preheated by tho vapor~ from the hi~h ~r~de concen~ratio~. The 96% ~ulphuric acid ~1875 kylh) ~0 di~charg~d from the v~el is indirsctly cool~d to 40C
in a cooler with agitator by mean~ of cool;ny water.
Le A 24 623 The operating parameters for the preliminary concentration and the high ~rade concentration are summarized in Table 2. When the vapors are indirectly cooled in stainless steel heat exchangQ tubes at the 6tage of preliminary concentration, a rise in the temperature of cooling water from 30C to 40C i~ per-mitted.
Multistage evaporation of water for preliminary concentration in apparatus constructed from inexpensive materials is possible only if the vapors are condensed with a cooling medium at a lower temperature or the vapors from the sacond stage undergo preliminary com prassion by steam boosters, 2b) Solution of problem by the process according to the invention: The preliminary concentrstion of sulphuric - acid from 30% H2504 to 80% H~504 is carried out in tWD
~ages in a plant such as that shown in the Figure but in which the circulation evaporator sy~tem is a single stage ~ystem, in contrast to that allustrated~ The 80%
acid discharged from the horizontal evaporator is cooled from 185C to 92C by the 42% acid which i6 to be fed into this e~aporator, and the 42% acid ;~ ther~by heated to 102C. Further cooling to 40~C i~ effocted by means _ of the 30Y acid which i5 thereby heated to 42C.
The comparison shows that the procQss accordin~ to the invention ha~ the following ~dvantage~:
1. The ~nargy saving i~ 30%. ~hen sondsnsate o heating ~team i~ u~ed for the generation of ~team the Raving is 36'X.
Le A ~4 S23 - 12 ~ l 326~55 2. The requiremen~ for cooling wa~er is only 60%.
. The dimensions of the forced circulation evapara~or sys~em are considerably smaller. The opera~ing ~emperature of 65C ins~ead of 100C enables inex-pensive ma~erials to be ~sed for the appara~us, e.g, rubberized containers and pipes.
~ _ Le A 24 623 - 13 - l 326755 o I` o r~ ~o ~ ,` o U~ ~
o O O ~ ~ o u) ~ o I` - o ~
r~ O ~ r o oo O ~r o OD
N U~
C~ D O a~ o ~ ~ .
u~ ~ o .~
_ I~ ~r~ .-- ~ N
_ __ . __ _...__ O O O O O ~ O ~ O
Ln CO ~ f ` O ~ N N ~C) N I` Lr ~) ~11 u, ~r O O O ~ O ~ O ~D O O O ~;r Ll') - o ~r o ~ !1~
, ~ .- ~In ~ ~ I` ~ ~ o ~r O ~ ~ ~rC
Qu~ ~ ~ ~h ~ ~ ~
~ ~ C~ ~ ~ ~ ~ ~ ~ ~ ~ ~ O 1~ _ X ~ E ~ X E~ ii ~ A .Y ~
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~ x ~ u u ~ ~o ~u o a1 a~
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Le A 24 623 . .
-~ - 1 4 - 1 32 67 55 OOOO~DIn o u~ co ~ O a~
o ..
o o CO oo . , ~ ~~ o n ~ ~ o . ~ In o ~ ~ u~ o o I` ~r o u~ ~ ~ ~ ~ o ~ ~
. ~ ~ o , , o o~
o o ~ o ~ ~ ~ o o O ~ ~O O er ~ ~r ~ o o~ ~ ~ ~
~ .
_ _ .
_ .....
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o a~
u~ rrl O ~ ~ ~
I` o ~ ~r oo o o o u~ o o ~ ~u~ ~ o u~ ~r o ~ o o 1~ ~ o o o ,_ o ~ ~
. ~ ~ ~ h ~ ~ ~ ~ S
.Y 3 `1 E ~ X ~ ~ ~ ~ ~ E
dP dP
~: :
:: :
~ h g h o o Ç ~
`~ ~ ~ O c~ 3 h rl q) .
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t~l a~ O ~a hO (1~ X~) ~ tJ~ cn 1 ~
O ,~ a) ~ h ~
R E~ 1~1 rl E~ O rl 0 ~ O al ~ X ~ t~ o 4~ O~rl O
E~
Le A 24 623 -
The~e are in any cas~ low owing to the simplici~y of construction and high specific evapor3~ion rate of ~he hori~ontal evaporator u~ed ac~ording to ~he invan~ion, 4. In the conv~ntional procas~ (la~, an evaporation ~omperature of up ~o 110C is raquired in ~he cir-c~lation evaporator ~tage 1~ if tha cond~nsation of vapor~ with ordinary cooling wa~er i3 ~o be c~rried out economically. This eliminates many Le A 24 623 inexpen iva matsrials for the construction of the pipas and eYaporator. In ~he proce ~ accord~ng to the invention, a tamperature of only 85C i8 r~-quired for a comparable acid concentration (~tage 2).
Example 2 6 t/h of 30% Sulphuric acid is to be concentrated by evaporation to 96% H2504 and the organic impurities are to be destroyed by oxida~ion with HN03 at about 330C. The vapor~ ~re to be condensed by indirect cooling. The temperature of the available cooling water i~ ~0C.
2a) Solution of problem ~ccording to the ~tate of the art:
The sulphuric acid i5 concentrated to 70% H250~ by _ evaporation at 100C in a ~ingle sta~e ~orced circula-tion evaporator with a he~t exchanger compo~ed of graphite tu~es. The 30% acid fed into the apparatu~ i8 preheated from ~0C to 46C b~ the 70% acid di6charged from the apparatus. The 70% acid, which is thereby cooled ~o 40C, i~ tran~Serred to the stage of high grade concentration and oxidative purification by the Pauling/Plinke method ~6ee Bodenbrenn~r fft al, DECHEMA-Monogr. 86 ~1980) 1~7). ~efore the ~cid i~ fed into the dephlegmator it is preheated by tho vapor~ from the hi~h ~r~de concen~ratio~. The 96% ~ulphuric acid ~1875 kylh) ~0 di~charg~d from the v~el is indirsctly cool~d to 40C
in a cooler with agitator by mean~ of cool;ny water.
Le A 24 623 The operating parameters for the preliminary concentration and the high ~rade concentration are summarized in Table 2. When the vapors are indirectly cooled in stainless steel heat exchangQ tubes at the 6tage of preliminary concentration, a rise in the temperature of cooling water from 30C to 40C i~ per-mitted.
Multistage evaporation of water for preliminary concentration in apparatus constructed from inexpensive materials is possible only if the vapors are condensed with a cooling medium at a lower temperature or the vapors from the sacond stage undergo preliminary com prassion by steam boosters, 2b) Solution of problem by the process according to the invention: The preliminary concentrstion of sulphuric - acid from 30% H2504 to 80% H~504 is carried out in tWD
~ages in a plant such as that shown in the Figure but in which the circulation evaporator sy~tem is a single stage ~ystem, in contrast to that allustrated~ The 80%
acid discharged from the horizontal evaporator is cooled from 185C to 92C by the 42% acid which i6 to be fed into this e~aporator, and the 42% acid ;~ ther~by heated to 102C. Further cooling to 40~C i~ effocted by means _ of the 30Y acid which i5 thereby heated to 42C.
The comparison shows that the procQss accordin~ to the invention ha~ the following ~dvantage~:
1. The ~nargy saving i~ 30%. ~hen sondsnsate o heating ~team i~ u~ed for the generation of ~team the Raving is 36'X.
Le A ~4 S23 - 12 ~ l 326~55 2. The requiremen~ for cooling wa~er is only 60%.
. The dimensions of the forced circulation evapara~or sys~em are considerably smaller. The opera~ing ~emperature of 65C ins~ead of 100C enables inex-pensive ma~erials to be ~sed for the appara~us, e.g, rubberized containers and pipes.
~ _ Le A 24 623 - 13 - l 326755 o I` o r~ ~o ~ ,` o U~ ~
o O O ~ ~ o u) ~ o I` - o ~
r~ O ~ r o oo O ~r o OD
N U~
C~ D O a~ o ~ ~ .
u~ ~ o .~
_ I~ ~r~ .-- ~ N
_ __ . __ _...__ O O O O O ~ O ~ O
Ln CO ~ f ` O ~ N N ~C) N I` Lr ~) ~11 u, ~r O O O ~ O ~ O ~D O O O ~;r Ll') - o ~r o ~ !1~
, ~ .- ~In ~ ~ I` ~ ~ o ~r O ~ ~ ~rC
Qu~ ~ ~ ~h ~ ~ ~
~ ~ C~ ~ ~ ~ ~ ~ ~ ~ ~ ~ O 1~ _ X ~ E ~ X E~ ii ~ A .Y ~
~r O
U~
_.
0~
U~ ) C
~ o a ~ ~ O ~ O
d~ O
tJ1 ~ ~ ~
~ ~ ~ ~ O ~ ..
~ ~ cn ~ c t~
O ~ 3 0 O ~ ~ 3 u~ u~
Ul ~- aJ 0 a) ~ 0 h 0 0 X ~ tJ~ t5' _~ ~ 4 G~ Q. O O u~
_1 E~i ~~ ~ Q, m ~1 ~ t~ Q5 ~1 ~ ~) Q ~ la ~ O la ~ O to 11;
~ x ~ u u ~ ~o ~u o a1 a~
E~ ~ ~ ~ ~ O C~
Le A 24 623 . .
-~ - 1 4 - 1 32 67 55 OOOO~DIn o u~ co ~ O a~
o ..
o o CO oo . , ~ ~~ o n ~ ~ o . ~ In o ~ ~ u~ o o I` ~r o u~ ~ ~ ~ ~ o ~ ~
. ~ ~ o , , o o~
o o ~ o ~ ~ ~ o o O ~ ~O O er ~ ~r ~ o o~ ~ ~ ~
~ .
_ _ .
_ .....
O O O ~9 0 0 el~
o a~
u~ rrl O ~ ~ ~
I` o ~ ~r oo o o o u~ o o ~ ~u~ ~ o u~ ~r o ~ o o 1~ ~ o o o ,_ o ~ ~
. ~ ~ ~ h ~ ~ ~ ~ S
.Y 3 `1 E ~ X ~ ~ ~ ~ ~ E
dP dP
~: :
:: :
~ h g h o o Ç ~
`~ ~ ~ O c~ 3 h rl q) .
~ N r1 .,~
~ t~ O ~C ~ 0 U~ ~ ~ ~ O
t~l a~ O ~a hO (1~ X~) ~ tJ~ cn 1 ~
O ,~ a) ~ h ~
R E~ 1~1 rl E~ O rl 0 ~ O al ~ X ~ t~ o 4~ O~rl O
E~
Le A 24 623 -
Claims (5)
1. A process for increasing the concentration of sulphuric acid to about 80% H2SO4 by multistage evaporation, wherein the evaporation to concentrations of 40 to 65% H2SO4 is carried out in one or more stages at reduced pressure and temperatures of not more than 120°C in circulation or falling film evaporators with graphite or Teflon heat exchangers, and one evaporator stage is heated by the vapors from a subsequent horizontal evaporator having a heat exchanger in the form of a bundle of tantalum tubes in which the sulphuric acid is evaporated to concentrations of 66 to 80% H2SO4 by evaporation at a slightly reduced pressure, normal pressure or excess pressure.
2. A process according to claim 1, wherein concentration of the sulphuric acid by evaporation in the horizontal evaporator is carried out under such conditions that the 65 - 80% sulphuric acid is discharged at temperatures of 160 to 195°C.
3. A process according to claim 1, wherein the horizontal evaporator is heated with heating steam at 8 - 20 bar and the steam released as a result of the release of pressure of the condensate of heating steam is introduced into the steam chamber of a heat exchanger of the circulation or falling film evaporator.
4. A process according to claim 1, wherein inserts are placed in the horizontal evaporator at right angles to the bundle of tubes of the heat exchanger.
5. A process according to claim 1, wherein the 40 - 65%
sulphuric acid fed into the horizontal evaporator is heated to a temperature in the region of its boiling point at the given evaporation pressure by the 65 - 80% sulphuric acid discharged from the horizontal evaporator.
sulphuric acid fed into the horizontal evaporator is heated to a temperature in the region of its boiling point at the given evaporation pressure by the 65 - 80% sulphuric acid discharged from the horizontal evaporator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863632623 DE3632623A1 (en) | 1986-09-25 | 1986-09-25 | METHOD FOR CONCENTRATING SULFURIC ACID |
| DEP3632623.2 | 1986-09-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1326755C true CA1326755C (en) | 1994-02-08 |
Family
ID=6310346
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000547576A Expired - Fee Related CA1326755C (en) | 1986-09-25 | 1987-09-23 | Process for concentrating sulphuric acid |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0262510B1 (en) |
| JP (1) | JPS6389410A (en) |
| CA (1) | CA1326755C (en) |
| DE (2) | DE3632623A1 (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3935892C2 (en) * | 1989-10-27 | 1994-08-25 | Metallgesellschaft Ag | Method and device for concentrating a liquid containing sulfuric acid and water |
| DE3938915C1 (en) * | 1989-11-24 | 1991-05-08 | Bayer Ag, 5090 Leverkusen, De | |
| DE4029737C1 (en) * | 1990-09-20 | 1991-12-05 | Metallgesellschaft Ag, 6000 Frankfurt, De | |
| DE4114334A1 (en) * | 1991-05-02 | 1992-11-05 | Buss Ag | THICK FILM EVAPORATOR MADE OF CORROSION-RESISTANT MATERIAL |
| DE19741511A1 (en) * | 1997-09-20 | 1999-04-01 | Metallgesellschaft Ag | Process for concentrating thin acid by utilizing process heat in a forced circulation evaporator system |
| DE19963509A1 (en) * | 1999-12-28 | 2001-07-05 | Merck Patent Gmbh | Process for the production of high-purity sulfuric acid |
| WO2008003297A2 (en) * | 2006-07-03 | 2008-01-10 | Lailach Guenter | Method and system for concentrating metal sulfate-containing sulfuric acid |
| CN101935077B (en) * | 2010-08-27 | 2012-06-20 | 南通京通石墨设备有限公司 | Waste acid concentration multistage treatment method |
| JP6001328B2 (en) * | 2012-05-23 | 2016-10-05 | パンパシフィック・カッパー株式会社 | Sulfuric acid acidic liquid concentration apparatus, sulfuric acid acidic liquid concentration method, and crude nickel sulfate recovery method |
| CN106477531B (en) * | 2016-12-01 | 2018-08-21 | 上海佳麟泵阀有限公司 | Prevent from generating the Waste Sulfuric Acid concentrating recovery device of electrochemical corrosion when operation |
| US20230117014A1 (en) * | 2020-03-16 | 2023-04-20 | Dupont Safety & Construction, Inc. | Concentration of sulfuric acid |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3015957A1 (en) * | 1980-04-25 | 1981-11-05 | Hoechst Ag, 6000 Frankfurt | Two stage concn. and purificn. of sulphuric acid contg. organic cpds. - by vacuum evapn. and nitric acid treatment in heat exchangers of optimum material |
| DE3409717C2 (en) * | 1984-03-16 | 1994-03-31 | Bayer Ag | Process for the preparation of nitrobenzene |
-
1986
- 1986-09-25 DE DE19863632623 patent/DE3632623A1/en not_active Withdrawn
-
1987
- 1987-09-16 DE DE8787113514T patent/DE3774821D1/en not_active Expired - Lifetime
- 1987-09-16 EP EP19870113514 patent/EP0262510B1/en not_active Expired - Lifetime
- 1987-09-23 CA CA000547576A patent/CA1326755C/en not_active Expired - Fee Related
- 1987-09-25 JP JP23907287A patent/JPS6389410A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0262510B1 (en) | 1991-11-27 |
| DE3632623A1 (en) | 1988-03-31 |
| DE3774821D1 (en) | 1992-01-09 |
| EP0262510A3 (en) | 1988-10-19 |
| EP0262510A2 (en) | 1988-04-06 |
| JPH0476326B2 (en) | 1992-12-03 |
| JPS6389410A (en) | 1988-04-20 |
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