CA1244228A - Process and apparatus for the concentration and purification of sulfuric acid which contains organic impurities - Google Patents
Process and apparatus for the concentration and purification of sulfuric acid which contains organic impuritiesInfo
- Publication number
- CA1244228A CA1244228A CA000447056A CA447056A CA1244228A CA 1244228 A CA1244228 A CA 1244228A CA 000447056 A CA000447056 A CA 000447056A CA 447056 A CA447056 A CA 447056A CA 1244228 A CA1244228 A CA 1244228A
- Authority
- CA
- Canada
- Prior art keywords
- acid
- zone
- conduit
- sulfuric acid
- vapor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- 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
- C01B17/90—Separation; Purification
- C01B17/905—Removal of organic impurities
-
- 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
- C01B17/90—Separation; Purification
Abstract
ABSTRACT OF THE DISCLOSURE
Diluted and contaminated sulfuric acid is subjected to an evaporation process. In a container, concentrate and vapors are separated from each other. The acid to be processed is introduced, if desired after the addition of an oxidant, at a relatively large distance from the point of separation of concentrate and vapors into a circulation conduit leading away from the concentrate zone of the container, this conduit returning via a heat exchanger into the vapor zone of the container.
Concentrated and purified sulfuric acid is removed from the concentrate zone of this apparatus, and a portion of this sulfuric acid is utilized, after being diluted with water, for the rectification of the vapors in a countercurrent mode, and then recycled into the container. The process is suitable for concentration and, if desired, for its purification of sulfuric acids having contaminations which could lead, in the conventional processes, to decompositions, froth formation, and/or solid deposits.
Diluted and contaminated sulfuric acid is subjected to an evaporation process. In a container, concentrate and vapors are separated from each other. The acid to be processed is introduced, if desired after the addition of an oxidant, at a relatively large distance from the point of separation of concentrate and vapors into a circulation conduit leading away from the concentrate zone of the container, this conduit returning via a heat exchanger into the vapor zone of the container.
Concentrated and purified sulfuric acid is removed from the concentrate zone of this apparatus, and a portion of this sulfuric acid is utilized, after being diluted with water, for the rectification of the vapors in a countercurrent mode, and then recycled into the container. The process is suitable for concentration and, if desired, for its purification of sulfuric acids having contaminations which could lead, in the conventional processes, to decompositions, froth formation, and/or solid deposits.
Description
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The present invention relates to a process and apparatus for the concentration and purification of sulfuric acid which contains organic impurities.
In many processing operations in organic chemistry, dilute sulfuric acid is obtained in more or less large amounts, and in most cases containing organic impurities.
The possibility of releasing such waste acids into the environment has become increasingly restric-tive. Therefore, it has become important to recon centrate these acids and~ if neceesary, purify them so that they can be reused in another process or in the same process.
In general, readil~ volatile organic compounds will be removed durins concentration together wîth the vapors/ whereas high-boiling organic impurities (for example aromatics) must be removed by oxidation at higher ~emperatures frequently with the addition of an oxidant ~
Quite a number of processes has become known ~or solving thls problem. In accordance with the long-known Pauling process~ the waste acid is concentrated ,.;~. ~3 .. . ~ ,~
in a directly heated castiron boiler equipped with a rectifying column~ and puriEied, insofar as possible, to remove high- and low-boiling compounds. In more recent processes, the thin, contaminated sulfur.ic acid is first preconcentrated to about 70%, frequently in multistage evaporation installations, then further concentrated in the range of 70-98% H2SO~ under vacuum, during which step readily volatile organic compounds are removed with the vapors, and subsequently freed of high boiling organic compounds in a separate apparatus at higher temperatures and often with the addition of an oxidizing agent (see DAS 2,242,055 D2 ~Thoma); DOS
The present invention relates to a process and apparatus for the concentration and purification of sulfuric acid which contains organic impurities.
In many processing operations in organic chemistry, dilute sulfuric acid is obtained in more or less large amounts, and in most cases containing organic impurities.
The possibility of releasing such waste acids into the environment has become increasingly restric-tive. Therefore, it has become important to recon centrate these acids and~ if neceesary, purify them so that they can be reused in another process or in the same process.
In general, readil~ volatile organic compounds will be removed durins concentration together wîth the vapors/ whereas high-boiling organic impurities (for example aromatics) must be removed by oxidation at higher ~emperatures frequently with the addition of an oxidant ~
Quite a number of processes has become known ~or solving thls problem. In accordance with the long-known Pauling process~ the waste acid is concentrated ,.;~. ~3 .. . ~ ,~
in a directly heated castiron boiler equipped with a rectifying column~ and puriEied, insofar as possible, to remove high- and low-boiling compounds. In more recent processes, the thin, contaminated sulfur.ic acid is first preconcentrated to about 70%, frequently in multistage evaporation installations, then further concentrated in the range of 70-98% H2SO~ under vacuum, during which step readily volatile organic compounds are removed with the vapors, and subsequently freed of high boiling organic compounds in a separate apparatus at higher temperatures and often with the addition of an oxidizing agent (see DAS 2,242,055 D2 ~Thoma); DOS
2,909,029 Al (Schott).
According to these modern processes, natural or forced circulation evaporators, for example according to Fig. 1 of European Application 80 103 186 (Publica-tion No. 0 021 210) are preferably utilized for concen-tration in the stage of 7~-98% H2SO4~ Independently of the type of structure in detail, such evaporation devices must be equipped with a rectifying column, the . .
acid to be concentrated being fed into the upper .
section of the rectifying column. The acid thereby acts as a reflux liquid. This reflux acid, always resupposes that the thin acid has a ~oncentra-.
tion of about 70~, but not more than 75%, flows countercurrently to the rising steam/acid mixture, is heated up, and is concentrated while absorbing the acid proportion from the vapors. This proceclure i5 not dependent on the type of evaporator, i.e. the latter can be a forced circulation, natural circulation, or also an ordinary boiler evaporator.
There are indeed acids, Eor example those con-taminated with aliphatic compounds or even with solid carbon particles, which cannot be processed by means of the above methods since they can lead, during concen-tration and puri~ication, to extensive froth formation and/or the separation of solid, coke-like deposits.
During an attempt to concentrate and puriy such acids in devices of the type described above, ~rothing is frequently observed as early as the zone oF the rectifying column, but also in the vaporization chamber. Accordingly such an operation becomes impossible. Furthermore, there is often a pronounced sedimentation of fine, coke-like particles leading to deposits and clogging in the apparatus. Also, a violent oxidation reaction of the organic impurities in the acid with the sulfuric acid itself is frequently observed, connected with a corresponding loss in acid under strong SO2 formation.
rrhe addition of an oxidant to the contaminated acid does not result in any substantial improve~enk since the oxidi~ing agents can be eliminated with the vapors in the rectifying column before they become effective, i.e. before they are able to react with the organic contaminants in the acid.
Similar behavior has also been found, for example, in waste acids from isobutanol production.
Although these acids can be reconcentrated within the desired range and recycled into the process, there is observed an increase in finely divided, soot-like carbon particles which are deposited in the entire cycle so that the entire acid charge must be replaced in relatively brief intervals. This is not only connected with great expense, but also entails environmental protection problems insofar as these acids are not treated by the expensive methods of thermal cracking and regeneration of fresh sulfuric acid.
The present invention has the purpose of pro viding a process as w~ll as an apparatus which makes it possible to concentrate and, if desired, purify prac-tically any preconcentrated sulfuric acid containing a greaier or lesser amount of organic impurities, without incurring, to an intolerable extent, frothing, loss of SO3, or carbon precipitation in a solid form.
~2~ 2~
~ or this purpose, the process of the present invention wherein the .sulfuric acid to be treated is continuously fed to an evaporation process while supplying heat, and is brought to a higher concentration with continuous vapor separationr is characteri~ed in that the sulfuric acid to be treated is introduced into the liquid phase of the acid being subjected to the evaporation process, at a distance from the vapor separation point corresponding to the necessary heat-up route.
This procedure achieves the result that the reactions of the impurities with the liquid phase o~
the acid, taking place during heating of the liquid phase to the evaporation temperature, proceed in a relatively slow fashion and cannot lead to froth formation as frequently occurs in the usual addition of certain acids to be processed into a gaseous phase, i.e. in a rectifying zone for the vapors. However, the vapors that are withdrawn are suitably rec~ified since, especially during concentration of the acid to 70~ or thereabove, it is possible at the temperatures necessary therefor for the vapors to contain a more or less large amount of ~2SO~ and, at higher concen-trations, also S03, and thus to incur an undesired loss of acid. This rectifying process is suitably effected by rectifying the vapors countercurrently with ~ i 4~Z~
water or with dilute, already concentrated acid, which latter is recycled into the evaporation proces~.
It is to be noted that during heating of the acid to be treatecl, certain impurities react directly with the acid even before reaching the evaporation tempera-ture, the gaseous reaction products being discharged with the vapors. This purifyiny effect, occurring in the concentration of sulfuric acid, is, however, fre~
quently inadequate especially if undesired solid carbon particles are contained in the concentrate or are precipitated therefrom. In order to remove such impurities, and other impurities remaining in the con-centrate, a suitable oxidant, e.g. nitric acid or hydrogen peroxide, can be added to the acid to be treated beore it is introduced into the evaporation process. Thus, the oxidant has available sufficient time for effectiveness and close contact with the impurities in order to react with the impurities by the time the vapors are separated from the concentrated liquid phase, so that such impurities can be withdrawn with the vapors in the form of gaseous compounds, inter alia also CO and CO2.
The apparatus for performing the process of the present invention, likewise representing the subject of the present invention, comprises at least one evaporation chamber with a lower concentrate zone and a ~2~
vapor zone located thereabove and conn~cted to a vapor discharge conduit, the feed condult for the acid to be treated being connected to the concentrate zone at a distance from the separating plane of the two zones which is larger than the spacing of the connection point oE the concentrate discharge conduit to the concentrate zone.
It may be advantageous to effect concentration of the acid by the circulation method~ In this case, the concentrate zone of the evaporation chamber can be connected ko the vapor zone by a circulation conduit emanating from the concentrate zone via a heat exchanger. The feed conduit for the acid to be processed terminates lnto the circulation conduit~
which conducts concentrated acid, advantageously by means of a pump, from the concentrate zone via the heat exchanger to the vapor zone, at an adequate spacing from the termination of the circulation conduit into the vapor zone~ acting as a phase separating point.
However, it can be also be advantageous to introduce the acid to ~e treated at a sufficient spacing below the acid level of a container forming the evaporation chamber, this level acting as a parting plane between the liquid phase and the vapors, in this connection, agitator elements can be provided ensuring a per~ect ~. ~
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mixing oE the already concentrated acid with the introduced acicl. In order to achieve recycling of H2SO~ and SO3 entrained by the vapors, a rectiying column can be arranged in the vapor outlet of the vapor zone which is fed with rediluted concen-trate acid or water countercurrently to the vapors. By means of these devices, it is also possible to perfectly concentrate and, if desired, purify waste sulfuric acids and/or sulfuric acids diluted and con-taminated in some other way.
The invention will now be described in greater detail below by way of example with reference to the accompanying drawings, wherein Fig~ 1 shows an example of a concentrating and purifying device operating according to a circulation method and Fig. 2 shows an example of a concentrating and purifyiny device operating according to a continuous method.
The circulation evaporator installation shown in Fig. 1 for the concentration of contaminated suluric acid comprises an evaporator vessel 1~ the interiox o~
which is subdivided ~y the liquid vessel lc of the sulfuric acid contained therein into a lower concentrate zone la and an uppex v~por zone lb. By way of a pump 2 and a heat exchanger 3, a circulation conduit 4 extends From the bottom of the vessel 1 to the vapor ~one lb of the vessel. A feed conduit 5 ~or the sulfuric acid to be p~ocessed, i.e. to be concentrated and purified, terminates in the ciecula tion conduit 4 upstream of the pump 2 and approximately at the lowest point in the circulation conduit 4 and thus at a relatively large distance from the termina-tion of the circulation conduit 4 in the vapor æone lb.
Furthermore, an inlet conduit 6 for an oxidant ls connected to the feed conduit 50 The mixing of the acid to be treated with the oxidant takes place preferably by means of a static mixer. The feed conduit 5 can also terminate in the circulation conduit 4 downstrea~l of the pump 2 as seen in the flow direction. Above the vessel 1, a rectifying column 7 in communication with the vapor zone lb is located, the vapor discharge conduit of this column being denoted as element 8. A discharge conduit 9 for the concentrated, purified acid is connected to the vessel 1 below the liquid level lc of this vessel. From the discharge conduit 9, a reflux conduit 10, into which terminates a water feed line 11, leads into the vapor discharge zone of the rectifying column 7.
At the be~innin~ of the concentration and purifi-cation process ~o be conducted with this apparatus, the . . .
~'~4~Z~3 concentrate zone la oE the ve~sel 1 is filled with already concentraked or pure sulfuric acid, preheated to operating temperature, which acid, however, at an~
case no longer reacts in the manner described above.
If now, during operation of the apparatus, sulfuric acid to be processed is continuously introduced via the feed conduit 5 into the concentrated acid conveyed from the concentrate zone la by pump ~ through the circula-tion conduit 4, then there is not only an intimate mixing of the two acid proportions, but heating of this mixture also takes place in the heat exchanger 3 so that upon entrance into the vapor ~one lb of the vessel 1, the vapors separated in vapor from during this circulation are separated at this location from the liquid phase which now is of a higher concentration and drops into the concentrate zone la. The acid vapors escape in the upward direction through the rectifying column 7. Depending on the degree of concentration of the acid fed via conduit 5 and on ~he acid temperature 2~ obtained in the circulation conduit 4, a specific acid concentration will arise in the concentrate zone la.
Even if acid of a lower concentration, of for example merely 50~, is introduced, an acid can be discharged which is far above 70% from conduit 9r with suffi-ciently long circulation.
~ 2 ~ ~
It has been found that certain contaminants are capable oE reacting with the acid proper due to heating and close contact with the acid in the circulation conduit 4 and, in certain cases, even in the concen-trate zone la, thus forming not only S02 but also other compounds produced by oxidation, which are withdrawn in the gaseous phase with the vapors. This leads, in any event, to a certain purification of the concentrated acid. ~owever, if a higher degree of purity is desired, or reactions of the impurities with the acid under formation of S02 and precipitation of solid deposits are to be avoided, then a suitable oxidant is introduced into the supplied acid by way of conduit SO
Since the distance o the feed point of the oxidant-treated acid from the point of introduction of the heated acid into the vapor zone lb is relatively large, here again the oxidant, increasingly heated up together with the reaction mixture, has adequate kime for reacting increasingly and effectively with the 20 oxidiza~le impurities. Consequently, the reaction products converted into the gaseous phase can be discharged with the vapors. Tn this way it is possible to avoid abruptly occurring reactions, deposits, and undue froth formation. The vapors are rectified in this case, since, at a corresponding temperature, the ,~ .
.
vapors contain H2S04 and S03, with the acid concentration beiny mostly abova 70%, which leads to undesirable losses of acid and/or environmental pol-lutionO This is done in countercurrent mode by already purified concentrate acid, diluted with water to suit-ably less than 70~, this acid being supplied via the reflux conduit 10 of the rectifying column 7. In spite of a relatively high temperature, this rectifying medium, thanks to its relative purity, cannot cause any reactions resulting in deposits and/or frothing in the rectifying column or in the vapor zone lb of the vessel 1, as would be the case with the use of sulfuric acid, to be concentrated and having certain impurities, a~
the rectifying agent.
An apparatus operating according to tha con~
tinuous method o~ the present invention is illustrated in Fig. 2. This apparatus comprises, as the evaporation chamber, a heatable vessel 21 subdivided analogously to the example described in Fig. 1 illtO a concentrate zone 21a and into a vapor zone 21b by the liquid level 21c of the sulfuric acid con~ained therein (which is concentrated at the beginning of the operation). A feed conduit 25 for the sulfuric acid to be treated is introduced into the vessel 21 and terminates, with its end section fashioned as a dip :
.
pipe extendiny ;.n the proximity oE the bottom of vessel 21 and accordingly at a relatively larye distance below the liquid level 21c. Outside of vessel 21, a supply conduit 26 for the introduction of an oxidizing agent is connected to the feed conduit 25. The vapor zone 21b of the vessel 21 is in commun.ication with a rectifying column 27, the vapor discharge conduit of which is denoted by element 28. Directly below the liquid level 21c, a discharge conduit 29 for the con-centrated acid is connected to the vessel 21. A refluxconduit 30 leads from the discharge conduit 29 to the rectifying column; the reflex conduit is provided with a water connection 31. In order to ensure also in this apparatus, operating by a continuous method, a flawless mixing of the supplied sulfuric acid to be processed with the already concentrated acid, a motor-drivable agitator 32 is arranged in the bottom portion of the concentrate zone 21a. This ensures also in this case that reactions, occurring due to impurities in t~e supplied acid with the latter and/or with any supplied oxidant during the heating process, can proceed effectively and in a controlled fashion whereby no undesired reactions can occur in the rectifying column 27 and/or in the vapor zone 21b due to a lack o~
introduced impurities.
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Consequently, it is possible by means of the dis-closed process to concentrate even dilute sulfuric acld into a relatively pure produet acid by evaporation whereas contaminants heretofore presenk did not readily permit such a processing operation. Thus it is possible to concentrate and purify, by means oE one and the same apparatus, sulfuric acids loaded with a great variety of organic impurities~
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims~
. .
According to these modern processes, natural or forced circulation evaporators, for example according to Fig. 1 of European Application 80 103 186 (Publica-tion No. 0 021 210) are preferably utilized for concen-tration in the stage of 7~-98% H2SO4~ Independently of the type of structure in detail, such evaporation devices must be equipped with a rectifying column, the . .
acid to be concentrated being fed into the upper .
section of the rectifying column. The acid thereby acts as a reflux liquid. This reflux acid, always resupposes that the thin acid has a ~oncentra-.
tion of about 70~, but not more than 75%, flows countercurrently to the rising steam/acid mixture, is heated up, and is concentrated while absorbing the acid proportion from the vapors. This proceclure i5 not dependent on the type of evaporator, i.e. the latter can be a forced circulation, natural circulation, or also an ordinary boiler evaporator.
There are indeed acids, Eor example those con-taminated with aliphatic compounds or even with solid carbon particles, which cannot be processed by means of the above methods since they can lead, during concen-tration and puri~ication, to extensive froth formation and/or the separation of solid, coke-like deposits.
During an attempt to concentrate and puriy such acids in devices of the type described above, ~rothing is frequently observed as early as the zone oF the rectifying column, but also in the vaporization chamber. Accordingly such an operation becomes impossible. Furthermore, there is often a pronounced sedimentation of fine, coke-like particles leading to deposits and clogging in the apparatus. Also, a violent oxidation reaction of the organic impurities in the acid with the sulfuric acid itself is frequently observed, connected with a corresponding loss in acid under strong SO2 formation.
rrhe addition of an oxidant to the contaminated acid does not result in any substantial improve~enk since the oxidi~ing agents can be eliminated with the vapors in the rectifying column before they become effective, i.e. before they are able to react with the organic contaminants in the acid.
Similar behavior has also been found, for example, in waste acids from isobutanol production.
Although these acids can be reconcentrated within the desired range and recycled into the process, there is observed an increase in finely divided, soot-like carbon particles which are deposited in the entire cycle so that the entire acid charge must be replaced in relatively brief intervals. This is not only connected with great expense, but also entails environmental protection problems insofar as these acids are not treated by the expensive methods of thermal cracking and regeneration of fresh sulfuric acid.
The present invention has the purpose of pro viding a process as w~ll as an apparatus which makes it possible to concentrate and, if desired, purify prac-tically any preconcentrated sulfuric acid containing a greaier or lesser amount of organic impurities, without incurring, to an intolerable extent, frothing, loss of SO3, or carbon precipitation in a solid form.
~2~ 2~
~ or this purpose, the process of the present invention wherein the .sulfuric acid to be treated is continuously fed to an evaporation process while supplying heat, and is brought to a higher concentration with continuous vapor separationr is characteri~ed in that the sulfuric acid to be treated is introduced into the liquid phase of the acid being subjected to the evaporation process, at a distance from the vapor separation point corresponding to the necessary heat-up route.
This procedure achieves the result that the reactions of the impurities with the liquid phase o~
the acid, taking place during heating of the liquid phase to the evaporation temperature, proceed in a relatively slow fashion and cannot lead to froth formation as frequently occurs in the usual addition of certain acids to be processed into a gaseous phase, i.e. in a rectifying zone for the vapors. However, the vapors that are withdrawn are suitably rec~ified since, especially during concentration of the acid to 70~ or thereabove, it is possible at the temperatures necessary therefor for the vapors to contain a more or less large amount of ~2SO~ and, at higher concen-trations, also S03, and thus to incur an undesired loss of acid. This rectifying process is suitably effected by rectifying the vapors countercurrently with ~ i 4~Z~
water or with dilute, already concentrated acid, which latter is recycled into the evaporation proces~.
It is to be noted that during heating of the acid to be treatecl, certain impurities react directly with the acid even before reaching the evaporation tempera-ture, the gaseous reaction products being discharged with the vapors. This purifyiny effect, occurring in the concentration of sulfuric acid, is, however, fre~
quently inadequate especially if undesired solid carbon particles are contained in the concentrate or are precipitated therefrom. In order to remove such impurities, and other impurities remaining in the con-centrate, a suitable oxidant, e.g. nitric acid or hydrogen peroxide, can be added to the acid to be treated beore it is introduced into the evaporation process. Thus, the oxidant has available sufficient time for effectiveness and close contact with the impurities in order to react with the impurities by the time the vapors are separated from the concentrated liquid phase, so that such impurities can be withdrawn with the vapors in the form of gaseous compounds, inter alia also CO and CO2.
The apparatus for performing the process of the present invention, likewise representing the subject of the present invention, comprises at least one evaporation chamber with a lower concentrate zone and a ~2~
vapor zone located thereabove and conn~cted to a vapor discharge conduit, the feed condult for the acid to be treated being connected to the concentrate zone at a distance from the separating plane of the two zones which is larger than the spacing of the connection point oE the concentrate discharge conduit to the concentrate zone.
It may be advantageous to effect concentration of the acid by the circulation method~ In this case, the concentrate zone of the evaporation chamber can be connected ko the vapor zone by a circulation conduit emanating from the concentrate zone via a heat exchanger. The feed conduit for the acid to be processed terminates lnto the circulation conduit~
which conducts concentrated acid, advantageously by means of a pump, from the concentrate zone via the heat exchanger to the vapor zone, at an adequate spacing from the termination of the circulation conduit into the vapor zone~ acting as a phase separating point.
However, it can be also be advantageous to introduce the acid to ~e treated at a sufficient spacing below the acid level of a container forming the evaporation chamber, this level acting as a parting plane between the liquid phase and the vapors, in this connection, agitator elements can be provided ensuring a per~ect ~. ~
z~
mixing oE the already concentrated acid with the introduced acicl. In order to achieve recycling of H2SO~ and SO3 entrained by the vapors, a rectiying column can be arranged in the vapor outlet of the vapor zone which is fed with rediluted concen-trate acid or water countercurrently to the vapors. By means of these devices, it is also possible to perfectly concentrate and, if desired, purify waste sulfuric acids and/or sulfuric acids diluted and con-taminated in some other way.
The invention will now be described in greater detail below by way of example with reference to the accompanying drawings, wherein Fig~ 1 shows an example of a concentrating and purifying device operating according to a circulation method and Fig. 2 shows an example of a concentrating and purifyiny device operating according to a continuous method.
The circulation evaporator installation shown in Fig. 1 for the concentration of contaminated suluric acid comprises an evaporator vessel 1~ the interiox o~
which is subdivided ~y the liquid vessel lc of the sulfuric acid contained therein into a lower concentrate zone la and an uppex v~por zone lb. By way of a pump 2 and a heat exchanger 3, a circulation conduit 4 extends From the bottom of the vessel 1 to the vapor ~one lb of the vessel. A feed conduit 5 ~or the sulfuric acid to be p~ocessed, i.e. to be concentrated and purified, terminates in the ciecula tion conduit 4 upstream of the pump 2 and approximately at the lowest point in the circulation conduit 4 and thus at a relatively large distance from the termina-tion of the circulation conduit 4 in the vapor æone lb.
Furthermore, an inlet conduit 6 for an oxidant ls connected to the feed conduit 50 The mixing of the acid to be treated with the oxidant takes place preferably by means of a static mixer. The feed conduit 5 can also terminate in the circulation conduit 4 downstrea~l of the pump 2 as seen in the flow direction. Above the vessel 1, a rectifying column 7 in communication with the vapor zone lb is located, the vapor discharge conduit of this column being denoted as element 8. A discharge conduit 9 for the concentrated, purified acid is connected to the vessel 1 below the liquid level lc of this vessel. From the discharge conduit 9, a reflux conduit 10, into which terminates a water feed line 11, leads into the vapor discharge zone of the rectifying column 7.
At the be~innin~ of the concentration and purifi-cation process ~o be conducted with this apparatus, the . . .
~'~4~Z~3 concentrate zone la oE the ve~sel 1 is filled with already concentraked or pure sulfuric acid, preheated to operating temperature, which acid, however, at an~
case no longer reacts in the manner described above.
If now, during operation of the apparatus, sulfuric acid to be processed is continuously introduced via the feed conduit 5 into the concentrated acid conveyed from the concentrate zone la by pump ~ through the circula-tion conduit 4, then there is not only an intimate mixing of the two acid proportions, but heating of this mixture also takes place in the heat exchanger 3 so that upon entrance into the vapor ~one lb of the vessel 1, the vapors separated in vapor from during this circulation are separated at this location from the liquid phase which now is of a higher concentration and drops into the concentrate zone la. The acid vapors escape in the upward direction through the rectifying column 7. Depending on the degree of concentration of the acid fed via conduit 5 and on ~he acid temperature 2~ obtained in the circulation conduit 4, a specific acid concentration will arise in the concentrate zone la.
Even if acid of a lower concentration, of for example merely 50~, is introduced, an acid can be discharged which is far above 70% from conduit 9r with suffi-ciently long circulation.
~ 2 ~ ~
It has been found that certain contaminants are capable oE reacting with the acid proper due to heating and close contact with the acid in the circulation conduit 4 and, in certain cases, even in the concen-trate zone la, thus forming not only S02 but also other compounds produced by oxidation, which are withdrawn in the gaseous phase with the vapors. This leads, in any event, to a certain purification of the concentrated acid. ~owever, if a higher degree of purity is desired, or reactions of the impurities with the acid under formation of S02 and precipitation of solid deposits are to be avoided, then a suitable oxidant is introduced into the supplied acid by way of conduit SO
Since the distance o the feed point of the oxidant-treated acid from the point of introduction of the heated acid into the vapor zone lb is relatively large, here again the oxidant, increasingly heated up together with the reaction mixture, has adequate kime for reacting increasingly and effectively with the 20 oxidiza~le impurities. Consequently, the reaction products converted into the gaseous phase can be discharged with the vapors. Tn this way it is possible to avoid abruptly occurring reactions, deposits, and undue froth formation. The vapors are rectified in this case, since, at a corresponding temperature, the ,~ .
.
vapors contain H2S04 and S03, with the acid concentration beiny mostly abova 70%, which leads to undesirable losses of acid and/or environmental pol-lutionO This is done in countercurrent mode by already purified concentrate acid, diluted with water to suit-ably less than 70~, this acid being supplied via the reflux conduit 10 of the rectifying column 7. In spite of a relatively high temperature, this rectifying medium, thanks to its relative purity, cannot cause any reactions resulting in deposits and/or frothing in the rectifying column or in the vapor zone lb of the vessel 1, as would be the case with the use of sulfuric acid, to be concentrated and having certain impurities, a~
the rectifying agent.
An apparatus operating according to tha con~
tinuous method o~ the present invention is illustrated in Fig. 2. This apparatus comprises, as the evaporation chamber, a heatable vessel 21 subdivided analogously to the example described in Fig. 1 illtO a concentrate zone 21a and into a vapor zone 21b by the liquid level 21c of the sulfuric acid con~ained therein (which is concentrated at the beginning of the operation). A feed conduit 25 for the sulfuric acid to be treated is introduced into the vessel 21 and terminates, with its end section fashioned as a dip :
.
pipe extendiny ;.n the proximity oE the bottom of vessel 21 and accordingly at a relatively larye distance below the liquid level 21c. Outside of vessel 21, a supply conduit 26 for the introduction of an oxidizing agent is connected to the feed conduit 25. The vapor zone 21b of the vessel 21 is in commun.ication with a rectifying column 27, the vapor discharge conduit of which is denoted by element 28. Directly below the liquid level 21c, a discharge conduit 29 for the con-centrated acid is connected to the vessel 21. A refluxconduit 30 leads from the discharge conduit 29 to the rectifying column; the reflex conduit is provided with a water connection 31. In order to ensure also in this apparatus, operating by a continuous method, a flawless mixing of the supplied sulfuric acid to be processed with the already concentrated acid, a motor-drivable agitator 32 is arranged in the bottom portion of the concentrate zone 21a. This ensures also in this case that reactions, occurring due to impurities in t~e supplied acid with the latter and/or with any supplied oxidant during the heating process, can proceed effectively and in a controlled fashion whereby no undesired reactions can occur in the rectifying column 27 and/or in the vapor zone 21b due to a lack o~
introduced impurities.
.~ ."
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Consequently, it is possible by means of the dis-closed process to concentrate even dilute sulfuric acld into a relatively pure produet acid by evaporation whereas contaminants heretofore presenk did not readily permit such a processing operation. Thus it is possible to concentrate and purify, by means oE one and the same apparatus, sulfuric acids loaded with a great variety of organic impurities~
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims~
. .
Claims (10)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for the concentration and purification of sulfuric acid which comprises at least one evaporation chamber containing a lower concentration zone and an upper vapor zone, said lower concentration zone and upper vapor zone being defined by the liquid level of the sulfuric acid contained therein, a vapor discharge conduit connected to the upper vapor zone, a purified acid discharge conduit connected to the lower concentration zone, a circulation conduit for recycling the concentrated acid from the bottom of the lower concentration zone back to the upper vapor zone, a feed conduit for introducing the acid to be treated into the circulation conduit at a distance from both the liquid level in the evaporation chamber and the purified acid discharge conduit, the distance being selected so that the length of a flow path, defined as the point where the feed conduit joins the circulation conduit, ensures sudden separation of liquid and vapor upon entrance into said evaporation chamber, and an inlet conduit is connected to the feed conduit for introducing an oxidizing material into the acid to be treated.
2. The apparatus of claim 1 wherein the circulation conduit is provided with a pump means and heat exchanger means.
3. The apparatus of claim 2 wherein an inlet conduit is connected to the feed conduit for introducing an oxidizing material into the acid to be treated.
4. The apparatus of claim 1 wherein the upper portion of the vapor zone of the evaporation chamber is connected to a rectifying column, and said vapor discharge column is connected to said rectifying column.
5. The apparatus of claim 4 wherein a reflux conduit provides communication between the purified acid discharge conduit and the upper portion of the rectifying column, and a water feed line is provided for introducing water into said reflux conduit.
6. A process for the concentration and purification of impure sulfuric acid into a concentrated sulfuric acid product substantially free of organic impurities, which comprises the steps of:
continuously introducing a sulfuric acid liquid feed into a vessel having an evaporation zone and a rectifying zone, said sulfuric acid feed comprising a mixture of impure acid and a first recycled portion of the concentrated sulfuric acid being produced;
adding an oxidant to the impure acid to react with the impurities contained in the acid so that a reaction between said impurities and said oxidant produces heat for effecting a sudden separation of liquid and vapor upon introduction of said feed into said vessel;
continuously withdrawing a purified sulfuric acid product having an acid concentration greater that 70% and substantially free of organic impurities from said vessel, and;
continuously recycling a second portion of said sulfuric acid product to said rectifying zone to countercurrently contact any vapors exiting from said evaporation zone, the concentration of said second recycled acid portion being reduced by dilution with water before it is introduced into said rectifying zone;
wherein the length of a flow path, defined as the point when said first recycled portion of the concentrated acid combines with said impure acid feed, is chosen to ensure said sudden separation of liquid and vapor upon entrance into said vessel.
continuously introducing a sulfuric acid liquid feed into a vessel having an evaporation zone and a rectifying zone, said sulfuric acid feed comprising a mixture of impure acid and a first recycled portion of the concentrated sulfuric acid being produced;
adding an oxidant to the impure acid to react with the impurities contained in the acid so that a reaction between said impurities and said oxidant produces heat for effecting a sudden separation of liquid and vapor upon introduction of said feed into said vessel;
continuously withdrawing a purified sulfuric acid product having an acid concentration greater that 70% and substantially free of organic impurities from said vessel, and;
continuously recycling a second portion of said sulfuric acid product to said rectifying zone to countercurrently contact any vapors exiting from said evaporation zone, the concentration of said second recycled acid portion being reduced by dilution with water before it is introduced into said rectifying zone;
wherein the length of a flow path, defined as the point when said first recycled portion of the concentrated acid combines with said impure acid feed, is chosen to ensure said sudden separation of liquid and vapor upon entrance into said vessel.
7. The process of claim 6, wherein said sulfuric acid feed is introduced into said evaporation zone of said vessel at a point above the liquid vapor interface.
8. The process of claim 6, wherein said sulfuric acid feed is heated before it is introduced into the vessel.
9. The process of claim 8, wherein the oxidant is selected from the group consisting of nitric acid and hydrogen peroxide.
10. The process of claim 6, wherein the second recycled acid portion which has been diluted with water has an acid concentration of less than 70%.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CHG723/83 | 1983-02-09 | ||
| CH723/83A CH654282A5 (en) | 1983-02-09 | 1983-02-09 | METHOD AND DEVICE FOR CONCENTRATING AND PURIFYING SULFURIC ACID CONTAINING ORGANIC IMPURITIES. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1244228A true CA1244228A (en) | 1988-11-08 |
Family
ID=4193680
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000447056A Expired CA1244228A (en) | 1983-02-09 | 1984-02-08 | Process and apparatus for the concentration and purification of sulfuric acid which contains organic impurities |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0117986B1 (en) |
| JP (1) | JPS59156902A (en) |
| AT (1) | ATE33485T1 (en) |
| CA (1) | CA1244228A (en) |
| CH (1) | CH654282A5 (en) |
| DE (1) | DE3470410D1 (en) |
| ES (1) | ES529598A0 (en) |
| FI (1) | FI75553C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0937680A1 (en) | 1998-02-23 | 1999-08-25 | Bayer Aktiengesellschaft | Apparatus for the concentration and the purification of sulfuric acid |
| CN105566170A (en) * | 2016-01-22 | 2016-05-11 | 绍兴文理学院 | Recycling method for dilute sulphuric acid |
| CN111573629A (en) * | 2020-05-29 | 2020-08-25 | 盛隆资源再生（无锡）有限公司 | Recovery treatment method of sulfuric acid waste acid |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4828660A (en) * | 1986-10-06 | 1989-05-09 | Athens Corporation | Method and apparatus for the continuous on-site chemical reprocessing of ultrapure liquids |
| SE464299B (en) * | 1988-11-16 | 1991-04-08 | Boliden Contech Ab | PROCEDURE FOR DETERMINING Sulfuric Acid Produced According to the Contact Method |
| EP0378873B1 (en) * | 1988-12-16 | 1993-02-03 | ENICHEM SYNTHESIS S.p.A. | Regeneration of exhausted sulfuric acid by means of hydrogen peroxide |
| ES2105969B1 (en) * | 1995-07-14 | 1998-07-01 | Gen Quimica S A | PROCEDURE FOR THE RECOVERY OF SULFURIC ACID FROM SULFURIC RESIDUAL CURRENTS OF MEDIUM CONCENTRATION CONTAMINATED WITH ORGANIC MATTER. |
| DE102007013983B3 (en) * | 2006-04-27 | 2007-12-13 | Plinke Gmbh | Device for the purification of waste sulfuric acid, comprises reactor, circulation pump, vertically or horizontally arranged heat exchangers having inner and outer tubes, mixer for oxidation agent and the acid, and connection pipelines |
| EP2011566B1 (en) * | 2007-07-06 | 2010-12-15 | PLINKE GmbH | Apparatus for cleaning waste sulphuric acid |
| CN101372320B (en) * | 2007-08-20 | 2011-09-07 | 普林克有限责任公司 | Equipment for purifying waste sulfuric acid |
| DE102007059802B3 (en) * | 2007-12-11 | 2008-08-28 | Plinke Gmbh | Apparatus for recovering pure sulfuric acid by evaporation, includes corrosion- and thermal stress-resistant heat exchanger with silicon-containing cast steel inner tube and steel outer tube |
| CN104474848A (en) * | 2014-11-17 | 2015-04-01 | 云南华联锌铟股份有限公司 | Comprehensive utilization method of contaminated acid of sulfide ore roasting acid making system |
| CN110508014A (en) * | 2019-08-05 | 2019-11-29 | 贵州民族大学 | A kind of extracting solution concentration systems |
| DE102020002434B4 (en) | 2020-04-23 | 2022-09-01 | Pfaudler Normag Systems GmbH | Process for reducing hydrogen peroxide consumption in the purification of waste sulfuric acid contaminated with organic compounds by oxidative treatment |
| DE102020002443B4 (en) | 2020-04-23 | 2022-09-01 | Pfaudler Normag Systems GmbH | Process for reducing nitric acid consumption in the purification of waste sulfuric acid contaminated with organic compounds by oxidative treatment |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE611992C (en) * | 1933-04-27 | 1935-04-12 | Ehr Harry Pauling Dipl Ing Dr | Process and device for the concentration of waste sulfuric acid |
| DE1233368B (en) * | 1962-08-13 | 1967-02-02 | Heraeus Schott Quarzschmelze | Process for the continuous distillation of sulfuric acid in apparatus made of ceramic materials |
| EP0021210B1 (en) * | 1979-06-13 | 1983-07-13 | Bayer Ag | Evaporator for concentrating mineral acids, especially sulfuric acid |
| EP0022473B1 (en) * | 1979-06-13 | 1983-10-19 | Bayer Ag | Process and apparatus for regenerating sulphuric acid |
-
1983
- 1983-02-09 CH CH723/83A patent/CH654282A5/en not_active IP Right Cessation
-
1984
- 1984-01-20 DE DE8484100580T patent/DE3470410D1/en not_active Expired
- 1984-01-20 AT AT84100580T patent/ATE33485T1/en not_active IP Right Cessation
- 1984-01-20 EP EP84100580A patent/EP0117986B1/en not_active Expired
- 1984-01-31 FI FI840396A patent/FI75553C/en not_active IP Right Cessation
- 1984-02-08 CA CA000447056A patent/CA1244228A/en not_active Expired
- 1984-02-08 JP JP59020127A patent/JPS59156902A/en active Pending
- 1984-02-09 ES ES529598A patent/ES529598A0/en active Granted
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0937680A1 (en) | 1998-02-23 | 1999-08-25 | Bayer Aktiengesellschaft | Apparatus for the concentration and the purification of sulfuric acid |
| CN105566170A (en) * | 2016-01-22 | 2016-05-11 | 绍兴文理学院 | Recycling method for dilute sulphuric acid |
| CN111573629A (en) * | 2020-05-29 | 2020-08-25 | 盛隆资源再生（无锡）有限公司 | Recovery treatment method of sulfuric acid waste acid |
Also Published As
| Publication number | Publication date |
|---|---|
| FI840396A0 (en) | 1984-01-31 |
| JPS59156902A (en) | 1984-09-06 |
| EP0117986A2 (en) | 1984-09-12 |
| ES8504623A1 (en) | 1985-04-16 |
| CH654282A5 (en) | 1986-02-14 |
| EP0117986A3 (en) | 1986-02-05 |
| FI75553B (en) | 1988-03-31 |
| FI75553C (en) | 1988-07-11 |
| FI840396A (en) | 1984-08-10 |
| ES529598A0 (en) | 1985-04-16 |
| ATE33485T1 (en) | 1988-04-15 |
| DE3470410D1 (en) | 1988-05-19 |
| EP0117986B1 (en) | 1988-04-13 |
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