CA2094453A1 - Process for concentrating and purifying sulphuric acid - Google Patents
Process for concentrating and purifying sulphuric acidInfo
- Publication number
- CA2094453A1 CA2094453A1 CA002094453A CA2094453A CA2094453A1 CA 2094453 A1 CA2094453 A1 CA 2094453A1 CA 002094453 A CA002094453 A CA 002094453A CA 2094453 A CA2094453 A CA 2094453A CA 2094453 A1 CA2094453 A1 CA 2094453A1
- Authority
- CA
- Canada
- Prior art keywords
- sulphuric acid
- max
- chromium
- nickel
- process according
- 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
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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
- C01B17/74—Preparation
- C01B17/76—Preparation by contact processes
- C01B17/80—Apparatus
- C01B17/806—Absorbers; Heat exchangers
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Materials Engineering (AREA)
- Engineering & Computer Science (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Cleaning Or Drying Semiconductors (AREA)
- Removal Of Specific Substances (AREA)
- Treatment Of Sludge (AREA)
- Silicon Compounds (AREA)
Abstract
Process for concentrating and purifying sulphuric acid A B S T R A C T
A process for concentrating sulphuric acid to 80 to 97%
sulphuric acid content and/or for purifying the sulphuric acid at temperatures from 90 to 350°C and optionally cooling is disclosed wherein the process takes place in a plant in which those components which are contacted by hot sulphuric acid are manufactured in whole or in part of wrought and/or cast materials com-prising austenitic iron-nickel-chromium-silicon alloys comprising 15.5 to 17.5 wt-% nickel, 10 to 12 wt-%
chromium, 5.7 to 6.5 wt-% silicon, up to Max. 0.06 wt-%
carbon, up to Max. 1.5 wt-% manganese, up to Max. 0.03 wt-% phosphorus, up to Max. 0.03 wt-% sulphur, up to Max. 0.15 wt-% titanium, up to Max. 0.8 wt-% zirconium, up to Max. 0.2 wt-% nitrogen, up to Max. 0.7 wt-%
molybdenum, and the remainder iron.
Le A 29 017-
A process for concentrating sulphuric acid to 80 to 97%
sulphuric acid content and/or for purifying the sulphuric acid at temperatures from 90 to 350°C and optionally cooling is disclosed wherein the process takes place in a plant in which those components which are contacted by hot sulphuric acid are manufactured in whole or in part of wrought and/or cast materials com-prising austenitic iron-nickel-chromium-silicon alloys comprising 15.5 to 17.5 wt-% nickel, 10 to 12 wt-%
chromium, 5.7 to 6.5 wt-% silicon, up to Max. 0.06 wt-%
carbon, up to Max. 1.5 wt-% manganese, up to Max. 0.03 wt-% phosphorus, up to Max. 0.03 wt-% sulphur, up to Max. 0.15 wt-% titanium, up to Max. 0.8 wt-% zirconium, up to Max. 0.2 wt-% nitrogen, up to Max. 0.7 wt-%
molybdenum, and the remainder iron.
Le A 29 017-
Description
~9~5~
Process for concentrating and purifying sulphuric acid The invention relates to a process for concentrating and/or purifying sulphuric acid to concentrations of from 80 to 97% H2S04 , wherein temperatures within the range 90 to 350 C may be used and plant components which come into contact with the sulphuric acid are of special alloys.
For ecological reasons, that proportion of industrially used sulphuric acid which has been recovered by concentrating diluted used acids to a suitable H2S04 concentration is constantly increasing. However, it can generally be assumed that concentrating used acids to a concentration suitable for re-use, optionally linked with purification, is uneconomical, compared with using pure, concentrated sulphuric acid prepared from pyritiferous ores or sulphur. The high cost of sulphuric acid recovery arises chiefly from the capital and maintenance costs of the plant used, and energy costs.
Concentration to 93 to 97% H2S04 has the advantage that the majority of organic impurities are destroyed by the oxidising action of the sulphuric acid or by any oxidising agents which may be added. Conventional processes which achieve such high concentration operate at normal pressure and at temperatures in the region of 320 C. Under such conditions the sulphuric acid can be contacted directly with hot combustion gases in brick-lined kettles. The cost of separating sulphuric acid vapour and sulphur dioxide from the waste gas is very great, and for this reason these processes are rarely used.
Alternatively, concentrations of from 95 to 96% H2So4 can be obtained by concentration in cast-iron pans which are Le A 29 017-FC - 1 -2~9~
suspended in a furnace and above which a reflux condenser is arranged, at approximately 320 C (Pauling process). Here both energy and also, especially, plant costs are very high, because of the low operational capacity per unit. These cast-iron pans are made with a wall thickness of from 60 to 100 mm in order to obtain a reasonable service life.
Processes have been developed in which sulphuric acid is concentrated under vacuum at lower temperatures, in order to avoid the disadvantages of these conventional processes. Depending on temperature and H2SO4 strength, a variety of materials may be used in these processes.
Tantalum is a preferred material, being weldable and having good corrosion resistance over a temperature range of up to 200 C, but it is very costly. In general, therefore, it is utilised only as a heat exchanger material, while the actual concentrator plant is of glass, glass-lined steel or lead-lined steel with an inner brick lining (Winnacker-Kuchler, Chemische Technologie, Vol. 2 (4th edition), Carl Hauser Verlag, Munich, Vienna 1982, pp. 70-72).
Problems frequently arise from the necessity to confine working temperatures to about 180 C, since organic impurities in the used acids are not adequately destroyed at such temperatures and the associated maximum concentration of 93% H2S04. For this reason a number of processes have been proposed which enable the working range to be extended to higher temperatures of up to 330 C.
According to US-A ~,972,987 ~he sulphuric acid which is to a large extent concentrated under vacuum is further concentrated and purified in a Pauling apparatus at 320 C and at normal pressure, to give 96% H2SO4.
I.e A 29 017 2 According to EP 16 987, the acid, which2 Q~s~ ~e5en concentrated to approx. 90% H2SO4, can be purified by heating in cast-iron or glass-lined kettles to 270 to 330 C by means of submerged infrared radiators and S concentrating to 96% H2SO4.
CA 115 8836 discloses a orocess in which t.he acid, pre-concentrated to 90% H2SO4, is concentrated at 140 to 300 C to at least 96% H2S04 and purified in a radiation-heated quartz tube at approx. 320 C after addition of anoxidising agent.
According to CA 115 2285, the sulphuric acid can be concentrated from approximately 75% to 90 - 98.3% under vacuum at temperatures of from 160 to 250 C in glass or glass-lined steel apparatus, wherein heat is supplied by means of heat transfer oil in glass-lined double-jacketed pipes. Double-jacketed cast silicon pipes have since become known for this application, in which the brittleness and sensitivity to thermal shock of this material represent a considera~le risk factor.
All these processes have the disadvantage of encountering the familiar corrosion problems which occur in sulphuric acid concentration, and presented by costly materials like tantalum, which to compound the problem is limited to a utility range of maximum 200 C, or by high-cost design. The safety hazards resulting from handling concentrated sulphuric acid at temperatures of from 200 to 330 C while using fragile materials such as quartz and cast silicon iron, and the multiplicity of sealing surfaces, and also use of double- jacke~ pipes as heat exchangers, are quit e considerable here.
The object was therefore to avoid the disadvantages of the known processes for concentrating and purifying used Le A 29 017 3 sulphuric acid, and to bring about a su~ 3 improvement in operating safety and in the economics of these processes.
It was, surprisingly, possible to achieve this object by finding special metallic materials which exhibit a high resistance to 80 to 97% sulphuric acid at temperatures of up to 350~ C~ and which are addit.ionally castable, forgea~le and grindable as well as weldable, and exhibit good characteristic values for mechanical strength and toughness.
The present invention provides a process for concentrating sulphuric acid to 80 to 97 wt-% H2S04 and optionally purifying the said sulphuric acid, at temperatures of from 90 to 350 C, characterised in that the concentration and optional purification of the sulphuric acid is/are performed in plant of which those portions which are impinged upon by the hot sulphuric acid are manufactured in whole or in part of wrought and/or cast materials and welding fillers, which comprise austenitic iron-nickel-chromium-silicon alloys having 15.5 to 17.5 wt-% nickel 10 to 12 wt-% chromium 5.7 to 6.5 wt-% silicon up to max. 0.06 wt-% carbon up to max. 1.5 wt-% manganese up to max. 0.03 wt-% phosphoru~
up to max. 0.03 wt-% sulphur up to max. 0.15 wt-% titanium up to max. 0.8 wt-% zirconium up to max. 0.2 wt-% nitrogen up to max. 0.3 wt-% molybdenum Le A 29 017 4 4 ~ ~
and ~he remainder iron together with minimal quantities of normally present impurities, including the deoxi-dising elements magnesium, aluminium and calcium.
In order to further improve hot workabili~y, these materials may additionally con~ain up to 0.01 w~-% boron and up to 0.25 wt-'~. rare earth metals.
The aforementioned austenitic alloys and materials suit-able for high concsntration of sulphuric acad are hereinafter designated "sulphuric acid austenite".
The ~erm "plan~" in the present context refers to any ~5 combination of apparatuses and pipelines for heating, concentrating, cleaning and/or cooling sulphuric acid, such as for example a system comprising a pan and a reflux conden6er, as in the Pauling process, or a sys~em comprising a forced circulation vacuum evapora~or and the necessary heaters and coolers.
A further embodiment of the invention comprises concen-~ra~ing sulphuric acid, at 90 to 350C, to 80 ~o 97%
H2S04 content~ wherein the ~hermal energy required for heating and evaporating ~he wa~er is supplied indirec~ly via heat exchangers, ~he heat-~ransmi~ing dividing walls of which are of sulphuric acid aus~eni~e, The technical aspect of ~he heat exchangers is advan-~ageously based on the process conditions in each case.
Within ~he meaning of the invention, for example, flue gas-heated fixed-head tubular heat exchanger, ~ube walls or tube spirals, and pans of sulphuric acid aus~enite may be utilised.
Le A 29 017 - 5 -2~9~3 Similarly, hea~ exchangers ~o be hea~ed by hea~ing s~eam or heat transfer oil and which are of sulphuric acid austenite may be used. These may for example be formed as fixed-head ~ubular or pla~e heat exchangers.
A particular advan~age of ~he inven~ion is ~ha~
sulphuric acid aus~eni~e is a weldable material, which means ~hat seals, which are critical especially when working at temperatures wi~hin ~he range 250 ~o 350C, can be avoided.
Apar~ from ~he hea~ exchangers, the en~ire appara~us for the concentra~ion and op~ional purifica~ion of sulphuric acid may be of sulphuric acid aus~eni~e, i.e.
even evaporators, piping and pumps which come into con~ac~ wi~h hot sulphuric acid at 80 ~o 97%
concen~ration, may be of sulphuric acid aus~eni~e.
Combinations of sulphuric acid aus~eni~e wi~h other materials, e.g. cast silicon-iron in ~he form of ~as~
silicon-iron pumps or glass-lined ma~erials in the form of glass-lined piping, are also possible.
The lnven~lon i9 explalned ion grea~er de~all by reference ~o the following Examples. The following examples illus~ra~e ~he presen~ inven~ion bu~ are no~
in~ended to limit i~s ~cope in any way.
~0 ExamDle A plan~ for concen~ra~ing 70% used sulphuric acid from nitroaroma~ics produc~ion ~o a concen~ra~ion of 96%
H2S04 was manufac~ured from a sulphuric acid aus~enite of ~he following composi~ion:
Le A 29 017 - 6 -17.49 w~-~/. nickel 11.34 wt-'~. chromium 5.94 w~-% silicon 0.68 w~ . manganese 0.41 w~-% zirconium 0.10 w~-% ~i~anium 0.09 w~-% molybdenum 0.021 w~-% phosphorus 0.015 wt-% carbon 0.001 w~-% sulphur and ~he remainder subs~an~iallv iron.
The plan~ comprised a concentrator vessel (diame~er 1.0 mJ heigh~ 3 m) wi~h reflux condenser above. The concentra~or vessel was connec~ed via piping to a cas~
silicon-iron pump and a pla~e heat exchanger (8 m2 exchange surface).
The pump ex~rac~ed 25 m3/h of 96% sulphuric acid a~
290C from ~he concen~ra~or vessel, and re~urned it ~o ~he concen~ra~or vessel, via ~he pla~e hea~ exchanger, in which i~ was heated ~o 310C. Heat ~ransfer oil ~5 which waa cooled from 350 ~o 320LC in ~he pla~e hea~
exchangerJ served as hea~ing medium. A pressure of 0.4 bar ~absolute) was main~ained in ~he concen~ra~or vessel. The 96% sulphuric acid leaving ~he concentra~or vessel was cooled ~o 80C in a fixed-head tubular heat exchanger. The coun~ercurren~ of 70~/. s~rength used acid containing nitroaromatics served as ~he cooling medium, which was heated ~o 154C and subsequen~ly fed into the head side of ~he reflux condenser. The evaporated water was condensed ~oge~her wi~h ~he vola~ile organic com-pounds. Following a residence ~ime of approxima~ely 55minutes in ~he plant, ~he concentra~ed sulphuric acid was almost colourless and could be re-u~ilised in ~he nitration of aromatic compounds.
Le A 29 017 - 7 -2 ~ 3 The wall thickness of ~he plant componen~s manufactured in sulphuric acid aus~eni~e and impinged upon by sulphuric acid (evapora~or wi~h reflux condenser, piping J plate and fixed-heat ~ubular hea~ exchangers), measured af~er 6 mon~hs' opera~ion~ showed no measurable loss due to corrosion. The corrosion rate was approx-imately 0.2 mmlyear, only in ~he region of ~he acid level in the concen~rator vessel.
~5 Le A 29 017 - 8 -
Process for concentrating and purifying sulphuric acid The invention relates to a process for concentrating and/or purifying sulphuric acid to concentrations of from 80 to 97% H2S04 , wherein temperatures within the range 90 to 350 C may be used and plant components which come into contact with the sulphuric acid are of special alloys.
For ecological reasons, that proportion of industrially used sulphuric acid which has been recovered by concentrating diluted used acids to a suitable H2S04 concentration is constantly increasing. However, it can generally be assumed that concentrating used acids to a concentration suitable for re-use, optionally linked with purification, is uneconomical, compared with using pure, concentrated sulphuric acid prepared from pyritiferous ores or sulphur. The high cost of sulphuric acid recovery arises chiefly from the capital and maintenance costs of the plant used, and energy costs.
Concentration to 93 to 97% H2S04 has the advantage that the majority of organic impurities are destroyed by the oxidising action of the sulphuric acid or by any oxidising agents which may be added. Conventional processes which achieve such high concentration operate at normal pressure and at temperatures in the region of 320 C. Under such conditions the sulphuric acid can be contacted directly with hot combustion gases in brick-lined kettles. The cost of separating sulphuric acid vapour and sulphur dioxide from the waste gas is very great, and for this reason these processes are rarely used.
Alternatively, concentrations of from 95 to 96% H2So4 can be obtained by concentration in cast-iron pans which are Le A 29 017-FC - 1 -2~9~
suspended in a furnace and above which a reflux condenser is arranged, at approximately 320 C (Pauling process). Here both energy and also, especially, plant costs are very high, because of the low operational capacity per unit. These cast-iron pans are made with a wall thickness of from 60 to 100 mm in order to obtain a reasonable service life.
Processes have been developed in which sulphuric acid is concentrated under vacuum at lower temperatures, in order to avoid the disadvantages of these conventional processes. Depending on temperature and H2SO4 strength, a variety of materials may be used in these processes.
Tantalum is a preferred material, being weldable and having good corrosion resistance over a temperature range of up to 200 C, but it is very costly. In general, therefore, it is utilised only as a heat exchanger material, while the actual concentrator plant is of glass, glass-lined steel or lead-lined steel with an inner brick lining (Winnacker-Kuchler, Chemische Technologie, Vol. 2 (4th edition), Carl Hauser Verlag, Munich, Vienna 1982, pp. 70-72).
Problems frequently arise from the necessity to confine working temperatures to about 180 C, since organic impurities in the used acids are not adequately destroyed at such temperatures and the associated maximum concentration of 93% H2S04. For this reason a number of processes have been proposed which enable the working range to be extended to higher temperatures of up to 330 C.
According to US-A ~,972,987 ~he sulphuric acid which is to a large extent concentrated under vacuum is further concentrated and purified in a Pauling apparatus at 320 C and at normal pressure, to give 96% H2SO4.
I.e A 29 017 2 According to EP 16 987, the acid, which2 Q~s~ ~e5en concentrated to approx. 90% H2SO4, can be purified by heating in cast-iron or glass-lined kettles to 270 to 330 C by means of submerged infrared radiators and S concentrating to 96% H2SO4.
CA 115 8836 discloses a orocess in which t.he acid, pre-concentrated to 90% H2SO4, is concentrated at 140 to 300 C to at least 96% H2S04 and purified in a radiation-heated quartz tube at approx. 320 C after addition of anoxidising agent.
According to CA 115 2285, the sulphuric acid can be concentrated from approximately 75% to 90 - 98.3% under vacuum at temperatures of from 160 to 250 C in glass or glass-lined steel apparatus, wherein heat is supplied by means of heat transfer oil in glass-lined double-jacketed pipes. Double-jacketed cast silicon pipes have since become known for this application, in which the brittleness and sensitivity to thermal shock of this material represent a considera~le risk factor.
All these processes have the disadvantage of encountering the familiar corrosion problems which occur in sulphuric acid concentration, and presented by costly materials like tantalum, which to compound the problem is limited to a utility range of maximum 200 C, or by high-cost design. The safety hazards resulting from handling concentrated sulphuric acid at temperatures of from 200 to 330 C while using fragile materials such as quartz and cast silicon iron, and the multiplicity of sealing surfaces, and also use of double- jacke~ pipes as heat exchangers, are quit e considerable here.
The object was therefore to avoid the disadvantages of the known processes for concentrating and purifying used Le A 29 017 3 sulphuric acid, and to bring about a su~ 3 improvement in operating safety and in the economics of these processes.
It was, surprisingly, possible to achieve this object by finding special metallic materials which exhibit a high resistance to 80 to 97% sulphuric acid at temperatures of up to 350~ C~ and which are addit.ionally castable, forgea~le and grindable as well as weldable, and exhibit good characteristic values for mechanical strength and toughness.
The present invention provides a process for concentrating sulphuric acid to 80 to 97 wt-% H2S04 and optionally purifying the said sulphuric acid, at temperatures of from 90 to 350 C, characterised in that the concentration and optional purification of the sulphuric acid is/are performed in plant of which those portions which are impinged upon by the hot sulphuric acid are manufactured in whole or in part of wrought and/or cast materials and welding fillers, which comprise austenitic iron-nickel-chromium-silicon alloys having 15.5 to 17.5 wt-% nickel 10 to 12 wt-% chromium 5.7 to 6.5 wt-% silicon up to max. 0.06 wt-% carbon up to max. 1.5 wt-% manganese up to max. 0.03 wt-% phosphoru~
up to max. 0.03 wt-% sulphur up to max. 0.15 wt-% titanium up to max. 0.8 wt-% zirconium up to max. 0.2 wt-% nitrogen up to max. 0.3 wt-% molybdenum Le A 29 017 4 4 ~ ~
and ~he remainder iron together with minimal quantities of normally present impurities, including the deoxi-dising elements magnesium, aluminium and calcium.
In order to further improve hot workabili~y, these materials may additionally con~ain up to 0.01 w~-% boron and up to 0.25 wt-'~. rare earth metals.
The aforementioned austenitic alloys and materials suit-able for high concsntration of sulphuric acad are hereinafter designated "sulphuric acid austenite".
The ~erm "plan~" in the present context refers to any ~5 combination of apparatuses and pipelines for heating, concentrating, cleaning and/or cooling sulphuric acid, such as for example a system comprising a pan and a reflux conden6er, as in the Pauling process, or a sys~em comprising a forced circulation vacuum evapora~or and the necessary heaters and coolers.
A further embodiment of the invention comprises concen-~ra~ing sulphuric acid, at 90 to 350C, to 80 ~o 97%
H2S04 content~ wherein the ~hermal energy required for heating and evaporating ~he wa~er is supplied indirec~ly via heat exchangers, ~he heat-~ransmi~ing dividing walls of which are of sulphuric acid aus~eni~e, The technical aspect of ~he heat exchangers is advan-~ageously based on the process conditions in each case.
Within ~he meaning of the invention, for example, flue gas-heated fixed-head tubular heat exchanger, ~ube walls or tube spirals, and pans of sulphuric acid aus~enite may be utilised.
Le A 29 017 - 5 -2~9~3 Similarly, hea~ exchangers ~o be hea~ed by hea~ing s~eam or heat transfer oil and which are of sulphuric acid austenite may be used. These may for example be formed as fixed-head ~ubular or pla~e heat exchangers.
A particular advan~age of ~he inven~ion is ~ha~
sulphuric acid aus~eni~e is a weldable material, which means ~hat seals, which are critical especially when working at temperatures wi~hin ~he range 250 ~o 350C, can be avoided.
Apar~ from ~he hea~ exchangers, the en~ire appara~us for the concentra~ion and op~ional purifica~ion of sulphuric acid may be of sulphuric acid aus~eni~e, i.e.
even evaporators, piping and pumps which come into con~ac~ wi~h hot sulphuric acid at 80 ~o 97%
concen~ration, may be of sulphuric acid aus~eni~e.
Combinations of sulphuric acid aus~eni~e wi~h other materials, e.g. cast silicon-iron in ~he form of ~as~
silicon-iron pumps or glass-lined ma~erials in the form of glass-lined piping, are also possible.
The lnven~lon i9 explalned ion grea~er de~all by reference ~o the following Examples. The following examples illus~ra~e ~he presen~ inven~ion bu~ are no~
in~ended to limit i~s ~cope in any way.
~0 ExamDle A plan~ for concen~ra~ing 70% used sulphuric acid from nitroaroma~ics produc~ion ~o a concen~ra~ion of 96%
H2S04 was manufac~ured from a sulphuric acid aus~enite of ~he following composi~ion:
Le A 29 017 - 6 -17.49 w~-~/. nickel 11.34 wt-'~. chromium 5.94 w~-% silicon 0.68 w~ . manganese 0.41 w~-% zirconium 0.10 w~-% ~i~anium 0.09 w~-% molybdenum 0.021 w~-% phosphorus 0.015 wt-% carbon 0.001 w~-% sulphur and ~he remainder subs~an~iallv iron.
The plan~ comprised a concentrator vessel (diame~er 1.0 mJ heigh~ 3 m) wi~h reflux condenser above. The concentra~or vessel was connec~ed via piping to a cas~
silicon-iron pump and a pla~e heat exchanger (8 m2 exchange surface).
The pump ex~rac~ed 25 m3/h of 96% sulphuric acid a~
290C from ~he concen~ra~or vessel, and re~urned it ~o ~he concen~ra~or vessel, via ~he pla~e hea~ exchanger, in which i~ was heated ~o 310C. Heat ~ransfer oil ~5 which waa cooled from 350 ~o 320LC in ~he pla~e hea~
exchangerJ served as hea~ing medium. A pressure of 0.4 bar ~absolute) was main~ained in ~he concen~ra~or vessel. The 96% sulphuric acid leaving ~he concentra~or vessel was cooled ~o 80C in a fixed-head tubular heat exchanger. The coun~ercurren~ of 70~/. s~rength used acid containing nitroaromatics served as ~he cooling medium, which was heated ~o 154C and subsequen~ly fed into the head side of ~he reflux condenser. The evaporated water was condensed ~oge~her wi~h ~he vola~ile organic com-pounds. Following a residence ~ime of approxima~ely 55minutes in ~he plant, ~he concentra~ed sulphuric acid was almost colourless and could be re-u~ilised in ~he nitration of aromatic compounds.
Le A 29 017 - 7 -2 ~ 3 The wall thickness of ~he plant componen~s manufactured in sulphuric acid aus~eni~e and impinged upon by sulphuric acid (evapora~or wi~h reflux condenser, piping J plate and fixed-heat ~ubular hea~ exchangers), measured af~er 6 mon~hs' opera~ion~ showed no measurable loss due to corrosion. The corrosion rate was approx-imately 0.2 mmlyear, only in ~he region of ~he acid level in the concen~rator vessel.
~5 Le A 29 017 - 8 -
Claims (8)
1. Process for concentrating sulphuric acid to 80 to 97% sulphuric acid content or for purifying the sulphuric acid at temperatures from 90 to 350°C and optionally cooling, wherein the process takes place in a plant in which those components which are contacted by hot sulphuric acid are manufactured in whole or in part of wrought or cast materials comprising austenitic iron-nickel-chromium-silicon alloys comprising 15.5 to 17.5 wt-% nickel 10 to 12 wt-% chromium 5.7 to 6.5 wt-% silicon up to Max. 0.06 wt-% carbon up to Max. 1.5 wt-% manganese up to Max. 0.03 wt-% phosphorus up to Max. 0.03 wt-% sulphur up to Max. 0.15 wt-% titanium up to Max. 0.8 wt-% zirconium up to Max. 0.2 wt-% nitrogen up to Max. 0.3 wt-% molybdenum and the remainder comprising iron.
2. Process according to Claim 1, wherein the wrought or cast materials also contain minimal quantities of the deoxidizing elements magnesium, aluminum and calcium, and optionally up to 0.01 wt-% boron and up to 0.25 wt-% rare earth metals.
Le A 29 017- - 9 -
Le A 29 017- - 9 -
3. Process according to Claim 1, wherein the heat ex-changers of the plant are manufactured of austenitic iron-nickel-chromium-silicon alloys of Claim 1.
4. Process according to Claim 3, wherein heat is supplied to the 80 to 97% sulphuric acid in the heat exchangers by a heating medium wherein the medium is flue gas, steam or heat transfer oil.
5. Process according to Claim 3, wherein the 80 to 97%
sulphuric acid is cooled from temperatures of between 90 to 350°C to lower temperatures in the heat exchangers, wherein the sulphuric acid to be concentrated or water is used as cooling medium.
sulphuric acid is cooled from temperatures of between 90 to 350°C to lower temperatures in the heat exchangers, wherein the sulphuric acid to be concentrated or water is used as cooling medium.
6. Process according to Claim 1, wherein the evaporator or piping of the plant are manufactured of austenitic iron-nickel-chromium-silicon alloys of Claim 1.
7. Process according to Claim 1, wherein the 80 to 97%
sulphuric acid, at a temperature of 90 to 350°C, is conveyed by pumps comprising austenitic iron-nickel-chromium-silicon alloys of Claim 1.
sulphuric acid, at a temperature of 90 to 350°C, is conveyed by pumps comprising austenitic iron-nickel-chromium-silicon alloys of Claim 1.
8. Process according to Claim 1, wherein the austenitic iron-nickel-chromium-silicon alloys comprise Le A 29 017 - 10 -17.49 wt-% nickel 11.34 wt-% chromium 5.94 wt-% silicon 0.015 wt-% carbon 0.68 wt-%. manganese 0.021 wt-% phosphorus 0.001 wt-% sulphur 0.10 wt-% titanium 0.41 wt-% zirconium 0.09 wt-% molybdenum and the remainder comprising iron.
Le A 29 017 - 11 -
Le A 29 017 - 11 -
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4213324A DE4213324A1 (en) | 1992-04-23 | 1992-04-23 | Process for concentrating and purifying sulfuric acid |
| DEP4213324.6 | 1992-04-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2094453A1 true CA2094453A1 (en) | 1993-10-24 |
Family
ID=6457298
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002094453A Abandoned CA2094453A1 (en) | 1992-04-23 | 1993-04-20 | Process for concentrating and purifying sulphuric acid |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0566949B1 (en) |
| JP (1) | JPH0680408A (en) |
| AT (1) | ATE125778T1 (en) |
| CA (1) | CA2094453A1 (en) |
| DE (2) | DE4213324A1 (en) |
| NO (1) | NO931369L (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19719394C1 (en) * | 1997-05-07 | 1999-01-07 | Bayer Ag | Process for concentrating or purifying sulfuric acid |
| DE19807632A1 (en) * | 1998-02-23 | 1999-09-02 | Bayer Ag | Device for concentrating and purifying sulfuric acid |
| US6405214B1 (en) * | 1998-12-17 | 2002-06-11 | Hewlett-Packard Company | Method of gathering usage information and transmitting to a primary server and a third party server by a client program |
| DE10231314B4 (en) * | 2002-07-10 | 2008-07-31 | Plinke Gmbh | Process for the use of stainless steel condensers in systems for stripping nitriding waste acids |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR854510A (en) * | 1938-05-10 | 1940-04-17 | Hercules Powder Co Ltd | Apparatus for concentration of acids |
| DE2360706C3 (en) * | 1973-12-06 | 1980-10-16 | Hoechst Ag, 6000 Frankfurt | Process for the regeneration of sulfuric acid |
| DE2845917C2 (en) * | 1978-10-21 | 1983-10-27 | Hoechst Ag, 6230 Frankfurt | Use of gray cast iron alloys for the manufacture of boilers for boiling concentrated sulfuric acid |
| EP0022181B1 (en) * | 1979-06-13 | 1983-10-12 | Bayer Ag | Process and apparatus for regenerating sulfuric acid |
-
1992
- 1992-04-23 DE DE4213324A patent/DE4213324A1/en not_active Withdrawn
-
1993
- 1993-04-13 AT AT93105950T patent/ATE125778T1/en active
- 1993-04-13 EP EP93105950A patent/EP0566949B1/en not_active Expired - Lifetime
- 1993-04-13 DE DE59300422T patent/DE59300422D1/en not_active Expired - Fee Related
- 1993-04-14 NO NO93931369A patent/NO931369L/en not_active Application Discontinuation
- 1993-04-19 JP JP5114151A patent/JPH0680408A/en active Pending
- 1993-04-20 CA CA002094453A patent/CA2094453A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE4213324A1 (en) | 1993-10-28 |
| NO931369D0 (en) | 1993-04-14 |
| NO931369L (en) | 1993-10-25 |
| JPH0680408A (en) | 1994-03-22 |
| DE59300422D1 (en) | 1995-09-07 |
| EP0566949A1 (en) | 1993-10-27 |
| ATE125778T1 (en) | 1995-08-15 |
| EP0566949B1 (en) | 1995-08-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |