CA1155634A - Production of liquid sulfur trioxide - Google Patents
Production of liquid sulfur trioxideInfo
- Publication number
- CA1155634A CA1155634A CA000355154A CA355154A CA1155634A CA 1155634 A CA1155634 A CA 1155634A CA 000355154 A CA000355154 A CA 000355154A CA 355154 A CA355154 A CA 355154A CA 1155634 A CA1155634 A CA 1155634A
- Authority
- CA
- Canada
- Prior art keywords
- sulfur trioxide
- gas
- condenser
- trioxide
- condensed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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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
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Treating Waste Gases (AREA)
Abstract
PRODUCTION OF LIQUID SULFUR TRIOXIDE
Abstract of the Invention Sulfur trioxide is recovered in liquid form by condensation from a gas containing sulfur trioxide.
The gas is cooled to a temperature from about 80°F.
to about 90°F. (about 26.7°C. to about 32°C.) and con-tinually introduced into a condenser whereby sulfur trioxide is condensed and continuously removed from the condenser surfaces as it condenses. The condensed sulfur trioxide is continuously removed from the condenser and melted to produce liquid sulfur trioxide.
The process is particularly suitable for condensing sulfur trioxide from a gas containing relatively low concentrations thereof.
Abstract of the Invention Sulfur trioxide is recovered in liquid form by condensation from a gas containing sulfur trioxide.
The gas is cooled to a temperature from about 80°F.
to about 90°F. (about 26.7°C. to about 32°C.) and con-tinually introduced into a condenser whereby sulfur trioxide is condensed and continuously removed from the condenser surfaces as it condenses. The condensed sulfur trioxide is continuously removed from the condenser and melted to produce liquid sulfur trioxide.
The process is particularly suitable for condensing sulfur trioxide from a gas containing relatively low concentrations thereof.
Description
~ 155634 PRODUCTION OF LI~UID SULFUR T~IOXIDE
Back~round and Prior Art ~his invention relates to a process for the productioll of sulfur trioxide in liquid form and more particularly to its recovery in liquid form by conden-sation from gases. It is particularly useful for the recovery or sulfur trioxide in liquid form rom gases relatively dilute in sulfur trioxide, particularly such gases containing less than 15% sulfur trioxide by volume. This process provides a method by which relatively pure sulfur trioxide can be recovered in liquid form from gases containing sulfur trioxide and other gaseous components. Liquid sulfur trioxide is a valuable product, being useful, for instance, as a reagent fox production of alkylbenzene sulfonates and in tertiary oil recovery.
In general, in present pract~ce, liquid sul-fur trioxide is obtained by absorption of sulfur trioxide from a gas containing the same in sulfuric acid to form oleum, followed by boiling the oleum in a separate operation and condensing the sulfur trioxide evolved.
Such a condensing operation can be troublesome because of freezing of sulfur trloxide on the condenser tubes.
The freezing point of sulfur trioxide is about 85F.
~29.5C.). In general, in condensing sulfur trioxide from a gas containing the same, difficulties are caused by the fact that the temperatures required for appreciable recovery of sulfur trioxide by condensa-tion are below this freezing point, resulting in the formation of solid sulfur trioxide, which can result in plugging of the equipment, requiring steps to clear the equipment and remove the sulfur trioxide. Solid sulfur trioxide may exist in three separate forms, generally referred to as the alpha-, beta- and gamma-forms, see for instance, Brasted, "Comprehensive Inorganic Chemistry", Vol. 8, pp. 134-138 (1961). The gamma-form exists in ice-like cryst~ls and is the most volatile and easiest to melt. The beta- and alph3-forms have asbestos-llke crystals and are more difficult to melt, with the alpha-form being the most difficult.
In general, when sulfur trioxide is condensed, a liquid is first formed. This them becomes converted to the gamma-solid form, which can become further converted to the beta- and alpha-forms.
In U.S. patent 2,510,684, there is provided a substantial amount of information concerning the conditions under which sulfur trioxide can be condensed from gases containing it. However, this patent requires that, to effect the condensation of the sulfur trioxide, the gaseous mixture contain much more than 15% sulfur dioxide. Condensation under these conditions is affected by the use of pressure and relatively high concentrations of sulfur dioxide.
Sulfur trioxide gas is c~nventionally pro-duced by combustion of sulfur ~r ~sulfur-containing wastes, such as sludges containing ~ulfuric acid, to produce sulfur dioxide, followed b~ catalytic oxidation of the sulfur dioxide to sulfur tri~xide in the presence 1 ~55~;~4 --3-- `
of a metallic catalyst. When the co~bustion is con-ducted with air, the gases leaving thie sulfur dioxide converter generally contain from abouit 5 to about 13%
sulfur trioxide by volume. If oxygen is utiliæed for combustion, the gas exiting the sulfur dioxide con-verter will contain a much greater co~centration of sul-fur trioxide, generally from 50 to 8ff~ by volume, and a correspondingly lesser amount of in/ert gases (nitro-gen, carbon dioxide, etc.) However, în order to condense this sulfur trioxide accord~ng to the process of U.S. patent 2,510,684, it would be necessary to conduct an incomplete conversion of the sulfur dioxide, in order that the gases leaving the converter contain at leas~ 15% S02. This would require recycle of the unconverted sulfur dioxide to the converter, which pro- -vides a disadvantage as opposed to once-through processes such as absorption of sulfur trioxide in sulfuric acid.
It is particularly difficult to recoYer sulfur trioxide ~y condensation from gases containing lt in relatively dilute concentrations, for example 15 vol.% or less.
Summary of the Invention In brief, this invention comprises a process for recovering sulfur trioxide in liquid form from a gas containing sulfur trioxide comprising adjusting the temperature of the gas to a temperature from about 80F. to about 90F. (about 26.7C. to about 32C.), continuously introducing the gas hav~ng such tempera-ture into a condensing apparatus maintained at a temperature of from about 53F. to a~out 0F. (about 11C. to about -18C.), whereby sul~ur trioxide is caused to condense from the gas; ~ontinuously removing condensed sulfur trioxide from the con~enser suraces, continuously conveying the condense~ sulfur trioxide out of the condensing apparatus, andl subsequently melting the condensed sulfur trioxide to produce liquid sulfur trioxide.
.
11~5~
The process as thus defined permits the recovery of sul~ur trioxide in liquid form from gases containing it without requiring absorption into sulfuric acid and boiling and distill~tion of the oleum thus produced. The process as herein defined also provides a satisfactory method of recovering sulfur trioxide in liquid form from gases containing relatively low concentrations of sulfur trioxide~ by direct condensation.
Description of the Draw_ g The drawing represents a sLmplified flow sheet for the conduct of the process according to one embodi ment of this invention.
Detailed Description of the Invention For purposes of convenience, this invention will be described with reference to the drawing, which relates to a process for recovery of sulfur trloxide in liquid form from gases containing relatively low concentrations of sulfur trioxide, generally from 5%
to less than 15% by volume. However, it should be understood that the principle of this invention is applicable to the recovery of sulfur trioxide from gases con~aining substantially greater concentrations thereof, for example, from gases produced by combustion of sulfur or sulfur-containing materials with oxygen or oxygen-enriched air (as-opposed to air). It should, furthermore, be understood that the principle of the present invention is equally applicable to the recovery of sulfur trioxide from gases containing the same resulting from any other source or method or production.
In general, it is not now economically practical to recover sulfur trioxide from gases containing concentra-tions thereof of less than about 5% by volume, although the process described herein is capable o~ recovering .. . . .
11556~4 sulur trioY.ide from such gases containing it in low concentrations.
Referring now to the clrawing, a gas contain-ing up to about 15% sul~ur triaxide emanating from a S source 1 and generally at an elevated temperature, is passed through line ~ into a heat exchanger 3, which may be cooled by introduction of water into the shell side thereof in line 26 and removal of heated water or steam in line 27. The gas thus cooled is then passed through line 4 into mist eliminator 5 in which acid mis~ is removed. The gas is then passed through line 6 into a heat exchanger 7 in which it is cooled to a temperature of from about 80F. to about 90F.
(about 26.7C. to about 32C.). As shown in the drawing~
the cooling is preferably accomplished by indirect heat exchange with gases from which sulfur trioxide has been removed, introduced into heat exchanger 7 through line 14 and removed through line 15.
The thus cooled g~s containing sulfur trioxide is passed through line ~ into a condensing apparatus generally indicated as 9, and maintained at a tempera-ture of from about 53F. to abaut 0F. (about 11C. to about -18C.~, preferably about 53F. to about 10F.
(about 11C. to about -12C.), and most preferably about 40F. to a~ ut 25F. (about 5C. to about -4C.).
This apparatus contains an interiorly located condensing section 10 surrounded by a cooling jacket 11. ~lithin the condensing section 10 are contained helical scraper blades 12, driven by a motor 13, the blades being arranged so as to scrape the inner surface of the con-densing chamber 10. The drawing depicts the condenser as being horizontally disposed. However, vertical or incllned condensers may be utilized.
The use of such a scraped surface condenser with helically arranged scraper blades enables the con-tinuous removal of product sulfur trioxide from the _fi_ interior sur~ace of the condenser as it is condensed, and continuous conveying of the condensed sulfur tri-oxlde through the condenser, preventing freezing ~nd plugging of equipment. Preferably, the helical blades S are mounted on a drum 12a closed at both ends, the axis or rotation of which is coincidental with the long axis of the condenser chamber. This continuous removal and conveying are enhanced by warming the in-terior of the drum 12a, for example by electrical heating or by passing a warmer fluid (liquid or gas) through it, as is conventional in such e~uipment, to prevent sticking of the solid sulfur trioxide to the surfaces. Split flights and vanes may also be provided in the condenser, to break up lumps of solid. Pre-ferably, the entering gas flow is directed through a relatively narrow annulus existing between the cold condenser surface and the rotating drum 12a which bears the scraper blades 12. The exact clearance between the condenser and the rotating drum is a function of the desired gas velocity and the amount of sulfur trioxide expected to be condensed and removed, and is readily determinable by those skilled in the art. The amount of sulfur trioxide expected to be condensed under these circumstances depends on the concentration of the sulfur trioxide in the incoming gas and the temperature and the pressure of the environment, and is readily determinable by methods known to those skilled in the art.
The uncondensed gases are removed from the condenser 9 through line 14 and may be advantageously utilized to cool the incoming gas in heat exchanger 7.
They are removed via line 15 and are either passed to treatment to remo~e pollutants and other undesirable material before being vented to the atmosphere, or passed to further processing, as discussed below ..
115~6~4 The sulfur trioxide which condenses on the interior surfaces of the condensing chamber 10 is removed by the blades 12 and carried thereby along the length of the chamber 10. The condensed sulfur trioxide may be in the form of predominantly gamma-crystals, or may be a slurry or "slush" of such crystals with liquid sulfur trioxide. The sulfur trioxide is removed from the condensing chamber via outlet 16 in which ~s located a star valve 17 which forms a rotating seal and also serves to extract condensed sulfur trioxide at a regular rate from the condenser. Outlet 16 and star valve 17 may be iacketed and heated in a similar manner to dru~ 12a, to pre-vent sticking of sulfur trioxide. The sulfur trioxide is conveyed by the star seal 17 into a melting tank 18 equipped with melting coils 19 through which may be introduced steam or hot water, and an agitator 26.
Sulfux trioxide is melted in melting tank 18 and liquid sulfur trioxide is removed via line 20. Preferably the melting and removai are performed continuously.
The condenser 9 is maintained at the appro-priate temperature by the use of a liquid or gaseous refrigerant in a typical refrigerant cycle When using a gas as a refrigerant, it is introduced into the shell 11 of the condenser 9 via line 21 and removed via line 22, passed through a compressor 23, cooled in heat exchanger 24, passed through expansion valve 25 and returned to the shell 11. As the refrigerant there may be used any gas which will provide the satisfactory cooling effect for the condenser, such as sulfur dioxide.
Preferably the jacket temperature is maintained at about 25F. ~4C.). A liquid refrigerant may be similarly used, without the employment of an expansion valve;
it will be vaporized in shell 11 by the condensing of - 35 the sulfur trioxide and re-liquefied in compressor 23 The pressure of the condenser and other equipment utilized to process sulfur trioxide gas is maintained substantially at atmospheric pressure.
However, pressures may be as high as 8-10 psig (0.56-0.7 kg/cm gauge) or, in a high pressure plant, 75 psig ~5.25 kg/cm2 gauge).
Sulfur trioxide thus recovered is substantially pure sulfur trioxide, although small amounts of sulfur dioxide may also be condensed and contained in the product; thus, the process according to the invention is capable of producing a relatively pure liquid sulur trioxide product from gases containing relatively small amounts of this substance. In general, as known in the art, the condenser will only serve to condense a portion of the sulfur trioxide contained in the gases treated. However, the refrigerant gas utiliæed to cool the condenser 9 can be varied in order to recover more sulfur trioxide. For e~ample, if additional recovery is desired, a refrigerant capable o~ producing lower gas temperatures in the condenser, such as dichlorodifluoromethane, could be utilized. Alternatively, the pressure at the inlet of compressor 22 could be lowered. These techni~ues for producis~g desired gas temperatures in a condenser by adjustment of a compression-exparlsion cycle are well known to those skilled in the art.
In general, recovery o~ additional sulfur trioxide from the uncondensed gases in line 15 is not advantageous since it would be necessary to compress such gases to a higher pressure. However, if such were desired, the gases would be re-introduced into the system via line 8. Preferably, the sulfur trioxide values in these gases would be utilized by psssing the gases through line 15 into a sulfuric acid drying tower or an absorption tower in an oleum plaslt. Al-ternatively, the gases could be passed through ~ ~55~
g purification equipment to remove sulfur trioxide and/or other pollutants, and then vented.
Example The following represents an example of a process according to the invention, with reference to the drawing.
A gas containlng 8.16% by volume sulfur tri-oxide and having a flow rate of 100 lb. mol. per hour (45.4 kg. mol. per hour) and at a temperature of 350 to 500F. (177 to 260C.) is introduced into a water-cooled heat exchanger 3 in which it is cooled to a temperature of about 130F. (54.5C.). The gas is then passed into a mist eliminator 5 and then further cooled to a temperature of 80 to 90F, (26.7 to 32C.) in heat exchanger 7 by heat exchange with exiting gases in line 14. The gas is then conve~ed via line 8 into a condenser 9 equipped with helically arranged blades 12 mounted on a rotating drum 12a driven by a motor 13. The condenser is equipped with a refri~erat~
ing jacket lI supplied with pure sulfur dioxide re-frigerant such that the jacket temperature is 25F. and the pressure is 4.38 psig. (0.31 kg./sq. cm.). In the condenser, the sulfur trioxide con~aining gas is cooled to 30F., whereupon approximately 30% of the sulfur trioxide in the gas is condensed, removed from the condenser through outlet, 16 melted in tank 18 and recovered as liquid product.
Back~round and Prior Art ~his invention relates to a process for the productioll of sulfur trioxide in liquid form and more particularly to its recovery in liquid form by conden-sation from gases. It is particularly useful for the recovery or sulfur trioxide in liquid form rom gases relatively dilute in sulfur trioxide, particularly such gases containing less than 15% sulfur trioxide by volume. This process provides a method by which relatively pure sulfur trioxide can be recovered in liquid form from gases containing sulfur trioxide and other gaseous components. Liquid sulfur trioxide is a valuable product, being useful, for instance, as a reagent fox production of alkylbenzene sulfonates and in tertiary oil recovery.
In general, in present pract~ce, liquid sul-fur trioxide is obtained by absorption of sulfur trioxide from a gas containing the same in sulfuric acid to form oleum, followed by boiling the oleum in a separate operation and condensing the sulfur trioxide evolved.
Such a condensing operation can be troublesome because of freezing of sulfur trloxide on the condenser tubes.
The freezing point of sulfur trioxide is about 85F.
~29.5C.). In general, in condensing sulfur trioxide from a gas containing the same, difficulties are caused by the fact that the temperatures required for appreciable recovery of sulfur trioxide by condensa-tion are below this freezing point, resulting in the formation of solid sulfur trioxide, which can result in plugging of the equipment, requiring steps to clear the equipment and remove the sulfur trioxide. Solid sulfur trioxide may exist in three separate forms, generally referred to as the alpha-, beta- and gamma-forms, see for instance, Brasted, "Comprehensive Inorganic Chemistry", Vol. 8, pp. 134-138 (1961). The gamma-form exists in ice-like cryst~ls and is the most volatile and easiest to melt. The beta- and alph3-forms have asbestos-llke crystals and are more difficult to melt, with the alpha-form being the most difficult.
In general, when sulfur trioxide is condensed, a liquid is first formed. This them becomes converted to the gamma-solid form, which can become further converted to the beta- and alpha-forms.
In U.S. patent 2,510,684, there is provided a substantial amount of information concerning the conditions under which sulfur trioxide can be condensed from gases containing it. However, this patent requires that, to effect the condensation of the sulfur trioxide, the gaseous mixture contain much more than 15% sulfur dioxide. Condensation under these conditions is affected by the use of pressure and relatively high concentrations of sulfur dioxide.
Sulfur trioxide gas is c~nventionally pro-duced by combustion of sulfur ~r ~sulfur-containing wastes, such as sludges containing ~ulfuric acid, to produce sulfur dioxide, followed b~ catalytic oxidation of the sulfur dioxide to sulfur tri~xide in the presence 1 ~55~;~4 --3-- `
of a metallic catalyst. When the co~bustion is con-ducted with air, the gases leaving thie sulfur dioxide converter generally contain from abouit 5 to about 13%
sulfur trioxide by volume. If oxygen is utiliæed for combustion, the gas exiting the sulfur dioxide con-verter will contain a much greater co~centration of sul-fur trioxide, generally from 50 to 8ff~ by volume, and a correspondingly lesser amount of in/ert gases (nitro-gen, carbon dioxide, etc.) However, în order to condense this sulfur trioxide accord~ng to the process of U.S. patent 2,510,684, it would be necessary to conduct an incomplete conversion of the sulfur dioxide, in order that the gases leaving the converter contain at leas~ 15% S02. This would require recycle of the unconverted sulfur dioxide to the converter, which pro- -vides a disadvantage as opposed to once-through processes such as absorption of sulfur trioxide in sulfuric acid.
It is particularly difficult to recoYer sulfur trioxide ~y condensation from gases containing lt in relatively dilute concentrations, for example 15 vol.% or less.
Summary of the Invention In brief, this invention comprises a process for recovering sulfur trioxide in liquid form from a gas containing sulfur trioxide comprising adjusting the temperature of the gas to a temperature from about 80F. to about 90F. (about 26.7C. to about 32C.), continuously introducing the gas hav~ng such tempera-ture into a condensing apparatus maintained at a temperature of from about 53F. to a~out 0F. (about 11C. to about -18C.), whereby sul~ur trioxide is caused to condense from the gas; ~ontinuously removing condensed sulfur trioxide from the con~enser suraces, continuously conveying the condense~ sulfur trioxide out of the condensing apparatus, andl subsequently melting the condensed sulfur trioxide to produce liquid sulfur trioxide.
.
11~5~
The process as thus defined permits the recovery of sul~ur trioxide in liquid form from gases containing it without requiring absorption into sulfuric acid and boiling and distill~tion of the oleum thus produced. The process as herein defined also provides a satisfactory method of recovering sulfur trioxide in liquid form from gases containing relatively low concentrations of sulfur trioxide~ by direct condensation.
Description of the Draw_ g The drawing represents a sLmplified flow sheet for the conduct of the process according to one embodi ment of this invention.
Detailed Description of the Invention For purposes of convenience, this invention will be described with reference to the drawing, which relates to a process for recovery of sulfur trloxide in liquid form from gases containing relatively low concentrations of sulfur trioxide, generally from 5%
to less than 15% by volume. However, it should be understood that the principle of this invention is applicable to the recovery of sulfur trioxide from gases con~aining substantially greater concentrations thereof, for example, from gases produced by combustion of sulfur or sulfur-containing materials with oxygen or oxygen-enriched air (as-opposed to air). It should, furthermore, be understood that the principle of the present invention is equally applicable to the recovery of sulfur trioxide from gases containing the same resulting from any other source or method or production.
In general, it is not now economically practical to recover sulfur trioxide from gases containing concentra-tions thereof of less than about 5% by volume, although the process described herein is capable o~ recovering .. . . .
11556~4 sulur trioY.ide from such gases containing it in low concentrations.
Referring now to the clrawing, a gas contain-ing up to about 15% sul~ur triaxide emanating from a S source 1 and generally at an elevated temperature, is passed through line ~ into a heat exchanger 3, which may be cooled by introduction of water into the shell side thereof in line 26 and removal of heated water or steam in line 27. The gas thus cooled is then passed through line 4 into mist eliminator 5 in which acid mis~ is removed. The gas is then passed through line 6 into a heat exchanger 7 in which it is cooled to a temperature of from about 80F. to about 90F.
(about 26.7C. to about 32C.). As shown in the drawing~
the cooling is preferably accomplished by indirect heat exchange with gases from which sulfur trioxide has been removed, introduced into heat exchanger 7 through line 14 and removed through line 15.
The thus cooled g~s containing sulfur trioxide is passed through line ~ into a condensing apparatus generally indicated as 9, and maintained at a tempera-ture of from about 53F. to abaut 0F. (about 11C. to about -18C.~, preferably about 53F. to about 10F.
(about 11C. to about -12C.), and most preferably about 40F. to a~ ut 25F. (about 5C. to about -4C.).
This apparatus contains an interiorly located condensing section 10 surrounded by a cooling jacket 11. ~lithin the condensing section 10 are contained helical scraper blades 12, driven by a motor 13, the blades being arranged so as to scrape the inner surface of the con-densing chamber 10. The drawing depicts the condenser as being horizontally disposed. However, vertical or incllned condensers may be utilized.
The use of such a scraped surface condenser with helically arranged scraper blades enables the con-tinuous removal of product sulfur trioxide from the _fi_ interior sur~ace of the condenser as it is condensed, and continuous conveying of the condensed sulfur tri-oxlde through the condenser, preventing freezing ~nd plugging of equipment. Preferably, the helical blades S are mounted on a drum 12a closed at both ends, the axis or rotation of which is coincidental with the long axis of the condenser chamber. This continuous removal and conveying are enhanced by warming the in-terior of the drum 12a, for example by electrical heating or by passing a warmer fluid (liquid or gas) through it, as is conventional in such e~uipment, to prevent sticking of the solid sulfur trioxide to the surfaces. Split flights and vanes may also be provided in the condenser, to break up lumps of solid. Pre-ferably, the entering gas flow is directed through a relatively narrow annulus existing between the cold condenser surface and the rotating drum 12a which bears the scraper blades 12. The exact clearance between the condenser and the rotating drum is a function of the desired gas velocity and the amount of sulfur trioxide expected to be condensed and removed, and is readily determinable by those skilled in the art. The amount of sulfur trioxide expected to be condensed under these circumstances depends on the concentration of the sulfur trioxide in the incoming gas and the temperature and the pressure of the environment, and is readily determinable by methods known to those skilled in the art.
The uncondensed gases are removed from the condenser 9 through line 14 and may be advantageously utilized to cool the incoming gas in heat exchanger 7.
They are removed via line 15 and are either passed to treatment to remo~e pollutants and other undesirable material before being vented to the atmosphere, or passed to further processing, as discussed below ..
115~6~4 The sulfur trioxide which condenses on the interior surfaces of the condensing chamber 10 is removed by the blades 12 and carried thereby along the length of the chamber 10. The condensed sulfur trioxide may be in the form of predominantly gamma-crystals, or may be a slurry or "slush" of such crystals with liquid sulfur trioxide. The sulfur trioxide is removed from the condensing chamber via outlet 16 in which ~s located a star valve 17 which forms a rotating seal and also serves to extract condensed sulfur trioxide at a regular rate from the condenser. Outlet 16 and star valve 17 may be iacketed and heated in a similar manner to dru~ 12a, to pre-vent sticking of sulfur trioxide. The sulfur trioxide is conveyed by the star seal 17 into a melting tank 18 equipped with melting coils 19 through which may be introduced steam or hot water, and an agitator 26.
Sulfux trioxide is melted in melting tank 18 and liquid sulfur trioxide is removed via line 20. Preferably the melting and removai are performed continuously.
The condenser 9 is maintained at the appro-priate temperature by the use of a liquid or gaseous refrigerant in a typical refrigerant cycle When using a gas as a refrigerant, it is introduced into the shell 11 of the condenser 9 via line 21 and removed via line 22, passed through a compressor 23, cooled in heat exchanger 24, passed through expansion valve 25 and returned to the shell 11. As the refrigerant there may be used any gas which will provide the satisfactory cooling effect for the condenser, such as sulfur dioxide.
Preferably the jacket temperature is maintained at about 25F. ~4C.). A liquid refrigerant may be similarly used, without the employment of an expansion valve;
it will be vaporized in shell 11 by the condensing of - 35 the sulfur trioxide and re-liquefied in compressor 23 The pressure of the condenser and other equipment utilized to process sulfur trioxide gas is maintained substantially at atmospheric pressure.
However, pressures may be as high as 8-10 psig (0.56-0.7 kg/cm gauge) or, in a high pressure plant, 75 psig ~5.25 kg/cm2 gauge).
Sulfur trioxide thus recovered is substantially pure sulfur trioxide, although small amounts of sulfur dioxide may also be condensed and contained in the product; thus, the process according to the invention is capable of producing a relatively pure liquid sulur trioxide product from gases containing relatively small amounts of this substance. In general, as known in the art, the condenser will only serve to condense a portion of the sulfur trioxide contained in the gases treated. However, the refrigerant gas utiliæed to cool the condenser 9 can be varied in order to recover more sulfur trioxide. For e~ample, if additional recovery is desired, a refrigerant capable o~ producing lower gas temperatures in the condenser, such as dichlorodifluoromethane, could be utilized. Alternatively, the pressure at the inlet of compressor 22 could be lowered. These techni~ues for producis~g desired gas temperatures in a condenser by adjustment of a compression-exparlsion cycle are well known to those skilled in the art.
In general, recovery o~ additional sulfur trioxide from the uncondensed gases in line 15 is not advantageous since it would be necessary to compress such gases to a higher pressure. However, if such were desired, the gases would be re-introduced into the system via line 8. Preferably, the sulfur trioxide values in these gases would be utilized by psssing the gases through line 15 into a sulfuric acid drying tower or an absorption tower in an oleum plaslt. Al-ternatively, the gases could be passed through ~ ~55~
g purification equipment to remove sulfur trioxide and/or other pollutants, and then vented.
Example The following represents an example of a process according to the invention, with reference to the drawing.
A gas containlng 8.16% by volume sulfur tri-oxide and having a flow rate of 100 lb. mol. per hour (45.4 kg. mol. per hour) and at a temperature of 350 to 500F. (177 to 260C.) is introduced into a water-cooled heat exchanger 3 in which it is cooled to a temperature of about 130F. (54.5C.). The gas is then passed into a mist eliminator 5 and then further cooled to a temperature of 80 to 90F, (26.7 to 32C.) in heat exchanger 7 by heat exchange with exiting gases in line 14. The gas is then conve~ed via line 8 into a condenser 9 equipped with helically arranged blades 12 mounted on a rotating drum 12a driven by a motor 13. The condenser is equipped with a refri~erat~
ing jacket lI supplied with pure sulfur dioxide re-frigerant such that the jacket temperature is 25F. and the pressure is 4.38 psig. (0.31 kg./sq. cm.). In the condenser, the sulfur trioxide con~aining gas is cooled to 30F., whereupon approximately 30% of the sulfur trioxide in the gas is condensed, removed from the condenser through outlet, 16 melted in tank 18 and recovered as liquid product.
Claims (7)
1. A process for recovering sulfur trioxide in liquid form from a gas containing sulfur trioxide comprising:
(a) Adjusting the temperature of the gas to a temperature of from about 80°F. to about 90°F.;
(b) continuously introducing the gas into a condensing apparatus maintained at a tempera-ture of from about 53°F. to about 0°F. whereby sulfur trioxide is caused to condense from the gas;
(c) continuously removing condensed sulfur trioxide from the condenser surfaces;
(d) continuously conveying the condensed sul-fur trioxide out of the condensing apparatus;
and (e) melting the condensed sulfur trioxide to produce liquid sulfur trioxide.
(a) Adjusting the temperature of the gas to a temperature of from about 80°F. to about 90°F.;
(b) continuously introducing the gas into a condensing apparatus maintained at a tempera-ture of from about 53°F. to about 0°F. whereby sulfur trioxide is caused to condense from the gas;
(c) continuously removing condensed sulfur trioxide from the condenser surfaces;
(d) continuously conveying the condensed sul-fur trioxide out of the condensing apparatus;
and (e) melting the condensed sulfur trioxide to produce liquid sulfur trioxide.
2. A process according to Claim 1 in which the gas to be treated contains between about 5 and about 15% by volume of sulfur trioxide.
3. A process according to Claim 1 in which uncondensed gas exiting the condenser is used to cool the gas in step (a) by indirect heat exchange.
4. A process according to Claim 1 in which the condenser is maintained at a temperature of from about 53°F. to about 10°F.
5. A process according to Claim 1 in which the condenser is maintained at a temperature of from about 40°F. to about 25°F.
6. A process according to Claim 1 in which the condenser is maintained at about atmospheric pressure.
7. A process according to Claim 1 in which the condensed sulfur trioxide is continuously melted in step (e) and liquid sulfur trioxide is continuously recovered from the melting step.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US5366679A | 1979-07-02 | 1979-07-02 | |
| US53,666 | 1979-07-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1155634A true CA1155634A (en) | 1983-10-25 |
Family
ID=21985766
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000355154A Expired CA1155634A (en) | 1979-07-02 | 1980-06-30 | Production of liquid sulfur trioxide |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS609964B2 (en) |
| CA (1) | CA1155634A (en) |
| DD (1) | DD151734A5 (en) |
| DE (1) | DE3023817A1 (en) |
| GB (1) | GB2051766B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5822303A (en) * | 1981-07-31 | 1983-02-09 | Kanto Denka Kogyo Kk | High vanadium alloy steel fine powder and manufacture thereof |
| DE102005032797B4 (en) * | 2005-07-14 | 2007-07-05 | Outokumpu Technology Oy | Process and installation for the safe condensation of pure SO3 from starting gases containing sulfur trioxide |
-
1980
- 1980-06-25 DE DE19803023817 patent/DE3023817A1/en not_active Withdrawn
- 1980-06-27 GB GB8021210A patent/GB2051766B/en not_active Expired
- 1980-06-30 CA CA000355154A patent/CA1155634A/en not_active Expired
- 1980-07-01 JP JP8988680A patent/JPS609964B2/en not_active Expired
- 1980-07-02 DD DD22233980A patent/DD151734A5/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE3023817A1 (en) | 1981-01-15 |
| JPS609964B2 (en) | 1985-03-14 |
| JPS569202A (en) | 1981-01-30 |
| GB2051766A (en) | 1981-01-21 |
| DD151734A5 (en) | 1981-11-04 |
| GB2051766B (en) | 1983-01-12 |
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