CA1274969A - Turbulent cocurrent contacting of gas and liquid in process where solids are formed or present - Google Patents
Turbulent cocurrent contacting of gas and liquid in process where solids are formed or presentInfo
- Publication number
- CA1274969A CA1274969A CA000525380A CA525380A CA1274969A CA 1274969 A CA1274969 A CA 1274969A CA 000525380 A CA000525380 A CA 000525380A CA 525380 A CA525380 A CA 525380A CA 1274969 A CA1274969 A CA 1274969A
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- contactor
- contaminant
- solids
- gas
- 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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- Gas Separation By Absorption (AREA)
Abstract
ABSTRACT
The present invention relates to a process for the improvement of mass transfer between a gas containing a contaminant and a liquid wherein solids are either present or formed during the removal of the contaminant in a contactor. The benefit of the process is that the configuration allows for recycle of the liquid. after regeneration. without the costly removal of all the solids. Another aspect of the invention is that the absorbed contaminant is chemically reacted to change is composition, thereby substantially negating the equilibrium effects in the absorption process and dependant upon that reaction the chemically changed contaminant can be precipitated out as a solid.
The present invention relates to a process for the improvement of mass transfer between a gas containing a contaminant and a liquid wherein solids are either present or formed during the removal of the contaminant in a contactor. The benefit of the process is that the configuration allows for recycle of the liquid. after regeneration. without the costly removal of all the solids. Another aspect of the invention is that the absorbed contaminant is chemically reacted to change is composition, thereby substantially negating the equilibrium effects in the absorption process and dependant upon that reaction the chemically changed contaminant can be precipitated out as a solid.
Description
~7~9fi9 TURBULENT, CCCURRENT, CONTACTING OF GAS ~ND LIQUID IN PROCESSES
~HERE SOLIDS ARE FORMED OR ARE OTHERWISE PRESENT
TECHNICAL FIELD
The present invention relates to a process for the improvement of mass transfer between a gas containing a contaminant and a liquid wherein solids are either present or formed during the contacting of the gas and the liquid. The invention also relates to a process configuration which allows for recycle of the liquid. after regeneration. without the costly removal of all the solids. Another aspect of the invention is that the absorbed contaminant is chemically reacted to change its composition.
thereby substantially negating the equilibrium effects in ~he absorption process and dependant upon that reaction the chemically changed contaminant can be precipitated out as a solid.
BACKGROUND OF THE INVENTION
Various processes have been known and utilized in the prior art for the removal of contaminants from--contaminant-containing gas streams.
Additionally. the use of a catalyst to chemically change the absorbed contaminant to help increase mass transfer is known.
In U.S. Pat. No. 4,014.983, a process is disclosed for the removal of hydrogen sulfide from a gas stream by reaction with sulfur dioxide to form sulfur in the presence of an aqueous chelated iron solution as a catalyst or oxidation-reduction reagent. The reaction of hydrogen sulfide with sulfur dioxide is carried out in a first contacting zone, and the chel~ted iron solution ls contacted with sulfur dioxide in a second contacting zone and then recycled to the first contacting zone.
9~
The contacting zones may comprise any suitable liquid vapor contacting means such as the conventional packed beds, plates, or trays.
~nother process Eor the removal of contaminants Erom a contaminant-containing gas is the StretEord process. In this process, the Eeed gas is contacted with the liquid in a venturi contactor and vertical tower which usually contains a packing. The solution absorbs the hydrogen sulfide from the gas it contacts, the absorbed hydrogen sulfide is oxidized to elemental sulfur by the vanadic sal-t in the solution. In turn the vanadic salt is reduced to the vanadous form. The rich solution from the contactor is sent to a reactor to provide sufficient reaction time for the oxidation of 15 absorbed hydrogen sulfide to elemental sulfur. The solution is then reacted to regenerate the catalyst and the sulfur is removed by froth floatation.
The ar-t as represented above has failed to disclose an efficient manner to remove contaminants from gas 20 streams without the use of large contactor e~ulpment and the need to remove the solids formed in the process prior to recycling the absorption solution to avoid plugging problems. Additionally, the prior art has failed to minimize capital expenditures. The present 25 invention provides a solution to problems such as noted above.
SUMMARY OF THE INVENTION
The presen-t invention relates to a process for 30 improved mass transfer between a gas containing a contaminant and a li~uid wherein solid materials are either formed by reaction or are present in either phase which comprises the steps of: contacting, in a contactor which employs means for maintaining high turbulence and 35 velocity during the contact cocurrently, said gas containing a contaminant and said liquid, thereby ~ 3~
absorbing the contaminant in said liquid; reacting, in situ, the absorbed contaminant to cause a chanye in the contaminant's composltion; optionally, precipitating out as solids the changed contaminant's composition;
separating out a contaminant-free gas Erom said liquid, prior to recycling said liquid to the contactor; and recycling said liquid to the contactor.
BRIEF DESCRIPTION OF THE DRAWING
The single Figure of the drawing is a schematic diagram of the process flow in its preferred embodiment.
DETAILED DESCRIPTION OF THE INVENTION
With reference to the drawing, a gas containing a contaminant, e.g. refinery gas with hydrogen sulfide or hydrogen sulfide and sulfur dio~ide as the contaminant, via line 1, along with a recycled liquid, e.g. a chelated iron solution, which may have entrained solids, via line 3, are fed to contactor 5, which has means for maintaining high turbulence and velocity during contact.
The high turbulence and velocity in the contactor promote an efficient mass transfer of the contaminant from the gas to the liquid and help keep the contactor free from solids deposition. During the contact between the gas containing a contaminant and the recycled liquid, the contaminant is absorbed in the liquid. The absorbed contaminant is then chemically reacted to cause a change in i-ts composition, e.g. producing elemental sulfur when a hydrogen sulfide and sulfur dioxide contamina-ted gas and a chelated iron solution liquid are the feeds to the contactor. This change in composition is important because it eliminates or at least negates the equilibrium effects on the mass transfer of -the contaminant from the gas to the liquid and makes the use of a cocurrent process practical.
In its preferred embodiment, contactor 5 is a static mixer; the term static mixer being defined as a ~' .~.~
cylindrical pipe having either screw~flight or corrugates plate type internals. ~dditionally, in one oE its embodiments, the chemical reaction causes not only a change in the composi-tion of the contaminant but causes the new composi-tion to precipitate out of solution.
In the case that the contactor is a static mixer, the contactor cross-sectional area should be such that the intensity of liquid flow lies preferably between about 150 and about 3,000 U.S. gallons per minute per square foot of cross-sectional area and more preferably between about 300 and about 1,200 U.S. gallons per minute per square foot of cross-sectional area. Below this preferred range, the mass transfer effectiveness of the equipment is reduced significan-tly because of lower velocities, increased size of the equipment, and an increased likelihood of solids deposition. Optionally, to improve the hydraulic conditions, unregenerated liquid from the liquid-gas separator may be recycled to the contactor. Above this preferred range, increased pressure drop causes power costs to become excessive and the reduced liquid residence time may not provide an adequate time for the necessary liquid phase reactions.
The absorber length will depend on the purification required, generally about 15 feet of internals will provide enough mass transfer to occur to enable some 90 weight percent of the contaminant to be removed.
Preferablyl the contactor is arranged vertically with fluid flow downward. A simple coarse-spray 30 distributor for the liquid is adequate since the internal surfaces insure good distribution before much downward distance is covered. Particulate solids may be allowed to remain in the liquid and will not block this -type of distributor. Occasionally, it will be necessary 35 to remove build-up of solids on the internals by high ~'7 - ~a -liquid irrigation. Solids removal, if required, can be achieved by injecting abrasive-coated sponge balls. The ball injectlon and removal systems are commercially available and are not part oE this invent:ion.
The eEfluent from contactor 5 is Eed to separator 7, where a contaminant-Eree or at least a contaminant-lean gas is removed from the process via line 9. The liquid along with the entrained solids, via line ll, and a reaction gas, via line 13, preferably, in a high liquid to gas ratio, are fed to reactor 15 for regeneration of the liquid. In the preferred embodiment, the reactor would have means for maintaining turbulence during -the regeneration, such as a static mixing section. In the case of the hydrogen sulfide-sulfur dioxide contaminant gas and the chelated ironsolution liquid, the reaction gas would be air.
The effluen-t from the regeneration reactor, via line 17 is fed to separator l9 for removal of the reaction gas, which is vented via line 21, the regenerated liquid along with the entrained solids is then fed, via line 23, to separator 25 for removal of some of the solids and any remaining reaction gas. It is important to note that all of the solids '.'~
~7~
need not be removed from the liquid. The solids. whlch are removed, exit via line 27, us~lally as a slurry mixture, and any remaining reactlon gas is vented via line 29. The reduced-solids. regenerated liquld is removed from separator ~5 via line 31 and is Eed to pump 33 for recycling ~o contactor 5, via line 3.
In the case where gas contamination levels are too high for effective removal in one contractor, a series of two or more contactor-separator units are posslble. With the use of two contactor-separator units, the effluent from the first contactor would be fed to the first separator and the contaminant-lean gas from the first separator would be fed along with fresh recycled liquid to a second contactor. The effluent from the second contac~or would be fed to the second separator. The contaminant-lean gas from the second separator would be removed from the process as treated gas and the liquid from both the first and second separators would be mixed and fed to the regeneration reactor. The cycle would follow a similar scheme as more contactor-separator units are added.
The present invention has been described for the purpose of removing contaminants from gas streams in which solids are either present or are formed. In addition though, this invention is applicable to any process whereln a particular component or possibly components of a gas phase are belng absorbed into the li~uid phase and either solids are present or are formed in the process.
The present invention has been described with reference to a preferred embodiment thereof. However, this embodiment should not be considered a limltatlon on the scope of the invention, which scope should be ascertalned by the following clalms.
~HERE SOLIDS ARE FORMED OR ARE OTHERWISE PRESENT
TECHNICAL FIELD
The present invention relates to a process for the improvement of mass transfer between a gas containing a contaminant and a liquid wherein solids are either present or formed during the contacting of the gas and the liquid. The invention also relates to a process configuration which allows for recycle of the liquid. after regeneration. without the costly removal of all the solids. Another aspect of the invention is that the absorbed contaminant is chemically reacted to change its composition.
thereby substantially negating the equilibrium effects in ~he absorption process and dependant upon that reaction the chemically changed contaminant can be precipitated out as a solid.
BACKGROUND OF THE INVENTION
Various processes have been known and utilized in the prior art for the removal of contaminants from--contaminant-containing gas streams.
Additionally. the use of a catalyst to chemically change the absorbed contaminant to help increase mass transfer is known.
In U.S. Pat. No. 4,014.983, a process is disclosed for the removal of hydrogen sulfide from a gas stream by reaction with sulfur dioxide to form sulfur in the presence of an aqueous chelated iron solution as a catalyst or oxidation-reduction reagent. The reaction of hydrogen sulfide with sulfur dioxide is carried out in a first contacting zone, and the chel~ted iron solution ls contacted with sulfur dioxide in a second contacting zone and then recycled to the first contacting zone.
9~
The contacting zones may comprise any suitable liquid vapor contacting means such as the conventional packed beds, plates, or trays.
~nother process Eor the removal of contaminants Erom a contaminant-containing gas is the StretEord process. In this process, the Eeed gas is contacted with the liquid in a venturi contactor and vertical tower which usually contains a packing. The solution absorbs the hydrogen sulfide from the gas it contacts, the absorbed hydrogen sulfide is oxidized to elemental sulfur by the vanadic sal-t in the solution. In turn the vanadic salt is reduced to the vanadous form. The rich solution from the contactor is sent to a reactor to provide sufficient reaction time for the oxidation of 15 absorbed hydrogen sulfide to elemental sulfur. The solution is then reacted to regenerate the catalyst and the sulfur is removed by froth floatation.
The ar-t as represented above has failed to disclose an efficient manner to remove contaminants from gas 20 streams without the use of large contactor e~ulpment and the need to remove the solids formed in the process prior to recycling the absorption solution to avoid plugging problems. Additionally, the prior art has failed to minimize capital expenditures. The present 25 invention provides a solution to problems such as noted above.
SUMMARY OF THE INVENTION
The presen-t invention relates to a process for 30 improved mass transfer between a gas containing a contaminant and a li~uid wherein solid materials are either formed by reaction or are present in either phase which comprises the steps of: contacting, in a contactor which employs means for maintaining high turbulence and 35 velocity during the contact cocurrently, said gas containing a contaminant and said liquid, thereby ~ 3~
absorbing the contaminant in said liquid; reacting, in situ, the absorbed contaminant to cause a chanye in the contaminant's composltion; optionally, precipitating out as solids the changed contaminant's composition;
separating out a contaminant-free gas Erom said liquid, prior to recycling said liquid to the contactor; and recycling said liquid to the contactor.
BRIEF DESCRIPTION OF THE DRAWING
The single Figure of the drawing is a schematic diagram of the process flow in its preferred embodiment.
DETAILED DESCRIPTION OF THE INVENTION
With reference to the drawing, a gas containing a contaminant, e.g. refinery gas with hydrogen sulfide or hydrogen sulfide and sulfur dio~ide as the contaminant, via line 1, along with a recycled liquid, e.g. a chelated iron solution, which may have entrained solids, via line 3, are fed to contactor 5, which has means for maintaining high turbulence and velocity during contact.
The high turbulence and velocity in the contactor promote an efficient mass transfer of the contaminant from the gas to the liquid and help keep the contactor free from solids deposition. During the contact between the gas containing a contaminant and the recycled liquid, the contaminant is absorbed in the liquid. The absorbed contaminant is then chemically reacted to cause a change in i-ts composition, e.g. producing elemental sulfur when a hydrogen sulfide and sulfur dioxide contamina-ted gas and a chelated iron solution liquid are the feeds to the contactor. This change in composition is important because it eliminates or at least negates the equilibrium effects on the mass transfer of -the contaminant from the gas to the liquid and makes the use of a cocurrent process practical.
In its preferred embodiment, contactor 5 is a static mixer; the term static mixer being defined as a ~' .~.~
cylindrical pipe having either screw~flight or corrugates plate type internals. ~dditionally, in one oE its embodiments, the chemical reaction causes not only a change in the composi-tion of the contaminant but causes the new composi-tion to precipitate out of solution.
In the case that the contactor is a static mixer, the contactor cross-sectional area should be such that the intensity of liquid flow lies preferably between about 150 and about 3,000 U.S. gallons per minute per square foot of cross-sectional area and more preferably between about 300 and about 1,200 U.S. gallons per minute per square foot of cross-sectional area. Below this preferred range, the mass transfer effectiveness of the equipment is reduced significan-tly because of lower velocities, increased size of the equipment, and an increased likelihood of solids deposition. Optionally, to improve the hydraulic conditions, unregenerated liquid from the liquid-gas separator may be recycled to the contactor. Above this preferred range, increased pressure drop causes power costs to become excessive and the reduced liquid residence time may not provide an adequate time for the necessary liquid phase reactions.
The absorber length will depend on the purification required, generally about 15 feet of internals will provide enough mass transfer to occur to enable some 90 weight percent of the contaminant to be removed.
Preferablyl the contactor is arranged vertically with fluid flow downward. A simple coarse-spray 30 distributor for the liquid is adequate since the internal surfaces insure good distribution before much downward distance is covered. Particulate solids may be allowed to remain in the liquid and will not block this -type of distributor. Occasionally, it will be necessary 35 to remove build-up of solids on the internals by high ~'7 - ~a -liquid irrigation. Solids removal, if required, can be achieved by injecting abrasive-coated sponge balls. The ball injectlon and removal systems are commercially available and are not part oE this invent:ion.
The eEfluent from contactor 5 is Eed to separator 7, where a contaminant-Eree or at least a contaminant-lean gas is removed from the process via line 9. The liquid along with the entrained solids, via line ll, and a reaction gas, via line 13, preferably, in a high liquid to gas ratio, are fed to reactor 15 for regeneration of the liquid. In the preferred embodiment, the reactor would have means for maintaining turbulence during -the regeneration, such as a static mixing section. In the case of the hydrogen sulfide-sulfur dioxide contaminant gas and the chelated ironsolution liquid, the reaction gas would be air.
The effluen-t from the regeneration reactor, via line 17 is fed to separator l9 for removal of the reaction gas, which is vented via line 21, the regenerated liquid along with the entrained solids is then fed, via line 23, to separator 25 for removal of some of the solids and any remaining reaction gas. It is important to note that all of the solids '.'~
~7~
need not be removed from the liquid. The solids. whlch are removed, exit via line 27, us~lally as a slurry mixture, and any remaining reactlon gas is vented via line 29. The reduced-solids. regenerated liquld is removed from separator ~5 via line 31 and is Eed to pump 33 for recycling ~o contactor 5, via line 3.
In the case where gas contamination levels are too high for effective removal in one contractor, a series of two or more contactor-separator units are posslble. With the use of two contactor-separator units, the effluent from the first contactor would be fed to the first separator and the contaminant-lean gas from the first separator would be fed along with fresh recycled liquid to a second contactor. The effluent from the second contac~or would be fed to the second separator. The contaminant-lean gas from the second separator would be removed from the process as treated gas and the liquid from both the first and second separators would be mixed and fed to the regeneration reactor. The cycle would follow a similar scheme as more contactor-separator units are added.
The present invention has been described for the purpose of removing contaminants from gas streams in which solids are either present or are formed. In addition though, this invention is applicable to any process whereln a particular component or possibly components of a gas phase are belng absorbed into the li~uid phase and either solids are present or are formed in the process.
The present invention has been described with reference to a preferred embodiment thereof. However, this embodiment should not be considered a limltatlon on the scope of the invention, which scope should be ascertalned by the following clalms.
Claims (13)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED
AS FOLLOWS:
1. A process for improved mass transfer between a gas containing a contaminant and a liquid wherein solid materials are either formed by reaction or are present in either phase which comprises the steps of:
(a) contacting, in a contactor which employs means for maintaining high turbulence and velocity during the contact, cocurrently said gas containing a contaminant and said liquid thereby absorbing the contaminant in said liquid;
(b) reacting, in situ, the absorbed contaminant to cause a change in the contaminant's composition;
(c) separating out a contaminant-lean gas from said liquid and any solids present therein;
(d) regenerating said liquid; and (e) recycling said liquid to the contactor.
(a) contacting, in a contactor which employs means for maintaining high turbulence and velocity during the contact, cocurrently said gas containing a contaminant and said liquid thereby absorbing the contaminant in said liquid;
(b) reacting, in situ, the absorbed contaminant to cause a change in the contaminant's composition;
(c) separating out a contaminant-lean gas from said liquid and any solids present therein;
(d) regenerating said liquid; and (e) recycling said liquid to the contactor.
2. The process of claim 1 which further comprises the step of removing part of solids, present in the liquid, from said liquid, prior to recycling said liquid to the contactor.
3. The process of claim 2 which further comprises the step of precipitating out as solids the changed contaminant's composition.
4. The process of claim 1 wherein the means for maintaining high turbulence is a static mixer.
5. The process of claim 3 wherein the means for maintaining high turbulence is a static mixer.
6. The process of claim 1 which further comprises the step of injecting abrasive-coated sponge balls to the contactor.
7. The process of claim 2 which further comprises the step of injecting abrasive-coated sponge balls to the contactor.
8. The process of Claim 1 which further comprises the step of recycling part of the liquid phase from the contaminant-lean gas liquid separator back to the contactor in order to increase the intensity of the liquid flow through the contactor.
9. The process of Claim 4 wherein the intensity of liquid flow through the contactor is in the range between 150 and about 3.000 U.S. gallons per minute per square foot of cross sectional area of said static mixer.
10. The process of Claim 5 wherein the intensity of liquid flow through the contactor is in the range between 150 and about 3,000 U.S. gallons per minute per square foot of cross sectional area of said static mixer.
11. The process of Claim 4 wherein the intensity of liquid flow through the contactor is in the range between 300 and about 1,200 U.S. gallons per minute per square foot of cross sectional area of said seatic mixer.
12. The process of Claim 5 wherein the intensity of liquid flow through the contactor is in the range between 300 and about 1.200 U.S. gallons per minute per square foot of cross sectional area of said static mixer.
13. The process of Claim 1 wherein said regeneration is carried out in a static mixer.
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Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA525380A CA1274969C (en) | 1985-12-20 | 1986-12-15 | Turbulent cocurrent contacting of gas and liquid in process where solids are formed or present |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US81161885A | 1985-12-20 | 1985-12-20 | |
| US811,618 | 1985-12-20 | ||
| CA525380A CA1274969C (en) | 1985-12-20 | 1986-12-15 | Turbulent cocurrent contacting of gas and liquid in process where solids are formed or present |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA1274969A true CA1274969A (en) | 1990-10-09 |
| CA1274969C CA1274969C (en) | 1990-10-09 |
Family
ID=25207060
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA525380A Expired CA1274969C (en) | 1985-12-20 | 1986-12-15 | Turbulent cocurrent contacting of gas and liquid in process where solids are formed or present |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1274969C (en) |
-
1986
- 1986-12-15 CA CA525380A patent/CA1274969C/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CA1274969C (en) | 1990-10-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 20031009 |