CA2089263A1 - Process for sulfur recovery from a gaseous stream containing hydrogen sulfide under high pressure - Google Patents
Process for sulfur recovery from a gaseous stream containing hydrogen sulfide under high pressureInfo
- Publication number
- CA2089263A1 CA2089263A1 CA002089263A CA2089263A CA2089263A1 CA 2089263 A1 CA2089263 A1 CA 2089263A1 CA 002089263 A CA002089263 A CA 002089263A CA 2089263 A CA2089263 A CA 2089263A CA 2089263 A1 CA2089263 A1 CA 2089263A1
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- Prior art keywords
- reactor
- sulfur
- process according
- catalyst
- gaseous stream
- Prior art date
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-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8603—Removing sulfur compounds
- B01D53/8612—Hydrogen sulfide
-
- 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
- C01B17/02—Preparation of sulfur; Purification
- C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
- C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
- C01B17/046—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process without intermediate formation of sulfur dioxide
-
- 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
- C01B17/02—Preparation of sulfur; Purification
- C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
- C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
- C01B17/046—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process without intermediate formation of sulfur dioxide
- C01B17/0469—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process without intermediate formation of sulfur dioxide at least one catalyst bed operating below the dew-point of sulfur
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Health & Medical Sciences (AREA)
- Materials Engineering (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
- Treating Waste Gases (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
TRANSLATION Amended Text from IPEA
Complete Application Text for Transition into the National Phase of the International Patent Application PCT/EP91/01523 A B S T R A C T
The process of this invention offers the possibility of desulfurizing gaseous streams under high pressure with comparatively low expenditure in apparatus but at a high recovery rate. For this purpose, H2S
is catalytically oxidized directly to sulfur in at least one reactor. With special advantage, two re-actors are used wherein the reactor first in the flow direction, an adiabatically operated reactor without internal cooling, is preferably traversed by the flow from the bottom toward the top, and the reactor that is the second one in the flow direction, a reactor internally cooled with special advantage to a tempera-ture below the sulfur dew point, is traversed by the flow preferably from the top toward the bottom. Usually, differing catalysts are utilized in the two reactors even though also both catalysts consist essentially of TiO2 and selectively oxidize directly H2S, but not H2 and CO. In the first reactor without internal cooling, H2S is selectively oxidized directly by the catalyst under high pressure. The reaction continues in the second, internally cooled reactor, condensed-out sulfur itself acting as a catalyst under the pre-vailing high pressure. Accordingly, there is no need for regeneration of this reactor from liquid sulfur.
Product sulfur is condensed out and separated from the high-pressure gas stream. The entire desulfuriza-tion can be still further improved by reduction of the sulfur compounds and/or sulfur vapors to H2S and/or by an adsorption, a chemisorption, or NaOH scrubbing of the H2S, the residual sulfur compounds and/or the sulfur vapor.
Complete Application Text for Transition into the National Phase of the International Patent Application PCT/EP91/01523 A B S T R A C T
The process of this invention offers the possibility of desulfurizing gaseous streams under high pressure with comparatively low expenditure in apparatus but at a high recovery rate. For this purpose, H2S
is catalytically oxidized directly to sulfur in at least one reactor. With special advantage, two re-actors are used wherein the reactor first in the flow direction, an adiabatically operated reactor without internal cooling, is preferably traversed by the flow from the bottom toward the top, and the reactor that is the second one in the flow direction, a reactor internally cooled with special advantage to a tempera-ture below the sulfur dew point, is traversed by the flow preferably from the top toward the bottom. Usually, differing catalysts are utilized in the two reactors even though also both catalysts consist essentially of TiO2 and selectively oxidize directly H2S, but not H2 and CO. In the first reactor without internal cooling, H2S is selectively oxidized directly by the catalyst under high pressure. The reaction continues in the second, internally cooled reactor, condensed-out sulfur itself acting as a catalyst under the pre-vailing high pressure. Accordingly, there is no need for regeneration of this reactor from liquid sulfur.
Product sulfur is condensed out and separated from the high-pressure gas stream. The entire desulfuriza-tion can be still further improved by reduction of the sulfur compounds and/or sulfur vapors to H2S and/or by an adsorption, a chemisorption, or NaOH scrubbing of the H2S, the residual sulfur compounds and/or the sulfur vapor.
Description
208926~
Complete Application Text - l -Specification PROCESS FOR SULFUR RECOVERY FROM A GASEOUS STREAM
CONTAINING HYDROGEN SULFIDE UND~R HIGH PR~SSURE
The invention relates to à process for the removal of H2S from a gaseous stream under high pres-sure by catalytic direct oxidation of the H2S without thermal combustion for the production of SO2, wherein the catalytic direct oxidation of the H2S is performed in at least one reactor with catalyst bed, internally cooled indirectly by way of a cooling medium.
In numerous crude gas streams, sulfur is contained primarily in the form of H2S. For sulfur removal and, respectively, sulfur recovery, such an H2S-containing, optionally also COS-containing crude gas stream is usually subjected to a physical or chemical washing step; if needed, a hydrolysis for COS
is additionally performed before the washing step.
One process of such a sulfur removal is disclosed, for example, in DE-OS 30 47 830. The regenerating gas is customarily worked up in a sulfur recovery plant, e.g. a Claus plant, with hydrogenation of the Claus tail gas which latter is then recompressed to upstream of the washing stage.
A process has been ~nown from EP-PA
0 283 ~93 describing a catalytic conversion of H2S
with SO2 to elemental sulfur in several reactors with catalyst beds below the sulfur solidification point or the sulfur dew point. By way of multiple-way fittings, the gaseous ~tream is conducted, with cyclic change of direction, over the catalyst beds in order to be able to regenerate, with supply of heat, the catalyst deactivated by elemental sulfur. Reactors ~089263 Complete Application Text - 2 -that can be utilized are conventional Claus reactors as well as also non-adiabatically operated reactors.
The cyclic operation requires that all catalyst beds must be of identical composition and structure.
However, these conventional processes re-quire a voluminous expenditure in apparatus, accompanied by considerable costs.
In many technically relevant applications, the H2S-containing crude gas streams are obtained as gaseous streams under high pressure. Thus, for ex-ample, for energy utilization in "GuD" power stations (gas- and steam-turbine power stations) coal is initially gasified at pressures of between about 20 and 70 bar. The resultant cracked gas is freed, by quenching and possibly by an additional soot scrubbing step, of halogens, their compounds, heavy hydrocarbons, soot, and dust. The thus-obtained H2S-containing H2/CO crude gas mixture is present as a gaseous stream with high pressure. Before the gaseous mixture is conducted into a gas turbine and combusted therein, it must be desulfurized.
Additional examples for H2S-containing high-pressure gases are constituted by H2S-containing natural gas or compressed biogas which, prior to their further processing, must likewise be subjected to desulfuriza-tion.
Desulfurization of a gaseous stream under high pressure is usually performed according to a pro-cess wherein a scrubbing step is employed. In contrast thereto, a process as described above with several cyclically traversed catalyst beds, or those that must be regenerated by heating, is deemed unsuitable in connection with gaseous streams under high pressure since the cyclic reversing of the gaseous streams under 208926;3 Complete Application Text - 3 -high pressure presents a large number of problems, precisely on account of the high pressure.
A process for the catalytic oxidation of H2S-containing gases has been known from DE-A
32 08 695 by direct catalytic oxidation of the H2S
to elemental sulfur in a tubular reactor with indirect removal of the heat of reaction with a coolant under pressures of 0.5 to 10 bar, preferably 0.6 to 5 bar, especially 0.8 to 2 bar, wherein the outlet temperature of the reaction gas from the reactor amounts to 180-400 C. The catalysts employed can contain iron, cobalt, nickel, molybdenum and/or their sulfides or oxides. The catalysts can be utilized as such or on a support material, such as aluminum silicates, calcium aluminum silicates, zeolites, and preferably aluminum oxide.
A process for the removal of H2S from waste gases has been known from EP-A 0 215 317 by reaction with SO2 with the formation of sulfur in accordance with the equation 2 H2S + S02 ~ 3 S + 2 H20 wherein H2S is converted entirely into elemental sulfur which latter remains as a charge on the catalyst.
The invention is based on the object of providing a process making it possible to desulfurize speci~ically a gaseous stream under high pressure of at least 5 bar in a simple and thus economical way.
This object has been attained according to this invention by performing the catalytic direct oxidation under a pressure of between 20 and 70 bar, especially preferably between 30 and S0 bar, and by maintaining the temperature in the internally cooled reactor below the sulfur dew point at least in the por,tion of the catalyst bed which is last traversed by the flow in the flow direction.
20~926~
Complete Application Text - 4 -Direct oxidation is to be understood, in this connection, to mean that no thermal combustion is utilized for the production of SO2, but rather a catalytic one is used wherein the desired reactions proceed directly. The oxygen required for the oxida-tion is added to the high-pressure gas stream up-stream of the direct oxidation reactor, for example in the form of air, pure 2 or also SO2.
This process according to the invention provides the essential advantage that the gaseous stream need not be cooled off first to approximately ambient temperature for the scrubbing step, as in the first-mentioned process according to the state of the art, and thereafter must be reheated for the gas turbine, as required, for example, in the practical example of a gas- and steam-turbine power station.
In this connection, inthis prior-art process, the thermal energy applied to the water condensation re-mains substantially unused. The condensed-out water additionally is lacking as the temperature-attenuating gaseous component during combustion in the gas turbine.
The process according to this invention achieves, in total, an increase in the total degree of efficiency of a gas- and steam-turbine power station as compared with a process according to the state of the art, especially since the scrubbing step used therein per se entails a considerable consumption of energy Moreover, gas loss by coabsorption is no longer incurred in the process of this invention.
However, even in comparison with a process as de-scribed above with cyclically traversed catalyst beds, 208~263 Complete Application Text - 5 -a better energy balance is obtained in the process ac-cording to this invention because at least the supply of heat for catalyst regeneration can be saved.
As per the invention, a reactor with catalyst bed internally cooled indirectly by way of a cooling medium is utilized as the reactor. This ensures a rapid course of the desired reactions in the reactor inlet zone where high temperatures are still prevailing, and a good sulfur yield by equilibrium adjustment at the lower temperatures in the proximity of the reactor outlet.
According to the invention, the temperature of the internally cooled reactor is maintained below the sulfur dew point at least in the portion of the catalyst bed last traversed in the flow direction.
Cooling of this reactor can be performed to close to the water dew point. Cooling media that can be used are all those known in this connection, especially water.
As has been found within the scope of this invention, the sulfur partially condensed out on the catalyst at temperatures below the sulfur dew point itself acts catalytically under the high pressure according to the invention and at these temperatures.
In accordance with the invention, the condensed-out product sulfur is utilized intentionally in this process with this catalytic activity. Accordingly, the basic problem, namely that the sulfur will clog the catalyst beds and thus interrupt the desired progression of the reaction, is effectively overcome.
Under the conditions of this invention as described herein, the sulfur thus acts itself as a catalyst, and deactivation of the catalyst by condensed-out sulfur can be avoided. Consequently, regeneration 208926~
Complete Application Text - 6 -of the reactor from liquid sulfur, heretofore necessary, is thus entirely eliminated. Switchover of the gaseous stream in the internally cooled re-actor for regenerating purposes, as required in the above-mentioned conventional process, is thereby likewise no longer necessary so that the process of this invention, as a result, needs only a substan-tially lower number of catalyst beds as compared with conventional methods. This means a substantial re-duction in apparatus expenditure, as well as animprovement in the availability and reliability.
Advantages result with the use of catalysts which oxidize H2S selectively, but not H2 and/or CO.
Suitable for this purpose are, in particular, cata-lysts based on TiO2 as the support material, thusconsisting substantially of TiO2 and being present in the form of bulk beds.
If, in the process of this invention, a further, adiabatically operated reactor without internal cooling is provided upstream of the coolqd reactor, then the temperatures upstream of the adiabatic reactor can be kept at an especially low level since they rise very quickly by the onset of the reactions(oxidation of H2S and Claus reaction).
Thls permits a satisfactory adjustment of the equi-librium and saves heating energy. As compared with an internally cooled reactor, impurities can be removed again from the catalyst bed in a relatively simple way. Also in the uncooled, adiabatically operated reactor, a catalyst is utilized with pref-erence which oxidizes selectively H2S, rather than H2 and/or CO and which consists essentially of TiO2. The catalyst can be present in the form of bulk beds, but also in honeycomb form. In spite of these partially coinciding properties, a different, 208~2~3 Complete Application Text - 7 -in each case specifically suited catalyst is employed as a norm in the two reactor types of the process according to this invention, i.e. in the uncooled, adiabatically operated reactor and in the internally cooled, quasi isothermically operated reactor.
According to the invention, the temperatùre of the internally cooled reactor which is the second one in the flow direction is maintained below the sulfur dew pOillt at least in the portion of the catalyst bed last traversed in the flow direction. Cooling of this reactor can be carried out to close to the water dew point. A11 coolants known in this connection, especially water, can be utilized as the cooling media.
For minimizing the impurities of the reac-tors, the adiabatically operated reactor is prefer-ably traversed by the flow from the bottom toward the top in the process according to this invention. The mechanical impurities first accumulate on the lower side of the catalyst bed and there form a layer which then drops onto the reactor floor due to its inherent weight and/or the action of gravity. The reactor floor can be equipped with a chute and a discharge means for the thus-produced impurities. A honey-comb catalyst can also be utilized as the catalystwhich is less sensitive to mechanical contaminants than bulk beds.
With special advantage, the feed for the gaseous stream is arranged on the underside of the adiabatically operated reactor, for example by lateral introduction of the gaseous stream at the reactor bottom, in such a way that clogging of the gaseous stream feed conduit can be precluded.
208926~
Complete Application Text - 8 -The internally cooled reactor is traversed by the flow preferably from the top toward the bottom so that condensed-out sulfur can be discharged from this reactor with the gaseous stream. Any dust that may have been introduced is flushed out of the in-ternally cooled reactor essentially by condensed-out sulfur. In case of a more extensive contamination of the internally cooled reactor, the latter can be additionally purged with li~uid product sulfur. The liquid product sulfur then absorbs the impurities.
Liquid sulfur is pressed out of the reactor by the gas and/or is drained off. Traces of halogens can be tolerated in the process of this invention.
The sulfur is separated from the high-pressure gas stream in a separator connected downstream of the internall~ cooled reactor. The gaseous stream can be additionally cooled between the internally cooled re-actor and the separator so that it is ensured that any sulfur vapor possibly still contained in the gas stream is condensed.
A further increase in the sulfur recovery rate can be attained in the process of this invention as follows:
By tolerating that the improvement in the total degree of efficiency for the practical example of a gas- and steam-turbine power station is some-what diminished, the sulfur recovery can be increased by fu~ther lowering the temperature in the internally cooled reactor to about 120-150 C. Since, with such a temperature selection in the internally cooled reactor, the thermodynamic equilibrium of the sulfur conversion according to the exothermic reaction 2H2S + 2 ~ 2H2O + 2/x Sx 208~26~
Complete Application Text - 9 -is shifted to a higher H2S conversion rate, an increase in the sulfur recovery rate is thus produced. However, water must be condensed out prior to entrance into the reactor so that the loss of thermal energy due to the water condensation must be taken into account when calculating the total degree of efficiency.
Special advantages result if, after the gaseous stream has passed through the direct oxidation in at least one reactor, the residual sulfur compounds and/or sulfur vapors contained in this gaseous stream are subsequently reduced and/or hydrogenated to H2S.
Gas desulfurization can be further improved by passing the gaseous stream, exiting from the at least one direct oxidation reactor or from the subse-quent reducing stage, on to an adsorption, chemisorp-tion, or chemical scrubbing, e.g. an NaOH washing step, preferably at a temperature akove 125 C, of the sulfur compounds, such as H2S, SO2, COS, CS2, the mercaptans, the thiophenes and/or the sulfur vapor, preferably on ZnO, Fe2O3 or impregnated active carbon.
A further saving in expenses is offered by the possibility of using a conventional Claus catalyst in the portion of the catalyst bed that is the last in the flow direction. The high degree of desulfurization and/or sulfur recovery rate attained according to this invention can be substantially maintained herein.
The process according to the invention achieves a sulfur recovery rate of about 95 to 99.9%
with an H2S content of the crude gas of 0.3 to about 20 vol-%. With a subsequently provided purification stage as described above, the sulfur removal from the gaseous stream can be brought very close to 100%.
20~9263 Complete Application Text - 10 -By the substantial reduction of the required parts of the plant as compared with conventional facilities, the requirements for operating personnel can be lowered in the process of this invention, in addition to the ensuing construction costs. At the same time, the plant becomes less trouble-prone.
The process of this invention will be described in greater detail below with reference to an embodiment for the practical case of a gas- and steam-turbine power station.
In the drawing:
Figure 1 shows a simplified process scheme for the desulfurization of the high-pressure gas of a gas- and steam-turbine power station in accordance with this invention.
First of all, coal is gasified in A. The thus-produced gas is passed on via conduit 1 to quenching B. In the latter stage, via conduit 2, halogens, their compounds, heavy hydrocarbons, soot, and dust are separated. The thus-prepurified high-pressure gas stream passes, water-saturated, under a pressure of between 20 and 70 bar and at a pressure-dependent temperature of between 160-230 C in conduit 3 over the border of the facility toward the desulfurization part of the plant.
This part of the plant is indicated in Fig-ure 1 by a dashed line. In order to prevent water from precipitating onto the catalyst, the gas is cooled in heat exchanger C to about 100 C in con-duit 4. The process water obtained in separator Dcan be utilized via conduit 5 in the quencher B or is conducted to wastewater treatment.
2 ~
Complete Application Text - 11 -The gas leaves the separator D via conduit and, after admixing air via conduit 16, is heated in heat exchanger E, preferably with crude gas, to about 130-200 C, in order to ensure a reliable initiation of the reactions. Via conduit 7, the gas is conducted from the bottom into the adiabatically operated re-actor F without internal cooling to preclude premature contamination of the catalyst by soot or other mech-anical impurities that may still be present in the gaseous stream. On account of the occurrence of the Claus reaction and/or the catalytic direct oxidation of H2S, the gas is heated up by about 10-50 C in the adiabatically operated reactor F, in dependence on the H2S concentration of the crude gas stream.
Via conduit 8, the gas is subsequently con-ducted from the top into the internally cooled reactor G where it is further reacted. Water is introduced as the cooling medium from the steam drum H
via conduit 9 into the reactor G which latter is preferably cooled in countercurrent direction. By way of the return conduit 10, the partially vaporized water passes back to the steam drum H. Any feed water needed can be supplied via conduit 11. Steam is availabe at 12 from the separator H. On account of countercurrent cooling, an equilibrium is established in the lower region of the reactor at approximately the cooling temperature of the feed water from conduit 9. This temperature is set to below the sulfur dew point, preferably in maximally close proximity to the water dew point in the gas. With this temperature choice, a maximum conversion is achieved in correspondence with the Claus reaction. This temperature is at about 100-130 C in dependence on the pressure and the H2S concentration of the crude gas stream.
208926~
Complete Application Text - 12 -At a temperature of about 120 C, a sulfur yield is thus obtained of about 95 - 99.8%, depending essen-tially on the H2S content of the crude gas.
Sulfur condensed onto the catalyst does not, however, deactivate the catalyst unduly since the sulfur at the prevailing high pressure is itself catalytically active. By conducting the flow through the internally cooled reactor G from the top toward the bottom, condensed-out sulfur can be discharged with the gaseous stream via conduit 13 out of the reactor G.
Finally, the product sulfur is separated in separator I
from the gaseous stream via conduit 14. Thereupon, the gaseous stream leaves this part of the facility and is finally conducted to the turbine (15).
This facility demonstrates an example for a high-quality desulfurization of a high-pressure gas stream of a gas- and steam-turbine power station with, as compared with the state of the art, a substantially lower expenditure in apparatus and with a very high sulfur recovery rate.
Complete Application Text - l -Specification PROCESS FOR SULFUR RECOVERY FROM A GASEOUS STREAM
CONTAINING HYDROGEN SULFIDE UND~R HIGH PR~SSURE
The invention relates to à process for the removal of H2S from a gaseous stream under high pres-sure by catalytic direct oxidation of the H2S without thermal combustion for the production of SO2, wherein the catalytic direct oxidation of the H2S is performed in at least one reactor with catalyst bed, internally cooled indirectly by way of a cooling medium.
In numerous crude gas streams, sulfur is contained primarily in the form of H2S. For sulfur removal and, respectively, sulfur recovery, such an H2S-containing, optionally also COS-containing crude gas stream is usually subjected to a physical or chemical washing step; if needed, a hydrolysis for COS
is additionally performed before the washing step.
One process of such a sulfur removal is disclosed, for example, in DE-OS 30 47 830. The regenerating gas is customarily worked up in a sulfur recovery plant, e.g. a Claus plant, with hydrogenation of the Claus tail gas which latter is then recompressed to upstream of the washing stage.
A process has been ~nown from EP-PA
0 283 ~93 describing a catalytic conversion of H2S
with SO2 to elemental sulfur in several reactors with catalyst beds below the sulfur solidification point or the sulfur dew point. By way of multiple-way fittings, the gaseous ~tream is conducted, with cyclic change of direction, over the catalyst beds in order to be able to regenerate, with supply of heat, the catalyst deactivated by elemental sulfur. Reactors ~089263 Complete Application Text - 2 -that can be utilized are conventional Claus reactors as well as also non-adiabatically operated reactors.
The cyclic operation requires that all catalyst beds must be of identical composition and structure.
However, these conventional processes re-quire a voluminous expenditure in apparatus, accompanied by considerable costs.
In many technically relevant applications, the H2S-containing crude gas streams are obtained as gaseous streams under high pressure. Thus, for ex-ample, for energy utilization in "GuD" power stations (gas- and steam-turbine power stations) coal is initially gasified at pressures of between about 20 and 70 bar. The resultant cracked gas is freed, by quenching and possibly by an additional soot scrubbing step, of halogens, their compounds, heavy hydrocarbons, soot, and dust. The thus-obtained H2S-containing H2/CO crude gas mixture is present as a gaseous stream with high pressure. Before the gaseous mixture is conducted into a gas turbine and combusted therein, it must be desulfurized.
Additional examples for H2S-containing high-pressure gases are constituted by H2S-containing natural gas or compressed biogas which, prior to their further processing, must likewise be subjected to desulfuriza-tion.
Desulfurization of a gaseous stream under high pressure is usually performed according to a pro-cess wherein a scrubbing step is employed. In contrast thereto, a process as described above with several cyclically traversed catalyst beds, or those that must be regenerated by heating, is deemed unsuitable in connection with gaseous streams under high pressure since the cyclic reversing of the gaseous streams under 208926;3 Complete Application Text - 3 -high pressure presents a large number of problems, precisely on account of the high pressure.
A process for the catalytic oxidation of H2S-containing gases has been known from DE-A
32 08 695 by direct catalytic oxidation of the H2S
to elemental sulfur in a tubular reactor with indirect removal of the heat of reaction with a coolant under pressures of 0.5 to 10 bar, preferably 0.6 to 5 bar, especially 0.8 to 2 bar, wherein the outlet temperature of the reaction gas from the reactor amounts to 180-400 C. The catalysts employed can contain iron, cobalt, nickel, molybdenum and/or their sulfides or oxides. The catalysts can be utilized as such or on a support material, such as aluminum silicates, calcium aluminum silicates, zeolites, and preferably aluminum oxide.
A process for the removal of H2S from waste gases has been known from EP-A 0 215 317 by reaction with SO2 with the formation of sulfur in accordance with the equation 2 H2S + S02 ~ 3 S + 2 H20 wherein H2S is converted entirely into elemental sulfur which latter remains as a charge on the catalyst.
The invention is based on the object of providing a process making it possible to desulfurize speci~ically a gaseous stream under high pressure of at least 5 bar in a simple and thus economical way.
This object has been attained according to this invention by performing the catalytic direct oxidation under a pressure of between 20 and 70 bar, especially preferably between 30 and S0 bar, and by maintaining the temperature in the internally cooled reactor below the sulfur dew point at least in the por,tion of the catalyst bed which is last traversed by the flow in the flow direction.
20~926~
Complete Application Text - 4 -Direct oxidation is to be understood, in this connection, to mean that no thermal combustion is utilized for the production of SO2, but rather a catalytic one is used wherein the desired reactions proceed directly. The oxygen required for the oxida-tion is added to the high-pressure gas stream up-stream of the direct oxidation reactor, for example in the form of air, pure 2 or also SO2.
This process according to the invention provides the essential advantage that the gaseous stream need not be cooled off first to approximately ambient temperature for the scrubbing step, as in the first-mentioned process according to the state of the art, and thereafter must be reheated for the gas turbine, as required, for example, in the practical example of a gas- and steam-turbine power station.
In this connection, inthis prior-art process, the thermal energy applied to the water condensation re-mains substantially unused. The condensed-out water additionally is lacking as the temperature-attenuating gaseous component during combustion in the gas turbine.
The process according to this invention achieves, in total, an increase in the total degree of efficiency of a gas- and steam-turbine power station as compared with a process according to the state of the art, especially since the scrubbing step used therein per se entails a considerable consumption of energy Moreover, gas loss by coabsorption is no longer incurred in the process of this invention.
However, even in comparison with a process as de-scribed above with cyclically traversed catalyst beds, 208~263 Complete Application Text - 5 -a better energy balance is obtained in the process ac-cording to this invention because at least the supply of heat for catalyst regeneration can be saved.
As per the invention, a reactor with catalyst bed internally cooled indirectly by way of a cooling medium is utilized as the reactor. This ensures a rapid course of the desired reactions in the reactor inlet zone where high temperatures are still prevailing, and a good sulfur yield by equilibrium adjustment at the lower temperatures in the proximity of the reactor outlet.
According to the invention, the temperature of the internally cooled reactor is maintained below the sulfur dew point at least in the portion of the catalyst bed last traversed in the flow direction.
Cooling of this reactor can be performed to close to the water dew point. Cooling media that can be used are all those known in this connection, especially water.
As has been found within the scope of this invention, the sulfur partially condensed out on the catalyst at temperatures below the sulfur dew point itself acts catalytically under the high pressure according to the invention and at these temperatures.
In accordance with the invention, the condensed-out product sulfur is utilized intentionally in this process with this catalytic activity. Accordingly, the basic problem, namely that the sulfur will clog the catalyst beds and thus interrupt the desired progression of the reaction, is effectively overcome.
Under the conditions of this invention as described herein, the sulfur thus acts itself as a catalyst, and deactivation of the catalyst by condensed-out sulfur can be avoided. Consequently, regeneration 208926~
Complete Application Text - 6 -of the reactor from liquid sulfur, heretofore necessary, is thus entirely eliminated. Switchover of the gaseous stream in the internally cooled re-actor for regenerating purposes, as required in the above-mentioned conventional process, is thereby likewise no longer necessary so that the process of this invention, as a result, needs only a substan-tially lower number of catalyst beds as compared with conventional methods. This means a substantial re-duction in apparatus expenditure, as well as animprovement in the availability and reliability.
Advantages result with the use of catalysts which oxidize H2S selectively, but not H2 and/or CO.
Suitable for this purpose are, in particular, cata-lysts based on TiO2 as the support material, thusconsisting substantially of TiO2 and being present in the form of bulk beds.
If, in the process of this invention, a further, adiabatically operated reactor without internal cooling is provided upstream of the coolqd reactor, then the temperatures upstream of the adiabatic reactor can be kept at an especially low level since they rise very quickly by the onset of the reactions(oxidation of H2S and Claus reaction).
Thls permits a satisfactory adjustment of the equi-librium and saves heating energy. As compared with an internally cooled reactor, impurities can be removed again from the catalyst bed in a relatively simple way. Also in the uncooled, adiabatically operated reactor, a catalyst is utilized with pref-erence which oxidizes selectively H2S, rather than H2 and/or CO and which consists essentially of TiO2. The catalyst can be present in the form of bulk beds, but also in honeycomb form. In spite of these partially coinciding properties, a different, 208~2~3 Complete Application Text - 7 -in each case specifically suited catalyst is employed as a norm in the two reactor types of the process according to this invention, i.e. in the uncooled, adiabatically operated reactor and in the internally cooled, quasi isothermically operated reactor.
According to the invention, the temperatùre of the internally cooled reactor which is the second one in the flow direction is maintained below the sulfur dew pOillt at least in the portion of the catalyst bed last traversed in the flow direction. Cooling of this reactor can be carried out to close to the water dew point. A11 coolants known in this connection, especially water, can be utilized as the cooling media.
For minimizing the impurities of the reac-tors, the adiabatically operated reactor is prefer-ably traversed by the flow from the bottom toward the top in the process according to this invention. The mechanical impurities first accumulate on the lower side of the catalyst bed and there form a layer which then drops onto the reactor floor due to its inherent weight and/or the action of gravity. The reactor floor can be equipped with a chute and a discharge means for the thus-produced impurities. A honey-comb catalyst can also be utilized as the catalystwhich is less sensitive to mechanical contaminants than bulk beds.
With special advantage, the feed for the gaseous stream is arranged on the underside of the adiabatically operated reactor, for example by lateral introduction of the gaseous stream at the reactor bottom, in such a way that clogging of the gaseous stream feed conduit can be precluded.
208926~
Complete Application Text - 8 -The internally cooled reactor is traversed by the flow preferably from the top toward the bottom so that condensed-out sulfur can be discharged from this reactor with the gaseous stream. Any dust that may have been introduced is flushed out of the in-ternally cooled reactor essentially by condensed-out sulfur. In case of a more extensive contamination of the internally cooled reactor, the latter can be additionally purged with li~uid product sulfur. The liquid product sulfur then absorbs the impurities.
Liquid sulfur is pressed out of the reactor by the gas and/or is drained off. Traces of halogens can be tolerated in the process of this invention.
The sulfur is separated from the high-pressure gas stream in a separator connected downstream of the internall~ cooled reactor. The gaseous stream can be additionally cooled between the internally cooled re-actor and the separator so that it is ensured that any sulfur vapor possibly still contained in the gas stream is condensed.
A further increase in the sulfur recovery rate can be attained in the process of this invention as follows:
By tolerating that the improvement in the total degree of efficiency for the practical example of a gas- and steam-turbine power station is some-what diminished, the sulfur recovery can be increased by fu~ther lowering the temperature in the internally cooled reactor to about 120-150 C. Since, with such a temperature selection in the internally cooled reactor, the thermodynamic equilibrium of the sulfur conversion according to the exothermic reaction 2H2S + 2 ~ 2H2O + 2/x Sx 208~26~
Complete Application Text - 9 -is shifted to a higher H2S conversion rate, an increase in the sulfur recovery rate is thus produced. However, water must be condensed out prior to entrance into the reactor so that the loss of thermal energy due to the water condensation must be taken into account when calculating the total degree of efficiency.
Special advantages result if, after the gaseous stream has passed through the direct oxidation in at least one reactor, the residual sulfur compounds and/or sulfur vapors contained in this gaseous stream are subsequently reduced and/or hydrogenated to H2S.
Gas desulfurization can be further improved by passing the gaseous stream, exiting from the at least one direct oxidation reactor or from the subse-quent reducing stage, on to an adsorption, chemisorp-tion, or chemical scrubbing, e.g. an NaOH washing step, preferably at a temperature akove 125 C, of the sulfur compounds, such as H2S, SO2, COS, CS2, the mercaptans, the thiophenes and/or the sulfur vapor, preferably on ZnO, Fe2O3 or impregnated active carbon.
A further saving in expenses is offered by the possibility of using a conventional Claus catalyst in the portion of the catalyst bed that is the last in the flow direction. The high degree of desulfurization and/or sulfur recovery rate attained according to this invention can be substantially maintained herein.
The process according to the invention achieves a sulfur recovery rate of about 95 to 99.9%
with an H2S content of the crude gas of 0.3 to about 20 vol-%. With a subsequently provided purification stage as described above, the sulfur removal from the gaseous stream can be brought very close to 100%.
20~9263 Complete Application Text - 10 -By the substantial reduction of the required parts of the plant as compared with conventional facilities, the requirements for operating personnel can be lowered in the process of this invention, in addition to the ensuing construction costs. At the same time, the plant becomes less trouble-prone.
The process of this invention will be described in greater detail below with reference to an embodiment for the practical case of a gas- and steam-turbine power station.
In the drawing:
Figure 1 shows a simplified process scheme for the desulfurization of the high-pressure gas of a gas- and steam-turbine power station in accordance with this invention.
First of all, coal is gasified in A. The thus-produced gas is passed on via conduit 1 to quenching B. In the latter stage, via conduit 2, halogens, their compounds, heavy hydrocarbons, soot, and dust are separated. The thus-prepurified high-pressure gas stream passes, water-saturated, under a pressure of between 20 and 70 bar and at a pressure-dependent temperature of between 160-230 C in conduit 3 over the border of the facility toward the desulfurization part of the plant.
This part of the plant is indicated in Fig-ure 1 by a dashed line. In order to prevent water from precipitating onto the catalyst, the gas is cooled in heat exchanger C to about 100 C in con-duit 4. The process water obtained in separator Dcan be utilized via conduit 5 in the quencher B or is conducted to wastewater treatment.
2 ~
Complete Application Text - 11 -The gas leaves the separator D via conduit and, after admixing air via conduit 16, is heated in heat exchanger E, preferably with crude gas, to about 130-200 C, in order to ensure a reliable initiation of the reactions. Via conduit 7, the gas is conducted from the bottom into the adiabatically operated re-actor F without internal cooling to preclude premature contamination of the catalyst by soot or other mech-anical impurities that may still be present in the gaseous stream. On account of the occurrence of the Claus reaction and/or the catalytic direct oxidation of H2S, the gas is heated up by about 10-50 C in the adiabatically operated reactor F, in dependence on the H2S concentration of the crude gas stream.
Via conduit 8, the gas is subsequently con-ducted from the top into the internally cooled reactor G where it is further reacted. Water is introduced as the cooling medium from the steam drum H
via conduit 9 into the reactor G which latter is preferably cooled in countercurrent direction. By way of the return conduit 10, the partially vaporized water passes back to the steam drum H. Any feed water needed can be supplied via conduit 11. Steam is availabe at 12 from the separator H. On account of countercurrent cooling, an equilibrium is established in the lower region of the reactor at approximately the cooling temperature of the feed water from conduit 9. This temperature is set to below the sulfur dew point, preferably in maximally close proximity to the water dew point in the gas. With this temperature choice, a maximum conversion is achieved in correspondence with the Claus reaction. This temperature is at about 100-130 C in dependence on the pressure and the H2S concentration of the crude gas stream.
208926~
Complete Application Text - 12 -At a temperature of about 120 C, a sulfur yield is thus obtained of about 95 - 99.8%, depending essen-tially on the H2S content of the crude gas.
Sulfur condensed onto the catalyst does not, however, deactivate the catalyst unduly since the sulfur at the prevailing high pressure is itself catalytically active. By conducting the flow through the internally cooled reactor G from the top toward the bottom, condensed-out sulfur can be discharged with the gaseous stream via conduit 13 out of the reactor G.
Finally, the product sulfur is separated in separator I
from the gaseous stream via conduit 14. Thereupon, the gaseous stream leaves this part of the facility and is finally conducted to the turbine (15).
This facility demonstrates an example for a high-quality desulfurization of a high-pressure gas stream of a gas- and steam-turbine power station with, as compared with the state of the art, a substantially lower expenditure in apparatus and with a very high sulfur recovery rate.
Claims (14)
1. Process for the removal of H2S from a gaseous stream with high pressure by catalytic direct oxidation of the H2S without thermal combustion for the production of SO2, wherein the catalytic direct oxidation of the H2S is performed in at least one reactor with catalyst bed indirectly cooled internally by way of a cooling medium, characterized in that the catalytic direct oxidation is conducted under a pressure of between 20 and 70 bar, especially prefer-ably between 30 and 50 bar, and the temperature in the internally cooled reactor is maintained below the sulfur dew point at least in the portion of the catalyst bed last traversed in the flow direction.
2. Process according to claim 1, characterized in that a catalyst is used which selectively oxidizes H2S.
3. Process according to one of claims 1 or 2, characterized in that the catalyst consists essentially of TiO2.
4. Process according to one of claims 1-3, characterized in that the portion of the catalyst that is the last in the flow direction consists of a conventional Claus catalyst.
5. Process according to one of claims 1-4, characterized in that a further, adiabatically operated reactor without internal cooling is arranged upstream of the internally cooled reactor.
Complete Application Text - 14 -
Complete Application Text - 14 -
6. Process according to claim 1 or 5, characterized in that a catalyst selectively oxidizing H2S is utilized in the uncooled reactor.
7. Process according to one of claims 5 or 6, characterized in that the catalyst of the uncooled reactor consists essentially of TiO2.
8. Process according to one of claims 1-7, characterized in that the reactor that is the first in the flow direction is traversed from the bottom toward the top, while the reactor that is the second one in the flow direction is traversed from the top toward the bottom.
9. Process according to one of claims 1-8, characterized in that the residual sulfur compounds and/or sulfur vapors contained in the gaseous stream after passing through at least one direct oxidation reactor are reduced and, respectively, hydrogenated to H2S.
10. Process according to one of claims 1-9, characterized in that the gaseous stream, after passing through at least one direct oxidation reactor or the reducing stage, is subjected to an adsorption for the removal of the residual H2S, other sulfur com-pounds and/or the sulfur vapor.
Complete Application Text - 15 -
Complete Application Text - 15 -
11. Process according to one of claims 1-9, characterized in that the gaseous stream, after passing through at least one direct oxidation reactor or the reducing stage, is freed of residual H2S, other sulfur compounds and/or sulfur vapor by chemisorption.
12. Process according to claim 11, characterized in that the chemisorption is conducted on ZnO, Fe2O3 or impregnated active carbon.
13. Process according to one of claims 1-9, characterized in that the gaseous stream, after passing through at least one direct oxidation reactor or the reducing stage, is subjected to an NaOH scrubbing step for removal of the residual H2S, other sulfur com-pounds and/or the sulfur vapor.
14. Process according to claim 13, characterized in that the chemical scrubbing step consists of an NaOH scrubbing step.
. 1 .
. 1 .
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4025471.2 | 1990-08-10 | ||
| DE4025471A DE4025471A1 (en) | 1990-08-10 | 1990-08-10 | METHOD FOR RECOVERY OF SULFUR FROM A H (ARROW DOWN) 2 (ARROW DOWN) S-CONTAINING GAS FLOW AT HIGH PRESSURE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2089263A1 true CA2089263A1 (en) | 1992-02-11 |
Family
ID=6412059
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002089263A Abandoned CA2089263A1 (en) | 1990-08-10 | 1991-08-09 | Process for sulfur recovery from a gaseous stream containing hydrogen sulfide under high pressure |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0542838B1 (en) |
| AT (1) | ATE146443T1 (en) |
| CA (1) | CA2089263A1 (en) |
| DE (2) | DE4025471A1 (en) |
| WO (1) | WO1992002449A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5676921A (en) * | 1994-03-17 | 1997-10-14 | Linde Aktiengesellschaft | Method for the recovery of elemental sulfur from a gas mixture containing H2 S |
| WO2008130475A1 (en) | 2007-04-18 | 2008-10-30 | Gas Technology Institute | Method for direct oxidation of hydrogen sulfide to elemental sulfur at low temperatures |
| CN111485064A (en) * | 2020-04-21 | 2020-08-04 | 武汉科技大学 | Hydrogen molten iron desulphurization method |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2702673B1 (en) * | 1993-03-16 | 1995-04-28 | Elf Aquitaine | Process for removing the H2S contained in a gas in a concentration of less than 5% by volume with recovery of this H2S in the form of sulfur. |
| EP0631978B1 (en) * | 1993-06-28 | 1996-05-08 | Shell Internationale Researchmaatschappij B.V. | Removing hydrogen sulphide from a gas stream |
| DE69412839T2 (en) * | 1994-12-23 | 1999-03-18 | Shell Internationale Research Maatschappij B.V., Den Haag/S'gravenhage | Removal of hydrogen sulfide from a gas stream |
| DE19507440A1 (en) * | 1995-03-03 | 1996-09-05 | Metallgesellschaft Ag | Process for desulfurizing a gas containing H2S |
| NZ507688A (en) * | 2000-04-19 | 2001-03-30 | Chen Jae Han | Sewing fabric sheets, typically having one smooth side and one fur-like side, by forming folded edge on first sheet and then sewing on edge abutting second sheet |
| CN101522562A (en) * | 2006-10-05 | 2009-09-02 | 国际壳牌研究有限公司 | Process for disposal of mercaptans |
| CA2744978A1 (en) * | 2008-11-28 | 2010-06-03 | Arnab Chatterjee | Process for the selective oxidation of hydrogen sulphide |
| CA2790039A1 (en) * | 2010-02-18 | 2011-08-25 | Shell Internationale Research Maatschappij B.V. | Process for selective oxidation of hydrogen sulphide |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1142326A (en) * | 1979-12-11 | 1983-03-08 | Hudson's Bay Oil And Gas Company Limited | High pressure process for recovery of sulphur from gases |
| DE3208695A1 (en) * | 1982-03-11 | 1983-09-22 | Basf Ag, 6700 Ludwigshafen | METHOD FOR DESULFURING H (ARROW DOWN) 2 (ARROW DOWN) GASES |
| DE3428452A1 (en) * | 1984-02-02 | 1985-08-08 | Linde Ag, 6200 Wiesbaden | Process and reactor for the catalytic conversion of hydrogen sulphide into elemental sulphur |
| DE3429979A1 (en) * | 1984-08-16 | 1986-02-27 | Bayer do Brasil S.A., Sao Paulo | Process for the removal of acidic and/or sulphur-containing gases from industrial gases or exhaust gases |
| DE3529665A1 (en) * | 1985-08-20 | 1987-02-26 | Metallgesellschaft Ag | METHOD FOR REMOVING SULDURATE FROM EXHAUST GASES |
-
1990
- 1990-08-10 DE DE4025471A patent/DE4025471A1/en not_active Ceased
-
1991
- 1991-08-09 EP EP91914464A patent/EP0542838B1/en not_active Expired - Lifetime
- 1991-08-09 DE DE59108424T patent/DE59108424D1/en not_active Expired - Fee Related
- 1991-08-09 AT AT91914464T patent/ATE146443T1/en not_active IP Right Cessation
- 1991-08-09 WO PCT/EP1991/001523 patent/WO1992002449A1/en active IP Right Grant
- 1991-08-09 CA CA002089263A patent/CA2089263A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5676921A (en) * | 1994-03-17 | 1997-10-14 | Linde Aktiengesellschaft | Method for the recovery of elemental sulfur from a gas mixture containing H2 S |
| WO2008130475A1 (en) | 2007-04-18 | 2008-10-30 | Gas Technology Institute | Method for direct oxidation of hydrogen sulfide to elemental sulfur at low temperatures |
| EP2155362A1 (en) * | 2007-04-18 | 2010-02-24 | Gas Technology Institute | Method for direct oxidation of hydrogen sulfide to elemental sulfur at low temperatures |
| EP2155362A4 (en) * | 2007-04-18 | 2011-12-07 | Gas Technology Inst | Method for direct oxidation of hydrogen sulfide to elemental sulfur at low temperatures |
| CN111485064A (en) * | 2020-04-21 | 2020-08-04 | 武汉科技大学 | Hydrogen molten iron desulphurization method |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0542838A1 (en) | 1993-05-26 |
| WO1992002449A1 (en) | 1992-02-20 |
| ATE146443T1 (en) | 1997-01-15 |
| DE4025471A1 (en) | 1992-02-13 |
| EP0542838B1 (en) | 1996-12-18 |
| DE59108424D1 (en) | 1997-01-30 |
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