JP3602268B2 - Method and apparatus for removing sulfur compounds contained in natural gas and the like - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to hydrogen sulfide (H ₂ S) contained in natural gas, petroleum accompanying gas, synthesis gas, process gas, coal gasification gas, heavy oil gasification gas, and the like (hereinafter, abbreviated as natural gas and the like in the present invention). ), A method and an apparatus for removing sulfur compounds such as mercaptans and sulfur oxides.
[0002]
[Prior art]
Impurity gases accompanying natural gas and the like include carbon dioxide (CO ₂ ), H ₂ S, COS, mercaptan, and heavy hydrocarbons. These impurity gases are accompanied by a decline in mining quality of natural gas and the like. In recent years, there is a tendency to increase gradually, and it is necessary to remove and purify these to obtain product gas.
[0003]
On the other hand, as a method for removing H ₂ S contained in a gas, there is a method by a Claus reaction. The Claus reaction, and SO ₂ by oxidizing a part of H _{2 S} in the gas by separating and recovering elemental sulfur is reacted with H _{2 S} of the SO ₂ and the remainder, H ₂ in the gas S is to be removed.
A method is also known in which the residual SO ₂ contained in the off-gas after the Claus reaction is hydrogenated in the presence of a catalyst to form H ₂ S, which is returned to the Claus reactor to increase the sulfur removal rate.
[0004]
By the way, as described above, various components other than H ₂ S are included as impurity components accompanying natural gas and the like. Such impurity gas is separated from natural gas and the like, and this impurity gas is separated by Claus. If an attempt is made to remove the sulfur contained in the reactor by leading it to the reactor, the following disadvantages occur.
{Circle around (1)} Since the impurity gas contains a large amount of components other than H ₂ S, for example, CO ₂ , the H ₂ S concentration decreases, the reaction rate in the Claus reaction decreases, and the removal rate decreases. descend.
(2) Heavy hydrocarbons (benzene, toluene, xylene, etc.) contained in the impurity gas are incompletely burned, soot is generated, the recovered sulfur is contaminated with soot, the quality of sulfur is reduced, and the soot is Claus. The catalyst layer may be clogged.
[0005]
Conventionally, as a method of causing a Claus reaction of a hydrogen sulfide-containing gas containing a large amount of CO ₂ , for example, there is a method disclosed in Japanese Patent Publication No. Sho 63-17488.
In this method, a part of an H ₂ S-containing gas containing 20% by volume or more of CO ₂ is supplied to a Claus plant, and the remainder is brought into contact with an absorbent that bypasses the Claus plant and selectively absorbs H ₂ S. The H ₂ S regenerated and separated by the absorbent is returned to the Claus plant.
However, this prior art cannot sufficiently solve the above-mentioned disadvantages.
[0006]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to solve the problem that even if an impurity gas accompanying natural gas or the like contains a large amount of CO ₂ , COS, BTX, mercaptan, etc. in addition to H ₂ S, sulfur in the impurity gas It is an object of the present invention to efficiently remove a compound by the Claus reaction and to prevent clogging of the Claus catalyst layer and deterioration in the quality of recovered sulfur due to soot generated from heavy hydrocarbons such as BTX.
[0007]
[Means for Solving the Problems]
The problem is that an impurity gas separated from natural gas or the like is sent to a concentration separation step, where the gas is separated into a concentrated gas mainly composed of H ₂ S in the impurity gas and a residual gas composed of residual components, and the concentrated gas is subjected to the Claus reaction. H ₂ S is collected and removed, and the off-gas from the Claus reaction step and all or a part of the residual gas are separately or combined sent to a tail gas treatment step, where they are heated and hydrogenated to convert these gases. the sulfur compounds in the H _{2 S,} is solved by returning the Claus reaction step and separating the H _{2 S.}
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example of an apparatus for performing the removal method of the present invention, which uses crude natural gas extracted as natural gas or the like.
The crude natural gas is sent from the pipe 1 to the first absorption tower 2, where the impurity gas accompanying the crude natural gas is non-selectively absorbed, and the purified product natural gas is led out from the top of the tower by the pipe 3. You. An aqueous solution such as a sulfolane-amine mixed solution, monoethanolamine, diethanolamine, diglycolamine, methanol, or glycol solution is supplied to the first absorption tower 2 as a non-selective absorption solution. CO ₂ and H ₂ S, small amounts of sulfur compounds such as mercaptans and small amounts of hydrocarbons such as BTX are absorbed.
[0009]
The absorbing solution that has absorbed the impurity gas is sent from the bottom of the tower to the first regeneration tower 5 via the pipe 4, where it is heated and the impurity gas is diffused. The impurity gas is composed of, for example, about 70 vol% CO ₂ , about 25 vol% H ₂ S, a small amount of mercaptan, and BTX hydrocarbon.
This impurity gas is withdrawn from the top of the first regeneration tower 5 by a pipe 6, and the regenerated absorbent is withdrawn from the bottom of the tower, returned to the first absorption tower 2 via a pipe 7, and reused. .
[0010]
The impurity gas from the pipe 6 is introduced into the second absorption tower 8. The second absorption tower 8 is selected from an alkanolamine such as diethanolamine, triethanolamine, diisopropanolamine, and methyldiethanolamine, a mixed solution of sulfolane-amine, an aqueous solution of polyethylene glycol dialkyl ether, and an aqueous solution of N, N-dimethylaminoacetate. A typical absorbing liquid is supplied, where most of the H ₂ S and some of the CO ₂ in the impurity gas are absorbed. Some of these absorbing liquids are used as non-selective absorbing liquids. However, by selecting the absorbing conditions, a selective absorbing liquid that mainly absorbs H ₂ S can be obtained.
Here, the absorption conditions are a temperature of 60 ° C. or lower, preferably 5 to 40 ° C., and a slight pressurization of substantially atmospheric pressure or 2 atm or less.
[0011]
From the top of the second absorption tower 8, residual gas comprising residual components not absorbed here is led out to the pipe 9. The residual gas is mostly a CO _2, this 0.1 ~5vol% of mercaptan and 0.1～5Vol% of BTX, contains 0.03 ~0.3vol% of _H 2 S .
The absorption liquid drained from the bottom of the second absorption tower 8 is sent to the second regeneration tower 11 via the pipe 10, where H ₂ S and CO ₂ that have been heated and absorbed are diffused, ₂ S is 50 vol% or more, for example, H ₂ S is about 65 vol%, CO ₂ is about 35 vol%, and a concentrated gas in which H ₂ S is concentrated is led out from the tower top.
[0012]
From the bottom of the second regeneration tower 11, the regenerated absorbent is returned to the second absorption tower 8 via the pipe 12, and is reused.
The second absorption tower 8 and the second regeneration tower 11 constitute a concentration and separation device of the present invention, and a plurality of these may be provided to increase the H ₂ S concentration.
[0013]
The concentrated gas from the second regeneration tower 11 is sent via a pipe 13 to a Claus sulfur recovery unit 14 composed of a Claus reactor and a multi-stage Claus catalyst layer. The Claus sulfur recovery unit 14 has a well-known configuration, and has a non-catalytic type and a catalytic type reactor. The catalyst is alumina, bauxite, titania, zirconia, silica, zeolite or a rare earth metal as a heat stabilizer. Alternatively, a material containing an oxide of an alkaline earth metal is used.
The reaction temperature is about 1000 to 1500 ° C. for the non-catalytic type, and about 200 to 350 ° C. for the catalytic type.
In the Claus sulfur recovery device 14, a part of the H ₂ S in the concentrated gas is oxidized to SO ₂ by an oxygen-containing gas such as air and air introduced through the pipe 15, and this SO ₂ and the remaining H ₂ becomes sulfur ₂ and _S react, most of the H _{2 S} is recovered from the pipe 16 becomes elemental sulfur by the reaction.
[0014]
The exhaust gas (off-gas) from the Claus sulfur recovery device 14 is a case where a trace amount of H ₂ S, SO ₂ , S, COS, CS ₂ and a large amount of CO ₂ , H ₂ O, residual oxygen and air are used as an oxygen source. It is included in the _{N 2} in. The temperature of this off gas is usually 130 to 170 ° C.
The off-gas from the Claus sulfur recovery unit 14 is sent from the pipe 17 to the heating furnace 18, and at the same time, all or part of the residual gas sent from the second absorption tower 8 via the pipe 9 is also supplied to the heating furnace 18.
[0015]
The heating furnace 18 is equipped with a normal combustion burner, and raises the temperature of the off-gas and the residual gas to a temperature required for the subsequent hydrogenation reaction by combustion with fuel and oxygen in the air.
Note that by burning the fuel by partial oxidation, it is possible to produce CO / H ₂ required for the hydrogenation reaction. Oh Rui furnace 1 8 is added if necessary to CO / H ₂ as the reducing agent necessary for the hydrogenation reaction in the tube 19. It is also possible to use a heat exchanger instead of the heating furnace 18.
[0016]
The heated gas is sent from a pipe 19 to a hydrogenation reactor 20, where sulfur compounds such as SO ₂ , mercaptan, and S contained therein are reduced to H ₂ S in the presence of a reduction catalyst.
The reduction catalyst used here is an oxide or sulfide of Ni-Mo, Co-Mo, Ni-Co-Mo, and these catalysts are oxide supports such as alumina, silica, magnesia, boria, thoria, and zirconia. May be carried.
The reduction reaction is carried out in a temperature range of 180 to 450 ° C., preferably 250 to 350 ° C., under atmospheric pressure or under slight pressure of 2 atm or less. A hydrogen-containing gas for reduction may be added, and if CO / H ₂ is sufficiently generated in the combustion process in the heating furnace 18, it may not be added again.
Mixing volume ratio of the sulfur compounds are reduced with CO / _{H 2} is 2: 1 to 15: 1, rather preferably from 3: 1 to 8: 1 is preferred.
[0017]
The hydrogenation gas from the hydrogenation reactor 20 contains several vol% of H ₂ S, a small amount of hydrocarbons such as BTX, unreacted mercaptan, H ₂ and large amounts of CO ₂ and N ₂ , After being extracted and cooled, it is sent to the third absorption tower 22. A part of the regenerated absorbing liquid from the second regenerating tower 11 is supplied to the third absorbing tower 22 via a pipe 23 as the absorbing liquid.
In the third absorption tower 22, a part of H ₂ S and CO _{2 in} the hydrogenated gas is absorbed, and the remaining large amount of CO ₂ and N ₂ , a small amount of hydrocarbon such as BTX, mercaptan, H ₂ , A gas containing a trace amount of H ₂ S is led from the top of the gas into the pipe 24, and this gas is discharged as it is to the atmosphere or burned and discharged to the stack.
[0018]
From the bottom of the third absorption tower 22, the absorbing solution having absorbed _{H 2} S and CO ₂ is returned to the second regeneration tower 11 through a pipe 25, where _{H 2} S and CO ₂ enrichment of target is dissipated The gas is sent to the Claus sulfur recovery unit 14.
In this embodiment, the heating furnace 18, the hydrogenation reactor 20, the third absorption tower 22, and the pipes associated therewith constitute a tail gas processing apparatus of the present invention.
[0019]
According to such a method for removing a sulfur compound, the concentration of H ₂ S in the concentrated gas introduced into the Claus sulfur recovery device 14 becomes higher than that of the impurity gas, and the concentration of CO ₂ accompanying the gas decreases. The reaction rate is higher and the recovery of sulfur is higher.
In addition, most of other sulfur compounds such as mercaptan and COS other than H ₂ S in the impurity gas are finally converted to H ₂ S, which is also removed by the Claus reaction. The total sulfur content in it will be very low. Furthermore, since heavy hydrocarbons such as BTX contained in the impurity gas are not introduced into the Claus sulfur recovery unit 14, soot is not generated in the Claus sulfur recovery unit 14, and the quality of the recovered sulfur is reduced. Lowering and blocking of the catalyst layer can be prevented.
[0020]
In the present invention, the absorbing solution of the third absorption tower 22 can be used from the aqueous solution used in the second absorption tower 8 and the second regeneration tower 11, but these absorption solutions are used in the second absorption tower 22. In the case where the absorption liquid is different from the absorption liquid in Step 8, it is necessary to separately provide a third regeneration tower to provide a separate system from the concentration and separation step.
[0021]
Further, in the present invention, H ₂ S can be separated from the hydrogenated gas from the hydrogenation reactor 20 by adsorption and returned to the Claus sulfur recovery unit 14. That is, instead of the third absorption tower 22, an adsorption tower is provided, and activated carbon or an aqueous solution of a compound capable of reacting with hydrogen sulfide is immersed therein, and an adsorbent such as alumina, iron oxide, or zinc oxide is filled therein. Thereby, H ₂ S may be adsorbed and separated.
[0022]
Furthermore, when the off-gas from the Claus sulfur recovery unit 14 contains CS ₂ and COS, the sulfur compound is brought into contact with a hydrolysis catalyst such as alumina after or simultaneously with the hydrogenation treatment to convert these sulfur compounds into H ₂ S This may be separated in the third absorption tower 22 and returned to the Claus sulfur recovery unit 14.
[0023]
FIG. 2 shows a second example of the present invention. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.
In this apparatus, a second heating furnace 26 is provided in addition to the heating furnace 18, and the residual gas from the second absorption tower 8 is sent to the second heating furnace 26 through a pipe 9, where the heating and reducing agent are heated by partial oxidation combustion. The heated gas is sent from a pipe 27 to a second hydrogenation reactor 28, where it is hydrogenated to convert sulfur compounds to H ₂ S, and the hydrogenated gas is sent from a pipe 29 to a third absorption tower 22. Things.
[0024]
In this case, since the residual gas is heated and hydrogenated separately from the off-gas from the Claus sulfur recovery unit 14, reaction conditions, catalysts, and hydrogenation conditions corresponding to the composition of the residual gas can be set. In addition, the emission of sulfur compounds can be further reduced.
[0025]
FIG. 3 shows a third example of the present invention. In this example, a fourth absorption tower 30 is provided downstream of the second hydrogenation reactor 28, and the heating gas from the second heating furnace 26 is supplied to a pipe 27. To the second hydrogenation reactor 28, where it is hydrogenated and then sent from the pipe 29 to the fourth absorption tower 30, where it absorbs H ₂ S and discharges the remaining gas as exhaust gas from the pipe 31. Things.
The absorption liquid used in the third absorption tower 22 is supplied to the fourth absorption tower 30 via a pipe 32, and the absorption liquid that has absorbed H ₂ S in the fourth absorption tower 30 passes through a pipe 33 to the second regeneration tower 11. Is returned to.
[0026]
In this case, the treatment of the residual gas and the treatment of the off-gas from the Claus sulfur recovery unit 14 are performed completely separately, so that heating conditions, reduction conditions, catalysts, absorption conditions, etc., corresponding to the respective compositions. Can be individually set in detail.
For this reason, the content of sulfur compounds and hydrocarbons in the exhaust gas is extremely low.
[0027]
【The invention's effect】
As described above, the present invention separates impurity gas accompanying natural gas, petroleum accompanying gas and the like into a concentrated gas mainly composed of H ₂ S and a residual gas composed of residual components, and treats the concentrated gas by a Claus reaction. The off-gas of the Claus reaction and the sulfur compound in the residual gas are hydrogenated to convert the sulfur compound in the gas into H ₂ S, and this H ₂ S is separated and returned to the Claus reaction.
[0028]
Therefore, be included in the gas, such as CO ₂ other than H _{2 S} is a large amount in the impurity gas, can increase the concentration of H _{2 S} in the concentrated gas subjected to the Claus reaction, Claus reaction rate becomes high This improves the sulfur removal rate. In addition, since heavy hydrocarbons such as BTX are not brought into the Claus sulfur recovery apparatus, soot is not generated due to the heavy hydrocarbons, so that the quality of recovered sulfur is reduced and the catalyst layer is not blocked. Further, sulfur compounds other than H ₂ S such as mercaptan in the impurity gas are finally converted to H ₂ S and removed by the Claus reaction, so that the total sulfur amount in the exhaust gas discharged to the atmosphere is further reduced. Can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first example of an apparatus of the present invention.
FIG. 2 is a schematic configuration diagram showing a second example of the device of the present invention.
FIG. 3 is a schematic configuration diagram showing a third example of the device of the present invention.
[Explanation of symbols]
2 First absorption tower 5 First regeneration tower 8 Second absorption tower 11 Second regeneration tower 14 Claus sulfur recovery unit 18 Heating furnace 20 Hydrogenation reactor 22 Third absorption tower 26 Second heating furnace 28 Second hydrogenation reaction furnace

Claims (4)

The impurity gas containing sulfur compounds such as hydrogen sulfide separated from natural gas etc. is sent to the concentration separation step, where it is converted into a concentrated gas mainly composed of hydrogen sulfide contained in the impurity gas and a residual gas composed of residual components. Separate and
The concentrated gas is sent to the Claus reaction step, where hydrogen sulfide is recovered as sulfur alone,
The residual gas and the off-gas discharged from the Claus reaction step are sent to a tail gas treatment step, where it is heated to a required reaction temperature, and then hydrogenated in the presence of a catalyst to convert the sulfur compounds contained in these gases into hydrogen sulfide, A method for removing sulfur compounds contained in natural gas and the like, wherein the hydrogen sulfide is separated and returned to the Claus reaction step. 2. The method according to claim 1, wherein said residual gas is sent to a second tail gas treatment step, where it is heated to a required reaction temperature, and then hydrogenated in the presence of a catalyst to convert sulfur compounds contained in this gas into hydrogen sulfide. Returning the hydrogen sulfide to the Claus reaction step. A concentration separation device for separating an impurity gas containing a sulfur compound such as hydrogen sulfide separated from natural gas or the like into a concentrated gas mainly composed of hydrogen sulfide contained therein and a residual gas composed of residual components,
A Claus reaction device for recovering hydrogen sulfide in the concentrated gas from the concentration separation device as simple sulfur by a Claus reaction,
The off-gas from the Claus reactor and the residual gas from the enrichment and separation unit are heated to the required reaction temperature, then hydrogenated in the presence of a catalyst to convert the sulfur compounds contained in these gases into hydrogen sulfide, An apparatus for removing sulfur compounds contained in natural gas or the like, which is provided with a tail gas treatment device for separating and returning to the Claus reactor. 4. The removal device according to claim 3, wherein only the residual gas from said concentration and separation device is heated to a required reaction temperature, and then hydrogenated in the presence of a catalyst to convert a sulfur compound contained in this gas into hydrogen sulfide. An apparatus for removing sulfur compounds contained in natural gas or the like, further comprising a second tail gas treatment device for returning hydrogen to the Claus reactor.

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