JPH07299320A - Removal of hydrogen sulfide - Google Patents

Abstract

PURPOSE:To suppress the amt. of a sulfuric acid by-product and to make an apparatus compact in removing hydrogen sulfide from hydrogen sulfide- containing gas and recovering sulfur and hydrogen gas. CONSTITUTION:When hydrogen sulfide is removed from hydrogen sulfide- containing gas and sulfur and hydrogen gas are removed by combining iron salt aq. soln. treatment and electrochemical regeneration treatment, the hydrogen sulfide-containing gas (a) and a sulfuric acid-iron sulfate soln. (e) containing a trivalent iron ion are brought into contact with each other while passed through the packed bed of an absorbing tower 1 in a co-current flow contact system to remove hydrogen sulfide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the method for removing hydrogen sulfide, and more specifically, it combines an aqueous solution of an iron salt and an electrochemical regeneration treatment to remove hydrogen sulfide from a gas containing hydrogen sulfide and to remove sulfur from the gas containing hydrogen sulfide. In a method for recovering hydrogen gas, the present invention relates to a method for removing hydrogen sulfide that suppresses the amount of by-product of sulfuric acid, downsizes the apparatus, and reduces the hydrogen sulfide treatment cost.

[0002]

2. Description of the Related Art Conventionally, hydrogen sulfide discharged during petroleum refining has been industrially processed by the Claus method. However, according to this method, although the sulfur component in hydrogen sulfide is recovered as sulfur, the hydrogen component is not recovered as hydrogen gas but becomes water, which cannot be efficiently utilized industrially. At present, as a method for recovering sulfur and hydrogen gas from hydrogen sulfide by oxidation and electrochemical treatment, a method using an iron salt aqueous solution containing trivalent iron ions is known. In such a method, various iron salt aqueous solutions containing trivalent iron ions are used, but in any case, a slight amount of sulfuric acid by-product is inevitable. As a result, sulfuric acid accumulates in the iron salt aqueous solution, eventually causing precipitation of the iron salt, which is a serious process defect.

As an improved technique for solving this drawback, the group of the present inventors has already developed a technique for reducing the amount of sulfuric acid by-product by using an aqueous solution of phosphoric acid-iron chloride. However, subsequent research showed that this improved technique increased the concentration of sulfuric acid in iron-based aqueous solutions when used for long-term circulation,
It was found that it was necessary to replenish a new iron-based aqueous solution at the same time as extracting the iron-based aqueous solution as a waste liquid at a constant rate.
Therefore, the group of the present inventors further research, contact a part of the iron salt aqueous solution containing byproduct sulfuric acid with hydrogen, reduce the byproduct sulfuric acid contained in the solution to generate hydrogen sulfide,
Control the sulfuric acid concentration in the system by returning the generated hydrogen sulfide to a hydrogen sulfide gas absorber (including the hydrogen sulfide concentrator if there is one upstream from the hydrogen sulfide gas absorber) and treating it. By this, it is possible to efficiently recover sulfur and hydrogen gas without producing industrial waste such as waste iron liquid, waste acid or waste iron salt, and further, a solution after recovering hydrogen sulfide by reducing by-product sulfuric acid. Is introduced into the cathode chamber of the electrochemical regenerator, and the outlet liquid of the cathode chamber is returned to the hydrogen sulfide gas absorption device or before or after the device (either continuously or discontinuously). It is possible to prevent the accumulation of iron ions in the catholyte (migration from the anolyte), which eliminates the problems of exchanging the catholyte and draining the waste liquid, which results in a longer closed system. That continuous operation for a certain period is possible Out, it filed a patent previously (Japanese Patent Application No. Hei 5-36653 specification, Japanese Patent Application No. 5-293100 specification).

However, in the above-mentioned method, since a by-product sulfuric acid reduction step is newly added, there is a problem that the hydrogen sulfide treatment cost is unavoidably increased due to the equipment cost and reduction treatment cost. Therefore, in order to reduce the hydrogen sulfide treatment cost, it is necessary to suppress the amount of sulfuric acid byproduct in the hydrogen sulfide gas absorption / oxidation process as much as possible and to make the apparatus compact.

[0005]

Under the above circumstances, the present invention combines the treatment with an aqueous solution of an iron salt and the electrochemical regeneration treatment to remove hydrogen sulfide from a hydrogen sulfide-containing gas and to remove sulfur and hydrogen. An object of the present invention is to provide a method for recovering hydrogen sulfide that suppresses the amount of sulfuric acid by-product, downsizes the apparatus, and reduces the hydrogen sulfide treatment cost.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the inventors of the present invention have found that a gas-liquid countercurrent method which has been generally used in the conventional hydrogen sulfide gas absorption / oxidation process is used. Although the absorption tower has a high hydrogen sulfide absorption efficiency but a large amount of sulfuric acid by-product, the absorption tower with a packed bed of gas-liquid co-current method has a very small amount of sulfuric acid by-product and has a simple structure and compact size. In addition, since the amount of sulfuric acid by-product is remarkably suppressed by using this absorption tower having a packed bed of gas-liquid co-current system, it is not necessary to provide a by-product sulfuric acid reduction step, and even if it is provided, a large reduction is achieved. It has been found that no equipment is required and therefore the hydrogen sulfide treatment apparatus including the absorption tower can be made compact as a whole. The present invention has been completed based on such findings.

That is, the present invention is directed to the absorption of hydrogen sulfide gas.
In the oxidation step, a hydrogen sulfide-containing gas is subjected to a contact treatment with a sulfuric acid-iron sulfate solution containing trivalent iron ions to absorb hydrogen sulfide to perform an oxidation reaction, and a solution containing divalent iron ions, sulfur and byproduct sulfuric acid. And then generate hydrogen sulfide gas
After introducing the outlet liquid of the oxidation step into the sulfur separation step to separate sulfur from the solution, the outlet solution of the sulfur separation step is introduced into the electrochemical regeneration treatment step to convert divalent iron ions into trivalent iron ions. While generating hydrogen and recovering it, the hydrogen sulfide-containing gas and the sulfuric acid-iron sulfate solution containing trivalent iron ions are passed through the packed bed in the absorption tower by the parallel flow contact method. The present invention provides a method for removing hydrogen sulfide, which is characterized by bringing them into contact.

Hydrogen Sulfide Gas Absorption / Oxidation Step (Vapor-Liquid Contact Step) In this step, a contact treatment between the hydrogen sulfide-containing gas and a sulfuric acid-iron sulfate aqueous solution containing trivalent iron ions is performed.
The hydrogen sulfide-containing gas treated in this step may be pure hydrogen sulfide gas, and is a gas inert to hydrogen sulfide and trivalent iron ions, such as hydrogen sulfide and hydrogen, carbon monoxide, carbon dioxide. , A mixed gas with hydrocarbons (methane, ethane, etc.), nitrogen, etc. may be used. Specific examples thereof include natural gas, a gas obtained during geothermal power generation, and a gas generated during desulfurization in oil refining. On the other hand, a sulfuric acid-iron sulfate aqueous solution containing trivalent iron ions (ferric iron ions) that oxidize hydrogen sulfide is used as the absorbing liquid to be brought into contact with the hydrogen sulfide-containing gas. A ferrous salt or other salts may be contained within a range that does not impair the purpose.

The ion concentration in the aqueous iron salt solution used is not particularly limited, but the ferric ion is in the range of 0.1 to 3.0 mol / liter, preferably 0.5 to 1.5 mol / liter. Is. When the ferric ion content is less than 0.1 mol / liter,
If the absorption rate of hydrogen sulfide decreases, and if it exceeds 3.0 mol / liter, there is a problem in solubility, which is not preferable. The ferrous ion is not essential, but ferrous sulfate is used, and is usually present in the range of 0.1 to 3.0 mol / liter, preferably 0.5 to 1.5 mol / liter. To do. The addition of ferrous ion is mainly for improving the efficiency in the electrochemical treatment, but if it is less than 0.1 mol / liter, the effect cannot be obtained, and if it exceeds 3.0 mol / liter, iron is added. Undesirably, precipitation of salts (particularly ferrous sulfate) occurs. Regarding sulfuric acid, it is in the range of 0.1 to 5 mol / liter, preferably 1 to 4 mol / liter. When the amount of sulfuric acid is less than 0.1 mol / liter, by-product of sulfuric acid increases, which may reduce the efficiency during electrochemical regeneration.
If it exceeds 5 mol / liter, precipitation of iron salt (particularly ferrous sulfate) occurs, which is not preferable.

In carrying out this hydrogen sulfide gas absorption / oxidation step, it is necessary in the present invention to use an absorption tower having a packed bed of a parallel flow contact system. In a countercurrent contact type absorption tower, although the absorption efficiency is good, the amount of sulfuric acid by-product increases.
On the other hand, the absorption tower having the packed bed of the parallel flow contact system has a feature that the absorption efficiency is slightly inferior, but the sulfuric acid by-product amount is remarkably small, as compared with the absorption tower of the countercurrent contact system. The co-current contact type absorption tower is not particularly limited as long as it is capable of gas-liquid co-current contact, and a conventionally known absorption tower, for example, an ejector scrubber or a venturi scrubber, may be adopted. Good. Also,
The type of filler constituting the packed bed is not particularly limited, either,
Specific examples include carbon particles, carbon fibers, and high-purity alumina fibers. Among such fillers, it is particularly preferable to use carbon fiber from the viewpoint of suppressing the amount of by-product of sulfuric acid and improving absorption efficiency. Two or more kinds of fillers may be used in combination, and for example, carbon particles and carbon fibers may be used in combination. In the present invention, by adopting the absorption tower having the packed bed of the parallel flow contact system, the amount of sulfuric acid by-product is reduced as compared with the countercurrent contact system, and at the same time, the apparatus can be made compact. In the reaction between hydrogen sulfide and trivalent iron ions, the sulfur immediately after being generated by the oxidation of hydrogen sulfide reacts with water existing in the reaction system at a stage where the reactivity is still high, so that sulfuric acid is by-produced. The degree of sulfuric acid by-product is affected by the dispersion state of sulfur. That is, the higher the degree of dispersion of sulfur immediately after generation in the reaction solution, the easier the reaction between sulfur and water proceeds, and the amount of sulfuric acid by-product increases. In the present invention, in the absorption tower having a packed bed of a co-current contact system, since the absorption / oxidation reaction of hydrogen sulfide is carried out while passing through the packed bed, the sulfur in a highly dispersed state immediately after generation is in contact with the packing material. As the sulfur dispersibility decreases, the amount of sulfuric acid by-product decreases. In addition, since the contact efficiency between gas and liquid is improved by providing the filling layer, the device can be made compact at the same time.

The reaction formula of the oxidation step for producing sulfur from hydrogen sulfide in this step is as follows. 2Fe ³⁺ + H ₂ S = 2Fe ²⁺ + 2H ⁺ + S (precipitation) (I) That is, hydrogen sulfide is oxidized by ferric ion to produce sulfur, and ferric ion is ferrous ion. Is reduced to. At the same time, in the reaction in this step, a small amount of sulfuric acid is also by-produced in the present invention. As a result, ferrous ions, sulfur and by-product sulfuric acid will be contained in the solution. In addition, excess trivalent iron ions, non-by-product sulfuric acid previously compounded, and the like may coexist in the solution.

The contact temperature between the hydrogen sulfide-containing gas and the sulfuric acid-iron sulfate solution containing trivalent iron ions in the packed bed in the absorption tower is usually 50 to 155 ° C., preferably 120 to 140.
℃. When the contact temperature is lower than 50 ° C., the absorption rate of hydrogen sulfide decreases, and the separation of sulfur becomes difficult. In addition, when the contact temperature is low, solid sulfur may be precipitated in the packed bed and the absorption efficiency of the hydrogen sulfide-containing gas may be reduced. In particular, in order to carry out the separation rapidly, it is preferable that the melting point of sulfur is not lower than 120 ° C., although the melting point of sulfur is different for each allotrope. By thus setting the melting point of sulfur or higher, sulfur is produced in a molten state, and the sulfur and the aqueous solution can be easily separated by the difference in specific gravity. At the same time,
It is also possible to prevent precipitation of solid sulfur in the packed bed as described above. On the other hand, if the temperature is too high, the viscosity of molten sulfur may increase and handling may become inconvenient.
The upper limit is usually 155 ° C or lower, preferably 140 ° C or lower. Further, the pressure during the reaction is not particularly limited as long as it is a pressure necessary for preventing the liquid from boiling and maintaining the above desired temperature within a range that does not hinder the operation, but it is usually 1 atm.
(1.01325 × 10 ⁵ Pa) or more, for example, 1 to 10
atm (1.01325 × 10 ^{5 to} 10.1325 × 10 ⁵
Pa). Also, preferably 2 to 5 atm (2.02
650 × 10 ^{5 to} 5.06625 × 10 ⁵ Pa).

In the present invention, in order to further improve the absorption efficiency of hydrogen sulfide gas, at least a part of the gas discharged from the above-mentioned co-current contact type absorption tower through the gas-liquid separator is optionally used. May be brought into countercurrent contact with a sulfuric acid-iron sulfate solution (circulating liquid) containing trivalent iron ions. The countercurrent contact type device used at this time is not particularly limited, and conventionally known devices such as a bubble column, a spray column,
A general-purpose absorption tower such as a wetting wall tower, a stirring absorption tower, a packed bubble tower, or a packed tower may be adopted.

Sulfur Separation Step In this step, from a solution containing divalent iron ions generated in the above hydrogen sulfide gas absorption / oxidation step, sulfur and a trace amount of by-product sulfuric acid (outlet liquid of the hydrogen sulfide absorption / oxidation step) The sulfur separation process is performed. The method for separating and treating sulfur is not particularly limited, and various physical or chemical methods can be used. For example, as a physical treatment method, a sedimentation method, a centrifugation method, or the like can be used,
As the chemical treatment method, a method of converting into another sulfur compound can be used. As a particularly preferable method, a method of performing liquid-liquid separation, that is, sedimentation separation by the difference in specific gravity and recovering the generated sulfur as molten sulfur, can be mentioned. The sulfur separator used in this sulfur separation step is not particularly limited, and various structures can be used. For example, a general thickener type, a superficial drum type, a settling basin type, etc. may be appropriately selected according to the size of the molten sulfur droplets to be separated and recovered and the designed recovery rate.

In the present invention, the sulfur produced in the hydrogen sulfide gas absorption / oxidation step is usually in a molten state,
It easily coalesces by contact with the packing material packed in the absorption tower. Therefore, even if the step of coalescing the molten sulfur droplets is not provided before the sulfur separation step, the liquid in the sulfur separation step-
Liquid separation proceeds efficiently. Of course, a step of coalescing the molten sulfur droplets may be provided if necessary.

Electrochemical Regeneration Treatment Step In this step, a solution after the sulfur is separated and recovered in the sulfur separation step (an outlet liquid of the sulfur separation step) is processed by using an electrochemical method such as electrolysis. By
In the anode part, ferrous ions (Fe ²⁺ ) contained in the solution in a large amount are converted into ferric ions (Fe ³⁺ ) to contain a large amount of trivalent iron ions (ferric ions). In addition to being regenerated into a solution (absorption liquid or circulating liquid), hydrogen gas is generated in the cathode portion to separate and recover the hydrogen gas. The reaction that proceeds here is represented by the following reaction formula. 2Fe ²⁺ + 2H ⁺ = 2Fe ³⁺ + H ₂ (gas) (II) That is, ferrous ions are oxidized and regenerated to ferric ions in the anode part, and hydrogen ions are reduced in the cathode part. Hydrogen gas is generated. The regenerated solution can be repeatedly used as a hydrogen sulfide absorbing liquid (circulating liquid) in the hydrogen sulfide gas absorption / oxidation step. The material of the portion that comes into contact with the circulating liquid is preferably non-silica.

As the electrochemical regeneration device for carrying out this electrochemical regeneration treatment step, for example, an electrolytic cell of the type commonly used for ordinary electrolysis can be used.
The electrolytic cell for carrying out such a step is provided with a diaphragm between the anode part and the cathode part, and the diaphragm divides the anode part into the anode chamber and the cathode part into the cathode chamber. There is. An acid resistant material such as graphite or carbon fiber is used for the electrodes. A cation exchange membrane is preferably used as the diaphragm. When an electrolytic cell is used as an electrochemical regeneration device for performing the electrochemical regeneration treatment step, the outlet liquid of the sulfur separation step is introduced into the anode chamber of the electrolytic cell. On the other hand, the cathode chamber is usually filled with an aqueous solution containing a predetermined concentration of hydrogen ions, for example, an aqueous solution of 0.5 to 5 mol / liter, preferably 1 to 4 mol / liter. If it is out of this range, the electrolysis voltage increases and the efficiency decreases, which is not preferable. Alternatively, it is performed by supplying water to such an extent that the diaphragm between the anode and the cathode is not dried and applying a voltage.

In the present invention, a by-product sulfuric acid reduction step can be optionally provided, as described later. In this case, it is preferable to introduce all or part of the outlet liquid of the by-product sulfuric acid reduction step into the cathode chamber. When the outlet liquid of the by-product sulfuric acid reduction step is introduced into the cathode chamber, it is possible to prevent iron ions from moving from the anolyte to the catholyte and accumulating in the catholyte. Therefore, in the case of a completely closed system, the replacement of the catholyte and the draining of the waste liquid are unnecessary, and the continuous operation for a longer period becomes possible. Here, the hydrogen ion concentration in the outlet liquid introduced into the cathode chamber is
The range of 0.5 to 5 mol / liter, preferably 1 to 4 mol / liter is desirable, and if it is out of this range, the electrolysis voltage increases and the efficiency decreases, which is not preferable. After separating the hydrogen gas generated in the cathode chamber or without separating the hydrogen gas, the outlet liquid of the cathode chamber liquid absorbs hydrogen sulfide gas.
It is returned before or after the oxidation step or the hydrogen sulfide gas absorption / oxidation step. Here, “after the hydrogen sulfide gas absorption / oxidation step” means the downstream side of the hydrogen sulfide gas absorption / oxidation step and the upstream side of the sulfur separation device.

When a cation exchange membrane is used as the membrane, a porous gas permeable electrode, for example, a graphite fiber cloth, preferably one carrying a catalyst such as platinum, is directly contacted with the membrane, if desired. May be. The electrolysis is usually performed at 25 to 160 ° C. Therefore, a preferable temperature level (120 to 14) in the hydrogen sulfide gas absorption / oxidation process is used.
Even at 0 ° C., electrolysis can be carried out without any problem, and such high temperature electrolysis can improve the economical efficiency. Further, the hydrogen generated by the electrochemical treatment is captured and recovered by a usual method as needed. A part of the recovered hydrogen can be used to reduce the by-product sulfuric acid contained in the treatment liquid to generate hydrogen sulfide in a by-product sulfuric acid reduction step that is optionally provided.

In the present invention, since the amount of sulfuric acid by-product in the hydrogen sulfide gas absorption / oxidation process is extremely small, continuous operation can be performed for a long period in a closed system without providing the by-product sulfuric acid reduction process. In order to enable continuous operation for a long period, the following by-product sulfuric acid reduction step may be provided, if desired.

By-product sulfuric acid reduction step In this step, a part of the outlet liquid of the sulfur separation step containing divalent iron ions and by-product sulfuric acid is brought into contact with hydrogen to reduce the by-product sulfuric acid contained in the solution. Then, hydrogen sulfide is produced, and hydrogen sulfide (hydrogen-containing) is returned before or after the hydrogen sulfide gas absorption / oxidation step or the hydrogen sulfide gas absorption / oxidation step to control the amount of by-product sulfuric acid in the system. The reaction formula for producing hydrogen sulfide by reducing by-produced sulfuric acid with hydrogen is as shown below. H ₂ SO ₄ + 4H ₂ = H ₂ S + 4H ₂ O (III) That is, sulfuric acid is reduced by hydrogen to generate hydrogen sulfide. The hydrogen reduction reaction of the sulfuric acid can be carried out by using various types that are generally used in a gas-liquid-solid (catalyst) system. For example, when the hydrogen reduction reaction is carried out using a slurry bed reactor, a catalyst having a small particle size can be used. As a result, the efficiency of contact with the aqueous sulfuric acid solution is increased, and the reaction can proceed efficiently. However, in this slurry bed reactor, after the reaction,
A liquid-solid separation device becomes necessary. Further, the hydrogen reduction reaction can be carried out using a gas-liquid co-current type irrigation packed column. In this case, the downflow method is suitable for use in a large-scale apparatus capable of mass processing. On the other hand, the upflow method is suitable for a small device. In addition, the hydrogen reduction reaction can be performed using a packed bubble column.

In carrying out the hydrogen reduction reaction, the amount of the outlet liquid of the sulfur separation step to be fed into the hydrogen reduction device is determined by the sulfuric acid by-product rate in the hydrogen sulfide absorption / oxidation step and the hydrogen in the by-product sulfuric acid reduction step. It is determined by the balance with the reduction reaction rate. For example, when the sulfuric acid byproduct rate is about 2%,
A solution corresponding to 1 to 5% by volume of the outlet liquid of the sulfur separation step may be fed. The hydrogen gas supplied for the hydrogen reduction reaction of the by-product sulfuric acid in the discharged outlet liquid is 5% from the hydrogen gas flow generated in the electrochemical regeneration treatment step.
An amount equivalent to ˜35% by volume (excess amount) or a required amount from external hydrogen may be introduced. Various catalysts can be used for the hydrogen reduction reaction. As one of the preferable catalysts, white metal-supported activated carbon can be exemplified, which allows the reaction to proceed efficiently.

The temperature in this hydrogen reduction reaction is usually 1
The temperature is in the range of 00 to 180 ° C, preferably 120 to 150 ° C. If the reaction temperature is lower than 100 ° C, the reaction rate becomes very small. On the other hand, if the temperature exceeds 180 ° C., the pressure increases, which is disadvantageous in terms of process, which is not preferable. Further, the pressure when performing the hydrogen reduction reaction, if the pressure necessary to prevent water evaporation of the iron salt aqueous solution, to maintain the desired temperature,
There is no particular limitation, usually 3 atm (3.03975 × 10
⁵ Pa) or more, preferably ^{5 to} 7 atm (5.06625)
It is in the range of × 10 ^{5 to} 7.09275 × 10 ⁵ Pa).
Hydrogen sulfide generated by hydrogen reduction of by-product sulfuric acid in the by-product sulfuric acid reduction step is the hydrogen sulfide gas absorption / oxidation step or before the hydrogen sulfide gas absorption / oxidation step (when there is a hydrogen sulfide concentrator on the upstream side, It may be there) or returned later.

Here, the reason why hydrogen sulfide generated by the hydrogen reduction reaction is returned to the hydrogen sulfide gas absorption / oxidation step is the same as that of the absorption gas (the hydrogen sulfide-containing gas first introduced into the hydrogen sulfide gas absorption / oxidation step). This is because the absorption and oxidation reaction of the recovered hydrogen sulfide can proceed sufficiently. Further, the reason for returning hydrogen sulfide before or after the hydrogen sulfide gas absorption / oxidation step is that hydrogen sulfide gas recovered from the by-product sulfuric acid reduction step is converted to liquid sulfur. This is because it is necessary to return the line to a line having a temperature level equal to or higher than the melting point, and it may be anywhere upstream of the sulfur separation step. Whether to return the hydrogen sulfide to the hydrogen sulfide gas absorption / oxidation step or before or after the hydrogen sulfide gas absorption / oxidation step may be determined in consideration of the balance of the entire system.

On the other hand, the recovered liquid in which the by-product sulfuric acid has been reduced (the outlet liquid of the by-product sulfuric acid reduction process) is returned to the sulfur separation process or before the process, or as described above, the entire recovered liquid. Alternatively, a part thereof is introduced into the cathode chamber of the electrochemical regeneration device during the electrochemical regeneration treatment step. The former reason is that a small amount of dissolved hydrogen sulfide is contained in the outlet liquid, and sulfur is generated when it joins the iron salt aqueous solution containing trivalent iron ions. On the other hand, the latter reason is as described above, and it is preferable to adopt the latter method from the viewpoint of long-term continuous operation. In the latter method, when only a part of the outlet liquid of the by-product sulfuric acid reduction process is introduced into the cathode chamber, the remaining outlet liquid of the hydrogen sulfide gas absorption / oxidation process or hydrogen sulfide gas absorption / oxidation process is used. Bring back before or after. In this way, by-product sulfuric acid contained in the solution is reduced with hydrogen to control the content of sulfuric acid in the system, whereby the entire system can be closed and continuously treated.

Next, an example of a preferred embodiment of the present invention will be described with reference to the accompanying drawings. 1 and 2 are schematic views showing different examples of the method for removing hydrogen sulfide of the present invention.
Shows a case where the hydrogen sulfide gas absorption / oxidation step is performed by an absorption tower having a co-current contact type packed bed, and FIG. 2 shows the hydrogen sulfide gas absorption / oxidation step having a co-current contact type packed bed and The following shows the case of sequentially performing the flow contact type absorption tower.

Description of FIG. 1 As shown in FIG. 1, a hydrogen sulfide gas absorption tower (parallel flow contact system, packed tower) 1 contains a hydrogen sulfide-containing gas a as a gas to be treated and trivalent iron ions. Sulfuric acid-iron sulfate solution e is introduced. With respect to this sulfuric acid-iron sulfate solution, a newly prepared solution may be introduced into the absorption tower 1 in the initial state. After starting the operation of the apparatus, the sulfuric acid-iron sulfate solution obtained in the electrochemical regenerator 3 (for example, an electrolytic cell) is supplied. The inside of the absorption tower 1 is heated by a heating device (not shown). In the absorption tower, the gas to be treated a and the sulfuric acid-
When the iron sulfate solution e is introduced and brought into parallel flow contact with each other, the oxidation reaction proceeds according to the above reaction formula (I), sulfur is produced, and at the same time, a solution containing divalent iron ions and a trace amount of by-product sulfuric acid is formed. can get. At this time, if the inside of the reaction system is equal to or higher than the melting point of sulfur, sulfur hardly adheres to the inner wall of the absorption tower 1 or the packed bed, which is preferable.

Next, the gas-liquid mixture discharged from the absorption tower 1 is introduced into the gas-liquid separator 4, and the oxidized gas b is discharged from the upper part of the gas-liquid separator 4 to the outside of the system. On the other hand, a solution containing divalent iron ions, sulfur, and a trace amount of by-product sulfuric acid is sent from the bottom of the gas-liquid separator 4 to the sulfur separator 2. In the sulfur separator 2, the sulfur is melted and is allowed to settle in the solution due to the difference in specific gravity, so that sulfur C can be easily fed from the bottom of the separator.
Is recovered. Also, if sulfur is separated in the molten state,
The internal structure of the sulfur separation device can be simplified.

Further, the solution (circulating liquid) after the sulfur recovery that comes out from the sulfur separation device is supplied to the electrochemical regeneration device 3 (for example, an electrolytic cell). In this electrolytic cell, the reaction formula
The reaction of (II) proceeds, ferrous ions are oxidized to ferric ions, and hydrogen gas d is recovered. As an apparatus used in this electrochemical regeneration treatment, as already mentioned above, an electrolytic cell of a conventionally used type can be used. A diaphragm is provided between the anode and the cathode in this electrolytic cell, and an acid resistant material such as graphite or carbon fiber is used for the electrode. It is preferable to use a cation exchange membrane as the diaphragm. The solution (circulating solution) containing divalent iron ions and a trace amount of by-product sulfuric acid supplied to the electrolytic cell has a low electrolytic performance when the concentration of sulfur in the solution is high. It is better to remove the sulfur in it as much as possible. Also,
If desired, a filter can be provided in front of the electrolytic cell. The sulfuric acid-iron sulfate solution obtained by the electrochemical regeneration device 3 is supplied to the absorption tower 1.

Description of FIG. 2 As shown in FIG. 2, the hydrogen sulfide gas absorption tower (parallel flow contact system, packed tower) 1 contains hydrogen sulfide-containing gas a to be treated and trivalent iron ions. Sulfuric acid-iron sulfate solution e is introduced. With respect to this sulfuric acid-iron sulfate solution, a newly prepared solution may be introduced into the absorption tower 1 in the initial state. After starting the operation of the apparatus, the sulfuric acid-iron sulfate solution obtained in the electrochemical regenerator 3 (for example, an electrolytic cell) is supplied. The inside of the absorption tower 1 is heated by a heating device (not shown). When the gas to be treated a and the sulfuric acid-iron sulfate solution e are introduced into the absorption tower 1 and are brought into contact with each other in parallel flow, an oxidation reaction proceeds according to the reaction formula (I), sulfur is generated, and at the same time divalent A solution containing the iron ion and a trace amount of by-product sulfuric acid is obtained. At this time, if the inside of the reaction system is equal to or higher than the melting point of sulfur, sulfur hardly adheres to the inner wall of the absorption tower 1 or the packed bed, which is preferable.

Next, the gas-liquid mixture discharged from the absorption tower 1 is introduced into the gas-liquid separator 4, and at least a part of the residual hydrogen sulfide-containing gas discharged from the upper part of the gas-liquid separator 4 is hydrogen sulfide. It is introduced into the gas absorption tower (countercurrent contact type) 5. Further, the hydrogen sulfide gas absorption tower 5 is supplied with a sulfuric acid-iron sulfate solution e ′ containing trivalent iron ions. With respect to this sulfuric acid-iron sulfate solution, a newly prepared solution may be introduced into the absorption tower 5 in the initial state. After starting the operation of the apparatus, the sulfuric acid-iron sulfate solution obtained in the electrochemical regenerator 3 (for example, an electrolytic cell) is supplied. Absorption tower 5
The inside of is heated by a heating device (not shown).
When the residual hydrogen sulfide-containing gas a and the sulfuric acid-iron sulfate solution e ′ are introduced into the absorption tower 5 and brought into countercurrent contact with each other, the oxidation reaction proceeds according to the reaction formula (I), and at the same time sulfur is produced. A solution containing divalent iron ions and a trace amount of by-product sulfuric acid is obtained. At this time, if the inside of the reaction system is equal to or higher than the melting point of sulfur, sulfur hardly adheres to the inner wall of the absorption tower 5, which is preferable. Oxidized gas b from the upper part of absorption tower 5
Is discharged out of the system.

On the other hand, a solution containing divalent iron ions, sulfur, and a trace amount of by-product sulfuric acid is sent from the bottom of the gas-liquid separator 4 to the sulfur separator 2 and also from the bottom of the absorption tower 5. Is sent to the sulfur separator 2. From this point onward, as shown in FIG.
In the same manner as in the above case, the sulfuric acid-iron sulfate aqueous solution obtained by the electrochemical regenerator 3 is supplied to the absorption tower 1 as a solution e and a part of the solution e ′ is supplied to the absorption tower 5. It

[0033]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 As an absorption tower, with an outer jacket, an inner diameter of 100 mm,
A parallel flow contact type having a resin lining structure with an internal volume of 8 liters and being filled with a carbon fiber felt was used. Hydrogen sulfide absorption liquid containing trivalent iron ions (composition at the time of introduction into absorption tower: FeSO ₄ 0.70 mol / liter, Fe (SO
₄ ) _1.5 0.50 mol / l and H ₂ SO ₄ 2.5 mol / l) were circulated in the absorption tower at 30 l / h. Then, hydrogen sulfide was supplied to the absorption tower at 3.7 mol / hour, and the reaction was carried out in parallel flow contact. Reaction temperature is 130
℃, the reaction pressure is 4.5atm (4.5596 × 10 ⁵ Pa)
And Then, the absorption liquid derived from the absorption tower is introduced into a sulfur separation device, and after the generated sulfur is separated and removed, an electrolytic cell (electrode area: 2,000 cm ² , anode chamber: carbon plate / carbon fiber cloth, diaphragm: Tokuyama Soda Co., Ltd., Neoceptor CM-
1, cathode: carbon fiber cloth with platinum catalyst / carbon plate) was introduced into the anode chamber. Further, an electrolytic solution containing H ₂ SO ₄ 2.5 mol / liter was circulated at 30 liter / hour in the cathode chamber. Electrolysis temperature is 50 ° C, current density is 100 mA / cm
The constant current operation of ² was performed. After continuous operation for 500 hours, the electrolytic solution (raw material solution) on the anode chamber side was extracted and the composition was analyzed. As a result, the H ₂ SO ₄ content was 2.64 mol / liter (initial value: 2.50 mol / liter), and the sulfuric acid byproduct rate was 1%. The hydrogen sulfide absorption rate was 99.0%.

Comparative Example 1 As an absorption tower, with an outer jacket, an inner diameter of 100 mm,
Reaction with hydrogen sulfide and circulating iron liquid in countercurrent contact using a countercurrent contact type with a resin lining structure with an internal volume of 8 liters and filled with commercially available coal-based activated carbon particles (average particle diameter 5 mm) The same procedure as in Example 1 was carried out except that the above was performed. After continuous operation for 500 hours, the electrolytic solution (raw material solution) on the anode chamber side was extracted and the composition was analyzed. As a result, H ₂ SO _{4 was} 2.78 mol / liter (initial value 2.50 mol / liter), and the sulfuric acid byproduct rate was 2%. The hydrogen sulfide absorption rate was 99.9%.

[0036]

According to the present invention, in a method for removing hydrogen sulfide from a gas containing hydrogen sulfide and recovering sulfur and hydrogen gas, an absorption tower having a packed bed of a cocurrent contact system in the hydrogen sulfide gas absorption / oxidation step. By using, by-product amount of sulfuric acid is suppressed and the device is made compact,
The hydrogen sulfide treatment cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a method for removing hydrogen sulfide of the present invention.

FIG. 2 is a schematic view showing a different example of the method for removing hydrogen sulfide of the present invention.

[Explanation of symbols]

 1: Hydrogen sulfide gas absorption tower (parallel flow contact method, packed tower) 2: Sulfur separator 3: Electrochemical regenerator 4: Gas-liquid separator 5: Hydrogen sulfide gas absorption tower (countercurrent contact method) a: Sulfide Hydrogen-containing gas b: Oxidized gas c: Sulfur d: Hydrogen gas e: Sulfuric acid-iron sulfate solution e ': Sulfuric acid-iron sulfate solution

Claims (3)

[Claims] 1. In the hydrogen sulfide gas absorption / oxidation step,
The hydrogen sulfide-containing gas is subjected to a contact treatment with a sulfuric acid-iron sulfate solution containing trivalent iron ions to absorb hydrogen sulfide and perform an oxidation reaction to generate a solution containing divalent iron ions, sulfur and byproduct sulfuric acid, Then, the outlet liquid of the hydrogen sulfide gas absorption / oxidation process is introduced into the sulfur separation process to separate sulfur from the solution, and then the outlet liquid of the sulfur separation process is introduced into the electrochemical regeneration treatment process to divalent iron. In regenerating ions to trivalent iron ions, and generating and recovering hydrogen, a hydrogen sulfide-containing gas and a sulfuric acid-iron sulfate solution containing trivalent iron ions are added,
A method for removing hydrogen sulfide, which comprises contacting while passing through a packed bed in an absorption tower by a parallel flow contact method. 2. A gas containing hydrogen sulfide and 3 in the absorption tower.
The method for removing hydrogen sulfide according to claim 1, wherein the contact with the sulfuric acid-iron sulfate solution containing valent iron ions is performed at a temperature equal to or higher than the melting point of sulfur. 3. The method for removing hydrogen sulfide according to claim 1, wherein the packed bed in the absorption tower is a carbon particle packed bed or a carbon fiber packed bed.