阅读说明：本技术 从含硫化氢气体中回收硫磺并同时制取氢气的方法 (Method for recovering sulfur from gas containing hydrogen sulfide and preparing hydrogen simultaneously ) 是由 俞英 黄海燕 王亚军 向言 吕增 刘嘉雯 姚苏桐 于 2019-11-18 设计创作，主要内容包括：本发明提供一种从含硫化氢气体中回收硫磺并同时制取氢气的方法,采用氧化吸收反应和电解再生反应相结合,在吸收反应器中使含硫化氢气体与含有络合态Fe(III)的吸收液接触反应,且反应体系的pH为5-10,接触反应中使硫化氢被氧化为硫磺,而吸收液中的Fe(III)至少部分被还原为Fe(II)；来自吸收反应器的富含硫磺的吸收液经分离出硫磺后作为阳极液送入电解反应器,经电解再生供吸收反应器循环使用,同时从电解反应器的阴极制取氢气。本发明方法吸收和电解反应效率都较高,且采用的吸收液具有较小的腐蚀性,更利于实现从硫化氢中回收硫磺同时制取氢气的连续化。(The invention provides methods for recovering sulfur from gas containing hydrogen sulfide and preparing hydrogen at the same time, which combines oxidation absorption reaction and electrolytic regeneration reaction, the gas containing hydrogen sulfide and absorption liquid containing Fe (III) in complex state are in contact reaction in an absorption reactor, the pH value of the reaction system is 5-10, the hydrogen sulfide is oxidized into sulfur in the contact reaction, and Fe (III) in the absorption liquid is at least partially reduced into Fe (II), the absorption liquid rich in sulfur from the absorption reactor is separated out to be used as anode liquid to be sent into the electrolytic reactor, and is recycled for the absorption reactor through electrolytic regeneration, and hydrogen is prepared from the cathode of the electrolytic reactor.)

1. The method for recovering sulfur from the gas containing hydrogen sulfide and preparing hydrogen simultaneously is characterized by comprising the following processes:

in an absorption reactor, hydrogen sulfide-containing gas is in contact reaction with absorption liquid containing Fe (III) in a complex state, the pH of a reaction system is 5-10, hydrogen sulfide is oxidized into sulfur in the contact reaction, and Fe (III) in the absorption liquid is at least partially reduced into Fe (II);

the absorption liquid rich in sulfur from the absorption reactor is separated to obtain sulfur, which is used as anode liquid to be sent into the electrolysis reactor, and the sulfur is recycled for the absorption reactor through electrolysis regeneration, and hydrogen is prepared from the cathode of the electrolysis reactor.

2. The process according to claim 1, wherein the conditions for reacting the hydrogen sulfide-containing gas with the absorption liquid to produce sulfur in the absorption reactor and reacting the hydrogen sulfide-containing gas with the absorption liquid to produce sulfur in contact therewith are atmospheric pressure, 10 to 100 ℃.

3. The method according to claim 1, wherein the absorption liquid is an aqueous solution prepared by using a complex Fe (III) salt; or the absorption liquid is an aqueous solution prepared from water-soluble iron salt and a complexing agent, the complexing agent can at least form stable complexation with Fe (III), and the mass concentration of the complexing agent is 0.1-50%.

4. The method according to claim 1 or 3, wherein the absorption liquid entering the absorption reactor is an aqueous solution having a Fe (III) concentration of 0.01mol/L or more.

5. A method according to claim 1, 3 or 4, characterized in that the absorption liquid further comprises an inorganic base and/or an inorganic acid to maintain the pH of the absorption liquid.

6. The method as claimed in claim 1, 3, 4 or 5, wherein the absorption liquid consists of H which complexes Fe (II) by not more than 0.7mol/L and Fe (III) by not less than 0.01mol/L and can adjust the pH of the absorption liquid to 5-10₂SO₄KOH or NaOH.

7. The process according to claim 1 or 2, wherein the hydrogen sulfide-containing gas has a hydrogen sulfide concentration of 0.02 to 80% by volume.

8. The process according to claim 1 or 3, wherein the complexing state Fe (III) is the reaction product of a complexing agent and Fe (III), the complexing agent comprising at least of the sodium/potassium or ammonium salt of ethylenediaminetetraacetic acid, hydroxyethylidene-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, and ethylenediamine-diorthohydroxyphenylacetic acid.

9. The process of claim 1, wherein the electrolytic reactor is a tank cell or a plate and frame cell and a diaphragm is provided to separate the anode and cathode compartments.

10. The method according to claim 9, characterized in that the electrolytic cell of the electrolytic reactor is a monopolar or bipolar electrolytic cell.

Technical Field

The invention relates to a method for recovering sulfur from gas containing hydrogen sulfide and simultaneously preparing hydrogen, in particular to methods for simultaneously preparing sulfur and hydrogen by combining a hydrogen sulfide absorption technology with an indirect electrolysis technology.

Background

In the secondary processing of sulfur-containing crude oil, most of the sulfides in the crude oil are converted into hydrogen sulfide which exists in the refinery tail gas, and in the purification process involving the gas containing hydrogen sulfide, such as the purification of natural gas, methane, shale gas, coal dry distillation gas, petroleum associated gas and the like, a large amount of hydrogen sulfide components are often accompanied, and the hydrodesulfurization process commonly adopted in high sulfur-containing gas fields and the petrochemical industry for producing high-quality fuel oil also produces a large amount of hydrogen sulfide-containing gas, hydrogen sulfide (H) every day₂S) is becoming more and more important.

Many reports have been made on such a desulfurization treatment method for a gas containing hydrogen sulfide, and from the aspect of effective utilization of resources, sulfur recovery by oxidizing hydrogen sulfide to elemental sulfur by an oxidation method is widely used in industry. The traditional method mainly comprises a Claus method (also called Claus method), and COPE (oxygen-enriched Claus process), Superclaus (super Claus) process, fluidized bed Claus process and the like which are improved on the basis of the Claus method, and the thinking is that organic amine is absorbed and H is enriched₂S, then oxidation reaction, H₂S, finally generating water and sulfur; also reported are selective oxidation processes, in which H is converted by means of a suitable catalyst₂S is directly oxidized into sulfur, and the reaction product is also generated water and sulfur.

The traditional method for recovering sulfur by pure oxidation only utilizes H₂The sulfur element in S and the hydrogen element are converted into water, in order to fully utilize the hydrogen sulfide resource in the gas, the design idea of decomposing and recovering the sulfur and simultaneously preparing the hydrogen by the hydrogen sulfide is developed, such as a pyrolysis method, a photolysis method, an electrolysis method and the like, more research electrolytic methods can be divided into a direct electrolytic method and an indirect electrolytic method, and more research and report are carried out on the advantages and the disadvantages of each electrolytic technology.

The indirect electrolysis method is characterized in that hydrogen sulfide is firstly oxidized into sulfur, then an oxidant is regenerated in an electrolytic cell, and hydrogen is released simultaneously, compared with the direct electrolysis desulfurization method, the method has the advantage that sulfur generated by oxidation is attached to the surface of an electrode, so that the electrode is passivated, and therefore, the indirect electrolysis desulfurization method is concerned more in the research of the electrolysis method.

In the technology of preparing hydrogen while desulfurizing by an electrolytic method, the research is focused on efficiently absorbing and oxidizing hydrogen sulfide in tail gas into elemental sulfur and effectively electrolyzing the absorption liquid separated from the elemental sulfur to prepare high-purity hydrogen. For example, in many studies, soluble iron salts are used as a hydrogen sulfide absorbent, and oxidation of ferric iron (fe (iii)) is utilized to contact hydrogen sulfide with the absorbent to generate oxidation reaction to precipitate elemental sulfur, the ferric iron is reduced to ferrous iron (fe (ii)), and the absorbent losing oxidation is regenerated through electrolysis reaction, that is, an electrochemical method is introduced, so that the ferrous iron is oxidized back to ferric iron at the anode, and hydrogen ions are generated to be reduced at the cathode to release hydrogen.

In spite of the research results, the technical idea of converting hydrogen sulfide into elemental sulfur by utilizing the oxidation of ferric iron salt dissolved in an iron-based absorbent to realize gas desulfurization has been fully proven and adopted, and in the implementation process, maintaining the stable existence of ferric iron in an absorbent solution is very important, so that the maintenance of the strong acidity of the absorbent is which is a key characteristic that must be satisfied in order to ensure the oxidation of ferric iron, and the reason for this is to inhibit the hydrolysis of ferric iron ions to generate ferric hydroxide precipitates, and at the same time, to maintain the higher acidity of the absorbent solution, and to facilitate the increase of conductivity, not only to reduce the electrolytic energy consumption, but also to improve the electrolytic efficiency, in addition to the conditions of the absorption and electrolysis processes, the influence of electrode characteristics, etc., on the iron-based absorption liquid, which is not studied, but also on the electrochemical density of ferrous iron chloride solution, and when the pH of the absorbent solution is close to the neutral pH of the absorbent solution, is not studied as the electrochemical density of ferrous chloride solution, and when the pH of the absorbent solution is changed sharply along with the pH of the anode solution.

It can be understood that the strong acid absorption liquid used in the absorption and electrolysis processes puts severe requirements on the operation conditions of the whole process and the acid corrosion resistance of equipment materials, the operation and equipment cost requirements are high, the applicable environment and difficulty block the industrialization promotion, and the practicability of the industrial operation is reduced.

Disclosure of Invention

The technical problem solved by the invention is to provide methods for recovering sulfur from gas containing hydrogen sulfide and preparing hydrogen at the same time, and through the adjustment of the composition of an iron-based absorbent, a integration process for absorbing and recovering sulfur and preparing hydrogen by hydrogen sulfide is still effectively realized without requiring strong acid conditions, the influence of the corrosivity of strong acid absorption liquid is solved, the utilization rate of hydrogen sulfide resources is improved, and the whole process is easy to realize industrialization.

The invention provides methods for recovering sulfur from gas containing hydrogen sulfide and preparing hydrogen simultaneously, which comprises the following processes:

in an absorption reactor, hydrogen sulfide-containing gas is in contact reaction with absorption liquid containing Fe (III) in a complex state, the pH of a reaction system is 5-10, hydrogen sulfide is oxidized into sulfur in the contact reaction, and Fe (III) in the absorption liquid is at least partially reduced into Fe (II);

the absorption liquid rich in sulfur from the absorption reactor is separated to obtain sulfur, which is used as anode liquid to be sent into the electrolysis reactor, and the sulfur is recycled for the absorption reactor through electrolysis regeneration, and hydrogen is prepared from the cathode of the electrolysis reactor.

According to the method, a combined reactor of an absorption reactor and an electrolysis reactor is adopted, the absorption oxidation process of hydrogen sulfide is combined with the electrolytic regeneration process of the iron-based absorption liquid, ferric ions in the absorption liquid exist in a complex state, the absorption reaction system does not limit strong acidity any more, the absorption reaction can be carried out near neutrality, the absorption liquid to be generated (also called as the liquid to be regenerated) fed into the electrolysis reactor can still realize effective electrolytic regeneration, high-purity hydrogen is obtained at the cathode of the electrolysis reactor, and the regenerated liquid obtained by electrolysis is recycled.

According to the scheme of the invention, in the absorption reactor, the hydrogen sulfide-containing gas reacts with the absorption liquid to generate sulfur, and the condition of the reaction of the hydrogen sulfide-containing gas and the sulfur is normal pressure and 10-100 ℃. The hydrogen sulfide-containing gas may be introduced into the absorption reactor simultaneously with the absorption liquid, so that the hydrogen sulfide-containing gas and the absorption liquid are simultaneously brought into contact with each other and reacted.

According to the scheme of the invention, in the absorption liquid circularly used between the absorption reactor and the electrolysis reactor, ferric iron Fe (III) and ferrous iron Fe (II) exist in a complex state (also called complex Fe (III) and complex Fe (II) in the invention), thereby ensuring the stability of Fe (III)/Fe (II) in the absorption liquid. The absorption liquid used in the invention can be prepared by complexing iron salt directly or by combining iron salt and a proper complexing agent. Specifically, the absorption liquid is an aqueous solution prepared by utilizing complex Fe (III) salt; or the absorption liquid is an aqueous solution prepared from water-soluble iron salt and a complexing agent, the complexing agent can at least form stable complexation with Fe (III), and the quality of the complexing agentThe complexing agent used in the absorbent solution of the present invention is preferably a substance having a strong complexing action with iron ions and capable of stabilizing itself and Fe (III)/Fe (II) complexes in a system having a pH of 5 to 10, and is or two or more kinds of mixed components as necessary, which can be selected and determined by those skilled in the art based on their own basic knowledge, and as a part of the examples of the present invention, Fe (III) in a complexed state is a reaction product of a complexing agent selected from corresponding sodium, potassium or ammonium salts, for example, sodium, potassium or ammonium salts of ethylenediaminetetraacetic acid (EDTA-Na, EDTA-K, EDTA-NH)₄) Sodium salt, potassium salt or ammonium salt of hydroxyethylidene diphosphonic acid (HEDP-Na, HEDP-K, HEDP-NH)₄) Sodium salt/potassium salt or ammonium salt of ethylenediaminetetramethylenephosphonic acid (EDTMPS-Na, EDTMPS-K, EDTMPS-NH)₄) Sodium salt, potassium salt or ammonium salt of diethylenetriamine penta (methylene phosphonic acid) (DTPMPA-Na, DTPMPA-K, DTPMPA-NH)₄) And sodium/potassium or ammonium salts of ethylenediamine-di-o-hydroxyphenylacetic acid (EDDHA-Na, EDDHA-K, EDDHA-NH)₄) And the like. The iron ions can be introduced by their soluble salts, such as sulfate, hydrochloride, etc., in the form of ammonium, sodium or potassium salts of complex iron in the absorption liquid. When the complex iron salt is used as it is, a complex iron salt corresponding to the above-mentioned complexing agent may be selected, specifically, for example, ferric ammonium EDTA and the like.

In the method, the absorption liquid containing the complex state Fe (III) and the complex state Fe (II) is used as the absorption desulfurizer, so that the chemical stability is better, the degradation failure is not easy to occur, and the loss in the absorption-regeneration process is less.

step, the absorption liquid used in this invention can absorb H in acid gas₂S absorption has stronger selectivity and can react with H under the conditions of weak acidity to weak base₂CO with S₂Only a small amount of the carbonate is absorbed, the generated carbonate can be separated out of the system along with the sulfur, and the hydrocarbon gas does not influence the absorption of the system.

The implementation principle of the method of the invention can be explained as follows: the acid gas containing hydrogen sulfide and absorption liquid enter an absorption reactor together, and the hydrogen sulfide is absorbedComplexed Fe (III) (actually still as Fe) in the reactor³⁺With Fe²⁺Is an intermediate circulating agent) to generate sulfur (elemental sulfur), and the complex Fe (III) is at least partially reduced to complex Fe (II). The reaction product is discharged out of the absorption reactor along with the absorption liquid, and after the sulfur particles are separated, the reaction product contains H⁺And the reaction liquid (which can be called absorption liquid to be regenerated or liquid to be regenerated) of the complex Fe (II) is sent to an electrolytic reactor to be used as anolyte to carry out electrochemical reaction, at least part of the complex Fe (II) is oxidized into complex Fe (III) at the anode, and the complex Fe (II) is sent back to the absorption reactor to be used as absorption liquid for recycling, and H entering the electrolyte⁺Is reduced to H at the cathode through the exchange membrane₂And collected. The reaction of the whole process is as follows:

in the absorption reactor: 2[ Fe (III) L]+H₂S＝2[Fe(II)L]+2H⁺+S↓

In the electrolytic reactor:

anode: 2[ Fe (II) L]＝2[Fe(III)L]+2e^－

Cathode: 2H₂O+2e^－＝H₂↑+2OH^-(basic)

Cathode: h⁺+2e^－＝H₂↓ (acidic)

Total reaction of the electrolytic reactor:

2[Fe(II)L]+2H₂O＝2[Fe(III)L]+H₂↑+2OH^-

or the like, or, alternatively,

2[Fe(II)L]+2H⁺＝2[Fe(III)L]+H₂↑

in the above reaction formula, [ Fe (III) L ] or [ Fe (II) L ] represents a complexed ferric ion Fe (III) or a complexed ferrous ion Fe (II).

According to the embodiment of the invention, the absorption liquid can enter the absorption reactor and simultaneously the gas containing the hydrogen sulfide is introduced. The gas to be treated is brought into the absorption reactor by using the absorption liquid, so that the full contact between the gas and the absorption reactor is promoted, and the absorption effect is improved. In the process, the liquid/gas volume ratio can be properly controlled according to the characteristics of the gas to be treated, for example, the liquid/gas volume ratio is controlled to be 5-20, which is favorable for the absorption reaction of most of the gas to be treated.

In the embodiment of the present invention, in the absorption liquid entering the absorption reactor, the concentration of fe (iii) (also understood as fe (iii) in the complexed state in the present invention) is greater than or equal to 0.01mol/L, which is more beneficial to ensure the absorption reaction with the hydrogen sulfide, it is understood that fe (iii) is advantageously in a high concentration, so the upper limit of fe (iii) concentration may not be required, and fe (iii) concentration is substantially saturated in solution at about 1.1mol/L under the conventional conditions, so controls the fe (iii) concentration in the absorption liquid to be 0.01-1.1mol/L, and comprehensively, for example, fe (iii) concentration in the absorption liquid may be controlled to be 0.17-1.1mol/L, or 0.3-1.1mol/L, since fe (iii) concentration in the absorption liquid will gradually decrease with the progress of the absorption reaction, but will be recovered in the electrolysis process, so that the composition of the hydrogen sulfide absorption liquid and the electrolysis process will be constant , and fe (iii) concentration will be more beneficial to be changed into fe (iii) in a comprehensive form after the absorption process (iii) is actually converted into fe (iii) and fe (iii) are also properly complexed state.

In the embodiment of the present invention, an inorganic base and/or an inorganic acid may be further included in the absorption liquid to maintain the pH of the absorption liquid, so as to inhibit hydrolysis of fe (iii). For example, sodium hydroxide, potassium hydroxide, sulfuric acid and the like are used in a relatively common manner, and the specific selection is not limited.

The method can control the composition of the absorbing solution to be Fe (II) complex less than or equal to 0.7mol/L, Fe (III) complex more than or equal to 0.01mol/L and H capable of adjusting the pH value of the absorbing solution to 5-10 by adjusting the concentration of the complexing agent, the respective concentrations of Fe (III) and Fe (II) and a proper pH range (controlling an alkali liquor system) so that the absorbing solution can better play a role in oxidizing and absorbing hydrogen sulfide while keeping the absorbing solution stable, and when the concentration of Fe (II) in a reaction system reaches a fixed level of , the absorbing effect can be influenced and the absorbing solution needs to be sent for regeneration₂SO₄KOH or NaOH.

According to the scheme of the invention, the absorbent is contacted with the hydrogen sulfide to complete the absorption reaction,fe (III) in the absorbent is at least partially reduced to generate Fe (II) and S in hydrogen sulfide^2-Since the reaction liquid is substantially a mixed system, the reaction liquid is rich in sulfur and the concentration of Fe (II) increases, and the reaction liquid is separated and regenerated by an appropriate method before being reused. Specific embodiments may be that the method for separating sulfur from the sulfur-rich absorption liquid comprises sedimentation separation, centrifugal separation, filtration separation or air flotation separation.

According to the invention, a sulfur separation device is usually arranged between an absorption reactor and an electrolysis reactor, solid-liquid separation is carried out on absorption liquid (also called reaction liquid) rich in sulfur after absorption reaction, the absorption liquid after sulfur separation is to-be-regenerated liquid rich in Fe (II), the absorption liquid is sent into an anode chamber of the electrolysis reactor and is used as anode liquid for electrolytic regeneration, the separation process is required to firstly separate the sulfur from the absorption liquid, sulfur particles are prevented from entering the electrolysis reactor in the process, the to-be-regenerated liquid rich in Fe (II) is collected and is used as anode liquid to be sent into the electrolysis reactor, the electrolyzed regeneration liquid is sent back to the sulfur separation device, the separated sulfur can be subjected to solid-liquid separation again in specific operation, and a small amount of collected absorption liquid residue can be used as absorption liquid for recycling together with regeneration liquid from electrolytic regeneration and is returned to the absorption reactor.

As described above, the iron in the iron-based absorption liquid used in the method of the present invention is stably present in a complex state, and the research of the inventors shows that the iron-based absorption liquid in the complex state can completely satisfy the absorption oxidation of hydrogen sulfide and the electrolytic regeneration of Fe (II), and simultaneously produce hydrogen at the cathode.

According to the present invention, there is no particular requirement for the configuration and material selection of the reactor in the case of conducting the electrolysis reaction, the electrolysis reactor is a tank-type electrode cell or a plate-and-frame type electrolysis cell, and a diaphragm is provided to separate the anode chamber and the cathode chamber, and steps are further carried out, the electrolysis cell of the electrolysis reactor is a single-pole or multi-pole electrolysis cell.

According to the method, high-purity hydrogen can be produced as a byproduct with low power consumption while the absorption liquid is regenerated (the power consumption for hydrogen production is 1/3-1/2 lower than that for hydrogen production by water electrolysis), so that H is increased₂Resource utilization of S, andby-product H₂Can be used as a supplementary raw material for hydrodesulfurization.

The process of the invention is suitable for the treatment of various types of acid gases containing hydrogen sulphide, such as the aforementioned refinery offgas, the products of the purification process involving hydrogen sulphide-containing gases (natural gas, biogas, shale gas, coal pyrolysis gas, petroleum associated gas, etc.) for which the range of applicability of the hydrogen sulphide content is not particularly critical, and for which no prior treatment (e.g. enrichment) is required, even for gases with a low hydrogen sulphide content, and for which high concentrations of H are required₂S(>80%) and lower H₂S content: (<2%) H of acid gas₂S is selectively absorbed, and the effect is better.

Specifically, the hydrogen sulfide-containing gas treated by implementing the method has a hydrogen sulfide volume concentration of 0.02-80%. That is, the application range can cover the low concentration H₂Desulfurization of the super Clause tail gas of S and natural gas or petroleum associated gas with high hydrogen sulfide content.

The invention relates to a method for recovering sulfur and hydrogen from hydrogen sulfide by using a double reactor, in particular to a method for recovering low-concentration H which is difficult to recover by a Clause method₂S feed gas (especially super Clause tail gas with a hydrogen sulfide content below 1%, e.g. 0.03-0.9%) will show great advantages. In the existing development stage of China, the environmental protection requirement is difficult to achieve by simply utilizing a Clause desulfurization method or a super Clause method (the method is applied to super Clause tail gas absorption with the hydrogen sulfide content as low as 0.03 percent or 0.04 percent, and can replace the existing amine method absorption process), and most small and medium-sized enterprises cannot bear the larger treatment cost of Scot tail gas treatment.

In conclusion, the research result of the invention is not only aiming at the supplement of the Clause desulfurization technology, but also aims at the improvement of the currently researched absorption and electrolysis double reactor technology, in particular to the improvement of the absorption technology, so that the whole technological process implemented in two reactors gets rid of the harsh conditions of the prior art requiring strong acid systems on the aspects of operation and equipment materials, brings convenience for the industrialization of the hydrogen sulfide electrolysis method, greatly reduces the equipment cost, and has critical breakthrough in the aspects of continuity of hydrogen production by utilizing hydrogen sulfide, hydrogen balance in the hydrogen sulfide hydrogen production process, circulation of absorption liquid and the like compared with the prior art due to the implementation environment and the system.

Compared with the prior art, the invention has the following advantages that:

to contain H₂Flow of S acid gas and H₂The requirements of coexisting impurity components and the like of S are wide, the process flow is simple, the operation condition is mild, the desulfurization effect is good (the absorption rate for times of hydrogen sulfide is high), and the utilization rate of hydrogen sulfide resources is improved;

the process of combining the double reactors provides an economic and environment-friendly way for recovering hydrogen and sulfur in hydrogen sulfide and treating hydrogen sulfide;

the absorption liquid can be directly recycled through electrolytic regeneration, and a large amount of equipment widely applied to in chemical production can be used in the process due to the reduction of the corrosivity of the absorption liquid, so that the method has higher practicability in industrial operation.

Drawings

FIG. 1 shows the principle and flow diagram of the process for recovering sulfur from hydrogen sulfide and simultaneously producing hydrogen according to the present invention.

Figure 2 is a graph of hydrogen sulfide absorption versus hydrogen sulfide content in a gas.

FIG. 3 is an anodic polarization curve of the absorption solution to be regenerated in the electrolytic cell according to an embodiment of the present invention.

FIG. 4 is a graph showing anodic oxidation current efficiency at different potentials of the cell during electrolysis in accordance with an embodiment of the present invention.

FIG. 5 shows a chromatogram of the gas evolved at the cathode during electrolysis in an example of the invention, demonstrating that high purity hydrogen was obtained from the cathode.

FIG. 6 is a graph showing the relationship between the absorption rate of hydrogen sulfide and the pH of the absorption liquid in the absorption reaction according to the example of the present invention.

FIG. 7 is a schematic view of an apparatus for measuring the hydrogen sulfide absorption rate by the static diffusion method in example 4.

Detailed description of the preferred embodiments

As described above, the present invention provides kinds of combined process method of double reactors of absorption reactor and electrolysis reactor, which realizes the recovery of sulfur and hydrogen from gas containing hydrogen sulfide, especially, the invention is improved by research aiming at the absorption liquid system of the absorption reaction process, and proves that the iron-based absorbent adopting complexation treatment is used for absorbing hydrogen sulfide oxide, so that the whole absorption reaction and electrolysis reaction system are controlled to be near neutral, compared with the current strong acid system, the operation condition is milder, and the invention has good effect in the processes of recovering sulfur by absorbing hydrogen sulfide oxide and preparing hydrogen by electrolyzing the absorption liquid into steps.

For example, the prior patent CN 200610058063.8 of the present application discloses jet absorption reactors capable of realizing internal circulation of gas-liquid mixture, wherein the absorption reactors are provided with nozzles consisting of an inner pipe and a sleeve, the absorption reactors are arranged at the upper part of the reaction pipe, the upper end and the lower end of the inner pipe are respectively provided with a liquid inlet and a liquid outlet, the sleeve is sleeved outside the inner pipe to form an annular space, the side wall of the sleeve is provided with a gas inlet communicated with the annular space, in operation, the absorption liquid is added from the liquid inlet of the inner pipe, the hydrogen-containing gas to be treated is introduced into the gas inlet, passes through the annular space and is carried by the absorption liquid while entering the reaction pipe, the absorption liquid enters the reaction pipe to be driven to be in a reaction liquid injection mode to be absorbed by the absorption liquid, and is finally recycled as a bivalent absorption liquid, the sulfur-containing gas is finally recycled as a reduction reaction liquid, the sulfur-reducing reaction liquid is finally recycled as a sulfur-enriched liquid, and the sulfur-enriched liquid is finally recycled as a sulfur-enriched liquid-absorbing reaction product after being recycled by the electrolytic reaction.

The invention is also not particularly limited with respect to the particular selection and operation of the electrolytic reactor, as well as the specific selection and operation of the electrolytic reactor, the invention is not particularly limited, for example, a tank or plate and frame type electrolytic reactor, commercially available products of other construction or technical process products, preferably bipolar plates, are employed to provide separate flow paths for the anolyte (liquid to be regenerated) and catholyte (electrolyte) without cross-flow during electrolysis, thereby ensuring the regeneration of the absorption liquid.

With reference to the flow scheme of fig. 1, the overall process for simultaneously producing hydrogen and sulfur from a gas containing hydrogen sulfide can be divided into three parts: hydrogen sulfide absorption process, sulfur separation process, absorption liquid regeneration and hydrogen preparation process.

The hydrogen sulfide-containing gas is carried into a hydrogen sulfide absorption reactor by the absorption liquid, and in the reaction system, the hydrogen sulfide in the gas immediately reacts with the complex Fe (III) in the absorption liquid as follows:

an absorption reactor: 2[ Fe (III) L]+H₂S＝2[Fe(II)L]+2H⁺+S↓

The reaction system may be added with suitable acid and alkaline substances to adjust pH to 5-10, such as sodium hydroxide, potassium hydroxide, sulfuric acid, etc., complexing agent L may be a complex product of sodium/potassium or ammonium salt of ethylenediamine tetraacetic acid, sodium/potassium or ammonium salt of hydroxyethylidene diphosphonic acid, sodium/potassium or ammonium salt of ethylenediamine tetramethylene phosphoric acid, sodium/potassium or ammonium salt of diethylenetriamine pentamethylene phosphonic acid, sodium/potassium or ammonium salt of ethylenediamine diorthohydroxyphenyl acetic acid, etc.,such as the corresponding complex iron salts, e.g. ferric ammonium EDTA, or the corresponding sodium, potassium salts, etc.; fe (III) or a complex state substance formed by complexing Fe (III) or water-soluble iron salt and a complexing agent, wherein the mass concentration of the complexing agent can be 0.1-50% according to the latter principle, so as to maintain that Fe (III) is not hydrolyzed basically in the absorption liquid, Fe (III) comes from water-soluble iron salt, such as hydrochloride, sulfate and the like, the concentration can also be determined according to the content of hydrogen sulfide in gas, and iron ions in the absorption liquid are present in the form of complexing iron salt, such as ferric ammonium EDTA, or corresponding sodium salt, potassium salt and the like; the products of the absorption reaction are complex Fe (II), H⁺And sulfur (S ↓).

The absorption liquid rich in sulfur (rich in Fe (II) L and part of Fe (III) L) is discharged from the absorption reactor, sent to a sulfur separation mechanism, and is separated out by proper modes (sedimentation, centrifugation, filtration, air flotation and the like), and the granular sulfur is subjected to fine processing (such as fine solid-liquid separation and purification) of steps to form a sulfur product, and is discharged from the separation mechanism, wherein the absorption liquid after sulfur separation is the liquid to be regenerated, and is sent to an anode chamber of an electrolytic reactor as anode liquid to participate in electrolytic reaction to be regenerated.

The liquid to be regenerated, which is free of solid particles after sulfur separation, undergoes hydrogen sulfide absorption reaction, and compared with the absorption liquid fed into the absorption reactor, the liquid to be regenerated contains relatively more Fe (II) L and less Fe (III) L, and the pH value is also lower along with the progress of the absorption reaction, so that the continuous use at least influences the reaction efficiency, but is beneficial to electrolytic regeneration. As mentioned above, in the electrolytic reactor used in the present invention, the electrolytic cell is divided into two parts of an anode chamber and a cathode chamber by the proton exchange membrane, so that the solution to be regenerated from the sulfur separation mechanism enters the anode chamber of the electrolytic cell, and the following reactions occur:

anode: 2[ Fe (II) L]＝2[Fe(III)L]+2e^－

H brought by hydrogen sulfide absorption reaction in liquid to be regenerated⁺Under the guidance of an electric field, the solution passes through a proton exchange membrane and enters a cathode chamber, so that the regenerated solution is recovered to be rich in Fe (III) L and in a higher pH state; meanwhile, in the cathode chamber of the electrolytic cell, an electrolyte (H)₂O) and migration from the proton exchange membrane to the cathodeH of polar chamber⁺On the negative side the following reaction takes place:

cathode: 2H₂O+2e^－＝H₂↑+2OH^-(pH＞7)

Cathode: 2H⁺+2e^－＝H₂↑(pH≤7)。

Since the reactants in the cathode compartment of the cell are primarily from species in which components of the solution in the anode compartment migrate through the proton exchange membrane, there is no significant consumption of the solution in the cathode compartment in the cell. Total reaction in the electrolytic reactor:

an electrolytic reactor: 2[ Fe (II) L]+2H⁺＝2[Fe(III)L]+H₂↑

The hydrogen sulfide gas is subjected to three processes of absorption, separation and electrolysis, and the total reaction in the whole system is as follows:

H₂S→H₂↑+S↓

in the actual operation, when considering the solid-liquid separation of the sulfur-rich absorption liquid discharged from the absorption reactor, firstly, the sulfur particles are not contained in the liquid to be regenerated after the sulfur is separated, and the separated solid sulfur can be further subjected to the fine separation of steps according to the need, namely, times of solid-liquid separation can be needed to ensure that the high-purity sulfur is collected, and at the moment, a small amount of separated absorption liquid is also Fe (II), L/Fe (III) L coexisting, and possibly a small amount of impurities or sulfur can be mixed with the regeneration liquid and returned to the absorption reactor³⁺The complex iron absorption liquid and hydrogen sulfide enter an absorption reaction system, the hydrogen sulfide is converted into sulfur and hydrogen ions through oxidation reaction, part of the absorption liquid contains Fe³⁺Conversion of the complex to Fe²⁺The complex is separated from sulfur and then enters an electrolytic cell, so that hydrogen ions in the complex are converted into hydrogen at a cathode, and part of Fe²⁺The complex is converted into Fe again at the anode³⁺The complex is returned to the hydrogen sulfide absorption system and the cycle is completed. Regarding the refining operation and the available equipment of the sulphur, any feasible solution is possible, for example, the refining process described in the aforementioned patents by the applicant. By the operation, the whole process realizes high efficiency and continuity.

The following is provided as an example to illustrate the implementation of the present invention, and is intended to help the reader better understand the technical spirit and the benefits of the present invention, and should not be construed as limiting the scope of the present invention.