A low by-product sulfur recovery process

Abstract

The application relates to the technical field of sulfur recovery, and particularly discloses a low-byproduct sulfur recovery process. The low-byproduct sulfur recovery process is characterized in that the process comprises the following steps: S1: sulfur-containing waste gas is sent into a desulfurization tower to be in reverse contact with desulfurization liquid sprayed at the top of the tower for desulfurization, and then the desulfurization liquid discharged at the bottom of the tower is sprayed into a regeneration tank for flotation to obtain sulfur foam and clear liquid; S2: the sulfur foam is transported into an elevated tank for preliminary sedimentation and separation, and high-concentration sulfur foam is obtained at the upper layer; S3: the high-concentration sulfur foam is transported into a filter for liquid-foam separation, and sulfur paste and filtrate are obtained after filtration; S4: the sulfur paste obtained after filtration is transported into a sulfur paste dilution tank, then sulfur residue solution is added into the sulfur paste dilution tank, and sulfur paste dilution liquid is obtained after uniform mixing; and S5: the sulfur paste dilution liquid is transported into a sulfur melting kettle for sulfur melting, and liquid sulfur generated is cooled and collected in a sulfur tank. The low-byproduct sulfur recovery process has the advantage of less byproducts.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sulfur recovery, more particularly, it relates to a low by-product sulfur recovery process. BACKGROUND

[0002] The wet oxidation method is widely used in the field of coal chemical industry, and the essence of the technology is a wet neutralization reaction process accompanied by oxidation reaction. Through catalytic oxidation, negative bivalent sulfur is oxidized into elemental sulfur, which is separated and smelted into sulfur. Not only can the emission of pollutants such as hydrogen sulfide be effectively reduced, but also by-products such as sulfur can be obtained, bringing good economic benefits.

[0003] The entire desulfurization process includes three links of absorption, regeneration and recovery of molten sulfur. The three links depend on and influence each other, so it is necessary to recover as much solid sulfur as possible to ensure the normal operation of the circulating system. In the recovery of molten sulfur, the treatment of molten sulfur residue is very important. If the molten sulfur residue is directly discharged, it will cause great harm to the ecological environment. If the molten sulfur residue is directly recovered into the lean liquid tank in the absorption link, the temperature of the lean liquid tank will rise due to the high temperature of the molten sulfur residue, the desulfurization reaction will be intensified in the oxygen-rich environment, the sulfur recovery efficiency will be affected, and the precipitates in the molten sulfur residue will also reduce the foam in the regeneration tank, affecting the flotation effect.

[0004] Therefore, some technicians hope to utilize the molten sulfur residue through cooling, such as cooling in a sedimentation tank and then recovering it into the lean liquid tank. However, due to the high temperature of the residue, the residue is easy to react with air in the sedimentation tank, the composition will change, and after recovery, the residue will still cause problems such as reduction of foam in the regeneration tank and acceleration of plugging of the desulfurization tower.

[0005] In addition, some technicians use a plate and frame filter to filter the molten sulfur residue and then directly recover it. However, due to the high content of sulfur in the molten sulfur residue, the filter is easy to be blocked, the production cost is increased due to frequent replacement of filter cloth. Moreover, the high filtration temperature also brings difficulties to the operation, and the filtered molten sulfur residue will still affect the temperature of the desulfurization liquid and is easy to generate more by-products.

[0006] The recovery efficiency and effect of the above-mentioned recovery methods of molten sulfur residue are poor, so how to utilize the molten sulfur residue is a technical problem to be solved at present. SUMMARY

[0007] In order to efficiently utilize the molten sulfur residue and reduce by-products, the present application provides a low by-product sulfur recovery process.

[0008] The present application provides a low by-product sulfur recovery process, which adopts the following technical scheme:

[0009] A low by-product sulfur recovery process, comprising the following steps:

[0010] S1: the sulfur-containing waste gas is sent into a desulfurization tower and is in contact with the desulfurization liquid sprayed at the top of the tower in a reverse direction to perform desulfurization, and then the desulfurization liquid discharged at the bottom is sprayed into a regeneration tank to obtain sulfur foam and clear liquid, and the clear liquid is returned to the desulfurization tower for recycling;

[0011] S2: the sulfur foam is transported to an elevated tank to perform preliminary settling separation, high-concentration sulfur foam is obtained at the upper layer, and the settling liquid obtained at the lower layer is returned to the desulfurization tower for recycling;

[0012] S3: the high-concentration sulfur foam is transported to a filter to perform liquid-foam separation, and sulfur paste and filtrate are obtained after filtration, and the filtrate is returned to the desulfurization tower for recycling;

[0013] S4: the sulfur paste obtained after filtration is transported to a sulfur paste dilution pool, then sulfur melt residue is added into the sulfur paste dilution pool, and sulfur paste dilution liquid is obtained after mixing uniformly;

[0014] S5: the sulfur paste dilution liquid is transported to a sulfur melt kettle to perform sulfur melting, the liquid sulfur generated is cooled and collected in a sulfur tank, and part of the sulfur melt residue is sent into the sulfur paste dilution pool in step S4, and the other part of the sulfur melt residue is cooled, settled and filtered to obtain a recovery liquid which is returned to the desulfurization tower for recycling.

[0015] By adopting the above technical scheme, the sulfur-containing waste gas generated in the production process is collected and transported into the desulfurization tower, the desulfurization liquid is circulated in the desulfurization tower, under the adsorption of the desulfurization liquid, the hydrogen sulfide and other components in the sulfur-containing waste gas are removed by using the wet sulfur recovery process, and are converted into elemental sulfur under the action of the catalyst. The desulfurization liquid containing elemental sulfur is sprayed from the bottom of the tower into the regeneration tank to perform flotation to obtain sulfur foam and clear liquid, and the clear liquid can be returned to the desulfurization tower for repeated use.

[0016] The sulfur foam obtained by flotation has a very large liquid content, and needs to be transported into an elevated tank to perform preliminary settling separation, so as to separate the sulfur foam from the desulfurization liquid as much as possible, high-concentration sulfur foam is obtained at the upper layer, and the settling liquid obtained at the lower layer can also be returned to the desulfurization tower for recycling.

[0017] Although the content of the desulfurization solution in the high-concentration sulfur foam is greatly reduced, the residual liquid still increases the energy consumption pressure of the subsequent molten sulfur process. A filter is used to separate the liquid and foam in the high-concentration sulfur foam. After filtration, sulfur paste and filtrate are obtained. The filtrate is returned to the desulfurization tower for further use. The sulfur paste is transported to the sulfur paste dilution pool for use. The filter in the application can use a sulfur foam vacuum filter. The filter medium uses nanometer ceramic membrane technology. Under the action of vacuum force, only the desulfurization solution passes through the nanometer ceramic pores, while the mechanical impurities, elemental sulfur and bubbles in the solution cannot pass through, thereby completing the liquid-foam separation. In addition, the filter in the application can also use a sulfur foam centrifugal filter. The solid phase is rapidly settled by centrifugal force. The clarified liquid with a lower specific gravity is discharged from the overflow port to realize the effect of continuous feeding and continuous separation.

[0018] The sulfur paste transported to the sulfur paste dilution pool needs to be diluted. In order to solve the problem that the molten sulfur residual liquid is difficult to utilize, the molten sulfur residual liquid is innovatively added to the sulfur paste dilution pool as the sulfur paste dilution liquid. The molten sulfur residual liquid and the sulfur paste are mixed to form the sulfur paste dilution liquid. In the dilution process, the surface activity of the sulfur elemental particle is improved by using the heat release effect. The aggregation and agglomeration of the sulfur elemental particle are more likely to occur in the molten sulfur stage, thereby improving the sedimentation separation efficiency of the sulfur elemental particle. When the surface activity of the sulfur elemental particle is increased, the sulfur elemental particle can be aggregated to form a large particle sulfur aggregate in a short time. At this time, the elemental sulfur on the surface of the large particle sulfur aggregate is rapidly oxidized to a high-valence sulfur oxide compound to form a surface oxidation layer, thereby inhibiting the penetration of the oxidation medium into the interior of the aggregate. The probability of the generation of the high-valence sulfur compound in the system is reduced. The occurrence of the side reaction in the dilution process and the molten sulfur process is greatly reduced. The content of the byproduct in the molten sulfur residual liquid and the sulfur product is reduced.

[0019] Preferably, in the step S4, the molten sulfur residual liquid is added together with a control material. The control material is mainly prepared from the following raw materials in parts by weight: 100-120 parts of a porous carrier, 30-35 parts of a stabilizer and 300-500 parts of a solvent.

[0020] Further preferably, the stabilizer is prepared by the following method:

[0021] 1) The wax, the inhibitor, the isocyanate monomer and the emulsifier are heated to 110-130 DEG C in a container, and then mixed at a stirring speed of 800-1000 rpm for 15-30 min to prepare an intermediate liquid. Then, water is added to the intermediate liquid, and the mixture is stirred for 5-10 min to prepare a precursor liquid.

[0022] 2) The precursor liquid is added to the polyol under continuous stirring. After constant temperature reaction at 135-150 DEG C for 4-6 h, the mixture is cooled, filtered, washed and dried.

[0023] Further preferably, the inhibitor is composed of alkyl quaternary ammonium salt and ferrocene in a mass ratio of (10-15):(0.5-1.2).

[0024] By adopting the technical scheme, the wax, the inhibitor, the isocyanate monomer and the emulsifier are prepared into an oil phase system at a suitable temperature and stirring speed, then a precursor of an O / W system is formed under the action of the emulsifier after water is added, then the isocyanate monomer and the polyol are subjected to interfacial polymerization at the oil-water interface under suitable temperature conditions, so that the wax and the inhibitor are coated inside, and the wax also coats the inhibitor inside in the subsequent cooling process, finally a stabilizer with a double-layer coating structure and a size of only several hundred nanometers is formed, then the stabilizer, the solvent and the porous material are mixed together, the pore structure of the porous carrier is used to fully absorb the stabilizer, and thus the control material is obtained.

[0025] After the control material is mixed with sulfur paste and sulfur residue to prepare a sulfur paste diluent, the control material is uniformly dispersed in the diluent system, the temperature of the sulfur residue is about 120 DEG C, at this time, the wax coating layer of the control material is in a semi-melted state, part of the inhibitor coated inside can be released, and then the part of the inhibitor migrates to the diluent system through the pore structure of the porous carrier. In addition, the inhibitor of the application uses alkyl quaternary ammonium salt and ferrocene in combination, and the ferrocene can change the oxidation-reduction potential to a certain extent, so as to affect the electronic properties of the oxidation-reduction center, inhibit the conversion of elemental sulfur to higher valence state, and greatly reduce the generation amount of sulfur by-products. In addition, the alkyl quaternary ammonium salt improves the activity of the ferrocene through the surface activation of the large steric hindrance cation, on the one hand, the conversion of elemental sulfur to high valence state is more difficult, on the other hand, the conversion of high valence sulfur by-products to elemental sulfur is also promoted to a certain extent, further reducing the concentration of by-products such as thiosulfate and sulfate, thereby improving the yield of elemental sulfur.

[0026] In addition, as the dilution process proceeds, the temperature of the final sulfur paste diluent decreases, at this time, the wax coating layer will re-solidify, reducing the release amount of the inhibitor, and at this time, the sulfur paste diluent still maintains a certain temperature, which can reduce the energy consumption in the subsequent sulfur melting stage. In the subsequent sulfur melting process, the temperature in the sulfur melting kettle gradually increases from about 70 DEG C to about 130 DEG C, at this time, the elemental sulfur becomes liquid sulfur and drops to the bottom of the kettle, and due to the difference in specific gravity, the control material is located in the upper layer, after the recovery of the liquid sulfur, the solid residue obtained after cooling, settling and filtering of the remaining liquid can be reused, reducing the production cost.

[0027] In addition, the recovered liquid after filtration is returned to the desulfurization liquid system, and the trace amount of alkyl quaternary ammonium salt and ferrocene released therein can improve the surface tension of the desulfurization liquid system to some extent, promote the generation of sulfur foam in the flotation stage of the jet regeneration tank, and inhibit the occurrence of side reactions in the regeneration process, thereby reducing the content of by-products and improving the yield of sulfur.

[0028] Preferably, the alkyl quaternary ammonium salt is at least one of benzyltriethylammonium chloride, hexadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, tetramethylammonium chloride, tetraethylammonium bromide, and tetrabutylammonium chloride.

[0029] The alkyl quaternary ammonium salts listed in the present application can achieve the corresponding technical effects. Preferably, the alkyl quaternary ammonium salt is composed of benzyltriethylammonium chloride and tetrabutylammonium chloride at a molar ratio of 1.5:0.6.

[0030] By using the above technical solution, the type of alkyl quaternary ammonium salt is optimized and adjusted, and the ion combination ability and freedom of the alkyl quaternary ammonium salt are controlled, thereby improving the active state of the cation and the promoting effect on the ferrocene component, further improving the inhibition of the sulfur element side reaction, and reducing the content of by-products.

[0031] Preferably, the porous carrier is one or more of porous iron oxide, porous silicon dioxide, porous carbon, porous copper oxide, porous aluminum oxide, porous ceramic, porous calcium carbonate, porous zeolite, porous aluminum phosphate, and porous rubber.

[0032] The porous carriers listed in the present application can achieve the corresponding technical effects. Further preferably, the porous carrier is composed of porous iron oxide and porous carbon at a mass ratio of 3:1.

[0033] By using the above technical solution, the type composition of the porous carrier is tested and screened, the pore structure state of the porous carrier is improved, and the stable existence does not affect the molten sulfur system, reduces the probability of promoting side reactions, and obtains more stable and efficient control effect.

[0034] Preferably, the average pore size of the porous carrier is 5-20 mu m.

[0035] By using the above technical solution, the larger pore size of the porous carrier has too large an adsorption amount of the stabilizer, and cannot well control the release amount of the inhibitor, resulting in too high a content of the inhibitor component in the system, which has an adverse effect on the overall sulfur recovery system. The smaller pore size of the porous carrier has a smaller adsorption amount of the stabilizer and a smaller release amount of the inhibitor, and cannot fully inhibit the effect. Therefore, the average pore size of the porous carrier is optimized and adjusted to balance the inhibition and release performance of the control material, and a better comprehensive desulfurization effect is obtained.

[0036] Preferably, the mass ratio of the stabilizer to the porous carrier is (0.025-0.028):1.

[0037] By adopting the technical solution, the mass ratio of the stabilizer to the porous carrier is optimized and adjusted, the adsorption capacity and release capacity of the buffer control material are further improved, the stability of the desulfurization liquid system is not affected, and a good inhibition effect of the side reaction is obtained.

[0038] Preferably, in the step S4, the mass ratio of the sulfur paste, the molten sulfur residue and the buffer control material is (5-7.5):(20-30):(0.05-0.065).

[0039] By adopting the technical solution, the mass ratio of the sulfur paste, the molten sulfur residue and the buffer control material is optimized and adjusted, the dispersion uniformity and stability of the sulfur paste slow-release liquid are improved, the favorable conditions for the subsequent molten sulfur stage are improved, and the content of the inhibitor in the sulfur paste slow-release liquid is also adjusted, thereby improving the stability of the materials in the molten sulfur kettle.

[0040] Preferably, in the step S5, after the other part of the molten sulfur residue is cooled, settled, and filtered, solid residues are obtained in addition to the recovery liquid, and the solid residues can be used repeatedly as the porous carrier after being immersed, washed, dried, and ground.

[0041] By adopting the technical solution, the solid residues obtained are immersed, washed, dried, and ground, the solid impurities attached to the surface of the porous carrier are removed, and the wax coating layer plays a good sealing role at this time, which can prevent the loss of the inhibitor during the immersion, and the use amount of the stabilizer can be appropriately reduced when the porous carrier is used repeatedly, thereby further saving the production cost and obtaining better economic benefits.

[0042] In summary, the present application has the following beneficial effects:

[0043] 1. Since the present application adopts the process of combining high tank settlement separation and filter liquid foam separation, the liquid content in the sulfur foam is greatly reduced, then the molten sulfur residue is used to dilute the sulfur paste, and stable and uniform sulfur paste diluent is obtained, which can promote the aggregation of elemental sulfur in the dilution stage and the molten sulfur stage, the oxidation film generated on the surface of the large particle sulfur aggregate is used to inhibit the penetration of the oxidation medium, the production of by-products is reduced, and the yield of elemental sulfur is also improved.

[0044] 2. In the present application, the buffer control material is preferably added during the dilution process of the molten sulfur residue, the release of the inhibitor is controlled by using the temperature change slow-release effect, the transformation of elemental sulfur into high-valence sulfur is effectively inhibited by the complexing effect of the alkyl quaternary ammonium salt and ferrocene in the inhibitor, the content of the by-products in the molten sulfur process is greatly reduced, and the production of sulfur foam in the desulfurization liquid regeneration process is also promoted, thereby obtaining good sulfur recovery effect and high utilization rate of the molten sulfur residue as a whole.

[0045] 3. The low by-product sulfur recovery process of the present application has a high elemental sulfur yield, and the probability of by-product reactions during the entire sulfur recovery process is low, and the content of by-products in the system is low. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 : The comprehensive data test chart of the low by-product sulfur recovery process of the present application examples 1-6 and comparative examples 1-6.

[0047] Figure 2 : The SEM chart of the stabilizer of the present application example 6. DETAILED DESCRIPTION

[0048] The present application is further described in detail below in conjunction with examples.

[0049] The raw materials of the present application examples and comparative examples are all ordinary commercial products except for special instructions.

[0050] EXAMPLE

[0051] Example 1

[0052] The low by-product sulfur recovery process of the present embodiment includes the following steps:

[0053] S1: The sulfur-containing waste gas with a hydrogen sulfide content of 3.5 g / m 3 was sent into a desulfurization tower to be in contact with the desulfurization liquid sprayed from the top of the tower in a reverse direction for desulfurization, the circulation amount of the desulfurization liquid was 600 m 3 / h, the hydrogen sulfide content after desulfurization was 10 mg / m 3 ; then the desulfurization liquid discharged from the bottom of the tower was pressurized to 0.4 MPa by a pump and then sprayed into a regeneration tank to obtain sulfur foam and clear liquid, the liquid content in the sulfur foam was 85%, and the clear liquid was returned to the desulfurization tower for circulation;

[0054] S2: The sulfur foam was transported to a high tank for preliminary settlement separation, high-concentration sulfur foam was obtained in the upper layer, the liquid content in the high-concentration sulfur foam was 40%, and settlement liquid was obtained in the lower layer and returned to the desulfurization tower for circulation;

[0055] S3: The high-concentration sulfur foam was transported to a vacuum filter by a pump for liquid-foam separation, the filter medium of the vacuum filter was a nano ceramic membrane, under the action of vacuum force, only liquid could pass through the nano ceramic membrane hole, and mechanical impurities and elemental sulfur and foam could not pass through; after filtration, sulfur paste and filtrate were obtained, the water content of the sulfur paste was 20%, the solid matter content in the filtrate was less than 50 ppm, and the filtrate was returned to the desulfurization tower for circulation;

[0056] S4: The sulfur paste obtained after filtration is delivered to a sulfur paste dilution tank, and then sulfur melt residue is added into the sulfur paste dilution tank, the mass ratio of the sulfur paste to the sulfur melt residue being 5:30, and a sulfur paste dilution liquid is obtained after uniform mixing;

[0057] S5: The sulfur paste dilution liquid is delivered into a sulfur melt kettle to produce sulfur melt, liquid sulfur generated is cooled and collected in a sulfur tank to obtain sulfur product, and part of the sulfur melt residue is delivered into the sulfur paste dilution tank in step S4, and the other part of the sulfur melt residue is cooled, settled, filtered, and then a recovery liquid is obtained and returned to the desulfurization tower for recycling.

[0058] In the sulfur recovery process of the embodiment, the total continuous circulation time is 72 h. When the equipment is started, since no sulfur melt residue is produced in step S5, the clear liquid in step S1 is used instead of the sulfur melt residue in step S4 to ensure smooth start of the circulation.

[0059] The composition of the desulfurization liquid in the embodiment is: sodium carbonate 23 g / L, sodium bicarbonate 3.5 g / L, and sodium vanadate 2 g / L.

[0060] After the equipment in the embodiment is started for 3 h, the clear liquid in step S1 is detected, and the content of sodium thiosulfate in the clear liquid is 108 mg / L.

[0061] Example 2

[0062] The low by-product sulfur recovery process in the embodiment includes the following steps:

[0063] S1: Sulfur-containing waste gas with a hydrogen sulfide content of 3.5 g / m 3 is delivered into a desulfurization tower to be desulfurized by being reversely contacted with desulfurization liquid sprayed from the top of the tower, the circulation amount of the desulfurization liquid being 600 m 3 / h, the hydrogen sulfide content after desulfurization being 10 mg / m 3 ; then the desulfurization liquid discharged from the bottom of the tower is pressurized to 0.4 MPa by a pump and then sprayed into a regeneration tank to obtain sulfur foam and clear liquid by flotation, the liquid content in the sulfur foam being 85%, and the clear liquid being returned to the desulfurization tower for recycling;

[0064] S2: The sulfur foam is delivered into an elevated tank to be preliminarily separated and settled, high-concentration sulfur foam is obtained in the upper layer, the liquid content in the high-concentration sulfur foam being 40%, and settlement liquid is obtained in the lower layer and returned to the desulfurization tower for recycling;

[0065] S3: The high-concentration sulfur foam is pumped into a vacuum filter for liquid-foam separation. The filter medium of the vacuum filter is a nano ceramic membrane. Under the action of vacuum force, only liquid can pass through the nano ceramic membrane holes, while mechanical impurities and elemental sulfur and foam cannot pass through. After filtration, sulfur paste and filtrate are obtained. The water content of the sulfur paste is 20%, and the solid content in the filtrate is less than 50 ppm. The filtrate is returned to the desulfurization tower for recycling.

[0066] S4: The sulfur paste obtained after filtration is transported to a sulfur paste dilution tank, and then molten sulfur residue and control material are added into the sulfur paste dilution tank. The mass ratio of the sulfur paste, the molten sulfur residue and the control material is 5:30:0.05. After being uniformly mixed, a sulfur paste dilution liquid is obtained.

[0067] S5: The sulfur paste dilution liquid is transported into a molten sulfur kettle for molten sulfur production. The produced liquid sulfur is cooled and collected in a sulfur trough to obtain sulfur product. Part of the molten sulfur residue is sent to the sulfur paste dilution tank in step S4, and the other part of the molten sulfur residue is cooled, settled and filtered to obtain a recovery liquid which is returned to the desulfurization tower for recycling.

[0068] In this embodiment, the sulfur recovery process is continuously cycled for 72 hours. When the equipment is started, since no molten sulfur residue has been produced in step S5, the molten sulfur residue added to the sulfur paste dilution tank in step S4 is replaced by the clear liquid in step S1 to ensure smooth cycling.

[0069] The desulfurization liquid used in this embodiment comprises: 23 g / L of sodium carbonate, 3.5 g / L of sodium bicarbonate and 2 g / L of sodium metavanadate.

[0070] After the equipment in this embodiment is started for 3 hours, the clear liquid in step S1 is detected. The content of sodium thiosulfate in the clear liquid is 115 mg / L.

[0071] The control material in this embodiment is made of the following raw materials by weight: 10 kg of porous carrier, 0.35 kg of stabilizer and 30 kg of solvent.

[0072] The porous carrier is porous calcium carbonate with an average pore size of 50 μm. The solvent is water.

[0073] The preparation method of the control material in this embodiment is as follows: the formula porous carrier, the stabilizer and the solvent are added into a reaction kettle and uniformly mixed. After being continuously stirred at a temperature of 60°C for 10 minutes, the mixture is filtered and dried to obtain the control material.

[0074] The stabilizer in this embodiment is prepared by the following method:

[0075] 1) The wax, inhibitor, isocyanate monomer and emulsifier were heated to 110°C in a container, then mixed at 800 rpm for 30 min to obtain an intermediate liquid, then water was added to the intermediate liquid and stirred for 10 min to obtain a precursor liquid;

[0076] 2) The precursor liquid was added to the polyol under constant stirring, and reacted at 150°C for 4 h, then cooled, filtered, washed and dried to obtain the product.

[0077] The wax is PP wax. The isocyanate monomer is TDI trimer. The emulsifier is polyoxyethylene fatty acid ester. The polyol is 1,4-butanediol. The inhibitor is dodecyltrimethylammonium chloride.

[0078] Example 3

[0079] The low by-product sulfur recovery process of the present embodiment comprises the following steps:

[0080] S1: The sulfur-containing waste gas with a hydrogen sulfide content of 3.5 g / m 3 was sent to a desulfurization tower and contacted with the desulfurization liquid sprayed from the top in a reverse direction for desulfurization. The circulation amount of the desulfurization liquid was 600 m 3 / h, and the hydrogen sulfide content after desulfurization was 10 mg / m 3 . Then the desulfurization liquid discharged from the bottom was pressurized to 0.4 MPa by a pump and then sprayed into a regeneration tank to obtain sulfur foam and clear liquid. The liquid content in the sulfur foam was 85%, and the clear liquid was returned to the desulfurization tower for recycling;

[0081] S2: The sulfur foam was transported to an upper tank for preliminary settlement and separation. The high-concentration sulfur foam was obtained in the upper layer, and the liquid content in the high-concentration sulfur foam was 40%. The settlement liquid was obtained in the lower layer and returned to the desulfurization tower for recycling;

[0082] S3: The high-concentration sulfur foam was transported to a vacuum filter by a pump for liquid-foam separation. The filter medium of the vacuum filter was a nano ceramic membrane. Under the action of vacuum force, only liquid could pass through the nano ceramic membrane hole, while mechanical impurities, elemental sulfur and foam could not pass through. After filtration, sulfur paste and filtrate were obtained. The water content in the sulfur paste was 20%, and the solid content in the filtrate was less than 50 ppm. The filtrate was returned to the desulfurization tower for recycling;

[0083] S4: The sulfur paste obtained after filtration was transported to a sulfur paste dilution tank, then molten sulfur residue and control materials were added to the sulfur paste dilution tank. The mass ratio of sulfur paste, molten sulfur residue and control materials was 7.5:20:0.065. After mixing uniformly, a sulfur paste dilution liquid was obtained.

[0084] S5: The sulfur paste dilution solution is transported into the molten sulfur kettle to produce molten sulfur, and the generated liquid sulfur is cooled and collected in the sulfur tank to obtain sulfur product. Part of the molten sulfur residue is sent to the sulfur paste dilution pool in step S4, and the other part of the molten sulfur residue is cooled, settled, filtered, and then the recovered liquid is returned to the desulfurization tower for recycling.

[0085] In this embodiment, the sulfur recovery process is continuously cycled for 72 hours. When the equipment is started, since no molten sulfur residue has been produced in step S5, the clear liquid in step S1 is used instead of the molten sulfur residue in step S4 to ensure smooth operation and cycling.

[0086] The desulfurization liquid used in this embodiment contains 23 g / L of sodium carbonate, 3.5 g / L of sodium bicarbonate, and 2 g / L of sodium metavanadate.

[0087] After the equipment in this embodiment has been started for 3 hours, the clear liquid in step S1 is taken for testing, and the content of sodium thiosulfate in the clear liquid is 120 mg / L.

[0088] The slow control material in this embodiment is made of the following raw materials by weight: 12 kg of porous carrier, 0.3 kg of stabilizer, and 50 kg of solvent.

[0089] The porous carrier is composed of porous iron oxide and porous carbon in a mass ratio of 3:1, the average pore size of the porous iron oxide is 20 μm, and the average pore size of the porous carbon is 5 μm. The solvent is water.

[0090] The preparation method of the slow control material in this embodiment is as follows: the formula porous carrier, stabilizer, and solvent are added to the reaction kettle and mixed uniformly, stirred at 60°C for 10 minutes, filtered and dried to obtain the slow control material.

[0091] The stabilizer in this embodiment is prepared by the following method:

[0092] 1) The wax, inhibitor, isocyanate monomer, and emulsifier are heated to 130°C in a container, then mixed at a stirring speed of 1000 rpm for 15 minutes to obtain an intermediate liquid, and then water is added to the intermediate liquid and stirred for 5 minutes to obtain a precursor liquid;

[0093] 2) The precursor liquid is added to the polyol under constant stirring, and the temperature is kept at 135°C for 6 hours, then cooled, filtered, washed, and dried to obtain the stabilizer.

[0094] The wax is PP wax. The isocyanate monomer is TDI trimer. The emulsifier is polyoxyethylene fatty acid ester. The polyol is 1,4-butanediol. The inhibitor is cetyltrimethylammonium bromide.

[0095] Example 4

[0096] The low by-product sulfur recovery process of the embodiment includes the following steps:

[0097] S1: send the sulfur-containing waste gas with a hydrogen sulfide content of 3.5 g / m 3 into a desulfurization tower to contact with the desulfurization liquid sprayed at the top of the tower in a reverse direction for desulfurization, the circulating amount of the desulfurization liquid is 600 m 3 / h, the hydrogen sulfide content after desulfurization is 10 mg / m 3 ; then the desulfurization liquid discharged at the bottom of the tower is pressurized to 0.4 MPa by a pump and then sprayed into a regeneration tank to float to obtain sulfur foam and clear liquid, the liquid content in the sulfur foam is 85%, and the clear liquid is returned to the desulfurization tower for recycling;

[0098] S2: the sulfur foam is transported to an upper tank to be preliminarily separated by sedimentation, high-concentration sulfur foam is obtained at the upper layer, the liquid content in the high-concentration sulfur foam is 40%, and the sedimentation liquid at the lower layer is returned to the desulfurization tower for recycling;

[0099] S3: the high-concentration sulfur foam is transported to a vacuum filter by a pump to be separated by liquid-foam separation, the filter medium of the vacuum filter is a nano ceramic membrane, under the action of vacuum force, only liquid can pass through the nano ceramic membrane hole, and mechanical impurities, elemental sulfur and foam cannot pass through; after filtration, sulfur paste and filtrate are obtained, the water content in the sulfur paste is 20%, the solid matter content in the filtrate is less than 50 ppm, and the filtrate is returned to the desulfurization tower for recycling;

[0100] S4: the sulfur paste obtained after filtration is transported to a sulfur paste dilution pool, then molten sulfur residue and control materials are added into the sulfur paste dilution pool, the mass ratio of the sulfur paste, the molten sulfur residue and the control materials is 6.5:28:0.06, and after being mixed uniformly, sulfur paste dilution liquid is obtained;

[0101] S5: the sulfur paste dilution liquid is transported to a molten sulfur kettle to be molten, the generated liquid sulfur is cooled and collected in a sulfur tank to obtain sulfur product, part of the generated molten sulfur residue is sent to the sulfur paste dilution pool in step S4, and the other part of the molten sulfur residue is cooled, settled and filtered to obtain recovery liquid which is returned to the desulfurization tower for recycling.

[0102] In the embodiment, the sulfur recovery process is continuously and circularly operated for 72 h, when the equipment is started, since the molten sulfur residue has not been produced in step S5, the molten sulfur residue added into the sulfur paste dilution pool in step S4 is replaced by the clear liquid in step S1 to ensure smooth start of the circulation.

[0103] The composition of the desulfurization liquid used in the embodiment is: sodium carbonate 23 g / L, sodium bicarbonate 3.5 g / L, and sodium metavanadate 2 g / L.

[0104] The clear liquid was taken after the device of the embodiment ran for 3 hours in step S1, and the content of sodium thiosulfate in the clear liquid was 113 mg / L.

[0105] The slow-release control material of the embodiment was made from the following raw materials by weight: porous carrier 11.5 kg, stabilizer 0.32 kg, and solvent 35 kg.

[0106] The porous carrier is composed of porous iron oxide and porous carbon at a mass ratio of 3:1, the average pore diameter of the porous iron oxide is 20 μm, and the average pore diameter of the porous carbon is 5 μm. The solvent is water.

[0107] The preparation method of the slow-release control material of the embodiment is as follows: the formula porous carrier, stabilizer, and solvent are added into a reaction kettle and uniformly mixed, continuously stirred at a temperature of 60 ℃ for 10 min, and then filtered and dried to obtain the slow-release control material.

[0108] The stabilizer of the embodiment is prepared by the following method:

[0109] 1) The wax, inhibitor, isocyanate monomer, and emulsifier are heated to 128 ℃ in a container, then mixed at a stirring speed of 900 rpm for 12 min to obtain an intermediate liquid, and then water is added into the intermediate liquid and continuously stirred for 5 min to obtain a precursor liquid.

[0110] 2) The precursor liquid is added into the polyol under continuous stirring, and then reacted at a constant temperature of 135 ℃ for 6 h, and then cooled, filtered, washed, and dried to obtain the stabilizer.

[0111] The wax is PP wax. The isocyanate monomer is TDI trimer. The emulsifier is polyoxyethylene fatty acid ester. The polyol is 1,4-butanediol. The inhibitor is benzyl triethyl ammonium chloride.

[0112] Example 5

[0113] The difference between the low byproduct sulfur recovery process of the embodiment and that of example 4 is that, in the preparation method of the stabilizer, the inhibitor is composed of alkyl quaternary ammonium salt and ferrocene at a mass ratio of 15:0.5, and the rest is the same as that in example 4.

[0114] The alkyl quaternary ammonium salt is composed of benzyl triethyl ammonium chloride and tetrabutyl ammonium chloride at a molar ratio of 1.5:0.6.

[0115] The preparation method of the stabilizer of the embodiment is the same as that of example 4.

[0116] Example 6

[0117] The low by-product sulfur recovery process of the embodiment is different from that of embodiment 4 in that the preparation method of the stabilizer is as follows: the inhibitor is composed of alkyl quaternary ammonium salt and ferrocene at a mass ratio of 10:1.2, and the rest is the same as in embodiment 4.

[0118] The alkyl quaternary ammonium salt is composed of benzyl triethyl ammonium chloride and tetrabutyl ammonium chloride at a molar ratio of 1.5:0.6.

[0119] The preparation method of the stabilizer of the embodiment is the same as that of embodiment 4.

[0120] Comparative example

[0121] Comparative example 1

[0122] The low by-product sulfur recovery process of the comparative example comprises the following steps:

[0123] S1: The sulfur-containing waste gas with a hydrogen sulfide content of 3.5 g / m 3 is sent into a desulfurization tower to be in countercurrent contact with the desulfurization liquid sprayed at the top of the tower for desulfurization. The circulation amount of the desulfurization liquid is 600 m 3 / h, and the hydrogen sulfide content after desulfurization is 10 mg / m 3 . Then, the desulfurization liquid discharged at the bottom of the tower is pressurized to 0.4 MPa by a pump and then sprayed into a regeneration tank for flotation to obtain sulfur foam and clear liquid. The liquid-carrying amount of the sulfur foam is 85%, and the clear liquid is returned to the desulfurization tower for circulation.

[0124] S2: The sulfur foam is transported to an upper tank for preliminary settlement and separation. High-concentration sulfur foam is obtained at the upper layer, and the liquid-carrying amount of the high-concentration sulfur foam is 40%. Settlement liquid is obtained at the lower layer and returned to the desulfurization tower for circulation.

[0125] S3: The high-concentration sulfur foam is transported to a sulfur melting kettle for sulfur melting. The generated liquid sulfur enters a sulfur tank for cooling and collection to obtain sulfur product. The generated sulfur melting residual liquid is cooled, settled, and filtered to obtain a recovery liquid which is returned to the desulfurization tower for circulation.

[0126] The sulfur recovery process of the comparative example is continuously circulated for a total of 72 h.

[0127] The composition of the desulfurization liquid used in the comparative example is as follows: sodium carbonate 23 g / L, sodium bicarbonate 3.5 g / L, and sodium vanadate 2 g / L.

[0128] After the equipment of the comparative example is started for 3 h, the clear liquid is taken in step S1 for detection. The content of sodium thiosulfate in the clear liquid is 105 mg / L.

[0129] Comparative example

[0130] Comparative example 2

[0131] The low by-product sulfur recovery process of the present comparative example is different from that of Example 2 in that the same amount of dodecyltrimethylammonium chloride is used to replace the buffer control material, and the rest is the same as in Example 2.

[0132] Comparative Example 3

[0133] The low by-product sulfur recovery process of the present comparative example is different from that of Example 2 in that the same amount of stabilizer is used to replace the buffer control material, and the rest is the same as in Example 2.

[0134] The preparation method of the stabilizer of the present comparative example is the same as that of Example 2.

[0135] Comparative Example 4

[0136] The low by-product sulfur recovery process of the present comparative example is different from that of Example 2 in that the inhibitor is ferrocene, and the rest is the same as in Example 2.

[0137] The preparation method of the stabilizer of the present comparative example is the same as that of Example 2.

[0138] Comparative Example 5

[0139] The low by-product sulfur recovery process of the present comparative example is different from that of Example 6 in that the stabilizer is composed of an alkyl quaternary ammonium salt and ferrocene in a mass ratio of 10:1.2, and the rest is the same as in Example 6.

[0140] The alkyl quaternary ammonium salt is composed of benzyltriethylammonium chloride and tetrabutylammonium chloride in a molar ratio of 1.5:0.6.

[0141] Comparative Example 6

[0142] The low by-product sulfur recovery process of the present comparative example is different from that of Example 6 in that in the preparation method of the stabilizer, no wax is added in step 1), and the rest is the same as in Example 6.

[0143] Performance detection test

[0144] Detection method

[0145] After the low by-product sulfur recovery processes of Examples 1-6 and Comparative Examples 1-6 were stably operated for 72 hours, the content of sodium thiosulfate in the desulfurization solution in the desulfurization tower and the molten sulfur residue in the molten sulfur kettle was tested, and the comprehensive test results are shown in Table 1. Figure 1 The stabilizer of Example 6 was taken for SEM test, and the test structure is shown in Table 2. Figure 2

[0146] Analyzing Examples 1 and Comparative Example 1 and combining Figure 1 ​It can be seen that the multi-stage separation process of high tank preliminary settling separation and vacuum filter liquid foam separation in Example 1 can greatly reduce the liquid content of sulfur foam, which prepares for the subsequent sulfur melting stage. On the other hand, after filtration through the nano ceramic membrane pores, the content of harmful by-products can be reduced to a certain extent, and the content of sodium thiosulfate in the sulfur melting stage and the shedding stage is controlled at a low level. In Comparative Example 1, the sulfur melting residue is directly returned to the desulfurization tower for use, which will cause the temperature of the desulfurization liquid to rise, causing more HS - to be converted into thiosulfate, causing the accumulation of by-products in the desulfurization liquid, resulting in a decrease in the production of sulfur foam and a decrease in the overall desulfurization efficiency.

[0147] Analysis of Examples 2-4 and combination Figure 1 It can be seen that, based on Example 1, the application adds a control material as an auxiliary additive, which is a porous carrier as an adsorption matrix, and the internal pore structure adsorbs a stabilizer component. The pore structure of the porous carrier can provide very good protection, reducing the leakage of the stabilizer component and maintaining the normal operation of the desulfurization liquid system and the sulfur melting system. And, referring to Figure 2 It can be seen that the stabilizer of the application is a double-layer coated structure with a diameter of about several hundred nanometers. The double-layer coated structure is a polyurethane coating layer and a wax coating layer, and the core coating is an inhibitor component. Through the slow-release effect of the double-layer coated structure, the release amount of the inhibitor component can be adjusted under different temperature conditions, which can ensure the inhibition of the adverse oxidation effect of the inhibitor component on elemental sulfur, and will not affect the stable operation of the desulfurization liquid system and the sulfur melting system.

[0148] In addition, the inhibitor of the application uses alkyl quaternary ammonium salt and ferrocene in combination, which can change the oxidation-reduction potential to a certain extent, thereby affecting the electronic properties of the oxidation-reduction center, inhibiting the conversion of elemental sulfur to higher valence state, and greatly reducing the generation amount of sulfur by-products. Moreover, in the subsequent circulation process, the trace amount of iron ions produced by the decomposition of ferrocene can also play a very good role in promoting the conversion of elemental sulfur, thereby reducing the generation amount of by-products. As can be seen from Example 4, after the introduction of the control material, the content of the by-product sodium thiosulfate in the desulfurization liquid is maintained at a low level, and the desulfurization system runs stably.

[0149] Analysis of Examples 2, Comparative Examples 2-6 and combination Figure 1It can be seen that in Comparative Example 2, the same amount of dodecyl trimethyl ammonium chloride is used to replace the buffer control material, which not only fails to control the content of the by-product salt in the desulfurization solution, but also destroys the stability of the desulfurization solution system, resulting in a decrease in desulfurization efficiency and a sharp increase in by-products. In Comparative Example 3, an equal amount of stabilizer is used to replace the buffer control material, and due to the lack of protection of the porous carrier, the release amount of the inhibitor cannot be controlled when the temperature changes, and the overall inhibition effect on the abnormal oxidation of sulfur is not enough, and the content of the by-product salt increases. In Comparative Example 4, ferrocene is used as an inhibitor component alone, and its long-term inhibition effect is poor, and the content of the by-product salt is still high after a long time of operation. In Comparative Example 5, the alkyl quaternary ammonium salt and ferrocene are directly adsorbed in the pore structure of the porous carrier, and due to the lack of the regulation effect of the double-layer coating structure, the stabilizer plays a certain inhibitory effect while damaging the stability of the desulfurization solution system, and the overall desulfurization effect is poor, and the content of the by-product salt cannot be effectively controlled. In Comparative Example 6, no wax is added, only a single-layer coating structure can be formed, the buffer control effect is poor, and the overall by-reaction inhibition effect is poor.

[0150] Analysis of Examples 5-6 and combination Figure 1 It can be seen that further optimization and adjustment of the mass ratio of the alkyl quaternary ammonium salt and ferrocene can improve the inhibition effect on the by-reaction in the system and reduce the content of the by-products in the desulfurization solution and the molten sulfur residue.

[0151] The low by-product sulfur recovery process of the present application has very stable and efficient desulfurization effect, and the content of the by-reaction product in the desulfurization solution system is small, which is suitable for long-time operation.

[0152] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low by-product sulfur recovery process characterized by, It comprises the following steps: S1: the sulfur-containing waste gas is sent into a desulfurization tower and is in contact with the desulfurization liquid sprayed at the top of the tower in a reverse direction to carry out desulfurization, and then the desulfurization liquid discharged at the bottom of the tower is sprayed into a regeneration tank to float to obtain sulfur foam and clear liquid, and the clear liquid is returned to the desulfurization tower to be recycled; S2: the sulfur foam is transported to a high tank to carry out preliminary settlement separation, high-concentration sulfur foam is obtained in the upper layer, and settlement liquid is obtained in the lower layer and is returned to the desulfurization tower to be recycled; S3: the high-concentration sulfur foam is transported to a filter to carry out liquid-foam separation, sulfur paste and filtrate are obtained after filtration, and the filtrate is returned to the desulfurization tower to be recycled; S4: the sulfur paste obtained after filtration is transported to a sulfur paste dilution tank, then molten sulfur residual liquid is added into the sulfur paste dilution tank, and after being mixed uniformly, sulfur paste dilution liquid is obtained; In the step S4, the molten sulfur residual liquid is added at the same time as the buffer control material, and the buffer control material is made of raw materials in the following proportions by weight: 100-120 parts of porous carrier, 30-35 parts of stabilizer, and 300-500 parts of solvent; the stabilizer is prepared by the following method: 1) the wax, inhibitor, isocyanate monomer and emulsifier are heated to 110-130 DEG C in a container, then mixed at a stirring speed of 800-1000 rpm for 15-30 min to prepare an intermediate liquid, then water is added into the intermediate liquid to continue stirring for 5-10 min to mix uniformly to prepare a precursor liquid; 2) the precursor liquid is added into polyol under continuous stirring, and after constant temperature reaction at 135-150 DEG C for 4-6 h, cooling, filtration, washing and drying are carried out to obtain the stabilizer, and the inhibitor is composed of alkyl quaternary ammonium salt and ferrocene in a mass ratio of (10-15):(0.5-1.2); S5: the sulfur paste dilution liquid is transported into a molten sulfur kettle to carry out molten sulfur, the liquid sulfur generated is cooled and collected in a sulfur tank, and part of the molten sulfur residual liquid is sent into the sulfur paste dilution tank in the step S4, and the other part of the molten sulfur residual liquid is cooled, settled, filtered to obtain a recovery liquid which is returned to the desulfurization tower to be recycled.

2. A low by-product sulfur recovery process according to claim 1, characterized in that, The alkyl quaternary ammonium salt is at least one of benzyl triethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, tetramethyl ammonium chloride, tetraethyl ammonium bromide and tetrabutyl ammonium chloride.

3. A low by-product sulfur recovery process according to claim 1, characterized in that, The porous carrier is one or more of porous iron oxide, porous silicon dioxide, porous carbon, porous copper oxide, porous aluminum oxide, porous ceramic, porous calcium carbonate, porous zeolite, porous aluminum phosphate and porous rubber.

4. The low by-product sulfur recovery process of claim 1, wherein, The average pore size of the porous carrier is 5-20 μm.

5. A low by-product sulfur recovery process according to claim 1, characterized in that, The mass ratio of the stabilizer to the porous carrier is (0.025-0.028):

1.

6. A low by-product sulfur recovery process according to claim 1, characterized in that, In the step S4, the mass ratio of the sulfur paste, molten sulfur residual liquid and buffer control material is (5-7.5):(20-30):(0.05-0.065).

7. A low by-product sulfur recovery process according to claim 1, characterized in that, In the step S5, after the other part of the molten sulfur residual liquid is cooled, settled and filtered, a solid residue is obtained in addition to the recovery liquid, and the solid residue is immersed, washed, dried and ground to be used repeatedly as the porous carrier.

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