A deep processing technology for sulfur paste as a by-product of coke oven gas desulfurization

Abstract

The invention belongs to the technical field of waste treatment in the coking industry and relates to a deep processing process for sulfur paste, a by-product of coke oven gas desulfurization. The process comprises the following steps: decolorization of the sulfur paste, first centrifugal filtration, acidification and impurity removal, preparation of sodium thiosulfate, second centrifugal filtration, concentration and precipitation of ammonium sulfate and ammonium thiocyanate, centrifugal separation, concentration of sodium thiosulfate, crystallization of sodium thiosulfate, first separation of sodium thiosulfate pentahydrate, purification of sodium thiosulfate pentahydrate and second separation of sodium thiosulfate pentahydrate. Through efficient conversion, separation and impurity removal, the solid waste sulfur paste can be processed into high-value-added sodium thiosulfate pentahydrate crystals, thereby truly realizing high-quality resource utilization of pollutants.

Description

Technical Field

[0001] The invention belongs to the technical field of waste treatment in the coking industry, and particularly relates to a deep processing process of sulfur paste, a by-product of coke oven gas desulfurization. Background Art

[0002] Currently, coke oven gas desulfurization primarily utilizes the HPF process, which produces a significant amount of sulfur paste. This paste primarily consists of sulfur, along with small amounts of organic compounds such as ammonium thiocyanate, ammonium thiosulfate, and tar. Currently, the market value of sulfur paste is very low, and it is generally treated as solid waste. Many companies either dump it in landfills or pay external companies to process it. These companies typically convert the paste into sulfuric acid, resulting in significant resource waste and ecological pollution. Existing sulfur paste technology development primarily focuses on sulfur recovery, but overall technology still needs improvement. This is primarily due to the low purity of the resulting sulfur and its environmental friendliness. Furthermore, there are few reports on the use of sulfur paste to produce other high-value chemical products, such as sulfuric acid and sodium metabisulfite.

[0003] Therefore, based on the characteristics of sulfur paste, a by-product of coke oven gas desulfurization, and the maximum resource utilization of solid waste, how to ensure the technological development of high-quality deep-processing products on the basis of environmental protection has become increasingly urgent. Summary of the Invention

[0004] The present invention aims to provide a process for deep processing of sulfur paste, a byproduct of coke oven gas desulfurization, to address the problem of handling the sulfur paste. By deep processing the sulfur paste, the solid waste sulfur paste is converted into high-value-added sodium thiosulfate pentahydrate crystals, truly achieving high-quality resource utilization of the pollutant. The present invention provides the following technical solutions:

[0005] A deep processing process for sulfur paste, a by-product of coke oven gas desulfurization, comprises a sodium thiosulfate preparation step and a sodium thiosulfate purification step which are carried out in sequence.

[0006] The sodium thiosulfate preparation process comprises the following steps:

[0007] Step 1: Decolorization of sulfur paste: Add 100-150 parts of sulfur paste, 700-1000 parts of water and 1-50 parts of activated carbon into a stirred tank A and stir for 40-80 minutes to obtain a decolorized sulfur paste mixture;

[0008] Step 2: First centrifugal filtration: The decolorized sulfur paste mixture is transferred to centrifuge A via a transfer pump and centrifuged at a speed of 1000-2000 r / min for 30-40 min. The solid obtained after centrifugation is the activated carbon cake, and the liquid obtained is the treated liquid A.

[0009] Step 3: Acidification and impurity removal: The treated liquid A is transferred to the reactor A, and 10-50 parts by mass of a 10-30% sulfuric acid solution is added to the reactor A. The mixture is stirred and reacted for 60-90 minutes. During the reaction, gas is generated, and a reaction liquid A is obtained. The gas is introduced into the alkali liquid tank for purification through a centrifugal induced draft fan. The gas reacts with the alkali liquid in the alkali liquid tank to obtain solid sulfur and other products. Other products are recovered in the recovery system.

[0010] Step 4: Preparation of sodium thiosulfate: Transfer reaction solution A and solid sulfur to an ultrasonic reactor, add 300-450 parts of sodium sulfite to the ultrasonic reactor, and perform ultrasonic reaction at 100-150° C. and 60-80% power for 60-90 minutes to obtain reaction solution B;

[0011] Step 5: Second centrifugal filtration: Transfer the reaction solution B in step 4 to centrifuge B and centrifuge at a speed of 1000-2000 r / min for 30-40 min to obtain sulfur cake and treated solution B.

[0012] The sodium thiosulfate purification process comprises the following steps:

[0013] Step a: Concentrating and precipitating ammonium sulfate and ammonium thiocyanate: Transfer the treated liquid B to an evaporator A, evaporate at 60-80°C until the Baume degree of the treated liquid B is 20°-40°, then stop evaporating to obtain a concentrated liquid A;

[0014] Step b: Centrifugal separation: Transfer the concentrated solution A to a centrifuge C, centrifuge at 1500-2500 r / min for 20-40 min, and filter to obtain a treated solution C and a mixed ammonium salt;

[0015] Step c: Concentrating sodium thiosulfate: transferring the treated liquid C to an evaporator B, evaporating the treated liquid C at 60-80°C until the Baume degree of the treated liquid C is 40°-60°, then stopping the evaporation to obtain a concentrated liquid B;

[0016] Step d: Crystallizing sodium thiosulfate: transferring the concentrated solution B to a crystallizer and crystallizing at room temperature to obtain a crystal solution;

[0017] Step e: First separation of sodium thiosulfate pentahydrate: transfer the crystallization liquid to a centrifuge D, centrifuge at 1500-2500 r / min for 20-40 min, and filter to obtain a treated liquid D and impurity-containing sodium thiosulfate pentahydrate crystals;

[0018] Step f: Purifying sodium thiosulfate pentahydrate: adding the impurity-containing sodium thiosulfate pentahydrate crystals to a stirred tank C, adding 100-200 parts of anhydrous ethanol, and stirring for 30-50 minutes to obtain a mixed solution;

[0019] Step g: Second separation of sodium thiosulfate pentahydrate: transfer the mixed solution to a centrifuge E, centrifuge at 2000-3000 r / min for 30-40 min, and filter to obtain an ethanol mixed solution and sodium thiosulfate pentahydrate crystals.

[0020] Preferred: Step 1: Decolorization of sulfur paste: 120 parts of sulfur paste, 850 parts of water and 25 parts of activated carbon, stir for 60 minutes.

[0021] Preferably: Step 2: First centrifugal filtration: Centrifuge A rotates at 1500 r / min for 35 min.

[0022] Preferably: Step 3: Add acid to remove impurities: 30 parts of 20% sulfuric acid solution, stir for 75 minutes.

[0023] Preferably: Step 4: Preparation of sodium thiosulfate: 370 parts by weight of sodium sulfite, 125° C. temperature, 70% ultrasonic power, ultrasonic reaction for 70 min.

[0024] Preferably: Step 5: Second centrifugal filtration: Centrifuge B at a speed of 1500 r / min for 35 min.

[0025] Preferably: Step a: Concentrating and precipitating ammonium sulfate and ammonium thiocyanate: The temperature of evaporator A is 70° C. and the Baume degree is 30°.

[0026] Preferably: Step b: Centrifugal separation: Centrifuge C at a speed of 2000 r / min, centrifugation for 30 min.

[0027] Preferably: Step c: Concentrating sodium thiosulfate: The temperature of evaporator B is 70° C. and the Baume degree is 50°.

[0028] Preferably: Step e: First separation of sodium thiosulfate pentahydrate: centrifuge D at a speed of 2000 r / min, centrifugation for 30 min.

[0029] Preferred: Step f: Purification of sodium thiosulfate pentahydrate: 150 parts of anhydrous ethanol, stirring for 40 min.

[0030] Preferably: Step g: Second separation of sodium thiosulfate pentahydrate: Centrifuge E at a speed of 2500 r / min, centrifugation for 35 min.

[0031] The present invention has the following advantages:

[0032] (1) The sulfur paste produced as a by-product of the coke oven gas desulfurization process is converted into sodium thiosulfate pentahydrate, an important raw material required in industrial production. This not only realizes the waste utilization of sulfur paste, but also realizes the high-quality resource utilization of sulfur paste, a pollutant.

[0033] (2) The deep processing technology of sulfur paste provided by the present invention has low difficulty in implementation, high conversion rate of sulfur paste, and the purity of the obtained product sodium thiosulfate pentahydrate is also high.

[0034] (3) In the sulfur paste processing technology involved in the present invention, only sulfur dioxide, a polluting gas, is produced, and the gas is treated by the alkali liquid tank. In the entire process, pollution-free emissions are achieved.

[0035] (4) In the sulfur paste processing technology involved in the present invention, the separation and purification process of sodium thiosulfate pentahydrate is simple to operate and the steps are brief, and high-purity sodium thiosulfate pentahydrate crystals can be recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a process flow chart of the present invention;

[0037] Figure 2 This is a process flow chart of the sodium thiosulfate preparation process of the present invention;

[0038] Figure 3 The present invention is a process flow chart for the purification process of sodium thiosulfate.

[0039] In the figure: 1. delivery pump 1, 2. centrifugal induced draft fan 2. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0041] Example 1: The sulfur paste produced as a by-product of coke oven gas desulfurization used in Example 1 was tested to have a sulfur content of 75.8%.

[0042] A deep processing process for sulfur paste, a by-product of coke oven gas desulfurization, includes a sodium thiosulfate preparation process and a sodium thiosulfate purification process.

[0043] The sodium thiosulfate preparation process comprises the following steps:

[0044] Step 1: Decolorization of sulfur paste: Add 100 kg of sulfur paste, 700 kg of water, and 10 kg of activated carbon to a stirred tank A and stir for 40 minutes to decolorize the sulfur paste to obtain a decolorized sulfur paste mixture. Water can be supplied via delivery pump 1.

[0045] Step 2: First centrifugal filtration: The decolorized sulfur paste mixture is transported to the centrifuge A via the delivery pump 11 and centrifuged at a speed of 1000 r / min for 30 min. The solid obtained after centrifugation is the activated carbon cake, and the liquid obtained is the treated liquid A.

[0046] Step 3: Acidification and Impurity Removal: Transfer treated liquid A to reactor A, add 10 kg of 10% sulfuric acid solution, and stir for 60 minutes. Gas is generated during the reaction, and the ammonium thiosulfate in the solution is converted to ammonium sulfate. The generated gas is sulfur dioxide, and reaction liquid A is obtained. The sulfur dioxide is introduced into the alkali liquid tank via centrifugal induced draft fan 2 for purification. The sulfur dioxide reacts with the alkali liquid in the alkali liquid tank to produce solid sulfur and other products. The other products are recovered in the recovery system. The solid sulfur can be transported along with the reaction liquid to the ultrasonic reactor for the next reaction, enabling its recovery and utilization. The generated sulfur dioxide gas is also recovered and purified. The ammonium sulfate can be crystallized and removed in a subsequent step. The alkali liquid in the alkali liquid tank is typically an alkaline substance such as sodium hydroxide solution or potassium hydroxide.

[0047] Step 4: Preparation of sodium thiosulfate: Transfer reaction solution A and solid sulfur to an ultrasonic reactor, add 300 kg of sodium sulfite to the ultrasonic reactor, and ultrasonically react at 100°C and 60% power for 60 minutes to obtain reaction solution B; sulfur and sodium sulfite react under boiling and superheated conditions to produce sodium thiosulfate. At this time, reaction solution B is mainly composed of a mixture of sodium thiosulfate solution, ammonium sulfate solution, and ammonium thiocyanate solution. Ultrasonic catalysis is carried out simultaneously during the reaction process to make the reaction more complete. Reaction solution A can be transferred to the ultrasonic reactor via transfer pump 1. The main chemical reactions involved are as follows: Na2SO3+S+5H2O Na2S2O3 5H2O.

[0048] Step 5: Second centrifugal filtration: Transfer the reaction solution B in step 4 to centrifuge B and centrifuge at 1000 r / min for 30 min to obtain a sulfur cake and treated solution B. The treated solution B is still mainly composed of sodium thiosulfate solution, ammonium sulfate solution and ammonium thiocyanate solution. The purpose of this step is to separate the remaining sulfur cake, which can be put into the stirred tank A to continue the next round of reaction.

[0049] The sodium thiosulfate purification process comprises the following steps:

[0050] Step a: Concentration and precipitation of ammonium sulfate and ammonium thiocyanate: Treated liquid B is transferred to evaporator A and evaporated at 60°C until its Baume reaches 20°. Evaporation is then stopped to produce concentrated liquid A. During this evaporation, mixed crystals of ammonium sulfate and ammonium thiocyanate continue to precipitate. Concentrated liquid A primarily consists of a mixture of sodium thiosulfate solution, ammonium sulfate crystals, and ammonium thiocyanate crystals.

[0051] Step b: Centrifugal Separation: Transfer concentrated solution A to centrifuge C and centrifuge at 1500 rpm for 20 minutes. Filter to obtain treated solution C and mixed ammonium salt. Treated solution C is a sodium thiosulfate solution, while the mixed ammonium salt is a mixture of ammonium sulfate crystals and ammonium thiocyanate crystals. This mixed crystal can be further separated in other processes to obtain higher-purity ammonium sulfate crystals and ammonium thiocyanate crystals. Concentrated solution A can be transferred to centrifuge C via transfer pump 1.

[0052] Step c: Concentrating sodium thiosulfate: Transfer the treated liquid C to an evaporator B and evaporate it at 60°C until the Baume degree of the treated liquid C reaches 40°, then stop evaporating to obtain a concentrated liquid B; the concentrated liquid B is the concentrated treated liquid C, i.e., the concentrated high-concentration sodium thiosulfate solution.

[0053] Step d: Crystallization of Sodium Thiosulfate: Concentrated Solution B is transferred to a crystallizer and crystallized at room temperature to obtain a crystallization solution. During the crystallization process, crystals precipitate in the crystallizer. These crystals are primarily sodium thiosulfate pentahydrate crystals, and the crystallization solution is primarily a mixture of sodium thiosulfate pentahydrate crystals and other impurity solutions.

[0054] Step e: First separation of sodium thiosulfate pentahydrate: Transfer the crystallization liquid to centrifuge D, centrifuge at 1500 r / min for 20 min, and filter to obtain treated liquid D and impurity-containing sodium thiosulfate pentahydrate crystals; treated liquid D is an impurity solution and enters the recovery system for unified treatment.

[0055] Step f: Purifying sodium thiosulfate pentahydrate: adding the impurity-containing sodium thiosulfate pentahydrate crystals to a stirred tank C, adding 100 kg of anhydrous ethanol, and stirring for 30 minutes to obtain a mixed solution; since the impurity-containing sodium thiosulfate pentahydrate crystals precipitated in step e may contain other impurities, the sodium thiosulfate pentahydrate crystals are washed with anhydrous ethanol to improve the purity of the sodium thiosulfate pentahydrate crystals. The mixed solution is a mixture of anhydrous ethanol and sodium thiosulfate pentahydrate crystals.

[0056] Step g: Second separation of sodium thiosulfate pentahydrate: The mixed solution is transferred to a centrifuge E, centrifuged at 2000 r / min for 30 min, and filtered to obtain an ethanol mixed solution and sodium thiosulfate pentahydrate crystals with a purity of more than 98%.

[0057] Example 2: The sulfur paste produced as a by-product of coke oven gas desulfurization used in Example 2 was tested to have a sulfur content of 77.8%.

[0058] A deep processing process for sulfur paste, a by-product of coke oven gas desulfurization, includes a sodium thiosulfate preparation process and a sodium thiosulfate purification process.

[0059] The sodium thiosulfate preparation process comprises the following steps:

[0060] Step 1: Decolorization of sulfur paste: 150 kg of sulfur paste, 1000 kg of water and 50 kg of activated carbon were added to a stirred tank A and stirred for 80 min to decolorize the sulfur paste to obtain a decolorized sulfur paste mixture.

[0061] Step 2: First centrifugal filtration: The decolorized sulfur paste mixture is transported to centrifuge A via the delivery pump 1 and centrifuged at a speed of 2000 r / min for 40 min. The solid obtained after centrifugation is the activated carbon cake, and the liquid obtained is the treated liquid A.

[0062] Step 3: Acidification and Impurity Removal: Transfer treated liquid A to reactor A, add 50 kg of 30% sulfuric acid solution, and stir for 90 minutes. Gas is generated during the reaction, and the ammonium thiosulfate in the solution is converted to ammonium sulfate. The generated gas is sulfur dioxide, and reaction liquid A is obtained. The sulfur dioxide is introduced into the alkali liquid tank via centrifugal induced draft fan 2 for purification. The sulfur dioxide reacts with the alkali liquid in the alkali liquid tank to produce solid sulfur and other products. The other products are recovered in the recovery system. The solid sulfur can be transported along with the reaction liquid to the ultrasonic reactor for the next reaction, enabling its recovery and utilization. The generated sulfur dioxide gas is also recovered and purified. The ammonium sulfate can be crystallized and removed in a subsequent step. The alkali liquid in the alkali liquid tank is typically an alkaline substance such as sodium hydroxide solution or potassium hydroxide.

[0063] Step 4: Preparation of sodium thiosulfate: Transfer reaction solution A and solid sulfur to an ultrasonic reactor. Add 450 kg of sodium sulfite to the ultrasonic reactor and ultrasonically react at 150°C and 80% power for 90 minutes to obtain reaction solution B. The sulfur and sodium sulfite react under boiling and superheated conditions to produce sodium thiosulfate. At this point, reaction solution B is mainly composed of a mixture of sodium thiosulfate solution, ammonium sulfate solution, and ammonium thiocyanate solution. Ultrasonic catalysis is also performed during the reaction to ensure a more complete reaction. The main chemical reactions involved are as follows: Na2SO3 + S + 5H2O Na2S2O3 5H2O.

[0064] Step 5: Second centrifugal filtration: Transfer the reaction solution B in step 4 to centrifuge B and centrifuge at 2000 r / min for 40 min to obtain a sulfur cake and treated solution B. The treated solution B is still mainly composed of sodium thiosulfate solution, ammonium sulfate solution and ammonium thiocyanate solution. The purpose of this step is to separate the remaining sulfur cake, which can be put into the stirred tank A to continue the next round of reaction.

[0065] The sodium thiosulfate purification process comprises the following steps:

[0066] Step a: Concentration and precipitation of ammonium sulfate and ammonium thiocyanate: Treated liquid B is transferred to evaporator A and evaporated at 80°C until its Baume reaches 40°. Evaporation is then stopped to produce concentrated liquid A. During this evaporation, mixed crystals of ammonium sulfate and ammonium thiocyanate continue to precipitate. Concentrated liquid A primarily consists of a mixture of sodium thiosulfate solution, ammonium sulfate crystals, and ammonium thiocyanate crystals.

[0067] Step b: Centrifugal separation: The concentrated liquid A is transferred to a centrifuge C, centrifuged at 2500 r / min for 40 minutes, and filtered to obtain a treated liquid C and a mixed ammonium salt; the treated liquid C is a sodium thiosulfate solution, and the mixed ammonium salt refers to a mixture of ammonium sulfate crystals and ammonium thiocyanate crystals. The mixed crystals can be further separated in other processes to obtain ammonium sulfate crystals and ammonium thiocyanate crystals with higher purity.

[0068] Step c: Concentrating sodium thiosulfate: Transfer the treated liquid C to an evaporator B and evaporate it at 80°C until the Baume degree of the treated liquid C reaches 60°, then stop evaporating to obtain a concentrated liquid B; the concentrated liquid B is the concentrated treated liquid C, i.e., the concentrated high-concentration sodium thiosulfate solution.

[0069] Step d: Crystallization of Sodium Thiosulfate: Concentrated Solution B is transferred to a crystallizer and crystallized at room temperature to obtain a crystallization solution. During the crystallization process, crystals precipitate in the crystallizer. These crystals are primarily sodium thiosulfate pentahydrate crystals, and the crystallization solution is primarily a mixture of sodium thiosulfate pentahydrate crystals and other impurity solutions.

[0070] Step e: First separation of sodium thiosulfate pentahydrate: Transfer the crystallization liquid to centrifuge D, centrifuge at 2500 r / min for 40 min, and filter to obtain treated liquid D and impurity-containing sodium thiosulfate pentahydrate crystals; treated liquid D is an impurity solution and enters the recovery system for unified treatment.

[0071] Step f: Purifying sodium thiosulfate pentahydrate: adding the impurity-containing sodium thiosulfate pentahydrate crystals to a stirred tank C, adding 200 kg of anhydrous ethanol, and stirring for 50 minutes to obtain a mixed solution; since the impurity-containing sodium thiosulfate pentahydrate crystals precipitated in step e may contain other impurities, the sodium thiosulfate pentahydrate crystals are washed with anhydrous ethanol to improve the purity of the sodium thiosulfate pentahydrate crystals. The mixed solution is a mixture of anhydrous ethanol and sodium thiosulfate pentahydrate crystals.

[0072] Step g: Second separation of sodium thiosulfate pentahydrate: The mixed solution is transferred to a centrifuge E, centrifuged at 2000 r / min for 40 min, and filtered to obtain an ethanol mixed solution and sodium thiosulfate pentahydrate crystals with a purity of more than 98%.

[0073] Example 3: The sulfur paste produced as a by-product of coke oven gas desulfurization used in Example 3 was tested to have a sulfur content of 76.8%.

[0074] A deep processing process for sulfur paste, a by-product of coke oven gas desulfurization, includes a sodium thiosulfate preparation process and a sodium thiosulfate purification process.

[0075] The sodium thiosulfate preparation process comprises the following steps:

[0076] Step 1: Decolorization of sulfur paste: 120 kg of sulfur paste, 850 kg of water and 25 kg of activated carbon were added to a stirred tank A and stirred for 60 min to decolorize the sulfur paste to obtain a decolorized sulfur paste mixture.

[0077] Step 2: First centrifugal filtration: The decolorized sulfur paste mixture is transported to centrifuge A via the delivery pump 1 and centrifuged at a speed of 1500 r / min for 35 min. The solid obtained after centrifugation is the activated carbon cake, and the liquid obtained is the treated liquid A.

[0078] Step 3: Acidification and Impurity Removal: Transfer treated liquid A to reactor A, add 25 kg of 20% sulfuric acid solution, and stir for 75 minutes. Gas is generated during the reaction, and the ammonium thiosulfate in the solution is converted to ammonium sulfate. The generated gas is sulfur dioxide, and reaction liquid A is obtained. The sulfur dioxide is introduced into the alkali tank via centrifugal induced draft fan 2 for purification. The sulfur dioxide reacts with the alkali solution in the alkali tank to produce solid sulfur and other products. The other products are recovered in the recovery system. The solid sulfur can be transported along with the reaction liquid to the ultrasonic reactor for the next reaction, enabling its recovery and utilization. The generated sulfur dioxide gas is also recovered and purified. The ammonium sulfate can be crystallized and removed in a subsequent step. The alkali solution in the alkali tank is typically an alkaline substance such as sodium hydroxide solution or potassium hydroxide.

[0079] Step 4: Preparation of sodium thiosulfate: Transfer reaction solution A and solid sulfur to an ultrasonic reactor. Add 370 kg of sodium sulfite to the ultrasonic reactor and ultrasonically react at 125°C and 70% power for 70 minutes to obtain reaction solution B. The sulfur and sodium sulfite react under boiling and superheated conditions to produce sodium thiosulfate. At this time, reaction solution B is mainly composed of a mixture of sodium thiosulfate solution, ammonium sulfate solution, and ammonium thiocyanate solution. Ultrasonic catalysis is carried out simultaneously during the reaction to ensure a more complete reaction. The main chemical reactions involved are as follows: Na2SO3 + S + 5H2O Na2S2O3 5H2O.

[0080] Step 5: Second centrifugal filtration: Transfer the reaction solution B in step 4 to centrifuge B and centrifuge at 1500 r / min for 35 minutes to obtain a sulfur cake and a treatment solution B. The treatment solution B is still mainly composed of sodium thiosulfate solution, ammonium sulfate solution and ammonium thiocyanate solution. The purpose of this step is to separate the remaining sulfur cake, which can be put into the stirred tank A to continue the next round of reaction.

[0081] The sodium thiosulfate purification process includes:

[0082] Step a: Concentration and precipitation of ammonium sulfate and ammonium thiocyanate: Treated liquid B is transferred to evaporator A and evaporated at 70°C until its Baume reaches 30°. Evaporation is then stopped to produce concentrated liquid A. During this evaporation, mixed crystals of ammonium sulfate and ammonium thiocyanate continue to precipitate. Concentrated liquid A primarily consists of a mixture of sodium thiosulfate solution, ammonium sulfate crystals, and ammonium thiocyanate crystals.

[0083] Step b: Centrifugal separation: The concentrated solution A is transferred to a centrifuge C, centrifuged at 2000 r / min for 30 minutes, and filtered to obtain a treated solution C and a mixed ammonium salt; the treated solution C is a sodium thiosulfate solution, and the mixed ammonium salt refers to a mixture of ammonium sulfate crystals and ammonium thiocyanate crystals. The mixed crystals can be further separated in other processes to obtain ammonium sulfate crystals and ammonium thiocyanate crystals with higher purity.

[0084] Step c: Concentrating sodium thiosulfate: Transfer the treated liquid C to an evaporator B and evaporate it at 70°C until the Baume degree of the treated liquid C reaches 50°, then stop evaporating to obtain a concentrated liquid B; the concentrated liquid B is the concentrated treated liquid C, i.e., the concentrated high-concentration sodium thiosulfate solution.

[0085] Step d: Crystallization of Sodium Thiosulfate: Concentrated Solution B is transferred to a crystallizer and crystallized at room temperature to obtain a crystallization solution. During the crystallization process, crystals precipitate in the crystallizer. These crystals are primarily sodium thiosulfate pentahydrate crystals, and the crystallization solution is primarily a mixture of sodium thiosulfate pentahydrate crystals and other impurity solutions.

[0086] Step e: First separation of sodium thiosulfate pentahydrate: Transfer the crystallization liquid to centrifuge D, centrifuge at 2000 r / min for 30 min, and filter to obtain treated liquid D and impurity-containing sodium thiosulfate pentahydrate crystals; treated liquid D is an impurity solution and enters the recovery system for unified treatment.

[0087] Step f: Purifying sodium thiosulfate pentahydrate: adding the impurity-containing sodium thiosulfate pentahydrate crystals to a stirred tank C, adding 150 kg of anhydrous ethanol, and stirring for 40 minutes to obtain a mixed solution; since the impurity-containing sodium thiosulfate pentahydrate crystals precipitated in step e may contain other impurities, the sodium thiosulfate pentahydrate crystals are washed with anhydrous ethanol to improve the purity of the sodium thiosulfate pentahydrate crystals. The mixed solution is a mixture of anhydrous ethanol and sodium thiosulfate pentahydrate crystals.

[0088] Step g: Second separation of sodium thiosulfate pentahydrate: The mixed solution is transferred to a centrifuge E, centrifuged at 2500 r / min for 35 min, and filtered to obtain an ethanol mixed solution and sodium thiosulfate pentahydrate crystals with a purity of more than 98%.

[0089] Example 4: The sulfur paste produced as a by-product of coke oven gas desulfurization used in Example 4 was tested to have a sulfur content of 82.7%.

[0090] A deep processing process for sulfur paste, a by-product of coke oven gas desulfurization, includes a sodium thiosulfate preparation process and a sodium thiosulfate purification process.

[0091] The sodium thiosulfate preparation process comprises the following steps:

[0092] Step 1: Decolorization of sulfur paste: Add 130 kg of sulfur paste, 850 kg of water, and 40 kg of activated carbon to stirred tank A and stir for 60 minutes to decolorize the sulfur paste to obtain a decolorized sulfur paste mixture. Water can be supplied via delivery pump 1.

[0093] Step 2: First centrifugal filtration: The decolorized sulfur paste mixture is transported to centrifuge A via pump 1 and centrifuged at 1400 r / min for 38 min. The solid obtained after centrifugation is activated carbon cake, and the liquid obtained is treated liquid A.

[0094] Step 3: Acidification and Impurity Removal: Transfer treated liquid A to reactor A, add 40 kg of 25% sulfuric acid solution, and stir for 65 minutes. Gas is generated during the reaction, and the ammonium thiosulfate in the solution is converted to ammonium sulfate. The generated gas is sulfur dioxide, and reaction liquid A is obtained. The sulfur dioxide is introduced into the alkali tank via centrifugal induced draft fan 2 for purification. The sulfur dioxide reacts with the alkali solution in the alkali tank to produce solid sulfur and other products. The other products are recovered in the recovery system. The solid sulfur can be transported along with the reaction liquid to the ultrasonic reactor for the next reaction, enabling its recovery and utilization. The generated sulfur dioxide gas is also recovered and purified. The ammonium sulfate can be crystallized and removed in a subsequent step. The alkali solution in the alkali tank is typically an alkaline substance such as sodium hydroxide solution or potassium hydroxide.

[0095] Step 4: Preparation of sodium thiosulfate: Transfer reaction solution A and solid sulfur to an ultrasonic reactor. Add 400 kg of sodium sulfite to the ultrasonic reactor and ultrasonically react at 110°C and 75% power for 80 minutes to obtain reaction solution B. The sulfur and sodium sulfite react under boiling and superheated conditions to produce sodium thiosulfate. At this time, reaction solution B is mainly composed of a mixture of sodium thiosulfate solution, ammonium sulfate solution, and ammonium thiocyanate solution. Ultrasonic catalysis is carried out simultaneously during the reaction to ensure a more complete reaction. The main chemical reactions involved are as follows: Na2SO3 + S + 5H2O Na2S2O3 5H2O.

[0096] Step 5: Second centrifugal filtration: Transfer the reaction solution B in step 4 to centrifuge B and centrifuge at 1200 r / min for 38 minutes to obtain a sulfur cake and a treatment solution B. The treatment solution B is still mainly composed of sodium thiosulfate solution, ammonium sulfate solution and ammonium thiocyanate solution. The purpose of this step is to separate the remaining sulfur cake, which can be put into the stirred tank A to continue the next round of reaction.

[0097] The sodium thiosulfate purification process comprises the following steps:

[0098] Step a: Concentration and precipitation of ammonium sulfate and ammonium thiocyanate: Treated liquid B is transferred to evaporator A and evaporated at 75°C until its Baume reaches 25°. Evaporation is then stopped to produce concentrated liquid A. During this evaporation, mixed crystals of ammonium sulfate and ammonium thiocyanate continue to precipitate. Concentrated liquid A primarily consists of a mixture of sodium thiosulfate solution, ammonium sulfate crystals, and ammonium thiocyanate crystals.

[0099] Step b: Centrifugal separation: The concentrated solution A is transferred to a centrifuge C, centrifuged at 2200 r / min for 35 minutes, and filtered to obtain a treated solution C and a mixed ammonium salt; the treated solution C is a sodium thiosulfate solution, and the mixed ammonium salt refers to a mixture of ammonium sulfate crystals and ammonium thiocyanate crystals. The mixed crystals can be further separated in other processes to obtain ammonium sulfate crystals and ammonium thiocyanate crystals with higher purity.

[0100] Step c: Concentrating sodium thiosulfate: Transfer the treated liquid C to an evaporator B and evaporate it at 75°C until the Baume degree of the treated liquid C reaches 55°, then stop evaporating to obtain a concentrated liquid B; the concentrated liquid B is the concentrated treated liquid C, i.e., the concentrated high-concentration sodium thiosulfate solution.

[0101] Step d: Crystallization of Sodium Thiosulfate: Concentrated Solution B is transferred to a crystallizer and crystallized at room temperature to obtain a crystallization solution. During the crystallization process, crystals precipitate in the crystallizer. These crystals are primarily sodium thiosulfate pentahydrate crystals, and the crystallization solution is primarily a mixture of sodium thiosulfate pentahydrate crystals and other impurity solutions.

[0102] Step e: First separation of sodium thiosulfate pentahydrate: Transfer the crystallization liquid to centrifuge D, centrifuge at 2200 r / min for 35 min, and filter to obtain treated liquid D and impurity-containing sodium thiosulfate pentahydrate crystals; treated liquid D is an impurity solution and enters the recovery system for unified treatment.

[0103] Step f: Purifying sodium thiosulfate pentahydrate: adding the impurity-containing sodium thiosulfate pentahydrate crystals to a stirred tank C, adding 130 kg of anhydrous ethanol, and stirring for 45 minutes to obtain a mixed solution; since the impurity-containing sodium thiosulfate pentahydrate crystals precipitated in step e may contain other impurities, the sodium thiosulfate pentahydrate crystals are washed with anhydrous ethanol to improve the purity of the sodium thiosulfate pentahydrate crystals. The mixed solution is a mixture of anhydrous ethanol and sodium thiosulfate pentahydrate crystals.

[0104] Step g: Second separation of sodium thiosulfate pentahydrate: The mixed solution is transferred to a centrifuge E, centrifuged at 2800 r / min for 38 min, and filtered to obtain an ethanol mixed solution and sodium thiosulfate pentahydrate crystals with a purity of more than 98%.

[0105] The specific parameters of the sodium thiosulfate pentahydrate crystals prepared based on the above Examples 1-4 are as follows:

[0106]

[0107] Recovery rate =

[0108] The present invention realizes the recycling and utilization of sulfur paste through a simple production process, converting the sulfur paste into sodium thiosulfate pentahydrate crystals with high cost performance. The sodium thiosulfate pentahydrate crystals prepared by the present invention have a purity of about 98%, which is relatively high, and a recovery rate of more than 80%, which is very high.

[0109] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for deep processing of sulfur paste as a by-product of coke oven gas desulfurization, characterized by: The method comprises a sodium thiosulfate preparation process and a sodium thiosulfate purification process which are carried out in sequence; the sodium thiosulfate preparation process comprises the following steps: Step 1: Decolorization of sulfur paste: Add 100-150 parts of sulfur paste, 700-1000 parts of water and 1-50 parts of activated carbon into a stirred tank A and stir for 40-80 minutes to obtain a decolorized sulfur paste mixture; Step 2: First centrifugal filtration: The decolorized sulfur paste mixture is transferred to centrifuge A via a transfer pump and centrifuged at a speed of 1000-2000 r / min for 30-40 min. The solid obtained after centrifugation is the activated carbon cake, and the liquid obtained is the treated liquid A. Step 3: Acidification and impurity removal: The treated liquid A is transferred to the reactor A, and 10-50 parts by mass of a 10-30% sulfuric acid solution is added to the reactor A. The mixture is stirred and reacted for 60-90 minutes. During the reaction, gas is generated, and a reaction liquid A is obtained. The gas is introduced into the alkali liquid tank for purification through a centrifugal induced draft fan. The gas reacts with the alkali liquid in the alkali liquid tank to obtain solid sulfur and other products. Other products are recovered in the recovery system. Step 4: Preparation of sodium thiosulfate: Transfer reaction solution A and solid sulfur to an ultrasonic reactor, add 300-450 parts of sodium sulfite to the ultrasonic reactor, and perform ultrasonic reaction at 100-150°C and 60-80% power for 60-90 minutes to obtain reaction solution B; Step 5: Second centrifugal filtration: Transfer the reaction solution B in step 4 to centrifuge B and centrifuge at a speed of 1000-2000 r / min for 30-40 min to obtain sulfur cake and treated solution B.

2. The process for deep processing of sulfur paste as a by-product of coke oven gas desulfurization according to claim 1, characterized in that: The sodium thiosulfate purification process comprises the following steps: Step a: Concentrating and precipitating ammonium sulfate and ammonium thiocyanate: Transfer the treated liquid B to an evaporator A, evaporate at 60-80°C until the Baume degree of the treated liquid B is 20°-40°, then stop evaporating to obtain a concentrated liquid A; Step b: Centrifugal separation: Transfer the concentrated solution A to a centrifuge C, centrifuge at 1500-2500 r / min for 20-40 min, and filter to obtain a treated solution C and a mixed ammonium salt; Step c: Concentrating sodium thiosulfate: transferring the treated liquid C to an evaporator B, evaporating the treated liquid C at 60-80°C until the Baume degree of the treated liquid C is 40°-60°, then stopping the evaporation to obtain a concentrated liquid B; Step d: Crystallizing sodium thiosulfate: transferring the concentrated solution B to a crystallizer and crystallizing at room temperature to obtain a crystal solution; Step e: First separation of sodium thiosulfate pentahydrate: transfer the crystallization liquid to a centrifuge D, centrifuge at 1500-2500 r / min for 20-40 min, and filter to obtain a treated liquid D and impurity-containing sodium thiosulfate pentahydrate crystals; Step f: Purifying sodium thiosulfate pentahydrate: adding the impurity-containing sodium thiosulfate pentahydrate crystals to a stirred tank C, adding 100-200 parts of anhydrous ethanol, and stirring for 30-50 minutes to obtain a mixed solution; Step g: Second separation of sodium thiosulfate pentahydrate: transfer the mixed solution to a centrifuge E, centrifuge at 2000-3000 r / min for 30-40 min, and filter to obtain an ethanol mixed solution and sodium thiosulfate pentahydrate crystals.

3. The process for deep processing of sulfur paste as a by-product of coke oven gas desulfurization according to claim 1, characterized in that: Step 1: Decolorization of sulfur paste: 120 parts of sulfur paste, 850 parts of water and 25 parts of activated carbon, stir for 60 minutes; Step 2: First centrifugal filtration: Centrifuge A at 1500 r / min for 35 min; Step 3: Add acid to remove impurities: 30 parts of 20% sulfuric acid solution, stir for 75 minutes; Step 4: Preparation of sodium thiosulfate: 370 parts by weight of sodium sulfite, 125°C temperature, 70% ultrasonic power, and ultrasonic reaction for 70 min; Step 5: Second centrifugal filtration: Centrifuge B at 1500 r / min for 35 min.

4. The process for deep processing of sulfur paste as a by-product of coke oven gas desulfurization according to claim 2, characterized in that: Step a: Concentrate and precipitate ammonium sulfate and ammonium thiocyanate: the temperature of evaporator A is 70°C and the Baume degree is 30°; Step b: centrifugation: centrifuge C at 2000 r / min for 30 min; Step c: Concentrate sodium thiosulfate: the temperature of evaporator B is 70°C and the Baume degree is 50°; Step e: First separation of sodium thiosulfate pentahydrate: centrifuge D at a speed of 2000 r / min for 30 min; Step f: Purification of sodium thiosulfate pentahydrate: 150 parts of anhydrous ethanol, stirring for 40 min; Step g: Second separation of sodium thiosulfate pentahydrate: centrifuge E at a speed of 2500 r / min for 35 min.

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