Sulfur foam slurry method feeding acid making process

Abstract

The invention relates to the technical field of slurry method feeding acid making, and particularly discloses a sulfur foam slurry method feeding acid making process which comprises the following steps: step 1, pretreatment: separating sulfur-containing foam into thick slurry and filtrate, concentrating the filtrate, and mixing the concentrated filtrate with the thick slurry to form incineration slurry; 2, incineration is conducted, specifically, the incineration slurry is mixed with air, the mixture is put into an incinerator to be combusted after being mixed, and SO2 flue gas is obtained; 3, purification is conducted, specifically, SO2 flue gas in the incineration workshop section is introduced into a dynamic wave washer, acid mist is removed through an electric demister, and purified wet flue gas is obtained; step 4, drying: introducing the purified wet flue gas subjected to acid mist removal into sulfuric acid for drying; and 5, conversion: feeding the dried product into a converter, carrying out a catalytic oxidation reaction to obtain SO3 gas, and absorbing SO3 by using water to prepare sulfuric acid. The technical problems that in the prior art, the process for recycling solid sulfur through sulfur-containing foam is not high in purity, selling is difficult, the price is low, much waste water needs to be discharged, and a new pollution source is generated are solved.

Description

Technical Field

[0001] The invention relates to the technical field of slurry-feed acid production, in particular to a sulfur foam slurry-feed acid production process. Background Art

[0002] Currently, the coking industry mostly uses coking coal as raw material, heating it to 950–1050°C in a coke oven in an airtight state. The coal then decomposes into coke, coal gas, and liquid products to produce coke. However, coal gas contains a large amount of sulfides, such as hydrogen sulfide (H2S) and sulfur dioxide (SO2). These substances are harmful to the environment and human health and need to be removed to meet environmental protection requirements.

[0003] The industry primarily uses the HPF desulfurization process to remove hydrogen sulfide and hydrogen cyanide from coke oven gas. This process involves wet oxidation desulfurization, using ammonia from the coke oven gas as an absorbent and HPF as a catalyst. The process involves pre-cooling the gas through a desulfurization tower, where it countercurrently contacts a desulfurization solution sprayed from the tower's top to absorb hydrogen sulfide and hydrogen cyanide. Simultaneously, the desulfurization solution absorbs ammonia from the gas, replenishing the alkalinity source in the desulfurization solution. After desulfurization, the hydrogen sulfide content in the gas is reduced to approximately 50 mg / m³ before being fed to the ammonium sulfate treatment section. The desulfurization solution, which has absorbed H₂S and HCN, flows from the bottom of the tower and is pumped into the regeneration tower via a desulfurization liquid circulation pump. Compressed air is introduced from the bottom of the regeneration tower, oxidizing the desulfurization solution within the tower, forming a sulfur-containing foam that floats on the expanded portion of the regeneration tower's top. The solution in the regeneration tower then flows back to the desulfurization tower through a level regulator for recycling. Sulfur foam is recovered by melting sulfur to recover solid sulfur. Although this method is mature and reliable, it only recovers the sulfur, leaving behind a large amount of by-product salts in the sulfur foam. This results in low sulfur purity, making it difficult to sell and fetching a low price, making its economic value low.

[0004] In order to change the current situation in which sulfur production using sulfur foam has low economic value, a process for directly producing sulfuric acid from sulfur foam has emerged in the industry. For example, patent document CN119793383A discloses a system for producing sulfuric acid from sulfur foam and desulfurization waste liquid. The system separates and concentrates the sulfur foam to obtain a concentrated slurry, calcines the concentrated slurry to generate SO2, and then uses water to absorb the SO2 to produce concentrated sulfuric acid.

[0005] Compared with traditional technologies, the above-mentioned prior art process of producing sulfuric acid from sulfur foam produces sulfuric acid with high purity and higher economic value. However, the method of directly calcining the concentrated slurry foam introduces a large amount of water into the incinerator. The water absorbs a large amount of heat and vaporizes, resulting in high energy consumption of the incinerator, which in turn leads to increased corporate costs. In addition, the water is in contact with the incinerator for a long time, which can easily cause oxidation corrosion of some metal parts of the incinerator at high temperatures. Summary of the Invention

[0006] The object of the present invention is to provide a sulfur foam slurry feeding acid production process to solve the technical problem mentioned above in the prior art process of producing sulfuric acid from sulfur foam, in which the sulfur foam is centrifuged to form a concentrated slurry and then directly fed into an incinerator for calcination, resulting in high energy consumption of the incinerator and thus increased enterprise costs.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows: a sulfur foam slurry feed acid production process, comprising the following steps: Step 1, pretreatment: The sulfur-containing foam is separated into a concentrated slurry and a filtrate in a centrifuge. The concentrated slurry is sent to a two-phase separator to separate liquid sulfur and a clear liquid. The clear liquid enters a single-effect concentration system. The concentrated brine produced by the single-effect concentration system is mixed with the liquid sulfur and the concentrated brine to form an incineration slurry. Step 2, sulfur incineration: mixing the incineration slurry with air, and then putting the mixture into the incinerator for combustion to obtain SO2 flue gas; Step 3: Purification: The SO2 flue gas from the incineration section is passed through a dynamic wave scrubber and an electrostatic demister is used to remove acid mist to obtain purified wet flue gas; Step 4, drying: passing the purified wet flue gas from which the acid mist has been removed into sulfuric acid for drying; Step 5: Conversion: The dried product is fed into a converter for catalytic oxidation to produce SO3 gas, which is then absorbed by water to produce sulfuric acid.

[0008] The beneficial effects of this embodiment are: 1. In the traditional technology, sulfur foam is melted to produce sulfur. Since a large amount of by-product salts in the sulfur foam are not recovered, they will exist as impurities in the sulfur during production, resulting in low sulfur purity. It is difficult to sell and the price is low. It also requires the discharge of a large amount of wastewater, creating a new source of pollution; the degree of comprehensive utilization is low. The existing technology centrifuges the sulfur foam and directly calcines the separated concentrated slurry. In the process of preparing sulfuric acid, the sulfur foam entering the incinerator is a concentrated slurry, which will bring in a large amount of water. The water absorbs a large amount of heat during the calcination process. In order to maintain the high temperature of incineration, the supply of fuel and oxygen can only be increased, resulting in very high energy consumption of the incinerator. The production cost of this process is also increased accordingly. However, when processing sulfur foam, the present application separates it into a concentrated slurry, and then uses a two-phase separator to separate liquid sulfur and concentrated salt solution to mix into an incineration slurry, and then calcines the incineration slurry. Compared with the existing technology, the incineration slurry has less water content and the energy consumption of the incinerator is low.

[0009] 2. In the existing technology, sulfur foam is directly calcined, which consumes a lot of energy. Therefore, some technologies directly dry the sulfur foam into powder for calcination, which completely avoids the introduction of moisture. However, this process requires heat to dry the sulfur foam, which has limited effect on reducing energy consumption. Moreover, when the dry sulfur powder is calcined in an incinerator, the powdered sulfur will burn rapidly. Due to the too fast combustion, it will cause explosion in the incinerator, and the temperature in the incinerator will rise rapidly in a short time, resulting in overburning. A large amount of sulfur dioxide will be generated in a short time, causing a sudden increase in pressure in the equipment, which is difficult to control and has the risk of uncontrolled explosion of the product. In addition, overburning will cause the sulfur to carbonize or form complex polymers, which will adhere to the inner wall of the incinerator or the surface of the converter catalyst, reducing the heat transfer efficiency and clogging the equipment flow channel. Therefore, the process of drying and calcining the sulfur foam needs to strictly control the amount of fuel, oxygen, and sulfur powder entering the incineration process to avoid uncontrolled product caused by explosion. However, the present application adopts the slurry method, adding partially concentrated brine to liquid sulfur, so that the burning slurry will not burn quickly during the calcination process, and the calcination process is more controllable.

[0010] Furthermore, in step 2, the air needs to be preheated before being mixed with the incineration slurry.

[0011] Furthermore, a boiler is provided behind the incinerator, and the heat source of the boiler is the SO2 flue gas emitted from the incinerator.

[0012] Furthermore, the air preheating uses a shell and tube heat exchanger, and the heat source of the air preheater is the SO2 flue gas coming out of the boiler in step 2.

[0013] Furthermore, in step 3, a packed washing tower is provided between the dynamic wave scrubber and the electric demisting device.

[0014] Furthermore, the filtrate in step 1 is divided into two parts, one part is concentrated and mixed with the concentrated slurry after concentration, and the other part is sent to the desulfurization tower for use as desulfurization liquid.

[0015] Furthermore, the filtrate concentration process in step 1 is carried out using a concentration tower, the top gas of the concentration tower is passed into a cooling tower for condensation, and the condensed condensate is sent to the incinerator in step 2 for incineration.

[0016] Furthermore, the conversion process in step 5 is divided into two conversions, the gas after the first conversion is used as a heat source for the intake of the second conversion, and the gas after the second conversion is used as a heat source for preheating the intake of the first conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0018] The following is further described in detail through specific implementation methods: The reference numerals in the accompanying drawings of the specification include: .

[0019] Implementation example Figure 1 As shown: A sulfur foam slurry feeding acid production process comprises the following steps: The raw materials processed in this project are desulfurization wastewater and sulfur foam from the desulfurization section of a coking plant. The main components of these wastewater and sulfur foam include suspended sulfur, ammonium thiocyanate, ammonium thiosulfate, ammonium sulfate, and volatile ammonia. Their detailed composition is shown in Table 1. The finished sulfuric acid produced can be sold as finished sulfuric acid or used as raw material for coking ammonium sulfate production. The process includes pretreatment, incineration, purification, conversion, drying, and tailings.

[0020] Table 1

[0021] Step 1: Separate the sulfur-containing foam into a concentrated slurry and a filtrate in a centrifuge. The concentrated slurry is sent to a two-phase separator to separate liquid sulfur and a clear liquid. The clear liquid enters a single-effect concentration system. The single-effect system produces a concentrated brine. The liquid sulfur and the concentrated brine are mixed to form an incineration slurry.

[0022] The sulfur-containing foam from the desulfurization regeneration tower is directly sent to the centrifuge and separated into thick slurry and filtrate by the centrifuge.

[0023] The thick slurry enters the slurry tank.

[0024] The filtrate enters the filtrate tank and is pumped to the desulfurization tower system for use as desulfurization liquid.

[0025] The concentrated slurry is pumped into a two-phase separator, and liquid sulfur is continuously produced at the bottom of the two-phase separator; the clear liquid produced at the top of the two-phase separator enters a single-effect concentration system, which uses a concentration tower to concentrate it into a concentrated brine (concentration 50-60%).

[0026] The concentrated salt solution is mixed evenly with the concentrated slurry to form an incineration slurry; the concentrated salt solution accounts for 5%-10% of the concentrated slurry. The incineration slurry is pumped to the incineration section.

[0027] Step 2, incineration section: Mix the incineration slurry with air, and then put the mixed mixture into an incinerator for combustion to obtain SO2 flue gas.

[0028] The incineration section is equipped with an incinerator, boiler and air preheater; The air is pressurized by the air blower and sent to the air preheater for heating.

[0029] After the incineration slurry enters the incineration section, it can be directly introduced into the incinerator and mixed with preheated air for incineration, which produces a large amount of SO2 high-temperature flue gas. The fuel used in the incinerator is coal gas.

[0030] The SO2 high-temperature flue gas coming out of the incinerator enters the boiler, exchanges heat with the boiler feed water, prepares high-pressure steam (4.3MPa), and recovers the heat energy of the SO2 high-temperature flue gas for the first time.

[0031] The SO2 flue gas discharged from the boiler outlet is directly introduced into the air preheater, where the preheated air is simultaneously cooled by the air, thus recovering the second heat energy. After cooling, the SO2 flue gas is transported to the purification section via pipelines.

[0032] The air preheater utilizes a common shell-and-tube heat exchanger structure. Three air preheaters are connected in series to control the temperature at each point in the preheater, preventing dew-point corrosion and extending the equipment's service life. The air preheater also incorporates an online ash cleaning device, with ash hoppers located at both the front and rear ends of the preheater to store a portion of the ash.

[0033] The application adopts specially designed low-nitrogen incinerator, high-temperature preheated air, low-nitrogen burner, distributed multi-stage combustion control and other measures, which not only enable the slurry to be completely burned, but also greatly reduce the consumption of coal gas, reduce the generation of NOx, reduce the generation of purified dilute acid, and improve combustion efficiency.

[0034] The boiler adopts a medium-pressure fire tube boiler with an online ash cleaning device at the tail of the boiler. A central regulating valve is installed inside the boiler to adapt to the state of the device when running under low load.

[0035] Step 3, purification section: the SO2 flue gas from the incineration section is passed into a dynamic wave scrubber to remove acid mist and obtain purified wet flue gas.

[0036] After the SO2 flue gas from the incineration section enters the purification section, it is directly passed into the dynamic wave scrubber and comes into close contact with the circulating dilute acid sprayed in the reverse nozzle; it humidifies, cools, lowers the temperature and performs preliminary washing and purification on the SO2 flue gas.

[0037] After exiting the dynamic wave scrubber, the SO2 flue gas is introduced into a packed scrubber, where it comes into countercurrent contact with the cooling circulating dilute acid sprayed from the top of the tower. This provides a second scrubbing and purification of the SO2 flue gas to remove impurities and steam.

[0038] The furnace gas coming out of the scrubbing tower enters a two-stage electrostatic precipitator to remove acid mist, remove residual dust, acid mist and other impurities, and reduce the acid mist content in the flue gas to 5mg / Nm3.

[0039] The purified wet flue gas is sent to the drying section.

[0040] To prevent overheating of the gas at the kinetic wave scrubber outlet, an elevated tank is installed at the top of the kinetic wave scrubber. If the circulating pump fails, it will promptly supply liquid to the overflow weir and emergency nozzle for several minutes, ensuring that operators have sufficient time to respond to emergencies and providing safety protection. If the dilute acid pressure at the kinetic wave scrubber inlet falls below a predetermined value, an automatic alarm or interlock will be activated.

[0041] The heat transfer equipment in the purification section adopts plate heat exchanger. A dilute acid plate heat exchanger is installed at the outlet of the circulation pump of the power wave scrubber and the outlet of the circulation pump of the packed tower. The circulating water is used to remove heat to maintain the heat balance of the purification section.

[0042] Step 4, drying section: the purified wet flue gas from which the acid mist has been removed is passed into sulfuric acid for drying.

[0043] The purified wet flue gas is mixed with air from the filter to remove dust before entering a drying tower, where 94% sulfuric acid absorbs moisture. The moisture content of the dried wet flue gas is below 0.1g / Nm³. After drying, the acid mist is removed by a mesh mat demister, resulting in pure SO₂ gas. This gas is then pressurized by a SO₂ blower and fed into the converter in the conversion section for catalytic oxidation.

[0044] Step 5: Conversion Section After pure SO2 gas enters the converter, it undergoes an oxidation reaction there to produce SO3. This SO3 is then introduced from the converter into the third heat exchanger (shell side). After being cooled by the third heat exchanger, it enters the first absorption tower, where 98.3% sulfuric acid is sprayed on the top of the tower to absorb the SO3 in the gas. Because the first conversion cannot completely convert SO2 to SO3, residual SO2 remains. Therefore, after the first absorption, the SO2 flue gas, which has absorbed SO3 in the first absorption tower, passes through the third heat exchanger (tube side) to heat up. After heating, it enters the conversion section for a second conversion. During this process, the SO3 gas converted from the first conversion undergoes a heat exchange with the flue gas from the first absorption tower after SO3 absorption in the third heat exchanger, fully utilizing the heat generated during the conversion process.

[0045] After the first absorption tower absorbs SO3, the acid flows out from the bottom of the tower into the circulation tank. After adding water to make the acid concentration reach 98.3%, it is sent to the first absorption tower acid cooler by the first absorption tower acid circulation pump. After being cooled by circulating cooling water, it enters the first absorption tower for circulation spraying.

[0046] After the first absorption tower absorbs SO3, the residual SO2 flue gas enters the converter for a second peroxidation reaction to generate SO3. After the conversion is completed, it is introduced into the fourth heat exchanger for cooling, and then enters the second absorption tower. The SO3 in the gas is absorbed by spraying sulfuric acid with a concentration of 98.3% at the top of the tower. The SO2 content in the flue gas after absorbing SO3 is already very low, so it is directly introduced into the tail absorption section for tail gas treatment.

[0047] After the second absorption tower absorbs SO3, the acid flows out from the bottom of the tower into the circulation tank. After adding water to make the acid concentration reach 98.3%, it is sent to the second absorption tower acid cooler by the second absorption tower acid circulation pump. After being cooled by circulating cooling water, it enters the second absorption tower for circulation spraying.

[0048] After each absorption of SO3, the sulfuric acid concentration flowing out of the absorption tower bottom into the circulation tank will be higher than 98.3%. After adding water to raise the acid concentration to 98.3%, its volume increases. Therefore, the excess 98.3% finished sulfuric acid is drawn out from the outlet of the absorption tower circulation pump, cooled to 40°C in the finished acid cooler, and then stored in the finished acid storage tank.

[0049] The conversion process of the present application adopts a two-conversion process. During the first conversion, pure SO2 gas is heat exchanged through the fourth and first heat exchangers. After the heat exchange temperature is increased, it enters the converter to undergo an oxidation reaction to generate SO3.

[0050] During the second conversion, the residual SO2 flue gas after the first absorption tower absorbs SO3 passes through the heat exchangers III and II, and then enters the converter for peroxidation reaction to generate SO3.

[0051] It is worth noting that during the first conversion, the pure SO2 gas passes through heat exchangers IV and I, where it heats up to 420°C before entering the converter. After conversion, it passes through heat exchanger III, where the converted gas is cooled to 180°C before entering the first absorption tower, where it absorbs the SO3 with 98.3% sulfuric acid. During the second conversion, the residual SO2 flue gas, after the SO3 absorption in the first absorption tower, passes through heat exchangers III and II, where it heats up to 420°C before entering the converter for the second conversion. The converted gas passes through heat exchanger IV, where it cools to approximately 160°C before entering the second absorption tower, where it absorbs the SO3 with 98.3% sulfuric acid.

[0052] The converter has four sections from top to bottom. During the first conversion, the top three sections are connected in series to perform three conversion reactions. The gas flows between the first and second sections of the converter through the first heat exchanger, and between the second and third sections through the second heat exchanger. Therefore, between the three conversion processes, gas is extracted to serve as a heat source for the first and second heat exchangers.

[0053] During the second conversion, only the fourth section of the converter is used to carry out one conversion reaction.

[0054] An electric heater is installed at the inlet of each of the first and fourth stages of the converter to preheat the conversion system. To regulate the reaction temperature of each stage, the conversion section is equipped with self-regulating devices, as well as necessary bypass lines and valves.

[0055] Step 6: Tail suction section The tail gas coming out of the second absorption tower enters the multi-stage composite washing tower for two washings. The absorbent is alkaline solution. The absorption liquid is oxidized in the multi-stage composite washing tower and then sent to sewage treatment. The flue gas after washing enters the tail suction electrostatic precipitator, and the qualified tail gas passing through the tail suction electrostatic precipitator is sent to the chimney for discharge.

[0056] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A sulfur foam slurry feed acid production process, characterized in that: The following steps are included: Step 1, pretreatment: The sulfur-containing foam is separated into a concentrated slurry and a filtrate in a centrifuge. The concentrated slurry is sent to a two-phase separator to separate liquid sulfur and a clear liquid. The clear liquid enters a single-effect concentration system. The concentrated brine produced by the single-effect concentration system is mixed with the liquid sulfur and the concentrated brine to form an incineration slurry. Step 2, sulfur incineration: mixing the incineration slurry with air, and then putting the mixture into the incinerator for combustion to obtain SO2 flue gas; Step 3: Purification: The SO2 flue gas from the incineration section is passed through a dynamic wave scrubber and an electrostatic demister is used to remove acid mist to obtain purified wet flue gas; Step 4, drying: passing the purified wet flue gas from which the acid mist has been removed into sulfuric acid for drying; Step 5: Conversion: The dried product is fed into a converter for catalytic oxidation to produce SO3 gas, which is then absorbed by water to produce sulfuric acid.

2. The sulfur foam slurry feeding acid production process according to claim 1, characterized in that: In step 2, the air needs to be preheated before being mixed with the incineration slurry.

3. The sulfur foam slurry feeding acid production process according to claim 2, characterized in that: A boiler is provided behind the incinerator, and the heat source of the boiler is the SO2 flue gas discharged from the incinerator.

4. The sulfur foam slurry feeding acid production process according to claim 3, characterized in that: The air is preheated using a shell and tube heat exchanger, and the heat source of the air preheater is the SO2 flue gas coming out of the boiler in step 2.

5. The sulfur foam slurry feeding acid production process according to claim 1, characterized in that: In step 3, a packed washing tower is further provided between the dynamic wave washer and the electric demisting device.

6. The sulfur foam slurry feeding acid production process according to claim 1, characterized in that: The clear liquid in step 1 is divided into two parts, one part is concentrated and then mixed with liquid sulfur, and the other part is mixed with the thick slurry and then enters the two-phase separator.

7. The sulfur foam slurry feeding acid production process according to claim 1, characterized in that: The concentration process in step 1 is carried out using a concentration tower, the top gas of the concentration tower is passed into a cooling tower for condensation, and the condensed condensate is sent to the incinerator in step 2 for incineration.

8. The sulfur foam slurry feeding acid production process according to claim 1, characterized in that: The conversion process in step 5 is divided into two conversions, the gas after the first conversion is used as a heat source for the intake of the second conversion, and the gas after the second conversion is used as a heat source for preheating the intake of the first conversion.

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