A system and method for producing sulfuric acid from sulfur foam and desulfurization waste liquid

Abstract

A system and method for preparing sulfuric acid from sulfur foam and desulfurization waste liquid, which is sequentially connected by a pretreatment unit, a combustion cooling unit, a dust removal and filtration unit, a conversion unit, an acid forming unit and a desulfurization unit. The pretreatment unit is used to prepare liquid sulfur and salt slurry from sulfur foam, the combustion cooling unit is used to prepare sulfur dioxide gas, the dust removal and filtration unit is used to remove dust in the flue gas, the conversion unit converts sulfur dioxide in the flue gas into sulfur trioxide, the acid forming unit combines sulfur trioxide in the flue gas with water into sulfuric acid steam, and the sulfuric acid steam is condensed into sulfuric acid and then sent to a sulfuric acid storage tank for storage, and the desulfurization unit removes trace sulfur dioxide from the flue gas sent by the acid forming unit. The present application converts the sulfur foam and desulfurization waste liquid generated after purification and desulfurization of the coking plant into the raw material of sulfuric acid required by the ammonium sulfate workshop inside the coking plant, no dilute sulfuric acid is discharged in the production process, no desulfurization product is discharged, heat is fully utilized, the amount of by-product steam is large, and waste is turned into treasure.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of sulfur foam and desulfurization waste liquid system and acid making method for preparing sulfuric acid, belong to chemical production technical field. BACKGROUND

[0002] The existing sulfur foam and desulfurization waste liquid preparation process for sulfuric acid, mainly divided into: (pretreatment) dry method for acid, (pretreatment) semi-dry method, (pretreatment) wet method for acid and (conversion) wet method for acid four kinds, the specific analysis of the four acid making processes as follows:

[0003] 1, (pretreatment) dry method for acid process: sulfur foam-filter-dryer-screening-crushing-incinerator-heat recovery boiler-dynamic wave scrubber-cooling washing tower-dry absorption tower-electric precipitator-fan-converter-absorption tower (two absorption)-sulfuric acid storage tank.

[0004] Although the dry method for acid produces less dilute acid, but the quality of dilute acid is poor, contains too much impurities, sent to ammonium sulfate workshop affects the quality of ammonium sulfate; dry pretreatment process, there is decomposition of salt substances, dry tail gas volume, processing difficulty; dry material is powder, strong corrosion, conveying equipment plugging phenomenon occurs from time to time, system continuity, stability is not good; using vertical incinerator, the combustion effect in the furnace is poor, often stop due to blockage.

[0005] 2, (pretreatment) semi-dry method for acid process: sulfur foam-filter-separator-oxidation tower-concentrated kettle-incinerator-heat recovery boiler-dynamic wave scrubber-packed washing tower-electric precipitator-dry tower-fan-converter-absorption tower (two absorption)-tail absorption dynamic wave-tail absorption packed tower-tail absorption electric precipitator.

[0006] Semi-dry method for acid uses filter to filter sulfur foam, blockage is serious, need artificial flushing, labor intensity is big, the scene environment smell is big; using fire tube heat recovery boiler, the internal blockage of furnace tube is serious, need artificial cleaning, labor intensity is big, safety is poor; using wet purification technology, loss a lot of heat in flue gas, consume a lot of circulating water; using two conversion two dry method for acid, chemical reaction heat cannot be used, equipment is much, process is long, power consumption is big; tail gas absorption uses tail gas dynamic wave, power consumption is big, absorption effect is not good.

[0007] 3, (pretreatment) wet method for acid main process flow: sulfur foam-centrifuge-concentrated tower-slurry tank-incinerator-heat recovery boiler-dynamic wave scrubber-cooling washing tower-dry absorption tower-electric precipitator-fan-converter-absorption tower (two absorption)-sulfuric acid storage tank.

[0008] The wet method for producing dilute sulfuric acid has too large production, which seriously affects the water balance and stable operation of the ammonium sulfate system, and the quality of the ammonium sulfate is poor due to the use of the dilute sulfuric acid; the fire tube waste heat boiler is used, the internal pipe of the boiler is seriously blocked, manual dust removal is needed, the labor intensity is large, and the safety is poor; the wet purification technology is used, a large amount of heat in the flue gas is lost, and a large amount of circulating water is consumed; the two-turn two-absorption dry method for producing acid is used, the chemical reaction heat cannot be utilized, the equipment is much, the process is long, and the power consumption is large.

[0009] 4. The main process flow of the (conversion) wet method for producing acid: molten sulfur device-burning device-purification device-denitration reactor-combined reactor-sulfuric acid vapor condenser-sulfuric acid mixing tank and-tail gas treatment device.

[0010] In the process, the wet purification technology is used, a large amount of heat in the flue gas is lost, and a large amount of circulating water is consumed; due to the use of the dilute acid purification process, the device produces dilute acid; due to the reduction of the temperature after the flue gas is purified, the flue gas waste heat needs to be used for temperature rising, the equipment is seriously corroded, and the steam production of the boiler is reduced. The tail gas absorption is primary absorption, although the desalted water is supplemented into the tower, the ammonia escape cannot be eliminated.

[0011] In summary, the common defects of the existing process for producing acid from the desulfurization waste liquid and the sulfur foam are that the waste heat boiler is seriously blocked and needs manual dust removal, the wet purification technology is used, the heat loss is large, the obtained byproduct is poor quality dilute sulfuric acid, the number of equipment is large, the process is long, the failure rate is high, and the operation power consumption is large. SUMMARY

[0012] In order to solve the defects of the prior art, the present application provides a system and a method for producing sulfuric acid from sulfur foam and desulfurization waste liquid, so as to extract liquid sulfur and salt slurry from the sulfur foam and send them to the incinerator for incineration to produce acid.

[0013] The technical scheme of the present application is as follows:

[0014] The first object of the present application is to provide a system for producing sulfuric acid from sulfur foam and desulfurization waste liquid, which is characterized by being composed of a pretreatment unit, an incineration and cooling unit, a dust removal and filtration unit, a conversion unit, an acid forming unit and a desulfurization unit connected in sequence.

[0015] The pretreatment unit adopts a high-efficiency concentration device (i.e. a desulfurization liquid concentrator), the produced salt slurry contains less water, and the coal gas consumption of the incinerator is greatly reduced; the secondary steam produced by the pretreatment unit is washed and purified by a steam washing tower, condensed by a condenser, and then sent to a secondary condensate storage tank, the secondary steam condensate in the secondary condensate storage tank has high purity, can be returned to the desulfurization section for reuse, or enters the cold drum section, and the problem of liquid expansion in the desulfurization section is solved.

[0016] The waste heat boiler is a water-cooled wall water tube boiler with automatic ash cleaning to eliminate blockage. A high-temperature filter is used to remove dust from the flue gas, and dry ash discharge not only maintains a high flue gas temperature but also eliminates the emission of dilute sulfuric acid.

[0017] The conversion unit adopts wet conversion acid production technology, which recovers a lot of heat and can produce a large amount of medium-pressure superheated steam as a by-product.

[0018] Sulfuric acid is produced in an acid tower, and the heat of chemical reaction is used to generate a large amount of hot air. This hot air is used as combustion air in the incinerator, greatly reducing gas consumption.

[0019] A two-stage desulfurization tower is used to recover sulfur dioxide from the tail gas, with a high recovery rate and elimination of ammonia escape. The produced ammonium sulfate is returned to the pretreatment unit for use, without generating secondary desulfurization waste.

[0020] The system of the present invention has a large capacity for treating desulfurization waste liquid, reaching 20-500t / d, and produces 10-300t / d of 98% acid.

[0021] 1. Pretreatment unit: The main purpose of this unit is to produce liquid sulfur and salt slurry with sulfur foam, and to purify the water evaporated from the desulfurization waste liquid and return it to the desulfurization section for reuse, or enter the cold drum section to solve the problem of liquid swelling in the desulfurization section.

[0022] The pretreatment unit includes a sulfur foam storage tank, a centrifuge, a concentrated sulfur foam tank, a sulfur-water separator, a liquid sulfur storage tank, a filtrate tank, a desulfurization liquid concentrator, and a salt slurry storage tank. The inlet and outlet of the sulfur foam storage tank are respectively connected to the coking desulfurization section and the centrifuge, and the outlet of the centrifuge is respectively connected to the concentrated sulfur foam tank and the filtrate tank; the concentrated sulfur foam tank is connected to the inlet of the sulfur-water separator, and the outlet of the sulfur-water separator is respectively connected to the liquid sulfur storage tank and the filtrate tank; the inlet of the desulfurization liquid concentrator is connected to the filtrate tank, and the outlet is connected to the salt slurry storage tank.

[0023] Sulfur foam from the coking desulfurization process is sent to a sulfur foam storage tank, where it is pumped to a centrifugal separator. The separated concentrated sulfur foam enters a concentrated sulfur foam tank, and the separated filtrate enters a filtrate tank. The concentrated sulfur foam in the concentrated sulfur foam tank is pumped to a sulfur-water separator, where it is heated by steam and separated into liquid sulfur, pulverized coal slag, and a clear liquid. The liquid sulfur is placed in a liquid sulfur storage tank and then pumped to the incinerator. The clear liquid enters a filtrate tank and is returned to the desulfurization system by a filtrate pump. The pulverized coal slag in the sulfur-water separator is manually removed regularly.

[0024] The desulfurization waste liquid is extracted from the filtrate tank and sent to the desulfurization waste liquid concentrator to obtain a density of 1.12~1.4g / cm 3The concentrated solution (i.e. salt slurry) has a water content of less than 60%, a temperature of 60-100°C, and good fluidity, is stored in a salt slurry storage tank, and is pumped to the incinerator by a salt slurry pump. The salt slurry storage tank is provided with steam heating and stirring devices, and the salt slurry in the storage tank has good fluidity at a temperature of 60-100°C. The pipelines for conveying the liquid sulfur and the salt slurry are steam-heated to ensure that the liquid sulfur and the salt slurry have good fluidity and do not precipitate and block the pipelines.

[0025] The sulfur-water separator has a top pressure of 0.3-0.6 MPa, a bottom pressure of 0.3-0.7 MPa, and uses heating steam with a pressure of 0.3-1.0 MPa. The temperature at the bottom of the sulfur-water separator is 125-160°C, and the temperature at the top is 100-140°C. The sulfur-water separator continuously feeds in, continuously discharges clear liquid, and intermittently discharges liquid sulfur and coal powder residue. The water vapor evaporated from the desulfurization liquid concentrator in the desulfurization waste liquid is washed by a steam washing tower, then cooled by a condenser into secondary steam condensate, and stored in a secondary condensate storage tank. The secondary steam condensate contains less than 10 g / L of salt, is sent to the desulfurization section for reuse, or is sent to the cold drum section to solve the problem of liquid expansion in the desulfurization section.

[0026] 2. Incineration and cooling unit: The main purpose of this unit is to produce sulfur dioxide gas. The incineration and cooling unit includes an incinerator, a waste heat boiler, a boiler feed water pump, an air blower, a coal gas blower, a steam drum, and a deaerator. The liquid sulfur storage tank and the salt slurry storage tank send liquid sulfur and salt slurry into the incinerator to produce sulfur dioxide gas, and the waste heat boiler removes heat from and cools the sulfur dioxide gas.

[0027] The liquid sulfur and the salt slurry are burned in the incinerator with hot air from the acid production unit with a temperature greater than 100°C. The temperature in the incinerator is controlled at 800-1200°C, and the oxygen content in the furnace gas is between 3-10%. Meanwhile, the incinerator is controlled at a negative pressure of 50-500 pa. The sulfur dioxide flue gas from the incinerator is removed of heat and dust by the waste heat boiler, and the temperature is reduced to 350-550°C. The waste heat boiler is a water-cooled wall water tube boiler, and the steam pressure of the boiler is 1.5-6.0 MPa. The boiler is equipped with mechanical and explosive ash removal devices to facilitate dust removal. The removed ash is discharged from the bottom of the boiler, and the inside of the boiler (the flue gas side) is under negative pressure.

[0028] The boiler feed water pump is connected to the inlet of the steam drum, and the steam drum supplies water to the waste heat boiler. The steam generated by the waste heat boiler is stored in the steam drum. The steam in the steam drum is sent to the inter-stage cooler, which uses the reaction heat in the converter to heat the saturated steam, generates superheated steam, and recovers heat. The steam drum supplies water to the final stage cooler, which absorbs heat from the flue gas of the converter, generates steam, and the steam enters the steam drum.

[0029] Air blower is to supply air to incinerator, gas blower is to supply coke oven gas to incinerator; deaerator is to remove oxygen from feed water of waste heat boiler to reduce corrosion of boiler tube.

[0030] 3. Dust removal and filtration unit: the main purpose of this unit is to remove dust in flue gas. The dust removal and filtration unit comprises high-temperature filter bag filter and compressed air back-blowing dust cleaning device.

[0031] After incineration of liquid sulfur and salt slurry, some dust is generated, mainly iron oxide, calcium oxide, magnesium oxide, etc. The dust is carried away by flue gas and intercepted by high-temperature filter. When the resistance of high-temperature filter increases, the compressed air back-blowing dust cleaning device is started to clean dust by back-blowing with compressed air.

[0032] The temperature of flue gas after high-temperature filter is 350-500℃. The material of filter bag of high-temperature filter is aluminum silicate fiber, ceramic fiber, graphite fiber or stainless steel, which is not corroded at high temperature of 350-550℃. The dust interception rate is greater than 90%, and the dust content at the outlet of flue gas of high-temperature filter is less than 500mg / Nm 3 The inside of high-temperature filter is under negative pressure.

[0033] 4. Conversion unit: the main purpose of this unit is to convert sulfur dioxide in flue gas into sulfur trioxide and recover the heat of conversion reaction (i.e. generate superheated steam). The conversion unit comprises converter (including first bed, second bed, third bed and fourth bed), inter-stage cooler (including first inter-stage cooler, second inter-stage cooler and third inter-stage cooler) and final-stage cooler. Flue gas passes through each catalyst bed and inter-stage cooler in turn, and is catalytically oxidized to SO3 under the action of sulfuric acid catalyst.

[0034] After dust removal, flue gas enters the converter through high-temperature induced draft fan. The converter is a four-stage sulfuric acid catalyst, the first three stages have inter-stage coolers, and the last stage has a final-stage cooler. The converter is provided with first bed, first inter-stage cooler, second bed, second inter-stage cooler, third bed, third inter-stage cooler, fourth bed and final-stage cooler from top to bottom. The inlet temperature of flue gas of first bed is 410-420℃, and the outlet temperature is 550-560℃. The inlet temperature of flue gas of second bed is 410-420℃, and the outlet temperature is 450-460℃. The inlet temperature of flue gas of third bed is 395-405℃, and the outlet temperature is 410-420℃. The inlet temperature of flue gas of fourth bed is 380-390℃, and the outlet temperature is 395-405℃. The flue gas is cooled to 240-279℃ in the final-stage cooler to enter the acid tower. The conversion rate of sulfur dioxide is 95-99%.

[0035] 5. Acid forming unit: The main purpose of this unit is to combine sulfur trioxide in the flue gas with water to form sulfuric acid vapor, and to condense the sulfuric acid vapor into sulfuric acid and then send it to the concentrated acid storage tank. The acid forming unit comprises an acid forming tower, a concentrated acid circulating tank, a concentrated acid circulating pump, a concentrated acid cooler, and a concentrated acid storage tank.

[0036] SO3 gas in the flue gas leaving the conversion unit reacts with water vapor in the flue gas (water vapor mainly comes from water vapor generated by burning salt slurry in the incinerator) to form gaseous H2SO4. The flue gas enters the acid forming tower and flows from bottom to top. After air cooling, the temperature of the flue gas is cooled to above 80°C. Gaseous sulfuric acid condenses into liquid sulfuric acid and flows into the sulfuric acid circulating tank. The hot sulfuric acid is sent to the concentrated acid cooler by the concentrated acid circulating pump. The cooled sulfuric acid with a temperature less than 70°C returns to the concentrated acid circulating tank. The sulfuric acid produced in the acid forming tower has a concentration of 78-98%. The generated sulfuric acid is sent from the concentrated acid cooler outlet to the concentrated acid storage tank.

[0037] The upper part of the acid forming tower is a tube heat exchanger, and the lower part is a concentrated acid circulating tank. The tube material of the tube heat exchanger is a sulfuric acid corrosion-resistant material such as glass or silicon carbide. Air is introduced into the acid forming tower to exchange heat with the flue gas containing gaseous sulfuric acid. The temperature of the flue gas containing gaseous sulfuric acid is reduced to 80-120°C. Gaseous sulfuric acid is converted into liquid sulfuric acid, and the concentration of the sulfuric acid is 78-98%.

[0038] An air fan sends air to the outside of the tube heat exchanger of the acid forming tower. After heat exchange with the flue gas containing gaseous sulfuric acid in the tube, the temperature of the air rises to 100-215°C. This hot air is used as the source of air for the incinerator. The concentrated acid circulating tank at the lower part of the acid forming tower is a carbon steel device lined with polytetrafluoroethylene and ceramic tiles. The acid temperature is 40-80°C.

[0039] 6. Desulfurization unit: The main purpose of this unit is to remove trace amounts of sulfur dioxide from the flue gas sent by the acid forming unit to meet environmental emission requirements. The desulfurization unit comprises two-stage packed towers, an electric precipitator, a tail suction circulating pump (used to circulate the absorption liquid and send the generated ammonium sulfate solution to the desulfurization liquid concentrator), and an ammonia water storage tank (used to store ammonia water). The two-stage desulfurization tower comprises a primary desulfurization tower and a secondary desulfurization tower.

[0040] Based on the actual situation of the coking plant, by-product ammonia water is used for desulfurization, and there is no need to purchase desulfurization agents. The flue gas enters the two-stage desulfurization tower. Ammonia water is introduced into the primary desulfurization tower to absorb sulfur dioxide in the flue gas. Desalted water is introduced into the secondary desulfurization tower to absorb escaped ammonia in the flue gas.

[0041] The sulfur dioxide in the flue gas reacts with the ammonia in the ammonia water to generate ammonium sulfite, and the ammonium sulfite reacts with the oxygen in the flue gas to generate ammonium sulfate, and the generated ammonium sulfate solution is sent to a desulfurization liquid concentrator of a pretreatment unit for concentration, and is used for producing sulfuric acid. After the flue gas after desulfurization is removed of particulates, liquid drops and acid mist by an electric precipitator, the tail gas is ensured to meet the standard for emission. The desulfurization efficiency is 80-99.9%, and the concentration of the desulfurization product ammonium sulfate is 5-30%.

[0042] A foam catcher is arranged between the acid forming tower and the first desulfurization tower, which is used for removing sulfuric acid mist, and the sulfuric acid mist is sent into a concentrated acid circulating tank. Similarly, the sulfuric acid mist removed by the electric precipitator is also sent into the concentrated acid circulating tank.

[0043] A second object of the present application is to provide a method for producing sulfuric acid by using sulfur foam and desulfurization waste liquid, which comprises the following steps:

[0044] (1) The sulfur foam from a coking desulfurization section is sent to a sulfur foam storage tank, and the sulfur foam in the sulfur foam storage tank is pumped into a centrifugal separator to separate concentrated sulfur foam into a concentrated sulfur foam tank, and the separated filtrate is into a filtrate tank;

[0045] (2) The concentrated sulfur foam in the concentrated sulfur foam tank is pumped into a sulfur water separator, and is separated into liquid sulfur, coal powder residue and clear liquid by steam heating; the liquid sulfur is sent into a liquid sulfur storage tank, and is pumped into a incinerator by a sulfur pump; the clear liquid is sent into the filtrate tank, and is pumped back to the desulfurization system by a filtrate pump;

[0046] (3) The desulfurization waste liquid is extracted from the filtrate tank and is sent to a desulfurization waste liquid concentrator to obtain concentrated liquid with a density of 1.12-1.4 g / cm 3 , i.e. salt slurry, and is stored in a salt slurry storage tank, and is pumped into the incinerator by a salt slurry pump;

[0047] (4) The liquid sulfur and the salt slurry are combusted in the incinerator with hot air sent from the acid forming tower; the temperature in the incinerator is controlled at 800-1200 ℃, and the incinerator is controlled at a negative pressure of 50-500 Pa at the same time;

[0048] (5) The sulfur dioxide flue gas from the incinerator is removed of heat and dust by a waste heat boiler, and the temperature is reduced to 350-550 ℃;

[0049] (6) The sulfur dioxide flue gas is sent into a dust removal and filtration unit, and is intercepted by a high temperature filter to remove the dust generated after the combustion of the liquid sulfur and the salt slurry; the temperature of the flue gas after the high temperature filter is 350-500 ℃, and the dust content is less than 500 mg / Nm 3 ;

[0050] When the resistance of the high temperature filter is increased, compressed air is used for back blowing and dust removal;

[0051] (7) The flue gas successively passes through the catalyst bed of each section of the conversion unit and the inter-section cooler, and is subjected to catalytic oxidation of sulfur dioxide into sulfur trioxide under the action of sulfuric acid catalyst; the high-temperature flue gas out of the fourth section is cooled to 240-279 DEG C by the final-section cooler and then is sent into the acid forming tower;

[0052] (8) The sulfur trioxide flue gas out of the conversion unit is subjected to combination reaction with water vapor to generate sulfuric acid in the acid forming tower, and is discharged from the outlet of the concentrated acid cooler to the concentrated acid storage tank;

[0053] (9) The flue gas from the conversion unit is sent into the desulfurization unit for tail gas treatment and then is discharged.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] 1) The system of the present application is continuously and stably operated, and the fluctuation of the desulfurization system has little influence on the acid making device;

[0056] 2) The system of the present application is operated in a fully-sealed mode, and the operation environment is excellent, without dust and waste gas escape;

[0057] 3) The liquid sulfur and salt slurry are respectively subjected to air atomization and then are fed into the incinerator, so that the liquid sulfur and salt slurry can be rapidly and completely combusted, the sublimed sulfur is avoided, the self-heating balance of the incinerator is met, the coal gas consumption is reduced, and the operation cost is lowered;

[0058] 4) The low-nitrogen combustion mode is adopted, the incineration temperature is 1000 DEG C-1150 DEG C, the generation of nitrogen oxides is greatly reduced, and the system does not need to be provided with a denitration device;

[0059] 5) The dry dedusting mode is adopted, no dilute acid is generated, the environmental protection pressure is eliminated, and the product quality of ammonium sulfate is ensured;

[0060] 6) The wet catalytic conversion is adopted, the cold and hot diseases are eliminated, and the steam production is greatly improved;

[0061] 7) The acid forming tower is adopted to make acid, the chemical reaction heat is recovered, the hot air is generated to supply the incinerator for combustion support, the coal gas consumption is reduced, and the steam production is improved;

[0062] 8) The system of the present application has high automation degree, and the DCS interface operation rate reaches 95%.

[0063] The present application converts the sulfur foam and desulfurization waste liquid generated after purification and desulfurization of the coking plant into the sulfuric acid raw material required by the ammonium sulfate workshop inside the coking plant, no dilute sulfuric acid is discharged during the production process, no desulfurization product is discharged, the heat is fully utilized, the steam production is large, the problems of high energy consumption, discharge of dilute sulfuric acid and long process flow of the existing dry acid making and wet acid making technologies are overcome, and the waste is really changed into treasure by the energy-saving and environment-protecting method. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0065] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0066] Example 1

[0067] like Figure 1 As shown in the figure, sulfur foam comes from the desulfurization section of the coking plant. The main components of sulfur foam are S, NH4CNS (ammonium thiocyanate), (NH4)2S2O3 (ammonium thiosulfate) and ammonium sulfate. The dilute sulfur foam is 49t / h (42.6m 3 / h), of which ammonium thiocyanate 177g / l, ammonium thiosulfate 41.6g / l, ammonium sulfate 44g / l, suspended sulfur 16g / l, separated by centrifuge, of which 4.5m 3 / h concentrated sulfur foam to the concentrated sulfur foam tank, 38m 3 / h clear liquid enters the filtrate tank, and most of the filtrate returns to the desulfurization section.

[0068] Sulfur foam delivery pump at 4.5m under 7kg pressure 3 / h transports concentrated sulfur foam to the sulfur-water separator. The pressure in the sulfur-water separator is maintained at 0.5MPa. It is heated by 180℃ steam through the coil to maintain the lower part of the sulfur-water separator at 145℃. After the sulfur foam stays in the tower for 12 hours, about 4.12m3 of sulfur clear liquid is removed. 3 / h to the filtrate tank.

[0069] Pump ~7m from the filtrate tank 3 / h filtrate is sent to the desulfurization liquid concentrator, and after concentration, 3844kg / h of concentrated liquid containing 50% water and 40% salt is obtained, that is, 92.26t / d.

[0070] Sulfur is discharged intermittently from the bottom of the sulfur-water separator, averaging 16.344 tons per day. Liquid sulfur and salt slurry are fed into the incinerator separately under compressed air atomization. Pulverized coal must be removed regularly from the sulfur-water separator. Extraction pipes are installed at the tops of the sulfur foam storage tank, concentrated sulfur foam tank, salt slurry storage tank, and filtrate tank. Fans draw non-condensable gases into the incinerator for incineration.

[0071] The temperature in the incinerator is controlled at 1000-1200°C, and the operation is kept at -50-500 Pa. When the temperature in the incinerator is reduced to 1000°C, the coke oven gas combustion is started to supplement the heat. The SO2 flue gas from the incinerator at about 1050°C is cooled to about 420-450°C by a waste heat boiler, and then enters a high-temperature filter for dust removal. The dry dust from the high-temperature filter is about 6 kg per day, and the dust content in the flue gas after the dust removal is less than 5 mg / m 3 , and the temperature is about 420°C.

[0072] The flue gas after the high-temperature dust removal is sent to a converter by a high-temperature induced draft fan. The converter is provided with a first bed, a first inter-stage cooler, a second bed, a second inter-stage cooler, a third bed, a third inter-stage cooler, a fourth bed and a final-stage cooler from top to bottom. The flue gas inlet temperature of the first bed is 410-420°C, and the outlet temperature is 550-560°C. The flue gas inlet temperature of the second bed is 410-420°C, and the outlet temperature is 450-460°C. The flue gas inlet temperature of the third bed is 395-405°C, and the outlet temperature is 410-420°C. The flue gas inlet temperature of the fourth bed is 380-390°C, and the outlet temperature is 395-405°C. The flue gas is cooled to 240-279°C in the final-stage cooler and then enters an acid forming tower. The conversion rate of sulfur dioxide is 99%.

[0073] The flue gas from the final-stage cooler enters the acid forming tower, and the SO3 gas in the flue gas reacts with the water vapor in the flue gas to form gaseous H2SO4. The flue gas flows from bottom to top in the acid forming tower, is cooled by air, and the temperature of the flue gas is cooled to above 80°C. The gaseous sulfuric acid is condensed into liquid sulfuric acid and flows into a concentrated acid circulating tank. The hot sulfuric acid is sent to a concentrated acid cooler by a concentrated acid circulating pump, and the sulfuric acid cooled to a temperature less than 70°C is returned to the concentrated acid circulating tank. The concentration of the sulfuric acid produced in the acid forming tower is 97%, and the generated sulfuric acid is sent to a concentrated acid storage tank from the outlet of the concentrated acid cooler.

[0074] The air is heated to about 215°C by heat exchange with the flue gas containing gaseous sulfuric acid, and the hot air is used as the source of air for the incinerator. The flue gas enters two-stage desulfurization towers. Ammonia water is introduced into the first-stage desulfurization tower to absorb the sulfur dioxide in the flue gas. Desalted water is introduced into the second-stage desulfurization tower to absorb the escaped ammonia in the flue gas. An electric precipitator is used to remove particulate matter, liquid droplets and acid mist in the flue gas to ensure that the tail gas meets the emission standard.

[0075] Sulfur dioxide in the flue gas reacts with ammonia in the ammonia solution to produce ammonium sulfite, which then reacts with oxygen in the flue gas to produce ammonium sulfate. The resulting ammonium sulfate solution is fed to the desulfurization liquid concentrator in the pretreatment unit for use in sulfuric acid production. The desulfurized flue gas passes through an electrostatic precipitator to remove particulate matter, droplets, and acid mist, ultimately meeting the "Coking Chemical Industry Pollutant Emission Standard" (GB16171-2012) and meeting emission standards. The two-stage desulfurization tower achieves a desulfurization efficiency of 99%, and the desulfurization product, ammonium sulfate, has a concentration of 20%. This is then fed to the pretreatment unit for concentration and used to produce sulfuric acid.

[0076] After treatment in these units, the sulfur foam and desulfurization wastewater are converted into concentrated sulfuric acid, eliminating both solid and liquid waste from the desulfurization process. The system produces 108 tons of 97% sulfuric acid daily, with a sulfur recovery rate of 99.9% from the sulfur foam.

[0077] Example 2

[0078] like Figure 1 As shown in the figure, sulfur foam comes from the desulfurization section of the coking plant. The main components of sulfur foam are S, NH4CNS, (NH4)2S2O3 and ammonium sulfate. The dilute sulfur foam is 24.5t / h (21.3m 3 / h), of which ammonium thiocyanate 177g / l, ammonium thiosulfate 41.6g / l, ammonium sulfate 44g / l, suspended sulfur 16g / l, separated by centrifuge, of which 2.25m 3 / h concentrated sulfur foam to the concentrated sulfur foam tank, 19m 3 / h clear liquid into the filtrate tank, most of the filtrate returns to the desulfurization section; sulfur foam delivery pump under 7 kg pressure 2.25m 3 / h concentrated sulfur foam is transported to the sulfur-water separator. The pressure in the sulfur-water separator is maintained at 0.5MPa. It is heated by 180℃ steam through the coil to maintain the lower part of the sulfur-water separator at 145℃. After the sulfur foam stays in the tower for 12 hours, about 2.06m3 of sulfur clear liquid is removed. 3 / h to the filtrate tank.

[0079] Pump ~3.5m from the filtrate tank 3 The filtrate is fed to the waste liquid concentration unit, where it is concentrated to produce 1922 kg / h (46.13 t / d) of concentrated liquid containing 50% water and 40% salt. Sulfur is intermittently removed from the bottom of the sulfur-water separator, averaging 8.172 t / d. Liquid sulfur and salt slurry are atomized by compressed air and fed to the incinerator, respectively. Pulverized coal must be removed regularly from the sulfur-water separator. Extraction pipes are installed at the top of the sulfur foam storage tank, concentrated sulfur foam tank, salt slurry storage tank, and filtrate tank. Fans draw non-condensable gases to the incinerator for incineration.

[0080] The temperature in the incinerator is controlled at 1000-1200°C, and the operation is kept at -50-500 Pa. When the temperature in the incinerator is reduced to 1000°C, the coke oven gas combustion is started to supplement the heat. The SO2 gas at about 1050°C from the incinerator is cooled to about 420-450°C by a waste heat boiler, and then enters a high-temperature filter for dust removal. The dry dust from the high-temperature filter is about 3 kg per day, and the dust content in the flue gas after the dust removal is less than 5 mg / m 3 , and the temperature is about 420°C.

[0081] The flue gas after the high-temperature dust removal is sent to a converter by a high-temperature induced draft fan. The converter is provided with a first bed, a first inter-stage cooler, a second bed, a second inter-stage cooler, a third bed, a third inter-stage cooler, a fourth bed and a final-stage cooler from top to bottom. The flue gas inlet temperature of the first bed is 410-420°C, and the outlet temperature is 550-560°C. The flue gas inlet temperature of the second bed is 410-420°C, and the outlet temperature is 450-460°C. The flue gas inlet temperature of the third bed is 395-405°C, and the outlet temperature is 410-420°C. The flue gas inlet temperature of the fourth bed is 380-390°C, and the outlet temperature is 395-405°C. The flue gas is cooled to 240-279°C in the final-stage cooler and then enters an acid forming tower. The conversion rate of sulfur dioxide is 99%.

[0082] The flue gas from the final-stage cooler enters the acid forming tower. The SO3 gas in the flue gas reacts with the water vapor in the flue gas to form gaseous H2SO4. The flue gas flows from bottom to top in the acid forming tower, is cooled by air, and the temperature of the flue gas is cooled to above 80°C. The gaseous sulfuric acid is condensed into liquid sulfuric acid and flows into a concentrated acid circulating tank. The hot sulfuric acid is sent to a concentrated acid cooler by a concentrated acid circulating pump, and the sulfuric acid cooled to a temperature less than 70°C returns to the concentrated acid circulating tank. The concentration of the sulfuric acid produced in the acid forming tower is 97%, and the generated sulfuric acid is sent to a concentrated acid storage tank from the outlet of the concentrated acid cooler.

[0083] The air is heated to about 215°C by exchanging heat with the process gas containing gaseous sulfuric acid. The hot air is used as the source of air for the incinerator.

[0084] The flue gas enters two-stage desulfurization towers. Ammonia water is introduced into the first-stage desulfurization tower to absorb the sulfur dioxide in the flue gas. Desalted water is introduced into the second-stage desulfurization tower to absorb the escaped ammonia in the flue gas. The electric precipitator is used to remove particulate matter, liquid droplets and acid mist in the flue gas to ensure that the tail gas meets the emission standard.

[0085] The sulfur dioxide in the flue gas reacts with ammonia in the ammonia water to generate ammonium sulfite, and the ammonium sulfite reacts with oxygen in the flue gas to generate ammonium sulfate. The generated ammonium sulfate solution is sent to the waste liquid concentrator of the pretreatment unit for producing sulfuric acid. The flue gas after desulfurization is sent to an electric precipitator to remove particulate matter, liquid droplets and acid mist, and then reaches the "Coke Chemical Industry Pollutant Discharge Standard" GB16171-2012 for standard discharge. The desulfurization efficiency of the two-stage desulfurization tower is 99%, and the desulfurization product ammonium sulfate concentration is 20%, which is sent to the pretreatment unit for concentration and used for producing sulfuric acid.

[0086] After the above-mentioned unit treatment, the sulfur foam and the desulfurization waste liquid become concentrated sulfuric acid, and the solid waste and liquid waste generated in the desulfurization section are eliminated. The daily production of 97% sulfuric acid is 54 tons, and the recovery rate of sulfur in the sulfur foam reaches 99.9%.

Claims

1. A method for producing sulfuric acid from sulfur foam and desulfurization waste liquid, characterized in that: A system for producing sulfuric acid from sulfur foam and desulfurization waste liquid is provided, the system comprising a pretreatment unit, an incineration and cooling unit, a dust removal and filtration unit, a conversion unit, an acid generation unit and a desulfurization unit connected in sequence; the method for producing sulfuric acid comprises the following steps: (1) Preprocessing The pretreatment unit is used to produce liquid sulfur and salt slurry from sulfur foam, and includes: a sulfur foam storage tank, a centrifugal separator, a concentrated sulfur foam tank, a sulfur-water separator, a liquid sulfur storage tank, a filtrate tank, a desulfurization liquid concentrator, and a salt slurry storage tank; the inlet and outlet of the sulfur foam storage tank are respectively connected to the desulfurization section and the centrifugal separator, and the outlet of the centrifugal separator is respectively connected to the concentrated sulfur foam tank and the filtrate tank; the concentrated sulfur foam tank is connected to the inlet of the sulfur-water separator, and the outlet of the sulfur-water separator is respectively connected to the liquid sulfur storage tank and the filtrate tank; the inlet of the desulfurization liquid concentrator is connected to the filtrate tank, and the outlet is connected to the salt slurry storage tank; ① The sulfur foam from the coking desulfurization section is sent to the sulfur foam storage tank, and the sulfur foam in the sulfur foam storage tank is pumped to the centrifugal separator to separate the concentrated sulfur foam into the concentrated sulfur foam tank, and the separated filtrate is sent to the filtrate tank; ② The concentrated sulfur foam in the concentrated sulfur foam tank is pumped to the sulfur-water separator, where it is heated by steam and separated into liquid sulfur, coal powder residue, and clear liquid. The liquid sulfur is sent to the liquid sulfur storage tank and sent to the incinerator by the sulfur pump. The clear liquid enters the filtrate tank and is sent back to the desulfurization system by the filtrate pump. The sulfur-water separator has a top pressure of 0.3-0.6 MPa and a temperature of 100-140°C, a bottom pressure of 0.3-0.7 MPa and a temperature of 125-160°C, and a heating steam pressure of 0.3-1.0 MPa. ③ Extract the desulfurization waste liquid from the filtrate tank and send it to the desulfurization waste liquid concentrator. The concentrated liquid from the desulfurization waste liquid concentrator has a density of 1.12~1.4 g / cm 3 The salt slurry has a moisture content of less than 60% and a temperature of 60~100℃, and is stored in a salt slurry storage tank and sent to the incinerator by a salt slurry pump; The salt slurry storage tank is equipped with a steam heating and stirring device, and the pipelines for transporting liquid sulfur and salt slurry are heated by steam; (2) Incineration and cooling The incineration and cooling unit includes an incinerator, a waste heat boiler, a boiler feed water pump, and a steam drum; ① The liquid sulfur storage tank and salt slurry storage tank respectively feed liquid sulfur and salt slurry into the incinerator, which are burned with hot air with a temperature greater than 100°C sent from the acid forming unit to produce sulfur dioxide gas. The oxygen content of the gas in the incinerator is between 3 and 10%, the temperature inside the furnace is controlled at 800 to 1200°C, and the negative pressure inside the incinerator is controlled at 50 to 500 Pa. ② The sulfur dioxide flue gas from the incinerator is passed through a waste heat boiler for heat removal and dust removal, and the temperature is reduced to 350-550°C. The waste heat boiler is a water-cooled wall water tube boiler with a steam pressure of 1.5-6.0 MPa; The boiler feed water pump is connected to the inlet of the steam drum, and supplies water to the waste heat boiler through the steam drum. The steam generated by the waste heat boiler enters the steam drum for storage; (3) Dust removal and filtration The dust removal and filtering unit includes a high-temperature filter; The sulfur dioxide flue gas is sent to the dust removal and filtration unit, and passes through the high-temperature filter to intercept the dust generated by the incineration of liquid sulfur and salt slurry; the flue gas temperature after leaving the high-temperature filter is 350~500℃, and the dust content is less than 500mg / Nm 3 ; When the resistance of the high-temperature filter increases, use compressed air to back-blow and clean the dust; (4) Conversion The conversion unit includes a converter, an interstage cooler, and a final stage cooler, and is used to convert sulfur dioxide in the flue gas into sulfur trioxide and recover the heat of the conversion reaction; The flue gas passes through the catalyst beds and inter-stage coolers of the conversion unit in sequence. Under the action of sulfuric acid catalyst, sulfur dioxide is catalytically oxidized into sulfur trioxide. The high-temperature flue gas is cooled to 240-279°C in the final cooler and then sent to the acidification tower. The steam in the drum is sent to the interstage cooler, which uses the reaction heat in the converter to heat the saturated steam, generating superheated steam and recovering the heat. The drum supplies water to the final stage cooler, which absorbs heat from the converter flue gas and generates steam that enters the drum. (5) Acidification The acid forming unit includes an acid forming tower, a concentrated acid circulation tank, a concentrated acid cooler, and a concentrated acid storage tank. The sulfur trioxide flue gas leaving the conversion unit enters the acid forming tower and combines with water vapor to form sulfuric acid vapor, and the sulfuric acid vapor is condensed into sulfuric acid by the concentrated acid cooler and then sent to the concentrated acid storage tank for storage; (6) Desulfurization The desulfurization unit includes a two-stage desulfurization tower and an electrostatic precipitator, which treats the flue gas sent from the acid generating unit and then discharges it.

2. The method for producing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, wherein: The filter bag of the high-temperature filter is made of aluminum silicate fiber, ceramic fiber, graphite fiber or stainless steel.

3. The method for producing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, wherein: The conversion unit is provided with a first bed layer, a first interstage cooler, a second bed layer, a second interstage cooler, a third bed layer, a third interstage cooler, a fourth bed layer and a final cooler in sequence from top to bottom; The flue gas inlet temperature of the first bed layer is 410-420°C, and the outlet temperature is 550-560°C; the flue gas inlet temperature of the second bed layer is 410-420°C, and the outlet temperature is 450-460°C; the flue gas inlet temperature of the third bed layer is 395-405°C, and the outlet temperature is 410-420°C; the flue gas inlet temperature of the fourth bed layer is 380-390°C, and the outlet temperature is 395-405°C; The flue gas is cooled to 240~279℃ in the final cooler and then goes to the acid tower.

4. The method for producing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: The upper part of the acid forming tower is a shell and tube heat exchanger, and the lower part is a concentrated acid circulation tank; the shell and tube heat exchanger is made of glass or silicon carbide, and the concentrated acid circulation tank is a carbon steel device lined with polytetrafluoroethylene and ceramic tiles in sequence.

5. The method for producing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: The two-stage desulfurization tower includes a primary desulfurization tower and a secondary desulfurization tower; ammonia water is introduced into the primary desulfurization tower to absorb sulfur dioxide in the flue gas; desalted water is introduced into the secondary desulfurization tower to absorb escaped ammonia in the flue gas.

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