System for preparing sulfuric acid from sulfur foam and desulfurization waste liquid and acid preparation method

Abstract

The invention discloses a system and a method for preparing sulfuric acid from sulfur foam and desulfurization waste liquid. The system is formed by sequentially connecting a pretreatment unit, an incineration cooling unit, a dust removal filtering unit, a conversion unit, an acid forming unit and a desulfurization unit. The pretreatment unit is used for preparing liquid sulfur and salt slurry from sulfur foam, the incineration cooling unit is used for preparing sulfur dioxide gas, the dust removal filtering unit is used for removing dust in flue gas, the conversion unit is used for converting sulfur dioxide in the flue gas into sulfur trioxide, and the acid forming unit is used for combining the sulfur trioxide in the flue gas with water into sulfuric acid steam; the sulfuric acid steam is condensed into sulfuric acid and then is conveyed into a sulfuric acid storage tank to be stored, and the desulfurization unit is used for removing trace sulfur dioxide from the flue gas conveyed by the acid forming unit. Sulfur foam and desulfurization waste liquid generated after purification and desulfurization in the coking plant are converted into sulfuric acid raw materials needed by an ammonium sulfate workshop in the coking plant, no dilute sulfuric acid or desulfurization product is discharged in the production process, heat is fully utilized, the amount of byproduct steam is large, and waste is turned into wealth.

Description

Technical Field

[0001] The invention relates to a system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid and an acid-making method, belonging to the technical field of chemical production. Background Art

[0002] The existing processes for producing sulfuric acid from sulfur foam and desulfurization waste liquid are mainly divided into four types: (pretreatment) dry acid production, (pretreatment) semi-dry acid production, (pretreatment) wet acid production and (conversion) wet acid production. The specific analysis of these four acid production processes is as follows:

[0003] 1. (Pretreatment) Dry acid production process is: sulfur foam - filter - dryer - screening - crushing - incinerator - waste heat boiler - dynamic wave scrubber - cooling scrubber - dry absorption tower - electric demister - fan - converter - absorption tower (two absorptions) - sulfuric acid storage tank.

[0004] Although the dry acid production method produces a small amount of dilute acid, the quality of the dilute acid is poor and contains too many impurities, which affects the quality of ammonium sulfate when sent to the ammonium sulfate workshop; the drying pretreatment process causes decomposition of salt substances, and the amount of drying exhaust gas is large, which is difficult to handle; the material after drying is a powder, which is highly corrosive, and the conveying equipment is often blocked, and the system continuity and stability are not good; the vertical incinerator is used, the combustion effect in the furnace is poor, and the furnace is often stopped due to blockage.

[0005] 2. (Pretreatment) Semi-dry acid production process: sulfur foam - filter - multiple separators - oxidation tower - concentration kettle - incinerator - waste heat boiler - dynamic wave scrubber - packed scrubber - electric demister - drying tower - fan - converter - absorption tower (two suctions) - tail suction dynamic wave - tail suction packed tower - tail suction electric demister.

[0006] The semi-dry acid production process uses filters to filter sulfur foam, which is severely blocked and requires manual flushing, which is labor-intensive and has a strong odor in the on-site environment. The fire tube waste heat boiler is used, and the furnace tubes are severely blocked inside, which requires manual cleaning, which is labor-intensive and has poor safety. The wet purification technology is used, which loses a large amount of heat in the flue gas and consumes a large amount of circulating water. The two-turn and two-absorption dry acid production process uses a lot of equipment, a long process, and a large amount of power consumption. The exhaust gas absorption uses an exhaust power wave, which consumes a lot of power and has a poor absorption effect.

[0007] 3. (Pretreatment) The main process flow of wet acid production: sulfur foam - centrifuge - concentration tower - slurry tank - incinerator - waste heat boiler - dynamic wave scrubber - cooling scrubber - dry absorption tower - electric demister - fan - converter - absorption tower (double absorption) - sulfuric acid storage tank.

[0008] The output of dilute acid in wet acid production is too large, which seriously affects the water balance and stable operation of the ammonium sulfate system. Due to the use of this dilute sulfuric acid, the quality of ammonium sulfate is poor; the use of fire tube waste heat boilers has serious blockage inside the furnace tubes, requiring manual cleaning, which is labor-intensive and has poor safety; the use of wet purification technology loses a large amount of heat in the flue gas and consumes a large amount of circulating water; the two-turn and two-absorption dry method is used to produce acid, and the heat of the chemical reaction cannot be utilized, so there are many equipment, a long process, and high power consumption.

[0009] 4. (Conversion) The main process flow of wet acid production: sulfur melting device - combustion device - purification device - denitrification reactor - combined reactor - sulfuric acid steam condenser - sulfuric acid mixing tank and - tail gas treatment device.

[0010] The process uses wet purification technology, which loses a lot of heat in the flue gas and consumes a lot of circulating water. The dilute acid purification process produces dilute acid in the device. Since the temperature of the flue gas is reduced after purification, it is necessary to use the flue gas waste heat to heat it up, which causes serious equipment corrosion and reduces the steam production of the boiler. The tail gas absorption is a primary absorption, and although desalted water is added to the tower, it cannot eliminate ammonia escape.

[0011] In summary, the common disadvantages of the existing processes for producing acid from desulfurized waste liquid and sulfur foam are: the waste heat boiler is severely blocked and requires manual cleaning; the wet purification technology is used, resulting in large heat losses and obtaining dilute sulfuric acid of poor quality as a by-product; there are many pieces of equipment, long processes, high failure rates, and high operating power consumption. Summary of the invention

[0012] To address the deficiencies of the prior art, the present invention provides a system and method for preparing 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 an incinerator for incineration to produce acid.

[0013] The technical solution of the present invention is as follows:

[0014] The first object of the present invention is to provide a system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid, which is characterized in that it consists of a pretreatment unit, an incineration and cooling unit, a dust removal and filtration unit, a conversion unit, an acid generating unit and a desulfurization unit connected in sequence.

[0015] The pretreatment unit adopts high-efficiency concentration equipment (i.e., desulfurization liquid concentrator), and the salt slurry produced contains less water, which greatly reduces the gas consumption of the incinerator; the secondary steam generated by the concentration of the pretreatment unit is washed and purified by the steam washing tower and condensed by the condenser before being sent to the secondary condensate storage tank. The secondary steam condensate in the secondary condensate storage tank has high purity and can be returned to the desulfurization section for reuse, or enter the cold drum section, eliminating the problem of liquid swelling in the desulfurization section.

[0016] The waste heat boiler adopts a water-cooled wall water tube boiler with automatic ash cleaning function to eliminate blockage. A high-temperature filter is used to remove dust in the flue gas, and dry ash discharge not only maintains a high temperature of the flue gas, 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] The acid tower is used to produce sulfuric acid, 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, which greatly reduces gas consumption.

[0019] A two-stage desulfurization tower is used to recover sulfur dioxide in 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, and no secondary desulfurization waste is generated.

[0020] The system of the present invention has a large capacity for treating desulfurized waste liquid, reaching 20-500 t / d, and produces 10-300 t / d of 98% acid. The specific conditions of each unit in the present invention are as follows:

[0021] 1. Pretreatment unit: The main purpose of this unit is to use sulfur foam to produce liquid sulfur and salt slurry, 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 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 coking 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.

[0023] The sulfur foam from the coking desulfurization section is sent to the sulfur foam storage tank, and the sulfur foam is pumped to the centrifugal separator. The separated concentrated sulfur foam enters the concentrated sulfur foam tank, and the separated filtrate enters the filtrate tank. The concentrated sulfur foam in the concentrated sulfur foam tank is pumped to the sulfur-water separator by the concentrated sulfur foam pump, and is separated into liquid sulfur, coal powder slag and clear liquid by steam heating. The liquid sulfur is placed in 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 coal powder 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 1.12-1.4 g / cm 3The concentrated liquid (i.e. salt slurry) has a water content of less than 60%, a temperature of 60-100°C, and good fluidity. It is stored in the salt slurry storage tank and pumped to the incinerator by the salt slurry pump. The salt slurry storage tank is equipped with a steam heating and stirring device. The salt slurry in the storage tank is at 60-100°C and has good fluidity. The pipeline for transporting liquid sulfur and salt slurry is steam-heated to ensure that the liquid sulfur and salt slurry have good fluidity and will not precipitate and block the pipeline.

[0025] The pressure at the top of the sulfur-water separator is 0.3-0.6MPa, the pressure at the bottom of the tower is 0.3-0.7MPa, and the pressure of the heating steam used is 0.3-1.0MPa; the temperature at the bottom of the sulfur-water separator is 125-160℃, and the temperature at the top is 100-140℃. The sulfur-water separator is continuously fed, the clear liquid is continuously discharged, and liquid sulfur and coal powder slag are intermittently discharged. The water vapor evaporated from the desulfurization waste liquid through the desulfurization liquid concentrator is washed by the steam washing tower, and then cooled by the condenser to form a secondary steam condensate, which is placed in the secondary condensate storage tank. The salt content in the secondary steam condensate is less than 10g / L, which is sent to the desulfurization section for reuse, or to the cold drum section to solve the problem of liquid swelling 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 gas blower, a steam drum, and a deaerator; the liquid sulfur storage tank and the salt slurry storage tank respectively send liquid sulfur and salt slurry into the incinerator to produce sulfur dioxide gas, and the waste heat boiler is used to transfer heat and cool the sulfur dioxide gas.

[0027] Liquid sulfur and salt slurry are burned in the incinerator with hot air with a temperature greater than 100°C sent from the acid forming unit. The temperature in the incinerator is controlled at 800-1200°C, the oxygen content of the furnace gas is between 3% and 10%, and the incinerator is controlled at a negative pressure of 50-500pa. The sulfur dioxide flue gas coming out of the incinerator is transferred through the 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 boiler steam pressure of 1.5-6.0Mpa. The boiler is equipped with mechanical vibration and blasting cleaning to facilitate dust removal. The cleaned dust is discharged from the bottom of the boiler, and the inside of the boiler (the flue gas side) is negative pressure.

[0028] The boiler feed pump is connected to the inlet of the drum, and supplies water to the waste heat boiler through the drum. The steam generated by the waste heat boiler enters the drum for storage. The steam in the drum is sent to the interstage cooler, which uses the reaction heat in the converter to heat the saturated steam, generate superheated steam and recover the heat. The drum supplies water to the final stage cooler, which absorbs heat from the converter flue gas, and the generated steam enters the drum.

[0029] The air fan supplies air to the incinerator, the gas fan replenishes the incinerator with coke oven gas fuel; the deaerator removes oxygen from the feed water of the waste heat boiler to reduce the corrosion of oxygen to the boiler tubes.

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

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

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

[0033] 4. Conversion unit: The main purpose of this unit is to convert sulfur dioxide in the flue gas into sulfur trioxide and recover the heat of the conversion reaction (i.e., to generate superheated steam). The conversion unit includes a converter (including the first bed, the second bed, the third bed, and the fourth bed), an interstage cooler (including the first interstage cooler, the second interstage cooler, and the third interstage cooler), and a final cooler. The flue gas passes through each catalyst bed and the interstage cooler in turn, and SO 2 Catalytic oxidation to SO 3 .

[0034] The flue gas after dust removal enters the converter through a high-temperature induced draft fan. The converter is a four-stage sulfuric acid catalyst. The first three stages have interstage coolers, and the last stage has a final stage cooler. The converter is equipped with the first bed layer, the first interstage cooler, the second bed layer, the second interstage cooler, the third bed layer, the third interstage cooler, the fourth bed layer and the final stage cooler from top to bottom. The flue gas inlet temperature of the first bed layer is 410-420℃, and the outlet temperature is 550-560℃. The flue gas inlet temperature of the second bed layer is 410-420℃, and the outlet temperature is 450-460℃. The flue gas inlet temperature of the third bed layer is 395-405℃, and the outlet temperature is 410-420℃. The flue gas inlet temperature of the fourth bed layer is 380-390℃, and the outlet temperature is 395-405℃. The flue gas is cooled to 240-279℃ in the final stage cooler to form an acid tower, and the sulfur dioxide conversion rate 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 then condense the sulfuric acid vapor into sulfuric acid and send it to the concentrated acid storage tank for storage. The acid forming unit includes an acid forming tower, a concentrated acid circulation tank, a concentrated acid circulation pump, a concentrated acid cooler, and a concentrated acid storage tank.

[0036] SO in the flue gas leaving the conversion unit 3 The gas reacts with the water vapor in the flue gas (the water vapor mainly comes from the water vapor generated by the combustion of salt slurry in the incinerator) to produce gaseous H 2 SO 4 , the flue gas enters the acid tower, flows from bottom to top, and is cooled by air. The temperature of the flue gas is cooled to above 80°C, and the gaseous sulfuric acid condenses into liquid sulfuric acid and flows into the sulfuric acid circulation tank. The hot sulfuric acid is sent to the concentrated acid cooler for cooling through the concentrated acid circulation pump. The sulfuric acid cooled to a temperature less than 70°C returns to the concentrated acid circulation tank. The concentration of sulfuric acid produced by the acid tower is 78-98%, and the generated sulfuric acid is discharged from the concentrated acid cooler 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 circulation tank. The tubes of the tube heat exchanger are made of glass or silicon carbide and other sulfuric acid corrosion-resistant materials. 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 drops to 80-120°C, and the gaseous sulfuric acid is converted into liquid sulfuric acid with a concentration of 78-98%.

[0038] The air blower sends air to the outside of the tube heat exchanger of the acid tower. After heat exchange with the flue gas containing gaseous sulfuric acid in the tube, the air temperature rises to 100-215℃. This hot air is used as the source of air for the incinerator. The concentrated acid circulation tank at the bottom of the acid tower is a carbon steel lined with polytetrafluoroethylene and ceramic tiles in sequence, and the acid temperature is 40-80℃.

[0039] 6. Desulfurization unit: The main purpose of this unit is to remove trace sulfur dioxide from the flue gas sent from the acid generating unit to meet environmental emission requirements. The desulfurization unit includes a two-stage packed tower, an electrostatic demister, a tail suction circulation pump (for circulating the absorption liquid and sending the generated ammonium sulfate solution to the desulfurization liquid concentrator), and an ammonia water storage tank (for storing ammonia water). The two-stage desulfurization tower includes a primary desulfurization tower and a secondary desulfurization tower.

[0040] Combined with the actual situation of the coking plant, by-product ammonia water is used for desulfurization, without the need to purchase desulfurizers. The flue gas enters a two-stage desulfurization tower. Ammonia water is introduced into the first desulfurization tower to absorb sulfur dioxide in the flue gas; desalted water is introduced into the second 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, which reacts with the oxygen in the flue gas to generate ammonium sulfate. The generated ammonium sulfate solution is sent to the desulfurization liquid concentrator of the pretreatment unit for concentration and used to produce sulfuric acid. The desulfurized flue gas is passed through an electrostatic precipitator to remove particulate matter, droplets, and acid mist to ensure that the exhaust gas meets the emission standards. The desulfurization efficiency is 80-99.9%, and the concentration of ammonium sulfate in the desulfurization product is 5-30%.

[0042] A foam trap is set between the acid forming tower and the primary desulfurization tower to remove sulfuric acid mist and send it to the concentrated acid circulation tank. Similarly, sulfuric acid droplets removed by the electrostatic precipitator are also sent to the concentrated acid circulation tank.

[0043] A second object of the present invention is to provide a method for preparing sulfuric acid from sulfur foam and desulfurization waste liquid, comprising the following steps:

[0044] (1) sending the sulfur foam from the coking desulfurization section to the sulfur foam storage tank, pumping the sulfur foam in the sulfur foam storage tank to a centrifugal separator, separating the concentrated sulfur foam into the concentrated sulfur foam tank, and separating the filtrate into the filtrate tank;

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

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

[0047] (4) Liquid sulfur and salt slurry are burned in the incinerator with the hot air sent from the acid tower; the temperature in the incinerator is controlled at 800-1200°C, and the negative pressure in the incinerator is controlled at 50-500Pa;

[0048] (5) The sulfur dioxide flue gas coming out of the incinerator is passed through the waste heat boiler to remove heat and dust, and the temperature is reduced to 350-550℃;

[0049] (6) 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°C, and the dust content is less than 500mg / Nm 3 ;

[0050] When the resistance of the high-temperature filter increases, use compressed air to back-blow and clean it;

[0051] (7) The flue gas passes through the catalyst beds and inter-stage coolers of the conversion unit in sequence, and sulfur dioxide is catalytically oxidized to sulfur trioxide under the action of sulfuric acid catalyst; the high-temperature flue gas from the fourth stage is cooled to 240-279°C by the final stage cooler and then sent to the acid tower;

[0052] (8) The sulfur trioxide flue gas leaving the conversion unit enters the acid tower to react with water vapor to generate sulfuric acid, and then goes to the concentrated acid storage tank from the outlet of the concentrated acid cooler;

[0053] (9) The flue gas from the conversion unit is sent to the desulfurization unit for tail gas treatment before being discharged.

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

[0055] 1) The system of the present invention operates continuously and stably, and the fluctuation of the desulfurization system has little impact on the acid-making unit;

[0056] 2) This system adopts fully sealed production operation, with excellent on-site operating environment and no dust or exhaust gas escape:

[0057] 3) The two-phase material feeding method is adopted. After the liquid sulfur and salt slurry are respectively atomized by air and enter the incinerator, they can be burned quickly and completely, avoiding the formation of sublimated sulfur, satisfying the self-heating balance of the incinerator, reducing gas consumption and lowering operating costs;

[0058] 4) Low-nitrogen combustion is adopted, and the incineration temperature is between 1000℃ and 1150℃, which greatly reduces the generation of nitrogen oxides, and the system does not need to be equipped with a denitrification device;

[0059] 5) Dry dust removal is adopted, no dilute acid is produced, environmental pressure is eliminated, and the product quality of ammonium sulfate is guaranteed;

[0060] 6) Adopt wet catalytic conversion to eliminate cold and hot diseases and greatly increase steam production;

[0061] 7) Use acid tower to produce acid, recover chemical reaction heat, generate hot air for combustion in incinerator, reduce gas consumption and increase steam production;

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

[0063] The present invention converts the sulfur foam and desulfurization waste liquid generated after purification and desulfurization in the coking plant into sulfuric acid raw materials required by the ammonium sulfate workshop within the coking plant. During the production process, no dilute sulfuric acid is discharged, no desulfurization product is discharged, the heat is fully utilized, and the amount of by-product steam 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 waste is truly turned into treasure through energy-saving and environmentally friendly methods. BRIEF DESCRIPTION OF THE 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 on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but 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, NH 4 CNS (ammonium thiocyanate), (NH 4 ) 2 S 2 O 3 (ammonium thiosulfate) and ammonium sulfate, dilute sulfur foam 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 4.5m at 7 kg pressure 3 / h to transport the concentrated sulfur foam to the sulfur-water separator. The pressure in the sulfur-water separator is maintained at 0.5MPa. The 180℃ steam is used to heat 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 4.12m of sulfur liquid is removed. 3 / h to the filtrate tank.

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

[0070] Sulfur is discharged intermittently from the bottom of the sulfur-water separator, with an average sulfur discharge of 16.344t / d; liquid sulfur and salt slurry are respectively fed into the incinerator under the atomization of compressed air. Coal powder needs to be removed regularly from the sulfur-water separator. There are exhaust pipes on the top of the sulfur foam storage tank, concentrated sulfur foam tank, salt slurry storage tank, and filtrate tank, and non-condensable gases are extracted by the fan to the incinerator for incineration.

[0071] The temperature in the incinerator is controlled at 1000-1200℃, and the furnace is maintained at minus 50-500Pa. When the temperature of the incinerator drops below 1000℃, the coke oven gas is turned on to burn for heat. The SO2 coming out of the incinerator is about 1050℃.2 After the flue gas recovers heat through the waste heat boiler, the temperature drops to about 420-450℃ and then enters the high-temperature filter for dust removal. The high-temperature dust collector discharges about 6kg of ash per day. The dust content of the flue gas after dust removal is less than 5mg / m 3 , temperature ~420℃.

[0072] The flue gas after high-temperature dust removal goes to the converter through a high-temperature induced draft fan. When the converter is provided with the first bed layer, the first interstage cooler, the second bed layer, the second interstage cooler, the third bed layer, the third interstage cooler, the fourth bed layer and the final cooler 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°C in the final cooler and goes to the acid tower, and the sulfur dioxide conversion rate is 99%.

[0073] The flue gas leaving the final cooler goes to the acid tower, and the SO in the flue gas 3 The gas reacts with the water vapor in the flue gas to produce gaseous H 2 SO 4 The flue gas enters the acid tower and flows from bottom to top. After being cooled by air, the temperature of the flue gas is cooled to above 80°C. The gaseous sulfuric acid condenses into liquid sulfuric acid and flows into the concentrated acid circulation tank. The hot sulfuric acid is sent to the concentrated acid cooler for cooling through the concentrated acid circulation pump. The sulfuric acid cooled to a temperature less than 70°C returns to the concentrated acid circulation tank. The sulfuric acid produced by the acid tower has a concentration of 97%. The generated sulfuric acid is discharged from the concentrated acid cooler to the concentrated acid storage tank.

[0074] After the air is heat exchanged with the flue gas containing gaseous sulfuric acid, the temperature of the air rises to ~215℃, and this hot air serves as the source of air for the incinerator. The flue gas enters a two-stage desulfurization tower. Ammonia water is introduced into the first stage desulfurization tower to absorb sulfur dioxide in the flue gas; desalted water is introduced into the second stage desulfurization tower to absorb escaped ammonia in the flue gas; the electrostatic precipitator is used to remove particulate matter, droplets, and acid mist in the flue gas to ensure that the exhaust gas meets the emission standards.

[0075] The sulfur dioxide in the flue gas reacts with the ammonia in the ammonia water to generate ammonium sulfite, which reacts with the oxygen in the flue gas to generate ammonium sulfate. The generated ammonium sulfate solution is sent to the desulfurization liquid concentrator of the pretreatment unit for the production of sulfuric acid. The desulfurized flue gas is removed by the electrostatic precipitator to remove particulate matter, droplets, and acid mist, and meets the "Coking Chemical Industry Pollutant Emission Standard" GB16171-2012, and meets the emission standards. The two-stage desulfurization tower has a desulfurization efficiency of 99%, and the concentration of the desulfurization product ammonium sulfate is 20%, which is sent to the pretreatment unit for concentration and used to produce sulfuric acid.

[0076] After the above-mentioned treatment units, sulfur foam and desulfurization waste liquid are converted into concentrated sulfuric acid, eliminating the solid waste and liquid waste generated in the desulfurization process. 108 tons of 97% sulfuric acid are produced every day, and the recovery rate of sulfur in sulfur foam reaches 99.9%.

[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, NH 4 CNS, (NH4) 2 S 2 O 3 and ammonium sulfate, dilute sulfur foam 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 enters the filtrate tank, and most of the filtrate returns to the desulfurization section; the sulfur foam delivery pump is 2.25m under a pressure of 7 kg 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 ~2.06m of sulfur clear liquid is removed. 3 / h to the filtrate tank.

[0079] Pump from the filtrate tank ~3.5m 3 / h filtrate goes to the waste liquid concentration device, and after concentration, a concentrated liquid containing 50% water and 40% salt is obtained, 1922kg / h, or 46.13t / d. Sulfur is intermittently discharged from the bottom of the sulfur-water separator, with an average sulfur discharge of 8.172t / d; liquid sulfur and salt slurry are respectively fed into the incinerator under the atomization of compressed air, and the sulfur-water separator needs to remove coal powder regularly. There are exhaust pipes on the top of the sulfur foam storage tank, concentrated sulfur foam tank, salt slurry storage tank, and filtrate tank, and the non-condensable gas is drawn by the fan to the incinerator for incineration.

[0080] The temperature in the incinerator is controlled at 1000-1200℃, and the furnace is maintained at minus 50-500Pa. When the temperature of the incinerator drops below 1000℃, the coke oven gas is turned on to burn for heat. The SO2 coming out of the incinerator is about 1050℃. 2 After the furnace gas recovers heat through the waste heat boiler, the temperature drops to about 420-450℃ and then enters the high-temperature filter for dust removal. The high-temperature dust collector discharges about 3kg of ash per day, and the dust content of the flue gas after dust removal is less than 5mg / m 3 , temperature ~420℃.

[0081] The flue gas after high-temperature dust removal goes to the converter through a high-temperature induced draft fan. When the converter is provided with the first bed layer, the first interstage cooler, the second bed layer, the second interstage cooler, the third bed layer, the third interstage cooler, the fourth bed layer and the final cooler 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°C in the final cooler and goes to the acid tower, and the sulfur dioxide conversion rate is 99%.

[0082] The flue gas leaving the final cooler goes to the acid tower, and the SO in the flue gas 3 The gas reacts with the water vapor in the flue gas to produce gaseous H 2 SO 4 , the flue gas enters the acid tower, flows from bottom to top, and is cooled by air. The temperature of the flue gas is cooled to above 80°C, and the gaseous sulfuric acid condenses into liquid sulfuric acid and flows into the concentrated acid circulation tank. The hot sulfuric acid is sent to the concentrated acid cooler for cooling through the concentrated acid circulation pump. The sulfuric acid cooled to a temperature less than 70°C returns to the concentrated acid circulation tank. The concentration of sulfuric acid produced by the acid tower is 97%, and the generated sulfuric acid is discharged from the concentrated acid cooler to the concentrated acid storage tank.

[0083] After the air is heat exchanged with the process gas containing gaseous sulfuric acid, the temperature of the air rises to ~215°C, and this hot air serves as the source of incinerator air.

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

[0085] The sulfur dioxide in the flue gas reacts with the ammonia in the ammonia water to generate ammonium sulfite, which reacts with the 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 the production of sulfuric acid. The desulfurized flue gas is removed by the electrostatic precipitator to remove particulate matter, droplets, and acid mist, and meets the "Coking Chemical Industry Pollutant Emission Standard" GB16171-2012, and meets the emission standards. The two-stage desulfurization tower has a desulfurization efficiency of 99%, and the concentration of the desulfurization product ammonium sulfate is 20%, which is sent to the pretreatment unit for concentration and used to produce sulfuric acid.

[0086] After the above-mentioned treatment units, the sulfur foam and desulfurization waste liquid are turned into concentrated sulfuric acid, eliminating the solid waste and liquid waste generated in the desulfurization process. 54 tons of 97% sulfuric acid are produced every day, and the recovery rate of sulfur in the sulfur foam reaches 99.9%.

Claims

1. A system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid, characterized in that: It includes a pretreatment unit, an incineration and cooling unit, a dust removal and filtration unit, a conversion unit, an acid-generating unit and a desulfurization unit connected in sequence; The pretreatment unit is used for preparing liquid sulfur and salt slurry from sulfur foam, and comprises: 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; The incineration and cooling unit includes an incinerator and a waste heat boiler; the liquid sulfur storage tank and the salt slurry storage tank respectively feed liquid sulfur and salt slurry into the incinerator to produce sulfur dioxide gas, and the waste heat boiler is used to transfer heat and cool the sulfur dioxide gas; The dust removal and filtration unit includes a high-temperature filter for removing dust from the flue gas; 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 acid generating unit comprises an acid generating tower, a concentrated acid circulation tank, a concentrated acid cooler, and a concentrated acid storage tank, which are used to combine sulfur trioxide in the flue gas with water to form sulfuric acid vapor, and condense the sulfuric acid vapor into sulfuric acid and then send it into the concentrated acid storage tank for storage; The desulfurization unit comprises a two-stage desulfurization tower and an electrostatic demister, and the flue gas sent from the acid generating unit is discharged after being subjected to tail gas treatment.

2. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: 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. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: The salt slurry storage tank is equipped with a steam heating and stirring device, and the pipeline for conveying liquid sulfur and salt slurry is heated by steam; The concentrated liquid from the desulfurization liquid concentrator has a density of 1.12 to 1.4 g / cm 3 The salt slurry has a moisture content of less than 60% and a temperature of 60-100°C.

4. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: Hot air with a temperature greater than 100°C is introduced into the incinerator, the oxygen content of the gas in the incinerator is between 3% and 10%, the temperature inside the furnace is 800 to 1200°C, and the incinerator is at a negative pressure of 50 to 500 Pa.

5. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 4, characterized in that: The waste heat boiler is a water-cooled wall water tube boiler, and the steam pressure of the waste heat boiler is 1.5-6.0Mpa.

6. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: The filter bag of the high temperature filter is made of aluminum silicate fiber, ceramic fiber, graphite fiber or stainless steel.

7. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: The converter 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 stage 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°C in the final cooler to go to the acid tower.

8. The system for preparing 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.

9. The system for preparing sulfuric acid from sulfur foam and desulfurization waste liquid according to claim 1, characterized in that: The two-stage desulfurization tower comprises 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 by using ammonia; desalted water is introduced into the secondary desulfurization tower to absorb escaped ammonia in the flue gas by using desalted water.

10. A method for preparing sulfuric acid from sulfur foam and desulfurization waste liquid, characterized in that: The system for preparing sulfuric acid using the sulfur foam and desulfurization waste liquid according to any one of claims 1 to 9 comprises the following steps: (1) sending the sulfur foam from the coking desulfurization section to the sulfur foam storage tank, pumping the sulfur foam in the sulfur foam storage tank to a centrifugal separator, separating the concentrated sulfur foam into the concentrated sulfur foam tank, and separating the filtrate into the filtrate tank; (2) The concentrated sulfur foam in the concentrated sulfur foam tank is pumped to a sulfur-water separator, and separated into liquid sulfur, coal powder slag and clear liquid by steam heating; the liquid sulfur is sent to a liquid sulfur storage tank and sent to an incinerator by a sulfur pump; the clear liquid enters a filtrate tank and is sent back to the desulfurization system by a filtrate pump; (3) Extract the desulfurization waste liquid from the filtrate tank and send it to the desulfurization waste liquid concentrator to obtain a density of 1.12-1.4 g / cm 3 The concentrated liquid, i.e. salt slurry, is stored in a salt slurry storage tank and is pumped to the incinerator by a salt slurry pump; (4) Liquid sulfur and salt slurry are burned in the incinerator with the hot air sent from the acid tower; the temperature in the incinerator is controlled at 800-1200°C, and the negative pressure in the incinerator is controlled at 50-500 Pa; (5) The sulfur dioxide flue gas from the incinerator is passed through the waste heat boiler to remove heat and dust, and the temperature is reduced to 350-550℃; (6) 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°C, 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 it; (7) The flue gas passes through the catalyst beds and inter-stage coolers of the conversion unit in sequence, and sulfur dioxide is catalytically oxidized to sulfur trioxide under the action of sulfuric acid catalyst; the high-temperature flue gas from the fourth stage is cooled to 240-279°C by the final stage cooler and then sent to the acid tower; (8) The sulfur trioxide flue gas leaving the conversion unit enters the acid tower to react with water vapor to generate sulfuric acid, and then goes to the sulfuric acid storage tank from the outlet of the concentrated acid cooler; (9) The flue gas from the conversion unit is sent to the desulfurization unit for tail gas treatment before being discharged.

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