Improved wet-splitting spent sulfuric acid regeneration system

Abstract

The utility model provides a kind of to improve wet method pyrolysis waste sulfuric acid regeneration system, the waste sulfuric acid regeneration process gas is recovered after waste heat, in turn through the dehydration unit, demisting unit and heating unit of regeneration system, finally into reactor and carry out reaction, again through wet method sulfuric acid cooler cooling obtains concentrated sulfuric acid product. Dehydration control water in process, to improve the concentration of product concentrated sulfuric acid, and avoid the dew point corrosion of subsequent reaction system heat exchanger equipment, optimize heat transfer network, save energy, improve product yield, to optimize the process and system of wet method pyrolysis waste sulfuric acid.

Description

Technical Field

[0001] This utility model belongs to the field of waste sulfuric acid regeneration technology, specifically relating to an improved wet pyrolysis waste sulfuric acid regeneration system for increasing the concentration of concentrated sulfuric acid products. Background Technology

[0002] Waste sulfuric acid is a viscous, colloidal liquid, dark red in color, with a distinctive odor. It is unstable, difficult to treat, and direct discharge causes severe pollution. The wet regeneration process for waste sulfuric acid, typically employing wet high-temperature pyrolysis, effectively solves the pollution problem, allowing the produced industrial sulfuric acid to be recycled back into the system.

[0003] The wet high-temperature pyrolysis regeneration process first recovers waste heat from the incinerator's waste heat boiler, then performs high-temperature dust removal. The process gas then enters the catalyst bed to be converted into SO3, followed by an acid mist control system to remove acid mist, and finally a condenser to absorb sulfur trioxide and generate concentrated sulfuric acid. Compared to the dry high-temperature pyrolysis regeneration process, the wet high-temperature pyrolysis regeneration process has advantages such as shorter procedures, higher operating efficiency, less wastewater, and smaller footprint.

[0004] However, due to the formation of an azeotrope from approximately 98.3 wt% concentrated sulfuric acid, it is difficult to further increase the product concentration. Therefore, the theoretical maximum concentration of concentrated sulfuric acid produced by the "wet process" for sulfuric acid production is about 98.3% w. In actual production, however, due to the influence of water content in the process gas, even if the fresh concentrated sulfuric acid product reaches the theoretical equilibrium concentration, it is only 95-97 wt%, and in actual production, it is only 95-96 wt%. The concentration of sulfuric acid product is related to the operating temperature and pressure at the bottom of the condenser and the water content of the process gas. For the "wet process" waste sulfuric acid regeneration process, since there is no dehydration and water control of the process gas, the water content in the process gas has a significant impact on the concentration of sulfuric acid product.

[0005] The "wet process" for waste sulfuric acid regeneration requires controlling the temperature at around 1000℃ during incineration. This involves high-temperature pyrolysis of the waste sulfuric acid, an endothermic reaction requiring additional fuel for heat. Commonly used fuels include acidic gases, natural gas, or dry gas, which produce gaseous water upon combustion. The process gas containing gaseous water undergoes high-temperature dust removal and heat exchange before entering the reactor to catalytically convert SO2 into SO3. After cooling, it enters the condenser to form acid. The concentrated liquid sulfuric acid produced at the bottom of the condenser is close to equilibrium. The concentration of this concentrated liquid sulfuric acid is related to temperature, pressure, and the water content in the process gas. Temperature and pressure are difficult to optimize further due to limitations in the condenser equipment; therefore, the concentration of the concentrated sulfuric acid product is highly dependent on the water content in the process gas. Traditional "wet process" waste sulfuric acid regeneration processes lack the means to adjust the water content in the process gas. Consequently, the concentration of the concentrated sulfuric acid product in devices using this technology often fluctuates significantly due to the water content in the process gas.

[0006] Therefore, it is necessary to further develop and improve the wet high-temperature pyrolysis waste sulfuric acid regeneration system to reduce the concentration of concentrated sulfuric acid products, increase sulfuric acid yield, reduce energy consumption, and reduce equipment corrosion. Utility Model Content

[0007] To address the aforementioned problems, this invention provides an improved wet pyrolysis waste sulfuric acid regeneration system. The dehydration unit 300 controls the moisture and SO2 content in the waste sulfuric acid regeneration process gas, removing moisture to control product concentration. Furthermore, waste heat is efficiently recovered to heat the process gas, achieving the necessary conditions for subsequent reactions. This improved wet pyrolysis waste sulfuric acid regeneration system increases product concentration, prevents dew point corrosion of equipment, improves sulfuric acid yield, optimizes heat exchange, and saves energy.

[0008] The purpose of this invention is also to provide an improved wet pyrolysis waste sulfuric acid regeneration system, the regeneration system comprising a dehydration unit, a demisting unit, a heating unit, a sulfur dioxide reactor and a sulfuric acid cooler connected in sequence.

[0009] The dewatering unit includes an overflow weir, a primary spray tank, and a secondary spray tank;

[0010] The overflow weir is located at the top of the primary spray tank; the bottom of the primary spray tank is equipped with upward spray nozzles.

[0011] The primary spray tank has an outlet near its bottom;

[0012] The upper part of the secondary spray tank is equipped with downward spray heads;

[0013] A demister is installed above the spray head at the upper part of the secondary spray tank;

[0014] The demisting unit includes a wet electrostatic precipitator, which contains multiple vertical anode tubes and cathode wires, forming a high-voltage electrostatic field in the anode tubes and cathode wires;

[0015] The heating unit includes a mixer and a multi-stage heat exchanger.

[0016] After waste heat recovery, the waste sulfuric acid regeneration process gas passes through a dehydration unit, a demisting unit, and a heating unit in sequence, and finally enters a sulfur dioxide reactor for reaction. It is then cooled and absorbed by a sulfuric acid cooler to obtain concentrated sulfuric acid product.

[0017] Furthermore, a dilute sulfuric acid outlet is provided at the bottom of the secondary spray tank, and the dilute sulfuric acid outlet of the secondary spray tank is connected to a dilute sulfuric acid filter.

[0018] Furthermore, the mixer includes a hot air distributor, a mixing chamber, a process gas inlet, and a mixed gas process gas outlet;

[0019] The mixing chamber has a process gas inlet at the bottom and a mixed process gas outlet at the top; the bottom end of the mixed process gas outlet is connected to the top of the mixing chamber, and it has a side outlet in an inverted L shape.

[0020] The hot air distributor is a long cylindrical shape and is inserted from the top of the mixed process gas outlet; the bottom of the hot air distributor is located in the middle or upper region of the mixing chamber.

[0021] Furthermore, the lower section of the hot air distributor is provided with evenly distributed distribution holes. Attached Figure Description

[0022] Figure 1 This diagram illustrates an improved wet pyrolysis waste sulfuric acid regeneration system according to the present invention.

[0023] Figure 2 This figure shows an axial sectional view of a mixer according to the present invention;

[0024] Figure 3 This diagram shows a schematic of a supporting brick structure according to the present invention;

[0025] Figure 4 This diagram illustrates the arrangement of supporting bricks and the function of the circular fixing piece in this invention.

[0026] Figure 5 This diagram shows a schematic of a distribution brick structure according to the present invention;

[0027] Figure 6 This diagram shows a structural schematic of a fixing plate and a supporting brick layer in this utility model.

[0028] Explanation of icon numbers

[0029] 100-sulfur dioxide reactor;

[0030] 200-Sulfuric Acid Cooler;

[0031] 300-Dehydration Unit;

[0032] 400 - Defogging unit;

[0033] 500 - Heating unit;

[0034] 301 - Overflow Weir;

[0035] 302-Level 1 Spray Tank;

[0036] 303-Secondary spray tank;

[0037] 304 - Demister;

[0038] 401 - Hot air distributor;

[0039] 4011 - Dispensing hole;

[0040] 402 - Mixing Chamber;

[0041] 4021 - Supporting brick layer;

[0042] 4022 - Distribute brick layers;

[0043] 403 - Process gas inlet;

[0044] 404 - Mixed gas process gas outlet;

[0045] 211-End face positioning groove;

[0046] 212-Through-through strip groove;

[0047] 213 - Circular fixing piece;

[0048] 214 - Fixing plate;

[0049] 221 - Square hollow steel section;

[0050] 222 - Strip notch;

[0051] 1-Heat Exchanger I

[0052] 3-Wet electrostatic precipitator;

[0053] 4-Mixer;

[0054] 5-Preheater;

[0055] 6- Fan;

[0056] 7-Heat Exchanger II;

[0057] 8-Heat Exchanger III;

[0058] 9-Heater;

[0059] 10-Wash water degassing skid;

[0060] 11-Dilute acid pump;

[0061] 12-Dilute sulfuric acid filter;

[0062] 13-Jet scrubbing tower pump;

[0063] 14-Dilute sulfuric acid cooler I;

[0064] 15-Dilute sulfuric acid cooler II. Detailed Implementation

[0065] The present invention will be described in detail below through specific embodiments, and the features and advantages of the present invention will become clearer and more explicit with these descriptions.

[0066] This invention provides an improved wet pyrolysis waste sulfuric acid regeneration system. The regeneration system includes a dehydration unit 300, a demisting unit 400, a heating unit 500, a sulfur dioxide reactor 100, and a sulfuric acid cooler 200 connected in sequence. The waste sulfuric acid regeneration process gas (containing trace amounts of SO3, such as 0.2% SO3) is processed by waste heat recovery and then passes through the dehydration unit 300, the demisting unit 400, and the heating unit 500 in sequence before finally entering the sulfur dioxide reactor 100 for reaction. The gas is then cooled and absorbed by the sulfuric acid cooler 200 to obtain concentrated sulfuric acid product.

[0067] The improved wet pyrolysis waste sulfuric acid regeneration method using the above-mentioned regeneration system includes: after recovering the waste heat of the waste sulfuric acid regeneration process gas, it is dehydrated and deacidified, and then heated before entering the sulfur dioxide reactor 100 for reaction, and then cooled and absorbed by the sulfuric acid cooler 200 to obtain the product fresh concentrated sulfuric acid.

[0068] The waste sulfuric acid regeneration process gas is the process gas obtained after pyrolyzing waste sulfuric acid at 1000-1050℃. The system in this invention is suitable for waste sulfuric acid regeneration. The waste sulfuric acid regeneration process gas of this invention is obtained from the high-temperature pyrolysis of waste sulfuric acid in an incinerator. There are no special requirements for the SO2 content in the waste sulfuric acid regeneration process gas, and all SO2 is converted from element S in the incinerated materials.

[0069] The temperature of the waste sulfuric acid regeneration process gas after waste heat recovery is not lower than 380℃, preferably 380-450℃, and more preferably 410-430℃.

[0070] The dehydration process involves spraying a washing liquid onto the waste sulfuric acid regeneration process gas after waste heat recovery to cool it down, causing the gaseous moisture in the high-temperature waste sulfuric acid regeneration process gas to cool, condense, and separate from the process gas. The washing liquid is water or dilute sulfuric acid, preferably 1-2 wt% recycled dilute sulfuric acid. After spraying, the temperature of the waste sulfuric acid regeneration process gas is 35-75℃, preferably 40-65℃, and more preferably 45-55℃.

[0071] Theoretically, in the subsequent acid formation reaction, 1 mol of SO3 reacts with 1 mol of H2O to produce 1 mol of H2SO4, thus requiring water. However, the water content should be slightly excessive, partly to provide the necessary reaction conditions and partly to maintain gas-liquid equilibrium and ensure a certain amount of gaseous water in the gas phase. However, excessive water will have two major consequences: firstly, the concentration of the regenerated fresh concentrated sulfuric acid will not reach the equilibrium concentration of 98.3 wt%; secondly, the dew point of SO3 in the condenser feed will increase, raising the risk of corrosion at the bottom of the reactor upstream of the condenser. After dehydration, the molar ratio of water to SO2 in the waste sulfuric acid regeneration process gas is adjusted to (1.15-1.5):1, preferably (1.15-1.3):1, and more preferably 1.2:1.

[0072] The acid mist removal is an electrostatic demisting method, which uses a high-voltage electric field to ionize acid mist particles in the waste acid process gas. Under the action of the electric field, the particles converge to form large droplets and are deposited out of the waste acid process gas.

[0073] After acid mist removal, the acid mist content in the waste sulfuric acid regeneration process gas is less than 3 mg / Nm³. 3 .

[0074] The waste sulfuric acid regeneration process gas is reheated to 350-450℃, preferably 380-440℃, and more preferably 400-420℃, and then enters the sulfur dioxide reactor 100 to be converted into process gas containing SO3. The gas is then cooled and absorbed by the sulfuric acid cooler 200 to obtain concentrated sulfuric acid product. This invention does not specifically limit the sulfur dioxide reactor 100 and the sulfuric acid cooler 200; any sulfur dioxide reactor capable of catalytically converting SO2 to SO3, and any sulfuric acid cooler capable of cooling and absorbing SO3 from the process gas, is acceptable.

[0075] The concentration of the concentrated sulfuric acid is 97.8-98.3 wt%, or even 97.9 wt%-98.2 wt%. In this invention, due to the precise control of the molar ratio of SO2 to H2O, the fresh concentrated sulfuric acid product formed in the acid-forming section of the sulfuric acid cooler 200 is closer to the equilibrium concentration, which is the biggest advantage of this invention. Another advantage is that it lowers the SO3 dew point of the feed to the sulfuric acid cooler 200, reducing the risk of corrosion to the equipment at the bottom of the reactor.

[0076] The waste heat recovery is achieved through heat exchanger I 1, preferably a finned tube heat exchanger, and preferably using molten salt as the cooling medium, such as a common ternary molten salt solid mixture of potassium nitrate, sodium nitrite, and sodium nitrate (e.g., a mass ratio of 53wt%:40wt%:7wt%). The temperature of the waste sulfuric acid regeneration process gas entering heat exchanger I 1 is 440-620℃, preferably 470-570℃, and more preferably 500-530℃. After waste heat recovery, the temperature of the waste sulfuric acid regeneration process gas is not lower than 380℃, preferably 380-450℃, and more preferably 410-430℃. Waste heat recovery can fully utilize heat and reduce system energy waste.

[0077] After waste heat recovery, the waste sulfuric acid regeneration process gas enters the dehydration unit 300. The dehydration unit 300 includes an overflow weir 301, a primary spray tank 302, and a secondary spray tank 303. In the dehydration unit 300, the waste sulfuric acid regeneration process gas is cooled, dehydrated, and impurities are removed.

[0078] The overflow weir 301 is located at the top of the primary spray tank 302, and washing liquid is introduced into the overflow weir 301. The bottom of the primary spray tank 302 is equipped with upward-spraying nozzles that spray the washing liquid upwards from the bottom. The waste sulfuric acid regeneration process gas first enters the overflow weir 301 from the top, and then enters the primary spray tank 302. More specifically, the overflow weir 301 is an annular groove located at the top of the primary spray tank 302, and the inner wall of the primary spray tank 302 extends to form the inner ring wall of the annular groove of the overflow weir 301. The overflow weir 301 is a conventionally used rectangular or sawtooth overflow. The washing liquid is introduced into the overflow weir 301, overflows the inner ring wall of the annular groove, and flows downwards along the inner wall of the primary spray tank 302, forming a liquid film. This prevents the high-temperature waste sulfuric acid regeneration process gas entering the primary spray tank 302 from directly contacting the inner wall of the primary spray tank 302, thus preventing corrosion. The primary spray tank 302 is equipped with upward-spraying nozzles at its bottom, spraying washing liquid upwards from the bottom. Waste sulfuric acid regeneration process gas enters the primary spray tank 302 from the top, coming into contact with the washing liquid sprayed from the bottom of the primary spray tank 302. This lowers the temperature, causing the water to condense into liquid, which then settles at the bottom and separates from the process gas. The washing liquid is water or dilute sulfuric acid, preferably 1-2 wt% recycled dilute sulfuric acid.

[0079] The primary spray tank 302 has an outlet near its bottom, through which the waste sulfuric acid regeneration process gas and the washing liquid deposited at the bottom enter the secondary spray tank 303. The secondary spray tank 303 is equipped with downward spray heads at its upper part, spraying the washing liquid downwards. The washing liquid comes into convective contact with the waste sulfuric acid regeneration process gas entering from the bottom, further cooling and removing moisture, causing it to settle to the bottom and form dilute sulfuric acid which is then discharged.

[0080] A demister 304 is installed above the spray head on the upper part of the secondary spray tank 303. After being sprayed, the waste sulfuric acid regeneration process gas enters the demister 304 upwards, which further removes liquid droplets and dust from the gas. After passing through the demister 304, the waste sulfuric acid regeneration process gas exits from the top outlet of the secondary spray tank 303 and enters the demister 3. The demister 3 in this invention is a conventional demister; any demister capable of performing demisting functions is acceptable.

[0081] After treatment by the dehydration unit 300, the molar ratio of gas and water content to SO2 content in the waste sulfuric acid regeneration process is adjusted to (1.15-1.5):1, preferably (1.15-1.3):1, and more preferably 1.2:1.

[0082] When the temperature of the waste sulfuric acid regeneration process gas at the outlet of the secondary spray tank 303 exceeds 75℃, open the fire water interlock valve and replenish water for 20-30 minutes to carry out emergency cooling.

[0083] The secondary spray tank 303 is equipped with a dilute sulfuric acid outlet at its bottom to discharge the dilute sulfuric acid from the bottom. The dilute sulfuric acid outlet of the secondary spray tank 303 is connected to the dilute sulfuric acid filter 12. The regeneration system also includes a jet scrubbing tower pump 13, which is used to extract dilute sulfuric acid from the dilute sulfuric acid filter 12 and send it to the overflow weir 301, the primary spray tank 302, the dilute sulfuric acid cooler I 14, the dilute sulfuric acid cooler II 15, and the top of the washing water degassing skid 10, respectively. The dilute sulfuric acid cooler I 14 and the dilute sulfuric acid cooler II 15 are arranged in parallel.

[0084] After being cooled by dilute sulfuric acid coolers I14 and II15, the temperature of the dilute sulfuric acid is 30-55℃, preferably 35-50℃, and more preferably 40-45℃. The cooled dilute sulfuric acid is then returned to the spray head of the secondary spray tank 303 as the secondary spray washing liquid. This liquid is used to spray and wash away the acid mist entrained in the gas.

[0085] The washing water degassing skid 10 has a distribution pipe and spray heads at the top, a ceramic packing layer in the middle, and an air-lift inlet and washing water outlet at the bottom. Dilute sulfuric acid from the secondary spray tank 303 passes through a dilute sulfuric acid filter 12. Excess dilute sulfuric acid is pumped by the jet washing tower pump 13 to the top of the washing water degassing skid 10, where it comes into convective contact with the air entering from the bottom. This air-lift process recovers SO2 dissolved in the washing water. The ceramic packing layer distributes the dilute sulfuric acid from the top and the air from the bottom, allowing for gas-liquid contact on the surface of the packing layer. The washing water after air-lift is pumped out by a dilute acid pump 11, while the SO2-containing air returns to the secondary spray tank 303 to recover the SO2. The dilute acid pump 11 is equipped with a minimum flow protection line. The flow rate of the washing water pumped by the dilute acid pump 11 controls the liquid level in the washing water degassing skid 10.

[0086] The bottom of the secondary spray tank 303 is also equipped with a dilute sulfuric acid drain port, which is used to discharge the residual dilute sulfuric acid at the bottom of the secondary spray tank 303 after the process is completed.

[0087] The demisting unit 400 includes a wet electrostatic precipitator 3, used to remove small-particle acid mist entrained in the waste sulfuric acid regeneration process gas, preventing corrosion of subsequent equipment and pipelines. The wet electrostatic precipitator 3 includes multiple vertical anode tubes and cathode wires, forming a high-voltage electrostatic field in the anode tubes and cathode wires. The acid mist particles in the waste sulfuric acid regeneration process gas are ionized, and the electrostatic field deposits ions onto the tube wall to form large droplets. The large droplets fall back into the acid tank of the wet electrostatic precipitator 3 under gravity, and then flow into the inlet of the dilute acid pump 11 by gravity.

[0088] The wet electrostatic precipitator 3 has a deionized water nozzle at the top of the high-voltage electrostatic field and a deionized water inlet at the bottom. The upper deionized water nozzle is used for intermittent washing of the anode tube bundle, and the lower deionized water inlet is used for intermittent washing of the bottom of the wet electrostatic precipitator.

[0089] The heating unit 500 includes a mixer 4 and a multi-stage heat exchanger.

[0090] The mixer 4 includes a hot air distributor 401, a mixing chamber 402, a process gas inlet 403, and a mixed gas process gas outlet 404.

[0091] The mixing chamber 402 has a process gas inlet 403 at the bottom and a mixed process gas outlet 404 at the top. The bottom end of the mixed process gas outlet 404 is connected to the top of the mixing chamber, and it is a side outlet, shaped like an inverted L, as shown in the figure below. Figure 2 As shown.

[0092] The hot air distributor 401 is a long cylindrical shape, inserted from the top of the mixed process gas outlet 404. Hot air enters from the top of the hot air distributor 401, and the bottom is the outlet. The bottom of the hot air distributor 401 is located in the middle or upper region of the mixing chamber 402. Preferably, the lower section of the hot air distributor 401 is provided with uniformly distributed distribution holes 4011, so that part of the hot air entering from the top of the hot air distributor 401 mixes countercurrently with the low-temperature acidic process gas through the bottom outlet of the long cylinder of the hot air distributor 401, and the other part of the air is ejected through the distribution holes 4011 and fully mixed with the mixed gas coming out of the mixing chamber 402 before entering the mixed process gas outlet 404 and leaving the mixer.

[0093] The diameter ratio of the distribution hole 4011 to the hot air distributor 401 is (60-160):600, preferably (70-140):600, more preferably (80-120):600, and the number of distribution holes 4011 is 10-40, preferably 16-24. The size and number of distribution holes 4011 can be adjusted according to the actual air volume. A suitable diameter ratio of the distribution hole 4011 to the hot air distributor 401 allows air to be ejected from the side distribution holes while maintaining a suitable flow rate and pressure of the air at the bottom outlet of the air distributor, ensuring the effect of counter-current mixing and lateral mixing.

[0094] Preferably, the ratio of the length of the hot air distributor 401 entering the mixing chamber 402 to the height of the mixing chamber 402 is (350-950):1540, more preferably (450-850):1540, and even more preferably (550-750):1540.

[0095] Preferably, the hot air temperature is 200-800℃, more preferably 300-600℃, and the temperature of the low-temperature acidic process gas is 0-100℃, more preferably 0-80℃.

[0096] In the mixing chamber 402, a support brick layer 4021 is disposed close to the shell. This layer is formed by a plurality of slotted support bricks arranged in a staggered manner. The support bricks have honeycomb-shaped square channels inside, serving as a sidewall insulation layer. Preferably, the inner wall of the mixing chamber 402 shell is lined with PFA (tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer), and a PTFE (polytetrafluoroethylene) gasket is disposed close to the PFA liner.

[0097] The two end connecting surfaces of the supporting brick are provided with end face positioning grooves 211, and the lower connecting surfaces of the vertically arranged supporting bricks are provided with through strip grooves 212 that penetrate the lower connecting surfaces of the supporting bricks laterally, as shown in the figure. Figure 3 and Figure 4 As shown.

[0098] Within the same horizontal layer, the support bricks are arranged horizontally end-to-end, with the end face positioning grooves 211 on the connecting surfaces aligned to form positioning slots, where the lower half of a circular fixing piece 213 is placed. The through-slot 212 of the upper layer support brick accommodates the upper half of the circular fixing piece 213, thus fixing the positions of the upper and lower layer support bricks in the direction perpendicular to the circular fixing piece 213, as detailed below. Figure 4 As shown. The total depth of the end face positioning groove 211 and the through strip groove 212 is greater than the diameter of the circular fixing piece 213, so that the connecting surfaces of the upper and lower supporting bricks are in close contact. The circular fixing piece 213 is a ceramic fixing piece.

[0099] The supporting brick layer 4021 extends to the top of the mixing chamber. An L-shaped fixing plate 214 is installed on top of the supporting brick layer 4021. The front bent portion of the fixing plate 214 snaps downwards to secure the supporting brick layer 4021, while the horizontal portion extends and is fixed to the top or side wall of the mixing chamber 402, thus firmly fixing the supporting brick layer 4021 to the side wall of the mixing chamber 402. Specifically, as shown... Figure 6 As shown.

[0100] The bottom of the mixing chamber 402 is provided with a layer of distributing bricks 4022, which is formed by vertically contacting distributing bricks. The distributing bricks have vertically honeycomb-shaped square channels inside. The bottom surface of the mixing chamber 402 is provided with equally spaced square hollow steel sections 221. Strip-shaped notches 222 are provided on both sides of the bottom of the distributing section. The distributing bricks are placed vertically on the square hollow steel sections 221. The strip-shaped notches 222 on the distributing section are in close contact with the upper end face and side face of the square hollow steel sections 221, specifically as follows... Figure 2 and Figure 5 As shown, preferably, the square hollow steel section 221 is wrapped with a PFA liner, and a PTFE gasket is placed between the square hollow steel section 221 and the distribution brick. The center-to-center distance between any two square hollow steel sections 221 is based on the width of the distribution brick in the direction between the two square hollow steel sections 221, specifically as follows: Figure 2 As shown.

[0101] The ratio of the height of the distribution brick layer 4022 to the height of the mixing chamber 402 is (150-450):1540, preferably (200-400):1540, and more preferably (250-350):1540.

[0102] The ratio of the cross-sectional area of ​​the distribution brick to the cross-sectional area of ​​the distribution brick layer 4022 is (80-220):1225, preferably (100-200):1225, and more preferably (120-180):1225.

[0103] The process gas inlet 403 is connected to the bottom of the mixing chamber 402. After the process gas enters the mixing chamber 402 through the process gas inlet 403, it is dispersed by the distribution brick layer 4022. Inside the mixing chamber 402, it is fully mixed with the hot air entering through the hot air distributor 401, and then discharged through the process gas outlet 404 on the side. The process gas inlet 403 is lined with a PFA layer to prevent corrosion from acidic gases.

[0104] The ratio of the cross-sectional area of ​​the process gas inlet 403 to the cross-sectional area of ​​the distribution brick layer 4022 is (0.9-2.7):5, preferably (1.1-2.3):5, and more preferably (1.3-1.9):5.

[0105] The diameter ratio of the process air inlet 403 to the hot air distributor 401 is (0.6-1.6):1, preferably (0.7-1.4):1, and more preferably (0.8-1.2):1.

[0106] Preferably, the process gas inlet 403 is provided with a pressure sensor monitoring port and / or a temperature monitoring port, which are used to house the pressure sensor and the temperature sensor, respectively.

[0107] The waste sulfuric acid regeneration process gas, after being treated by the demister unit 400, is mixed with hot air at 380-440°C in the mixer 4. The flow ratio of the waste sulfuric acid regeneration process gas to the hot air is (1.4-2):1, preferably (1.4-1.8):1, and more preferably (1.5-1.6):1. The temperature of the mixed process gas exiting the mixer 4 is 165-235°C, preferably 175-215°C, and more preferably 185-195°C. The mixed process gas is then heated to 400-440°C by a multi-stage heat exchanger.

[0108] Preferably, the heating unit 500 includes a preheater 5, a heat exchanger II 7, and a heat exchanger III 8, with a fan 6 installed after the preheater 5 to control the outlet pressure of the mixed process gas to 2-2.5 kPag.

[0109] After passing through preheater 5, the temperature of the mixed process gas is 190-230℃, preferably 195-220℃, and more preferably 200-210℃. After passing through heat exchanger II 7, the temperature of the mixed process gas is 310-410℃, preferably 330-390℃, and more preferably 350-370℃. After passing through heat exchanger III 8, the temperature of the mixed process gas is 370-480℃, preferably 390-460℃, and more preferably 400-440℃.

[0110] The preheater 5, heat exchanger II 7, and heat exchanger III 8 are preferably finned heat exchangers, and the heat transfer medium is molten salt.

[0111] Preferably, the heating unit 500 includes a heater 9, which is an electric heater located at the rear end of the heat exchanger III8. The heater 9 is activated only when the system is just started up and the temperature of the mixed process gas passing through the heat exchanger III8 does not meet the process requirements of the subsequent sulfur dioxide reactor 100.

[0112] In this invention, the molten salt from the sulfur dioxide reactor 100 first enters heat exchanger III8 to heat the process gas, where its temperature decreases from 450-470℃ to 430-450℃. Then, the molten salt enters a molten salt preheater, where its temperature decreases from 430-450℃ to 330-370℃. Subsequently, the molten salt enters heat exchanger I1 from the preheater to cool the high-temperature process gas and recover heat, where its temperature increases from 330-370℃ to approximately 360-400℃. Finally, the molten salt enters heat exchanger II7 to heat the mixed process gas exiting from blower 6, where its temperature decreases from 360-400℃ to approximately 300-340℃. The molten salt exiting heat exchanger II7 is ultimately incorporated into the molten salt pipeline and sent to the steam generator to generate steam.

[0113] The improved wet pyrolysis waste sulfuric acid regeneration system of this invention has the following beneficial effects:

[0114] (1) The improved wet pyrolysis waste sulfuric acid regeneration system in this utility model is equipped with a dehydration unit 300 to achieve dehydration and water control of the waste sulfuric acid regeneration process gas, and to accurately control the ratio of water and sulfur dioxide in the process gas to meet the optimal acid formation conditions at the bottom of the sulfuric acid cooler 200.

[0115] (2) Set up a comprehensive heat exchanger with molten salt before and after dehydration and water control to optimize the heat exchange network;

[0116] (3) A wet electrostatic precipitator 3 is installed at the dehydration and water control outlet to reduce acid mist entrainment;

[0117] (4) The drainage water cooled by dehydration and water control is equipped with an air-lift device washing water degassing skid 10 to recover the sulfur dioxide dissolved in the drainage water and improve the yield of sulfuric acid.

[0118] (5) After dehydration and water control, a new type of mixer 4 is set up to inject high-temperature air into the low-temperature acidic process gas to avoid dew point corrosion caused by operation fluctuations.

[0119] Example

[0120] After decomposition at 1100℃, waste sulfuric acid is cooled to obtain waste sulfuric acid regeneration process gas at 500-530℃, with a flux of 7892 Nm³. 3 A flow rate of 24716 kg / h enters finned tube heat exchanger I1 and is cooled to 410-430℃. The cooling medium of heat exchanger I1 is a hot molten salt mixture of potassium nitrate, sodium nitrate and sodium nitrite in a mass ratio of 53:7:40. The measured outlet temperature is 384℃ and the flow rate is 24716 kg / h.

[0121] The waste sulfuric acid regeneration process gas at 410-430℃ has a velocity of 7892 Nm³. 3 A flow rate of 55,000 kg / h of dilute sulfuric acid with a mass concentration of approximately 1.3% enters the overflow weir 301. The circulating flow rate of the sulfuric acid is 55,000 kg / h, and the temperature is 55°C. The sulfuric acid enters the annular groove of the overflow weir 301 and flows down the inner wall of the primary spray tank 302 to protect the primary spray tank 302 and prevent its inner wall from being corroded by the high-temperature waste sulfuric acid regeneration process gas.

[0122] After the waste sulfuric acid regeneration process gas flows out from the overflow weir 301, it enters the first-stage spray tank 302 from the top. Dilute sulfuric acid with a mass concentration of about 1.3% is sprayed into the tank at a flow rate of 110,000 kg / h at the bottom, and the gas is convectively contacted to cool down the waste sulfuric acid regeneration process gas.

[0123] The waste sulfuric acid regeneration process gas enters from the bottom of the secondary spray tank 303, and comes into direct contact with the dilute sulfuric acid sprayed from the upper part, which has a mass concentration of approximately 1.3%, a flow rate of 80,000 kg / h, and a temperature of 55°C. Afterward, it exits from the top through the demister 304 above the spray head. At this point, the temperature of the waste sulfuric acid regeneration process gas is approximately 55°C, the moisture content is approximately 16.1 wt%, and the SO2 content is 13.5 wt%.

[0124] The approximately 1.3wt% dilute sulfuric acid discharged from the bottom of the secondary spray tank 303 is sent to the overflow weir 301, the primary spray tank 302, the dilute sulfuric acid cooler I 14, and the dilute sulfuric acid cooler II 15 at flow rates of 55,000 kg / h, 110,000 kg / h, 72,000 kg / h, and 72,000 kg / h respectively, via the dilute sulfuric acid filter 12 and the jet scrubbing tower pump 13. The remaining dilute sulfuric acid is sent to the top of the washing water degassing skid 10. After being cooled by the dilute sulfuric acid cooler I 14 and the dilute sulfuric acid cooler II 15, the temperature of the dilute sulfuric acid is 40℃, and it is then sent to the spray head of the secondary spray tank 303 at a flow rate of 80,000 kg / h.

[0125] The remaining dilute sulfuric acid is sent to the washing water degassing skid 10, with a flow rate of 77.95 Nm³ at the bottom. 3 The SO2 in dilute sulfuric acid is recovered by air convection contact at a temperature of 20°C per hour and then sent back to the secondary spray tank 303.

[0126] The waste sulfuric acid regeneration process gas discharged from the top of the secondary spray tank 303 has a velocity of 6928 Nm³. 3 The waste sulfuric acid regeneration process gas enters the wet electrostatic precipitator 3 at a flow rate of approximately 4500 kg / h. The wet electrostatic precipitator 3 is intermittently sprayed with deionized water at a flow rate of approximately 4500 kg / h to clean the internal anode tubes and cathode wires. After treatment, the gas is discharged from the top of the wet electrostatic precipitator 3 at a temperature of 55℃, with a moisture content of 16.1 wt% and an SO2 content of 13.5 wt%.

[0127] The waste sulfuric acid regeneration process gas exiting the wet electrostatic precipitator 3 has a concentration of 6928 Nm³. 3 An airflow of 4467 Nm³ / h enters mixer 4 and mixes with air at 400°C. 3 The process gas was mixed at a temperature of 182°C, and the moisture content was 9.8 wt% and the SO2 content was 8.2 wt%.

[0128] The mixed process gas has a concentration of 11395.6 Nm³. 3 The gas flows sequentially from preheater 5 to fan 6 at a flow rate of [flow rate] / h. The heating medium in preheater 5 is 280℃ steam. The mixed process gas temperature at the outlet of fan 6 is approximately 210℃. Then, at a flow rate of 11395.6 Nm³... 3 The flow rate of the mixed process gas sequentially enters finned tube heat exchanger II7 and finned tube heat exchanger III8. The temperature of the mixed process gas at the outlet of finned tube heat exchanger II7 rises to 361°C, and the heating medium for heat exchanger II7 is hot molten salt at 384°C. The temperature of the mixed process gas at the outlet of finned tube heat exchanger III8 rises to 406°C, and the heating medium for heat exchanger III8 is hot molten salt at 461°C.

[0129] Heater 9 is installed at the rear end of heat exchanger Ⅲ8. When the system is started, it is used to assist heat exchanger Ⅲ8, and the temperature of the mixed process gas entering sulfur dioxide reactor 100 is raised to 406°C.

[0130] Hot molten salt from sulfur dioxide reactor 100 first enters finned tube heat exchanger III8 to heat the process gas, where its temperature decreases from approximately 461°C to approximately 438°C. Then, the hot molten salt enters a hot molten salt preheater, where its temperature decreases from approximately 438°C to approximately 348°C. Subsequently, the hot molten salt enters finned tube heat exchanger I1 to cool the high-temperature process gas and recover heat, where its temperature increases from approximately 348°C to approximately 384°C. Finally, the hot molten salt enters finned tube heat exchanger II7 to heat the process gas exiting fan 6, where its temperature decreases from approximately 384°C to approximately 316°C. The hot molten salt exiting finned tube heat exchanger II7 is ultimately incorporated into the hot molten salt pipeline and sent to the steam generator to produce steam.

[0131] The mixed process gas reacts in sulfur dioxide reactor 100, where the catalyst is a vanadium-based catalyst (BASF CAT.O4-110 / O4-111 / O4-115 / O4-116 combined catalyst). The reaction temperature is approximately 400°C. The gas then enters sulfuric acid cooler 200 for condensation to obtain concentrated sulfuric acid. The process gas in sulfuric acid cooler 200 is cooled to approximately 110°C, and its concentration is 98.3 wt%, which is higher than the 95-97 wt% of the product obtained by existing wet waste sulfuric acid regeneration processes.

[0132] The present invention has been described in detail above with reference to specific embodiments and accompanying drawings. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the present invention, and all such modifications and improvements fall within the scope of the present invention. The protection scope of the present invention is defined by the appended claims.

Claims

1. An improved wet pyrolysis waste sulfuric acid regeneration system, characterized in that, The regeneration system includes a dehydration unit (300), a demisting unit (400), a heating unit (500), a sulfur dioxide reactor (100), and a sulfuric acid cooler (200) connected in sequence. The dewatering unit (300) includes an overflow weir (301), a primary spray tank (302), and a secondary spray tank (303). The overflow weir (301) is located at the top of the primary spray tank (302); the bottom of the primary spray tank (302) is provided with upward spray nozzles; The primary spray tank (302) has an outlet near its bottom; The secondary spray tank (303) is equipped with a downward spray head at its upper part; A demister (304) is installed above the spray head on the upper part of the secondary spray tank (303). The demisting unit (400) includes a wet electrostatic precipitator (3), which contains multiple vertical anode tubes and cathode wires, forming a high-voltage electrostatic field in the anode tubes and cathode wires; The heating unit (500) includes a mixer (4) and a multi-stage heat exchanger.

2. The regeneration system according to claim 1, characterized in that, The bottom of the secondary spray tank (303) is provided with a dilute sulfuric acid outlet, and the dilute sulfuric acid outlet of the secondary spray tank (303) is connected to the dilute sulfuric acid filter (12).

3. The regeneration system according to claim 1, characterized in that, The mixer (4) includes a hot air distributor (401), a mixing chamber (402), a process gas inlet (403), and a mixed gas process gas outlet (404). The mixing chamber (402) is provided with a process gas inlet (403) at the bottom and a mixed process gas outlet (404) at the top; the bottom end of the mixed process gas outlet (404) is connected to the top of the mixing chamber, and the outlet is located on the side, in the shape of an inverted L. The hot air distributor (401) is a long cylindrical shape and is inserted from the top of the mixed process gas outlet (404); the bottom of the hot air distributor (401) is located in the middle or upper region of the mixing chamber (402).

4. The regeneration system according to claim 3, characterized in that, The lower section of the hot air distributor (401) is provided with evenly distributed distribution holes (4011).

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