Method for preparing sulfuric acid through double-phase destructive distillation of sulfur foam generated by desulfurization system

Abstract

The invention discloses a method for preparing sulfuric acid by double-phase destructive distillation of sulfur foam generated by a desulfurization system, which comprises the following steps: 1) pretreatment: concentrating dilute sulfur foam into 20-51% concentrated sulfur slurry, melting sulfur to obtain 95-100% high-purity hot sulfur slurry and waste liquid, and evaporating and concentrating the waste liquid into 50-73% hot salt slurry; 2) incineration and purification: respectively conveying the hot sulfur slurry and the hot salt slurry to an efficient mixed incineration device for incineration, and treating furnace gas through a waste heat boiler and a purification device to obtain 10-20% dilute sulfuric acid; 3) two-conversion and two-absorption treatment: carrying out drying, catalytic conversion and absorption on the purified furnace gas, and concentrating into 93-98% concentrated sulfuric acid; and 4) tail gas treatment: treating the acid-making tail gas by an activated carbon desulfurizer and a catalyst, and then emptying or intensively treating the acid-making tail gas. The method realizes efficient utilization of sulfur and waste liquid, and is simple in process flow, low in energy consumption, remarkable in environmental protection benefit and suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of sulfuric acid preparation, and specifically refers to a method for preparing sulfuric acid by double dry distillation of sulfur foam generated by a desulfurization system. Background Art

[0002] In the existing sulfur foam and waste liquid acid production, it is mainly divided into three acid production methods: dry method, semi-dry method and wet method. The main problems existing in the current three acid production processes are as follows:

[0003] 1) When using the dry acid production method, the moisture in the slurry in the pretreatment section is overly dried to make dry sulfur salt powder, resulting in the addition of many devices; and dust and pungent odors overflow and fill the production workshop, affecting the operating environment; the degree of automation in the pretreatment is not high, and the manual labor intensity is large; the exhaust gas emission from drying is large and difficult to meet the discharge standards for treatment; the swelling of the desulfurization system cannot be solved, and the by-salt in the desulfurization liquid is high;

[0004] 2) When using the wet acid production method, due to too much moisture in the slurry in the pretreatment section entering the incinerator, the dilute acid generated by incineration contains too much water, resulting in incomplete digestion in the ammonium sulfate workshop and causing the system to swell. The excess dilute acid requires an increase in the cost and difficulty of secondary treatment; and the combustion heat is insufficient and oxygen-enriched combustion needs to be provided, which increases the generation of dilute acid and the production cost; the acid production load <70 seriously corrodes the equipment; a large number of sulfur foam storage tanks are required for maintenance;

[0005] 3) When using the semi-dry acid production method, the production efficiency of the main equipment is not high, and many devices need to be added to adjust the slurry concentration. Due to poor atomization effect and easy blockage of the nozzle, a filtration and slag discharge system needs to be added; the impurities in the sulfur slurry are filtered and discharged outside to the coal pile, bringing pungent odors to the production workshop, causing secondary pollution and increasing the difficulty of environmental protection acceptance of the system; when the salt slurry is sprayed into the horizontal incinerator, due to the short falling space of the salt slurry and insufficient cracking time, a large amount of salt mixture is generated at the bottom of the horizontal incinerator, which is extremely hard and very difficult to remove. Moreover, the maintenance space of the horizontal incinerator is too low for manual maintenance, and the horizontal waste heat boiler is also prone to blockage due to the introduction of salt and other mixtures and requires frequent maintenance, affecting normal production; the swelling of the desulfurization system cannot be solved, and the by-salt in the desulfurization liquid is high.

[0006] Therefore, there is an urgent need for a method for preparing sulfuric acid by dry distillation of sulfur and waste liquid generated by a desulfurization system, which has important economic value and environmental protection significance. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned technical defects and provide a method for preparing sulfuric acid by double dry distillation of sulfur foam generated by a desulfurization system.

[0008] To solve the above technical problem, the technical solution provided by the present invention is a method for preparing sulfuric acid by double dry distillation of sulfur foam generated by a desulfurization system, including the following steps:

[0009] Step 1) Pretreatment

[0010] The dilute sulfur foam generated by the desulfurization system enters a high-efficiency centrifugal device to be concentrated into a concentrated sulfur pulp with a concentration of 20 - 51% and stored in a concentrated sulfur foam storage tank. Then, the concentrated sulfur foam is transported to a high-efficiency sulfur melting device. After sulfur melting, high-purity hot sulfur pulp with a purity of 95 - 100% and waste liquid can be obtained;

[0011] The waste liquid is evaporated and concentrated by a high-efficiency evaporation device into a hot salt pulp with a concentration of 50 - 73%;

[0012] Step 2) Incineration and purification

[0013] The obtained hot sulfur pulp is transported to the bottom of a high-efficiency mixing incinerator, and the obtained hot salt pulp is transported to the middle and upper parts of the high-efficiency mixing incinerator. After atomization, it is sprayed into the incinerator, so that the sulfur and salt in it fully react and crack after incineration treatment;

[0014] The high-temperature furnace gas generated after incineration recovers heat through an anti-blocking waste heat boiler, and the furnace gas temperature drops to 320 - 450°C. Then, the furnace gas is washed by a purification device to remove dust and impurities;

[0015] Dilute sulfuric acid can be obtained in the desorption tower and is transported to the ammonium sulfate system for recycling;

[0016] Step 3) Two-stage conversion and two-stage absorption treatment

[0017] The purified furnace gas obtained enters a dryer tower for drying and then enters a converter. Under the condition of 320 - 450°C, SO2 in the furnace gas containing water vapor is oxidized to SO3 under the action of a catalyst. After the converted gas mixture is treated in the first absorption tower, it is transported to the converter and the second absorption tower again, so that SO3 undergoes hydration and condensation, and is concentrated into concentrated sulfuric acid with a concentration of 93 - 98% under the condition of about 250°C. At the same time, acid-making tail gas can be obtained;

[0018] Step 4) Tail gas treatment section

[0019] The obtained acid-making tail gas enters a tail gas treatment device containing activated carbon desulfurizer and catalyst to adsorb SO2 gas in the gas, and at the same time reacts with oxygen and water in the tail gas to produce sulfuric acid under the action of the catalyst, and then is washed and regenerated with different dilute sulfuric acids. The tail gas meets the standards and is discharged or discharged into the coke oven chimney for centralized treatment.

[0020] Furthermore, the incineration temperature of the high-efficiency mixing incinerator in Step 2 is 1000 - 1100°C.

[0021] Furthermore, the concentration of the dilute sulfuric acid generated in the desorption tower in Step 2 is 10 - 20%.

[0022] Further, the heat recovered by the anti-blocking waste heat boiler in step 2 is used to generate saturated steam, and the generated steam is depressurized and then incorporated into the plant for centralized use.

[0023] Further, the purification device in step 2 includes a kinetic wave scrubber, a desorption tower, a cooling tower, and an electrostatic demister.

[0024] Further, the catalyst used in step 3 is vanadium pentoxide.

[0025] The advantages of the present invention compared with the prior art are as follows:

[0026] 1) In the method provided by the present invention, there is no discharge of waste residue and waste liquid during application, no irritating odor and dust leakage, and no secondary pollution to the production workshop and the surrounding environment;

[0027] 2) The process flow of the method provided by the present invention is short, the floor area is small, the equipment is few, and the investment is saved by more than 25%;

[0028] 3) The core equipment in the method provided by the present invention has high production efficiency and saves production costs, including a high-efficiency centrifugal device, a high-efficiency sulfur melting device, a high-efficiency evaporation device, and a special incineration device, etc.;

[0029] 4) The pure sulfur slurry and the concentrated salt slurry have low water content and high ignition point when fed. After entering the incinerator, they can quickly release heat, and the heat balance in the incinerator can be maintained by their own heat release. During normal production, no gas or oxygen-enriched combustion is required, reducing the operating cost.

[0030] 5) The production and maintenance methods in the method provided by the present invention are flexible. According to needs, either mixed salt and sulfur can be used to produce sulfuric acid, or the two materials can be used to produce sulfuric acid separately. Moreover, the low-quality sulfur paste and by-product salts in the original inventory can be dissolved and then used to produce sulfuric acid. When the sulfuric acid production system is under maintenance, the sulfur can be made into slices for storage or sale, and the filtered clear liquid can be returned to the desulfurization system for reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a process flow chart of a method for preparing sulfuric acid by double-phase dry distillation of sulfur foam generated by a desulfurization system according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following further elaborates on a method for preparing sulfuric acid by double-phase dry distillation of sulfur foam generated by a desulfurization system according to the present invention in conjunction with embodiments.

[0033] Example 1

[0034] 1) Pretreatment:

[0035] The desulfurization system needs to process 100 cubic meters of sulfur foam per hour. The sulfur foam is concentrated by a high-efficiency centrifugal device. 50 cubic meters of concentrated sulfur liquid per hour is transported to the high-efficiency sulfur melting device by a transfer pump under a pressure of 12 kg. The pressure inside is maintained at 0.48 MPa and heated by 180°C steam through a coil. 25 cubic meters of desulfurized waste liquid from the high-efficiency sulfur melting device and 50 cubic meters of waste liquid separated by the high-efficiency centrifugal device enter the high-efficiency evaporation device together to be evaporated and concentrated into a 70% hot salt slurry. 52.50 cubic meters of clear liquid after condensation in the condensation tower is returned to the desulfurization system for reuse or used in the cold drum section;

[0036] 2) Incineration and purification:

[0037] The hot sulfur slurry is transported to the bottom of the high-efficiency mixing incineration device, and the hot salt slurry is transported to the middle and upper parts of the device. After atomization, it is sprayed into the incineration. The incineration temperature of the high-efficiency mixing incineration device is controlled at 1050°C to make sulfur and salt fully react and crack. The specific reactions are as follows:

[0038] Reaction: S + O2 = SO2

[0039] Cracking: NH4SCN + 3O2 = N2 + CO2 + SO2 + 2H2O

[0040] 2(NH4)2S2O3 + 5O2 = 2N2 + 4SO2 + 8H2O

[0041] (NH4)2S2O3 + O2 = N2 + 2SO2 + 4H2O

[0042] 2(NH4)2CO3 + 3O2 = 2N2 + 2CO2 + 8H2O

[0043] (NH4)2S6 + 8O2 = N2 + 6SO2 + 4H2O

[0044] 4NH3 + 3O2 = 2N2 + 6H2O

[0045] The high-temperature furnace gas generated after incineration enters the anti-blocking waste heat boiler to recover heat. The temperature of the furnace gas drops to 450°C. The heat recovered by the anti-blocking waste heat boiler is used to generate saturated steam. After the steam is depressurized, it is incorporated into the plant for centralized use;

[0046] The furnace gas after the waste heat boiler absorbs the waste heat enters the dynamic wave scrubber to be washed with the circulating dilute acid of the reverse spray pipe. The wet furnace gas at the outlet of the dynamic wave scrubber enters the packed scrubber to be washed and purified again with the cooling circulating dilute acid sprayed from the top of the tower. After removing the impurities and steam therein, it enters the electric demister to remove acid mist, dust and impurities. The purified furnace gas is sent to the drying tower in the drying and absorption section;

[0047] 3) Two-stage conversion and two-stage absorption treatment:

[0048] The cold gas dried in the drying tower and demisted by the wire mesh demister at the top of the tower is boosted by the SO2 blower and then enters the III heat exchanger and the I heat exchanger in sequence. After being heated, the temperature rises to 420 °C and enters the first stage of the converter for conversion. After the reaction, the furnace gas temperature rises to about 450 °C and enters the I heat exchanger to exchange heat with the cold gas from the SO2 blower for cooling. The cooled furnace gas enters the catalyst bed of the second stage of the converter for catalytic reaction, and then exits the converter and enters the II heat exchanger to cool down and then enters the catalyst bed of the third stage of the converter for further reaction. The gas exiting from the third stage of the converter enters the tube side of the III heat exchanger, the temperature drops to 175 °C and enters the first absorption tower to absorb SO3 in the gas. After removing the acid mist in the gas through the wire mesh demister at the top of the tower, it enters the V heat exchanger, the IV heat exchanger, and the II heat exchanger in sequence. The gas is heated to 420 °C and enters the catalyst bed of the fourth stage of the converter for the second conversion. The gas exiting from the fourth stage bed enters the IV heat exchanger to exchange heat and cool with the cold furnace gas, and the temperature drops to 410 °C and enters the catalyst bed of the fifth stage of the converter for catalytic reaction. The gas exiting from the fifth stage bed enters the V heat exchanger to exchange heat and cool with the cold furnace gas, and the temperature drops to about 155 °C and enters the second absorption tower to absorb a small amount of SO3 in the gas;

[0049] To raise the temperature of the furnace gas during startup, an electric heater is installed at the inlet of each of the first and fourth stages of the catalyst. To adjust and control the temperature in the conversion section, necessary process pipeline bypasses are set;

[0050] Furnace gas condensation stage: The furnace gas containing SO3 coming out of the conversion stage enters the acid gas condenser for cooling. SO3 in the furnace gas undergoes hydration and condensation into concentrated sulfuric acid. The reaction formula is: SO3 + H2O = H2SO4;

[0051] The heat generated in the drying tower and the absorption tower is carried away by their respective circulating acids, and the heat is removed by cooling water in their respective concentrated acid heat exchangers. To maintain the balance of the circulating acid concentration in each tower, the 94% sulfuric acid produced in the drying tower is cascaded to the absorption tower, and at the same time, the corresponding 98% sulfuric acid is cascaded back from the absorption tower to the drying tower to keep the acid concentration and water balance in the drying tower circulation system;

[0052] The drying and absorption unit maintains the circulating acid concentration in each tower and the liquid level in the circulation tank by acid cascading, adding water, and producing finished acid. The cooling circulating water connection method of the drying and absorption acid coolers is in parallel, and after heat exchange, it enters the circulating water station for cooling. The obtained finished sulfuric acid with a concentration of 93% - 98% is led out from the absorption acid cooler or the outlet of the SO2 removal tower respectively, flows to the underground tank of the finished acid, and is cooled to 38 °C by the finished acid pump through the finished acid cooler and then sent to the acid-using workshop or the sulfuric acid tank area.

[0053] 4) Tail gas treatment section:

[0054] When the SO2 in the acid-making tail gas passes through the bed layer of the treatment device, it is selectively adsorbed by the desulfurizer and reacts with the oxygen and water in the tail gas under the action of the catalyst to form sulfuric acid, which is stored in the micropores of the catalyst. When the sulfuric acid in the catalyst reaches a certain saturation concentration, it is washed.

[0055] The tail gas treatment adopts a cascade cyclic regeneration method. By using dilute acids with different concentrations for staged leaching, the sulfuric acid in the bed layer is finally converted into the regeneration liquid, the activity of the desulfurizer is restored, and at the same time, a dilute acid product with a concentration of 5% - 20% is obtained and sent to the drying and absorption section for diluting concentrated sulfuric acid. The bed layer of the desulfurization unit after regeneration is relatively wet, and the carrier of the catalyst is a hydrophobic activated carbon material. It is left to stand and drain before being reused. After being treated in the tail gas treatment device, it meets the standards and is discharged. The clean tail gas meets the "Emission Standards for Pollutants in Coking Chemical Industry" and is discharged up to the standard through the chimney, or the tail gas from the absorption tower is sent to the coke oven chimney for centralized treatment. The process flow is short, and the investment and production costs are also saved.

[0056] The device and equipment described in the present invention can be equipped with intelligent control, and the production workshop can achieve unattended operation, enabling the equipment and devices in each section to be linked for intelligent production.

[0057] The above embodiments are only partial implementation manners of the present invention. In actual applications, the process parameters, etc. can be appropriately adjusted according to specific requirements. Through the method of the present invention, high-purity sulfuric acid can be efficiently and environmentally prepared by using the sulfur and waste liquid generated by the desulfurization system, and it has broad application prospects.

[0058] The above describes the present invention and its implementation manners. This description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. All in all, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative work without departing from the purpose of the present invention's creation, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing sulfuric acid by double-phase dry distillation of sulfur foam generated by a desulfurization system, characterized in that, It includes the following steps: Step 1) Pretreatment The dilute sulfur foam generated by the desulfurization system enters a high-efficiency centrifugal device to be concentrated into a concentrated sulfur slurry with a concentration of 20-51% and stored in a concentrated sulfur foam storage tank. Then, the concentrated sulfur foam is transported to a high-efficiency sulfur melting device. After sulfur melting, high-purity hot sulfur slurry with a purity of 95-100% and waste liquid can be obtained; The waste liquid is evaporated and concentrated by a high-efficiency evaporation device into a hot salt slurry with a concentration of 50-73%; Step 2) Incineration and purification The obtained hot sulfur slurry is transported to the bottom of a high-efficiency mixed incineration device, and the obtained hot salt slurry is transported to the middle and upper parts of the high-efficiency mixed incineration device. After atomization, it is sprayed into the incinerator so that the sulfur and salt in it fully react and crack after incineration treatment; The high-temperature furnace gas generated after incineration recovers heat through an anti-blocking waste heat boiler, and the temperature of the furnace gas drops to 320-450°C. Then, the furnace gas is washed by a purification device to remove dust and impurities; Dilute sulfuric acid can be obtained in the desorption tower and is transported to the ammonium sulfate system for recycling; Step 3) Two-stage conversion and two-stage absorption treatment The purified furnace gas obtained enters a dryer tower for drying and then enters a converter. Under the condition of 320-450°C, SO2 in the furnace gas containing water vapor is oxidized to SO3 under the action of a catalyst. After the converted gas mixture enters the first absorption tower for treatment, it is transported to the converter and the second absorption tower again. SO3 undergoes hydration and condensation to be concentrated into concentrated sulfuric acid with a concentration of 93-98% under the condition of about 250°C, and at the same time, acid-making tail gas can be obtained; Step 4) Tail gas treatment section The obtained acid-making tail gas enters a tail gas treatment device containing activated carbon desulfurizer and catalyst to adsorb SO2 gas in the gas, and at the same time reacts with oxygen and water in the tail gas to generate sulfuric acid under the action of the catalyst, and then is washed and regenerated with different dilute sulfuric acids. The tail gas meets the standards and is discharged or discharged into the coke oven chimney for centralized treatment.

2. The method according to claim 1, characterized in that, The incineration temperature of the high-efficiency mixed incineration device in Step 2 is 1000-1100°C.

3. The method according to claim 1, wherein The concentration of the dilute sulfuric acid generated in the desorption tower in Step 2 is 10-20%.

4. The method according to claim 1, wherein The heat recovered by the anti-blocking waste heat boiler in Step 2 is used to generate saturated steam, and the generated steam is depressurized and incorporated into the centralized use of the factory area.

5. The method according to claim 1, wherein The purification device in Step 2 includes a kinetic wave scrubber, a desorption tower, a cooling tower and an electrostatic demister.

6. The method according to claim 1, wherein The catalyst used in Step 3 is vanadium pentoxide.

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