A dry process for acid production from viscose fibre plant off-gas

Abstract

The present application relates to a kind of dry method for viscose fiber factory waste gas recovery, including the following sequentially performed steps: (1) waste gas incineration;(2) purification;(3) deacidification mist;(4) drying;(5) sulfur combustion;(6) high temperature furnace gas B is imported into the acid making device to obtain finished product concentrated sulfuric acid.The present application overcomes the shortcomings of existing viscose factory waste gas acid making process equipment, such as easy to be corroded, frequent shutdown, difficult to maintain, low acid production, easy to escape sulfur waste gas, easy to mix furnace gas and external air, low economic benefit, complex process, and many by-products, etc.By adding liquid sulfur mixed combustion, controlling the temperature of each step, setting a booster fan in the front section of the drying tower, a main fan in the rear section, and reasonably arranging the inlet positions of furnace gas and external air, the present application has the advantages of simple process, large-scale acid production, no sulfur waste gas escaping, more environmentally friendly, no mixing of furnace gas and external air, high economic benefit, few by-products, and low maintenance cost.

Description

Technical Field

[0001] This invention relates to a dry acidification process for waste gas recovery in viscose fiber factories, applicable to the viscose fiber production industry. Background Technology

[0002] The production process of viscose fiber generates a large amount of sulfur-containing waste gas. Among them, the sulfur-containing waste gas from the acid station workshop is called rich gas. This waste gas is characterized by a small gas volume and a high H2S concentration. Since sulfuric acid is one of the raw and auxiliary materials required for viscose fiber production, recovering hydrogen sulfide (H2S) in the rich gas and converting it into sulfuric acid is a relatively common treatment method. The process of producing sulfuric acid using hydrogen sulfide acidic gas as raw material can be divided into two types of acid production processes according to the process conditions of sulfur dioxide catalytic conversion: dry acid production and wet acid production ("A Review of the Principle and Process of Sulfuric Acid Production from Refinery Acid Gas" [J]. Sulfur and Phosphorus Design and Powder Engineering, 2010(06):5-17+51). Wet acid production technology has a simple process flow and is considered the best process for treating hydrogen sulfide-containing waste gas (Introduction to Lenzing (Nanjing) Viscose Waste Gas Wet Acid Production Unit [C]. / / Proceedings of the 35th China Sulfur and Sulfuric Acid Technology Conference (2015). 2015:64-66.). Existing viscose fiber factories also mostly use wet acid production technology to treat waste gas. However, in actual use in our unit, wet acid production units often encounter problems such as equipment corrosion, difficult maintenance, and frequent shutdowns leading to low acid production.

[0003] While dry acid production processes are beneficial for reducing equipment corrosion, viscose fiber plants using dry acid production processes with waste gas as the sole raw material face challenges such as insufficient waste gas volume, small acid production scale, and low economic efficiency. To address the issue of insufficient waste gas volume, waste gas and sulfur are often used together as raw materials for acid production. Patent document CN201410651147.7 discloses a method for combined sulfur and waste gas acid production, primarily addressing the problems of low equipment utilization and insufficient system load due to insufficient waste gas volume when using existing acid production methods alone, necessitating the activation of electric furnaces for heat compensation, leading to system fluctuations and increased electricity costs. By combining two acid production methods, this method improves the utilization rate of both units, reduces production costs, and extends equipment lifespan, offering the advantage of low cost. However, this process requires two acid conversion units, resulting in high investment and maintenance costs. Patent document CN 201811433117.3 discloses a process and system for the combined production of sulfur from adhesive waste gas (TRS) and sulfuric acid. It utilizes a newly designed TRS sulfur melting tank to melt TRS sulfur, which is then initially purified before incineration. The resulting SO2 flue gas is mixed with H2S waste gas and then subjected to secondary combustion in a waste gas incinerator. The SO2 concentration is first adjusted, and then the gas is cooled through three washing cycles in a purification system to form pure SO2 flue gas. Finally, qualified sulfuric acid is produced through conversion and absorption. Although this patent uses a single sulfuric acid production unit, its process route is complex, the acid production scale is small, and it suffers from problems such as large heat loss and difficulty in treating sulfur slag and desulfurization waste liquid.

[0004] Furthermore, if viscose fiber factories adopt a dry acid production process where the flue gas generated from the combustion of waste gas is sent to the drying tower of the sulfuric acid production unit for drying, there are problems such as a large amount of flue gas byproducts generated from the combustion of waste gas, low air pressure in the drying tower, easy cross-contamination with the outside air entering the drying tower, and environmental pollution. On the other hand, if a dry acid production process is adopted where the flue gas generated from the combustion of waste gas is sent to a dedicated drying tower for drying, and then the dried flue gas is incorporated into the sulfuric acid production unit, there are problems such as a large amount of flue gas byproducts generated from the combustion of waste gas, large investment, and high maintenance costs.

[0005] Therefore, it has become an urgent task to provide a dry acid production process for the recovery of waste gas from viscose fiber factories that is simple in process, has a large acid production scale, produces few furnace gas by-products from waste gas combustion, does not allow cross-contamination between furnace gas and external air, has high economic benefits, low maintenance costs, low heat loss, and is environmentally friendly. Summary of the Invention

[0006] To overcome the shortcomings of existing wet acid production processes in viscose fiber factories, such as equipment corrosion, frequent shutdowns, difficult maintenance, and low acid yield, and the drawbacks of dry acid production processes, such as small-scale acid production, low economic efficiency, easy cross-contamination between furnace gas and external air, environmental pollution, high investment, and high maintenance costs, this invention provides a dry acid production process for recovering waste gas from viscose fiber factories. This process involves recovering heat from the furnace gas generated by combustion of waste gas, purifying it, removing acid mist, and then drying it together with air fed into a drying tower. The gas is then mixed with liquid sulfur and burned before entering the acid conversion unit. The process parameters are optimized by controlling each step. A booster fan is installed at the front of the drying tower, and a main fan is installed at the rear. The reasonable arrangement of the furnace gas and external air inlets at the bottom of the drying tower results in a simple process, large-scale acid production, greater environmental friendliness, no cross-contamination between furnace gas and external air, high economic efficiency, and low maintenance costs. The technical solution of this invention is as follows:

[0007] A dry acid production process for recovering waste gas from a viscose fiber factory includes the following steps performed in sequence:

[0008] (1) Waste gas incineration

[0009] Sulfur-containing waste gas from the acid station workshop of the viscose fiber factory is mixed with external air filtered by an air filter at a volume ratio of 1:6 to 1:7 and then sent into an incinerator with a furnace temperature of 1000 to 1100°C for combustion to obtain furnace gas A containing sulfur dioxide; then furnace gas A is cooled to 339 to 341°C.

[0010] (2) Purification

[0011] The furnace gas A obtained in step (1) is sent to a dynamic wave scrubber for the first washing and purification. Dilute sulfuric acid with a mass concentration of 5% to 6% is sprayed into the furnace gas A for adiabatic evaporation, which humidifies the furnace gas A and cools it down to 69 to 70°C. Then, the washed and purified furnace gas A is sent to a packed scrubbing tower for the second washing and purification. Dilute sulfuric acid with a mass concentration of 5% to 6% is sprayed into the furnace gas A from the top of the packed scrubbing tower downwards, so that the furnace gas A comes into countercurrent contact with the dilute sulfuric acid, removing impurities and cooling the furnace gas A down to 39 to 40°C.

[0012] (3) Remove acid mist

[0013] Acid mist was removed from the furnace gas A after two-stage purification, reducing the acid mist content in furnace gas A to 5 mg / Nm³. 3 the following;

[0014] (4) Drying

[0015] The drying tower comprises a drying chamber and a bottom chamber connected vertically. An air outlet is located at the top of the drying tower, and air inlets G1 and G2 are respectively located on the side wall of the bottom chamber. One end of the main blower is connected to the air outlet of the drying tower, and the other end is connected to the air inlet of the sulfur incinerator. The furnace gas A, after acid mist removal, is pressurized by a booster blower and enters the bottom chamber through air inlet G1. External air, filtered by an air filter, enters the bottom chamber through air inlet G2. Air inlets G1 and G2 are located at the same horizontal level, with a distance of 2.8–4.2 m between them. The main blower draws the furnace gas A (after acid mist removal) and the external air together into the drying chamber for drying, reducing the moisture content of both to 0.1 g / Nm³. 3 The rated air volume ratio of the booster fan to the main fan is 1:9 to 1:11; the pressure at the outlet of the booster fan is 0.1 to 0.2 kPa, and the pressure inside the bottom chamber is -0.3 to -0.4 kPa.

[0016] (5) Sulfur combustion

[0017] After drying, the furnace gas A and the outside air are transported to the sulfur incinerator by the main blower after exiting the drying tower. At the same time, liquid sulfur is injected into the sulfur incinerator and mixed and burned to generate furnace gas B at 940-960°C. Then, the furnace gas B is cooled to 418-422°C.

[0018] (6) Acid production

[0019] Furnace gas B is introduced into the acid production device. The sulfur dioxide in furnace gas B undergoes an oxidation reaction under the action of a catalyst to produce sulfur trioxide. The sulfur trioxide is absorbed by sulfuric acid with a mass concentration of 98.3%, and then diluted with water to obtain sulfuric acid with a mass concentration of 98%, which is the finished product concentrated sulfuric acid.

[0020] The amount of external air used in step (4) is determined by the amount of oxygen required to ensure the complete combustion of liquid sulfur in step (5) and the complete conversion of sulfur dioxide in furnace gas B into sulfur trioxide in step (6).

[0021] The dry acid production process for recovering waste gas from a viscose fiber factory, as described in this application, incorporates a booster fan at the front of the drying tower to address the issue of insufficient pressure in the transport of sulfur-containing waste gas. Furthermore, this application includes a main fan at the rear of the drying tower and optimizes the arrangement of the furnace gas and external air inlets (inlets G1 and G2 are at the same horizontal level with sufficient spacing) and adjusts the pressure inside the bottom chamber to be lower than the external atmospheric pressure. This resolves the problem of furnace gas escaping into the external environment due to cross-contamination between the furnace gas and external air. This process not only treats hydrogen sulfide-containing waste gas, ensuring its emissions meet environmental protection requirements, but also avoids the problems associated with wet acid production processes, such as equipment corrosion, maintenance difficulties, and frequent shutdowns. It also reduces the high investment and maintenance costs associated with dry acid production using combined waste gas and sulfur. A single acid production unit is sufficient to produce the sulfuric acid needed for viscose fiber production, solving the tail gas emission problem and recovering sulfur resources. It boasts advantages such as environmental friendliness, low maintenance costs, minimal heat loss, and high economic benefits, achieving significant social and economic benefits. It fills the technological gap in rich gas treatment for viscose plants and offers advantages such as environmental protection, practicality, and energy saving. The booster fan and main fan are preferably made of corrosion-resistant materials.

[0022] In step (1), the furnace gas A is cooled and its heat is recovered by a waste heat boiler; in step (2), the furnace gas A is washed and purified for the second time and then cooled and its heat is recovered by a plate heat exchanger; in step (5), the furnace gas B is cooled and its heat is recovered by a waste heat boiler.

[0023] Heat recovery is more energy-efficient and environmentally friendly.

[0024] An oxygen content analyzer is installed on the outlet flue of the waste heat boiler to control the oxygen concentration in the furnace gas A flowing out of the incinerator, so that the volume percentage of oxygen is 10% to 11%.

[0025] By optimizing the amount of oxygen and controlling the reaction temperature at each step, complete combustion of exhaust gas can be ensured, thereby reducing the formation of reaction byproducts such as sulfur monoxide, sulfur trioxide, and nitrogen oxides.

[0026] The inner diameter of the silo is 3.8–4.2 m, and the height is 2.8–3.2 m.

[0027] The drying tower of this application is equipped with a large-capacity bottom chamber. With the reasonable arrangement of air inlets G1 and G2, and by adjusting the pressure inside the bottom chamber to be lower than the external atmospheric pressure, it can further help to avoid cross-contamination between furnace gas and external air.

[0028] In step (3), the furnace gas A, after two-stage purification, is sequentially passed through a primary electrostatic precipitator and a secondary electrostatic precipitator to remove acid mist.

[0029] Setting up a two-stage defogging system improves the defogging effect.

[0030] Both the booster fan and the main fan are corrosion-resistant centrifugal blowers.

[0031] The selected booster fan and main fan are more durable.

[0032] The catalyst in step (6) is vanadium pentoxide.

[0033] The preferred catalysts are common and have high catalytic efficiency.

[0034] In step (5), liquid sulfur is pressurized by a liquid sulfur feed pump and injected into the sulfur incinerator (7) through a sulfur gun.

[0035] This optimization allows for more complete combustion of liquid sulfur.

[0036] Compared with the prior art, this invention application has the following advantages:

[0037] ① This application recovers heat, purifies, and removes acid mist from the furnace gas generated by the combustion of waste gas from viscose fiber factories. After drying, the gas is dried together with the external air fed into the drying tower. Then, it is mixed with liquid sulfur and burned before entering the acid conversion device. The application also optimizes the temperature and process parameters of each step by controlling the temperature. A booster fan is installed at the front of the drying tower and a main fan is installed at the rear. The reasonable arrangement of the furnace gas and external air inlet positions at the bottom of the drying tower solves the problems of equipment corrosion, frequent shutdowns, difficult maintenance, and low acid production in the existing wet acid production process of viscose factory waste gas, as well as the problems of small acid production scale, low economic benefits, easy cross-contamination between furnace gas and external air, environmental pollution, large heat loss, large investment, and high maintenance costs in the dry acid production process. It also avoids the problem of sulfur slag and waste liquid treatment in the process of converting waste gas into sulfur using complexed iron additives. It has the advantages of simple process, large acid production scale, no sulfur waste gas escape, more environmentally friendly, no cross-contamination between furnace gas and external air, high economic benefits, few by-products, and low maintenance costs.

[0038] ② Setting up waste heat boilers and waste heat boilers can recover as much heat as possible. The acid mist removed is also used to prepare sulfuric acid. Recovering this part of the sulfur resources helps to avoid the generation of waste liquid and is more environmentally friendly and energy-saving.

[0039] ③ The oxygen content analyzer is used to optimize the amount of oxygen added, and together with the optimal reaction temperature control of each step, further reduce the generation of reaction byproducts such as sulfur monoxide, sulfur trioxide and nitrogen oxides;

[0040] ④ This application solves the problem of insufficient exhaust gas conveying pressure by combining the booster fan and the main fan;

[0041] ⑤ By rationally arranging the inlet positions of the furnace gas and external air in the bottom chamber of the drying tower, the problem of cross-contamination between the furnace gas and external air is solved, which helps to prevent sulfur dioxide from escaping and causing environmental pollution. Attached Figure Description

[0042] Figure 1 This is a flowchart of the dry acid production process for waste gas recovery in viscose fiber factories, as described in this invention.

[0043] Label Explanation:

[0044] 1. Incinerator, 2. Power wave scrubber, 3. Packed scrubbing tower, 4. Drying tower, 5. Boiler, 6. Main blower, 7. Sulfur incinerator, 8. Acid production unit, 9. Waste heat boiler, 10. Primary electrostatic precipitator, 11. Secondary electrostatic precipitator, 12. Oxygen content analyzer. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figure 1 As shown, the dry acid production process for waste gas recovery in a viscose fiber factory according to the present invention includes the following steps performed in sequence:

[0048] (1) Waste gas incineration

[0049] Sulfur-containing waste gas from the acid station workshop of the viscose fiber factory is mixed with external air filtered by an air filter at a volume ratio of 1:6.5 and then sent into incinerator 1 at a furnace temperature of 1050℃ for combustion to obtain furnace gas A containing sulfur dioxide; then furnace gas A is cooled to 340℃.

[0050] (2) Purification

[0051] The furnace gas A obtained in step (1) is sent to the dynamic wave scrubber 2 for the first washing and purification. The furnace gas A is humidified and cooled to 69.5°C by adiabatic evaporation by spraying 5.6% dilute sulfuric acid from the top of the packed scrubber 3. Then the washed and purified furnace gas A is sent to the packed scrubber 3 for the second washing and purification. The furnace gas A is sprayed with 5.6% dilute sulfuric acid from the top of the packed scrubber 3 downwards, so that the furnace gas A and the dilute sulfuric acid come into countercurrent contact, removing impurities and cooling the furnace gas A to 39.5°C.

[0052] (3) Remove acid mist

[0053] Acid mist was removed from the furnace gas A after two-stage purification, reducing the acid mist content in furnace gas A to 5 mg / Nm³. 3 the following;

[0054] (4) Drying

[0055] The drying tower 4 comprises a drying chamber and a bottom chamber connected sequentially. The top of the drying tower 4 has an air outlet, and the side walls of the bottom chamber have air inlets G1 and G2, respectively. One end of the main blower 6 is connected to the air outlet of the drying tower 4, and the other end is connected to the air inlet of the sulfur incinerator 7. The furnace gas A, after acid mist removal, is pressurized by the booster blower 5 and enters the bottom chamber through air inlet G1. External air, filtered by an air filter, enters the bottom chamber through air inlet G2. Air inlets G1 and G2 are at the same horizontal level and are 3.5m apart. The main blower 6 draws the furnace gas A (after acid mist removal) and the external air together into the drying chamber for drying, reducing the moisture content of both to 0.1g / Nm³. 3 The rated air volume ratio of the booster fan 5 to the main fan 6 is 1:10; the pressure at the outlet of the booster fan 5 is 0.15 kPa, and the pressure inside the bottom chamber is -0.35 kPa.

[0056] (5) Sulfur combustion

[0057] After drying, the furnace gas A and the outside air exit the drying tower 4 and are transported to the sulfur incinerator 7 by the main blower 6. At the same time, liquid sulfur is injected into the sulfur incinerator 7 and mixed and burned to generate furnace gas B at 950°C. Then, the furnace gas B is cooled to 420°C.

[0058] (6) Acid production

[0059] Furnace gas B is introduced into sulfuric acid production device 8. The sulfur dioxide in furnace gas B undergoes an oxidation reaction under the action of a catalyst to produce sulfur trioxide. The sulfur trioxide is absorbed by sulfuric acid with a mass concentration of 98.3%, and then diluted with water to obtain sulfuric acid with a mass concentration of 98%, which is the finished product concentrated sulfuric acid.

[0060] The amount of external air used in step (4) is determined by the amount of oxygen required to ensure the complete combustion of liquid sulfur in step (5) and the complete conversion of sulfur dioxide in furnace gas B into sulfur trioxide in step (6).

[0061] In step (1), the furnace gas A is cooled and its heat is recovered by the waste heat boiler 9; in step (2), the furnace gas A is washed and purified for the second time and then cooled and its heat is recovered by the plate heat exchanger; in step (5), the furnace gas B is cooled and its heat is recovered by the waste heat boiler 10.

[0062] An oxygen content analyzer 13 is installed on the outlet flue of the waste heat boiler 9 to control the oxygen concentration in the furnace gas A flowing out of the incinerator 1, so that the oxygen volume percentage is 10.5%.

[0063] The inner diameter of the silo is 4m and the height is 3m.

[0064] In step (3), the furnace gas A after two-stage purification is passed through a primary electrostatic precipitator 11 and a secondary electrostatic precipitator 12 in sequence to remove acid mist.

[0065] Both the booster fan 5 and the main fan 6 are corrosion-resistant centrifugal blowers.

[0066] The catalyst in step (6) is vanadium pentoxide.

[0067] In step (5), liquid sulfur is pressurized by a liquid sulfur feed pump and injected into the sulfur incinerator 7 through a sulfur gun.

[0068] Example 2

[0069] like Figure 1 As shown, the dry acid production process for waste gas recovery in a viscose fiber factory according to the present invention includes the following steps performed in sequence:

[0070] (1) Waste gas incineration

[0071] Sulfur-containing waste gas from the acid station workshop of the viscose fiber factory is mixed with external air filtered by an air filter at a volume ratio of 1:6 and then sent into incinerator 1 at a furnace temperature of 1100℃ for combustion to obtain furnace gas A containing sulfur dioxide; then furnace gas A is cooled to 339℃.

[0072] (2) Purification

[0073] The furnace gas A obtained in step (1) is sent to the dynamic wave scrubber 2 for the first washing and purification. The furnace gas A is humidified and cooled to 69°C by adiabatic evaporation by spraying 6% dilute sulfuric acid in a circulating manner. Then, the washed and purified furnace gas A is sent to the packed scrubber 3 for the second washing and purification. The furnace gas A is sprayed with 6% dilute sulfuric acid from the top of the packed scrubber 3 downwards, so that the furnace gas A and the dilute sulfuric acid come into countercurrent contact, removing impurities and cooling the furnace gas A to 39°C.

[0074] (3) Remove acid mist

[0075] Acid mist was removed from the furnace gas A after two-stage purification, reducing the acid mist content in furnace gas A to 5 mg / Nm³. 3 the following;

[0076] (4) Drying

[0077] The drying tower 4 comprises a drying chamber and a bottom chamber connected vertically. The top of the drying tower 4 has an air outlet, and the side walls of the bottom chamber have air inlets G1 and G2, respectively. One end of the main blower 6 is connected to the air outlet of the drying tower 4, and the other end is connected to the air inlet of the sulfur incinerator 7. The furnace gas A, after acid mist removal, is pressurized by the booster blower 5 and enters the bottom chamber through air inlet G1. External air, filtered by an air filter, enters the bottom chamber through air inlet G2. Air inlets G1 and G2 are at the same horizontal level and are 2.8m apart. The main blower 6 draws the furnace gas A (after acid mist removal) and the external air together into the drying chamber for drying, reducing the moisture content of both to 0.1g / Nm³. 3 The rated air volume ratio of the booster fan 5 to the main fan 6 is 1:9; the pressure at the outlet of the booster fan 5 is 0.1 kPa, and the pressure inside the bottom chamber is -0.4 kPa.

[0078] (5) Sulfur combustion

[0079] After drying, the furnace gas A and the outside air exit the drying tower 4 and are transported to the sulfur incinerator 7 by the main blower 6. At the same time, liquid sulfur is injected into the sulfur incinerator 7 and mixed and burned to generate furnace gas B at 940°C. Then, the furnace gas B is cooled to 422°C.

[0080] (6) Acid production

[0081] Furnace gas B is introduced into sulfuric acid production device 8. The sulfur dioxide in furnace gas B undergoes an oxidation reaction under the action of a catalyst to produce sulfur trioxide. The sulfur trioxide is absorbed by sulfuric acid with a mass concentration of 98.3%, and then diluted with water to obtain sulfuric acid with a mass concentration of 98%, which is the finished product concentrated sulfuric acid.

[0082] The amount of external air used in step (4) is determined by the amount of oxygen required to ensure the complete combustion of liquid sulfur in step (5) and the complete conversion of sulfur dioxide in furnace gas B into sulfur trioxide in step (6).

[0083] In step (1), the furnace gas A is cooled and its heat is recovered by the waste heat boiler 9; in step (2), the furnace gas A is washed and purified for the second time and then cooled and its heat is recovered by the plate heat exchanger; in step (5), the furnace gas B is cooled and its heat is recovered by the waste heat boiler 10.

[0084] An oxygen content analyzer 13 is installed on the outlet flue of the waste heat boiler 9 to control the concentration of oxygen in the furnace gas A flowing out of the incinerator 1, so that the volume percentage of oxygen is 10%.

[0085] The inner diameter of the silo is 4.2m and the height is 2.8m.

[0086] In step (3), the furnace gas A after two-stage purification is passed through a primary electrostatic precipitator 11 and a secondary electrostatic precipitator 12 in sequence to remove acid mist.

[0087] Both the booster fan 5 and the main fan 6 are corrosion-resistant centrifugal blowers.

[0088] The catalyst in step (6) is vanadium pentoxide.

[0089] In step (5), liquid sulfur is pressurized by a liquid sulfur feed pump and injected into the sulfur incinerator 7 through a sulfur gun.

[0090] Example 3

[0091] like Figure 1 As shown, the dry acid production process for waste gas recovery in a viscose fiber factory according to the present invention includes the following steps performed in sequence:

[0092] (1) Waste gas incineration

[0093] Sulfur-containing waste gas from the acid station workshop of the viscose fiber factory is mixed with external air filtered by an air filter at a volume ratio of 1:7 and then sent into incinerator 1 at a furnace temperature of 1000℃ for combustion to obtain furnace gas A containing sulfur dioxide; then furnace gas A is cooled to 341℃.

[0094] (2) Purification

[0095] The furnace gas A obtained in step (1) is sent to the dynamic wave scrubber 2 for the first washing and purification. The furnace gas A is humidified and cooled to 70°C by adiabatic evaporation by spraying 5% dilute sulfuric acid in a circulating manner. Then, the washed and purified furnace gas A is sent to the packed scrubber 3 for the second washing and purification. The furnace gas A is sprayed with 5% dilute sulfuric acid from the top of the packed scrubber 3 downwards, so that the furnace gas A and the dilute sulfuric acid come into countercurrent contact, removing impurities and cooling the furnace gas A to 40°C.

[0096] (3) Remove acid mist

[0097] Acid mist was removed from the furnace gas A after two-stage purification, reducing the acid mist content in furnace gas A to 5 mg / Nm³. 3 the following;

[0098] (4) Drying

[0099] The drying tower 4 comprises a drying chamber and a bottom chamber connected sequentially. The top of the drying tower 4 has an air outlet, and the side walls of the bottom chamber have air inlets G1 and G2, respectively. One end of the main blower 6 is connected to the air outlet of the drying tower 4, and the other end is connected to the air inlet of the sulfur incinerator 7. The furnace gas A, after acid mist removal, is pressurized by the booster blower 5 and enters the bottom chamber through air inlet G1. External air, filtered by an air filter, enters the bottom chamber through air inlet G2. Air inlets G1 and G2 are at the same horizontal level and are 4.2m apart. The main blower 6 draws the furnace gas A (after acid mist removal) and the external air together into the drying chamber for drying, reducing the moisture content of both to 0.1g / Nm³. 3 The rated air volume ratio of the booster fan 5 to the main fan 6 is 1:11; the pressure at the outlet of the booster fan 5 is 0.2 kPa, and the pressure inside the bottom chamber is -0.3 kPa.

[0100] (5) Sulfur combustion

[0101] After drying, the furnace gas A and the outside air exit the drying tower 4 and are transported to the sulfur incinerator 7 by the main blower 6. At the same time, liquid sulfur is injected into the sulfur incinerator 7, and they are mixed and burned to generate furnace gas B at 960°C. Then, the furnace gas B is cooled to 418°C.

[0102] (6) Acid production

[0103] Furnace gas B is introduced into sulfuric acid production device 8. The sulfur dioxide in furnace gas B undergoes an oxidation reaction under the action of a catalyst to produce sulfur trioxide. The sulfur trioxide is absorbed by sulfuric acid with a mass concentration of 98.3%, and then diluted with water to obtain sulfuric acid with a mass concentration of 98%, which is the finished product concentrated sulfuric acid.

[0104] The amount of external air used in step (4) is determined by the amount of oxygen required to ensure the complete combustion of liquid sulfur in step (5) and the complete conversion of sulfur dioxide in furnace gas B into sulfur trioxide in step (6).

[0105] In step (1), the furnace gas A is cooled and its heat is recovered by the waste heat boiler 9; in step (2), the furnace gas A is washed and purified for the second time and then cooled and its heat is recovered by the plate heat exchanger; in step (5), the furnace gas B is cooled and its heat is recovered by the waste heat boiler 10.

[0106] An oxygen content analyzer 13 is installed on the outlet flue of the waste heat boiler 9 to control the concentration of oxygen in the furnace gas A flowing out of the incinerator 1, so that the volume percentage of oxygen is 11%.

[0107] The inner diameter of the silo is 3.8m and the height is 3.2m.

[0108] In step (3), the furnace gas A after two-stage purification is passed through a primary electrostatic precipitator 11 and a secondary electrostatic precipitator 12 in sequence to remove acid mist.

[0109] Both the booster fan 5 and the main fan 6 are corrosion-resistant centrifugal blowers.

[0110] The catalyst in step (6) is vanadium pentoxide.

[0111] In step (5), liquid sulfur is pressurized by a liquid sulfur feed pump and injected into the sulfur incinerator 7 through a sulfur gun.

Claims

1. A dry acid production process for recovering waste gas from a viscose fiber factory, characterized in that: The steps are as follows, performed in sequence: (1) Waste gas incineration The sulfur-containing waste gas from the acid station workshop of the viscose fiber factory is mixed with the external air filtered by the air filter at a volume ratio of 1:6 to 1:7 and then sent into the incinerator (1) with a furnace temperature of 1000 to 1100°C for combustion to obtain furnace gas A containing sulfur dioxide; then the furnace gas A is cooled to 339 to 341°C. (2) Purification The furnace gas A obtained in step (1) is sent to the dynamic wave scrubber (2) for the first washing and purification. The furnace gas A is humidified and cooled to 69-70°C by adiabatic evaporation by spraying 5%~6% dilute sulfuric acid on it. Then the washed and purified furnace gas A is sent to the packed scrubber (3) for the second washing and purification. The furnace gas A is sprayed with 5%~6% dilute sulfuric acid from the top of the packed scrubber (3) downwards, so that the furnace gas A comes into countercurrent contact with the dilute sulfuric acid, removing impurities and cooling the furnace gas A to 39-40°C. (3) Remove acid mist Acid mist was removed from the furnace gas A after two-stage purification, reducing the acid mist content in furnace gas A to 5 mg / Nm³. 3 the following; (4) Drying The drying tower (4) includes a drying chamber and a bottom chamber connected vertically. The top of the drying tower (4) is provided with an air outlet, and the side walls of the bottom chamber are provided with air inlets G1 and G2 respectively. One end of the main blower (6) is connected to the air outlet of the drying tower (4), and the other end is connected to the air inlet of the sulfur incinerator (7). The furnace gas A after removing acid mist is pressurized by the booster blower (5) and enters the bottom chamber through the air inlet G1. The external air after being filtered by the air filter enters the bottom chamber through the air inlet G2. The air inlets G1 and G2 are located at the same horizontal height and the distance between them is 2.8~4.2m. The main blower (6) draws the furnace gas A after removing acid mist and the external air together into the drying chamber for drying, so that the moisture content of both is reduced to 0.1g / Nm. 3 The rated air volume ratio of the booster fan (5) to the main fan (6) is 1:9 to 1:11; the pressure at the outlet of the booster fan (5) is 0.1 to 0.2 kPa, and the pressure inside the bottom chamber is -0.3 to -0.4 kPa; the inner diameter of the bottom chamber is 3.8 to 4.2 m, and the height is 2.8 to 3.2 m. (5) Sulfur combustion After drying, the furnace gas A and the outside air exit the drying tower (4) and are transported to the sulfur incinerator (7) by the main blower (6). At the same time, liquid sulfur is injected into the sulfur incinerator (7) and mixed and burned to generate furnace gas B at 940~960℃. Then the furnace gas B is cooled to 418~422℃. (6) Acid production Furnace gas B is introduced into the acid production device (8). The sulfur dioxide in furnace gas B undergoes an oxidation reaction under the action of a catalyst to generate sulfur trioxide. The sulfur trioxide is absorbed by sulfuric acid with a mass concentration of 98.3%, and then diluted with water to obtain sulfuric acid with a mass concentration of 98%, which is the finished product concentrated sulfuric acid. The amount of external air used in step (4) is based on the amount of oxygen required to ensure the complete combustion of liquid sulfur in step (5) and the complete conversion of sulfur dioxide in furnace gas B into sulfur trioxide in step (6).

2. The dry acid production process for recovering waste gas from viscose fiber factories according to claim 1, characterized in that: In step (1), the furnace gas A is cooled and its heat is recovered by the waste heat boiler (9); in step (2), the furnace gas A is washed and purified for the second time and then cooled and its heat is recovered by the plate heat exchanger; in step (5), the furnace gas B is cooled and its heat is recovered by the waste heat boiler (10).

3. The dry acid production process for recovering waste gas from viscose fiber factories according to claim 2, characterized in that: An oxygen content analyzer (13) is installed on the outlet flue of the waste heat boiler (9) to control the concentration of oxygen in the furnace gas A flowing out of the incinerator (1), so that the volume percentage of oxygen is 10%~11%.

4. The dry acid production process for waste gas recovery in viscose fiber factories according to claim 1, characterized in that: In step (3), the furnace gas A after two-stage purification is passed through a primary electrostatic precipitator (11) and a secondary electrostatic precipitator (12) in sequence to remove acid mist.

5. The dry acid production process for waste gas recovery in viscose fiber factories according to claim 1, characterized in that: Both the booster fan (5) and the main fan (6) are corrosion-resistant centrifugal blowers.

6. The dry acid production process for recovering waste gas from a viscose fiber factory according to claim 1, characterized in that: The catalyst in step (6) is vanadium pentoxide.

7. The dry acid production process for recovering waste gas from a viscose fiber factory according to claim 1, characterized in that: In step (5), liquid sulfur is pressurized by a liquid sulfur feed pump and injected into the sulfur incinerator (7) through a sulfur gun.

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