Alkali washing treatment system for waste gas in high-strength and high-modulus PVA fiber production process

Abstract

The utility model provides an alkali wash treatment system for waste gas in a high-strength and high-modulus PVA (Polyvinyl Alcohol) fiber production process, which is structurally characterized in that a gas collecting hood is arranged and is used for intensively collecting acid waste gas and feeding the acid waste gas into a spray tower; an alkali wash solution continuous adding unit is arranged, is used for generating, adding and recycling an alkali wash solution and comprises a storage tank and an alkali wash solution tank provided with a PH electrode probe, the storage tank is used for storing and feeding a sodium hydroxide solution into the alkali wash solution tank, and the alkali wash solution tank is used for generating the alkali wash solution as a spraying solution and feeding the spraying solution to all spraying openings of a spraying tower; the recycling tank is also used for recycling alkali-washed spraying liquid from the spraying tower and condensate water from the water vapor condensing device, and the PH value of the spraying liquid in the tank is detected in real time through a PH electrode probe; a spray tower is arranged and is used for carrying out alkali washing on the acid waste gas; and a water vapor condensing device is arranged and is used for condensing and discharging the waste gas subjected to alkali washing. According to the utility model, the complete purification and environment-friendly emission of waste gas can be realized, and the continuous supplement of the alkali wash can be realized on the premise of reducing the waste of the alkali wash.

Description

Technical Field

[0001] This utility model relates to the field of high-strength, high-modulus PVA fiber manufacturing technology, and more specifically to an alkaline washing treatment system for waste gas during the production process of high-strength, high-modulus PVA fibers. Background Technology

[0002] When producing high-strength, high-modulus PVA fibers using a boron crosslinking wet spinning process, acetic acid is added as a stabilizer to form a buffer solution to adjust the pH value of the raw solution. However, during the spinning process, after the fibers are neutralized and washed, a large amount of sodium acetate is converted into acetic acid under the action of sulfuric acid. This acetic acid volatilizes significantly under the high-temperature conditions of the coagulation bath, forming a pungent acidic waste gas with the water vapor in the coagulation bath, seriously threatening the health of workers. Simultaneously, the waste gas contains water vapor, which is highly corrosive to equipment and buildings. While the existing technology of using sodium hydroxide solution for alkaline washing of the waste gas is relatively mature, several problems remain unresolved in the actual treatment process: firstly, how to achieve efficient collection of the waste gas; secondly, how to achieve complete reaction and purification of the waste gas; and thirdly, how to achieve continuous replenishment of the alkaline washing solution to reduce alkali waste. Utility Model Content

[0003] To solve the above-mentioned technical problems, this utility model proposes an alkaline washing treatment system for waste gas in the production process of high-strength and high-modulus PVA fibers, which can achieve complete purification and environmentally friendly emission of waste gas, and can continuously replenish alkaline washing liquid while reducing the waste of alkaline washing liquid.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An alkaline washing treatment system for waste gas produced during the production of high-strength, high-modulus PVA fibers, characterized by the following features:

[0006] A gas collection hood is installed to collect acidic waste gas and send it into the spray tower.

[0007] A continuous alkaline washing solution addition unit is set up for the generation, addition and recycling of alkaline washing solution. It includes a storage tank and an alkaline washing solution tank equipped with a pH electrode probe. The storage tank is used to store and feed sodium hydroxide solution into the alkaline washing solution tank. The alkaline washing solution tank is used to generate alkaline washing solution as spray liquid and send it to various spray nozzles of the spray tower. It is also used to recycle the spray liquid after alkaline washing from the spray tower and the condensate from the water vapor condensation device. The pH value of the spray liquid in the tank is detected in real time by the pH electrode probe.

[0008] The spray tower is used for alkaline washing of acidic waste gas and the subsequent discharge. It receives acidic waste gas from the gas collection hood at the bottom of the tower, and spray nozzles are distributed at intervals between the top and bottom of the tower along the height of the tower. Spraying liquid is sprayed into the tower from different heights through the spray nozzles, and alkaline washing is achieved by contacting the acidic waste gas in the tower. The waste gas after alkaline washing is discharged from the top of the tower into a water vapor condensation device, and the spraying liquid after alkaline washing is discharged from the bottom of the tower into the alkaline washing liquid tank.

[0009] The water vapor condensation device is set up to condense and discharge the waste gas after alkaline washing. The waste gas after alkaline washing is condensed into two parts: one part is gas that is discharged outward, and the other part is the condensate water that is discharged into the alkaline washing liquid tank.

[0010] The structural features of this utility model also lie in:

[0011] The acidic waste gas contains water vapor and acetic acid. When it comes into contact with the spray liquid, the acidic waste gas is alkalinely washed by the spray liquid through the acid-base neutralization reaction between acetic acid and sodium hydroxide.

[0012] The alkaline washing solution is a mixture of sodium hydroxide solution and water at a ratio of 1:60000, wherein the concentration of sodium hydroxide solution is 32% and the alkaline washing solution with a pH value ≥10 is sent to the spray nozzles of the spray tower as a spraying liquid.

[0013] The acidic waste gas collected by the gas collection hood is acetic acid waste gas volatilized from the bath of the spinning process. The acidic waste gas collected by the gas collection hood is transported through the pre-alkali washing air supply duct connecting the gas outlet of the gas collection hood and the gas inlet of the spray tower at the bottom of the tower, and is then sucked into the spray tower by the fan.

[0014] In the alkaline washing solution continuous addition unit:

[0015] The storage tank is equipped with a sodium hydroxide inlet and a sodium hydroxide outlet. Sodium hydroxide solution is injected into the tank through the sodium hydroxide solution inlet and transported through a sodium hydroxide pipeline connecting the sodium hydroxide solution outlet and the sodium hydroxide injection port on the alkaline washing tank, and then pumped into the alkaline washing tank by the first transfer pump.

[0016] The alkaline washing solution tank is also equipped with a spray liquid outlet, a spray liquid return port, and a condensate return port. The spray liquid is transported through a spray liquid conveying pipeline connecting the spray liquid outlet and each spray port, and then pumped to each spray port by a second conveying pump. The spray liquid from the spray tower after alkaline washing flows into the alkaline washing solution tank by gravity through a spray liquid collection pipeline connecting the spray liquid return port and the spray liquid discharge port at the bottom of the spray tower. The condensate from the steam condensation device flows into the alkaline washing solution tank by gravity through a condensate collection pipeline connecting the condensate return port and the condensate discharge port of the steam condensation device. The height of the spray liquid return port is lower than that of the spray liquid discharge port, and the height of the condensate return port is lower than that of the condensate discharge port.

[0017] The spray tower has an air outlet at the top. After alkaline washing, the waste gas is discharged into the steam condenser through an air duct that connects the air outlet to the gas inlet of the steam condenser. The spray nozzles are evenly spaced along the height of the tower.

[0018] The water vapor condensation device is a gas collection box.

[0019] The water vapor condensation device is a semi-enclosed gas collection box.

[0020] Compared with existing technologies, the beneficial effects of this utility model are reflected in:

[0021] This invention, by setting up a continuous alkaline washing solution addition unit, enables continuous and stable operation of the alkaline washing process and real-time monitoring of the pH value of the alkaline washing solution. It eliminates the uncertainty caused by traditional manual continuous alkali addition, and avoids the problems of insufficient acetic acid removal due to insufficient alkali addition or scale buildup and waste in the alkaline washing solution tank due to excessive alkali addition. The acidic waste gas in the spray tower can undergo multiple acid-base neutralization reactions with the spray solution, ensuring complete removal of acetic acid gas and achieving thorough purification of the acidic waste gas. It also allows for the condensation and reuse of water vapor, completely solving the existing problem of acidic waste gas emissions during the production of high-strength, high-modulus PVA fibers. This significantly improves the workshop environment, increases the collection efficiency of acidic waste gas, reduces the corrosion of equipment and buildings by acidic waste gas, and helps extend the service life of equipment. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of this utility model.

[0023] In the picture:

[0024] 1. Gas collection hood; 11. Air supply duct before alkaline washing; 12. Fan; 13. Air outlet of the hood;

[0025] 21 Storage tank; 211 Sodium hydroxide inlet; 212 Sodium hydroxide outlet; 213 Sodium hydroxide pipeline; 214 First transfer pump; 22 Alkaline washing solution tank; 221 Spray liquid outlet; 222 Spray liquid transfer pipeline; 223 Second transfer pump; 224 Spray liquid return port; 225 Spray liquid collection pipeline; 226 Condensate return port; 227 Condensate collection pipeline; 23 pH electrode probe;

[0026] 3. Spray tower; 31. Spray nozzle; 32. Spray liquid discharge port; 33. Tower body air inlet; 34. Tower body air outlet; 35. Post-alkali washing air supply duct;

[0027] 4. Water vapor condensation device; 41. Condensate discharge port. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0029] Please refer to Figure 1 The structure of the alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers in this embodiment includes:

[0030] A gas collection hood 1 is installed to collect acidic waste gas and send it into the spray tower 3.

[0031] An alkaline washing solution continuous addition unit is set up for the generation, addition and recycling of alkaline washing solution. It includes a storage tank 21 and an alkaline washing solution tank 22 equipped with a pH electrode probe 23. The storage tank 21 is used to store and feed sodium hydroxide solution into the alkaline washing solution tank 22. The alkaline washing solution tank is used to generate alkaline washing solution as spray liquid and send it to the spray nozzles 31 of the spray tower 3. It is also used to recycle the spray liquid after alkaline washing from the spray tower 3 and the condensate from the water vapor condensation device. The pH value of the spray liquid in the tank is detected in real time by the pH electrode probe 23.

[0032] A spray tower 3 is set up for alkaline washing of acidic waste gas and the discharge of the alkaline washing solution. The acidic waste gas is received from the gas collection hood 1 at the bottom of the tower. Spray nozzles 31 are distributed at intervals between the top and bottom of the tower along the height direction of the tower. Spraying liquid is sprayed into the tower from different heights through the spray nozzles 31, and alkaline washing is achieved by contacting the acidic waste gas in the tower. The waste gas after alkaline washing is discharged from the top of the tower to the water vapor condensation device. The spraying liquid after alkaline washing is discharged from the bottom of the tower to the alkaline washing liquid tank 22.

[0033] A water vapor condensation device 4 is installed to condense and discharge the waste gas after alkaline washing. The waste gas after alkaline washing is condensed into two parts: one part is gas that is discharged outward, and the other part is condensate water that is discharged into the alkaline washing liquid tank 22.

[0034] In practice, the corresponding structural configuration of this alkaline washing treatment system also includes:

[0035] Acidic waste gas contains water vapor and acetic acid. When it comes into contact with the spray liquid, the acidic waste gas is alkalinely washed by the spray liquid through the acid-base neutralization reaction between acetic acid and sodium hydroxide.

[0036] The alkaline washing solution is made by mixing sodium hydroxide solution and water at a ratio of 1:60000, wherein the concentration of sodium hydroxide solution is 32% and the alkaline washing solution with a pH value ≥10 is sent to the spray nozzles 31 of the spray tower 3 as a spraying liquid.

[0037] The acidic waste gas collected by the gas collection hood 1 is acetic acid waste gas volatilized from the second and third baths of the spinning process. The acidic waste gas collected by the gas collection hood 1 is transported through the pre-alkali washing air supply duct 11 connecting the gas outlet 13 of the gas collection hood 1 and the gas inlet 33 of the spray tower 3 at the bottom of the tower, and is then drawn into the spray tower 3 by the fan 12.

[0038] More specifically, the gas collection hood 1 is a detachable cover plate that seals the upper end of the bath tank. The cover plate has openings that serve as the hood's air outlet 13. The hood's air outlet 13, the fan 12's air inlet, the fan 12's air outlet, and the tower's air inlet 33 are connected via a pre-alkaline washing air duct 11. This waste gas collection method reduces waste gas escape, creates negative pressure inside the hood, significantly improves suction, and increases waste gas collection efficiency.

[0039] In practical work, to effectively collect waste gas, the absorption velocity (called the control velocity) at the location of the gas collection hood 1 should be determined based on the air movement speed around the pollution source and the harmfulness of the waste gas. For a given type of gas collection hood 1, the larger the air volume, the larger the air velocity at the hood opening, and the larger the control velocity, the easier it is for the gas to be collected. To create negative pressure inside the hood, the total balance between the intake and exhaust air volumes inside the sealed hood must be satisfied when determining the exhaust volume. In most cases, the exhaust volume mainly consists of two aspects: 1) the air volume brought in by moving materials; 2) the air volume absorbed at the leakage points of the sealed hood. In this embodiment, the bath is sealed with a stainless steel cover gas collection hood 1, and the sealing performance is good. Therefore, the air volume is calculated according to the leakage area, as shown in the following formula:

[0040] Q = 3600β·V·ΣF

[0041] Q – Exhaust volume, m 3 / h;

[0042] ΣF——Total area of ​​openings and leakage points on the sealed enclosure, in meters 2;

[0043] β—Design safety factor, generally β = 1.05 to 1.1;

[0044] V—the wind speed through the leak or opening, in m / s, generally V = 1 to 4 m / s;

[0045] Where ΣF=0.5·0.1=0.05m 2 ; β is taken as 1.1; V is taken as 2 m / s; Substituting into the formula, we get:

[0046] Q=3600·1.1·2·0.5·0.1·2=792m 3 / h

[0047] Based on the number of bath tubs, and taking an air leakage coefficient of 1.2, the required total air volume can be calculated; then, the selection and quantity of fan 12 are determined according to the operating conditions.

[0048] In the alkaline washing solution continuous addition unit:

[0049] The storage tank 21 is equipped with a sodium hydroxide inlet 211 and a sodium hydroxide outlet 212. Sodium hydroxide solution is injected into the tank through the sodium hydroxide solution inlet and transported through the sodium hydroxide pipeline 213 connecting the sodium hydroxide solution outlet and the sodium hydroxide injection port on the alkaline washing tank 22, and pumped into the alkaline washing tank 22 by the first transfer pump 214.

[0050] The alkaline washing liquid tank 22 is also equipped with a spray liquid outlet 221, a spray liquid return port 224, and a condensate return port 226. The spray liquid is transported through a spray liquid conveying pipe 222 connecting the spray liquid outlet 221 and each spray port 31, and pumped to each spray port 31 by a second conveying pump 223. The spray liquid from the spray tower 3 after alkaline washing flows into the alkaline washing liquid tank 22 by gravity through a spray liquid collection pipe 225 connecting the spray liquid return port 224 and the spray liquid discharge port 32 at the bottom of the spray tower 3. The condensate from the steam condensation device flows into the alkaline washing liquid tank 22 by gravity through a condensate collection pipe 227 connecting the condensate return port 226 and the condensate discharge port 41 of the steam condensation device. The height of the spray liquid return port 224 is lower than that of the spray liquid discharge port 32, and the height of the condensate return port 226 is lower than that of the condensate discharge port 41.

[0051] The first delivery pump 214 is a metering pump.

[0052] The alkaline washing solution tank 22 is also equipped with a water inlet for injecting water into the tank.

[0053] The required pH value of the alkaline washing solution is ≥10. When the pH electrode probe 23 detects that the pH of the alkaline washing solution in the alkaline washing solution tank 22 is <10, the system receives feedback, and the first transfer pump 214 starts, delivering sodium hydroxide solution to the alkaline washing solution tank 22 through the first transfer pump 214. When the pH electrode probe 23 detects that the pH of the alkaline washing solution in the alkaline washing solution tank 22 is >12, the system receives feedback, and the first transfer pump 214 shuts down. Thus, the system achieves automated detection, continuous operation, and continuous correction. The pH electrode probe 23 and the first transfer pump 214 are connected to the control system (DCS).

[0054] The top of the spray tower 3 has a tower body outlet 34. The alkaline-washed exhaust gas is discharged into the water vapor condenser through the alkaline-washed exhaust pipe 35 connecting the tower body outlet 34 and the gas inlet of the water vapor condenser. The spray nozzles 31 are evenly distributed along the tower body along the tower height.

[0055] In this embodiment, there are three spray nozzles 31.

[0056] The water vapor condensation device 4 is a gas collection box, or more specifically, a semi-enclosed gas collection box.

[0057] When producing high-strength, high-modulus PVA fibers using a boron crosslinking wet spinning process, acetic acid is added as a stabilizer to form a buffer solution and adjust the pH value of the raw solution. However, during the spinning process, after the fibers are neutralized and washed, a large amount of sodium acetate is converted into acetic acid under the action of sulfuric acid. This acetic acid volatilizes in large quantities under the high temperature conditions of the coagulation bath, forming a pungent acidic waste gas with the water vapor in the coagulation bath. The alkaline washing treatment system of this embodiment is used for the centralized collection and continuous alkaline washing treatment of this acidic waste gas, so that the acidic waste gas is purified and discharged, thereby improving the production workshop environment and benefiting the protection of personnel's physical and mental health and environmental protection. The working principle of the alkaline washing treatment system of this embodiment is as follows:

[0058] Acidic waste gas is collected by the gas collection hood 1 and then sent to the spray tower 3. Sodium hydroxide solution is pumped from the storage tank 21 into the alkaline washing solution tank 22, where it mixes with water to form a spray solution. The spray solution is pumped to three spray nozzles 31 at different heights in the spray tower 3, and sprayed into the tower from each nozzle 31 to contact the acidic waste gas entering from the bottom of the tower, resulting in an acid-base neutralization reaction. The spray solution after the reaction flows back to the alkaline washing solution tank 22 and can be recycled for spraying. The pH value of the solution in the alkaline washing solution tank 22 is measured by the pH electrode probe 23, and the amount of sodium hydroxide solution added is adjusted according to the pH value. The waste gas after alkaline washing is discharged from the top of the tower and enters the water vapor condenser, where the large amount of water vapor it carries is condensed to form condensate, which is discharged from the water vapor condenser back to the alkaline washing solution tank 22, realizing the condensation and reuse of water vapor, while the gas is discharged outside the water vapor condenser.

[0059] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers, characterized in that: A gas collection hood is installed to collect acidic waste gas and send it into the spray tower. A continuous alkaline washing solution addition unit is set up for the generation, addition and recycling of alkaline washing solution. It includes a storage tank and an alkaline washing solution tank equipped with a pH electrode probe. The storage tank is used to store and feed sodium hydroxide solution into the alkaline washing solution tank. The alkaline washing solution tank is used to generate alkaline washing solution as spray liquid and send it to various spray nozzles of the spray tower. It is also used to recycle the spray liquid after alkaline washing from the spray tower and the condensate from the water vapor condensation device. The pH value of the spray liquid in the tank is detected in real time by the pH electrode probe. The spray tower is used for alkaline washing of acidic waste gas and the subsequent discharge. It receives acidic waste gas from the gas collection hood at the bottom of the tower, and spray nozzles are distributed at intervals between the top and bottom of the tower along the height of the tower. Spraying liquid is sprayed into the tower from different heights through the spray nozzles, and alkaline washing is achieved by contacting the acidic waste gas in the tower. The waste gas after alkaline washing is discharged from the top of the tower into a water vapor condensation device, and the spraying liquid after alkaline washing is discharged from the bottom of the tower into the alkaline washing liquid tank. The water vapor condensation device is set up to condense and discharge the waste gas after alkaline washing. The waste gas after alkaline washing is condensed into two parts: one part is gas that is discharged outward, and the other part is the condensate water that is discharged into the alkaline washing liquid tank.

2. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1, characterized in that: The acidic waste gas contains water vapor and acetic acid. When it comes into contact with the spray liquid, the acidic waste gas is alkalinely washed by the spray liquid through the acid-base neutralization reaction between acetic acid and sodium hydroxide.

3. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1 or 2, characterized in that: The alkaline washing solution is a mixture of sodium hydroxide solution and water at a ratio of 1:60000, wherein the concentration of sodium hydroxide solution is 32% and the alkaline washing solution with a pH value ≥10 is sent to the spray nozzles of the spray tower as a spraying liquid.

4. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1, characterized in that: The acidic waste gas collected by the gas collection hood is acetic acid waste gas volatilized from the bath in the spinning process. The acidic waste gas collected by the gas collection hood is transported through the pre-alkali washing air supply duct connecting the gas outlet of the gas collection hood and the gas inlet of the spray tower at the bottom of the tower, and is then drawn into the spray tower by the fan.

5. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1, characterized in that, In the alkaline washing solution continuous addition unit: The storage tank is equipped with a sodium hydroxide inlet and a sodium hydroxide outlet. Sodium hydroxide solution is injected into the tank through the sodium hydroxide solution inlet and transported through a sodium hydroxide pipeline connecting the sodium hydroxide solution outlet and the sodium hydroxide injection port on the alkaline washing tank, and then pumped into the alkaline washing tank by the first transfer pump. The alkaline washing solution tank is also equipped with a spray liquid outlet, a spray liquid return port, and a condensate return port. The spray liquid is transported through a spray liquid conveying pipeline connecting the spray liquid outlet and each spray port, and then pumped to each spray port by a second conveying pump. The spray liquid from the spray tower after alkaline washing flows into the alkaline washing solution tank by gravity through a spray liquid collection pipeline connecting the spray liquid return port and the spray liquid discharge port at the bottom of the spray tower. The condensate from the steam condensation device flows into the alkaline washing solution tank by gravity through a condensate collection pipeline connecting the condensate return port and the condensate discharge port of the steam condensation device. The height of the spray liquid return port is lower than that of the spray liquid discharge port, and the height of the condensate return port is lower than that of the condensate discharge port.

6. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1, characterized in that: The spray tower has an air outlet at the top. After alkaline washing, the waste gas is discharged into the steam condenser through an air duct that connects the air outlet to the gas inlet of the steam condenser. The spray nozzles are evenly spaced along the height of the tower.

7. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1, characterized in that: The water vapor condensation device is a gas collection box.

8. The alkaline washing treatment system for waste gas during the production of high-strength, high-modulus PVA fibers according to claim 1, characterized in that: The water vapor condensation device is a semi-enclosed gas collection box.

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