Deodorization system and method in water-soluble fiber production process

Abstract

The invention relates to the technical field of organic solvent separation, and particularly discloses a deodorization system and method in a water-soluble fiber production process, the treatment system comprises a degassing tower and a purifying tower which are communicated through a pipeline; the top of the degassing tower is sequentially communicated with a first condenser and a second condenser, and the top of the purifying tower is provided with a third condenser. The treatment method adopts the treatment system and comprises three treatment stages of step-by-step feeding, extraction separation and rectification purification. By adopting the technical scheme provided by the invention, the technical problem that the physical and psychological health of employees and the surrounding environment of a factory are seriously influenced by stink generated on a working site due to volatilization of smelly substances such as mercaptan, thioether and dimethyl disulfide dissolved in a use process of a circulating methanol solvent in water-soluble fiber production can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of organic solvent separation, in particular to a deodorization system and method in a water-soluble fiber production process. Background Art

[0002] The water-soluble fiber is obtained from polyvinyl alcohol (PVA) through the dry-wet gel spinning process technology. PVA is dissolved in a mixed solvent of dimethyl sulfoxide (DMSO) and water, and the spinning raw material is obtained through filtration and degassing. The desired water-soluble fiber is obtained through subsequent processes.

[0003] In the production process, dimethyl sulfoxide (DMSO) is used as the main solvent for dissolving PVA. It easily diffuses into the methanol (MeOH) coagulation bath and extraction bath, so that the production of water-soluble fibers will produce a large amount of spinning waste liquid containing DMSO, MeOH and H2O. This waste liquid is currently often recycled through separation. The current process flow for separating spinning waste liquid is as follows: the waste liquid from spinning enters the methanol distillation tower for atmospheric distillation, and the methanol at the top of the tower is condensed in the cooler and then enters the storage tank for recycling. The bottom liquid of the methanol distillation tower is sent to the distillation kettle for vacuum slag removal, and the gas phase enters the vacuum distillation tower to separate and purify dimethyl sulfoxide and methanol for recycling.

[0004] However, through the current distillation separation process, the separated circulating methanol has a strong odor. The reason is that DMSO is easily decomposed to produce odorous light components such as methyl mercaptan, methyl sulfide, and dimethyl disulfide. These light components have a close boiling point to methanol. During the methanol distillation process, they are easy to enter the recycled methanol solution with methanol, resulting in the recycled methanol solution being smelly and impure. During the use of the circulating methanol solvent, odorous substances such as mercaptans, sulfides, and dimethyl disulfide dissolved in the solvent evaporate to the site to produce a foul odor, which seriously affects the physical and mental health of employees and the environment around the factory. Summary of the invention

[0005] The present invention provides a deodorization system and method in a water-soluble fiber production process, which are used to separate odorous substances such as methyl mercaptan, methyl sulfide, dimethyl disulfide, etc. dissolved in circulating methanol in the water-soluble fiber production, so as to realize odorless and environmentally friendly operation of the device.

[0006] The present invention provides the following technical solutions:

[0007] A deodorization system in a water-soluble fiber production process comprises a degassing tower and a purification tower connected by pipelines; the degassing tower is provided with a methanol feed port and an extractant feed port; a first condenser and a second condenser are sequentially connected at the top of the degassing tower, and a third condenser is provided at the top of the purification tower.

[0008] Furthermore, a methanol feed pump and an extractant feed pump are provided in the middle of the degassing tower.

[0009] Furthermore, the first condenser is provided with a reflux pipe H1, the inlet of the reflux pipe H1 is connected to the first condenser pipeline, and the outlet of the reflux pipe H1 is connected to the upper part of the degassing tower; the outlet of the second condenser is connected to an incinerator.

[0010] In this scheme, the first condenser is used to make the high-boiling-point substances in the mixed components undergo phase change, thereby separating them from low-boiling-point substances, such as methyl mercaptan and methyl sulfide, and the high-boiling-point substances flow back to the degassing tower. The second condenser is used to condense the low-boiling-point light components, which are then discharged into the incinerator for incineration.

[0011] Furthermore, a first reboiler is provided at the bottom of the degassing tower, a reflux pipe H2 is provided between the first reboiler and the degassing tower, an inlet of the reflux pipe H2 is connected to the first reboiler, and an outlet is connected to the bottom of the degassing tower; the first reboiler is connected to the purification tower.

[0012] In this scheme, the extracted material is reboiled and vaporized in the first reboiler and then returned to the bottom of the degassing tower to provide energy for the distillation separation of the degassing tower.

[0013] Furthermore, the third condenser is provided with a reflux pipe H3 and a distillation pipe G10, the inlet of the reflux pipe H3 is connected to the third condenser pipeline, and the outlet of the reflux pipe H3 is connected to the upper part of the purification tower.

[0014] In this scheme, the third condenser is used to condense, separate and purify the methanol after distillation. Most of the methanol flows out through the distillation pipe after condensation, and a small part of the methanol flows back to the purification tower through the reflux pipe H3 for further distillation and purification.

[0015] Furthermore, a second reboiler is provided at the bottom of the purification tower, a reflux pipe H4 is provided between the second reboiler and the purification tower, the inlet of the reflux pipe H4 is connected to the second reboiler, and the outlet is connected to the bottom of the purification tower; the second reboiler is also provided with a distillation pipe.

[0016] In this scheme, the mixture after distillation and purification is heated and vaporized in the second reboiler and then returned to the purification tower to provide energy for distillation and purification in the purification tower.

[0017] The present invention also provides a deodorization method in the water-soluble fiber production process, which uses the above-mentioned deodorization system in the water-soluble fiber production process and includes the following steps:

[0018] S1: Pre-feeding stage, first 30% of the extractant is pumped into the degassing tower, and then the circulating methanol liquid is pumped into the extractant after heating;

[0019] S2: Extraction and separation stage, when reflux appears at the top of the tower, the remaining extractant is continuously pumped into the degassing tower; the extractant extracts the methanol in the circulating methanol liquid to form aqueous phase methanol, and the odorous substances in the circulating methanol liquid form separation steam;

[0020] S3: Reflux stage, the separated steam rises and flows into the top of the degassing tower, and then passes through the first condenser to form odorous substance steam and methanol reflux liquid. The odorous substance steam then passes through the second condenser to form condensate and then burns; the methanol reflux liquid flows back into the degassing tower through the reflux pipe H1;

[0021] S4: In the distillation and purification stage, the aqueous methanol is heated in the purification tower to form steam, which is then condensed to form methanol distillate.

[0022] Furthermore, the addition ratio of the extractant to the circulating methanol is 1 to 3:1.

[0023] In this scheme, the addition ratio of the extractant to the circulating methanol can increase the difference in volatility between the components in the circulating methanol solution, so that water and odorous impurities such as mercaptans and sulfides form azeotropes that are easier to evaporate.

[0024] Furthermore, the reflux ratio of the degassing tower top is 10-30, and the tower bottom temperature is 80-90°C; the reflux ratio of the purification tower top is 1-3, and the tower bottom temperature is 110-120°C.

[0025] In this scheme, the top reflux ratio of the degassing tower is controlled at 10-30 to ensure the separation effect of methanol and light components. The bottom temperature of the tower is 80-90°C, which can fully heat and vaporize the circulating methanol and light components for separation. This temperature is lower than the boiling point of high-boiling light components such as dimethyl disulfide and azo, so the preliminary separation of high-boiling light components can also be achieved.

[0026] The reflux ratio at the top of the purification tower is set to be small, so the cost can be reduced. The temperature at the bottom of the tower is high, which can well vaporize the extractant and methanol, facilitating subsequent separation.

[0027] Furthermore, the temperature of the first condenser is 50-60°C, the temperature of the second condenser is 15-20°C, and the cooling medium is RW12 circulating water; the temperature of the third condenser is 50-60°C, and the cooling medium is 33°C circulating water.

[0028] In this scheme, the temperature of the first condenser is lower than the boiling point of methanol but higher than the boiling point of substances such as methyl sulfide, so the separation of methanol and light components such as methyl sulfide can be achieved. The temperature of the second condenser is relatively low, which is used to cause methyl sulfide and other substances to undergo phase change and condense before incineration. The temperature of the third condenser is greater than the boiling point of methanol and lower than the boiling point of the extractant, so the extractant can be separated from methanol, and the purity of methanol after purification and distillation can reach 99.9%.

[0029] Beneficial effects of the present invention:

[0030] 1. The principle of this application is simple, desalted water is used as the extractant, the raw materials are cheap and common, and it is suitable for large-scale industrial production. At the same time, desalted water is used as the extractant, and no new impurities are introduced, ensuring that the purified methanol can be used continuously.

[0031] 2. The present application adds materials in steps during the pre-feeding stage, first pumping a portion of the extractant into the degassing tower, forming a hot steam atmosphere in the degassing tower, so that the circulating methanol liquid pumped in later can begin to be heated, vaporized, extracted and distilled, reducing the loss of the circulating methanol liquid. At the same time, the extractant pumped in first can directly react with the circulating methanol liquid pumped in later to undergo extraction reaction after forming steam, reducing the reaction time.

[0032] 3. The application has significant effects. The removal rate of odorous substances in the circulating methanol treated by the application scheme can reach 100%, and the purity of the circulating methanol after purification can reach 99.9%.

[0033] 4. The present application further incinerates the separated odorous gas for post-treatment, thus reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a schematic structural diagram of a deodorization system in a water-soluble fiber production process. DETAILED DESCRIPTION

[0035] The following is further described in detail through specific implementation methods:

[0036] The symbols in the drawings of the specification include: degassing tower 1, purification tower 2, first condenser 3, second condenser 4, incinerator 5, first reboiler 6, third condenser 7, second reboiler 8, extractant pump 9, circulating methanol pump 10;

[0037] Extractant feed pipe G1, circulating methanol feed pipe G2, connecting pipe G3, connecting pipe G4, connecting pipe G5, connecting pipe G6, connecting pipe G7, connecting pipe G8, connecting pipe G9, distillation pipe G10, connecting pipe G11, distillation pipe G12, reflux pipe H1, reflux pipe H2, reflux pipe H3, reflux pipe H4.

[0038] Example

[0039] like Figure 1 As shown, a deodorization system in a water-soluble fiber production process includes a degassing tower 1 and a purification tower 2. In this embodiment, the degassing tower 1 and the purification tower 2 are both packed towers.

[0040] The top of the degassing tower 1 is connected to a first condenser 3 and a second condenser 4 via connecting pipes G3 and G4. The first condenser 3 is provided with a reflux pipe H1, which is connected to the upper part of the degassing tower 1. The second condenser 4 is connected to an incinerator 5, and the condensate can be passed into the incinerator 5 for incineration. The methanol-water mixed condensate containing high-concentration mercaptans, sulfides, dimethyl disulfide and other malodorous components is pumped to the incinerator 5 for treatment. The temperature in the incinerator 5 is controlled at 750-850°C. The flue gas after combustion is transported to the desulfurization and denitrification device through the connecting pipe G6 and then meets the emission standards. The desulfurization and denitrification device is in Figure 1 Not shown in FIG.

[0041] An extractant feed pipe G1 and a circulating methanol feed pipe G2 are provided in the middle of the degassing tower 1. Both feed pipes G1 and G2 are provided with corresponding extractant pumps 9 and circulating methanol pumps 10. The connection port of the feed pipe G1 and the degassing tower 1 is higher than the feed pipe G2.

[0042] A connecting pipe G7 is provided at the bottom of the degassing tower 1 , and the connecting pipe G7 is connected to a first reboiler 6 . The first reboiler 6 is provided with a reflux pipe H2 , and the reflux pipe H2 is connected to the lower part of the degassing tower 1 .

[0043] The first reboiler 6 is connected to the purification tower 2 via a connecting pipe G8. The top of the purification tower 2 is connected to a third condenser 7 via a connecting pipe G9. The third condenser 7 is provided with a reflux pipe H3 and a distillation pipe G10. The reflux pipe H3 is connected to the upper part of the purification tower 2.

[0044] A connecting pipe G11 is provided at the bottom of the purification tower 2 , and the connecting pipe G11 is connected to a second reboiler 8 . The second reboiler 8 is provided with a reflux pipe H4 and a distillation pipe G12 . The reflux pipe H4 is connected to the lower part of the degassing tower 1 .

[0045] This embodiment also describes a deodorization method in a water-soluble fiber production process, using the above-mentioned deodorization system in a water-soluble fiber production process, including the following steps:

[0046] S1: Pre-feeding stage, firstly 30% of the extractant is pumped into the degassing tower 1, and then the circulating methanol liquid is pumped into the extractant after the temperature is increased.

[0047] Specifically, the device is turned on, and the extractant pump 9 pumps 30% of the extractant into the degassing tower 1, so that the extractant first forms a steam cycle in the tower. In this embodiment, the extractant is desalted water. When the tower bottom temperature rises to 84°C, the circulating methanol pump 10 is turned on to pump the circulating methanol to be separated into the degassing tower 1. The extractant pumped in first can extract the circulating methanol just introduced, thereby accelerating the reaction speed.

[0048] S2: extraction and separation stage, when reflux appears at the top of the tower, the remaining extractant is continuously pumped into the degassing tower 1; the extractant extracts the methanol in the circulating methanol liquid to form aqueous phase methanol, and the odorous substances in the circulating methanol liquid form separation steam;

[0049] Specifically, when reflux liquid appears in the reflux pipe H1, the extractant pump 9 is turned on again to slowly and continuously pass the extractant into the degassing tower 1, and the ratio of the extractant to methanol in the tower is maintained at 1.5. At this ratio, the difference in volatility between the components in the circulating methanol solution can be increased, so that water and odorous impurities such as mercaptans and sulfides form azeotropes that are easier to evaporate.

[0050] S3: Reflux stage, the separated steam rises and flows into the top of the degassing tower 1, and then passes through the first condenser 3 to form odorous substance steam and methanol reflux liquid. The odorous substance steam then passes through the second condenser 4 to form condensate and then burns; the methanol reflux liquid flows back into the degassing tower 1 through the reflux pipe H1;

[0051] Specifically, under the action of the extractant, the odorous substances (methyl mercaptan, methyl sulfide, dimethyl disulfide, etc.) in the circulating methanol are separated from the circulating methanol after forming steam, and enter the connecting pipe G3 with the mixed steam to meet the first condenser 3. The condensation temperature of the first condenser 3 is 50°C, and the extractant and methanol in the mixed steam undergo phase change and flow back to the degassing tower 1 from the reflux pipe H1, maintaining a reflux ratio of 10, and the odorous substances enter the second condenser 4 through the connecting pipe G4. The condensation temperature of the second condenser 4 is 15°C, and the odorous substances undergo phase change here to form condensate that flows into the connecting pipe G5, and is discharged after being incinerated by the incinerator 5.

[0052] S4: In the distillation and purification stage, the aqueous methanol is heated in the purification tower 2 to form steam, which is then condensed to form methanol distillate.

[0053] Specifically, the extracting distillation liquid after extracting and distilling flows into the connecting pipe G7, and after being heated and vaporized in the first reboiler 6, it returns to the bottom of the degassing tower 1 through the reflux pipe H2, which can further remove odorous substances and provide energy for the distillation and separation of the degassing tower 1. The reboiling temperature of the first reboiler 6 is 60°C. At this temperature, methanol and the extractant will not be reboiled, so they flow into the purification tower 2 through the connecting pipe G8. At this time, the bottom temperature of the purification tower 2 is 115°C, which can make methanol and the extractant boil and vaporize quickly to form steam. The steam enters the third condenser 7 through the connecting pipe G9. The condensation temperature of the third condenser 7 is 50°C. The extractant is pre-cooled to form a condensate that flows back to the purification tower 2 through the reflux pipe H3, and the reflux ratio here is kept at 1.5. Methanol is distilled out through the distillation pipe G10.

[0054] The condensate and the unvaporized methanol refluxed into the purification tower 2 flow into the connecting pipe G11 at the bottom of the purification tower 2, and after being heated and vaporized in the second reboiler 8, flow back to the bottom of the purification tower 2 through the reflux pipe H4, thereby improving the methanol recovery efficiency and providing energy for purification and separation in the purification tower 2. The reboiler temperature of the second reboiler 8 is 90°C, which will not vaporize the extractant, and the extractant is discharged through the distillation pipe 12.

[0055] The circulating methanol after the above steps was sampled and analyzed, and the results are as follows in Table 1:

[0056] Table 1 Experimental data of circulating methanol extraction and distillation in Example 1

[0057] Methanol% DMSO% Methyl mercaptan% Methyl sulfide% Dimethyl disulfide % Azo% acetone% Acetaldehyde% Methanol Recycling 96.268 0.2 0.031 0.18 0.63 0.43 0.017 0.043 1h tower kettle 25.30 0.89 0 0 0 0 0 0.022 2h tower kettle 28.92 0.437 0 0 0 0 0 0 2h Tower Top 9.56 4.122 0.289 0.590 3.789 0.66 0.2 0.039

[0058] As shown in Table 1, the circulating methanol can remove odorous substances such as methyl sulfide, methyl mercaptan, dimethyl disulfide, acetone, and acetaldehyde from the circulating methanol through desalted water extraction and distillation, and the removal rate of these substances is 100%. The odorous substances are gathered at the top of the tower and are safely discharged after condensation and incineration without polluting the environment. The methanol extracted from the top of the purification tower has a purity of up to 99.9%.

[0059] Embodiment 2

[0060] The difference between this embodiment and embodiment 1 is that the addition ratio of the extractant to the circulating methanol is 2, the top reflux ratio of the degassing tower 1 is 20, the top reflux ratio of the purification tower is 2, the first condenser temperature is 55°C, and the third condenser temperature is 55°C.

[0061] Embodiment 3

[0062] The difference between this embodiment and embodiment 1 is that the addition ratio of the extractant to the circulating methanol is 2.5, the top reflux ratio of the degassing tower 1 is 30, the top reflux ratio of the purification tower is 2.5, the temperature of the first condenser is 60°C, and the temperature of the third condenser is 60°C.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that the S1 pre-charging stage is not adopted. The specific steps are to first start the device, then start the extractant pump 9 to pump in the extractant, and finally start the circulating methanol pump 10 to pump in the circulating methanol.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 2 is that the S1 pre-charging stage is not adopted, and the other steps are the same as above.

[0067] Comparative Example 3

[0068] The difference between this comparative example and the third embodiment is that the S1 pre-feeding stage is not adopted, and the other steps are the same as above.

[0069] In the above comparative experiments, as the ratio of the addition of the extractant to the circulating methanol increases, the content of odorous substances such as mercaptans and sulfides in the degassing tower bottom can be reduced. The increase in the ratio of the addition of the extractant to the circulating methanol will increase the distillation energy consumption of the methanol purification tower. Through comparative experiments, the use of S1 pre-feeding can more effectively remove odorous substances in the circulating methanol. The comparative results are shown in Table 2:

[0070] Table 2

[0071] Methanol content at the top of the degassing tower / % Methanol content in degassing tower kettle / % Purity of methanol extracted from the extraction process / % Embodiment 1 9.56 38.56 99.9 Embodiment 2 6.32 28.92 99.95 Embodiment 3 6.15 23.14 99.98 Comparative Example 1 10.75 36.78 99.89 Comparative Example 2 7.56 28.12 99.9 Comparative Example 3 6.28 28.92 99.9

[0072] The above are only embodiments of the present invention. The invention is not limited to the field involved in this implementation case. The common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A deodorization system in a water-soluble fiber production process, characterized in that: The invention comprises a degassing tower (1) and a purification tower (2) connected by a pipeline; the degassing tower (1) is provided with a methanol feed port and an extractant feed port; a first condenser (3) and a second condenser (4) are sequentially connected at the top of the degassing tower (1), and a third condenser (7) is provided at the top of the purification tower (2).

2. The deodorizing system in the water-soluble fiber production process according to claim 1, characterized in that: A methanol feed pump (9) and an extractant feed pump (10) are provided in the middle of the degassing tower (1).

3. The deodorizing system in the water-soluble fiber production process according to claim 2, characterized in that: The first condenser (3) is provided with a reflux pipe (H1), the inlet of the reflux pipe (H1) is connected to the pipeline of the first condenser (3), and the outlet of the reflux pipe (H1) is connected to the upper part of the degassing tower (1); the outlet of the second condenser (4) is connected to an incinerator (5).

4. The deodorizing system in the water-soluble fiber production process according to claim 3, characterized in that: The bottom of the degassing tower (1) is connected to a first reboiler (6), a reflux pipe (H2) is provided between the first reboiler (6) and the degassing tower (1), the inlet of the reflux pipe (H2) is connected to the first reboiler (6), and the outlet is connected to the bottom of the degassing tower (1); the first reboiler (6) is connected to the purification tower (2).

5. The deodorizing system in the water-soluble fiber production process according to claim 4, characterized in that: The third condenser (7) is provided with a reflux pipe (H3) and a distillation pipe (G10), the inlet of the reflux pipe (H3) is connected to the pipeline of the third condenser (7), and the outlet of the reflux pipe (H3) is connected to the upper part of the purification tower (2).

6. The deodorizing system in the water-soluble fiber production process according to claim 5, characterized in that: The bottom of the purification tower (1) is connected to a second reboiler (8), a reflux pipe (H4) is provided between the second reboiler (8) and the purification tower (2), the inlet of the reflux pipe (H4) is connected to the second reboiler (8), and the outlet is connected to the bottom of the purification tower (2); the second reboiler (8) is also provided with a distillation pipe (G12).

7. A deodorization method in a water-soluble fiber production process, using the deodorization system in a water-soluble fiber production process according to any one of claims 1 to 6, comprising the following steps: S1: Pre-feeding stage, firstly, 30% of the extractant is pumped into the degassing tower (1), and then the circulating methanol liquid is pumped into the extractant after the temperature is raised; S2: extraction and separation stage, when reflux appears at the top of the tower, the remaining extractant is continuously pumped into the degassing tower (1); the extractant extracts the methanol in the circulating methanol liquid to form aqueous methanol, and the odorous substances in the circulating methanol liquid form separation steam; S3: reflux stage, the separated steam rises and flows into the top of the degassing tower (1) and then passes through the first condenser (3) to form odorous substance steam and methanol reflux liquid. The odorous substance steam then passes through the second condenser (4) to form condensate and then burns; The methanol reflux liquid flows back into the degassing tower (1) through the reflux pipe (H1); S4: In the distillation and purification stage, the aqueous methanol is heated in the purification tower (2) to form steam, which is then condensed to form methanol distillate.

8. The deodorizing method in the water-soluble fiber production process according to claim 7, characterized in that: In S1, the overall addition ratio of the extractant to the circulating methanol is 1 to 3:

1.

9. The deodorizing method in the water-soluble fiber production process according to claim 8, characterized in that: The degassing tower (1) has a top reflux ratio of 10 to 30 and a bottom temperature of 80 to 90° C.; the purification tower (2) has a reflux ratio of 1 to 3 and a bottom temperature of 110 to 120° C.

10. The deodorizing method in the water-soluble fiber production process according to claim 9, characterized in that: The temperature of the first condenser is 50-60°C, the temperature of the second condenser is 15-20°C, and the cooling medium is 12°C circulating water; the temperature of the third condenser is 50-60°C, and the cooling medium is 33°C circulating water.

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