Cotton linter cooking process based on electric heating digester

Abstract

The invention relates to the technical field of refined cotton production processes, in particular to a cotton linter cooking process based on an electric heating cooking boiler, which comprises the following steps: dispersing cotton linters after cotton opening to obtain treated cotton linters; the treated cotton linters are put into an electric heating digester, the digesting conditions are set, and the mass ratio of alkali liquor to the cotton linters in the digesting conditions is (10-12): 1; the method comprises the following steps: fully dipping cotton linters under the action of a penetrant, then carrying out alkaline cooking, rapidly cooling a cooked cotton linter sample, washing until filtrate is neutral, removing excessive moisture in cotton pulp, and carrying out vacuum drying to determine the polymerization degree of the cotton linters. According to the method, the cooking condition of a large liquid ratio is controlled, so that the temperature control in the cooking process is more constant, and the polymerization degree and the uniformity of the sample are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of refined cotton production technology, specifically to a cotton linter cooking process based on an electrically heated cooking pot. Background Technology

[0002] After more than 30 years of development, the refined cotton industry has formed a relatively complete product system, and its products are widely used in cotton cellulose industries such as nitrocellulose, cellulose acetate, and ether cellulose. However, currently, the highest stable degree of polymerization of refined cotton products in China can reach 2900 DP, but the product uniformity is not high.

[0003] With the development of the new energy and semiconductor industries, new quality requirements have been put forward for the supporting refined cotton industry. High degree of polymerization and high uniformity products have become the current development trend. At present, the traditional process mainly uses steam to heat the steaming equipment. Steam heating efficiency is relatively low, often resulting in a temperature difference of nearly 20°C between the gas phase and liquid phase inside the large steaming ball. This causes uneven heating of the cotton linters inside the steaming ball, resulting in large deviations in the degree of polymerization of the same batch of products measured multiple times. A single measurement result is not representative, and multiple measurements are often required to obtain the average value of the product's degree of polymerization, which is time-consuming and labor-intensive.

[0004] To minimize the temperature difference between the gas and liquid phases, the cooking method adopted by the company involves a cooking temperature fluctuation of about 10°C. This exposes a large amount of cotton linters to the gas phase, which on the one hand easily leads to the disordered oxidation and degradation of cellulose, and on the other hand, the cotton linters do not come into sufficient contact with the cooking liquid during cooking, making it difficult to remove impurities such as lignin evenly. This often requires higher cooking temperatures, which accelerates the degradation of cellulose and is not conducive to the formation of high-polymerization products. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the purpose of this invention is to provide a cotton linter cooking process based on an electrically heated cooking pot. The realization of a high liquid-to-cook ratio cooking condition in this invention enables constant temperature control of the cooking pot and greatly improves the uniformity of sample polymerization.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A cotton linter cooking process based on an electrically heated cooking pot includes the following steps: After the cotton fibers are opened, they are dispersed to obtain the processed cotton fibers.

[0007] The treated cotton linters are placed in an electric heating cooker, and the cooking conditions are set. The mass ratio of alkali solution to cotton linters in the cooking conditions is 10~12:1. Through electric heating, the cotton linters are kept in the liquid phase during the heating process, and the heating is uniform.

[0008] The natural structure of cotton linter fibers hinders the contact between the alkali solution and the fiber interior. With the help of a penetrant, the surface tension of the alkali solution can be significantly reduced, increasing the wetting ability of the cooking liquor on the cotton linter. This makes it easier for the cooking liquor to penetrate into the secondary wall of the cotton linter fibers, accelerating the penetration and diffusion of the cooking liquor and the swelling effect of the raw materials. It also allows for full contact with impurities such as cellulose, lignin, and hemicellulose. After the cotton linter is fully impregnated, it is subjected to alkaline cooking. The cooked cotton linter sample is then rapidly cooled and washed until the filtrate is neutral to remove excess water from the cotton pulp. After vacuum drying, a high-polymerization and highly uniform cotton linter product based on an electrically heated cooking pot is obtained.

[0009] Compared to traditional steam heating processes, this invention employs a high-liquid-ratio cooking process based on an electrically heated cooking vessel, resulting in higher electrothermal efficiency. During the heating process, a large amount of cotton lint remains in the liquid phase, allowing for more effective temperature control and more uniform heating of the cotton lint, leading to greater homogeneity in the degree of polymerization of the same batch of products. Furthermore, the high-liquid-ratio cooking conditions allow for more thorough contact between the cooking liquor and the cotton lint and impurities, thus enhancing its removal of lignin and other impurities. The implementation of this high-liquid-ratio cooking process based on the electrically heated cooking vessel ensures constant temperature control within the cooking vessel, significantly improving the degree of polymerization and uniformity of the samples.

[0010] In a preferred embodiment of the present invention, the alkaline solution is sodium hydroxide or potassium hydroxide, and the mass percentage concentration of the alkaline solution is 0.8% to 2%.

[0011] In a preferred embodiment of the present invention, the penetrant components are sodium isooctanol polyoxyethylene ether phosphate and water, and the mass percentage of sodium isooctanol polyoxyethylene ether phosphate in the penetrant is 25% to 40%.

[0012] In a preferred embodiment of the present invention, the cooking method is as follows: the cooking is completed under nitrogen conditions by idling, heating once, releasing gas, heating twice and holding. Under nitrogen conditions, the cotton linters can be effectively prevented from contacting air in the alkaline solution at high temperature, thereby inhibiting the decrease in degree of polymerization. The cooking time and temperature of the present invention are the optimal parameters obtained by a series of experiments to effectively remove lignin and minimize the decrease in degree of polymerization.

[0013] In a preferred embodiment of the present invention, nitrogen gas is introduced for 10 to 20 minutes to replace the air in the electric heating cooking pot, and then the pot is run idle for 40 to 60 minutes.

[0014] In a preferred embodiment of the present invention, the initial heating temperature is 109°C to 111°C, and the gas is released for 8 min to 12 min to reach atmospheric pressure.

[0015] In a preferred embodiment of the present invention, the secondary heating temperature is 119℃~121℃, and the holding time is 38 min~42 min.

[0016] In a preferred embodiment of the present invention, the cotton linter raw material is selected from Class I Grade III linter.

[0017] In a preferred embodiment of the present invention, the electric heating cooking pot is provided with a drain basket, the bottom of the drain basket is provided with filter holes, and a baffle is provided in the drain basket to prevent the short cotton fibers from slipping off, so as to make the mixing more uniform.

[0018] The electric cooking pot of this invention is made entirely of 316 high-quality stainless steel, which can significantly improve the corrosion resistance of the cooking pot; the heating part adopts a heating coil to directly heat the pot body, which has the advantages of rapid heating, simple structure, convenient maintenance, and economical replacement.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The cotton linter cooking process based on an electric heating cooker of the present invention involves dispersing the opened cotton linters, placing the treated cotton linters into an electric heating cooker, and controlling the mass ratio of alkali solution to cotton linters to be 10~12:1. The natural structure of cotton linter fibers hinders the contact between the alkali solution and the fiber interior. Under the action of a penetrant, the surface tension of the alkali solution can be significantly reduced, increasing the wetting ability of the cooking liquor on the cotton linters, making it easier for the cooking liquor to penetrate into the secondary wall of the cotton linter fibers, accelerating the penetration and diffusion of the cooking liquor and the swelling effect of the raw materials, fully contacting impurities such as cellulose, lignin, and hemicellulose, and cooking the cotton linters after they are fully impregnated. The cooked cotton linter sample is then rapidly cooled, washed until the filtrate is neutral, and excess water in the cotton pulp is removed. After vacuum drying, the sample is used to determine the degree of polymerization of the cotton linters. Compared to traditional steam heating processes, this invention employs a high-liquid-ratio cooking process based on an electrically heated cooking vessel, resulting in higher electrothermal efficiency. During the heating process, a large amount of cotton lint remains in the liquid phase, allowing for more effective temperature control and more uniform heating of the cotton lint, leading to more consistent polymerization results within the same batch of products. Furthermore, the high-liquid-ratio cooking conditions allow for more thorough contact between the cooking liquor and the cotton lint and impurities, thus enhancing its effectiveness in removing lignin, hemicellulose, and other impurities. The implementation of this high-liquid-ratio cooking process based on the electrically heated cooking vessel ensures constant temperature control within the cooking vessel, significantly improving the polymerization degree and uniformity of the samples.

[0020] 2. The high liquid ratio electrothermal cooking process of the present invention has higher heating efficiency than the traditional cooking process, can better stabilize the cooking temperature, remove lignin, thereby improving the degree of polymerization and uniformity of refined cotton, and can eliminate the process defects of poor uniformity when the current mainstream low liquid ratio cooking process is used to produce high degree of polymerization products. Attached Figure Description

[0021] Figure 1 In the figure, (a) is a top view of the pot body of the electric heating cooking pot of the present invention, and (b) is a cross-sectional view, wherein 1 is a sealing gasket, 2 is a thermometer, 3 is the pot body, and 4 is a fixing post.

[0022] Figure 2 In the diagram, (a) is a bottom view of the lid portion of the electric heating cooking pot of the present invention, (b) is a top view, and (c) is a front view, wherein 5 is a nut, 6 is a vent, 7 is a needle valve, 8 is a pressure gauge, and 9 is a safety valve.

[0023] Figure 3 In the figure, (a) is a top view of the drain basket in the electric heating cooking pot of the present invention, and (b) is a cross-sectional view, wherein 10 is the drain basket, 11 is the filter hole, and 12 is the baffle.

[0024] Figure 4 In the figures, (a) is the cotton linter product prepared under the high liquid-to-volume cooking conditions based on an electric heating cooker in Example 1 of the present invention, and (b) is the cotton linter product produced under the conditions of Comparative Example 1. Detailed Implementation

[0025] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0027] Example 1 A cotton linter cooking process based on an electrically heated cooking pot includes the following steps: (1) Remove the cotton fibers from the first grade of third grade short cotton fibers, tear the intertwined cotton fibers apart, and make the cotton fibers fully dispersed.

[0028] (2) Test samples were taken from different parts of the cotton linter sample. The treated cotton linter sample was placed in an electric heating cooker. The cooking conditions were set as follows: the mass ratio of alkali solution to cotton linter was 12:1, the alkali solution was sodium hydroxide with a mass percentage concentration of 0.8%, and a penetrant was added to the electric heating cooker. Under the action of the penetrant, the cotton linter was fully impregnated. The penetrant was sodium isooctanol polyoxyethylene ether phosphate and water. The mass percentage of sodium isooctanol polyoxyethylene ether phosphate in the penetrant was 35%. Then, the cooker was run empty under nitrogen for 60 minutes. The temperature was raised to 110°C for the first time within 60 minutes, and the gas was released for 10 minutes. The temperature was raised to 120°C for the second time within 40 minutes and maintained for 40 minutes. After the cooker was depressurized, the cotton linter sample was quickly taken out and placed in ice water to cool down quickly. After taking samples from multiple random locations, the samples were washed repeatedly with distilled water about 5 to 6 times until the pH of the cotton pulp filtrate was 7.

[0029] (3) Place the cotton linters into a Buchner funnel and filter under reduced pressure to remove excess water. Take them out, place them in an evaporating dish, tear them open, and put them directly into a 60°C vacuum drying oven to dry for 3 hours while maintaining a vacuum of 0.09 MPa. This is used to determine the degree of polymerization.

[0030] Example 2 A cotton linter cooking process based on an electrically heated cooking pot includes the following steps: (1) After removing the cotton, the third-grade cotton linters are torn apart to allow the cotton fibers to be fully dispersed.

[0031] (2) Test samples were taken from different parts of the cotton linter sample. The treated cotton linter sample was placed in an electric heating cooker. The cooking conditions were set as follows: the mass ratio of alkali solution to cotton linter was 10:1, the alkali solution was sodium hydroxide with a mass percentage concentration of 1.4%, and the cotton linter was fully impregnated under the action of a penetrant. The penetrant was sodium isooctanol polyoxyethylene ether phosphate and water. The mass percentage of sodium isooctanol polyoxyethylene ether phosphate in the penetrant was 40%. Then, the sample was run in nitrogen for 40 minutes. The temperature was raised to 110°C for the first time within 40 minutes, and the gas was released for 8 minutes. The temperature was raised to 120°C for the second time within 38 minutes and maintained for 38 minutes. After the cooker was depressurized, the cotton linter sample was quickly taken out and placed in ice water to cool down quickly. After taking samples from multiple random locations, the sample was washed repeatedly with distilled water about 5 to 6 times until the pH of the cotton pulp filtrate was 7.

[0032] (3) Place the cotton linters into a Buchner funnel and filter under reduced pressure to remove excess water. Take them out, place them in an evaporating dish, tear them open, and put them directly into a 60°C vacuum drying oven to dry for 3 hours while maintaining a vacuum of 0.09 MPa. This is used to determine the degree of polymerization.

[0033] Example 3 A cotton linter cooking process based on an electrically heated cooking pot includes the following steps: (1) After removing the cotton, the third-grade cotton linters are torn apart to allow the cotton fibers to be fully dispersed.

[0034] (2) Test samples were taken from different parts of the cotton linter sample. The treated cotton linter sample was placed in an electric heating cooker. The cooking conditions were set as follows: the mass ratio of alkali solution to cotton linter was 11:1, the alkali solution was sodium hydroxide with a mass percentage concentration of 2%, and the cotton linter was fully impregnated under the action of a penetrant. The penetrant was sodium isooctanol polyoxyethylene ether phosphate and water, and the mass percentage of sodium isooctanol polyoxyethylene ether phosphate in the penetrant was 25%. Then, the sample was run in nitrogen for 50 minutes, and then the temperature was raised to 110°C for the first time within 50 minutes. The gas was released for 12 minutes, and the temperature was raised to 120°C for the second time within 42 minutes and maintained for 40 minutes. After the cooker was depressurized, the cotton linter sample was quickly taken out and placed in ice water to cool down quickly. After taking samples from multiple random locations, the sample was washed repeatedly with distilled water about 5 to 6 times until the pH of the cotton pulp filtrate was 7.

[0035] (3) Place the cotton linters into a Buchner funnel and filter under reduced pressure to remove excess water. Take them out, place them in an evaporating dish, tear them open, and put them directly into a 60°C vacuum drying oven to dry for 3 hours while maintaining a vacuum of 0.09 MPa. This is used to determine the degree of polymerization.

[0036] Comparative Example 1 A cotton linter cooking process based on an electrically heated cooking pot includes the following steps: (1) After removing the cotton, the third-grade cotton linters are torn apart to allow the cotton fibers to be fully dispersed.

[0037] (2) Test samples were taken from different parts of the cotton linter sample. The treated cotton linter sample was placed in an electric heating cooker. The cooking conditions were set as follows: the mass ratio of alkali solution to cotton linter was 3:1, the alkali solution was sodium hydroxide with a mass percentage concentration of 3%, and a penetrant was added to the electric heating cooker. Under the action of the penetrant, the cotton linter was fully impregnated. The penetrant was sodium isooctanol polyoxyethylene ether phosphate and water. The mass percentage of sodium isooctanol polyoxyethylene ether phosphate in the penetrant was 35%. Then, the cooker was run empty under nitrogen for 60 minutes. The temperature was raised to 110°C for the first time within 60 minutes, and the gas was released for 10 minutes. The temperature was raised to 120°C for the second time within 40 minutes and maintained for 40 minutes. After the cooker was depressurized, the cotton linter sample was quickly taken out and placed in ice water to cool down quickly. After taking samples from multiple random locations, the samples were washed repeatedly with distilled water about 5 to 6 times until the pH of the cotton pulp filtrate was 7.

[0038] (3) Place the cotton linters into a Buchner funnel and filter under reduced pressure to remove excess water. Take them out, place them in an evaporating dish, tear them open, and put them directly into a 60°C vacuum drying oven to dry for 3 hours while maintaining a vacuum of 0.09 MPa. This is used to determine the degree of polymerization.

[0039] The electric cooking pot used in this invention is the Fuaibo electric cooking pot, and the standard is based on GB / T 2678.1.

[0040] Results Analysis Table 1. Polymerization degree of products obtained from multi-point sampling under high liquid-to-ratio cooking conditions in an electrically heated cooker and under conventional conditions. Table 1 shows the degree of polymerization results of the products prepared under the high liquid-to-liquid ratio cooking conditions in Example 1 of the present invention and Comparative Example 1. According to the data in Table 1, the average degree of polymerization of the products prepared by the method of the present invention is increased by approximately 8.1% compared to the traditional process, and the relative standard deviation decreases from 9.4% to 2.6%, indicating that the cooking conditions of the present invention are more conducive to improving the degree of polymerization and uniformity of the samples.

[0041] The electric cooking pot of this invention is made entirely of 316 high-quality stainless steel, which can significantly improve the corrosion resistance of the cooking pot; the heating part adopts a heating coil to directly heat the pot body, which has the advantages of rapid heating, simple structure, convenient maintenance, and economical replacement.

[0042] Figure 1 In the image, (a) is a top view of the pot body portion of the electric heating cooking pot of the present invention, and (b) is a sectional view. Figure 1 The top view is a top view, and the bottom view is a cross-sectional view cut along the diameter of the circle's center. The thermometer 2 is located inside the pot body 3 and is connected to an external PID temperature controller, which can monitor the internal temperature of the pot body in real time. The internal space of the pot body is used to place the drain basket. The eight fixing posts 4 on the top of the pot body are used to connect the pot body and the pot lid. The connection requires a sealing gasket 1 to keep the inside of the pot body a sealed space.

[0043] Figure 2 In the diagram, (a) is a bottom view of the lid portion of the electric heating cooking pot of the present invention, (b) is a top view, and (c) is a front view. Figure 2 As shown, this part is the pot lid, and the eight nuts 5 are used for connection. Figure 1 (a) The pot body has a fixed stake 4; the three vents 6 at the bottom of the pot lid are composed of a large number of small holes and are mainly used for releasing steam during the cooking process, which is released through the needle valve 7; as the temperature rises, the pressure inside the pot will increase, and the pressure gauge 8 on the top of the pot lid can monitor the internal situation in real time; the safety valve 9 is mainly used for the rapidly rising high pressure inside the pot, and automatically releases steam when it suddenly exceeds the set pressure; handles are provided on both sides of the pot lid for easy movement when opening and closing the lid.

[0044] Figure 3 In the image, (a) is a top view of the drain basket in the electric heating cooking pot of the present invention, and (b) is a cross-sectional view. Figure 3 The top view is a bottom view, and the bottom view is a cross-sectional view cut along the diameter of the circle's center. The drain basket 10 is placed inside the pot during steaming. The bottom of the drain basket 10 is equipped with filter holes 11 to facilitate the separation of cotton lint from the cooking liquid when the lid is opened, so that it can be placed in ice water more quickly. The drain basket is also equipped with a baffle 12 to prevent the cotton lint from slipping and to make it mix more evenly.

[0045] Figure 4 In the figures, (a) is the cotton linter product prepared under the high liquid-to-volume cooking conditions based on an electric heating cooker in Example 1 of the present invention, and (b) is the cotton linter product produced under the conditions of Comparative Example 1, such as... Figure 4 As shown, the refined cotton products under the cooking conditions of the present invention have fewer and smaller black spots. Therefore, compared with Comparative Example 1, the present invention has a better effect on removing impurities such as lignin.

[0046] In summary, compared to traditional steam heating processes, this invention employs a high-liquid-ratio cooking process based on an electrically heated cooking pot. This process offers higher electrothermal efficiency, a smaller temperature difference between the liquid and gas phases during heating, and more accurate temperature control during cooking. This results in more uniform heating of the cotton linters and greater uniformity in the degree of polymerization of the same batch of products. Furthermore, the high-liquid-ratio cooking conditions, with a mass ratio of alkali solution to cotton linters of 10-12:1, allow the cooking liquor to react more fully with the cotton linters, thus enhancing its lignin removal effect. The implementation of this high-liquid-ratio cooking process based on an electrically heated cooking pot ensures constant temperature control within the cooking pot, significantly improving the degree of polymerization and uniformity of the samples.

[0047] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0048] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A cotton linter cooking process based on an electrically heated cooking pot, characterized in that, Includes the following steps: After the cotton is opened, the short cotton fibers are dispersed to obtain the processed short cotton fibers. The treated cotton linters are placed in an electric heating cooker, and the cooking conditions are set. The mass ratio of alkali solution to cotton linters in the cooking conditions is 10~12:

1. The cotton linters are kept in the liquid phase and heated evenly by electric heating during the heating process. A penetrant is added to the electric cooking pot to reduce the surface tension of the alkaline solution. The cotton linters are then fully impregnated and subjected to alkaline cooking. The cooked cotton linter sample is cooled and washed until the filtrate is neutral. Excess water in the cotton pulp is removed and the product is obtained by vacuum drying.

2. The cotton linter cooking process based on an electrically heated cooking pot according to claim 1, characterized in that, The alkaline solution is sodium hydroxide or potassium hydroxide, and the mass percentage concentration of the alkaline solution is 0.8%~2%.

3. The cotton linter cooking process based on an electrically heated cooking pot according to claim 1, characterized in that, The penetrant consists of sodium isooctanol polyoxyethylene ether phosphate and water, with the sodium isooctanol polyoxyethylene ether phosphate comprising 25% to 40% by mass.

4. The cotton linter cooking process based on an electrically heated cooking pot according to claim 1, characterized in that, The cooking method is as follows: the cooking is completed under nitrogen conditions by idling, heating once, releasing gas, heating twice and holding.

5. The cotton linter cooking process based on an electrically heated cooking pot according to claim 4, characterized in that, Introduce nitrogen for 10-20 minutes to replace the air in the electric cooking pot, then run it idle for 40-60 minutes.

6. The cotton linter cooking process based on an electrically heated cooking pot according to claim 4, characterized in that, The initial heating temperature is 109℃~111℃, and the gas is released for 8 min~12 min to reach atmospheric pressure.

7. The cotton linter cooking process based on an electrically heated cooking pot according to claim 4, characterized in that, The secondary heating temperature is 119℃~121℃, and the holding time is 38 min~42 min.

8. The cotton linter cooking process based on an electrically heated cooking pot according to claim 1, characterized in that, The raw material for cotton linters is selected from Class I Grade III linters.

9. The cotton linter cooking process based on an electrically heated cooking pot according to claim 1, characterized in that, The electric heating cooking pot is provided with a drain basket (10), the bottom of the drain basket (10) is provided with filter holes (11), and a baffle (12) is provided in the drain basket (11).

10. The cotton linter cooking process based on an electrically heated cooking pot according to claim 1, characterized in that, The electric cooking pot is made of 316 stainless steel, and the heating element uses a heating coil to directly heat the pot body.

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