Environment-friendly preparation method of viscose-based carbon fiber pre-oxidized felt by catalytic heat treatment and special equipment thereof

Abstract

The application provides an environment-friendly viscose-based carbon fiber pre-oxidized felt catalytic heat treatment preparation method and special equipment thereof, and the specific steps are as follows: viscose fiber is needled into a felt, is subjected to pickling treatment, and is dried to obtain a viscose fiber felt; a catalyst is prepared by mixing a silica sol, an amide and a small molecule alcohol, the viscose fiber felt is impregnated with the catalyst and dried to obtain a pretreated viscose fiber felt; then the pretreated viscose fiber felt is subjected to heat treatment and is cooled to obtain a product. The special equipment comprises a waste gas combustion chamber, a heat exchange chamber, a temperature adjusting chamber and a furnace body. The waste gas generated in the preparation process is recycled by the special equipment, so that the waste gas is effectively utilized and treated. The preparation process is simple, safe and environment-friendly, effectively solves the pain points of serious equipment corrosion, serious pollution and high energy consumption in the industry, and greatly improves the product production efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of viscose-based carbon fiber, in particular, relates to a kind of environmentally friendly viscose-based carbon fiber pre-oxidation felt catalytic heat treatment preparation method and special equipment thereof. BACKGROUND

[0002] Viscose-based carbon fiber felt has excellent properties such as heat insulation, heat preservation and ablation resistance, and is an indispensable heat insulation material in a non-oxidizing atmosphere at high temperature (2000-3300°C). Its precursor is viscose fiber, which belongs to regenerated cellulose and has a crystal structure of cellulose II type. The molecular formula is (C6H 10 O5) n , and the carbon content is 44.44%, i.e. the theoretical carbon yield. However, during the pyrolysis of viscose fiber, tar and small molecule volatile substances such as CO, CO2, CH4, HCOOH, etc. are generated, resulting in a carbon yield of only about 15% in actual production. The generation of tar not only reduces the carbon yield, but also pollutes the fiber, affects the performance of the product, and seriously pollutes the production equipment and the environment, increasing the cost of equipment maintenance and environmental protection.

[0003] The production process of viscose-based carbon fiber mainly has two stages, i.e. a thermal decomposition stage and a carbonization stage. The thermal decomposition of viscose fiber mainly forms solid residues, tar and gaseous products. There are mainly two competing reactions in this stage. One is dehydration, atomic rearrangement and formation of carbonyl groups, which further form carbon four residual chains, and in the carbonization stage, the six-membered carbon ring structure of graphite sheet is formed by polymerization; the other is the breakage of glycosidic bonds between cellulose pyranose glucose structural units to produce levoglucosan (1,6-dehydration-β-D-glucose) and other oxygen-containing compounds, which further form volatile tar, and the generation of these oxygen-containing compounds is the main factor for the reduction of carbon yield. In order to improve the carbon yield of viscose-based carbon fiber production and reduce the generation of tar, a catalyst is generally used for pretreatment before low-temperature carbonization treatment. An effective catalyst needs to have the following functions: reducing the temperature required for pyrolysis reaction and moderating the reaction intensity, reducing the temperature required for dehydration reaction and prolonging the reaction temperature zone; making the viscose fiber fully dehydrated during pyrolysis, reducing the yield of levoglucosan and tar, and improving the carbon yield.

[0004] The commonly used catalysts currently include inorganic catalysts, organic catalysts and inorganic-organic mixed catalysts. Such compounds can catalyze the reactions related to the elimination of hydroxyl groups or esterification of hydroxyl groups, promote the dehydration of cellulose at low temperature, reduce the generation of volatile substances, and the highest carbon yield can reach 39.3%. However, the commonly used catalysts such as ammonium sulfate, ammonium chloride, diammonium hydrogen phosphate and dihydrogen ammonium phosphate are easy to corrode the equipment, and the exhaust gas (mainly composed of tar and catalyst decomposition products) also has the characteristics of being difficult to incinerate, increasing the difficulty of waste gas treatment, and being not conducive to environmental protection requirements.

[0005] At present, the main way of treating waste gas in this field is spray tower absorption method and condensation method. The spray tower absorption method introduces waste gas into a purification tower, so that the tar and catalyst decomposition in the waste gas are neutralized by the absorption liquid, and then the waste gas is dehydrated and demisted by a demisting plate and discharged into the atmosphere by a fan. However, this method produces wastewater with high chemical oxygen demand (COD) and high salt content, which is difficult to treat. The condensation method condenses harmful substances such as tar in the waste gas to achieve the purpose of purification or recovery. However, this method has high cost, and the condensed tar causes serious corrosion and pollution to the equipment, which needs frequent cleaning and maintenance. Both methods cannot utilize the energy of tar itself, and cause secondary pollution.

[0006] Therefore, it is of great value and significance to research and obtain a high-efficiency and environmentally-friendly catalytic heat treatment preparation method for viscose-based carbon fiber pre-oxidized felt and a special equipment thereof. SUMMARY

[0007] The present application aims to provide an environmentally-friendly catalytic heat treatment preparation method for viscose-based carbon fiber pre-oxidized felt and a special equipment thereof, to solve the technical problems of serious equipment corrosion, serious pollution, and high energy consumption.

[0008] To achieve the above-mentioned purpose, the present application provides an environmentally-friendly catalytic heat treatment preparation method for viscose-based carbon fiber pre-oxidized felt, and the specific steps are as follows:

[0009] S1. Spunlacing viscose fibers into felt, acid pickling treatment, drying, and obtaining viscose fiber felt;

[0010] S2. Mixing silica sol, amide, and small molecule alcohol uniformly according to a mass ratio of 2-6:1-2:0.1-1, and using deionized water to configure a catalyst with a total mass concentration of 3-10%; then impregnating the viscose fiber felt with the catalyst and drying to obtain pretreated viscose fiber felt;

[0011] S3. Then, the pretreated viscose fiber felt is heat treated, heated to 260-300℃, and treated for 30-60 minutes, and then cooled to obtain viscose-based carbon fiber pre-oxidized felt;

[0012] The waste gas generated by heat treatment is mixed with nitrogen after heat exchange according to a volume ratio of 2-8:1 for recycling.

[0013] Preferably, in step S1, the acid pickling treatment uses any one of hydrochloric acid, acetic acid, sulfamic acid, methyl sulfonic acid, p-toluene sulfonic acid, or citric acid aqueous solution, or a mixture of any two of the above aqueous solutions, with a total mass concentration of 0.5-5%.

[0014] Preferably, in step S1, the drying method is 110℃ drying for 40 minutes.

[0015] Preferably, in step S2, the particle size of the silica sol is less than 10 microns, the amide is caprolactam or acrylamide, and further preferably acrylamide, and the small molecule alcohol is pentaerythritol.

[0016] Preferably, in step S2, the mass ratio of silica sol, amide, and small molecule alcohol is 6:2:1 or 3:2:0.5.

[0017] Preferably, in step S2, the mass ratio of catalyst to viscose fiber felt is 8-12:1-3, and further preferably 10:1, and the impregnation treatment time is 20-120 minutes.

[0018] Preferably, in step S2, the specific method of drying is: taking out and rolling to a water felt mass ratio of less than 0.6, repeating impregnation-rolling twice, and sending into a drying oven to dry at 105-140℃ until the water content is less than 5%.

[0019] Preferably, the waste gas generated by heat treatment is mixed with nitrogen after combustion and heat exchange at a volume ratio of 6:1 for recycling.

[0020] The special equipment for heat treatment to realize the foregoing method includes a waste gas combustion chamber, a heat exchange chamber, a temperature adjusting chamber, and a furnace body. Along the transmission direction of the pretreated viscose fiber felt, the furnace body is divided into four parts: an incoming felt air seal section, a catalytic heat treatment section, a cooling section, and an outgoing felt air seal section. An exhaust fan is arranged in the catalytic heat treatment section, which discharges the generated waste gas into the waste gas combustion chamber. After combustion, the waste gas interacts with nitrogen in the heat exchange chamber, and then enters the temperature adjusting chamber to be adjusted to a certain temperature before returning to the catalytic heat treatment section through an air inlet fan for recycling.

[0021] Preferably, there are two exhaust fans near one side of the incoming felt air seal section, and one air inlet fan near one side of the cooling section.

[0022] Preferably, the certain temperature is 260-300℃.

[0023] The present application has the following advantages:

[0024] The present application provides a method for preparing an environmentally friendly viscose-based carbon fiber pre-oxidized felt by catalytic heat treatment, and the specific steps are as follows: viscose fiber is needled into a felt, acid washing treatment is performed, and drying is carried out to obtain a viscose fiber felt; silica sol, amide, and small molecule alcohol are configured into a catalyst, and then the viscose fiber felt is impregnated with the catalyst and dried to obtain a pretreated viscose fiber felt; and then the pretreated viscose fiber felt is heat treated and cooled. The present application has the advantages of simple preparation process, safety, and environmental protection, effectively solves the problems of severe equipment corrosion, severe pollution, and high energy consumption in the industry, and greatly improves the production efficiency of products.

[0025] The application also provides a special heat treatment equipment for realizing the method, which comprises a waste gas combustion chamber, a heat exchange chamber, a temperature adjusting chamber and a furnace body, the furnace body is divided into a mat feeding air seal section, a catalytic heat treatment section, a cooling section and a mat discharging air seal section along the transmission direction of the pretreated viscose fiber mat, an exhaust fan is arranged in the catalytic heat treatment section, the exhaust fan discharges the generated waste gas into the waste gas combustion chamber, the waste gas is combusted, interacts with nitrogen in the heat exchange chamber, then enters the temperature adjusting chamber to be adjusted to a certain temperature, and returns to the catalytic heat treatment section through an air feeding fan to realize recycling.

[0026] The specific advantages of the application are as follows:

[0027] 1. The application uses silica sol, amide and small molecule alcohol as a non-strong acid catalyst, which significantly reduces the corrosion problem of traditional strong acid catalysts to equipment. Organic amide attacks the primary hydroxyl group of the glucose molecule of viscose fiber through amide reaction, reduces the generation of levoglucon product, and silica sol and small molecule alcohol can swell the viscose fiber so that the catalyst acts on the inside of the viscose fiber and can further catalyze the decomposition of the product into gas small molecules, thereby greatly reducing the generation of tar product. At the same time, these decomposition generated hydrogen, methane, ethylene and other gas small molecules (small carbon hydrocarbons) have combustible properties and can be directly incinerated. Therefore, the catalyst can reduce the corrosion of the catalyst to the production equipment while ensuring the catalytic effect, and the exhaust gas can be incinerated.

[0028] 2. The catalyst used in the application is an environmentally friendly catalyst, and the generated waste gas can be harmlessly treated through combustion reaction. The special equipment for heat treatment of viscose-based carbon fiber pre-oxidized mat provided by the application uses the generated waste gas for combustion heating, and the waste gas can be discharged after secondary incineration treatment, finally realizing no tar and no wastewater discharge in the production process, effectively solving the problems of serious pollution and high energy consumption in the industry.

[0029] In addition to the objects, features and advantages described above, the application has other objects, features and advantages. The application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, illustrate the preferred embodiments of the application and assist in the explanation of the application. In the drawings:

[0031] Figure 1 It is a structural schematic diagram of the special equipment for heat treatment.

[0032] Figure 2 It is a structural schematic diagram of the special equipment for heat treatment. Figure 1 It is a structural schematic diagram of the special equipment for heat treatment. DETAILED DESCRIPTION

[0033] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0034] like Figure 1 The heat treatment equipment shown includes a waste gas combustion chamber, a heat exchange chamber, a temperature control chamber, and a furnace body. Along the conveying direction of the pretreated viscose fiber felt, the furnace body is divided into four parts: a felt inlet gas seal section, a catalytic heat treatment section, a cooling section, and a felt outlet gas seal section. Figure 2 An exhaust fan is installed in the catalytic heat treatment section. The exhaust fan discharges the generated waste gas into the waste gas combustion chamber. After combustion, the waste gas interacts with nitrogen in the heat exchange chamber, and then enters the temperature regulation chamber to be regulated to a certain temperature. Finally, it returns to the catalytic heat treatment section through the inlet fan, realizing recycling. There are two exhaust fans, located near the inlet felt gas seal section; there is one inlet fan, located near the cooling section. Example 1:

[0035] A method for preparing environmentally friendly viscose-based carbon fiber pre-oxidation felt by catalytic heat treatment, the specific steps of which are as follows:

[0036] S1. The viscose fiber is needle-punched into a felt, pickled and dried at 110°C for 40 min to obtain viscose fiber felt. The pickling solution is a mixture of aminosulfonic acid and citric acid with a total mass concentration of 3%.

[0037] S2. Mix silica sol (particles <10μm), acrylamide, and pentaerythritol in a mass ratio of 6:2:1, add deionized water to prepare a catalyst with a mass concentration of 5%; impregnate viscose fiber felt with the catalyst in a mass ratio of 10:1 for 20 min, remove and roll dry, repeat the impregnation-rolling process twice until the water-felt mass ratio is 0.5, and send it to a drying oven at 110℃ to dry until the water content is 3% to obtain the impregnated and dried viscose fiber felt;

[0038] The mass ratio of catalyst to viscose fiber felt can be 8-12:1-3, such as 8:1, 8:3, 12:2, etc. In this embodiment, it is preferably 10:1.

[0039] S3. The impregnated and dried viscose fiber felt is sent to a special heat treatment equipment. Figure 1 The gas is heated to 260℃ and processed for 60 minutes. The generated exhaust gas is discharged into the exhaust gas combustion chamber through the exhaust fan. The heat generated by the combustion of the exhaust gas interacts with nitrogen in the heat exchange chamber. The gas after combustion is mixed with nitrogen in the temperature regulation chamber at a volume ratio of 6:1 and adjusted to 260℃ before being discharged into the furnace body through the air intake fan, thus completing the recycling process.

[0040] S4. After cooling, viscose fiber catalytic dehydration felt is obtained, which is viscose fiber pre-oxygenated felt.

[0041] The generated waste gas is discharged through the exhaust pipe after secondary incineration treatment. There is no sewage discharge in this process. According to the detection method of GB / T 40200-2021, the polycyclic aromatic hydrocarbon emission concentration is 0.03 mg / m 3 , the NOx emission concentration is 1.05 mg / m 3 , the SOx emission concentration is 0.01 mg / m 3 , and the particulate matter emission concentration is 0.3 mg / m 3 , which meets the existing air pollutant emission limit value of GB 16297. Example 2:

[0042] An environmental-friendly catalytic heat treatment method for preparing viscose-based carbon fiber pre-oxidized felt is as follows:

[0043] S1. The viscose fiber is needled into a felt, acid washed and dried at 110℃ for 40min to obtain a viscose fiber felt, wherein the acid washing uses a mixture of sulfamic acid and citric acid with a total mass concentration of 3% as the acid washing solution;

[0044] S2. Mix silicon sol (particle <10μm), acrylamide and pentaerythritol according to the mass ratio of 3:2:0.5, add deionized water to prepare a catalyst with a mass concentration of 5%; dip the viscose fiber felt in the catalyst for 20min according to the mass ratio of catalyst to viscose fiber felt of 8:1, take out and roll dry, repeat the dipping-rolling dry twice until the water felt mass ratio is 0.5, and send it into a drying oven at 110℃ to dry until the water content is 3%, to obtain the impregnated and dried viscose fiber felt;

[0045] The mass ratio of catalyst to viscose fiber felt can be 8-12:1-3, such as 8:1, 8:3, 12:2, etc. The preferred mass ratio in this embodiment is 10:1. S3. The impregnated and dried viscose fiber felt is sent into a special heat treatment equipment, heated to 260℃, and treated for 60min. The generated waste gas is discharged into a waste gas combustion chamber through an exhaust fan. The heat generated by the waste gas combustion is exchanged with nitrogen in a heat exchange chamber. The burned gas is mixed with nitrogen in a temperature adjusting chamber according to the volume ratio of 6:1, adjusted to 260℃, and then discharged into the furnace body through an air inlet fan to complete the recycling.

[0046] S4. Cooling after discharging, obtaining a viscose fiber catalytic dehydration felt, which is a viscose fiber pre-oxidized felt.

[0047] The generated waste gas is discharged through the exhaust pipe after secondary incineration treatment. There is no sewage discharge in this process. According to the detection method of GB / T 40200-2021, the polycyclic aromatic hydrocarbon emission concentration is 0.05 mg / m 3 , the NOx emission concentration is 1.13 mg / m 3The SOx emission concentration was 0.01 mg / m³. 3 The particulate matter emission concentration was 0.2 mg / m³. 3 It complies with the emission limits for air pollutants from existing pollution sources specified in GB 16297.

[0048] Comparative Example

[0049] A method for preparing viscose-based carbon fiber pre-oxidized felt by catalytic heat treatment, the specific steps of which are as follows:

[0050] S1. The viscose fiber is needle-punched into a felt, pickled and dried at 110°C for 40 min to obtain viscose fiber felt. The pickling solution is a mixture of aminosulfonic acid and citric acid with a total mass concentration of 3%.

[0051] S2. Mix ammonium sulfate and ammonium chloride at a mass ratio of 3:1, add deionized water and triethanolamine to adjust the pH to 5 to obtain a catalyst with a mass concentration of 5%; impregnate the viscose fiber felt with the catalyst for 20 minutes, take it out and roll it dry, repeat the impregnation-rolling process twice until the water-felt mass ratio is 0.5, and send it to a drying oven at 110℃ to dry until the water mass content is 3% to obtain the impregnated and dried viscose fiber felt;

[0052] S3. The impregnated and dried viscose fiber felt is fed into a dedicated heat treatment device and heated to 260℃ for 60 minutes. The resulting waste gas is discharged into a spray tower via an exhaust fan, where the tar in the waste gas is absorbed and neutralized by the absorbent liquid in the spray tower. The waste gas is then dehydrated and demisted by a demister plate before being discharged by the fan. The absorbent wastewater is recycled and treated before being discharged. The furnace body of the heat treatment equipment remains the same; only the recovery device is replaced with a spray tower for recovery.

[0053] S4. After cooling, viscose fiber catalytic dehydration felt is obtained, which is viscose fiber pre-oxygenated felt.

[0054] The generated exhaust gas is discharged through an exhaust stack, and its polycyclic aromatic hydrocarbon emission concentration was measured to be 0.69 mg / m³ according to the testing method in GB / T 40200-2021. 3 The NOx emission concentration was 1.23 mg / m³. 3 The SOx emission concentration was 0.78 mg / m³. 3, meet the existing pollution source air pollutant emission limit value provisions in GB 16297. The wastewater generated in production is detected to have a chemical oxygen demand (COD) of 40000 mg / L and a biochemical oxygen demand (BOD) of 2000 mg / L, and has high pollution. After chemical treatment, the wastewater is discharged according to the wastewater comprehensive discharge standard in GB 8978. The ammonium sulfate and ammonium chloride catalysts used in the comparative example should be recovered and treated by using a spray tower method. The generated waste gas is introduced into the spray tower, neutralized by the absorption liquid, and discharged up to the standard, but at the same time, the absorption liquid containing high chemical oxygen demand and high biochemical oxygen demand still needs subsequent treatment.

[0055] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an environmentally friendly viscose-based carbon fiber pre-oxidized felt by catalytic heat treatment, characterized in that, The specific steps are as follows: S1. The viscose fibers are needled into a felt, acid-washed, dried, and a viscose fiber felt is obtained; S2. The silica sol, amide, and small molecule alcohol are mixed uniformly at a mass ratio of 2-6:1-2:0.1-1, and a catalyst with a total mass concentration of 3-10% is prepared by using deionized water; then the viscose fiber felt is impregnated with the catalyst and dried to obtain a pretreated viscose fiber felt; the particle size of the silica sol is <10 μm, the amide is caprolactam or acrylamide, and the small molecule alcohol is pentaerythritol; the mass ratio of the catalyst to the viscose fiber felt is 8-12:1-3, and the impregnation treatment time is 20-120 minutes; S3. Then the pretreated viscose fiber felt is heat-treated, heated to 260-300°C, treated for 30-60 minutes, and cooled to obtain a viscose-based carbon fiber pre-oxidized felt; The waste gas generated by heat treatment is mixed with heat-exchanged nitrogen at a volume ratio of 2-8:1 after combustion and recycled.

2. The method of claim 1, wherein, In step S1, the acid-washing treatment uses any one of hydrochloric acid, acetic acid, sulfamic acid, methylsulfonic acid, p-toluenesulfonic acid, or citric acid aqueous solution, or a mixture of any two of the aqueous solutions, with a total mass concentration of 0.5-5%.

3. The method of claim 1, wherein, In step S1, the specific drying method is drying at 110°C for 40 minutes.

4. The method of claim 1, wherein, In step S2, the mass ratio of the silica sol, amide, and small molecule alcohol is 6:2:1 or 3:2:0.

5.

5. The method of claim 1, wherein, In step S2, the specific drying method is: taking out and roll-drying to a water felt mass ratio <0.6, repeating impregnation-roll-drying twice, feeding into a drying oven, and drying at 105-140°C until the water content is less than 5%.

6. The method of claim 1, wherein, The waste gas generated by heat treatment is mixed with heat-exchanged nitrogen at a volume ratio of 6:1 after combustion and recycled.

7. A device for preparing a catalytic heat-treated carbon fiber pre-oxidized felt according to the method of claim 1, characterized in that, The furnace body is divided into four parts along the transmission direction of the pretreated viscose fiber felt: a felt inlet air seal section, a catalytic heat treatment section, a cooling section, and a felt outlet air seal section. An exhaust fan is arranged in the catalytic heat treatment section, which exhausts the generated waste gas into the waste gas combustion chamber. The waste gas is combusted and then interacts with nitrogen in the heat exchange chamber. Subsequently, it is adjusted to a certain temperature in the temperature adjustment chamber and then returned to the catalytic heat treatment section through an air inlet fan to realize recycling.

Images