According to preliminary statistics, as of the end of 1996, there were 89 papermaking enterprises that had a total of alkaline recovery equipment throughout the country, with an annual recovery capacity of 655,000 tons of alkali, and an annual recovery of approximately 420,000 tons of alkali. Among them, there are 40 alkali recovery manufacturers mainly based on wood pulp, and the recovery of alkali capacity is about 500,000 tons. In 1996, the recovery amount of alkali was 330,000 tons. There are about 20 alkali recovery plants mainly made of wheat straw pulp (pulp making capacity is 250,000 tons. The recovery of alkali capacity was about 60,000 tons. In 1996, the recovery of alkali was 8,000 tons, which was 40% higher than the 5,700 tons in 1995.
As we all know, wood pulp alkali recovery is very mature both at home and abroad. China's wood pulp alkali recovery accounted for about 80% of the country's total capacity and the actual amount of alkali recovered, and the benefit of the recovery of alkali is better. The profit per ton of alkali can be about 1,000 yuan. Alkali recovery of mash, bagasse pulp, bamboo pulp, etc. is also successful. Recovery of more than 500 yuan per ton of alkali can be achieved.
China is a large country of straw pulp, and wheat straw pulp is the main ingredient in straw pulp. The annual output of chemical ramie pulp is about 7 million tons. In order to break through the difficulties of wheat straw slurry alkali recovery, it has been explored for nearly 20 years, and 20 wheat straw pulp alkali recovery production lines have been built, including successful experience and lessons learned from failure. In 1996, nine wheat straw pulp mills had adhered to the alkali recovery production. Among them, the largest scale is 100t/d wheat straw pulp alkali in Henan Luohe First Paper Mill; the smallest one is the 25t/d wheat straw pulp alkali recovery in Shandong Zhangqiu Paper Mill was put into operation in October 1995, and it has been insisting on production for more than one year. Pure wheat straw alkali recovery to the Shandong Anqiu paper factory adhere to the best, has been insisting on production for more than a year. Pure wheat straw alkaline recovery is best adhered to by Shandong Anqiu paper mill. It has been continuously produced for 7 years. The original design was 10,000 tons of wheat straw pulp. After years of improvement, actual pulp production has reached about 50t/d (an annual output of wheat straw pulp 1.5- 20,000 tons), the recovery of alkali increased year by year, the recovery cost decreased year by year, according to the plant manager Wang disclosed that in 1995 the company's alkali recovery profit 500,000 yuan in 1996, a profit of 1 million yuan.
However, the black liquor extraction rate, extraction concentration, and extraction temperature of the plant are still low, and the evaporation capacity is seriously insufficient. Electrostatic dedusting has not yet been put into use normally. The plant is actively taking measures for further transformation. If it can be realized on schedule, the expected recovery rate can be achieved. Can be greatly improved, economic benefits can be better. Luohe No.1 Paper Mill has made many improvements to the alkali furnace and achieved good results. The concentration of black liquor into the furnace is around 24Be', and it can also be normal furnace and normal combustion. In the case of a sufficient supply of black liquor, the furnace After normal, all 4 oil guns can be removed and still burn normally. It can be up to 10 days without refueling. The biggest problem of this plant is that the extraction is backward and simple, resulting in a low extraction rate and extraction concentration. It should be determined to completely renovate the extraction section to ensure that the alkali furnace can eat well and ensure continuous combustion. At present, despite the fact that the alkali recovery system has not yet reached continuous production (alkali stoves are not fully charged), the recovery cost can already be equal to that of purchased bases, or it can be profitable. If it can achieve continuous system-wide recovery, the recycling cost can be greatly reduced. Get better economic benefits. Luohe First Paper Mill and Zhongyu Paper Mill first used plate evaporators in the black liquor evaporation section of wheat straw pulp, which has been in operation for more than one year. Practice has proved that the plate evaporator is suitable for the black liquor evaporation of wheat straw pulp. It is a better evaporation equipment at present, with high evaporation efficiency and less scaling, and the dirt flakes are easy to fall off and easy to remove, making up for the black liquor of wheat straw. Scale defects.
China's wheat straw pulp production is the largest, wheat straw is rich in raw materials (always every year), and wheat straw pulp is mainly used to produce cultural paper (such as writing paper, printing paper, etc.), which can meet quality requirements and achieve a good economy. Benefits (For example, many wheat straw pulp mills in Shandong can obtain benefits of 1,000 yuan-2,000 yuan per ton of wheat straw pulp). In the coming years (at least within 10-20 years), wheat straw is still the major papermaking raw material in China. Alkali recovery from wheat straw is still one of our main directions. However, the natural defects of wheat straw raw materials, such as high silicon content, many heterocells, fine fibers and high polysaccharide content, have brought a series of difficulties to black liquor extraction, evaporation, combustion, causticization, and white mud washing. There are still 11 uncompleted wheat straw pulp bases recovered. The reason for this is that, apart from factors such as management, technology, and ideological understanding, there are serious shortcomings in engineering design. For example: 1 black liquor extraction is insufficient, most of the selected domestic belt washing machine, and the use of small washing capacity, generally about 1/3 of the extraction capacity; 2 evaporation is insufficient, mostly tube evaporator, and the evaporation area is small , Generally, it is also about 1/3 of the difference; 3 Preparation of materials Most plants only dry preparation, mud sand in addition to not clean, resulting in a series of silicon interference. The extraction is not good, resulting in high evaporation costs, evaporation is not good, resulting in black liquor supply is not enough; forcing the combustion to start and stop frequently, amazingly high fuel consumption, there was a wheat straw mill test, out of 8 tons of alkali, burn more than 20 Tons of oil, such alkali recovery cannot be maintained.
Summarizing some of the above experiences and lessons learned, we should focus on the following key issues in the recovery of wheat straw alkali:
1. Black liquor extraction is the first hurdle and is also the basis for the recovery of the alkali. The design must fully guarantee the extraction capacity. With the Nissan slurry capacity, one ton of extraction equipment per ton of pure wheat straw should be provided. For example, 50t/d wheat straw pulp should be equipped with at least 50 square meters washing machine, 75t/d wheat straw pulp should be equipped with 75 square meters pulp washer, or 40 square meters two columns; 100t/d wheat straw pulp should be equipped with 100 square meters One column, or two columns of 50 square meters. The type of washing machine, the current domestic new cone-shaped valve vacuum washing machine is more advanced and reliable, Shandong Pushui paper mill selected this washing machine is also the first domestic wheat straw pulp mill to use this new equipment for alkali recovery system, According to the on-site inspection of the test vehicle, the extraction rate was about 85%, the concentration was 5Be' or more, and the temperature was 60 degrees Celsius. A gratifying step was taken. In terms of imported equipment, Hanyang Paper Factory introduced the British BC company's spiral mesh belt washing machine for black liquor extraction, with an extraction rate of 97%, a concentration of 7.5 Be' and a temperature of 85 degrees Celsius. If it can be transplanted into wheat straw black liquor, the extraction rate is expected to reach 90%. The 18-square-meter stainless steel spiral net experimental machine has been put into trial operation at the Anqiu paper mill. According to the preliminary understanding, the black border phenomenon has been eliminated and the extraction rate is expected to reach 85% or more.
The preliminary requirements for wheat black liquor extraction are above 85%, above 60 degrees Celsius, and above 6Be'. The goal of further development is to extract more than 90% of the temperature, and the temperature is above 80 degrees Celsius and the concentration is above 8Be'. The three indicators of extraction rate, temperature, and concentration should be one unitary body, and three are indispensable. If we can achieve the above goals, the alkaline recovery of wheat straw pulp will achieve breakthrough results.
2. To ensure evaporation capacity. For each ton of pulp produced by Nissan, 50 square meters of evaporation area should be allocated. 50t/d wheat straw pulp, the total evaporation area should reach 2500 square meters; 100t/d wheat straw pulp should be equipped with 5000 square meters evaporator. The structure and composition of the evaporator are currently reasonable with three tubes and two plates, which can ensure evaporation efficiency and save investment. If the funds are sufficient, more plate evaporators will be used and the effect will be better.
3. The ability to combust should be balanced with the pulping capacity to ensure full operation of the caustic furnace. Furnace air temperature should be guaranteed to be above 250 degrees Celsius, which is conducive to the full combustion of black liquor, in order to save fuel consumption and reduce costs (the Luohe paper mill has gained experience).
4. Washing with white mud should be carried out in two cascade washing machines in series. After washing, the white mud will have a higher dryness and a lower residual alkali content, which will help reduce the alkali loss and facilitate the transport and storage of the white mud. Get experience).
5. Preparation of materials should be combined with dry and wet methods, which is conducive to the removal of mud and sand from the raw materials. This is beneficial for extraction, evaporation, combustion, and causticization.
6. Synchronous silicon removal of wheat straw pulp has achieved results and passed the identification. According to the one-month continuous production test, addition of silicon agent and no addition of silicon agent, there are significant differences in the black liquor extraction, evaporation, combustion, causticization. After the simultaneous removal of silicon, the viscosity of black liquor is low, water is easy to be considered, the evaporation strength is increased, the scale of the evaporator is reduced, the cushion in the furnace is loose and flammable, the white mud is easy to wash, and the residual alkali is low. After silicon is removed synchronously, the effects of energy saving, consumption reduction, and production increase can be achieved. The initial measurement of the profit per ton of pulp can be increased by 30 yuan. A greater effect of simultaneous silicon removal is a significant decrease in the viscosity of the rich black liquor. Taking 40% solids concentrated black liquor as an example, the viscosity of black liquor without wheat removal is 400 centipoise, and the viscosity of concentrated black liquor after simultaneous silicon removal is only 98 centipoise, and the viscosity drops by 3/4. At room temperature, the black liquor of wheat straw black that had not been desiliconized was already solidified, and the black liquor of 46% wheat straw after the removal of silicon could still flow freely at room temperature. This also shows that after the removal of silicon measures, wheat straw black liquor can be further concentrated, and it is possible to increase the furnace concentration to more than 55%, which will achieve better results in improving the combustion of alkali furnaces.
The general view of the positive and negative aspects of experience and lessons, especially the Anqiu paper mill's long-standing experience in alkaline recovery, the fundamental way out of the chemical wheat straw pulp mill, is still the best way to do a good job of traditional alkali recovery, this view has been domestic More and more people know. Accordingly, the State Development Planning Commission has included traditional soda recovery in the energy conservation project of the Ninth Five-Year Plan. In 1996, it approved 19 wheat straw alkali recovery projects (a single-scale wheat straw pulp of 75t/d-100t/d). Among them, 11 projects have injected capital in succession and construction is being stepped up. Three of them have the fastest progress: Dongying (Huatai Group) 75t/d wheat straw pulp alkali recovery project has entered the installation phase, and is expected to test in July 1997; Shouguang (Chenming Group) 100t/d alkali recovery construction is about to be completed, 1997 October test; Linqing paper mill 100t / d recovery of the end of 1997 test. These companies all regard the alkali collection as a life project. After these projects are put into production, they will create a new path for the Chinese wheat straw pulp mill.
As we all know, wood pulp alkali recovery is very mature both at home and abroad. China's wood pulp alkali recovery accounted for about 80% of the country's total capacity and the actual amount of alkali recovered, and the benefit of the recovery of alkali is better. The profit per ton of alkali can be about 1,000 yuan. Alkali recovery of mash, bagasse pulp, bamboo pulp, etc. is also successful. Recovery of more than 500 yuan per ton of alkali can be achieved.
China is a large country of straw pulp, and wheat straw pulp is the main ingredient in straw pulp. The annual output of chemical ramie pulp is about 7 million tons. In order to break through the difficulties of wheat straw slurry alkali recovery, it has been explored for nearly 20 years, and 20 wheat straw pulp alkali recovery production lines have been built, including successful experience and lessons learned from failure. In 1996, nine wheat straw pulp mills had adhered to the alkali recovery production. Among them, the largest scale is 100t/d wheat straw pulp alkali in Henan Luohe First Paper Mill; the smallest one is the 25t/d wheat straw pulp alkali recovery in Shandong Zhangqiu Paper Mill was put into operation in October 1995, and it has been insisting on production for more than one year. Pure wheat straw alkali recovery to the Shandong Anqiu paper factory adhere to the best, has been insisting on production for more than a year. Pure wheat straw alkaline recovery is best adhered to by Shandong Anqiu paper mill. It has been continuously produced for 7 years. The original design was 10,000 tons of wheat straw pulp. After years of improvement, actual pulp production has reached about 50t/d (an annual output of wheat straw pulp 1.5- 20,000 tons), the recovery of alkali increased year by year, the recovery cost decreased year by year, according to the plant manager Wang disclosed that in 1995 the company's alkali recovery profit 500,000 yuan in 1996, a profit of 1 million yuan.
However, the black liquor extraction rate, extraction concentration, and extraction temperature of the plant are still low, and the evaporation capacity is seriously insufficient. Electrostatic dedusting has not yet been put into use normally. The plant is actively taking measures for further transformation. If it can be realized on schedule, the expected recovery rate can be achieved. Can be greatly improved, economic benefits can be better. Luohe No.1 Paper Mill has made many improvements to the alkali furnace and achieved good results. The concentration of black liquor into the furnace is around 24Be', and it can also be normal furnace and normal combustion. In the case of a sufficient supply of black liquor, the furnace After normal, all 4 oil guns can be removed and still burn normally. It can be up to 10 days without refueling. The biggest problem of this plant is that the extraction is backward and simple, resulting in a low extraction rate and extraction concentration. It should be determined to completely renovate the extraction section to ensure that the alkali furnace can eat well and ensure continuous combustion. At present, despite the fact that the alkali recovery system has not yet reached continuous production (alkali stoves are not fully charged), the recovery cost can already be equal to that of purchased bases, or it can be profitable. If it can achieve continuous system-wide recovery, the recycling cost can be greatly reduced. Get better economic benefits. Luohe First Paper Mill and Zhongyu Paper Mill first used plate evaporators in the black liquor evaporation section of wheat straw pulp, which has been in operation for more than one year. Practice has proved that the plate evaporator is suitable for the black liquor evaporation of wheat straw pulp. It is a better evaporation equipment at present, with high evaporation efficiency and less scaling, and the dirt flakes are easy to fall off and easy to remove, making up for the black liquor of wheat straw. Scale defects.
China's wheat straw pulp production is the largest, wheat straw is rich in raw materials (always every year), and wheat straw pulp is mainly used to produce cultural paper (such as writing paper, printing paper, etc.), which can meet quality requirements and achieve a good economy. Benefits (For example, many wheat straw pulp mills in Shandong can obtain benefits of 1,000 yuan-2,000 yuan per ton of wheat straw pulp). In the coming years (at least within 10-20 years), wheat straw is still the major papermaking raw material in China. Alkali recovery from wheat straw is still one of our main directions. However, the natural defects of wheat straw raw materials, such as high silicon content, many heterocells, fine fibers and high polysaccharide content, have brought a series of difficulties to black liquor extraction, evaporation, combustion, causticization, and white mud washing. There are still 11 uncompleted wheat straw pulp bases recovered. The reason for this is that, apart from factors such as management, technology, and ideological understanding, there are serious shortcomings in engineering design. For example: 1 black liquor extraction is insufficient, most of the selected domestic belt washing machine, and the use of small washing capacity, generally about 1/3 of the extraction capacity; 2 evaporation is insufficient, mostly tube evaporator, and the evaporation area is small , Generally, it is also about 1/3 of the difference; 3 Preparation of materials Most plants only dry preparation, mud sand in addition to not clean, resulting in a series of silicon interference. The extraction is not good, resulting in high evaporation costs, evaporation is not good, resulting in black liquor supply is not enough; forcing the combustion to start and stop frequently, amazingly high fuel consumption, there was a wheat straw mill test, out of 8 tons of alkali, burn more than 20 Tons of oil, such alkali recovery cannot be maintained.
Summarizing some of the above experiences and lessons learned, we should focus on the following key issues in the recovery of wheat straw alkali:
1. Black liquor extraction is the first hurdle and is also the basis for the recovery of the alkali. The design must fully guarantee the extraction capacity. With the Nissan slurry capacity, one ton of extraction equipment per ton of pure wheat straw should be provided. For example, 50t/d wheat straw pulp should be equipped with at least 50 square meters washing machine, 75t/d wheat straw pulp should be equipped with 75 square meters pulp washer, or 40 square meters two columns; 100t/d wheat straw pulp should be equipped with 100 square meters One column, or two columns of 50 square meters. The type of washing machine, the current domestic new cone-shaped valve vacuum washing machine is more advanced and reliable, Shandong Pushui paper mill selected this washing machine is also the first domestic wheat straw pulp mill to use this new equipment for alkali recovery system, According to the on-site inspection of the test vehicle, the extraction rate was about 85%, the concentration was 5Be' or more, and the temperature was 60 degrees Celsius. A gratifying step was taken. In terms of imported equipment, Hanyang Paper Factory introduced the British BC company's spiral mesh belt washing machine for black liquor extraction, with an extraction rate of 97%, a concentration of 7.5 Be' and a temperature of 85 degrees Celsius. If it can be transplanted into wheat straw black liquor, the extraction rate is expected to reach 90%. The 18-square-meter stainless steel spiral net experimental machine has been put into trial operation at the Anqiu paper mill. According to the preliminary understanding, the black border phenomenon has been eliminated and the extraction rate is expected to reach 85% or more.
The preliminary requirements for wheat black liquor extraction are above 85%, above 60 degrees Celsius, and above 6Be'. The goal of further development is to extract more than 90% of the temperature, and the temperature is above 80 degrees Celsius and the concentration is above 8Be'. The three indicators of extraction rate, temperature, and concentration should be one unitary body, and three are indispensable. If we can achieve the above goals, the alkaline recovery of wheat straw pulp will achieve breakthrough results.
2. To ensure evaporation capacity. For each ton of pulp produced by Nissan, 50 square meters of evaporation area should be allocated. 50t/d wheat straw pulp, the total evaporation area should reach 2500 square meters; 100t/d wheat straw pulp should be equipped with 5000 square meters evaporator. The structure and composition of the evaporator are currently reasonable with three tubes and two plates, which can ensure evaporation efficiency and save investment. If the funds are sufficient, more plate evaporators will be used and the effect will be better.
3. The ability to combust should be balanced with the pulping capacity to ensure full operation of the caustic furnace. Furnace air temperature should be guaranteed to be above 250 degrees Celsius, which is conducive to the full combustion of black liquor, in order to save fuel consumption and reduce costs (the Luohe paper mill has gained experience).
4. Washing with white mud should be carried out in two cascade washing machines in series. After washing, the white mud will have a higher dryness and a lower residual alkali content, which will help reduce the alkali loss and facilitate the transport and storage of the white mud. Get experience).
5. Preparation of materials should be combined with dry and wet methods, which is conducive to the removal of mud and sand from the raw materials. This is beneficial for extraction, evaporation, combustion, and causticization.
6. Synchronous silicon removal of wheat straw pulp has achieved results and passed the identification. According to the one-month continuous production test, addition of silicon agent and no addition of silicon agent, there are significant differences in the black liquor extraction, evaporation, combustion, causticization. After the simultaneous removal of silicon, the viscosity of black liquor is low, water is easy to be considered, the evaporation strength is increased, the scale of the evaporator is reduced, the cushion in the furnace is loose and flammable, the white mud is easy to wash, and the residual alkali is low. After silicon is removed synchronously, the effects of energy saving, consumption reduction, and production increase can be achieved. The initial measurement of the profit per ton of pulp can be increased by 30 yuan. A greater effect of simultaneous silicon removal is a significant decrease in the viscosity of the rich black liquor. Taking 40% solids concentrated black liquor as an example, the viscosity of black liquor without wheat removal is 400 centipoise, and the viscosity of concentrated black liquor after simultaneous silicon removal is only 98 centipoise, and the viscosity drops by 3/4. At room temperature, the black liquor of wheat straw black that had not been desiliconized was already solidified, and the black liquor of 46% wheat straw after the removal of silicon could still flow freely at room temperature. This also shows that after the removal of silicon measures, wheat straw black liquor can be further concentrated, and it is possible to increase the furnace concentration to more than 55%, which will achieve better results in improving the combustion of alkali furnaces.
The general view of the positive and negative aspects of experience and lessons, especially the Anqiu paper mill's long-standing experience in alkaline recovery, the fundamental way out of the chemical wheat straw pulp mill, is still the best way to do a good job of traditional alkali recovery, this view has been domestic More and more people know. Accordingly, the State Development Planning Commission has included traditional soda recovery in the energy conservation project of the Ninth Five-Year Plan. In 1996, it approved 19 wheat straw alkali recovery projects (a single-scale wheat straw pulp of 75t/d-100t/d). Among them, 11 projects have injected capital in succession and construction is being stepped up. Three of them have the fastest progress: Dongying (Huatai Group) 75t/d wheat straw pulp alkali recovery project has entered the installation phase, and is expected to test in July 1997; Shouguang (Chenming Group) 100t/d alkali recovery construction is about to be completed, 1997 October test; Linqing paper mill 100t / d recovery of the end of 1997 test. These companies all regard the alkali collection as a life project. After these projects are put into production, they will create a new path for the Chinese wheat straw pulp mill.
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