Method for treating mud produced in a carbonation process for sugar

Abstract

The application discloses a treatment method of filter mud generated by a carbonization method for sugar production, and belongs to the technical field of food processing.The method is as follows: 1, sugar washing: a, five water tanks are arranged in sequence and connected, and the five water tanks are respectively filled with clean water, first water, second water, third water and fourth water; b, the cleaning method is that the filter mud is cleaned four times; c, the amount of water for washing each water tank is 1-4 times the mass of the filter mud; and d, the concentration of water for washing each water tank is accumulated and increased after each time of cleaning the filter mud, and is stable; 2, sugar extraction: the concentrated water after the fourth water washing is concentrated, a, pretreatment, b, membrane concentration; c, evaporation; and d, sugar syrup returns to a sugar workshop; 3, calcium oxide and carbon dioxide circulation; 4, waste heat recovery; 5, water circulation; and 6, water washing water supplementing.The beneficial effects are as follows: the existing filter mud for sugar production is treated as waste and entrusted to environmental protection, resources are wasted, a large amount of processing fee needs to be paid for entrusting, the filter mud is directly recycled in the sugar production process through the treatment method, and 100% resource utilization is achieved, and a large amount of cost is saved for sugar production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of food processing, and relates to a treatment method of filter mud generated in a sugar making process. BACKGROUND

[0002] In the sugar making process in China, a part of organic impurity waste, commonly known as filter mud, is generated. At present, the filter mud is generally treated by "sulfidation method" and "carbonization method", and the two methods are both externally commissioned for treatment.

[0003] The disadvantage is that, in addition to other organic impurities, calcium carbonate is the raw material of the "carbonization method", and sugar is a marketable product. Treating the filter mud as waste for compensation not only causes waste but also increases the environmental burden. SUMMARY

[0004] The purpose of the present application is to provide a treatment method of filter mud generated by the carbonization method for sugar making, which can further improve the sugar yield of the filter mud by the method and greatly reduce the environmental burden.

[0005] The treatment method of the present application is as follows:

[0006] 1. Sugar washing:

[0007] a. Five water tanks are arranged in sequence and connected, and the five water tanks are respectively clean water, first water, second water, third water and fourth water. The clean water is RO water with an electrical conductivity of less than 30 μs / s, the first water is water for washing the filter mud once, and the concentration is the lowest. The second water is water for washing the filter mud twice, and the concentration is higher than that of the first water. The third water is water for washing the filter mud three times, and the concentration is higher than that of the second water. The fourth water is water for washing the filter mud four times, and the concentration is the highest.

[0008] b. The washing method is to wash the filter mud four times. The filter mud is first washed with the most concentrated fourth water, and the concentrated water washed out is used to recover sugar. The filter mud after the fourth water washing is sequentially washed with the third water, the second water, the first water and the clean water. The water after washing is returned to the fourth water tank for the third water, the third water tank for the second water, the second water tank for the first water, and finally the clean water tank for the first water. The water is washed in a cycle, and a clean water is added each time, and the fourth water washing concentrated water is discharged to maintain water balance in the washing process.

[0009] c. The amount of water washing of each water is 1-4 times the mass ratio of the filter mud.

[0010] d. The concentration of each water washing is accumulated and increased after each washing of the filter mud, but tends to be balanced and stable after more than 10 times of washing.

[0011] 2. Sugar extraction:

[0012] The fourth water washing concentrated water is concentrated, and the flow is,

[0013] a, pretreatment, remove the suspended solids in four water washing concentrated water. Filter with 0.1 μm filter, then filter with ultrafiltration;

[0014] b, membrane concentration, concentrate with nanofiltration membrane. The sugar in four water washing concentrated water is concentrated, the low valence dissolved in four water washing concentrated water is separated from the sugar by the membrane into fresh water, realizing the separation of sugar and low valence salt;

[0015] c, evaporation, when the membrane concentration reaches the limit, the sugar concentration of four water washing concentrated water is ≤15%. Evaporate with MVR in the first stage, the concentration ratio is 2 times, the sugar concentration is ≤60%; evaporate with thin film evaporator in the second stage, to produce sugar syrup. The sugar concentration is controlled in the range of 60% to 90% according to the requirements of sugar making workshop;

[0016] d, the sugar syrup returns to the sugar making workshop;

[0017] 3, calcium oxide and carbon dioxide circulation, the filter mud (calcium carbonate) after sugar washing is made into balls or bricks. First, dry with the remaining heat of calcination, then blow oxygen calcination to promote the complete decomposition of organic impurities in the filter mud, and improve the calcination temperature to facilitate the decomposition of calcium carbonate. Control the calcination temperature at 1000-1100℃, and the time at 35-40 minutes, so that the calcium carbonate is completely decomposed into calcium oxide and carbon dioxide. Recover the calcium oxide and carbon dioxide for recycling in the sugar making process;

[0018] 4, waste heat recovery, the high temperature calcium oxide and carbon dioxide generated by calcination are recovered by waste heat recovery technology respectively. The waste heat of calcium oxide is used for drying calcium carbonate balls or bricks, and the waste heat of carbon dioxide is used for heating the filter mud washing water;

[0019] 5, water circulation, the low valence salt and small molecule components in the membrane concentrated fresh water are further separated by RO membrane, and the fresh water with an electric conductivity of less than 30 μs / s returns to the clean water tank for recycling to wash the filter mud; the cooling water with an electric conductivity of less than 30 μs / s directly returns to the clean water tank for recycling. The RO membrane concentrated water is discharged according to the local environmental protection requirements or evaporated to zero emission;

[0020] 6, water washing water supplement, the main component of the filter mud after washing with clean water is calcium carbonate, with a water content of 40%. This part of water cannot be recovered in the drying and calcination process, and municipal tap water is separated by RO membrane, and the fresh water with an electric conductivity of less than 30 μs / s is supplemented. The RO membrane concentrated water is discharged according to the local environmental protection requirements or evaporated to zero emission.

[0021] The beneficial effects of the present application are: since the existing sugar making production is to treat the filter mud as waste for environmental protection, not only the resources are wasted, but also a large amount of processing fee is needed for outsourcing, through the treatment of the present application, the resources are recycled directly in the sugar making process, and the resources are 100% recycled. A large amount of cost is saved for sugar making, and a large contribution is made for energy saving and emission reduction. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a process flow diagram of the present application. DETAILED DESCRIPTION

[0023] The present application is further described below in conjunction with the accompanying drawings:

[0024] Example 1

[0025] 1. Sugar washing:

[0026] 1.1 Five water tanks are set up, which are clean water, first water, second water, third water and fourth water. The clean water is RO water with conductivity less than 30 μs / s. The first water is water for washing filter mud once, and its concentration is the lowest. The second water is water for washing filter mud twice, and its concentration is higher than that of the first water. The third water is water for washing filter mud three times, and its concentration is higher than that of the second water. The fourth water is water for washing filter mud four times, and its concentration is the highest.

[0027] 1.2 The washing method is that the filter mud is washed four times. The filter mud is first washed with the fourth water with the highest concentration, and the concentrated water washed out is used to recover sugar. The filter mud washed with the fourth water is then washed with the third water, the second water, the first water and the clean water in sequence. The water after washing is returned to the fourth water tank for the third water, the third water tank for the second water, the second water tank for the first water, and finally the first water tank for the clean water. The washing is recycled in this way, and one tank of clean water is added each time, and the concentrated water of the fourth water is discharged to maintain the water balance in the washing process.

[0028] 1.3 The amount of water in each water washing is twice the amount of filter mud, i.e. the amount of clean water for each washing of one ton of original filter mud is 2 tons.

[0029] 1.4 The concentration of water in each water washing is accumulated and increased after each washing of the filter mud, but tends to be balanced and stable when the washing is more than 10 times. That is, the sugar content in the filter cake is equal to the sugar content in the concentrated water of the fourth water washing, and the sugar washing-out rate of the filter mud is more than 99.97%.

[0030] 2. Sugar recovery:

[0031] The concentrated water of the fourth water washing is concentrated, and the flow is as follows:

[0032] 2.1 Pretreatment, to remove the suspended matter in the concentrated water of the fourth water washing. The concentrated water is filtered with a 0.1 μm filter, and then filtered with an ultrafilter.

[0033] 2.2 Membrane concentration, to concentrate the sugar in the concentrated water of the fourth water washing. The low-valence salt dissolved in the concentrated water of the fourth water washing is separated from the sugar through the membrane into the fresh water.

[0034] 2.3 Evaporation, film concentration to the limit, four water washes the sugar concentration of concentrated water ≤15%. The first section of MVR evaporation is used, and the concentration ratio is 2 times the sugar concentration ≤60%; the second section of thin film evaporator is used for evaporation, and sugar syrup is prepared. The sugar concentration is controlled in the range of 60% to 90% according to the requirements of the sugar workshop;

[0035] 2.4 Sugar syrup returns to the sugar workshop;

[0036] 3. Calcium oxide and carbon dioxide cycle, the filter mud (calcium carbonate) after washing sugar is made into balls or bricks. First, dry with the remaining heat of calcination, then blow oxygen calcination to promote the complete decomposition of organic impurities in the filter mud, and increase the calcination temperature to facilitate the decomposition of calcium carbonate. Control the calcination temperature at 1000-1100℃, and the time at 35-40 minutes, and the calcium carbonate is completely decomposed into calcium oxide and carbon dioxide. Recover the calcium oxide and carbon dioxide for recycling in the sugar making process;

[0037] 4. Waste heat recovery, the high temperature calcium oxide and carbon dioxide generated by calcination are recovered by waste heat recovery technology respectively. The waste heat of calcium oxide is used for drying calcium carbonate balls or bricks, and the waste heat of carbon dioxide is used for heating the filter mud washing water;

[0038] 5. Water cycle, the low salt and small molecule components in the film concentrated fresh water are further separated by RO membrane, and the conductivity of the fresh water is controlled to be less than 30us / s to return to the clean water tank for recycling the filter mud; the conductivity of the evaporation cooling water is less than 30us / s, which is directly returned to the clean water tank for recycling. The RO membrane concentrated water is discharged according to the local environmental protection requirements or evaporated to zero emission;

[0039] 6. Water washing water, the main component of the filter mud after washing with clean water is calcium carbonate, and the water content is 40%. This part of water cannot be recovered in the drying and calcination process, and municipal tap water is separated by RO membrane, and the conductivity of the fresh water is less than 30us / s for supplement. The RO membrane concentrated water is discharged according to the local environmental protection requirements or evaporated to zero emission;

[0040] Taking 120 tons / day of filter mud produced by a sugar factory as an example, the filter mud contains 30% water, 12% sugar and soluble salt, and 3% other organic impurities. The filter mud treatment system operates for 20 hours a day, and processes 6 tons of filter mud per hour, and 12 tons of water per hour for each water washing.

[0041] The first cleaning cycle, all four water washing waters are clean water: the fourth water washing concentrated water concentration is 4.96%, the water output is 12.2 tons, and the sugar washing rate is 84.02%; the first water washing water concentration is 0.003%, and the total sugar content of the filter mud (calcium carbonate) is 0.5 kg;

[0042] The second washing cycle, the fourth wash concentrate concentration is 5.59%, the output is 12.3 tons, and the sugar washing rate is 95.39%; the first wash water concentration is 0.005%, and the total sugar content of the filter mud (calcium carbonate) is 0.8 kg.

[0043] The third washing cycle, the fourth wash concentrate concentration is 5.75%, the output is 12.32 tons, and the sugar washing rate is 98.38%; the first wash water concentration is 0.006%, and the total sugar content of the filter mud (calcium carbonate) is 0.9 kg;

[0044] In the fourth washing cycle, the concentration of the fourth wash concentrate is 5.8%, the output is 12.33 tons, and the sugar washing rate is 99.37%; the concentration of the first wash concentrate is 0.0064%, and the total sugar content of the filter mud (calcium carbonate) is 0.91 kg.

[0045] In the twentieth washing cycle, the concentration of the fourth wash concentrate was 5.835%, the output was 12.34 tons, and the sugar washing rate was 99.979%; the concentration of the first wash concentrate was 0.0066%, and the total sugar content of the filter mud (calcium carbonate) was 0.94 kg.

[0046] After four water washes, 99.99% of the sugar and soluble salts in the sugar-containing filter mud can be washed out. The remaining solids after washing are calcium carbonate.

[0047] The filter mud is washed 20 times daily, with a total effluent volume of 234.17 tons from the fourth wash, containing 14.23 tons of sugar. Membrane concentration is increased 1.5 times, recovering 79 tons of syrup at 18% concentration and 155 tons of circulating water. The syrup is then concentrated 2 times via an MVR evaporator, recovering 20 tons of syrup at 78% concentration and 59 tons of condensate. Finally, a thin-film evaporator is used to adjust the syrup concentration to 90% before returning it to the sugar production workshop.

[0048] The filter mud after sugar washing is made into balls or bricks. It is first dried using the residual heat of calcium oxide, then calcined with oxygen, controlling the calcination temperature at 1000-1100℃ for 35-40 minutes. This promotes the complete decomposition of calcium carbonate and organic impurities in the filter mud, generating calcium oxide and carbon dioxide. After cooling, the calcium oxide and carbon dioxide are recovered and recycled back to the workshop for reuse.

[0049] The high-temperature calcium oxide and carbon dioxide produced during calcination are recovered using waste heat recovery technology. The waste heat from the calcium oxide is used to dry the washed filter mud balls (bricks), and the waste heat from the carbon dioxide is used to heat the filter mud washing water. The temperature of the filter mud washing water is not lower than 40℃.

[0050] This invention can achieve a sugar recovery rate of over 99%, a calcium recycling rate of over 98%, and a carbon dioxide recycling rate of over 70% in filter mud.

Claims

1. A method for treating filter mud produced by a carbonization method for sugar production, the method comprising: A. washing sugar a. arranging five water tanks in series and connecting them, and the five water tanks contain clean water, first water, second water, third water, and fourth water, respectively; the clean water is RO water with an electrical conductivity of less than 30 μs / s; the first water is water used for washing filter mud once, and has the lowest concentration; the second water is water used for washing filter mud twice, and has a higher concentration than the first water; the third water is water used for washing filter mud thrice, and has a higher concentration than the second water; and the fourth water is water used for washing filter mud four times, and has the highest concentration; b. the washing method comprises washing the filter mud four times; the filter mud is first washed with the fourth water with the highest concentration, and the concentrated water obtained is used to recover sugar; the filter mud washed with the fourth water is then washed with the third water, the second water, the first water, and the clean water in sequence; the water after washing is returned to the fourth water tank, the third water tank, the second water tank, and the first water tank in sequence, and clean water is added each time; the fourth water is discharged to recover concentrated water, and the water balance is maintained during the washing process; c. the amount of water in each water tank is 1-4 times the mass of the filter mud; d. the concentration of the water in each water tank increases after each washing of the filter mud, but tends to be balanced and stable after more than 10 times of washing; B. sugar recovery concentrating the concentrated water from the fourth water washing, and the process is a. pretreatment, removing suspended solids in the concentrated water from the fourth water washing; filtering with a 0.1 μm filter, and then filtering with an ultrafilter; b. membrane concentration, concentrating with a nanofiltration membrane; the sugar in the concentrated water from the fourth water washing is concentrated, the low-valent salt dissolved in the concentrated water from the fourth water washing passes through the membrane into fresh water, and sugar and low-valent salt are separated; c. evaporation, when the membrane concentration reaches the limit, the sugar concentration in the concentrated water from the fourth water washing is ≤15%; MVR is used for the first-stage evaporation, and the concentration ratio is 2 times, and the sugar concentration is ≤60%; a thin-film evaporator is used for the second-stage evaporation, and sugar syrup is produced; the sugar concentration is controlled in the range of 60%-90% according to the requirements of the sugar production workshop; d. the sugar syrup is returned to the sugar production workshop; C. calcium oxide and carbon dioxide circulation the filter mud after washing, i.e. calcium carbonate, is made into balls or bricks; the balls or bricks are first dried with the remaining heat from calcination, and then calcined by blowing oxygen, so that the organic impurities in the filter mud are completely decomposed, and increasing the calcination temperature is beneficial to the decomposition of calcium carbonate; the calcination temperature is controlled in the range of 1000-1100 °C, and the time is 35-40 minutes, so that the calcium carbonate is completely decomposed into calcium oxide and carbon dioxide; the recovered calcium oxide and carbon dioxide are used in the sugar production process; D. waste heat recovery the high-temperature calcium oxide and carbon dioxide produced by calcination are recovered by waste heat recovery technology; the waste heat from the calcium oxide is used for drying the calcium carbonate balls or bricks, and the waste heat from the carbon dioxide is used for heating the water used for washing the filter mud; E. water circulation the fresh water after membrane concentration contains low-valent salt and small-molecule components, and is further separated by an RO membrane; the fresh water with an electrical conductivity of less than 30 μs / s is returned to the clean water tank for recycling to wash the filter mud; the cooling water after evaporation has an electrical conductivity of less than 30 μs / s, and is directly returned to the clean water tank for recycling; the concentrated water from the RO membrane is discharged or evaporated according to the local environmental protection requirements; F. water washing and water supplement The main component of the washed filter mud is calcium carbonate, with a water content of 40%. The water in this part cannot be recovered during the drying and calcining processes. The municipal tap water is separated by an RO membrane, and the conductivity of the fresh water is less than 30 μs / s. The RO membrane concentrated water is discharged according to the local environmental protection requirements or evaporated to zero emission.

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