Treatment method of filter mud generated by carbonation-method sugar preparation

Abstract

The invention relates to a method for treating filter mud produced by a carbonization method for preparing sugar, which belongs to the technical field of food processing and comprises the following steps of: 1, washing sugar: a, arranging and communicating five water tanks in a positive sequence, and respectively filling clean water, first water, second water, third water and fourth water into the five water tanks; and b, the cleaning method comprises the step of cleaning the filter mud for four times. And c, the amount of water for washing each time is 1-4 times of that of the filter mud according to the mass ratio. And d, the concentration of each washing water is accumulated, increased and stable after the filter mud is washed each time. 2, sugar extraction: four times of washing concentrated water concentration: a, pretreatment, and b, membrane concentration; c, evaporating; and d, returning the syrup to a sugar manufacturing workshop. And 3, calcium oxide and carbon dioxide circulation. And 4, waste heat recovery. And 5, water circulation. And 6, water is supplemented for washing. The method has the beneficial effects that the existing sugar refining filter mud as a waste material is entrusted to be subjected to environment-friendly treatment, resources are wasted, a large amount of treatment cost needs to be entrusted, and the sugar refining filter mud is directly recycled in the sugar refining process through the method, so that 100% resource utilization is realized. A large amount of cost is saved for sugar manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing and relates to a method for treating filter mud generated in a sugar making process. Background Art

[0002] The sugar-making process in my country produces some organic impurity waste, commonly known as filter mud. Currently, it is generally treated by "sulfurization method" and "carbonization method", both of which are outsourced for a fee.

[0003] The disadvantage is that, in addition to other organic impurities, the filter mud contains calcium carbonate, which is the raw material for the carbonization process, and sugar, which is a product with market value. Treating the filter mud as waste and disposing it for a fee is both wasteful and increases the environmental burden. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for treating filter mud produced by carbonization sugar production, which can further improve the sugar yield of the filter mud and greatly reduce the environmental burden.

[0005] The processing method of the present invention is as follows:

[0006] 1. Washing sugar:

[0007] a. Arrange the five water tanks in order and connect them. The five water tanks contain clean water, first-stage water, second-stage water, third-stage water, and fourth-stage water respectively. The clean water is RO water with a conductivity of less than 30μs / second. The first-stage water is the water used to wash the filter mud once and has the lowest concentration. The second-stage water is the water used to wash the filter mud twice and has a higher concentration than the first-stage water. The third-stage water is the water used to wash the filter mud three times and has a higher concentration than the second-stage water. The fourth-stage water is the water used to wash the filter mud four times and has the highest concentration.

[0008] b. The cleaning method is to wash the filter mud four times. First, wash it with the four most concentrated waters, and the concentrated water from the washing is used to recover sugar. The filter mud after the four-water washing is then washed with three-water, two-water, one-water and clean water in sequence. After the washing, the three-water returns to the four-water tank, the two-water returns to the three-water tank, the one-water returns to the two-water tank, and finally the clean water returns to the one-water tank. The washing cycle is repeated, and each time a stream of clean water is added, the concentrated water from the fourth water washing is discharged to maintain the water balance during the washing process;

[0009] c. The amount of water for each wash is 1-4 times the mass of the filter mud;

[0010] d. The concentration of each wash water increases cumulatively after each cleaning of the filter mud, but it tends to be balanced and stable after cleaning more than 10 times.

[0011] 2. Sugar content:

[0012] The process of four-step water washing and concentrated water is:

[0013] a. Pre-treatment: remove suspended solids from the concentrated water of the fourth washing process. Filter with a 0.1μm filter and then with ultrafiltration;

[0014] b. Membrane concentration: using nanofiltration membrane to concentrate. The sugar in the concentrated water from the four-stage concentrated water is concentrated, and the low-valent salts dissolved in the concentrated water from the four-stage concentrated water pass through the membrane into the fresh water, achieving separation of sugar and low-valent salts;

[0015] c. Evaporation: When the membrane concentrates to its limit, the sugar concentration of the concentrated water from the four washes is ≤15%. The first stage of MVR evaporation is used, with a concentration ratio of 2 and a sugar concentration of ≤60%. The second stage of thin film evaporation is used to produce syrup. The sugar concentration is controlled within the range of 60% to 90% according to the requirements of the sugar production workshop.

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

[0017] 3. Circulate calcium oxide and carbon dioxide to make the filter mud (calcium carbonate) after sugar washing into balls or bricks. First, dry it with the residual heat from calcination, then calcine it with oxygen blowing to completely decompose the organic impurities in the filter mud. Increasing the calcination temperature is conducive to the decomposition of calcium carbonate. Control the calcination temperature at 1000-1100℃ and the time for 35-40 minutes. The calcium carbonate is completely decomposed into calcium oxide and carbon dioxide. The recovered calcium oxide and carbon dioxide are recycled in the sugar production process.

[0018] 4. Waste heat recovery: The high-temperature calcium oxide and carbon dioxide produced by calcination are recovered using waste heat recovery technology. The waste heat of calcium oxide is used to dry calcium carbonate balls or bricks, and the waste heat of carbon dioxide is used to heat filter mud washing water;

[0019] 5. Water circulation: The membrane-concentrated fresh water contains low-valent salts and small molecules, which are further separated using RO membranes. The conductivity of the fresh water is controlled to be less than 30μs / second and is returned to the clean water tank for filtration mud washing. The evaporative cooling water conductivity is less than 30μs / second and is directly returned to the clean water tank for recycling. The RO membrane concentrate is discharged in compliance with local environmental protection requirements or evaporated to zero discharge.

[0020] 6. Washing water replenishment: After washing the filter sludge with clean water, its primary component is calcium carbonate with a moisture content of 40%. This water cannot be recycled during the drying and calcination processes. Instead, it is replenished with municipal tap water, separated by an RO membrane, with a conductivity of less than 30 μs / second. RO membrane concentrate is discharged in compliance with local environmental regulations or evaporated to zero discharge.

[0021] The present invention has the beneficial effect of recycling sugar filter mud directly within the sugar production process, significantly saving costs and significantly contributing to energy conservation and emission reduction. Existing sugar production processes often outsource sugar filter mud for environmentally friendly treatment, wasting resources and incurring significant outsourcing costs. This invention, however, allows for 100% resource recovery and reuse within the sugar production process. This significantly reduces costs for sugar production and contributes significantly to energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings:

[0024] Example 1

[0025] 1. Washing sugar:

[0026] 1.1 Set up 5 water tanks, namely clean water, first-stage water, second-stage water, third-stage water and fourth-stage water. The clean water is RO water with a conductivity of less than 30μs / second. The first-stage water is the water used to wash the filter mud once and has the lowest concentration. The second-stage water is the water used to wash the filter mud twice and has a higher concentration than the first-stage water. The third-stage water is the water used to wash the filter mud three times and has a higher concentration than the second-stage water. The fourth-stage water is the water used to wash the filter mud four times and has the highest concentration.

[0027] 1.2 The cleaning method is to wash the filter mud four times. First, wash it with the four most concentrated waters, and the concentrated water from the washing is used to recover sugar. The filter mud after washing with four waters is then washed with three waters, two waters, one water and clean water in turn. After washing, the three waters return to the four water tanks, the two waters return to the three water tanks, the one water returns to the two water tanks, and finally the clean water returns to the one water tank. The washing cycle is repeated, and one clean water is added each time, and the concentrated water from the fourth water washing is discharged to maintain the water balance during the washing process;

[0028] 1.3 The amount of water used for each wash is twice the amount of filter mud, i.e., 2 tons of water is used for each ton of original filter mud;

[0029] 1.4 The concentration of each wash water increases cumulatively after each mud cleaning, but reaches a balance and becomes stable after more than 10 cleanings. That is, the sugar content in the filter cake is equal to the sugar content of the concentrated water from the four washes, and the mud sugar recovery rate is above 99.97%.

[0030] 2. Sugar content:

[0031] The process of four-step water washing and concentrated water is:

[0032] 2.1 Pre-treatment: remove suspended solids from the concentrated water of the fourth washing process. Filter with a 0.1μm filter and then with ultrafiltration;

[0033] 2.2 Membrane concentration, using nanofiltration membrane concentration. The sugar in the concentrated water from the four-way concentrated water is concentrated, and the low-valent salts dissolved in the concentrated water from the four-way concentrated water pass through the membrane into the fresh water, achieving separation of sugar and low-valent salts;

[0034] 2.3 Evaporation: When the membrane concentrates to the limit, the sugar concentration of the four-way water wash concentrate is ≤15%. The first stage of MVR evaporation is used, and the concentration ratio is 2 times, and the sugar concentration is ≤60%. The second stage of thin film evaporation is used to produce syrup. The sugar concentration is controlled within the range of 60% to 90% according to the requirements of the sugar production workshop.

[0035] 2.4 The syrup returns to the sugar making workshop;

[0036] 3. Circulate calcium oxide and carbon dioxide to make the filter mud (calcium carbonate) after sugar washing into balls or bricks. First, dry it with the residual heat from calcination, then calcine it with oxygen blowing to completely decompose the organic impurities in the filter mud. Increasing the calcination temperature is conducive to the decomposition of calcium carbonate. Control the calcination temperature at 1000-1100℃ and the time for 35-40 minutes. The calcium carbonate is completely decomposed into calcium oxide and carbon dioxide. The recovered calcium oxide and carbon dioxide are recycled in the sugar production process.

[0037] 4. Waste heat recovery: The high-temperature calcium oxide and carbon dioxide produced by calcination are recovered using waste heat recovery technology. The waste heat of calcium oxide is used to dry calcium carbonate balls or bricks, and the waste heat of carbon dioxide is used to heat filter mud washing water;

[0038] 5. Water circulation: The membrane concentrates fresh water containing low-valent salts and small molecules, which are further separated by RO membranes. The conductivity of the fresh water is controlled to be less than 30μs / second and then returned to the clean water tank for filtration mud washing. The evaporative cooling water conductivity is less than 30μs / second and directly returned to the clean water tank for recycling. The RO membrane concentrate is discharged in compliance with local environmental protection requirements or evaporated to zero discharge.

[0039] 6. Washing water replenishment: After washing the filter mud with clean water, the main component is calcium carbonate with a water content of 40%. This water cannot be recycled during the drying and calcination process. It is replenished with municipal tap water after RO membrane separation, with a fresh water conductivity of less than 30μs / second. The RO membrane concentrate is discharged in accordance with local environmental protection requirements or evaporated to zero discharge;

[0040] For example, a sugar refinery produces 120 tons of filter mud per day. The mud contains 30% moisture, 12% sugar and soluble salts, and 3% other organic impurities. The filter mud treatment system operates 20 hours per day, processing 6 tons of filter mud per hour and 12 tons of water per wash cycle per hour.

[0041] In the first washing cycle, all four washes were made of clean water: the concentrate from the fourth wash was 4.96% with a water output of 12.2 tons and a sugar recovery rate of 84.02%. The concentrate from the first wash was 0.003% with a total sugar content of 0.5 kg in the filter mud (calcium carbonate).

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

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

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

[0045] In the 20th washing cycle, the fourth wash concentrate concentration was 5.835%, the water output was 12.34 tons, and the sugar recovery rate was 99.979%. The first wash concentrate concentration was 0.0066%, and the total sugar content of the filter mud (calcium carbonate) was 0.94 kg.

[0046] After four water washings, the sugar and soluble salts in the sugary filter mud can be washed out to 99.99%, and the remaining solid matter after washing is calcium carbonate.

[0047] The filter mud is washed 20 times daily, with the fourth wash producing 234.17 tons of concentrated water, containing 14.23 tons of sugar. The syrup is then concentrated 1.5 times using a membrane concentrate, recovering 79 tons of 18% syrup and 155 tons of recycled water. The syrup is then concentrated 2 times using an MVR evaporator, recovering 20 tons of 78% syrup and 59 tons of condensate. Finally, a thin-film evaporator adjusts the syrup's concentration to 90% before returning it to the sugar refinery.

[0048] The filter mud after sugar washing is made into balls or bricks. It is first dried using the residual heat from the calcium oxide, then calcined with oxygen at a temperature of 1000-1100°C for 35-40 minutes. This completely decomposes the calcium carbonate and organic impurities in the filter mud, producing calcium oxide and carbon dioxide. After cooling, the calcium oxide and carbon dioxide are recycled back into the workshop.

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

[0050] The invention can increase the sugar recovery rate in the filter mud to more than 99%, the calcium circulation rate to more than 98%, and the carbon dioxide circulation rate to more than 70%.

Claims

1. A method for treating filter mud produced by carbonization sugar production, the method comprising: A. Sugar washing a. Arrange five water tanks in a positive order and connect them. The five water tanks contain clean water, first-stage water, second-stage water, third-stage water, and fourth-stage water, respectively. The clean water is RO water with a conductivity of less than 30 μs / s. The first-stage water is water used to wash the filter mud once and has the lowest concentration. The second-stage water is water used to wash the filter mud twice and has a higher concentration than the first-stage water. The third-stage water is water used to wash the filter mud three times and has a higher concentration than the second-stage water. The fourth-stage water is water used to wash the filter mud four times and has the highest concentration. b. The cleaning method is to wash the filter mud four times; first wash it with the four most concentrated water, and the concentrated water from the washing is used to recover sugar; the filter mud after the four water washing is then washed with three water, two water, one water and clean water in sequence; the water after the washing is returned to the four water tank with the three water, the three water to the three water tank, the one water to the two water tank, and finally the clean water to the one water tank, and the washing cycle is repeated, adding one clean water each time and discharging the concentrated water from the fourth water washing to maintain the water balance during the washing process; c. The amount of water for each wash is 1-4 times the mass of the filter mud; d. The concentration of each wash water increases cumulatively after each cleaning of the filter mud, but tends to be balanced and stable after cleaning more than 10 times; B. Sugar Extraction The process of four-step water washing and concentrated water is as follows: a. Pre-treatment: remove suspended solids from the concentrated water of the four washing processes; filter with a 0.1μm filter and then filter with ultrafiltration; b. Membrane concentration, using nanofiltration membrane for concentration; The sugar in the concentrated water from the fourth washing process is concentrated, and the low-valent salt dissolved in the concentrated water from the fourth washing process enters the fresh water through the membrane, realizing the separation of sugar and low-valent salt; c. Evaporation: When the membrane concentrates to the limit, the sugar concentration of the four-way water washing concentrate is ≤15%; the first stage of MVR evaporation is used, the concentration ratio is 2 times, and the sugar concentration is ≤60%; the second stage of thin film evaporation is used to make syrup; the sugar concentration is controlled within the range of 60% to 90% according to the requirements of the sugar workshop; d. The syrup returns to the sugar making workshop; C. Calcium oxide and carbon dioxide cycle The filter mud after sugar washing, namely calcium carbonate, is made into balls or bricks. The mud is first dried with the residual heat from calcination, and then calcined with oxygen blowing to completely decompose organic impurities in the mud. Increasing the calcination temperature is beneficial to the decomposition of calcium carbonate. The calcination temperature is controlled at 1000-1100°C for 35-40 minutes, and the calcium carbonate is completely decomposed into calcium oxide and carbon dioxide. The calcium oxide and carbon dioxide are recovered and recycled in the sugar production process. D. Waste heat recovery The high-temperature calcium oxide and carbon dioxide produced by calcination are recovered using waste heat recovery technology; the waste heat of calcium oxide is used to dry calcium carbonate balls or bricks, and the waste heat of carbon dioxide is used to heat filter mud washing water; E. Water cycle Membrane concentrated fresh water contains low-valent salts and small molecular components, which are further separated by RO membranes. The conductivity of the fresh water is controlled to be less than 30μs / second and is returned to the clean water tank for recycling and sludge washing. The conductivity of the evaporated cooling water is less than 30μs / second and is directly returned to the clean water tank for recycling. The RO membrane concentrated water is discharged in accordance with local environmental protection requirements or evaporated to zero discharge. F. Washing and replenishing water 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 during the drying and calcination process. It is supplemented with municipal tap water after separation through RO membrane. The fresh water conductivity is less than 30μs / second; the RO membrane concentrated water meets the discharge standards or evaporates to zero discharge according to local environmental protection requirements.

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