Method for realizing circulating clarification utilization of sugar industry filter mud based on calcination

Abstract

The invention discloses a method for realizing circulating clarification utilization of sugar industry filter mud based on calcination, which comprises the following steps: filter mud drying: scattering and drying wet filter mud to obtain dry filter mud; suspension flash burning: mixing the dry filter mud with limestone powder, calcining by utilizing secondary hot air in a suspension cooling process, removing organic matters in the dry filter mud and partially decomposing calcium carbonate in the mixed material; performing fluidized bed roasting: introducing high-pressure air into the mixed material subjected to suspension flash burning treatment to enable the material to utilize waste heat of the material in a boiling state to complete deep decomposition of calcium carbonate so as to obtain a high-temperature finished product; suspension cooling: cooling the high-temperature finished product to obtain a low-temperature finished product; digesting: digesting a low-temperature finished product to prepare lime milk; and flue gas reutilization: the CO2-containing flue gas generated by suspension flash burning is sequentially used as a drying heat source for filter mud drying, and is used for a sugar juice clarification and carbonation process after being purified. According to the invention, the pollution problem is solved, resource utilization is realized, the use of limestone is reduced, the flue gas heat of the system is fully utilized, and the energy consumption is reduced.

Description

Technical Field

[0001] This invention belongs to the field of sugar industry filter mud treatment technology, and particularly relates to a method for recycling and clarifying sugar industry filter mud based on calcination. Background Technology

[0002] The sugar clarification process in the sugar industry is mainly divided into two types: the sulfite process and the carbonation process. Currently, the vast majority of beet sugar factories and some sugarcane sugar factories use the carbonation process. Sugar produced by the carbonation process has high purity, low color value, and good storage resistance, which is significantly better than the sulfite process commonly used by sugarcane sugar factories. The carbonation process mainly includes the following steps: First, lime milk is added to the exudate twice to coagulate, precipitate, and decompose proteins, colloids, and other non-sugar components; then, after two carbon saturations, CO2 reacts with the lime milk to form CaCO3 particles, which adsorb the precipitate and most of the non-sugar impurities; finally, the juice is filtered to obtain clear juice and filter mud.

[0003] Because the carbonate clarification process consumes large amounts of lime and carbon dioxide, many sugar factories are equipped with lime kilns. In order to generate kiln gas with high CO2 content while producing lime, coke is generally used as fuel to calcine lumpy limestone in the lime kiln. However, calcining limestone consumes a lot of fuel, and the production cost of using coke is high.

[0004] The use of the carbonation process for clarification inevitably generates a large amount of sugar-refining filter mud. Fresh sugar-refining filter mud has a moisture content of 35-45%. Its main component is calcium carbonate, along with a certain proportion of organic matter (such as protein, sugars, pectin, pectic acid, etc.) and small amounts of metal oxides such as magnesium, silicon, iron, and aluminum. Approximately 0.65 tons of sugar-refining filter mud are generated for every ton of sugar produced. As one of the largest solid wastes in the sugar industry, sugar-refining filter mud has long been primarily disposed of through open-air dumping and landfilling. Besides occupying land resources, its high content of organic matter and sugars makes it highly susceptible to mold, foul odors, and the growth of harmful substances, thus polluting the environment. Due to the large production volume, high moisture content, and inability to be directly recycled, there is currently no thorough and effective treatment method for sugar-refining filter mud, making its disposal a major challenge for the sugar industry.

[0005] Chinese Patent Publication No. CN108129002A discloses a method for recycling clarifying agents in sugar sludge using a suspension calcination process. The method involves first pretreating the sugar sludge, then transporting it to a suspension preheating device. The preheated material is then fed into a suspension decomposition device for CaCO3 decomposition. Afterward, it is introduced into a deep decarbonization device to generate high-temperature lime. This lime is then cooled by a fluidized suspension cooling device to obtain powdered active lime. The byproduct CO2 is used to saturate the CO2 required in the next process. The obtained powdered active lime is mixed with water to form lime milk, which is then mixed with a raw sugar solution. CO2 is then added to the mixture to form CaCO3 particles. These particles adsorb impurities, forming a paste-like precipitate, which is the sugar sludge. On the one hand, this method involves drying and dehydrating the sugar filter mud, pre-treating it into powder, preheating it to the critical decomposition temperature, then decomposing and further decarbonizing it. Each of these processes—pre-treatment, decomposition, and deep decarbonization—consumes a significant amount of heat. Furthermore, the preheating process removes organic matter from the filter mud, necessitating an increased number of preheating stages to bring the outlet flue gas temperature to a reasonable range, resulting in heat waste. On the other hand, impurities (such as silicon and aluminum oxides) are not discharged and continuously accumulate within the system. With each cycle, impurities introduced by the new sugar juice are captured and added to the filter mud in the next cycle, leading to a continuous increase in the total amount of filter mud. Simultaneously, while calcium carbonate, as an effective component, can be regenerated during the cycle, its relative proportion is continuously diluted due to the absolute accumulation of impurities. This significantly reduces the effective calcium carbonate content in the filter mud, decreases the adsorption activity of the impurity-rich clarifying agent, and reduces the clarification efficiency of the sugar juice, affecting the quality of the finished sugar. Therefore, this method cannot achieve multiple cycles of filter mud reuse.

[0006] In summary, the problems with existing technologies are: 1. Sugar factories generate a large amount of sugar filter mud, which is polluting the environment due to long-term stockpiling and landfilling. There is still no thorough and effective treatment method, which restricts the development of the sugar industry.

[0007] 2. Although there is a technology that uses suspension firing to treat sugar filter mud and achieve filter mud recycling, on the one hand, the whole process consumes a lot of energy and the heat is not effectively utilized; on the other hand, due to the enrichment of impurities during the recycling process, the adsorption activity of the clarifying agent will be affected, making it impossible to achieve multiple recycling of filter mud. Summary of the Invention

[0008] To address the challenges of resource utilization and high energy consumption in sugar processing filter mud, this invention provides a method for the recycling and clarification of filter mud based on calcination. The wet filter mud generated during the sugar juice clarification process undergoes a series of processes including filter mud drying, suspension flash calcination, fluidized bed roasting, suspension cooling, digestion, and flue gas reuse, yielding lime milk and CO2-containing flue gas suitable for the sugar juice clarification process. To ensure long-term stable system operation, an appropriate amount of limestone powder is added during the suspension flash calcination stage to maintain a balance of effective components, and quantitative discharge prevents impurity accumulation, maintaining a dynamic balance of solid content during the recycling process. The CO2-containing flue gas generated during suspension flash calcination is first used for drying the wet filter mud and then for saturation in the sugar juice clarification process, achieving dual recovery of materials and heat. Through multi-stage suspension cooling, high-temperature hot air is recovered and used as secondary air for the suspension flash calcination process, reducing system heat consumption. This invention not only solves the filter mud pollution problem but also achieves efficient recycling of filter mud, reducing limestone consumption and system energy consumption. It has significant economic and environmental benefits and can be widely applied in the sugar industry, possessing important practical significance.

[0009] This invention is implemented as follows: a method for recycling and clarifying filter mud in the sugar industry based on calcination. The wet filter mud generated during the sugar juice clarification process is dried, subjected to suspension flash calcination, fluidized bed roasting, suspension cooling, digestion, and flue gas reuse to obtain lime milk and CO2-containing flue gas, which are then used in the sugar juice clarification process. The specific process is as follows: Filter mud drying: The wet filter mud produced during the sugar juice clarification process is broken up and dried to obtain dry filter mud. This process uses the CO2-containing flue gas generated during the suspension flash combustion process as a heat source. Suspension flash calcination: The dry filter mud obtained from the filter mud drying process is mixed with supplemented limestone powder and then fed into a suspension flash calcination device. The secondary hot air from the suspension cooling process is used as secondary air for calcination to remove organic matter from the dry filter mud and partially decompose the calcium carbonate in the mixture. Fluidized bed roasting: The mixture after the suspension flash roasting process is fed into the fluidized bed roasting device, and high-pressure air is introduced to make the material use its own residual heat in the boiling state to complete the deep decomposition of calcium carbonate and obtain a high-temperature finished product mainly composed of calcium oxide. Suspension cooling: The high-temperature finished product obtained from the boiling roasting process is sent to a suspension cooling device for cooling to obtain a low-temperature finished product; Digestion: The low-temperature product obtained from the suspension cooling process is digested to produce lime milk; Flue gas reuse: The CO2-containing flue gas generated during the suspension flash combustion process is first used as the drying heat source in the filter mud drying process and then purified before being used in the saturation process of sugar juice clarification.

[0010] In the above technical solution, preferably, the method further includes quantitative discharge: after the suspension cooling process and / or digestion process, the material containing impurities in the corresponding process is quantitatively discharged from the system; the amount of limestone powder added during the suspension flash burning process and the amount of material quantitatively discharged are controlled so that the total amount of solid material circulating in the sugar juice clarification system is kept in dynamic balance.

[0011] In the above technical solution, preferably, a suspension preheating process is provided between the filter mud drying process and the suspension flash burning process. The suspension preheating process involves mixing the dry filter mud with supplemented limestone powder, first feeding it into a suspension preheating device for preheating, and then feeding the preheated mixture into a suspension flash burning device. The suspension preheating process uses the CO2-containing flue gas generated in the suspension flash burning process as a heat source before feeding it into the filter mud drying process.

[0012] In the above technical solution, a further preferred embodiment is that the suspension preheating device is provided with 1-3 stages of preheating units, and the temperature of the flue gas after heat exchange with the mixed material is 500-800℃.

[0013] In the above technical solution, preferably, an indirect heat exchange process is provided between the filter mud drying process and the suspension flash burning process. The indirect heat exchange is as follows: cold air enters the indirect heat exchange device and exchanges heat with the CO2-containing flue gas generated in the suspension flash burning process to obtain hot air. The hot air enters the limestone grinding device and / or the fuel grinding device. The CO2-containing flue gas after heat exchange enters the filter mud drying process.

[0014] In the above technical solution, preferably, during the filter mud drying process, the temperature of the dried filter mud is 100-200℃.

[0015] In the above technical solution, preferably, during the suspension flash burning process, the calcium carbonate content in the limestone powder is higher than 90%, and the calcium carbonate content in the mixture of dry filter mud and limestone powder is higher than 75%; the organic matter removal rate in the dry filter mud after the suspension flash burning process is greater than 99%, and the calcium carbonate decomposition rate in the mixture is greater than 50%.

[0016] In the above technical solution, preferably, during the suspension flash combustion process, the temperature of the CO2-containing flue gas is 800~950℃, and the CO2 concentration in the flue gas is 25%-45%.

[0017] In the above technical solution, preferably, the suspension flash combustion process of the mixture is heated by fuel combustion, and the ash content in the fuel is less than 25%.

[0018] In the above technical solution, preferably, during the fluidized bed roasting process, the temperature is maintained above 800℃, the residence time of the material in the fluidized bed roasting device is greater than 10s, and the calcium carbonate decomposition rate is greater than 90%.

[0019] In the above technical solution, preferably, the suspension cooling device is provided with at least two cooling units, including a primary cooling unit and a final cooling unit; cold air first enters the final cooling unit to exchange heat with the material, and the resulting primary hot air is all or partly introduced into the primary cooling unit, where it exchanges heat with the high-temperature finished product to form high-temperature secondary hot air, which is used as secondary air for the suspension flash burning process; the primary hot air that does not enter the primary cooling unit is discharged.

[0020] In the above technical solution, preferably, during the suspension cooling process, the temperature of the primary hot air generated is 100-300℃; and the temperature of the secondary hot air generated is 500-700℃.

[0021] In the above technical solution, a further preferred embodiment is that a portion of the exhaust hot air enters the limestone grinding device, and the ground limestone powder is fed into the suspension flash calcination device, wherein the fineness of the limestone powder is less than 200 micrometers.

[0022] In the above technical solution, a further preferred embodiment is that a portion of the exhaust primary hot air enters the fuel grinding device, and the ground fuel is fed into the suspension flash combustion device.

[0023] In the above technical solution, preferably, 10%-30% of the material discharged after the suspension cooling process is discharged as lime powder.

[0024] This invention first uses a suspension flash calcination process to efficiently remove organic matter from dry filter mud and partially decompose calcium carbonate. Then, fluidized bed roasting allows the material to undergo further decomposition using its own residual heat. Finally, suspension cooling yields highly active calcium oxide, which can be used as a clarifier for sugar juice clarification. This method not only fundamentally solves the environmental pollution problem caused by the long-term stockpiling of filter mud in sugar factories, but also achieves resource utilization of the filter mud through a recycling system, reducing the use of limestone in the sugar industry and resulting in significant economic benefits.

[0025] The present invention has the following advantages and beneficial effects: 1. This invention employs a two-step calcination process. First, a suspension flash calcination process efficiently removes organic matter from the dry filter mud and partially decomposes calcium carbonate. The dry filter mud can directly enter the suspension flash calcination process without preheating, where all organic matter is removed, releasing heat that can be used for calcium carbonate decomposition. This achieves the simultaneous removal of organic matter from the filter mud and the effective utilization of all its heat, reducing fuel consumption. Subsequently, fluidized bed roasting allows the material to undergo deep decomposition using its own residual heat, eliminating the need for additional fuel. Finally, suspension cooling yields highly active calcium oxide, which can be used as a cleaning agent for sugar juice clarification. This process not only fundamentally solves the environmental pollution problem caused by long-term stockpiling of filter mud in sugar factories but also achieves resource utilization of the filter mud through a recycling system, reducing the use of limestone in the sugar industry and resulting in significant economic benefits.

[0026] 2. This invention supplements limestone powder during the suspension flash burning process, which can maintain and increase the concentration and total amount of effective detergent components in the circulation system. During the filter mud circulation process, the continuous accumulation of impurities such as silicon and aluminum in the filter mud can reduce the adsorption activity of the clarifying agent, thus affecting the quality of the sugar juice. By adding high-purity limestone powder, these losses can be directly and effectively compensated, ensuring that the calcium source for generating active calcium oxide in the system is sufficient and stable. This ensures that the final lime milk has sufficient concentration and reactivity to meet the process requirements of sugar juice clarification. This invention also incorporates a quantitative discharge step, discharging a portion of the material after suspension cooling and / or digestion. Without discharge, the amount of material entering the clarification and calcination processes, as well as the amount requiring transportation, would increase, leading to higher system energy consumption and equipment load. Multiple cycles would render the entire recycling process unfeasible both in terms of equipment and economics. Quantitative discharge maintains a constant amount of material entering the sugar juice clarification process, ensuring stable operation of the filter mud recycling process. Furthermore, the discharged material is calcined filter mud, primarily composed of calcium oxide, which can be used as a desulfurizing agent and also enables the reuse of waste resources. By controlling the amount of limestone powder added and the amount of material discharged quantitatively, the total amount of solid material circulating in the sugar juice clarification system is kept in dynamic balance. Thus, while ensuring the clarification effect of the sugar juice and the quality of the finished sugar, the efficient, stable and unlimited resource recycling of sugar filter mud is realized.

[0027] 3. This invention can also incorporate a suspension preheating process between the filter mud drying process and the suspension flash calcination process. After mixing the dry filter mud with supplemented limestone powder, it is first fed into a suspension preheating device for preheating, and then the preheated mixture is fed into the suspension flash calcination device. During the suspension preheating process, the organic matter in the filter mud is removed, and the released heat can be used to break up and dry the wet filter mud. This fully utilizes the heat from the organic matter without causing energy waste.

[0028] 4. This invention generates CO2-containing flue gas required for sugar juice clarification through a suspension flash combustion process. The CO2 concentration in the flue gas is 25%-45%. The hot flue gas generated by the suspension flash combustion process is first used for the filter mud drying process, then washed and dust removed by water, and finally used for sugar juice clarification. This not only obtains the raw material CO2 required for sugar juice clarification, but also makes full use of the heat of the hot flue gas to dry the wet filter mud, solving the problems of high moisture content in sugar filter mud, making it difficult to use directly, and high energy consumption for drying alone.

[0029] 5. The present invention sets up a suspension cooling process and rationally designs the cooling air volume so that the hot air from the first-stage cooling unit is used as secondary air for the suspension flash combustion process. Part of the hot air from the final-stage cooling unit enters the first-stage cooling unit, and the other part is used for limestone grinding and fuel grinding. This can achieve full cooling of materials and full recovery of waste heat, and can effectively reduce the system heat consumption. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method for recycling and clarifying sugar industry filter mud based on calcination, provided in Embodiment 1 of the present invention. Figure 2 This is a flowchart of a method for recycling and clarifying sugar industry filter mud based on calcination, provided in Embodiment 2 of the present invention. Figure 3 This is a flowchart of the method for recycling and clarifying sugar industry filter mud based on calcination, provided in Embodiment 3 of the present invention. Figure 4 This is a flowchart of the method for recycling and clarifying sugar industry filter mud based on calcination, provided in Embodiment 4 of the present invention. Figure 5 This is a flowchart of a method for recycling and clarifying sugar industry filter mud based on calcination, provided in Embodiment 5 of the present invention.

[0031] In the picture: The dashed line with arrows indicates the airflow direction, and the solid line with arrows indicates the material flow direction. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] Example 1 Please see Figure 1This invention provides a method for the recycling and clarification of filter mud in the sugar industry based on calcination, comprising processes of filter mud drying, suspension flash calcination, fluidized bed roasting, suspension cooling, digestion, and flue gas reuse. The wet filter mud produced during the sugar juice clarification process is dried, suspended flash calcination, fluidized bed roasting, suspension cooling, digestion, and flue gas reuse to obtain lime milk and CO2-containing flue gas, which are then used in the sugar juice clarification process. Details are as follows: Sugar juice clarification: After pretreatment, sugar raw materials are used to obtain exudate containing sugar and various non-sugar components. The exudate is then subjected to a process of adding lime, main lime, carbon 1 saturation, carbon 2 saturation, and sulfur bleaching to obtain clear juice. The process of adding lime and main lime requires the addition of lime milk, and the process of carbon 1 saturation and carbon 2 saturation requires the addition of flue gas containing CO2. After carbon 1 saturation and carbon 2 saturation, the sugar juice is filtered to obtain a large amount of wet filter mud.

[0034] Filter mud drying: The wet filter mud produced during the carbon 1 and carbon 2 saturation processes has a moisture content of 35%~45%. This wet filter mud is fed into a dispersing and drying device via a feeding device. Using the CO2-containing flue gas generated during the suspension flash combustion process as a heat source, the wet filter mud is dispersed and dried until the moisture content is less than 2%. The temperature of the dried filter mud after drying is maintained at 100-200℃ to prevent the release of organic matter during the drying process. Generally, the temperature at which organic matter begins to be removed is above 300℃. If the temperature of the dried filter mud after drying is controlled above 300℃, organic matter will be removed during the drying process, reacting with O2 in the drying flue gas and releasing heat. This heat will then be used for flue gas heating, resulting in heat waste.

[0035] Suspension flash calcination: The dried filter mud is mixed with a certain proportion of limestone powder and fed into a suspension flash calcination device for co-calcination. Secondary hot air from the suspension cooling process is used as secondary air for calcination, removing organic matter from the dry filter mud and partially decomposing the calcium carbonate in the mixture. The material exiting the suspension flash calcination device has an organic matter removal rate of over 99% and a calcium carbonate decomposition rate of over 50%. The dry filter mud enters the suspension flash calcination process directly without preheating, ensuring that all organic matter is removed during the process, releasing heat. This heat can be used for calcium carbonate decomposition, achieving effective utilization of all the heat while removing organic matter from the dry filter mud, thus reducing fuel consumption.

[0036] In a preferred embodiment, the limestone powder contains more than 90% calcium carbonate. The amount of limestone powder added is adjusted according to the calcium carbonate content in the dry filter mud. During the suspension flash calcination process, the proportion of limestone powder added to the mixture is 10%-30%, ensuring that the calcium carbonate content in the mixture of dry filter mud and limestone powder is higher than 75%. The main component of the filter mud is calcium carbonate (approximately 80% or more), along with a certain proportion of organic matter and small amounts of metal oxides such as magnesium, silicon, iron, and aluminum. Without the addition of limestone powder, as the filter mud is recycled more frequently, the addition of fuel ash will increase the accumulation of silicon and aluminum oxides in the filter mud, reducing the calcium carbonate content. This, in turn, leads to a decrease in the calcium oxide produced during calcination, affecting the clarification effect of the sugar juice. Therefore, adding an appropriate amount of limestone powder ensures that the amount of calcium oxide produced during decomposition is sufficient and stable. This solves the problem of insufficient lime milk produced due to the decrease in calcium carbonate content in the filter mud during recycling, allowing the filter mud to be recycled multiple times continuously. This ensures stable operation of the sugar juice clarification process and does not affect the sugar production yield or quality.

[0037] Specifically, limestone powder can be added to the air duct from the dispersing and drying device to the suspension flash burning device.

[0038] As a preferred implementation method, under the combined action of organic matter in the dry filter mud and external fuel, the temperature of the CO2-containing flue gas generated during the suspension flash combustion process is 800~950℃, and the CO2 concentration in the flue gas is 25%-45%, ensuring that while removing organic matter from the dry filter mud, all the heat is effectively utilized for the decomposition of calcium carbonate.

[0039] In a preferred embodiment, during the suspension flash calcination process, the heat for the suspension flash calcination of the mixture is provided by fuel combustion, and the ash content in the fuel must be less than 25%. The ash from the fuel combustion will enter the calcined finished product for use in the sugar juice clarification process, which reduces the calcium carbonate content in the resulting wet filter mud. Therefore, in order to reduce the amount of added limestone powder, the ash content in the fuel needs to be controlled.

[0040] Specifically, conventional bituminous coal can be used as fuel. The composition of bituminous coal is 2%-10% moisture, 5%-25% ash, 10%-30% volatile matter, and 50%-70% fixed carbon.

[0041] Fluidized bed roasting: The mixture exiting the suspension flash calciner enters the fluidized bed roasting unit. High-pressure air is introduced into the fluidized bed roasting unit, and the material, under fluidized bed conditions, utilizes its own residual heat to complete the deep decomposition of calcium carbonate, obtaining a high-temperature finished product mainly composed of calcium oxide. In this process, the calcium carbonate decomposition rate is greater than 90%, and the calcium oxide content in the high-temperature finished product is greater than 50%. The temperature inside the fluidized bed roasting unit is maintained above 800℃. Generally, the residence time of the material in the fluidized bed roasting unit is not less than 10 seconds.

[0042] Specifically, the high-pressure air volume causes the mixture to be in a bubbling and boiling state. Generally, the air velocity of the high-pressure air in the fluidized bed roasting device is less than 2 m / s.

[0043] Suspension cooling: The high-temperature finished product and hot air from the boiling roasting device enter the suspension cooling device for cooling to obtain a low-temperature finished product.

[0044] In a preferred embodiment, the suspension cooling device includes at least two cooling stages: a primary cooling stage and a final cooling stage. The cold air entering the final cooling stage exchanges heat with the material to obtain primary hot air. Depending on the air volume required for the suspension flash burning process, all or part of this primary hot air enters the primary cooling stage, where it exchanges heat with the high-temperature finished product to further increase its temperature, forming high-temperature secondary hot air. This secondary hot air is used as secondary air for the suspension flash burning process. The hot material exiting the primary cooling stage enters the final cooling stage for further cooling to reach the required product temperature, resulting in a low-temperature finished product. The suspension cooling process achieves thorough material cooling and full waste heat recovery, effectively reducing system heat consumption and investment costs. The temperature of the cooled low-temperature finished product is below 150°C.

[0045] In one preferred embodiment, the temperature of the secondary hot air generated during the suspension cooling process is 500-700°C. This high-temperature secondary hot air can be used as secondary air to assist fuel combustion during the suspension flash combustion process.

[0046] In one preferred embodiment, the temperature of the primary hot air generated during the suspension cooling process is 100-300°C. The primary hot air that does not enter the primary cooling unit is discharged, and the discharged primary hot air can also be introduced into other processes that require drying heat sources.

[0047] Digestion: The low-temperature finished product from the suspension cooling device is used as a cleaning agent and enters the digestion device. After adding water, lime milk is obtained, which is used for the ash addition process and the main ash addition process in the sugar juice clarification process.

[0048] Flue gas reuse: The CO2-containing flue gas generated during the suspension flash combustion process is first used in the filter mud drying process to recover and utilize the heat in the flue gas. After water washing and dust removal, it is then used in the first and second carbon saturation processes of the sugar juice clarification process. This not only obtains the raw material CO2 required for sugar juice clarification but also makes full use of the heat of the hot flue gas to dry the wet filter mud, solving the problems of high moisture content in sugar-making filter mud making it difficult to use directly and high energy consumption for drying alone.

[0049] Quantitative discharge: After the suspension cooling process, a portion of the material containing impurities from the corresponding process is quantitatively discharged from the system. The amount of limestone powder added during the suspension flash burning process and the amount of material quantitatively discharged are controlled to maintain a dynamic balance in the total amount of solid material circulating in the sugar juice clarification system. That is, after the suspension cooling process, a portion of the low-temperature finished product containing impurities is diverted from the system and discharged. The material used for digestion during this process is the remaining portion of the low-temperature finished product obtained from the suspension cooling process after quantitative discharge.

[0050] In one preferred embodiment, 10%-30% of the low-temperature finished product after suspension cooling is discharged as lime powder. The discharged lime powder can be sold or used as a desulfurizing agent in the desulfurization process of sugar factories.

[0051] In summary, this invention removes organic matter and decomposes calcium carbonate in sugar mill filter mud through suspension flash calcination and fluidized bed roasting processes, obtaining the calcium oxide and CO2 required for sugar juice clarification. This solves the pollution problems caused by the stockpiling and landfilling of sugar mill filter mud, realizes the resource utilization of filter mud, reduces the use of limestone, and has good economic benefits. Simultaneously, by adding an appropriate amount of limestone powder according to the calcium carbonate content in the filter mud, the amount of calcium oxide produced by calcination and decomposition within the system is sufficient and stable, solving the problem of calcium carbonate content decreasing in the filter mud after multiple cycles, without affecting the sugar juice clarification process. By quantitatively discharging the calcined filter mud, the amount of material entering the sugar juice clarification process can be kept constant, enabling stable operation of the filter mud recycling process.

[0052] Example 2 like Figure 2 As shown, unlike Example 1, the quantitative discharge involves: after the digestion process, a portion of the material containing impurities from the corresponding process is quantitatively discharged from the system. The amount of limestone powder added during the suspension flash burning process and the amount of material quantitatively discharged are controlled to maintain a dynamic balance in the total amount of solid material circulating in the sugar juice clarification system. That is, after the digestion process, the lime milk undergoes sedimentation or centrifugation to discharge the solid residue containing impurities, and the separated clear liquid is reused in the sugar juice clarification process.

[0053] Example 3 like Figure 3 As shown, based on Example 1, the exhaust primary hot air can be used in both the limestone grinding process and the fuel grinding process. Specifically, a portion of the primary hot air generated during the suspension cooling process enters both the limestone grinding unit and the fuel grinding unit.

[0054] Limestone grinding process: A portion of the primary hot air generated during the suspension cooling process enters the limestone grinding unit for drying the limestone powder. The ground limestone powder is then metered and added as external limestone powder to the suspension flash calcination unit. The fineness of the limestone powder is less than 200 micrometers.

[0055] Fuel grinding process: The primary hot air generated during the suspension cooling process enters the fuel grinding device for fuel drying. The ground fuel is metered and then transported to the suspension flash combustion device.

[0056] Example 4 like Figure 4 As shown, unlike Example 1, a suspension preheating process is set between the filter mud drying process and the suspension flash burning process: after the dry filter mud is mixed with the supplemented limestone powder, it is first sent to the suspension preheating device for preheating, and then the preheated mixture is fed into the suspension flash burning device. The suspension preheating process uses the CO2-containing flue gas generated in the suspension flash burning process as a heat source before being sent to the filter mud drying process.

[0057] When the CO2-containing flue gas generated by suspension flash combustion generates excess heat, the mixture can be heated through a suspension preheating process. During suspension preheating, organic matter in the dry filter mud is removed, and the released heat can be used to break up and dry the wet filter mud. This fully utilizes the heat of the organic matter and avoids energy waste.

[0058] Example 5 like Figure 5 As shown, unlike Example 1, an indirect heat exchange process is set between the filter mud drying process and the suspension flash combustion process. Indirect heat exchange: cold air enters the indirect heat exchange device and exchanges heat with the CO2-containing flue gas generated in the suspension flash combustion process to obtain hot air. The hot air enters the limestone grinding device and / or the fuel grinding device, and the CO2-containing flue gas after heat exchange enters the filter mud drying process. At this time, all the primary hot air formed by suspension cooling is introduced into the first-stage cooling unit.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for realizing the utilization of sugar industry filter mud recycling clarification based on calcination, characterized by, The wet filter mud generated in the sugar juice clarification process is dried by filter mud drying, suspended flash burning, boiling roasting, suspended cooling, digestion, and smoke gas recycling to obtain lime milk and CO2-containing smoke gas for use in the sugar juice clarification process; the specific process is as follows: Filter mud drying: the wet filter mud generated in the sugar juice clarification process is scattered and dried to obtain dry filter mud, and the CO2-containing smoke gas generated in the suspended flash burning process is used as a heat source; Suspended flash burning: the dry filter mud obtained in the filter mud drying process is mixed with supplementary limestone powder and then fed into a suspended flash burning device, the secondary hot air from the suspended cooling process is used as secondary air for calcination, and the heat generated by fuel combustion is used to remove organic matter in the dry filter mud and partially decompose calcium carbonate in the mixture; Boiling roasting: the mixture treated by the suspended flash burning process is fed into a boiling roasting device, high-pressure air is introduced to make the mixture in a boiling state to complete the deep decomposition of calcium carbonate by using its own waste heat, and a high-temperature product mainly composed of calcium oxide is obtained; Suspended cooling: the high-temperature product obtained by the boiling roasting process is fed into a suspended cooling device for cooling to obtain a low-temperature product; Digestion: the low-temperature product obtained by the suspended cooling process is digested to produce lime milk; Smoke gas recycling: the CO2-containing smoke gas generated in the suspended flash burning process is first used as the drying heat source in the filter mud drying process and then used in the saturation process of the sugar juice clarification process after purification.

2. The method of claim 1, wherein the method is based on calcination to achieve utilization of sugar industry filter mud recycling clarification, characterized by, The method also includes quantitative discharge, quantitative discharge: after the suspended cooling process and / or the digestion process, part of the material containing impurities corresponding to the process is discharged from the system; the amount of supplementary limestone powder in the suspended flash burning process and the amount of material discharged are controlled to maintain the dynamic balance of the total amount of solid material circulating in the sugar juice clarification system.

3. The method of claim 1, wherein the method is based on calcination to achieve utilization of sugar industry filter mud recycling clarification, characterized by, A suspended preheating process is also provided between the filter mud drying process and the suspended flash burning process, and the suspended preheating process is as follows: the dry filter mud is mixed with supplementary limestone powder, then fed into a suspended preheating device for preheating, and then the preheated mixture is fed into the suspended flash burning device; the suspended preheating process uses the CO2-containing smoke gas generated in the suspended flash burning process as a heat source and then feeds into the filter mud drying process.

4. The method of claim 3, wherein the method is based on calcination to achieve utilization of sugar industry filter mud recycling clarification. The suspended preheating device is provided with 1-3 preheating units, and the temperature of the smoke gas after heat exchange with the mixture is 500-800℃.

5. The method of utilizing sugar industry filter mud cycle clarification based on calcination as claimed in claim 1, wherein, An indirect heat exchange process is also provided between the filter mud drying process and the suspended flash burning process, and the indirect heat exchange process is as follows: cold air enters an indirect heat exchange device and exchanges heat with the CO2-containing smoke gas generated in the suspended flash burning process to obtain hot air, the hot air enters a limestone powder grinding device and / or a fuel grinding device, and the CO2-containing smoke gas after heat exchange enters the filter mud drying process.

6. The method of utilizing sugar industry filter mud cycle clarification based on calcination as claimed in claim 1, wherein, In the filter mud drying process, the temperature of the dried dry filter mud is 100-200℃.

7. The method of utilizing sugar industry filter mud cycle clarification based on calcination as claimed in claim 1, wherein, In the suspended flash burning process, the calcium carbonate content in the limestone powder is higher than 90%, and the calcium carbonate content in the mixture of dry filter mud and limestone powder is higher than 75%; the organic matter removal rate of the dry filter mud after the suspended flash burning process is greater than 99%, and the calcium carbonate decomposition rate of the mixture is greater than 50%.

8. The method for utilization of sugar industry filter mud recycling clarification based on calcination according to claim 1 or 7, characterized in that, In the suspended flash burning process, the temperature of the CO2-containing smoke gas generated is 800-950℃, and the CO2 concentration in the smoke gas is 25%-45%.

9. The method for utilization of sugar industry filter mud recycling clarification based on calcination according to claim 1, characterized in that, In the fluidized roasting process, the temperature is kept above 800℃, the material stays in the fluidized roasting device for more than 10s, and the calcium carbonate decomposition rate is more than 90%.

10. The method for utilization of sugar industry filter mud recycling clarification based on calcination according to claim 1, characterized in that, The suspension cooling device is provided with at least two-stage cooling units, including a first-stage cooling unit and a last-stage cooling unit; cold air first enters the last-stage cooling unit to exchange heat with the material, and the first hot air formed is all or partially introduced into the first-stage cooling unit to exchange heat with the high-temperature finished product to form high-temperature secondary hot air, which is used as the secondary air for the suspension flash calcining process; the first hot air not entering the first-stage cooling unit is discharged.

11. The method for utilization of sugar industry filter mud recycling clarification based on calcination according to claim 10, characterized in that, In the suspension cooling process, the wind temperature of the first hot air generated is 100-300℃, and the temperature of the secondary hot air generated is 500-700℃.

12. The method for utilization of sugar industry filter mud recycling clarification based on calcination according to claim 10, characterized in that, Part of the discharged first hot air enters a limestone grinding device and / or a fuel grinding device, and the ground limestone powder is used as the supplementary limestone powder, and the ground fuel is used as the fuel for the suspension flash calcining process.

13. The method of utilizing sugar industry filter mud cycle clarification based on calcination as claimed in claim 2, wherein, After the suspension cooling process, 10%-30% of the material discharged quantitatively is discharged as the lime powder.

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