A method for energy cascade utilization and improving borax yield in boron chemical production

Abstract

This invention discloses a method for energy cascade utilization and improving borax yield in boron chemical production. The carbonized slurry undergoes a second heat exchange with a secondary re-slurry in a heat exchanger before entering a slurry tank. The slurry flowing out of the tank mixes with the secondary re-slurry and enters a primary filtration process. After primary filtration, the mixed raw liquid enters a controlled filtration process. The filter residue enters a boron mud re-slurry process. The re-slurry from the boron mud re-slurry process enters a primary re-slurry process. The re-slurry from the primary re-slurry process enters a secondary re-slurry process. The re-slurry from the secondary re-slurry process undergoes a first heat exchange with the flue gas from the calcination desulfurization tower in a heat exchanger, and then undergoes a second heat exchange with the carbonized slurry before mixing with the slurry flowing out of the tank. This cycle is repeated. The advantages of this invention are: by performing multiple filtrations, the boron recovery rate is improved; at the same time, the clever combination of different heat exchangers enables heat recovery and utilization in different processes, resulting in energy conservation, environmental protection, and improved production efficiency.

Description

Technical Field

[0001] This invention relates to the field of boron chemical technology, specifically a method for improving recovery rates. Background Technology

[0002] In the boron filtration workshop, wet boron concentrate is conveyed by a belt conveyor into the calcination furnace in the calcination workshop. The concentrate is reheated at 1400℃ using gas generated from a gasifier. After desulfurization, the flue gas at approximately 300℃ is directly discharged, and its heat is not effectively utilized. The calcined boron powder is then transported to the batching room where it is mixed with soda ash and mother liquor. The resulting slurry is then fed into the carbonization reactor for the carbonization reaction. In the lime kiln workshop, calcined coal particles and limestone produce quicklime and kiln gas. This kiln gas is filtered, washed, and compressed by an air compressor to achieve a CO2 concentration of 37%, which is then supplied to the carbonization reaction. In the boiler workshop, saturated steam is generated by heating the tailings pond with bituminous coal, which is then used to heat the carbonization reaction. The slurry is then subjected to carbonization reaction in a high-pressure reactor under specific temperature and pressure conditions, with the kiln gas introduced into the mixture. After the carbonization reaction is completed, the slurry is filtered through a plate and frame filter press in a slurry tank. This process involves a two-step washing: first, the filter cake is rinsed with a small amount of water; then, it is rinsed a second time with 85°C hot water generated by directly heating 20°C return water from the boiler with saturated steam to fully recover the boron-containing components in the slag. After filtration, the slag is directly transported to the boron mud tailings pond. The mixed raw liquid is then filtered under controlled conditions by a small plate and frame filter press to form a clear raw liquid, at which point the temperature of the clear raw liquid is approximately 80°C. The clear raw liquid is then pumped into a crystallization tank for cooling and crystallization. The crystallization tank is cooled by coiled water cooling, with the coiled water being return water from the tailings pond, having an inlet temperature of 18°C ​​and a flow rate of 300 m³ / h. 3 / h. The highest temperature of the tailings pond return water after heat exchange with the crystallization liquid is 45℃, and it is directly discharged to the concentrator. The temperature of the crystallization liquid after cooling is 20℃, and then it enters the centrifuge. The mother liquor produced by centrifugation is transported back to the batching room for batching, and finally produces borax decahydrate with a purity of 95%.

[0003] The shortcomings of this solution are as follows:

[0004] 1. The slag after one filtration still contains soluble boron. Current technology directly transports it to the boron mud tailings pond, resulting in a low boron recovery rate.

[0005] 2. The heat of the flue gas at around 300℃ after calcination desulfurization is not fully utilized and is directly discharged into the air, resulting in energy loss;

[0006] 3. The 85℃ hot water required for the washing water of the plate and frame filter press is obtained by directly heating the 20℃ tailings pond return water with boiler steam. This scheme results in a large amount of steam consumption, increased coal consumption, and increased costs.

[0007] 4. The temperature of the slurry after the carbonization reaction reaches 120℃. The heat in the slurry is not recovered again, and the slurry is directly filtered through the plate and frame filter press, resulting in heat loss. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a method for the cascade utilization of energy and the improvement of borax yield in boron chemical production. The carbonized slurry undergoes a second heat exchange with the secondary re-slurry in a heat exchanger before entering a slurry tank. The slurry flowing out of the tank is mixed with the secondary re-slurry and then enters a primary filtration process. After primary filtration, the mixed raw liquid enters a controlled filtration process. The filter residue enters a boron mud re-slurry process. The re-slurry from the boron mud re-slurry process enters a primary re-slurry process, and the re-slurry from the primary re-slurry process enters a secondary re-slurry process. The re-slurry from the slurry process undergoes a primary heat exchange with the flue gas from the calcination desulfurization tower via a heat exchanger, followed by a secondary heat exchange with the carbonized slurry via a heat exchanger. It then mixes with the slurry flowing from the slurry tank, and this process is repeated. The flue gas from the calcination desulfurization tower is 150°C after desulfurization. The re-slurry is 25°C before the primary heat exchange with the flue gas and 50°C after the primary heat exchange. The carbonized slurry is 125°C, and after a secondary heat exchange with the 50°C re-slurry, it reaches 85°C. The re-slurry is 85°C after the secondary heat exchange.

[0009] The filter residue from the primary and secondary re-slurry processes is discharged into the boron mud tailings pond.

[0010] The primary filtration process uses a polypropylene diaphragm plate and frame. The moisture content of the boron sludge is reduced from 40% to 30%.

[0011] The primary heat exchange involves the flue gas from the calcination desulfurization tower exchanging heat with softened water in a closed-loop circulation via a fluoroplastic heat exchanger. The softened water then exchanges heat with the secondary reslurry via a tube-and-shell heat exchanger.

[0012] The secondary heat exchange involves the carbonized slurry undergoing heat exchange with softened water in a closed-loop circulation through a tube heat exchanger, and the softened water then undergoes heat exchange with the secondary re-slurry through a tube heat exchanger.

[0013] The boron mud re-slurry process involves mixing boron mud at 80°C after primary filtration with tailings pond return water at 18°C ​​to form a re-slurry at 25°C.

[0014] The temperature of the softened water in the closed-loop circulation during the primary heat exchange is 80°C; the temperature of the softened water in the closed-loop circulation during the secondary heat exchange is 95°C.

[0015] The advantages of this invention are: by performing multiple filtrations, the boron recovery rate is improved, and by cleverly combining different heat exchangers, heat recovery and utilization are achieved in different processes, which is energy-saving, environmentally friendly, and improves production efficiency. Attached Figure Description

[0016] Figure 1This is a schematic diagram illustrating the principle of the present invention;

[0017] Figure 2 This is a schematic diagram of the heat exchange principle. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings. As shown in the drawings, the carbonized slurry is heated twice by a heat exchanger and then enters the slurry tank. The slurry flowing out of the slurry tank is mixed with the secondary re-slurry and then enters the primary filtration process. After primary filtration, the mixed raw liquid enters the controlled filtration process. The filter residue enters the boron mud re-slurry process. The re-slurry from the boron mud re-slurry process enters the primary re-slurry process. The re-slurry from the primary re-slurry process enters the secondary re-slurry process. The re-slurry from the secondary re-slurry process is heated once by a heat exchanger and then heated twice by a heat exchanger and mixed with the slurry flowing out of the slurry tank. This process is repeated continuously.

[0019] The flue gas from the calcination desulfurization tower is 150°C after desulfurization. The secondary re-slurry is 25°C before the first heat exchange with the flue gas from the calcination desulfurization tower, and 50°C after the first heat exchange. The carbonized slurry is 125°C, and after a second heat exchange with the 50°C secondary re-slurry through a heat exchanger, it is 85°C. The secondary re-slurry is 85°C after the second heat exchange.

[0020] The filter residue from the primary and secondary re-slurry processes is discharged into the boron mud tailings pond.

[0021] The primary filtration process uses a polypropylene diaphragm plate and frame. The moisture content of the boron sludge is reduced from 40% to 30%.

[0022] The primary heat exchange involves the flue gas from the calcination desulfurization tower exchanging heat with softened water in a closed-loop circulation via a fluoroplastic heat exchanger. The softened water then exchanges heat with the secondary reslurry via a tube-and-shell heat exchanger.

[0023] The secondary heat exchange involves the carbonized slurry undergoing heat exchange with softened water in a closed-loop circulation through a tube heat exchanger, and the softened water then undergoes heat exchange with the secondary re-slurry through a tube heat exchanger.

[0024] The boron mud re-slurry process involves mixing boron mud at 80°C after primary filtration with tailings pond return water at 18°C ​​to form a re-slurry at 25°C.

[0025] The temperature of the softened water in the closed-loop circulation during the primary heat exchange is 80°C; the temperature of the softened water in the closed-loop circulation during the secondary heat exchange is 95°C.

[0026] The purpose of using a closed-loop circulation system of softened water for heat exchange is to avoid clogging of the heat exchange tubes and ensure the normal operation of the heat exchange equipment.

Claims

1. A method for energy cascade utilization and improving borax yield in boron chemical production, characterized in that: After carbonization, the slurry undergoes a second heat exchange with the secondary re-slurry in a heat exchanger before entering the slurry tank. The slurry flowing out of the slurry tank is mixed with the secondary re-slurry and then enters the primary filtration process. After primary filtration, the mixture with the original liquid enters the controlled filtration process, and the filter residue enters the boron mud re-slurry process. The re-slurry from the boron mud re-slurry process enters the primary re-slurry process, and the re-slurry from the primary re-slurry process enters the secondary re-slurry process. The re-slurry from the secondary re-slurry process undergoes a first heat exchange with the flue gas from the calcination desulfurization tower in a heat exchanger, and then undergoes a second heat exchange with the carbonized slurry in a heat exchanger. It is then mixed with the slurry flowing out of the slurry tank, and the cycle repeats continuously. The flue gas from the calcination desulfurization tower is 150°C after desulfurization. The secondary re-slurry is 25°C before the first heat exchange with the flue gas from the calcination desulfurization tower, and 50°C after the first heat exchange. The carbonized slurry is 125°C, and after a second heat exchange with the 50°C secondary re-slurry through a heat exchanger, it is 85°C. The secondary re-slurry is 85°C after the second heat exchange. The temperature of the softened water in the closed-loop circulation system during the primary heat exchange is 80°C; the temperature of the softened water in the closed-loop circulation system during the secondary heat exchange is 95°C. The filter residue from the primary and secondary re-slurry processes is discharged into the boron mud tailings pond. The boron mud re-slurry process involves mixing boron mud at 80°C after primary filtration with tailings pond return water at 18°C ​​to form a re-slurry at 25°C.

2. The method for energy cascade utilization and improving borax yield in boron chemical production according to claim 1, characterized in that: The primary filtration process uses a polypropylene diaphragm plate and frame to reduce the moisture content of the boron mud from 40% to 30%.

3. The method for energy cascade utilization and improving borax yield in boron chemical production according to claim 1, characterized in that: The primary heat exchange involves the flue gas from the calcination desulfurization tower exchanging heat with softened water in a closed-loop circulation via a fluoroplastic heat exchanger. The softened water then exchanges heat with the secondary reslurry via a tube-and-shell heat exchanger.

4. The method for energy cascade utilization and improving borax yield in boron chemical production according to claim 1, characterized in that: The secondary heat exchange involves the carbonized slurry undergoing heat exchange with softened water in a closed-loop circulation through a tube heat exchanger, and the softened water then undergoes heat exchange with the secondary re-slurry through a tube heat exchanger.

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