Continuous crystallization high-efficiency low-consumption sodium carbonate production process

Abstract

The invention is suitable for the technical field of sodium carbonate production, and provides a continuous crystallization high-efficiency low-consumption sodium carbonate production process, which comprises the following steps: S1, recovery treatment of returned sand broken stone: mixing the returned sand broken stone with limestone and coke, adding into a stone separator, crushing, then transferring into a lime kiln, heating, decomposing, and recovering quick lime, quicklime is used for recovering fixed ammonia in the mother liquor; s2, third-stage carbonization: transferring a proper amount of ammonia brine and carbon dioxide into a third-stage carbonization tower in sequence; s3, continuous crystallization; s4, centrifuging and calcining: pumping crystal mush of the DTB crystallizer into a centrifugal machine, spraying a saturated Na2CO3 solution after a crystal cake is formed, and calcining and converting to prepare sodium carbonate; preferably, the weight ratio of the returned sand gravel to the limestone to the coke in the S1 is (50-120): (10-30): (1-5). According to the invention, by recycling the returned sand gravel, not only is the cost of raw materials reduced, but also the problem of solid waste discharge is solved; through three-stage carbonization and continuous crystallization processes, the quality of sodium carbonate is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of soda ash production technology, specifically to a high-efficiency, low-consumption soda ash production process with continuous crystallization. Background Technology

[0002] Soda ash is one of the most important basic raw materials in the chemical industry, and along with caustic soda, it is considered the "mother of industry." It is widely used in glass, chemical, metallurgical, textile, and detergent industries. There are three main processes for the production of soda ash: the ammonia-soda process, the combined alkali process, and the natural soda process.

[0003] Chinese patent application number CN201610728813.1 and publication number CN106365179B addresses the shortcomings of existing technologies in the production of soda ash using the ammonia-soda process, which produce ammonia-containing wastewater containing large amounts of sodium chloride and calcium chloride, causing environmental pollution. This patent provides an environmentally friendly ammonia-soda process for soda ash production, along with the production system and treatment method for the ammonia-containing wastewater. The environmentally friendly ammonia-soda process system involves an ammonia-absorbing device absorbing ammonia gas to obtain ammonia-water brine. This brine then enters an ammonia-water carbonation device for carbonation, producing a sodium bicarbonate solution. This solution is then separated in a mother liquor distillation device, and the resulting sodium bicarbonate is calcined in a calcination device to produce soda ash and CO2. The ammonia-containing liquid separated in the mother liquor distillation device enters the ammonia-containing wastewater collection tank of the ammonia-containing wastewater treatment system. Using this system and method for soda ash production not only offers good environmental performance but also saves on the amount of raw salt used in the alkali-process soda ash production.

[0004] Chinese patent application number CN202411654320.9 and publication number CN119160919B discloses a production process for heavy soda ash, including the following steps: (1) at room temperature, dissolve light ash in soft water to saturation, homogenize under high pressure, add a flocculant, stir, and centrifuge; (2) evaporate the saturated light ash aqueous solution, centrifuge, add a saturated sodium carbonate alcohol aqueous solution, and centrifuge; (3) mix the refined light ash with the saturated sodium carbonate alcohol aqueous solution, place it in a hydration machine for hydration reaction, homogenize under high pressure, and centrifuge; (4) add a pre-saturated sodium carbonate alcohol aqueous solution to the soda ash solution for pressure filtration, wash, place it in a heavy ash calcination furnace for dehydration, and obtain heavy soda ash. The production process of this invention can reduce the salt content and other impurities of heavy soda ash and improve the uniformity of the particle size distribution of heavy soda ash.

[0005] Existing soda ash production processes suffer from low production efficiency, high energy consumption, and environmental pollution. Particularly during continuous crystallization, the complexity of operation and difficulty in control often lead to unstable product quality, while also generating large amounts of waste liquid and waste, putting pressure on the environment. Therefore, developing a high-efficiency, low-energy-consumption continuous crystallization soda ash production process is of great significance for improving soda ash production efficiency, reducing energy consumption, and minimizing environmental pollution. Summary of the Invention

[0006] The purpose of this invention is to provide a high-efficiency, low-consumption soda ash production process with continuous crystallization, in order to solve the problems of low production efficiency, high energy consumption, and environmental pollution in existing soda ash production processes.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency, low-consumption process for continuous crystallization of soda ash, comprising the following steps:

[0008] S1, Recycling and processing of returned sand and gravel:

[0009] The returned sand and crushed stone are mixed with limestone and coke, added to a stone separator, crushed, and then transferred to a lime kiln for heating and decomposition to recover quicklime. The quicklime is used to recover fixed ammonia from the mother liquor, as detailed below:

[0010] Quicklime is mixed with water, heated, and refined into lime milk. Then, it is sent to the ammonia stripping tower along with the mother liquor. The recovered ammonia gas is fully absorbed by refined brine to prepare ammonia brine.

[0011] S2, tertiary carbonization:

[0012] An appropriate amount of ammonia brine and carbon dioxide are transferred together to a three-stage carbonization tower.

[0013] S3, continuous crystallization:

[0014] The carbonized liquid in S2 was used as the mother liquor and transferred to the DTB crystallizer. The temperature was lowered to 35°C, and the polyepoxysuccinic acid solution was continuously pumped into the bottom of the guide tube of the DTB crystallizer to inhibit the formation of needle crystals. Every 10-15 minutes, 100 ppm of nano-SiO2 dispersion was pulsed into the baffle area to destroy the microcrystalline aggregates.

[0015] 30% of the crystal slurry is extracted from the annular baffle area and transported to the tubular hot melter by an axial flow pump. At 85°C, the fine crystals are completely dissolved again. The mother liquor after hot melting is returned to the bottom of the crystallizer and mixed with the crystal slurry in the cold zone to achieve temperature-concentration balance.

[0016] The crystal slurry is pumped out from the conical bottom and enters the centrifugal section through an insulated jacketed pipe;

[0017] S4, centrifugation and calcination:

[0018] The crystal slurry from the DTB crystallizer is pumped into a centrifuge. After the crystal cake is formed, it is sprayed with a saturated Na2CO3 solution and calcined to produce soda ash.

[0019] Preferably, the weight ratio of returned sand and gravel to limestone and coke in S1 is (50-120):(10-30):(1-5).

[0020] Preferably, the settings parameters for the three-stage carbonization tower in S2 are as follows:

[0021] First-stage carbonization tower: temperature 65-70℃, carbon dioxide concentration 25-30%, pH value 9-10;

[0022] Second-stage carbonization tower: temperature 60-65℃, carbon dioxide concentration 35-40%, pH value 8-8.5;

[0023] Third-stage carbonization tower: temperature 55-60℃, carbon dioxide concentration 20-25%, pH value 7.5-8.

[0024] Preferably, the centrifugation speed of S4 is 2000-2500 rpm.

[0025] Preferably, the temperature of the saturated Na2CO3 solution sprayed in S4 is 55-65℃.

[0026] Preferably, the calcination temperature in S4 is 200-300℃.

[0027] Preferably, the cooling gradient in S3 is 1-2℃ / min.

[0028] Preferably, the rate at which the polyepoxysuccinic acid solution is continuously pumped into the bottom of the guide tube of the DTB crystallizer in S3 is 0.5-1 L / min.

[0029] Preferably, the slurry pumping rate in S3 is 1.5-2 m / s. 3 / h.

[0030] The present invention has at least the following beneficial effects:

[0031] (1) The present invention provides a continuous crystallization high-efficiency and low-consumption soda ash production process. By recycling and utilizing returned sand and gravel, it not only reduces the cost of raw materials, but also solves the problem of solid waste discharge, realizing the recycling of resources and environmentally friendly protection.

[0032] (2) The present invention provides a high-efficiency and low-consumption soda ash production process with continuous crystallization, which greatly improves the quality of soda ash through three-stage carbonization and continuous crystallization process. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Currently, the CaCO3 in limestone cannot be completely decomposed, resulting in a large amount of solid waste—returned sand and gravel—generated after the CaO digestion of quicklime. This returned sand and gravel is small in size and prone to cracking when heated. It also contains a large amount of carbon nuclei, magnesium-aluminum-silicon-iron compounds, and nodules. Continued calcination of this material makes it impossible to control the coke ratio and severely affects kiln ventilation, leading to uncontrolled kiln temperature and large-scale nodule formation. As limestone mining gradually decreases and limestone prices continue to rise, the production cost of soda ash is increasing. Recycling and reusing this returned sand and gravel can not only effectively reduce the cost of soda ash but also solve the problem of solid waste emissions, achieving cleaner production.

[0035] Based on the recycling of returned sand and gravel, the present invention provides the following partial embodiments:

[0036] Example 1

[0037] This embodiment provides a high-efficiency, low-consumption process for continuous crystallization of soda ash, including the following steps:

[0038] S1, Recycling and processing of returned sand and gravel:

[0039] The returned sand and crushed stone are mixed with limestone and coke in a weight ratio of 50:10:1, added to a stone separator, crushed, and then transferred to a lime kiln for heating and decomposition to recover quicklime. The quicklime is used to recover fixed ammonia from the mother liquor (carbonized liquid containing NH4Cl in S2), as detailed below:

[0040] Quicklime is mixed with water, heated, and refined into lime milk. Then, it is sent to the ammonia stripping tower along with the mother liquor. The recovered ammonia gas is fully absorbed by refined brine to prepare ammonia brine.

[0041] S2, tertiary carbonization:

[0042] An appropriate amount of ammonia brine and carbon dioxide are transferred together to a three-stage carbonization tower.

[0043] The settings parameters for the three-stage carbonization tower are as follows:

[0044] First-stage carbonization tower: temperature 65℃, carbon dioxide concentration 25%, pH value 9;

[0045] Second-stage carbonization tower: temperature 60℃, carbon dioxide concentration 35%, pH value 8;

[0046] Third-stage carbonization tower: temperature 55℃, carbon dioxide concentration 20%, pH value 7.5;

[0047] S3, continuous crystallization:

[0048] The carbonized liquid in S2 was used as the mother liquor and transferred to the DTB crystallizer. The temperature was gradually reduced to 35℃ at a rate of 1℃ / min. The polyepoxysuccinic acid solution was continuously pumped into the bottom of the guide tube of the DTB crystallizer at a rate of 0.5L / min to inhibit the formation of needle crystals. Every 10 min, 100ppm of nano-SiO2 dispersion was pulsed into the baffle area to destroy the microcrystalline aggregates.

[0049] 30% of the crystal slurry is extracted from the annular baffle area and transported to the tubular hot melter by an axial flow pump. At 85°C, the fine crystals are completely dissolved again. The mother liquor after hot melting is returned to the bottom of the crystallizer and mixed with the crystal slurry in the cold zone to achieve temperature-concentration balance.

[0050] The crystal slurry descends from the cone base at a rate of 1.5m. 3 The flow rate is pumped out at a rate of / h and enters the centrifugal section through an insulated jacketed pipeline;

[0051] S4, centrifugation and calcination:

[0052] The crystal slurry from the DTB crystallizer is pumped into a centrifuge at a speed of 2000 rpm. After the crystal cake is formed, it is sprayed with a saturated Na2CO3 solution at a temperature of 55°C and calcined at a temperature of 200°C to obtain soda ash.

[0053] Example 2

[0054] This embodiment provides a high-efficiency, low-consumption process for continuous crystallization of soda ash, including the following steps:

[0055] S1, Recycling and processing of returned sand and gravel:

[0056] The returned crushed stone is mixed with limestone and coke in a weight ratio of 100:20:3, added to a stone separator, crushed, and then transferred to a lime kiln for heating and decomposition to recover quicklime. The quicklime is used to recover fixed ammonia from the mother liquor, as detailed below:

[0057] Quicklime is mixed with water, heated, and refined into lime milk. Then, it is sent to the ammonia stripping tower along with the mother liquor. The recovered ammonia gas is fully absorbed by refined brine to prepare ammonia brine.

[0058] S2, tertiary carbonization:

[0059] An appropriate amount of ammonia brine and carbon dioxide are transferred together to a three-stage carbonization tower.

[0060] The settings parameters for the three-stage carbonization tower are as follows:

[0061] First-stage carbonization tower: temperature 68℃, carbon dioxide concentration 27%, pH value 9.5;

[0062] Second-stage carbonization tower: temperature 62℃, carbon dioxide concentration 36%, pH value 8.2;

[0063] Third-stage carbonization tower: temperature 58℃, carbon dioxide concentration 22%, pH value 7.8;

[0064] S3, continuous crystallization:

[0065] The carbonized liquid in S2 was used as the mother liquor and transferred to the DTB crystallizer. The temperature was gradually reduced to 35℃ at a rate of 2℃ / min. The polyepoxysuccinic acid solution was continuously pumped into the bottom of the guide tube of the DTB crystallizer at a rate of 0.8L / min to suppress the formation of needle crystals. Every 12min, 100ppm of nano-SiO2 dispersion was pulsed into the baffle area to destroy the microcrystalline aggregates.

[0066] 30% of the crystal slurry is extracted from the annular baffle area and transported to the tubular hot melter by an axial flow pump. At 85°C, the fine crystals are completely dissolved again. The mother liquor after hot melting is returned to the bottom of the crystallizer and mixed with the crystal slurry in the cold zone to achieve temperature-concentration balance.

[0067] The crystal slurry descends from the cone base at a rate of 1.6m. 3 The flow rate is pumped out at a rate of / h and enters the centrifugal section through an insulated jacketed pipeline;

[0068] S4, centrifugation and calcination:

[0069] The crystal slurry from the DTB crystallizer is pumped into a centrifuge at a speed of 2200 rpm. After the crystal cake is formed, it is sprayed with a saturated Na2CO3 solution at a temperature of 60°C and calcined at a temperature of 250°C to produce soda ash.

[0070] Example 3

[0071] This embodiment provides a high-efficiency, low-consumption process for continuous crystallization of soda ash, including the following steps:

[0072] S1, Recycling and processing of returned sand and gravel:

[0073] The returned sand and crushed stone are mixed with limestone and coke in a weight ratio of 120:30:5, added to a stone separator, crushed, and then transferred to a lime kiln for heating and decomposition to recover quicklime. The quicklime is used to recover fixed ammonia from the mother liquor, as detailed below:

[0074] Quicklime is mixed with water, heated, and refined into lime milk. Then, it is sent to the ammonia stripping tower along with the mother liquor. The recovered ammonia gas is fully absorbed by refined brine to prepare ammonia brine.

[0075] S2, tertiary carbonization:

[0076] An appropriate amount of ammonia brine and carbon dioxide are transferred together to a three-stage carbonization tower.

[0077] The settings parameters for the three-stage carbonization tower are as follows:

[0078] First-stage carbonization tower: temperature 70℃, carbon dioxide concentration 30%, pH value 10;

[0079] Second-stage carbonization tower: temperature 65℃, carbon dioxide concentration 40%, pH value 8.5;

[0080] Third-stage carbonization tower: temperature 60℃, carbon dioxide concentration 25%, pH value 8;

[0081] S3, continuous crystallization:

[0082] The carbonized liquid in S2 was used as the mother liquor and transferred to the DTB crystallizer. The temperature was gradually reduced to 35℃ at a rate of 2℃ / min. The polyepoxysuccinic acid solution was continuously pumped into the bottom of the guide tube of the DTB crystallizer at a rate of 1L / min to inhibit the formation of needle crystals. Every 15min, 100ppm of nano-SiO2 dispersion was pulsed into the baffle area to destroy the microcrystalline aggregates.

[0083] 30% of the crystal slurry is extracted from the annular baffle area and transported to the tubular hot melter by an axial flow pump. At 85°C, the fine crystals are completely dissolved again. The mother liquor after hot melting is returned to the bottom of the crystallizer and mixed with the crystal slurry in the cold zone to achieve temperature-concentration balance.

[0084] The crystal slurry descends from the cone base at a rate of 2m. 3 The flow rate is pumped out at a rate of / h and enters the centrifugal section through an insulated jacketed pipeline;

[0085] S4, centrifugation and calcination:

[0086] The crystal slurry from the DTB crystallizer is pumped into a centrifuge at a speed of 2500 rpm. After the crystal cake is formed, it is sprayed with a saturated Na2CO3 solution at a temperature of 65°C and calcined at a temperature of 300°C to produce soda ash.

[0087] The products prepared in the above embodiments were subjected to relevant tests, and the results are as follows:

[0088]

[0089] In summary, the high-efficiency, low-consumption continuous crystallization process for producing soda ash of this invention, by recycling returned sand and gravel, not only reduces raw material costs but also solves the problem of solid waste emissions, achieving resource recycling and environmentally friendly protection. During the three-stage carbonization process, precise control of the temperature, carbon dioxide concentration, and pH value of each stage of the carbonization tower effectively improves carbonization efficiency, providing high-quality mother liquor for subsequent continuous crystallization. In the continuous crystallization stage, a DTB crystallizer is used, and gradient cooling and the addition of polyepoxysuccinic acid solution and nano-SiO2 dispersion effectively inhibit the formation of needle-like crystals, destroy microcrystalline aggregates, and improve crystal quality and yield. Finally, high-purity soda ash product is obtained through centrifugation and calcination conversion. Compared with existing technologies, the production process of this invention has advantages such as high production efficiency, low energy consumption, and minimal environmental pollution, and has significant industrial application value.

[0090] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency, low-consumption process for continuous crystallization of soda ash, characterized in that, Includes the following steps: S1, Recycling and processing of returned sand and gravel: The returned sand and crushed stone are mixed with limestone and coke, added to a stone separator, crushed, and then transferred to a lime kiln for heating and decomposition to recover quicklime. The quicklime is used to recover fixed ammonia from the mother liquor, as detailed below: Quicklime is mixed with water, heated, and refined into lime milk. Then, it is sent to the ammonia stripping tower along with the mother liquor. The recovered ammonia gas is fully absorbed by refined brine to prepare ammonia brine. S2, tertiary carbonization: An appropriate amount of ammonia brine and carbon dioxide are transferred together to a three-stage carbonization tower. S3, continuous crystallization: The carbonized liquid in S2 was used as the mother liquor and transferred to the DTB crystallizer. The temperature was lowered to 35°C, and the polyepoxysuccinic acid solution was continuously pumped into the bottom of the guide tube of the DTB crystallizer to inhibit the formation of needle crystals. Every 10-15 minutes, 100 ppm of nano-SiO2 dispersion was pulsed into the baffle area to destroy the microcrystalline aggregates. 30% of the crystal slurry is extracted from the annular baffle area and transported to the tubular hot melter by an axial flow pump. At 85°C, the fine crystals are completely dissolved again. The mother liquor after hot melting is returned to the bottom of the crystallizer and mixed with the crystal slurry in the cold zone to achieve temperature-concentration balance. The crystal slurry is pumped out from the conical bottom and enters the centrifugal section through an insulated jacketed pipe; S4, centrifugation and calcination: The crystal slurry from the DTB crystallizer is pumped into a centrifuge. After the crystal cake is formed, it is sprayed with a saturated Na2CO3 solution and calcined to produce soda ash.

2. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that, The weight ratio of returned sand and gravel to limestone and coke in S1 is (50-120):(10-30):(1-5).

3. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that, The settings parameters for the three-stage carbonization tower in S2 are as follows: First-stage carbonization tower: temperature 65-70℃, carbon dioxide concentration 25-30%, pH value 9-10; Second-stage carbonization tower: temperature 60-65℃, carbon dioxide concentration 35-40%, pH value 8-8.5; Third-stage carbonization tower: temperature 55-60℃, carbon dioxide concentration 20-25%, pH value 7.5-8.

4. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that: The speed of the S4 centrifuge is 2000-2500 rpm.

5. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that: The temperature of the saturated Na2CO3 solution sprayed in S4 is 55-65℃.

6. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that: The calcination temperature in S4 is 200-300℃.

7. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that: The cooling gradient in S3 is 1-2℃ / min.

8. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that: The rate at which the polyepoxysuccinic acid solution in S3 is continuously pumped into the bottom of the guide tube of the DTB crystallizer is 0.5-1 L / min.

9. The high-efficiency, low-consumption soda ash production process with continuous crystallization according to claim 1, characterized in that: The slurry pumping rate in S3 is 1.5-2 m / s. 3 / h.

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