System and method for preparing industrial salt and alkali from salt and alkali associated ore

Abstract

The invention belongs to the field of salt and alkali associated ores, and discloses a system and method for preparing industrial salt and alkali from salt and alkali associated ores, the system comprises a main pipeline and two secondary pipelines, the main pipeline comprises a pretreatment device, a carbonation tower, a centrifugal machine, a fluidized bed dryer and a baking soda packaging machine which are sequentially connected through pipelines; wherein one secondary pipeline carbonation tower is simultaneously and sequentially connected with a crystallizer, a fluidization dryer and an industrial salt packaging machine through pipelines, and the other secondary pipeline centrifugal machine is simultaneously connected with a calcining furnace and a sodium carbonate packaging machine through pipelines. The effect of simultaneously producing the sodium carbonate, the baking soda and the industrial salt from the saline-alkaline brine is realized, and the saline-alkaline with economic value in the saline-alkaline brine is completely processed and utilized.

Description

A system and method for preparing industrial salt and alkali from associated saline-alkali minerals. Technical Field

[0001] This invention belongs to the field of associated salt and alkali minerals, and relates to a system and method for preparing industrial salt and alkali from associated salt and alkali minerals. Background Technology

[0002] Salt-alkali associated minerals are a common geological phenomenon in which minerals such as salts (e.g., sodium chloride) and alkalis (e.g., sodium carbonate, sodium bicarbonate) exist as companion substances. These minerals are distributed in many parts of the world, and are particularly abundant in the salt-alkali belts of Tongbai in Henan, Tibet, and Inner Mongolia in my country.

[0003] Currently, the utilization of saline-alkali associated minerals mainly relies on traditional mining and processing technologies. These technologies typically include steps such as ore crushing, screening, dissolving, and evaporation crystallization to separate and extract the salts and alkalis. However, these traditional technologies have many drawbacks, such as high energy consumption, low efficiency, and significant environmental pollution.

[0004] In particular, traditional processes often fail to effectively separate and efficiently utilize salt and alkali from associated salt and alkali ores during the production of industrial salt and alkali. This results in a significant waste of resources and energy, while the generated waste can also cause serious environmental pollution.

[0005] In addition, although there are advanced processes such as underground circulating salt-alkali-calcium co-production of alkali, which have improved the utilization efficiency of salt-alkali resources to some extent, these processes are mainly for specific raw materials (such as raw materials in underground salt-alkali lakes) and have limited applicability to associated minerals of salt-alkali.

[0006] CN101585549A discloses a method for preparing industrial salt and a method for electrolytically producing caustic soda. The method uses sodium polyacrylate as an anti-caking agent. It also discloses a method for electrolytically producing caustic soda, where sodium polyacrylate is used as an anti-caking agent in the industrial salt used for caustic soda production. Using low molecular weight sodium polyacrylate as the anti-caking agent, the sodium polyacrylate adsorbs onto the surface of sodium chloride crystals, forming a hydrophobic layer that hinders moisture exchange between the sodium chloride crystals and the air, thus preventing caking. Using industrial salt with sodium polyacrylate as an anti-caking agent as raw material for electrolytic caustic soda production reduces the amount of flocculant used and lowers production costs during the brine purification process in the diaphragm method, which is beneficial for diaphragm method caustic soda production. For ion-exchange membrane method caustic soda production, the low molecular weight sodium polyacrylate avoids the introduction of difficult-to-remove ferrocyanide ions during the primary brine purification, which is beneficial for ion-exchange method caustic soda production. However, no process for directly using associated minerals of salt and alkali to prepare industrial salt and alkali has been reported.

[0007] Therefore, there is an urgent need for a new and efficient process for preparing industrial salt and alkali from associated saline-alkali minerals to solve the problems existing in the current technology and realize the sustainable utilization of saline-alkali mineral resources. Summary of the Invention

[0008] To address the problems existing in the prior art, the purpose of this invention is to develop a new method for processing soda ash and industrial salt from high-salt natural soda ash ore, making full use of the alkaline substances and sodium chloride contained in the brine for separate processing, thereby achieving the efficient development of high-salt natural soda ash ore.

[0009] The above-mentioned objective of the present invention is achieved by the following technical solution:

[0010] A system for preparing industrial salt and alkali from associated salt and alkali minerals includes a main pipeline and two secondary pipelines. The main pipeline includes a pretreatment device, a carbonation tower, a centrifuge, a fluidized bed dryer, and a sodium bicarbonate packaging machine connected in sequence. One secondary pipeline, the carbonation tower, is simultaneously connected to a crystallizer, a fluidized bed dryer, and an industrial salt packaging machine in sequence. The other secondary pipeline, the centrifuge, is simultaneously connected to a calcining furnace and a soda ash packaging machine.

[0011] Furthermore, the pretreatment device includes a sedimentation tank and a filter.

[0012] Furthermore, the crystallizer is an MVR crystallizer.

[0013] A systematic method for preparing industrial salt and alkali from saline-alkali associated minerals includes the following steps:

[0014] Step 1: The pretreated brine reacts countercurrently with carbon dioxide in a carbonation tower to produce sodium bicarbonate, forming a baking soda slurry. Sodium chloride remains in the brine, thus separating the alkalis and sodium chloride.

[0015] Step 2: The baking soda slurry is cooled to remove the heat of reaction and then pumped back to the baking soda crystallizer using a circulating pump. The temperature of the baking soda slurry should be controlled below 35°C.

[0016] Step 3: Use a baking soda slurry pump to transport the slurry to a baking soda centrifuge for initial solid-liquid separation. The separated liquid is transported back to the carbonation tower. The separated baking soda wet filter cake is used to produce baking soda products and soda ash products respectively.

[0017] Step 4: After washing with water, part of the baking soda wet filter cake is transferred to a high-temperature calcining furnace for calcination using a screw feeder, while the other part of the baking soda wet filter cake is transferred to a drying fluidized bed using a screw feeder.

[0018] Step 5: Sodium carbonate in the brine in the carbonation tower is converted into sodium bicarbonate. After the low-alkali, high-salt brine is taken out, hydrochloric acid is added. Then, the sodium chloride brine enters the crystallizer. The secondary steam generated in the crystallizer is compressed by a compressor and its temperature rises. The secondary steam is used to heat the brine for evaporation and crystallization. When sodium chloride reaches supersaturation, sodium chloride crystals are precipitated. The sodium chloride slurry is pumped to a centrifuge for preliminary solid-liquid separation. The separated liquid is transported back to the crystallizer. The separated wet filter cake enters a drying fluidized bed for drying and is sent to an industrial salt screening machine by a bucket elevator. The lower layer product after screening is qualified industrial salt product, which is sent to the industrial salt packaging system for packaging by a belt conveyor.

[0019] Furthermore, in the fourth step, a portion of the baking soda wet filter cake is unstable at high temperatures and decomposes to produce sodium carbonate, carbon dioxide, and water. After the carbon dioxide is recovered, it is dried, compressed, and cooled before being reused in the carbonation tower. The cooled sodium carbonate is sent to the soda ash screening machine by a bucket elevator. The lower layer product after screening is qualified soda ash, which is then sent to the soda ash packaging system by a belt conveyor for packaging.

[0020] Furthermore, the sodium carbonate produced in the fourth step is cooled to below 70°C by a cooler, and the final surface moisture content is less than 0.1 wt%.

[0021] Furthermore, in the fourth step, another portion of the baking soda wet filter cake is cooled using a fluidizing gas containing mainly carbon dioxide and a heat exchanger. The product is then sent to a baking soda screening machine using a baking soda bucket elevator. The lower layer of the screened product is a qualified baking soda product, which is then conveyed by a belt conveyor to a baking soda packaging system for packaging.

[0022] Furthermore, in the fourth step, the baking soda is cooled to below 40°C and removed from the carbonized fluidized bed, with a surface moisture content of no more than 0.1 wt%.

[0023] Furthermore, in the fifth step, the purity of the final industrial salt product meets the national standard GB / T5462-2015 "Industrial Salt" for superior grade.

[0024] Furthermore, in the fifth step, the secondary steam generated in the crystallizer is compressed by a compressor and its temperature rises by 15-20°C.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] Existing natural alkali processing technologies are only suitable for processing soda ash from low-salinity natural alkali mines (salt content ≤0.3wt%, natural alkali mine brine), and cannot process alkali and salt from high-salinity natural alkali mines (salt content ≥0.3wt%, natural alkali mine brine). This invention utilizes a carbonation process combined with the low solubility of sodium bicarbonate. First, sodium bicarbonate in the saline-alkali brine is crystallized out, achieving "salt-alkali" separation in the brine. Subsequently, an evaporation and concentration process is used to crystallize the salt, enabling the simultaneous production of soda ash, sodium bicarbonate, and industrial salt from the saline-alkali brine. This allows for the complete processing and utilization of economically valuable salts and alkalis in the saline-alkali brine, realizing the profitable development of high-salinity natural alkali mines. Attached Figure Description

[0027] Figure 1 is a process flow diagram for preparing industrial salt and alkali from associated salt and alkali minerals. Detailed Implementation

[0028] The implementation of this invention is given in the following embodiments. Unless otherwise specified, the experimental methods used in this invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used are all commercially available.

[0029] Example 1

[0030] (1) The brine extracted from high-salt natural alkali mines is refined by filtration process to remove suspended solids. The main purpose is to reduce insoluble matter in the brine so that the final alkali product meets the national standard requirements (water-insoluble matter content in soda ash ≤ 0.2wt%).

[0031] (2) The refined brine enters the carbonation tower from the top of the carbonation tower and reacts countercurrently with the carbon dioxide added at the bottom of the carbonation tower. The sodium carbonate in the brine reacts with the carbon dioxide to produce sodium bicarbonate. Due to the low solubility of sodium bicarbonate, sodium bicarbonate crystallizes out in the carbonation tower to form a baking soda slurry (a mixture of sodium bicarbonate crystals and liquid). The main purpose is to allow the alkaline substances (sodium carbonate and sodium bicarbonate) in the brine to react with carbon dioxide to produce sodium bicarbonate, which crystallizes out at a lower temperature. Sodium chloride, due to its high solubility and low temperature sensitivity, remains in the brine, thus achieving the separation of alkalis and sodium chloride in the brine.

[0032] (3) The baking soda slurry is cooled to remove the heat of reaction and then pumped back to the baking soda crystallizer by a circulating pump. The temperature of the baking soda slurry is controlled below 35°C. The main purpose is to remove the heat generated by the reaction of sodium carbonate and carbon dioxide. At the same time, since sodium bicarbonate has low solubility at low temperatures, lowering the temperature of the baking soda slurry can increase the sodium bicarbonate crystallization yield and improve the utilization rate of alkaline substances in the brine.

[0033] (4) The generated baking soda slurry is pumped to a baking soda centrifuge, where the baking soda is subjected to preliminary solid-liquid separation. The separated liquid is returned to the carbonation tower, and the separated baking soda wet filter cake is used to produce baking soda and soda ash products respectively.

[0034] (5) A portion of the sodium bicarbonate wet filter cake is washed with water and then transferred to a high-temperature calcining furnace by a screw feeder for calcination. The main purpose is to remove the brine on the surface of the sodium bicarbonate crystals so that the final alkali product meets the national standard requirements (sodium chloride content ≤0.3wt%). Since sodium bicarbonate is unstable at high temperatures, it decomposes to produce sodium carbonate, carbon dioxide and water. After carbon dioxide is recovered, it is dried, compressed and cooled and then reused in the carbonation tower. The sodium carbonate produced by decomposition is cooled to below 70°C by a cooler, and the final moisture content is less than 0.1wt% (surface). The cooled sodium carbonate is sent to the soda ash screening machine by a bucket elevator. The lower layer product after screening is qualified soda ash product, which is sent to the soda ash packaging system by a belt conveyor for packaging.

[0035] (6) Another portion of the baking soda wet filter cake is transferred to a drying fluidized bed using a screw feeder. It is fluidized with hot gas, primarily containing carbon dioxide, and the temperature is controlled below 70°C. The dried baking soda then enters a carbonized fluidized bed, where it is cooled with fluidizing gas primarily containing carbon dioxide and a heat exchanger. The baking soda is cooled to below 40°C and leaves the carbonized fluidized bed, with a surface moisture content not exceeding 0.1 wt%. The main purpose of using hot carbon dioxide gas to dry and cool the baking soda is to reduce the decomposition rate of sodium bicarbonate. Specifically, sodium bicarbonate decomposes to produce sodium carbonate + water + carbon dioxide, and carbon dioxide + water + sodium carbonate react to produce sodium bicarbonate. Sufficient carbon dioxide in the gas is beneficial for the reaction of carbon dioxide + water + sodium carbonate to produce sodium bicarbonate. A baking soda bucket elevator is used to send the product to a baking soda screening machine. The lower layer after screening is qualified baking soda product, which is then conveyed by a belt conveyor to the baking soda packaging system for packaging.

[0036] (7) Sodium carbonate in the brine inside the carbonation tower is converted into sodium bicarbonate. Due to the low solubility of sodium bicarbonate, it precipitates when it is supersaturated, thus reducing the amount of sodium carbonate and sodium bicarbonate in the brine. The alkali content (sodium bicarbonate + sodium carbonate) in the brine at the top of the carbonation tower decreases. After the low-alkali, high-salt brine is taken out, hydrochloric acid is added. Sodium bicarbonate and sodium carbonate react with hydrochloric acid to produce sodium chloride + water + carbon dioxide. The main purpose is to convert the small amount of sodium carbonate and sodium bicarbonate in the brine into sodium chloride, thereby improving the purity of the final industrial salt product (the national standard "Industrial Salt" GB / T5462-2015 requires a sodium chloride content of ≥99.1wt% for superior grade products). Subsequently, the sodium chloride brine enters the MVR. The secondary steam generated by the MVR crystallizer is compressed by a compressor and its temperature rises by 15-20°C. This secondary steam is used to heat the brine for evaporation and crystallization. When sodium chloride reaches supersaturation, sodium chloride crystals precipitate. The sodium chloride slurry is pumped to a centrifuge for preliminary solid-liquid separation. The separated liquid is returned to the MVR crystallizer, and the separated wet filter cake enters a drying fluidized bed for drying. The final moisture content is less than 0.1 wt% (surface). The dried sodium chloride crystals are cooled to below 70°C by a cooler and then sent to an industrial salt screening machine by a bucket elevator. The lower layer after screening is qualified industrial salt product, which is then conveyed by a belt conveyor to the industrial salt packaging system for packaging.

[0037] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A system for preparing industrial salt and alkali from associated saline-alkali minerals, characterized in that, It includes one main pipeline and two secondary pipelines. The main pipeline includes a pretreatment unit, a carbonation tower, a centrifuge, a fluidized bed dryer, and a sodium bicarbonate packaging machine connected in sequence. One secondary pipeline, the carbonation tower, is connected in sequence to a crystallizer, a fluidized bed dryer, and an industrial salt packaging machine. The other secondary pipeline, the centrifuge, is connected in sequence to a calcining furnace and a soda ash packaging machine.

2. The system for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 1, characterized in that, The pretreatment equipment includes a sedimentation tank and a filter.

3. The system for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 1, characterized in that, The crystallizer is an MVR crystallizer.

4. A systematic method for preparing industrial salt and alkali from associated saline-alkali minerals, characterized in that, Includes the following steps: Step 1: The pretreated brine reacts countercurrently with carbon dioxide in a carbonation tower to produce sodium bicarbonate, forming a baking soda slurry. Sodium chloride remains in the brine, thus separating the alkali and sodium chloride. Step 2: The baking soda slurry passes through a cooler to remove the heat of reaction and is then pumped back to the baking soda crystallizer using a circulating pump. The temperature of the baking soda slurry should be controlled below 35°C. Step 3: Use a baking soda slurry pump to transport the slurry to a baking soda centrifuge for initial solid-liquid separation. The separated liquid is transported back to the carbonation tower. The separated baking soda wet filter cake is used to produce baking soda products and soda ash products respectively. Step 4: A portion of the baking soda wet filter cake is washed and then transferred to a high-temperature calcining furnace for calcination using a screw feeder. Another portion of the baking soda wet filter cake is transferred to a drying fluidized bed using a screw feeder. Step 5: Sodium carbonate in the brine in the carbonation tower is converted into sodium bicarbonate. After the low-alkali, high-salt brine is taken out, hydrochloric acid is added. Subsequently, the sodium chloride brine enters the crystallizer. The secondary steam generated in the crystallizer is compressed by a compressor and its temperature is raised. The secondary steam is used to heat the brine for evaporation and crystallization. When sodium chloride reaches supersaturation, sodium chloride crystals precipitate. The sodium chloride slurry is pumped to a centrifuge for preliminary solid-liquid separation using a slurry pump. The separated liquid is transported back to the crystallizer. The separated wet filter cake enters the drying fluidized bed for drying and is then sent to an industrial salt screening machine using a bucket elevator. The lower layer product after screening is qualified industrial salt product and is sent to the industrial salt packaging system for packaging by a belt conveyor.

5. The method for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 4, characterized in that, In the fourth step, a portion of the baking soda wet filter cake is unstable at high temperatures and decomposes to produce sodium carbonate, carbon dioxide, and water. After the carbon dioxide is recovered, it is dried, compressed, and cooled before being reused in the carbonation tower. The cooled sodium carbonate is sent to the soda ash screening machine by a bucket elevator. The lower layer product after screening is qualified soda ash, which is then sent to the soda ash packaging system by a belt conveyor for packaging.

6. The method for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 5, characterized in that, The sodium carbonate produced in the fourth step is cooled to below 70°C by a cooler, and the final surface moisture content is less than 0.1 wt%.

7. The method for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 4, characterized in that, In the fourth step, another portion of the baking soda wet filter cake is cooled using a fluidizing gas containing carbon dioxide and a heat exchanger. The product is then sent to a baking soda screening machine using a baking soda bucket elevator. The lower layer of the product after screening is a qualified baking soda product, which is then conveyed by a belt conveyor to a baking soda packaging system for packaging.

8. The method for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 7, characterized in that, In the fourth step, the baking soda is cooled to below 40°C and removed from the carbonized fluidized bed, with a surface moisture content of no more than 0.1 wt%.

9. The method for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 4, characterized in that, In the fifth step, the purity of the final industrial salt product meets the national standard GB / T5462-2015 "Industrial Salt" for superior grade.

10. The method for preparing industrial salt and alkali from associated saline-alkali minerals according to claim 4, characterized in that, In the fifth step, the secondary steam generated in the crystallizer is compressed by a compressor and its temperature rises by 15-20°C.

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