System for producing heavy sodium carbonate by using low-concentration sodium carbonate solution through one-step method

Abstract

The utility model discloses a system for producing heavy soda ash by using a low-concentration sodium carbonate solution through a one-step method. The system comprises an MVR (mechanical vapor recompression) evaporator, a thickener, a high-temperature pressure stirring tank, a flash evaporation decompression barrel, a centrifugal machine and a flash evaporation drying machine. The method has the advantages that after the low-concentration sodium carbonate solution is evaporated and concentrated by the MVR evaporator, part of water is separated by the thickener, then sodium carbonate monohydrate is converted into anhydrous sodium carbonate by the high-temperature pressure stirring tank, and crystal forms are recombined in the conversion process, so that the condition that the powder is loose and the crystal forms are broken after the sodium carbonate monohydrate is dehydrated under the anhydrous condition is completely avoided; and four procedures of steam calcining, crushing, screening and fine powder returning and batching are omitted, so that the technological process is simplified, and the energy consumption is reduced.

Description

Technical Field:

[0001] The utility model relates to the technical field of heavy soda ash production, and specifically relates to a system for producing heavy soda ash by one-step method from low-concentration sodium carbonate solution. Background Art:

[0002] Our company has currently developed a process for alkaline leaching of solid waste from electrolytic aluminum plants to recover the effective components therein. The concentration of the sodium carbonate solution obtained after alkaline leaching is about 10%. According to the prevailing technology in the soda ash production industry, MVR is used for evaporation and concentration. After the sodium carbonate reaches the saturation concentration, monohydrate sodium carbonate is crystallized out. The monohydrate sodium carbonate is indirectly heated and calcined with high-temperature steam to dehydrate and produce lumpy anhydrous sodium carbonate. The lumpy anhydrous sodium carbonate is then crushed and screened to obtain anhydrous sodium carbonate with a loose bulk density meeting the requirements, that is, heavy soda ash. The fine screened materials must be returned to the batching before calcination, and the batching ratio reaches 40%. However, this method requires removing 14.51% of the crystal water, resulting in extremely high energy consumption. After evaporation and concentration, high-temperature pressure evaporation at a temperature of 160°C or air heating for calcination and dehydration are required, with high energy consumption. Moreover, the lumpy materials after calcination need to be crushed and screened, and the fine powder is returned to the batching before calcination. The process is relatively complex. If the batching ratio is unreasonable, it will lead to insufficient fluidity of the product and affect normal production. Content of the Utility Model:

[0003] The purpose of the utility model is to provide a system for producing heavy soda ash by one-step method from low-concentration sodium carbonate solution.

[0004] The utility model is implemented by the following technical solutions: A system for producing heavy soda ash by one-step method from low-concentration sodium carbonate solution, which includes an MVR evaporator, a thickener, a high-temperature pressure stirring tank, a flash depressurization barrel, a centrifuge, and a flash dryer. The low-concentration sodium carbonate solution feeding pipe is connected to the inlet of the MVR evaporator. The outlet of the MVR evaporator is connected to the inlet of the thickener. The slurry outlet of the thickener is connected to the inlet of the high-temperature pressure stirring tank. The outlet of the high-temperature pressure stirring tank is connected to the inlet of the flash depressurization barrel. The outlet of the flash depressurization barrel is connected to the inlet of the centrifuge. The slurry outlet of the centrifuge is connected to the inlet of the flash dryer. The outlet of the flash dryer is connected to a heavy soda ash discharging pipe.

[0005] Further, the overflow port of the thickener is connected to the inlet of the mother liquor tank, and the outlet of the mother liquor tank is connected to the inlet of the MVR evaporator.

[0006] Further, the liquid outlet of the centrifuge is connected to the inlet of the mother liquor tank, and the outlet of the mother liquor tank is connected to the inlet of the MVR evaporator.

[0007] Advantages of the present utility model: After the low-concentration sodium carbonate solution is evaporated and concentrated by the MVR evaporator, it is first separated from part of the water by the thickener, and then passed through the high-temperature pressure stirring tank to convert monohydrate sodium carbonate into anhydrous sodium carbonate. The crystal form recombines during the transformation process, completely avoiding the situation of loose powder and broken crystal form after dehydration of monohydrate sodium carbonate under anhydrous conditions. Moreover, the four processes of steam calcination, crushing, screening, and returning fine powder to the batching are omitted, simplifying the process flow and reducing energy consumption. Description of the drawings:

[0008] Figure 1 It is the overall structure diagram of the present utility model;

[0009] MVR evaporator 1, thickener 2, high-temperature pressure stirring tank 3, flash evaporation decompression barrel 4, centrifuge 5, flash dryer 6, low-concentration sodium carbonate solution feed pipe 7, heavy soda ash discharge pipe 8, mother liquor tank 9. Specific implementation manners:

[0010] In the description of the present utility model, it should be noted that when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present utility model. In addition, when terms such as "first", "second", "third" appear, they are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0011] As Figure 1 shown, a system for one-step production of heavy soda ash from low-concentration sodium carbonate solution includes an MVR evaporator 1, a thickener 2, a high-temperature pressure stirring tank 3, a flash evaporation decompression barrel 4, a centrifuge 5, and a flash dryer 6. The low-concentration sodium carbonate solution feed pipe 7 is connected to the inlet of the MVR evaporator 1, the outlet of the MVR evaporator 1 is connected to the inlet of the thickener 2, the slurry outlet of the thickener 2 is connected to the inlet of the high-temperature pressure stirring tank 3, the outlet of the high-temperature pressure stirring tank 3 is connected to the inlet of the flash evaporation decompression barrel 4, the outlet of the flash evaporation decompression barrel 4 is connected to the inlet of the centrifuge 5, the slurry outlet of the centrifuge 5 is connected to the inlet of the flash dryer 6, and the outlet of the flash dryer 6 is connected to a heavy soda ash discharge pipe 8. The overflow port of the thickener 2 is connected to the inlet of the mother liquor tank 9, the liquid outlet of the centrifuge 5 is connected to the inlet of the mother liquor tank 9, and the outlet of the mother liquor tank 9 is connected to the inlet of the MVR evaporator 1.

[0012] Working principle:

[0013] (1) The low-concentration sodium carbonate fed by the low-concentration sodium carbonate solution feed pipe 7 enters the MVR evaporator 1, where it is concentrated and crystallized until monohydrate sodium carbonate is produced and continues to be evaporated and concentrated.

[0014] (2) The monohydrate sodium carbonate crystal slurry discharged from the MVR evaporator 1 is sent to the thickener 2, and the thickener 2 is used to increase the solid content of the slurry, with the solid content controlled at 40%-60% to obtain a high-content monohydrate sodium carbonate slurry.

[0015] (3) The high-content monohydrate sodium carbonate slurry discharged from the thickener 2 is sent to the high-temperature pressure stirring tank 3, where the temperature of the slurry is controlled at 120-160 °C and stirred for 30-150 minutes to obtain a high-temperature sodium carbonate slurry. The overflow liquid discharged from the thickener 2 is collected in the mother liquor tank 9 and then returned to the MVR evaporator 1 for sodium carbonate recovery.

[0016] (4) The high-temperature sodium carbonate slurry discharged from the high-temperature pressure stirring tank 3 is sent to the flash evaporation decompression barrel 4 to release the pressure.

[0017] (5) The high-temperature sodium carbonate slurry discharged from the flash evaporation decompression barrel 4 is sent to the centrifuge 5 to separate anhydrous sodium carbonate with free water to obtain crystal mother liquor, which is sent to the mother liquor tank 9 and then returned to the MVR evaporator 1 for sodium carbonate recovery. The 14.51% of the crystal water in the heavy soda ash does not need to be removed by high-temperature calcination, but is returned to the low-energy-consuming MVR system for evaporation, which can save evaporation costs.

[0018] (6) The anhydrous sodium carbonate separated by the centrifuge 5 is sent to the flash dryer 6, where the flash inlet air temperature is 160-300 °C, and the dried heavy soda ash product is discharged from the system through the heavy soda ash discharge pipe 8.

[0019] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for producing dense soda ash by a one-step method from a low-concentration sodium carbonate solution, characterized in that, It includes an MVR evaporator, a thickener, a high-temperature pressure stirring tank, a flash decompression tank, a centrifuge, and a flash dryer. The low-concentration sodium carbonate solution feed pipe is communicated with the inlet of the MVR evaporator. The outlet of the MVR evaporator is communicated with the inlet of the thickener. The slurry outlet of the thickener is communicated with the inlet of the high-temperature pressure stirring tank. The outlet of the high-temperature pressure stirring tank is communicated with the inlet of the flash decompression tank. The outlet of the flash decompression tank is communicated with the inlet of the centrifuge. The slurry outlet of the centrifuge is communicated with the inlet of the flash dryer. A heavy soda ash discharge pipe is communicated with the outlet of the flash dryer.

2. The system for producing dense soda ash by a one-step method from a low-concentration sodium carbonate solution according to claim 1, characterized in that, The overflow port of the thickener is communicated with the inlet of the mother liquor tank. The outlet of the mother liquor tank is communicated with the inlet of the MVR evaporator.

3. The system for producing dense soda ash by a one-step method from a low-concentration sodium carbonate solution according to claim 1, wherein The liquid outlet of the centrifuge is communicated with the inlet of the mother liquor tank. The outlet of the mother liquor tank is communicated with the inlet of the MVR evaporator.

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