阅读说明：本技术 一种混合废盐制备碳酸钠联产硫酸铵与氯化铵的方法 (Method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride by using mixed waste salt ) 是由 张洋 范兵强 张贺东 申长帅 郑诗礼 曹宏斌 陈沛松 于 2021-12-09 设计创作，主要内容包括：本发明提供了一种混合废盐制备碳酸钠联产硫酸铵与氯化铵的方法,将硫酸钠与氯化钠混合盐的分离与高值化结合起来,主要利用两次复分解反应将混合废盐制备为碳酸钠,并联产硫酸铵与氯化铵；碳酸钠纯度满足GB/T 210.1-2004中Ⅱ类合格品中轻质碳酸钠的要求,硫酸铵纯度满足GB/T 535-2020中Ⅰ型产品的要求,氯化铵纯度满足GB/T 2946-2018中农业用氯化铵一等品的要求；且所述方法流程简单,成本低廉,钠元素的利用率大于90%。(The invention provides a method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride by using mixed waste salt, which combines the separation and high-valued treatment of mixed salt of sodium sulfate and sodium chloride, mainly uses double decomposition reactions to prepare the mixed waste salt into sodium carbonate and coproduces the ammonium sulfate and ammonium chloride; the purity of the sodium carbonate meets the requirement of light sodium carbonate in class II qualified products in GB/T210.1-2004, the purity of the ammonium sulfate meets the requirement of type I products in GB/T535-2012020, and the purity of the ammonium chloride meets the requirement of first-class agricultural ammonium chloride products in GB/T2946-2018; the method has simple flow and low cost, and the utilization rate of the sodium element is more than 90 percent.)

1. A method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride from mixed waste salt is characterized by comprising the following steps:

(1) carrying out primary reaction on the mixed waste salt and a first reaction solution, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

(2) reacting and crystallizing the second reaction solution and the crude sodium sulfate product obtained in the step (1), and performing second solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate complex salt; cooling and crystallizing the first mother liquor obtained in the step (1), and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated sodium sulfate solution obtained in the step (2), and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother liquor; mixing a solvent with the sodium sulfate-ammonium sulfate complex salt obtained in the step (2), enriching, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

(4) calcining the sodium bicarbonate obtained in the step (3) to obtain sodium carbonate; and (4) evaporating and crystallizing the fourth mother liquor obtained in the step (3), and carrying out sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor.

2. The method according to claim 1, characterized in that in the mixed waste salt in the step (1), the mass ratio of sodium sulfate to sodium chloride is (1-9): 1.

3. The method according to claim 1 or 2, wherein the temperature of the primary reaction in the step (1) is 40 to 60 ℃ and the time is 30 to 180 min.

4. The method as claimed in claim 1, wherein the second mother liquor obtained by cooling crystallization in step (2) and the sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization are mixed and recycled to step (1) to be used as the first reaction solution for primary reaction.

5. The method according to claim 1, wherein in the secondary reaction in the step (3), the ratio of the molar amount of sodium atoms in the saturated solution of sodium sulfate to the molar amount of nitrogen atoms in the ammonium bicarbonate is (0.8-1.5): 1.

6. The method according to claim 1 or 5, characterized in that the third mother liquor obtained in step (3) is recycled to step (2) to be used as the second reaction liquid for reaction and crystallization.

7. The method according to claim 1, wherein the temperature of the enrichment in the step (3) is 85-110 ℃ and the time is 20-120 min.

8. The method of claim 1, wherein the deammoniated solid obtained in step (3) is recycled to step (2) to be used as the crude sodium sulfate for reaction crystallization.

9. The method according to claim 1, wherein the temperature of the evaporative crystallization in the step (4) is 60-80 ℃.

10. The process according to claim 1 or 9, characterized in that the fifth mother liquor obtained in step (4) is recycled to step (3) for enrichment as the solvent.

Technical Field

The invention belongs to the technical field of chemical processes, and particularly relates to a method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride by using mixed waste salt.

Background

The waste salt refers to solid waste containing inorganic salt main components, such as various waste residues, dust and other waste materials discharged in the industrial production process, and at present, the byproduct crystalline salt generated in the industrial production is generally called waste salt, and mainly comes from high-salt wastewater generated in various industries such as pesticides, pharmacy, fine chemical industry, printing and dyeing and the like, and has the characteristics of large disposal difficulty, high cost, environmental hazard and the like due to wide sources, various types and high toxic and harmful substances.

The yield of mixed waste salt with sodium chloride and sodium sulfate as main components is huge, the annual output of China is about 1000 ten thousand tons, most of the waste salt is collected and treated in a centralized way, and the conventional treatment method of the mixed waste salt mainly separates the sodium sulfate and the sodium chloride and mainly comprises a saltpeter method separation method and a nanofiltration separation method.

CN113060889A discloses a control method of a hot salt and nitrate separation process, which comprises the following steps: the first step is as follows: MVR evaporation crystallization process, the second step: controlling a mother liquor reflux process: the chloride ion online monitoring device measures the chloride ion content in the mother liquor tank, and controls the mother liquor to flow back to the evaporator to continue evaporation crystallization or to be sent to a subsequent freezing nitrate separation device; the third step: cooling and freezing to obtain nitre, and a fourth step: and (5) single-effect evaporation crystallization. The invention can improve the yield of the salt and the nitre and improve the purity of the sodium chloride in the mixed salt; the method solves the problems of low yield of salt and nitrate and low purity of sodium chloride in the treated mixed salt in the prior art. However, the salt-nitrate separation method has large material circulation amount and high energy consumption, and the obtained products of sodium sulfate and sodium chloride have poor quality, low value and poor market absorption capacity.

CN110548750A discloses a process for recycling waste salt and a special device thereof, wherein, sodium chloride and sodium sulfate are taken as main waste salt, sodium chloride and sodium sulfate saturated brine are respectively added into the main waste salt and are continuously stirred, salt washing mother liquor is obtained by filtering, and the separated sodium chloride and sodium sulfate solid is dried; freezing the salt washing mother liquor, evaporating and crystallizing crystals, chemically removing impurities from the frozen mother liquor, removing organic and inorganic impurity ions, performing organic separation on impurity-removed effluent, utilizing the produced water in a mother liquor field, performing oxidation treatment on the produced water, performing nanofiltration on the produced water, returning nanofiltration concentrated water to a salt washing system, and evaporating and drying the nanofiltration produced water to obtain sodium chloride solid; according to the method, through effective combination of a series of processes such as salt washing, freezing, organic separation, oxidation, nanofiltration salt separation, evaporation and the like, sodium chloride and sodium sulfate in the waste salt are separated and purified, organic matters and other impurity ions in the waste salt are effectively separated or removed, the treatment cost of hazardous waste is reduced, the recycling of the two waste salts is realized, and the economic value is created.

CN107304090A discloses a method for recycling high-salinity wastewater containing sodium chloride and sodium sulfate, wherein the high-salinity wastewater containing sodium chloride and sodium sulfate enters a primary nanofiltration device; the trapped liquid of the primary nanofiltration enters a diluting chamber of a monovalent ion selective electrodialyzer, and the permeate of the primary nanofiltration enters a concentrating chamber of the monovalent ion selective electrodialyzer after being concentrated by a first reverse osmosis device; fresh water at the outlet of the monovalent ion selective electrodialyzer enters a second reverse osmosis device, and a sodium sulfate product is obtained from a concentrated solution of the second reverse osmosis through a sodium sulfate crystallization system; concentrated water at the outlet of the monovalent ion selective electrodialyzer enters a secondary nanofiltration device, trapped liquid of the secondary nanofiltration returns to the primary nanofiltration device for treatment, and permeate of the secondary nanofiltration passes through a sodium chloride evaporation crystallization system to obtain a sodium chloride product; the crystallization mother liquor returns to the inlet of the diluting chamber of the monovalent ion selective electrodialyzer; the method can obtain I-type industrial anhydrous sodium sulfate and primary refined industrial salt, and realizes resource utilization of wastewater.

The nanofiltration separation method can separate sodium chloride and sodium sulfate to a certain extent, but cannot realize complete separation of two ions, so sodium sulfate and sodium chloride products with high quality cannot be obtained, and the process has high energy consumption and is not economical.

Sodium sulfate and sodium chloride are mainly upstream raw materials in the chemical industry, are used as byproducts of solid waste treatment, have low market acceptance and limited market absorption capacity due to lack of relevant standards, are mainly stockpiled and have serious threat to the environment due to soluble salts. Currently, in the face of increasingly severe environmental regulations, the problem of waste salt has become an important bottleneck restricting the development of related enterprises.

Therefore, there is a need to develop a new technology for waste salt treatment to truly realize resource utilization of waste salt, and to assist enterprises in realizing technology upgrade and sustainable development.

Disclosure of Invention

The invention aims to provide a method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride by using mixed waste salt, which combines the separation and high-valued treatment of mixed salt of sodium sulfate and sodium chloride, mainly uses double decomposition reaction to prepare the mixed waste salt into sodium carbonate and coproduces the ammonium sulfate and the ammonium chloride; the purity of the sodium carbonate meets the requirement of light sodium carbonate in class II qualified products in GB/T210.1-2004, the purity of the ammonium sulfate meets the requirement of type I products in GB/T535-2012020, and the purity of the ammonium chloride meets the requirement of first-class agricultural ammonium chloride products in GB/T2946-2018.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention aims to provide a method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride by using mixed waste salt, which comprises the following steps:

(1) carrying out primary reaction on the mixed waste salt and a first reaction solution, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

(2) reacting and crystallizing the second reaction solution and the crude sodium sulfate product obtained in the step (1), and performing second solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate complex salt; cooling and crystallizing the first mother liquor obtained in the step (1), and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated sodium sulfate solution obtained in the step (2), and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother liquor; mixing a solvent with the sodium sulfate-ammonium sulfate complex salt obtained in the step (2), enriching, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

(4) calcining the sodium bicarbonate obtained in the step (3) to obtain sodium carbonate; and (4) evaporating and crystallizing the fourth mother liquor obtained in the step (3), and carrying out sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor.

The separation and high-value processing of the mixed salt of sodium sulfate and sodium chloride are combined, the mixed waste salt is prepared into sodium carbonate by mainly utilizing double decomposition reactions, and ammonium sulfate and ammonium chloride are co-produced; the purity of the sodium carbonate meets the requirement of light sodium carbonate in class II qualified products in GB/T210.1-2004, the purity of the ammonium sulfate meets the requirement of type I products in GB/T535-2012020, and the purity of the ammonium chloride meets the requirement of first-class agricultural ammonium chloride products in GB/T2946-2018.

It is worth to say that the second mother liquor contains sodium sulfate, sodium chloride and a small amount of ammonium chloride; the third mother liquor contains ammonium sulfate and a small amount of sodium bicarbonate; the deammoniated solid contains sodium sulfate; the fifth mother liquor contains sodium sulfate and a small amount of ammonium sulfate; the method carries out solid-liquid separation for six times, wherein the modes of the first solid-liquid separation, the second solid-liquid separation, the third solid-liquid separation, the fourth solid-liquid separation, the fifth solid-liquid separation and the sixth solid-liquid separation are all any one or the combination of at least two of hydraulic cyclone separation, centrifugal separation, sedimentation separation or filtration separation.

It is worth to be noted that, the method of the present invention adopts a continuous production mode in practical application, when the treatment is started, the first reaction solution is an additional ammonium sulfate solution, the second reaction solution is an additional ammonium sulfate solution, and the solvent is water; after the whole treatment process can be completely operated, stopping adding an ammonium sulfate solution for carrying out primary reaction, and mixing a second mother solution obtained by cooling crystallization and a sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization to obtain a first reaction solution; in addition, stopping adding the ammonium sulfate solution for secondary reaction, and taking a third mother solution obtained by the secondary reaction as a second reaction solution; stopping adding water, and taking a fifth mother liquor obtained by evaporation crystallization as a solvent.

In the mixed waste salt in the step (1), the mass ratio of sodium sulfate to sodium chloride is (1-9): 1, and may be, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, but the present invention is not limited to the above-mentioned numerical values, and other numerical values not listed in the above-mentioned numerical value range are also applicable.

In a preferred embodiment of the present invention, the temperature of the primary reaction in step (1) is 40 to 60 ℃, for example, 40 ℃, 42 ℃, 44 ℃, 46 ℃, 48 ℃, 50 ℃, 52 ℃, 54 ℃, 56 ℃, 58 ℃, 60 ℃ and the like, and the time is 30 to 180min, for example, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min and the like, but not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable.

Further, the final temperature of the cooling crystallization in the step (2) is-5 to 40 ℃, and may be, for example, -5 ℃, -2 ℃, 0 ℃, 3 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, etc., but is not limited to the recited values, and other values not recited in the above range of values are also applicable.

Further, the cooling crystallization time in the step (2) is 30 to 180min, for example, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min, etc., but is not limited to the recited values, and other values not recited in the above range of values are also applicable.

According to the preferable technical scheme of the invention, the second mother liquor obtained by cooling and crystallizing in the step (2) and the sodium sulfate-ammonium sulfate complex salt obtained by reaction and crystallization are mixed and recycled to the step (1) to be used as the first reaction liquid for carrying out primary reaction.

Further, the temperature of the reactive crystallization in the step (2) is 10 to 60 ℃, and may be, for example, 10 ℃, 12 ℃, 15 ℃, 18 ℃, 20 ℃, 25 ℃, 28 ℃, 30 ℃, 33 ℃, 37 ℃, 40 ℃, 42 ℃, 46 ℃, 50 ℃, 53 ℃, 55 ℃, 58 ℃, 60 ℃ or the like, but is not limited to the recited values, and other values not recited in the above numerical range are also applicable.

Further, the reaction crystallization time in the step (2) is 1 to 3 hours, and for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, etc. may be mentioned, but it is not limited to the recited values, and other values not recited in the above range of values are also applicable.

Further, the chemical formula of the sodium sulfate-ammonium sulfate complex salt obtained by the reaction and crystallization in the step (2) is NaNH₄SO₄·2H₂O。

In the second reaction in step (3), the ratio of the molar amount of sodium atoms in the saturated solution of sodium sulfate to the molar amount of nitrogen atoms in the ammonium bicarbonate is (0.8 to 1.5):1, and may be, for example, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, but not limited to the above-mentioned values, and other values not listed in the above-mentioned numerical range are also applicable.

Further, the temperature of the secondary reaction in the step (3) is 25 to 40 ℃, and may be, for example, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃, 30 ℃, 31 ℃, 32 ℃, 33 ℃, 34 ℃, 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃, 40 ℃, etc., but is not limited to the recited values, and other values not recited in the above range of values are also applicable.

Further, the time of the secondary reaction in the step (3) is 30 to 180min, for example, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min, etc., but is not limited to the enumerated values, and other unrecited values within the above numerical range are also applicable.

And (3) recycling the third mother liquor obtained in the step (3) to the step (2) as the second reaction liquid for reaction and crystallization.

Further, the solvent in step (3) comprises deionized water.

Further, the mass ratio of the solvent to the sodium sulfate-ammonium sulfate double salt in the step (3) is (0.5 to 2):1, and for example, it may be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or the like, but is not limited to the above-mentioned numerical values, and other numerical values not mentioned in the above-mentioned numerical value range are also applicable.

As a preferred embodiment of the present invention, the temperature of the enrichment in step (3) is 85 to 110 ℃, for example, 85 ℃, 86 ℃, 87 ℃, 88 ℃, 89 ℃, 90 ℃, 92 ℃, 94 ℃, 5 ℃, 96 ℃, 98 ℃, 100 ℃, 102 ℃, 104 ℃, 105 ℃, 106 ℃, 108 ℃, 110 ℃, etc., and the time is 20 to 120min, for example, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min, 115min, 120min, etc., but is not limited to the recited values, and other values not recited in the above range of values are also applicable.

The enrichment temperature is 85-110 ℃, the solubility of the ammonium sulfate is high in the temperature range, the ammonium sulfate can be dissolved, but the solubility of the sodium sulfate is reduced along with the temperature rise in the temperature range, and the sodium sulfate is basically not dissolved when the ammonium sulfate is dissolved, so that the purposes of enriching the ammonium sulfate and separating the ammonium sulfate from the sodium sulfate are achieved.

As a preferable technical scheme of the invention, the deammoniated solid obtained in the step (3) is recycled to the step (2) and used as the crude sodium sulfate product for reaction and crystallization.

Further, the temperature of the calcination in the step (4) is 150 to 300 ℃, for example, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃ and the like can be used, but the calcination is not limited to the recited values, and other values not recited in the above numerical range are also applicable.

Further, the calcination time in the step (4) is 20 to 120min, for example, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min, 115min, 120min, etc., but is not limited to the enumerated values, and other values not enumerated within the above numerical range are also applicable.

In a preferred embodiment of the present invention, the temperature of the evaporative crystallization in step (4) is 60 to 80 ℃, and may be, for example, 60 ℃, 62 ℃, 64 ℃, 65 ℃, 66 ℃, 68 ℃, 70 ℃, 72 ℃, 74 ℃, 75 ℃, 76 ℃, 78 ℃, 80 ℃, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.

Further, the sixth solid-liquid separation mode in the step (4) is a combination of hydrocyclone separation and centrifugal separation.

As a preferable technical scheme of the invention, the fifth mother liquor obtained in the step (4) is recycled to the step (3) to be used as the solvent for enrichment.

As a preferred technical scheme of the invention, the method comprises the following steps:

(1) carrying out primary reaction on the mixed waste salt and the first reaction solution at the temperature of 40-60 ℃ for 30-180 min, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

wherein in the mixed waste salt, the mass ratio of sodium sulfate to sodium chloride is (1-9): 1;

(2) reacting the second reaction solution with the crude sodium sulfate product obtained in the step (1) at the temperature of 10-60 ℃ for crystallization for 1-3 h, and performing secondary solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt; cooling and crystallizing the first mother liquor obtained in the step (1) for 30-180 min to the end temperature of-5-40 ℃, and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

mixing the second mother liquor obtained by cooling crystallization and the sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization, and recycling the mixture to the step (1) as the first reaction liquid for carrying out primary reaction;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated sodium sulfate solution obtained in the step (2) at the temperature of 25-40 ℃ for 30-180 min, and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother liquor; mixing a solvent with the sodium sulfate-ammonium sulfate complex salt in the step (2), enriching for 20-120 min at the temperature of 85-110 ℃, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deaminized solid;

wherein the ratio of the molar weight of sodium atoms in the saturated solution of sodium sulfate in the secondary reaction to the molar weight of nitrogen atoms in the ammonium bicarbonate is (0.8-1.5): 1; the solvent comprises deionized water; the mass ratio of the solvent to the sodium sulfate-ammonium sulfate complex salt is (0.5-2) to 1; recycling the third mother liquor obtained in the step (3) to the step (2) as a second reaction liquid for reaction and crystallization; recycling the solid with ammonium removed obtained in the step (3) to the step (2) as a crude product of sodium sulfate for reaction and crystallization;

(4) calcining the sodium bicarbonate obtained in the step (3) at the temperature of 150-300 ℃ for 20-120 min to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3) at the temperature of 60-80 ℃, and performing sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

and (4) recycling the obtained fifth mother liquor to the step (3) to be used as a solvent for enrichment.

The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.

Compared with the prior art, the invention has the following beneficial effects:

the method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride from mixed waste salt combines the separation and high-valued treatment of mixed salt of sodium sulfate and sodium chloride, prepares the mixed waste salt into sodium carbonate, and coproduces the ammonium sulfate and ammonium chloride; the purity of the sodium carbonate meets the requirement of light sodium carbonate in class II qualified products in GB/T210.1-2004, the purity of the ammonium sulfate meets the requirement of type I products in GB/T535-2012020, and the purity of the ammonium chloride meets the requirement of first-class agricultural ammonium chloride products in GB/T2946-2018; the method has simple flow and low cost, and the utilization rate of sodium is more than 90 percent.

Drawings

FIG. 1 is a flow chart of the method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride from mixed waste salt.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

It is worth mentioning that the method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride by using mixed waste salt is shown in figure 1, and the method comprises the following steps:

(1) carrying out primary reaction on the mixed waste salt and a first reaction solution, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

(2) reacting and crystallizing the second reaction solution and the crude sodium sulfate product obtained in the step (1), and performing second solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate complex salt; cooling and crystallizing the first mother liquor obtained in the step (1), and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

mixing the second mother liquor obtained by cooling crystallization and the sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization, and recycling the mixture to the step (1) as the first reaction liquid for carrying out primary reaction;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated sodium sulfate solution obtained in the step (2), and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother liquor; mixing a solvent with the sodium sulfate-ammonium sulfate complex salt obtained in the step (2), enriching, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

recycling the third mother liquor obtained in the step (3) to the step (2) as a second reaction liquid for reaction and crystallization; recycling the solid with ammonium removed obtained in the step (3) to the step (2) as a crude product of sodium sulfate for reaction and crystallization;

(4) calcining the sodium bicarbonate obtained in the step (3) to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3), and performing sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

and (4) recycling the obtained fifth mother liquor to the step (3) to be used as a solvent for enrichment.

Example 1

The embodiment provides a method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride by using mixed waste salt, which comprises the following steps:

(1) carrying out primary reaction on the mixed waste salt and an ammonium sulfate solution at the temperature of 40 ℃ for 180min, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

wherein, in the mixed waste salt, the mass ratio of sodium sulfate to sodium chloride is 5: 1;

(2) reacting and crystallizing the ammonium sulfate solution and the crude sodium sulfate product in the step (1) at the temperature of 60 ℃ for 1h, and performing secondary solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt; cooling and crystallizing the first mother liquor obtained in the step (1) for 180min to the end temperature of-5 ℃, and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

mixing the second mother liquor obtained by cooling crystallization and the sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization, and recycling the mixture to the step (1) to be used as an ammonium sulfate solution for primary reaction;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated solution of sodium sulfate in the step (2) at the temperature of 30 ℃ for 100min, and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother solution; mixing a solvent with the sodium sulfate-ammonium sulfate double salt in the step (2), enriching for 20min at the temperature of 110 ℃, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

wherein, the ratio of the molar weight of sodium atoms in the saturated solution of sodium sulfate in the secondary reaction to the molar weight of nitrogen atoms in the ammonium bicarbonate is 0.8: 1; the solvent comprises deionized water; the mass ratio of the solvent to the sodium sulfate-ammonium sulfate complex salt is 1: 1; recycling the third mother liquor obtained in the step (3) to the step (2) as an ammonium sulfate solution for reaction and crystallization; recycling the solid with ammonium removed obtained in the step (3) to the step (2) as a crude product of sodium sulfate for reaction and crystallization;

(4) calcining the sodium bicarbonate obtained in the step (3) at the temperature of 220 ℃ for 80min to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3) at the temperature of 80 ℃, and performing sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

and (4) recycling the obtained fifth mother liquor to the step (3) to be used as a solvent for enrichment.

Example 2

The embodiment provides a method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride by using mixed waste salt, which comprises the following steps:

(1) carrying out primary reaction on the mixed waste salt and an ammonium sulfate solution at the temperature of 50 ℃ for 100min, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

wherein, in the mixed waste salt, the mass ratio of sodium sulfate to sodium chloride is 1: 1;

(2) reacting and crystallizing the ammonium sulfate solution and the crude sodium sulfate product in the step (1) at the temperature of 10 ℃ for 3 hours, and performing secondary solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt; cooling and crystallizing the first mother liquor obtained in the step (1) for 100min to the end temperature of 20 ℃, and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

mixing the second mother liquor obtained by cooling crystallization and the sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization, and recycling the mixture to the step (1) to be used as an ammonium sulfate solution for primary reaction;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated solution of sodium sulfate in the step (2) at the temperature of 25 ℃ for 180min, and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother liquor; mixing a solvent with the sodium sulfate-ammonium sulfate complex salt in the step (2), enriching at 85 ℃ for 120min, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

wherein the ratio of the molar weight of sodium atoms in the saturated solution of sodium sulfate in the secondary reaction to the molar weight of nitrogen atoms in the ammonium bicarbonate is 1: 1; the solvent comprises deionized water; the mass ratio of the solvent to the sodium sulfate-ammonium sulfate complex salt is 2: 1; recycling the third mother liquor obtained in the step (3) to the step (2) as an ammonium sulfate solution for reaction and crystallization; recycling the solid with ammonium removed obtained in the step (3) to the step (2) as a crude product of sodium sulfate for reaction and crystallization;

(4) calcining the sodium bicarbonate obtained in the step (3) at the temperature of 150 ℃ for 120min to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3) at the temperature of 60 ℃, and performing sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

and (4) recycling the obtained fifth mother liquor to the step (3) to be used as a solvent for enrichment.

Example 3

The embodiment provides a method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride by using mixed waste salt, which comprises the following steps:

(1) carrying out primary reaction on the mixed waste salt and an ammonium sulfate solution at the temperature of 60 ℃ for 30min, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

wherein, in the mixed waste salt, the mass ratio of sodium sulfate to sodium chloride is 9: 1;

(2) reacting and crystallizing the ammonium sulfate solution and the crude sodium sulfate product in the step (1) at the temperature of 40 ℃ for 2 hours, and performing secondary solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt; cooling and crystallizing the first mother liquor obtained in the step (1) for 30min to the end temperature of 40 ℃, and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

mixing the second mother liquor obtained by cooling crystallization and the sodium sulfate-ammonium sulfate double salt obtained by reaction crystallization, and recycling the mixture to the step (1) to be used as an ammonium sulfate solution for primary reaction;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated solution of sodium sulfate in the step (2) at the temperature of 40 ℃ for 30min, and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother solution; mixing a solvent with the sodium sulfate-ammonium sulfate double salt in the step (2), enriching for 80min at the temperature of 100 ℃, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

wherein the ratio of the molar weight of sodium atoms in the saturated solution of sodium sulfate in the secondary reaction to the molar weight of nitrogen atoms in the ammonium bicarbonate is 1.5: 1; the solvent comprises deionized water; the mass ratio of the solvent to the sodium sulfate-ammonium sulfate complex salt is 0.5: 1; recycling the third mother liquor obtained in the step (3) to the step (2) as an ammonium sulfate solution for reaction and crystallization; recycling the solid with ammonium removed obtained in the step (3) to the step (2) as a crude product of sodium sulfate for reaction and crystallization;

(4) calcining the sodium bicarbonate obtained in the step (3) at the temperature of 300 ℃ for 20min to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3) at the temperature of 70 ℃, and performing sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

and (4) recycling the obtained fifth mother liquor to the step (3) to be used as a solvent for enrichment.

Example 4

This example provides a method for preparing sodium carbonate and co-producing ammonium sulfate and ammonium chloride from mixed waste salts, which is described with reference to example 1, except that: the second mother liquor, the third mother liquor, the deammoniated solid and the fifth mother liquor are not recycled; namely, the method comprises the steps of:

(1) carrying out primary reaction on the mixed waste salt and an ammonium sulfate solution at the temperature of 40 ℃ for 180min, and carrying out primary solid-liquid separation to obtain a first mother solution and a crude product of sodium sulfate;

wherein, in the mixed waste salt, the mass ratio of sodium sulfate to sodium chloride is 5: 1;

(2) reacting and crystallizing the ammonium sulfate solution and the crude sodium sulfate product in the step (1) at the temperature of 60 ℃ for 1h, and performing secondary solid-liquid separation to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt; cooling and crystallizing the first mother liquor obtained in the step (1) for 180min to the end temperature of-5 ℃, and carrying out solid-liquid separation for the third time to obtain ammonium chloride and a second mother liquor;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated solution of sodium sulfate in the step (2) at the temperature of 30 ℃ for 100min, and carrying out solid-liquid separation for the fourth time to obtain sodium bicarbonate and a third mother solution; mixing a solvent with the sodium sulfate-ammonium sulfate double salt in the step (2), enriching for 20min at the temperature of 110 ℃, and performing fifth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

wherein, the ratio of the molar weight of sodium atoms in the saturated solution of sodium sulfate in the secondary reaction to the molar weight of nitrogen atoms in the ammonium bicarbonate is 0.8: 1; the solvent comprises deionized water; the mass ratio of the solvent to the sodium sulfate-ammonium sulfate complex salt is 1: 1;

(4) calcining the sodium bicarbonate obtained in the step (3) at the temperature of 220 ℃ for 80min to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3) at the temperature of 80 ℃, and performing sixth solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

wherein the second mother liquor, the third mother liquor, the deammoniated solid, and the fifth mother liquor are treated as waste.

Comparative example 1

The comparative example provides a method for preparing sodium carbonate and co-producing ammonium sulfate by using mixed waste salt, which comprises the following steps:

(1) salt separation: mixing the mixed waste salt and deionized water to prepare mixed salt wastewater, heating the mixed salt wastewater until the mixed salt wastewater boils, performing first solid-liquid separation to obtain a first mother liquor and condensed water, performing freeze crystallization on the first mother liquor, and performing second solid-liquid separation to obtain a sodium sulfate crude product and a second mother liquor; carrying out secondary evaporation crystallization on the second mother liquor, and carrying out third solid-liquid separation to obtain a sodium chloride crude product;

(2) reacting and crystallizing the ammonium sulfate solution and the crude sodium sulfate product in the step (1) at the temperature of 60 ℃ for 1h, and performing solid-liquid separation for the fourth time to obtain a saturated sodium sulfate solution and a sodium sulfate-ammonium sulfate double salt;

(3) carrying out secondary reaction on ammonium bicarbonate and the saturated sodium sulfate solution obtained in the step (2) at the temperature of 30 ℃ for 100min, and carrying out fifth solid-liquid separation to obtain sodium bicarbonate and a third mother liquor; mixing a solvent with the sodium sulfate-ammonium sulfate double salt in the step (2), enriching for 20min at the temperature of 110 ℃, and performing sixth solid-liquid separation to obtain a fourth mother liquor and a deammoniated solid;

wherein, the ratio of the molar weight of sodium atoms in the saturated solution of sodium sulfate in the secondary reaction to the molar weight of nitrogen atoms in the ammonium bicarbonate is 0.8: 1; the solvent comprises deionized water; the mass ratio of the solvent to the sodium sulfate-ammonium sulfate complex salt is 1: 1; recycling the third mother liquor obtained in the step (3) to the step (2) as an ammonium sulfate solution for reaction and crystallization; recycling the solid with ammonium removed obtained in the step (3) to the step (2) as a crude product of sodium sulfate for reaction and crystallization;

(4) calcining the sodium bicarbonate obtained in the step (3) at the temperature of 220 ℃ for 80min to obtain sodium carbonate; evaporating and crystallizing the fourth mother liquor obtained in the step (3) at the temperature of 80 ℃, and performing seventh solid-liquid separation to obtain ammonium sulfate and a fifth mother liquor;

and (4) recycling the obtained fifth mother liquor to the step (3) to be used as a solvent for enrichment.

The purity of the sodium carbonate obtained in the above examples and comparative examples was tested according to GB/T210.2-2004 "sodium carbonate for Industrial use and test method part 2: test methods in Industrial sodium carbonate test methods.

The results of the purity tests of the sodium carbonate obtained in the above examples and comparative examples are shown in table 1.

Second, the contents of nitrogen (N) in ammonium sulfate and ammonium chloride obtained in the above examples and comparative examples were measured according to the method in GB/T535-2020 ammonium sulfate for Fertilizer grade.

The results of the measurement of the nitrogen (N) content in ammonium sulfate and ammonium chloride obtained in the above examples and comparative examples are shown in table 1.

And (III) the recovery rate of the sodium element in the above examples and comparative examples is tested by the following method:

mass M was determined using the separation method described in the examples₀Separating the mixed waste salt to obtain the product with the mass of M₁Respectively measuring the content C of sodium element in the mixed waste salt by using inductively coupled plasma atomic emission spectrometry (ICP-AES)₀And the content C of sodium element in sodium carbonate₁Then the sodium element utilization rate =。

The results of the sodium utilization tests of the above examples and comparative examples are shown in table 1.

TABLE 1

The following points can be derived from table 1:

(1) from the examples 1-3, the method for preparing sodium carbonate and coproducing ammonium sulfate and ammonium chloride by using the mixed waste salt can be seen to obtain sodium carbonate, ammonium sulfate and ammonium chloride, the purity of the obtained sodium carbonate is more than or equal to 98 percent, the requirement of a type I product in GB/T535-2020 is met, the content of nitrogen (N) in the obtained ammonium sulfate is more than or equal to 20.5 percent, the requirement of the type I product in GB/T535-2020 is met, the content of nitrogen (N) in the obtained ammonium chloride is more than or equal to 25.4 percent, the requirement of a first-class agricultural ammonium chloride in GB/T2946-2018 is met, and the utilization rate of sodium elements is more than 90 percent;

(2) comparing example 1 with example 4, it can be seen that, in example 4, since the second mother liquor, the third mother liquor, the solid removed from ammonium and the fifth mother liquor are not recycled, a small amount of sodium sulfate in the second mother liquor, a small amount of sodium bicarbonate in the third mother liquor, sodium sulfate in the solid removed from ammonium and a small amount of sodium sulfate in the fifth mother liquor cannot be effectively utilized, so that the utilization rate of sodium element is reduced to 80.2%;

(3) comparing example 1 with comparative example 1, it can be seen that, in comparative example 1, the sodium sulfate and sodium chloride in the mixed waste salt are separated by an evaporative crystallization method, the energy consumption is high, the separation effect is not good, the sodium sulfate crude product contains a small amount of sodium chloride, and the purity of the prepared sodium carbonate is not high, only 94.2%, and the nitrogen (N) content in the ammonium sulfate is 20.1%.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.