阅读说明：本技术 一种利用纯碱蒸馏液生产液体盐的新型工艺 (Novel process for producing liquid salt by using sodium carbonate distillate ) 是由 宋信信 熊泽华 邓强 李春林 胡景 邱常义 于 2019-11-26 设计创作，主要内容包括：本发明提供一种利用纯碱蒸馏液生产液体盐的新型工艺。本发明将纯碱蒸馏液注入卤井溶解岩盐矿生产卤水,其中蒸馏液的Ca<Sup>2+</Sup>与岩盐卤井中的SO<Sub>4</Sub><Sup>2-</Sup>生成石膏而沉淀,并降低卤水中的硫酸根含量生产低硝卤水,低硝卤水再生产液体盐。相对于其他液体盐工艺或纳滤膜技术而言,本发明利用纯碱蒸馏液在地下脱硝,可大大节省地面脱硝的相关设备投资,且生成的石膏泥直接留在盐腔内。该方法既节省了脱硝费用,又减轻了环保压力。(The invention provides a novel process for producing liquid salt by using a sodium carbonate distillate. The invention injects the sodium carbonate distillate into a brine well to dissolve rock salt mine to produce brine, wherein Ca of the distillate 2+ With SO in rock salt brine wells 4 2‑ Gypsum is generated and precipitated, sulfate radical content in brine is reduced to produce low-nitrate brine, and liquid salt is produced from the low-nitrate brine. Compared with other liquid salt processes or nanofiltration membrane technologies, the method utilizes the soda distillate to denitrate underground, so that the equipment investment related to ground denitration can be greatly saved, and the generated gypsum mud is directly left in the salt cavity. The method saves the denitration cost and lightens the environmental protection pressure.)

1. A novel process for producing liquid salt by using a sodium carbonate distillate is characterized by comprising the following steps:

a. injecting the sodium carbonate distillate into different mirabilite rock salt mine brine wells to recover brine, respectively obtaining low-nitrate brine, nitre brine and calcium brine, and reacting the nitre brine and the calcium brine according to the volume ratio of 1: 0.2-6 to obtain the low-nitrate brine;

b. removing ammonia from the low-nitrate brine obtained in the step a to obtain deamination low-nitrate brine, and performing sedimentation and solid-liquid separation;

c. and c, transferring the clear liquid in the step b into a reaction clarifying barrel, purifying brine, filtering and clarifying, transferring the clear liquid into a liquid salt barrel to obtain liquid salt, injecting sediment at the bottom into a brine well to recover brine, and keeping the sediment in a brine well dissolving cavity.

2. The novel process for producing liquid salt by using the sodium carbonate distillate as claimed in claim 1, wherein the NaCl content in the low-nitrate brine, the nitrate brine and the calcium brine in the step a is 250-330 g/L.

3. The novel process for producing liquid salt using the distilled liquid of soda ash as claimed in any one of claims 1 and 2, wherein Na is contained in the low-nitre brine₂SO₄The content is 0-20 g/L; na in the nitro halide₂SO₄The content of CaCl in the calcium halide is 10-32 g/L₂The content is 0-70 g/L.

4. The novel process for producing liquid salt using soda ash distillate as claimed in claim 3, wherein Na is added to the low-nitre brine₂SO₄The content is 3-18 g/L; na in the nitro halide₂SO₄The content is 12-25 g/L; CaCl in the calcium halide₂The content is 25-55 g/L.

5. The novel process for producing liquid salt using sodium carbonate distillate as claimed in claim 4, wherein Na is added into the low-nitre brine₂SO₄The content is 5-12 g/L; na in the nitro halide₂SO₄The content is 16-22 g/L.

6. The novel process for producing liquid salt from soda ash distillate as claimed in claim 1, wherein the ammonia is removed from the low-nitrate brine in step b by adding sodium hypochlorite in the following amount:

in the formula:

V_NaClOvolume of sodium hypochlorite required for Ammonia removal reaction, mL

T_NH3-total amount of ammonia in low-nitrate brine to be ammonia-removed, mg/L

V_BrineVolume of Low Nitro brine to be Ammonia stripped, L

ω_Cl-the available chlorine content of sodium hypochlorite.

7. The novel process for producing liquid salt by using the sodium carbonate distillate as claimed in claim 1, wherein the solid-liquid separation mode in the step b is one of natural sedimentation, centrifugal dehydration and vacuum dehydration.

8. The novel process for producing liquid salt by using the soda ash distillate as claimed in claim 1, wherein the precipitated solid gypsum obtained by the solid-liquid separation in the step b is transferred to a gypsum slurry barrel to be used as a gypsum product.

9. The novel process for producing liquid salt using soda ash distillate as claimed in claim 1, wherein the brine in step c is purified by one of lime-soda ash method, two-soda method, lime-flue gas-soda ash method; the injection mode of the brine purification precipitate is one of a multistage centrifugal pump and a high-pressure injection of a precipitation pump.

Technical Field

The invention relates to the field of liquid salt production, in particular to a novel process for producing liquid salt by using a soda ash distillate.

Background

Sodium chloride, commonly known as common salt (herein referred to as salt, the same applies hereinafter). Salt is a necessity in daily life of human beings, is a basic seasoning on a dining table and is called 'Baiweiwang'; in the industrial production of salt, the element has the name of "industrial mother". The salt chemical industry mainly comprises two industries of chlor-alkali and soda ash (commonly called as 'double alkali'), wherein the 'double alkali' is the development basis of the national industry, and the yield of the 'double alkali' directly marks the state of national economy and social development. China forms a salt chemical industry pattern taking 'two alkalis' as leading parts, and the 'two alkalis' raw material salt mainly takes solid salt as main material. Because the well mineral salt product has the advantages of good quality, high purity, low subsequent purification treatment cost and the like, the well mineral salt product is deeply favored by the industry of 'two alkalis', and under the drive of the industry of 'two alkalis', the well mineral salt with high energy consumption has no reduction trend but has hot tide of extension and new construction; the brine extracted from well and mineral salt needs to be subjected to the processes of steam heating, evaporation concentration, sodium chloride crystallization, solid-liquid separation, re-drying and the like to produce solid salt, and belongs to high-energy-consumption industries. When the enterprises of 'two alkali' use the solid salt as the basic raw material for production, the solid salt needs to be dissolved into saturated liquid brine again; the process of converting solid salt into liquid salt by enterprise users of liquid salt raw materials such as 'two bases' and the like consumes a large amount of energy compared with the process of directly using liquid salt, and is contrary to the aims of energy conservation and consumption reduction.

The method for preparing the sodium carbonate by the ammonia-soda process has the advantages of mature technology, short process route, cheap and easily available raw materials, high product quality and the like, so that the method becomes the most popular method for preparing the sodium carbonate in the alkali industry. However, the soda ash production process requires discharge of a large amount of waste residues and soda ash distillate (also called soda ash plant waste liquid and soda ash waste liquid). According to statistics, about 11m of waste slag and waste liquid needs to be discharged when each 1 ton of soda ash is produced³. At present, most ammonia alkali plants at home and abroad are built by facing the sea, the alkali residue is filled in the sea to build land, a dam is built and stockpiled, and the soda distillate is discharged into the sea after being pretreated. The distillate problem of the ammonia alkali factory greatly limits the regional distribution of the alkali factory, so that the transportation distance of products and raw materials is long, and the industrial layout distribution is unreasonable. In fact, the soda ash distillate contains a large amount of CaCl₂And NaCl, directly discharged not onlyWasting resources and causing environmental pollution. At present, a plurality of documents propose reasonable treatment of the distillate and secondary utilization of the soda distillate to change waste into valuable. The secondary utilization of the soda distillate has good reference and practical value for the internal ammonia alkali factory.

The sodium carbonate distillate contains calcium chloride, and is called light calcium liquid, and its component content varies with manufacturer, time, raw material and operation condition, and its composition is shown in table 1.

TABLE 1 composition of the sodium carbonate distillate components (unit: g/L)

The liquid salt is a sodium chloride solution with the main content of sodium chloride and other indexes meeting the requirements of users of salt raw materials such as caustic soda, sodium carbonate and the like. Compared with solid salt, the liquid salt has the advantages of short production flow, less working procedures, low energy consumption, low cost, convenient loading and unloading and the like. From the viewpoint of energy conservation, environmental protection and sustainable development, the liquid salt will inevitably replace solid salt to become the basic raw material of the two-alkali industry in the future. In developed countries such as the United states, the English and the French, the liquid salt has a dominant position in industrial salt, wherein in super large countries such as the United states, the chemical salt is almost all the liquid salt, and the proportion of the liquid salt reaches more than 97%. The development of liquid salt in China is slow, and the difference between the production and use conditions of the liquid salt and developed countries is large. Therefore, the development of the novel liquid salt process will undoubtedly accelerate the development of the liquid salt industry in China.

At present, the preparation process of liquid salt is rarely reported in China. CN201310239663.4 "an apparatus for preparing edible liquid salt based on brine" discloses an apparatus for filtering and separating liquid salt from brine, which mainly comprises a multi-stage filter, a cation exchanger and an anion exchanger. CN20121054219.7 'a method for extracting potassium and co-producing liquid salt from concentrated seawater', discloses a method for extracting potassium and co-producing liquid salt from concentrated seawater, which improves the comprehensive utilization rate of concentrated seawater and reduces the production cost of potassium extraction. The reports of industrialized mass production of liquid salt are less, and CN201610938543.7 'a double-membrane method refined liquid salt zero-emission production process' discloses a method for dissolving mineral salt with water to obtain dissolved brine, removing calcium and magnesium ions by a dosing machine, and separating the brine and solid salty mud by a ceramic membrane ultrafiltration device. When the method is used for producing liquid salt, a large amount of capital is required to buy ultrafiltration and nanofiltration devices, and the treatment efficiency of the devices is limited, so that the devices are difficult to apply to large-scale production.

In conclusion, the liquid salt industry in China is relatively lagged behind, the research on new processes is relatively less, and the literature report of the process for producing liquid salt by combining soda ash distillate is not seen at present. Obviously, if a new process for producing liquid salt by using the soda ash distillate can be developed, the environmental protection pressure of an inland ammonia alkali plant can be relieved, the resource can be recycled, and an environment-friendly enterprise is realized.

Disclosure of Invention

Aiming at the defects of the existing liquid salt preparation technology, the invention aims to provide a novel process for producing liquid salt by using soda distillate, which realizes the comprehensive utilization of the soda distillate, reduces the environmental protection pressure and reduces the production energy consumption.

In order to realize the aim, the novel process for producing the liquid salt by using the sodium carbonate distillate provided by the invention comprises the following specific steps:

a. injecting the sodium carbonate distillate into different brine wells for brine extraction to respectively obtain low-nitrate brine, nitre brine and calcium brine, and reacting the nitre brine and the calcium brine according to the volume ratio of 1: 0.2-6 to obtain the low-nitrate brine; (ii) a

The NaCl content in the low-nitrate brine, the nitrate brine and the calcium brine is 250-360 g/L.

Na in the low-nitrate brine₂SO₄The content is 0-20 g/L;

preferably, Na in the low-nitrate brine₂SO₄The content is 3-18 g/L;

more preferably, Na in the low-nitrate brine₂SO₄The content is 5-12 g/L;

na in the nitro halide₂SO₄The content is 10 to 32g/L,

preferably, Na in the nitrobittern₂SO₄The content is 12 to 25g/L,

more preferably, Na in the nitrobittern₂SO₄The content is 16-22 g/L;

CaCl in the calcium halide₂The content is 0 to 70g/L,

preferably, CaCl in the calcium halide₂The content is 25-55 g/L.

The nitro halide and the calcium halide react according to the volume ratio of 1: 0.2-6, wherein the molar ratio of the sodium sulfate to the calcium chloride is 1: 1.01-1.05, and the reaction equation is Na₂SO₄+CaCl₂＝CaSO₄↓ +2 NaCl. This is because the reaction is carried out in an atmosphere of sodium chloride solution, and the CaSO is suppressed when the amount of calcium ions is slightly excessive₄The dissolved homoionic effect is stronger than that of the sodium chloride for promoting CaSO₄Effect of dissolved salts, CaSO₄Reaches a minimum solubility of CaSO₄The calcium sulfate is more precipitated when the solubility of the sulfate reaches the lowest point, and the utilization rate of the sulfate radical is highest. Although the excess of calcium ions can promote the precipitation of calcium sulfate, the utilization rate of sulfate radicals is high, because the solubility of calcium sulfate is increased in a sodium chloride solution, the calcium ions cannot be excessive, and the calcium ions are excessive. In order to ensure that the calcium ions in the waste calcium liquid are slightly excessive but not too much, the molar ratio of the calcium ions to the waste calcium liquid is determined to be 1: 1.01-1.05, and the corresponding volume ratio is 1: 0.2-6.

b. Removing ammonia from the low-nitrate brine obtained in the step a to obtain deamination low-nitrate brine, and settling and performing solid-liquid separation;

the low-nitrate brine is subjected to ammonia removal by adding sodium hypochlorite, and the amount of the added sodium hypochlorite is specifically as follows:

in the formula:

V_NaClOvolume of sodium hypochlorite required for Ammonia removal reaction, mL

T_NH3-total amount of ammonia in low-nitrate brine to be ammonia-removed, mg/L

V_BrineVolume of Low Nitro brine to be Ammonia stripped, L

ω_ClContent of available chlorine in sodium hypochlorite

In the chlor-alkali industry, most of the production of chlor-alkali is a method of electrolyzing a sodium chloride solution to obtain sodium hydroxide, chlorine and hydrogen, if ammonia exists in the sodium chloride solution, the ammonia can be combined with chloride ions in the sodium chloride solution under the production condition of chlor-alkali to form an explosive chemical substance, and great threat is caused to the production safety of chlor-alkali. The removal of ammonia from sodium chloride solutions, i.e. liquid salts, is therefore of particular importance.

The solid-liquid separation mode is one of natural sedimentation, centrifugal dehydration and vacuum dehydration;

and transferring the precipitated solid gypsum obtained by solid-liquid separation into a gypsum slurry barrel to be used as a gypsum product.

c. And c, transferring the clear liquid in the step b into a reaction clarifying barrel, purifying brine, filtering and clarifying, transferring the clear liquid into a liquid salt barrel to obtain liquid salt, injecting sediment at the bottom into a brine well to recover brine, and keeping the sediment in a brine well dissolving cavity.

The brine purification mode is one of lime-soda ash method, two-soda method and lime-flue gas-soda ash method.

The injection mode of the brine purification precipitate is one of a multistage centrifugal pump and a high-pressure injection of a precipitation pump.

Injecting the distillate generated in the ammonia soda process into the halogen well at high pressure by using a centrifugal pump, wherein the sodium chloride and sodium sulfate in rock salt are dissolved in the sodium carbonate distillate, and Ca in the sodium carbonate distillate is not dissolved in the halogen well²⁺With SO in brine₄ ^2-And gypsum is generated and precipitated in a brine well dissolving cavity, and sodium chloride is the main component of brine, namely sodium chloride and sodium sulfate in rock salt dissolved by injecting soda distillate into the well to generate nitre brine with high sodium sulfate content, or low-nitre brine with low sodium sulfate content or calcium brine with high calcium content.

Purifying the brine by a lime-soda process or a two-soda process to respectively generate calcium carbonate and magnesium hydroxide precipitates to remove calcium and magnesium ions in the brine, transferring clear liquid after clarification into a liquid salt barrel to obtain liquid salt, and extracting brine by using a centrifugal pump or a precipitation pump to inject the precipitate calcium magnesium mud and the like into a well at high pressure, wherein the calcium magnesium mud can be precipitated in a dissolving cavity of the brine well.

The invention has the beneficial effects that:

1. the invention utilizes the soda distillate to produce liquid salt, realizes the salt and alkali co-production, widens the application range of the soda distillate and provides a new mode for the alkali industry in inland regions.

2. The low-nitrate brine is prepared in the salt cavity by using the soda distillate, so that the investment of a ground denitration device can be reduced, and the operating cost including the management, maintenance and medicament cost in the future is saved.

3. The nitrate brine prepared from the soda distillate in the salt cavity is reacted with the calcium brine to obtain low-nitrate brine, and the low-nitrate brine is prepared into liquid salt, so that a new idea is provided for the comprehensive utilization of the mirabilite rock salt mine brine well.

3. Gypsum generated in the denitration reaction process is directly left in the salt cavity, so that the problem that the salt gypsum generated in the denitration is accumulated on the ground is solved; the high-purity gypsum obtained in the production process of the liquid salt can be directly used as a product, and the produced calcium-magnesium sludge is backfilled into a well, so that the environmental pollution can be avoided, and the environmental protection pressure of enterprises is reduced.

4. The invention also provides a method for removing ammonia from the liquid salt, and the liquid salt after ammonia removal can be used for alkali production industry and chlor-alkali industrial production.

Detailed Description

In order to more clearly and completely describe the technical scheme of the invention, the invention is further illustrated by the following specific examples, and it should be understood that the specific examples described herein are only for explaining the invention, and are not intended to limit the invention, and various changes can be made within the scope defined by the claims of the invention.