Method for producing liquid salt by treating high sulfate radical type salt lake by using ammonia distillation waste liquid-carbide slag-carbon dioxide-containing waste gas

Abstract

The invention provides a method for producing liquid salt by treating a high sulfate radical type salt lake by utilizing ammonia distillation waste liquid-carbide slag-carbon dioxide-containing waste gas, which comprises the following steps: injecting the ammonia distillation waste liquid into a dry high sulfate radical type salt lake, dissolving solid salt, and removing precipitate to obtain crude brine; adding excessive carbide slag to carry out neutralization reaction, removing precipitate, and reserving clear liquid; injecting the clear liquid into a reactor, adopting a bubbling carbonation method, introducing alkali-making carbonized tail gas, removing precipitate, introducing gas discharged by an alkali-making lime kiln into the clear liquid, carrying out carbonization neutralization until the pH value is 7-8, separating out the precipitate, and reserving the clear liquid to obtain a salt solution; a saturated sodium carbonate solution is added into the salt solution, so that Ca < 2 + > in the salt solution is smaller than 100 mg / L, and liquid salt is obtained. According to the method for producing the liquid salt, solid, liquid and gas waste are used as raw materials, a large amount of fresh water resources are saved, continuous production is achieved, and the method is economical and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of salt production in high sulfate salt lakes, and in particular relates to a method for producing liquid salt in high sulfate salt lakes by treating ammonia evaporation waste liquid-carbide slag-carbon dioxide-containing waste gas. Background Art

[0002] Since the mining of Jilantai Salt Lake, sodium chloride has been the main source of mining, which has led to the relative enrichment of calcium, magnesium, sulfate and other ions in the brine, aging of the brine, and the appearance of complex salts such as magnesium salt and calcium glauberite in the crystallized regenerated salt, which has seriously affected the product quality. The treatment process for this type of high-sulfate salt lake is usually to freeze and remove nitrate in winter. This treatment process requires the use of a large amount of fresh water resources and relies on the winter environment. It cannot achieve continuous production and has poor economic benefits. Summary of the invention

[0003] In view of this, in order to solve the above technical problems, the present invention proposes a method for producing liquid salt by treating high-sulfate salt lakes with ammonia evaporation waste liquid-carbide slag-carbon dioxide-containing waste gas. Ammonia evaporation waste liquid, carbide slag, carbon dioxide-containing waste gas and other liquid, solid and gaseous wastes are used as raw materials to treat high-sulfate salt lakes, and fractional crystallization and precipitation are performed, thereby saving a large amount of fresh water resources, realizing continuous production, and being economical and environmentally friendly.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] A method for producing liquid salt by treating a high sulfate salt lake using ammonia evaporation waste liquid-carbide slag-carbon dioxide-containing waste gas, comprising the following steps:

[0006] S1. Extracting crude brine: injecting ammonia evaporation waste liquid into a dried-up high-sulfate salt lake to dissolve solid salt, then extracting the dissolved liquid and removing the precipitate to obtain crude brine;

[0007] S2, neutralization reaction: inject the crude brine into the reactor, add an excess of carbide slag containing Ca(OH)2 to carry out neutralization reaction, remove the precipitate, and retain the clear liquid;

[0008] S3, carbonation neutralization: inject the clear liquid obtained in S2 into the reactor, adopt the bubbling carbonation method, pass the carbonation tail gas containing CO2 from the alkali production to generate a precipitate, remove the precipitate, and then pass the gas discharged from the alkali lime kiln into the clear liquid to carbonize and neutralize it until the pH is 7-8, separate the precipitate, and keep the clear liquid to obtain a salt solution;

[0009] S4. Brine refining: Add saturated sodium carbonate solution to the salt solution to make the Ca in the salt solution 2+ <100mg / L, obtain liquid salt.

[0010] The composition of Jilantai Salt Lake brine is as follows:

[0011] Average composition of brine in Jilantai Salt Lake (g / L)

[0012] Calcium carbonate Calcium bicarbonate Calcium sulfate Magnesium sulfate Sodium sulfate Magnesium chloride Sodium chloride 0.14 0.39 2.03 41.06 5.75 50.05 247.16

[0013] The main components of ammonia evaporation waste liquid are NaCl and CaCl2, with a pH value of 11-12. Random discharge will seriously pollute the environment. The typical components of ammonia evaporation waste liquid are as follows:

[0014]

[0015] Since the solid-liquid ratio of ammonia evaporation waste liquid reaches 30%, and the water content in ammonia evaporation waste liquid accounts for 70%, the ammonia evaporation waste liquid can be used to replace fresh water for lake salt mining. At the same time, the calcium chloride and calcium hydroxide components in the ammonia evaporation waste liquid are used to pre-treat sulfate ions and part of magnesium ions in the salt lake brine, recover water and sodium chloride, and produce crude liquid salt. This step is carried out in the salt lake, and the reaction formula is as follows:

[0016] CaCl2+MgSO4→MgCl2↓+CaSO4↓

[0017] Ca(OH)2+MgSO4→Mg(OH)2↓+CaSO4↓;

[0018] After the dissolved liquid is extracted, it is allowed to settle. After the precipitate is removed, the crude brine is subjected to the next step of neutralization reaction;

[0019] After the crude brine is injected into the reactor, an excess of carbide slag containing Ca(OH)2 is added into the reactor. The crude brine reacts with the slag to convert the sodium sulfate in the crude brine into sodium hydroxide to form liquid caustic soda:

[0020] Na2SO4+Ca(OH)2=2NaOH+CaSO4↓;

[0021] After removing the precipitate, the resulting clear solution is subjected to the next step of carbonization neutralization;

[0022] The Ca(OH)2 content in the clear liquid is relatively low, so the bubbling carbonation method is adopted. The carbonation tail gas containing CO2 from the alkali production is introduced from the bottom of the reactor. CO2 reacts with Ca(OH)2 to generate precipitated CaCO3. The clear liquid after solid-liquid separation contains a certain amount of soluble Ca(OH)2, which is forced to be carbonized and neutralized by the gas discharged from the alkali lime kiln to make the pH of the waste liquid reach 7.00-8.00, and CaCO3 precipitation is generated at the same time, and light CaCO3 by-product is precipitated. The reaction principle is as follows:

[0023] Ca(OH)2+CO2→CaCO3↓+H2O;

[0024] After removing the precipitate, the salt solution is then subjected to the next step of brine refining;

[0025] The CaSO4 precipitate generated during the process is removed, but CaSO4 has a certain solubility. Its solubility in the salt solution is relatively high (about 6000-8000 mg / L), so the salt solution contains a high mass concentration of Ca 2+ (about 2500mg / L), in order to meet the hardness requirements (Ca 2+ <100mg / L), use saturated sodium carbonate solution to remove Ca in water 2+ , the reaction principle is as follows:

[0026] Na2CO3+Ca2+→2Na + +CaCO3↓

[0027] The obtained liquid salt meets the QBT 1879-2020 liquid salt standard.

[0028] Furthermore, in S1, the ammonia evaporation waste liquid is the waste liquid produced by the ammonia-soda process to produce soda ash.

[0029] Furthermore, in S1, the amount of ammonia waste liquid added is controlled to be 6 to 8 g / L of calcium sulfate dissolved in the dissolving liquid.

[0030] Furthermore, in the S2, the content of Ca(OH)2 in the carbide slag is 60wt% to 80wt%.

[0031] Furthermore, in S3, the volume content of CO2 in the gas discharged from the soda lime kiln is 4.0%.

[0032] Compared with the prior art, the method of producing liquid salt by treating a high sulfate salt lake by using ammonia evaporation waste liquid-carbide slag-carbon dioxide-containing waste gas has the following advantages:

[0033] Ammonia evaporation waste liquid, carbide slag and waste gas containing carbon dioxide are used as raw materials to treat high sulfate salt lakes, and graded crystallization and precipitation are carried out to effectively purify the brine and improve the quality of crystallized regenerated salt. Ammonia evaporation waste liquid, carbide slag and waste gas containing carbon dioxide are used to react with high sulfate brine. Compared with the existing freezing denitrification process, it saves a lot of fresh water resources, is independent of ambient temperature, and can be produced continuously. At the same time, it also realizes the reuse of waste liquid, solid waste and waste gas, which can produce good social and economic benefits and is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0035] Figure 1This is a process flow chart for producing liquid salt from a high sulfate salt lake by treating waste liquid ammonia - carbide slag - waste gas containing carbon dioxide according to the present invention. DETAILED DESCRIPTION

[0036] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0037] The present invention will be described in detail below with reference to the embodiments.

[0038] Liquid salt is prepared using water from Jilantai Salt Lake. The composition of Jilantai Salt Lake water is shown in the following table:

[0039] Average composition of brine in Jilantai Salt Lake (g / L)

[0040] Calcium carbonate Calcium bicarbonate Calcium sulfate Magnesium sulfate Sodium sulfate Magnesium chloride Sodium chloride 0.14 0.39 2.03 41.06 5.75 50.05 247.16

[0041] like Figure 1 As shown, the process is as follows:

[0042] S1. Extraction of crude brine: 1 million m 3 The ammonia wastewater was injected into a dried-up high-sulfate salt lake to dissolve the solid salt. The dissolved liquid was then extracted, allowed to stand, and the precipitate was removed to obtain 2.4 million m3 of crude brine. 3 (The amount of ammonia waste liquid added is based on the control of sulfate ions, and the calcium sulfate is controlled at 6-8g / L);

[0043] S2, neutralization reaction: inject the crude brine into the reactor, add 7.2 million tons of carbide slag containing 60wt% to 80wt% Ca(OH)2, and carry out neutralization reaction (it is calculated that the theoretical consumption of carbide slag per cubic meter of crude brine is 3kg), remove the precipitate after the precipitate is generated, and retain the clear liquid;

[0044] S3, carbonization neutralization: inject the clear liquid obtained in S2 into the reactor, adopt the bubbling carbonation method, introduce the carbonized tail gas containing CO2 from the alkali production to generate a precipitate, remove the precipitate, then introduce the gas discharged from the alkali lime kiln (CO2 volume content is 4.0%) into the clear liquid, perform carbonization neutralization, until the pH value is 7-8, (it is calculated that the theoretical consumption of flue gas containing CO2 per cubic meter of crude brine is 3kg), generate a precipitate, separate the precipitate, retain the clear liquid, and obtain a salt solution;

[0045] S4. Brine refining: Add saturated sodium carbonate solution to the salt solution to make the Ca in the salt solution 2+ <100mg / L, 1.55 million m 3 Liquid salt.

[0046] The consumption indicators of producing liquid salt by using this example process to treat high sulfate salt lake are shown in the following table:

[0047]

[0048] As can be seen from the above table, in this embodiment, fresh water resources are not used. Instead, the rich water content of the ammonia evaporation waste liquid is utilized to carry out salt lake mining, thereby saving a large amount of fresh water resources. At the same time, the calcium chloride and calcium hydroxide components contained in the ammonia evaporation waste liquid are utilized to pretreat sulfate ions and part of magnesium ions in the salt lake brine. In addition, since the waste gas containing carbon dioxide is utilized, the emission of carbon dioxide can be reduced.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing liquid salt by treating a high sulfate salt lake using ammonia evaporation waste liquid-carbide slag-carbon dioxide-containing waste gas, characterized in that: The steps include: S1. Extracting crude brine: injecting ammonia evaporation waste liquid into a dried-up high-sulfate salt lake to dissolve solid salt, then extracting the dissolved liquid and removing the precipitate to obtain crude brine; S2, neutralization reaction: inject the crude brine into the reactor, add an excess of carbide slag containing Ca(OH)2 to carry out neutralization reaction, remove the precipitate, and retain the clear liquid; S3, carbonation neutralization: inject the clear liquid obtained in S2 into the reactor, adopt the bubbling carbonation method, pass the carbonation tail gas containing CO2 from the alkali production to generate a precipitate, remove the precipitate, and then pass the gas discharged from the alkali lime kiln into the clear liquid to carbonize and neutralize it until the pH is 7-8, separate the precipitate, and keep the clear liquid to obtain a salt solution; S4. Brine refining: Add saturated sodium carbonate solution to the salt solution to make the Ca in the salt solution 2+ <100mg / L, obtain liquid salt.

2. The method for producing liquid salt from a high sulfate salt lake by treating waste ammonia liquid-carbide slag-carbon dioxide-containing waste gas according to claim 1, characterized in that: In S1, the ammonia evaporation waste liquid is the waste liquid produced by the ammonia-soda process to produce soda ash.

3. The method for producing liquid salt from a high sulfate salt lake by treating waste ammonia liquid-carbide slag-carbon dioxide-containing waste gas according to claim 1, characterized in that: In S1, the amount of ammonia waste liquid added is controlled to be 6-8 g / L of calcium sulfate dissolved in the dissolving liquid.

4. The method for producing liquid salt from a high sulfate salt lake by treating waste liquid ammonia-carbide slag-carbon dioxide-containing waste gas according to claim 1, characterized in that: In the S2, the content of Ca(OH)2 in the carbide slag is 60wt% to 80wt%.

5. The method for producing liquid salt from a high sulfate salt lake by treating waste liquid ammonia-carbide slag-carbon dioxide-containing waste gas according to claim 1, characterized in that: In S3, the volume content of CO2 in the gas discharged from the soda lime kiln is 4.0%.

Images