CN115893465A - Waste salt recycling process - Google Patents
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- CN115893465A CN115893465A CN202211502275.6A CN202211502275A CN115893465A CN 115893465 A CN115893465 A CN 115893465A CN 202211502275 A CN202211502275 A CN 202211502275A CN 115893465 A CN115893465 A CN 115893465A
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- 238000000034 method Methods 0.000 title claims abstract description 80
- 150000003839 salts Chemical class 0.000 title claims abstract description 72
- 239000002699 waste material Substances 0.000 title claims abstract description 60
- 230000008569 process Effects 0.000 title claims abstract description 45
- 238000004064 recycling Methods 0.000 title claims abstract description 32
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 84
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims abstract description 76
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 52
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims abstract description 51
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 48
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 48
- 235000017557 sodium bicarbonate Nutrition 0.000 claims abstract description 38
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims abstract description 38
- 239000012535 impurity Substances 0.000 claims abstract description 28
- NKWPZUCBCARRDP-UHFFFAOYSA-L calcium bicarbonate Chemical compound [Ca+2].OC([O-])=O.OC([O-])=O NKWPZUCBCARRDP-UHFFFAOYSA-L 0.000 claims abstract description 24
- 229910000020 calcium bicarbonate Inorganic materials 0.000 claims abstract description 24
- 238000002425 crystallisation Methods 0.000 claims abstract description 24
- 230000008025 crystallization Effects 0.000 claims abstract description 24
- 238000007710 freezing Methods 0.000 claims abstract description 19
- 230000008014 freezing Effects 0.000 claims abstract description 19
- 150000001768 cations Chemical class 0.000 claims abstract description 15
- 239000012528 membrane Substances 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 14
- 238000001223 reverse osmosis Methods 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 10
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims abstract description 10
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 9
- 230000001376 precipitating effect Effects 0.000 claims abstract description 4
- 229910001415 sodium ion Inorganic materials 0.000 claims abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 66
- 239000000243 solution Substances 0.000 claims description 56
- 239000007788 liquid Substances 0.000 claims description 52
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 41
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 35
- 229910001868 water Inorganic materials 0.000 claims description 35
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 33
- 238000000926 separation method Methods 0.000 claims description 32
- 239000007787 solid Substances 0.000 claims description 28
- 238000010438 heat treatment Methods 0.000 claims description 25
- 238000006243 chemical reaction Methods 0.000 claims description 24
- 238000001914 filtration Methods 0.000 claims description 20
- 239000000706 filtrate Substances 0.000 claims description 18
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 18
- 229910001385 heavy metal Inorganic materials 0.000 claims description 17
- 239000002244 precipitate Substances 0.000 claims description 16
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 12
- 239000011259 mixed solution Substances 0.000 claims description 12
- 238000010521 absorption reaction Methods 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 9
- 238000000605 extraction Methods 0.000 claims description 8
- 238000005119 centrifugation Methods 0.000 claims description 7
- 239000006228 supernatant Substances 0.000 claims description 7
- 239000001569 carbon dioxide Substances 0.000 claims description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 239000013505 freshwater Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 3
- 238000003763 carbonization Methods 0.000 claims description 2
- 230000018044 dehydration Effects 0.000 claims description 2
- 238000006297 dehydration reaction Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 230000007935 neutral effect Effects 0.000 claims description 2
- 239000012047 saturated solution Substances 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 abstract description 16
- 239000000126 substance Substances 0.000 abstract description 9
- 239000003513 alkali Substances 0.000 abstract description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 32
- 235000011132 calcium sulphate Nutrition 0.000 description 19
- 235000011121 sodium hydroxide Nutrition 0.000 description 17
- 235000017550 sodium carbonate Nutrition 0.000 description 16
- 239000011780 sodium chloride Substances 0.000 description 16
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 9
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 239000002893 slag Substances 0.000 description 6
- 239000005416 organic matter Substances 0.000 description 5
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 4
- 229910000019 calcium carbonate Inorganic materials 0.000 description 4
- 235000010216 calcium carbonate Nutrition 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 4
- 239000002440 industrial waste Substances 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 238000010000 carbonizing Methods 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 208000012839 conversion disease Diseases 0.000 description 3
- 238000001728 nano-filtration Methods 0.000 description 3
- 230000003472 neutralizing effect Effects 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 238000010992 reflux Methods 0.000 description 3
- 239000010802 sludge Substances 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012065 filter cake Substances 0.000 description 2
- 239000002920 hazardous waste Substances 0.000 description 2
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000010446 mirabilite Substances 0.000 description 2
- 239000010812 mixed waste Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 238000009621 Solvay process Methods 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 239000012296 anti-solvent Substances 0.000 description 1
- 150000001555 benzenes Chemical class 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 159000000007 calcium salts Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000008280 chlorinated hydrocarbons Chemical class 0.000 description 1
- -1 chlorine ions Chemical class 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004043 dyeing Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229940011871 estrogen Drugs 0.000 description 1
- 239000000262 estrogen Substances 0.000 description 1
- 235000011167 hydrochloric acid Nutrition 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000009284 supercritical water oxidation Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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- Removal Of Specific Substances (AREA)
Abstract
The invention discloses a waste salt recycling process which is characterized in that concentrated sulfuric acid is used for removing organic matters, separating and recycling chloride ions, then alkali is used for precipitating and removing impurity cations, calcium bicarbonate and sodium sulfate are used for reacting to generate calcium sulfate and sodium bicarbonate, and finally sodium bicarbonate is separated out by freezing crystallization and a reverse osmosis membrane circulating system, so that sodium ions, chloride ions and sulfate ions in waste salt are recycled and converted into substances with higher values. The process has the advantages of high feasibility, high resource utilization degree, small investment, low risk and low operation cost, is greener and lower in carbon compared with other conventional processes, particularly has great commercial application value in a sulfate radical resource utilization mode, and is worthy of popularization and application.
Description
Technical Field
The invention belongs to the fields of chemical industry and environmental protection, and particularly relates to a separation and recycling process of industrial waste salt taking sodium sulfate and sodium chloride as main components.
Background
The industrial waste salt is solid waste which is mainly double salt (sodium sulfate and sodium chloride) and is accompanied with a small amount of heavy metals and organic matters (such as benzene series, chlorinated hydrocarbons and other difficultly-degraded matters) generated in the production processes of petrochemical industry, coal chemical industry, pharmacy, printing and dyeing and other industries and in the waste water treatment link. According to statistics, the annual output of the waste salt in the whole country is about 2100 ten thousand tons at present, and the annual output of the waste salt in the chemical industry only reaches 300 ten thousand tons. The industrial waste salt has large production amount and complex components, and contains pollutants such as organic matters, heavy metals and the like, and most of the industrial waste salt is definitely classified as hazardous waste in the national records of hazardous waste in 2021. If the landfill is safely carried out, the cost is about 3000 yuan/ton. At present, because the disposal cost is too high and the recycling technology cost is also very high, a large amount of waste salt is stored in China, and a green environment-friendly treatment process for reduction, stabilization and recycling is urgently needed.
The waste salt resource utilization generally comprises three links: pretreatment (removal of organic matters and heavy metals), double-salt separation and resource utilization. There are many methods and processes for double salt separation and resource utilization.
For waste salt pretreatment (for removing organic matters and heavy metals), the conventional method is to oxidize the organic matters by using an oxidant (hypochlorite, persulfate, ozone, hydrogen peroxide and the like), and then adding alkali to precipitate the heavy metals to form hydroxides. Adsorption methods are also used to remove organic substances and heavy metals, and catalytic oxidation, supercritical water oxidation, dry oxidation, and the like are also used to remove organic substances by oxidation.
In the direction of separating and recycling chloride ions, the related patents: a method for treating industrial mixed waste salt by using sulfuric acid (application/patent No. 202010642443.6), a resource utilization method for treating industrial mixed waste salt by using sulfuric acid (application/patent No. 202010075482.2) and the like propose a method for preparing sodium sulfate and hydrochloric acid by reacting sulfuric acid with sodium chloride. The basic process used in these patents is the first step of the lubran soda process (the french doctor lubran patented in 1791, which was eliminated by the soda industry). In addition, the method has been studied in a paper "research on hydrochloric acid and sodium sulfate from sodium chloride and sulfuric acid" published by Luaijun in 2006 to some extent. Since the hydrochloric acid concentration of about 20% forms an azeotropic mixture with water, when sulfuric acid is used for preparing hydrochloric acid, the sulfuric acid concentration cannot be too low, otherwise a large amount of chloride ions cannot volatilize out, but cannot be too high, or sulfuric acid vapor enters the hydrochloric acid to affect the purity of the product.
Based on the principles of an ammonia-soda process and a combined alkali-making process, a large number of researchers have developed the resource research of waste salt, such as a method for preparing sodium bicarbonate and ammonium chloride by using sodium chloride waste salt (application/patent number 202210632325.6), a green low-carbon process for producing soda and caustic soda by using waste salt and waste residue (application/patent number 202111610153.4), a method for preparing sodium carbonate and byproducts potassium sulfate, ammonium sulfate and ammonium chloride by using waste salt (application/patent number 202111498227. X) and the like. These patents have respective innovative points in the resource conversion of sodium chloride and sodium sulfate, but they do not leave ammonia or ammonium, and thus they belong to a broad class of methods. In the methods, the consumption of ammonia or ammonium is large, the operation cost is also high, but at present, other more mature, stable and low-cost methods for separating and recycling the waste salt are not available for a while, and only can be used for treatment.
In 1999, sunjie published a paper, "Re-research on the process of preparing soda from mirabilite by conversion method", which describes that sodium sulfate is converted into sodium carbonate solution by using bisphenol A as a conversion agent, and then causticized to obtain caustic soda, light calcium carbonate, calcium sulfate dihydrate, etc. However, bisphenol A has the effect of simulating estrogen and is insoluble in water, and the method involves more liquid-solid reactions and is slow, so that the method has low commercial value.
In addition, there are also techniques for the isolation of the double salt by the antisolvent method, which are disclosed in the following patents: a method for separating waste mixed salt containing sodium sulfate and sodium chloride (application/patent No. 202111498543.7) utilizes the solubility characteristics of sodium chloride and sodium sulfate in ethylene glycol and ethanol to separate the two. Although ethylene glycol and ethanol can be recycled, part of the ethanol remains in the crystalline solid, so that the product is impure. In addition, the ethanol is used, the whole process needs explosion-proof design, the cost is high, and therefore the process has low commercial value.
Some researchers have proposed the nanofiltration process for double salt separation, such as Zhou Yan published "salt separation process research on sodium sulfate and sodium chloride high-salt wastewater" and Zhang Xu published "discussion on the process parameters of nanofiltration-reverse osmosis-MVR salt separation"). The nanofiltration method is simple and efficient, and has low operation cost, but the current commercial nanofiltration membrane does not exist. In addition, the membrane filtration has large investment, and if the pretreatment is not clean, the membrane can be polluted, so the method is still studied and has no large-scale application.
There is another method for recycling green and low-carbon resources, and the patent: a method for converting sodium sulfate into sodium bicarbonate by using calcium oxide and carbon dioxide (application/patent No. 201910933767.2), which only uses carbon dioxide and calcium oxide to convert sodium sulfate into sodium bicarbonate, calcium sulfate and calcium carbonate. In the mixed solution of calcium carbonate and sodium sulfate, carbon dioxide is introduced, and the amount of calcium bicarbonate produced is very small, so that the amount of sodium bicarbonate in the final liquid phase is very low. In addition, calcium sulfate and calcium carbonate in a solid phase are difficult to separate, the content of calcium sulfate is very low, and the value is very low. Although simple, this method has a very low yield and, in addition, the solid-liquid phase reaction is very slow, so that it is not commercially useful.
The resource utilization of sodium chloride, if the sodium chloride is a relatively pure sodium chloride solution, the most mature method is an ion membrane caustic soda method, namely the electrolysis of the sodium chloride solution to produce chlorine, hydrogen and sodium hydroxide. The method is stable and mature, and is the most typical process in the industry at present.
Based on the waste salt treatment requirement and the characteristics and the defects of the prior treatment technologies, the invention needs to invent a process with short process flow, low investment, low operation cost, high value of resource products and industrial application value.
Disclosure of Invention
Aiming at the defects or shortcomings of the prior art, the invention aims to provide a waste salt recycling process, namely, in the recycling link, the calcium salt is used for realizing recycling and is converted into a product with higher value.
In order to achieve the purpose, the invention adopts the following technical solutions:
a process for recycling waste salt comprises a first link and a second link;
the first link is as follows: dehydrating, carbonizing and oxidizing organic matters in the waste salt by using concentrated sulfuric acid, forming chlorine ions into hydrogen chloride by using a method of preparing volatile acid by using non-volatile acid, evaporating and separating, and then precipitating impurity cations by using sodium hydroxide to realize comprehensive treatment of three contents of pretreatment, separation and recycling;
and the second link is to neutralize the final liquid with sulfuric acid, add calcium bicarbonate to perform resource conversion on sodium sulfate to generate calcium sulfate precipitate and sodium bicarbonate, separate the sodium bicarbonate by methods such as freezing crystallization and the like, and finally perform heat treatment on the obtained sodium bicarbonate to prepare soda ash so as to realize resource conversion of the sodium sulfate. The two links comprise the following specific steps:
(1) In the first step, the waste salt organic matters are dehydrated, carbonized and oxidized, and chloride ions are formed into hydrogen chloride to be evaporated and separated: a certain amount of high-concentration sulfuric acid solution is added into a reaction kettle (with a vacuum extraction system and an absorption device), and then a certain amount of waste salt is slowly added while stirring until a porridge-like mixture is formed. After the waste salt is added, the waste salt is slowly heated, and the waste salt is fully stirred in the heating process, so that a large amount of gas is generated in the heating process, and the gas is absorbed by water to form hydrochloric acid. After heating to a certain temperature, keeping for a period of time to realize dehydration, carbonization and oxidation of the organic matters.
Further, the concentration range of the high-concentration sulfuric acid solution is 70-80%. If the concentration of the sulfuric acid is lower than 70 percent, the organic matters are difficult to dehydrate, carbonize and oxidize; if the concentration of sulfuric acid is too high, a small amount of sulfuric acid may be present in the volatilized vapor, resulting in impure product hydrochloric acid.
Further, adding a certain amount of waste salt, wherein the ratio of the added amount to the sulfuric acid solution is 1: 1-0.75 (weight/g of waste salt: volume/mL of sulfuric acid), and more preferably 1:0.9.
furthermore, the heating is slowly carried out, the heating rate is preferably 5-10 ℃/min, and cannot be too fast, so that various reactions are fully completed.
Further, the reaction principle of generating a large amount of gas is as follows:
2NaCl+H 2 SO 4 ＝Na 2 SO 4 +2HCl↑
the gas will also contain small amounts of moisture and CO 2 。
Further, the mixture is heated to a certain temperature, and is kept for a period of time, wherein the temperature is generally 150-170 ℃, and the time is 0.5-2 h. If the temperature is too high, the sulfuric acid molecules will boil out, absolutely not allowing the sulfuric acid solution to boil. The boiling point of 70% strength sulfuric acid is 170 ℃ and the boiling point of 80% strength sulfuric acid is 211 ℃.
Further, the concentrated sulfuric acid can treat the organic matters, because the concentrated sulfuric acid can dehydrate and carbonize most of the organic matters at 150-170 ℃, the organic matters originally dissolved in water can be changed into water-insoluble matters, and a small amount of organic matters can be oxidized into carbon dioxide and water under the condition.
Furthermore, the treatment of organic matter in the waste salt with concentrated sulfuric acid is economical only when the organic matter content is low. If the waste salt contains too much organic matter, more than 5%, the organic matter must be removed by oxidation at high temperature to make it more economical.
(2) Precipitation of impurity cations with sodium hydroxide in the first stage: and (3) separating the mixed liquor finally obtained in the step (1), wherein the liquid is basically sulfuric acid, the water content of the liquid can be regulated and reused in the step (1), and the solid is a mixture of sodium sulfate, impurity cations, carbon and other substances. The obtained solid is dissolved by water, and then concentrated sodium hydroxide solution is added to adjust the pH value to be strong alkaline, so that most heavy metals can be precipitated. Then solid-liquid separation is carried out again, the solid is impurity cation precipitate, carbon and other impurities, and the main components of the liquid are sodium sulfate and sodium hydroxide.
Furthermore, the main components of the mixed liquor obtained finally in the step (1) are sodium sulfate, sulfuric acid, impurity cations, carbon and other substances.
Further, the mixed liquid obtained finally may be subjected to solid-liquid separation by standing for layering, filtration, centrifugation or the like. The mixed liquid is almost still layered and filtered, and the still layering is preferred in view of cost.
Further, the liquid is basically sulfuric acid, the water content can be adjusted and recycled to the step (1), and the liquid also contains a small amount of carbon, but the recycling of the liquid is not influenced. The water content is adjusted to make the concentration range of the sulfuric acid return to 70-80%.
Further, the solid obtained by dissolving with water is just dissolved by pure water without adding excessive water.
Further, the concentrated sodium hydroxide solution adjusts the pH to be strongly alkaline, ranging from 11 to 13, preferably 12, so that most heavy metals can form hydroxide precipitates. The concentrated sodium hydroxide solution used should be a near saturated solution to avoid adding too much water when adjusting the pH.
Further, the solid-liquid separation is performed again, and the separation mode can be a filtration mode, a centrifugation mode or the like, and more preferably, the filtration is selected.
(3) In the second step, sulfuric acid is used for neutralization, and then calcium bicarbonate is added for resource conversion of sodium sulfate: and (3) regulating the pH of the liquid finally obtained in the step (2) to be neutral by using concentrated sulfuric acid, then adding a certain amount of calcium bicarbonate solution with higher concentration for conversion reaction to obtain calcium sulfate precipitate with high purity and sodium bicarbonate solution with higher concentration after the reaction, and performing solid-liquid separation by filtering and other modes to obtain a calcium sulfate product with high purity.
Further, the liquid obtained at the end of the step (2) mainly contains sodium sulfate and sodium hydroxide, wherein the concentration of the sodium sulfate is high, and the saturation degree is over 90 percent.
Furthermore, a certain amount of calcium bicarbonate solution with higher concentration is added, the addition amount is calculated according to the amount of sulfate radicals in the solution, so that the calcium bicarbonate solution and the solution react just completely, and the saturation degree of the calcium bicarbonate solution with higher concentration is generally between 70% and 90%. The concentration of the calcium bicarbonate solution is too low, the concentration of the sodium bicarbonate generated after the reaction is very low, and the freezing crystallization can not be separated out, so that the commercial value of the whole process is low, and even the commercial value is not basically high; too high a concentration reacts with almost saturated sodium sulfate to form too much sodium bicarbonate, which is precipitated and mixed in the calcium sulfate precipitate, resulting in impure calcium sulfate product. The method can be widely applied to converting mirabilite or other salts mainly containing sodium sulfate into high-purity calcium sulfate and sodium bicarbonate, is very green and low-carbon, and has high commercial value.
Further, the conversion reaction is carried out according to the reaction equation:
Ca(HCO 3 ) 2 +Na 2 SO 4 ＝CaSO 4 ↓+2NaHCO 3
further, the solid-liquid separation by filtration or the like may be performed by centrifugation, a screw, or the like.
(4) In the second step, sodium bicarbonate is separated by freezing crystallization and the like: and (4) performing freezing crystallization on the liquid obtained finally in the step (3) and the like to precipitate partial sodium bicarbonate. Then, solid-liquid separation is performed by filtration or the like. The obtained solid is the sodium bicarbonate with high purity, the filtrate is concentrated by reverse osmosis membrane and other modes, the fresh water can be reused for production, the concentrated water is returned to the freezing and crystallizing device, the circulation and crystallization are carried out continuously, most of the sodium bicarbonate can be separated out, and the ratio of sodium ions in the whole waste salt to be recycled exceeds 95%.
Further, the liquid obtained at the end of the step (3) contains sodium bicarbonate as a main component, but also contains a very small amount of impurities such as chloride ions and sulfate ions.
Further, the above-mentioned method of performing freeze crystallization or the like may be a method of precipitating a part of sodium bicarbonate or a method of performing evaporative crystallization or the like, but freeze crystallization is preferred and energy saving is relatively high. The temperature drop range of the freezing crystallization is generally that the room temperature is reduced to-5 ℃ to 5 ℃.
Further, the solid-liquid separation may be performed by a method such as filtration, or a method such as centrifugation or a screw may be used.
Further, the concentration by the reverse osmosis membrane may be performed by a method such as evaporation crystallization, but the concentration by the reverse osmosis membrane is preferable, and energy saving is relatively achieved.
Further, because the reaction conversion and resource utilization of chloride ions and sulfate ions in each step cannot reach 100%, and the removal of impurity cations cannot reach 100%, the contents of chloride ions, sulfate ions and the like in the liquid treated in the step (4) are accumulated continuously after freezing crystallization and continuous circulation treatment of a reverse osmosis membrane, but the accumulated contents need to be discharged from a circulation system after being accumulated to a certain degree, otherwise, the purity of sodium bicarbonate is influenced. Discharging the liquid of the circulating system, and performing evaporative crystallization to obtain waste salt. The waste salt is subjected to component analysis, and if the components of impurities such as heavy metals and the like are not high, the waste salt can be recycled; if the component ratio of impurities such as heavy metals is high, only safe landfill treatment can be carried out.
(5) And in the second step, the obtained sodium bicarbonate is subjected to heat treatment to prepare soda: and (5) heating the sodium bicarbonate obtained in the step (4) to about 135 ℃, and decomposing to generate sodium carbonate, water and carbon dioxide to obtain the high-purity soda ash.
Further, the heating is to about 130 ℃, which is in the range of 130 ℃ to 140 ℃, more preferably 135 ℃.
The invention has the characteristics and advantages that:
(1) Sodium ions, chloride ions and sulfate ions in the waste salt are recycled and converted into sodium carbonate, hydrochloric acid and calcium sulfate with high purity, and the conversion rate is high.
(2) In the pretreatment stage, organic matter removal, separation and resource utilization of chloride ions are combined in one unit, so that the process flow is shortened, and the investment is reduced.
(3) In the process of recycling sodium sulfate, compared with the traditional process, ammonia or ammonium is not used, calcium bicarbonate is used, the production risk is reduced, the environmental pollution is less, the green and environment-friendly effects are really realized, the product purity is high, and the method is a new process for producing soda ash and has industrial value.
(4) The whole process flow is short, the operation cost is low, the feasibility is high, the required materials are common industrial products, the materials are easy to obtain, and the price is low.
Generally, the process provided by the invention has the advantages of high feasibility, high resource degree, small investment, low risk and low operation cost, is more green and low-carbon compared with other conventional processes, especially has a great commercial application value in a sulfate radical resource mode, and is worthy of popularization and application.
Drawings
FIG. 1 is a schematic diagram of the process employed in the present invention.
Detailed Description
The invention will be further described with reference to the following example and embodiment in conjunction with fig. 1. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
Example 1: as shown in fig. 1, a waste salt recycling process includes the following steps:
1. 200mL of 70% sulfuric acid was added to a reaction kettle (with a vacuum extraction system and an absorption apparatus), the vacuum extraction and absorption apparatus was started, and 200 g of waste salt was slowly added with stirring to form a porridge-like suspension.
2. Slowly heating to 150 deg.C, heating at a rate of 5 deg.C/min, and keeping at 150 deg.C for 0.5h to completely dehydrate, carbonize and oxidize organic substances, convert chloride ions into hydrogen chloride, volatilize, and absorb in an absorption device to obtain high-purity hydrochloric acid.
3. And (3) cooling the final mixed solution in the step 2 to room temperature, pouring the cooled mixed solution into an acid-resistant container, and allowing the mixed solution to stand for layering.
4. And (3) after the mixed solution is fully layered, pouring out the supernatant (which can contain a little solid and is about 50 mL), wherein the main component of the supernatant is sulfuric acid, the water content is adjusted to be 30%, and then the supernatant is recycled to the step 1, and the main component of the lower-layer solid is sodium sulfate.
5. The solids in step 4 were dissolved with pure water in an amount to just dissolve all solids, not to add much. Then using concentrated sodium hydroxide solution to regulate pH value to 12, fully stirring to make most impurity cations form hydroxide precipitate, then filtering and separating. The filter residue is impurity cation precipitate, carbon and the like, and is treated according to sludge; the filtrate is a mixed solution of sodium sulfate and sodium hydroxide.
6. And (4) neutralizing the filtrate obtained in the step (5) by concentrated sulfuric acid to obtain a high-purity sodium sulfate solution, wherein the saturation degree of the sodium sulfate solution is over 90 percent.
7. And (4) adding a calcium bicarbonate solution with higher saturation into the sodium sulfate solution obtained in the step (6) to generate calcium sulfate and sodium bicarbonate. The quantity of calcium bicarbonate added and the degree of saturation of the solution must be calculated so that the sodium bicarbonate formed does not precipitate out, but is mixed with the precipitated calcium sulphate. If the saturation of sodium sulphate is 90%, the solution should have a saturation of not more than 85.4%, optionally 85%, calculated as complete reaction, of calcium bicarbonate added.
8. And (3) after the reaction in the step (7) is completed, performing solid-liquid separation in a filtering mode, wherein the solid is high-purity calcium sulfate (actually calcium sulfate dihydrate), and the main component of the liquid is sodium bicarbonate.
9. And (4) freezing and crystallizing the filtrate obtained in the step (8), cooling the temperature from room temperature to about 5 ℃ to precipitate sodium bicarbonate, and then carrying out solid-liquid separation by a filtration mode.
10. And (3) carrying out heat treatment on the solid obtained in the step (9), controlling the temperature at 130 ℃, and changing sodium bicarbonate into soda ash. The sodium carbonate has high purity which can reach the analytical grade, but may contain a small amount of impurities such as calcium sulfate, and further purification is needed if the sodium carbonate is to obtain the superior grade.
11. Concentrating the filtrate obtained in the step 9 by using a reverse osmosis membrane, recycling fresh water into the step 5, refluxing concentrated water into the step 9, and performing freeze crystallization again.
12. If the sodium bicarbonate crystals obtained in the step 9 contain a small amount of chloride ions and sulfate ions by analysis, the liquid for freezing crystallization contains a large amount of sodium chloride and sodium sulfate, and at this time, the liquid needs to be discharged from a circulation system formed by combining freezing crystallization and reverse osmosis membrane treatment, and is evaporated and crystallized to obtain waste residue salt.
13. Analyzing the components of the waste slag salt obtained in the step 12, and returning the waste slag salt to the step 1 for recycling as waste salt if the components of impurities such as heavy metals are not high; if the component ratio of impurities such as heavy metals is high, safe landfill treatment is performed.
Example 2: as shown in figure 1, the process for recycling waste salt comprises the following steps:
1. 200mL of 75% sulfuric acid was added to a reaction vessel (equipped with a vacuum extraction system and an absorption apparatus), the vacuum extraction and absorption apparatus was started, and 266 g of waste salt was slowly added with stirring to form a porridge-like suspension.
2. Slowly heating to 160 ℃, wherein the heating rate is 8 ℃/min, then preserving heat for 1h at 160 ℃, fully dehydrating, carbonizing and oxidizing organic matters, fully converting chloride ions into hydrogen chloride, volatilizing the hydrogen chloride, and absorbing the hydrogen chloride in an absorption device to obtain the high-purity hydrochloric acid.
3. And (3) cooling the final mixed solution in the step 2 to room temperature, and filtering by using a sand core filter.
4. The main component of the filtrate obtained in the step 3 is sulfuric acid, the concentration is about 40mL, the water content is adjusted to 25%, the filtrate is recycled to the step 1, and the main component of the filter cake is sodium sulfate solid.
5. The solid in step 4 was dissolved with pure water in an amount that just dissolved all the solid, but not much. Then using concentrated sodium hydroxide solution to regulate pH value to 13, fully stirring to make most impurity cations form hydroxide precipitate, then filtering and separating. The filter residue is impurity cation precipitate, carbon and the like, and is treated according to sludge; the filtrate is a mixed solution of sodium sulfate and sodium hydroxide.
6. And (4) neutralizing the filtrate obtained in the step 5 by concentrated sulfuric acid to obtain a high-purity sodium sulfate solution, wherein the saturation degree of the sodium sulfate solution reaches 95%.
7. And (4) adding a calcium bicarbonate solution with higher saturation into the sodium sulfate solution obtained in the step (6) to generate calcium sulfate and sodium bicarbonate. The quantity of calcium bicarbonate added and the degree of saturation of the solution must be calculated so that the sodium bicarbonate formed does not precipitate out, but is mixed with the precipitated calcium sulphate. If the saturation degree of sodium sulfate is 95%, the saturation degree of the calcium bicarbonate solution should not exceed 83.8%, and optionally 83%.
8. And (4) after the reaction in the step (7) is completed, performing solid-liquid separation in a centrifugal mode, wherein the solid is high-purity calcium sulfate (actually calcium sulfate dihydrate), and the main component of the liquid is sodium bicarbonate.
9. And (4) freezing and crystallizing the filtrate obtained in the step (8), cooling the temperature from room temperature to about 0 ℃ to precipitate sodium bicarbonate, and then carrying out solid-liquid separation by a centrifugal mode.
10. And (3) carrying out heat treatment on the solid obtained in the step (9), controlling the temperature at 135 ℃, and changing sodium bicarbonate into soda ash. The sodium carbonate has high purity, can reach analytical grade, but may contain a small amount of impurities such as calcium sulfate, and further purification is needed if the sodium carbonate is to obtain high-grade purity.
11. Concentrating the filtrate obtained in the step 9 by using a reverse osmosis membrane, recycling fresh water into the step 5, refluxing concentrated water into the step 9, and performing freeze crystallization again.
12. If the sodium bicarbonate crystals obtained in the step 9 contain a small amount of chloride ions and sulfate ions by analysis, the liquid for freezing crystallization contains a large amount of sodium chloride and sodium sulfate, and at this time, the liquid needs to be discharged from a circulation system formed by combining freezing crystallization and reverse osmosis membrane treatment, and is evaporated and crystallized to obtain waste residue salt.
13. Analyzing the components of the waste slag salt obtained in the step 12, and returning the waste slag salt to the step 1 for recycling as waste salt if the components of impurities such as heavy metals are not high; if the component ratio of impurities such as heavy metals is high, safe landfill treatment is performed.
Example 3: as shown in fig. 1, a waste salt recycling process includes the following steps:
1. 200mL of 80% sulfuric acid was added to a reaction vessel (with a vacuum extraction system and an absorption apparatus), the vacuum extraction and absorption apparatus was started, and 250 g of waste salt was slowly added with stirring to form a porridge-like suspension.
2. Slowly heating to 170 ℃, the heating rate is 10 ℃/min, then preserving heat for 2h at 170 ℃, fully dehydrating, carbonizing and oxidizing the organic matters, fully converting chloride ions into hydrogen chloride, volatilizing the hydrogen chloride, and absorbing the hydrogen chloride in an absorption device to obtain the high-purity hydrochloric acid.
3. And (3) cooling the final mixed solution in the step 2 to room temperature, and performing solid-liquid separation in a centrifugal mode.
4. The main component of the filtrate obtained in the step 3 is sulfuric acid, the concentration is about 40mL, the water content is adjusted to be 20%, the filtrate is reused in the step 1, and the main component of the filter cake is sodium sulfate solid.
5. The solid in step 4 was dissolved with pure water in an amount that just dissolved all the solid, but not much. Then using concentrated sodium hydroxide solution to regulate pH value to 11, fully stirring to make most impurity cations form hydroxide precipitate, then filtering and separating. The filter residue is impurity cation precipitate, carbon and the like, and is treated according to sludge; the filtrate is a mixed solution of sodium sulfate and sodium hydroxide.
6. And (3) neutralizing the filtrate obtained in the step (5) by using concentrated sulfuric acid to obtain a high-purity sodium sulfate solution, wherein the saturation degree of the sodium sulfate solution reaches 93%.
7. And (4) adding a calcium bicarbonate solution with higher saturation into the sodium sulfate solution obtained in the step (6) to generate calcium sulfate and sodium bicarbonate. The quantity of calcium bicarbonate added and the degree of saturation of the solution must be calculated so that the sodium bicarbonate formed does not precipitate out, but is mixed with the precipitated calcium sulphate. The saturation degree of sodium sulfate is 93%, and the saturation degree of the calcium bicarbonate solution added in the solution is not more than 84.5%, and 84% can be selected.
8. And (3) after the reaction in the step (7) is completed, performing solid-liquid separation in a filtration mode and the like, wherein the solid is high-purity calcium sulfate (actually calcium sulfate dihydrate), and the main component of the liquid is sodium bicarbonate.
9. And (4) freezing and crystallizing the filtrate obtained in the step (8), cooling the temperature from room temperature to about-5 ℃ to precipitate sodium bicarbonate, and then performing solid-liquid separation in a filtration mode.
10. And (3) carrying out heat treatment on the solid obtained in the step (9), controlling the temperature at 140 ℃, and changing sodium bicarbonate into soda ash. The sodium carbonate has high purity, can reach analytical grade, but may contain a small amount of impurities such as calcium sulfate, and further purification is needed if the sodium carbonate is to obtain high-grade purity.
11. Concentrating the filtrate obtained in the step 9 by using a reverse osmosis membrane, recycling fresh water into the step 5, refluxing concentrated water into the step 9, and performing freeze crystallization again.
12. If the sodium bicarbonate crystals obtained in the step 9 are analyzed to contain a small amount of chloride ions and sulfate ions, the liquid for freezing crystallization contains a large amount of sodium chloride and sodium sulfate, and the liquid is discharged from a circulation system formed by combining freezing crystallization and reverse osmosis membrane treatment, and is evaporated and crystallized to obtain waste salt.
13. Analyzing the components of the waste slag salt obtained in the step 12, and returning the waste slag salt to the step 1 for recycling as waste salt if the components of impurities such as heavy metals are not high; if the component ratio of impurities such as heavy metals is high, safe landfill treatment is performed.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A waste salt recycling process is characterized by comprising the following steps:
1) Adding a high-concentration sulfuric acid solution into a reactor, slowly adding waste salt while stirring until a porridge-like mixture is formed, slowly heating after adding the waste salt, fully stirring in the heating process, generating a large amount of gas in the process, and absorbing the gas with water to form hydrochloric acid; after heating to a certain temperature, keeping for a period of time to realize dehydration, carbonization and oxidation of the organic matters; after the reaction is finished, carrying out solid-liquid separation on the obtained mixed solution, wherein the main component of the supernatant is sulfuric acid, the water content of the supernatant is adjusted for recycling, and the solid is a mixture of sodium sulfate, impurity cations and carbon; dissolving the obtained solid with water, adding concentrated sodium hydroxide solution to adjust pH to strong alkalinity, precipitating most heavy metals, and performing solid-liquid separation again to obtain solid which is impurity cation precipitate and carbon, and liquid mainly contains sodium sulfate and sodium hydroxide; the reactor is provided with a vacuum extraction system and an absorption device;
2) Adjusting the pH of the liquid obtained in the step 1) to be neutral by using concentrated sulfuric acid, then adding a calcium bicarbonate solution with higher concentration, carrying out conversion reaction, obtaining calcium sulfate precipitate with high purity and a sodium bicarbonate solution with higher concentration after reaction, and carrying out solid-liquid separation by filtering and other modes to obtain high-purity calcium sulfate; freezing and crystallizing the liquid after solid-liquid separation to separate out partial sodium bicarbonate; then solid-liquid separation is carried out again in a filtering mode, the obtained solid is high-purity sodium bicarbonate, the filtrate is concentrated in a reverse osmosis membrane mode, fresh water can be reused for production, concentrated water returns to a freezing crystallization device, circulation and crystallization are carried out continuously in such a way, most of sodium bicarbonate is separated out, and the ratio of sodium ions in the whole waste salt to be recycled exceeds 95%; and heating the obtained sodium bicarbonate to decompose the sodium bicarbonate to generate sodium carbonate, water and carbon dioxide, thereby obtaining the high-purity sodium carbonate.
2. The waste salt recycling process as claimed in claim 1, wherein in the step 1), the concentration of the high-concentration sulfuric acid solution is 70-80% by mass; the ratio of the waste salt to the sulfuric acid solution is 1: 1-0.75 waste salt weight/g: sulfuric acid volume/mL.
3. The process of claim 1, wherein in the step 1), the slow heating is performed at a heating rate of 5 to 10 ℃/min;
heating to a certain temperature, and keeping for a period of time, wherein the temperature is 150-170 ℃, and the keeping time is 0.5-2 h.
4. The process of claim 1, wherein in the step 1), the obtained mixed solution is subjected to solid-liquid separation in a standing and layering manner, a filtration manner or a centrifugation manner.
5. The waste salt recycling process according to claim 1, wherein in the step 1), the main component of the supernatant is sulfuric acid, the water content of the supernatant is adjusted for recycling, and the concentration range of the sulfuric acid is adjusted to 70% -80% by adding water for recycling;
the solid obtained by dissolving the water is just dissolved by pure water without adding excessive water;
adding concentrated sodium hydroxide solution to adjust the pH value to be strong alkaline, wherein the range is 11-13; the concentrated sodium hydroxide solution used should be a near saturated solution so as not to add too much water when adjusting the pH.
6. The process as claimed in claim 1, wherein in step 1), the solid-liquid separation is performed again by filtration or centrifugation;
the liquid finally obtained in the step (1) mainly comprises sodium sulfate and sodium hydroxide, and the saturation degree of the sodium sulfate is over 90 percent.
7. The process as claimed in claim 1, wherein in step 2), a solution of calcium bicarbonate with a higher concentration is added, the amount of calcium bicarbonate solution added is calculated according to the amount of sulfate in the solution, so that the calcium bicarbonate solution and the solution react completely, and the saturation of the solution of calcium bicarbonate with a higher concentration is 70-90%.
8. The process as claimed in claim 1, wherein in step 2), the solid-liquid separation is performed by filtration or by centrifugation or screw.
9. The process of claim 1, wherein in the step 2), the liquid after the solid-liquid separation is frozen and crystallized to precipitate part of the sodium bicarbonate, or is crystallized by evaporation; the temperature of the frozen crystal is decreased to-5 ℃ at room temperature.
10. The process of claim 1, wherein in the step 2), the obtained sodium bicarbonate is heated to 130-140 ℃.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109731450A (en) * | 2018-12-26 | 2019-05-10 | 北京利德衡环保工程有限公司 | A kind of two-part flue gas aftertreatment technology |
| CN110563007A (en) * | 2019-09-29 | 2019-12-13 | 上海交通大学 | Method for converting sodium sulfate into sodium bicarbonate by using calcium oxide and carbon dioxide |
| CN110695059A (en) * | 2019-10-23 | 2020-01-17 | 绍兴市上虞众联环保有限公司 | Industrial organic waste salt treatment process |
| CN113149038A (en) * | 2020-01-22 | 2021-07-23 | 浙江龙盛集团股份有限公司 | Resource utilization method for treating industrial mixed waste salt by using sulfuric acid |
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| CN109731450A (en) * | 2018-12-26 | 2019-05-10 | 北京利德衡环保工程有限公司 | A kind of two-part flue gas aftertreatment technology |
| CN110563007A (en) * | 2019-09-29 | 2019-12-13 | 上海交通大学 | Method for converting sodium sulfate into sodium bicarbonate by using calcium oxide and carbon dioxide |
| CN110695059A (en) * | 2019-10-23 | 2020-01-17 | 绍兴市上虞众联环保有限公司 | Industrial organic waste salt treatment process |
| CN113149038A (en) * | 2020-01-22 | 2021-07-23 | 浙江龙盛集团股份有限公司 | Resource utilization method for treating industrial mixed waste salt by using sulfuric acid |
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