CN107523844B - The method for preparing bichromate using ferrochrome - Google Patents
The method for preparing bichromate using ferrochrome Download PDFInfo
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- CN107523844B CN107523844B CN201710802268.0A CN201710802268A CN107523844B CN 107523844 B CN107523844 B CN 107523844B CN 201710802268 A CN201710802268 A CN 201710802268A CN 107523844 B CN107523844 B CN 107523844B
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- 238000000034 method Methods 0.000 title claims abstract description 76
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 title claims abstract description 50
- 229910000604 Ferrochrome Inorganic materials 0.000 title claims abstract description 23
- 239000000243 solution Substances 0.000 claims abstract description 133
- 239000007788 liquid Substances 0.000 claims abstract description 78
- 238000006243 chemical reaction Methods 0.000 claims abstract description 44
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 12
- 238000005868 electrolysis reaction Methods 0.000 claims description 90
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 claims description 82
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 51
- 239000003792 electrolyte Substances 0.000 claims description 34
- 239000003513 alkali Substances 0.000 claims description 32
- 239000008151 electrolyte solution Substances 0.000 claims description 27
- PXLIDIMHPNPGMH-UHFFFAOYSA-N sodium chromate Chemical compound [Na+].[Na+].[O-][Cr]([O-])(=O)=O PXLIDIMHPNPGMH-UHFFFAOYSA-N 0.000 claims description 26
- 239000000047 product Substances 0.000 claims description 22
- 239000011268 mixed slurry Substances 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 12
- 238000000926 separation method Methods 0.000 claims description 11
- 239000002893 slag Substances 0.000 claims description 11
- QLOKJRIVRGCVIM-UHFFFAOYSA-N 1-[(4-methylsulfanylphenyl)methyl]piperazine Chemical compound C1=CC(SC)=CC=C1CN1CCNCC1 QLOKJRIVRGCVIM-UHFFFAOYSA-N 0.000 claims description 10
- 239000012527 feed solution Substances 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 9
- 238000010924 continuous production Methods 0.000 claims description 8
- 239000002994 raw material Substances 0.000 claims description 8
- 230000035484 reaction time Effects 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 239000012670 alkaline solution Substances 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 4
- 229960004887 ferric hydroxide Drugs 0.000 claims description 4
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 238000000746 purification Methods 0.000 claims description 4
- 239000013589 supplement Substances 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 239000002585 base Substances 0.000 claims description 3
- 238000009826 distribution Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 230000000750 progressive effect Effects 0.000 claims description 3
- 239000012066 reaction slurry Substances 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 2
- 239000013078 crystal Substances 0.000 claims description 2
- 238000002425 crystallisation Methods 0.000 claims description 2
- 238000001694 spray drying Methods 0.000 claims description 2
- 239000011651 chromium Substances 0.000 abstract description 14
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 13
- 229910052804 chromium Inorganic materials 0.000 abstract description 11
- 239000000203 mixture Substances 0.000 abstract description 3
- 239000002253 acid Substances 0.000 abstract 4
- 239000012266 salt solution Substances 0.000 abstract 4
- 230000036647 reaction Effects 0.000 abstract 2
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 26
- 229910052799 carbon Inorganic materials 0.000 description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 12
- 150000001844 chromium Chemical class 0.000 description 12
- 239000011859 microparticle Substances 0.000 description 9
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 9
- JHWIEAWILPSRMU-UHFFFAOYSA-N 2-methyl-3-pyrimidin-4-ylpropanoic acid Chemical compound OC(=O)C(C)CC1=CC=NC=N1 JHWIEAWILPSRMU-UHFFFAOYSA-N 0.000 description 8
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 8
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 8
- 239000011575 calcium Substances 0.000 description 8
- 229910052791 calcium Inorganic materials 0.000 description 8
- 239000011734 sodium Substances 0.000 description 7
- VQWFNAGFNGABOH-UHFFFAOYSA-K chromium(iii) hydroxide Chemical compound [OH-].[OH-].[OH-].[Cr+3] VQWFNAGFNGABOH-UHFFFAOYSA-K 0.000 description 6
- 238000011161 development Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 3
- 150000001768 cations Chemical class 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000009776 industrial production Methods 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- KIEOKOFEPABQKJ-UHFFFAOYSA-N sodium dichromate Chemical compound [Na+].[Na+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KIEOKOFEPABQKJ-UHFFFAOYSA-N 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 206010024796 Logorrhoea Diseases 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- 238000010923 batch production Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 2
- 229910000423 chromium oxide Inorganic materials 0.000 description 2
- PHFQLYPOURZARY-UHFFFAOYSA-N chromium trinitrate Chemical compound [Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O PHFQLYPOURZARY-UHFFFAOYSA-N 0.000 description 2
- DSHWASKZZBZKOE-UHFFFAOYSA-K chromium(3+);hydroxide;sulfate Chemical compound [OH-].[Cr+3].[O-]S([O-])(=O)=O DSHWASKZZBZKOE-UHFFFAOYSA-K 0.000 description 2
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 2
- 229910000356 chromium(III) sulfate Inorganic materials 0.000 description 2
- 235000015217 chromium(III) sulphate Nutrition 0.000 description 2
- 239000011696 chromium(III) sulphate Substances 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 2
- 239000004571 lime Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 235000017550 sodium carbonate Nutrition 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- -1 tanning Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 229910021555 Chromium Chloride Inorganic materials 0.000 description 1
- 206010010774 Constipation Diseases 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- ZTXONRUJVYXVTJ-UHFFFAOYSA-N chromium copper Chemical compound [Cr][Cu][Cr] ZTXONRUJVYXVTJ-UHFFFAOYSA-N 0.000 description 1
- 229940090961 chromium dioxide Drugs 0.000 description 1
- 229910021563 chromium fluoride Inorganic materials 0.000 description 1
- QSWDMMVNRMROPK-UHFFFAOYSA-K chromium(3+) trichloride Chemical compound [Cl-].[Cl-].[Cl-].[Cr+3] QSWDMMVNRMROPK-UHFFFAOYSA-K 0.000 description 1
- WYYQVWLEPYFFLP-UHFFFAOYSA-K chromium(3+);triacetate Chemical compound [Cr+3].CC([O-])=O.CC([O-])=O.CC([O-])=O WYYQVWLEPYFFLP-UHFFFAOYSA-K 0.000 description 1
- IAQWMWUKBQPOIY-UHFFFAOYSA-N chromium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Cr+4] IAQWMWUKBQPOIY-UHFFFAOYSA-N 0.000 description 1
- AYTAKQFHWFYBMA-UHFFFAOYSA-N chromium(IV) oxide Inorganic materials O=[Cr]=O AYTAKQFHWFYBMA-UHFFFAOYSA-N 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 229940030341 copper arsenate Drugs 0.000 description 1
- 238000001784 detoxification Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000004043 dyeing Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- MOUPNEIJQCETIW-UHFFFAOYSA-N lead chromate Chemical compound [Pb+2].[O-][Cr]([O-])(=O)=O MOUPNEIJQCETIW-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000009273 molten salt oxidation Methods 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 238000007500 overflow downdraw method Methods 0.000 description 1
- 239000002304 perfume Substances 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 229940072033 potash Drugs 0.000 description 1
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Substances [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 1
- 235000015320 potassium carbonate Nutrition 0.000 description 1
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- XCVRTGQHVBWRJB-UHFFFAOYSA-M sodium dihydrogen arsenate Chemical compound [Na+].O[As](O)([O-])=O XCVRTGQHVBWRJB-UHFFFAOYSA-M 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- FTBATIJJKIIOTP-UHFFFAOYSA-K trifluorochromium Chemical compound F[Cr](F)F FTBATIJJKIIOTP-UHFFFAOYSA-K 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/14—Alkali metal compounds
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/02—Process control or regulation
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/70—Assemblies comprising two or more cells
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Automation & Control Theory (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The present invention relates to a kind of methods for preparing bichromate using ferrochrome, comprising steps of using self-circulation mode carry out cell reaction, be controlled automatically at 20 DEG C~60 DEG C, according to 1 control loop of formula react time,Obtain high chromium concentration acid salt solution；High chromium concentration acid salt solution progress hydro-thermal reaction is obtained into high-purity chromium acid salt solution；High-purity chromium acid salt solution is configured to the chromatedsolution that mass percent concentration is 20%~40%, and it carries out being mixed and made into anode mixture feeding liquid for 23%~50% dichromate solution with mass percent concentration, cathode is provided and is mixed into feed liquid, cell reaction is carried out, dichromate solution is obtained.
Description
Technical Field
The invention relates to a development and utilization technology of chromite, in particular to a method for preparing dichromate by utilizing ferrochrome.
Background
The chromium salt product plays a rather important irreplaceable role in national economy and people's life, and the chromium salt industry is one of the most competitive resource raw material industries in the world. Chromate as a mother product of chromium salt is an important chemical raw material indispensable to national economic development. The chromium salt products using chromate as raw material comprise: dichromate, chromic anhydride, chromium oxide, chrome yellow, and chromate (basic chromium sulfate), and the like. These products are widely used in the industries of metallurgy, pigment, tanning, dye, perfume, metal surface treatment, welding electrode, coinage, catalyst, printing and dyeing, medicine, etc., and according to statistics, 10% of the commercial products in the market are related to chromium salt. The chromium salt industry in China starts from 1958, and the production capacity is 400kt/a in 2014, so that the chromium salt industry becomes the country with the largest global chromium salt yield.
The chromium salt products have various varieties, the varieties are not less than 100, and more than 30 varieties are produced in China. Sodium bichromate, chromic anhydride, chromic acid concentrate (basic chromium sulfate) and chromium oxide are the four products with the largest consumption of chromium salt. In addition, potassium bichromate, chromium chloride, chromium nitrate, chromium fluoride, chromium copper arsenate, sodium chromate, chromium dioxide, ammonium bichromate, chromium acetate and other chromium-containing reagents are also provided, and a plurality of chromium salt product series are produced and processed by using chromate as basic raw materials.
At present, the traditional process for industrially producing chromate is a roasting method for filling lime in a rotary kiln, and the traditional process is divided into three types of roasting with calcium, roasting with less calcium and roasting without calcium according to the filling amount of the lime.
Most of chromate enterprises in China adopt a calcium roasting process, namely chromite powder is mixed with soda ash, sintering-preventing calcium-containing auxiliary materials with ore amount more than twice are added, high-temperature oxidation is carried out in a rotary kiln, and a sodium chromate solution is obtained after clinker is leached. The calcium roasting method discharges a large amount of chromium-containing waste residues while obtaining a chromate solution, 2.5 t-3 t of chromium residues are discharged when one ton of sodium chromate is produced in the production process, and a large amount of chromium-containing waste water and waste gas are also generated, the three wastes, particularly the chromium-containing waste residues, are the primary Cr (VI) pollution sources, and the chromium salt industry is also the first of the heavy pollution industry.
In order to reduce the chromium emission in the calcium roasting method, a calcium-free roasting process is developed, calcium-containing auxiliary materials are not added in the process of producing the chromate, 0.6 t-1.0 t of chromium slag is discharged every ton of sodium chromate is produced, the content of Cr (VI) in the slag is reduced to be below 0.2 percent from 3 percent to 6 percent, the chromate is not contained, the detoxification is easy, and the comprehensive cost of the sodium bichromate is obviously reduced after the obtained chromate is reprocessed into the sodium bichromate.
In addition, the institute of process engineering of the Chinese academy of sciences invented a new process for producing potassium chromate, namely a potassium-alkali liquid phase oxidation method, also called a sub-molten salt oxidation method or an alkali fusion method. The method uses potassium hydroxide with a theoretical amount which is several times of that of the chromite to react, the reaction temperature is controlled to be about 320 ℃, the potassium hydroxide is melted to form a liquid phase, and the liquid phase, the chromite and air form a suspension system, so that the potassium chromate solution is prepared.
In addition, Tianjin Pisen technology ltd has invented a new technology for producing sodium chromate, namely a hydrothermal alkali-dissolution oxidation technology, and a technology for preparing sodium chromate by using a high-carbon molten chrome iron thermal oxidation method. For example, ferrochrome powder, sodium hydroxide and water are mixed in a reaction kettle, heated to about 280-320 ℃, oxygen is introduced into the reaction kettle, certain reaction temperature and pressure are maintained, and after reaction is continued for a preset time, the temperature is naturally reduced to room temperature, so that sodium chromate solution is obtained.
Various methods for preparing chromate in the industry currently reduce or reduce Cr in chromium slag to a certain extent6+The discharge amount of the slag is not completely avoided, but the existence of hexavalent chromium elements in the slag can not be completely avoided. To this end, the applicant has developed the name "using electricityThe invention patent 201310672022.8 of the device and the method for preparing the sodium chromate solution by the solution method overcomes the technical problem, realizes the green and pollution-free preparation of the sodium chromate solution, and has no hexavalent chromium element in slag. On the basis of the technical development, the applicant summarizes the problems in the development process and further vigorously develops the process method and equipment.
Disclosure of Invention
Accordingly, the present invention provides a method for preparing dichromate from ferrochrome.
A method for preparing dichromate by utilizing ferrochrome comprises the following steps:
step 1, providing an electrolysis device, comprising:
the electrolytic cell comprises a cylindrical main body part and a conical collecting part connected below the main body part, wherein the main body part is communicated with the collecting part, the upper end of the main body part is provided with an electrolyte inlet, and the lower end of the main body part is provided with an electrolyte outlet;
a double cathode device in which an inner cathode is disposed in the electrolytic cell, a cylindrical main body portion of the electrolytic cell serving as an outer cathode;
the double-anode device comprises a cylindrical inner anode and a cylindrical outer anode sleeved outside the cylindrical inner anode, the inner anode and the outer anode form an annular structure, the double-anode device is arranged in the cylindrical main body part of the electrolytic cell, an inner cathode of the double-cathode device is sleeved inside the inner anode, massive industrial ferrochrome is filled between the inner anode and the outer anode, and the distances between the outer cathode and the outer anode and between the inner cathode and the inner anode are kept consistent;
the insulating separator is arranged in the electrolytic bath and used for supporting the double-anode device;
the device comprises a plurality of settling tanks, a plurality of settling tanks and a plurality of electrolytic tanks, wherein each settling tank is composed of a cylindrical main body and a conical collecting part below the main body, each settling tank is provided with a feed inlet and a discharge outlet, the discharge outlet is higher than the feed inlet, the conical bottom is provided with a solid slag discharge outlet, the feed inlet of the first settling tank is connected with the discharge outlet of the electrolytic tank through a conduit, the discharge outlet of the first settling tank is connected with the feed inlet of the second settling tank through a conduit, and the discharge outlet of the last settling tank is communicated with the electrolytic tank through a conduit according to the;
the anode of the power supply is electrically connected with the outer anode and the inner anode of the double-anode device at the same time, and the cathode of the power supply is electrically connected with the cathode;
step 2, leading an electrolyte solution into an electrolytic cell from the electrolyte inlet, switching on a power supply, carrying out an electrolytic reaction, obtaining a solid-liquid mixed slurry in the electrolytic cell, wherein the electrolyte solution enters the electrolytic cell from the electrolyte inlet in a self-circulation mode in the electrolytic process, the obtained solid-liquid mixed slurry passes through a plurality of settling tanks from an electrolyte outlet in sequence through a guide pipe, and flows back into the electrolytic cell from a liquid outlet of the last settling tank through the guide pipe, the temperature of the solution in the electrolytic cell is automatically controlled to be 20-60 ℃ in the electrolytic process, the time of the electrolyte circulation reaction is controlled according to the formula 1, and a high-concentration chromate solution is obtained after solid-liquid separation;
wherein,
c1is the concentration of soluble alkali solution (e.g., NaOH or KOH solution) in the electrolyte solution, g/L;
V1is the volume of soluble alkali solution (e.g., NaOH or KOH solution), L, in the electrolyte solution;
M1is the molar mass of a soluble base (e.g., NaOH or KOH) in the electrolyte solution, g/mol;
M2as chromate (e.g. Na) in chromate solutions2CrO4Or K2CrO4) Molar mass of (a), g/mol;
i is the current value, A;
η is current efficiency,%;
n is the amount of electricity per ampere hour corresponding to the formation of chromate (e.g. Na)2CrO4Or K2CrO4) Amount of (3), g/Ah; when sodium chromate is generated, n is 1.01, and when potassium chromate is generated, n is 1.23;
step 3, introducing the high-concentration chromate solution obtained in the step 2 into a reaction kettle for hydrothermal reaction, heating to 180-300 ℃ under the pressure of 2-10 MPa, reacting for 2-12 h to obtain hydrothermal reaction slurry, and performing solid-liquid separation to obtain a high-purity chromate purification solution;
step 4, preparing the high-purity chromate solution obtained in the step 3 into a chromate solution with the mass percent concentration of 20-40%, mixing the chromate solution with a dichromate solution with the mass percent concentration of 23-50% to prepare an anode mixed feeding solution, wherein the volume ratio of dichromate to chromate in the anode mixed feeding solution is 1.5: 1-5: 1, and introducing the anode mixed feeding solution into an anode chamber; mixing a sodium hydroxide solution with the mass percentage concentration of 30% -32% with pure water to prepare a cathode mixed feed liquid, wherein the cathode mixed feed liquid is a soluble alkali solution with the mass percentage concentration of 27% -30%, and introducing the cathode mixed feed liquid into a cathode chamber;
step 5, when the anode mixed feed liquid in the step 4 is high-purity chromate solution, switching on direct current to carry out electrolytic reaction, when the electrolytic reaction is started, the dichromate in the anode mixed feed liquid is dichromate which is not generated in the electrolytic process, the soluble alkali in the cathode mixed feed liquid is soluble alkali which is not generated in the electrolytic process, when the electrolytic reaction is continuously carried out, the dichromate in the anode mixed feed liquid is dichromate generated in the electrolytic process, and the soluble alkali in the cathode mixed feed liquid is soluble alkali generated in the electrolytic process; controlling the current density to be 2kA/m2～4kA/m2The electrolysis reaction temperature is 70-90 ℃, and the pressure difference between the cathode chamber and the anode chamber is 200mmH2O～500mmH2O, anode feeding temperature is 50-85 ℃, cathode feeding temperature is 55-90 ℃, and after electrolytic reaction, dichromate solution and oxygen are obtained in the anode chamber, and soluble alkali and hydrogen are obtained in the cathode chamber.
Optionally, directly spray-drying the dichromate solution obtained by the electrolysis in the step 5 to obtain a dichromate product; or further evaporating and concentrating to 75-77% mass concentration, and preparing the dichromate crystal by using a cooling crystallization method.
Optionally, in the step 5, in the continuous electrolytic reaction process, the flow rate of the industrial chromate solution in the anode mixed feed solution is 80L/h to 400L/h, and the circulation flow rate of the dichromate generated in the electrolytic process is 450L/h to 600L/h.
Optionally, in the step 5, in the continuous electrolytic reaction process, the flow rate of pure water constituting the cathode mixed feed solution is 10L/h to 30L/h, and the circulation flow rate of the soluble alkali solution generated in the electrolytic process is 800L/h to 1000L/h.
Optionally, the volume ratio of dichromate to chromate in the anode mixed feed solution is 3: 1.
Optionally, in the step 5, the pressure difference between the cathode chamber and the anode chamber is controlled to be 400mmH2O。
Optionally, a plurality of sets of the electrolysis devices provided in the step 1 are connected in series through a conduit to form a multi-stage series electrolysis device, and the multi-stage series electrolysis device is used for the electrolysis process in the step 2 to realize step-by-step electrolysis and continuous production; the mixed slurry produced by each set of electrolytic tank is sequentially fed into a plurality of settling tanks matched with the electrolytic tank through a guide pipe, and is subjected to progressive settling in the settling tanks, fine ferrochrome, solid ferric hydroxide and sodium chromate alkaline solution in the mixed slurry are separated, the mixed feed liquid at the discharge port of the last settling tank is fed back to the original electrolytic tank through a tee-joint material distribution port to realize that 85-97% of the mixed feed liquid is returned to the original electrolytic tank to maintain normal electrolysis, and the rest 3-15% of the mixed feed liquid is used as the next stage of electrolytic raw material to be fed into the next stage of electrolytic tank, and so on; continuously replenishing fresh electrolyte solution in the first-stage electrolytic cell, and continuously obtaining a high-concentration chromate solution product from a discharge hole of a last-stage settling tank of the last-stage electrolytic cell.
Optionally, in the process of step-by-step electrolysis and continuous production of the multistage series-connected electrolysis devices, the first-stage electrolysis cell continuously supplements the amount of new electrolyte solution, the amount of mixed feed liquid of the discharge port of the last settling tank of each stage of electrolysis cell enters the next-stage electrolysis cell through the three-way material distributing port, and the amount of qualified high-concentration chromate solution product continuously produced by the last-stage electrolysis cell are controlled by controlling the amount of soluble alkali to be consumed in unit electrolysis reaction time through the formula (1); the mixed feed liquid after settlement separation of the settling tanks in the plurality of sets of electrolytic tanks in series is measured by the formula (1) in unit reaction time and is used as next-stage electrolytic feed liquid to enter the next-stage electrolytic tank, and the rest mixed feed liquid is completely returned to the original electrolytic tank to maintain the liquid level of the electrolytic tank to ensure continuous and normal electrolysis, thereby realizing continuous electrolysis.
Compared with the prior art, the invention has the following advantages:
firstly, in the preparation method, an electrolyte self-circulation mode is adopted, the electrolyte enters an electrolytic cell, solid-liquid mixed slurry generated after electrolysis flows to a settling tank from an outlet at the lower end of the electrolytic cell, passes through the settling process of a plurality of settling tanks and then flows back to the electrolytic cell, and the temperature of the whole electrolytic reaction system is naturally controlled to be about 20-60 ℃ and preferably about 30 ℃ by the circulation flow mode of the electrolyte or solution in the electrolytic cell, so that the process equipment is greatly simplified.
Secondly, among the electrolytic device, adopt double anode, double cathode device, pack the garrulous blocky industry chromium iron between interior anode and outer anode, such double anode configuration, the purpose is in order to improve and directly utilize a big piece of chromium iron to carry out the current that produces and distribute inequality, system temperature is difficult to control, the slag phase is difficult to clear up and the negative and positive pole interval constantly increases scheduling problem along with time, has improved electrolysis efficiency, has increased the electrolysis area, reduces the electric energy consumption.
Thirdly, the high-concentration chromate solution obtained in the electrolysis process contains a certain amount of micro-particle carbon, after the hydrothermal reaction, part of chromate is reduced into chromium hydroxide by the micro-particle carbon, so that the chromate is consumed, namely the impurity of the micro-particle carbon is removed by the chromate solution, and the purity of the rest chromate solution is obviously improved, so that the high-purity chromate solution is obtained.
And finally, adding a small amount of sodium dichromate solution for starting the electrolytic reaction into the high-purity sodium chromate solution, controlling the proportion of anode mixed feed solution, matching with cathode reactant, carrying out the electrolytic reaction to obtain a dichromate solution, and crystallizing after evaporation concentration to obtain a dichromate product.
More importantly, a plurality of sets of electrolytic devices are connected in series through a conduit to form a multi-stage continuous electrolytic system, so that large-scale industrial production is realized, and it can be understood that in the process from a small-scale laboratory to large-scale industrial production, although batch production formed by single set of circulation reaction of one set of electrolytic devices is changed into continuous production formed by series reaction of a plurality of sets of electrolytic devices to form stage-by-stage electrolytic reaction, the batch production seems to be relatively simple superposition, however, the process control of a plurality of series electrolytic reactions is the key point and difficulty of all production, and certain technical know how parameter control is needed.
In the multi-stage continuous electrolysis process, the process control is very important, the mixed slurry produced by electrolysis of each set of electrolytic tank sequentially enters a plurality of settling tanks matched with the electrolytic tank through guide pipes, fine ferrochrome, solid ferric hydroxide and sodium chromate alkaline solution in the mixed slurry are separated after being settled step by step in the settling tanks, the mixed material liquid at the discharge port of the last settling tank returns to the original electrolytic tank through a three-way material distributing port to maintain normal electrolysis for most of the mixed material liquid (for example, 85-97 percent), and the rest part (3-15 percent) is used as the next-stage electrolysis raw material to enter the next-stage electrolytic tank, and so on; fresh electrolyte solution is continuously replenished into the first-stage electrolytic cell, high-concentration chromate solution is continuously obtained from a discharge port of a last-stage settling tank of the last-stage electrolytic cell, after a plurality of sets of electrolytic cells are connected in series, the electrolysis parameters of each set of electrolytic cell are different, so that the composition of mixed feed liquid produced by electrolysis of each set of electrolytic cell is also different, the ferrochromium is electrolyzed step by step into chromate mixed feed liquid with different concentrations through the series connection of the plurality of sets of electrolytic cells, and finally, qualified high-concentration chromate solution is obtained after the last-stage electrolysis for the subsequent 3 rd-step reaction.
In the process of step-by-step electrolysis and continuous production of the multistage series-connected electrolysis devices, the first-stage electrolysis bath continuously supplements the amount of new electrolyte solution, the amount of mixed feed liquid of the discharge port of the last settling tank of each stage of electrolysis bath enters the mixed feed liquid of the next-stage electrolysis bath through the three-way material distributing port, and the amount of qualified high-concentration chromate solution products continuously produced by the last-stage electrolysis bath are controlled by controlling the amount of soluble alkali to be consumed in unit electrolysis reaction time through a formula (1); the mixed feed liquid after settlement separation of the settling tanks in the plurality of sets of electrolytic tanks in series is measured by the formula (1) in unit reaction time and is used as next-stage electrolytic feed liquid to enter the next-stage electrolytic tank, and the rest mixed feed liquid is completely returned to the original electrolytic tank to maintain the liquid level of the electrolytic tank to ensure continuous and normal electrolysis, thereby realizing continuous electrolysis.
Drawings
FIG. 1 is a schematic view of the structure of an electrolytic apparatus of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention is a result of continuous development based on the applicant's invention patent 201310672022.8 entitled "apparatus and method for preparing sodium chromate solution by electrolysis".
The invention provides a method for preparing dichromate by utilizing ferrochrome, which comprises the following specific steps.
Step 1, an electrolysis device is provided. As shown in fig. 1, includes: an electrolytic cell includes a cylindrical main body portion 11 and a conical collecting portion 12 connected below the main body portion 11. The inner wall of the body 11 is made of a cathode material, such as carbon steel stainless steel or nickel, and thus the inner wall of the body 11 serves as a cathode in this embodiment. It is of course also possible to provide additional insertion or placement of the cathode into the electrolysis cell. An insulating spacer 13 is provided in the cell (for supporting the double anode unit 20, described later, while ensuring insulation between the anode and the cathode), and the spacer 13 is made of a non-metal material, and may be a mesh structure or a plurality of through holes formed in a flat plate, so long as the electrolyte solution can flow throughout the cell to relieve constipation.
The side walls of the main body 11 of the electrolytic cell adjacent to the openings 1/3 and 2/3 are provided with two electrolyte inlets 14a and 14b, respectively, the electrolyte inlet 14a being for introducing the electrolyte raw material and the electrolyte inlet 14b being for introducing the recovered electrolyte from the settling tank. The lower end of the main body 11 near the conical collecting part 12 is provided with a discharge port 15 for discharging the electrolytic slurry.
The electrolysis apparatus comprises a double cathode apparatus, an inner cathode 10 is disposed in the electrolysis tank, a cylindrical main body portion 11 of the electrolysis tank serves as an outer cathode, and the inner cathode 10 and the outer cathode 11 are made of carbon steel, stainless steel or nickel.
The electrolysis apparatus further comprises a double anode arrangement 20 disposed in the electrolysis cell. Specifically, the double-anode device 20 comprises a cylindrical inner anode 22 and a cylindrical outer anode 21 sleeved outside the cylindrical inner anode 22, the inner anode 22 and the outer anode 21 form an annular structure, and the block-shaped ferrochrome 23 is filled between the inner anode 22 and the outer anode 21. The inner cathode 10 of the double cathode device is sleeved inside the inner anode 22. The distances between the outer cathode 11 and the outer anode 21 and between the inner cathode 10 and the inner anode 22 are kept uniform. This distance is consistent in the sense that: the distance between the inner wall (outer cathode) of the main body 11 and the outer anode 21 is equal to the distance between the inner cathode 10 and the inner anode 22.
The bulk ferrochrome 23 is ferrochrome obtained by pulverizing industrial ferrochrome and treating an oxide layer on the surface of the industrial ferrochrome, has excellent conductivity, is supported by an annular structure consisting of an inner anode and an outer anode, and is used as an anode after being electrified.
The cylindrical structures of the inner anode 22, the outer anode 21 and the inner cathode 10 are net-shaped structures, or a plurality of through holes are formed in the cylindrical structures, so that the electrolyte can flow among the inner anode 22, the outer anode 21 and the inner cathode 10 conveniently. The cylindrical structures of the inner anode 22, the outer anode 21 and the inner cathode 10 may be the same or different, and the cross-sectional shape of the cylindrical structures may be circular, oval, triangular, square or other polygonal shapes, or various irregular shapes, as long as the inner and outer anodes may form an annular structure for filling the bulk ferrochrome 23.
In this embodiment, the outer anode 21 includes a bottom and a cylindrical sidewall, the inner anode 22 is a cylinder with two open ends, and the lower end of the cylinder of the inner anode 22 is welded to the bottom of the outer anode 21.
The electrolysis apparatus also comprises a plurality of settling tanks 17, although a single settling tank 17 may be provided in a simple reaction. The upper end of each settling tank is provided with a feed inlet 17a, the lower end is provided with a discharge outlet 17b, the feed inlet 17a of the first settling tank 17 is connected with the discharge outlet 15 of the electrolytic cell through a conduit 16, the discharge outlet 17b of the first settling tank 17 is connected with the feed inlet 17a of the second settling tank 17 through a conduit 16, according to the connection mode, the discharge outlet 17b of the last settling tank 17 is communicated with the electrolytic cell through the conduit 16, and the mode together with the electrolytic cell can be directly connected to an electrolyte inlet 14a, or another electrolyte inlet 14b can be arranged at the position adjacent to the electrolyte inlet 14a, in the embodiment, the discharge outlet 17b of the last settling tank 17 is communicated with the electrolyte inlet 14b through the conduit 16.
An electrolyte solution 30 is introduced into the cell from an electrolyte inlet 14a of the cell, the electrolyte solution 30 being a soluble sodium or potassium alkali solution.
The positive pole of the power supply is electrically connected to the bi-anode device 20 and the negative pole of the power supply is electrically connected to the bi-cathode structure. When the positive pole of the power supply is electrically connected to the double anode device 20, in particular, to the outer anode 21 and the inner anode 22 simultaneously; when the negative electrode of the power source is electrically connected to the double cathode structure, specifically, to the inner cathode 10 and the outer cathode (the cylindrical body portion 11 of the electrolytic cell) at the same time.
In addition, the bottom of the electrolytic cell is provided with a filtering structure, so that after the electrolysis is finished, the electrolytic cell can be directly used for solid-liquid separation. The filter structure and the electrolytic tank are integrated, for example, the bottom of the electrolytic tank is provided with a controllable filter screen structure, and the filter screen structure is in a closed state in the electrolytic process; when solid-liquid separation is needed, the filter screen structure is opened, and the electrolytic cell itself becomes a filter, so that the solid and the solution are separated.
2, leading an electrolyte solution into an electrolytic cell from the electrolyte inlet 14a, wherein the electrolyte solution is a soluble alkali solution (such as a sodium alkali solution or a potassium alkali solution), switching on a power supply to carry out an electrolytic reaction to obtain a solid-liquid mixed slurry in the electrolytic cell, leading the electrolyte solution 30 into the electrolytic cell from the electrolyte inlet 14 in a self-circulation mode in the electrolytic process, leading the obtained solid-liquid mixed slurry to pass through a plurality of settling tanks 17 from an electrolyte outlet 15 through a guide pipe 16 in sequence, and returning the obtained solid-liquid mixed slurry into the electrolytic cell from a discharge port 17b of the last settling tank 17 through the guide pipe 16, automatically controlling the temperature of the solution in the electrolytic cell at 20-60 ℃ in the electrolytic process, preferably about 30 ℃, controlling the time of the circulating reaction of the electrolyte according to the formula 1 to obtain a high-concentration chromate solution (such as a high-concentration sodium chromate solution or a high-concentration potassium chromate solution) and a solid slag material, the high strength chromate solution has a particulate carbon content of about 1g/L to about 5 g/L.
Wherein,
c1is the concentration of soluble alkali solution (e.g., NaOH or KOH solution) in the electrolyte solution, g/L;
V1is the volume of soluble alkali solution (e.g., NaOH or KOH solution), L, in the electrolyte solution;
M1is the molar mass of a soluble base (e.g., NaOH or KOH) in the electrolyte solution, g/mol;
M2as chromate (e.g. Na) in chromate solutions2CrO4Or K2CrO4) Molar mass of (a), g/mol;
i is the current value, A;
η is current efficiency,%;
n is the amount of electricity per ampere hour corresponding to the formation of chromate (e.g. Na)2CrO4Or K2CrO4) Amount of (3), g/Ah; when sodium chromate is formed, n is 1.01, and when potassium chromate is formed, n is 1.23.
The invention designs a double-anode and double-cathode electrolytic device, and matches with the self-circulation flow mode of the electrolyte, the high-concentration chromate solution (such as a high-concentration sodium chromate solution or a high-concentration potassium chromate solution) obtained in the whole circulation type electrolytic process contains a certain amount of micro-granular carbon, and the high-concentration chromate solution containing the micro-granular carbon is subjected to hydrothermal reaction, so that the chromium hydroxide solid can be directly obtained. The present invention utilizes sodium chromate solution (without obtaining chromium hydroxide directly, sodium chromate must be converted into sodium dichromate, then converted into dry chromic acid, and then chromic anhydride is used to prepare chromium hydroxide).
The soluble sodium alkali solution is a sodium hydroxide solution, a sodium carbonate solution or a mixed solution of the two solutions; the soluble potash solution is a potassium hydroxide solution, a potassium carbonate solution or a mixed solution of the two solutions.
It can be understood that the electrolytic device can use a set of devices to complete the preparation of high-concentration chromate solution by circulating electrolysis; the preparation of high-concentration chromate solution can also be realized by connecting a plurality of same electrolysis devices in series through a conduit.
In order to realize industrial large-scale industrial production, a plurality of sets of electrolytic devices are generally adopted and connected in series through a guide pipe to form a multi-stage series electrolytic device, and the multi-stage series electrolytic device realizes stage-by-stage electrolysis and continuous production; the mixed slurry produced by each set of electrolytic tank is sequentially fed into a plurality of settling tanks matched with the electrolytic tank through a guide pipe, and is subjected to progressive settling in the settling tanks, fine ferrochrome, solid ferric hydroxide and sodium chromate alkaline solution in the mixed slurry are separated, the mixed feed liquid at the discharge port of the last settling tank is fed back to the original electrolytic tank through a tee-joint material distribution port to realize that 85-97% of the mixed feed liquid is returned to the original electrolytic tank to maintain normal electrolysis, and the rest 3-15% of the mixed feed liquid is used as the next stage of electrolytic raw material to be fed into the next stage of electrolytic tank, and so on; continuously replenishing fresh electrolyte solution in the first-stage electrolytic cell, and continuously obtaining a high-concentration chromate solution product from a discharge hole of a last-stage settling tank of the last-stage electrolytic cell for the subsequent 3 rd-step reaction.
In the process of step-by-step electrolysis and continuous production of a multi-stage series-connected electrolysis device, a first-stage electrolytic tank continuously supplements the amount of new electrolyte solution, the amount of mixed feed liquid of a discharge port of a last settling tank of each stage of electrolytic tank enters a next-stage electrolytic tank through a three-way feed port, and the amount of qualified high-concentration chromate solution product continuously produced by the last-stage electrolytic tank are controlled by controlling the amount of soluble alkali to be consumed in unit electrolysis reaction time through a formula (1); the mixed feed liquid after settlement separation of the settling tanks in the plurality of sets of electrolytic tanks in series is measured by the formula (1) in unit reaction time and is used as next-stage electrolytic feed liquid to enter the next-stage electrolytic tank, and the rest mixed feed liquid is completely returned to the original electrolytic tank to maintain the liquid level of the electrolytic tank to ensure continuous and normal electrolysis, thereby realizing continuous electrolysis.
And 3, introducing the high-concentration chromate solution obtained in the step 2 into a reaction kettle for hydrothermal reaction, heating to 10-300 ℃ under the pressure of 2-10 MPa, reacting for 2-12 h to obtain hydrothermal reaction slurry, performing solid-liquid separation to obtain a high-purity chromate purification solution, and filtering, crystallizing and separating the high-purity chromate purification solution to obtain a high-purity chromate product.
The high-concentration chromate solution obtained in the electrolysis process contains a certain amount of micro-particle carbon, and after hydrothermal reaction, part of chromate is reduced into chromium hydroxide by the micro-particle carbon, so that the chromate is consumed, namely the impurity of the micro-particle carbon is removed by the chromate solution, and the purity of the rest chromate solution is obviously improved.
Step 4, preparing the high-purity chromate solution (such as a high-purity sodium chromate solution or a potassium chromate solution) obtained in the step 3 into a chromate solution (such as a sodium chromate solution or a potassium chromate solution) with a mass percent concentration of 20-40%, and mixing the chromate solution with a dichromate solution (such as a sodium dichromate solution or a potassium dichromate solution, wherein the mixing principle is consistent in cation, for example, the sodium chromate solution is selected for the first 20-40%, the sodium dichromate is selected for the first 20-40%, and the potassium dichromate is selected for the first 20-40%), so as to prepare an anode mixed feed solution, wherein the volume ratio of the dichromate to the chromate in the anode mixed feed solution is 1.5: 1-5: 1, and introducing the anode mixed feed solution into an anode chamber; mixing 30-32% by mass of sodium hydroxide solution with pure water to prepare cathode mixed feed liquid, wherein the cathode mixed feed liquid is 27-30% by mass of sodium hydroxide solution, and introducing the cathode mixed feed liquid into a cathode chamber.
Step 5, connecting direct current to carry out electrolytic reaction, and forming anode mixture when the electrolytic reaction is startedThe dichromate in the feeding liquid is the dichromate generated in the non-electrolysis process, the sodium hydroxide in the cathode mixed feeding liquid is the sodium hydroxide generated in the non-electrolysis process, when the electrolysis reaction is continuously carried out, the dichromate in the anode mixed feeding liquid is the dichromate generated in the electrolysis process, and the sodium hydroxide in the cathode mixed feeding liquid is the sodium hydroxide generated in the electrolysis process; controlling the current density to be 2kA/m2～4kA/m2The electrolysis reaction temperature is 70-90 ℃, and the pressure difference between the cathode chamber and the anode chamber is 200mmH2O～500mmH2O, anode feeding temperature is 50-85 ℃, cathode feeding temperature is 55-90 ℃, and after electrolytic reaction, dichromate solution and oxygen are obtained in the anode chamber, and sodium hydroxide and hydrogen are obtained in the cathode chamber.
The above-mentioned processes for preparing sodium dichromate (or potassium dichromate solution) in steps 4 and 5 are carried out by referring to the applicant's patent "a process for producing sodium dichromate by cation membrane electrolysis" (patent No. 201310525165.6).
The invention is characterized in that: the ferrochrome is electrolyzed by a specific double-anode and double-cathode electrolysis device to prepare high-concentration chromate (such as sodium chromate or potassium chromate solution), then a high-purity chromate solution is obtained through hydrothermal reaction, the mass concentration of the obtained high-purity chromate solution is adjusted, a cation membrane electrolysis device is additionally arranged, a small amount of dichromate solution used for starting the electrolysis reaction is only needed to be added, the dichromate solution can be prepared, and a dichromate product (such as sodium dichromate or potassium dichromate product) can be obtained after concentration.
Compared with the prior art, the invention has the following advantages:
firstly, in the preparation method, an electrolyte self-circulation mode is adopted, the electrolyte enters an electrolytic cell, solid-liquid mixed slurry generated after electrolysis flows to a settling tank from an outlet at the lower end of the electrolytic cell, passes through the settling process of a plurality of settling tanks and then flows back to the electrolytic cell, and the temperature of the whole electrolytic reaction system is naturally controlled to be about 20-60 ℃ and preferably about 30 ℃ by the circulation flow mode of the electrolyte or solution in the electrolytic cell, so that the process equipment is greatly simplified.
Secondly, among the electrolytic device, adopt double anode, double cathode device, pack the garrulous blocky industry chromium iron between interior anode and outer anode, such double anode configuration, the purpose is in order to improve and directly utilize a big piece of chromium iron to carry out the current that produces and distribute inequality, system temperature is difficult to control, the slag phase is difficult to clear up and the negative and positive pole interval constantly increases scheduling problem along with time, has improved electrolysis efficiency, has increased the electrolysis area, reduces the electric energy consumption.
Thirdly, the high-concentration chromate solution obtained in the electrolysis process contains a certain amount of micro-particle carbon, after the hydrothermal reaction, part of chromate is reduced into chromium hydroxide by the micro-particle carbon, so that the consumption is realized, namely the impurity of the micro-particle carbon is removed by the chromate solution, and the purity of the rest chromate solution is obviously improved.
And finally, adding a small amount of sodium dichromate solution for starting the electrolytic reaction into the high-purity sodium chromate solution, controlling the proportion of anode mixed feed solution, matching with cathode reactant, carrying out the electrolytic reaction to obtain a dichromate solution, and crystallizing after evaporation concentration to obtain a dichromate product.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (8)
1. A method for preparing dichromate by utilizing ferrochrome comprises the following steps:
step 1, providing an electrolysis device, comprising:
the electrolytic cell comprises a cylindrical main body part and a conical collecting part connected below the main body part, wherein the main body part is communicated with the collecting part, the upper end of the main body part is provided with an electrolyte inlet, and the lower end of the main body part is provided with an electrolyte outlet;
a double cathode device in which an inner cathode is disposed in the electrolytic cell, a cylindrical main body portion of the electrolytic cell serving as an outer cathode;
the double-anode device comprises a cylindrical inner anode and a cylindrical outer anode sleeved outside the cylindrical inner anode, the inner anode and the outer anode form an annular structure, the double-anode device is arranged in the cylindrical main body part of the electrolytic cell, an inner cathode of the double-cathode device is sleeved inside the inner anode, massive industrial ferrochrome is filled between the inner anode and the outer anode, and the distances between the outer cathode and the outer anode and between the inner cathode and the inner anode are kept consistent;
the insulating separator is arranged in the electrolytic bath and used for supporting the double-anode device;
the device comprises a plurality of settling tanks, a plurality of settling tanks and a plurality of electrolytic tanks, wherein each settling tank is composed of a cylindrical main body and a conical collecting part below the main body, each settling tank is provided with a feed inlet and a discharge outlet, the discharge outlet is higher than the feed inlet, the conical bottom is provided with a solid slag discharge outlet, the feed inlet of the first settling tank is connected with the discharge outlet of the electrolytic tank through a conduit, the discharge outlet of the first settling tank is connected with the feed inlet of the second settling tank through a conduit, and the discharge outlet of the last settling tank is communicated with the electrolytic tank through a conduit according to the;
the anode of the power supply is electrically connected with the outer anode and the inner anode of the double-anode device at the same time, and the cathode of the power supply is electrically connected with the cathode;
step 2, leading an electrolyte solution into an electrolytic cell from the electrolyte inlet, switching on a power supply, carrying out an electrolytic reaction, obtaining a solid-liquid mixed slurry in the electrolytic cell, wherein the electrolyte solution enters the electrolytic cell from the electrolyte inlet in a self-circulation mode in the electrolytic process, the obtained solid-liquid mixed slurry passes through a plurality of settling tanks from an electrolyte outlet in sequence through a guide pipe, and flows back into the electrolytic cell from a liquid outlet of the last settling tank through the guide pipe, the temperature of the solution in the electrolytic cell is automatically controlled to be 20-60 ℃ in the electrolytic process, the time of the electrolyte circulation reaction is controlled according to the formula 1, and a high-concentration chromate solution is obtained after solid-liquid separation;
wherein,
c1is the concentration of soluble alkali solution in the electrolyte solution, g/L;
V1is the volume of soluble alkali solution in the electrolyte solution, L;
M1is the molar mass of soluble base in the electrolyte solution, g/mol;
M2the molar mass of chromate in the chromate solution, g/mol;
i is the current value, A;
η is current efficiency,%;
n is the amount of chromate generated corresponding to the electric quantity per ampere hour, g/Ah; when sodium chromate is generated, n is 1.01, when potassium chromate is generated, n is 1.23;
step 3, introducing the high-concentration chromate solution obtained in the step 2 into a reaction kettle for hydrothermal reaction, heating to 180-300 ℃ under the pressure of 2-10 MPa, reacting for 2-12 h to obtain hydrothermal reaction slurry, and performing solid-liquid separation to obtain a high-purity chromate purification solution;
step 4, preparing the high-purity chromate solution obtained in the step 3 into a chromate solution with the mass percent concentration of 20-40%, mixing the chromate solution with a dichromate solution with the mass percent concentration of 23-50% to prepare an anode mixed feeding solution, wherein the volume ratio of dichromate to chromate in the anode mixed feeding solution is 1.5: 1-5: 1, and introducing the anode mixed feeding solution into an anode chamber; mixing 30-32% by mass of sodium hydroxide solution with pure water to prepare cathode mixed feed liquid, wherein the cathode mixed feed liquid is 27-30% by mass of soluble alkali solution, and introducing the cathode mixed feed liquid into a cathode chamber;
and 5, when the anode mixed feeding liquid in the step 4 is a high-purity chromate solution, switching on direct current to carry out electrolytic reaction, when the electrolytic reaction is started, forming dichromate in the anode mixed feeding liquid as dichromate not generated in the electrolytic process, forming soluble alkali in the cathode mixed feeding liquid as soluble alkali not generated in the electrolytic process, and after the electrolytic reaction is continuously carried out, forming the dichromate in the anode mixed feeding liquid as the soluble alkali generated in the electrolytic processThe dichromate produced in the electrolytic process forms soluble alkali in the cathode mixed feed liquid as the soluble alkali produced in the electrolytic process; controlling the current density to be 2kA/m2～4kA/m2The electrolysis reaction temperature is 70-90 ℃, and the pressure difference between the cathode chamber and the anode chamber is 200mmH2O～500mmH2O, anode feeding temperature is 50-85 ℃, cathode feeding temperature is 55-90 ℃, and after electrolytic reaction, dichromate solution and oxygen are obtained in the anode chamber, and soluble alkali and hydrogen are obtained in the cathode chamber.
2. The method of claim 1, wherein: directly spray-drying the dichromate solution obtained by electrolysis in the step 5 to obtain a dichromate product; or further evaporating and concentrating to 75-77% mass concentration, and preparing the dichromate crystal by using a cooling crystallization method.
3. The method of claim 1, wherein: in the step 5, in the continuous electrolytic reaction process, the flow rate of the industrial chromate solution in the anode mixed feed solution is 80L/h-400L/h, and the circulation flow rate of the dichromate generated in the electrolytic process is 450L/h-600L/h.
4. The method of claim 1, wherein: in the step 5, in the continuous electrolytic reaction process, the flow rate of pure water for forming the cathode mixed feeding liquid is 10L/h-30L/h, and the circulation flow rate of the soluble alkali solution generated in the electrolytic process is 800L/h-1000L/h.
5. The method of claim 1, wherein: in the step 4, the volume ratio of dichromate to chromate in the anode mixed feed solution is 3: 1.
6. The method of claim 1, wherein: in the step 5, the pressure difference between the cathode chamber and the anode chamber is controlled to be 400mmH2O。
7. The method of claim 1, wherein: a plurality of sets of the electrolysis devices provided in the step 1 are connected in series through a guide pipe to form a multi-stage series connection electrolysis device, and the multi-stage series connection electrolysis device is used for the electrolysis process in the step 2 to realize step-by-step electrolysis and continuous production; the mixed slurry produced by each set of electrolytic tank is sequentially fed into a plurality of settling tanks matched with the electrolytic tank through a guide pipe, and is subjected to progressive settling in the settling tanks, fine ferrochrome, solid ferric hydroxide and sodium chromate alkaline solution in the mixed slurry are separated, the mixed feed liquid at the discharge port of the last settling tank is fed back to the original electrolytic tank through a tee-joint material distribution port to realize that 85-97% of the mixed feed liquid is returned to the original electrolytic tank to maintain normal electrolysis, and the rest 3-15% of the mixed feed liquid is used as the next stage of electrolytic raw material to be fed into the next stage of electrolytic tank, and so on; continuously replenishing fresh electrolyte solution in the first-stage electrolytic cell, and continuously obtaining a high-concentration chromate solution product from a discharge hole of a last-stage settling tank of the last-stage electrolytic cell.
8. The method of claim 7, wherein: in the process of step-by-step electrolysis and continuous production of the multistage series-connected electrolysis devices, the first-stage electrolysis bath continuously supplements the amount of new electrolyte solution, the amount of mixed feed liquid of the discharge port of the last settling tank of each stage of electrolysis bath enters the mixed feed liquid of the next-stage electrolysis bath through the three-way material distributing port, and the amount of qualified high-concentration chromate solution products continuously produced by the last-stage electrolysis bath are controlled by controlling the amount of soluble alkali to be consumed in unit electrolysis reaction time according to a formula 1; the mixed feed liquid after settlement separation of the settling tanks in the plurality of sets of electrolytic tanks is measured by the formula 1 in unit reaction time and enters the next stage of electrolytic tank, and the rest of the mixed feed liquid is completely returned to the original electrolytic tank to maintain the liquid level of the electrolytic tank so as to ensure continuous and normal electrolysis and realize continuous electrolysis.
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