WO2022094780A1 - Méthode de cristallisation d'heptahydrate de sulfate ferreux pendant un procédé de production de dioxyde de titane basé sur une méthode à l'acide sulfurique - Google Patents
Méthode de cristallisation d'heptahydrate de sulfate ferreux pendant un procédé de production de dioxyde de titane basé sur une méthode à l'acide sulfurique Download PDFInfo
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- WO2022094780A1 WO2022094780A1 PCT/CN2020/126385 CN2020126385W WO2022094780A1 WO 2022094780 A1 WO2022094780 A1 WO 2022094780A1 CN 2020126385 W CN2020126385 W CN 2020126385W WO 2022094780 A1 WO2022094780 A1 WO 2022094780A1
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- crystallization
- cooling
- ferrous sulfate
- vacuum
- titanium dioxide
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title claims abstract description 80
- 238000000034 method Methods 0.000 title claims abstract description 71
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 title claims abstract description 53
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 53
- 239000004408 titanium dioxide Substances 0.000 title claims abstract description 40
- 238000002425 crystallisation Methods 0.000 claims abstract description 187
- 230000008025 crystallization Effects 0.000 claims abstract description 168
- 239000007788 liquid Substances 0.000 claims abstract description 84
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 70
- 238000001816 cooling Methods 0.000 claims abstract description 70
- 239000010936 titanium Substances 0.000 claims abstract description 70
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 70
- 238000007710 freezing Methods 0.000 claims abstract description 40
- 230000008014 freezing Effects 0.000 claims abstract description 40
- 238000001704 evaporation Methods 0.000 claims abstract description 27
- 230000008020 evaporation Effects 0.000 claims abstract description 27
- 230000008569 process Effects 0.000 claims abstract description 25
- 239000002002 slurry Substances 0.000 claims abstract description 23
- 238000002156 mixing Methods 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000000926 separation method Methods 0.000 claims abstract description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 64
- 239000000463 material Substances 0.000 claims description 44
- 239000013078 crystal Substances 0.000 claims description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 230000007797 corrosion Effects 0.000 claims description 4
- 238000005260 corrosion Methods 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 239000007769 metal material Substances 0.000 claims description 4
- 238000005057 refrigeration Methods 0.000 claims description 4
- 238000005903 acid hydrolysis reaction Methods 0.000 claims description 3
- 238000004062 sedimentation Methods 0.000 claims description 3
- 230000009471 action Effects 0.000 claims description 2
- 230000006911 nucleation Effects 0.000 claims description 2
- 238000010899 nucleation Methods 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 230000032683 aging Effects 0.000 claims 2
- 239000006227 byproduct Substances 0.000 claims 1
- 238000000247 postprecipitation Methods 0.000 claims 1
- 238000007738 vacuum evaporation Methods 0.000 claims 1
- 230000007547 defect Effects 0.000 abstract description 3
- 230000000694 effects Effects 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 11
- 238000005265 energy consumption Methods 0.000 description 10
- 235000003891 ferrous sulphate Nutrition 0.000 description 10
- 239000011790 ferrous sulphate Substances 0.000 description 10
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 8
- 239000002609 medium Substances 0.000 description 7
- 238000009835 boiling Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 4
- 239000002826 coolant Substances 0.000 description 4
- 239000000498 cooling water Substances 0.000 description 4
- 230000007812 deficiency Effects 0.000 description 4
- 239000012530 fluid Substances 0.000 description 3
- 239000012595 freezing medium Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000011344 liquid material Substances 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- XBDUTCVQJHJTQZ-UHFFFAOYSA-L iron(2+) sulfate monohydrate Chemical compound O.[Fe+2].[O-]S([O-])(=O)=O XBDUTCVQJHJTQZ-UHFFFAOYSA-L 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- MTJGVAJYTOXFJH-UHFFFAOYSA-N 3-aminonaphthalene-1,5-disulfonic acid Chemical compound C1=CC=C(S(O)(=O)=O)C2=CC(N)=CC(S(O)(=O)=O)=C21 MTJGVAJYTOXFJH-UHFFFAOYSA-N 0.000 description 1
- 238000010793 Steam injection (oil industry) Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000002178 crystalline material Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- -1 ferrous heptahydrate Chemical class 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 description 1
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 1
- 239000008258 liquid foam Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- RVUXIPACAZKWHU-UHFFFAOYSA-N sulfuric acid;heptahydrate Chemical compound O.O.O.O.O.O.O.OS(O)(=O)=O RVUXIPACAZKWHU-UHFFFAOYSA-N 0.000 description 1
- 229910000349 titanium oxysulfate Inorganic materials 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/02—Crystallisation from solutions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/04—Oxides; Hydroxides
- C01G23/047—Titanium dioxide
- C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/14—Sulfates
-
- 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
- Y02P20/10—Process efficiency
Definitions
- the invention relates to a crystallization method of ferrous sulfate heptahydrate, in particular to a crystallization method of ferrous sulfate heptahydrate in the production process of titanium dioxide by sulfuric acid method.
- the titanium raw material is decomposed by sulfuric acid into a mixed solution containing titanyl sulfate, ferrous sulfate, part of free sulfuric acid and acid-insoluble impurities, and the acid-insolubles are separated by sedimentation.
- a mixed solution containing titanyl sulfate, ferrous sulfate, part of free sulfuric acid and acid-insoluble impurities, and the acid-insolubles are separated by sedimentation.
- -65 °C acid hydrolysis mixed titanium liquid in order to meet the requirements of subsequent processing to hydrolyze and precipitate titanium dioxide, it is necessary to remove a part of ferrous sulfate in the mixed titanium liquid; the method of removal is to crystallize the mixed titanium liquid in the form of cooling to precipitate heptahydrate sulfuric acid
- the ferrous crystals are then separated from the solid and liquid to reduce the ferrous sulfate content in the mixed titanium liquid.
- the freezing crystallization method is as shown in Figure (3) in the patent publication number CN108726578 "A continuous crystallization process of ferrous sulfate in the production of titanium dioxide by sulfuric acid method", and the mixed titanium liquid material at 53-65 ° C is sent to the tube heat exchange.
- the circulating cooling water is used for cooling to 37-45 °C, and the mixed liquid material is sent to the high-level tank and then continuously sent to the "scraper-wall type hollow plate cooling continuous crystallizer".
- the cooling medium in the hollow plate cooled to 12-14 °C, and the crystallization process is completed through the discharge port.
- the high enthalpy (heat at 55-65°C) of the mixed titanium liquid material is removed in the form of heat exchange with circulating cooling water, which is not used for the evaporation of water in the mixed titanium liquid, which increases the titanium content of the subsequent process.
- Liquid concentration evaporation load and steam consumption not only poor utilization of energy efficiency, but also waste of this relatively high enthalpy heat loss;
- the second is the use of hollow plate refrigeration medium for heat transfer, due to the high specific gravity and high viscosity of mixed titanium liquid, relying on spiral
- the energy consumption of circulating refrigeration is high; thirdly, due to the low cooling rotation speed of the hollow plate, a large stagnant layer and flow dead zone are formed, resulting in the crystallization of ferrous sulfate heptahydrate on the heat exchange cooling plate.
- Scraper-type "cleaning" due to the existence of the gap between the scraper and the cooling plate interface, and the large gradient of supersaturation in cooling, the small primary crystalline ferrous heptahydrate is densely adhered to the heat exchange plate, reducing the heat and mass transfer efficiency, It not only reduces the heat exchange efficiency, the scraper is "out of reach” for the scaling on its gap, and it is difficult to clean up, which does not get rid of the shortcomings of traditional coil cooling and crystallization; fourth, the crystallization efficiency and energy consumption are not fundamentally solved from the crystallization kinetics mechanism. The liquid continues to cool down with the rotating plate heat exchanger forward.
- the crystallization saturation temperature When the crystallization saturation temperature is reached, there is no large number of crystal seeds, and the crystallization ion aggregation ability of the solution tends to be strong, forming a large number of unit cells and crystal nuclei. Because of its large surface energy, In order to reduce its surface energy, it not only tends to crystallize on the wall of the heat exchange plate (to form a scale layer), but also tends to crystallize on the wall of the crystallizer, which cannot be removed due to static state until the production cannot be continued and the production is stopped for cleaning.
- Vacuum crystallization is as in the early U.S. patent "The production method of ferrous sulfate monohydrate" (US4055631), in order to produce ferrous sulfate monohydrate, first the high temperature 65 °C saturated ferrous sulfate solution produced by the decomposition of sulfuric acid and iron ore is vacuum evaporated Remove heat and cool down to 30°C to obtain ferrous sulfate heptahydrate crystals, which are then separated and mixed with the hot solution heated on the surface to obtain ferrous sulfate tetrahydrate; the temperature can only be lowered to 30°C, and this vacuum crystallization cannot meet the requirements of sulfuric acid method titanium dioxide.
- the multi-stage vacuum evaporation and crystallization method is shown in Figure 1.
- the first stage uses a water ring vacuum pump to reduce the temperature of the mixed titanium liquid from 55 ° C to 40 ° C.
- the pressure is 10KPa
- the steam jet pump is used for the second and third stages to vacuumize the mixed titanium solution to continue to cool down the mixed titanium solution until most of the ferric sulfate in the mixed titanium solution is crystallized as ferrous sulfate heptahydrate, and the temperature in the final vacuum crystallizer is controlled at 15 °C Around, the pressure is 5KPa.
- This vacuum crystallization method consumes a large amount of steam when the two-stage and three-stage steam jet pump is evacuated, and only consumes the kinetic energy of the steam without consuming the enthalpy in the steam, and the latent heat of the jet steam is completely lost.
- the temperature area adopts vacuum surface adiabatic evaporation, the cooling time is long and the steam consumption is large; the cooling curve is shown in Figure 2.
- the temperature of the titanium liquid drops from 55 °C to 35 °C, and the time is 30 minutes, that is, 1 minute and a half minutes. Decreases by 1°C; from 35°C to 20°C, it takes 50 minutes, that is, 3.3 minutes to reduce 1°C, which is more than double the time before.
- the time is 50 minutes, that is, 10 minutes. Lowering the temperature by 1°C requires more than 3 times of time, which is 10 times the time of the initial 30 minutes.
- CN105289036 "A Novel Method for Vacuum Crystallizing Ferrous Sulfate from Titanium Liquid in Titanium Dioxide Production Process" are the traditional steam jet pump Or the steam compressor in “an isogradient cooling crystallization system (CN206198744U)” is replaced by the steam generated by freezing the surface of the mixed titanium liquid by adiabatic evaporation, that is, the steam produced by low temperature heat exchange or direct working fluid condensation adiabatic evaporation, the same It is to make up for the fact that the water ring vacuum pump cannot reach the required system pressure of ⁇ 5KPa when the temperature is 15-20°C, to cool the low-temperature adiabatic evaporated steam to produce volume shrinkage and reduce the boiling point of the mixed titanium liquid.
- the vacuum crystallization method and system of mixed titanium liquid ferrous sulfate heptahydrate improved by vacuum crystallization and isothermal gradient cooling using compressed steam and working fluid cooling and cooling system still have three major deficiencies: one is the high vacuum boiling evaporation zone Heat removal, that is, adiabatic evaporation takes away heat to reduce the temperature of the material, the high temperature zone (60-30°C) cools down quickly, and the low temperature zone (30-15°C) under the same vacuum conditions, the boiling and evaporation driving force is small, the cooling rate is reduced, and time-consuming energy consumption.
- the second is adiabatic surface evaporation.
- the ferrous sulfate heptahydrate was crystallized in the production process of titanium dioxide by the sulfuric acid method, and the combined high-level enthalpy and low-level enthalpy of the mixed titanium liquid were used to carry out vacuum and freezing combined cooling three times for continuous crystallization, and the crystal slurry was used for forced circulation crystallization.
- a continuous crystallization production method that increases the turbulence on the heat exchange interface and reduces the fouling of fine saturated crystals caused by the retention layer, which affects the heat exchange efficiency, has not been reported.
- the object of the present invention is to provide a new method for the crystallization of ferrous sulfate heptahydrate in the production process of sulfuric acid method titanium dioxide.
- the mixed titanium liquid at about 55°C is continuously added into the vacuum surface adiabatic evaporation cooling crystallizer, and the vacuum formed by the water-ring vacuum pump is used to make the feed liquid boil and cool down, and the temperature is maintained at about 35°C.
- the feed liquid at about 35°C is discharged into the circulating crystallization mixing tank, combined with the crystallization circulating crystal slurry liquid at about 15°C separated from the frozen crystallizing tank, and then sent to the heat exchanger by the circulating pump, where it is mixed with
- the frozen liquid medium is subjected to heat exchange to reduce the temperature of the material, and the material at about 15°C from the heat exchange enters the frozen crystallization tank, where the crystals are aged to obtain a coarse and uniform ferrous sulfate heptahydrate crystal slurry;
- most of the slurry is continuously circulated back to the circulating crystallization mixing tank as a circulating crystallization slurry to mix with the material and liquid discharged from the vacuum crystallizer, and part of the slurry is continuously sent to the next process for solid-liquid separation.
- the crystallization method of ferrous sulfate heptahydrate in the production process of titanium dioxide by sulfuric acid method protected by the present invention not only utilizes the adiabatic effect of vacuum crystallization on the high enthalpy of mixed titanium liquid Evaporation heat, and the heat exchange cooling efficiency of freezing crystallization to the low enthalpy of mixed titanium liquid is utilized; the forced circulation large flow magma circulation continuous freezing crystallization saves the existing vacuum crystallization technology for generating high vacuum and low temperature boiling evaporation and cooling.
- the energy consumption of jet steam also eliminates the problems of low heat exchange efficiency and fine crystallization caused by scaling at the interface of the low-temperature freezing and crystallization heat exchanger due to low turbulence. It not only greatly shortens the cooling time of ferrous sulfate heptahydrate crystallization of mixed titanium liquid, but also improves the crystallization production efficiency, and adopts continuous automation technology, which simplifies the operation of intermittent production start-up and shutdown; while improving the heat utilization efficiency of the crystallization process, it can greatly It greatly improves labor productivity, saves energy consumption and production costs, and overcomes the limitations and deficiencies of existing vacuum crystallization and freezing crystallization heat and energy utilization.
- the energy utilization efficiency in the crystallization process and the economic utilization of heat in the mixed titanium liquid are improved, the economic benefit of the producer is increased, and the economic purpose of energy saving and consumption reduction of ferrous sulfate heptahydrate cooling and crystallization in the production process of sulfuric acid method titanium dioxide is achieved.
- the mixed titanium liquid at 55°C was continuously added to the vacuum crystallizer, and the material liquid was boiled by the vacuum formed by the water ring vacuum pump to carry out the first step of cooling and crystallization, maintaining the temperature of the material in the vacuum crystallizer at 35°C, and removing the liquid from the vacuum crystallizer.
- Continuously discharge the 35°C feed liquid enter the circulating crystallization mixing tank and combine with the 15°C circulating crystallization slurry liquid separated from the frozen crystallization tank, carry out the second step of cooling and crystallization, and then force it into the heat exchanger through the circulating pump.
- the heat exchange is carried out with the freezing liquid medium in the heat exchanger, and the third step is to cool down to the final required crystallization temperature.
- the slurry at 15 °C from the heat exchanger enters the freezing crystallization tank, and the crystals are aged and matured in the freezing crystallization tank.
- Part of the aged and matured crystalline material is continuously returned to the circulating crystallization mixing tank as a circulating crystallization crystal slurry material, and is produced by circulating cooling, and part of the material is continuously sent to the next process as a crystalline finished material for solid-liquid separation.
- the crystallization method of ferrous sulfate heptahydrate in a sulfuric acid method titanium dioxide production process protected by the present invention retains the advantages of vacuum crystallization and freezing crystallization, and overcomes both.
- the high enthalpy of the mixed titanium liquid is used, and the adiabatic evaporation of vacuum crystallization is used to increase the concentration of the mixed titanium liquid by more than 5%, reducing the steam required for the concentration of the titanium liquid in the subsequent process by more than 200kg;
- the crystallization cooling low temperature area adopts frozen crystallization Overcome the cooling time in the low temperature zone of vacuum crystallization and the steam consumption of 1400Kg to improve the vacuum degree by the steam jet pump;
- the forced crystallization slurry circulation is adopted for the refrigeration heat exchange, which improves the heat exchange efficiency, shortens the heat exchange time, and strengthens the heat exchanger.
- the circulating crystallization slurry provides a huge crystallization center, which prevents the supersaturated solution caused by homogeneous nucleation from scaling and depositing in the heat exchanger wall and crystallization system, reducing the efficiency and the shortcomings and deficiencies of final shutdown and cleaning .
- efficient production To achieve the economic purpose of energy saving and consumption reduction, efficient production.
- the mixed titanium solution is a precipitation titanium solution obtained by acid hydrolysis, sedimentation and separation of acid-insoluble matter in the production of titanium dioxide by the sulfuric acid method.
- the temperature range of the mixed titanium liquid is 40-65°C, more preferably 50-60°C, and most preferably 55°C.
- the concentration range of titanium dioxide in the mixed titanium solution is 120-140 g/LTiO2, more preferably 125-135 g/LTiO2, and most preferably 130 g/LTiO2.
- the absolute pressure of the vacuum crystallizer is 30-10KPa, more preferably 20-10KPa, and most preferably 10KPa.
- the temperature range of the material to be discharged from the vacuum crystallizer is 30-40°C, preferably 35°C.
- the temperature range of the slurry returned from the freezing crystallization tank to the circulating crystallization mixing tank is 10-20°C, more preferably 15-20°C, and most preferably 17°C.
- the slurry mass ratio (frozen crystallization mass/vacuum crystallization mass) entering the circulating crystallization mixing tank from the freezing crystallization tank and the vacuum crystallizer is 2-6, more preferably 3-5, and most preferably 4.
- the temperature of the material entering the circulating pump after mixing from the circulating crystallization mixing tank is in the range of 20-25°C, preferably 22°C.
- the heat exchanger can be a shell and tube heat exchanger made of corrosion-resistant metal material, a graphite shell-and-tube heat exchanger and a graphite block hole heat exchanger, preferably a shell-and-tube heat exchanger made of a corrosion-resistant metal material.
- the temperature of the material coming out of the heat exchanger after refrigerating heat exchange is in the range of 10-20°C, more preferably 15-20°C, and most preferably 17°C.
- the temperature range of the crystallization Chenhua slurry is 10-20°C, more preferably 15-20°C, and most preferably 17°C.
- the concentration range of titanium dioxide in the cooling crystallizer is 150-170g/LTiO2, more preferably 155-165g/LTiO2, and most preferably 160g/LTiO2
- the heat held by the high-level enthalpy and the low-level enthalpy in the mixed titanium liquid are treated separately, and a continuous and differentiated cooling crystallization technology is performed; Adopt vacuum adiabatic evaporation to remove the heat of high enthalpy and heat exchange of freezing medium to remove the heat of low enthalpy.
- the cooling time of crystallization is greatly shortened, the production efficiency of crystallization is improved, and the continuous automation process is adopted, which simplifies the operation of intermittent production start-up and shutdown, improves the heat utilization efficiency of the crystallization process, and greatly improves labor productivity, saving energy consumption and energy consumption.
- the production cost overcomes the limitations and deficiencies of the existing vacuum crystallization and freezing crystallization heat and energy utilization; it improves the energy utilization efficiency in the crystallization process and the heat classification and economic utilization in the mixed titanium liquid, which increases the economic benefit of the producer.
- the economic purpose of ferrous sulfate heptahydrate cooling and crystallization in the production process of titanium dioxide by sulfuric acid method is to save energy and reduce consumption.
- the invention utilizes the high enthalpy of the mixed titanium liquid to conduct adiabatic evaporation and cooling, and without steam, the titanium dioxide concentration of the mixed titanium liquid is increased by more than 5% compared with the heat exchange and cooling of the frozen crystallization cold medium, and 200Kg of subsequent titanium liquid concentrated steam can be saved per ton of product above.
- the invention adopts the freezing medium for heat exchange to remove the low-level enthalpy of the mixed titanium liquid, it saves 1400 kg of externally supplied steam compared with the steam jet pump required for the vacuum crystallization adiabatic evaporation cooling.
- the invention not only improves the efficiency of freezing and heat exchange, but also improves and prolongs the production cycle of freezing and crystallization heat exchange, and reduces the scaling and cleaning problems of existing freezing and crystallization heat exchangers and crystallizers.
- the invention carries out the continuous cooling and crystallization production method of the mixed titanium liquid, which simplifies the process, shortens the production cycle, reduces the equipment sets, saves energy and reduces consumption, improves the efficiency, and reduces the The production cost of cooling crystallization increases the benefit.
- the temperature range of the feed mixed titanium liquid is 40-65°C, preferably 50-60°C; the concentration range of titanium dioxide in the mixed titanium liquid is 120-140g/LTiO2, preferably 125-135g/LTiO2; vacuum crystallizer
- the absolute pressure in the medium is 30-10KPa, preferably 20-10KPa; the temperature range of the vacuum crystallizer is 30-40°C, preferably 35°C; the temperature range of the frozen crystallization tank slurry is 10-20°C, the best is 15-20 °C;
- the slurry mass ratio (frozen crystallization quality/vacuum crystallization quality) of the circulating crystallization mixing tank is 2-6, preferably 3-5;
- the feeding temperature range of the circulating pump is 20-25 °C, the best at 22°C; the temperature range of the discharge temperature of the heat exchanger is 10-20°C, preferably 15-20°C; the temperature range of the crystallization slurry in the cooling crystallization tank is 10-20°C, preferably 15-20°C; the
- Fig. 2 steam jet multi-stage vacuum crystallization cooling curve
- Fig. 3 a kind of isocratic cooling crystallization system technological process
- Fig. 4 a kind of ferrous sulfate continuous crystallization process (frozen crystallization process) in the production of titanium dioxide by sulfuric acid method;
- Fig. 5 "a kind of crystallization method of ferrous sulfate heptahydrate in the production process of titanium dioxide by sulfuric acid method" process of the present invention.
- the mixed titanium liquid with a temperature of 55 °C in the production process of sulfuric acid method titanium dioxide was continuously fed into a 30 cubic vacuum crystallizer. After adding about 20 cubic meters of material liquid, the vacuum crystallizer was turned on to stir, and the water ring was started. type vacuum pump, and start the circulating cooling water at the same time, until the material liquid reaches 30 cubic volume, after the material overflow starts to appear in the overflow port of the vacuum mold, stop feeding, and the equipment continues to run until the temperature of the material in the vacuum mold drops to 35 °C, absolutely The pressure is 10KPa.
- the mixed titanium liquid at a temperature of 60 °C from the sulfuric acid method titanium dioxide production process was continuously fed into a 30 cubic vacuum crystallizer. After adding about 20 cubic meters of material liquid, the vacuum crystallizer was turned on to stir, and the water ring was started. At the same time, start the circulating cooling water until the material liquid reaches 30 cubic volume. After the material overflow starts to appear at the overflow port of the vacuum crystallizer, stop feeding, and the equipment continues to run until the temperature of the material in the vacuum crystallizer drops to 40 °C.
- the pressure is 10KPa.
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- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
L'invention concerne une méthode de cristallisation d'heptahydrate de sulfate ferreux pendant un procédé de production de dioxyde de titane basé sur une méthode à l'acide sulfurique. La méthode comprend : l'ajout en continu d'une solution de titane mélangée à un cristalliseur sous vide, la réalisation d'une évaporation adiabatique à l'aide d'un vide formé au moyen d'une pompe à vide à anneau d'eau, et la réalisation d'une première étape de refroidissement par élimination de la chaleur avec une enthalpie de niveau élevé ; après la première étape de refroidissement, la réalisation d'une seconde étape de refroidissement et de cristallisation au moyen de l'entrée en continu dans un réservoir de mélange de cristallisation en circulation et le mélange avec une suspension cristallisée circulante provenant de la cristallisation par congélation ; la mise en œuvre d'une troisième étape de refroidissement par envoi forcé à un échangeur de chaleur de congélation par l'intermédiaire d'une pompe de circulation pour l'échange de chaleur jusqu'à ce qu'une température de cristallisation finale souhaitée soit atteinte ; et l'envoi en continu d'une partie d'une suspension cristallisée au procédé suivant pour une séparation solide-liquide pour obtenir un heptahydrate de sulfate ferreux. La méthode permet d'économiser une grande quantité de vapeur consommée pour éliminer la chaleur avec une enthalpie de faible niveau au moyen d'une cristallisation sous vide existante, et permet en outre de compenser les défauts de cristallisation d'une congélation existante ne faisant pas appel à un effet de concentration provoqué par une évaporation adiabatique avec une enthalpie de niveau élevé d'une solution de titane mélangée et de l'efficacité d'un échangeur de chaleur de congélation qui est faible lorsque la mise à l'échelle se produit.
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PCT/CN2020/126385 WO2022094780A1 (fr) | 2020-11-04 | 2020-11-04 | Méthode de cristallisation d'heptahydrate de sulfate ferreux pendant un procédé de production de dioxyde de titane basé sur une méthode à l'acide sulfurique |
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PCT/CN2020/126385 WO2022094780A1 (fr) | 2020-11-04 | 2020-11-04 | Méthode de cristallisation d'heptahydrate de sulfate ferreux pendant un procédé de production de dioxyde de titane basé sur une méthode à l'acide sulfurique |
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