CN112850772A - Method for preparing calcium sulfate by using calcium-containing waste liquor of fluorite ore - Google Patents
Method for preparing calcium sulfate by using calcium-containing waste liquor of fluorite ore Download PDFInfo
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Abstract
The invention provides a method for preparing a calcium sulfate product by using calcium-containing waste liquor of fluorite ore, which comprises the following steps: s1: mixing calcium-containing waste liquor and SO-containing waste liquor of fluorite ore4 2‑Sequentially adding the ionic solution into a reaction container to perform crystallization precipitation reaction; s2: controlling the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction to obtain calcium sulfate crystal slurry; s3: and (2) filtering, leaching and drying the calcium sulfate crystal slurry obtained in the step (S2) to obtain a solid-phase product which is a needle-shaped or whisker-shaped sponge body of calcium sulfate, wherein the filtrate is dilute hydrochloric acid, the average particle size of the calcium sulfate is more than or equal to 150 mu m, the dry-basis purity is more than or equal to 95 percent, the whiteness is more than or equal to 90, the calcium sulfate crystal is a high-quality crystalline calcium sulfate product, the whole process is simple and easy to implement, and the method effectively utilizes resources and reduces pollution.
Description
Technical Field
The invention relates to a harmless treatment method of calcium-containing waste liquid, in particular to a method for preparing a high-quality calcium sulfate product by using the calcium-containing waste liquid generated by acid leaching and purifying fluorite concentrate.
Background
Fluorite, also known as fluorite, is the main source of fluorine element in industry, and is one of 20 important nonmetallic mineral raw materials in the world. The fluorite has wide application, and has wider and wider application prospect with the progress of science and technology. At present, the method is mainly applied to metallurgy, aluminum smelting, glass, ceramics, cement and chemical industries. The pure colorless transparent fluorite can be used as an optical material, and the fluorite with bright color can also be used as a gem jade and an industrial art engraving raw material. Fluorite is also a basic raw material in the fluorine chemical industry, and the product of the fluorite is widely applied to the fields of aerospace, aviation, refrigeration, medicine, pesticide, corrosion prevention, fire extinguishing, electronics, electric power, machinery, atomic energy and the like.
The fluorite ore comprises CaF as main component2The two minerals are calcium-containing minerals, the surface chemical properties of the minerals are similar, the floatability of the minerals is similar, the effective separation of fluorite and calcite cannot be completely realized by the conventional flotation process, and the grade of fluorite concentrate is low. In order to further improve the grade of fluorite concentrate, most fluorite production enterprises add hydrochloric acid into fluorite concentrate pulp for leaching, and change a small amount of calcium carbonate remained in fluorite concentrate into calcium chloride solution for removal, so as to further improve the grade of fluorite concentrate, but at the same time, CaCl in the calcium chloride solution2Is rich continuouslyCollect to reach a certain concentration (generally CaCl)2The content reaches 20 percent), and the fluorite concentrate can not be used for hydrochloric acid leaching and size mixing, and becomes CaCl which must be discharged2Acid waste liquor, these high concentrations of CaCl2The acidic waste liquid becomes a large pollution source of the environment pollution of fluorite ore mining enterprises, and how to use the part of CaCl2The realization of low-cost harmless treatment of the acid waste liquid becomes a practical problem for fluorite ore mining enterprises.
For CaCl in industry2The mother liquor is treated by adopting a multi-effect evaporation process to recover CaCl in the mother liquor2The process is suitable for high-concentration CaCl2Mother liquor (more than 30%) when CaCl2When the concentration is lower than 30%, the evaporation capacity is too large, the energy consumption is high, the treatment cost is high, the economic benefit is poor, and the method is not suitable for use. Treating low-concentration CaCl2The process for enriching CaCl in the mother liquor comprises electrodialysis, reverse osmosis membrane concentration, nanofiltration membrane filtration, ion exchange adsorption, etc2However, these processes often have large investment, high energy consumption and high operation cost, and the economic cost and the investment cost-effectiveness ratio are not critical, so that the CaCl formed by the processes in the impurity removal of fluorite concentrate is greatly limited2Application in waste liquid treatment. At present, most of calcium-containing waste liquid of fluorite ore is treated by adopting sulfuric acid and CaCl2Method for removing Ca from waste liquid by reaction to produce gypsum2+And meanwhile, dilute hydrochloric acid is obtained and can be recycled for removing calcium from fluorite concentrate, but the method has the defects that the obtained calcium sulfate has extremely fine granularity (the average granularity is only 5-20 microns), the dehydration efficiency of filtering, drying and the like is low, the energy consumption is high, the impurity content of the calcium sulfate is high, the calcium sulfate cannot be converted into a calcium sulfate product with higher use value to be sold outside, and the waste liquid treatment benefit is poor.
The invention of CN111547756A discloses a method for treating calcium chloride waste liquid containing organic matters, which comprises the following steps: s1, adding sodium sulfate into the organic matter-containing calcium chloride waste liquid to perform precipitation reaction to generate calcium sulfate and sodium chloride, wherein the mass ratio of the calcium chloride to the sodium sulfate in the waste liquid is 1.05-1.1: 1; s2, adding excessive sodium carbonate into the waste liquid after the precipitation reaction, standing for clarification, and performing solid-liquid separation to obtain a precipitated solid and a solid-free aqueous solution; s3, washing and filter-pressing the settled solids to obtain a calcium sulfate product; adding hydrochloric acid into the solid-free aqueous solution, adjusting the pH value to 6.8-7.2, then evaporating and crystallizing to obtain solid salt containing organic matters, and removing the organic matters in the solid salt by adopting a self-propagating pyrolysis incineration process to obtain a sodium chloride product. However, the invention does not relate to means of controlling the particle size and purity of the calcium sulfate product, and the like, and the process is complicated, so that the production and manufacturing cost and energy consumption are increased.
The invention of CN102453951B discloses a method for preparing high-quality calcium sulfate whisker by using alkali making waste liquid and waste sulfuric acid, which adopts CaCl discharged from alkali making industry2The solution and waste sulfuric acid produced in sulfuric acid industry are combined to produce calcium sulfate, and the high-quality calcium sulfate whisker is produced. The invention adopts the waste liquor CaCl of the alkali production industry2The solution reacts with waste sulfuric acid generated in sulfuric acid industry as raw materials, and crystal growth is controlled by using the nucleation and growth theory of crystals, so that the high-quality calcium sulfate whisker with the particle size of less than 4 mu m and the length-diameter ratio of more than 200 is obtained. Although the invention relates to a process for obtaining the calcium sulfate whisker by controlling the growth of calcium sulfate crystal, the invention needs heating and heat preservation, has higher energy consumption, requires heat preservation of a reaction container and a pipeline, needs washing by deionized water or absolute ethyl alcohol after treatment, has more rigorous process control, and nevertheless, the finally obtained calcium sulfate whisker has smaller grain diameter, and simultaneously obtains dilute HCl which is difficult to reuse, and has lower overall economic benefit.
The invention of CN101367538B discloses a method for preparing calcium sulfate by using sulfate-containing brine and calcium-containing brine, wherein two refined brines are continuously and uniformly mixed with a circulating liquid of a circulating lifting device in a controlled crystallization reactor to form dihydrate calcium sulfate crystals with larger particle size, and then the dihydrate calcium sulfate crystals are settled, centrifugally washed and dried to prepare a high-purity dihydrate calcium sulfate product. Although the harmless treatment of the calcium-containing waste liquid is novel in process, the average particle size of the finally obtained calcium sulfate dihydrate is 0.1-0.3 mm, the content of the dried calcium sulfate can reach more than 98 percent, and the requirement of GB1852-2007 on calcium sulfate as a food additive is met, the calcium sulfate-containing waste liquid needs to be firstly refined with sulfate-containing brine and calcium-containing brine in advance,special reaction equipment such as a crystallization control reactor and a circulation lifting device is required, the maintenance cost is high, the process condition is harsh, and SO is generated4 2-And Ca2+The molar ratio is strictly controlled at 1:1, which is difficult to control accurately in practical production, and SO is contained in bittern containing sulfate4 2-The mass concentration is low, and in actual production, a crystallization reactor and a matched settler, a delivery pump and a pipeline are large, so that the investment is high. In addition, the invention does not apply mathematical algorithm to realize automatic control, which is not beneficial to the process control of large-scale production, so the invention can not be simply used for the environmental-friendly wastewater treatment project with strict requirements on investment and operation cost.
In summary, it is an urgent need to solve the problem to find a harmless and recycling treatment process for preparing a high-quality calcium sulfate product by using calcium-containing waste liquid generated by acid leaching and purifying fluorite concentrate.
Disclosure of Invention
Aiming at the problems, the invention provides a method for preparing a calcium sulfate product by using calcium-containing waste liquor of fluorite ore. Wherein, the fluorite concentrate is acid-leached and purified to produce calcium (mainly CaCl)2) The waste liquid is obtained by mechanical crystallization technique by adding SO4 2-Ionic solution of Ca2+The calcium sulfate is transformed into the form of crystalline calcium sulfate to be separated out, so that a high-quality crystalline calcium sulfate product with a certain particle size is obtained, the whole process is simple and easy to implement, and the method is a method for effectively utilizing resources and reducing pollution.
The specific scheme of the invention is as follows:
a method for preparing calcium sulfate by using calcium-containing waste liquor of fluorite ore comprises the following steps:
s1: mixing calcium-containing waste liquor and SO-containing waste liquor of fluorite ore4 2-Sequentially adding the ionic solution into a reaction container to perform crystallization precipitation reaction;
s2: controlling the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction to obtain calcium sulfate crystal slurry;
s3: filtering, leaching and drying the calcium sulfate crystal slurry obtained in the step S2 to obtain a solid phase product which is a needle-shaped or whisker-shaped sponge body of calcium sulfate, wherein the filtrate is dilute hydrochloric acid, the average particle size of the calcium sulfate is more than or equal to 150um, the dry-base purity is more than or equal to 95 percent, and the whiteness is more than or equal to 90 percent;
further, the method further includes S4: and concentrating the dilute hydrochloric acid obtained in the step S3, and returning the concentrated hydrochloric acid to the fluorite concentrate acid leaching tank for recycling.
Further, the production manner of step S1 is continuous production or batch production.
In the invention, the continuous production efficiency is high, but the grain size of the crystal is usually slightly smaller than that of the intermittent production, on the contrary, the grain size of the crystal produced by the intermittent production is better controlled, but the production efficiency is low.
Further, in step S1, the SO is contained4 2-The ionic solution may be sulfuric acid, or various water-soluble sulfates such as sodium sulfate, magnesium sulfate, and potassium sulfate.
Further, in step S1, the reaction vessel may be a beaker, a sedimentation tank, a stirred tank, a reaction kettle or a crystallizer.
Further, in step S2, Ca in the calcium-containing waste liquid of fluorite ore2+The mass percent of the ions is 2-25%, and the SO is contained4 2-SO in solution of ions4 2-The mass percentage of the ions is 1 to 50 percent; the Ca2+Ions with said SO4 2-The molar ratio of the ions is 1:1.1 to 1: 0.7.
Further, in step S2, the calcium-containing waste liquid and the SO-containing waste liquid are controlled4 2-Controlling the crystallization rate of calcium sulfate in the crystallization precipitation reaction by the feeding rate of the ionic solution and/or the crystallization precipitation reaction time of the calcium sulfate, wherein the feeding rate of the calcium-containing waste liquid is not higher than 45 Kg/(m) calculated according to the effective volume of the reaction container3H) the SO content4 2-The ionic solution is fed at a rate not higher than 105 Kg/(m)3H), the crystallization precipitation reaction time of the calcium sulfate is not less than 3 h. The larger the amount of the added material in unit volume per unit time is, the faster the precipitation reaction rate is, the more crystal nuclei are formed, and the more crystal nuclei are formed and leveled under the condition that the solute amount of the calcium sulfate is the sameThe less solute is distributed to each crystal nucleus for growth, so that the smaller the final crystal grains are, the larger the crystal cannot grow.
Further, in step S2, the generation amount of calcium sulfate crystal nuclei is controlled by adjusting the stirring speed of the reaction vessel, wherein the stirring speed is controlled to be 0 to 2 m/S.
In the present invention, the faster the stirring rate, the smaller the crystal size, and vice versa. However, the stirring rate is too low, resulting in uneven mixing and insufficient reaction. Generally, under other process conditions favorable for crystal growth, in a common beaker or reaction kettle without a special structure, if the stirring linear velocity reaches more than 2m/s, the average particle size of the calcium sulfate is only 30-40 um; under the same condition, if the stirring linear velocity is preferably controlled to be 0.8-1.2 m/s, the average grain diameter of the calcium sulfate crystal can reach 80-400 microns, preferably 150-400 microns.
Further, the stirring speed of the reaction vessel is adjusted by the process parameters such as the average particle size of calcium sulfate obtained by detection, the solid-liquid mass ratio of the crystal slurry circulation zone and the like.
In the present invention, the factor affecting the crystallization rate of calcium sulfate or the growth amount of calcium sulfate crystal nuclei is actually the distribution environment of the flow field inside the reaction vessel, which depends mainly on the feed rate of the calcium-containing waste liquid, the SO-containing waste liquid, and the distribution environment of the flow field inside the reaction vessel as explained above4 2-The feeding speed of the ionic solution, the stirring speed and other means are used for obtaining the environment which is beneficial to the growth of the calcium sulfate crystal.
Furthermore, the purpose of adjusting the internal flow field of the reaction vessel is to promote the formation of a flow field environment which inhibits the generation of crystal nuclei and promotes the growth of crystals inside the reaction vessel, and the flow field environment is expressed as Ca in the flow field2+Concentration gradient and SO4 2-The concentration gradient is relatively gentle, the solid-liquid mass ratio of the crystal slurry circulation area is relatively high, the solid-liquid mass ratio of the crystal growth area is very low, the fluid of the crystal growth area is basically not influenced by the stirring speed of the stirrer, and the calcium sulfate supersaturated solution is ensured to have a metastable area suitable for crystal growth, because the slower the fluid flows, the more the calcium sulfate crystal nucleus can be ensured not to be protected by the calcium sulfate crystal nucleusSecondary collision damage (thereby preventing the formation of more new nuclei and promoting the distributed growth of limited solute onto a smaller number of nuclei) promotes the growth of calcium sulfate crystals.
Further, in step S1 or S2, calcium sulfate seed crystals are added in a molar percentage of 1 to 10% for increasing the growth rate of calcium sulfate crystals, based on the total amount of said theoretically generated needle-like or whisker-like sponge of calcium sulfate.
Further, in step S2, the reaction temperature of the calcium sulfate crystals is controlled to be 10 ℃ to 120 ℃, and the mass percentage of the calcium sulfate crystals in the calcium sulfate crystal slurry is 1% to 25%.
Further, in step S3, the calcium sulfate crystal slurry is rapidly filtered and leached, and the filtering time is controlled to be 90-120S under vacuum negative pressure, so as to obtain a filter cake with a water content of less than 15%, wherein the material of the filter screen for filtering is filter paper or filter cloth with an aperture of 80-200 meshes, the leaching water used for leaching is tap water or deionized water, and the amount of the leaching water is 10-100% of the volume of the calcium sulfate crystal.
Further, in step S3, the needle-shaped or whisker-shaped calcium sulfate sponge is a high-quality calcium sulfate product, including but not limited to, building gypsum, cement retarder, modeling material, paper filler, paint filler, sewage treatment catalyst, food additive, medical gypsum, and the like.
Further, in step S3, in the filtrate, the mass percentage of the dilute hydrochloric acid is 1% to 16%, and the residual Ca is2+The mass percentage of the component (A) is 0.2-5%.
The invention has the following beneficial technical effects:
1. the invention obviously improves the treatment process of the calcium-containing waste liquid generated by acid leaching and purifying fluorite concentrate in the prior art. Because the existing treatment process usually obtains calcium sulfate solid with smaller particle size (5-20 microns), the post-treatment processes such as filtration, drying and the like are not smooth, the processes are more complicated, the efficiency is low and the energy consumption is high; in addition, the calcium sulfate solid is easy to agglomerate, has high impurity content and cannot be converted into high-quality calcium sulfate products with higher use value, such as medical gypsum or food additives, and the like, so that the conventional calcium-containing waste liquid treatment process in the prior art has low added value and low economic benefit. The calcium sulfate crystal with large particle size obtained on the basis of the invention is a calcium sulfate needle-shaped or whisker-shaped sponge body, the physical and chemical properties of the calcium sulfate crystal can reach that the average particle size is more than or equal to 150um, the dry-basis purity is more than or equal to 95 percent, and the whiteness is more than or equal to 90 percent, thus being a high-quality calcium sulfate product.
2. The invention utilizes the mechanical crystallization technology to carry out harmless process treatment on the calcium-containing waste liquid of fluorite ore. In the process, the crystallization rate of calcium sulfate is controlled by a certain means: (1) controlling the growth rate of calcium sulfate crystals by controlling the raw material feeding rate and/or the crystallization precipitation reaction time of calcium sulfate; (2) the generation quantity of calcium sulfate crystal nucleus is controlled by adjusting the stirring speed and the internal flow field of the reaction container, and high-quality calcium sulfate crystal can be obtained by any one or combination of the two.
3. The method has the advantages of simple process flow, simple and smooth operation, less investment, low energy consumption, low operation cost and good project benefit, and realizes CaCl2Innocent treatment and resource utilization of the acid waste liquid, and avoiding a large amount of CaCl2The acid waste liquid brings huge ecological environment potential safety hazard to the surrounding environment of a factory, the use of fresh hydrochloric acid on fluorite ore is greatly reduced or stopped, and the safe operation environment of fluorite ore flotation production is improved. The invention relates to calcium-containing waste liquid, in particular to CaCl generated by fluorite ore beneficiation2The harmless resource treatment of the waste liquid provides a new technology and a new idea, and has high application and popularization values and investment values.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention;
FIGS. 2 a-2 b are SEM images of the white acicular gypsum product of example 1; FIG. 2a is a 200-fold SE plot and FIG. 2b is a 500-fold SE plot.
Examples
The invention is illustrated in detail below with reference to examples:
example 1
The method comprises the following specific steps:
s1: calcium-containing waste liquor of fluorite ore and dilute sulphuric acid are sequentially added into a crystallizer for crystallization and precipitation reaction,
ca in calcium-containing waste liquor of fluorite ore2+Is 12.49 percent by mass, and the mass percent of dilute sulfuric acid is 10 percent by mass, wherein, Ca2+Ions and SO4 2-The molar ratio of ions is 1: 0.7;
s2: the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction is controlled by the following means to obtain calcium sulfate crystal slurry,
wherein the feeding rate of the calcium-containing waste liquid is controlled to be 23.5 kg/(m) at room temperature3H) the feed rate of dilute sulfuric acid was 56 kg/(m)3H), the crystallization precipitation reaction time of the calcium sulfate is 5h, and the stirring linear velocity of the crystallizer is 0.8 m/s;
s3: rapidly filtering the calcium sulfate crystal slurry obtained in the step S2 through 120-mesh common filter cloth, leaching for 1 time with tap water, wherein the water consumption is 20% of the volume of the calcium sulfate crystal, so as to obtain a filter cake with the water content of 10.83%, and the filtrate is dilute hydrochloric acid;
drying the filter cake at 80 deg.C to obtain white acicular gypsum product with average particle diameter of 155um and whiteness of 91.71, and beta-CaSO4·1/2H2The content of O reaches 95.57 percent by mass, and the gypsum can be made into various building gypsum or model gypsum through simple processing;
s4: the filtrate obtained in the step S3 contains 3.5% by mass of HCl and residual Ca2+After the diluted hydrochloric acid with the mass percentage of 1.89% is concentrated to 15% of HCl mass percentage, the diluted hydrochloric acid returns to a fluorite concentrate acid leaching tank for recycling.
As can be seen from the SEM images of FIGS. 2 a-2 b at different magnifications, the dihydrate gypsum product of example 1 has fibrous crystals, which are formed by the aggregation of a plurality of fine needle-like crystals, and has a length of about 400 microns and a width of about 50 microns, which is consistent with the shape of natural gypsum crystals.
Example 2
The method comprises the following specific steps:
s1: will predict the production of the resulting CaSO4The seed crystal of 5 percent (mol percentage), the calcium-containing waste liquor of fluorite ore and dilute sulphuric acid are sequentially added into a stirring tank for crystallization and precipitation reaction, and the production methodThe formula is a batch production method,
ca in calcium-containing waste liquor of fluorite ore2+19.81% by mass and 20% by mass of dilute sulfuric acid, wherein Ca is2+Ions and SO4 2-The molar ratio of ions is 1: 1;
s2: the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction is controlled by the following means to obtain calcium sulfate crystal slurry,
wherein, the crystallization precipitation reaction time of the calcium sulfate is controlled to be 3 hours at the temperature of 45 ℃, and the stirring linear velocity of the stirring tank is controlled to be 0.8 m/s;
s3: rapidly filtering the calcium sulfate crystal slurry obtained in the step S2 through a common filter cloth of 200 meshes, leaching for 2 times with tap water, wherein the water consumption is 50% of the volume of the calcium sulfate crystal, so as to obtain a filter cake with the water content of 14.70%, and the filtrate is dilute hydrochloric acid;
drying the filter cake at 80 deg.C to obtain white acicular gypsum product with average particle size of 202um and whiteness of 91.83, and its product beta-CaSO4·1/2H2The content of O reaches 85.32 percent by mass, and the gypsum can be made into various building gypsum or model gypsum through simple processing;
s4: the filtrate obtained in the step S3 contains 9.30% by mass of HCl and residual Ca2+After the dilute hydrochloric acid with the mass percent of 0.15% is concentrated to the mass percent of HCl of 15%, the dilute hydrochloric acid returns to the fluorite concentrate acid leaching tank for recycling.
Example 3
The method comprises the following specific steps:
s1: will predict the production of the resulting CaSO4The seed crystal of 2 percent (mol percentage), the calcium-containing waste liquid of fluorite ore and dilute sulphuric acid are sequentially added into a reaction kettle for crystallization and precipitation reaction, the production mode is intermittent production,
ca in calcium-containing waste liquor of fluorite ore2+Is 24.85 percent by mass, and the mass percent of dilute sulfuric acid is 50 percent by mass, wherein, Ca2+Ions and SO4 2-The molar ratio of ions is 1: 0.95;
s2: the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction is controlled by the following means to obtain calcium sulfate crystal slurry,
wherein the crystallization precipitation reaction time of calcium sulfate is controlled to be 24 hours at 115 ℃, and the stirring linear velocity of the reaction kettle is 0.8-1.0 m/s;
s3: rapidly filtering the calcium sulfate crystal slurry obtained in the step S2 through a common filter cloth of 100 meshes, leaching for 5 times by using deionized water, wherein the water consumption is 100% of the volume of the calcium sulfate crystal, so as to obtain a filter cake with the water content of 8.20%, and the filtrate is dilute hydrochloric acid;
drying the filter cake at 80 deg.C to obtain white acicular gypsum product with average particle size of 190um and whiteness of 92.77, and its product beta-CaSO4·1/2H2The content of O reaches 99.7 percent by mass, and the gypsum can be used as a raw material for preparing model gypsum, filler gypsum or medical gypsum;
s4: the filtrate obtained in the step S3, wherein the HCl content is 15.67 percent by mass and the residual Ca is2+The dilute hydrochloric acid with the mass percentage of 0.62 percent is directly returned to the fluorite concentrate acid leaching tank for recycling.
Example 4
The method comprises the following specific steps:
s1: will predict the production of the resulting CaSO4The seed crystal of 8 percent (mol percentage), the calcium-containing waste liquid of fluorite ore and dilute sulphuric acid are sequentially added into a beaker for crystallization and precipitation reaction, the production mode is one-time reaction,
ca in calcium-containing waste liquor of fluorite ore2+9.41 percent by mass and 10 percent by mass of dilute sulfuric acid, wherein Ca is2+Ions and SO4 2-The molar ratio of ions is 1:0.9, and the feeding mode is that dilute sulphuric acid is slowly dripped into calcium-containing waste liquid;
s2: the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction is controlled by the following means to obtain calcium sulfate crystal slurry,
wherein the crystallization precipitation reaction time of calcium sulfate is controlled to be 12 hours at 95 ℃, and the stirring linear velocity of the crystallizer is 0.5-0.8 m/s;
s3: rapidly filtering the calcium sulfate crystal slurry obtained in the step S2 through a common filter cloth of 80-120 meshes, leaching for 3 times by using deionized water, wherein the water consumption is 60% of the volume of the calcium sulfate crystal, the filtering time is controlled to be 120S under vacuum negative pressure, a filter cake with the water content of 8.20% is obtained, and the filtrate is dilute hydrochloric acid;
drying the filter cake at 80 deg.C to obtain white needle-like gypsum sponge product with average particle diameter of 390um and whiteness of 93.29, and beta-CaSO4·1/2H2The content of O reaches 99.9 percent by mass, and the gypsum can be used as a raw material for preparing model gypsum, filler gypsum or medical gypsum;
s4: the filtrate obtained in the step S3 contains 2.67% by mass of HCl and residual Ca2+The diluted hydrochloric acid with the mass percentage of 0.20 percent is concentrated until the HCl mass percentage is 15 percent, and then the diluted hydrochloric acid is returned to the fluorite concentrate acid leaching tank for recycling.
Example 5
S1: will predict the production of the resulting CaSO4The seed crystal of 10 percent (mol percentage), the calcium-containing waste liquid of fluorite ore and dilute sulphuric acid are sequentially added into a sedimentation tank with stirring to carry out crystallization and sedimentation reaction, the production mode is one-time reaction,
ca in calcium-containing waste liquor of fluorite ore2+Is 12.49 percent by mass, and the mass percent of dilute sulfuric acid is 10 percent by mass, wherein, Ca2+Ions and SO4 2-The molar ratio of ions is 1:1.05, and the feeding mode is that dilute sulphuric acid is slowly dripped into calcium-containing waste liquid;
s2: the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction is controlled by the following means to obtain calcium sulfate crystal slurry,
wherein, the crystallization precipitation reaction time of the calcium sulfate is controlled to be 5 hours at normal temperature, and the stirring linear velocity of the crystallizer is 0.5-0.8 m/s;
s3: rapidly filtering the calcium sulfate crystal slurry obtained in the step S2 through a common filter cloth of 80-120 meshes, leaching for 3 times by using deionized water, wherein the water consumption is 60% of the volume of the calcium sulfate crystal, the filtering time is controlled to be 120S under vacuum negative pressure, a filter cake with the water content of 8.15% is obtained, and the filtrate is dilute hydrochloric acid;
drying the filter cake at 80 deg.C to obtain white needle-like gypsum sponge product with average particle diameter of 185um and whiteness of 93.10, and beta-CaSO4·1/2H2The content of O reaches 99.5 percent by mass, and the gypsum can be used as model gypsum,Preparing raw materials of filler gypsum or medical gypsum;
s4: the filtrate obtained in the step S3 contains 2.80% by mass of HCl and residual Ca2+The diluted hydrochloric acid with the mass percentage of 0.20 percent is concentrated until the HCl mass percentage is 15 percent, and then the diluted hydrochloric acid is returned to the fluorite concentrate acid leaching tank for recycling.
Comparative example 1
S1: 9.41 percent of calcium-containing waste liquor of fluorite ore and 10 percent of dilute sulfuric acid according to molar ratio of CaCl2:H2SO4Sequentially adding the diluted sulfuric acid into a beaker according to the ratio of 1:0.9, wherein the reaction mode is one-time reaction, and the feeding mode is that the diluted sulfuric acid is quickly added into the calcium-containing waste liquid at one time;
s2: controlling the stirring linear speed to be 5m/s at the reaction temperature of 95 ℃, and reacting for about 30min to obtain calcium sulfate crystal slurry;
s3: filtering and leaching the calcium sulfate crystal slurry obtained in the step S2, wherein the material of a filter screen is ordinary filter paper of 80-120 meshes, leaching is carried out for 1 time, the leaching water is deionized water, the water consumption is 10% of the volume of the calcium sulfate crystal, the vacuum negative pressure value reaches 0.09MPa during filtering, a filtered filter cake and a filtered filtrate are obtained after filtering for 13min, and the free water content of the filter cake is 26.80%;
drying the filter cake at 80 ℃ to obtain a white whisker-shaped gypsum sponge product with the whiteness of 82.56 and the average particle size of 18um, namely the product beta-CaSO4·1/2H2The mass content of O reaches 79.17 percent;
s4: the filtrate obtained in step S3 is dilute hydrochloric acid, wherein the mass percent of HCl is 3.05%, and the residual Ca is2The weight percentage of the hydrochloric acid is 0.29 percent, and the diluted hydrochloric acid is concentrated to 15 percent of HCl by weight percentage and then returned to a fluorite concentrate leaching tank for calcium removal and purification of fluorite concentrate.
Comparative example 2
S1: calcium-containing waste liquor of fluorite ore with the mass percent of 12.49 percent and dilute sulphuric acid with the concentration of 10 percent are mixed according to the molar ratio of CaCl2:H2SO4Sequentially adding 1:1.05 into a beaker, wherein the reaction mode is one-time reaction, and the feeding mode is that dilute sulfuric acid is rapidly added with CaCl at one time2In waste liquid;
s2: at normal temperature, controlling the stirring linear velocity to be 3m/s, and reacting for about 30min to obtain calcium sulfate crystal slurry;
s3: and (5) filtering and leaching the calcium sulfate crystal slurry obtained in the step (S2), wherein the material of a filter screen is ordinary filter paper of 80-120 meshes, leaching is carried out for 1 time, the leaching water is tap water, the water consumption is 10% of the volume of the calcium sulfate crystal, the vacuum negative pressure value reaches 0.09MPa during filtering, a filtered filter cake and a filtrate are obtained after filtering for 20min, and the free water content of the filter cake is 31.70%.
Drying the filter cake at 80 deg.C to obtain white whisker-shaped gypsum sponge product with whiteness of 80.39, average particle diameter of 12um, and beta-CaSO4·1/2H2The mass content of O reaches 77.98 percent.
S4: the filtrate obtained in step S3 is dilute hydrochloric acid, wherein the HCl content is 3.23% by mass, and the residual Ca is2The weight percentage of the hydrochloric acid is 0.18 percent, and the diluted hydrochloric acid is concentrated to dilute hydrochloric acid with 15 percent of HCl weight percentage and then returned to a fluorite concentrate leaching tank for calcium removal and purification of fluorite concentrate.
The experimental data of examples 1 to 5 according to the invention are compared with comparative examples 1 to 2 in Table 1.
TABLE 1 comparison of the experimental data of inventive examples 1 to 5 and comparative examples 1 to 2
As can be seen from the data in Table 1, the particle size numerical value which is several times to tens times larger than that of the existing calcium sulfate gypsum crystal is obtained by improving the process parameters of the existing calcium-containing waste liquid of fluorite ore, particularly by means of controlling the raw material feeding rate and/or the calcium sulfate crystallization precipitation reaction time, adjusting the stirring rate of a reaction container, the internal flow field and the like, and the whiteness and the purity of the calcium sulfate product are also obviously improved, so that the calcium sulfate gypsum product is endowed with higher quality and use value; meanwhile, the improved treatment process has the advantages of simple flow, simple and convenient operation, high efficiency, low energy consumption, application and popularization value and investment value.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, but any modifications or equivalent variations made according to the technical spirit of the present invention are within the scope of the present invention as claimed.
Claims (10)
1. A method for preparing calcium sulfate by using calcium-containing waste liquor of fluorite ore is characterized by comprising the following steps:
s1: mixing fluorite ore with calcium-containing waste liquid and SO-containing waste liquid4 2-Sequentially adding the ionic solution into a reaction container to perform crystallization precipitation reaction;
s2: controlling the crystallization rate of calcium sulfate generated in the crystallization precipitation reaction to obtain calcium sulfate crystal slurry;
s3: and (4) filtering, leaching and drying the calcium sulfate crystal slurry obtained in the step (S2) to obtain a solid phase product which is a needle-shaped or whisker-shaped sponge of calcium sulfate dihydrate, wherein the filtrate is dilute hydrochloric acid, the average particle size of the calcium sulfate is more than or equal to 150 mu m, the dry-basis purity is more than or equal to 95 percent, and the whiteness is more than or equal to 90.
2. The method according to claim 1, further comprising S4: and concentrating the dilute hydrochloric acid filtrate obtained in the step S3, and returning the concentrated hydrochloric acid filtrate to the fluorite concentrate acid leaching tank for recycling.
3. The method according to claim 1, wherein the production mode of step S1 is continuous production or batch production.
4. The method of claim 1, wherein in step S2, Ca is contained in the calcium-containing waste liquid of fluorite ore2+The mass percent of the ions is 2-25%, and the SO is contained4 2-SO in solution of ions4 2-The mass percentage of the ions is 1 to 50 percent; the Ca2+Ions with said SO4 2-The molar ratio of the ions is 1:1.1 to 1: 0.7.
5. The method of claim 4, wherein the calcium-containing waste liquid and the SO-containing waste liquid are controlled in step S24 2-Controlling the crystallization rate of calcium sulfate in the crystallization precipitation reaction by the feeding rate of the ionic solution and/or the crystallization precipitation reaction time of the calcium sulfate, wherein the feeding rate of the calcium-containing waste liquid is not higher than 45 Kg/(m) calculated according to the effective volume of the reaction container3H) the SO content4 2-The ionic solution is fed at a rate not higher than 105 Kg/(m)3H), the crystallization precipitation reaction time of the calcium sulfate is not less than 3 h.
6. The method of claim 4, wherein in step S2, the generation amount of calcium sulfate crystal nuclei is controlled by adjusting the stirring speed of the reaction vessel, and the stirring linear speed is controlled to be 0 to 2 m/S.
7. The method according to claim 1, wherein in step S1 or S2, calcium sulfate seed crystals are added in a molar percentage of 1% to 10% for increasing the crystallization rate of calcium sulfate, based on the total amount of said needle-like or whisker-like sponge of calcium sulfate theoretically produced.
8. The method according to claim 1, wherein in step S2, the reaction temperature of the calcium sulfate crystals is controlled to 10 ℃ to 120 ℃, and the mass percentage of the calcium sulfate crystals in the calcium sulfate crystal slurry is 1% to 25%.
9. The method according to claim 1, wherein in step S3, the calcium sulfate crystal slurry is rapidly filtered and leached, and the filtering time is controlled to be 90-120S under vacuum negative pressure, so as to obtain a filter cake with a water content of less than 15%, wherein the material of the filter screen for filtering is filter paper or filter cloth with a pore size of 80-200 meshes, the leaching water used for leaching is tap water or deionized water, and the amount of water used for leaching is 10-100% of the volume of the calcium sulfate crystal.
10. The method according to claim 9, wherein in step S3, the filtrate contains 1-16% by weight of dilute hydrochloric acid and residual Ca2+The mass percentage of the component (A) is 0.2-5%.
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