Receiving and dissolving calcium carbonate. Big encyclopedia of oil and gas

The invention relates to the chemical technology of nitric acid processing of phosphate raw materials to obtain calcium carbonate by conversion of calcium nitrate in the production of NPK fertilizers. The method of obtaining calcium carbonate includes: interaction of calcium nitrate with a solution of ammonium carbonate, precipitation of the target product from the suspension, washing it, heat treatment at temperatures of 400 ... 700 ° C and grinding. The invention makes it possible to simplify the technology of processing calcium carbonate, a by-product in the production of NPK fertilizers into a filler for use in various industries. 1 wp f-ly, 2 tab.

The method relates to the chemical technology of nitric acid processing of phosphate raw materials to obtain calcium carbonate by converting calcium nitrate in the production of NPK fertilizers.

The invention can find application in the production of calcium carbonate used as a filler in polymer, paint and varnish and other industries.

Calcium carbonate is a by-product in the production of NPK fertilizers such as nitroammofoska, and its production is based on the interaction (conversion) of a calcium nitrate solution with an ammonium carbonate solution:

Ca (NO 3) 2 + (NH 4) 2 CO 3 → CaCO 3 ↓ + 2NH 4 NO 3

The resulting precipitate of calcium carbonate is isolated and washed on filters from the mother liquor and dried. The finished product is a fine powder containing up to 97% of the main substance (Complex nitric acid processing of phosphate raw materials / Goldinov A.L., Kopylev B.A. et al. - L .: Chemistry, 1982. - 207 p.).

One of the disadvantages of the method is the inevitable in production conditions contamination of the obtained calcium carbonate with water-soluble nitrogen-containing compounds of the mother liquor (NH 4 NO 3, Ca (NO 3) 2, (NH 4) 2 CO 3, NH 3, etc.). The presence of water-soluble impurities limits the use of the product as a filler in the production of plastics, paints and varnishes, industrial rubber goods and other materials, since in this case their interaction with organic substances is possible, thermal decomposition during elevated temperatures, deterioration of the operational properties of filled products. In addition, the presence of hygroscopic salts NH 4 NO 3 and Ca (NO 3) 2 can lead to loss of flowability of calcium carbonate during transportation and storage, complicate its dosage and dispersion.

A known method for producing calcium carbonate with a low content of water-soluble impurities (RU 2281921 C1, publ. 20.08.2006). According to this method, calcium carbonate is obtained at 50-80 ° C and an excess of an ammonium carbonate solution of 0.05-0.5% in terms of CO 2 free, the concentration of the calcium nitrate solution is maintained within 10-13% by dilution with a solution of ammonium nitrate. The precipitate isolated by filtration is washed and dried. Washing is carried out at the ratio S: W - (1-3): 1 in one or two stages with the supply of filtrate from the second stage to the first, which allows to reduce the content of ammonium water-soluble impurities in calcium carbonate to 0.03-0.2% in terms of for ammonium nitrate.

The disadvantages of this method include an increase in the load on the equipment due to the introduction of additional amounts of ammonium nitrate solution into the process and incomplete washing of water-soluble impurities.

Incomplete washing is due to the fact that during mass crystallization at high values ​​of supersaturation, the rapid growth of calcium carbonate particles proceeds by the polynuclear mechanism with the formation of particles in the form of spherical polycrystalline intergrowths. In this case, bulk sorption (occlusive capture) of the mother liquor in the intercrystalline space and internal pores of growing particles of calcium carbonate inevitably occurs. In this case, increasing the efficiency of washing the calcium carbonate precipitate by displacement or dilution will not lead to complete removal of the captured water-soluble impurities. Since the resulting calcium carbonate does not meet the requirements for fillers in its dispersed composition, fine grinding is an obligatory stage for its use in this direction. When the particles are destroyed, the intercrystalline cavities will open up and the previously occluded impurities will emerge onto the resulting surface, which will increase the content of water-soluble compounds in the crushed product. In turn, the organization of an additional stage of washing already crushed product cannot be recognized rational decision the issue due to difficulties with filtration and washing of ultrafine particles, complication of the technological scheme, the need to utilize wash water, etc. Similar problems will arise when using grinding in aquatic environment.

The closest in essence to the proposed method is a method of obtaining precipitated calcium carbonate from calcium carbonate obtained in the production of NPK fertilizers (US 6790424 B2, publ. 09/14/2004), by carrying out the following successive stages:

Obtaining calcium carbonate in the production of NPK fertilizers;

Heat treatment of wet calcium carbonate for 30-90 minutes at temperatures of 850-950 ° C to obtain calcium oxide CaO;

Absorption of water vapor and gases (СО 2, NH 3, NOx) emitted during firing in a scrubber;

Grinding and cooling the fired product to 40-50 ° С;

Quenching with water to obtain a suspension of milk of lime with a concentration of 15 ... 23% in solid phase;

Removing heavy particles from lime milk suspension by sedimentation, or wet screening through a 60-100 mesh sieve, or both;

Dilution of a suspension of milk of lime to a solids content in the range of 10 ... 20%;

Carbonization of milk of lime at 25 ... 45 ° C with a gas mixture of CO 2 - air with a volume fraction of CO 2 in the range from 25 to 75% and a flow rate of 10-15 cm / sec through the suspension;

Isolation by filtration or centrifugation of the calcium carbonate precipitate and drying.

The precipitated calcium carbonate obtained by this method has a purity of more than 97%, a brightness of more than 96%, a bulk density of 0.40-0.65 g / ml, the average size particles of 5-20 microns and can be used in the production of plastics, rubber, paints and other products.

The disadvantages of this method are the complexity and multistage nature of the process, the need to use additional substances to obtain the product - carbon dioxide and water.

The problem to be solved by the invention is to simplify the technology for processing calcium carbonate - a by-product in the production of NPK fertilizers into a filler for use in various industries.

The technical result consists in simplifying the method for producing calcium carbonate that meets the requirements for dispersed fillers for plastics, varnishes, paints and other products.

The technical result is achieved by the fact that in the proposed method, including the interaction of a solution of calcium nitrate with a solution of ammonium carbonate, the isolation and washing of the sediment of the target product, heat treatment and grinding, heat treatment of calcium carbonate is carried out at a temperature of 400-700 ° C.

The difference between the method is carrying out heat treatment at temperatures of 400-700 ° C. In this case, wet calcium carbonate is subjected to heat treatment after washing or pre-dried to a moisture content of less than 1%.

A sample of calcium carbonate obtained in the operating production of NPK fertilizers with a residual moisture content of 11.5% after filtration and washing is subjected to heat treatment at different temperatures in a muffle furnace. The processing time is kept constant at 1 hour. The sample after heat treatment is ground for 10 minutes in a laboratory vibration mill to a fineness corresponding to 100% passage through a sieve with a mesh size of 45 μm. The crushed product is analyzed for the content of water-soluble nitrogen-containing impurities, both their total content, taking into account bound forms by complete acid decomposition of the sample, and in a surface-bound form using aqueous extraction. The pH of the aqueous suspension is also measured. For comparison, a similar analysis of a crushed sample of calcium carbonate is carried out without preliminary heat treatment. The results are shown in Table 1.

The experiments are carried out as described in Example 1, but calcium carbonate, previously dried to a moisture content of 1%, is taken as an initial sample (Table 2).

Removal of water-soluble nitrogen-containing impurities both in an accessible surface-adsorbed form and in a bound occluded form by heat treatment makes it possible to obtain, when grinding calcium carbonate, a product that meets the requirements for fillers in terms of the content of water-soluble impurities. Apparently, the decrease in the content of water-soluble impurities is due to the thermal instability of nitrogen-containing compounds at high temperatures. It is known (Technology mineral salts... Part 2 / Pozin M.E. et al. - Chemistry, 1970. - 1558 p.) That a noticeable decomposition of ammonium nitrate begins at ~ 150 ° C, and the process proceeds intensively when heated above 200 ° C. At 500 ° C and above, calcium nitrate completely dissociates into CaO and NO 2.

The lower limit of the declared temperature range of heat treatment is 400 ° C, since at this temperature there is a noticeable decrease in the content of water-soluble substances in the resulting product. The upper limit of the declared range is limited to a temperature of 700 ° C, since at more high temperature, as can be seen from the results, the dissociation of calcium carbonate becomes noticeable, which is evident from the increase in pH.

Obtained by the proposed method, calcium carbonate has the following physicochemical properties: average particle size ~ 5 microns, sieve residue No. 045 no more than 0.1%, whiteness ~ 95%, bulk density 0.6-0.7 g / cm 3, the content of water-soluble impurities is less than 0.1% and can be used as a dispersed filler in the production of plastics, paints and varnishes and other products.

Thus, at a temperature of heat treatment in the range of 400 ... 700 ° C, a solution to the problem is provided, both for wet calcium carbonate and pre-dried. The limitation of the upper limit of moisture content of dry calcium carbonate 1% is associated with the deterioration of its properties at more high humidity, which is manifested in the loss of flowability and clumping of the product during storage and transportation.

1. A method of obtaining calcium carbonate, including the interaction of calcium nitrate with a solution of ammonium carbonate, the separation of the sediment of the target product from the suspension, its washing, heat treatment, grinding, characterized in that the heat treatment is carried out at 400-700 ° C.

2. A method according to claim 1, characterized in that the calcium carbonate is dried to a moisture content of less than 1% before heat treatment.

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The invention relates to chemical technology, in particular to the production of highly dispersed calcium carbonate CaCO3, - calcium carbonate, which is an extremely important intermediate for various branches of chemical and other industries

The invention can be used in the chemical, paint and varnish and paper industries. For the manufacture of aqueous mineral materials a) provide at least one mineral material in the form of an aqueous suspension or in dry form, b) provide at least one partially or completely lithium-neutralized water-soluble organic polymer selected from the group of acrylic homopolymers or methacrylic acid and / or copolymers of acrylic and / or methacrylic acid with one or more acrylic, vinyl or allyl monomers, the mole fraction of non-neutralized acid groups being in the range from 0% to 10%, c) combining at least one partially or a fully lithium-neutralized water-soluble organic polymer from step b) with at least one mineral material from step a). The obtained mineral materials or their aqueous suspensions are used in the production of paper, plastics and paints. The invention allows to obtain a material having a stable pH, low Brookfield viscosity, which remains stable over time, and requiring a reduced content of dispersant and / or grinding agent. 8 n. and 26 p.p. f-crystals, 13 tab., 13 ex.

The invention can be used in the chemical industry. A method for the production of calcium carbonate-containing materials, the surface of the particles of which has improved adsorption properties of the dispersant, includes the following steps: a) obtaining at least one calcium carbonate-containing material in the form of an aqueous suspension or in dry form; b) obtaining at least one lithium ion-containing compound selected from the group consisting of lithium hydroxide or lithium oxide, or inorganic and / or organic monomeric lithium salts selected from the group consisting of mono- or polybasic salts acids, for example lithium carbonate, lithium sulfates, lithium citrate, lithium bicarbonate, lithium acetate, lithium chloride, lithium phosphate, in dry form or in aqueous solution, and mixtures thereof; c) a combination of at least one lithium ion-containing compound of step b) and at least one calcium carbonate-containing material of step a). The invention makes it possible to obtain a material containing calcium carbonate in dry form or in the form of a suspension having a high concentration of dry matter and, at the same time, a low Brookfield viscosity, which remains stable over time, and a good buffering capacity with respect to pH. 7 n. and 37 p.p. f-crystals, 2 dwg., 10 tbl., 9 ex.

The invention can be used in biological and medical research. Porous particles of calcium carbonate are formed as a result of the reaction CaCl2 + 2NaHCO3 → CaCO3 ↓ + 2NaCl + 2H +, and an aqueous solution of quantum dots modified with an excess amount of mercaptoacetic acid having a concentration of 0.05-4 mg / ml is poured into 0.3 M NaHCO3 solution. The resulting suspension, containing porous particles of calcium carbonate with included quantum dots, is washed 1-3 times with water and once with ethanol, treated with ultrasound after each washing. Then the resulting particles are coated with polyethyleneimine or 6 layers of water-soluble polyelectrolytes from the series including DEAE-dextran, chitosan, carrageenan. EFFECT: reduced time for obtaining porous calcium carbonate particles with 100% of included quantum dots. 1 wp f-ly, 6 ave.

The invention can be used in the chemical industry in the processing of phosphogypsum - a waste product of extraction phosphoric acid. To obtain high-purity calcium carbonate and nitrogen-sulfate fertilizers, phosphogypsum is converted with an ammonium carbonate solution to obtain a solution of ammonium sulfate and phosphomel. Phosphomel is dissolved in nitric acid, the insoluble residue is separated by filtration from the calcium nitrate solution. Next, the interaction of a solution of calcium nitrate with ammonium carbonate is carried out to obtain a production pulp of calcium carbonate in a solution of ammonium nitrate, the precipitation of high-purity calcium carbonate from it and the processing of the solution of ammonium nitrate into a nitrogen-sulfate fertilizer. The production pulp is divided into two parts, one of which is fed to filtration to separate the precipitate of high-purity calcium carbonate, and the second to preliminary mixing with an ammonium carbonate solution until the concentration of ammonium carbonate in the liquid phase is 4.0-8.0%. In the process of precipitation of high-purity calcium carbonate, the temperature is maintained at 40-45 ° C and the concentration of excess ammonium carbonate in the liquid phase of the pulp is 0.5-1.0%. A solution of ammonium nitrate obtained after separating the precipitate of calcium carbonate is mixed with a solution of ammonium sulfate obtained after the conversion of phosphogypsum, the mixture is evaporated, granulated and dried. The invention improves the efficiency complex processing phosphogypsum, filtration performance at the stage of precipitation of high-purity calcium carbonate, the yield of ammonium nitrate in the liquid phase. 1 wp f-crystals, 2 tbl., 4 ex.

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The invention can be used in the chemical industry. The method for processing phosphogypsum into ammonium sulfate and phosphomel includes the conversion of phosphogypsum with an ammonium carbonate solution, followed by separation of the phosphomelite precipitate from the ammonium sulfate solution by filtration. The conversion is carried out with a solution of ammonium carbonate with a concentration of 3-7%. The conversion slurry is divided into two streams, one of which is directed to the stage of diluting ammonium carbonate to the specified concentration for 3-5 minutes, and the second to filtration to separate the phosphomelite precipitate from the ammonium sulfate solution. The invention allows to increase the yield of ammonium sulfate in the liquid phase of the production pulp on average up to 97.6%, to increase the filtration performance of phosphomel, to simplify the equipment technological process and reduce energy costs. 1 wp f-crystals, 3 tbl., 4 ex.

The invention can be used in the production of household solar collectors. The fluid used as a heat carrier and applicable for converting light radiation into heat contains water and a powdered mineral. Powdered mineral has a high ability to dissipate solar radiation and has a mass concentration of 1% to 3% and an average particle size of 0.8 to 10 µ. Particles of a powdered mineral with a high scattering ability have an average coefficient of light energy dissipation of more than 0.7. Calcium carbonate can be taken as the powdered mineral. The fluid may also contain antifreeze, surfactant, antifoam, and bactericide. The invention improves the absorption capacity of the fluid. 3 n. and 12 p.p. f-ly, 4 pr.

Calcium ... What do you know about it? "This is metal" - only and many will answer. What calcium compounds exist? With this question, everyone will start scratching their heads. Yes, there is not much knowledge about the latter, and about calcium itself, too. Okay, we'll talk about it later, but today let's take a look at at least three of its compounds - calcium carbonate, hydroxide and bicarbonate.

1. Calcium carbonate

It is a salt formed by calcium and carbonic acid residue. The formula of this carbonate is CaCO 3.

Properties

It looks like a white powder, insoluble in water and ethyl alcohol.

Obtaining calcium carbonate

It is formed when calcium oxide is calcined. Water is added to the latter, and then carbon dioxide is passed through the resulting solution. The reaction products are the desired carbonate and water, which are easily separated from each other. If it is heated, then decomposition will occur, the products of which will be carbon dioxide and When this carbonate and carbon monoxide (II) dissolve in water, calcium bicarbonate can be obtained. If you combine carbon and calcium carbonate, the products of this reaction are also carbon monoxide.

Application

This carbonate is the chalk that we regularly see in schools and other primary and higher education institutions. They also whitewash ceilings, paint tree trunks in spring and alkalize the soil in the gardening industry.

2. Calcium hydrogen carbonate

Is Has the formula Ca (HCO 3) 2.

Properties

It dissolves in water, like all hydrocarbons. However, he makes her tough for a while. In living organisms, calcium bicarbonate and some other salts with the same residue have the function of regulators of the constancy of reactions in the blood.

Receiving

It is obtained by the interaction of carbon dioxide, calcium carbonate and water.

Application

It is contained in drinking water, where its concentration can be different - from 30 to 400 mg / l.

3. Calcium hydroxide

Formula - Ca (OH) 2. This substance is a strong base. In various sources it can be called slaked lime or "fluff".

Receiving

Formed when calcium oxide and water interact.

Properties

It is in the form of a white powder, slightly soluble in water. With an increase in the temperature of the latter, the numerical value of solubility decreases. It also has the ability to neutralize acids, with this reaction the corresponding calcium salts and water are formed. If you add carbon dioxide dissolved in water to it, you get the same water, and also calcium carbonate. With continued bubbling of CO 2, the formation of calcium bicarbonate will occur.

Application

They whitewash the premises, wooden fences, and also coat the rafters. With the help of this hydroxide, lime mortar, special fertilizers and silicate concrete are prepared, and carbonate concrete is also removed (soften the latter). By means of this substance, potassium and sodium carbonates are causticized, root canals of teeth are disinfected, leather is tanned and some plant diseases are cured. Calcium hydroxide is also known as food supplement E526.

Conclusion

Now do you understand why I decided to describe these three substances in this article? After all, these compounds "meet" among themselves during the decomposition and receipt of each of them. There are many other related substances, but we'll talk about them another time.

Page 1

Dissolution of calcium carbonate upsets the equilibrium and leads to the decomposition of other components of the cement. Carbonic acid acts similarly on metal pipes. First, carbonates dissolve in it, which are an integral part of rusty-carbonate deposits in the water supply network, then the pipe material undergoes electrochemical corrosion with the formation of new deposits.

Dissolution of calcium and strontium carbonates and separation of Sr2 - ions. The turbidity of the solution indicates the presence of Sr2 - ions in the solution.

The method is based on the dissolution of calcium carbonate in hydrochloric acid and subsequent titration of this solution with alkali.

The method is based on the dissolution of calcium carbonate in hydrochloric acid and subsequent gravimetric determination of the insoluble residue.

Studies have shown that the dissolution of calcium carbonate and, accordingly, the neutralization of the reaction mixture of formalin with ammonium chloride occurs much more slowly and more evenly in comparison with a solution of hydrochloric acid.

Aggressive leaching - occurs due to the dissolution of calcium carbonate and leaching of calcium oxide from betohydrate. Depending on the cement content and the conditions in which the structure is located, the water possesses this aggressiveness with the HCO3 content ranging from 0 4 to 1 5 mg-eq.

Carbon dioxide - causes the destruction of concrete as a result of the dissolution of calcium carbonate under the influence of aggressive carbon dioxide.

We carried out experiments to study the kinetics of calcium carbonate dissolution in Trilon B solutions at different initial pH and different temperatures processing.

Explain, using the solubility product rule, the dissolution of calcium carbonate in water containing carbon dioxide.

In fig. 83 presented the results of experiments on the dissolution of calcium carbonate with a solution of hydrochloric acid obtained by mixing ammonium chloride and formalin in the ratio of 18: 41, depending on time and temperature. For comparison, the same graphs of the dissolution of calcium carbonate in 15% hydrochloric acid are shown. As can be seen from the graphs, even at room temperature, the reaction of limestone with pure hydrochloric acid proceeds very quickly. With an increase in temperature, the reaction proceeds so rapidly that, starting from 60 to 100 C, within 5 min the solubility of the sample reaches more than 80% of the theoretically possible.

The effect of aggressive carbonic acid on concrete is to dissolve calcium carbonate, which is formed during the hardening of cement and transforms it into a highly soluble bicarbonate.

For the conditions of problem 7 - 15, we assume that the dissolution of calcium carbonate occurred in such a way that for each hour half of the total amount that was before the beginning of this hour was dissolved.

The carbonic acid aggressiveness of water is expressed in the destruction of concrete as a result of the dissolution of calcium carbonate under the action of carbonic acid.

The formation of stalactites and stalagmites in the caves of limestone mountains is explained by the dissolution of calcium carbonate in water containing carbon dioxide, and its re-precipitation from aqueous solutions acidic calcium carbonate.

The general acid type of aggressiveness is due to a low pH value, which increases the dissolution of calcium carbonate. The sources of hydrogen ion here are humic acids, characteristic of bog waters, and hydrolysis of salts heavy metals in the zones of sulfide oxidation. Generally acidic aggressiveness is possessed by waters of the I hydrochemical zone and waters of bog sediments, which are widespread within the II zone. The waters of outwash, alluvial, glacial and interglacial (intermoraine) deposits, characterized by a high pH of 6 5 - 7 5, do not possess this type of aggressiveness in the overwhelming majority of cases.

The invention relates to the chemical technology of nitric acid processing of phosphate raw materials to obtain calcium carbonate by conversion of calcium nitrate in the production of NPK fertilizers. The method of obtaining calcium carbonate includes: interaction of calcium nitrate with a solution of ammonium carbonate, precipitation of the target product from the suspension, washing it, heat treatment at temperatures of 400 ... 700 ° C and grinding. The invention makes it possible to simplify the technology of processing calcium carbonate, a by-product in the production of NPK fertilizers into a filler for use in various industries. 1 wp f-ly, 2 tab.