CS236636B1 - Manufacturing process of pure calcium carbonate - Google Patents

Description

The invention provides a process for the production of pure calcium carbonate from calcium oxide and / or its hydration products, as well as from low-grade calcium raw materials, e.g. carbide lime, which is a significant contaminated calcium hydroxide, which is lost in the production of acetylene by decomposing calcium carbide with water.

Calcium carbonate is used for industrial purposes or in natural form (notably as calcite mineral, limestone limestone, or floated chalk, less frequently than aragonite mineral, or produced synthetically [RH BUCKIE: Precipitation of Calcium Carbonates. Their Properties and Applications. New West Virginia Pulp and Paper Co. (1948)] by converting carbon dioxide to calcium hydroxide (usually in the form of lime milk), and by reacting carbon dioxide and ammonia or ammonium carbonate or sodium carbonate with an aqueous calcium chloride solution, respectively. hard water by precipitation of calcium bicarbonate with lime milk (USSR 91199 and 169 160; US Patents 1,493,847, 1,654,009,

863,945, 2,216,889, 2,263,656, 2,374,741 and

379 035; French Patent 684,797; German Patents 889,438, 2,230,516, 2,251,099 and

505 304; British Patent 1,447,566; Canadian

I Patent 587,671; Japanese patents 3215—55, 4377—56, 8737—72, 69 672—77, 107 219—77, 110 805—77, 117 417—77 and 38 537—78].

In such cases, calcium carbonate is generally more or less contaminated with at least admixtures of silicon, iron, aluminum, magnesium and other elements depending on their content in the raw materials used.

In industry, calcium carbonate is used either directly, e.g. as a filler, additive or pigment in the plastics, rubber, dye, paper, pharmaceutical, cosmetic, food, glass and chemical industries [P. D. RITCHIE: Plasticisers, Stabilisers and Fillers. London. Iliffe Books. (1972); DE D. DEANIN and N. R. SCHOTT: Fillers and Reinforcements for Plastics. Washington. American Chemical Society. (1974); W.V. TITOW and B.J. LANHAM: Reinforced Thermoplastics. London. Applied Science Publishers. (1975); H. S. KATZ and J.V. MILEWSKI: Handbook of Fillers and Reinforcements for Plastics. London. Van Nostrand Reinhold Company. (1978)], or is used as an intermediate in the preparation of high purity calcium oxide and hydroxide, which is used in the oil processing industry at 2336636.

236638 makes greases and lubricating oil additives. ·. For industrial purposes, the unaltered quality of calcium carbonate and the products made therefrom requires that the use of natural raw materials cannot generally be guaranteed.

Of quicklime or slaked lime may be the podium MS. 207 300 by selective leaching of the calcium oxide or hydroxide with an aqueous solution of ammonium formate and then precipitating the obtained leach with carbon dioxide in the presence of ammonia to prepare pure calcium carbonate, but this process has some disadvantages resulting from the use of ammonia which volatile as a component of the leaching solution , smells and forms explosive mixtures with air.

The present invention relates to a process for the production of pure calcium carbonate from raw materials and / or industrial wastes containing, as a main constituent, calcium oxide and / or calcium hydroxide, which is carried out in such a way that it is present in 1 to 40 wt. parts, preferably 5 to 15 wt. parts, raw material and / or industrial waste, at a temperature of 0 ° ^C to 100 ^° C, causes 100 wt. parts of a leaching solution containing a salt or salts removed by the interaction of inorganic and / or organic acids forming soluble calcium salts, preferably hydrochloric acid, nitric acid, formic acid or acetic acid, with a stoichiometric or greater amount of organic nitrogen base or bases preferably containing in the molecule at least one hydroxyl group, such as e.g. monoethanolamine, or diethanolamine, and from the obtained solution of calcium salt or calcium salts, after separation of the undissolved residue, mainly derived from feedstock, from a solution of carbon dioxide at a temperature of 10 to 100 ° C, a solution pH of 7 to 10 and a gas pressure of 0 Calcium carbonate precipitates, which is generally separated in connection with washing and drying.

The process according to the invention is therefore based on the selective leaching of calcium oxide, which is the main component of so-called calcium oxide. quicklime, e.g. thermal decomposition of natural limestone, eventually the product of its hydration, slaked lime, lime milk, resp. calcium hydroxide falling off e.g. in the production of acetylene by decomposition of calcium carbide, an aqueous solution of an inorganic or organic acid salt and an alkanolamine, optionally an alkylamine, preferably the chloride, nitrate, formate or acetate of monoethanolamine (2-aminoethanol, 2-hydroxyethylamine j) or diethanolamine (2,2‘-dihydroxyethylamine).

By leaching, an aqueous solution of the calcium salt of the respective acid is formed, while the silicon, iron, aluminum and other elements derived from the starting material remain undissolved and separated from the calcium salt solution by conventional methods, e.g. filtration or centrifugation, less preferred sedimentation and decantation. By filtering the carbon dioxide at a temperature of 10 to 100 ° C, most preferably at 20 to 50 ° C, at an optimum pH of 7 to 10 and at an optimum pressure of a carbon dioxide-containing gas of 0.1 to 0.3 MPa, it precipitates easily. filterable calcium carbonate. The precipitated calcium carbonate is further isolated by conventional methods, most often by filtration or centrifugation, and it is appropriate to combine the filtration of the calcium carbonate with its washing with water or an organic solvent, e.g. to remove and dry any organic compounds contaminating the starting material or product, if any.

The leaching solution is simultaneously regenerated to form the alkanolamine salt or alkylamine used for leaching. The regenerated leaching solution can be reused in the next production cycle to selectively leach calcium oxide or hydroxide from another portion of the starting calcium raw material.

An advantage of the process for producing pure calcium carbonate according to the present invention is the wide availability of raw materials or even chemical production wastes. Thus, not only are the technically and economically higher yields of the calcium raw materials, but also the disposal of lime waste deposits, which can also be significant from an environmental point of view. Another advantage is the possibility of utilizing a wide variety of technically readily available nitrogen bases such as alkylamines and derivatives thereof, e.g.

ethylenediamine (1,2-diaminoethane);

H ₂ NCH ₂ CH ₂ NH ₂ , piperidine C ₅ H ₁₀ NH, alkanolamines and derivatives thereof, e.g. monoethanolamine (2-aminoethanol, 2-hydroxyaminoethane, 2-hydroxyethylamine), HOCH ₂ CH ₂ NH ₂ , diethanolamine [imino-bis (2-ethanol), 2,2'-dihydroxyethylamine, bis (2-hydroxyethyl) amine] (HOCH ₂ CH _{2] 2} NH, triethanolamine (2,2 ', 2 "-trihydroxytrietylamínj (HOCH ₂ CH ₂ N j _3, l-amino-2-propanol (2-hydroxy-propylamino, 2-hydroxyaminopropán j CH ₃ CH (OH) CH ₂ NH ₂ ,

1,3-diamino-2-propanol (2-hydroxytrimethylenediamine) H ₂ NCH ₂ CH (OH) CH ₂ NH ₂ ,

N, N'-bis (hydroxyethyl) ethylenediamine (HOCH ₂ CH ₂ NHCH ₂ ) ₂ ,

N, N, N ', N'-tetrakis (hydroxyethyl) ethylenediamine (HOCH ₂ CH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ CH 2 OH) 2,

1,4-diethanolpiperazine (1,4-dihydroxydiethylpiperazine)

HOCH ₂ CH ₂ N (CH ₂ CH ₂ ) ₂ NCH ₂ CH ₂ OH and i. The advantage of the production method according to this invention is compared to the otherwise interesting solution according to the Czech · Copyright Certificate • 207 300 is also. the fact that, unlike ammonia, alkylamines · are less volatile and alkanolamines are virtually non-volatile and odorless substances that do not form explosive mixtures with air, which is important from a safety perspective.

In addition, the high solubility of carbon dioxide in the solutions of said nitrogenous bases compared to the ammonia solution is also advantageous, thereby ensuring a higher utilization of carbon dioxide even without the necessity of using pressure reactors. The precipitation of calcium carbonate from the calcium salt solution with carbon dioxide may be carried out at both elevated and reduced pressure, but from a technical point of view the pressure of a carbon dioxide containing gas in the range of 0.1 MPa to 0.3 MPa is most suitable. The absorption of carbon dioxide in the solution resulting from the leaching of the calcium raw material can be carried out in a conventional manner, e.g. bubbling through the solution, passing through countercurrent absorption towers, such as solid packed columns or cascade trays, further injecting the solution into a stream of carbon dioxide-containing gas and i.

The carbon dioxide for precipitation according to the invention can be used both pure and in admixture with air, nitrogen, carbon monoxide, methane and other gases which do not react with the components of the leaching solution. In such cases, when using carbon dioxide-containing gases, this method can additionally be used as a method for concentrating by-gas, e.g. carbon monoxide.

In addition to the aforementioned individual organic nitrogen bases, mixtures of organic nitrogen bases, or systems containing anions of several inorganic or organic acids, may also be applied, but preferably, in terms of production stability in particular, the use of both nitrogen base and its salt is used.

Most preferred are nitrogenous organic bases containing at least one carbon atom bonded to the carbon atom per molecule and salts thereof, e.g. monoethanolamine formate or diethanolamine chloride and the like.

Suitable raw materials for the production of pure calcium carbonate according to the invention are, in particular, calcium oxide, generally as quicklime, or its hydration products (calcium hydroxide, slaked lime), as well as by-products or calcium hydroxide with a high content of silicon, iron, aluminum, magnesium and other elements.

It is also possible to use less valuable secondary calcium raw materials, such as so-called. carbide lime, which is often industrial since the decomposition of calcium carbide by water in the production of acetylene. Mixtures of calcium hydroxide and .alpha. calcium chloride with. admixtures of organic substances, resulting from the production of trichlorethylene by dehydrochlorination of tetrachloroethane, from the production of propylene oxide by the chlorohydrin process, from the production of -epichlorohydrin and the like. At the same time, the utilization of waste leads to an improvement of the environment around the plants for the production and processing of calcium carbide, calcareous plants, etc.

The lime raw materials may be added to the reaction medium in lumpy, granular, granular, powder or slurry form, optionally in the form of suspensions, solutions, and the like. In this case, they are dosed most often, depending on the content of the calcium component, most preferably in a ratio of 5 to 15 wt. parts of calcium raw material (calculated on the dry matter) per 100 parts by weight of the leaching solution.

The process according to the invention can be carried out discontinuously, semi-continuously and continuously. It is generally a closed production cycle in which no harmful gaseous pollutants or waste water are produced, since the regenerated leaching solution, containing mainly the salt of the nitrogen base used, returns to sleep for reuse. The calcium carbonate produced is of high purity (> 99% CaCO3) and does not contain any substances which, after its thermal decomposition, remain in the resulting calcium oxide or its hydration product. Further details of the process according to the invention as well as other advantages are evident from the examples.

Example 1

100 wt. parts by weight of quicklime having a composition of 95.6% by weight of calcium oxide; % calcium carbonate, 0.3 wt. % silica, 0.2 wt. % alumina, 0.1 wt. Iron oxide, ground and sieved through a 0.06 mm sieve, is added in portions up to 1600 wt. parts of a 20 ° C warm aqueous solution containing 400 wt. parts of monoethanolamine formate and 30 wt. parts of monoethanolamine. The undissolved residue is separated from the solution heated to 50-60 ° C by reaction heat and fed from the filtrate cooled to 30-40 ° C. Upon reaching pH 7.5, practically quantitatively precipitates calcium carbonate, which is filtered off, washed with water and dried. Yield 167 wt. parts by weight of calcium carbonate containing 99.9 wt. The calcium oxide, after recalculation to the annealed state, corresponds to an SS% yield based on the calcium oxide content of the feedstock.

»7 t».

EXAMPLE 1, d 2,? parts of calcium carbide lime from raw materials and / or industrial calcium oxide, 23.3% by weight of calcium carbonate, 7.5% by weight of insoluble residue and 43.4% by weight of moisture are crushed to a granular state with stirring add in portions up to 750 wt. parts of a 30 ° C warm aqueous solution containing 90 wt. parts by weight of diethanolamine chloride and 5 wt. parts of monoethanolamine. The insoluble residue is separated from the solution by filtration and calcium carbonate is precipitated from the filtrate in a solid packed column through which the solution circulates to reach a pH of 8 containing 65% by volume of carbon dioxide and 35% by volume of carbon monoxide, methane and hydrogen. The yield of calcium carbonate after filtration, washing and drying is 32 wt. parts, which corresponds to a yield of 95% based on the calcium hydroxide content of the feedstock.

Example 3

100 wt. parts by weight of slaked lime of 41% by weight of calcium hydroxide, 1% by weight of calcium oxide, 1% by weight of magnesium oxide and 54% by weight of moisture are added in portions to 1000 wt. parts of a 40 ° C warm aqueous solution containing 100 wt. parts by weight of ethylenediamine nitrate and 5 wt. parts of ethylenediamine carbonate originating from a previous production cycle. The undissolved residue is separated from the solution by filtration and calcium carbonate is precipitated from the filtrate with a stream of carbon dioxide containing 35% air volume at 30 ° C after reaching pH 8. The yield of calcium carbonate after filtration, washing and drying is 50 wt. parts, which corresponds to a yield of 90% based on the calcium hydroxide content of the feedstock.

Example 4

100 wt. parts of quicklime composition as in Example 1 are dissolved in 1600 wt. parts of a 50 ° C warm aqueous solution containing 500 wt. parts of piperidine formate. The undissolved residue is separated from the solution by filtration and calcium carbonate is precipitated from the filtrate with a stream of carbon dioxide containing 10% / b nitrogen at 40 ° C to pH 7.5. The yield of calcium carbonate after filtering, washing and drying is 165 wt. parts, which corresponds to a yield of 96% based on the calcium oxide content of the feedstock.

P r ί a 1 a d 5 • 100 wt. parts of carbide lime having a composition of 36% by weight of calcium hydroxide, 7% by weight of calcium carbonate, 5% by weight of insoluble residue and 52 washes. weight of moisture is dissolved in 700 wt. parts of a 30 ° C warm aqueous solution containing 200 wt. parts by weight of 1,4-diethanolpiperazine acetate and 50 wt. parts of 1,4-diethanolpiperazine carbonate originating from a previous production cycle. The undissolved residue was separated from the solution by filtration and calcium carbonate precipitated out of the filtrate with a stream of carbon dioxide at 20 ° C. The yield of calcium carbonate after filtration, washing and drying is 49 wt. parts, which corresponds to a yield of 95% with respect to the calcium oxide content of the feedstock.

Example 6

100 wt. parts of waste lime carbide composition as in Example 5 are suspended in 300 wt. parts of an aqueous solution containing 3.5% by weight of calcium chloride. To this suspension is added 500 wt. parts by weight of a solution containing 90 wt. parts by weight of 1,3-diamine-2-propanol chloride and 25 wt. parts of monoethanolamine. Solid carbon dioxide is added in portions at 20 ° C in a sealed reactor until complete precipitation of calcium carbonate at 20 ° C. The yield of calcium carbonate after filtration, washing and drying is 55 wt. parts, which corresponds to a 95% yield based on the content of reactable calcium compounds in the initial suspension.

Example 7

100 wt. parts of lime with a composition of 55% by weight of calcium oxide, 20% by weight of calcium hydroxide, 13 pens. weight of calcium carbonate and 12 washes. weight of insoluble residue is dissolved in 1000 wt. parts of a 70 ° C warm aqueous solution containing 400 wt. parts by weight of N, N, N chloridu, N‘-tetrakis (hydroxyethyl) ethylenediamine chloride and 30 wt. parts of monoethanolamine.

The undissolved residue was separated from the solution by filtration and calcium carbonate precipitated from the filtrate with a stream of carbon dioxide at 70 [deg.] C at 50 psi. The yield of calcium carbonate after filtration, washing and drying is 120 wt. parts, which corresponds to a yield of 95% with respect to the content of soluble calcium components in the feedstock.

Claims (2)

SUBJECT Process for the production of pure calcium carbonate from raw materials and / or industrial wastes containing as main constituent calcium oxide and / or calcium hydroxide, characterized in that for 1 to 40 wt. 100 parts by weight of raw material and / or industrial waste are stored at 0 to 100 ° C. parts of a leaching solution containing a salt or salts derived by the interaction of inorganic and / or organic acids forming soluble calcium salts, such as hydrochloric acid, nitric acid, formic acid or acetic acid, with a stoichiometric or greater amount of organic nitrogen base or bases molecule of at least one hydroxy group of the invention, such as pionoethanolamine or diethanolamine, and from the obtained solution of calcium salt or calcium salts, after separation of the insoluble residue from the solution by action of carbon dioxide at a temperature of 10 to 100 ° C, pH of solution T to 10 and An atmosphere of 0.09 to 2 MPa, preferably 0.1 to 0.3 MPa, precipitates a precipitate which is generally separated in conjunction with washing and drying. 2. The process according to claim 1, wherein the leaching solution for selectively leaching the calcium component is a solution remaining after precipitation and separation of the precipitate formed.