RU2229442C2 - Method of preparing chemically precipitated calcium carbonate - Google Patents

Abstract

FIELD: inorganic compounds technology. SUBSTANCE: invention provides preparation of product having commercial value in mechanical rubber, cable, perfumery, cosmetic, and paper industries, which as well can be used in preparation of fillers. Clarified distiller liquid from soda production is fed into reactor provided with heating system and stirrer. Temperature is raised to 60-80^o and 0.02 to 0.07 wt % of organic additive, namely oxyethylenated monoalkylphenols based on propylene trimer, is added, said additive having empirical formula C₉H₁₉C₆H₄O(C₂H₄O)_nH wherein C₉H₁₉ represents isononyl radical, n number of ethylene residues attached to one alkylphenol molecule, and n=9-12. Thereupon carbonate-bicarbonate solution, which is sodium bicarbonate production waste (filtration stage mother liquor) showing total alkalinity 130-400 g/l, is added in 0.3-0.5% stoichiometric excess with respect to calcium chloride. Treatment proceeds for 20-30 min until pH 7.2-7.4 is attained. Resulting precipitate is separated, washed, and dried. Precipitated calcium carbonate contains 0.002-0.006% chlorine, has whiteness 95.0-98.0% and bulk density 120-600 kg/m³. EFFECT: enabled utilization of soda production waste. 4 cl, 1 dwg, 1 tbl

Description

The invention relates to the chemical and petrochemical industries, and more particularly to a method for the production of chemically precipitated calcium carbonate (chemically precipitated chalk), which can be used as fillers for the rubber, cable, perfumery, cosmetic, paper and other industries.

A known method of producing chemically precipitated calcium carbonate by treating soda distillation liquid with a sodium carbonate solution in the presence of sodium bicarbonate when heated to pH 7.2-8.2, followed by filtration, separation, drying and isolation of the target product [A.S. USSR No. 522136, IPC C 01 F 11/18, 1975].

The disadvantage of this method is the significant chloride content in the finished product.

There is also a method of producing chemically precipitated calcium carbonate by treating soda distillation liquid with a solution of sodium carbonate in the presence of sodium bicarbonate and disodium salt of sulfocarboxylic acids of the C ₁₇ -C ₂₀ fraction by heating, followed by filtration, separation, drying and isolation of the target product [A.C. . USSR No. 510434, IPC C 01 F 11/18, 1975].

The disadvantage of this method, as well as the previous one, is the significant content of chlorides in the finished product.

To reduce chlorides, it is proposed to obtain chemically precipitated sodium carbonate by treating soda distillation liquid with a sodium carbonate solution in the presence of sodium bicarbonate and additionally introducing primary alcohols into the distillation liquid in the amount of 0.005-0.05 wt.% Of the weight of the distillation liquid [A.S. USSR No. 510436, IPC C 01 F 11/18, 1975], or alkylsulfoureid [A.S. USSR No. 560820, IPC C 01 F 11/18, 1975], or carbamide orthophosphate in an amount of 0.01-0.05 wt.% Of the weight of the distiller liquid [A.S. USSR No. 560829, IPC C 01 F 11/18, 1975] or to supply a soda solution at first 25-30% of what is needed for processing with the subsequent introduction of the remaining amount of soda solution, while the amount of distillation liquid is supplied in an amount providing 0.5 -1.2% of the stoichiometry of calcium chloride [A.S. USSR No. 648521, IPC C 01 F 11/18, 1975], or apply a soda solution to a pre-mixed distillation liquid with sodium bicarbonate [A.S. USSR No. 691402, IPC C 01 F 11/18, 1978].

The main disadvantages of the known methods are the low consumer qualities of the target product: the relatively low whiteness of the target product, high residual alkalinity, high bulk density, low degree of disposal of waste soda production.

Also known is a method of producing chemically precipitated calcium carbonate by treating soda distillation liquid with a soda solution, which uses soda waste - estimates and / or solutions from washing soda carriers, with an excess of calcium ions equal to 2-20% of stoichiometry and concentration soda solution of at least 120 g / dm by the content of sodium oxide [Pat. RF № 2171227, IPC С 01 F 11/18, 2000].

This method allows the use of waste soda production while their disposal and to obtain chemically precipitated calcium carbonate with a high rate of whiteness, but at the same time it has drawbacks: relatively low bulk density, impurity content in the finished product, not high enough whiteness.

In addition, the implementation of the method according to the proposed method involves a large amount of wastewater due to the concentration of soda solutions, especially when using soda solutions after washing soda carriers.

The closest technical solution to the claimed prototype is a method for producing chemically precipitated calcium carbonate by treating soda distillation liquid containing a paste based on sodium alkyl monosulfonate of the general formula:

C _n H _{2n + 1} SO ₃ Na, where n = 12-17,

in an amount of 0.005-0.05%, a solution of sodium carbonate in the presence of sodium bicarbonate at a temperature of 30 ° C for 20 minutes, followed by separation of the precipitate, washing and drying it [A.S. USSR No. 729126, MPK C 01 F 11/18, 1975].

The known method allows to reduce the chloride content in the target product, but at the same time has the main disadvantage - insufficient whiteness of the target product due to the formation of practically insoluble organic salts of alkaline earth elements when using alkyl sulfonates as an additive, high bulk density and, in addition, its high cost through the use of target products of sodium carbonate and bicarbonate.

The technical task of the invention is to improve the consumer properties of the target calcium carbonate, namely: reducing impurities, increasing whiteness, reducing bulk density, as well as expanding the raw material base for using the target product and reducing its cost and, as a result, the disposal of soda production waste.

The technical problem is achieved by the fact that as an organic additive use ethoxylated monoalkylphenols based on propylene trimers (Neonol) of the following general formula:

C ₉ H ₁₉ C ₆ H ₄ O (C ₂ H ₄ O) nH,

where C ₉ H ₁₉ is an isononyl alkyl radical;

n is the number of moles of ethylene attached to one mole of alkyl phenol equal to 9-12,

and its amount is 0.02-0.07 wt.% from the distillation liquid, and sodium carbonate is used as carbonate and bicarbonate feedstock - mother liquor from the filtration stage with a total alkalinity of 130-400 g / l, in an amount of an excess of 0.3-0.5 wt.% from stoichiometry for calcium chloride, and the processing of distillation liquid is carried out at 20-80 ° C.

Distinctive features of the claimed invention from the prototype are the use of sodium bicarbonate production waste from the stage of filtering a suspension of sodium bicarbonate (mother liquor) as a bicarbonate feedstock; use of Neonol as an organic additive; processing the distiller liquid with solutions of sodium carbonate and bicarbonate at 20-80 ° C to a pH of 7.2-7.4.

The use of Neonol as an additive is due to the fact that the polyvalent elements Fe ⁺³ , Mn ^{+ 3-7} present in the feedstock upon interaction with hydroxyethyl groups form complex compounds (podands) that are readily soluble in water, which are removed from the system at the stage of filtration and washing , which allows to increase whiteness and reduce the bulk density of the target product.

The use of sodium bicarbonate production wastes and clarified distillation liquid as feedstock allows to reduce the cost of the finished product and, accordingly, to utilize sodium bicarbonate production wastes.

During the processing of the distiller liquid, which contains calcium salts, the following main reactions proceed with an excess of waste from the production of sodium bicarbonate (mother liquor):

CaCl ₂ + Na ₂ CO ₃ → CaCO ₃ + 2NaCl

CaCl ₂ + 2 NaHCO ₃ → CaCO ₃ + 2NaCl + CO ₂ + H ₂ O

Ca (OH) ₂ + ₂ NaHCO ₃ → CaCO ₃ + CO ₂ + H ₂ O + 2NaOH

Depending on the initial alkalinity of the mother liquor, the degree of utilization of the starting components and, accordingly, the yield of calcium carbonate and its indicators also depend.

If the initial alkalinity of the mother liquor does not correspond to an indicator of 130-400 g / l, then it is regulated by an additional supply of Na ₂ CO ₃ to an alkalinity of 130-400 g / l.

When carrying out the synthesis of the claimed method, the starting products must meet the following requirements:

1. Distiller liquid - according to TU 2152-032-00204872-97;

composition, wt.% (almost constant):

CaCl ₂ 9.21

NaCl 5.42

Ca (OH) ₂ 0.16

CaSO ₄ 0.07

NH ₃ 0.18

H ₂ O 84.96

2. The waste production of sodium bicarbonate - mother liquor - has the following composition:

Na ₂ CO ₃ - 18.8-22.7 n.d. = 49.8-60.1 g / l,

NaHCO ₃ - 33.3-36.0 n.d. = 133.9-151.2 g / l,

NaCl - 0.92-1.43 n.d. = 2.7-6.0 g / l,

3. Neonols - TU 2483-077-05766801-98.

In the proposed method, the following Neonols are used:

С ₉ Н ₁₉ С ₆ Н ₄ O (С ₂ Н ₄ O) ₉ Н - Neonol AF-9;

С ₉ Н ₁₉ С ₆ Н ₄ O (С ₂ Н ₄ O) ₁₀ Н - Neonol AF-10,

С ₉ Н ₁₉ С ₆ Н ₄ O (С ₂ Н ₄ O) ₁₂ Н - Neonol AF-12.

The process of obtaining precipitated sodium carbonate is carried out according to the scheme depicted on the four as follows.

A distilled (clarified) liquid in an amount of 1 m ³ pre-purified from suspended impurities in an amount of 1 m ^{3 is} fed into a reactor 1 equipped with heating and a stirrer, the temperature in the reactor is brought to 20-80 ° С and Neonol additive is added in an amount of 0.02- by a stream II 0.07 wt.% With stirring. Then through the heat exchanger 2 stream III serves mother liquor in excess of 0.3-0.5% of stoichiometry for calcium chloride with an initial alkalinity of 130-400 g / l in an amount of 0.268-0.810 m ³ . The processing of distillation fluid is carried out for 20-30 minutes to a pH of 7.2-7.4. Next, the resulting suspension of calcium carbonate is fed to the filter 3, where at the same time washing the precipitate of the obtained calcium carbonate from chlorides is carried out with water supplied by stream IV. Next, the obtained wet cake is served in the dryer 4. After that, the dried calcium carbonate enters the storage hopper 5 and then to the consumer.

Get the finished product with a whiteness of 95-98%, bulk density -120-130 kg / m ³ , the chloride content of 0.002-0.003 wt.%.

The essence of the method is confirmed by the examples shown in the table.

Based on the above examples, we can conclude that the proposed method for producing chemically precipitated calcium carbonate will allow to obtain the target product with high consumer performance, namely: the whiteness of the target product is 95-98%; low chlorine content and low bulk density, which will satisfy the requirements of the consumer and apply it in the perfume industry.

In addition, the proposed method will allow to utilize such waste soda production as clarified distillation liquid and waste sodium bicarbonate, which in significant quantities do not currently find qualified use, but are discharged into the so-called “White Seas”.

Claims (4)

1. The method of producing chemically precipitated calcium carbonate by treating soda distillation liquid with carbonate and bicarbonate solutions in the presence of an organic additive by heating, followed by separation of the precipitate, washing and drying thereof, characterized in that as an organic additive, ethoxylated monoalkylphenols based on the following propylene trimers are used composition: С ₉ Н ₁₉ С ₆ Н ₄ О (С ₂ Н ₄ О) nН, where C ₉ H ₁₉ is an isononyl alkyl radical; n = 9-12 is the number of moles of ethylene attached to one mole of alkyl phenol; as the carbonate and bicarbonate raw materials, sodium bicarbonate production waste is used - mother liquor from the filtration stage with a total alkalinity of 130-140 g / l, in an amount constituting an excess of 0.3-0.5 wt.% of calcium chloride stoichiometry, and processing soda production distiller liquid is carried out at a temperature of 60-80 ° C to a pH of 7.2-7.4. 2. The method according to claim 1, characterized in that the clarified distiller liquid is used — the clarified part after settling of the distiller suspension. 3. The method according to claims 1 and 2, characterized in that Neonol AF-9, Neonol AF-10 or Neonol AF-12 are used as ethoxylated monoalkylphenols based on propylene trimers. 4. The method according to claims 1 and 2, characterized in that the amount of Neonol is 0.02-0.07 wt.% From distillation liquid.