RU2255899C1 - Calcium chloride manufacture process - Google Patents

Abstract

FIELD: inorganic compounds technology.

SUBSTANCE: invention relates to methods for manufacturing calcium chloride when reusing chlorine-containing calcium production emission gases and, more specifically, to employment of anhydrous calcium chloride in electrolytic production of metallic calcium. Manufacture of calcium chloride comprises: preparation of sorbent, in particular mixture of suspensions of lime milk and acetylene production waste at volume ratios (90-0):(10-100); chlorination of sorbent with chlorine-air mixture at 35-40°C; decomposition of calcium hypochlorite when concentration of calcium oxide reaches 60-80 g/L; two-step cleaning of destroyed pulp by treating it with aqueous hydrochloric acid while consecutively lowering pH in the first step to 11-10 and, in the second step, to 9-8; filtration of pulp after each cleaning step; and drying cleaned concentrated calcium chloride solution with mixture of air and direct flue gases.

EFFECT: reduced consumption of materials and power.

2 dwg, 4 tbl

Description

The invention relates to methods for producing calcium chloride in the process of disposal of chlorine-containing gas discharges of calcium production.

Anhydrous calcium chloride is a widely used industrial chemical used as deicer, desiccant for gases and liquids, in the production of concrete, etc. However, the most important area of application of anhydrous calcium chloride is the electrolytic production of calcium metal.

A known method of producing calcium chloride (UK patent 2264113 A, M. C. C 01 F 11/28, N. C. C1A), claimed 12.02.1993, including the preparation of the sorbent - milk of lime, chlorination of the sorbent at a temperature of 50-90 ° With chlorine, the destruction of hypochlorite in parts of chlorinated pulp with a pH of 9-11 in the presence of a catalyst for the decomposition of calcium hypochlorite, purification of the pulp with hydrochloric acid to pH 6-8 with stirring, filtering a solution of calcium chloride followed by regeneration of the catalyst by treating the precipitate after filtration with hydrochloric acid.

Chlorination takes place in a continuous contact apparatus with vigorous stirring of the sorbent with chlorine due to the high feed rates (4000 g / min) of the sorbent containing 30% CaCl ₂ , 1.3% Ca (OH) ₂ , 0.2% Ca (ClO) ₂ and 1000 ppm of catalyst in the form of a mixture of Fe / Ni, and the circulation of part of the chlorinated pulp. At the outlet of the chlorinator, most of the chlorinated pulp containing 34.5% CaCl ₂ , 0.5% Ca (OH) ₂ , 0.5% Ca (ClO) ₂ and 1000 ppm of catalyst in the form of a Fe / Ni mixture is returned to the chlorinator mixed with the original milk of lime, the other part is sent for the destruction of hypochlorite, purification and filtration. The return of most of the chlorinated mixture to the reactor is caused by the need to create sufficient flow turbulence in the chlorinator to prevent clogging of the reactor due to solidification of the reaction mixture.

The disadvantage of this method is that the calcium chloride powder from the solutions obtained according to this technological scheme is limitedly suitable and, for example, cannot be used as a raw material for electrolysis in the production of calcium metal. This is due to the fact that the final product does not have the necessary purity. So at the stage of purification, the solution is treated with hydrochloric acid to a pH of 6-8, which does not create conditions for at least incomplete precipitation of the Mg impurity present in the original lime [Musakin A.P. Tables and diagrams of analytical chemistry. L .: Chemistry, 1975, 133 pp.]. The pH of the medium at which the hydroxides of impurities remain in a stable state or in a state of incomplete precipitation is in the ranges:

Mg (OH) ₂ - incomplete deposition of 10.8-12.2

total precipitation 12.2-14.0

Fe (OH) ₂ - incomplete precipitation 6.9-10.0

total precipitation 10.0-14.0

Fe (OH) ₃ - incomplete deposition of 2.2-3.8

total precipitation 3.9-14.0

Al (OH) ₃ - incomplete deposition of 3.8-5.0 and 7.5-11.0

total precipitation 5.0-8.0

It is also doubtful that the authors chose the temperature regime of the chlorination process in the range of 50-90 ° C. It is well known that the solubility of gaseous chlorine and calcium oxide decreases at temperatures> 50 ° C, as well as the fact that the reaction of interaction of chlorine and calcium oxide occurs through the dissolution stage. Known data on the chlorination of milk of lime in the foam apparatus, where the optimum temperature for the absorption of chlorine defined interval 45-55 ° C [Furman A.A. Inorganic chlorides (chemistry and technology). M.: Chemistry, 1980, 416 p.].

It follows from the description that the chlorinating agent is liquid or gaseous chlorine, the excess of which creates the conditions for the formation of undesirable by-products, for example calcium chlorate, in the places of the reactor with an increased concentration of chlorine (stagnant zones). This forces to intensify the process, which makes it difficult to manage.

Among the known methods for producing calcium chloride, the closest in technical essence is the method for producing calcium chloride described in the book by N. A. Doronin "Calcium" (M .: Gosatomizdat, 1962, 175 p.).

This method of producing calcium chloride includes the preparation of a sorbent - milk of lime with a concentration of calcium oxide> 120 g / l, chlorination of the sorbent with a chlorine-air mixture in the presence of a catalyst, destruction of hypochlorite simultaneously with chlorination, additional destruction of hypochlorite, 2-stage cleaning followed by filtration after each stage and drying the resulting solution of calcium chloride.

Milk of lime is obtained by slaking lime with an aqueous solution of calcium chloride. Lime is a powdery product of calcining carbonate rocks containing calcium oxide (~ 80%), impurities of Mg, Al, Si, Fe in the amount of 6-7% and solid mineral impurities (sand, stones). Moreover, the content of impurities may increase depending on the field of the feedstock - limestone.

The preparation of milk of lime includes a sequence of the following operations: transportation of annealed lime from storage bins for slaking in special lime-collecting plants; slaking lime by adding an aqueous solution of calcium chloride, draining the resulting pulp into a classifier, where the pulp is divided into milk of lime and sand (unextinguished grains and stones).

Chlorination of pulp with a concentration of calcium oxide> 120 g / l is carried out in mechanical absorbers in the presence of a decomposition catalyst for hypochlorite, for example, in the form of an aqueous solution of nickel chloride. The chlorine-air mixture coming from the electrolysis compartment containing chlorine up to 20 g / m ³ has a temperature of 110-130 ° С at the inlet of the absorber. Milk of lime is poured into an absorber with a temperature of 80 ° C. During the circulation in the absorber, the chlorinated pulp is heated to 85-110 ° C with hot steam. The process proceeds with a simultaneous decrease in the concentration of calcium oxide to 6-20 g / l and the accumulation of calcium chloride ~ 350 g / l in the pulp. The catalyst at a temperature of about 80 ° C inhibits the formation of calcium hypochlorite with the conversion of the latter to calcium chloride.

When the content of calcium oxide in the pulp is 15-20 g / l simultaneously with chlorination, calcium hypochlorite is destroyed by heating the pulp with hot steam to a temperature of 70-80 ° C. When the content of calcium oxide is not more than 20 g / l, but not less than 6 g / l, as well as calcium chloride not less than 300 g / l and if there are traces of hypochlorite, the flow of the chlorine-air mixture into the absorber is stopped.

Finished pulp is discharged into intermediate reactors. If the pulp contains traces of hypochlorite, then it is destroyed by heating in reactors. For this, the pulp with working mixers is heated with hot steam to 80-90 ° C for 10-20 minutes. After the complete destruction of calcium hypochlorite, which is established by a high-quality reaction with potassium iodide, the pulp is transferred to purification from impurities.

Cleaning with subsequent filtration of the pulp is carried out in two stages. In the first stage of purification by neutralizing the pulp with hydrochloric acid, the content of excess calcium oxide in the pulp is adjusted to 0.15 g / l, which corresponds to a pH of 7-8. In case of excess hydrochloric acid, quicklime is added to the pulp to obtain an alkalinity of 0.15 g / l CaO. With this alkalinity, the bulk of the impurities (iron, aluminum) passes into an insoluble form, the resulting hydroxides of iron and aluminum pass into the precipitate. Next, the pulp is transferred to the first filtration in order to separate insoluble solids and hydroxides of iron and aluminum.

Ион

связывается в виде ВаSО₄ путем ввода в раствор сухой соли хлорида бария. Магний частично осаждается путем прибавления к раствору извести в виде гидроокиси кальция до щелочности 0,3-0,6 г/л СаО (рН 10-12). После этого очищенный раствор поступает на вторую фильтрацию для отделения микровзвесей твердых частиц, не задержанных фильтровальной тканью при первой фильтрации.In the second stage of purification, the solution is purified from magnesium and ion

And he

binds as BaSO ₄ by adding a dry salt of barium chloride to the solution. Magnesium is partially precipitated by adding lime in the form of calcium hydroxide to an alkalinity of 0.3-0.6 g / l CaO (pH 10-12). After that, the purified solution enters the second filtration to separate micro suspensions of solid particles not retained by the filter cloth during the first filtration.

The dried solution of calcium chloride is dried in spray dryers by spraying the solution with injection nozzles in a stream of hot air at a temperature of 290-320 ° C. Air is heated in 2-3-section heat exchangers due to heat exchange with flue gases. Before drying, the chloride solution is transferred to a foam scrubber, where calcium chloride is captured from the exhaust gases after the cyclone and the chloride concentration in the solution increases (up to 500 g / l) as a result of water evaporation. After drying, dry calcium chloride, having about 5% moisture, settles in the lower conical part of the dryer, from where it is unloaded and packed in a container with the help of a screw.

The disadvantage of this method is the increased consumption of feedstock - lime and energy.

The total amount of lime waste in the form of stones, sand, cake at the stages of milk preparation, chlorination, filtration is from 36 to 52%. The presence in the technological scheme of the operation of the preparation of milk of lime complicates the already multi-stage scheme.

Carrying out the chlorination of the sorbent is accompanied by a significant consumption of hot steam for heating the pulp before and during chlorination. The practice of heating the sorbent did not reveal a significant effect on the sorption process. When heated, coarsening of suspension particles occurs, which leads to a decrease in the contact area of the reagents and, accordingly, a decrease in the rate of the chemisorption reaction. Chlorination at temperatures of 85-110 ° C reduces the solubility of chlorine in the sorbent, thereby reducing the degree of absorption of chlorine from the cold water. Experimental data are known, according to which the maximum degree of absorption of chlorine by milk of lime is achieved at temperatures of 35-45 ° C [Biryukova LV, Mironov AM Chem.prom. 1967, No. 4. S.41-43]. Moreover, achieving sorption temperatures of 85-110 ° C is not possible due to the design features of the absorber, an apparatus where deep mixing of the suspension is not provided, but only surface spraying of the suspension with horizontal mixers occurs. The ratio of the volume of the absorber to 80 m ³ and the cross-sections of the pipelines for cold water and steam supply, as well as heat loss through the walls of the apparatus and with the exhaust gases, make it impossible to heat the pulp to a temperature of 85 ° C, at which the destruction of hypochlorite begins. Therefore, calcium hypochlorite will accumulate. Its destruction at the last stage of chlorination at a concentration of calcium oxide of 15-20 g / l and the duration of treatment of the pulp with hot steam (not more than an hour before reaching an oxide concentration of 6 g / l, at which the flow of the chlorine-air mixture is stopped) cannot ensure the destruction of hypochlorite "to traces. " Therefore, surgery - the additional destruction of hypochlorite - is necessary.

The proposed scheme for the purification of a solution of calcium chloride seems unsatisfactory, mainly due to the use of two reagents - hydrochloric acid and lime. The use of barium chloride is not of a general nature, since the contamination of lime with sulfate ions depends on its quality.

The drying process is accompanied by a large consumption of natural gas only for heating the air and a significant amount of heat leaves with the waste flue gases.

The objective of the present invention is to develop a method for producing calcium chloride, which allows to reduce the consumption of energy and material resources spent on obtaining calcium chloride.

The problem is achieved in that the method of producing calcium chloride, including the preparation of a sorbent with a concentration of calcium oxide> 120 g / l, chlorination of the sorbent with a chlorine-air mixture simultaneously with the destruction of the formed calcium hypochlorite, the further destruction of calcium hypochlorite, two-stage cleaning followed by filtration after each cleaning step and drying purified concentrated solution of calcium chloride, according to the invention as a sorbent using a mixture of suspensions of milk of lime and waste acet flax production in volume ratios (90-0) :( 10-100), the chlorination process is carried out at a temperature of 35-40 ° C, the destruction of hypochlorite is started when the concentration of calcium oxide is 60-80 g / l, in the first stage of cleaning the destroyed pulp is treated hydrochloric acid to a pH of 11.0-10.5, and in the second stage to a pH of 8.0-7.5, drying the purified concentrated solution of calcium chloride is carried out with a mixture of air and direct flue gases.

The essence of the method of producing calcium chloride is that at the stages of the process material and energy resources are saved due to:

- the use as a sorbent instead of milk of lime partially or completely suspension based on waste acetylene production, the so-called carbide sludge. This type of waste in the production of sorbent is excluded, such as stones and large fractions of sand;

- carrying out chlorination at a temperature of 40 ° C, corresponding to the maximum degree of absorption of chlorine, and the use of hot steam only in the second half of the chlorination process and only in the first compartment of the absorber along the cold water, in an area with a maximum concentration of chlorine;

- conducting two-stage purification by successive lowering of the pH of the solution using only one reagent - hydrochloric acid;

- direct heating by flue gases during the drying process of the sprayed solution of calcium chloride. In this case, the heat of the flue gases is used to the maximum by mixing them with air to obtain a drying agent.

Carbide sludge, which is an aqueous suspension of a dark gray color, is a secondary product of acetylene production and is obtained by the reaction of calcium carbide with water during the production of acetylene at an acetylene station according to the following scheme:

Analysis of the composition and properties of carbide sludge showed that the proposed sorbent corresponds to the technological characteristics of the used sorbent

- milk of lime,

namely:

- the content of calcium hydroxide in the original carbide sludge is 200-300 g / l;

- the total amount and nature of impurities in carbide sludge, with the exception of the carbon fraction, corresponds to the average amount and nature of impurities in lime. Optical, thermogravimetric and chemical analyzes of a part of carbide sludge insoluble in water and hydrochloric acid showed the presence of impurities of aluminum, iron, titanium, manganese and calcium in an amount of up to 6.8 wt.%, As well as up to 1.2 wt.% Of the carbon fraction;

- a comparison of the particles of insoluble fractions of the treated calcareous pulp (pulp ready for filtration) and carbide sludge showed that serious filtration difficulties should not be expected. By the methods of sieve analysis and scattering of the laser beam, the particle size of the said fractions was determined. Particles of calcareous pulp are generally larger than particles of carbide sludge (50 μm), their size is determined by the range of 50-1000 μm, some of which (32.9%) consists of particles of ~ 200 μm. In this case, the minimum particle size of the pulp and carbide sludge is almost the same (0.08 and 0.04 μm), taking into account the error in measuring particles of this size using the laser beam scattering method;

- the effectiveness of the proposed sorbent for trapping chlorine is comparable to milk of lime. With a decrease in the concentration of calcium hydroxide to 12-17.9 g / l, the concentration of chlorine in the emission does not exceed the permissible level (0.048 g / m ³ ).

To explain the invention, an example of the method is described below with reference to the accompanying drawings, in which:

figure 1 shows a laboratory installation for chlorination of sorbents;

figure 2 shows the conditional hardware-technological scheme for producing powder of calcium chloride.

Example 1

The proposed method for the production of calcium chloride was experimentally tested using seven sorbents of the following composition with a calcium oxide content of 120 g / l:

1 - milk of lime;

2 - a mixture of carbide sludge and milk of lime in a volume ratio of 10:90;

3 - a mixture of carbide sludge and milk of lime in a volume ratio of 25:75;

4 - a mixture of carbide sludge and milk of lime in a volume ratio of 50:50;

5 - a mixture of carbide sludge and milk of lime in a volume ratio of 75:25;

6 - a mixture of carbide sludge and milk of lime in a volume ratio of 90:10;

7 - diluted carbide sludge.

To obtain an experimental amount of a concentrated solution of calcium chloride, 140 ml of each sorbent was prepared. Milk of lime was obtained by slaking lime with an aqueous solution of calcium chloride (30 g / l). Mixtures were prepared by pouring carbide sludge into lime milk in volume ratios of 90:10; 75:25; 50:50; 25:75; 10:90. Carbide sludge was obtained by diluting the original carbide sludge (with CaO 300 g / l) with an aqueous solution of calcium chloride. Before all chlorination, a decomposition catalyst of the resulting calcium hypochlorite was added to all sorbents to a concentration of 1.37 g / l in the sorbent. An aqueous solution of nickel (II) chloride was used as a catalyst.

Chlorination of the prepared sorbents with a chlorine-air mixture (HVS) was carried out to determine the concentration of chlorine at the discharge from the flask with the sorbent during chlorination. Chlorination was carried out in a flow-type laboratory setup (Fig. 1), consisting of a sequentially connected absorption bottle 1 with a magnetic stirrer 2 for mixing the sorbent, two Drexels 3 with an absorption solution - 10% potassium iodide solution, gas meter 4 with a vacuum hose pump 5. The installation was connected to the main chlorine pipeline 6. The concentration of chlorine in the chlorine-air mixture (HVS) passing through the chlorine pipeline at a rate of 1 l / min was measured by passing 2 l of HVS through Drexel with a solution of potassium iodide, and then titrated iodine 0.1 n was titrated. with sodium thiosulfate solution, the chlorine content was calculated taking into account the titration data of the volume of the missed HVS.

During sorption, non-absorbed chlorine, passing through Drexel, stained the solution from yellow to brown. Therefore, after every 300-600 liters of cold water, it is necessary to replace the potassium iodide solution with fresh. The sorption process was considered complete when the color of the fresh potassium iodide solution in Drexels became dark brown within 10-15 minutes. During and after sorption, titration of the intermediate and final solutions of potassium iodide is carried out. According to titration of released iodine 0.1 n. a solution of sodium thiosulfate and the amount of chlorine passed through the sorbent calculate the amount of chlorine in the discharge from the absorption flask with the sorbent. Table 1 shows the main parameters and results of chlorination of sorbents. From the table it follows that with an almost equal amount of cold water passed through (1861-2700 l) with an average chlorine content of 8-10 g / m ^3, equal volumes of sorbents effectively absorb chlorine. The relatively large concentration of chlorine in the discharge from sorbents based on carbide sludge is actually significantly lower than the permissible level (48 mg / m ³ ).

To assess the filterability of the mentioned sorbents, seven samples of sorbents with a calcium oxide concentration of 17-19 g / l, corresponding to the oxide concentration at the end of the chlorination process, were prepared. Samples were obtained by neutralizing hydrochloric acid sorbents with an initial concentration of calcium oxide of 120 g / l and a pH of 12.

The first chemical purification of the prepared samples was carried out by neutralizing hydrochloric acid with an excess of calcium oxide hydrate to a pH of 10.5–11.0, at which impurity hydroxides remained in a stable state or an incomplete precipitation state. After cleaning, the 1st filtration was performed on one layer of the filter fabric of TLF, vacuum ~ 15 mm Hg. created using a water-jet pump. Visually, a light suspension was observed in the filtrate. The filter cake was a dark gray layer, which, when dried, brightened, cracked, and easily separated from the filter cloth. The obtained filtrates were analyzed for the content of calcium oxide, calcium chloride and impurities of iron and magnesium. The results of the analyzes are given in table. 2.

The second chemical purification was carried out by neutralizing the filtrates with hydrochloric acid to a pH of 8.0-9.0 to obtain an alkalinity of solutions corresponding to a calcium oxide content of 0.15-1.5 g / l. After this cleaning, the solutions were completely transparent and did not need additional filtration.

Table 2 shows the main characteristics of the solutions obtained after chlorination and purification. The data in Table 2 indicate that, as a result of the chlorination of sorbents based on carbide sludge and after the destruction of calcium hypochlorite, the content of the main components (CaO, CaCl ₂ , Cl (ClO) ₂ ) is almost the same. Of particular importance are the results of determining the concentration of impurities in the resulting calcium chloride solutions after purification and filtration. From table 2 it follows that the content of iron and magnesium in solutions based on carbide sludge does not exceed the level of the content of these impurities in a solution of calcium chloride obtained by chlorination of milk of lime.

To obtain an experimental amount of calcium chloride powder, the purified solution containing calcium chloride ~ 300 g / l was evaporated to dryness in a porcelain cup. The remaining solid mass was crushed and dried thoroughly in a corundum crucible at a temperature of 300 ° C to constant weight. The resulting calcium chloride powders had a moisture content of about 5%.

Example 2

The method of producing calcium chloride was tested in an industrial environment at OJSC Machine-Building Plant using two proposed sorbents in volume ratios of 85:15 and 70:30.

The method of producing calcium chloride includes preparing the sorbent, chlorinating the sorbent with a chlorine-air mixture to obtain a concentrated calcium chloride solution, destroying hypochlorite during the second half of the chlorination process at a calcium oxide concentration of 60-80 g / l, two-stage purification with filtration after each stage and drying of the purified chloride solution calcium.

To prepare the sorbent, a suspension of carbide sludge with a concentration of calcium oxide> 120 g / l was pumped into an intermediate tank 1 (figure 2). Here, carbide sludge was diluted with an aqueous solution of calcium chloride from reactor 2 to a calcium hydroxide concentration of 120-150 g / l. After that, milk of lime with a concentration of calcium oxide of 120-150 g / l was poured into the container 1 in a volume ratio of 15:85; 30:70. Milk of lime was prepared by extinguishing lime in lime kiln 3 with a solution of calcium chloride obtained after washing pipes, equipment, equipment, followed by separation of the sand fraction in classifier 4.

Chlorination of the prepared sorbent with a chlorine-air mixture (HVS) was carried out in horizontal apparatus 5 (absorbers). During the passage of cold water with a temperature of 110-130 ° C through the working space of the absorber, the pulp was heated only to a temperature of 35-40 ° C, sufficient for the main processes: diffusion of chlorine in the gas phase, diffusion of dissolved calcium hydroxide, hydrolysis of chlorine, the interaction of products of chlorine hydrolysis with calcium hydroxide, which ensures the complete absorption of chlorine. Upon reaching a concentration of calcium oxide of 60-80 g / l, direct steam was supplied to the first compartment of the absorber, to the zone of maximum chlorine content. It was in this compartment that the pulp was heated to 80 ° C, at which the destruction of accumulated hypochlorite begins. The duration of the treatment of pulp with hot steam for 6-8 hours until the end of chlorination, i.e. to a concentration of calcium oxide of 6-20 g / l, does not provide a reduction in hypochlorite to 30 g / l.

Then, the chlorinated pulp was poured into an apparatus 6 for additional destruction of calcium hypochlorite, where it is treated with hot steam to a temperature of 80-90 ° C for 1.5-2 hours with vigorous stirring. After the destruction of hypochlorite, the calcium chloride pulp contained CaCl ₂ 250-350 g / l; CaO 6-20 g / l; Ca (ClO) ₂ <1 g / L; the main impurities are in solution in the form of hydroxides of iron, aluminum, magnesium. The density of the solution is 1.19-1.26 g / cm ³ , the temperature is 90-100 ° C.

The destroyed pulp with a pH of 12-13 was sent for purification from impurities to reactor 7. At the first stage of purification, the pulp was treated with hydrochloric acid to a pH of 10.5-11.0, which neutralized the excess calcium oxide hydrate remaining after the chlorination process was completed, and did not allow impurities to pass into a soluble form. Impurities of Fe ²⁺ , Fe ³⁺ , Al ³⁺ and Mg ²⁺ remain in the form of colloidal particles of various sizes.

After the first purification step, the pulp was fed to filter presses 8, where, passing through the TFL-5 fabric, the solid fraction of the pulp (sands, clay, impurity hydroxides, carbonate and calcium hydroxide) was removed. In the filtrate, the alkalinity of the solution was <0.6-1.4 g / l CaO. The filtrate may contain micro suspensions of solid particles not retained by TLF-5 tissue during the first filtration.

At the second stage of chemical purification, the concentration of calcium hydroxide was reduced to the minimum values of 0.05-0.2 g / l by treatment of a solution of calcium chloride with hydrochloric acid to a pH of 8.0-9.0, while the conditions for coagulation (enlargement) are also created colloidal particles of the remaining hydroxides. After the second purification step, a second control filtration was performed. The concentration of magnesium in a semi-dissolved state does not exceed the permissible concentrations of magnesium in a purified solution of calcium chloride (0.02 g / l).

The dried solution of calcium chloride was dried in a furnace-drying unit 9 with a drying agent, which is a mixture of air and direct flue gases obtained from the combustion of natural gas. In a dryer, a solution of calcium chloride sprayed with nozzles was in contact with hot gases (260-320 ° C) and dried. The gases leaving the furnace-drying unit were cleaned from dust of calcium chloride in cyclones 10 and sent to a foam scrubber 11 to trap calcium chloride and increase the concentration of calcium chloride in solution as a result of evaporation of water. A dry powder containing up to 96% CaCl ₂ , about 4% moisture, CaO - 0.01%; Fe <0.002%; Mg - 0.015 wt.%, Deposited in the lower part of the dryer, from where it was unloaded in airtight containers for transfer to the electrolysis compartment.

At each stage of the process of producing calcium chloride, the content of calcium oxide, chloride and hypochlorite was controlled, industrial test data are shown in tables 3, 4. From the data of table. 3 it follows that the concentration of calcium oxide, chloride and hypochlorite in these chlorinated sorbents are comparable, and the concentration of chlorine at the outlet of the absorber does not exceed the permissible level of 48 mg / m ³ . From the data in table 4 it is seen that after the destruction of hypochlorite, concentrated solutions of calcium chloride with an acceptable hypochlorite content (<1 g / l) are obtained. Cleaning and filtering ensures the necessary purity of concentrated solutions of calcium chloride (the content of impurities of iron and magnesium is less than 0.02 g / l).

After evaporation of the calcium chloride solution and drying it with the proposed drying agent, a powder is obtained that meets the requirements for the production of calcium metal.

The proposed method for producing calcium chloride in comparison with the known allows to significantly reduce material and energy resources in the production of calcium chloride powder, thereby reducing the cost of producing calcium metal.

Table 1
The main parameters and results of experimental chlorination of sorbents Measurable Sorbents with a CaO concentration of 120 g / l. parameter Milk of lime Mixture of milk and carbide sludge 90:10 A mixture of izv. milk and carbide sludge 75:25 A mixture of izv. milk and carbide sludge 50:50 A mixture of izv. milk and carbide sludge 25:75 A mixture of izv. milk and carbide sludge 10:90 Carbide sludge The volume of missed cold water, l. 2400 2500 2600 2170 2700 2106 1861 The average chlorine content in the cold water, g / m 8.74 8.5 8.4 8.84 8.23 9.13 10.25 The average chlorine content in the emission, g / m 0.0033 0.0053 0.007 0.013 0.017 0.013 0.019 CaO, g / l. twenty fifteen 17.1 2 20.5 15.1 17.98 CaCl ₂ , g / l. 240 235 242 251.9 235 231 210 Ca (ClO) ₂ , g / l. 1,6 1.8 0.8 0.71 0.71 0.01 0.35 table 2
The main characteristics of the solutions obtained after chlorination and purification. Measured parameter Sorbents with a CaO concentration of 120 g / l. Milk of lime Mixture of milk and carbide sludge 90:10 A mixture of izv. milk and carbide sludge 75:25 A mixture of izv. milk and carbide sludge 50:50 A mixture of izv. milk and carbide sludge 25:75 A mixture of izv. milk and carbide sludge 10:90 Carbide sludge After chlorination
The content of calcium oxide, g / l fifteen 17 19 5.5 twenty 15.1 16 The content of calcium chloride, g / l 250 255 259 251.9 260 231 221.2 The content of calcium hypochlorite, g / l. <1.0 <1.0 0.93 0.71 0.73 0.01 0.01 After cleaning and filtering The content of calcium oxide, g / l 0.2 0.15 0.21 0.05 1.48 0.4 1,6 The content of calcium chloride, g / l 300 290 310 251.9 322 314 217 The iron content, g / l 0.02 0.02 0.02 0.02 <0.02 <0.02 <0.02 The magnesium content, g / l 0.02 0.02 0.02 0.02 <0.02 <0.02 <0.02

Table 4
The main characteristics of the solutions obtained after industrial chlorination and purification. Concentration measured Sorbents parameters. Milk of lime A mixture of izv. milk and carbide sludge 85:15 A mixture of izv. milk and carbide sludge 70:30 After the destruction of hypohoritis CaO, g / l. 16 10,2 8 CaCl ₂ , g / l. 258.1 261 244 Ca (ClO) ₂ , g / l. <1 <1 <1 After cleaning and filtering CaO, g / l. 0.05 0.05 0.05 CaCl ₂ , g / l. 260 267 257 Iron, g / l 0.02 0.02 0.02 Magnesium, g / l 0.02 0.02 0.02

Claims (1)

A method of producing calcium chloride, including the preparation of a sorbent with a concentration of calcium oxide> 120 g / l, chlorination of the sorbent with a chlorine-air mixture simultaneously with the destruction of the resulting calcium hypochlorite, additional destruction of calcium hypochlorite, two-stage cleaning of the destroyed pulp with subsequent filtration after each cleaning step and drying of the purified concentrated chloride solution calcium, characterized in that as a sorbent use a mixture of suspensions of milk of lime and waste acetylene production in volume ratios (90-0) :( 10-100), the chlorination process is carried out at a temperature of 35-40 ° C, the destruction of hypochlorite is started when the concentration of calcium oxide is 60-80 g / l, in the first stage of cleaning, the destroyed pulp is treated with hydrochloric acid to a pH of 11.0-10.5, and in the second stage to a pH of 8.0-9.0, drying of the purified concentrated solution of calcium chloride is carried out with a mixture of air and direct flue gases.

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