The method of obtaining magnesium and chlorine by electrolysis of anhydrous chlorides

 

The invention relates to ferrous metallurgy and can be used in the production of magnesium and chlorine by electrolysis of anhydrous chlorides. In the proposed method, including the electrolysis of anhydrous chlorides, the use of generated chlorine in the chlorine consuming production and neutralization of chlorine and hydrogen chloride gases with an alkaline sorbent with getting harmegnies solutions according to the invention, the neutralization of gases are in the presence of urea, taken in the amount of 10-80 kg in recalculation on 100% urea 1 m3alkaline sorbent, the alkaline sorbent use of oxide compounds of magnesium, magnesite and/or brucite, neutralization is carried out at 30-100oWith, and received harmegnies solution is treated with gaseous hydrogen chloride or hydrochloric acid at pH ~ 1.0 to 5.5 and is directed to anhydrous magnesium chloride. Ensures utilization of gases and eliminates the stage of disposal of waste milk. 4 C.p. f-crystals, 2 tab.

The invention relates to ferrous metallurgy and can be used in the production of magnesium and chlorine by electrolysis of anhydrous chlorides.

In the production of magnesium by electrolysis, odstv magnesium with chlorine consuming technologies, for example, titanium, rare metals, organochlorine products synthesis, liquefied chlorine, etc. the degree of chlorine is 96-98%. Exhaust gases containing chlorine, hydrogen chloride, carbon dioxide and others, before release to the atmosphere purified from contaminants.

A method of obtaining magnesium and chlorine by electrolysis of anhydrous carnallite and magnesium chloride /A. I. Ivanov, M. N. Lyandres, O. C. Prokofiev. Production of magnesium. M.: metallurgy, 1979, 376 S./. Neutralization of exhaust gases from chlorine and hydrogen chloride carried out with the milk of lime containing 95-105 g/DM3The CaO.

The milk of lime is circulated in the system of the collection tank - pump - scrubber to a residual Cao content of ~ 20 g/DM3and then excreted from the system. Run the following reaction: CA(Oh)2+ NS--> CaCl2+ 2H2O CA(OH)2+ 2Cl2-->CaCl2+ Ca(OCl)2+ 2H2O the Disadvantage of this method is the formation of calcium hypochlorite.

The resulting milk of lime contains up to 100 g/DM3"active" chlorine (calcium hypochlorite), the discharge of which into the waters invalid. Therefore, these effluents before discharge is subjected to neutralization. Decomposition hypochlo is b> + NS-->CaCl2+ 2Cl2+ 2H2O In this way it is possible to obtain chlorine. However, due to the explosion process associated with the formation of chlorine dioxide, this method is not widespread.

The closest analogue to the claimed method according to the totality of symptoms is a well-known method for the production of magnesium and chlorine /M. A. Adanson. Production of magnesium and chlorine by the electrolysis of molten magnesium chloride. M.: metallurgy, 1964, 126 S./.

The essence of the method lies in the fact that forming chlorine-containing exhaust gases are treated with the milk of lime in the scrubber. Generated waste the milk of lime containing up to 100 g/DM3hypochlorite of calcium and up to 20 g/DM3of calcium oxide, neutralized in two stages: acute vapor at a temperature of 85-95oWith a catalyst content of 2 g/DM3CA(lO)2and then the hydrogen sulfide or polysulfides of sodium.

The disadvantages of this method is the following.

Due to the small surface area of contact between the catalyst and delaborated solution decomposition of calcium hypochlorite is not only for the version catalytic decompositionbut according to the variant thermal time is e solutions are not implemented, and the method of decomposition of CA(lO3)2in terms of gas purification unacceptable, discharge from wastewater invalid, because it causes significant damage to the environment.

The proposed solution is aimed at the production of magnesium and chlorine by electrolysis of anhydrous chlorides, the use of chlorine in the production of magnesium and chlorine consuming industries, clean exhaust gases magnesium and chlorine consuming industries with getting harmegnies solutions utilized after treatment with hydrogen chloride or hydrochloric acid to a pH of 1.0 to 5.5 as a raw material for producing anhydrous magnesium chloride.

This task is solved by the proposed method of obtaining magnesium and chlorine, the essence of which consists in the following essential features: - neutralization of exhaust gases from chlorine and hydrogen chloride are alkaline sorbent in the presence of urea, taken in the amount of 10-80 kg (in terms of 100% urea) at 1 m3alkaline sorbent.

Distinctive features are: - as alkaline sorbent use of oxide compounds of magnesium, magnesite and/or brucite; - the process is conducted at a temperature of 30-100oWith; - harmegnies solutions obtained after obezvrezhivaniju is directed to anhydrous chlorides of magnesium, returned in the process.

The proposed method is as follows.

During electrolysis, for example, molten carnallite formed magnesium and chlorine, used in the production of magnesium to suppress hydrolysis of magnesium chloride in the process of dehydration, and chlorine consuming production, for example, in the production of titanium. The waste exhaust gases containing chlorine and hydrogen chloride, purified alkaline sorbent (brucite or milk of magnesia) in the presence of urea or waste production (nous generated during periodic cleaning of process equipment, when collecting placers urea, holding warehouse operations and others), taken in the amount of 10-80 kg/m3at a temperature of 30-100oC. the Resulting harmegnies solution is treated with hydrogen chloride or hydrochloric acid at pH 1.0 to 5.5, and then is directed to anhydrous magnesium chloride.

As studies have shown, purification of exhaust gases from chlorine and hydrogen chloride with an alkaline reagent in the presence of urea, which is a reducing agent, proceeds without the formation of hypochlorites and chlorates, eliminating the need for the next stage of neutralization trabea method is utilized in the form of chlorides.

The process proceeds according to the following reactions:
2Mg(OH)2+ 2Cl2-->MgCl2+ Mg(OCl)2+ 2H2O
3Mg(OCl)2+ 2(H2N)2WITH --> 3MgCl2+ 4H2O + 2SD2+ 2N2
These reactions proceed in parallel, urea is used for the decomposition of the resulting magnesium hypochlorite (active chlorine), and thus does not form chlorate.

The use of urea at the stage of purification of exhaust gases from chlorine alkaline sorbents has not previously been used and in this case gave the following results:
- utilization of chlorine in the form of chlorides, namely, chloride of magnesium, which is the raw material for the production of magnesium.

The solutions obtained after neutralization of gases, in addition to contain magnesium chloride and magnesium carbonate formed by the reaction:

This leads to unnecessary loss of magnesium.

To avoid the loss of magnesium solution is further treated with gaseous hydrogen chloride or hydrochloric acid at pH of 1.0 to 5.5.

When magnesium carbonate is dissolved and goes into the chloride. The resulting solution of magnesium chloride is directed to anhydrous magnesium chloride used as a raw material for magnesium.

Optimal sup>3the formation of hypochlorites and chlorates. At a flow rate of urea more than 80 kg/m3not observed the formation of oxygen compounds of chlorine. In addition, this causes considerable unnecessary consumption of urea.

At a temperature of less than 30oSince there is a slight formation of hypochlorite and at a temperature of more than 100oWith increasing energy costs, because to achieve the set temperature is not enough exhaust gas heat.

Processing solutions after neutralization of gases with gaseous hydrogen chloride or hydrochloric acid at pH > 5,5 impractical, because the dissolution rate of magnesium carbonate is small, and at pH <1, the content of free hydrochloric acid is ~ 15-20 g/DM3that complicates further processing solutions to produce the anhydrous salt.

Quantitative substantiation of the parameters of the process are given in the examples.

Analysis of patent and scientific and technical documentation suggests that the sources are not detected description methods similar to those suggested and coinciding with the claimed technical solution essential features.

The analysis of the prior art in respect of the aggregate of the armed forces is no criterion of "novelty."

Check the conformity of the invention the requirement of "inventive step" in relation to the essential features suggests that the proposed method is not necessary for professionals in the obvious way from the prior art. In particular, the prior art does not explicitly imply the fact that the purification of exhaust gases from the chlorine in the presence of urea leads to the achievement of the technical result - the disposal of chlorine in the form of chlorides.

Information confirming the possibility of carrying out the invention shown in the example.

Example
In the electrolysis of carnallite per 1 ton of magnesium obtained 2,85 t chlorine, which is used to obtain the anhydrous chloride salts of magnesium and titanium. The degree of chlorine was 98-99%. The waste exhaust gases containing 3.6 CL2g/m3sent for cleaning alkaline reagent in the presence of urea. As urea used nous, which was dissolved in water at the rate of 200 kg/m3. The consumption of urea was 10-80 kg/m3. When such consumption does not generate oxygen-containing chlorine compounds in the process of circulation of the pulp when cleaning the exhaust guest of the process increases.

The effect of consumption of urea and temperature on the process of purification of exhaust gases from chlorine and hydrogen chloride are given in table.1 and 2.

As follows from the data table. 1 and 2, the optimal conditions for the neutralization of chlorine and its utilization in the form of chlorides are consumption 100% carbamide 10-80 kg per 1 m3the alkaline reagent and the temperature of 30-100oC.

The higher the chlorine concentration, the faster triggered alkaline sorbent, and formed a solution of magnesium chloride.

Formed harmegnies solution after neutralization of gases containing 180-220 g/DM3MgCl2and 15-30 g/DM3MgCO3handle 15% hydrochloric acid to pH 5.0. While the carbonate goes into solution in the form of magnesium chloride. The resulting solution was evaporated to a concentration of 300-350 g/DM3MgCl2and sent for obtaining anhydrous magnesium salts.

Thus, the proposed method for the production of magnesium and chlorine by electrolysis of anhydrous chlorides can be disposed of chlorine gases in the form of chlorides with the receipt of magnesium chloride is returned to the process, and to avoid a stage of neutralization of waste milk, because in the process of cleaning gases from the chlorine in the presence of urea are not formed chlorates and hypochlorites.

3alkaline sorbent.

2. The method according to p. 1, characterized in that the alkaline sorbent use of oxide compounds of magnesium, magnesite and/or brucite.

3. The method according to p. 1, characterized in that the neutralization is carried out at 30-100oC.

4. The method according to p. 1, characterized in that harmegnies solution is treated with gaseous hydrogen chloride or hydrochloric acid at pH~ of 1.0 to 5.5.

5. The method according to p. 2 or 4, characterized in that harmegnies solutions directed to anhydrous magnesium chloride.

 

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SUBSTANCE: claimed method includes junk charge into premelted flux at ratio of 1:(5-10); heating up to melt temperature; smelting under flux layer, and separation of metal from flux. Equimolar mixture of sodium chloride and potassium chloride with addition of 2.9-52.6 % (in respect to total flux weight) magnesium fluoride is used as flux, and in melting process flux layer with thickness of 4.5-20 cm is maintained. Method affords the ability to conserve original composition and eliminate additional burdening with magnesium.

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4 cl, 3 tbl, 5 ex

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