RU2166008C1 - Method of detoxification of chlorine-containing gases from magnesium production - Google Patents

Abstract

FIELD: gas treatment. SUBSTANCE: objective of invention is to eliminate disadvantages and increase reliability of chlorine-to-hydrogen chloride conversion process. Method involves mixing of chlorine-containing gases with air to form chlorine-air mixture, which is transferred to fuel- combustion torch. During the burning process, chlorine is reduced to hydrogen chloride for further reuse. According to invention, prior to be transferred to torch, chlorine-air mixture is continuously mixed with fuel to form-gas-fuel mixture, to which again chlorine-containing gas, for instance anodic chlorine with content of chlorine 70-93%, is admixed to raise content of chlorine in chlorine-air mixture to 200 g per 1 cu.m air. Chlorine-air mixture is mixed with fuel at ratio 1:(20-30) and concentration of chlorine in chlorine-air mixture before addition of fuel is maintained from 5 to 150 g/1 cu.m air. Initial chlorine- containing gas can be magnesium chloride electrolysis sanitary-aspiration gases, dehydrated carnallite chlorination process gases, or fluidized-bed furnace emission gases. Reuse of hydrogen chloride obtained is effected with suspension of magnesium-containing oxide raw material giving magnesium chloride or with calcium hypochlorite calcium chloride. EFFECT: increased reliability of chlorine-to-hydrogen chloride conversion. 9 cl, 2 ex

Description

 The invention relates to ferrous metallurgy, to methods for the neutralization of exhaust gases, in particular chlorine, obtained in the process of producing magnesium by electrolysis of molten salts.

 Known methods for the neutralization of chlorine-containing gases of magnesium production (autosw. USSR N 140211, publ. BI N 15 1961; autosw. N 197951 publ. BI N 13 1967; autosw. N 306861 publ. BI 20 1971; 695685 publ BI N 41 1979) by burning chlorine-containing gas in a flare with fuel (gaseous or liquid). At high temperatures, a chlorine-containing gas in a mixture with air interacts with hydrocarbons, turning into hydrogen chloride.

 The disadvantage of these methods is that the combustion process is unstable, disruption of the flame is possible.

A known method of the neutralization of chlorine-containing gases of magnesium production (RF patent N 1629243, publ. BI 7 1991) is a prototype that includes feeding a mixture of chlorine with air to a fuel flame to a concentration of 200-480 g of chlorine per 1 m ^{3 of} air, restoring the mixture during combustion to hydrogen chloride at a thermal tension in the combustion zone of 10-40 gJ / m ³ with an air flow coefficient of 1.1-1.6, followed by disposal of the resulting hydrogen chloride.

The disadvantage of this method is that when mixing chlorine with air to a concentration of chlorine in a mixture of 200-300 g per 1 m ^{3 of} air there is a "breakthrough" of the flame into the burner, popping, unstable combustion and stall. In this case, the burner is heated up.

 The objective of the invention is to eliminate the disadvantages and increase the reliability of the conversion of chlorine to hydrogen chloride.

This problem is solved by the fact that in the method of neutralizing chlorine-containing gases of magnesium production, including mixing chlorine-containing gases with air to produce a chlorine-air mixture, supplying the mixture to the fuel combustion flame, restoring the mixture to hydrogen chloride during the combustion process, followed by disposal of the resulting hydrogen chloride, it is new that the pre-chlorine-air mixture is continuously mixed with fuel before being fed to the combustion torch to obtain a gas-fuel mixture, then again into the resulting mixture under chlorine-containing gas is mixed and mixed with the gas-fuel mixture to a chlorine content of at least 200 g / m ³ .

 In addition, the chlorine-air mixture is mixed with fuel at a ratio of 1: (20-30).

In addition, the concentration of chlorine in the chlorine-air mixture before mixing with the fuel support 5-150 g per 1 m ³ air.

 In addition, as a chlorine-containing mixture supplied for mixing with the fuel, use the gases of the plumbing pump from the electrolysis of chloromagnesium raw materials, gases from the chlorination process of dehydrated carnallite, exhaust gases from fluidized bed furnaces.

 In addition, after mixing with the fuel, anode chlorine from an electrolysis process with a concentration of 70-93% is used as a chlorine-containing gas.

 In addition, natural gas is fed to the mixing perpendicular to the movement of the chlorine-air mixture.

 In addition, chlorine-containing gas is supplied perpendicular to the movement of the gas-fuel mixture stream.

 In addition, the disposal of the obtained hydrogen chloride is carried out by a suspension of magnesium-containing oxide raw materials, followed by obtaining magnesium chloride.

 In addition, the disposal of the obtained hydrogen chloride is carried out by calcium hypochlorite to produce calcium chloride.

Mixing the chlorine-air mixture before burning with natural gas allows the reaction processes to be carried out at a relatively low rate. This is determined by diffusion processes in which intermediate reaction products are formed:
CH ₄ + Cl ₂ = CH ₃ Cl + HCl (1)
CH ₃ Cl + Cl ₂ = CH ₂ Cl ₂ + HCl (2)
CH ₂ Cl ₂ + Cl ₂ = CHCl ₃ + HCl (3)
CHCl ₃ + Cl ₂ = CCl ₄ + HCl (4)
Subsequent supply of chlorine to the resulting gas-fuel mixture with a chlorine concentration of 70-93% allows to reduce the rate of interaction of the remaining part of the fuel with the chlorine-air mixture, which reduces the unstable combustion of the flame, increases the reliability of the conversion process.

 The fuel supply perpendicular to the chlorine-air mixture allows uniform mixing of the components in the mixture and thereby increase the reliability of the hydrogen chloride conversion process.

 The supply of chlorine-containing gas perpendicular to the gas-fuel mixture allows for uniform mixing of the components in the mixture and thereby increase the reliability of the process of conversion of hydrogen chloride.

 An analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information, and identification of sources containing information about analogues of the claimed invention, made it possible to establish that the applicant did not find a source characterized by features that are identical to all essential features of the invention. The definition from the list of identified analogues of the prototype, as the closest in the totality of the features of the analogue, allowed us to establish a set of significant distinctive features in relation to the applicant’s perceived technical result in the claimed method set forth in the claims.

 Therefore, the claimed invention meets the condition of "novelty."

 To verify the compliance of the claimed invention with the condition "inventive step", the applicant conducted an additional search for known solutions in order to identify features that match the distinctive features of the claimed method from the prototype. The search results showed that the claimed invention does not follow explicitly from the prior art for the specialist, since the influence of the transformations provided for by the essential features of the claimed invention is not revealed from the prior art determined by the applicant to achieve a technical result. Therefore, the claimed invention meets the condition of "inventive step".

 Examples of the method.

Example 1. Chlorine-containing gases of magnesium production (anode chlorine gas), consisting of 75% chlorine and 20 vol.% Air, are mixed with air to a chlorine concentration of 115 g / m ^{3 of} air in a chlorine-air mixture. The consumption of chlorine is 100 m ³ / h and air 2000 m ³ / h. The chlorine-air mixture is continuously mixed in the pipe with fuel, for example natural gas, containing, vol.%: CH ₄ 95.8-99.7; C ₂ H ₆ 0.1-6%; C ₃ H ₈ to 0.1; CO ₂ to 0.2; N ₂ 0.2-4.0, in a ratio of 1: (20-30), and the fuel is supplied continuously and perpendicular to the movement of the chlorine-air mixture in an amount of 1000 m ³ / hour. Then, a chlorine-containing gas (anode chlorine) with a concentration of 70-93% is fed perpendicularly to the mixture in a gas-fuel mixture that moves through the pipe at a certain speed, mixed with a gas-fuel mixture to a chlorine concentration of at least 200 g / m ^{3 of} air and fed to the burner for burning. The temperature in the combustion zone is 1010-1600 ^o C. The combustion process is stable, without explosion and leakage of chlorine. The combustion products of fuel and chlorine have a temperature of 1240 ^o C and consist, total.%: CO ₂ 6,1; H ₂ O 2.4; N ₂ 61.8; O ₂ 9.3; HCl 20.4; Cl ₂ O. The resulting hydrogen chloride is disposed of by passing through magnesium oxide feed, for example brucite or through calcium hypochlorite.

 Example 2

As a chlorine-containing mixture supplied for mixing with fuel, use the gases of a plumbing pump from the electrolysis of chloromagnesium raw materials (chlorine content in gases up to 6 g / m ³ ), or gases from the chlorination process of dehydrated carnallite (chlorine content not more than 20 g / m ³ ) , or exhaust gases from fluidized bed furnaces (chlorine content not more than 0.5 g / m ³ ). The chlorine-air mixture is continuously mixed in the pipe with fuel, for example natural gas, containing, vol.%: CH ₄ 95.8-99.7; C ₂ H ₆ 0.1-6; C ₃ H ₈ to 0.1; CO ₂ to 0.2; N ₂ 0.2-4.0, in a ratio of 1: (20-30), and the fuel is supplied continuously and perpendicular to the movement of the chlorine-air mixture in an amount of 1000 m ³ / hour. Then, a chlorine-containing gas (anode chlorine) with a concentration of 70-93% is fed perpendicularly to the mixture in a gas-fuel mixture that moves through the pipe at a certain speed, mixed with a gas-fuel mixture to a chlorine concentration of at least 200 g / m ^{3 of} air and fed to the burner for burning. The temperature in the combustion zone is 1010-1600 ^o C. The combustion process is stable, without explosion and leakage of chlorine. The combustion products of fuel and chlorine have a temperature of 1240 ^o C and consist, total.%: CO ₂ 6,1; H ₂ O 2.4; N ₂ 61.8; O ₂ 9.3; HCl 20.4; Cl ₂ 0. The resulting hydrogen chloride is disposed of by passing through magnesium oxide feed, for example brucite or through calcium hypochlorite.

 Thus, the proposed method for the neutralization of chlorine-containing gases from magnesium production will allow the process to be carried out stably and reliably, eliminating the “breakthroughs” of the flame into the burner, popping, unstable combustion and stall.

Claims (9)

1. A method of neutralizing chlorine-containing gases of magnesium production, including mixing chlorine-containing gases with air to produce a chlorine-air mixture, supplying the mixture to a fuel combustion torch, restoring the mixture to hydrogen chloride during subsequent combustion, and then utilizing the resulting hydrogen chloride, characterized in that it is preliminarily a chlorine-air mixture before feeding to the combustion torch is continuously mixed with fuel to obtain a gas-fuel mixture, then chlorine-containing gas is again fed into the resulting mixture, I mix to chlorine in the mixture at least 200 g per 1 m ³ of air.  2. The method according to claim 1, characterized in that the chlorine-air mixture is mixed with fuel at a ratio of 1: (20-30). 3. The method according to claim 1, characterized in that the concentration of chlorine in the chlorine-air mixture is maintained between 5 and 150 g per 1 m ^{3 of} air before mixing with the fuel.  4. The method according to claim 1, characterized in that as a chlorine-containing mixture supplied for mixing with fuel, use gases of a plumbing pump from the process of electrolysis of chloromagnesium raw materials, gases from the chlorination process of dehydrated carnallite, exhaust gases from fluidized bed furnaces.  5. The method according to claim 1, characterized in that after mixing with the fuel, anode chlorine is used as the chlorine-containing gas from the electrolysis process with a concentration of 70 - 93%.  6. The method according to claim 1, characterized in that the natural gas is fed to the mixing perpendicular to the movement of the chlorine-air mixture.  7. The method according to claim 1, characterized in that the chlorine-containing gas is fed perpendicular to the movement of the gas-fuel mixture stream.  8. The method according to claim 1, characterized in that the recycling of the obtained hydrogen chloride is carried out in suspensions of magnesium-containing oxide raw materials, followed by the production of magnesium chloride.  9. The method according to claim 1, characterized in that the disposal of the obtained hydrogen chloride is carried out by calcium hypochlorite, followed by the production of calcium chloride.