RU2173296C2 - Hydrogen chloride production process and furnace for implementation of the process - Google Patents

Abstract

FIELD: inorganic compounds technologies and nonferrous metallurgy. SUBSTANCE: in magnesium production process, hydrogen chloride is burned in carbon-hydrogen fuel torch in presence of hydrogen-containing material, for example water vapor, and combustion products are rapidly cooled (quenched) when mixed with jets of cold (10-50 C) secondary air getting in through nozzles disposed in lining. Furnace has casing, burner, combustion chamber, and cooling chamber. Between the two latter, there are canals in lining having inlet openings on outside surface of lining and outlets into furnace. Canals are oriented tangentially and at angle 60-90 deg. to longitudinal wall of furnace. EFFECT: increased degree of hydrogen chloride conversion and enabled production of specified composition of gasair mixture. 4 cl, 2 dwg, 2 ex

Description

 The invention relates to the field of metallurgy of non-ferrous metals, in particular to the production of magnesium.

 In the process of magnesium electrolysis, a chlorine-containing gas (70-75% chlorine) is formed - "anodic chlorine", which can be used in the form of hydrogen chloride to suppress the hydrolysis of magnesium chloride during dehydration of carnallite in a fluidized bed.

The flue gases of the fluidized bed furnace must contain 0.5-6.0% hydrogen chloride, have a temperature of 400-500 ^o C.

 A known method of burning chlorine to produce synthetic hydrogen chloride by supplying a chlorine-containing gas with water vapor to a gas or liquid fuel combustion torch (MI Levinsky et al. Hydrogen chloride and hydrochloric acid. Overview. M .: Chemistry, 1985).

In this case, equilibrium is established:
H ₂ O + Cl ₂ ---> 2HCl + 0.5 O ₂ + 20.8 kcal
Thermodynamic calculations of the reaction showed that the equilibrium composition of the reaction products depends on temperature, oxygen content and water vapor in the gas phase. To shift the equilibrium towards the formation of hydrogen chloride, a high temperature (not lower than 1500 ^o C), an excess of water vapor and a minimum amount of oxygen are required.

 After burning chlorine-containing gas, the combustion products are cooled in various ways using water, air or a solution of hydrochloric acid as a cooling agent. Burning products are quenched (J.G. Hornath and J.O.S. Macdonald, Process technology international, January 1973, s. 61).

 Known processes of high-temperature combustion used by companies producing organochlorine products in the processing of organochlorine waste (XOO) with their transformation into gaseous hydrogen chloride (V.I. Abramova and others. Processing, use and disposal of waste in the production of organochlorine products. Overview. Ser . "Chlorine industry." M., 1977).

When burning organochlorine products and chlorine at temperatures above 1400 ^o C do not form dioxins. The formation of dioxins can occur at a temperature of 750-600 ^o C. With incomplete combustion of the fuel, when there is carbon in the combustion products, and with slow cooling of the latter, the formation of dioxins is possible. To prevent this process and achieve the most complete conversion of chlorine to hydrogen chloride, it is necessary to quickly cool the flue gases to a temperature of 400-500 ^o C.

The process of the company "Ron-Pulenk" includes the combustion of XOO in a cyclone furnace at a temperature of 1200 ^o C, cooling of the combustion products in a graphite heat exchanger with water, absorption of hydrochloric acid and distillation.

 In Japan, the USA and Western Europe, the Nitteu process is used: high-temperature combustion of OW using a cyclone furnace, quenching of combustion products in a submersible cooling apparatus with hydrochloric acid solution, desorption with water, and subsequent extractive distillation. The furnace in which the XOW is burned consists of a body, a burner, a combustion chamber and a gas outlet.

 The disadvantage of these processes is the use of water and solutions of hydrochloric acid as a cooling agent, which will inevitably lead to a significant increase in the content of water vapor in the gas phase, and this is unacceptable for the gas used in KS furnaces. In addition, the degree of conversion of hydrogen chloride was only 95-96%.

An object of the invention is to obtain a mixture of hydrogen chloride with air of a given composition that does not contain dioxins, and providing a high degree of conversion of hydrogen chloride. The method consists in burning chlorine-containing gas in a fuel flame at a temperature of at least 1400 ^° C in the presence of hydrogen-containing materials and cooling the combustion products to a temperature of 400-500 ^° C by direct contact with secondary air passed through nozzles in the walls of the lining of the furnace. Hydrogen-containing materials are water vapor.

 In this case, the combustion chamber is separated from the cooling chamber due to the supply of secondary air in the form of jets creating a turbulent gas curtain.

A furnace for burning chlorine-containing gases in a flame of carbon-hydrogen fuel in the presence of a hydrogen-containing substance consists of a casing, a burner, a combustion chamber and a cooling chamber. Between the cooling chamber and the combustion chamber there are channels in the lining having inlet openings on the outer surface of the lining and exits into the furnace, while the channels are tangentially directed at an angle of 60-90 ^° to the longitudinal wall of the furnace.

The length of the firebox has two chambers with different temperatures. In the combustion chamber, the temperature is 1400-1800 ^o C, in the cooling and quenching chamber of combustion products - 400-500 ^o C. The temperature difference between the chambers is ensured by cooling the flue gases with secondary air, the amount of which is 2-5 times the amount of flue gases. Secondary air is supplied by directed jets from the channels in the lining of the furnace, which create a turbulent gas curtain of secondary air and flue gases, eliminating the ingress of cold secondary air into the combustion chamber. In this curtain there is a sharp cooling of the combustion products (quenching) to a temperature of 400-500 ^o C. At these temperatures, dioxins do not form even in the presence of chlorine and carbon in the gas environment; the presence of the latter is unlikely during normal operation of the nozzle and the temperature in the combustion area of 1400-1800 ^o C.

Rapid quenching of combustion products also dramatically inhibits the interaction of oxygen and hydrogen chloride in a reverse reaction:
2 HCl + 1 / 2O ₂ ---> Cl ₂ + H ₂ O.

 All this provides a high degree of conversion of hydrogen chloride and eliminates the formation of dioxins in environmentally hazardous quantities.

 The method and the furnace are illustrated by drawings, in which the furnace is shown in section.

 Figure 1 shows a longitudinal section of the furnace.

 In FIG. 2 shows a cross-section of the furnace along the secondary air supply channels.

 The furnace consists of a casing 1, a lining 2, a burner 3, a combustion chamber 4, a cooling chamber 5, channels for supplying secondary air 6, pipes 7 for supplying secondary air, an outlet 8 for a gas-air mixture.

The secondary air channels are located in one plane perpendicular to the axis of the furnace, and are directed towards the outlet 8 at an angle from 90 ^o to 60 ^o to the longitudinal wall of the furnace. To create high turbulence in the air curtain between the chambers of the furnace 4 and 5, channels 6 enter the furnace tangentially. To exclude the influx of secondary air into the combustion chamber, its speed in the channels should be in the range of 8-20 nm / s.

 The method is as follows.

Carbon-hydrogen fuel, air, a chlorine-containing gas, a hydrogen-containing product, for example water vapor, are fed into the furnace through the burner 3. In the combustion chamber 4, hydrogen and chlorine react with the formation of a gas mixture containing hydrogen chloride with a temperature of 1400-1800 ^o C. The combustion products enter from the combustion chamber 4 into the cooling chamber 5, passing an air curtain from secondary air having a temperature of 10-60 ^o C. Due to the turbulence of the air jets and their general movement towards the outlet 8, a vacuum is created in this chamber and air does not enter the combustion chamber. The combustion products are ejected, thoroughly mixed with air, quickly cooled to a temperature of 400-500 ^o C and through the cooling chamber are removed from the furnace.

 The proposed method and the furnace were tested in laboratory conditions.

 Examples of the method.

 Example 1

The combustion of chlorine-containing gas is carried out at a temperature of 1600 ^o C in a typical cylindrical furnace. Cold secondary air was supplied into the combustion chamber through one nozzle through the side wall of the furnace. Combustion products with a temperature of 1600 ^o C were mixed with air at a temperature of 18 ^o C and a gas-air mixture of the required composition was obtained with a temperature at the outlet of the furnace 400-500 ^o C. The gas temperature after the secondary air inlet pipe before leaving the furnace varied from 1600 to 400-550 ^o C. The degree of conversion was 90%.

 Example 2

The combustion of chlorine-containing gas was carried out at a temperature of 1600 ^o C in a typical cylindrical furnace with a system of channels made in the lining in accordance with figures 1 and 2. In the combustion chamber, the temperature was 1600 ^o C, in the cooling chamber 400-500 ^o C. The whole temperature difference of gases between the chambers was in the area of the secondary air nozzles having a temperature of 18 ^o C. The degree of conversion of hydrogen chloride was 99.3%.

 Thus, the use of the method and the furnace makes it possible to solve the problem and obtain a gas-air mixture of a certain composition and temperature, used as flue gas in fluidized bed furnaces, and to ensure a high degree of conversion of hydrogen chloride.

Claims (4)

1. The method of producing hydrogen chloride from chlorine-containing gases, including burning them in a flame of carbon-hydrogen fuel in the presence of hydrogen-containing materials at a temperature of 1400-1800 ^o C and subsequent cooling, characterized in that the cooling of the combustion products to 400-500 ^o C is carried out by supply of secondary air in the form of jets at a speed of 8-20 nm / s.  2. The method according to claim 1, characterized in that water vapor is used as the hydrogen-containing material.  3. The method according to p. 1, characterized in that the secondary air is supplied with directional jets that create a turbulent gas curtain of secondary air and flue gases, eliminating the ingress of cold secondary air into the combustion chamber. 4. A furnace for producing hydrogen chloride by burning chlorine-containing gases in a flame of carbon-hydrogen fuel in the presence of hydrogen-containing materials, including a casing, a burner, a combustion chamber, characterized in that it additionally has a cooling chamber, while there are channels in the cooling chamber and the combustion chamber the lining having inlet holes on the outer surface of the lining and exits into the furnace, while the channels are directed tangentially and at an angle of 60-90 ^o to the longitudinal wall of the furnace.

Images