TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Arrangement: The mixing unit is inclined at 10-35 degrees from the horizontal surface. The exhaust unit side of the mixing unit is provided with the liquid extracting unit. Weir (III) is provided before the liquid extracting unit in the exhaust unit side of the mixing unit. The return opening of the refrigerant liquid from the exit and heat-exchange unit of refrigerant liquid to the mixing unit from mixing unit to the heat-exchange unit is opened in the layer of refrigerant liquid with big specific gravity. Preferred Process: The negative pressure of exhaust unit produced with the suction exhaust apparatus, is utilized. The refrigerant liquid of mixing unit is moved with respect to the gas containing zinc chloride and heat-exchange is carried out by direct gas-liquid contact between the gas and refrigerant liquid. The refrigerant liquid is sent to the heat-exchange unit and heat is removed from the refrigerant liquid in the heat-exchange unit, and the refrigerant liquid is returned to the mixing unit and circulated. Some of the refrigerant liquid is extracted from the liquid extracting unit, and the gas discharged from the mixing unit is exhausted from the exhaust unit. The liquid extracting unit is sealed with the extracted refrigerant liquid. The refrigerant liquid which collects the condensed component forms in a mixing unit, a layer of refrigerant liquid with small specific gravity and a layer of refrigerant liquid with big specific gravity. After sending out the refrigerant liquid with big specific gravity to heat-exchange unit and removing heat, it is returned to the mixing unit and circulated. The gas containing zinc chloride contains zinc chloride, and zinc and/or silicon tetrachloride gas, or a mixture of gas further containing inert gas. The refrigerant liquid is a melt solution containing zinc chloride melt solution, zinc melt solution or zinc chloride, and zinc. The refrigerant liquid extracted from the mixing unit is a mixed melt solution of zinc melt solution mixed and zinc chloride melt solution, or zinc chloride melt solution. The refrigerant liquid extracted from the heat-exchange unit is a mixed melt solution of zinc chloride melt solution in zinc melt solution, or zinc melt solution. The gas containing zinc chloride is introduced at 800-1100 degrees C. By controlling the circulating load of refrigerant liquid circulating through the mixing unit and heat-exchange unit, and the amount of heat removal of heat-exchange unit, the temperature of exhaust gas which maintains the temperature of refrigerant liquid returned to the mixing unit at 420-650 degrees C, is kept at 700 degrees C or less. The liquid extracted from the mixing unit is a mixed melt solution in which dust-like silicon is further mixed. The heat amount by which the refrigerant liquid is heat-removed is equivalent to the sum of latent heat of condensed component and the heat amount required for cooling the introduced gas.