Titanium Smelting Flue Gas Treatment
Abstract: Flue gases generated in the process of smelting titanium is hazardous to the environment and human health, so the treatment of such gas is very important. This article presents comprehensive information on the engineering principles and treatments applicable to titanium smelting flue gas treatment. It starts with the introduction on the composition of titanium smelting flue gas, and then proceeds with the fundamentals of gas cooling and dust removal, overheat elimination, sulfur dioxide removal, nitrogen oxides removal, and hazardous air pollutant removal. Finally, the commonly used processes which combine existing technologies for the flue gas treatment of titanium smelting processes are presented.
Keywords: Titanium, Smelting, Flue Gas, Treatment
Introduction
Titanium is an important industrial metal which is mainly used for the production of airframes, engines and various aerospace components. The smelting process of titanium generally involves the steps of titanium oxide oxidation, reduction, and ventilation of off-gas and fumes. The smelting process can generates flue gases with high pollutant concentrations containing dust, sulfur dioxide, nitrogen oxides and many other hazardous air pollutants. In order to prevent the excessive release of hazardous pollutants in to the atmosphere, it is important to properly treat these flue gas.
Composition of Titanium Smelting Flue Gas
The composition of titanium smelting flue gas mainly depends on the chemical properties of the titanium raw material, the melting temperature, the firing process and the type of smelting furnace. The flue gas of titanium smelting process is mainly composed of air and some other volatile compounds such as carbon monoxide, carbon dioxide and nitrogen oxides. The titanium smelting process also involves the generation of particulate matter, such as fly ash and smoke, along with sulfur dioxide, hydrochloric acid, hydrofluoric acid and other acids.
Fundamentals of Flue Gas Treatment
Cooling and Dust Removal
To reduce the temperature of the flue gas generated in the titanium smelting process, cooling can be achieved by different methods, such as by adding water, or by using a cooling tower. The dust removal process involves using a cyclone, multiple mechanical collectors, or electrostatic precipitator (ESP).
Overheat Elimination
In order to reduce the temperature of the flue gas generated in titanium smelting process, a number of techniquesare commonly used, such as air preheating, air cooling and rotary kiln.
Sulfur Dioxide Removal
The flue gas generated during the titanium smelting process contains sulfur dioxide generated by the combustion of the sulfur containing raw materials. The sulfur dioxide in the flue gas can be removed by using a variety of chemical and physical treatments processes, such as dry scrubbing, wet scrubbing, and electrostatic precipitation.
Nitrogen Oxides Removal
Nitrogen oxides (NOx) is one of the most hazardous air pollutants, and its emission source is mainly combustion and burning process of titanium smelting process. To reduce the concentration of nitrogen oxides in the flue gas, a number of NOx removal processes can be used, such as selective catalytic reduction (process) or selective non-catalytic reduction (SNCR).
Hazardous Air Pollutant Removal
The titanium smelting process also generates hazardous air pollutants, such as fly ash and other particulate matter, hydrogen chloride, arsenic and cadmium. To reduce the concentration of these pollutants in the flue gas, a number of advanced treatments can be used, such as biofilters, condensers, fabric filters, and activated carbon injection.
Conclusions
In order to minimize the environmental impact of titanium smelting processes, it is critical to properly treat the associated flue gas. The treatment of titanium smelting flue gas involves cooling, dust removal, overheat elimination, sulfur dioxide removal, NOx removal and hazardous air pollutant removal. Different existing technologies can be potentially combined to develop efficient and integrated flue gas treatment processes for titanium smelting applications.
