What does this mean specifically for the Smelting industry? Increasingly tighter emission limits.
In smelting plants, the main emission sources are electric furnaces. The smelting process goes as follows: The furnace generates CO-rich dust-laden off-gas, which is then extracted from the furnace straight to the gas handling and cleaning system, and then finally, into the atmosphere.
The new demand for electric furnace gas handling systems must not compromise the safety or reliability of the product. So the challenge remains: Is there an econominically feasible solution for meeting both environmental and technological requirements?
Requirements for Electric Furnace Gas Cleaning
Smelting reduction reactions generate CO-gas as a byproduct due to the lack of oxygen in the process. This is because CO-rich off-gas is toxic and explosive when mixed with oxygen. Off-gas temperatures are also very high, at times reaching over 1000 degrees celsius. In addition to CO-gas, other harmful components (such as sulfur compouds, nitrogen oxides, chlorides, fluorides and mercury) may be present in the off-gas atmosphere depending on the furnace feed materials.
Considering these issues, conditions for gas cleaning are quite unique, and have strictly imposed technological demands.
The most important requirement for electric furnace gas cleaning is safety. Due to the risk of explosion when mixing CO-gas and oxygen, each gas handling system needs to be designed extra tight in order to eliminate air ingress during the process. Thus, systems operating on overpressure are preferred over under pressure systems.
High availability and reliability are also required from gas cleaning solutions. The operation of furnaces needs to be stable, and any gas handling system cannot compromise this. Therefore, gas cleaning solutions need to be unwaveringly robust whilst requiring little maintenance. With this, investment and operating costs need to remain reasonable.
The most topical qualification for gas cleaning at the moment is, of course, the important environmental concern. Gas cleaning systems need to meet emission limits set by officials, legislations and regulations, all whilst remaining effective and efficient.
Metso Outotec Provides Solutions
Here at Metso Outotec, our gas handling portfolio is exceedingly extensive. We supply products and solutions for several different processes and needs, such as: Gas cleaning and cooling for both particulate and gaseous emissions, off-gas incineration, wet and dry gas handling, hot gas quenching, and so much more.
Gas handling conditions in electric furnaces are especially challenging due to the high temperatures as well as the toxic and explosive CO-gas. Fortunately, our products are specifically designed for the unique conditions and requirements of closed electric furnace applications.
Outotec Venturi Scrubber
The Outotec Venturi Scrubber is a widely known and utilised product within the Smelting industry. With its proven track record of being a high-pressure scrubber, the product allows for safe and effective cleaning of any harmful or explosive process gases.
The scrubber inhales furnace off-gases and produces overpressure to the gas line. This overpressure prevents air from entering the line, thus enabling safer handling of CO gas. In addition to cleaning, the scrubber also cools the gas and quenches the sparks – further eliminating any risk of explosion.