This steel melt shop has two melting routes, with two medium frequency Induction Furnaces of 20T/ 8000 KW having 150,000 TPA capacity that melts scrap efficiently. The charge-mix when melted will generate metallurgical smoke due to oxidation having solid particles as well as gaseous pollutants. The steel melting scrap charge may have dust and rust, which on heating disintegrates from metal. The gaseous pollutant will consist of Iron oxide, Carbon monoxide and Carbon dioxide, Hydrocarbon and small proportion of Sulphur dioxide. In case scrap consists of galvanized parts, small percentage of volatized zinc can be found in gases. The gases sucked from the Induction Furnaces are to be cleaned by removing dust and particulate matter to obtain necessary emissions as per local regulations.
Similar challenge in secondary route i.e. for AOD convertor where melted metal from induction furnaces are kept for decarburization, reduction, desulphurization. Due to these processes very high temperature i.e. 450 deg. C. dusty fumes generated with the dust load around 3-5 gm/Nm3 needs to reduce to desired outlet condition as per local regulations.
Rieco has considered the two different FES systems for Induction furnaces and AOD converter to release clean air from common stack at the end.
1. FES for fumes from induction furnace
Dusty fumes exhausted from induction furnace at high temperature (120 deg. C) and gas volume around 1,73,000 m3/hr. These fumes were captured by side draft hood having the inbuilt Axial flow fan for effective local suction draft which helps to reduce the work zone emissions. A Swiveling mechanism has been provided to take away the hood from one furnace (Working) and other furnace (Stand by) and for easy loading and unloading operation of charge. Spark arrestor provided before the bag filter to arrest the spark if any which travel along with the fume gases. Primary fumes first pass through spark arrestor and then connected to specially designed Rieco Bag House and clean gas will pass to atmosphere through exhaust Stack.
2. FES for fumes from AOD convertor:
Rieco offered and supplied separate Fume extraction system for the AOD converter route. Fumes at the inlet of FD cooler are at 450 Deg C and volume of 1,15,000 m3/hr. From AOD, gases are passed though the water-cooled duct and temperature reduction up to 300 Deg C. The main challenge was to reduce the temperature of gases from 300 Deg C to suitable to withstanding temperature of filter media i.e. approximately 120 Deg C. For this purpose, Rieco’s highly efficient air to air forced draught hear exchanger was installed before Bag House. These gases then pass through Special design Rieco make Bag House. Emergency dilution air damper is provided before the Bag House to safeguard the bags from abrupt high temperature. These dusty fumes will be separated in the Bag House and clean air will pass to atmosphere, through common stack.
High dust removal efficiency, Clean gas dust concentration of 30 mg/Nm3 is guaranteed and achieved with work zone emissions less than 5 mg at 1 m distance from source with RIECO’s expertise of in-office support and on-site highly skilled service personnel.
By achieving the desired parameters at the outlet of Fume Extraction system operators can do their work efficiently. Work zone area conditions have been improved drastically. Product recovery also got possible due to the installation of Fume extraction systems.