Molten steel is produced by the converter process. This device recovers and uses the high temperature waste gas generated in large quantity during blowing in the converter (basic oxygen furnace: equipment used to produce crude steel from pig iron, steel scrap, etc.). Accompanying this process, about 100Nm3 of high temperature gas (CO) with a heating value of approximately 2,000 kcal/Nm3 is generated.
Heat recovery methods are classified as (1)combustion method (boiler method) and (2)non-combustion method (method of recovering gas in an unburned condition: OG method. The advanced type is called the closed OG method). Recently, the closed OG method has become the main stream. The OG facilities are designed to recover about 70% of the latent heat and sensible heat. The converter gas recovered is mixed with other by-product gases (coke oven gas, blast furnace gas), then used by the heating equipment of the ironworks. Steam is mainly used by the degassing equipment of the steel making factory. Today, gas recovery system are installed on every BOF in Japan.
- Fuel savings: 0.84 GJ/t-steel
- CO2 Reduction: 79.8 kg-CO2/t-steel
- Increases the Induced Draft Fan (IDF) efficiency by lowering the temperature of the exhaust gas, achieving high-speed oxygen feeding
- Suppressed combustion reduces the quantity of flue-gas and thus reduces the cost of fans and dust removal.
- Reduced water for off-gas cooling
Utilization of high temperature gas (CO) generated in the converter process with a heating value of approximately 2,000 kcal/Nm3.
- Equipment cost: JPY 600-1,100million (110 t/charge converter scale; includes construction cost)
- Payback time: 4.7 years
The Japan Iron and Steel Federation