Management of Greenhouse Gas Emissions in Integrated Steel Plant...

Management of Greenhouse Gas Emissions in Integrated Steel Plant Major constituents of greenhouse gases are carbon di oxide (CO2), methane (CH4), nitrous oxide (N2O), various fluorocarbons, sulphur hexafluoride, halons, and ozone in troposphere. Each of these gases has a different greenhouse warming potential (GWP) and their effects on atmosphere are not in direct proportion to their quantity of emissions. The GWP of a greenhouse gas is a measure which indicates of how much a given mass of gas contributes to the global warming. The GWPs of different greenhouse gases are given on a relative scale. This scale compares the GWP of the gas in question to the GWP of carbon di oxide gas which is considered as 1.0. Over 100 years of time horizon the GWP of methane is 21, whereas the GWP of nitrous oxide is 310 (Fig 1). Hydro fluorocarbons (HFC) which are used in some of the air conditioning systems of the steel plant have a GWP of up to 11700. Sulfur hexafluoride (SF6) used in some of the circuit breakers of the electrical transmission system of the steel plant has a GWP of up to 23900. Fig 1 Global warming potential of greenhouse gases The manufacture of iron and steel is an energy intensive activity that generates carbon dioxide, methane, and nitrous oxide emissions at various stages during the production process. Although CO2 is easily the main GHG emitted from an integrated iron and steel plant, N2O and CH4 emissions are not necessarily be small. The greenhouse gas which is the most relevant from the steel plant is CO2. The Steel Industry represents 6 % to 7 % of global anthropogenic CO2 emissions according to the Intergovernmental Panel for Climate Change (IPCC), but only 4 % to 5 % according...

Oxy- Fuel Combustion and its Application in Reheating Furnace Jan13

Oxy- Fuel Combustion and its Application in Reheating Furnace...

Oxy- Fuel Combustion and its Application in Reheating Furnace Steel reheating is an energy intensive process requiring uniform temperature distribution within reheating furnaces. Historically, recuperators have been used to preheat combustion air, thereby conserving energy. More recent innovations include oxygen (O2) enrichment and the use of regenerative burners, which provide higher preheat air temperatures than recuperators. These processes have limitations such as equipment deterioration, decreasing energy efficiency over time, high maintenance costs, and increased NOx emissions with increased air preheat temperature, unless special equipment is used. Three things are necessary for the starting and sustenance of combustion. These are fuel, oxygen and sufficient energy for ignition. The efficiency of the combustion process is highest if fuel and oxygen can meet and react without any restrictions. But during heating practice, besides efficient combustion, transfer of heat is also of practical considerations. Normal air used for combustion contains nitrogen (N2) and argon (Ar) besides oxygen. In an air – fuel burner the burner flame contains nitrogen from the combustion air. A significant amount of the fuel energy is used to heat up this nitrogen. The hot nitrogen leaves through the stack, creating energy losses. Hence air does not provide optimum conditions for combustion as well as heat transfer. Heat absorbed by nitrogen either gets wasted or is to be recovered for the purpose of energy conservation. Present day best air- fuel heating system in the reheating furnace need at least 310 M Cal for a ton of steel for achieving the right temperature of the steel product for rolling. Historically, the primary use of oxy-fuel combustion has been in welding and cutting of metals, especially steel, since oxy-fuel allows for higher flame temperatures than can be achieved with an air-fuel flame. Introduction of an innovative oxy...