Co2 Accounting and Abatement: An Approach for Iron and Steel Industry

The issue of energy use in iron and steel making operations has been focused by several authors. Since current operations use predominantly fossil fuel based carbon bearing inputs, energy use is related to CO2 emissions which is a Green House Gas. Abatement of CO2 emissions requires a proper CO2 accounting procedure to be established for an existing operation. Varied approaches have been used, but information on mass and energy balance for individual process steps and the plant as a whole have scarcely been correlated to emission patterns for individual process steps as well as the total plant. In the accounting procedure suggested, the first step is to establish a carbon balance encompassing input carbon, fuel gases generated and solid/liquid fuel produced. Once the quantities of by-product fuel gases are established through carbon accounting, consumption route of these gases are examined using a carbon flux diagram, to ascertain which process steps emit maximum CO2. Predictive models can be used to work out downstream fuel gas streams requirements as well as surplus generated. Use of analytical models for reduction of CO2 emissions at source can be combined with an objective of overall cost reduction objective for evolving implementation strategies without sequestration. Greater CO2 abatement can be obtained through use of carbon capture and sequestration, as applied to steel mills. An example case for sequestering the stove flue gas of a conventional blast furnace using an amine system for capture combined with slag sequestration is discussed. Use of a ‘top gas recycle system’ with CO2 separation using VPSA is shown to lead to greater degree of abatement. The emission allocation issues, related to Life Cycle Analysis are important for arriving at the total emission pattern. Implementing carbon abatement requires additional auxiliary technology development, such as recovery of low grade heat, for supporting energy requirements associated with CO2 separation.