REDUCTION OF CO2, S02 AND NO2 EMISSION IN CHEMICAL - PROCESS INDUSTRIES

Abstract

The combustion of fossil fuels to satisf' the heating demand of the process industries is the main - source of environmental pollution. Combustion products such as carbon dioxide, sulphur dioxide and nitrogen dioxide are the major causes of global warming, acid rains and smog. This work aimed at reducing gaseous pollutant of CO2, SO2 and NO2 while minimizing total annual cost (TAC) incurred to the plant. In this work, a simple superstructure for heat integration is presented. Superstructure is a stage-wise representation where each hot stream can exchange heat with each cold stream within each stage. MINLP model is used to solve the exchanger network. The hot utility requirement of the process stream is supplied using four fuels such as diesel, natural gas, coal and jatropha biodiesel and three utility systems like Ilirnace, gas turbine and steam turbine. CO2. SO2 and NO2 emissions are maintained within the imposed limits of these emissions in the plant. The objective function to be optimized is the TAC of the plant. Different constrains of the MINLP model are emission and energy. Thus, the present mathematical model is formulated to find the focI-utility system combination having minimum TAC constrained to CO2. SO2 and NO2 emissions. The developed model is used to solve four case studies, which are considered from open literature. The results of all these case studies show that in terms of global emission natural gas-gas turbine has the lowest CO2 and SO2 emission while diesel-gas turbine has the lowest NO2 emission. Economic analysis of all the systems shows that coal-steam turbine system has the minimum TAC. Replacing natural gas-gas turbine system with coal-steam turbine system reduces TAC by 54.98%. However, CO2, SO2 and NO2 emission increases by 18.87%, 95.99% and 10.195% respectively due to replacing natural gas-gas turbine system with coal-steam turbine system. Replacing coal with natural gas in steam turbine experienced a decline of CO2, SO2 and NO2 emission by 41.18%, 97.17% and 34.57% respectively. While comparing results of present study with that of published work it is found that CO2 and SO2 emissions is in accordance with the work of Smith and Delaby (1991). Replacing coal with natural gas in steam turbine reduces CO2 emission by 70%, which is also observed by Gota (2009).