Emission reduction potential in PTA production plant through cogeneration technology

Abstract

The focus of this research was to investigate and study the cogeneration potential in PTA production plant for reducing the emission to the environment due to high energy consumption in the respective plant. Currently, the total power requirement of the plant is about 26 MW per month in which fortunately, the Energy Improvement Team manage to locally generate 6 MW by using the expander and another 6 MW by using the steam turbine. However, through this new improvement project, it still contributes up to approximately 49,500 tonne CO2 emission per year. In view of that situation, the potential of cogeneration is studied in this research with the main objective to reduce the carbon dioxide emission to the environment. Gas turbine system is selected over other Cogeneration or Combined Heat and Power (CHP) technologies due to several reasons such as power demand are continuous as well as high availability of natural gas in the plant[1]. In this study, the by product from the gas turbine (exhausted hot gases from turbine), will be utilized for local heating; the hot oil system facility. A preliminary design of gas turbine engine with heat recovery system has been carried out and research study had attested cogeneration has high potential to reduce the emission up to approximately 40,500 tonnes per year with reasonable annual percentage of emission savings up to 18.2%. The gas turbine design also manages to reduce the utilities and electricity costs in the plant of approximately RM 14 million per year which is accounted for 25% savings. Shaft work produced by the turbine is used to power the air compressor of axial flow type which amount up to 20 392.64 kW and producing net power of 29.61 MW before being transformed into electricity for domestic application in PTA plant and sales purpose. For the heat recovery system, an amount of 20 934 kW have been recovered from the exhausted air with temperature of 493.29 °C. Overall thermal efficiency of the system is determined to be 70.71% while the payback period of the gas turbine engine is determined to be 6 years with net present value of RM 347 491 087 and rate of return of 18.91%. Therefore, it is really a valuable and worth effort to install the new gas turbine engine in the respective plant. Through the implementation of this new gas turbine, not only the emission can be reduced but also impact a significant reduction in operating cost. Therefore, it is really a valuable and worth effort to install the new gas turbine engine in the existing PTA plant to sustain the environment.