Analysis Of Coal Gasification Process With CO₂ Emission

With the ever-increasing development of economy, coal chemical technology has been constantly developed and improved. However, coal will still keep a leading position in the energy structure in China, and a large amount of CO2 emissions in the coal utilization process is the focus of attention. Therefore, how to improve the efficient, clean and comprehensive utilization of coal is the current urgent problems to be solved. As one of the core process, coal gasification process is studied in this thesis. The aim of this work is to reveal the energy utilization and CO2 emission in the coal gasification process.Texaco coal gasifier is used as the case study. Using ASPEN PLUS chemical process simulation software, Texaco coal gasification model is established. The relevant data of process streams and units based on process simulation are obtained.A combined method of energy analysis is proposed, which combined entropy with exergy analysis, This thesis investigated energy utilization of the process using the energy equilibrium algorithm, exergy analysis method, and the combined method. Using the energy equilibrium algorithm, the distribution of total energy of the process is obtained. The effect of energy loss through exergy analysis method is presented. The energy, entropy production and distribution of exergy loss for the case is obtained by means of the combined method. According to the above-mentioned work, the relationship between exergy loss and CO2 emission is established. After the calculation, the distribution of CO2 emission and exergy loss coefficient are presented. The results showed that the coal gasifier is the key unit for energy conservation and emission reduction.The process is simulated respectively under the pressures (2.75MPa/4MPa) and oxygen-coal ratio (0.85/0.90/0.92) through changing the operating parameters of the gasifier. Four indicators, e.g. the entropy production, exergy loss, exergy loss coefficient and the converted amount of CO2 emission, are calculated based on the simulated data. Comparing the results with the original working condition, results showed that:the increased pressures lead to the decrease of four indicators of each module; the increased oxygen-coal ratio lead to the increase of four indicators.