(240b) Study On Energy Consumption and Emission Generation for A Chemical Plant Under Different Start-up Strategies

Chemical plant start-ups are very critical dynamic operations, which consume huge amount of energy for heating, cooling, compression and other usages; meanwhile, they also generates large quantities of off-spec products for flaring, causing significant and intensive air emissions. Many studies have been conducted on the energy consumption minimization or energy efficiency improvement for normal chemical process production.  However, quantitative studies of the energy consumption and emission generation analysis on chemical plant start-ups are still lacking.  In this study, plant-wide dynamic simulations are employed to study energy consumption and emission generation for a chemical plant under different start-up strategies, so that the quantitative technological support can be provided to identify the most desirable start-up operation.

In order to examine impact from different start-up strategies for the sake of flare minimization, two start-up designs with different recycling stream patterns and two start-up operating strategies with different time  arrangement are performed.  Besides the plant-wide model, rigorous dynamic simulations are also conducted for critical units to examine their operating safety.   Based on the multiple dynamic simulations, the dynamic profiles of energy and emission during the plant start-up can be obtained and summarized.  Details of energy consumption on cooling and heating duties of distillation towers, auxiliary heat exchanger duties, and power consumption for compressor system are provided for each start-up case.  Simultaneously, the identifications of emission sources, including the speciation and the percentage information, as well as the dynamic emission profiles during an ethylene plant start-up are obtained.  Through comprehensive analysis and comparison, the most desirable start-up solution is identified.  This study not only characterizes the emission generation during the plant start-up, supporting flare minimization activities that benefits environmental sustainability, but also enhances critical research on energy and raw material consumptions during plant-start-up that finally benefits the industrial sustainability.