Study On Life Cycle Assessment And Energy-Saving And Emission Reduction Of Coal To Ethylene Glycol Production Process

The development of modern coal chemical industry（CCI）has become the main way to solve the dependence of natural gas and oil import in China,but it has the characteristics of high carbon emissions and large emissions of waste,which restricts the development of the industry.At present,the environmental impact and energy saving and emission reduction potential of modern coal chemical production process are not clear.Therefore,based on the life cycle theory,this study analyzes the environmental impact and carbon footprint of the coal to ethylene glycol production process in modern CCI.Firstly,the units with the maximal environmental impact in the coal-to-ethylene glycol production process were found through life cycle assessment,and the main environmental impact contribution links of each unit were analyzed.At the same time,the environmental impact of the two paths for synthesizing ethylene glycol from syngas and natural gas was compared and analyzed.The key factors for energy saving and emission reduction were found by combining uncertainty and sensitivity analysis,and the changes of environmental impact and carbon emission reduction from coal to ethylene glycol under different scenarios were considered.Finally,the change of historical carbon emissions of modern CCI is analyzed,and different development scenarios are set up to analyze the future trend of carbon emissions of the industry,providing theoretical support for the low-carbon and sustainable development of modern CCI in the future.The main conclusions are as follows:（1）Using simapro 9 software and the evaluation method of recape2016,taking 1t ethylene glycol as the research object,the evaluation range is from"cradle"to"gate".The results show that the total impact of each unit on the environment is PSA unit>air separation unit>ethylene glycol synthesis unit>coal mining unit>thermoelectric unit>water system unit>coal gasification unit>coal transportation unit and HTPc is the index with the maximal impact on the environment.（2）The calculated carbon footprint of unit ethylene glycol product is 11.65 t CO₂.PSA unit accounts for 40.20%of the carbon footprint,making it the key emission reduction unit.The consumption of electricity and coal is the main contribution link of the system.Sulfur recovery and waste heat power generation can reduce carbon emissions,bringing 6.078 kg/t and 889 kg/t carbon surplus,respectively.（3）By comparing the three ethylene glycol production paths of coal,syngas and natural gas,it is found that the total environmental impact is in the order of natural gas>coal>syngas;The carbon footprint of ethylene glycol production from natural gas and syngas path is 62.41%and 43.67%lower than that from coal path.Under scenario substitution,the total environmental impact of wind power generation is reduced by 50.44%,12.77%and 20.61%,respectively.（4）Scenario analysis of energy saving and emission reduction in the process of coal to ethylene glycol production shows that under the premise of constant carbon content of raw coal,the total environmental impact of the system using bituminous coal is 12.32%lower than that of lignite.When the total calorific value of fuel is unchanged,the total environmental impact of thermal power unit of bituminous coal is reduced by 87.60%compared with lignite.When the boiler is burned with natural gas as fuel,the direct carbon dioxide emission is reduced by 44.17%.In addition,the old equipment in the production process will be updated,and energy-saving technologies such as sewage heat source recovery pump will be installed,which can save electricity and reduce the carbon emission of power consumption by 10.37%（about 48,000 t CO₂）.（5）Predict the capacity of each sub industry of modern CCI in the future,set different development scenarios,and analyze the carbon emission trend of modern CCI from 2020 to 2035.Under the basic development scenario,the carbon emission will continue to increase,reaching 392 million tons in 2035;Under the policy constraint scenario,the peak will reach about 304 million tons in 2034;Under the enhanced control scenario,it reached the peak in 2028,about 244 million tons of CO₂,decreased to 213 million tons in 2035,and decreased by 45.67%compared with the basic scenario in the same year.