Selection And Application Of Coal Gasification Technology For The Project Of 1.8 Million Tons Of Methanol And 0.7 Million Tons Of Polyolefin

The main processes of typical olefin production from coal include coal gasification,carbon monoxide shift conversion and purification,methanol synthesis and distillation,and methanol to olefins.Polymerization grade ethylene and propylene are obtained in olefin separation unit,and finally PE and PP products are produced by polymerization and extrusion granulation.Based on the coal gasification unit for 1.8 million tons methanol 700000 tons polyolefin project in Pucheng,Shaanxi Coal and Chemical Industry Group Company,the principle and development of coal gasification was firstly introduced,then the comparison of advantages and disadvantages of advanced airflow coal gasification technologies such as GE water slurry gasification and Shell dry pulverized coal gasification was analyzed in detail.Considering coal adaptability,target product selection,technical maturity and some others,the reasons for choosing 8.7 MPa GE coal water slurry pressurized gasification technology for this project are explained.The pressurized gasification technology of 8.7 MPa GE coal water slurry adopted in this project is the key demonstration in the development policy of the national coal deep processing industry.It has created the highest pressure of coal water slurry gasification,the largest gas production of a single gasifier,and the largest total production capacity of gasification units in the world.Under the same design load,the number of gasifier units has been reduced.The methanol synthesis reaction of the converted and purified syngas without compression has realized the isobaric synthesis,which could greatly reduce the energy consumption by 42 %in the methanol synthesis unit,and improve the absorption efficiency of methanol washing at low temperature.Furthermore,the equipment volume of low temperature methanol washing unit is reduced because of methanol cycle reduction by 36 % and cooling consumption decreasing by 70 %,and the efficiency of energy saving and emission reduction is remarkable.On October 26,2014,as the first large-scale industrial demonstration plant of 8.7 MPa coal water slurry pressurized gasification in the world,the first one-off feeding was successful.During the early stage of operation,many problems such as serious water belt in gasifier process,short operation period of process burner,frequent cavitation erosion of cold water pump,frequent failure and shutdown of high pressure coal slurry pump,and so on,have been exposed to restrict the long period,safe and stable operation of the equipment.All of the problems have been effectively solved in the subsequent technical transformation and process optimization,which provides a reference for the research and application of high pressure grade coal gasification technology.In addition,the ash water pretreatment and ammonia evaporation process were also applied in the project for the disposal of coal gasification wastewater with high hardness,solid content,and ammonia nitrogen,which is the initiative technology in industry.