Simulation Study Of MW_th Coal/Oxygen Carrier Chemical Looping Gasification Process

Facing the trend of global warming,China's energy structure and national strategic policy of"carbon neutral”and "carbon peak",it is urgent to develop clean coal conversion process,accelerate energy conversion into clean energy and enhance the efficient utilization of carbon resources.Chemical looping technology is a clean and efficient energy conversion technology.In this paper,with the aid of chemical software Aspen Plus,based on chemical looping,a new process of chemical looping gasification or combustion is sought to develop to achieve clean and efficient utilization of coal..The influence of key parameters(coal rank,moisture in coal,gasification temperature,water-carbon ratio,oxygen-carbon ratio)on the chemical looping gasification process was analyzed on a pilot scale.The results show that the syngas yield of YangChang's coal(NX)in the Ningxia Hui Autonomous Region and Shenmu's coal(SX)in Shanxi province is higher than 2.0 Nm3/kg(coal),and the cold gas efficiency is higher than 0.9.The syngas yield from coal of YN is lower than 1.0 Nm3/kg(coal)and the cold gas efficiency is the lowest.The syngas yield and the cold gas efficiency are as follows:NX>SX>Yili's coal(XJ)in Xinjiang province>Yili's coal(NM)Neimenggu province>YN;The lower the moisture content of coal,the higher the fixed carbon content,which is conducive to the generation of syngas;The higher the moisture content in coal,the more unfavorable it is for gasification,since moisture will increase steam and take away heat.When the moisture content of lignite decreases from 22.38%to 0,the yield of syngas increases,and the cold gas efficiency increases from 0.678 to 0.912,increasing by 34.5%.The required heat of the gasification reactor decreased from 1.92 MW to 1.75 MW,and the required heat decreased by 8.89%;The operation range of chemical looping gasification is:gasification temperature:850-950?,oxygen to carbon ratio:1.0-3.0,water to carbon ratio:1.0?2.0;In the process of chemical looping gasification,H2S and COS are the main sulfur pollutants,while NH3 and HCN are the main nitrogen pollutants;In terms of raw material selection,in order to get more syngas,coal with high fixed carbon,less moisture and low volatile matter should be selected as raw material.The drying device is added before the coal enters the gasifier to improve the yield of syngas and the efficiency of cold gas.A new process of producing H2 and NH3 with coal based double chemical looping was developed,and the process parameters and energy consumption were optimized,and the feasibility of the process was demonstrated by economic analysis.It was found that compared with CLG and CLHG,the hydrogen and N2 yield increased by 25.63%and 12.90%,and 49.96%and 39.22%,respectively;As the downstream unit,CLHG plays the role of secondary combustion for hydrogen production,and CLG is the main H2 generating unit;Gasification temperature,S/C and O/C control the total hydrogen production rate by influencing the CO and water vapor content in the syngas,and thus affecting the downstream WGS and CLHG units;The study found that when the gasification temperature is 900?,steam-carbon ratio is 0.84 and oxygen-carbon ratio is 1.5,the hydrogen production rate of the system was the maximum;After the optimization of the heat exchange network design,about 61.58%of the total utility consumption is saved,so the total utility cost is reduced by 48.69%;.An economic estimation study found that the production cost of ammonia is 108.66 $/tNH3.Finally,cost of equipment is the main factors influencing ammonia production cost were proposed by sensitivity analysis.Finally,a new process of chemical looping combustion carbon capture coupled with CO2 activation to produce low carbon olefins is designed,the process conditions are determined,the thermal efficiency of the system is simulated,and a simple economic estimate is made for the system,the feasibility of the process is demonstrated,and the advantages of the process are expounded.Its system includes:chemical looping combustion system,steam reforming system and activation system;The main equipment is four circulating fluidized beds:fuel reactor(850??1100?,oxygen to carbon ratio of 2.0?3.0,water vapor to carbon ratio of 0.5?1.0),air reactor(950??1200?),steam reforming reactor(adiabatic,10 bar),activation reactor(250??300?,10 bar?30 bar);The production cost of olefins is 5233 RMB/ton and the production profit is 38.5%;The process raw materials from a wide range of carbon capture and carbon sequestration process is simplified,low energy consumption,low cost;Olefins production process is simple,high benefit advantages.