Conceptual Design Of Coke-oven Gas Assisted Slagging Gasification To SNG Process

Natural gas is a kind of important clean energy.To improve its consumption in China's energy structure is a meaningful measure of sustainable development.With the increasing contradiction between supply and demand of natural gas,the project of coal to natural gas(SNG)has been developing rapidly.Coal to SNG project can achieve effective conversion of coal energy.But at the same time,a large number of wastewater,which is difficult to deal with,and carbon dioxide are generated.Through the study of coal to SNG project,it is found that the pressured fixed-bed gasifier is widely used,but it has some problems,such as producing large amount of waste water,which has complex composition and is difficult to deal with.Meanwhile,the water gas shift(WGS)unit needs to be set up to increase the hydrogen content for increasing the H/C ratio,resulting in a large amount of carbon dioxide.In view of the above problems,it is found that the slagging gasifier developed on the basis of pressured fixed-bed gasifier has higher gasification efficiency and less waste water,which has greater advantages in efficiency and environmental protection.In addition,coke oven gas(COG)which is hydrogen-rich and carbon-less can realize complementarity of elements.COG is a kind of gas produced in the coke industry,and its H/C ratio can reach 6.5.Therefore,a new technology of COG assisted slagging gasification to produce SNG was proposed in this paper.Based on the typical process of coal to SNG,the slagging gasification technology was adopted,which is more efficient and environmentally friendly.COG separation unit and dry reforming unit were added.The addition of COG could increase the H/C ratio and remove the WGS unit in the traditional process.In this paper,a part of methane separated by COG was used to react with the carbon dioxide produced by the system,which could be used to recycle carbon resources.The simulation software Aspen Plus was used to model and simulate the new process.And techno-economic analysis of the new process were made.The results showed that compared to the coal to SNG process,the energy efficiency of the new process was increased by 6.7%;the production cost was reduced by 18%,and the emissions of carbon dioxide and waste water were reduced by 94.8% and 83% respectively.The effect of energy saving and emission reduction was obvious.