Chemical-looping Gasification Of Sludge/coal With Iron-based Oxygen Carrier

With the acceleration of industrialization and urbanization in China,wastewater discharge is yearly increased,and the wastewater treatment rate is also increasing.As a secondary product of wastewater treatment,sludge treatment has become an urgent problem to be solved.How to reduce sludge,harmless,stabilization,and resource treatment has become one of the topics of great concern in China and even the world.As the main energy resource in China,coal is widely used and causes great pollution.Therefore,it is necessary to propose new coal utilization technologies to reduce pollutant emissions.Hydrogen as an efficient and clean green energy has an extensive developing prospect in the future.In this paper,a sludge/coal chemical looping gasification system for hydrogen production is proposed,which can produce hydrogen-rich syngas while efficiently treating sludge,and achieve near-zero discharge of pollutants,which is of great environmental friendliness.In this paper,the reaction process of sludge/coal chemical looping gasification was systematically studied by experiment and model fitting,mainly including the following three aspects:1、Conditional experiments were carried out on a high-temperature fluidized bed to explore the effects of reaction temperature,OC/coal ratio,water vapor volume fraction and sludge addition ratio on the experimental results.When the reaction temperature is 900℃,the mass ratio of O/C is 5.80,the volume fraction of water vapor is 72 vol.%,and the S/C is 0.2,the H2 concentration in the outlet gas can reach 75.6 vol.%,and the syngas production is 97.5 L·min·kg-1.The cycle experiment on this basis showed that the addition of sludge did not change the phase composition of the oxygen carriers,but could improve the H2 concentration and syngas production.The presence of sludge ash after four cycles will decrease the reaction carbon conversion rate,and increase the carbon conversion rate after ash separation.2、Adding a certain amount of sludge ash in the reaction process can increase H2 concentration and syngas production.When adding 10 wt.%sludge ash,H2 concentration can be greatly improved.However,excessive sludge ash addition can cause agglomeration and sintering of oxygen carriers.3、Sludge/coal chemical looping gasification reaction process can be fitted by a random pore model.The addition of sludge can reduce the activation energy of coal chemical-looping gasification reaction,accelerate the gasification reaction rate and increase the carbon conversion rate.