Study On Desulfurization Performance Of Activated Coke Prepared From Sludge And Biomass

Sludge is an inevitable by-product in the wastewater treatment process.It contains many organic compounds and harmful substances,and is a kind of waste with very complex properties.Waste biomass has a high C/H value and can be used as a precursor material for the preparation of activated coke.There is a large amount of SO₂ gas in the flue gas,and it is discharged into the environment without purification treatment such as adsorption and removal,which will cause serious harm to people’s health and living environment.This paper uses sewage sludge from Jinan Everbright No.3 Plant and waste poplar bark from furniture manufacturing as raw materials.The effects of blending ratio,carbonization temperature,activation atmosphere and activation method on the yield,specific surface area,pore structure and surface functional groups of semi-coke and activated coke were investigated.Then semi-coke and activated coke were modified with different concentrations of ammonia solution,and the effects of ammonia concentration and modification temperature on the specific surface area,pore structure and surface functional groups of activated coke were investigated.Finally,the combination of activated coke desulfurization experiment（adsorption experiment）and graphene model adsorption simulation（adsorption simulation）was used to deeply explore the changes of physical and chemical properties and adsorption principle during the preparation,modification and adsorption of activated coke.In the carbonization process,the effects of biomass proportion and carbonization temperature on semi-coke yield and semi-coke specific surface area were investigated.By further selecting 9 groups of semi-coke products for activation treatment,and comparing the specific surface area and pore structure of the activated coke,the optimal carbonization conditions were determined.The optimal carbonization conditions are that the proportion of biomass is 2/3,the carbonization temperature is 300℃,the semi-coke yield is 71.56%,and the specific surface area is 0.6708 m2/g.Compared with the activated coke prepared by the "one-step activation method",it is found that the "two-step activation method" is easier to obtain the activated coke with large specific surface area and rich pore structure.Subsequently,the "two-step activation method" was activated at a temperature of 800℃ for 1 h to explore the effects of different types and concentrations of activators on the physicochemical properties.Experiments show that when activated with 20%concentration of steam,the specific surface area of the activated coke is larger and the pore structure is more developed.By comparing the SEM images and FTIR patterns of activated coke,it was found that the effects of steam and CO₂ gas on the pore structure during the activation process were different.Steam activation mainly plays the role of opening and expanding pores,and promotes the formation of mesoporous structure.CO₂ gas activation mainly develops the microporous structure of activated coke.Steam activation generates C=O bonds at the active sites at the semi-coke edge,while CO₂ gas activation generates saturated C-O bonds.Activated coke with better physical properties can be obtained by the above method,but the chemical properties of activated coke have little effect.In this paper,by combining the adsorption of SO₂（experiment）with the simulated adsorption process（simulation）,it was confirmed that nitrogen-containing functional groups can be introduced on the surface of activated coke by heating and modifying ammonia water.The chemical properties of the activated coke are greatly improved,thereby significantly improving the adsorption performance of the activated coke.Through the simulation process,it is found that the doping of N atoms leads to a uniform electrostatic potential distribution and a change of the surface polarity.Pyridine N atoms are used as electron donors and pyrrolic N atoms are used as electron acceptors.Both pyridine functional groups and pyrrole functional groups can promote the physical adsorption of SO₂ and H2O on the graphene surface.The presence of H2O promotes the adsorption of SO₂,and on graphene containing pyridine functional groups,dipole-dipole interactions and hydrogen bonds can be formed between SO₂ and H2O.On the graphene containing pyrrole functional groups,hydrogen bonds can be formed between SO₂ and H2O.O₂ has no effect on the physical adsorption of SO₂ on the graphene model.