Experimental Study On Mercury Removal And Desulfurization From Flue Gas By Sorbent With Non-thermal Plasma Treated

Coal combustion is the largest anthropogenic pollution source of dust,NO_x,SO₂ and mercury.As the largest coal producer and consumer in the world,China's environmental pollution problem has aroused great concern.The activated carbon injection?ACI?technology has been recognized as the most promising control technology for removing mercury from the coal-fired flue gas,but the cost is too high and the regeneration effect is poor.The development of efficient and economical mercury removal or combined removal technology has great significance.The non-thermal plasma?NTP?is recognized as one of the most promising technologies for Hg0 removal,and it can realize the simultaneous removal for multi-pollutants,with high efficiency,simple system,no secondary pollution and so on.In this paper,the desulphurization effect of adsorbent is enhanced by non-thermal plasma modification technology for the purpose of synergistic mercury desulfurization.The effects of non-thermal plasma modification on the mercury removal and desulfurization of composite calcium based adsorbents were investigated.The experiment was explored with the assistance of BET,SEM-EDS and other characterization methods.The experimental results show that the chemical adsorption of activated carbon is the control step on the surface adsorption.The activated carbon with low temperature plasma treatment has higher mercury removal efficiency.The activated carbon achieves the optimum modification effect at 30W for 10 min,and the unit mass of mercury adsorbed increased by about 80%.The mercury removal efficiency of the activated carbon after modification in the N2 atmosphere has almost no change,while the oxygen-containing functional groups of activated carbon modified in the air and O2 atmosphere were obviously increased and the mercury removal efficiency were improved.Activated carbon after modification in the HCl atmosphere formed C-Cl bond which rapidly increasing the oxidation capacity.In order to prepare the adsorbent having good mercury removal and desulfurization performance,a calcium-based composite sorbent was prepared by hydration of activated carbon with calcium oxide.Desulfurization efficiency and mercury removal efficiency of the adsorbent were increased after plasma treated.The results show that addition of calcium carbonate adheres to the surface of activated carbon after hydration with activated carbon and calcium oxide,and the effect of mercury removal is optimal when the mass ratio of AC to CaO is 1,the hydration time is 1h and the temperature is 70 ?.The calcium-based composite sorbent produced a significant etch effect after the plasma modified.The high-energy electrons,free radicals produced by plasma and adsorbent impact on surface increase the number of oxygen-containing functional groups on the surface of the calcium-based composite sorbent.The mercury removal efficiency of the calcium-based composite sorbent was significantly improved under the condition of 40W for 10 min.The mercury removal efficiency and the unit mass of mercury adsorption capacity were 40.7%and 34.7%higher than that of the unmodified adsorbent.Adequate O2 can promote the desulfurization of calcium-based composite sorbent.There was strong competitive adsorption between NO and SO₂.After plasma modification,calcium-based composite sorbent was more favorable for removal of SO₂.When the oxygen content is 6%,700 ppm of SO₂ was benificial to the efficiency of mercury removal of activated carbon,calcium-based composite sorbent and calcium oxide.The mercury removal efficiency of the calcium-based composite sorbent after plasma modification was increased from 67.2%to 91.2%because the plasma modification improved the number of oxygen-containing functional groups on the surface of the adsorbent and the activity of the adsorbent.When the adsorption temperature is 120?,the effect of low concentration SO₂ on mercury removal was relatively weak.However,.if the concentration of SO₂ was controlled at 700 ppm or 1000 ppm,the mercury removal efficiency was maintained at more than 90%for a long time,increasing mercury removal efficiency.In a relatively high SO₂ concentration,a large inhibitory effect on the mercury removal of modified calcium-based adsorbents appeared,which was mainly affected by oxygen-containing functional groups and competitive adsorption between SO₂ and Hg0.O2 plays an important role in the simultaneous removal of Hg0 and SO₂ by addition of calcium-based adsorbents,the mercury removal efficiency of adsorbents increased from 23.7%to 91.2%,and the desulfurization efficiency also increased.Mainly due to the carbonyl and lactone groups and other functional groups on the adsorbent surface increased with the existence of O2,the synergistic removal of SO₂ and Hg is much promoted.