Removal Of NH₃ And H₂S Derived From Livestock Farm By Modified Activated Carbon

In recent years, with the increase of demand and the promotion of profit of stock and poultry product, intensive farms have developed rapidly, it is also convenient to satisfy the market demand and improve the economic benefit. Meanwhile, the environmental problem appears, especially the pollution of odorous gas. It seriously affects people's physical and mental health and threatens the safety of environment. The research and control of odorous gas have wide practical significance. NH3 and H2S as the main odorous gases from livestock farm are urgent to be removed efficiently. Adsorption has the advantage of rapid removal reaction rate and high removal efficiency, and it has been paid more attention than before.In this paper, activated carbons (diameter:3mm) from the Xinhua Chemical Plant are selected as raw activated carbon (RAC). High-pressure hydrothermal method, impregnation method and the combinatory method are used to modify RAC. The NH3 and H2S removal performance of modified activated carbons have been evaluated in fixed bed. It is concluded that activated carbon which is modified by high-pressure hydrothermal method at 270? for 3h firstly then by impregnation method in 10%CuCl2 at 60? for 2h has the best adsorption performance.The operation conditions of adsorption on modified activated carbon have been investigated in fixed bed. Considering the characteristic of these two gases, adsorption equilibrium can be in balance of physical adsorption and chemical adsorption at 50?, so 50? is the optimal temperature of NH3 and H2S adsorption; the space velocity determines the remaining time in reactor and the best space velocity is 900b-1; 550-650mg/m3 is the optimal inlet concentration range of NH3 and H2S.Modified activated carbons have been studied as a regenerative adsorbent and the results show that at staged heating condition, the method of 20%O2+15%H2O in N2 has best regeneration performance. The modified activated carbons have adsorbed-regenerated for multi-cycles and the results show that with the increase of cycle time, both the adsorption capacity and the removal rate decrease with time.The samples of modified activated carbon have been characterited by BET, Boehm and FTIR methods. The results demonstrate that the pore structure can be promoted greatly by high-pressure hydrothermal method and the surface chemical properties can get further promotion by impregnation method on the basis of high-pressure hydrothermal method. So combinatory method has the best modification performance.After adsorption, specific surface area, pore volume and the amount of surface functional group decrease greatly. Regeneration can restore pore volume and surface functional groups to a great extent. Due to part sintering of activated carbons and halfway decomposition of adsorption production in regeneration process, the pore structure collapses partly and the surface functional groups are restored partly. That makes regenerated activated carbons not restore to the level of fresh modified activated carbon. Adsorption-regeneration cycle is not only the pore block-open cycle, but also the surface functional groups consumption-restoration cycle. With the increase of cycle time, both the restoration rate of specific surface area and pore volume and the amount of surface functional groups which are beneficial to adsorption decrease.In this paper, the adsorption of NH3 and H2S by modified activated carbons is the combinatory action of pore structure, surface chemical properties and the modifier.In summary, this paper focuses on the removal of NH3 and H2S derived from livestock farms by modified activated carbon. The regeneration methods and regeneration performance have also been investigated. It has great significance on industrialization in future. However, the mechanism for adsorption and regeneration is still relatively few, and further research can be done in mechanism.