Activated Carbon Preparation And Recovery Of Potassium And Phosphorus From The Ash Of Power Plant Firing Agro-residue

Power generation from biomass has been developed rapidly.Grate boiler is the mainstream boiler of biomass power generation,which mainly burn crop straw.The ash residue of grate boiler contains unburned carbon,potassium and phosphorus.Its shortage of nitrogen and inconvenience in use is not recycled well to farmland.This paper carries out the study on activation carbon production and nutrients recovery from the ash of power plant firing agro-residue and the new ways of resource utilization to improve the sustainability of the industry in economy and ecology.The potassium and phosphate are recoveried and separation of unburned carbon from the ash of power plant firing agro-residue(8.88%fixed carbon,64.00%SiO2)with using two-step acid solution.At the same time,filtration and separation process,material balance calculation,analysis of potassium,phosphorus and heavy metals cadmium lead chromium in solid-liquid mass distribution of each phase will be concerned.The recovery process of two acidification steps was determined by the determination of the separation speed and the recovery rate of the element with acid solution.The results show that the pH 3.5 is adjusted with concentrated hydrochloric acid in the first step acid solution,which will contribute to separate between solid and liquid phases.The potassium liquid(recovery rate was 68.17%),carbon residue 1(9.69%fixed carbon)and bottom ash will be obtained in the first step acid solution.Second step acid solution of raw materials is bottom slag of first step acid solution.The bottom slag is dipped in acid solution with concentrated hydrochloric acid to adjust pH to 0.8 in order to extract more phosphorus.Than,phosphorus solution(the recovery rate is 86.51%),carbon residue 2(11.63%fixed carbon)and silicon slag(87.67%SiO2).The results show that straw ash is a good source of potassium and phosphorus.When nutrients is recycled from the ash of power plant firing agro-residue,the breeze C is mixed with breeze D,which are recored as breeze of agro-residue.A two-step acid solution is used to deal with the ash residue of rice husk from power plant in the same way.The breeze C is mixed with breeze D,which are recored as breeze of rice husk.The breeze of agro-residue and rice husk will be activated with KOH after alkali solution.At last,the activated carbon of agro-residue and rice husk will be achieved,the ash content of which were 4.23%and 3.32%respectively,the specific surface area of which are 1165 m2/g and 1794 m2/g respectively.The ash content and surface area of agro-residue and rice husk meet the standard requirements related to conventional activated carbon.From the surface area,the activated carbon of rice husk reach the basic standard of advanced activated carbon,and its particle size of D50 and D90 were 29.6 pm and 87.8 ?m,respectively.Activated carbon is commonly used as adsorbent and can achieve the target of enrichment separation by adsorption-stripping.However,the activated carbon insulation feature hinders strongly the heat transfer on the activated carbon surface during the thermal regeneration process and probably results in hot spots and auto-ignition.Aluminum nitrate is used as the aluminum source and activated carbon of rice husk is used as carbon source.The coefficient of thermal conductivity of activated carbon will be improved from 0.25W/(m K)to 0.54W/(m·K)through high temperature nitriding reaction(1550?)on the surface of activated carbon in situ generated heat conductor(AlN).