Study On Leaching Potassium From Plant Ash

The plant ash is rich in potassium. Leaching of potassium elements from plant ash as the potash fertilizer can effectively reduce the importing quantities of potash fertilizer in our country. With currently enormous construction of the straw power generation, leaching of abundant biotic potassium in the plant ash is catching more and more attention.The experiment of leaching potassium from plant ash was studied in this paper. The technical conditions were explored. The effect of technical conditions such as leaching time, leaching temperature and the particle diameter of plant ash on the recovery rate of potassium was investigated to find out the optimal conditions and increase the recovery rate of potassium.The experiments demonstrated that the stirring rate, particle diameter of plant ash, the mass ratio of ash-water and the leaching temperature had a significantly effect on leaching speed and recovery rate. The recovery rate was increased with the speedup of the stirring rate. When the stirring rate was above 500 rpm, the leaching process agreed well with the Avrami model. The apparent activation energy was 10.04 kJ/mol indicated that the leaching process was controlled by the internal diffusion. The leaching speed of potassium ion increased with the decrease of the mass ratio of ash-water, at the same time the relative loss of potassium ion and the concentration of potassium ion in leaching solution decreased. Rising the leaching temperature and decrease the the particle diameter of ash could lead to faster leaching speed and higher recovery rate.From the results of orthogonal experiment, it was concluded that the fractor affected the recovery rate followed this order: stirring rate>particle diameter of ash>leaching temperature>time of leaching>mass ratio of ash-water. The optimal leaching conditions as following: plant ash was smaller than 50 mesh, 99℃, stirring rate was 400 rpm, the mass ratio of ash-water was 1:2 and leaching time was about 60 minutes. After thrice leaching under the conditions above, 93.82% potassium ccould be extracted in a solution contain 3.94% potassium (quality percent according to potassium oxide).When seawater was used as the leaching agent, the content of potassium chloride in leaching solution increased, the content of potassium carbonate decreased and the content of potassium sulphate keep constant. The economic benefit was lower when seawater was used as the leaching agent than fresh water, and the addition of sodium salts made the separation of potassium chloride, potassium carbonate and potassium sulphate more difficult.