Examination of Potassium Recovery from Bamboo Chip Fuel Residue after Combustion

Potassium recovery from bamboo chip fuel residue after combustion was evaluated. The extraction conditions, which include the kinds of extract and the solid (weight)-liquid (volume) ratio, as well as the recovery method, which includes precipitation due to the difference in temperature after concentration by heating, were investigated. The condition for highly efficient potassium extraction was 1 . 0 mol L − 1 HCl solution with a solid-liquid ratio of 1 : 10 and a potassium recovery ratio of 85 . 4 wt% from the extract. However, the most suitable extraction method, based on the reagent cost, was 0 . 01 mol L − 1 HCl solution, which allowed a potassium extraction ratio of 65 . 5 wt%, using pulverized combustion residue. The amount of water-soluble potassium (W-K 2 O) was 53 . 7 wt% in the recovered matter, with the chemical form of KCl. Therefore, the potassium content of the recovered matter met the requirement for potassium chloride in fertilizers based on the Fertilizers Regulation Act of Japan. In addition, the amounts of harmful elements, such as arsenic, cadmium, chrome, lead and nickel, were within the permissible range in incinerated sludge fertilizer, based on the same law. Thus, it was concluded that the recovered matter was utilizable as a potassium fertilizer.