Recycling of Phosphorus - Application of Slag and Ashes in Agriculture

Several attempts were made to generate a slag based phosphorus fertilize to supply farmers with a product similar to the well known Thomas slag. The paper describes the development and advantages of a phosphorus fertilizer developed by treatment of liquid BOF slag with phosphorus containing ashes. In lab scale experiments the amount of phosphorus was increased, compared to non treated BOF slag, and is almost 100 % plant available. The results achieved in lab scale experiments have been transferred successfully into operational practice of the steel production. The designed process is virtually energy-neutral by exploitation of the thermal and chemical energy contents of the BOF slag. The new fertilizer owns the proven fertilizer qualities of the Thomas slag and could be marketed as Thomas lime of second generation and is introduced as “converter lime Type C, ground BOF slag after addition of phosphorus materials in the liquid state” in the German Fertilizer Regulation, June 2015.