A simplified and enhanced process to produce thermofertiliser obtained from potassium and phosphorous-bearing minerals is provided, where these elements may or may not be in citric acid or insoluble in water. The process also includes the use of specific additives, at the beginning of the process or immediately before the beginning of the thermal treatment step, in order to increase the potassium and phosphorous contents in the product and the overall efficiency of the process and also to promote the production of a high quality thermofertiliser.