Descaling method of phospheric acid concentration heat exchanger

The invention discloses a method for decaling phosphoric acid concentration heat exchanger, namely a technique of adopting a washing-liquor composed of thin fluosilicic acid solution, organic phosphonic acid sustained-releasing agent and film forming matter and firstly washing the heat exchanger with water and then washing out the foul with the washing liquor. In the washing liquor, the fluosilicic acid is a 5%-20% thin acid, the organic phosphonic acid sustained-releasing agent includes amino tri- sub-methylene phosphoric acid, hydroxyl sub-ethyl di-phosphoric acid and hydroxyl-l, 1-subethyl di-phosphoric acid; the film forming matter includes nitrous phenylhydroxylamine ammonium salt and wuluotuopin as well as sodium molybdate. As using, adding in surface active agent alkyl sulphonate. The invention can make high efficiency and thorough decaling the graphite heat exchanger and simultaneously effectively control the corrosion of the washing liquor to the equipment and as compared with traditional washing methods, the invention improves the productivity of the equipment.