METHOD OF CLEANING INNER SURFACE OF HEAT EXCHANGE EQUIPMENT Russian patent published in 2000 - IPC

FIELD: chemical methods of removing difficultly soluble deposits from inner surfaces of tubular space of heat exchange apparatus in production of carbamide. SUBSTANCE: cleaning is performed in three stages: at first stage, tubular space of apparatus is filled with phosphoric acid of 60-65% which is kept in this space for 30- 40 minutes at boiling point of 110-120 C. Then acid is drained into receiver and dissolved sediment is washed off with demineralized water for 1.5 hours. At second stage, acid is kept for 1-1.5 hours at the same temperature and washing-off of sediment is continued for 2.5-3 hours. At third stage, acid is kept for 4.5 hours at boiling point; final washing is effected with demineralized water for 10-12 hours. EFFECT: 100-% cleaning of apparatus; enhanced efficiency in restoration of heat exchange; reduced power requirements. 1 tbl