Method for applying gas at two sequential pressures to microporous membrane filter

摘要

A process to clean esp. a microporous membrane filter (14) uses an assembly (10) to filter a liquid containing a substance such as a suspension or emulsion. The novelty is that the process incorporates the following steps: (a) The unfiltered liquid inlet (20) and outlet (30) valves are closed and gas introduced at determined pressure (P1) to filter chamber (18); filtrate is displaced from the filtrate chamber (18) through the membrane filter (14) into a chamber containing unfiltered liquid (16); the concentration is not controlled; gas bubbles do not reach the chamber containing unfiltered liquid (16) through the membrane (14). (b) The concentrate outlet valve (30) is closed and the gas pressure is raised from the initial value (P1) to a higher value (P2) for a predetermined time (T); the gas in the liquid close to the membrane (14) loosens deposits on the membrane (14) but without gas bubbles escaping into the liquid within the chamber (16). (c) The gas pressure in the chamber (16) is quickly relaxed.