The problem of abnormal high pressure difference occurred on ultra-filter in pre-desalting system of make-up water for boilers of 4×600 MW units at Zheneng Lanxi Power Plant has been analysed

it is believed from analysis that the main causes are as follows:(1) concentration of effective chroline in sodium hypochlorite used for killing bacteria is too low

affecting the effectiveness of killing bacter;(2) stopage of dosing bactericide into clarifying basin makes the microorganism content in the inlet water of ultra-filter to increase

leading to accelerate reproduction of microorgainsms on the surface of ultra-filtering films

resulting in blockage of fouling materials.After adopting corresponding measures

the pressure difference of said ultra-filter can return to normal value within a shorter time.