The candle filter is a fully enclosed filter system. The main components are material tanks, gas storage tanks, filter pumps, candle filters, pipelines, valves, PLC electrical controls, etc.
When filtering, the material to be filtered is fed into the filter with a pump. When the liquid passes through the filter cloth, solid substances in the liquid will gradually accumulate on the surface of the filter cloth. When these solid substances reach a certain thickness, a filter cake is formed. Because the gap between the filter cake particles is small, it prevents the escape of particulate impurities in the liquid, so that the filtrate becomes clear. Before the filter cake layer is formed, the discharged "clear liquid" is returned to the raw material tank for circulation. Filter until the filter cake layer is formed (which can meet the filtering requirements), the filter provides a signal to the PLC to control the clear liquid to no longer circulate, and the clear liquid is sent to the next process through the filter valve for normal filtration.
After normal filtration for a period of time, when the filter cake layer on the porous candle wick reaches a certain thickness, the rate at which the filtrate passes through the filter cake decreases, the filtration efficiency becomes worse, and the filter pressure rises (above 0.5MPc). Then the pressure difference switch (or pressure Sensor) provides a signal to the PLC to stop the filter pump, close the feed valve, open the positive blowing valve, and then drain the residual liquid in the filter. When the liquid in the filter is lower than the filter element, open the drain valve and the residual liquid passes through the drain valve At this time, the pressure in the filter drops rapidly. The PLC receives the low pressure signal, closes the forward blowing valve, and opens the reverse blowing valve (compressed air, nitrogen or saturated steam) for back blowing to make the filter cake fall off. After a certain period of time ( 30 seconds), stop the back-blowing, open the slag discharge port of the filter to discharge the slag, close the slag discharge port after the slag discharge, complete a filtration cycle, return to the initial state before filtration, and prepare for the next round of filtration.