the pulse blow controller is the control equipment of cleaning blow system for pulse blow bag filter. the output signals of the controller control the electromagnetic pulse valve to blow pressure air, which removes the dust of the filter bag in sequence to control the resistance of the bag filter and to ensure the normal operation of the filter.
the dust adheres to the side faced to dust of the filter bag, and forms the dust cake, therefore the resistance (pressure drop between input/output) of the filter increases. if the dust can’t be removed in time, the drawing air pressure of the collect input port will decrease, so the less processing air floe, the lower efficiency of the whole system. if the resistance can’t be controlled and increases continuously, the filter will cease working. otherwise the over cleaning will lower the filter resistance and the dust particulates exhaust will increase. therefore the proper and effective cleaning is the key to control the resistance of the bag filter.
there are two kinds of pulse blow controllers:
1) time order control (fixed time control): the sequence blow of the electromagnetic pulse valve is controlled by set time.
2) pressure difference control (fixed pressure difference control): the blow of the electromagnetic pulse valve is controlled by the resistance change of the bag filter.
the time order control (open-loop control) is more simple, reliable and convenient for maintenance. the time parameter is seted and changed, and the blow cycle is adjusted by the operation experience. but the blow parameter can’t be changed by the resistance change of the filter.
the pressure difference control (closed-loop control) is more reasonable, because the blow of the pulse valve is controlled by the filter resistance change. but the maintenance cost is higher. if the sample port of the pressure difference control is suitable for bigger changes of dust air flow, to keep stationary operation of the filter.
terminology and definition of pulse blow controller
pulse interval: the interval time between adjacent two output electric signals of the controller.
pulse interval: the interval time between adjacent two output electric signal of the controller.
cleaning: the adhesion dust layer on the filtering medium is removed to recover the filter capacity of the filtering medium.
pulse blow cleaning: the pressure air released instantly by the pulse valve produces a shock vibrant reversal flow, which expands the filter bag fast to remove the dust.
cleaning duration: each continual blow time of a single pulse valve, seted and controlled by the controller.
cleaning interval: the blow interval tome between two adjacent pulse valves, seted and controlled by the controlled by the controller.
cleaning continual time: each cleaning time of a bag filter from beginning to the end.
cleaning waiting time: during when the bag filter doesn’t need to keep on cleaning due to pressure drop or time parameter set after finishing one clean.
cleaning cycle: the interval time between two adjacent cleans of whole bag filter, which includes the cleaning time and the waiting time.
repeatedly blow time: during when the controller outputs the electric signals, which make every valve blow two times or above (including the interval time between two blows)
the pulse blow controller was used in pulse bag filters early in 70th of last century, but equipped with only fixed time, controller makes it easier to be disturbed and difficult to resist high temperature, dust and electromagnetic interference, with the development of electronic technology from separated elements, logic integrated circuit, special ic to single-chip computer, the element volume reduces greatly with the same function of previous controllers. the resistant interference performance also continues improves with the increased integration. especially the single-chip computer contains the central process unit (cpu); input/output interface (i/o), timer, memory and software supports, the function expands significantly, such as set time, set pressure difference, on line or off line control. if the programmable logic controller (plc) is used to cleaning control of bag filters, it’s easy to achieve the control of temperature, material level, dust removing, dust transportation, and alarms for various faults. it more adverse circumstances. therefore the equipment quality can be improved significantly.