Control circuit for the operating cycle of a filter - initiates auxiliary operations by optimising the average output over regulated time period

摘要

The flow of filtrate through a filter is measured and the flow is integrated. A separate integrator relays the time taken for the filtration to a summator where the time for an auxiliary operation, e.g. removal of filter cake, is added. The sum of these 2 is fed to a dividing unit in which the integrated flow is divided by the time summated to give an output which is the average output flow. This signal is monitored by an optimiser which, when the average output reaches its maximal average value, initiates a signal to a controller that stops the filtration and begins one or more auxiliary operations. At the same time this controller returns the 2 integrators to their initial position before the cycle commenced. Each control block formulates one criterion for initiation of an auxiliary operation. In the case where there are a number of control groups in sequence each setting criteria for initiating different auxiliary operations the control groups are connected to the optimising component and to all the other groups in such a way that at the time of operation of a control group all the preceding groups are returned to the initial position and all consecutive groups cut the signal coming from the particular group. The system is used for filters where continuous operation is interrupted by auxiliary operations, e.g. removing of filter cake when filtering a liq. containing sediment that builds up on the filter cloth and ensures the max. average output of the filter in the case of changes in its working conditions.