METHOD AND APPARATUS FOR IMPROVING THE OPERATION OF A DISC FILTER

The present invention relates to a method and an apparatus for improving the operation of a disc filter. In particular the invention relates to increasing the discharge consistency of fiber suspensions treated with disc filters in the paper and pulp industry. As is known the consistency of a fiber suspension can be raised with disc filters to approx. 16 % measured on a filter disc. However, when a cake of pulp is detached from the filter surface the detaching water jet reduces the consistency to approx. 12 % measured in the pulp discharged from the thickener. In all prior art devices the detaching liquid jet is continuous and liquid is sprayed onto the filter surface even though the pulp cake already has been detached or would be detached from the filter surface by itself due to the force of gravitation. This results in unnecessary dilution of the pulp. In order to avoid the above mentioned drawback a method and an apparatus (11, 12, 13, 14) have been developed with which the detaching liquid jet sprayed from a nozzle (7) is made intermittent so as not to add unnecessary liquid to the pulp. This increases the consistency of the pulp discharged from the thickener at least by 2 % which is a remarkable advantage both for the operation of the thickener itself and also for the operations subsequent to the thickening.