MICROPROCESSOR BASED MULTIPARAMETER CONTROLLER FOR BATCH DIGESTERS

Abstract

The paper mill is basically a continuous process and pulping is the beginning phase in the manufacture of paper.. Pulping is done in a batch digester or continuous digester. To obtain a uniform and good quality of pulp, various variables of the digester should be controlled properly. Automatic controller may be evolved for controlling these variables accuratelyi The present work was undertaken to develop a microprocessor-based controllers for single batch digester and multiple diges-ters.. Controllers for the two cases have been developed successfully. The software created is versatile and efficient. The hardware includes thumbwheel switches for adjusting set points, A/D converters and D/A converters for interfacing the microprocessor with the digester for feeding back values of controlled variables and outputting control signals to various control valves, indicators to display the ongoing phase ofthe digester and alarm to annunciate completion of the batch. The microprocessor-based. controllers for single and multidigester control have been tested under different simulated conditions of digesters.'The multidigester controller has also been checked for different sequence of switching digesters: The results are gratifying.