Control of Sludge Dewatering with Microwave Transmitter

S. Tuomas, D. Olli, V. Rauli, Y.-V. Pirjo, N. Milla, and N. Jouko (Finland)


: Control, chemical conditioning, pulp and paper industry, microwave transmitter, bio sludge


Pulp and paper industry in Europe is impelled to cut down the amount of solid waste used nowadays in land filling. To avoid land filling sludges are usually burned, but because of their low dry solids contents, sludges need to be dewatered before burning. Dewaterisation takes place usually by mechanical means. Chemical pre-conditioning is used to ensure adequate flock strength during pressing in order to avoid solids in filtrate. The aim of this study was to find out a reliable measurement solution for dry solids content and to develop method for the controlling the dosing of conditioning agent in mechanical sludge dewatering. Study was divided in to three tasks. In the first task, the reliability of microwave transmitter as a solids content measurement device was tested. The second task was the optimisation of polyelectrolyte dosage in sludge treatment, and the third task was the implementation of sludge treatment control method. The accuracy of microwave measurement proved to be good basis for controlling the sludge handling process. Despite varying solids content the mass-based control maintained the level of polyelectrolyte constant and upholds the operation of the filter stable. This will lead to savings in sludge handling costs in the pulp and paper mill.

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