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Proceedings of Symposium on Energy Engineering in the 21<sup>st</sup> Century (SEE2000) Volume I-IV

ISSN:
1-56700-132-7 (Print)

DRYING OF VALUE-ADDED LIQUID WASTES

Marzouk Benali
Natural Resources Canada - CANMET/Energy Diversification Research Laboratory 1615, Lionel-Boulet Boulevard, P.O. Box 4800, Varennes (Quebec) J3X 1S6 Canada

Mouloud Amazouz
Natural Resources Canada - CANMET/Energy Diversification Research Laboratory 1615, Lionel-Boulet Boulevard, P.O. Box 4800, Varennes (Quebec) J3X 1S6 Canada

Tadeusz Kudra
Natural Resources Canada - CANMET/Energy Diversification Research Laboratory 1615, Lionel-Boulet Boulevard, P.O. Box 4800, Varennes (Quebec) J3X 1S6 Canada

Abstract

The estimated quantity of sludge generated by the Canadian pulp and paper industry in 1995 was about 2.2 million tones of dry solids (tds) while that of municipal and meat-processing sludge was equal to 612,000 and 20,000 tds, respectively. As a result of landfill directives and national legislation which impose minimum solids content of 35% and carbon limit for wastes to be landfilled, major R&D efforts are directed in developing an effective and environmentally acceptable methods of sludge treatment and disposal. Thermal drying could be an attractive solution to sludge disposal especially for complex wastes containing fibres and/or sticky components such as animal fat. Because most of dry wastes have an intrinsic value, they can be beneficially recycled in agriculture, used as a fuel or serve as an inert support in such products as a cat litter. The proposed Jet Spouted Bed Dryer with inert particles (JSBD) is an advanced and energy efficient technology to obtain powders from solutions, slurries and pastes by drying on the surface of inert particles brought into intensive and random motion. The dryer presented here was developed to process otherwise hard-to-dry pulp and paper secondary sludge and meat processing sludge as currently used technologies do not guarantee product of required quality. Experimental results obtained on a 50kW-test bench demonstrate the technical feasibility of drying such sludges, which may contain up to 15% of fibres or up to 60% of fat. Also it is possible to obtain dry product in the form of fine powder with narrow size distribution and with an average particle diameter equal to 40 µm for meat processing sludge, and 136 µm for pulp and paper secondary sludge.