CO-drying characteristics of sticky sewage sludge pre-conditioned with biomass and coal

Abstract

The sticky sewage sludge was pre-conditioned using biomasses and pulverized coal and thin-layer drying experiments were conducted to investigate the co-drying characteristics of the mixtures. Parametric studies were carried out to investigate the effects of mixing ratio, layer thickness, hot air temperature and velocity on the drying process and to obtain the optimum drying conditions. The effective diffusivities and activation energies in the drying process of sludge and biomass/coal mixtures were determined. Experimental results showed pre-conditioning can increase the bed porosity and improve the drying rate, allowing a 50% reduction of the total drying time for the sludge/sawdust mixtures. The mixing ratio, layer thickness and hot air temperature had significant effects on the sludge drying rate. Addition of sawdust and bran reduced the drying activation energy of sewage sludge from 16.67 kJ/mol for pure sludge to 12.97 kJ/mol, 10.99 kJ/mol respectively.