Mechanical and thermal dewatering of residual sludge

摘要

The management of residual sludge is an important subject.New environmental laws require the elimination of this waste by only two ways:incineration and agricultural use.In order to reach this goal,mechanical dewatering can be used as a first step due to its low energy cost.However,the final moisture content reached through this method is not generally sufficient and drying becomes obligatory.In this work we studied the first step:mechanical dewatering.Some experiments were carried out on a laboratory filtration-compression cell and the use of the Ruth relationship approach was tested in order to characterise slurry in filtration.We also studied the second step:thermal dewatering.From laboratory convective drying experiments,a macroscopic approach in terms of kinetics curve and drying potential was developed.This criterion,which groups a set of external conditions into a unique parameter (temperature,relative humidity,air velocity),allows for easy classification of different operating strategies.