Experimental modelling of mechanical peat dewatering

Dewatering of peat slurry has been carried out using a versatile, computer-controlled piston press. The effects of five operating variables on pressing were investigated. The collected data were subjected to multivariate data analysis (PLS2) in which the dewatering parameters were related to the operating variables via an empirical mathematical model. The goal of peat dewatering studies is to obtain a dry solids content of 35 per cent with an economically viable production capacity. The results proved that this goal is some way to being achieved. Peat could be dewatered to a solids content of over 35 per cent in less than 60 s under optimal conditions. Pressure is a dominant factor in the process and should be 3 to 5 MPa. The DS-load of the experiment can exceed 2 kg/m²; dosage of anionic polyelectrolyte can be as low as 0.5 – 0.6 kg/tDS and the pH level must be below 3.7. pH-lowering with H₂SO₄ does not increase markedly the sulphur content in the cake if a pH value greater than 3 is used. Chemical costs are 4 – 5 USD/tDS and are no longer preventing the process from becoming economic. Problems remain with the pressing technique, although new press types entering the market will probably in time permit economic dewatering of peat.