Experimental study on drying characteristics of sewage sludge at low temperature

Drying characteristics of sewage sludge were studied of laboratory scale. Special made sludge additive agent was used to improve sewage sludge drying performance, and drying experiment was performed under different sludge additive agent ratio (0, 20% and 30%), drying temperature (50 degrees C, 60 degrees C and 75 degrees C) and drying air velocity (2.2m/s, 1.94m/s and 1.67m/s). A new mode about water existent form in sewage sludge was brought forward. Experiments proved that sludge additive agent can improve the drying performance of sewage sludge by breaking down the water chains and reducing the water affinity between sludge solid granules. It was found that there was an optimal sludge additive agent ratio which can lead the best drying performance. The higher drying temperature and drying air velocity was, the larger drying rate would be.