Sewage sludge valorization by flash pyrolysis in a conical spouted bed reactor

Sewage sludge valorization by flash pyrolysis has been carried out in a conical spouted bed reactor with continuous biomass feed and char removal. The effect of temperature on product yields and composition has been studied in the 450-600 degrees C range and a maximum liquid yield of 77 wt.% daf (dry and ash free basis) has been obtained at 500 degrees C. The liquid collected has a water content of 23-27 wt.% and is mainly composed of oxygen-containing compounds (phenols, ketones and acids amongst others), whose yield decreases with temperature, and nitrogen-containing compounds, such as amides and pyrroles. In addition, the importance of an efficient char removal system has been assessed by operating with and without char accumulation in the bed. The char fraction retains most of the heavy metals contained in the sludge and they may have applications in agriculture or as adsorbent. (C) 2015 Elsevier B.V. All rights reserved.