Catalytic Drying of Digested Sludge

Abstract

Recently, we patented an efficient process for the drying of digested sludge with zero liquid emission. The main components of this drying system are a conical spouted bed dryer and a natural gas combustion chamber that burns the Volatile Organic Compounds (VOC) in the drying gases. The proposed integrated spouted bed drying process is simple and safe. It is also robust and easy to maintain since there is no moving mechanical part in the set-up. Although the system is quite thermally efficient, the operating and the investment costs are still relatively high. In order to avoid the combustion chamber and its accessories operating at high temperature and to reduce the energy consumption, a catalytic fluidized bed dryer may replace these units. It is proposed, then, to produce in situ the energy for the drying by catalytic oxidation of hydrocarbons and to destroy catalytically the VOCs generated by the drying. The purpose of this paper is to show the feasibility of this new process, called the catalytic drying of digested sludge. Based on the experimental work, advantages and limitations of this process are also discussed.