Gasification of Sewage Sludge in a Rotary Kiln Reactor – A Case Study with Incorporation of Sewage Sludge Ash in Brick Production

A. Bubalo, D. Vouk, D. Maljković and T. Bolanča

Abstract
The gasification of sewage sludge (SS) was studied in a semi-industrial pilot plant consisting of a rotary kiln reactor. The gasification process was preceded by drying the SS in an integrated tubular rotating structure with built-in worm conveyors, to increase the dry matter (DM) content in the SS (> 90 wt.%). The released hydrogen-rich syngas from the gasification process of SS had low heating value (LHV) of approximately 8.83 MJ N–1 m–3 (equal to 2.45 kWh N–1 m–3) due to the high content of combustible gases H2 (41.5 vol.%) and CH4 (3.2 vol.%). Also investigated was the incorporation of sewage sludge ash (SSA) generated in the process of gasification as a partial substitute for clay in the production of clay bricks. Amounts of 5 wt.%, 10 wt.%, 20 wt.% of clay were replaced by SSA. By incorporating SSA at 5 wt.%, the new brick product achieved 4.5 % higher compressive strength compared to the control brick.

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Keywords
sewage sludge, gasification, syngas, sewage sludge ash, brick production, circular economy