Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Sewage sludge handling trials

Work was carried out to identify potential problems of feeding sewage sludge pellets into a gasifier. As part of this, conveying trials were undertaken to assess the handleability and degradation properties of the sewage sludge pellets. Two transport systems were investigated, namely feeding via a tapered screw and by a lean phase pneumatic conveyer. In addition, the degradation behaviour of the sludge pellets when discharged from a reception hopper and passed across a rotary valve was studied.

Conveying and degradation data for the sludge pellets was then compared to that for a reference coal. Throughout all the tests, the sewage sludge pellets showed very little degradation, even when conveyed at very high air speeds and delivery rates. The results also showed that it was possible to convey the pellets at relatively low air velocities.

Analysis was also undertaken to assess the flow characteristics of the sludge pellets using Johanson Indicizer(TM) systems to identify potential problems for feeding the sludge pellets from storage hoppers to the gasifier. The results showed that as long as the material was kept as dry as possible to prevent cohesive arching, and stored in a hopper with adequate outlet dimensions and wall angles, few problems should be encountered when handling this particular material.

To provide information on safety and design issues of storage of sewage sludge, spontaneous heating and heat explosion tests were carried out in atmospheres containing 3 to 21% oxygen. The tests indicated that the ignition temperature for the sewage sludge pellets was higher than that of the reference coal. Dust explosion tests indicated that the explosion indices were more severe for coal than for the sewage sludge pellets.

Reported by

EMC Environment Engineering Ltd
Floor 3 Vantage Point Business Village Micheldean
GL17 0DD Cheltenham
United Kingdom
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