Issues related to waste sewage sludge drying under superheated steam

Abstract

Sewage sludge was dried in a rotary drum dryer under superheated steam. Particle size and moisture content were shown to have signifi cant infl uences on sticking and agglomeration of the materials. Pouring partially dried sludge (70-80% moisture content, wet basis) directly into the screw feeder of the drum dryer resulted in a signifi cant sticking to the surface of the drum and the fi nal particle size of the product was greater than 100 mm in diameter. The moisture content of this product was slightly less than its initial value. To overcome this issue, the sludge was mixed with lignite at variety ratios and then chopped before being introduced to the feeding screw. It was found that mixing the sludge with lignite and then sieving the chopped materials through a four millimetre mesh sieve was the key to solve this issue. This technique signifi cantly reduced both stickiness and agglomeration of the material. Also, this enabled for a signifi cant reduction in moisture content of the fi nal product.

An Overview of the Thermochemical Valorization of Sewage Sludge: Principles and Current Challenges

“…For example, Schnell et al [82] reported that during screw conveyance in sludge drying, the adhesion of the sludge to the screw itself caused extreme forces on the screw conveyor, damaging it completely. To avoid this problem, sewage sludge can be pre-mixed with dry material before drying to avoid this problem of adhesion on the equipment [84], or multi-stage dryers or remixing systems can be used for sewage sludge drying [85].…”

Value Proposition of Different Methods for Utilisation of Sugarcane Wastes

“…Some valuable volatile organic compounds generated from the drying material can be recovered and separated by a condenser [46,47]. Some applications involving steam drying are drying of fuels and biofuels with high moisture contents prior to combustion in a boiler and cattle feed exemplified by sugar beet pulp, lumber, paper pulp, paper and sludge [48].…”

Pre-Drying of Chlorine–Organic-Contaminated Soil in a Rotary Dryer for Energy Efficient Thermal Remediation

“…Poós et al [ 16 ] experimentally studied the morphology of sludge with different moisture contents in a rotary dryer and used a re-mixing technique to reduce the moisture content of the inlet sludge and found that the sludge gradually granulated when the moisture content was reduced to 65%. Hamawand et al [ 17 ] studied the effect of moisture content on sludge stickiness and agglomeration in a drum dryer. They found that mixing the sludge with lignite significantly reduced both the stickiness and agglomeration of the sludge and led to a significant reduction in the moisture content of the final product.…”