Innovative Cooling Solution for Biosolids
Sutherland, N. and Nix, A., Solex Thermal Science Inc., Canada
(free)
Abstract
Biosolids that undergo a mechanical heating and drying process then granulation or pelletizing should be cooled before storage, bulk load out, or packaging. If the biosolids are not cooled appropriately they can experience auto-ignition that may lead to smoldering and potentially fires or explosions. The cooling process should ensure that each particle is thermally stable through to its core and has a narrow temperature profile about the bulk solids average temperature.
Traditional cooling technology employed has been belt coolers and fluid bed coolers. Many of the recent plants or new expansions and revamps (particularly in North America) are using plate type cooler technology as supplied by Solex Thermal Science. The Solex biosolids cooler does not use air for cooling therefore it does not create high dust emissions and as a result consumes very little energy compared to traditional technologies. The heat transfer is by conductivity with the biosolids flowing slowly vertically downward between heat exchanger plates that internally have water (or process effluent, cooling tower water, or process chilled water) flowing counter-current to indirectly cool the solids.
Keywords: Biosolids, Cooling, Heating, Bulkflow, Solids, Powder, Indirect Heat Exchanger,
Introduction
Traditionally, rotary drum, fluid bed, and jacketed screw conveyor technologies have been the industry standard for heating and cooling bulk solids and powders. In this presentation I will take a look at specialty designed equipment (see Fig.1) for heating or cooling bulk solids and powders with technology developed approximately twenty five years ago by Cominco Fertilizers, (now Agrium Inc).
The driving force behind this development was the high CAPEX and OPEX costs of rotary drum and fluid bed equipment, in particular, the retrofitting of a fluid bed cooler and the associated air handling, chilling and wet scrubbing system costs. The innovative yet very simple technology of the Solex Heat Exchanger has enabled it to find a niche in the powder and bulk solids handling industry worldwide. The Solex Heat Exchanger is a simple piece of equipment designed for heating or cooling powders and bulk solids. This technology combines mass flow of bulk solids with conventional plate heat exchanger design.
