Veolia introduces Exelys continuous thermal hydrolysis plants

Veolia Water Technologies has launched Package Exelys, a standard range of continuous thermal hydrolysis units for small to medium sludge digestion plants.

Thermal hydrolysis is a well proven pre-treatment technology for sludge digesters that increases digester throughput, pasteurises the sludge, enhances biogas production, and reduces the final biosolids volume for disposal.

Veolia’s Exelys heats dewatered sludge to 165°C and holds it for 20-30 minutes in a continuous rather than a batch process, which differentiates Exelys from similar products.

The continuous process means that the reactor volume is used for 100% of the time by comparison with a batch reactor which, because of the fill-react-discharge cycle, effectively operates at only about 30% utilisation, and with less concentrated sludge.

As a result, the Exelys reactor can treat over three times the amount of sludge solids compared to a similar sized batch reactor.

Continuous operation means that the steam demand is constant, which improves boiler efficiency and, since Exelys can handle higher sludge concentrations than batch systems, the steam demand per tonne of dry solids is lower.

The Package Exelys range has four standard plants with dry solids capacities up to 30t/day.

The plants have all the features of the Exelys process but are assembled at works off site on skids and include feed sludge heating and steam injection equipment.

Package Exelys is designed as a plug-and-play system, fully tested before leaving the factory, minimising site installation and commissioning time.

An optional waste heat recovery boiler can be added to recover the heat from the hydrolysed sludge.