Topic Home
Sludge drying
An overview of sludge drying − an introduction to sludge drying theory and technologies
Solar dryers
Solar dryers take the form of large greenhouses into which the sludge is fed either continuously or in batches. Solar drying provides the lowest energy demand of all dryers, as low as 50 kWh/t, but incurs a large footprint due to the constraints on the available thermal energy. Although heating is provided at zero or minimal cost, energy is demanded by both the mechanical agitation of the sludge solids and deodorisation of the exhaust air. Supplementary heating, often using a waste heat source, is often needed to sustain a reasonable drying rate.
Topic
Introduction to sludge drying
Processes where moisture is removed from sludge as water vapour are known as 'sludge drying'
Topic
Sludge treatment − properties of drying sludge
When sludge dries, it goes through three different phases as the water evaporates
Topic
Sludge treatment − sludge drying operation
Sludge drying processes operate at solids temperatures of 60-93 °C to encourage water to evaporate and leave a solid residue
Topic
Sludge treatment − sludge dryer configurations
Sludge drying processes are generally configured as convective, conductive, or as solar dryers
Topic
Sludge treatment − solar dryers
Solar dryers make use of renewable solar energy to dry sludge and need a larger footprint to allow for increased drying times
Solar dryers related videos
Solar dryer, OTEX
A video to demonstrate the principles of the OTEX solar sludge dryer.
Solar dryers features and blogs
Feature
Co-processing of sewage digestate by hydrothermal carbonisation
Hydrothermal carbonisation (HTC) can be used to co-process anaerobic digestion (AD) digestate and lignocellulosic (or plant-based) feedstocks to improve the the hydrochar product quality. This AD waste co-processing route has been studied at bench scale. Read article
More Solar dryers topics…
Discover
Convective dryers
Convective (or direct) dryers remove moisture from sludge by bringing the sludge particles into direct contact with hot gas
Discover
Belt dryers
Belt dryers comprise a conveyor belt which slowly transports the sludge solids through a stream of heated air
Discover
Flash dryers
Flash dryers use a rapid stream of rising hot air which both suspends and dries the solids.
Discover
Fluidised bed dryers
In fluidised-bed dryers the sludge particles are gently agitated and heated by a stream of upward-flowing pre-heated gas
Discover
Rotary drum dryers
Rotating drum dryers have a drum rotating at 4-8 RPM through which the sludge passes along with a stream of warm air
Discover
Conductive dryers
For conduction drying, the sludge is heated indirectly by bringing it into contact with a heated surface
Discover
Disc dryers
Disc dryers are based on vertical externally-heated discs or rings rotating in the sludge as it passes through the dryer.
Discover
Paddle dryers
Paddle dryers are based on externally-heated paddles rotating in the mass of sludge solids held in a stationary vessel
Discover
Pelletizers
Pelletizers
-
Conditioning
Conditioning is the pretreatment of sludge upstream of thickening and dewatering to promote solid-liquid separation
-
Thickening
Thickening processes concentrate the sludge by removing part of the free water, such that the product can still be pumped
-
Dewatering
Dewatering processes mechanically remove a significant proportion of the sludge water to produce a 15-45% cake product
-
Drying
In sludge drying the sludge moisture is removed as water vapour by heating, generating a pelleted or powdered product
More process and operation topics…
Discover
Sludge stabilisation
Sludge stabilisation − alkaline stabilisation, lime and solids dosing, plus anaerobic and aerobic digestion
Discover
Thermochemical processes
Thermochemical methods are used to either significantly reduce the sludge solids content or pre-treat sludge upstream of AD
Discover
Sludge quality
Sludge is the main waste stream from the treatment of wastewater