Mechanical dewatering of sludge is efficient up to a dry substance of 20 to 30 %, leaving in one metric ton of filtercake still 700 to 800 kg of water. This residual water can only be removed with high amounts of thermal energy used to evaporate this water. At solar drying, the residual water is evaporated utilizing solar energy only.
The radiation is warming up the filtercake in the drying halls and leads to the evaporation of water.
The evaporation rate is significantly determined by the location of the system and is basically higher as you get closer to the equator.
The WendeWolf Process:
Thoroughly tilling and turning as well as a fast and reliable aeration of the filtercake are important factors to achieve an efficient drying system.
The innovative WendeWolf machine can be operated in batch or in conveying mode, an adaption to changing requirements is easy possible and intended.
Layers of 40 cm and more allow a reliable and homogenous aerated storage of filtercake in months with low solar radiation.
A separate and sometimes complex storage of sludge or filtercake in external buildings can be avoided completely.
With more than 20 years of experience in far over 200 systems worldwide, WendeWolf standing for a reliable, efficient and environmental friendly sludge drying technology.
The built up of odors during the drying process is consequently avoided, a safe and trouble-free operated system at high availabilities and low operation costs is guarantee
Evaporation and air movement:
The energy source for the solar sludge drying process is basically the solar radiation. This radiation is transmitted through the building shell and absorbed by the sewage sludge and is warming up this sludge. This causes an increase of the vapor pressure in the sludge and is therefore driving out water molecules into the air above.
Without air movement, this evaporation is causing a saturated layer of air right above the sludge surface.
This humid layer of air leads to a decreased evaporation rates, this need to be avoided. Thus, the halls need to be ventilated proper.
The fresh air is let in through openings at the bottom of the side walls, the exhaust air is discharged through the roof flaps – wet, warm air is lighter than dry air.
The internal ventilators are destroying the saturated layer of air, this assists the drying process.
Additional heating systems:
The specific evaporation rate can be increase by utilizing additional (waste) heat sources, this will decrease the overall size of the drying plant.
As there is warm water available, for instance cooling water from a gas engine or the energy taken with heat pumps from the wastewater outflow, this can be utilized with a floor heating (A) or with an air heating (B) system.
Surplus digestion gas can be utilized in direct infrared heating systems (C)
WendeWolf Control Software
The unique WendeWolf operating software incorporates the monitoring and controlling of the climate in the drying halls as well as the operation of the WendeWolf for sludge drying and conveying purposes. The drying process itself can be operated by a fully automated program, the turning cycles are prompted according to the actual weather situation or by time controls.
The climate within the drying hall is optimized according to the weather data to ensure the ideal inside climate for optimized water evaporation.
For the conveying operation of the drying plant and the input and displacing of the sludge as well as for the accumulation and clearing out of the pellets are preset programs utilized.
Loading: To distribute newly brought-in sludge.
Heaps of up to 100 cm are cut down and distributed to an even sludge layer.
Turning: Turns, mixes and aerates the sludge.
This improves the drying performance, ventilates the sludge and prevents odor formation.
Displacing: To convey the sludge to any target position.
The sludge can be moved in either direction of the drying hall.
Accumulating: To stack up dried pellets up to a height of 80 cm.
This allows an intermediate storage of pellets in the drying hall.
Clearing: To clear out dried sludge towards the end of the drying hall for instance into a storage bunker or towards a conveyor
– Operation in Batch or Conveying mode
– Aerated storage of Filtercake in Drying Halls
– Homogenous and odor free process
– Fine coarse pellets output
– Storage of dried pellets in drying hall over 80 cm height
– Filtercake layer over 40 cm height
– More than 400 m³ per hour tilling and turning
– Cutting down of filter cake piles with more than 100 cm height
– No back mixing necessary
– Utilization of waste heat or other energy sources
– Rigid, robust and low maintenance design