CRS Air Handling System
The CRS Air Handling System ensures that air is continuously delivered to the waste during the enclosed composting stage to maintain aerobic conditions within the waste during decomposition. These aerobic conditions are essential for the reduction of unwanted odours and the maintenance of moist, warm conditions within the waste to accelerate the decomposition process. The CRS Air Handling System also prevents unwanted temperature rise within the Composting Tunnel by automatically introducing fresh air to the system if the temperature rises above a set limit.
The CRS Air Handling Unit is regulated by a Programmable Logic Controller. This is programmed at the time of installation of the Composting Facility. The electrical control has a mains isolator, and stop, manual and automatic settings. A temperature controller is used to set an upper temperature threshold above which fresh air is introduced into the system. The temperature controller interfaces between the Programmable Logic Controller and the thermocouples in the temperature probes measuring the temperature of the air being drawn from above the waste.
During normal operation the CRS Air Handling system circulates air within the Composting Tunnel in a closed loop. The air is moved by 3 centrifugal fans constructed of stainless steel with built in condensation drains. Two fans are in continuous use to circulate the air whilst the third fan is only used to introduce fresh air into the system when required. The air is drawn from the space between the roof and the waste and is then blown through sealed pipe work to the air delivery pipes that run along the bottom of the Composting Tunnel. The CRS Air Handling Unit has three air outlets. Two air outlets blow air through the air delivery pipe whilst the third blows air into the CRS Odour Control System when required.
The circulating air ensures that the moisture and heat are conserved, avoiding unwanted drying and cooling within the waste. Condensation can occur in the Air Handling Unit. The condensate is collected in a condensation tank situated at the base of the unit and is discharged automatically every 2-4 hours.
Automatic introduction of fresh air to the system, via a series of air inlet valves on the Air Handling Unit, is triggered when the air temperature above the waste exceeds the upper limit set by the operator using the temperature controller. The Air Handling Unit has four air inlets. Two are connected to the air manifold system and draw air into the unit from beneath the roof of the Composting Tunnel. The other inlets have motor controlled flap valves and allow air from the atmosphere into the Air Handling Unit. The amount of air blown by the Air Handling Unit is variable according to the back pressure and the aperture of the air distribution pipes.
The CRS Air Handling Unit continues to introduce fresh air until the temperature falls below the threshold value. Once the temperature is reduced, the unit will automatically recommence the closed loop recirculation of the air.
When the CRS Air Handling Unit draws fresh air into the system from outside an equal volume of “foul” air must be exhausted through the CRS Odour Control System to neutralise any odours.
Each Air Handling Unit can provide aeration for up to four standard CRS Composting Tunnels.
