Highly effective filter media and a unique backwashing mechanism
PETRECO HYDROMATION filters use crushed black walnut shells, known for their strong affinity for oil, as the filter media. The filter bed is cleaned using a unique backwashing mechanism, which can typically use feedwater instead of filtered water. Compared with other technologies, nutshell filters can handle higher inlet solids and oil. Because there is no gas-scouring stage during backwash, HYDROMATION filters have a lower utility requirement compared with other media filters.
During the filtration cycle, the suspended solids and oil are removed from the process liquid and accumulate in the filter media bed until backwash is initiated.
Backwashing process
The first step in the backwash sequence is the agitation cycle. During this cycle, only the backflow valve is open while the media agitator turns the vessel contents into a slurry. This ensures separation of the captured oil and solids from the media.
Next, the filter enters the backwash cycle. The agitator continues to agitate the media and rotates the backwash scrubber basket. Liquid flows into the filter vessel through both the dirty inlet and the backflow valve. The highly concentrated dirty liquid in the vessel flows out through the slots in the rotating wedge wire scrubber basket and out through the backwash valve. This process reduces waste volume to typically just 0.5%–1% of the unit's daily throughput, with virtually no media loss.
After backwashing, there is a delay while both the backwash valve and backflow valve close, the agitator stops, and the media settles. Once this is complete, the recirculation cycle starts. The recirculation valve opens, and liquid flows through the filter media bed. The filter bed is set or compressed, and any residual dirty liquid present in the vessel is removed. Once recirculation has finished, the filter is again ready for filtration.
