Recycling of spent washing water from cleaning of electrostatic air filters
Electrostatic Precipitation units applied as tunnel air filters is cleaned at regular intervals by means of water containing small concentration of a special formulated detergent.
Spent EP cleaning water contains impurities (mainly silt and carbon particles), which is to be removed to allow re-use as EP washing medium.
Water regeneration package described below is based on well proven technology, is mechanically simple and its operation may be fully automatic performed based on remote surveillance
Primary cleaning cycle (Step 1):
Spent washing medium is collected in buffer reservoir, hereafter termed Dirty Water Tank.
Primary cleaning cycle should be carried out immediately after EP washing is finished in order to avoid settling of solids in Dirty Water Tank.
Spent water is pumped from Dirty Water tank at design capacity (2 m3/h) to a special formulated dual medium filter, in which 99.5% of all impurities (particles) is retained.
Filtered water is collected in Clean Water Tank. This water is fit for re-use as cleaning agent.
Filter regeneration: Backfludshing
Inpurities retained during primary cleaning cycle must be removed to aviod clogging of media filter. This is obtained by pumping clean water from clean water tank through the filter in opposite direction of the normal filtration, by which retained inpurities is flushed out of the filter. Backflush stream is collected in a settling tank where particles is allowed to settle. Estimated settling period: 3 days Settled solids is then drained off by operating the sludge pump as concentrated slurry (approx 5% by weight) for external disposal.
Secondary Cleaning cycle (Step 2):
Water from primary cleaning cycle still contains soluble detergents, which may cause storage problems due to bacterial activity. To avoid this, a secondary cleaning process is employed.
Procedure, Step 2
Water stored in Clean WaterTank is recycled through 2 patented electrolysis units, where DC current produces highly reactive oxidants, which kills bacteria, destroys unwanted organics, and supplies oxygen to the water, thus, avoiding storage problems.
To keep a stored volume of 100 m3 in good condition, water is recycled through a electrolysis unit where a DC current of 200 Amperes is supplied.Treated water from Step 2 is passed through the media filters before return to Clean water tank, this prevents any biological activity in the filter medium and ensures stable long term performance of the media filters.
Secondary cleaning cycle may be performed at intervals determined by experience, E.G. twice a month.
Important note, water recycling/re-use:
The combined application of Step 1 and Step 2 will remove all suspended materials and prevent biological activity during storage.
Detergents consumed in the EP cleaning cycle will form micelles with the impurities washed off the electrostatic panels, these micelles is then removed in the primary cleaning cycle (Step 1).
Excessive (un-used) detergents will remain in the treated water and may be utilized in the next EP Cleaning sequence. The amount of detergent added at each EP cleaning cycle must be adjusted in order to stabilize the active detergent concentration over longer terms.
Water quality monitoring
A couple of parameters should be monitored (once a month) to detect any accumulation of unwanted dissolved components:
--Ph value and chloride content
Low ph and high Chloride concentration may lead to potential corrosion problems.
--Water hardness (Ca++, Mg++)
affects efficiency of the EP washing process and causes potential scaling problems .
In general, Ca++ and Mg++ ions will consume anionic surfactants and silicates, thus reducing the active cleaner concentration in the wash water.
Initial water used for EP cleaning should therefore be soft water with a low chloride content.
It is recommended to install in line monitoring of ph and conductivity in Clean Water tank, which will provide adequate information on water quality.
General flowsheet, Water treatment system (Blue: Step 2)
Advantages of the CTA Waste Water Threatment System:
Saves the environment, the water is recycled and is used over and over again
Removes 100% of all pollution from the water
Safe deposit of contaminated waste
2 patented electrolysis units remove 100% of all chemicals used during washing
Compact size to simplify installation
Less installation costs, all parts integrated in one easy-to-fit module