FLOCCULANTS are continually getting a bad rap in our industry, even though they are absolutely necessary for protecting your machinery and enabling you to meet increasingly difficult environmental requirements. New flocculants are much more environmentally friendly today. In fact, flocculants from the same family are also being used to purify drinking water, washing fruit, etc. Flocculants (a polyelectrolyte with either cationic or anionic load and high molecular weight), attract and combine sediments for exceptionally fast settling.
The microscope photograph to the right shows a sawn piece of stone, with an 80-micron scale for size. The quartz particle (blue via polarized microscopy) has been fractured and ripped by the diamond saw blade. To the left of the image, you will find sharp, angular pieces of less than 50 micron size which non-flocculant systems cannot remove. Quartz, with a hardness of 7 on Moh’s Scale, has no regular cleavage, so can gouge and abrade steel. These particles will circulate in the “clean” water, find themselves in machine bearings, seals and parts, and shorten the life of these critical components.Flocculant, as it causes particles to bind and sink, also improves water release, which will produce a drier mud cake. A drier mud cake means less sludge volume, and reduced disposal costs.
Cakes freely release from the filter press (as seen below right), and no scraping or high-pressure washing is required. (It is recommended that you wash the filter press from below at the end of each week only, not each cycle).
We believe in a two-part system: first clean the water, and then second, process the mud. There are many other ways to clean water, but the two-part design system is by far the world’s leading method.
Polyelectrolyte is a non-hazardous chemical, which destabilizes the electrons on the surface of the suspended particles, causing them to attach to each other through hydrogen bonding – the same type of bond that holds the water molecules in ice together. These clumps of suspended solids naturally sink 10 times faster due to their increased mass, resulting in faster recirculation of high-purity water. An equivalent silo decanter would have to be 10-times larger to achieve the same clarity without flocculant.
Approximately 1 kg of powder is used to make 1000 liters of liquid. One liter of this liquid, is then used to treat from 1000 to 1500 liters of water. So concentration is very low, at 1 to 5 ppm or 0.1% by weight. Although the flocculant is normally slightly acidic or basic as a concentrate, the PH of the process water treated with our flocculant has been tested and shown to keep a PH of about 7, making it register neither as acidic nor basic, reinforcing the non-corrosive nature of the water containing our flocculants.
However, it is important to monitor electrolyte levels in order to keep a good balance, as extreme amounts of flocculant can become an irritant. For bearings and machine parts, however, residual angular quartz particulates are considerably worse.
Cyclonic systems spin water in order to benefit from the differences in specific gravity, i.e., the relative weight of water molecules versus stone particulates. When stone particulates are too small, the outside surface area of the particulate becomes greater relative to the particle’s mass, and at some point, the centrifugal force of the system is not great enough to overcome the electronic attraction of suspended particulates. The result is that larger particles are evacuated, but smaller ones remain in the mix. (You can spin a water-jar filled with steel pellets, and the pellets will go to the outside. But you cannot spin a chocolate milkshake to separate the chocolate from the vanilla). These types of systems were designed for food processing plants producing tomato paste, orange juice and similar, where pasty output and larger particle sizes are not a problem.
Filter-Press Only systems without preliminary mud separation are very effective in cleaning water, but maintenance is high: plates must be coated prior to operation, and cakes can stick to the filter cloth, requiring manual scraping of the mud or cleaning by high-pressure water.
Non-Flocculant systems, as mentioned above, are designed to remove only the heaviest of particulates due to the relatively small decanter size, leaving quartz particles of 50 to 60 microns size to re-circulate indefinitely in the water circuit.