FIELD OF THE INVENTION:
This invention relates to a device and method for the removal of colloidal particles and microorganisms from cooling tower water in thermal power plants. BACKGROUND OF THE INVENTION:
Water used in the cooling tower often contains salts such as chlorine, sulphates and carbonates and metal ions such as iron and magnesium. Besides this airborne dust and grit further contaminate the water. The presence of these impurities in water can cause many problems like fouling, lime scale formation, corrosion and biological growth etc. In addition to these problems process water would also be contaminated depending up on the cooling tower building material such as concrete, wood, plastic and metal. The microorganisms present in the water cause damage to the heat exchangers. Since, bacteria and other pathogenic microorganisms present in the water grow rapidly because favorable conditions exits in the cooling tower, these organisms form "Slime layer" and this contains both organic and inorganic matter. Some microorganisms excrete polymers, which can form a gel like network around cell after hydrolysis takes place and is known as bio-film. This would cause a speedy corrosion of walls in the heat exchanger. The bio-film invariably acts as safeguard for these microorganisms. Over a period the bio-film creates an isolation layer on heat exchange systems, which results in improper functioning. Removal of microorganisms is very difficult using conventional methods especially when the bio-film is present.
Normally hydrocyclones or high capacity centrifugal separators are employed for the removal of pollutants present in cooling tower water. The main drawbacks associated with these units are as follows:
LHigh capital cost.
2. Requires regular maintenance.
3.Consumes lot of power for pumping huge quantities of water (>30,000 m3/hr)
4. Requires large space for installation and operation.
5. Require sumps and piping works etc.
6. Loss of lots of process water along with impurities.
Above all the efficiency of these units is also not very high. Therefore a simple and novel alternative technique has been proposed for cleaning of cooling tower water.
OBJECTIVES OF THE INVENTION:
The objective of this invention is to propose a device method for the removal of colloidal particles and microorganisms from cooling tower water in thermal power plants which is:
1. Simple
2. Cost effective
3. Does not lead to loss of process water along with impurities
These and other objectives of the invention will be apparent from the ensuing description.
BRIEF DESCRIPTION OF THE INVENTION ACCOMPANYING DRAWINGS:
The invention will now be explained in greater details with the help of the accompanying drawings where Figure 1 depicts the device according to the invention.
DESCRIPTION OF THE INVENTION:
According to this invention a device is provided for the removal of colloidal particles and microorganisms from cooling tower water in thermal power plants comprising of a rectangular panel (aluminium) with a screen mat (fiber), a layer of charcoal placed over the screen mat with layer of sponge thereon and a further layer of charcoal' on the sponge. A high quality sponge is sandwiched with coconut charcoal and placed over the screen mat and fixed with proper sealing arrangement. The shape of the exposed sponge may be in the form of square or rectangular.
The number of panels as per the cooling tower area requirement will be prepared and fixed at the bottom most portion of the cooling tower. The water falls in the cooling tower in the form of droplets more precisely like rainwater. These water droplets are allowed to pass through the rectangular panels (exploiting natural gravitational force). While penetrating through sponge the water comes in contact with charcoal. The charcoal absorbs most of the metal ions present in the water and the sponge arrests the solid particles present in the water. The water is expected to exit in the form of thread like discharge, hence bottom most splitter is more suitable for this. It is to be noted that this technology works effectively when the solids concentration is very less in the water. The filtering panel is fixed with simple fixing arrangement so that over loaded sponge can be periodically removed, washed and re-used.
The efficiency and sensitivity of the method depends on parameters such as quality of the sponge and charcoal, thickness or density of the sponge and
amount of sponge to be used, permeability of the filtering media, solid holding capacity and the intervals after which the media is replaced.
This technology provides much better quality re-circulating water, which will improve the efficiency of heat exchangers, and this in turn increases the productivity and efficiency of the plant. The main advantages associated with this technique are that it does not require any extra space and can be fitted in the existing cooling towers and it will function without the use of electrical and mechanical energy. It is expected to be highly efficient compared to existing processes and operates at very low cost. The technique is operator friendly and the device can be maintained at minimum cost.

WE CLAIM:
1. A device for the removal of colloidal particles and microorganisms from cooling tower water in thermal power plants comprising a panel with a screen mat, a layer of charcoal placed over the screen mat with layer of sponge thereon and overlaid with a further layer of charcoal.
2. The device as claimed in claim 1, wherein said screen mat is made from metals or fibers.
3. The device as claimed in claim 1, where the charcoal is coconut charcoal
4. The device as claimed in claim 1, wherein the sponge is fixed to be panel with sealing arrangement.