This invention pertains to a technique for on-line cleaning of fouled PVC fills of cooling towers uncovered to air/watpr borne mud/bio -fouling.
BACKGROUND OF INVENTION
Many of the facility stations are utilizing recircultaing type cooling water system for condensation of steam. Within the recircultaing system the cooling water is handed by condenser tubes to condense the steam coming from low pressure turbines. The heated water is taken to cooling towers where the recent water is transformed into small droplets and the air is allowed to take away the heat of the water droplets. There are several types of cooling towers reminiscent of pure draft, forced draft, and so forth. since its first introduction to the market within the 1970s, cooling tower film fill know-how has significantly increased thermal efficiency and decreased the size of cooling towers. However, the slim spaces between film fill sheets make them vulnerable to fouling. Without correct chemical treatment, deposits can accumulate throughout the movie fill resulting in diminished tower efficiency, increased fouling and plugging of the fill. These phenomena could ultimately result in collapse of the tower structure. This doc describes a brand new strategy to remedy the high efficiency movie fill fouling problem in power plants. The plants have a long historical past of fill fouling problems as a result of a very complicated make-up water chemistry and
dusty environmental situations. Regular cleansing methods were not capable of remove the fouling from the fills and thus restore the efficiency of cooling towers. Distinctive chemical cleaning procedures have been developed that may remove the dust primarily based foulants during operation of the items successfully and enhance the performance of the cooling towers and in addition take away calcium carbonate based mostly deposits. The procedure developed additionally helps in cleaning the cooling water system of suspended material & biofilm.
Cooling towers are important part of power plants & many other industries where the water used for cooling the method fluid equivalent to steam is once more cooled by forming a spray and the compelled/natural draft of air cools the droplets of water. The cooled water is again sent again to the heat exchanger/condenser for cooling the process fluid. Fills help in proper cooling of circulating water. The PVC Film sort fills are very efficient in cooling the circulating water, but they are equally prone to fouling from air/water borne mud particles and microbes. As soon as fouling begins in the fills the dust/suspended particles keep on with the wet floor to the fills and with time begin clogging the slim corrugated area of the fill packs. This leads to reduced circulate of water by way of the fill packs and thus reduced stream of water by way of the fill packs and thus diminished efficiency of the cooling towers. This also ends in extreme masses on the cooling tower constructions and damages them. In excessive circumstances it can result in collapse of the cooling towers. Normal mechanical cleansing strategies are tedious, time consuming and harm the fills.
Movie fill is a densely packed plastic, typically PVC. It creates a big wetted floor that will increase evaporation however is prone to deposit buildup and plugging. Plugging may be as a result of microbiological organisms, oils, scale, mud, corrosion products and water treatment inhibitors. Film fill that’s partially plugged can cut back cooling tower efficiency. Severely fouled film fill has been recognized to collapse into the cooling tower basin.
OBJECTS OF INVENTION
The principle object of this invention, is to develop a method for on-line cleaning of fouled PVC fills of cooling towers.
The other object is to develop a method for on-line cleaning of fouled PVC fills of cooling towers explosed to air/water borne mud/bio fouling.
One other object is to develop a suitable cleaning method that can take away the foulants from the cooling tower fills without eradicating the fill packs.
One more object is to develop an acceptable cleansing method that may take away the foulants in unit working circumstances.
Assertion OF INVENTION
This invention relates to a technique for online cleaning of fouled PVC fills of cooling towers uncovered to air/water borne mud/bio-fouling utilizing a mixture of an oxidizer like hydrogen peroxide at a focus range of zero.1 to zero.2% by weight; surfactant like Linear alkyl benzene sulphorate 5-20ppm and dispersant like Polyacrylate, 2-15ppm wherein
fouling material is bacteria and silt/clay/suspended dust and using Ethylenediamine tetra acetic acid within the vary of 0.05% to 0.2% weight by volume at a pH vary of 9.5 to eleven within the presence of corrosion inhibitor Rodine 2000 (Henkel Chemicals) or equivalent inhibitor (having related composition as Rodine 2000, which is a proprietary chemical of Henkel chemicals) for dissolution of calcium carbonate based mostly scale deposit from PVC fills.
Transient DESCRIPTION OF ACCOMPANYING DRAWING
A potion of the fouled PVC Movie sort fill pack was obtained from site and different chemicals have been used to scrub the fouled fills. The primary photograph shows the condition of the as-received fouled fill pack. The second photograph exhibits the situation of the cleaned fill pack. The cleansing was effected utilizing the claimed cleansing chemicals/ process and greater than 90% foulants have been faraway from the intently packed fills.
DETAILED DESCRIPTION OF INVENTION
Two on-line chemical methods have been developed to scrub the fouled fills of the cooling chemical towers. ‘One technique consists of therapy of cooling towers with hydrogen peroxide, surfactant and a polymeric dispersant to remove mud/silt & microbiological primarily based fouling. The opposite methodology consists of remedy of cooling towers with EDTA at higher pH (above 9.5 to eleven) in presence of corrosion inhibitor to take away calcium carbonate based scale/fouling deposits. Both methods are for on-line cleaning but may also be used off-line. In conditions where both kind of
foulants are present, than first the system is to be handled with EDTA
resolution adopted by washing with Hydrogen
peroxide/surfactant/dispersant. Subsequently periodic washing with Hydrogen perodixe/surfactant/dispersant can assist in stopping further fouling of PCV movie sort fills of cooling towers.
On-line chemical strategies have been developed based mostly on the precept of oxidizing the biomass after which removing the fouled particles using a mix of anionic surfactant and polymeric dispersant from the fill packs (applicable for foulants based mostly on dust/silt and microbiological species). For foulants consisting of calcium carbonate scale and mud/silt together with microbiological species, preliminary washing with EDTA (ethylenediamine tetra acetic acid, a chelant) at higher pH with corrosion inhibitor has additionally been developed. The strategies developed can be utilized for cleansing the fouled fill packs without stopping the unit or cooling towers. The strategy is secure for the opposite supplies used within the cooling water system of the power plants. The tactic makes use of oxidizing brokers comparable to Hydrogen Peroxide supplemented by Chlorine, Chlorine dioxide, Sodium hypochlorite, etc for killing the biomass adopted by removing of particulate matter sticking to the fill surfaces by utilizing the surfactant and the polymeric dispersant which help the dislodged suspended matter to remain in suspension until they’re taken out of the system by blow down. EDTA helps in dissolving calcium carbonate based scales.
Fill design has modified dramatically in recent years from wood or plastic splash-type to plastic film-sort. Film fill is a density packed plastic typically PVC. It creates a big wetted floor that will increase evaporation but is prone to deposit buildup and plugging. Plugging can be as a result of
microbiological organisms, oils, scale, mud, corrosion merchandise and a few water therapy inhibitors. Film fill that is partially plugged can reduce
cooling tower efficient. Severely fouled film fill has been known to collapse into the cooling tower basin.
Since its first introduction to the market within the 1970s, cooling tower movie fill technology has considerably elevated thermal efficiency and decreased the dimensions of cooling towers. However, the slender areas between movie fill sheets make them prone to fouling. Without correct chemical remedy, deposits can accumulate inside the film fill leading to lowered tower effectivity, increased fouling and plugging of the fill.
These phenomena could eventually lead to collapse of the tower construction.
A lot of the power stations where PVC film sort fills have been used reported fouling of the fill packs outcomes into lack of heat price and in some cases damages to the help constructions of cooling towers. The weight of many fill packs had gone up (almost to 180 Kg towards the virgin weight of PVC fill pack of 20 Kg). The efficiency of cooling towers had come down considerably resulting into loss of heat charge 85 loss to the station since resulting from loss of efficiency of cooling towers, the temperature of cooling water additionally increases inflicting issues in condenser vacuum.
Investigation staff members visited the stations and analysed the problem. Primarily based on the analysis it was observed that improper water treatment of cooling and water and suspended particles/micro organism are primarily accountable PVC fill pack fouling.
Contemplating the assorted components and causes identified, it was determined that R&D ought to develop a complete non-proprietary chemical remedy for cooling water methods for such to resolve the issue of CT fill fouling and other associated issues in CW system. Accordingly R&D had taken up the event of chemical therapy program and research to develop a procedure to scrub the fouled PVC fill packs online.
R&D developed a chemical process for on-line cleansing of fouled PVC fill packs and a chemical therapy program was also developed to prevent additional fouling of the fill packs. The cleansing procedure consists of oxidizing the adherent biofilm on Fill packs by a strong oxidizer like
Hydrogen peroxide (0.1 – 0.2%) and then detaching the surfactant (Linear alkylbenzene sulphonate, 5-20 ppm) and a dispersant
(Polycrylate, 2-15 ppm). Utilizing this procedure passable cleansing of the fouled CT fills might be achieved (Images as given above). Periodic cleaning of the cooling water System can assist in controlling additional fouling of CT fills and thus enhance effectivity of the cooling towers.
Further it was noticed that with prolonged operation with fouled fills, native evaporation of water takes place resulting in deposition of calcium carbonate primarily based scale, which is sort of adherent and reduces the effectivity of the cooling towers. A web-based chemical cleaning method utilizing EDTA (Ethlenediamine tetra acetic acid) at higher pH and using a
corrosion Inhibitor was developed for this utility. Combination of each the methods can assist in removing the fouling deposits from PVC film sort fills of cooling towers in addition to from the CW system, thereby improving the general performance, life and effectivity of cooling towers/cooling water systems.