Descaling of cooling tower and corrosion protection
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Date
2019-06-18
Authors
Faidi, Dina
Madina, Haneen
khader , Muna
Hariri, Taqwa
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Abstract
Palestinian Poultry Corporation, also known as Aziza Company, has large numbers of cooling towers that provide cooling to chicken incubators. These special strains of chickens are brought up for ovulating eggs to hatching units. Most of these units are located in Jericho city. The towers provide cooling through the flow of water and air flow across it. The water has high salinity which is about 1.3%. The cooling towers suffer from significant internal and external tenacious scaling. The scale formation threats the successful performance of the cooling towers, and inhibit the provision of sufficient and acceptable working condition to cooling system.
Poor working conditions mean the narrowing of water/air passages on cooling tower. This leads to a decrease in the amount of evaporated water and increasing of incubator temperatures.
Traditionally lime scale can be removed by 10% hydrochloric acid but it is very corrosive for iron and steel structures, and may expose workers and environment to possible health risks.
It is important to avoid downtime cost that significantly affects profitability. The aim of project is to remove gathered scales within a short timeframe by using products that would not harm the integrity of the cooling tower or compromise worker safety.
We aim to provide a chemical blend which would not erode metal surfaces or create wastewater treatment issues. The anticipated liquid blend must achieve descaling without dismantling any item on the system. The removed scales may be used as road dumping material.
In this spring semester we have carried out manual and analytical analysis on cooling water and on deposits to know the composition of each and to understand the nature of composition of scale formed. The X-rays diffraction analysis and ICP Atomic Emission spectroscopy analysis help to determine concentrations of trace to major elements and can detect most elements and salts that occur in handled samples.
The analysis has shown that the treated sample are rich of Sodium, Calcium Magnesium and potassium salts. There are strong indication of occurring silica in the samples.
Maybe the interaction of the different salt crystals is responsible of formation of insoluble salts.
New materials such as poly phosphates, sulfamic acid H3NSO3, and ammonium fluoride are suggested to descale the cooling towers. These are discussed later in the literature review section.
Steel metallic structures should be treated with a preventive layer and by using corrosion inhibitors in cooling water. The source of corrosion is the salty water used in cooling tower.