Analysis of water quality stability by self-cleaning filter

2021-07-02

Self-cleaning filters are applied to various water treatment fields, including surface water, ground water, circulating cooling water, etc. Among them, various water qualities are designed, so the stability of the water quality directly affects the filtering effect of the filter. In many areas of our country, the surface water and groundwater are mostly carbonate-type water. When carbonate-type water is used as circulating cooling water, if the content of insoluble salts such as CaC03 in the water exceeds the saturation value, it will cause scaling. Such water is called fouling water. Conversely, when it is lower than the saturation value, the previously precipitated insoluble salts will dissolve in the water again. Such water is called corrosive water. When the content of these salts in the water is just in the saturated state, there is neither scaling nor erosion. Such water is called stable water. The water quality stability of circulating cooling water refers to the above-mentioned properties of water.
                                                             
During the operation of the circulating cooling water system, scale precipitation may occur in various parts. In the condenser or on the packing of the cooling tower, the most common scale is CaC03, the main reasons are: 　
(1) The concentration of circulating water increases the hardness of carbonate in the water;
(2) The loss of CO2 in circulating water promotes the transfer of HC03 to CO-;
(3) The temperature rise of the circulating water reduces the solubility of calcium magnesium carbonate and promotes the precipitation of CaCO3 from the water.
In addition, when the water contains phosphate or high silicic acid, calcium phosphate scale and silicate scale may also be generated, but the most common is still carbonate scale.