Learn what is industrial circulating water treatment and what chemical pumps are used
Today we will talk about what is industrial circulating water. First understand what is water treatment? What is water treatment? The water treatment mentioned here is not a general sewage treatment, but an industrial water treatment. On the contrary, we often do not treat sewage.
Today we will talk about what is industrial circulating water. First understand what is water treatment?
What is water treatment
The water treatment mentioned here is not sewage treatment in the general sense, but industrial water treatment. On the contrary, what we treat is often not sewage, but normal water that can be used. There are many sources of this water, such as the surface Water, river water, and treated domestic sewage (we call it reclaimed water). These waters are also called make-up water. When the make-up water enters the cooling system of the factory, it becomes the circulating water we often say. The function of these circulating water is often cooling. The circulating water cooling system of most factories is open, that is, a part is exposed to the air, and the part exposed to the air (usually a cooling tower, which is cooled by the heated circulating water). Over time, it will often evaporate, be polluted by dust, and produce adverse effects such as bacteria and algae. Water treatment is to minimize this part of the impact.
Why do we need water treatment
In the make-up water we use, no matter which kind of make-up water, the most cation content is often Ca +, and the most lunar content is often HCO3- or sulfate. For example, when these ions have higher ion concentrations, carbonic acid is formed. Calcium or calcium sulfate scales, and most of them are calcium carbonate scales (yes, the kind in your kettle), these deposits will reduce the heat exchange efficiency of the heat exchanger, and more serious will promote some bacteria such as The reproduction of iron bacteria leads to corrosion and perforation of the pipe wall and leakage. At the same time, with the evaporation of water, the content of various ions is gradually increasing, and the increase of these ions can also cause structure or corrosion. After treatment, the circulating water can ensure the effect of reducing scaling, reducing corrosion and reducing the growth of bacteria and algae after the ion concentration increases.
Factors affecting scale
In addition to inorganic scale, there are also dirt in the circulating water. These dirt are often due to the presence of many sediments, humus and various suspended matter and colloids in the surface water. It may also be due to the influx of more water into the water. Dust, resulting in increased turbidity of water. The main reason for the formation of inorganic scales is the increase in the concentration of scale-forming ions in water due to the evaporation of water.
Factors affecting corrosion
① The pH value mainly depends on the solubility of the metal oxide in water and the pH value. Generally speaking, for nickel, iron, and magnesium materials, the lower the pH, the faster the corrosion (for iron, when the pH is high, the iron also needs to be dissolved to form ferrite).
② Anions, different ions in water have the following order in increasing the metal corrosion rate: NO3- <CH3COO- <Cl- <ClO4-, among which we mainly detect the chloride ion concentration.
③ Complexing agent, our main consideration is NH3. When leakage occurs in some pipelines of chemical plants, ammonium ion will increase sometimes, which will accelerate the corrosion.
④ Hardness. When the concentration of calcium and beauty ions is too high, it will interact with carbonate, phosphate or silicate in water to form calcium carbonate, calcium phosphate and calcium silicate scales, causing corrosion under the scales.
⑤ Metal ions, copper, silver and other heavy metal ions in cooling water are harmful to several common metals such as steel, aluminum, and magnesium. These ions often form micro-cells and cause corrosion of the base metal.
⑥ The corrosion rate of dissolved gas, low carbon steel, copper and copper alloys will increase with the increase of oxygen content. When the pH of water is low, carbon dioxide will cause dissolution and destruction of the metal surface film. When cooling water is loyal to oxidants, ammonia can selectively attack copper. Hydrogen sulfide will accelerate the corrosion of copper, steel and alloy steel, but it is not corrosive to aluminum. Sulfur dioxide reduces pH and increases corrosion.
Concentration of radon, most metals corrode furniture as the concentration increases in non-oxidizing calculations, and in the oxidizing calculation, as the concentration increases, the corrosion rate has a highest value, and a protective film will be formed after the highest value, which corrodes The rate drops.
⑧ Suspended solids. When the cooling water flow rate decreases, suspended solids easily form loose deposits on the surface of the heat exchanger, causing corrosion under the scale.
⑨ Flow rate. When the flow rate is low, the flow of dissolved oxygen in the water will increase and the metal corrosion rate will increase.
⑩Temperature, in general, the rate of metal corrosion increases with temperature.
Effect of chlorine on corrosion
① For carbon steel: When the residual chlorine concentration in water reaches 0.5 mg / L, the corrosion rate of carbon steel rises rapidly, and when it reaches 0.7 mg / L, it begins to exceed the upper limit of the design code.
② Nickel-containing cast iron, less than 2mg / L, little effect
③ Copper-based alloy, less than 2mg / L, little effect
④Aluminium is corroded, but not serious
⑤Stainless steel, depending on the material