With the rapid economic development, industrial high-salt wastewater is increasingly polluting the environment. In addition to organic pollutants, these wastewater also contain a large amount of inorganic salts. The common feature of this type of concentrated wastewater is that it cannot be simply treated with biochemical treatment, and the physical and chemical treatment process is more complicated and the treatment cost is high. It is recognized by the sewage treatment industry as a highly difficult wastewater treatment. If industrial high-salt wastewater is discharged directly without treatment, it is bound to cause great harm to water organisms, drinking water, and industrial and agricultural production water.
In recent years, with the further improvement of environmental protection and energy saving requirements, MVR evaporators have gradually become the primary choice of evaporation crystallization devices including wastewater concentration treatment with relatively low operating costs. MVR (Mechanical Vapor Recompression Technology) is an effective energy-saving technology that reuses the energy of its own secondary steam, thereby reducing the demand for external energy.
In the evaporation of the MVR evaporator system, the amount of raw steam required is very small, so that the steam to be discarded is fully utilized, and the thermal efficiency is improved. Moreover, the MVR evaporator does not require a large flow of circulating cooling water, and can reduce a large number of supporting facilities (Such as large boiler room, large cooling water tower), MVR evaporator has compact equipment, small footprint, high degree of automation, economical and durable, and convenient operation. However, the MVR evaporator is inevitably corroded during the cycle. Wen Yangjun summarized the common corrosion of MVR evaporator as follows: metal corrosion, temperature corrosion, cavitation phenomenon, high-temperature corrosive liquid or vapor leakage in four aspects.
1. Metal corrosion: MVR evaporators are generally made of titanium, stainless steel 2205, 316L, 304 and other metal materials. Metal corrosion cannot be avoided. Metal corrosion means that metal materials are damaged by the surrounding medium. It is a very common form of corrosion. . Metal corrosion is divided into chemical corrosion and electrochemical corrosion.
2. Temperature corrosion: Temperature corrosion is generally a chemical reaction. The corrosion rate increases by about 1 to 3 times for every 10°C increase in temperature, but there are exceptions: PH corrosion, generally the lower the pH value, the greater the metal corrosion.
3. Cavitation: The pump in the MVR evaporator system will encounter cavitation. Cavitation refers to the phenomenon of cave-like corrosion damage to the metal surface in contact with the fluid under the conditions of high-speed flow and pressure changes. Cavitation types are divided into impeller cavitation, interstitial cavitation, and whirlpool cavitation.
4. Leakage of high-temperature corrosive liquid or steam: This kind of leakage often occurs in weak links such as welds, flanges, packings, expansion joints, etc. of MVR equipment and pipelines.
The above-mentioned four kinds of corrosion phenomena are common in MVR evaporator systems, so when the MVR evaporator is corroded, how should users deal with it? Wen Yangjun summarized the common corrosion protection methods of MVR evaporator as follows:
1. Use corrosion-resistant metal materials. Such as high-grade stainless steel series, titanium, etc., effectively prevent material corrosion.
2. Add corrosion inhibitor. In corrosive media, adding a small amount of corrosion inhibitor can greatly reduce metal corrosion.
3. Anti-corrosion coating method. On the metal surface of the evaporator, a certain anti-corrosion coating is applied to provide a good anti-corrosion zone protection to avoid corrosion caused by direct contact between the metal surface and the corrosive medium.
Understanding the common corrosion problems of MVR evaporators and paying attention to protection methods are very helpful to prolong the service life of MVR evaporators, but it is more important to know how to choose a professional and reliable evaporator equipment service provider!
☑ Electric drive;
☑ Evaporation of ton of water generally consumes about 10-50 kWh of electricity (depending on the characteristics of raw water), and the energy consumption is only 3-5% of ordinary evaporation process;
☑ It can be in the form of horizontal pipe or stand pipe, each has its advantages, depending on the characteristics of the raw water;
☑ Fully automatic control, simple operation, low operator requirements;
☑ Different materials can be selected, including high-grade stainless steel series, titanium, etc. to effectively prevent material corrosion;
☑ No need for steam and cooling water supply, saving resources;
☑ Large vapor-liquid separation area and high separation height can ensure the quality of distilled water;
☑ The circulating water has a lower lift and less power consumption;
☑ There is little water in hot wells, and changes in liquid level provide stable control points;
☑ Fully automatic online cleaning, convenient for cleaning and maintenance;
☑ The system has a small footprint;
☑ The amount of repairs and maintenance is small, and the service life exceeds 20 years.
Wenyang Environmental Technology focuses on the customization of MVR evaporators, multi-effect evaporators, three-effect evaporators, and forced circulation evaporators. Because of their focus, they are professional. Welcome to inquire!