MVR evaporator is an upgrade of the traditional evaporator. MVR is the abbreviation of Mechanical Vapor Recompression, commonly known as heat pump.

Working principle of MVR evaporator:
The steam compressor equipment is used to pressurize and heat the secondary steam generated by evaporation, and then heat the material as a heat source, thus saving the use of fresh steam and the use of a large amount of circulating cooling water in traditional evaporator. See Figure 1 for the conventional process.

Equipment composition:
Heat exchanger, gas-liquid separator, secondary separator, steam compressor, distilled water tank, vacuum pump, forced circulation pump (used for forced circulation evaporator), etc. When there is crystallization demand, thickener, centrifuge, mother liquor tank and drying equipment are also required, and high boiling mother liquor treatment equipment is also required.

Application scenario:
It is applicable to milk, glucose, concentration of traditional Chinese medicine, salt making, wastewater treatment and other industries. It is mainly used for evaporation of materials with boiling point rise less than 12 ℃. Materials with higher boiling point rise have lower cost performance when applied.

Process description:
The material preheated to the set temperature enters the large pipe of the evaporator and exchanges heat with the saturated water vapor of the shell side after mixing with the concentrated solution. Due to the effect of the static head, the material after the temperature rise does not evaporate, and is flashed in the crystallization separator. The secondary steam generated by the flash enters the steam compressor after purification, and then returns to the shell side of the heat exchanger as a heat source after pressurization and heating, The condensed distilled water is collected by the distilled water tank and then discharged from the system through the distilled water pump and the distilled water plate for heat recovery. The concentrated solution will continue to be concentrated and evaporated in the system. When it reaches the design concentration, it will be discharged from the system through the discharge pump. If it is a crystallization system, it will need to be separated from the crystallization through the thickener and centrifuge. The mother liquor will continue to return to the evaporator for further evaporation.

Process characteristics:
1. Only a small amount of steam is needed to reduce the operating costs of enterprises and reduce environmental pollution;
2. The compressor is used to provide heat source. Compared with the traditional evaporator, the temperature difference is much smaller, which can achieve mild evaporation, greatly improve the product quality and reduce the scaling rate;
3. Without condenser, the structure and process are very simple, fully automatic operation, continuous operation, safe and reliable;
4. The materials are evaporated at low temperature without producing foam, and the liquid is uniform without material loss and coking.

Common faults of MVR evaporator
MVR evaporator has been widely used in MVR evaporation, MVR distillation and other fields due to its excellent energy-saving performance in recent years. However, MVR evaporator also has its disadvantages, such as low operating flexibility, high requirements for materials and high primary investment. Common faults of MVR evaporator generally include steam compressor surge, evaporation capacity drop, easy scaling, etc. For this, we have an article to introduce - talk about the selection of evaporation process.