MVR is a steam mechanical recompression technology, and the MVR evaporator is an energy-saving technology that reuses the energy generated by its own secondary steam, thereby reducing the demand for external energy.

The working process of MVR is to compress the low-temperature steam through a compressor, increase the temperature and pressure, increase the enthalpy, and then enter the heat exchanger for condensation to fully utilize the latent heat of the steam. Except for starting the car, there is no need to generate steam during the entire evaporation process. The secondary steam coming out of the evaporator is compressed by the compressor, and the pressure and temperature increase, resulting in an increase in enthalpy. It is then sent to the heating chamber of the evaporator as heating steam to maintain the boiling state of the material liquid, while the heated steam itself condenses into water. In this way, the steam that was originally to be discarded is fully utilized, latent heat is recovered, and thermal efficiency is improved. The economy of generating steam is equivalent to 30 effects of multi effect evaporation.

To make the manufacturing of the evaporation device as simple and easy to operate, centrifugal compressors and Roots compressors can be used. These machines have higher volumetric flow rates in the compression ratio range of 1:1.2 to 1:2.

The working process involves compressing the low-temperature steam through a compressor, increasing the temperature and pressure, increasing the enthalpy, and then entering the heat exchanger for condensation to fully utilize the latent heat of the steam. Except for start-up, there is no need to generate steam during the entire evaporation process.

As shown in the figure, the secondary steam generated during the evaporation process is compressed and then returned to the evaporator as heating steam.

The temperature of the secondary steam generated by evaporation is relatively low, but it contains a large amount of latent heat. After being compressed by the compressor to increase the temperature (pressure), the secondary steam is sent back to the heat exchanger of the original evaporator as a heat source to maintain the boiling state of the material liquid, while the heated steam itself condenses into water. The economy is equivalent to 20 effects of multi effect evaporation.

1) No need to generate steam

2) Low energy consumption and low operating costs

3) Can be combined with crystallizers to create continuous crystallizers in MVR form

Comparison of the cost per ton of water evaporated by MVR evaporator and multi effect evaporator:

Note: The price of industrial steam is based on 180 yuan/ton; The electricity price is set at 0.6 yuan/kWh

The working process of MVR technology is to compress the steam at low temperature through the MVR compressor, increase the temperature and pressure, increase the enthalpy, and then enter the heat exchanger for condensation to fully utilize the latent heat of the steam. Except for start-up, there is no need to generate steam during the entire evaporation process. Compress the secondary steam generated during the evaporation process and return it to the evaporator as heating steam.

The temperature of the secondary steam generated by evaporation is relatively low, but it contains a large amount of latent heat. After being compressed by the MVR evaporator compressor to increase the temperature (pressure), the secondary steam is sent back to the heat exchanger of the original evaporator as a heat source to maintain the boiling state of the material liquid, while the heated steam itself condenses into water. The economy is equivalent to 20 effects of multi effect evaporation.The MVR evaporator fully utilizes the secondary steam and does not waste the thermal energy of the secondary steam.

In order to reduce operating costs, this plan adopts MVR technology. This project uses imported fans to compress the secondary steam and achieve the evaporation temperature difference required for system operation. Except for using steam to preheat the system when it is turned on, the entire system only needs to use electricity during normal operation and does not require additional steam generation. The suction end of the fan is partially vacuum, which can reduce the flash steam formed when the crystal slurry enters the centrifuge. The system operation does not require the addition of steam, as all high-temperature condensate generated by the system is used to preheat the material to near the boiling point; The thermal energy generated when the fan compresses steam will be used to preheat the remaining materials and compensate for the heat loss generated by the system, providing sufficient thermal energy to ensure the discharge of air and non condensing steam.

The fan is driven by a variable frequency control motor. Variable frequency control can enable the fan to operate at the optimal speed, eliminating the loss of inlet guide vanes; By soft starting, the impact on the entire system is reduced, and the service life of the fan and motor is extended. When it is necessary to operate below the system design capacity, adjusting the frequency converter can ensure the economic operation of the system.

1. No need to use raw steam

Except for start-up, there is no need to generate steam during the entire evaporation process.

2. Low energy consumption and low operating costs

The energy-saving effect is very significant, and the energy consumption of the MVR system is equivalent to 20 times that of a multi effect evaporator.

With the further improvement of environmental protection and energy conservation requirements, MVR evaporators have gradually become the preferred choice for evaporation devices, including wastewater concentration treatment, with very low operating costs. In the past two years, the domestic mechanical steam compression fan industry has flourished, and the share of domestic compressors in China has been continuously decreasing. So, how to choose the most critical steam compressor in the MVR evaporator? Today I'll tell you a few things to pay attention to when choosing a steam compressor correctly!

A steam compressor is a key equipment in a heat recovery system that compresses the steam generated to increase the temperature and pressure of the steam. The function is to pressurize and heat up low-pressure (or low-temperature) steam to meet the temperature and pressure requirements of the process or engineering.

Mechanical steam compressors are divided into two types: Roots steam compression fans and centrifugal steam compression fans, while centrifugal steam compression fans are further divided into ordinary centrifugal compression fans and single-stage high-speed centrifugal steam compressors. Different types of fans have their own characteristics and advantages under different application conditions.

Roots compression fans belong to volumetric fans. Compared to ordinary centrifugal compression fans, they have a higher compression ratio and a single stage compression temperature rise of up to 25 degrees Celsius.

For Roots steam compression fans, due to their lower speed, they have better stability.

Generally speaking, the speed of Roots steam compression fan is between 980-1450r/min, the speed of ordinary centrifugal steam compression fan is between 6000-9000r/min, and the maximum speed of single-stage high-pressure centrifugal fan can reach 30000r/min.

Of course, for Roots fans, their disadvantages are also very obvious. Their small single-stage volume flow rate, low efficiency, and short maintenance cycle (usually 2000h/time) are their congenital defects; At the same time, the noise spectrum of Roots blower is relatively wide, with 63-8000Hz low intermediate frequency noise as the main component, and the noise during operation can reach over 100 decibels, causing significant harm to personnel health.

Ordinary centrifugal steam compression fans generally compress and heat up to 8-10 degrees Celsius. Currently, the main application models are imported compression fans, which have the advantages of high efficiency and stable performance.

In working conditions that require a higher compression ratio, two centrifugal steam compression fans can be connected in series to achieve a higher compression temperature rise, but at the same time, the efficiency of the fans will decrease.

In general, boiling up occurs during the evaporation process, and some solutions may even experience high boiling up. In this case, two or three stage fans need to be connected in series for use.

The notable feature of a single-stage high-speed centrifugal compression fan is its high fan speed and high compression ratio, resulting in a higher compression temperature rise, up to 25-30 degrees Celsius. At the same time, it also has high efficiency, low energy consumption, and larger processing capacity, making it more widely used.