1. Introduction of MVR process

1. Principle of MVR

MVR is the abbreviation of mechanical vapor recompression ( mechanical vapor recompression ). The MVR evaporator is an energy-saving technology that re-uses the energy of the secondary steam generated by itself, thereby reducing the demand for external energy.

The working process of MVR is to compress the low-temperature steam through the compressor, increase the temperature and pressure, and increase the enthalpy, and then enter the heat exchanger for condensation to make full use of the latent heat of the steam. In addition to start-up, there is no need for raw steam during the entire evaporation process. The secondary steam from the evaporator is compressed by the compressor, the pressure and temperature increase, and the heat enthalpy increases, and then sent to the heating chamber of the evaporator for use as heating steam. Keep the feed liquid in a boiling state, while the heating steam itself condenses into water. In this way, the steam that was originally to be discarded can be fully utilized, the latent heat can be recovered, and the thermal efficiency can be improved. The economy of raw steam is equivalent to 30 effects of multi-effect evaporation.

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

2. MVR process flow

The system consists of single-effect or double-effect evaporator, separator, compressor, vacuum pump, circulation pump, operating platform, electrical instrument control cabinet, valves, pipelines and other systems, with simple structure and convenient operation and maintenance.

2. Introduction of evaporator

1. MVR falling film evaporator

working principle:

The material liquid is added from the upper tube box of the heat exchanger, and the material is distributed to each heat exchange tube through the liquid distributor, and a uniform liquid film is formed along the inner wall of the heat exchange tube, and the liquid film in the tube is absorbed by the shell side during the downward flow. The heating steam is heated, and it boils and evaporates while flowing downward. The material at the bottom of the heat exchange tube becomes concentrated liquid and secondary steam.

The concentrated liquid falls into the down tube box, and the secondary steam enters the gas-liquid separator. The liquid droplets entrained by the secondary vapor are removed in the gas-liquid separator, and the pure secondary vapor is transported from the separator to the compressor. The compressor compresses the secondary vapor and sends it as heating vapor to the shell side of the heat exchanger for the heat source of the evaporator. Realize continuous evaporation process.

Features:

1. High heat exchange efficiency

2. Small footprint

3. The material stays for a short time, which is not easy to cause the material to deteriorate.

4. Suitable for materials with higher viscosity.

Applications:

The falling film evaporator is suitable for the pre-concentration process of the MVR evaporation and crystallization process. It can evaporate materials with high viscosity, especially for heat-sensitive materials, but it is not suitable for processing materials with crystallization.

2. MVR forced circulation evaporator

working principle:

The forced circulation evaporator is composed of an evaporation separator, a heat exchanger and a forced circulation pump. The material in the heat exchange tube of the heat exchanger is heated by the steam outside the heat exchange tube to increase its temperature. Under the action of the circulation pump, the material rises into the evaporation separator, and the material evaporates in the evaporation separator due to the drop of the static pressure of the material.

Evaporation produces secondary steam that overflows from the material, and the material is concentrated to produce supersaturation and crystal growth. The desupersaturated material enters the forced circulation pump, and enters the heat exchanger under the action of the circulation pump. The material is continuously evaporated and concentrated or concentrated and crystallized in this way. .

The crystal slurry is output from the circulation pipeline with a discharge pump. The secondary steam in the evaporative separator is purified by the separation and defoaming device on the upper part of the evaporative separator and then sent to the compressor. Cycle continuous evaporation.

Features:

1. Low heat transfer coefficient;

2. The heat exchange surface is not easy to form scaling or crystallization.

Applications:

It is suitable for easy fouling, crystallization, high-viscosity material evaporation concentration or evaporation crystallization process.

3. MVR evaporation OSLO crystallizer _

working principle:

OSLO evaporation crystallizer is composed of OSLO evaporator, heat exchanger and forced circulation pump. The material in the heat exchange tube of the heat exchanger is heated by the steam outside the heat exchange tube to increase its temperature. Under the action of the circulating pump, the material rises to the OSLO evaporative crystallizer, and in the OSLO evaporative crystallizer, the material evaporates due to the drop of the static pressure of the material.

Evaporation produces secondary steam that overflows from the material, and the material is concentrated to produce supersaturation. The supersaturated solution descends in the center tube of the OSLO evaporation crystallizer and fully contacts the small crystals in the solution to make the crystals grow further. The larger crystals grow after being washed out. The elutriation of the elutriation column precipitates the large crystals to the bottom of the elutriation column and transports them to the thickener with a slurry pump. Smaller crystals continue to grow in the OSLO crystallizer.

The clarified liquid is sent to the heat exchanger by the forced circulation pump to continue heating, and the material is continuously evaporated and concentrated or concentrated and crystallized in such a cycle. The secondary steam in the OSLO evaporative crystallizer is purified by the separation and defoaming device on the upper part of the separator and then sent to the compressor. The compressor compresses the secondary steam and sends it to the shell side of the heat exchanger to be used as evaporator heating steam. Realize continuous evaporation of thermal energy cycle.

main feature:

1) Large crystal size and uniform particle size

2) The equipment is bulky and expensive

Scope of application:

It is suitable for the production of materials requiring larger crystal size.

4. MVR evaporation DTB crystallizer _

working principle:

DTB type crystallizer is a typical crystallizer with internal circulation of magma. Since the inner guide tube is installed in the crystallizer, a circulation channel is formed, so that the crystal slurry has good mixing conditions, and the supersaturation can be quickly eliminated in the evaporative crystallization, and the supersaturation of the solution can be kept at a relatively low level.

Especially suitable for products with steep solubility curves. The DTB type crystallizer has good performance, high production strength, can produce larger grains, and is not easy to scar inside the crystallizer. It has become one of the main forms of continuous crystallizer.

main feature:

High production strength, large crystal particles and stable performance.

Scope of application:

It is suitable for the production of materials with large crystal particle size and high production intensity.

3. Technical summary

In general, the technical characteristics of the mvr evaporator are as follows:

( 1 ) Clean energy, high thermal efficiency, low power consumption, and no pollution.

( 2 ) The " zero discharge " of industrial wastewater has reached the national discharge standard.

( 3 ) The material to be processed has a wide range of adaptation.

( 4 ) One body with multiple effects, saving manufacturing cost.

( 5 ) Low temperature evaporation, room temperature evaporation (non-standard, non-pressure vessel design basis).

( 6 ) It can discharge continuously and intermittently.

( 7 ) High degree of automation and low operating cost.

( 8 ) Small size and strong mobility.