MVR.pdf

Summary：

MVR evaporator is the abbreviation of Mechanical Vapor Recompression. MVR re-uses the secondary steam energy produced by its own, thereby reducing the demand for external energy. Early in the 1960s, Germany and France have successfully applied this technology in chemical, pharmaceutical, paper, sewage treatment, seawater desalination and other industries. Its working process is compressing low temperature steam by the compressor, raising temperature and pressure, increasing enthalpy and entering into heat transfers for condensation, to make full use of steam latent heat. In addition to drive start, the whole evaporation process needs no steam.

In the multi-effect evaporation process, the secondary steam of the first effect of the evaporator cannot directly used as the self-effectiveness heat source, only can be used as the secondary or subsidiary effective heat sources. If it is used as the self-effectiveness heat source, additional energy must be supplied to it, so as to raise the temperature (pressure). The steam jet pump can only compression partial of the secondary steam, however MVR evaporator can compress all the secondary steam in the evaporator.

The solution is in an evaporation tank, and it can circulate in the heating pipe through the material circulation pump. Initial steam is heated from outside of the pipe via fresh steam; the solution is heated to be boiling to generate the secondary steam, which is sucked again by the steam compressor. After pressurization, the secondary steam’s temperature increases, and the steam is used as the heat source to enter the heat exchanger for circulation evaporation. After normal start up, the steam compressor inhales the secondary steam, which is pressurized and changed into heating steam, so circulation evaporation continuously go on. The evaporated moisture eventually become condensed water and then be discharged.

Main features of MVR evaporation system：

.Save energy consumption.

.In addition to preheating, the normal work needs no steam, to reduce environmental pressure.

.Need no cooling system, so that the cooling water can be saved.

.Compared with multi-effectiveness evaporation, it has features, such as simple process, compact equipment and small floor space.

.Compared with the traditional evaporation system, the heat exchange temperature difference is small, and the heat exchanging area is large.

.The product is evaporated mildly due to the low temperature difference designed for the system; therefore, concentrated liquid is not easy to occur high temperature metamorphism, coking and so on.

Main uses of MVR evaporation system：

.Traditional Chinese medicine concentration (can be evaporated water, ethanol, methanol, etc.).

.Sugar, milk, juice, beverage concentrate.

.Salt wastewater concentration and crystallization (NaCl, Na2SO4, NH4Cl, etc.) salt crystallization.

.Papermaking wastewater concentration.

.Chemical wastewater treatment.

.Distillation (can be used for distillation of ethanol, methanol, acetone, etc.)

.Organic acid, chemical solvent distillation.

Working principle of MVR evaporation system refer to

Main features of Roots series RVC type steam compressor:

Compressor model meaning：

R　V　C　－　10　A　－　22

R：Roots，Roots type

V：Vapor，Vapor

C：Compressor，Compressor

Maximum evaporation under low temperature conditions (kg/h, 10 C)

A： material code

22：power code, kW，kW

Relying on our company for many years the production of vacuum pump Roots experience, and combined with the requirements of MVR vapor compression, we developed a Roots series RVC type steam compressor, the main features are as follows:

.Pump cavity is without oil, to avoid the oil vapor pollution evaporation system.

.The vibration is small and the noise is small.

.Mechanical friction loss is small, so the driving power is small.

.Easy to maintain and repair, low cost, high life expectancy.

.In order to improve the characteristics of the compressed water vapor and organic solvent, the emulsification of the oil in the bearing cavity and the corrosion of the pump cavity are solved.

.Unique overheating eliminates design. By connecting the saturated steam return pipeline, so that roots compressor compressed heat is greatly reduced and the pump rotor cavity, pump body, end caps of temperature equilibrium, to avoid the due to impact by thermal expansion unevenness in the pump, pump seal burned, the pump was stuck phenomenon.

.Because of our company's unique heat elimination design, no need to spray liquid from the pump to cool down, so as to avoid the liquid caused by the pump cavitation damage.

.In order to improve the heat transfer coefficient of the heat exchanger, the heat transfer coefficient of the heat exchanger is improved by increasing the flow rate of the main heat exchanger by the flow rate of the flow.

.In order to solve the special design of various solvents, the RVC Roots compressor is safe and efficient in the compression of various solvents.

Its working principle may refer to Roots vacuum pump working principle

Material selection of Roots compressor 　

Material code 　　　

A： rotor nodular cast iron NiP coating, pump body, end cap gray cast iron NiP coating　　　　

B： rotor ductile iron PFA 316L coating, pump body, end cap gray cast iron PFA 316L coating　　　　

C： C PFA HASTELLOY coating, pump body, end cover gray cast iron C PFA HASTELLOY coating　　 　　

D：rotor, pump body, end cover SAF2205 dual phase stainless steel pump body

E： other materials 　　 　

Accessories image area:

NiP coated rotor，NiP coated pump body and end cap，Hastelloy alloy + PFA coated rotor，Hastelloy alloy + PEA coating pump body，stainless steel rotor,stainless steel pump body

Roots compressor and centrifugal compressor are mainly used in MVR evaporation system. The main features are as follows:

RVC Series Roots Steam Compressor Technical Parameter Specification

 Outline sketch map of Roots series RVC type steam compressor

MVR evaporation compressor type selection table (calculation in pure water)

Comparison of energy consumption of MVR evaporation system:

If the concentrated liquid has been pre heated, evaporation per1000kg water:

The use of a single-effect concentration needs consuming steam about 1200kg, the cost of about 240 yuan (cooling water consumption and pump vacuum, etc. are not included in the calculation).

The use of double-effect concentration needs consuming steam about 600kg, the cost of about 120 yuan (cooling water consumption and pump vacuum, etc. are not included in the calculation).

Triple-effect concentration needs consuming steam about 400kg, the cost of about 80 yuan (cooling water consumption and pump vacuum etc. are not included in the calculation)

MVR concentration does not need steam, only consuming power of 20~25 degrees, the cost is about 20 yuan, and does not require steam, cooling water and vacuum pump.

MVR system also applies to methanol, ethanol and other solvent evaporation process. 　　

Common solvent MVR evaporation energy consumption (in addition to the special description, heat transfer temperature difference is calculated by 10 ℃):

Note:

1. In addition to the special explanation, the table data doesn't consider the impact of boiling point rising, such as the material is more complex or correlative data is uncertain; it is recommended to contact with my company for MVR evaporation tests to determine the key parameters.

2. If it needs to design a reasonable waste heat exchanger to recovering waste heat, the maintenance of the necessary steam (or other heat media) consumption is very little or needs no external heat source.

3. If it needs to design an external forced circulation pump, the power consumed is calculated additionally.

Attached: flow diagram of Chinese medicine MVR concentration (for water solution concentration of low boiling point rising)

Sodium chloride wastewater MVR evaporation crystallization, different feeding concentration, energy consumption comparison of different processes:

 (power kW, evaporation by 1000kg/h, evaporation temperature by 80℃, heat transferring temperature difference of 5℃; cycle pump and other power are not included)

When the high boiling point of the low concentration of material and ethanol, methanol and other MVR distillation conditions, the use of double stage evaporation plus of double-stage compression scheme is more energy saving.

MVR equipment application：

Processing equipment display: