Application of Smart Instruments in MVR Evaporation System

Industry Background

In recent years, due to increasingly strict environmental policies, particularly the proposal of "carbon peak" and "carbon neutrality" targets, MVR (Mechanical Vapor Recompression) evaporators have gained significant popularity compared to traditional single-effect and multiple-effect evaporators. MVR evaporators offer high thermal efficiency, energy savings, and low power consumption, making them widely adopted in various industries such as chemical, pharmaceutical, paper, environmental, wastewater treatment, and seawater desalination. Currently, the structure of the domestic evaporator market in China is still predominantly composed of traditional multiple-effect evaporators, with a smaller proportion of MVR evaporators. However, as the government continues to implement energy-saving and emission reduction policies and businesses face increasingly intense market competition, more companies are expected to adopt MVR evaporator technology as a substitute for traditional evaporator technology. This shift is driven by the desire to improve energy efficiency, minimize environmental impact, and gain a competitive edge in the market.

Application System

MVR, short for Mechanical Vapor Recompression, is an energy-saving technology that recycles its own generated secondary steam, thus minimizing the reliance on external energy sources.

MVR Operating Principle

MVR evaporator differs from common single-effect evaporator or multi-effect evaporator, as well as from common falling film evaporator. MVR evaporator is an individual device that employs a staged evaporation approach based on the desired product concentration.

Operating Process

The operating process of MVR evaporators involves compressing low-temperature steam in a compressor, which increases its temperature, pressure, and enthalpy. The steam then enters a heat exchanger to condense, effectively utilizing the latent heat of the steam. Except for the initial startup, there is no need for live steam during the entire evaporation process, as secondary steam is generated from the evaporator.

MVR evaporator uses compressor to enhance the energy of secondary steam and make use of the increased energy. It recovers the latent heat of secondary steam by insulating the compression of the evaporator-generated secondary steam in the compressor. After increasing its pressure and temperature, the steam is sent back to the heating chamber of the evaporator as heating steam. The condensation releases heat, allowing for the latent heat of the steam to be recycled. Before the cold charge re-enters the evaporator, it absorbs heat from the condensate through a heat exchanger, elevating its temperature while also cooling the condensate and finished liquid, further improving heat utilization.

Components of MVR Evaporation System

• Evaporator: the main device, including heaters, separators, circulation pumps and other devices.

• Compressor System: The core device of the entire MVR evaporation system, compressing secondary steam to provide an evaporation heat source and increasing the enthalpy of secondary steam.

• Preheater: Utilizes waste heat and raises the temperature of the incoming material.

• Vacuum System: Maintains the vacuum level of the entire system, extracting non-condensable gases and gas entrained in the solution to achieve a stable evaporation state in the system.

• Control System: PLC or DCS system. Control and adjustment of compressor speed, valves, flowmeters, temperature, and pressure to achieve automatic evaporation, cleaning, and shutdown operations. It features automatic alarms and system protection to maintain dynamic balance.

Applications of MVR Evaporation System in Other Industries

• Environmental Protection Field

MVR evaporator in the environmental protection field is used for treating industrial wastewater. The Industrial wastewater is evaporated, concentrated, and recycled. For example: wastewater treatment in electroplating, coating production, pharmaceutical and pesticide, metal processing, papermaking, and crude oil production industries. 

• Chemical Industry

MVR evaporator is widely used in the production of chemical raw materials such as sodium sulfate, sodium persulfate, and sodium hypochlorite, the purification of fragrances, the treatment of industrial process water, seawater desalination, the concentration and crystallization of organic additives, etc.

• Pharmaceutical Industry

Most pharmaceutical industries use traditional evaporators, which not only reduce the quality of drugs but also waste a large amount of energy. Therefore, the energy-saving nature of MVR evaporators makes them widely used in the pharmaceutical industry. It is commonly used for the evaporation, concentration, crystallization, and drying of Western medicine production and the concentration of traditional Chinese medicine.

• Food Industry

In the deep processing of food, evaporation technology is widely used to achieve dehydration function, such as concentrating corn slurry and extracting glucose, amino acids, etc.

• Beverage Industry

MVR evaporator is used in the beverage industry for concentration treatment. For example: tomato sauce, fruit juice, fruit jam, etc.

Case Background and Measurement Requirements

Case Background

A South China-based environmental company specializes in industrial wastewater treatment projects. They utilize MVR evaporators to eliminate organic and inorganic substances from the wastewater, enabling water resource reuse and providing a cost-effective solution to industrial wastewater challenges. Throughout the treatment process, there is a need to measure pressure, liquid level, temperature, and flow-related parameters.

Measurement Requirements

The wastewater goes through multiple evaporation cycles in the MVR evaporator for water resource recovery. During this process, the industrial wastewater is typically contained within a sealed pressure vessel at high temperature and high pressure, which poses corrosive properties. Meanwhile, the measured medium can solidify or crystallize due to changes in ambient temperature. It is necessary to strictly purify the measuring probe when each medium batch is replaced. In the case of suspended liquids and high-viscosity mediums, the measuring probe must be kept clean and hygienic.

Previously, the customer used a foreign brand's smart pressure transmitters and flowmeters. However, due to annual price negotiations with end customers, the customer urgently needed to reduce costs in the supply chain and sought domestically produced alternatives that could meet the operating conditions. They conducted several years of testing while seeking suitable products. As a result, this environmental company urgently required smart pressure transmitters and flowmeters that could withstand chemical corrosion and have a long lifespan. These instruments are crucial for reliable and long-term measurement of industrial wastewater within the MVR evaporator.

Solutions

Micro Sensor recommends using the MDM7000-LP Smart Differential Pressure Transmitter With Remote Diaphragm Seal and the MDM7000-LT Smart Differential Pressure Level Transmitter to measure the gas and liquid pressure in the container medium. These two smart differential pressure transmitters utilize advanced monocrystalline silicon piezoresistive technology, making them suitable for demanding applications with highly corrosive chemicals. Therefore, it is particularly applicable to continuous measurement of industrial medium in MVR evaporation system.

MDM7000-LP Smart Differential Pressure Transmitter With Remote Diaphragm Seal is used to monitor the level of the separator in real-time and control the feed-in, ensuring the efficient operation of the entire system. MDM7000-LT Smart Differential Pressure Level Transmitter is used to monitor the level of the condensed tank in real time, allowing for timely water replenishment to the condenser, enabling rapid condensation. At the same time, it monitors the level height of the raw material tank and mother liquor tank. When the liquid is consumed, add raw liquid to ensure the normal progress of the process.

MTM4831 Temperature Transmitter is also equipped in the heater and separator, which is used to monitor the steam temperature in the heater, continuously heat the raw liquid, separate the solution and solute, and simultaneously monitor the temperature of the separator's chamber to ensure efficient separation of solute and solvent.

MFE600E Electromagnetic Flowmeter is also equipped in the feed pump, which is used to calculate the volume and cumulative flow rate of the raw liquid being pumped.

This configuration significantly enhances the safety and efficiency of the MVR evaporator equipment. With its unique corrosion-resistant measurement construction, Micro Sensor’s equipment has a considerable lifespan and does not cause leaks, thus significantly reducing risks for the operators. The need for constant maintenance and product replacement, which used to be a source of concern, is no longer an issue.

Recommended Products

1. MDM7000-LP Smart Differential Pressure Transmitter With Remote Diaphragm Seal

• Range: 0.4bar~30bar • Accuracy: ±0.05%, ±0.075% URL + effect of diaphragm system • Operating temperature: -10°C~70°C • Output: 4mA~20mA DC+HART; 4mA~20mA DC+HART (Intrinsically safe) • Certifications: PCEC, ATEX, IECEx, CSA, CE, RoHS, CCS, HART

2. MDM7000-LT Smart Differential Pressure Level Transmitter

3. MTM4831 Temperature Transmitter

• Range: -200°C～0°C~500°C; • Accuracy: ±1.0%FS (-200°C...0°C~500°C); • ±0.5°C(-40°C...0°C~150°C )； • ±0.25°C(-20°C...0°C~105°C ) • Operating temperature: -25°C~70°C； • Output: 4mA~20mA DC; 4mA~20mADC+HART; 4mA~20mADC+RS485; RS485; thermal resistance; • Certifications: Flameproof, Intrinsically safe, CCS

4. MFE600E Electromagnetic Flowmeter

• Range: Diameter DN25~DN200 • Accuracy: ±0.2%FS; ±0.5%FS • Operating temperature: -40°C~60°C • Output: 4mA~20mA DC; Hart; Frequency, Pulse; RS485 (ModBus protocol) RS232 output • Certifications: TS, CNEX, CE, CCS

In the MVR evaporator system, Micro Sensor can provide a range of corresponding smart measuring instruments according to the application conditions, such as smart pressure transmitters, level transmitters, temperature transmitters, flowmeters, etc. These instruments can be used to record, monitor, and control specifications in the production process at different monitoring and control points.