The main features of a multi effect evaporator are:
1. Efficient defoaming: The system is equipped with efficient defoaming device to avoid material foam entrainment leading to material loss.
2. Automatic control: Adopting a liquid level automatic control system, automatic feeding and automatic discharge of condensate.
3. Long service life of the overall tube plate: The heater, preheater, and condenser tube plates use integral tube plates to extend the service life of the equipment.
4. Energy saving and consumption reduction: The discharge adopts a separation device to increase the crystal content of the discharge, obtain most of the crystals after separation, have little reflux of the mother liquor, require less heat energy to be consumed again, and save energy.
Multi effect evaporators have evolved from primitive evaporators to single effect, double effect, three effect, four effect, or more effect evaporators, all aimed at gradually reducing energy consumption.
Single effect evaporation consumes 1.1 to 1.2 tons of steam per ton of water, double effect evaporation consumes 0.6 to 0.7 tons of steam per ton of water, triple effect evaporation consumes 0.37 to 0.46 tons of steam per ton of water, four effect evaporation consumes 0.3 to 0.35 tons of steam per ton of water, and five effect evaporation consumes 0.24 to 0.3 tons of steam per ton of water.
Multi effect evaporators can adopt various forms such as forced circulation, natural circulation, falling film, rising film, and plate type evaporators, as well as various combinations to optimize the process flow.
Working principle of multi effect evaporator:
The principle of a multi effect evaporator is to use fresh steam to drive the first effect to produce evaporation, and then use the secondary steam generated by the first effect to drive the next effect evaporation, in order to achieve the goal of energy conservation. In order to reduce the consumption of primary steam, the secondary steam generated in production is introduced into two evaporators for heating steam. The secondary steam generated by the two evaporators can also be introduced into three evaporators for heating steam, and each evaporator is called a first effect, and so on. In this way, several evaporators are operated in series to form a multi effect evaporator.
Composition of the multi effect evaporator system:
It is composed of various heaters, evaporation separators, condensers (mixed or surface type), forced circulation pumps, various material and liquid transfer pumps, vacuum pumps, condensate pumps, operating platforms, electrical instrument control cabinets, and pipeline valves within the boundary.
Application field of multi effect evaporator:
Single effect, double effect, triple effect, and multi effect forced circulation evaporators are suitable for evaporation and concentration in industries such as chemical, food, pharmaceutical, environmental engineering, waste liquid evaporation and recovery, with scaling, crystallinity, thermal sensitivity (low temperature), high concentration, high viscosity, and insoluble solids. Widely used as an evaporation concentrate for water or organic solvent solutions in industries such as medicine, food, chemical, and light industry, and can be widely used for waste liquid treatment in these industries. Especially suitable for heat sensitive materials, evaporators operate continuously under vacuum and low temperature conditions, with high evaporation capacity, energy saving and consumption reduction, low operating costs, and the ability to ensure the invariance of materials during the evaporation process.
Energy saving, environmental protection and resource utilizationZheJiang VNOR Environmental Protection Technology Co., Ltd (Stock code: 872205) focuses on the development, production, and sales of all types of evaporation and crystallization projects using MVR evaporators,multi-effect evaporators and heat pump evaporators which are extensively used in the waste water treatment, Pharmaceutical, and chemical industries.
With the aid of specialists in evaporation crystallization technology, we are able to offer customers the best system solutions in terms of design, fabrication, installation & commissioning, and after-sale service.
PRINCIPLE OF MVR EVAPORATOR
MVR evaporator is a relatively energy-saving and efficient system commonly used in the evaporation and crystallization industry. MVR evaporator is the abbreviation of vapor mechanical re-compression technology. 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 core equipment of the MVR evaporator is the steam compressor system, which mainly compresses water vapor. Currently, integral skid-mounted centrifugal fans, roots compressors, and high-speed centrifugal compressors are widely used in China, equipped with sealing systems, lubrication systems, oil cooling systems, control and monitoring systems, and drive systems.
COMMON PROBLEMS AND SOLUTIONS OF MVR EVAPORATOR
What is the boiling point rise? How to solve scaling?
Boiling point rise refers to the temperature of different salt solutions at boiling, sodium chloride saturated boiling point rise 107 ºC, ammonium chloride is 115 ºC; scaling solution is difficult, it is best to do to prevent, one to control Ca2+, Mg2+, two to control silicon; if scaling occurs, water washing and acid washing.
What is the maximum temperature rise of the inlet and outlet?
The temperature rise of a domestic compressor is 22°C, and the temperature rise of an imported compressor is 8-9°C.
Can't the boiling point rise exceed 15 ºC?
It is best not to raise the boiling point above 10-12ºC; The total temperature rise of the compressor is 22ºC. If the boiling point rises above 15ºC, the evaporation effect will be very bad if considering the loss of 2ºC and the temperature difference of 5ºC. We hope that the effective evaporation temperature difference will be as large as possible, and 7-8ºC will be better.
Is the heat transfer coefficient of forced circulation evaporation only 600 to 800?
The heat transfer coefficient of the falling film is generally 1200-1500, and the forced circulation is 600-800. Try to choose a more conservative heat exchange coefficient, a larger heat exchange area, and a sufficient temperature rise for the compressor to ensure the final evaporation, which can make the system more reliable.
All steam compressors need to be filled with water. How much is the water consumption?
All steam compressors need to be filled with water, because there will be an overheating process during the compression of secondary steam, which needs to be turned into saturation.Generally speaking, one ton of steam will replenish about 50 kilograms of water, but domestic compressors and imported compressors have different opportunities.
There is a membrane separation concentrated water for electroplating wastewater, with a salt content of only over 4W, mainly sodium sulfate and sodium chloride. Is MVR economical to consider?
The most important thing about economy is to consider the investment cost of electricity consumption and steam. If the price of steam exceeds 150 yuan and the price of electricity is about 1 yuan, the MVR system is more cost-effective.
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