Industrial mechanical vapour recompression MVR
A heat pump uses energy to transfer heat from a lower temperature source to a higher temperature demand using additional energy. For industrial heat pumps, the heat source is process waste heat.
Mechanical vapour recompression (MVR) is an open heat pump system in which the pressure and temperature of the vapour, together with the corresponding saturation temperature, are increased by means of compression. Steam recompression is a specific variation of MVR. Low-pressure steam exhaust from industrial operations, such as evaporators or cookers, is usually vented to the atmosphere or condensed in a cooling tower, while other plant operations on the same site may require intermediate-pressure steam. Instead of expanding high pressure steam across a throttling valve to meet these needs, low-pressure waste steam can be mechanically compressed to a higher pressure so that it can be reused. Steam recompression relies upon a mechanical compressor to increase the temperature of the latent heat in steam to render it usable for process duties. The advantage lies in the fact that the required compression energy is very small compared to the amount of latent heat present in the recycled steam.
The energetic performance of steam recompression is expressed in the coefficient of performance (COP). The COP gives the ratio of the net recovered heat and the energy used by the compressor. In this case, the net heat is the steam production including the additional steam yield by water injection. Typical economical and energy-efficient applications have a minimum COP of 3.5. Some applications of MVR have a COP of 10 or even higher.
The key elements for a high COP are the following:
A low ratio of the absolute steam pressures. A guideline for the maximum ratio is 6, but in daily practice the ratio is about 3.
A minimum capacity. A guideline is a minimum of one tonne of steam per hour.Water injection after compression.
MVR evaporators minimize energy consumption
MVR evaporators (sometimes referred to as a Vapor Compression Evaporator) removes water from mill liquors or effluents with minimum energy consumption and maximum plant availability while delivering high condensate quality.
The evaporators have lamella heating surfaces. Inherently non-foaming, these evaporators are ideally suited for the low dry solids applications of MVR evaporation with capacities from 10 to 200 t/h in a single unit.
MVR evaporators operate on a “heat pump” principle. The evaporated water vapor is recompressed with a simple, low-speed centrifugal fan or compressor which increases the saturation temperature of the vapor. After the fan, vapor can be used as heating steam in the same unit. The recompressed vapor condenses and releases its latent heat through the heat transfer surface for further evaporation of the liquor or effluent.
Double-effect forced circulation evaporator is composed of heater, separator, vapor-liquid separator, condenser, vacuum pump, forced circulation pump, discharging pump, condensate pump, electrical cabinet, operation platform and all the pipe fittings, valves, instruments and etc.
Heater: Two sets of vertical type tubular heater connect in series. The feed liquid is pumped into the first heater by forced circulation pump, then enters into the second heater. The heated liquid flow downwards in tubes, and flow into separator by tangential direction, better performance of vapor-liquid separation.
Separator: Vertical type, the secondary steam is discharged from the top, pass through a vapor-liquid separator before entering into condenser. The bottom of separator is connected with a forced circulation pump.
Vapor-liquid separator: Is used to prevent tiny liquid drops produced during evaporation from escaping with secondary steam, reducing loss of feed liquid and prevent pollution to pipeline and cooling water.
Condenser: Condensate the huge secondary steam produced during evaporation into liquid by cooling water, making concentration carrying on smoothly. Meanwhile, separate non-condensable vapor from secondary steam and cooling water, make it easily pumped out by vacuum pump to guarantee vacuum degree.
Very low specific energy consumption
No steam or cooling water required
Not necessary to integrate with existing evaporators
Location can be chosen relatively freely
Excellent condensate segregation
Easy capacity control
Proven in multiple applications in kraft and mechanical pulp mills
|Product Name||MVR Evaporator|
|Application||Waste Water Treatment|
|Features||Energy Saving/Low operation cost|
Working principle technical drawing