Multi-stage flash evaporator

A multi-stage-flash cross-tube evaporator comprising:

• an evaporator shell of elongated shape, including an evaporator shell bottom and an end wall, the end wall extending substantially vertically and transversely to a longitudinal axis of the evaporator shell;
• a plurality of first partition walls, each first partition wall being arranged substantially parallel to the end wall and dividing the evaporator shell internally into a plurality of flash stages, openings in the first partition walls allowing a solution flowing on the evaporator shell bottom to pass from each flash stage to the next and allowing the solution to flash down in each consecutive flash stage to a lower temperature compared to the temperature of the solution in the previous flash stage and to evaporate in each flash stage a portion of the solution, releasing a vapor;
• wherein each of at least two of the flash stages comprises:
• a double pass tube bundle extending across the evaporator shell substantially transversely to the longitudinal axis of the evaporator shell, the double pass tube bundle including a first tube bundle pass having a first plurality of tubes and a second tube bundle pass having a second plurality of tubes;
• means for the first tube bundle pass to receive a first coolant stream and convey the first coolant stream within the first plurality of tubes;
• means for the second tube bundle pass to receive a second coolant stream and convey the second coolant stream within the second plurality of tubes such that the first and the second coolant streams flow in counter-current directions through the first and second tube bundle passes;
• and
• means for fluidly isolating the first coolant stream from the second coolant stream.