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How do multiple-effect vacuum evaporators reduce the amount of steam needed to make salt?

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Cluster of translucent, white salt crystals with sharp cubic shapes viewed under a microscope at high magnification against a dark background. — salt Salt crystal magnified.

Multiple-effect vacuum evaporators significantly reduce the amount of steam required for salt production by reusing heat across a series of vessels. In this system, the vacuum pressure in each successive vessel is carefully adjusted so that the vapor generated in one unit remains hot enough to boil the brine in the next.12

By utilizing the vapor from the first vessel to supply the heat necessary to operate the second, and subsequently using the vapor from the second to heat the third, the system maximizes energy efficiency. This process allows for a dramatic reduction in fuel consumption; for example, while open pans require 4,500 to 5,400 kg of steam to produce one ton of salt, a triple-effect evaporator requires only 630 kg of steam to achieve the same output.12