Multi-stage vacuum distilling, cooling and freezing processes and apparatuses for solution separation and seawater desalination

A multi-stage vacuum distilling process for solution separation, comprising the steps of providing a tower-like multi-stage vacuum distilling system;

• setting said multi-stage vacuum distilling system to an initial state thereof;
• performing a constant temperature distilling process, transferring of solutions, and recycling of a hot circulating solution to separate said solution and recover most part of heat energy for use repeatedly;
• and setting a vacuum distilling temperature for each stage of said multi-stage vacuum distilling system according to a temperature gradient of said hot circulating solution, so that said solution separation is achieved in the form of multi-stage vacuum distillation;
• wherein both said vacuum distilling temperature and a saturated vapor pressure corresponding thereto decrease from upper to lower stages in said multi-stage vacuum distilling system, allowing expanded ranges of usable vacuum distilling temperature and pressure as well as an increased number of vacuum distilling stages and more of said solution separable with one unit of energy.

A multi-stage vacuum cooling and freezing process for solution separation, which utilizes freezing and melting to produce condensate and may be used to assist in multi-stage vacuum distillation to increase the number of stages thereof, comprising the steps of providing and combining a tower-like multi-stage vacuum cooling system and a tower-like multi-stage vacuum freezing system;

• setting said multi-stage cooling and freezing systems to an initial state thereof;
• and performing transferring of solutions, a constant temperature distilling process, and a drain-to-vacuum and freezing process to produce ice crystals in a degassed solution;
• wherein said multi-stage vacuum freezing system using a low-temperature solution discharged at the lowest stage of said multi-stage vacuum cooling system as an initial solution needed to perform said multi-stage vacuum freezing to save energy needed for pre-cooling, and using vapors produced in multi-stage vacuum distilling and cooling processes as condensation heat required to melt said ice crystals produced in said degassed solution;
• low-temperature concentrated solution and molten ice crystals produced through said multi-stage vacuum freezing process being used to cool a hot circulating solution discharged from the last stage of multi-stage vacuum distillation and to maintain the temperature of a vacuum vessel for collecting the condensate produced in said multi-stage vacuum distillation, enabling an expanded distilling temperature range and accordingly increased stages for the multi-stage distillation and increased yield of solution separable with one unit of energy.