Low-temperature distillation


Direct spray distillation is a water treatment process applied in seawater desalination and industrial wastewater treatment, brine and concentrate treatment as well as zero liquid discharge systems. It is a physical water separation process driven by thermal energy. Direct Spray Distillation involves evaporation and condensation on water droplets that are sprayed into a chamber that is evacuated from non-condensable permanent gases like air and carbon dioxide. Compared to other vaporization systems, no phase change happens on solid surfaces such as tube bundle heat exchangers.

Applications

Currently, only one application type is known for the DSD technology called low temperature distillation. The LTDis process runs under partial pressure in the evaporator and condenser chambers and with process temperatures of below 100 °C. The first large-scale LTDis systems for industrial water treatment are now in operation.
ProcessClassification
Separation mechanismPhase change through boiling
Physical processboiling and condensation, multi stage
Energy supplythermal energy driven
Scalecentral plant, large scale

History

The DSD process was invented in the late 1990 by Mark Lehmann with the first successful demonstration of the process in a factory hall of the Obrecht AG, Doettingen, Switzerland. The results of the experiments were evaluated and double-checked by Prof. Dr. Kurt Heiniger and Dr. Franco Blanggetti. During the next years, the process has been further researched in the framework of many thesis supervised by Prof. Dr. Kurt Heiniger and Mark Lehmann. The objective has been the examination of the influence of non-condensable gases in lowered pressure environments on the heat transfer during the condensation process on cooled droplets. It has been found that the droplet size and distribution as well as the geometry of the condensation reactor has the most significant influence on the heat transfer. Due to the absence of common tube bundle heat exchangers, the achievable efficiency gains result from the minimized heat resistance during the condensation process.