CAST Flash Vacuum Distillation

CAST utilizes various aspects of flash distillation and vacuum evaporation in conjunction with a patented vapor/liquid separation system.  It is this unique combination of fundamental physical principles and patented components that produces many of CAST’s competitive advantages.

CAST systems utilize the flash mode of evaporation, as opposed to nucleate boiling and/or thin film.  Flash evaporation occurs when the heated and pressurized process solution is sprayed into the vacuum maintained in the process vessel.  This form of evaporation takes place without the need of a heat exchange surface.  Nucleate boiling and thin film evaporation require intimate contact between the evaporating liquid and the heat exchange surface, and hence, are subject to the scaling, salting and fouling not typical in flash evaporation based systems.  Additionally, this design allows CAST systems to use external, commercially available heat exchangers, as opposed to the costly, custom built and maintenance intensive heat exchangers used in other systems.  The flow rate through CAST system heat exchangers produces high shear forces, low temperature differentials and low surface film temperatures.  The high shear forces aide in maintaining a clean heat transfer surface while the low temperature differential and surface film temperature aide in the prevention of heat exchanger corrosion and thermal degradation of process solutions.  This allows CAST systems to be operated with a low temperature heat source, hot water, low-pressure steam or waste heat supplies.

The spraying of the process solution in flash evaporation based systems (CAST) contributes to the excellent quality of the condensate/distillate produced.  The process solution, containing the contaminants exits the spray nozzle with a high downward velocity.  The vapor forming at the spray cone is moving upward away from the sprayed process solution.  This is called forced disengagement.  The vapor being formed in any evaporative process tends to entrain and carry a certain amount the process solution (and contaminants) from which it was generated. The process is known as carry over.  Nucleate boiling and thin film wastewater evaporator systems promote carry over; where flash evaporation based systems reduce carry over.  This type of sprayed flash evaporation is capable of operating with viscous liquids that cannot be handled by the competition.  Additionally, the spraying of the process solutions permits a unique feed arrangement.  Material can be introduced above the liquid surface of the process solution and below the spray cone; this allows any dissolved or entrained gasses to be desiccated from the feed during introduction.  Any foam formed during desiccation is collapsed by the sprayed process solution.  This allows CAST systems to operate on foaming solution that can not be handled by the competition.

CAST systems use a proprietary method of developing the vacuum on the process vessel and removing the distillate from the system.  The method allows distillate to be continuously discharged from the system without the use of the complicated or batch methodologies employed by traditional wastewater evaporators.  This technique eliminates any fugitive discharges, and was instrumental obtaining the US EPA and MA DEP RCRA permit exemption.

The vacuum used in CAST systems causes the water to evaporate at a much lower than normal temperature, typically 100-140 ºF.  This facilitates the use of engineering plastics, thus greatly reducing the overall cost of manufacturing, and the use of low temperature heat sources, thus greatly reducing the cost of operation.

CAST systems incorporate a sight glass/level control design not offered by any of the competitors.  This design enhances the reliability of the system, while reducing maintenance, and offering a value added benefit.

CAST systems are controlled by programmable logic controllers using CPS designed software that is capable of detecting and reporting operation flaws, managing machine operation, executing emergency shut-down, and on-line telephone diagnostics.

The design of the CASTion system allows the use of simple technologies, hot water heaters, cooling towers and pumps, as opposed to other wastewater evaporators’ refrigeration systems and/or high pressure steam boilers and other complicated/non-reliable components.  These technologies are rugged, reliable, and universally available and accepted, thus greatly adding to the overall simplicity and ease of operation of CAST systems.

CAST systems are constructed from time tested quality components produced by leading industrial suppliers.  The systems are constructed to be low maintenance and simple to service.  The many proprietary details of construction and common sense design, in conjunction with advantages outlined above, make the CAST system the “state-of-the-art” bench mark for wastewater evaporator applications.