Evaporation units are used for densification of salts concentrated in waste water and acceleration of their further crystallization. Evaporation is also used for decontamination of a small amount of highly concentrated waste water.
TECHNOLOGICAL PROCESS SCHEME
TECHNOLOGICAL PROCESS DESCRIPTION
When evaporating a high volume of water it is preferable to use multi-hulled evaporation units, consisting of several evaporation apparatuses connected in sequence. In this type of unit, evaporation is performed under multiple natural circulation of the solution.
Evaporated liquid is supplied to the heating unit and then in the first evaporation case consisting of heat-exchange unit and separator. Heating steam is input into the heating chamber through a nozzle, where it is condensed. Condensate is removed and eliminated into the condensate receiver. The solution partially evaporated in the first case is removed into the second case for further evaporation.
Steam generated in the steam space of the first case through a liquid trap is supplied to the heating chamber of the second case, where it is already regarded as heating steam.
The technical regime of further cases is similar to the regime of the first case.
Secondary steam of the last case as surely as in single-hull vacuum-evaporation apparatus is supplied to the condenser cooled by water.
The necessary temperature difference of heating steam and boiling solution in every case is achieved by means of the fact that primary steam pressure in every case is always just over secondary steam pressure. Secondary steam pressure in every preceding case in turn is always higher secondary steam pressure in successive cases. Therefore secondary steam pressure in the evaporation unit is gradually reduced from the first case to each successive one. In the first cases, solution is usually under some pressure and under vacuum in the last ones.
- Energy consumption decrease