Filling of the unit is driven by the vacuum created by the compressor. Then the heat energy generated by the LOFT direct heating module is transferred to the wastewater via compression of inflowing ambient air. This configuration permits attainment of the steady-state operating temperature after only approx. 40 minutes of continuous operation.
LOFT Vacuum Evaporators – Process Description
The wastewater evaporation unit operates solely with thermal (evaporative) separation. The LOFT DESTIMAT® LE evaporator can be operated fully automatically in three-shift continuous operation at its specified nominal capacity. The capacity figures we specify for the unit apply to inlet process wastewater and not to clean inlet water as is the case with many competitors.
The LOFT DESTIMAT® LE evaporator excels with its simple and rugged design. For instance it does not incorporate pumps or heating modules (heat input is via compressor). As a result it provides highest operational reliability even when processing problem wastewaters, e.g. at wastewater disposal contractors.
Once the process temperatures are attained, a PLC-controlled process valve gradually closes and the evaporation process begins. The process automatically draws in as much wastewater as distillate is let out.
The LOFT evaporator is also particularly reliable in operation with regard to its liquid level monitoring, as the monitoring device is continuously flushed by process water flowing by at high speed and is also automatically cleaned off with compressed air at the end of each cycle. This arrangement avoids monitoring errors.
The vapour flowing convectively downwards in the heat exchanger shell of the LOFT DESTIMAT® LE reaches speeds of up to 12 m/s during the evaporation process. The fast-flowing vapour cleans the tubes continuously, providing excellent cleaning even when problem wastewaters are processed.
The core component of the multistage vapour cleaning is the centrifugal cyclone separator which removes entrained wastewater and foam so thoroughly that a Demistor fines filter can be used to filter out microparticulants. This configuration ensures the outstanding distillate quality of LOFT units as frequently confirmed by users comparing to competitive evaporators.
The vapour compressor recompresses the cleaned vapour to ambient pressure, at the same time increasing its temperature to approx. 120 °C. The vapour then flows into the shell side of the tube-in-shell heat exchanger where it provides its heat of condensation to the evaporating wastewater within the tubes. The distillate generated is cooled in a countercurrent heat exchanger against inlet wastewater and flows from there to the distillate receiving tank. The entire concentration process is controlled by a PLC control system which adjusts the final concentration by various parameters such as time, throughput, pressure and temperature.
The exact control of process parameters, which can be easily adapted by the user to a wide variety of inlet wastewaters, permits attainment of extremely high concentrations in the outlet concentrate.
The concentrate is ejected by compressed air into the collecting tank and the evapoator begins a new cycle.
Along with the evaporator unit, LOFT designs and supply all required peripheral equipment such as vessels, neutralization units, coalescence separators, piping, etc.
