I. Key Findings

The buffer tank’s volume is insufficient to cushion the airflow pulses generated by the vacuum pump’s intermittent suction. The resulting continuous and violent fluctuations in the airflow within the evaporation chamber directly reduce the separation efficiency of the demister, significantly exacerbating foam entrainment and material carryover issues.

II. How Airflow Pulses Compromise Demister Separation

Under stable and steady airflow conditions, foam rises slowly. As it passes through the wire mesh, droplets collide with and adhere to the metal wires due to gravity and inertia, and the liquid flows back into the chamber, ensuring thorough gas-liquid separation.

If the buffer tank is too small, the vacuum pump’s suction pulses go unmitigated, causing the airflow within the chamber to fluctuate wildly and frequently generate instantaneous negative pressure surges: the airflow surges upward at high speed in an instant, forcing thin foam and fine salt-laden droplets to penetrate the demister mesh. Before they can complete gravitational settling and separation, they are drawn into the downstream condensation piping.

The pulsating gas flow causes the liquid surface to churn violently, causing the foam layer to fluctuate up and down. The foam presses tightly against and squeezes the wire mesh, allowing large amounts of mother liquor to penetrate the separator along with the gas flow.

III. Derived Chain Reactions Exacerbating Separation Failure

Vacuum readings fluctuate continuously, the evaporation boiling point shifts constantly, steam production varies erratically, and foam generation is unstable—all of which further amplify the carryover caused by gas flow turbulence;

Airflow pulses create negative pressure shock waves in the piping, slightly amplifying minute gas leaks from equipment manholes and flanges; non-condensable air enters the chamber, creating turbulence that disrupts the foam-liquid film and generates more ultrafine aerosols;

Frequent, high-speed airflow scours the mesh, causing previously adhered salt sludge and silica scale to be dislodged and carried away by the airflow, resulting in a continuous rise in the conductivity of the condensate.

IV. Differences in Operating Conditions Amplify Negative Effects

In the late stages of concentration, the mother liquor has high viscosity and the foam is highly resilient, making it inherently difficult to break the foam; when combined with pulsed airflow, the decline in separation efficiency is most pronounced. When multiple units share a single vacuum piping system, flow shocks caused by the start-up and shutdown of individual units, compounded by insufficient buffer tank capacity, cause airflow fluctuations that exponentially exacerbate material carryover.