Falling Film Evaporator

Overview

The Falling Film Evaporator concentrates dairy and food liquids by spreading the feed as a thin film down heated vertical tubes under vacuum. Operating at 0.05 to 0.1 bar absolute drops the boiling point so heat-sensitive products evaporate gently. The machine is organised into seven systems: the Vessel Body, the Calandria Bundle, the Distribution Plate, the Vapor Separator, the Condenser, the Vacuum System and the Control Unit.

Vessel Body

The Vessel Body is the stainless steel chamber that houses evaporation and separation. Its core is the Shell, a welded SS304 or SS316L cylinder rated for full vacuum and steam pressure. Because external pressure tries to collapse the drum, Reinforcing Rings are welded around the exterior to hold its shape. A flanged Inspection Port gives access for cleaning and visual checks between runs.

Calandria Bundle

Heating is done by the Calandria Bundle, an array of vertical tubes carrying steam on the outside while product flows inside. The Tube Bundle uses seamless SS304 tubes of 2 to 8 mm bore, expanded into a forged Tube Sheet drilled to the tube pattern. Saturated steam enters at the Steam Inlet and condensate leaves through the Steam Outlet with a steam trap. A Flow Divider inside the calandria envelope routes steam evenly so every tube section receives the same heat.

Distribution Plate

Even wetting of every tube is what keeps the film thin and stops dry, scorched spots. The Distribution Plate handles this. A Spray Nozzle atomises the incoming feed, a Splash Plate spreads the spray into a continuous film over the tube tops, and the Feed Conduit carries liquid from the external feed pump to the nozzle.

Vapor Separator

Vapor leaving the tubes carries entrained droplets that must be removed before condensation. The Vapor Separator does this in two stages. The Cyclone Body spins the vapor so heavier droplets are thrown to the wall, and the Demister Pad catches sub-micron mist on a wire or fiberglass mesh. Collected liquid runs back through the Separator Drain to the bottom of the evaporator.

Condenser and Vacuum System

The cleaned vapor is condensed in the Condenser. Its Condenser Tubes are cooled by water from the Cooling Pump, with a thermostatic Cooling Valve holding the inlet between 5 and 15 °C. Condensate leaves through the Condensate Outlet under a backpressure valve that prevents flashing. The vacuum that drives the whole process comes from the Vacuum System: a Vacuum Pump (steam jet ejector or rotary vane), a Vacuum Valve regulating the setpoint, and a Vacuum Gauge logging pressure.

Control Unit

Coordination falls to the Control Unit. A Level Controller keeps the liquid level inside its setpoints, the Feed Pump meters feed at 5 to 30 L/h, and the Product Pump draws off concentrate at a matched rate. The Control PLC ties these loops together, holding vacuum and steam pressure while raising alarms on out-of-range conditions.