A. H. Lundberg Associates, Inc. provides falling film evaporator technology for use in many applications. Falling film technology has certain advantages over rising film technology. Two items stand out. First is the technology allows for very low delta T on a body without losing stability. As a result, the technology is suited for seven or eight effect operation and also for applications with fixed steam pressure and system vacuum such as a pre-evaporator system. The second item is that the liquor is distributed across the tube bundle via a distribution tray. This insures wetting of all the tubes and minimizes dry spots so that the falling film technology is more resistant to scaling.

While some locations have used falling film technology for concentrator service to high solids, it has met with mixed success. We, therefore, limit the outlet solids to the low 60% range in most applications.

The above advantages are provided at the cost of increased system complexity and energy consumption. The liquor is pumped from the vapor head up to the distribution plate above the tubes. Since there is a residence time in each vapor head, there is a requirement for level control. Because of the increased instrumentation, piping and pumps, a falling film system is more expensive than a rising film system of similar capacity.

Each Lundberg Associates falling film body is provided with an inlet steam bustle for the heating element. This distributes steam evenly to the entire bundle. The shell is typically baffled longitudinally to make it a two pass arrangement providing for positive NCG venting and condensate segregation as necessary. For ease of construction the liquor is recycled external to the heating element. The liquor distribution plate has a leveling mechanism to insure even distribution.

The vapor head onto which the heater is mounted provides the reservoir for the recirculation pump. In the higher solids effects it also provides residence time for the solids and crystals to equilibrate after leaving the heating element. The vapor head also provides space for the separation of liquor from the vapor. The vapor exits the vapor head though internal chevron type separators to remove any entrained liquor droplets and assure the highest possible condensate quality.