Plate evaporators: an important addition to BMA’s product range
At BMA it has always been our policy to invest in an extension of our product range, so we can respond to our customers’ requirements. Falling-film evaporators with fully-welded blocks of plates - the multi-plate hybrid evaporators - have therefore been included in BMA's product portfolio. Since we can offer both the tried-and-tested tubular falling-film evaporator technology and the multi-plate hybrid evaporator technology, we are in a position to respond to diverse needs with perfect evaporator solutions.
The name HYBRID is derived from the two different kinds of flow ducts that multi-plate hybrid evaporators incorporate. With a tube side, which has a tube-like cross section and is thus similar to the tube-bundle heat exchanger, and a corrugated side with a cross section like that of the plate heat exchanger, this special heat exchanger combines the specific properties and advantages of the two original versions within one single unit.
The basic element of any of the plate-type falling-film evaporators is a plate with a constant width. The length of the plate can be varied. Several plates placed one on top of the other and welded together form one heat-exchanger block. A number of these blocks can be connected in series to meet specific performance requirements. The block of plates thus produced is connected with side plates and tie bars to form a unit of high pressure resistance. The fully-welded plate block can then be welded into any type of pressure-resistant housing.
The juice to be concentrated in the evaporator is passed through a pipe to the juice distribution section. This section mainly serves to calm the juice flow, separate solids, and provide for primary and secondary juice distribution. Secondary juice distribution ensures uniform wetting of the tube-shaped plate cross section.
Juice flow through the series-connected plate blocks is from top to bottom, with no additional distribution systems between the blocks. Uniform distribution of the juice is achieved by the large number of tubes – about 5,500 per square metre of contact area between the blocks. The thermal energy required to effect phase change in the tube-side juice solution is generated by heating-steam condensation on the corrugated side and by the propelling force of the temperature gradient between the different media.
Vapour and juice are separated at the bottom end of the evaporator. This is where BMA's proven concept is used, which has already successfully stood its test in numerous applications with tubular falling-film evaporators. Since there is a clear separation between the pressure in the vapour chest and that of the juice distribution chamber, there is no interaction between the two chambers. That improves the system's control behaviour.
Another possible use for the plate technology is the conversion of Robert evaporators, which involves replacing the old tubular heating chamber with blocks of plates. The very decisive advantage of this option is that the heating surface can be substantially increased at a moderate price.
Customer benefits
- High energy savings potential
- Improved juice colour due to short retention times
- Low investment cost
- Conversion of existing Robert evaporators to provide up to three times the original heating surface
- Excellent system control due to short reaction times
