a modern evaporator, the sap first flows into the "sap pan"
(also known as the "flue pan"), where the sap is heated
and evaporation is maximized.
In many sugarhouses
the sap may have been preheated or partially evaporated before reaching
the evaporator, through the use of techniques such as reverse osmosis,
preheating, or vapor compression systems. You can read more about
these systems by clicking here.
Because a tremendous
amount of steam is created during syrup production, evaporators also
include a hood or fan system that channels the steam outside. Many
evaporators have a "piggy-back" system that improves efficiency
by using the hot steam to preheat sap.
leaving the sap pan, the concentrated sap flows into one or many finishing
pans, where the final stage of the evaporation takes place. A finishing
pan is typically a large, open pan heated from below.
In the the photo
to the left, sap flows into the first finishing pan (there are three)
towards the right of the photo.
As the sap evaporates
and becomes denser, more incoming sap pushes it into the next finishing
pan, and eventually into the third pan. By the time the sap reaches
the end of the final finishing pan on the left, it has become syrup.
An automatic drawoff valve releases syrup that will then travel through
a filter and into a storage container.
producers use a single finishing pan on a separate burner, as shown
in the photo below. Single finishing pans are used by producers who
do not have an automatic drawoff system or do not have the time during
sap evaporation to control final syrup density. Other producers use
this type of finishing pan to reheat stored syrup when it is ready