Distillation Process Analyzer DPA-4.5
Design and function
4.3 Measuring principle
Distillation
Variant LowP
Fill level
Distillation process
The distillation is performed in a similar manner as with ASTM
D 86. The shape of the distillation flask and the sample quantity
are specified in detail there. During the distillation, the sample is
heated continuously in the distillation flask at atmospheric
pressure. The resulting vapor is cooled down in a cooling pipe. The
sample, which is liquid again, flows from the cooling pipe into a
receiver and is collected there. The distillation flask is heated up in
such a way that condensed sample flows into the receiver at a
constant and precisely defined rate.
At the
DPA-4.5 LowP
the compartment is supplied with vacuum
before starting the distillation. The complete distillation takes place
under reduced pressure. Thus, the final boiling point of the product
is lowered (according to ASTM D 86 the FBP may not exceed
400 °C).
Nitrogen is added to the sample in the receiver. Along with the
nitrogen, the fill level in the receiver is measured via a differential
pressure measuring device.
The product’s distillation sequence results from the continuously
measured distillate quantity in the receiver while the vapor
temperature at the neck of the distillation flask is measured
simultaneously. The measured vapor temperatures are corrected
in terms of the normal pressure (1.013 bar) respectively calculated
to temperature at normal pressure (AET) according to ASTM D
1160.
The appropriate vapor temperature for a specified quantity of
distillate, or the quantity of distillate for a precisely specified vapor
temperature, can be determined and displayed. The special
measuring points are:
Initial Boiling Point
(IBP)
Vapor temperature at which the first drop of distillate falls from the
cooling pipe into the receiver.
Final Boiling Point (FBP)
The vapor temperature at the end of distillation. This is normally
the case when the sample is completely evaporated.
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December 2013