Download instrumentation study- black liquor solids content

Group Project 3025
Page 87
Report One
Oven-drying procedures have been the basisfor TAPPI methods for black
liquor solids determinations.
These procedures have evolved to try to-overcome
the problems mentioned above.
Parker et al. discuss the latest Proposed Method in
their paper.
In this revised procedure, black liquor samples are dried at 105°C.
for a minimum of six hours.
An inert surface extender.(such as sand or alundum)
and a controlled flow of dried air are used to increase drying rate and eliminate
moisture entrapment.
Strong black liquors are diluted to allow volumetric handling
and to reduce scum formation.
1.
..
The
procedure can be summarized as follows.
Dry and weigh 25-30 g. of inert material in a wide, shallow glass container.
Add sufficient liquor sample to give 1-3 g. of dry solids and weigh.
Add
10-20 ml. of water to dilute and distribute samples in excess of 30% solids.
2.
Dry the liquor for a minimum of 6 hours in a gravity convection oven controlled
at 105°C. ± 3°C. with an air space of one cubic foot or less, adapted to pass
dried, preheated air at a replacement rate of about twice per minute.
After
the initial:drying and weighing, drying is repeated, for one-hour intervals until
the weight loss is less than 0.1% solids per hr.
3.
Duplicate determinations on the same sample should differ by no more than 0.3%
solids.
It is important, when using this procedure, to keep the sample size within
the recommended range.
An excessively large sample will lower the surface/volume
ratio of the liquor and lead to scum formation..
cate.
All tests should be run in dupli-
This procedure is not intended as a rapid or routine control method.
It
may be used to calibrate such procedures.
One of the big drawbacks to oven-drying procedures is the length of time
needed to carry out the test.
TAPPI Method T 625 ts- 64 called for a 24-hour drying