Lek Sikong, Manoon Masniyom, and Sukpong Sirinupong

pp. 341 - 349

Abstract

The objective of this research is to investigate the possibility of using kaolinite from Ranong province
as media in the oil palm shell and kernel separation process by means of heavy media separation. The effect
of specific gravity of the slurry, type and amount of dispersant and type of clays on suspension of media and
efficiency of separation were studied. It was found that the specific gravity of oil palm shell and kernel are
1.40 and 1.20 respectively. While the average specific gravity of kaolinite grade MRD-B85, RANONG-325
and commercial clay from Univanich Group. PCL., are 2.54, 2.65 and 2.46 respectively. It was apparent that
the viscosity of clay slurry increased with the specific gravity of the slurry. For MRD-B85 and RANONG325 clays which have the average particle sizes of 10 and 12 microns, the pH of their slurries of about 5.84
and 6.33 respectively were obtained and at these conditions stability of the slurry rarely occurred and they
could not be used for separation. However, these clays can also be utilized as media when dispersant such as
Calgon or sodium silicate is applied to their slurries. It was found that the efficiency of separation depends on
specific gravity and viscosity of the slurry, type and particle size of kaolinite and dosage of dispersant. The
optimum separating conditions for MRD-B85 clay were the dosage of Calgon of 0.15% (or 1.5 kg/t of clay)
at the specific gravity of the slurry of 1.20-1.24 (27-32% Solids) in which a pH of 6.14 and viscosity of 104 cP
to very low value (could not be measured) were obtained. Thus, kernel yielded 97.57-100% and shell contamination of 1.48-6.32% was achieved. While sodium silicate was applied to the slurry about 0.15% at the specific gravity of 1.22, pH of 6.74 and viscosity of 238 cP were obtained and kernel could be recovered 100%
with shell contamination of 8.36%. When 0.15% Calgon or 0.25% sodium silicate was introduced to the
RANONG-325 clay slurry at the specific gravity of 1.22 the optimum separating conditions were found in
which pH of 6.65-6.85 and very low viscosity were obtained. At these conditions, kernel yielded about 100%
and shell contamination of 1.80-6.31% was achieved. Moreover, when using clay of Univanich Group PCL.,
which is a mixed clay with the finer particle size of about 6.3 microns, as the medium, lower viscosity of 36 cP
could be obtained when specific gravity of the slurry had been adjusted to 1.22 at pH 8.29. At these conditions, the good result of kernel yield 93.56% with shell contamination of 5.87% was achieved without using
dispersant. However, if the dispersant was applied (0.1%Calgon or sodium silicate at specific gravity of the
slurry of 1.22), the efficiency could be improved to give a kernel recovery of about 95% with shell contamination of 3.83-4.61%.