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Standardized Norden Efficiency Factor
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It is quite popular not to state the E factor for the specific operating conditions,
but to use a standardized efficiency factor recalculated to a standardized outlet
consistency L Std:
EStd _
log
Lin
Lout
cin _ cF
cout _ cWL _ _
log 1 _
WL _ Lout
LStd _ _ _55_
where L Std is the liquor flow rate at the standardized outlet consistency N Std.
The standardized E factor has a practical importance in the design of a specific
piece of washing equipment for a particular purpose. Despite being often observed,
it is less meaningful to use the standardized E factor for comparison of
different types of washing equipment.
Remembering the definition of the dilution factor DF as per Eq. (16),
WL _ Lout _ P _ DF _56_
and considering
LStd _ P _1_ NStd _ 1_ _57_
the modified efficiency factor can also be expressed as
EStd _
log
Lin
Lout
cin _ cF
cout _ cWL _ _
log 1 _
DF
1_ NStd _ 1 _ _ _58_
The most widely used standardized outlet consistency N Std is 10%. Hence
E 10 _
log
Lin
Lout
cin _ cF
cout _ cWL _ _
log 1 _
DF
9 _ _ _59_
In analogy to Eqs. (56) and (57),
Lout _ P _1_ Nout _ 1_ _60_
WL _ P _1_ Nout _ 1__ P _ DF _61_
5.5 Washing Efficiency 545
and therefore
WL
Lout _ 1 _
DF
1_ Nout _ 1 _62_
The modified efficiency factor E 10 can then be calculated from any E factor by
combining Eqs. (52), (59) and (62):
E 10 _ E
log 1 _
DF
1_ Nout _ 1 _ _
log 1 _
DF
9 _ _ _63_
546 5 Pulp Washing
Example: Determination of the standardized E factor
The specifications and results from the E factor example have been:
Discharge consistency, N out = 13%
Pulp production capacity, P = 40 odt h–1
Wash liquor flow rate, WL = 345 t h–1
Liquor flow rate in pulp discharge, L out = 268 t h–1
E factor, E = 9.7
With the dilution factor
DF _
WL _ Lout
P _
345 _ 268
40 _ 1_ 93 t odt_1
we get the E factor for 10% standard discharge consistency:
E 10 _ E
log 1 _
DF
1_ Nout _ 1 _ _
log 1 _
DF
9 _ _ _ 9_ 7 _
log 1 _
1_ 93
1_0_ 13 _ 1 _ _
log 1 _
1_ 93
9 _ _ _ 12_ 6
5.6
Дата публикования: 2015-01-23; Прочитано: 760 | Нарушение авторского права страницы | Мы поможем в написании вашей работы!
