Appeal No. 1998-3168
Application No. 08/420,730
1. A method of producing steam having less sulfur-
containing noncondensible gases than steam produced by
flashing black liquor, including sulphur [sic] compounds,
directly into steam, comprising the steps of:
(a) passing hot black liquor, including sulphur [sic]
compounds, at a temperature of about 120-165EC from a digester
through a heat exchanger; and
(b) passing an evaporable liquid to be evaporated through
the heat exchanger into heat exchange contact with the hot
black liquor so that the evaporable liquid is heated so that
it is ultimately evaporated to produce steam having less
sulfur-containing noncondensible gases than steam produced by
flashing black liquor, including sulphur [sic] compounds,
directly into steam.
The examiner relies upon the following references as
evidence of obviousness:
Dean 2,029,360Feb. 4, 1936
Schlichtig 3,641,784 Feb. 15, 1972
Elmore et al. (Elmore) 4,897,157 Jan. 30, 1990
Appellant's claimed invention is directed to a method and
system for producing steam that has less sulfur-containing
noncondensible gases than steam produced by the flashing of
black liquor. The method entails passing hot black liquor
through a heat exchanger for heating an evaporable liquid,
i.e., water, that is ultimately evaporated to produce steam.
The produced steam, which has little, if any, sulfur-
containing noncondensible gases, can be used to treat
comminuted cellulosic fibers prior to the introduction of the
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