DETAILED DESCRIPTION To avoid confusion, the detailed description of this invention will be with reference to ozone gas even though other gaseous bleaching reagents, such as chlorine monoxide, chlorine dioxide, and others are possible.
Moreover, the expressions "bleaching agent" or "chemical treating agent" or "chemical reactant" will refer to the mixture of ozone in carrier gas (oxygen) plus the other gases and vapors present, at equilibrium, in various sections of the reactor apparatus.
It is the nature of the measurement of pulp properties, such that those properties which are true measures of lignin content require longer times to conduct.
Generally, with current technology, it takes at least about five minutes to measure such properties for example as Kappa number, K number, Klason lignin and the like.
Properties which can be measured quickly or continuously on-line, such as brightness are not consistent because of fluctuations in the measurement due to many variables such as fiber type, pH, consistency, temperature and the like which effect the measurement but do not reflect changes in lignin content.
These fluctuations are generally modest over short periods of time, for example up to 30 minutes of pulp processing in a bleach plant, but can be much greater over longer periods.
Previous attempts to rely on brightness alone to control a fast, short time, bleaching process have failed for this reason.
The present invention overcomes this deficiency by correlating a rapid or continuous measure of pulp property such as brightness with a true pulp property measure such as Kappa number, K number, Klason lignin or similar measure of lignin content.
It is this correlation when applied to control the application of a chemical treatment agent to pulp that is termed "coupled control".
In a production mill setting, this correlation is performed on-line.
During the period between successive lignin content measurements, the secondary pulp property such as brightness is used to control application of chemical treating agents to the pulp
|
Manufacturing Materials 
