Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With testing – sampling or analyzing
Patent
1997-12-22
1999-10-12
Popovics, Robert J.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With testing, sampling or analyzing
162198, 162263, 210768, 210791, 210 85, 210415, 7386323, 7386324, 7386383, D21C 706, D21F 108
Patent
active
059649844
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention refers to a method and apparatus for working-up a sample liquid of a pulp and paper industry process water, such as pulp slurry or white water, in an apparatus including a sample flow chamber, a filtrate flow chamber and a filter connecting said sample flow chamber with said filtrate flow chamber.
Due to environmental concerns and the rising cost of chemical additives, paper mills are tending to increasingly close the wet end of the paper machine. This leads to accumulation of dissolved and colloidal substances (DCS), originating from the wood fibers and, as a consequence, process disorders. Deteriorated runability and/or inferior paper quality are frequently experienced. Various chemicals are added to reduce these problems, but the physio-chemical and chemical interactions between DCS and such compounds are complex and often poorly understood. As a result, an overdosage and/or poor utilization of additives is a well known scenario experienced in paper mills.
Considerable laboratory work has been carried out to characterize the chemical nature and behavior of DCS. Such work has provided new and valuable insight into some of the interactions between these components. In order to gain a better knowledge of the dynamics of the chemical interactions, a continuous monitoring of DCS would be of great advantage.
In order to characterize a sample, extraneous material that may hinder or even prevent monitoring and/or analysis equipment from functioning, should be removed. In order to analyze DCS components in e.g. a paper machines white water, varying amounts of fibers and fines present, should be removed.
These fibers (>20 .mu.m) could theoretically be removed from the DCS (<10 .mu.m) by size exclusion. Traditional techniques of filtration, however, show the tendency to remove colloidal substances, as well as, fibers, due to an absorption of lipophilic droplets and colloidal particles in the fiber mat formed on the filter. Successful laboratory methods utilize a centrifuge. A method of continuous centrifugation has been proposed, however this requires a large, expensive and inconvenient decanting centrifuge.
It is an object of the present invention to provide a method and an apparatus, for working-up sample liquid, in which above problems have been minimized.
It is a further object of a preferred embodiment of the present invention to provide a method and apparatus of the above type which allows a continuous monitoring of DCS i process water.
It is a still further object of the preferred embodiment of the present invention to provide a method and an apparatus for continuous on-line fractionation of solid and colloidal substances in process water.
Toward the fulfillment of the above mentioned and other objects, the method and the apparatus according to the present invention are characterized by what is stated in the appended claims.
A working-up of a sample liquid of a pulp and paper industry process water can thereby be achieved according to the present invention by fibers and filler materials, and dissolved and colloidal substances, through an inlet into a sample flow chamber, from the sample flow chamber, into an adjacent filtrate chamber, thereby separating in the filter from a minor portion of said introduced flow of sample liquid, corresponding to <1%, typically <0.1% of the total introduced flow of sample liquid, a predetermined fraction of solid substances, and the filter by inducing in the sample flow chamber turbulence or a high flow velocity of sample liquid adjacent the filter.
According to a preferred embodiment of the present invention a flow of filtrate, corresponding to less than or about 0.1% of the total flow of sample liquid introduced into the sample flow chamber, is forced to flow through the filter. Thereby only a small amount of solid substance is separated in the filter and added into the remaining main flow of sample liquid being discharged from the sample flow chamber. The added amount of solid substance is that sma
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Holmbom Bjarne
Rice Matthew
Roeraade Johan
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