Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Patent
1985-10-15
1987-09-01
Levy, Stewart J.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
73 53, G01N 1507
Patent
active
046899880
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a device for measuring individually the content of each type of substance in a suspension with at least two types of suspended substances provided the density of the substance in each type is approximately equal and the densities of the substances included in the individual types are known.
In preparation of paper, especially fine paper, a so-called stock is used, which consists of a mixture of fiber material and filler, usually kaolin, in a suspension. The stock is applied to the endless wire of a paper making machine, part of the particles of the stock remaining on the wire and forming a sheet while the remaining part of the particles passes through the wire together with the major portion of the liquid and forms the so-called white water. The term retention is used as a measure of the efficiency of the paper making machine. This term is the quotient between the particle material forming the sheet and the material supplied to the wire. Addition of chemicals will enable a control of the retention, which will make it possible, among other things, to give the sheet a high content of filler. In order to enable control of the retention measuring equipment is needed giving a measure of the retention, especially for the two particle types individually, as it may be difficult to obtain a sufficient retention of filler. In the control the so-called first pass retention is interesting, which is defined applied to the paper making machine. water. white water independently of the presence of fiber material. A procedure often used with retention control comprises measurement of turbidity and density each separately. In measurement of the turbidity which is most sensitive to clay a device is used in which the damping of light passing through a particle suspension is determined. The essential disadvantage of this procedure is the dependence of a signal sensitivity on the particle size. Difficulties will arise in establishing whether the particle concentration or the particle size or both have changed when the resulting measuring signal is changed. Certainly the density measurement is sensitive to the change in concentration of the investigated suspension but measurement of clay is disturbed by the presence of fibers. For physical reasons there is no great changes of success when combining turbidity and density measurement.
SUMMARY OF THE INVENTION
It has now surprisingly been found according to the invention that two quite different properties of the suspension can be determined by a suitable arrangement of two measuring instruments known per se measuring two different properties of a suspension. Thus, a measuring device of the kind mentioned in the introductory section above comprises according to the invention a density meter known per se arranged to measure the density of the suspension and the density of the liquid in which the substances are suspended, for determination of the density differences; an apparatus known per se and intended for measurement of the particle concentration, which is arranged to measure the ratio of the volume of the suspension substances to the volume of the liquid; and a calculating unit electrically connected to the density meter and the apparatus, which unit is arranged to combine signals received from the density meter and the apparatus in order to calculate the concentrations of each the substance types on the basis thereof. As the density of cellulose and clay is higher than the density of water the density of a suspension of cellulose and clay particle will be dependent on concentration. The essential advantage of density measurement is its independence of particle size. The essential disadvantage is that the measuring signal must be adjusted with respect to the fiber concentration sensed by the density meter with another sensitivity constant. This adjustment is carried out using said particle concentration meter which is capable of suppressing the contributions from small particles such as clay but otherwise is independent o
REFERENCES:
patent: 3728893 (1973-04-01), Janssen
patent: 4112741 (1978-09-01), Kerfoot et al.
patent: 4266188 (1981-05-01), Thompson
patent: 4441960 (1984-04-01), Karnis et al.
Einarsson Jens
Rydefalk Staffan
Levy Stewart J.
Svenska Traforskningsinstitutet
Williams Hezron E.
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