Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Patent
1995-06-27
1997-04-15
Drodge, Joseph W.
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
73 6169, 210 94, 2101981, 210709, 210770, B01D 2132
Patent
active
056206097
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the control of processes for dewatering suspensions, especially coagulation and/or flocculation followed by sedimentation, in response to measurement of turbidity.
Various systems are known for determining the turbidity of a liquid. Many of the systems involve filling a cell of glass or transparent plastic and determining the optical properties of the cell filled with the liquid. Such systems in which optical properties are determined using an arrangement where a transparent material is in contact with the liquid all suffer from the disadvantage that contamination of the transparent material will influence the results.
A system that avoids this disadvantage is the Surface Scatter Turbidimeter SS6 manufactured by the Hach Company (see U.S. Pat. No. 3,309,956). In this system there is a upwardly extending elongate body defining a longitudinal central bore and having an open upper end, a feed positioned to feed suspension continuously into the body below the upper end, a collector positioned around the upper end to collect suspension that overflows from the upper end while defining a liquid surface at the open upper end, a light source positioned to direct a ray of light to strike this liquid surface at an angle such that light is scattered from it, and a collector positioned to receive the scattered light. In use, the suspension under test is forced to flow continuously upwardly through the body so as to provide a continuously replenished fresh layer of suspension at the upper surface which is typical of the whole body of the suspension, and the scattering of light from this typical upper surface is a measure of the turbidity of the suspension that is being tested. In order that measurable results can be achieved it is, of course, necessary that the suspension should be dilute and have adequate light scattering properties. This system would be inoperable if used with a suspension that did not have adequate light scattering properties.
There are many industrial processes where a suspension is dewatered by, for instance, sedimentation, filtration or centrifugation. Examples include sewage sludge, papermaking thinstocks and thickstocks, and inorganic suspensions. It is standard practice to flow such a suspension though a service line towards a dewatering plant where the suspension is dewatered, and to flocculate or otherwise chemically modify the suspension prior to dewatering by adding polymeric flocculant or other chemical dewatering modifier by appropriate chemical dosing equipment. Optimum dewatering depends on the nature of the suspension, but this tends to be variable. Accordingly various techniques have been developed for controlling the dewatering, either manually or automatically, in response to measurement of some physical property of the suspension.
In particular, it is known to use supernatant or filtrate turbidity measurements for monitoring and controlling sedimentation or other dewatering processes, especially when the clarity of the supernatant or filtrate is important. Usually an optimum turbidity is determined for a particular process by running plant trials of the process under different conditions, typically with different amounts or types of dewatering treatment chemical. Subsequently, when the process is run commercially, the process conditions are adjusted to maintain the turbidity at the optimum predetermined level.
In a typical process, the suspension to be dewatered flows along a conventional service flow pipeline, past a dosing point at which a dewatering treatment chemical is added to the suspension to a dewatering plant at which it is allowed to settle. Settling of the suspension usually takes place in a large sedimentation tank and may take two hours or more. After settling, turbidity measurements are taken on the supernatant. If this is done using a turbidimeter submerged in the tank or after the tank, it is necessary to wait for settlement before useful turbidity measurements can be taken. This means that the overall treatment process will have ad
REFERENCES:
patent: 3309956 (1967-03-01), Hach
patent: 3869903 (1975-03-01), Beach et al.
patent: 4116832 (1978-09-01), Tardivel
patent: 4194391 (1980-03-01), Rosenberger
patent: 4318296 (1982-03-01), Parker et al.
patent: 4876881 (1989-10-01), Pope
International Search Report for PCT/GB 94/00119, 27 Apr. 1994.
Allied Colloids Limited
Drodge Joseph W.
LandOfFree
Process and apparatus for dewatering controlled by monitoring li does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and apparatus for dewatering controlled by monitoring li, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and apparatus for dewatering controlled by monitoring li will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-358203