US 4,282,745 AGranted

Particle size determination

AssigneeEnglish Clays Lovering Pochin & Company Limited

InventorKenneth J. Burr

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Abstract

In order to determine the proportion of particles of less than a predetermined size in a fluid suspension, the fluid suspension is placed in a vessel (1) and is thoroughly mixed therein by mixing means (36,37). A sample of suspension is then withdrawn from a predetermined level within the vessel (1) by means of a sampling tube (9) and is transferred by way of a flexible tube (22) to a container (15). The particle concentration of this sample is then monitored by passing x-rays from a source (17) through the container (15) and detecting the emerging x-rays with a detector (18). The sample is then drained from the container (15). After allowing the suspension in the vessel (1) to settle for a time sufficient to enable particles of said predetermined size to sink from the surface of the suspension to said predetermined level within the vessel (1) according to Stokes' law, a further sample of suspension is withdrawn from said predetermined level and transferred to the container (15). The x-ray monitoring process is then repeated with this further sample. The complete testing cycle takes place automatically under the control of a control system coupled to a plurality of motors (such as 6) and valves (25, 28, 30, 34).

Apparatus for determining the proportion of particles having a size of less than a predetermined size in a fluid suspension, which apparatus comprises:

(a) at least one vessel for containing a fluid suspension;
(b) mixing mean for thoroughly mixing the suspension in said vessel;
(c) a container connected to sampling means;
(d) transfer means for enabling said sampling means to selectively withdraw samples of the suspension from a predetermined level within said vessel and for transferring the samples to the container before and after settling for a preselected time in the vessel respectively, the relationship between said predetermined level and preselected time being such as to permit particles of said predetermined size to sink from the surface of the suspension to said predetermined level according to Stokes' law;
(e) monitoring means for monitoring the particle concentration within the container to produce an output dependent on said concentration;
and
(f) control means for controlling the transfer means (i) so that the sampling means withdraws from said vessel a first sample of thoroughly mixed suspension from said predetermined level and the first sample is transferred to the container for monitoring and for draining and flushing the first sample after monitoring, and (ii) so that the sampling means withdraws from said vessel a second sample of suspension taken from the same predetermined level as was the first sample for monitoring after allowing the suspension in said vessel to settle for said preselected time sufficient to enable particles of said predetermined size to sink from the surface of the suspension to said predetermined level within the vessel according to Stokes' law and the second sample is transferred to the container for monitoring;
said control means being adapted to determine the proportion of particles having a size of less than said predetermined size in the fluid suspension using the outputs from said monitoring means resulting from monitoring of the first and second samples.

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Abstract

Claims18