Agitating – Stirrer within stationary mixing chamber – Pump type
Patent
1987-02-02
1989-05-23
Hornsby, Harvey C.
Agitating
Stirrer within stationary mixing chamber
Pump type
366332, 366337, 366339, 366340, 366243, 138 37, 138 39, B01F 512
Patent
active
048325007
DESCRIPTION:
BRIEF SUMMARY
This invention relates to what will be referred to, generally, as mixing apparatus and processes. More specifically, within that general definition, the invention relates to reactor and other vessels where a system of two or more phases must be kept in suspension: this includes solid/liquid systems where particles under normal conditions would sediment upwards or downwards, liquid/liquid systems of immiscible fluids that must be maintained in uniform suspension, and liquid/gas systems in which it is desired to mix the gas bubbles with the liquid as uniformly as possible to maximise mass transfer effects. The invention also finds particular application to vessels in which it is desired to maximise heat and mass transfer between the vessel walls and the fluid within the vessel. The invention finds further particular application to vessels in which it is desired to maximise the "surface purging" effect exercised upon the walls of the vessel by the liquid within it, thereby keeping those walls as free as possible from fouling or the accumulation of any solid material. This aspect of the invention could be particularly important in relation to tubular filtration and ultrafiltration equipment.
While the invention is therefore applicable to the agitation of a unitary fluid mass, and to some batch processes and to the apparatus for carrying them out, it is however specially applicable to continuous processes in which two or more constitutents enter an elongated reactor vessel separately at one end and are required to achieve "near plug flow" through the vessel before leaving it at the other end. That is to say, the residence time--which may be long, measured in hours or even days--of all the constituents within the vessel must be as uniform as possible.
The invention arises from appreciating that by imposing the oscillating motion--in addition to any steady motion that may also be present--upon fluent material contained within a vessel, so that that material is caused to cross and re-cross stationary obstacles of a particular kind, mixing of an unexpectedly vigorous kind is effected.
The invention is to be contrasted with the kind of apparatus and processes described, for example, in UK Pat. No. 1442754 and corresponding U.S. Pat. No. 4,075,091. In the preferred apparatus described in those specifications, blood is pumped from end to end down a long tubular conduit the wall of which is of gently-undulating or "furrowed" configuration, and a longitudinal pulsating velocity is superimposed upon the basic longitudinal flow of the blood. The result of this combination of geometry and motion is said to be the repeated generation, within each successive "furrow" of the inner wall of the conduit, of vortices the axes of which lie transverse to the general direction of flow. Without creating turbulence which could be harmful to the blood, such vortices promote vigorous transfer of gas to or from the blood across the vessel wall, if that wall is made of appropriate and permeable material. The apparatus therefore has potential uses as a blood oxygenator or dialyser. If the chamber walls are of metal instead of being permeable, such apparatus can promote good heat transfer between the media within and outside the vessel, as the specification also suggests. However the claims and indeed the general teaching of such patents are confined to apparatus by which heat or mass transfer may be effected, through the vessel wall, between blood within and some other medium outside. Where blood is the fluid being treated there are special reasons for ensuring that the vortices, however vigorous, are confined to the furrows, leaving the main part of the blood flow through the unobstructed central part of the bore of the conduit relatively undisturbed. The present invention arises from appreciating the potential of apparatus with some similarities, but also with the important difference that the gentle undulations are replaced by obstacles of a quite different character, leading to mixing which affects the entire fluid content of the vesse
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Brunold Colin R.
Dickens Andrew W.
Hunns Jeremy C. B.
Mackley Malcolm R.
Williams Huw R.
Hornsby Harvey C.
National Research Development Corporation
O'Leary K. L.
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