Conveyors: fluid current – Fluid current conveyor outlet means – With material separating receptacle
Reexamination Certificate
1999-07-12
2001-12-04
Ellis, Christopher P. (Department: 3651)
Conveyors: fluid current
Fluid current conveyor outlet means
With material separating receptacle
C406S146000, C406S172000, C406S168000, C406S167000
Reexamination Certificate
active
06325572
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns an apparatus and a process for pneumatically conveying powdery substances having a container using at least one filter in pipe systems. The invention also concerns the use of said apparatus and/or said process.
EP-A-0 574 596 describes an installation for pneumatically transshipping cement from ships into silos by means of a so-called lock container comprising a plurality of container segments; disposed in the uppermost container segment is an exhaust air filter while the lowermost container segment tapers in a funnel-like configuration.
The chemical. pharmaceutical and foodstuff industries also involve conveying powdery substances and transporting them in a controlled atmosphere. The known installations for conveying powdery substances of that kind are generally matched in regard to their structure to the product which is to be subsequently conveyed; those installations involve individual fabrications which give rise to high levels of installation costs. A further disadvantage with the known installations is inter alia that the required filters already clog up after a short period of operation. As a consequence of that problem, production of the powdery substances is frequently subjected to disturbances which result in production failures that have an adverse effect on costs. It has not been possible at the present time to overcome those deficiencies.
The operation of introducing powder into reaction vessels or reactors within explosive areas is generally effected manually by way of a lock arrangement or a protective valve as most reactors do not have the container comprising a plurality of container segments; disposed in the uppermost container segment is an exhaust air filter while the lowermost container segment tapers in a funnel-like configuration.
The chemical pharmaceutical and foodstuff industries also involve conveying powdery substances and transporting them in a controlled atmosphere. The known installations for conveying powdery substances of that kind are generally matched in regard to their structure to the product which is to be subsequently conveyed; those installations involve individual fabrications which give rise to high levels of installation costs. A further disadvantage with the known installations is inter alia that the required filters already clog up after a short period of operation. As a consequence of that problem. production of the powdery substances is frequently subjected to disturbances which result in production failures that have an adverse effect on costs. It has not been possible at the present time to overcome those deficiencies.
The operation of introducing powder into reaction vessels or reactors within explosive areas is generally effected manually by way of a lock arrangement or a protective valve as most reactors do not have the necessary space for an adequate loading installation. Such a mode of operation however does not comply with the applicable safety rules for obviating the risk of explosion: if the reactor is inerted, the step of manually introducing powders from the manhole results in atmospheric pressures and eliminates the protective effect of the inert gas. Upon manual introduction of solid material, the inerting effect is eliminated within a short period of time (O2 concentration >8%) and is not restored even after prolonged operational N2-flushing.
Furthermore the dust can result in contamination of the environment; the gas vapours which are developed give rise to the risk of asphyxiation for the operating personnel. The risks of explosion during the conveying procedure are possible in particular when the following factors come together at the same time:
oxidisable powder;
powder/oxygen ratio is within an explosion limit (varies according to the respect product involved); and
formation of an ignition source (electrostatic discharge, flame, hot spot, sparks).
In consideration of those aspects the inventor set himself the aim of eliminating the acknowledged disadvantages and permitting inexpensive conveying of powdery substances, including sticky substances. In particular the invention seeks to provide that powdery solids can be introduced into reactors or the like units with an enhanced level of safety. 2 Amended Page
That object is attained by the teaching set forth hereinbelow.
SUMMARY OF THE INVENTION
In accordance with the invention, in the above-mentioned apparatus for pneumatically conveying powdery substances of a specific weight of 0.1 to 15 g/cm
3
and with a grain size range of between 0.1 and 300 &mgr;m as the conveyed material, the ratio of the length of the container forming a pump chamber for temporarily receiving the conveyed material, to its internal diameter, is between 0.5 and 10.0 and the plate-like filter element is provided between a vacuum conduit of a vacuum pump for sucking in the conveyed material and the pump chamber, wherein a conveyor gas conduit of a conveyor gas source is connected to the space—in a dome cover—which is connected to the vacuum pump, and a respective automatic closure member is arranged both in the vacuum conduit and also in the conveyor gas conduit.
In addition, for handling of the filter, it has been found desirable for it to be in the form of a plate-like filter membrane which is preferably interchangeably disposed in a frame of a filter insert.
Advantageously, associated with the container according to the invention are four automatic blocking or closure elements which are controllable with each other, more specifically a respective one at each of the feed conduit and the discharge conduit and at the conduits for vacuum and conveying medium.
During a suction intake phase the closure element of the feed conduit opens whereas the discharge conduit remains closed. By virtue of the vacuum connection which is open in that situation, material to be conveyed is sucked into the pump chamber; after a predetermined period of time the feed conduit closes and the discharge is opened. The conveyed material is ejected by pressure—compressed air or nitrogen for filter cleaning purposes. The filter in the upper part of the container retains the finest particles and is cleaned in each emptying cycle.
Before the powder is introduced into the downstream-disposed reactor—for example a mixer, a crusher or the like unit in which a reaction takes place—air and powder are separated from each other by closure of the vacuum shut-off valve being delayed with respect to opening of the conveyed material intake. So that no gases of the reactor are sucked in when the discharge conduit is opened, the reactor is firstly put under pressure and only then is the emptying valve opened. Moreover the vacuum conduit can only be opened when the discharge conduit is closed.
A ratio of container length to container diameter in the range of between 0.5 and 10.0. preferably between 2.0 and 8.0. has been found desirable. The container width or the container diameter itself is advantageously between 10 and 500 mm, in particular between 50 and 400 mm, while the container length is between 200 and 1000 mm, in particular between 400 and 900 mm. This therefore involves a comparatively narrow container. wherein preferably the diameter of the container determines the size of the filter.
It is in accordance with the invention for the apparatus to be operated with a reduced pressure for sucking in the conveyed material of between 1 and 25 mbar, in particular between 5.0 and 20 mbar. The increased pressure for discharge of the conveyed material should for that purpose be between 0.5 and 5.0 bar. in particular between 1.0 and 3.0 bar.
In accordance with a further feature of the invention the filter is to be designed in such a way that a differential pressure of between 100 and 300 mbar occurs at its side remote from the vacuum pump.
It is also advantageous to provide a flat grid or mesh which at the vacuum side is associated with the filter as a support means. The preferred mesh size thereof is to be between 5 and 50 mm, preferably between 10 and 40 mm. A grid or mesh can als
Bachman & LaPointe P.C.
Ellis Christopher P.
Ridley Richard
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