Conveyors: fluid current – Slug conveying
Patent
1996-09-16
1998-08-11
Hoge, Gary C.
Conveyors: fluid current
Slug conveying
B65G 5366
Patent
active
057918295
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of slowly conveying bulk, particularly plug-like, material pneumatically in a pipe as well as to a device for implementing the method.
2. Description of the Prior Art
Methods of piping high bulk concentrations by thrust are known in which the bulk material is conveyed in the form of a closed rod thereof or in the form of discrete plugs (plug conveyance). Whilst good results have been achieved for plug or slow conveyance in small to medium pipe diameters and short to medium lengths thereof, considerable problems may be encountered where longish conveyance distances and/or large pipe diameters are involved, depending on the properties of the bulk material concerned.
The reason for this is the near instant expansion of the compressed volume of gas between the plug just about to leave the pipe and the plug following it. This dynamic expansion process produces strong acceleration and an increase in the-velocity of the plug following, due to the absence of any counter-pressure at the front end thereof. As a result of this, transient blockages materialize at the diverting positions in the conveying line and at temporary pile-ups (strands) in horizontal pipe sections which are transmitted as jolts to the piping system, the function modules thereof as well as to the bearing and supporting structure of the system. The dynamic stress in these modules, bearings and supporting structures may lead at critical positions to joints or components of the piping system becoming loose and possible to malfunctioning due to fatigue fracture. The inner dynamic action triggered by the dynamic expansion results in turn in haphazard deposits, sporadic fluctuating conveyance and thus in the shock forces being aggravated. These acceleration and deceleration actions in the piping system produce excessive mass forces and elevated friction forces due to added compression of the bulk material in the plug and thus result in additional energy losses as compared to a smoother means of conveyance. For the above reasons higher attrition and thread percentages materialize than is the case with a smoother, shock-reduced plug or slow means of conveyance.
From DE 40 39 496 A1 a method is known of continuously conveying bulk material, in which the bulk material is charged from a catchment vessel via a rotary vane feeder and transported by means of a conveying medium into a conveying pipe, the conveying medium being introduced into the conveying pipe via a pneumatic pipe. With the aid of a regulating means the ratio of bulk throughput and conveying medium is maintained constant in the conyeying pipe, the intention being to maintain conveyance constant despite the leakage air flow escaping via the rotary vane feeder. In a variant specially devised for plug conveyance the conveying medium is supplied intermittently and the conveying pipe features a syphon-type bend following the feed point, because this assists forming the plug.
Despite this "pulsing" at the start of the conveying pipe an unwanted dynamic expansion of the end of the pipe materializes with this method and the means thereof, too. This method prevents the dynamic expansion actions only at the end of a short conveying pipe length. When longer piping is involved specific dynamic relationships of plug length, plug spacing and pile-ups automatically materialize as a function of the piping diameters, the properties of the bulk material involved and the conveying distance, i.e. practically independently of the conditions existing at the start of the piping.
SUMMARY OF THE INVENTION
It is thus an object of the invention to reduce the high-energy and abrupt, dynamic expansion of the volume of the conveying medium between the plug being discharged and the one following it and to reduce the resulting aforementioned effects.
This object is achieved by the reducing the volume of cushions of conveying medium under pressure between successive plugs in a downstream area of the pipe in relation to the volume of c
REFERENCES:
patent: 3380780 (1968-04-01), Allen et al.
patent: 4904127 (1990-02-01), Morimoto et al.
patent: 5240355 (1993-08-01), Hudalla
Ernst Reinhard
Iltzsche Manfred
Metzler Eugen
Feiereisen Henry M.
Hoge Gary C.
Waeschle Maschinenfabrik GmbH
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