GB2300033A - Prevention of residue build-up on surfaces - Google Patents

Abstract

Apparatus for the prevention of build-up of solid residues on inner surfaces of an item 7 comprises a plurality of electrically conducting plates 6 attached to the outer surface of the item and a plurality of coils 1 adjacent to the plates which are periodically energised by the discharge of electrical energy to form a strong repulsive field in each plate, the movement of which is transmitted to the item. The item may be a container, pipe or duct containing or transporting particulate material. The discharges may be controlled by a pulse generation means. The electrically conducting plates are preferably fabricated from aluminium or an alloy thereof as 100 to 300 mm diameter discs and have a thickness in the range 10 to 20 mm. Preferably each plate is formed with a rim which extends around the periphery of the associated coil. The coils may have a planar construction, formed as a printed circuit. Each plate and its associated coil may be contained in sealed units.

Description

AGITATION AND PREVENTION OF RESIDUE BUILD-UP OF SUBSTANCES IN CONTAINERS, PIPES AND O SURFACES.

This invention relates to an apparatus and process for the prevention of build-up of solid residues of substances on the surfaces of containers and pipes which contain or carry particulate material.

Fine partici:late materials, due to their physical nature, tend to cohere and form agglomerates unless they are electrically charged or otherwise rendered repellent to each other. As a result the surfaces of containers of particulate materials tend tc become covered with layers of agglomerated particles. Such accumulations of material cannot be discharged easily from containers resulting in wastage of material and contamination of new batches of material with residues from earlier batches. When transported along pipes or ducts, for instance under the influence of an air or gas draft, the flow pattern can be distorted by aggregation of particles which deposit causing eddies and further deposits.

On occasions particle deposits can be dislodged by hitting the outside of a container or pipe with a rod or other percussive device. Such treatment requires regular human intervention and may result in permanent physical damage to the structure due to the uncontrolled nature of the impacts. The present invention provides apparatus and a process which prevents the build-up of solid residues.

The apparatus is adapted to work unattended and ensure that particulate materials can flow freely at all time whether from a container or along a duct or pipe.

According to the present invention there is provided apparatus for the prevention of build-up of solid residues on surfaces comprising a plurality of electrically conducting plates having a surface attached to the outer surface attached to the outer surface of a container, pipe or duct containing or transporting particulate material, a plurality of coils located adjacent to the unattached surfaces of the plates and pulse generation means adapted to discharge periodically sufficient electrical energy into each coil that a strong repulsive field is formed in each plate.

There is also provided a process for the prevention of build-up of solid residues on the inner surface of a container or pipe comprising periodically discharging sufficient electrical energy into a coil that a strong repulsive field is formed in a conducting plate having one surface attached to the outer surface of the container or pipe.

The electrically conducting plates are preferably aluminium or aluminium alloy discs and preferably have a thickness in the range 10 mm to 20 mm and a diameter from 100 mm to 300 mm. Each plate is placed close to a coil which, when energized by the passage of a pulse of electric current, induces eddy currents in the plate which create a magnetic field in opposition to that generated by the coil.

The repulsive force between the two magnetic fields drives each plate away from its associated coil and, due to the attachment of the plate to its outer surface, transfer this force to the container. The coils have a planar construction in their preferred form and may be formed using printed circuit techniques or by winding. The coils are preferably formed as a sealed units so as to prevent the ingress of moisture or other contaminents when used in an industrial environment. Such coils have a diameter, if circular, similar to that of the associated plate. In most embodiments the coils are formed from copper and the turns have sufficient thickness and cross-section, if printed, or diameter, if wound, to allow the passage pulses of current having a high peak value without appreciable temperature rise from resistive losses.In a preferred embodiment the coil and the plate are contained in a single sealed unit. The shock wave caused by the current pulse through the coil is transmitted through the side of the unit to the container or other surface to which it is attached. In order to enhance the effect of the magnetic filed induced by the coil the plate may be formed with rims which extend around the periphery of the coil.

The pulse generation means comprises a timing oscillator wh i c h controls the frequency and duration of the pulses it generates. These parameters can be varied by alteration of the oscillator frequency or, more preferably, using variable factor division of a master oscillator using a crystal or similar resonator as a frequency standard.

In a most preferred embodiment the pulses are provided by a microprocessor which can also be programmed to perform other functions associated with the apparatus.

The current pulses are preferably formed by rapid discharge of one or more capacitors through each coil at periodic intervals. While mechanical switching may be used it is preferred to use semi-conductor switches, such as thyristors, which can be triggered easily from a low level output. The pulse energy depends on the value of capacitor chosen and the voltage to which it is charged.

The preferred pulse energy lies in the range 10 to 400 mJ depending on the size of the plate and the resilience of the surface to which it is attached. The periodicity of the pulses lies in the range of one to sixty seconds with a preferred value of one pulse every eight seconds. In the preferred embodiment in which the pulse generator includes a programmed microprocessor the current pulses are triggered in accordance with a program held in ROM, EPROM or other memory device. Such programs enable pulses to be sent to different coil units at different periodicities and for the periodicity to be changed at regular, irregular or random intervals. In the case of coil units used in conjunction with storage containers the pulse periodicity can be related to the volume present in the container and/or the demand from it.

The pulse generator units may provide separate current pulses to each of a plurality of coils units. The number of coil units used will depend on the size of the container to which they are attached, larger vessels will require a larger number of coil units than smaller vessels or ones with great resiliency such as those manufactured from synthetic polymers. The pulse generator units will normally contain controls allowing the frequency and/or the energy of the pulses to the various coil units to be adjusted for optimum effect after installation. In most installations the pulse generator will be supplied with electrical energy from the mains supply. However where such supplies are absent the pulse generator can be adapted to operate fom batteries, preferably re-chargeable cells.

The leads from the pulse generator to the coil units are preferably screened to limit the dissemination of electromagnetic interference and meet the reqirements of EU legislation.

Due to the possibility of heavy energy demand from the mains or other power supply on start-up the various sections of the pulse generator may be brought into operation successively in accordance with a pre-programmed routine stored within a microprocessor.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic diagram showing the operation of a coil unit and plate, and Figure 2 is a block diagram of an installation of apparatus for the prevention of build-up of solid residues according to the invention.

A planar coil 1, see Figure 1, is connected through a switch 2 to a capacitor 3. The capacitor 3 is charged to an appropriate voltage from a direct current power supply through the leads 4 and 5. A plate 6 is located in close proximity to the coil 1 and is attached to the outer surface of the side of a container 7. In practice the switch 2, represented as a mechanical contact, is a thyristor or silicon controlled rectifier which receives low level switching pulses from a pulse generator unit, not shown, causing the capacitor 3 to discharge through the coil 1. The energy supplied to the coil 1 from the capacitor 3 will be mainly converted to electromagnetic energy in the coil 1 inducing eddy currents, due to the rapid rate of change of current flow, in plate 6.In accordance with the laws of electromagnetism the eddy currents will create an electromagnetic field in opposition to that created by the coil. The resulting movement of the plate 3 away from the coil will be transmitted to the surface of the container 7 dislodging any accumulated particulate material on its inner surface.

A complete installation of the apparatus according to the invention, see Figure 2, consists of a pulse generator unit 10 supplied with power through a mains input lead 11. The unit 10 provides a plurality of outputs 12 to coil units 13. The unit 10 contains a crystal controlled oscillator whose output, after division, supplies periodic switching pulses whose periodicity is controlled by a switch unit 14. The switch unit may be a standard rotary switch or a set of DIL switches. The unit 10 also contains a high voltage power supply for charging the capacitors associated with each output 12. At intervals, determined by the setting of the control 14, each unit 13 is supplied with a high current pulse by connection of a capacitor or a bank of capacitors in parallel charged from the high voltage power supply.The energy of each pulse is selected by choice of the value of the capacitor or the number of capacitors in a bank. Each capacitor or capacitor bank is connected to its output 12 through a semiconductor switch which is triggered at predetermined intervals by a trigger pulse from the timer or timing oscillator.

Each output 12 is connected by leads 15 to a coil unit 13 containing a sealed planar coil and an associated aluminium plate. Each unit 13 is attached to the side of a vessel 16 shown in cross section. The periodic pulses of energy sent from the pulse unit 10 to the coil units 13 cause a mechanical movement of the plate which causes the side of the vessel 16 to move. The movement is small in amplitude but rapid in motion sending so that any material adhering to the inner surface of the vessel 16 is dislodged and falls under the action of gravity to the base of the vessel. In order to prevent current reversal and the generation of unwanted oscillations a diode is connected across each coil with its polarity the reverse of that of the supply. The coil is preferably sealed between plates of reinforced phenolic resin such as the material sold under the reqistered trade mark 'Tufnol'.

In a preferred embodiment the pulse unit 10 consists of a programmed microprocessor supplying the periodic pulses of energy to the coil units 13. In such an arrangement not only can the periodicity of tte pulses be controlled using the microprocessor clock but the periodicity can be controlled individually for each coil unit and the whole system continuously monitored. In such an embodiment the sides of a vessel containing a particulate solid may be mechanically vibrated in a random fashion with the spatial distribution of mechanical pulses and their frequency determined in accordance with a preset program.

Claims (18)

1. Apparatus for the prevention of build-up of solid residues on surfaces comprising a plurality of electrically conducting plates having a surface attached to the outer surface of a container pipe or duct containing or transporting particulate material. a plurality of coils located adjacent to the unattached surfaces of the plates and pulse generation means adapted to discharge periodically sufficient electrical energy into each coil that a strong repulsive field is formed in each plate.

2. Apparatus as claimed in claim 1 in which the electrically conducting plates are fabricated from aluminium or an alloy thereof.

3. Apparatus as claimed in either claim 1 or claim 2 in which the electrically conducting plates have a thickness in the range 10 to 20 mm.

4. Apparatus as claimed in any of the preceding claims in which the electrically conducting plates are discs having a diameter in the range 100 to 300 mm.

5. Apparatus as claimed in any of the precedina claims in which the coils have a planar construction.

6. Apparatus as claimed in claim 5 in which the planar coils are formed as a printed circuit.

7. Apparatus as claimed in any of the preceding claims in which each plate and its associated coil are contained in a sealed unit.

8. Apparatus as claimed in any of the preceding claims in which each plate is formed with a rim which extends around the periphery of the associated coil.

9. Apparatus as claimed in any of the preceding claims in which the pulse generation means comprises a timing oscillator which controls the frequency and duration of the pulses it generates.

10. Apparatus as claimed in claim 9 in which the pulse generation means comprises a microprocessor forming the timing oscillator and which controls other functions associated with the apparatus.

11. Apparatus as claimed in claim 10 in which a program for discharging electrical energy into the coils and for other functions is held in a ROM or EPROM associated with the microprocessor.

12. Apparatus as claimed in any of the preceding claims in which the electrical energy discharged into each coil lies in the range 10 to 400 mJ.

13. Apparatus as claimed in any of the preceding claims in which the periodicity of the discharges lies in the range one to sixty seconds.

14. Apparatus as claimed in claim 12 in which the periodicity is eight seconds.

15. Apparatus for the prevention of build-up of solid residues on surfaces as claimed in claim 1 and as herein described.

16. Apparatus for the prevention of build-up of solid residues on surfaces as herein described with reference to the accompanying drawings.

17. A process for the prevention of build-up of solid residues on surfaces comprising periodically discharging sufficient electrical energy into a coil that a strong repulsive field is formed in a conducting plate having one surface attached to the outer surface of a container or pipe.

18. Processes for the prevention of build-up of solid residues on surfaces as herein described.