GB2219784A - Discharging a bulk material container - Google Patents

Abstract

In order to adapt a bulk transport container or hold of a ship to allow particulate contents thereof (e.g. cement) to be fluidised, there are provided a platform (22) which serves as a false floor for supporting the contents above the base (12) of a container (10), the platform being permeable to gas flow (e.g. by being made of a porous metal or plastics material) and beneath it are air lines (40) for providing low or medium pressure air from a jet pump (Fig. 3) so as to fluidise the particles above the platform; filters with dust caps (44,46) at the top of the container to remove the dust formed when the container is filled, and an exhaust pipe for removing excess pressurised gas, and at least one outlet (32) for discharge of the particulate contents. Preferably disintegration nozzles (24) are provided in the false floor, especially around the outlet therein for supply of high pressure air from lines (26). The air supply may be passed through a filter, a heater and a dehumidifier to prevent condensation. <IMAGE>

Description

Elements for adapting a bulk transport container or hold of a ship to fluidise and discharge its contents and method there for.

This invention relates to an assemblage of parts for adapting a bulk transport container or the hold of a ship carrying dry powdered or granular bulk cargo to fluidise and discharge the contents thereof by means of a selfcontained propulsion system. The apparatus is especially suitable for retrofitting 20 foot or 40 footIS containers, overage bulk carriers and barges.

Most bulk cargos tend to compact when they are stowed in ISO containers or the hold of a vessel. Powdered cargos such as cement, apatite, gypsum, tapioca, or fertilisers, in particular, tend to form hard crystalline structures with lumps and on discharge they often develop 'shoulders' or agglomerations which collapse when the cargo below these 'shoulders' is removed, often producing large quantities of dust. Because of this dust problem, it is difficult todischarge powdered or granular cargo and many ports ban or severely restrict the discharge on environmental grounds.

In order to overcome the dust problem one solution has been to bag these cargos into 50kg or 100kg sacks, or even 'big bags'of'l5DOkg size. These bags are then packed on lorries or stowed in containers. Another typical solution has been to use pneumatic vessels to carry and discharge dusty cargos.

Such prior solutions, however, suffer from the disadvantage that bagging operations are costly and time-consuming and pneumatic vessels are expensive to build, maintain and operate. Indeed, ordinary carriers are better suited to two-way traffic since pneumatic vessels can often only take cargo in one direction, having to return in ballast.

For sea vessels) one solution was to create what i known as a 'fluidised' hold. The prior method of building a- fluidised hold consists of building a false floor in part of the hold of angled plates made of perforated steel sheets, below which are located air blowers. Resting on the surface of these perforated sheets is a continuous imperforate layer of bulkslide fabric, like a glossy tarpaulin.In operat ion, the air from the blowers passing through the perforated sheets causes the bulkslide fabric to vibrate. This vibra tion fluidises the supeadjacent powdered cargo which flows down the angled plane to a collection trough containing a horizontal helical screw which interlinks with a vertical helix which carries the cargo to deck level.

The disadvantage of this method is that the vibrating floor merely causes the particulate. contents to turn over so that an inadequate flow is achieved. Moreover, moisture build up -within the vessel further aggravates flow by causing the particles to compact.

The present invention improves on this system by utili sing new materials and methods to effect an improved fluidis ation and discharge.

The invention accordingly provides. an assemblage of parts for adapting a bulk transport container or hold of a ship to fluidise particulate contents thereof for discharge from the container, comprising; a platform for supporting the particulate contents above the base of the container, the platform being permeable to gas flow; means for providing a pressurised gas from below and through the platform to fluidise the superadjacent particulate contents; means at the upper part of the container or hold for collecting any stray particles from the. contents; means for removing excess pressurised gas from the container, and one or more outlets in the platform for discharge of the fluidised particulate contents.

Preferably, the platform is made of a porous metal or plastics material.

The pores are preferably of size 15 to 60 microns depsnrling on the typeof cargo to be fluidised.

The invention also provides, a method of fluidising the particulate contents of a bulk transport container or hold of a ship comprising: fitting the above'. defined parts to said container; filling said container with particulate matter; providing a supply of pressurized gas through the platform, and pumping the fluidised particulate contents to discharge them to a chosen location. A gas pressure of 2 atm is suitable.

The apparatus and method of fluidisation in accordance with the invention overcomes the problems of the prior art in that: In the hold of a sea vessel, condensation in the ullage is prevented so cargo is kept both dry and free of unwanted gases, and dust pollution in the working environment is reduced. Also, cargo may be discharged in all weathers and manpower can be reduced as the entire operation is controlled by a single control panel. Moreover, the apparatus is highly maintenance-efficient as there are practically no moving parts other than the valves.

Likewise, with ISO containers, the invention provides an efficient bulk distribution system. ISO containers are multimodal in that they can be transported by land, sea, rail or air and the invention enables these containers to be loaded directly from bulk carriers so there is no need for a shore-based silo or a bagging plant, thus saving time in delivery. Moreover, as little as 15-20 metric tons may be delivered at a time.

The invention is illustrated by way of example in the accompanying drawings, in which: Fig. 1 is a cross-sction across a bulk transport container which has been fitted with parts in accordance 'ith the invention; Fig. 2 is a view, from above, of the container of Fig. 1, with part of the false floor broken away; Fig. 3A is a perspective view of a jet pump that can be used in accordance with the invention; Fig. 38 is a perspective view of the hopper of a jet pump, and Fig. 4 is a schematic diagram of an air heating and conditioning aspect of the method.

Referring to Fig. 1, the reference numeral 10 indicates a bulk transport container or hold of a ship having a base 12, side walls 14, 16 and top 18.

A series of steel sheets 20 of varying heights extend perpendicularly from the base 12 and support a false floor 22 made of sintered steel mesh or sintered polyethylene of sufficient strength appropriate to the size of the ISO container (suitable thickness about 1.6 cm) or hold (suitable thickness about 0.03 cm).

The steel mesh used can be that provided by GKN of Sutton-in-Ashfield and the polyethylene used can be that provided by Atlas Equipment (London) Ltd. Incorporated into the false floor 22 there can also be occasional spaced disintegration nozzles 24 which are linked 26 to a high pressure air line which periodically jets high pressure air through the nozzle 24 to disintegrate any crystalline formations or hard shoulders which may have formed in the cargo.

The false floor slopes downwards at an angle of about 200 to 250 to the vertical, from the front 28 of the container 10 towards the back 20; while also sloping downwardly from the rear 30 of the container 10 at an angle of about 320 (Fig. 2). About 61 cm from the rear of the container is an outlet aperture or drop-off 32 in the false floor 22 and a hopper body 34 of a jet pump 36 encloses the outlet.

The jet pump 62(Fig.3A) 3A) can be of a known commercial type, such as supplied by Genflo Pumps Limited of Stamford, and has a supply 54 for compressed air, an outlet 60 for discharge of the particulate contents, and a7- islet eel to a hopper body 66 beneath a hopper 34.

The hopper 34 of the jet pump 62 may be covered by a grate 58 to screen out oversize particles (Fig.

38).

Into the compartments 38 formed between the base 12 of the container 10 and the false floor 22, by the steel sheets 20, there are low/medium pressure air lines 40 which fill these compartments 38 with air. This air is blown through microscopic pores 42 in the false floor 22 to create an agitation in the lower strata of the cargo ('fluidisation') which allows the cargo to slide down the slope of the false floor 22 towards the jet pump hopper 34. At the top of the container 10 (see Fig. 1) are two dust collectors 44 and 46 to filter dust formed when the container 10 is filled. The container 10 is filled through inlet opening 48 which is sealed after filling.

Referring to Fig. 2, the false floor 22 covers the compartments 38 formed by sheets 20, and the low/medium pressure air pipes 40. The optional disintegration nozzles 24, embedded in the false floor 22 are most numerous around the declivity of the false floor 22 leading to the jet pump hopper 34. At the rear side of the container 10 is air inlet 50 which is coupled to an external air compressor (not shown). A 2-way or 3-way line diverter 52 of a known commercial type, such as provided by Atlas Equipment (London) Ltd, is coupled to the air inlet 50 and splits the air flow into; (i) a pipe leading to the air blowers 40 located in the base (ii) the disintegration nozzles 24 (if present) and'(iii) to the jet pump 62.Alternatively, a series of valves in the false floor divide the inlet air between the medium-pressure lines and the jet pump; and if the disintegration nozzles are used, the nozzle feed lines. A control panel 56 regulates the amount of air through the line diverter 52.

If more than one kind of cargo is to be fluidised in a single vessel or if the hold is particularly large, one or more false floors 22 may be constructed side by side, in which case air lines from the compressor and the cargo discharge pipes ara supplied to each false floor.

In the case of the hold of a marine vessel, additionally passing through the inlet 48 is a pipe to extract the air in the ullage and recycle it through a reactivator/dehumidifier (Fig. 4), of a known commercial type such as provided by Atlas Equipment (London) Ltd.

The air from the hold is pumped through a filter 72 and through a large dehumidifier wheel of lithium chloride 74. In this wheel the recycled air mixes with heated air which is pumped through a filter 76 and a reactivation heater 78. It then enters the reactivator surrounding the lithium chloride wheel and mixes with the recycled air. The pump 80 moves this dried and heated reactivated air back to the hold through a recycle pipe 82. The excess air is pumped away through an exhaust pipe 84.

A distinctive feature of this invention is the means and method of fluidisation of the cargo. In operation, pressurised gas such as air is blown from the air blowers 40 and through pores 41 in the false bottom 22, so as to cause vibration of the superadjacent dry cargo stored in the hold. This vibration causes the lower strata of the dry cargo to 'flow' or to behave as if it were a fluid. If disintegration nozzles 24 are installed in the false floor they also blow air therethrough to break up any crystalline formations.

A computer-controlled servo-electric valve system regulates the air blowers so that they blow intermittently around the base of the hold in a predetermined manner which causes the superadjacent cargo to shake and agitate.

The air delivered through the false floor 22 percolates through the cargo from the base 12 of the container 10 and escapes from the ullage through the two dust collectors 44, 46. The false bottom 22 is installed over the base 12 of the container 10 in such a manner as to create an angled surface down which the fluidised cargo flows. The fluidised cargo is then sucked out of the container 10 by the jet pump 62, fed by compressed air also from the compressor.

The fluidised cargo is pumped from the outlet 60 to a location where the cargo is to be used. The jet pump 62 is driven in the usual manner. A source of air flow from the compressor enters the inlet 54 and passes through the nozzle 64. As this flow passes through the hopper body 66 it causes an induced flow from the hopper. This passes out of the hopper body 66 through the mixing chamber 68 and past the diffusers 70 to the outlet 60. The hopper of the jet pump is continuously voided by an induced flow caused by highpressure air delivered through the pipe 54 from the line diverter.

In the hold of a ship, the air delivered from an external compressor is passed through an air filter 76, a reactivation heater 78 and a dehumidifier 74.

This stabilises the dew point and prevents condensation.

The air percolates through the cargo from the base of the hold and is removed and recycled from the ullage.

This prevents condensation in the ullage and removes hazardous or unwanted gas build up. The medium-pressure air from below thus serves to fluidise the lower strata of the cargo and to dry and dehumidify the cargo.

Also, the increased pressure in the ullage is relieved by the recycling of the air.

If only a single hold is fluidised the air compressor may be mounted on deck near to the fluidised hold.

If more than one hold is fluidised a central compressor should be used with the pipes mounted on deck, alongside the cargo discharge pipes.

In some cases it may be necessary to strengthen the side walls of ISO containers td withstand storage of these bulk cargos. In such an event sheets of strong plastic or plywood should be attached to the side walls. In any event, the inside of the container should be sprayed with a commercial epoxy resin spray to seal the container against the discharge of dust.

The apparatus of the invention may also be combined with bilge pumps located below the false floor which remove moisture passing through the false floor.

This is of particular value for coal barges where a larger mbsh size is used for the false floor. This removes large amounts of moisture during the voyage, increasing the value of the coal at the discharge point.

Claims (12)

CLAIMS:

1. An assemblage of parts for adapting a bulk transport container or hold of a ship to fluidise particulate contents thereof for discharge from the container comprising: a platform for supporting the particulate contents above the base of the container, the platform being permeable to gas flow; means for providing a pressurised gas from below and through the platform to fluidise the superadjacent particulate contents; means at the upper part of the container or hold for collecting any stray particles from the contents; means for removing excess pressurised gas from the container or hold and one or more outlets in the platform for discharge- of the fluidised particulate contents.

2. An assemblage as claimed in Claim 1, in which the platform is made of a porous metal or plastics material.

3. An assemblage as claimed in Claim 1 or 2, in which the platform has pores of size 15 to 60 microns and adapted for the gas to be-passed through the pores at a pressure of 2 atmospheres.

4. An assemblage as claimed - --i- any of the preceding claims, in which the platform surface slopes downwards towards the or each outlet.

5. An assemblage as claimed in any of the preceding claims, in which the platform has embedded therein disintegration nozzles which are coupled to a high pressure gas line.

6. An assemblage as claimed in any of the preceding claims, in which the gas is passed through a filter, a reactivation heater and a dehumidifier before being passed through the platform.

7. An assemblage as claimed in any of the preceding claims, including a jet pump coupled to the or each outlet of the platform for conveying the fluidised matter to a chosen discharge location.

8. An assemblage for adapting a bulk transport container or hold of a ship to fluidise particulate contents thereof, sub tal,tially as hereinbefore described with reference to or as shown in the drawings.

9. A bulk transport container or hold of a ship having fitted thereto the parts as claimed in any of the preceding claims.

10. A bulk transport container or hold of a ship having fitted thereto the parts for allowing the fluidising of particulate contents thereof, substantially as hereinbefore described, with reference to or as shown in the drawings.

11. Method of fluidising the particulate contents of a bulk transport container or hold of a ship comprising: fitting the parts as claimed in any of Claims 1 to 8 to a said container; filling said container with particulate matter; providing a supply for pressurized gas through the platform and pumping the fluidised particulate contents to discharge them to a chosen location.

12. A method of fluidising the particulate contents of a bulk transport container or hold of a ship, substantially as hereinbefore described.