PIPES UNITS

TECHNICAL FIELD

[0001] The application relates generally to mining slurries and, more particularly, to the cleaning of conduits carrying said slurries.

BACKGROUND OF THE ART

[0002] The processing of bauxite, an aluminum ore, generates thick slurries. These thick slurries are then treated to produce alumina and other products.

[0003] The thick, viscous slurries often need to be heated prior to being subjected to additional downstream treatment. One technique for heating the thick slurry involves the use of a jacketed pipe-heater unit, or simply a jacketed pipes unit (hereafter "JPU"). Each JPU contains one or more inner tubes which carry the thick slurry to be heated. A heat exchange fluid, such as heated water vapour, is provided within the JPU. The heat exchange fluid transfers its heat to the thick slurry carried within the inner tubes of the JPU.

[0004] WO 2005/1 19154 A1 to De Boer discloses a slurry heating system. The system has tube heat exchanger units, where each unit includes a plurality of inner tubes arranged in parallel for single-pass operation. The inner tubes are contained within an outer tube with a removable cover at each end to allow physical access to the inner tubes for cleaning purposes. The inner tubes contain slurry to be heated, in isolation from a heating medium contained within the outer tube, surrounding the inner tubes. The slurry heating system has at least two of these units arranged in series, with adjacent units in the series being connected by an interconnecting pipe.

[0005] It is known that scale develops along the inner surface of the inner tubes which carry the thick slurry above a certain temperature. These inner tubes must be cleaned by reducing or removing the scale in order to continue treating the thick slurry.

[0006] One cleaning technique involves chemical treatment. A chemical such as sulphuric acid is conveyed through the inner tubes to remove the scale formed against an inner surface thereof. Another cleaning technique involves mechanical treatment. A fluid such as water is conveyed under high pressure through the inner tubes, which is referred to as "hydro scrubbing". [0007] Another mechanical treatment involves using one or more pigs. A pig generally forms a seal with the inner surfaces of the inner tubes, and is conveyed therethrough via a pressurized fluid. As it is conveyed, the pig scrapes or abrades away the scale formed along the inner surface.

[0008] Various disadvantages are associated with conventional cleaning techniques. Chemical treatments require that environmental and health and safety safeguards be put in place prior to cleaning, which adds delays and complexity to the cleaning treatment. Hydro scrubbing and the use of pigs can require a water supply and the use of energy-consuming high-pressure pumps, which adds to operating costs and complicates set-up. Generally, these cleaning treatments require a significant amount of down time during which treatment of the thick slurry must be stopped. This equates to lost productivity, and hence, lost revenue.

[0009] The Applicant is aware of the following documents: GB 2 196 716 A, US 2010/0065140 A1 , and WO 95/12464.

SUMMARY

[0010] In one aspect, there is provided a coupling device for transferring a pig between inner tubes of a jacketed pipes unit extending in parallel therethrough between opposed ends thereof, the coupling device characterised in that it comprises: a mounting block mountable to one of the ends of the jacketed pipes unit, the mounting block defining a first surface and an opposed second surface, and at least first and second openings extending through the mounting block between the first and second surfaces, each opening in fluid communication with a corresponding inner tube of the jacketed pipes unit upon the mounting block being mounted thereto; and a looping conduit connecting two of the inner tubes of the jacketed pipes unit in serial flow communication, the looping conduit extending between a first loop end and an opposed second loop end, the first loop end mounted to the second surface of the mounting block about the first opening and in fluid communication therewith, and the second loop end mounted to the second surface of the mounting block about the second opening and in fluid communication therewith, the looping conduit in use transferring the pig from one of the inner tubes of the jacketed pipes unit to another one of the inner tubes.

[0011] In another aspect, there is provided a system for cleaning inner tubes of jacketed pipes units, the inner tubes of each jacketed pipes unit extending therethrough between opposed ends thereof, the jacketed pipes units arranged in a train and in serial flow communication between a train inlet and a train outlet, the system comprising: a pig sender for conveying a pig through one of the inner tubes to clean said inner tube; and a pig receiver for receiving the pig after having cleaned said inner tube; characterised in that it comprises at least one coupling device as described above.

[0012] In a further aspect, there is provided a method for cleaning inner tubes extending in parallel through a jacketed pipes unit, the method comprising the steps of: conveying a pig through a first inner tube of the jacketed pipes unit along a first direction to clean the first inner tube; and conveying the pig through a second inner tube of the jacketed pipes unit along a second direction to clean the second inner tube; characterised in that it comprises the step of connecting in serial flow communication the first and second inner tubes to convey the pig between the first and second inner tubes, and in that the second direction is opposite to the first direction to reverse a direction of travel of the pig through the jacketed pipes unit.

DESCRIPTION OF THE DRAWINGS

[0013] Reference is now made to the accompanying figures in which:

[0014] Fig. 1 A is a schematic representation of a train of interconnected jacketed pipes units;

[0015] Fig. 1 B is a cross-sectional schematic view of one of the jacketed pipes units of the train of Fig. 1A;

[0016] Fig. 2A is a front perspective view of a coupling device, according to an embodiment of the present disclosure;

[0017] Fig. 2B is a rear perspective view of the coupling device of Fig. 2A;

[0018] Fig. 2C is a side elevation view of the coupling device of Fig. 2A;

[0019] Fig. 3A is a perspective view of a pig sender or a pig receiver mounted to a coupling device, according to another embodiment of the present disclosure;

[0020] Fig. 3B is a side elevation view of what is shown in Fig. 3A;

[0021] Fig. 4A is a schematic representation of a system for cleaning inner tubes of jacketed pipes units, according to yet another embodiment of the present disclosure; [0022] Fig. 4B is a schematic representation of a coupling device for mounting to one of the ends of the jacketed pipes units of Fig. 4A;

[0023] Fig. 4C is a schematic representation showing a direction of travel of a pig through the inner tubes of the jacketed pipes units of Fig. 4A;

[0024] Fig. 5A is a schematic representation of another system for cleaning inner tubes of jacketed pipes units, according to yet another embodiment of the present disclosure;

[0025] Fig. 5B is a schematic representation of a coupling device for mounting to one of the ends of the jacketed pipes units of Fig. 5A;

[0026] Fig. 5C is a schematic representation showing a direction of travel of a pig through the inner tubes of the jacketed pipes units of Fig. 5A;

[0027] Fig. 6A is a schematic representation of yet another system for cleaning inner tubes of jacketed pipes units, according to yet another embodiment of the present disclosure;

[0028] Fig. 6B is a schematic representation of a coupling device for mounting to one of the ends of the jacketed pipes units of Fig. 6A;

[0029] Fig. 6C is a schematic representation of another coupling device for mounting to one of the ends of the jacketed pipes units of Fig. 6A; and

[0030] Fig. 6D is a schematic representation showing a direction of travel of a pig through the inner tubes of the jacketed pipes units of Fig. 6A.

DETAILED DESCRIPTION

[0031] Figs. 1A and 1 B show an example of a bauxite digestion train 10 having multiple jacketed pipes units 1 1 , or "JPUs 1 1 ". Slurry from the processing of bauxite, for example, is conveyed through the JPUs 1 1 of the train 10 along a slurry flow direction 18, from a train inlet 13 to a train outlet 14. In the example shown in Figs. 1A and 1 B, each JPU 1 1 is joined to an adjacent JPU 1 1 via a bend 15, which can be any curved conduit which is bolted or otherwise attached to the JPUs 1 1 it connects so as to form a closed, serpentine circuit of JPUs 1 1. This places the JPUs 1 1 in serial flow communication along the slurry flow direction 18 from the train inlet 13 to the train outlet 14. Each JPU 1 1 can be made of any suitable material and take any suitable shape, and is generally made from steel and is cylindrical. [0032] Each JPU 1 1 contains one or more inner tubes 12 which extend generally, but not exclusively, in parallel to one another within the JPU 1 1 between its opposed ends. Each JPU 1 1 is therefore any outer conduit which "jackets" or encloses the inner tubes 12. The number of inner tubes 12 within each JPU 1 1 can vary depending on the slurry being conveyed, the desired amount of temperature increase of the slurry, and the spacing constraints of the site, to name but a few factors. The inner tubes 12 convey the slurry along the slurry flow direction 18 from the train inlet 13, within the various interconnected JPUs 1 1 , through corresponding inner tubes 12 in the bends 15, and to the train outlet 14. The inner tubes 12 can therefore be any conduit made of a suitable metal material used to both convey the slurry through the JPU 1 1 , and to receive the slurry therefrom.

[0033] During processing, the slurry is heated in the train 10 such that its temperature increases as it is conveyed through each inner tube 12 from the train inlet 13 to the train outlet 14 along the slurry flow direction 18. The heating of the inner tubes 12 can be accomplished using different techniques. In the example provided in Fig. 1A, a flash tank 16 supplies a fluid such as steam at an elevated temperature into one or more JPUs 1 1 . The steam is conveyed through the interior of each JPU 1 1 and around the exterior of the inner tubes 12, thereby heating the inner tubes 12 and the slurry contained therein. Downstream of the flash tank 16 along the slurry flow direction 18, and if so desired, a boiler 17 can be used to provide additional heated fluid (e.g. steam) to further heat the inner tubes 12. As with the flash tank 16, the boiler 17 conveys steam through the interior of one or more JPUs 1 1 and around the exterior of the inner tubes 12, thereby heating the inner tubes 12 and the slurry contained therein. With either one of the flash tank 16 or the boiler 17, or both, the heated fluid can be conveyed through the JPUs 12 in a direction opposite to that of the slurry flow direction 18. Similarly, valves can be employed to regulate the amount and pressure of heated fluid supplied by the flash tank 16 and/or boiler 17.

[0034] It is known that scale develops over time on the inner surfaces of the inner tubes 12 which convey slurry that has been heated above a certain temperature. It eventually becomes necessary to clean the inner surfaces of these inner tubes 12 by reducing or removing the scale therefrom. Mechanical cleaning techniques generally involve scraping or abrading away the scale formed on the inner surfaces by using a mechanically abrasive device, such as a pig, or by hydro blasting. Irrespective of the mechanical cleaning technique being used, it is necessary to access the interior of one or more inner tubes 12 of one or more JPUs 1 1 to clean the inner surfaces of the inner tubes 12. The inner tubes 12 are typically accessed by removing one or more of the bends 15 from the ends of the JPUs 1 1. The highly- pressurized fluid and/or the pig can then be inserted into the inner tubes 12 and conveyed through the train 10.

[0035] Hydro blasting generally requires that each bend 15 be removed from the end of each JPU 1 1 so that access can be gained to the inner tubes 12 of each JPU 1 1. This involves a significant amount of labour and is time consuming, often requiring that the train 10 be shut down for days at a time. These long suspensions of slurry processing in the bauxite digestion train 10 result in lost revenue.

[0036] The use of one or more pigs can reduce the system down time compared to hydro blasting, but still requires a significant amount of labour. Pigs come in different shapes and configurations, but are generally abrading objects which fit tightly within a given inner tube 12 and which are propelled through the inner tube 12 by applying fluid pressure behind the pig. One example of a pig includes a cylindrical object fitted with brushes and/or scrapers along its outer periphery which is used for removing deposits (i.e. scale) from the inner surface of the inner tube 12. The pigs are generally launched in one inner tube 12 from one of the ends of a JPU 1 1 after its bend 15 has been removed, or from the train outlet 14 or train inlet 13. The pig circulates through the inner tube 12, cleaning as it goes, until it reaches the end of its path at a pig receiver. The pig receiver can then send the pig back through the same inner tube 12 whence it came. It will be appreciated that this involves a significant amount of labour considering that multiple inner tubes 12 must be cleaned in this way.

[0037] A coupling device according to the present disclosure, now described, can be used to assist in such cleaning of the inner tubes 12.

[0038] Figs. 2A to 2C show an example of a coupling device 20 for transferring a pig between inner tubes of a JPU. The coupling device 20 transfers or conveys the one or more pigs received from one of the inner tubes to another one of the inner tubes of the same JPU, where these inner tube generally extend in parallel to one another within the same JPU. The coupling device 20 is therefore an adapter which adapts or modifies the travel path of the pig through the inner tubes of the JPUs. The coupling device 20 has a mounting block 30 for mounting the coupling device 20 to a free end of the JPU, and a looping conduit 40 for directing the travel of the pig, both of which are now described in greater detail.

[0039] The mounting block 30 is mounted to, and removable from, one of the ends of the JPU. This generally, but not exclusively, occurs after the bend of that JPU has been removed. The mounting block 30 is thus mountable to the end of the JPU, and consequently to the inner tubes contained therein. In most instances, the end of the JPU will have a flange to which the outer peripheral flange portion of the mounting block 30 can be mated against and secured to by bolts. Although shown as substantially cylindrical, the mounting block 30 can take other forms (rectangular, triangular, etc.) provided that it can form an impermeable seal with the end of the JPU to which it is secured. The mounting block 30 defines a first surface 31 and a second surface 32, and has at least a first and a second opening 33.

[0040] The first surface 31 mates against the flange of the end of the JPU to which the mounting block 30 is attached. It is generally, but not exclusive, a planar surface corresponding to the shape of the surface of the flange of the JPU in order to form a seal between the mounting block 30 and the JPU. The second surface 32 is opposed to the first surface 31 in that it is located on an opposite side of the mounting block 30, as more clearly shown in Fig. 2C. The second surface 32 faces away from the JPU, and as will be described in greater detail below, receives various structures which are secured thereto. It too is generally a planar, cylindrical surface.

[0041] Each of the at least first and second openings 33 extend through the body of the mounting block 30 between the first and second surfaces 31 ,32. Each opening 33 is generally a cylindrical bore that extends parallel to a central axis of the mounting block 30 in a substantially linear manner. Each opening 33 is configured to be in fluid communication with one of the inner tubes of the JPU once the mounting block 30 is mounted and secured to the JPU. The expression "fluid communication" refers to the ability of each opening 33 to receive a pig and the pressurized fluid used to convey it from the corresponding inner tube, and also to its ability to convey the pig and pressurized fluid into another corresponding inner tube.

[0042] It can thus be appreciated that the number of openings 33 within the mounting block 30 largely depends on the number of inner tubes of the JPU to which the mounting block 30 is mounted, and the number of inner tubes that must be placed in fluid communication. For example, the three openings 33 of the mounting block 30 shown in Fig. 2A may correspond to a JPU having three inner tubes, and also to a JPU where it is desired to place two of the three inner tubes in fluid communication. Alternatively, the mounting block 30 could have only two openings 33 for a JPU that has only two inner tubes, such that all the openings 33 of the mounting block 30 are in fluid communication with all the inner tubes of the JPU. Similarly, the location and configuration of the openings 33 about the center axis of the mounting block 30 largely depends on the location and configuration of the inner tubes with which they will enter into fluid communication. It will thus be appreciated that many permutations of the number, location, and configuration of the openings 33 are within the scope of the present disclosure.

[0043] The looping conduit 40 connects two of the inner tubes of the same JPU together in serial flow communication. The expression "serial flow communication" refers to the ability of the looping conduit 40 to fluidly communicate two inner tubes together, such that the pig can flow from one of the inner tubes directly into the other inner tube, thereby creating a travel path for the pig between the two inner tubes. This is in contrast to the fluid travel within the inner tubes when they are not linked by the looping conduit 40, in that both inner tubes extend generally in parallel to one another such that the slurry and/or the pig cannot be conveyed between them. It can thus be appreciated that the looping conduit 40 can be any piping, ducting, or other fluid connector which accomplishes such functionality. The looping conduit 40 extends between a first loop end 41 and a second loop end 42.

[0044] The first loop end 41 forms one of the extremities of the looping conduit 40. It is mounted to the second surface 32 of the mounting block 30. The first loop end 41 can be bolted, welded, or otherwise secured to the second surface 32 in order to provide a secure and sealed attachment. The first loop end 41 is mounted about the first opening 33 of the mounting block 30 such that it is in fluid communication therewith, thereby allowing the first loop end 41 to receive or convey the pig and pressurized fluid. The second loop end 42 is similarly connected or joined to the second surface 32 of the mounting block at a different location than the first loop end 41 , such that it is in fluid communication with the second opening 33 of the mounting block 30. It can thus be appreciated that the length of the looping conduit 40 is defined between the two opposed extremities of the first and second loop ends 41 ,42. [0045] When in use, the looping conduit 40 transfers the pig from one of the inner tubes 12 of the JPU 1 1 to another one of the inner tubes of the same JPU via the first and second loop ends 41 ,42. Specifically, the looping conduit 40 can direct the pig from a first inner tube, which enters the looping conduit 40 via the first loop end 41 , along the length of the looping conduit 40 and out of the looping conduit 40 via the second loop end 42 to a second inner tube of the same JPU, or a different JPU. It will be appreciated that the pig can also travel through the looping conduit 40 in a direction opposite to the one just described. If desired, the direction of travel of the pig and the pressure it is subjected to can be controlled within the looping conduit 40. This can be done with a valve or a directing mechanism. Figs. 2A to 2C show one possible valve, such as a drain valve 44 for draining the inner tube after pigging, which can be controlled by a valve wheel 45. It will be appreciated that varying the pressure of the pressurized fluid within the looping conduit 40 can affect the speed of travel of the pig therethrough.

[0046] The shape and orientation of the looping conduit 40 can vary. In the embodiment of Figs. 2A to 2C, the looping conduit 40 has an elbow or bended conduit section 43 which connects and extends between the first and second loop ends 41 ,42. The bended conduit section 43 is bent at an angle of about 180°. Such an inclination of the bended conduit section 43 allows it to reverse the travel of the pig through the JPU. This is more clearly understood in the possible scenario where the pig enters the looping conduit 40 from a first inner tube via the first loop end 41. The bended conduit section 43 curves the travel of the pig about 180° as it travels through the looping conduit 40 such that it exits the looping conduit 40 via the second loop end 42 and enters a second inner tube. The pig will now be travelling in the second inner tube along a direction which is opposite to, or the reverse of, the direction it was travelling along in the first inner tube. The bended conduit section 43 also allows reverse travel of the pig in the opposite direction as that described. Of course, other shapes and configurations for the looping conduit 40 are possible provided that it transfers the pig from one inner tube to another inner tube.

[0047] In the optional embodiment where the mounting block 30 has three openings 33 and the JPU has three inner tubes, the first loop end 41 can be mounted to a first opening 33 and the second loop end 42 can be mounted to a second opening 33. The third opening 33 is thus unoccupied, and is in fluid communication with a corresponding third inner tube of the JPU to which the mounting block 30 is mounted. [0048] One or more devices can be attached to this third opening 33. One of these possible devices is an elongated conduit 22, an example of which is shown in Figs. 2A to 2C. The elongated conduit 22 extends along a length defined between a first conduit end 23 and a second conduit end 24. The elongated conduit 22 is generally oriented perpendicularly to the second surface 32 of the mounting block 30. It is mounted to, and removable from, the second surface 32 via the first conduit end 23. The elongated conduit 22 can also be inclined at an angle relative to the plane defined by the second surface 32, depending on space restrictions and the desired launch or catch angle, among other factors. The first conduit end 23 is mounted about the third opening 33 and is in fluid communication therewith. The elongated conduit extends away from the second surface 32 toward the second conduit end 24, which is an unobstructed or free extremity of the elongated conduit 22. It will thus be appreciated that an object or fluid can be conveyed/received through the elongated conduit 22 and into/from the corresponding third inner tube of the JPU.

[0049] One of the possible objects and fluids which can be conveyed or received through the elongated conduit 22 is a pig and pressurized fluid. Referring to Figs. 3A and 3B, a pig sender 25 or a pig receiver 26 can be mounted to, and removed from, the second conduit end 24 of the elongated conduit 22. The pig sender or receiver 25,26 can have a flange at one extremity thereof which is bolted to a flange at the second conduit end 24, or can be attached to the elongated conduit 22 via intermediate tubing. The pig sender or receiver 25,26 can also be supported by an appropriate stand or other structural support. When the elongated conduit 22 is used, the first and second loop ends 41 ,42 may be inclined downward at an angle, such as about 45°, relative to a plane perpendicular to the plane formed on the second surface 32. This provides clearance between the looping conduit 40 and the elongated conduit 22, as can be better seen in Fig. 3B.

[0050] The pig sender 25, or pig launcher, sends or conveys the pig and the pressurized fluid through the elongated conduit 22, through the mounting block 30, and into the third inner tube. The pig and pressurized fluid can be loaded into the free end of the pig sender 25 which is not mounted to the second conduit end 24. The pig receiver 26, or pig catcher, receives or catches the pig and/or the pressurized fluid which travels through an inner tube, through the mounting block 30, and through the elongated conduit 22 before arriving in the pig receiver 26. It will be appreciated that the pig sender and receiver 25,26 can be the same device. In such an embodiment, the pig sender 25 is transformed into a pig receiver 26, and vice versa, through the use of a directional valve 27 or mechanism. It will also be appreciated that the pig sender or receiver 25,26 can be mounted directly to the second surface 32 of the mounting block 30, about one of the openings 33, and thus can bypass the elongated conduit 22.

[0051] Figs. 4A to 4C show a system 50 for cleaning the inner tubes 12 of JPUs 1 1 of an existing bauxite digestion train 10. The system 50 can be used to clean one or more of the inner tubes 12 of the JPUs 1 1 of the train 10. One or more trains 10 can be stacked one atop the other in a given slurry processing facility to optimise space constraints. In such a configuration, a separate system 50 can be used to clean each train 10 in the stack. The system 50 has one or more pig senders 25, one or more pig receivers 26, and one or more coupling devices 20, such as those described above.

[0052] The pig senders 25 are used to convey or launch the pig through one or more of the inner tubes 12 of some part of the train 10 in order to clean the inner tubes 12. Similarly, the pig receivers 26 receive or catch the "dirty" pig after it has cleaned the one or more inner tubes 12. The travel path of the pig through the inner tubes 12 is not restricted to being a direct path between one pig sender 25 and a corresponding pig receiver 26. Indeed, the pig may travel through more than one inner tube 12 after having been launched from the pig sender 25 and before it arrives at a corresponding pig receiver 26. Figs. 4A to 4C show just such a system 50.

[0053] In the train 10 of Figs. 4A to 4C, each JPU 1 1 has a first inner tube 12i, a second inner tube 12ii, and a third inner tube 12iii. The three inner tubes 12i, 12ii, 12iii can be separate from one another and can merge together into their corresponding JPU at the train inlet 13. The three inner tubes 12i, 12ii, 12iii can also become separate again at the train outlet 14. The coupling device 20 is mounted to a free end of one of the JPUs after the corresponding bend 15 has been removed. The coupling device 20 in this embodiment has three corresponding openings defined in its mounting block. As can be seen in Fig. 4B, a pig receiver 26 (or alternatively, a pig sender 25) is mounted, optionally via an elongated conduit, to the free third opening of the coupling device 20. The third opening is one of the openings not already occupied by the looping conduit of the coupling device 20. At the train outlet 14 or train inlet 13, a pig sender 25 (or alternatively, a pig receiver 26 depending on what is mounted to the coupling device 20) is mounted to the third inner tube 12iii, i.e. to the same inner tube 12iii which is in fluid communication with the third opening of the coupling device 20. A second pig sender 25 (or pig receiver 26) can be mounted to the first inner tube 12i at the train outlet 14 or train inlet 13, and a second pig receiver 26 (or pig sender 25) can be mounted to the second inner tube 12ii at the train outlet 14 or train inlet 13 as well.

[0054] This configuration of the system 50 is shown schematically in Fig. 4C. Such a configuration allows the pig to travel through the inner tubes 12i, 12ii, 12iii along two different circuits. The first circuit is along the third inner tube 12iii, and extends from the pig sender 25 at the train outlet 14 or train inlet 13, through the third inner tubes 12iii along multiple JPUs, before arriving at the pig receiver 26 mounted to the coupling device 20. From the pig receiver 26, it can be sent back along the same circuit. This allows the back and forth cleaning of the third inner tubes 12iii, which can be particularly suitable where the third inner tubes 12iii have accumulated more or harder scale when compared to the first and second inner tubes 12i, 12ii, and thus would require more time to clean.

[0055] The second circuit is along the first and second inner tubes 12i, 12ii. The pig sender 25 at the train outlet launches the pig through the first inner tube 12i such that it cleans the first inner tubes 12i of multiple interconnected JPUs. When the pig arrives at the coupling device, the looping conduit 40 curves the travel of the pig and sends it back through the mounting block and into the second inner tube 12ii. From the coupling device, the pig travels back along an opposite direction from where it came, and through the second inner tubes 12ii of the interconnected JPUs cleaning as it goes before arriving at the pig receiver 26 mounted to the second inner tube 12ii at the train outlet. If desired, the pig can be sent back through the second circuit in the reverse direction. Such a one-time pass cleaning may be suitable where the scale accumulated on the inner surfaces of the first and second inner tubes 12i, 12ii is softer than that in the third inner tubes 12iii.

[0056] It can thus be appreciated that the system 50 represented in Fig. 4C is a "one-third, two-third" system 50 in that it provides a dedicated pig sender 25 and pig receiver 26 to one of the three inner tubes 12i, 12ii, 12iii, while providing one pig sender 25 and one pig receiver 26 to the other two inner tubes 12i, 12ii, 12iii of the JPUs. This allows the third inner tubes 12iii to be cleaned simultaneously with the first and second inner tubes 12i, 12ii, which minimises and significantly reduces the down time of the train when compared to conventional mechanical treatments.

[0057] This reduction in down time can be explained by the fact the coupling device 20 only requires that one of the bends be removed from only one of the JPUs. By creating at least one circuit whereby the pig can be sent back and forth through the inner tubes of the system 50, the coupling device 20 significant reduces the labour (and thus the time) required to clean the inner tubes.

[0058] Figs. 5A to 5C show another system 150 for cleaning the inner tubes 12 of JPUs 1 1 of an existing bauxite digestion train 10. Each JPU 1 1 in the system 150 also has a first inner tube 12i, a second inner tube 12ii, and a third inner tube 12iii. The coupling device 20 is mounted to a free end of one of the JPUs 1 1 after the corresponding bend 15 has been removed. The coupling device 20 therefore has three corresponding openings defined in its mounting block. As can be seen in Fig. 5B, a pig sender 25 (or alternatively, a pig receiver 26) is mounted, optionally via an elongated conduit, to the free third opening of the coupling device 20. At the train outlet 14 or train inlet 13, a pig receiver 26 (or alternatively, a pig sender 25 depending on what is mounted to the coupling device 20) is mounted to the first inner tube 12i, which is not the same inner tube 12 that is in fluid communication with the third opening of the coupling device 20. The outlets of the second and third inner tubes 12ii, 12iii are linked together at the train outlet 14 or train inlet 13 with a jumpover spool or bend such that they are placed in serial flow communication.

[0059] This configuration of the system 150 is shown schematically in Fig. 5C. Such a configuration allows the pig to travel through the inner tubes 12i, 12ii, 12iii along a single circuit, as can be seen from the arrows. The circuit extends from the pig sender 25 mounted to the third opening of the coupling device, through the third inner tubes 12iii along multiple JPUs, before arriving at the train outlet. There, the pig is conveyed by the jumpover spool directly into the second inner tube 12ii at the train outlet, where it travels back through the JPUs and through the second inner tubes 12ii before arriving at the coupling device. When the pig arrives at the coupling device, the looping conduit 40 curves the travel of the pig and sends it back through the mounting block and into the first inner tube 12i. From the coupling device, the pig travels back along an opposite direction from where it came, and through the first inner tubes 12i cleaning as it goes before arriving at the pig receiver 26 mounted to the first inner tube 12i at the train outlet. If desired, the pig can be sent back through the same circuit in the reverse direction.

[0060] It can thus be appreciated that with relatively minimal effort, the system 150 and coupling device allow for the creation of a cleaning circuit which links all three inner tubes 12i, 12ii, 12iii in serial flow communication. Thus, the relatively quick removal of a bend and attachment of the coupling device, and the relatively quick installation of a jumpover spool linking the second and third inner tubes 12ii, 12iii, allow for all the inner tubes 12i, 12ii, 12iii to be linked as a single, continuous inner tube 12 requiring only one pig sender 25 and only one pig launcher 26. This significantly reduces the work required to clean the inner tubes 12i, 12ii, 12iii, and thus the downtime required.

[0061] Figs. 6A to 6D show yet another system 250 for cleaning the inner tubes 12 of JPUs 1 1 of an existing bauxite digestion train 10. Each JPU 1 1 in the system 250 also has a first inner tube 12i, a second inner tube 12ii, and a third inner tube 12iii. A first coupling device 20i is mounted to a free end of one of the JPUs 1 1 after the corresponding bend 15 has been removed. A second coupling device 20ii is mounted to the free end of another, separate JPU 1 1 after its bend 15 has been removed. Generally, but not exclusively, the second coupling device 20ii is mounted downstream of the first coupling device 20i, along the slurry flow direction 18.

[0062] Each coupling device 20i,20ii in this embodiment has three openings defined in their mounting blocks to correspond to the three inner tubes 12i, 12ii, 12iii of each JPU 1 1 . As can be seen in Fig. 6B, a pig sender 25 (or alternatively, a pig receiver 26) is mounted, optionally via an elongated conduit, to the free third opening of the second coupling device 20ii. A pig receiver 26 (or alternatively, a pig sender 25 depending on what is mounted to the second coupling device 20ii) is mounted to the free third opening of the first coupling device 20i, as shown in Fig. 6C. The pig sender 25 mounted to the second coupling device 20ii is in fluid communication with an inner tube that is not the same inner tube that is in fluid communication with the pig receiver 26 mounted to the first coupling device 20i. For example, the pig sender 25 can be in fluid communication with the first inner tube 12i, while the pig receiver 26 can be in fluid communication with the second inner tube 12ii.

[0063] This configuration of the system 250 is shown schematically in Fig. 6D. Such a configuration allows the pig to travel through the inner tubes 12i, 12ii, 12iii along a single circuit, as can be seen from the arrows. The circuit extends from the pig sender 25 mounted to the third opening of the second coupling device, through the first inner tubes 12i along multiple JPUs, before arriving at the first coupling device. When the pig arrives at the first coupling device, its looping conduit 40 curves the travel of the pig and sends it back through the mounting block and into the third inner tube 12iii. From the first coupling device 20i, the pig travels back along an opposite direction from where it came, and through the third inner tubes 12iii cleaning as it goes before arriving back at the second coupling devicen 20ii. When the pig arrives at the second coupling device, its looping conduit 40 curves the travel of the pig and sends it back through the mounting block and into the second inner tube 12ii. From the second coupling device 20ii, the pig travels back along an opposite direction from where it came, and through the second inner tube 12ii cleaning as it goes before arriving at the pig receiver 26 mounted to the third opening of the first coupling device 20i. If desired, the pig can be sent back through the same circuit in the reverse direction.

[0064] It can thus be appreciated that with relatively minimal effort, the system 250 with two coupling devices allow for the creation of a cleaning circuit which links all three inner tubes 12i, 12ii, 12iii. Thus, the relatively simple removal of two bends and the attachment of two coupling devices allow for all the inner tubes 12i, 12ii, 12iii to be linked as a single, continuous inner tube 12 requiring only one pig sender 25 and only one pig launcher 26. This significantly reduces the work required to clean the inner tubes 12i, 12ii, 12iii, and thus the downtime required.

[0065] Regardless of the system configuration used, the inner tubes of the JPUs can be cleaned in a significantly shorter amount of time, and with less cleaning equipment. Once so cleaned, there is an improved heat exchange between the heated fluid within the JPUs and the slurry carried by the inner tubes. Furthermore, the adaptability of the coupling device allows it to be mounted to any one of the JPUs. For example, it can be attached to any JPU where there is the hardest scale on the inner tubes to clean. Other, softer scale can be cleaned using hydro blasting or chemical treatments.

[0066] There is also disclosed a method for cleaning inner tubes extending in parallel through a jacketed pipes unit. The method includes the step of conveying, generally under pressure, a pig and pressurized fluid through a first inner tube of the JPU along a first direction to clean the first inner tube. The method also includes conveying the pig through a second inner tube of the JPU along a second direction to clean the second inner tube. Either one of these steps can include actively conveying the pig, or simply receiving it from another inner tube. The pig can be conveyed by using the pig sender described above.

[0067] The method also includes the step of connecting in serial flow communication the first and second inner tubes to convey the pig between the first and second inner tubes, or vice versa. This connection can be made by the using the looping conduit of the coupling device described above. The second direction is opposite to the first direction, such that the direction of the travel of the pig can be reversed within the same JPU. While being conveyed, the direction of travel of the pig can be curved about 180° between the first and second inner tubes.

[0068] Optionally, the method can include the step of conveying the pig through a third inner tube of the jacketed pipes unit to clean the third inner tube. This can be done with the elongated conduit discussed above. This step can include supplying the pig to the third inner tube from a first supply separate from a second supply of the pig conveyed between the first and second inner tubes. This can be achieved by using a pig sender which is distinct from the pig sender used for the first and second inner tubes.

[0069] Further optionally, the method can include the step of connecting in serial flow communication a third inner tube to an outlet of the second inner tube to convey the pig from the second inner tube to the third inner tube, thereby cleaning the third inner tube. This configuration is described and shown in Figs. 5A to 6D, and represents the linking of the inner tubes to form a single, continuous inner tube.

[0070] The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, although the embodiments disclosed herein are described as being used with a slurry derived from the processing of bauxite, it will be appreciated that the coupling device, system, and method can be used with other slurries, or with other solid-liquid mixtures requiring heating. In addition, the coupling device, system, and method disclosed herein can be used to convey objects other than a pig. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.