FIELD OF THE INVENTION

[0001 ] The invention relates to a brine processing system. In particular, the invention relates, but is not limited, to a modular brine processing system comprising a plurality of demountable tanks configured to process brine in an environmentally safe manner.

BACKGROUND TO THE INVENTION

[0002] Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge.

[0003] Brine is often an undesirable by-product produced by various industrial processes. For example, in reverse osmosis (RO) water processing, salted water (e.g. sea water or water otherwise contaminated with salts such as in those produced during coal seam gas (CSG) production) is forced through a partially permeable membrane to separate unwanted ions and solids, such as salts, from the water. This results in clean water and a concentrated brine containing the unwanted solids. Such brine is generally considered to be a waste by-product that can pose a significant environmental risk and effective handling and treatment is required.

[0004] Particularly in CSG operations, the brine is transferred to an evaporation pond of dam where remaining water can be evaporated to further concentrate the brine to solids for disposal. Flowever, as the salt concentration increases the rate of evaporation decreases. This can result in the brine remaining as a brine which is difficult to dispose of effectively. Furthermore, the evaporation ponds often crust over, effectively preventing further evaporation of sludge and brine trapped underneath the crust.

[0005] These factors reduce the effective storage volume and evaporation ability of the evaporation pond requiring either removal of the unevaporated sludge and brine, which results in higher operational transport and/or disposal costs, or additional evaporation ponds to allow for a greater volume of brine to be stored and processed, which results in higher land requirements and/or capital costs. Additionally, in many cases the evaporation pond results in contamination rendering the land unsuitable for other uses, such as agriculture, in the future.

OBJECT OF THE INVENTION

[0006] It is an aim of this invention to provide a brine processing system which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.

[0007] Other preferred objects of the present invention will become apparent from the following description.

SUMMARY OF INVENTION

[0008] In one form, although it need not be the only or indeed the broadest form, there is provided a brine processing system comprising a plurality of demountable tanks, each demountable tank comprising a plurality of precast wall panels retained by a tensioning system to form a continuous wall, wherein the plurality of tanks are fluidly connected in a series such that brine inlet into a first of the plurality of demountable tanks flows, through the series, to a last of the plurality of demountable tanks.

[0009] Preferably there are at least three demountable tanks connected in series. Even more preferably there are between five and ten demountable tanks connected in series. Each demountable tank may have a maximum capacity of between 10 megalitres and 100 megalitres. The plurality of demountable tanks may have a black wall.

[0010] Each demountable tank may comprise a tank liner. Each demountable tank may comprise a leak detection system. The leak detection system may comprise a leak detection liner located between the tank liner and the tank walls and floor. The leak detection liner may comprise an outlet fluidly connected to a leak detection sump. The leak detection sump may comprise an internal sump and an external sump. The leak detection liner may comprise a communication device to transmit a signal if liquid is detected in a sump.

[0011 ] The wall panels may be made of a cementitious material. The wall panels may comprise precast concrete panels. The wall panels may be substantially planar. The wall panels may be rectangular. The wall panels may have side walls at a transverse angle to the plane of the panel. The side walls may be angled from 0° to 5° relative to the orthogonal axis of the plane of the panel. Adjacent wall panels of the continuous wall may directly abut each other. The wall panels may have at least one channel that receives the tensioning system. The continuous wall is preferably circular or, at least, substantially circular. In a preferred form there are between 20 and 500 wall panels. The wall panels may be between 1 and 5 metres high, even more preferably between 2 and 4 metres high, and in a preferred form of around 3 metres high.

[0012] The tensioning system may comprise a cable tensioning system. The cable tensioning system may comprise at least one cable extending around a plurality of the wall panels. The cable may be external to the wall panels, may be internal to the wall panels, or partially external and partially internal to the wall panels. The cable tensioning system may comprise a cable anchor at least one end of the cable. The cable tensioning system may comprise a cable anchor at each end of the cable. The tensioning system may comprise a single cable tensioning system extending the perimeter of the continuous wall. The cable tensioning system may comprise a plurality of cables each extending around a portion of the perimeter of the continuous wall. The continuous wall preferably has no support structures, such as buttresses, extending radially or perpendicularly to the wall panels.

[0013] The plurality of demountable tanks are preferably fluidly connected such that brine flows through the series by gravity. One or more pumps may be provided to convey the brine through at least a portion of the plurality of demountable tanks. The salinity concentration of the brine may increase as it flows along the series due to evaporation in the tanks. The last of the plurality of demountable tanks may be saturated. The salts may be concentrated out of the brine through crystallisation. The brine processing system may further comprise one or more crystallisers that receive concentrated brine from the last of the plurality of demountable tanks. The crystalliser may be configured to allow harvesting of salt solids from the concentrated brine. The crystalliser may comprise a demountable crystallisation tank. A buffer brine storage may be provided before the first of the series of demountable tanks.

[0014] In another form, there may be provided a method of processing brine comprising: constructing a plurality of demountable tanks at a site by: erecting a plurality of precast wall panels to form a continuous wall for each demountable tank; tightening a tensioning system to hold the plurality of wall panels in an interference fit; applying a liner to the walls and floor of each demountable tank; fluidly connecting the plurality of demountable tanks in a series; inputting a brine liquid into the first demountable tank in the series; flowing the brine liquid from the first demountable tank in the series to the last demountable tank in the series such that salt concentration increases over the series though evaporation; transferring concentrated brine from the last demountable tank in the series to one or more crystallisers; and harvesting salt solids from the one or more crystallisers.

[0015] The method preferably utilises the hereinbefore described brine processing system.

[0016] Fluid flow through the demountable tanks in the series may be due to gravity and/or a pump. The brine flow may be continuous. The brine is preferably concentrated through fractional crystallisation. The salt solids harvested from the crystalliser may be transported for stockpiling and/or disposal. [0017] The step of constructing a plurality of demountable tanks at a site may comprise levelling a ground surface to form a floor. The floor may be earthen. The method may comprise creating a pad for the floor. The method may comprise creating a concrete pad. The method may comprise supporting the plurality of precast wall panels with temporary supports until the tensioning system is tightened to hold the wall panels in the interference fit.

[0018] Further features and advantages of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures, wherein:

Figure 1 illustrates a plan schematic of a series of demountable tanks; Figure 2 illustrates a side elevation schematic of a series of demountable tanks;

Figure 3 illustrates a plan schematic of a brine processing system;

Figure 4 illustrates a perspective view of a demountable tank;

Figure 5 illustrates a cross sectional view of adjacent wall panels of the demountable tank;

Figure 6 illustrates a diagrammatic cross-sectional view of a leak detection system of a demountable tank; and

Figure 7 illustrates a graph showing an estimated brine processing system capacity over an 11 year project.

DETAILED DESCRIPTION OF THE DRAWINGS

[0020] Figures 1 and 2 illustrate schematic views of a series of seven demountable tanks 100 fluidly connected in series from a first tank 100A to a last tank 100G. Brine can be fed into the first tank 100A via inlet 104 where it can slowly traverse the series of tanks, typically by gravity or pump feed, until it arrives at the last tank 100G. The last tank 100G may be a crystallisation tank configured to crystallise salt solids in concentrated brine. Due to evaporation, salt concentration increases along the series. With the 7 tank embodiment illustrated in figures 1 and 2, target salt concentrations are 3% for tank 100A, 8% for tank 100B, 13% for tank 100C, 18% for tank 100D, 21% for tank 100E, and 23% for tank 10OF. The last tank 10OF is for crystallisation and harvesting of salt solids.

[0021 ] Figure 3 illustrates a brine processing system having a brine source 10 such as a Coal Seam Gas (CSG) production process or a desalination plant. The brine is fed into a deep buffer brine storage 12 as needed. Brine can be drawn from the buffer brine storage 12 into a plurality of demountable tanks 14. As the brine traverses the series of demountable tanks 14 its concentration increases, through evaporation, preferably until the brine is saturated. The concentrated brine is then fed to a crystalliser 16 where crystallised salt solids are harvested and transferred, for example by truck, to a stockpile 18 which is preferably covered to reduce saline runoff. The salt solids can drain in the stockpile 18 before being transported, for example by truck, to a disposal location such as a dry landfill cell 20. Any losses 22 from the processing

[0022] The buffer is primarily used to balance variability in brine being fed from the source 10 to a continuous stream being supplied to the plurality of demountable tanks 14. The demountable tanks 14, connected in series, comprise a plurality of demountable tanks 100 with increasing density. It is expected that the demountable tanks 14 will produce 330g/L saturated brine from a brine of, for example, 30-40g/L.

[0023] Figure 4 illustrates a demountable tank 100 during construction with optional temporary supports 102. The tank 100 is substantially circular comprising a plurality of precast wall panels 110 arranged adjacent one another. The panels 110 are planar such that each forms a circle segment. In the illustrated tank 100 there are approximately 200 wall panels 110. Once the wall of the tank 100 has been erected and retained by a tensioning system the temporary supports 102 can be removed and the tank 100 should be self standing. The floor 140 of the tank 100 may be an earthen or manufactured (e.g. concrete) pad. The pay may be concave or dished as illustrated in figure 6.

[0024] As shown in figure 5, the wall panels 110 have side walls 1 12 that are at a transverse angle, preferably between 0° and 5° to an orthogonal axis of the plane of the panels 110. The wall panels 1 10 also have a channel 114 configured to receive a cable from a cable tensioning system. The tensioning cable (not shown) is passed through the channels 114 of adjacent wall panels 110 and tensioned at cable anchors 120 in selected wall panels 110. A plurality of tensioning cables, anchored by a plurality of cable anchors 120, may be provided to extend around the continuous wall.

[0025] The angled side walls 112 allow the wall panels 110 to abut each other and provide support in a ‘keystone’ manner such that they cannot fall inward. The cable tensioning system retains the wall panels 110 in such an arrangement and provide support such that the wall panels cannot fall outward. In use, radial forces from liquid 20 contained therein provides a radial force against the wall panels 110. The tensioning system must therefore be of sufficient strength to not just hold the wall panels 110 in place in a freestanding manner, but also to be able to withstand the radial forces caused by brine contained in the tank 100.

[0026] T o construct the demountable tanks 100, a suitable site is preferably first determined. The site may be prepared first, such as by levelling a ground surface and/or creating a pad to form a floor of the tank 100. One a suitable ground surface has been determined, a plurality of precast wall panels 110 can be erected to form a continuous wall 100. Temporary supports 102 may be utilised to support the wall panels 110 during construction. A tensioning system is then applied to the wall panels 110 and tightened to old the wall panels 110 in an interference fit.

[0027] Figure 6 illustrates a liner and leak detection system comprising a first liner 150, a geonet layer 152, a leak detection liner 154, and a cushioning layer which may be in the form of a geotextile 156. An internal sump 158 is fluidly connected to the leak detection liner 154 which is in turn fluidly connected to an external sump 160 having a communication system 162 to transmit a signal indicating detection of a leak. The sumps 158, 160 may also have a pump (not shown) to return leaked fluid back into tank 100. In the event of a leak in the first liner 150, fluid enters a geonet cavity formed by the geonet layer 152 and is caught by the leak detection layer whereby it can flow into the sump and back into the tank 100 as illustrated by the arrows. Water from the internal sump is preferably gravity fed to the external sump which can activate a pump, preferably a solar pump, to return water to the tank 100.

[0028] Figure 7 illustrates a graph showing an estimated brine processing system capacity over an 11 year project. Line 300 tracks total capacity of the demountable tanks 100. Histogram lines 310 track estimated brine output from a brine source, such as a CSG operation. Line 320 tracks the ratio which is effectively a utilisation of installed capacity. As the tanks 100 are constructed the capacity increases rapidly at the beginning of the project. As can be seen, each tank 100 can start receiving brine as soon as constructed with additional tanks 100 added at later dates as need arises. Furthermore, as brine supply reduces from the source, tanks 100 can start being decommissioned in a modular manner to maintain a suitable utilisation.

[0029] In use, the crystallisation tank is given a salt floor of predetermined depth (e.g. 200mm). This salt floor protects the liners. Drains can be cut into the salt to allow bitterns to drain to a sump for removal. When salt is harvested from the crystallisation tank, the dept can be controlled to retain the salt floor. The harvest depth is preferably controlled using GPS for this purpose. Depth gauges, preferably in the form of visual indicators, such as fluorescent markers, may be provided to indicate depth during harvest. For the 11 year project it is estimated that 1 gigalitre of water will be managed with 25-30 kt of salt and solids being harvested, for safe disposal, in this manner.

[0030] Advantageously, the brine processing system can be constructed quickly and relatively cost effectively at a site in a modular and adaptable manner. It can be a temporary or permanent installation with tank casting performed off-site. As processing requirements change the number of tanks, and hence processing capacity, can be increased or decreased incrementally. This assists with spreading capital expenditure over the life of a project.

[0031] Furthermore, by utilising a plurality of tanks brine evaporation is improved. For example, brine evaporated to crystallisation in two equal surface area tanks with two density stages run in series is around 20% more efficient than a single equivalent sized tank. The improvement is largely due to lower average salinity for a given tank size which increases evaporation. With tanks the brine is safely contained with no seepage as often occurs with evaporation ponds or dams. The tanks can also have black walls to increase incident radiation and increases in the temperature of brine contained therein to further improve evaporation.

[0032] The brine processing system provides a low operational cost, low C02 emission facility with lower upfront capital costs and often lower total capital costs. The tanks can also be decommissioned and relocated, for re use, at completion to allow return of the land to other uses such as, for example, agriculture.

[0033] It should be appreciated that saline liquids with a lower concentration of salts than may technically be considered a brine could be processed and no limitation is meant thereby. For example, brine may be considered to have a salinity level of at least a 5%, but the invention could well be utilised with liquids having lower concentrations such as 2% or 3%. It should also be appreciated that a series of tanks could comprise one or more tanks fluidly connected in parallel as well.

[0034] In this specification, adjectives such as first and second, left and right, top and bottom, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Where the context permits, reference to an integer or a component or step (or the like) is not to be interpreted as being limited to only one of that integer, component, or step, but rather could be one or more of that integer, component, or step etc.

[0035] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The invention is intended to embrace all alternatives, modifications, and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

[0036] As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or operations, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0037] In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.