A boiler

Abstract

The present invention relates to a saltwater boiler that address or alleviates some of the issues associated with present methodologies in generating freshwater and / or electricity.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of water and / or electricity generation. Particularly, the present invention relates to a boiler. Most particularly, the present invention relates to a saltwater boiler. BACKGROUND TO THE INVENTION

[0002] Any reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in Australia or elsewhere.

[0003] Daily essential requirements in today’s environment include water, food and electricity. As the population of the world increases, water and electricity production needs to increase. However, in many situations, water, food and electricity are not readily available. In addition to this, water is also required in agriculture to grow crops for food and / or water for livestock. Water and electricity typically require significant machinery to produce.

[0004] This is particularly an issue in developing and regional areas as there is limited availability of fresh water and electricity. In places where saltwater is available, it may be possible to convert the saltwater to fresh water. In this regard, reverse osmosis or other conventional desalination methods (for instance, multi-stage flash (MSF) or multi-effect distillation (MED)) may be used to produce freshwater from saltwater. However, significant power or electrical needs are required for reverse osmosis.

[0005] It would be advantageous to address one or more of the above issues and / or to provide the consumer with a commercial alternative to the presently available solutions. SUMMARY OF THE INVENTION

[0006] In a first aspect, although it need not be the only or indeed the broadest aspect, the invention resides in a saltwater boiler comprising: a vessel having a top and a bottom, wherein the vessel further comprises a saltwater inlet adapted to provide saltwater, a steam outlet adapted to release steam, and a brine outlet adapted to remove concentrated salt solution; and a plurality of firetubes therethrough adapted to heat the saltwater in the vessel, wherein the plurality of firetubes are orientated latitudinally relative to the vessel.

[0007] In one embodiment, the plurality of firetubes form a tube stack.

[0008] In some embodiments, the vessel comprises a steam accumulator region, a boiling region and a brine concentrating region. In embodiments the steam accumulator region is located at or adjacent the top, the brine concentrating region is located at or adjacent the bottom, and the boiling region is located therebetween.

[0009] In certain embodiments, the boiling region comprises a working region and a nucleate boiling region, wherein the working region is adjacent the steam accumulation region and wherein the nucleate boiling region is adjacent the brine concentration region.

[0010] In embodiments, the steam outlet is a central vertical outlet. In an embodiment, the brine outlet is a central vertical outlet.

[0011] In one embodiment, the saltwater inlet is a horizontal inlet.

[0012] In an embodiment, the saltwater inlet is adapted to provide laminar flow of saltwater to the vessel.

[0013] In one embodiment, the saltwater inlet is adapted to provide crossflow relative to the plurality of firetubes.

[0014] In a particular embodiment, the saltwater inlet is adapted to provide saltwater at the same rate as steam and brine exiting the vessel.

[0015] In some embodiments, the plurality of firetubes are adapted to heat a medium therein to a temperature of about the nucleate boiling temperature of the medium.

[0016] In embodiments, the plurality of firetubes have a pitch of between 1.02 and 1.3.

[0017] In certain embodiments, the steam outlet comprises a turbine and / or steam superheater.

[0018] In one embodiment, the saltwater boiler when used in boiling saltwater. In embodiments, the saltwater boiler when used in generating electricity.

[0019] In a second aspect, the invention resides in a method of producing freshwater from saltwater comprising: providing a vessel having a steam outlet at a top thereof, a brine outlet at a bottom thereof, and a saltwater inlet at a middle thereof, wherein the vessel comprises a plurality of firetubes extending transverse or latitudinal relative thereto, heating fluid medium in the plurality of firetubes, to thereby produce freshwater from saltwater.

[0020] The saltwater boiler or vessel and components / features thereof may be as substantially described herein for the first aspect.

[0021] The various features and embodiments of the present invention referred to in the individual sections above and in the description which follows apply, as appropriate, to other sections, mutatis mutandis. Consequently, features specified in one section may be combined with features specified in other sections as appropriate.

[0022] Further features and advantages of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, embodiments of the invention will be described by way of example only with reference to the accompanying drawings, in which: FIG 1 shows an end elevation view of the present boiler; FIG 2 shows a side elevation view of the present boiler; FIG 3 shows the fluid flow in operating boilers; FIG 4 shows the boiling temperature range of the present boiler; FIG 5 shows indicative operating temperatures and outputs of systems containing the boiler; and FIG 6 shows heat from the heat source being passed through the system in a sequence of decreasing heat input requirements. DETAILED DESCRIPTION OF THE INVENTION

[0024] Embodiments of the present invention reside primarily in a boiler. Accordingly, the assembly, device, apparatus or method steps have been illustrated in the drawings, showing only those specific details that are necessary for understanding the embodiments of the present invention, but so as not to obscure the disclosure with excessive detail that will be readily apparent to those of ordinary skill in the art having the benefit of the present description.

[0025] In this specification, adjectives such as first and second, upper and lower, 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.

[0026] Words such as “comprises” or “includes” are intended to define a nonexclusive inclusion, such that an assembly, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed, including elements that are inherent to such an assembly, method, article, or apparatus.

[0027] As used herein, the term ‘about’ means the amount is nominally the number following the term ‘about’ but the actual amount may vary from this precise number to an unimportant degree.

[0028] As used here, the term ‘brine’ refers to water having salts therein. The term ‘brine’ is not limited to water having sodium chloride therein; rather, the term ‘brine’ encompasses water having salt and impurities therein. For instance, brackish water, bore water and / or aquifer falls within the scope of brine. The ‘brine’ as used herein in relation to the ‘brine outlet’ refers to a concentrated salt solution (that is, a solution with increased salt content).

[0029] The present invention is predicated on the finding that the present invention can be utilized to produce fresh water directly from saltwater. The present invention alleviates one or more of the issues mentioned hereinabove.

[0030] Shown in FIG 1 is an embodiment of a boiler. The boiler 100 comprises a vessel 110 having a top 110a and a bottom 110b. The vessel 110 further comprises a saltwater inlet 111 adapted to provide saltwater to the internal volume of the vessel 110. The vessel 110 further comprises a brine outlet 112 adapted to remove brine or concentrated salt solution from the internal volume of the vessel 110. The vessel 110 further comprises a steam outlet 113 adapted to facilitate removal of generated steam from the vessel 110.

[0031] It will be appreciated that the saltwater inlet may comprise a single saltwater inlet. Alternatively, the saltwater inlet may comprise a plurality of inlets. It will be appreciated that the saltwater inlet may suitably comprise a singular pipe, a plurality of pipes, a singular duct and / or a plurality of ducts.

[0032] The boiler 110 further comprises a plurality of firetubes 114 therethrough. The plurality of firetubes 114 is suitably a tube stack 114a. The firetubes 114 are adapted to facilitate movement of a heat medium therein, and transfer thermal energy from the heat medium to the saltwater in the vessel.

[0033] In a preferred embodiment, the plurality of firetubes are located transverse or horizontally relative to the vessel. The advantage of this orientation is that turbulent flow is minimized. The inventor believes that this results in an efficient arrangement for heat transfer. It is also postulated that this arrangement is more practical to design, fabricate, design and maintain and this leads to other commercial advantages.

[0034] The vessel 110 suitably comprises a number of regions. In an embodiment, the vessel 110 comprises a steam accumulator region S, a boiling region B and a brine concentrating region C. Preferably, the steam accumulator region S is located adjacent or at the top of the vessel 110. Preferably, the brine concentrating region C is located adjacent or at the bottom of the vessel 110. Preferably, the boiling region B is located between the steam accumulator region S and the brine concentrating region C. In one embodiment, the boiling region B comprises a working region W and a nucleate boiling region N. The working region W is located adjacent the steam accumulation region S. The nucleate boiling region N is located adjacent the brine concentrating region C.

[0035] The working region W is adapted to function to assist in the control of the boiling regime. The filled volume can vary with operational parameters and requirements. The nucleate boiling region N suitably contains the plurality of firetubes 114. The nucleate boiling region N is adapted to induce the liquid vapour phase change. As the saltwater is heated, the freshwater generates steam and rises. The steam rises to the steam accumulation region and the salt is left behind which falls or drops to the brine concentrating region.

[0036] Nucleate boiling refers to boiling that occurs when the surface temperature of a substrate (e.g., the firetube) is hotter / higher than the saturated fluid temperature by a certain amount but wherein the heat flux is below the critical heat flux. In one embodiment, the surface temperature of the firetube is at least 10eC, or at least 30eC higher than the boiling point of water. In an embodiment, the surface temperature of the firetube(s) is between about 10eC and 30eC higher than the boiling point of water. In one embodiment, the firetube(s) are adapted to heat to a temperature of at least 110eC, at least 130eC, or between about 110eC and 130eC. In one embodiment, these temperatures are at atmospheric temperature and pressure.

[0037] In one embodiment, the volume of the boiling region B to the brine concentrating region C should be a minimum of approximately 10:1.

[0038] In one embodiment, the brine outlet 112 is a vertical outlet located at or adjacent the bottom 110b. In one embodiment, the steam outlet 113 is a vertical outlet located at or adjacent the top 110a. In one embodiment, the saltwater inlet 111 is centrally located in the vessel. In an embodiment, the saltwater inlet is a horizontal inlet. In one embodiment, all saltwater inlets are centrally located in the vessel. In one embodiment, the boiler comprises a single saltwater inlet. Preferably, the saltwater inlet 111 is adapted to provide saltwater to the boiling region B. In a preferred embodiment, the saltwater inlet 111 is adapted to provide saltwater to the nucleate boiling region N. In a preferred embodiment, the tube stack 114a is located in the nucleate boiling region N.

[0039] The brine or salt concentrate is envisaged to be processed by a crystallizer and / or evaporator for salt collection. The removed water is envisaged to be fresh water that will be useful. Furthermore, the isolated salt can be reused or recycled for a number of uses in industry. Alternatively, the brine can be processed into salt via other methods (e.g. salt pans). The evaporator or crystallizer is envisaged to take up far less plant space than methods such as evaporative salt pans. Alternatively, the brine can be recycled back to the seawater input side and mixed with incoming seawater, increasing feed salinity, for a period, if required

[0040] In some embodiments, the steam outlet 113 is in fluid communication with a turbine (not shown). The steam outlet 113 may suitably comprise a valve which opens and closes fluid communication. In this regard, the valve may be utilized to increase the pressure prior to releasing the steam to generate electricity through the turbine. It is envisaged that the electricity produced may be utilized as a power source, used to power another water source (such as reverse osmosis), and / or reused for the present process in heating medium for the firetubes. Alternatively, such electricity could be stored for future use. In this regard, electricity may be stored in the form of a battery or the like.

[0041] Alternatively, or additionally, the steam outlet 113 may be connected to a condenser to capture fresh water. In an embodiment, the steam outlet 113 may be connected to a reservoir for collecting liquid fresh water.

[0042] In an embodiment, the saltwater inlet 111 is adapted to provide saltwater to the vessel in a laminar flow. In this regard, it is envisaged that the smooth fluid flow in regular paths results in more efficient heat transfer from the firetubes to the saltwater. In one embodiment, the pressure and flow through the inlet is by gravity, a pressure pump and / or valves. In an embodiment, the inlet and outlet is sized and dimensioned to minimize vortices / turbulent flow characteristics and to maximum laminar flow. In an embodiment, the inlet and outlet further comprise plates and / or screens to assist in producing laminar flow. Furthermore, it is envisaged that laminar flow also minimizes circulation, mixing and / or disruption between the saltwater and concentrate. In this regard, heat is directly transferred from the firetube to the saltwater which then rises; however, concentrated saline is envisaged to collect in the lower end of the vessel. The inventor envisages that this results in less heat being lost to the saline concentrate, and more being used to heat the saltwater to produce steam. Furthermore, the inventor also envisages that this will encourage salts to descend under gravity rather than being re-mixed with raw feed water. Another advantageous property of this aspect is that this alleviates scale build-up on the pipe surface and this indirectly leads to better thermal efficiency. As this occurs, the heated saltwater rises to the top and steam is formed. The laminar flow allows the concentrated saline and the heated saltwater to remain generally separate and unmixed. It is postulated that this alleviates the issue of unnecessary thermal energy loss.

[0043] Furthermore, the saltwater inlet 111 may further comprise a screen to assist in providing laminar flow. In an embodiment, the saltwater inlet 111 may further be adapted to provide crossflow relative to the plurality of firetubes. In an alternative embodiment, the saltwater inlet 111 may be adapted to provide parallel or counter-flow relative to the plurality of firetubes. This provides smooth and efficient energy transfer. In an embodiment, the plurality of firetubes are designed as a single pass.

[0044] In an embodiment, the saltwater inlet 111 is regulated by a valve. In one embodiment, the saltwater inlet is adapted to provide saltwater to the vessel at the same rate that steam and / or brine is exiting the vessel 110.

[0045] In one embodiment, the saltwater inlet is provided with a filter to remove particulate matter from the saltwater. In an embodiment, the filter may comprise mesh screen(s), sand filters, and catchment traps. It will be appreciated that essentially any filter can be utilized with the present invention and that the above merely exemplifies some of the examples of the filter. In one embodiment, the filter is located outside of the internal volume of the vessel. In an embodiment, the saltwater inlet is gravity fed into the vessel.

[0046] The term ‘firetube’ as used herein refers to a tube or pipe that runs through the vessel having a heated medium therein. The heated medium transfers thermal energy to the saltwater in the vessel through the tube or pipe. It will be appreciated that any heated medium can be utilized in this manner. It will also be appreciated that essentially any heating mechanism or source can be utilized. In this regard, the heating mechanism is not limited to combustion. In one embodiment, the thermal energy arises from solar. It will be appreciated that the term ‘firetube’ as used herein can be interchanged with the term ‘heating element’. It will be appreciated that any medium can essentially be utilized in the firetubes. Non-limiting examples include molten salt or oil.

[0047] In an embodiment, the vessel is cylindrical or trapezoid shaped. In one embodiment, the trapezoid shape is prismatic. In an embodiment, the vessel is spherical or cylindrical shape. In an embodiment, the vessel is a rectangular octagonal prism having substantially squared ends. In a preferred embodiment, the length is greater than its width and height such that it can be considered to lie in a horizontal position. It is postulated that the trapezoidal prismatic shape assists in accumulating steam in the steam accumulator region S.

[0048] It is envisaged that the thermal heat required by the firetubes can be provided by any means. As mentioned above, the thermal heat can be provided by solar power. The solar power may be provided from a solar power tower facility, parabolic trough and / or linear Fresnel array. It will be appreciated that combustion is not necessary to heat the present medium.

[0049] Alternatively, another renewable energy source may be utilized, such as geothermal energy. Batteries and the like may also be utilized. Thermal batteries may also be utilized for heat storage.

[0050] In one embodiment, the working fluid / heat transfer medium is contained within pipework of the firetube and travels within a closed loop. The medium is heated within the solar array and conveyed through the firetubes before being returned to the solar array for re-heating.

[0051] It is envisaged that the working fluid enters the internal volume of the vessel at or near the tube stack, at the nucleate boiling region N (e.g., at a temperature that will provide a nominal surface pipe surface temperature (at 1atm) of 120eC, and an excess temperature at the pipe surface of a nominal 20eC) and can exit at the opposing side of the vessel. The temperature of the pipe surface, and the pressure in the boiler will increase with increasing heat input until reaching set steady-state operating conditions.

[0052] Heat from the heat source is passed through the system in a sequence of decreasing heat input requirements (1 through 5, shown in Figure 6). The precise heat input requirements of each section outside of the boiler will be dependent on the systems implemented. Nominal temperatures have been indicated to illustrate the process. Within the nucleate boiling region of the boiler apparatus the surface temperature of the tube stack will be within the nucleate boiling temperature range, and below the critical flux temperature. Residual heat in the concentrate output may also be utilised elsewhere.

[0053] The tube stack may suitably comprise of a horizontal, square, inline configuration with a nominal tube pitch of at least 1.02, at least 1.30, or between 1.02 and 1.3. It is postulated that this pitch is an effective range of heat transfer. Preferably, an inline square configuration is utilized for fabrication and maintenance purposes. In one embodiment, each firetube has a diameter of between about 50mm and about 150mm, between about 75mm and about 125mm, between about 80mm and about 110mm, or between about 90mm and about 100mm. In an embodiment, each tube has a length of typically between about 1m and about 20m, between about 5m and about 15m, between about 6m and about 12m, about 6m, or about 12m.

[0054] In an embodiment, the boiler operates within the nucleate pool boiling regime where excess temperature (at the pipe surface) = Te (Te is evaporation temperature) and 10°C <Te<30°C. Primary convection effects occur directly within the boiler region defined by the dimensions of the tube stack / bundle. It is expected that the boiler will operate at modern boiler operating temperature and pressures which may reach pressures under operation of up to, circa, 4MPa, and temperatures ranging between 200eC<T<400eC.

[0055] In an embodiment, the present boiler is operated at a pressure of between about 0.5 atm and about 2 atm, between about 0.7 atm and about 1.5 atm, between about 0.8 atm and about 1.2 atm, or about 1 atm. In embodiments, the present boiler is operated at a temperature of at least 100eC, at least about 102sC, at least about 105eC, between about 100eC and about 150eC, between about 100eC and about 140eC, between about 100eC and about 120eC, between about 102sC and about 130eC, between about 102sC and about 120eC, or about 130eC.

[0056] As liquid seawater phase changes to water vapour it is no longer able to hold the dissolved mineral content (primarily NaCI). These minerals condense out of solution or suspension and fall to the brine accumulator under gravity while water vapour rises to the steam accumulator region. Example

[0057] In use, the boiler may be considered to comprise six (6) flow directions. 1. Heat enters from one end of the vessel through a firetube and exits the vessel on the other end; 2. Saltwater enters from the middle of the left and / or right sides of the vessel, centrally; 3. Steam exits from the top of the vessel; and 4. Concentrate exits from the bottom of the vessel.

[0058] Shown in FIG 3 is an embodiment of the flow of fluid in a conventional boiler and the present invention (labelled ‘SDS’). As shown, in conventional boilers, a blowdown is required to be removed from the boiler to avoid concentration of impurities during the continued evaporation of steam. In contrast, the present invention does not require this as impurities can be removed with the concentrated salt solution. Additionally, conventional boilers also have turbulent flow therein, whereas the present invention utilizes laminar flow therein such that the boiler is more energy efficient. In an embodiment, the present invention does not utilize baffles.

[0059] FIG 4 shows the boiling regime. In this regard, the present invention (SDS operational range) is within the nucleate boiling range. In contrast, typical boilers operate in the flash boiling range.

[0060] It will be appreciated by the person skilled in the art that the boiler may be fit with a steam superheater and / or a high pressure turbine to generate increased amounts of electricity. For instance, further thermal energy may be used to increase the pressure of the steam from a concentrated solar power tower.

[0061] For illustrative purposes, FIG 5 shows indicative operating temperatures and outputs of systems containing the boiler. In this regard, a number of different heat sources, condensers, turbines and processes can be utilized with the present boiler to improve the outputs thereof. It will be appreciated that a plurality of outcomes in relation to power to water generation can be achieved.

[0062] 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.

[0063] 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. Accordingly, this 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.

Claims

1. A saltwater boiler comprising:a vessel having a top and a bottom, wherein the vessel further comprises a saltwater inlet adapted to provide saltwater, a steam outlet adapted to release steam, and a brine outlet adapted to remove concentrated salt solution; anda plurality of firetubes therethrough adapted to heat the saltwater in the vessel, wherein the plurality of firetubes are orientated latitudinally relative to the vessel.

2. A method of producing freshwater from saltwater comprisingproviding a vessel having a steam outlet at a top thereof, a brine outlet at a bottom thereof, and a saltwater inlet at a middle thereof, wherein the vessel comprises a plurality of firetubes extending transverse or latitudinal relative thereto,heating fluid medium in the plurality of firetubes,to thereby produce freshwater from salt water.

3. The saltwater boiler of claim 1 or the method of claim 2, wherein the plurality of firetubes form a tube stack.

4. The saltwater boiler or the method of any one of the preceding claims, wherein vessel comprises a steam accumulator region, a boiling region and a brine concentrating region.

5. The saltwater boiler or the method of claim 4, wherein the steam accumulator region is located at or adjacent the top, the brine concentrating region is located at or adjacent the bottom, and the boiling region is located therebetween.

156. The saltwater boiler or the method of claim 5, wherein the boiling region comprises a working region and a nucleate boiling region, wherein the working region is adjacent the steam accumulation region and wherein the nucleate boiling region is adjacent the brine concentration region.

7. The saltwater boiler or the method of any one of the preceding claims, wherein the steam outlet is a central vertical outlet and / or wherein the brine outlet is a central vertical outlet.

8. The saltwater boiler or the method of any one of the preceding claims, wherein the saltwater inlet is a horizontal inlet.

9. The saltwater boiler or the method of any one of the preceding claims, wherein the saltwater inlet is adapted to provide laminar flow of saltwater to the vessel.

10. The saltwater boiler or the method of any one of the preceding claims, wherein the saltwater inlet is adapted to provide crossflow relative to the plurality of firetubes.

11. The saltwater boiler or the method of any one of the preceding claims, wherein the saltwater inlet is adapted to provide saltwater at the same rate as steam and brine exiting the vessel.

12. The saltwater boiler or the method of any one of the preceding claims, wherein the plurality of firetubes are adapted to heat a medium therein to a temperature of between about 10°C and about 30°C above the nucleate boiling temperature of the medium.

13. The saltwater boiler or the method of any one of the preceding claims, wherein the plurality of firetubes have a pitch of between 1.02 and 1.3.

14. The saltwater boiler or the method of any one of the preceding claims, wherein the outlet comprises a turbine and / or steam superheater.

15. The saltwater boiler or the method of any one of the preceding claims, when used to boil saltwater.

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