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Title:
A COOLING SYSTEM
Document Type and Number:
WIPO Patent Application WO/2017/156575
Kind Code:
A1
Abstract:
A cooling system including a first inlet assembly connected to a mixing assembly, the first inlet assembly including a vaporising pump configured to be connected to a first fluid source, and a second inlet assembly connected to the mixing assembly, the second inlet assembly configured to be connected to a second fluid source, wherein a first fluid is pumped by the vaporising pump from the first fluid source to the mixing assembly in order to be mixed with a second fluid from the second fluid source such that a mixture having a predetermined state is substantially achieved.

Inventors:
MCINTYRE, Jamie Peter (115 Riverside Place, MorningsideBrisbane, Queensland 4170, 4170, AU)
Application Number:
AU2017/050223
Publication Date:
September 21, 2017
Filing Date:
March 14, 2017
Export Citation:
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Assignee:
ENERMECH PTY LTD (115 Riverside Place, MorningsideBrisbane, Queensland 4170, 4170, AU)
International Classes:
B01D1/14; B01F3/04; F25B39/02
Foreign References:
US20070130964A12007-06-14
US4607489A1986-08-26
US3788825A1974-01-29
US4481780A1984-11-13
US5669235A1997-09-23
Other References:
GREEN, D. ET AL.: "Perry's Chemical Engineers", HANDBOOK, 2008, New York, pages 8.20 - 8.21, page 22.44, ISBN: 0-07-159313-6
Attorney, Agent or Firm:
FISHER ADAMS KELLY CALLINANS (Level 6, 175 Eagle StreetBrisbane, Queensland 4000, 4000, AU)
Download PDF:
Claims:
CLAIMS

1 . A cooling system, the system including:

a first inlet assembly connected to a mixing assembly, the first inlet assembly including a vaporising pump configured to be connected to a first fluid source;

a second inlet assembly connected to the mixing assembly, the second inlet assembly configured to be connected to a second fluid source, wherein a first fluid is pumped by the vaporising pump from the first fluid source to the mixing assembly in order to be mixed with a second fluid from the second fluid source such that a mixture having a predetermined state is substantially achieved.

2. The cooling system of claim 1 , wherein the first fluid is liquid nitrogen.

3. The cooling system of claim 2, wherein as the first fluid is pumped through the vaporising pump it is converted from liquid nitrogen to substantially gaseous nitrogen.

4. The cooling system of any one of the preceding claims, wherein the second fluid is liquid nitrogen.

5. The cooling system of claim 4, wherein, as the second fluid is mixed with the first fluid, the second fluid decreases the temperature of the first fluid.

6. The cooling system of claim 5, wherein, as the second fluid decreases the temperature of the first fluid, the second fluid is converted from liquid nitrogen to substantially gaseous nitrogen.

7. The cooling system of claim 6, wherein the first inlet assembly includes a flow sensor which is located downstream of the vaporising pump.

8. The cooling system of any one of the preceding claims, wherein the mixing assembly includes a nozzle which extends into a hollow body of the mixing assembly.

9. The cooling system of claim 8, wherein the nozzle includes a plurality of apertures.

10. The cooling system of claim 9, wherein the apertures form a first pattern and a second pattern, and wherein the apertures in the first pattern are offset to the apertures in the second pattern.

1 1 . The cooling system of any one of claims 8-10, wherein the nozzle is connected to a cryogenic flexible hose.

12. The cooling system of any one of claims 8-1 1 , wherein the nozzle is releasably connected to the hollow body.

13. The cooling system of any one of claims 8-12, wherein the hollow body is substantially cylindrical.

14. The cooling system of any one of claims 8-13, wherein the hollow body includes a straight section and a curved section, and wherein the curved section is between approximately 45 to 180 degrees.

15. The cooling system of any one of claims 8-14, wherein the mixing assembly includes one or more protrusions which extend across the hollow body and are connected thereto.

16. The cooling system of claim 15, wherein the one or more protrusions include two protrusions that are located at different locations along a longitudinal axis of the hollow body.

17. The cooling system of any one of claims 8-16, wherein the hollow body includes an outlet.

18. The cooling system of claim 17, wherein the cooling system further comprises an outlet assembly which is connected to the outlet of the hollow body.

19. The cooling system of claim 18, wherein the outlet assembly comprises an outlet fluid line and an exhaust fluid line.

20. The cooling system of claim 19, wherein the outlet assembly comprises one or more valves which are configured to divert flow between the outlet fluid line and the exhaust fluid line.

21 . The cooling system of any one of claims 1 -20, wherein the cooling system includes a controller.

22. The cooling system of claim 21 , wherein the first inlet assembly includes one or more valves.

23. The cooling system of claims 22, wherein the second inlet assembly includes one or more valves.

24. The cooling system of claim 23, wherein the controller is configured to control the vaporising pump and/or the one or more valves of the first inlet assembly and/or the second inlet assembly.

25. The cooling system of any one of claims 21 -24, wherein the first inlet assembly includes one or more pressure sensors and/or one or more temperature sensors.

26. The cooling system of claim 25, wherein the second inlet assembly includes one or more pressure sensors and/or one or more temperature sensors.

27. The cooling system of claim 26, wherein the mixing assembly includes one or more pressure sensors and/or one or more temperature sensors.

28. The cooling system of claim 27, wherein the controller is configured to receive an indication from the one or more temperature sensors, the one or more pressure sensor and/or the one or more flow sensors of the first inlet assembly, the second inlet assembly and/or the mixing assembly.

29. The cooling system of claim 28, wherein, in response to the controller receiving an indication that the mixture of the first fluid and the second fluid is not at the predetermined state, the controller is configured to adjust the vaporising pump and/or the one or more valves of the first inlet assembly, the second inlet assembly and/or one or more valves of the outlet assembly to substantially achieve the predetermined state.

30. The cooling system of any one of the preceding claims, wherein the second inlet assembly includes a main fluid line and a return fluid line.

31 . The cooling system of any one of the preceding claims, wherein the vaporising pump is configured to operate at different pumping speeds.

32. The cooling system of any one of the preceding claims, wherein the vaporising pump is a positive displacement pump and/or a centrifugal pump.

33. A method of cooling, the method comprising the steps of:

pumping a first fluid with a vaporising pump from a first fluid source to a mixing assembly;

delivering a second fluid from a second fluid source into the mixing assembly; and

allowing the first fluid to be mixed with the second fluid such that a mixture having a predetermined state is substantially achieved, wherein the first fluid substantially changes from a liquid to a gas as it moves through the vaporising pump and into the mixing assembly.

34. The method of claim 33, wherein the step of pumping the first fluid with the vaporising pump from the first fluid source to the mixing assembly includes measuring the flow of the first fluid.

35. The method of claim 33 or 34, wherein the step of delivering the second fluid from the second fluid source into the mixing assembly includes measuring the flow of the second fluid.

36. The method of any one of claims 33-35, wherein the step of delivering the second fluid from the second fluid source into the mixing assembly includes distributing the second fluid out of a nozzle.

37. The method of any one of claims 33-36, wherein the step of allowing the first fluid to be mixed with the second fluid such that the mixture having the predetermined state is substantially achieved includes measuring the state of the mixture.

38. The method of claim 37, wherein the step of measuring the state of the mixture includes measuring an associated temperature and/or pressure of the mixture.

39. The method of claim 38, wherein, in response to determining that the mixture has a state that is different to the predetermined state required, the method further includes the step of adjusting the flow of the first fluid and/or second fluid being delivered to the mixing assembly.

40. The method of claim 39, wherein the method further includes measuring the state of the mixture after it exits the mixing assembly in order to determine whether the mixture includes liquid nitrogen.

41 . The method of claim 40, wherein, in response to determining that liquid nitrogen is present in the mixture after exiting the mixing assembly, the method further includes diverting the mixture from an outlet fluid line to an exhaust fluid line.

42. The method of claim 41 , wherein, in response to stopping the flow of the first fluid and the second fluid into the mixing assembly, the method further includes exhausting the remaining mixture from an exhaust fluid line.

Description:
A COOLING SYSTEM

FIELD OF THE INVENTION

[0001 ] The invention relates to a cooling system. In particular, the invention relates, but is not limited, to a cooling system for an ethylene storage system.

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 in Australia or elsewhere.

[0003] Liquefied natural gas (LNG) is coal seam gas that has been converted into liquid form through cooling. As part of this cooling process, coal seam gas is typically cooled through an ethylene refrigeration system.

[0004] The use of ethylene as a refrigerant is expensive and, therefore, to improve efficiency and decrease costs, nitrogen is used as a medium to initially remove temperature from the ethylene refrigeration system.

[0005] To avoid damaging the ethylene refrigeration system, the nitrogen must cool down the system without liquid nitrogen being present. In order to avoid the presence of liquid nitrogen, nitrogen pumps have been used to vaporise liquid nitrogen. However, further improvements to this system will assist in ensuring that the flow cooling the system contains no liquid nitrogen and that the temperature of the nitrogen is maintained within a specific range in order to effectively cool the ethylene refrigeration system.

OBJECT OF THE INVENTION

[0006] It is an aim of this invention to provide a cooling 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 not necessarily the only or broadest form, the invention resides in a cooling system, the system including: a first inlet assembly connected to a mixing assembly, the first inlet assembly including a vaporising pump configured to be connected to a first fluid source; a second inlet assembly connected to the mixing assembly, the second inlet assembly configured to be connected to a second fluid source, wherein a first fluid is pumped by the vaporising pump from the first fluid source to the mixing assembly in order to be mixed with a second fluid from the second fluid source such that a mixture having a predetermined state is substantially achieved.

[0009] Preferably, the first fluid is liquid nitrogen.

[0010] Preferably, as the first fluid is pumped through the vaporising pump it is converted from liquid nitrogen to substantially gaseous nitrogen.

[001 1 ] Preferably, the second fluid is liquid nitrogen.

[0012] Preferably, as the second fluid is mixed with the first fluid, the second fluid decreases the temperature of the first fluid.

[0013] Preferably, as the second fluid decreases the temperature of the first fluid, the second fluid is converted from liquid nitrogen to substantially gaseous nitrogen.

[0014] Preferably, the vaporising pump is configured to operate at different pumping speeds.

[0015] Preferably, the vaporising pump is a positive displacement pump and/or a centrifugal pump.

[0016] Preferably, the first inlet assembly includes a flow sensor. Preferably, the flow sensor is located downstream of the vaporising pump. [0017] Preferably, the first inlet assembly includes one or more valves. Preferably, the one or more valves of the first inlet assembly include a ball valve.

[0018] Preferably, the first inlet assembly includes one or more pressure sensors and/or one or more temperature sensors.

[0019] Preferably, the second inlet assembly includes one or more valves. Preferably, the one or more valves of the second inlet system include one or more thermal relief valves, one or more check valves, one or more globe valves, one or more ball valves and/or one or more proportional control valves.

[0020] Preferably, the second inlet assembly includes a main fluid line and a return fluid line.

[0021 ] Preferably, the second inlet assembly includes one or more pressure sensors and/or one or more temperature sensors.

[0022] Preferably, the mixing assembly includes a nozzle. Preferably, the nozzle extends into a hollow body of the mixing assembly.

[0023] Preferably, the nozzle includes a plurality of apertures. Preferably, the apertures form a first pattern and a second pattern. Preferably, the apertures in the first pattern are offset to the apertures in the second pattern.

[0024] Preferably, the nozzle is connected to a cryogenic flexible hose.

[0025] Preferably, the nozzle is releaseably connected to the hollow body.

[0026] Preferably, the hollow body is substantially cylindrical.

[0027] Preferably, the hollow body includes a straight section and a curved section. Preferably, the curved section is between approximately 45 to 180 degrees.

[0028] Preferably, the mixing assembly includes one or more protrusions. Preferably, the one or more protrusions extend across the hollow body and are connected thereto.

[0029] Preferably, the one or more protrusions include two protrusions that are located at different location along a longitudinal axis of the hollow body.

[0030] Preferably, the mixing assembly includes one or more pressure sensors and/or one or more temperature sensors. [0031 ] Preferably, the hollow body includes an outlet.

[0032] Preferably, the system includes an outlet assembly. Preferably, the outlet assembly is connected to the outlet of the hollow body.

[0033] Preferably, the outlet assembly includes an outlet fluid line.

[0034] Preferably, the outlet assembly includes an exhaust fluid line.

[0035] Preferably, the outlet assembly includes one or more valves.

Preferably, the one or more valves of the outlet assembly are configured to divert flow between the outlet fluid line and the exhaust fluid line.

[0036] Preferably, the system includes a controller.

[0037] Preferably, the controller is configured to control the vaporising pump and/or the one or more valves of the first inlet assembly and/or the second inlet assembly.

[0038] Preferably, the controller is configured to receive an indication from the one or more temperature sensors, the one or more pressure sensor and/or the one or more flow sensors.

[0039] Preferably, in response to the controller receiving an indication that the mixture of the first fluid and the second fluid is not at the predetermined state, the controller is configured to adjust the vaporising pump and/or the one or more valves to substantially achieve the predetermined state.

[0040] In another form the invention resides in a method of cooling, the method including the steps of:

pumping a first fluid with a vaporising pump from a first fluid source to a mixing assembly; delivering a second fluid from a second fluid source into the mixing assembly; and allowing the first fluid to be mixed with the second fluid such that a mixture having a predetermined state is substantially achieved, wherein the first fluid substantially changes from a liquid to a gas as it moves through the vaporising pump and into the mixing assembly. [0041 ] Preferably, the step of pumping the first fluid with the vaporising pump from the first fluid source to the mixing assembly includes measuring the flow of the first fluid.

[0042] Preferably, the step of delivering the second fluid from the second fluid source into the mixing assembly includes measuring the flow of the second fluid.

[0043] Preferably, the step of delivering the second fluid from the second fluid source into the mixing assembly includes distributing the second fluid out of a nozzle. Preferably, the nozzle includes a plurality of apertures.

[0044] Preferably, the step of allowing the first fluid to be mixed with the second fluid such that the mixture having the predetermined state is substantially achieved includes measuring the state of the mixture.

[0045] Preferably, the step of measuring the state of the mixture includes measuring an associated temperature and/or pressure of the mixture.

[0046] Preferably, in response to determining that the mixture has a state that is different to the predetermined state required, the method further includes the step of adjusting the flow of the first fluid and/or second fluid being delivered to the mixing assembly.

[0047] Preferably, the method further includes measuring the state of the mixture after it exits the mixing assembly in order to determine whether the mixture includes liquid nitrogen.

[0048] Preferably, in response to determining that liquid nitrogen is present in the mixture after exiting the mixing assembly, the method further includes diverting the mixture from an outlet fluid line to an exhaust fluid line.

[0049] Preferably, in response to stopping the flow of the first fluid and the second fluid into the mixing assembly, the method further includes exhausting the remaining mixture from an exhaust fluid line.

[0050] Further features and advantages of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0051 ] 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 schematic of a cooling system, according to an embodiment of the invention;

Figure 2 illustrates a mixing assembly of the cooling system shown in figure 1 , connected between a first inlet assembly and an outlet assembly, according to an embodiment of the invention;

Figure 3 illustrates a nozzle of the cooling system shown in figure 1 , according to an embodiment of the invention;

Figure 4 illustrates a second inlet assembly of the cooling system shown in figure 1 , according to an embodiment of the invention ; and

Figure 5 illustrates a flow chart of a method of cooling, according to an embodiment of the invention, with reference to figure 1 .

DETAILED DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 illustrates a schematic of a cooling system 10, according to an embodiment of the invention. The cooling system 10 includes a first inlet assembly 100, a second inlet assembly 200, a mixing assembly 300, an outlet assembly 400 and a controller 500.

[0053] The first inlet assembly 100 includes a first fluid source 1 10, a vaporising pump 120, a valve assembly 130 and a sensor assembly 140. The first fluid source 1 10 includes a first fluid in the form of liquid nitrogen.

[0054] The vaporising pump 120 is connected downstream of the first fluid source 1 10. The vaporising pump 120 is configured to pump nitrogen from the first fluid source 1 10 to the mixing assembly 300. Moreover, as the vaporising pump 120 pumps nitrogen from the first fluid source 1 10 to the mixing assembly 300, the vaporising pump 120 assists in converting the nitrogen from liquid nitrogen, as present in the fluid source 1 10, to gaseous nitrogen. Substantially gaseous nitrogen is delivered into the mixing assembly 300 from the vaporising pump 120.

[0055] As shown further in figure 2, the valve assembly 130 of the first inlet assembly 100 includes a plurality of first ball valves 131 , denoted as 131 a and 131 b. A second ball valve 132 is located between the first ball valves 131 . The vaporising pump 120 is located downstream of the first ball valve 131 a. The vaporising pump 120 and first fluid source 1 10 is not shown in figure 2.

[0056] The sensor assembly 140 includes a flow meter 141 , a pressure sensor 142 and a temperature sensor 143. The flow meter 141 is configured to measure the quantity of nitrogen gas moving from the vaporising pump 120 into the mixing assembly 300. The pressure sensor 142 and temperature sensor 143 assist in monitoring the state of the gaseous nitrogen. By way of example, both sensors 142, 143 may assist in providing an indication on whether the nitrogen is in a gaseous state before entering into the mixing assembly 300. The first inlet assembly 100 is connected at an end of the mixing assembly 300, as further discussed below.

[0057] The second inlet assembly 200 includes a second fluid source 210, a valve assembly 230 and a sensor assembly 240. The second fluid source 210 contains pressurised liquid nitrogen. Downstream of the second fluid source 210 is the valve assembly 230 and the sensor assembly 240. The valve assembly 230 and the sensor assembly 240 are connected together via a main fluid line 215 and a return fluid line 216.

[0058] As shown further in figure 4, the valve assembly 230 includes a plurality of thermal relief valves 231 (denoted as 231 a, 231 b, 231 c, 231 d), a plurality of globe valves 232 (denoted as 232a, 232b, 232c, 232d), a plurality of one-way valves 233 (denoted as 233a, 233b), a vapour trap 234, and a proportional control valve 235. The thermal relief valves 231 a, 231 b are located along the main fluid line 215. Globe valve 232a and one-way valve 233a are located between the thermal relief valves 231 a, 231 b along the main fluid line 215. The proportional control valve 235, globe valve 232d and oneway valve 233b are located downstream from the thermal relief valve 231 b along the main fluid line 215.

[0059] The vapour trap 234 is connected between the main fluid line 215 and the return fluid line 216. Similarly, the globe valve 232c is connected between the main fluid line 215 and the return fluid line 216. The globe valve 232b, thermal valves 231 c, 231 d and proportional control valve 235 are located along the return fluid line 216.

[0060] The sensor assembly 240 includes a flow meter 241 , a pressure sensor 242 and a temperature sensor 243. The flow meter 241 is configured to measure the quantity of liquid nitrogen moving from the second fluid source 210 to the mixing assembly 300. The pressure sensor 142 and temperature sensor 143 assist in monitoring the state of the gaseous nitrogen. By way of example, both sensors 142, 143 may assist in providing an indication on whether the nitrogen is in a liquid state before entering into the mixing assembly 300. The second inlet assembly 200 is connected at an end of the mixing assembly 300, by a flexible (cryogenic) hose 250, as further outlined below.

[0061 ] The mixing assembly 300 includes a hollow body 310, a plurality of protrusions in the form of mixing plates 320 and a nozzle 330. The hollow body 310 includes a plurality of straight sections and a plurality of curved sections. In this embodiment, the straight sections and the curved sections form somewhat of an s-shape. The hollow body 31 0 includes the mixing plates 320 therein. In particular, the mixing plates 320 extend from an inner surface of the hollow body 310 towards the middle thereof. The mixing plates 320 extend transversely from the inner wall and are staggered along the hollow body 310. This takes the mixture of nitrogen through a non-linear path along the straight sections of the hollow body 310.

[0062] The nozzle 330 is connected to the flexible hose 250. The nozzle 330 is shown further in figure 3. The nozzle 330 includes an inlet connector 332 having an inlet flange 333. The inlet connector 332 is configured to be connected to the flexible hose 250. The inlet flange 333 is configured to be connected to a flange 312 that is connected to the hollow body 310.The inlet connector 332 is connected to an injector 334. The injector 334 includes a first set of apertures 336 and a second set of apertures 338. The first set of apertures 336 are spaced around the injector 334. The second set of apertures 338 are spaced around the injector at an offset position to the first set of apertures 336.

[0063] The outlet assembly 400 includes an outlet fluid line 410, an exhaust fluid line 420, a valve assembly 430 and a sensor assembly 440. Parts of the valve assembly 430 are either associated with the outlet fluid line 410 or exhaust fluid line 420. Similarly, parts of the sensor assembly 440 are either associated with the outlet fluid line 410 or exhaust fluid line 420. The outlet fluid line 410 is connected directly to the mixing assembly 300.

[0064] The valve assembly 430 includes a first ball valve 431 , a second ball valve 432 and safety valve 433. The first ball valve 431 is in the form of a short spindle auto ball valve. The first ball valve 431 is connected along the outlet fluid line 410. The second ball valve 432 is in the form of a long spindle auto ball valve. The second ball valve 432 is connected along the exhaust fluid line 420. The safety valve 433 is connected between the outlet fluid line 410 and exhaust fluid line 420 via a separate fluid line. The safety valve 433 is connected upstream of the first ball valve 431 , along the outlet fluid line 410, and downstream of the second ball valve 432, along the exhaust fluid line 420.

[0065] The controller 500 is in communication with the vaporising pump 120, the valve assemblies 130, 230, 430 and sensor assemblies 140, 240, 340, 440. Based on one or more indications associated with the sensor assemblies140, 240, 340, 440, the controller 500 is configured to determine the state of the mixture in and/or leaving the mixing assembly 300. That is, the controller 500 is configured to determine whether the mixture is in a liquid state, a gas state and/or at a predetermined state (or range) which has been specified. [0066] Typically, the controller 500 controls the vaporising pump 120 and the valve assemblies 130, 230 to achieve the predetermined state. In this embodiment, the predetermined state is where the gaseous nitrogen from the vaporising pump 120 is cooled by the liquid nitrogen, from the second fluid source 210, and the mixture as a whole forms a gas.

[0067] In response to the controller 500 determining that the mixture is not at the predetermined state (i.e. not a gas), the controller 500 is configured to control the vaporising pump 120 and/or the valve assemblies 130, 230, 430 to achieve the predetermined state. Furthermore, in the event that the controller 500 determines that liquid nitrogen is present in the mixture that may potentially leave the outlet fluid line 410, the controller is configured to divert the mixture to the exhaust fluid line 420. This process is further outlined in the method below.

[0068] Figure 5 illustrates a flow chart for a method 1000 of cooling, according to an embodiment of an invention, with reference to the cooling system 10 in figure 1 .

[0069] At step 1 100, the vaporising pump 120 begins pumping liquid nitrogen from the first fluid source 1 10. As the liquid nitrogen is pumped through the vaporising pump 120 it is substantially converted into gaseous nitrogen and is directed into the hollow body 31 0 of the mixing assembly 300. The flow sensor 141 detects the amount of gaseous nitrogen passing thereby. The pressure sensor 142 and the temperature sensor 143 assist in measuring the state of the nitrogen passing thereby.

[0070] At step 1200, which may occur concurrently with step 1 100, a quantity of liquid nitrogen is directed from the second fluid source 210, through the main fluid line 215 and into the nozzle 330. The liquid nitrogen is injected out of the apertures 336, 338 of the injector 334 into the hollow body 310. As the liquid nitrogen is injected into the hollow body 310, the gaseous nitrogen from the first inlet assembly 100 is cooled by the liquid nitrogen. This in turn results in the liquid nitrogen changing into gaseous nitrogen as heat is transferred to the liquid nitrogen, from the gaseous nitrogen, whilst an equilibrium is being reached.

[0071 ] At step 1300, the mixture between the gaseous nitrogen and liquid nitrogen turning into gaseous nitrogen travels through the hollow body 310. That is, the mixture travels past the mixing plates 320 which in turn generates turbulent flow. This assists in further mixing the gaseous nitrogen with the liquid nitrogen and turning the liquid nitrogen substantially into gaseous nitrogen. As the mixture moves through the hollow body 310, it turns substantially into gaseous nitrogen that is cooler than the gaseous nitrogen from the first inlet assembly 100.

[0072] At step 1400a, in response to the mixture achieving a predetermined state (i.e. the mixture is substantially in a gaseous state) as it travels from an outlet of the mixing assembly 300, the mixture is directed out of the outlet fluid line 410. Normally, the gaseous nitrogen mixture is directed towards an ethylene refrigeration system to provide cooling thereof.

[0073] In the alternative, at step 1400b, in response to the mixture being outside of a predetermined state (i.e. the mixture is not substantially in a gaseous state) as it travels from the outlet of the mixing assembly 300, the controller 500 is configured to divert the mixture through the exhaust fluid line 420. Furthermore, at this stage, the controller 500 may also divert liquid nitrogen through the return fluid line 216, via the valve assembly 230, so that further liquid nitrogen is not injected into the hollow body 310. Further nitrogen gas may however, be delivered to the hollow body 310 through step 1 1 00.

[0074] At step 1500, in response to the controller 500 receiving an indication to stop delivering nitrogen, the vaporising pump 120 is shut down and an associated valve of the valve assembly 230 is shut off to prevent flow through the main fluid line 215 and into the mixing assembly 300. The remaining nitrogen in mixing assembly 300 and upstream thereof is directed out of the exhaust fluid line 420. [0075] By cooling the gaseous vapour from the vaporising pump 120 with liquid nitrogen from the second fluid source 210, it is evident that the gaseous nitrogen delivered from the outlet fluid line 410 more readily cools downstream equipment in the form of, for example, the ethylene refrigeration system.

[0076] Furthermore, by monitoring the state of the nitrogen mixture, steps can be taken to avoid delivering liquid nitrogen to the downstream equipment, which may damage the equipment. By way of example, in response to detecting that liquid nitrogen is present in the mixture leaving the mixing assembly 300, the liquid nitrogen may be diverted to the exhaust fluid line 420.

[0077] The nozzle 330 provides an effective means to provide a flash of liquid nitrogen into the stream of gaseous nitrogen from the vaporising pump 120. Similarly, the mixing plates 320 assist in mixing the gaseous nitrogen with the liquid nitrogen by inducing turbulent flow therein.

[0078] 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.

[0079] 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.

[0080] 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.