METHOD AND APPARATUS FOR COOLING HYDROGEN

Abstract

The invention relates to a method for cooling hydrogen, in which method liquefied natural gas is heated by indirect heat exchange in a first heat exchanger with an intermediate fluid flow, the intermediate fluid flow is cooled, a hydrogen gas flow is cooled in a second heat exchanger without being condensed, and a gas flow derived from the cooled intermediate fluid is heated in a second heat exchanger to a temperature of between 150 C. and 90 C., which gas flow is withdrawn from the second heat exchanger at said temperature and compressed in a compressor with an inlet temperature of between 150 C. and 90 C.

Claims

1-15. (canceled)

16. A method for cooling hydrogen, wherein i) heating either a liquefied natural gas or a vaporized natural gas, the vaporized natural gas being at a temperature lower than 50 C., to a temperature higher than 0 C. by indirect heat exchange in a first heat exchanger with a flow of intermediate fluid at a pressure of between 3 and 70 bar abs if the intermediate fluid is not nitrogen and between 3 and 25 bar if the intermediate fluid is nitrogen which is cooled down to a temperature higher than or equal to 145 C.; ii) cooling the flow of intermediate fluid at a first temperature higher than or equal to 145 C.: a) by introducing the flow of intermediate fluid at said first temperature into a second heat exchanger where the flow of intermediate fluid is cooled by indirect heat exchange, and/or b) by expansion in a turbine optionally driving a compressor of the method, or a valve; iii) cooling a flow of gaseous hydrogen in the second heat exchanger without condensing, iv) heating a gaseous flow derived from the intermediate fluid cooled in step a) and/or b) in the second heat exchanger to a second temperature of between 150 C. and 90 C., and then withdrawing the gaseous flow from the second heat exchanger at said second temperature and then compressing the gaseous flow in a compressor to form a compressed intermediate fluid, wherein the compressor has an inlet temperature of between 150 C. and 90 C., wherein at least one part of the compressed intermediate fluid is cooled first in the first heat exchanger and then heated from a temperature of at most 110 C.; and v) at least one part of the heated intermediate fluid constitutes the flow of intermediate fluid of step i), wherein the at least one part of the compressed intermediate fluid, cooled first in the first heat exchanger, is then heated in the second heat exchanger from the temperature of at most-110 C. so as to constitute the flow of intermediate fluid of step i).

17. The method as claimed in claim 16, wherein the maximum temperature difference between countercurrent fluids in the first exchanger is lower than 25 C., preferably lower than 20 C., or even lower than 15 C.

18. The method as claimed in claim 16, wherein the intermediate fluid contains more than 50 mol % nitrogen, preferably at least 90 mol % nitrogen or even at least 99 mol % nitrogen.

19. The method as claimed in claim 16, wherein liquefied natural gas is vaporized in the first heat exchanger and heated there up to a temperature higher than 0 C.

20. The method as claimed in claim 16, wherein the flow of gaseous hydrogen cooled in the second heat exchanger condenses in another heat exchanger following cooling down to its liquefaction temperature.

21. The method as claimed in claim 16, wherein vaporized liquefied natural gas or natural gas heated in the first heat exchanger is sent to a conversion unit to be converted into hydrogen.

22. The method as claimed in claim 16, wherein for start-up the liquefied natural gas is vaporized in a heat exchanger by heat exchange with water, for example seawater.

23. The method as claimed in claim 16, wherein a part of the compressed intermediate fluid is cooled first in the first heat exchanger down to an intermediate temperature of the first heat exchanger, for example between 40 C. and 90 C., preferably between 45 C. and 70 C., and is sent to cool an auxiliary heat exchanger and then is sent after being heated in the auxiliary heat exchanger to be cooled in the first heat exchanger.

24. The method as claimed in claim 23, wherein the auxiliary heat exchanger serves to cool a flow of gas containing carbon dioxide and at least one other component in an apparatus for separating and/or liquefying carbon dioxide.

25. The method as claimed in claim 23, wherein the part of the compressed intermediate fluid is heated with heating means connected in parallel with the auxiliary heat exchanger.

26. The method as claimed in claim 16, wherein a part of the cold generated by liquefied natural gas or vaporized natural gas serves to cool cooling water of a compressor of the method and/or to cool the flow of gaseous hydrogen upstream of a drying step and/or of the second heat exchanger.

27. The method as claimed in claim 16, wherein the flow of gaseous hydrogen cooled in step iii) is then liquefied by heat exchange with a refrigeration cycle.

28. An apparatus for cooling hydrogen, the apparatus comprising: a source of natural gas in either liquid or gaseous form, wherein the gaseous natural gas is at a temperature lower than 50 C.; a first heat exchanger in fluid communication with the source of natural gas, wherein the first heat exchanger is configured to heat the natural gas to a temperature higher than 0 C. by indirect heat exchange; a second heat exchanger configured to cool a flow of gaseous hydrogen without condensing; a compressor; means for sending a flow of intermediate fluid at a pressure of between 3 and 70 bar abs if the intermediate fluid is not nitrogen and between 3 and 25 bar if the intermediate fluid is nitrogen to be cooled in the first heat exchanger down to a temperature higher than or equal to 145 C.; means for sending the flow of intermediate fluid at a first temperature higher than or equal to 145 C. to be cooled: a) by introducing the flow of intermediate fluid at said first temperature into the second heat exchanger where the flow of intermediate fluid is cooled by indirect heat exchange, and/or b) by expanding the flow of intermediate fluid in valve or a turbine, wherein the turbine is optionally configured to drive the compressor; means for sending a gaseous flow derived from the intermediate fluid cooled in step a) and/or b) to be heated in the second heat exchanger up to a second temperature of between 150 C. and 90 C.; means for withdrawing the gaseous flow from the second heat exchanger at said second temperature; means for sending the withdrawn gaseous flow to the compressor with an inlet temperature of between 150 C. and 90 C. to be compressed; means for sending at least one part of the compressed intermediate fluid to be cooled first in the first heat exchanger; and means for sending the at least one part of the cooled intermediate fluid into the first exchanger, to be heated from a temperature of at most 110 C., at least one part of the heated intermediate fluid constituting the flow of intermediate fluid, wherein the means for sending the at least one part of the intermediate fluid to be heated are connected so that the at least one part is heated in the second heat exchanger from the temperature of at most 110 C. so as to constitute the flow of intermediate fluid.

29. The apparatus as claimed in claim 28, further comprising the turbine and a phase separator configured to separate a fluid coming from the turbine, the gaseous flow being the overhead gas and/or the vaporized liquid from the separator.

30. The apparatus as claimed in claim 28, further means for liquefying the hydrogen cooled in the cooling apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

[0051] FIG. 1 illustrates a liquefaction method according to the invention.

[0052] FIG. 2 illustrates another liquefaction method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0053] A dedicated heat exchanger E1 serves to recover the cold energy from the liquefied natural gas 1 at 150 C. using an intermediate fluid that is cooled by the liquid 1 in the exchanger E1. The exchanger E1 may be a brazed plate and fin exchanger made of stainless steel or of steel. Otherwise, the exchanger E1 may be a shell and tube exchanger.

[0054] The liquid 1 is heated, for example up to 15 C., and optionally vaporized so as to cool the fluid 5 down to a temperature lower than 50 C., preferably lower than 120 C. In the example it is cooled down to 140 C.

[0055] The gas 1 enters at the cold end of the exchanger E1 and leaves at the hot end as fluid 3.

[0056] In the example, the fluid 5 is nitrogen. It may, for example, be natural gas or methane. Preferably, the fluid 5 is inert. The fluid 5 is preferably at a pressure of between 3 and 70 bar abs if the intermediate fluid is not nitrogen and between 3 and 25 bar if the intermediate fluid is nitrogen.

[0057] The nitrogen 13 leaves the exchanger E2 at a temperature lower than 90 C., for example at 120 C., or even between 150 C. and 110 C., and is compressed in a compressor C, for example a centrifugal compressor, to approximately 20 bar. Then the nitrogen at 20 bar is optionally divided into two parts 15, 17, the part 17 not necessarily being present. The part 17 may be cooled partially in the exchanger E1 and then is sent to an element to be cooled 31. Thus the heated part 19 is sent to the hot end of the exchanger E1. The part 15, 21 is sent at 20 C. to the hot end of the exchanger E1 and is cooled there down to 140 C. forming a gas 5 that is sent to the exchanger E2 at a temperature of 140 C., therefore colder than the temperature at which the gas 13 is withdrawn from the exchanger E2. The gas 5 is heated in the exchanger E2 up to 20 C. and then is cooled against the LNG in the exchanger E1. The cooled gas at 140 C. is sent to be cooled, in this example first by passing into the exchanger E2 and then by expansion in a turbine T having an inlet temperature lower than 100 C., for example 120 C. The expanded fluid 7 at 1.5 bar in the turbine T is two-phase and is sent to a phase separator where it forms a liquid 9 and a gas 11. The liquid is vaporized in a heat exchanger E3 and joins the gas 11 so as to be heated in the exchanger E2 constituting the flow 13 to be sent to the cold compressor C. The flow 13 may be constituted by the vaporized liquid 9 and/or the gas 11.

[0058] Thus the nitrogen, or another fluid, for example helium or a mixed refrigerant, circulates in a closed cycle, taking cold energy from the LNG.

[0059] The gaseous hydrogen 23 at ambient temperature, for example 20 C., enters at the hot end of the heat exchanger E2 that it passes through from one end to the other so as to be cooled down to 180 C. It is then cooled in the heat exchanger E3 against the liquid of the phase separator so as to form gaseous hydrogen 25 at 190 C.

[0060] The hydrogen 25 is then cooled and liquefied in another heat exchanger in a known manner. A cycle of hydrogen, helium or mixed refrigerants optionally including rare gases provides the necessary cold energy.

[0061] Thus the LNG provides at least a part of the cold energy necessary for the precooling of the gaseous hydrogen down to 190 C. This fraction may be at least 50%, at least 75%, or at least 99% of the cold energy necessary for the cooling of the gaseous hydrogen down to 190 C. The LNG may even provide all the necessary cold energy apart from that coming from the turbine T.

[0062] During start-up of the apparatus, the LNG may be vaporized in an independent vaporizer, for example of the Open Rack Vaporizer type, by heat exchange with water, optionally seawater. This vaporizer comprises a series of vertical tubes in which the LNG that is vaporized circulates, the water running over the outside of the tubes. Other types of exchanger can obviously be envisaged.

[0063] The method may also provide cold to another element 31, cooled by the cycle. In the figure, it can be seen that a part 17 of the gas compressed in the compressor C is cooled in the heat exchanger down to an intermediate temperature, in this case 50 C., is withdrawn from the exchanger in a central zone of the heat exchanger and serves to cool the element 31 by being itself heated to form the gas 19 that joins the flow 15 compressed in the compressor C so as to form the flow 21 that enters the exchanger E1 at 20 C. As the pressure drops for the flow 18, 19 are limited, a small expansion of the flow 15 in a valve will be sufficient to allow the flows 15, 19 to mix.

[0064] The element 31 may for example be a liquefier for another gas or an apparatus for separation by distillation and/or partial condensation at a temperature lower than 0 C., for example a carbon dioxide liquefier.

[0065] If the fraction 17 is present but the element 31 is not in operation, a heater, for example an electric heater or a heat exchanger heated with hot water, will serve to heat the fraction 17 so as to form the flow 19.

[0066] FIG. 2 shows a variant of [FIG. 1] in which the gas 5 is not cooled in the exchanger E2 but only in the turbine E. Thus the gas 5 enters the turbine E at the temperature at which it leaves the heat exchanger E1. The gas 13 is compressed in the cold compressor 1 and then in a booster CI coupled to the turbine E. It is the gas compressed in the booster CI that is sent to the exchanger E1 so as to recover cold from the LNG 1.

[0067] The natural gas 3 produced may be sent to a hydrocarbon conversion unit to be converted and/or as fuel. The unit may be of the POX, ATR or SMR type.

[0068] The hydrogen to be liquefied can obviously come from this unit.

[0069] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0070] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0071] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of comprising). Comprising as used herein may be replaced by the more limited transitional terms consisting essentially of and consisting of unless otherwise indicated herein.

[0072] Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0073] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0074] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0075] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.