Method and apparatus to compress hydrogen gas with vapor control

Abstract

A method and apparatus for compressing gaseous hydrogen or other gases utilize a liquid compressor to achieve high pressure while controlling vapor content. Gaseous hydrogen from a source at an inlet pressure is compressed in a liquid compression chamber using an incompressible liquid, preferably water or a water-based liquid, to a predetermined pressure at which vapor in the compressed gas is below the required concentration level for applications. The compressed gas flows into a high-pressure gas chamber, where it is isolated from the compression liquid once the predetermined pressure is reached, ensuring the vapor content remains below a specified threshold. The compressed gas is then transferred to a storage tank at a lower storage pressure. Embodiments include cooling the high-pressure chamber, adding freezing-point-lowering additives to the liquid. The invention enhances compression efficiency, reduces costs, and meets stringent purity requirements for applications such as fuel cells.

Claims

1. A method for compressing gaseous hydrogen while controlling a concentration of water vapor in the compressed gaseous hydrogen, the method comprising: a. providing a source of gaseous hydrogen containing water vapor from 0 to 95% in volume, inclusive; b. delivering the gaseous hydrogen from said source into a first chamber having a fixed first volume until the gaseous hydrogen in said first chamber attains a first predetermined pressure; c. introducing an incompressible compression liquid water medium into said first chamber to compress said gaseous hydrogen contained therein, thereby reducing the volume occupied by said gaseous hydrogen and correspondingly increasing its pressure; d. permitting said gaseous hydrogen, during compression, to flow from said first b chamber to a second chamber of fixed second volume through a first means of fluid interconnection that allows passage of said hydrogen into said second chamber but prevents said compression liquid water from entering said second chamber, such that pressures in both chambers equalize and increase concurrently until a second predetermined pressure is established in said second chamber, wherein said second predetermined pressure is selected such that a vapor concentration in said gaseous hydrogen inside said second chamber is at or below a predefined concentration level; e. terminating fluid communication between said first chamber and said second chamber by closing said first fluid interconnection means when the pressure within said second chamber attains said second predetermined pressure level, thereby isolating said gaseous hydrogen within said second chamber from said gaseous hydrogen and said compression liquid water within said first chamber; f. transferring said isolated gaseous hydrogen from said second chamber to a storage tank through a second means of fluid interconnection, wherein said storage tank being configured to store said gaseous hydrogen at or below a third predetermined pressure level that is lower than said second predetermined pressure, and wherein a vapor concentration in said gaseous hydrogen within said storage tank is at or below said predefined concentration level.

2. The method as claimed in claim 1, wherein said first means for fluidly interconnecting said first chamber and said second chamber remains closed during the transfer of said gaseous hydrogen from said second chamber to said storage tank.

3. The method for compressing gaseous hydrogen of claim 1, wherein said second predetermined pressure ranges from 100 to 5000 bars, inclusive, and the compression temperature in the first chamber ranges from 0.1 C. to 50 C., inclusive, with both said second predetermined pressure and said compression temperature selected such that the vapor content of the gaseous hydrogen within said second chamber at said second predetermined pressure is at or below the predefined concentration level.

4. The method for compressing gaseous hydrogen of claim 1, further comprising b measuring and monitoring a vapor content in the gaseous hydrogen inside said second chamber using a vapor measurement device, wherein said second predetermined pressure b is achieved when the vapor content inside said second chamber is at or below the predefined concentration level.

5. The method for compressing gaseous hydrogen of claim 1, further comprising a temperature control device configured to maintain the temperature inside said second chamber at a predetermined temperature ranging from 50 C. to 50 C., inclusive, wherein the predetermined temperature is selected such that a vapor content in the gaseous hydrogen within said second chamber at said second predetermined pressure is at or below the predefined concentration level.

6. The method according to claim 1, wherein one or more inorganic compounds are added to said liquid water to form a compression liquid, said compression liquid having a lower freezing temperature relative to pure water, thereby enabling the compression process in said first chamber to be conducted below a freezing temperature of pure water.

7. The method according to claim 6, wherein the one or more inorganic compounds are selected from a group consisting of sodium chloride (NaCl), calcium chloride (CaCl.sub.2), magnesium chloride (MgCl.sub.2), and mixtures thereof, and are introduced into said liquid water in concentrations not exceeding their respective solubility limits in water at a compression temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of compressing hydrogen in accordance with the present invention.

(2) FIG. 2 is a schematic diagram of compressing hydrogen of FIG. 1, having a thermally insulated high-pressure gas chamber.

(3) FIG. 3 is a schematic diagram of three-stage hydrogen compression in accordance with the present invention.

(4) FIG. 4 is a schematic diagram of compressing hydrogen of FIG. 1, having multiple high-pressure gas chambers.

(5) FIG. 5 is a schematic diagram of compressing hydrogen of FIG. 1, having multiple liquid compression chambers.

DETAILED DESCRIPTION OF THE INVENTION

(6) Referring to FIG. 1, a hydrogen compression system according to an embodiment of the present invention is illustrated and designated generally as 10. The system compresses gaseous hydrogen using an incompressible liquid, preferably water or a water-based liquid also known as aqueous solution, as the compression medium. The system comprises the following components: a liquid compression chamber 11, configured as in a liquid piston compressor; a high-pressure hydrogen gas chamber 21, fluidly connected to the output port of the liquid compression chamber 11 via a first feedline controlled by valve 15; a liquid pump 12, in fluid communication with the liquid compression chamber 11 via a second feedline; a liquid reservoir 13, connected to the liquid pump 12 via a third feedline and to the liquid compression chamber 11 via a fourth feedline controlled by valve 16, for storing and circulating the compression liquid; and a gaseous hydrogen storage tank 31, significantly larger in volume than the high-pressure gas chamber 21, fluidly connected thereto via a fifth feedline controlled by valve 22. Valves 14, 15, and 22, which regulate hydrogen gas flow during compression, are solenoid-operated (e.g., gate or check valves) and remotely adjustable between fully open and fully closed positions. The chambers 11 and 21, and the storage tank 31, maintain fixed volumes throughout the compression process.

(7) Gaseous hydrogen from a low-pressure source 2 enters the liquid compression chamber 11 through an inlet port controlled by valve 14. The inlet pressure, designated P1, corresponds to the pressure of the hydrogen source, typically ranging from 1 to 30 bars when derived from a production process such as electrolysis. In a multi-stage compression configuration, the source may be a prior compression stage, providing an inlet pressure at substantially higher level, for example, in the range of several hundred bars.

(8) As hydrogen from source 2 enters the liquid compression chamber 11, the compression liquid within is displaced into the reservoir 13 through valve 16, propelled by the inlet pressure P1. Valve 16, a solenoid-operated gate valve, is remotely controlled between fully open and fully closed positions. The reservoir 13 maintains a pressure at or below P1. Under certain conditions, the liquid in chamber 11 is first drained to the reservoir 13 to reduce the chamber pressure before valve 14 opens to admit the source hydrogen.

(9) Once the source hydrogen fills the liquid compression chamber 11 to a predetermined volume (e.g., 90%-95% of its capacity), valves 14 and 16 are closed. The liquid pump 12, such as a rotary pump driven by an electric motor, then delivers the compression liquid from the reservoir 13 into chamber 11. As the liquid fills the fixed-volume chamber 11, the hydrogen pressure increases, and the hydrogen gas flows through valve 15 into the high-pressure gas chamber 21, also of fixed volume. The pressures within chambers 11 and 21 then equalize and increase concurrently as the liquid compression operation continues. The volume ratio between chambers 11 and 21 is configured such that, when the liquid occupies approximately 90%-95% of chamber 11, the hydrogen in chamber 21 reaches a predetermined compression pressure, P2.

(10) At the conclusion of the compression cycle, the pressure in chambers 11 and 21 stabilizes at or near P2. Valve 15 then closes, followed by the opening of valve 22, allowing the compressed hydrogen to flow from the high-pressure gas chamber 21 to the storage tank 31, driven by the pressure differential. The storage tank 31, designed with a substantially larger volume than chamber 21, stores the hydrogen up to a storage pressure P3, predetermined by its intended use and typically significantly lower than P2. As hydrogen transfers, the pressure in chamber 21 decreases while that in tank 31 increases, equilibrating at a level not exceeding P3. Once valve 15 is closed, the compressed hydrogen in chamber 21 and tank 31 is isolated from the compression liquid in chamber 11, thereby maintaining the vapor content at essentially the same level thereafter.

(11) The described operation may be repeated multiple times, compressing hydrogen from the low-pressure source (P1) to the compression pressure (P2) within the system, then transferring it from chamber 21 to the storage tank 31 until the tank pressure reaches P3.

(12) While FIG. 1 depicts hydrogen inlets and outlets entering chamber 11 at its top, such positioning is not essential. It is sufficient that these ports are located at the chamber's highest level to retain the compression liquid within chamber 11, preventing its entry into the high-pressure gas chamber 21 via the first feedline and valve 15, or backflow into the hydrogen source 2 via the inlet feedline and valve 14.

(13) Alternative measures may prevent the compression liquid from entering the high-pressure gas chamber 21 or the hydrogen source 2. For instance, chamber 21 may be positioned above chamber 11 with an extended feedline, leveraging gravity to prevent the compression liquid reaching chamber 21. Alternatively, a liquid trap may be installed along the first feedline before valve 15 to capture any liquid before it reaches chamber 21. Another approach involves designing chamber 11 and controlling the compression process to minimize liquid splashing, maintaining a distinct interface between the hydrogen gas and the compression liquid. Similar configurations may prevent the compression liquid backflow into the source line 2 during hydrogen intake.

(14) While the foregoing measures prevent the compression liquid ingress into the high-pressure gas chamber 21, they do not preclude the transfer of vaporized liquid or moisture mixed with the compressed hydrogen. Thus, chamber 21 contains primarily compressed hydrogen and vapor at or below its saturation limit in hydrogen, with no significant condensed liquid present during operation under this embodiment. Optionally, a liquid trapping device may be attached to chamber 21 to collect any condensate should condensation occur intermittently.

(15) In accordance with the present invention, the predetermined compression pressure P2 is selected to ensure that the vapor concentration in the compressed hydrogen inside the high-pressure gas chamber 21 is below the purity limit required for its intended application, such as the limits specified in SAE J2719 and ISO 14687 for Proton Exchange Membrane (PEM) fuel cells. Across various applications, P2, determined by the vapor content in compressed hydrogen during liquid compression, substantially exceeds the storage pressure P3, which is established based on the requirements for storage or end use.

(16) The relationship between the source pressure P1, the predetermined compression pressure P2, and the storage pressure P3 is exemplified as follows. Hydrogen produced via electrolysissuch as through an alkaline or PEM electrolyzertypically exhibits a pressure of 1-30 bars (P1) and a water vapor content of approximately 8% by volume, or approximately 80000 mol/mol. For transportation in a truck trailer to a hydrogen fueling station servicing hydrogen fuel cell electric vehicles, the hydrogen often is stored at 300 bars (P3) with a water vapor content not exceeding 5 mol/mol. Under the present invention, achieving this vapor limit at a compression temperature of 5 C. requires a predetermined compression pressure P2 above approximately 1650 bars.

(17) The determination of P2 in this invention leverages the established principle that the saturated vapor content in hydrogen is inversely proportional to pressure. Table 1 below presents selected minimum values of P2 required to reduce the water vapor content in hydrogen below specified limits when water is employed as the compression liquid, in accordance with the present invention.

(18) TABLE-US-00001 TABLE 1 Minimum compression pressure (P2) in bars required to limit water vapor contents in hydrogen at different compression temperatures. Compression Temperature Water content limit in hydrogen (mol/mol) ( C.) 50 20 10 5 20 460 1100 2200 4500 5 160 420 850 1650 1 130 320 650 1250

(19) Alternatively, a vapor measurement and monitoring device can be installed to measure and monitor the vapor concentration inside the high-pressure gas chamber 21 during the liquid compression process. The compression pressure P2 is reached when the vapor concentration measured inside the gas chamber 21 is at or below a predefined concentration level.

(20) As indicated in Table 1, the minimum compression pressure P2 required to achieve a specified water vapor content in hydrogen decreases with decreasing temperature. Accordingly, reducing the temperature of the liquid compression process lowers the necessary P2 for a given water vapor limit, offering operational advantages. This reduction can be facilitated by incorporating small quantities of additives into the compression liquid to depress its freezing point. For instance, sodium chloride (NaCl) or calcium chloride (CaCl.sub.2) may be added to water, significantly lowering its freezing point and enabling compression at reduced temperatures.

(21) During operation of the compression system according to the present invention, water vapor in the hydrogen condenses as the gas is compressed. When a water-based liquid is employed as the compression medium, as preferred, this condensed vapor is absorbed by the compression liquid, mitigating any significant adverse impact by the water, either from condensation or from hydrogen source, on the compression process beyond a gradual increase in the volume of the compression liquid. The liquid reservoir readily accommodates this volume expansion. Additionally, any resultant changes in the chemical composition of the water-based liquid may be adjusted within the reservoir through the addition of appropriate additives.

(22) In an embodiment illustrated in FIG. 2, the high-pressure gas chamber 21, containing compressed hydrogen, is housed within a thermally insulated container 23 equipped with a cooling medium to maintain chamber 21 at a temperature below the freezing point of the compression liquid in the liquid compression chamber 11. This configuration permits liquid compression in chamber 11 to occur above the liquid's freezing point while facilitating additional condensation of vapor in chamber 21 due to the reduction in temperature. The resulting condensate is removed from chamber 21 through valve 26, collected in a liquid trap 24, and subsequently drained externally via valve 25, further reducing the vapor content of the compressed hydrogen at the compression pressure P2.

(23) In an alternative embodiment, the feedline connecting chamber 21 to the storage tank 31 is thermally insulated and cooled to a temperature below the freezing point of the compression liquid in chamber 11. This cooling extracts additional vapor from the compressed hydrogen via condensation prior to its entry into tank 31. Liquid collection and drainage lines, integrated into this feedline, remove the condensate, ensuring the hydrogen delivered to tank 31 meets vapor content requirements.

(24) In another embodiment, depicted in FIG. 3, hydrogen compression is executed in multiple stages, each comprising a liquid compression chamber (e.g., 11a, 11b, 11c) paired with a high-pressure gas chamber (e.g., 21a, 21b, 21c). The stages are serially connected, whereby hydrogen compressed to an intermediate pressure in one stage (e.g., from P1 to P2a in Stage 1) is fed into the subsequent stage for further compression (e.g., from P2a to P2b in Stage 2, and to P2 in Stage 3). This multi-stage approach optimizes compression ratios, particularly when the predetermined compression pressure P2, required for vapor control, is high and impractical to achieve in a single stage.

(25) In a further embodiment, shown in FIG. 4, a single liquid compression chamber 11 is fluidly connected to multiple high-pressure gas chambers (e.g., 21a, 21b, 21c), with valves regulating sequential connections to one chamber at a time. This configuration enhances throughput, proving advantageous when the transfer of compressed hydrogen from a high-pressure gas chamber to the storage tank 31 is slower than the compression process in chamber 11.

(26) In yet another embodiment, illustrated in FIG. 5, multiple liquid compression chambers (e.g., 11a, 11b, 11c) are connected to a single high-pressure gas chamber 21, with valves controlling sequential operation of one liquid compression chamber at a time. This arrangement increases throughput when the compression rate in the liquid compression chambers is slower than the transfer rate of hydrogen from chamber 21 to the storage tank 31. In this embodiment, each liquid compression chamber has its own liquid reservoir as shown in FIG. 5. Alternatively, all liquid compression chambers can share one liquid reservoir through separate feedlines, pumps and control valves.

(27) In a further embodiment, the high-pressure gas chamber 21 includes a desiccant material (e.g., silica gel or molecular sieves) to adsorb residual water vapor from the compressed hydrogen. This desiccant, regenerable via heating or pressure cycling, provides a supplementary means to achieve vapor levels below the specified threshold, enhancing flexibility for applications with stringent purity requirements.

(28) The embodiments described herein are broadly applicable to other gases b beyond hydrogen, including nitrogen, helium, argon, carbon dioxide, and air. These gases all exhibit the general relationship wherein increased compression pressure reduces the saturation vapor content in the compressed gas, with temperature exerting a similar influence on vapor content, as observed in hydrogen.

(29) The foregoing description pertains to specific embodiments of the present invention. Various modifications and variations may be implemented without departing from the spirit and broader scope of the invention as defined by the appended claims, which are to be construed in accordance with established principles of patent law, including the doctrine of equivalents. This disclosure is provided for illustrative purposes and is not intended to exhaustively describe all possible embodiments or to restrict the scope of the claims to the precise elements illustrated or detailed herein. For instance, any individual element of the invention may be substituted with alternative elements that offer substantially equivalent functionality or otherwise ensure satisfactory performance. Such alternatives encompass currently known substitutes recognized by those skilled in the art, as well as future developments that a skilled artisan might, upon their emergence, identify as viable replacements. Moreover, the disclosed embodiments comprise multiple features that collectively contribute to a range of advantages; however, the invention is not limited to embodiments incorporating all such features or delivering all described benefits, unless explicitly stated otherwise in the issued claims. References to elements in the singular, using articles such as a, an, the, or said, shall not be interpreted as restricting those elements to a single instance.

REFERENCE NUMERALS

(30) 2 source of hydrogen 10 a hydrogen gas compression system in accordance with the present invention 11 liquid compression chamber 12 liquid pump 13 liquid reservoir 14 gas feedline and valve interconnecting hydrogen source 2 and liquid compression chamber 11 15 gas feedline and valve interconnecting liquid compression chamber 11 and high-pressure gas chamber 21 16 liquid feedline and valve interconnecting liquid compression chamber 11 and liquid reservoir 13 21 high-pressure hydrogen gas chamber 22 gas feedline and valve interconnecting high-pressure gas chamber 21 and storage tank 31 23 temperature control device to maintain the temperature in chamber 21 24 water collection and trapping device 25 feedline and valve to release water collected in device 24 to outside of the system. 26 feedline and valve interconnecting the chamber 21 and water collection device 24 31 hydrogen gas storage tank