You can find numerous hydrogen compressor and pump systems in use nowadays. Types of compressors consist of diaphragm, reciprocating piston, and centrifugal. Pumping systems for hydrogen applications include various kinds of positive displacement techniques. Each diaphragm compressor and pump system operates utilizing various methods, and each can be used for specific reasons and for specific markets.

Introducing visitors to this topic, we requested a number of hydrogen compressor and pump manufacturers to explain the techniques used in hydrogen programs today.

Basic principles

Hydrogen is definitely the simplest and a lot abundant aspect in the world. (See CGI, Feb. 2008, p. 52.) It is really an effective, low-polluting, renewable energy. Emerging hydrogen technologies require storage space and using hydrogen at higher demands.

Compressors are utilized to raise the pressure of gaseous hydrogen (H2). In general, nevertheless, fluids are not deemed compressible. Pumps consequently are utilized to increase the pressure of liquid hydrogen (LH2) in the use point by offering a continuing stream. Restrictions and final use back pressure make the stress improve. LH2 at high-pressure will then be changed into vapour as it passes by way of a vaporizer, and is utilized or kept at the raised stress. Gaseous compressors and liquid pumping systems both are used in hydrogen applications.

Although the basic principles of compressing and pumping are common to the majority of fumes and liquids, you can find unique distinctions and specifications, including safety, when dealing with hydrogen. One of the largest difficulties to using hyrogen is its safe containment, due to the reduced molecular mass.


Three of the fundamental kinds of compressors – diaphragm, reciprocating piston, and centrifugal (also referred to as radial) – have various characteristics that will make them appropriate for utilization in various settings.

Diaphragm Compressors

“Diaphragm compressors,” recommends Osama Al-Qasem with Pdc Machines Inc., “are the ideal choice for compressing gases without taking on contamination in the procedure mass media or leakage of gas to ambient air.” H2 is isolated through the mechanised elements of the compressor and through the atmosphere with a set of three metallic diaphragms. They are clamped among two exactly contoured concave cavities in top and lower dishes. The 3 diaphragms are nested and take action together as one. The top diaphragm is in touch with the H2 and also the bottom is in contact with the hydraulic oil. A 3-diaphragm set can be used to ensure there is absolutely no go across-toxic contamination in between the hydraulic oil and the H2 being compressed. The center diaphragm, employed for leak recognition, has lines scribed on edges. When a leak develops inside the upper or lower diaphragm, or if the O-bands put on, the mass media will seep along the scribe outlines into an accumulator. When an accumulator stress gets to a set limit, the co2 compressor will instantly quit. “As static closes are employed,” recommends Al-Qasem, “there is no seepage of fumes towards the atmosphere, and no requirement to purge or vent the crankcase.”

A engine-powered crankshaft connected to a piston moves a column of hydraulic fluid up and down. Pressure happens as the hydraulic fluid is forced upwards to fill up the lower oil-dish cavity, applying a consistent force against the base of the diaphragm set, deflecting it in to the H2-loaded gas-dish cavity previously mentioned. The displacement of the diaphragm up against the gasoline-dish cavity compresses the H2, pushing it the discharge check valve. Since the piston, which movements the hydraulic fluid, strokes downwards, the diaphragm is drawn back down to the lower cavity, the inlet check valve opens, as well as the top cavity fills up with H2. The cycle is repetitive.

The key benefit to diaphragm compressors can there be will not be the concern for seepage similar to other compressors or pumps.

Stephen St. Martin of Gas & Air Techniques, Inc. reviews that “Diaphragm compressors are utilized to compress H2 in cylinder trans-satisfying and pipe trailer offloading procedures, and then for gasoline recuperation through the vapor space of cryogenic storage space vessels. Due to its high pressure capability, and inherently oil-free compression, the diaphragm compressor is additionally frequently used in car hydrogen fueling stations, where pressures of 10,000 psi and above are presently used.”

The hydrogen energy cell demands ultra-purity H2 to function properly. “The diaphragm compressors,” according to Osama Al-Qasem, “are created to offer precisely this function. Hundreds of diaphragm compressors have been set up globally within the renewable power system to find option resources for oil.” Al-Qasem claims that 85 to 90 % of the market needing diaphragm compressors had been provided by Pdc.

Diaphragm compressors are ideal for high pressure applications. It is not astonishing that diaphragm compressors are perfect for hydrogen applications, specifically in the development in the growing hydrogen economy. Osama Al-Qasem pointed out one unique and interesting emerging “double-green” technology. Pdc has compressors used together with wind turbines. The electrical power from wind turbines can be used to provide a water electrolyzer to electrochemically split water into its elements, hydrogen and oxygen. One feature which makes the marriage of these two technologies such an fascinating match is that the electrolyzer can operate with adjustable energy enter, as windmills turn at different speeds, in accordance with the wind. Hydrogen thus created is compressed and kept for later use, either in a stationary energy cell to generate electrical power if you have no wind, or to supply a hydrogen vehicle.

Hydrogen compressor applications are many. They include making use of solar power to electrolyze water to create H2, which, like the windmill application, will be compressed and kept for later use, either in a fixed fuel cell to produce electricity when there is no sunshine, or energy a hydrogen car. Compressors are utilized at hydrogen energy cell stations, such as these for automobiles, buses, fork-lifts, scooters, and residential re-fuelers for energy cell (FC) cars; for satisfying and away-loading H2 from pipe trailers, gas cylinders, and storage space tanks; for your pressure of syngas from renewable resources; and for wind and solar technology. H2 compressors are employed such disparate programs as gasoline blending, trying to recycle, and mixing, metal handling, hydrogenation of edible oils, specialized gasoline filtering, float glass production, and power herb turbine chilling. Gases for semiconductor, electronics and fiber optics production require compressors. They are also utilized for feedstock for chemical substance, petrochemical and pharmaceutic industries, pressure boosting and storage of fumes from on-site generation systems, and for energy back-up using hydrogen FC for telecom towers, as well as study and development.

Multi-phase Reciprocating Piston Compressors

Multiple-stage reciprocating piston compressors are generally employed for compression of H2 gasoline. Piston compressors work on the simple idea. Rick Turnquist, with RIX Industries instructs, “The piston inside a big cylinder pushes a fixed amount of gas into a smaller sized tube, therefore creating a pressure increase. This is based on the best gasoline legislation, which in abbreviated type is: PV=nT (pressure x volume = Moles of gas by heat). Therefore as volume will go down, pressure increases (note right after the final phase the stress improve is forced from the back stress in the user’s tank or piping).”

Turnquist continues to clarify that “H2 compressors are similar to these employed to compress other fumes; nevertheless there are sometimes design differences because of the tiny molecular dimensions of the H2. These may be: an exclusive valve style; unique piston ring components; overlapping piston diamond ring style to reduce seepage; lower compression proportions; or tube and head castings may have to be impregnated to avoid leaks due to casting porosity. Additionally, the quality of steel used in the pressure finish elements may must be changed.”

Hydrogen, like all fumes, is heated by compression. “Intercooling” of the gas is necessary when using multiple-stage high-pressure compressors.

The greatest end-users of multiple-phase reciprocating screw air compressor are refineries and chemical plants. Customers consist of this kind of businesses as Air Products, Praxair, and Chevron Research. These compressors can also be used lrnhbl some refueling programs, for syngas, pilot plants, and laboratory RAndD.

Centrifugal Compressors

Centrifugal compressors are rarely employed for hydrogen applications as a result of molecule’s reduced molecular weight. Nevertheless, centrifugal compressors are used in cryogenic H2 programs where stream is comparatively high and also the stress head preferred is comparatively reduced. Barbers Nichols Inc. (BNI), designer and producer of specialized turbo-machinery, makes cryogenic H2 centrifugal compressors for 2 applications. Those two programs include sub-cooling H2 by sketching down fluid boil-away gas stress below atmospheric. Jeff Shull, with Barber Nichols, explains that “this produces a much more packed liquid that can then be used in a rocket more efficiently (occupies less space and reduces overall weight). BNI utilized 4 individual centrifugal stages (four solitary phase machines each with a motor) to draw in down the pressure to roughly 3 psia with the atmospheric pressure electric outlet and high runs to get a propellant densification check at NASA. BNI’s H2 cryogenic compressors utilize a engine and bearings operating at space heat having an overhung impeller over a hollow shaft to reduce warmth enter for the fluid. No powerful closes are utilized so designs are hermetic. BNI has additionally supplied several H2 circulators in supercritical programs (supercritical H2 is a lot more like a liquid compared to a gas, however) for cryogenic chilling.”

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