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Hydrogen is the lightest element present, which makes compression fundamentally more difficult. As it has a very low energy density in relation to the volume flow (energy content per volume unit), large electrolysis plants also have to compress correspondingly high volume flows, which has an effect on the sizes and, thus, on the investment costs, footprint, etc. of the machine equipment. In addition, hydrogen is very reactive, i.e. highly flammable. Special attention is, therefore, paid to the required explosion protection. The formation of an ignitable mixture with the atmospheric oxygen must be avoided at all costs.

The advantages of screw compressors for the compression of hydrogen

For the compression of hydrogen in the low-pressure range, screw compressors are a sensible solution or supplement to high-pressure compressors. Due to their design-related internal compression without free inertia forces, screws are above all reliable and flexible endurance runners with very low maintenance intensity and comparatively low operating costs in full and partial load operation. The AERZEN range includes both oil-free (VRA and VRW series) and oil flooded (VMY series) versions and achieves top marks in the fields of efficiency, installation space, economy and process reliability. All solutions are reconciled by the AERZEN process gas specialists to the customer’s individual process.

VRW: maximum efficiency and increased differential pressure in one stage

The oil-free compressors of the VRW series (volume flows up to 6,000 m³/h, differential pressures from 3 to 9 bar) have been specially developed for the compression of saturated electrolysis hydrogen with unrivalled efficiency and differential pressure. Compression is based on the principle of oil-flooded screw compressors – with a small but subtle difference: the oil was replaced by water. The water serves both to cool the gas and to seal the gap, enabling compression to higher differential pressures with high efficiency. This stage can, thus, replace a two-stage system with classic oil-free screw compressors and is even more energy-efficient. For the customers, this results in significant advantages in terms of footprint as well as investment and operating costs.

VMY: highest differential pressures, maximum flexibility

The oil-injected screw compressors of the VMY series deliver the highest differential pressures and compression ratios in the AERZEN product portfolio (volume flows from 190 to 23,000 m³/h, differential pressures from 3 to 20 bar) and are characterised by maximum reliability and low operating costs. They are insensitive to fluctuating process parameters and gas compositions and are equipped with a control valve for infinitely variable control of the volume flow. The secondary rotor is not driven by timing gears (as with oil-free compressors), but by direct power transmission from the driven rotor. The oil injection quantity regulates the outlet temperature and, in case of humid gases, it is ensured that the oil is always compressed above the specific dew point temperatures. This reliably prevents the failure of water in the oil/gaseous mixture.

You will find AERZEN at ACHEMA 2024 in hall 8, stand D38.