Hydrogen turbo compressors

Hydrogen has a lower molar mass and a higher volumetric flow than natural gas, which requires higher compression effort, and its smaller molecular size also poses an additional sealing challenge to minimise external leakage. For relatively large volumetric flows and moderate pressure lifts (<200 bar), such as for hydrogen pipeline transmission and underground storage, centrifugal type turbo-compressors will be needed, and although they have been used for petrochemical applications, their efficiency remains low. In a centrifugal compressor, the high-speed rotation of the impeller imposes high-velocity energy into the gas, which is then converted to pressure. Research is testing hydrogen-resistant impeller materials that can withstand higher centrifugal forces (i.e. increase tip speed) and hydrogen embrittlement. In addition to the high tip speed and choice of impeller material, the method of mounting the impeller to the shaft would differ from that of a typical hydrocarbon centrifugal compressor.