Compressor Issues for Hydrogen Production and Transmission Through a Long Distance Pipeline Network

Autor: Fred Starr, S. D. Peteves, Evangelos Tzimas, Calin-Cristian Cormos
Rok vydání: 2008
Předmět:
Zdroj: Scopus-Elsevier
ISSN: 2668-8212
0034-7752
DOI: 10.37358/rc.08.4.1806
Popis: A hydrogen energy system will require the production of hydrogen from coal-based gasification plants and its transmission through long distance pipelines at 70 - 100 bar. To overcome some problems of current gasifiers, which are limited in pressure capability, two options are explored, in-plant compression of the syngas and compression of the hydrogen at the plant exit. It is shown that whereas in-plant compression using centrifugal machines is practical, this is not a solution when compressing hydrogen at the plant exit. This is because of the low molecular weight of the hydrogen. It is also shown that if centrifugal compressors are to be used in a pipeline system, pressure drops will need to be restricted as even an advanced two-stage centrifugal compressor will be limited to a pressure ratio of 1.2. High strength steels are suitable for the in- plant compressor, but aluminium alloy will be required for a hydrogen pipeline compressor. The introduction of hydrogen in the energy system as an energy alternative carrier is drawing much interest in Europe, offering significant advantages including reduction of greenhouse gas emissions, enhancing energy suppling security and improving economical competitiveness. Even at the present time, hydrogen has a major use in the petrochemical and oil refining industries, where it is mainly produced from natural gas and oil (1). In the future, coal based gasification however, is likely to play a key role in European large-scale hydrogen production (2). These will be based on entrained flow gasification as this type of gasifier maximises hydrogen production and facilitates the capture of carbon as CO 2, whereby it can be stored in geological reservoirs or used for enhanced oil recovery. A condition for the successful penetration of hydrogen in the energy system is its supply from the production facility at high pressure, as this will enable hydrogen to be transmitted via long distance pipelines (3). The hydrogen transmission pressure should be similar to that in the natural gas pipeline network, i.e. in excess of 70 bar. For a natural gas pipeline network, this pressure level is kept reasonably constant using booster stations with centrifugal compressors, which are set at about every 50 - 100 km and raise pressures by a factor of 1.2 - 1.4 at each compressor station. In general these compressors are of single or two stage type and are driven by an aeroderived gas turbine, fuelled by natural gas from the pipeline. The operating speed of the gas turbine and the pipeline compressor are similar, simplifying the drive mechanism. For the same energy throughputs as a natural gas system, a hydrogen pipeline will be subjected to similar or even slightly higher pressure drops. Although the low density and viscosity of hydrogen will reduce pressure drops for the same flow rate as natural gas, because hydrogen has to be transmitted at 3 - 4 times the flow rate, to compensate for its much lower calorific value (10.8 MJ/Nm 3 compared with 35 - 40 MJ/Nm 3 for natural gas) pressure drops will be in fact greater. Unfortunately the compression of hydrogen using centrifugal machines is extremely difficult because of its low density. This is caused by the low molecular weight of hydrogen, requiring the use of multistage
Databáze: OpenAIRE
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