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Challenges for turbomachinery engineers working with engineering/EPC organizations.
Hydrogen fuel has attracted interest due to its high potential in terms of energy per unit of mass. However, designing new machines (or modifying existing ones) for hydrogen poses several challenges.
EPC Business Opportunities for hydrogen related projects can be divided into two major types: Green field development projects (Hydrogen Generation projects, Hydrogen Transportation and Pipeline projects, Hydrogen Fuel station projects, etc.) and Brown field projects (modification of the existing facilities, such as upgrading the existing gas turbines to run with H2 fuel).
This article focuses upon an important interface engineering detail to be investigated by an Engineer at various stages of the project. Emphasis is given to Centrifugal Compressors for Hydrogen Service and Gas Turbines with Hydrogen as a Fuel. Reciprocating compressors are more tolerant to molecular weight of the gas and hence significant changes in the core design of the reciprocating compressor is not required for Hydrogen Gas.
While working on a conceptual design for a Green Field project, the machine type is selected based on the preliminary process parameters from the available range of machine design parameters. Preliminary machine type selection is carried out from various machine manufacturers’ published product catalogues, keeping in mind the possibility to have a healthy commercial competition during further development of the project.
A wide range of product databases for the selection of machines designed for conventional fossil fuels are available. Working on a conceptual study of hydrogen related projects is going to be challenging for an engineer since product ranges compatible with hydrogen gas can be limited. This may lead to an increased time frame for the machine selection process. This stage would be a good opportunity for an engineer to interact with the machine manufacturers and explain to them the required machine specifications for the process. It could be exciting to work with manufacturers’ research and development team and find a solution required for the process in absence of readily available design.
Hydrogen compressors are typically found in refinery applications. Hence Hydrogen compressor designs have been developed to suit the refinery application range and scale. However, significant modification is required in the design of such compressors to make them suitable for the pipeline compressors application considering higher volumetric flowrate of the pipeline compressors than the refinery one. Specifically for the centrifugal compressors, machine manufacturers have developed the concepts of compact compressor train casings arrangement (Figure-1) which is quite different than the typical compressor train casings arrangement in series (Figure-2). Thus, it is imperative that an engineer stays up to date on any and all design developments.
During the FEED stage, an engineer moves into the equipment selection report preparation with an advancement of the plant design. Preparing a machine selection report for machines running on a conventional fossil fuel is relatively easy because necessary data is provided by the machine manufacturers (like machine efficiency, reliability, availability, emissions data, etc.). Preparation of the machine selection report for the machines using hydrogen gas is challenging due to limited data for the newly developed (or upgraded) machines. It’s likely that the engineer will have to rely on data derived from the testing of prototypes. Therefore, comparing two designs based on the available prototype data is a risk to be evaluated in detail during the machine selection process. At this stage, preliminary interface data (like utility consumption, layout arrangement, control system integration, etc.) should be carefully evaluated to ensure a robust technical comparison of the various machines. There are chances that available interface information from manufactures is based on their theoretical calculations and derived from prototypes. An engineer should therefore decide appropriate contingencies before passing on the machine interface information to other engineering disciplines for the plant design at FEED Stage. At this stage, there is an opportunity for an engineer to prepare the machine selection reports for the newly designed/upgraded machines for hydrogen gas which can be further used as a reference for the future projects.
In the absence of industry benchmarks for machines running on hydrogen, cost estimation will rely entirely upon commercial data provided by manufacturers. The absolute cost of the newly developed machines is expected to remain high as it will contain some portion of the cost invested by manufacturers in design developments and patents. Penalties associated with plant performance will be carefully reviewed and well documented with the end users for the new machines in absence of any proven track record for performance. For example, emissions guarantee of gas turbines running on hydrogen fuel will be reviewed carefully considering higher flame temperatures and risk of associated NOx content due to higher flame temperature. Considering all the associated risks, it will be challenging for an engineer to estimate the correct cost of such machines.
DETAIL DESIGN STAGE
At this stage, the detail technical offers from manufacturers are available for detail review and technical scrutiny. While preparing a detailed Technical Bid Analysis tabulation, an Engineer has an opportunity to analyze and compare the machines of different manufacturers with respect to the machine auxiliaries, utility requirement, lubricants requirements, maintenance, and spares requirement. For the new/upgraded machines, it could be possible to have deviations from the project specifications and international standards that are not previously approved by the end users. Interface data contingency considered during the FEED or at estimation stage are to be carefully optimized at this stage based on the detail information from the manufacturers.
Few interface related challenges for the newly developed machines can be understood from the example of the centrifugal compressor developed for Hydrogen service as shown in Figure-1. Piping layout around the machine will be significantly different and more complex than the piping layout of the conventional machines with separate casings in series shown in Figure-2. Design of machine auxiliaries like lube oil consoles, seal gas treatment unit, fuel gas treatment unit (in case of gas turbine), and inter stage coolers will differ from conventional units. Location of these auxiliaries with respect to the machine skid needs careful evaluation to ensure proper functioning of the unit (for example, Location of Lube oil Rundown tank with respect to the centerline of the compressor). Shelter design and material handling facilities also need to be designed considering the compressor and auxiliary layout plan. This is expected to be complex for the compressors shown in Figure-1.
If an engineer is working on upgrading a gas turbine to run on hydrogen, a careful analysis of hazardous area classification for the nearby instruments should be undertaken following the retrofit. Results of hazardous area classification study may require instruments/equipment within the vicinity of the package to be upgraded due to the stringent area classification requirement for hydrogen. Similarly, fire detection and fire suppression systems may need to be upgraded.
Turbomachinery engineers working with engineering/EPC organizations ensure the interface and integrity of the turbomachines within the plant. It will be an exciting opportunity for an Engineer to overcome the interface challenges of newly developed machines for hydrogen gas, which is going to remain a source of energy for the coming decades.