Abstract
The storage and transportation of renewable H2 using natural gas (NG) pipelines is regarded as a promising solution to overcome the challenges with renewable energy storage and distribution. However, among other concerns regarding safety and reliability, further investigation is still required to unveil all the aspects associated with the technoeconomics of the technology. Levelized H2 separation cost (LHSC) is a crucial metric to evaluate and compare the cost-effectiveness of H2 blending technology as an alternative to other incubators for H2 transportation such as compressed or liquefied H2 tube trailers. H2 extraction from the NG distribution system (NGDS), where the operating pressure is moderate values and H2 contents can be up to 30-50%, have been already studied in the literature using a standalone pressure swing adsorption (PSA) process. However, utilizing the PSA technique for mixtures with low H2 contents of 5-10% as allowable in the NG transmission system (NGTS) requires much larger PSA equipment with high capital expenses and additional significant costs needed for the recompression to reinject the NG into the gas pipelines. To customize the PSA separation technology for such scenarios, a hybrid process scheme has been proposed in the literature. This configuration comprises one membrane stage followed by a PSA purification step. This study presents a rigorous techno-economic model for the aforementioned process scheme using an integrated platform developed based on Aspen Adsorption V11 and Aspen Costume Modeler. The system is composed of one stage hollow fiber matrimid membrane module followed by a 4-bed adsorption process operating on 8 sequential steps. to fulfil H2 market purity requirements with an acceptable recovery rate for H2. To reduce the computational time, we used a cyclic steady-state approach to solve the governing equations of the PSA. The system is studied for different scenarios relevant to NGTS operating conditions. The results show that the viability of hydrogen blending technology from technoeconomic standpoint becomes questionable, particularly at lower grid pressures when allowable hydrogen content is less than 10%. However, for industries requiring lower hydrogen purity levels (below 90-99%), this transportation method seems promising.
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