Hydrogen concentration control method with sweep gas on hydrogen deblending system equipped with a polymer membrane

• The hydrogen deblending system with a polymer membrane have been developed for mixture gas (20% of hydrogen) users. • The responses of the system using the sweep gas method to the stepwise change of the feed gas hydrogen concentration were investigated. • In the best controlled case, the hydrogen concentration of the permeation gas could be controlled at 20 % ± 1.0 %. Transporting hydrogen mixed with natural gas in existing natural gas pipelines is showing promise as a low-cost hydrogen transportation method. In this process, the hydrogen is deblended at the demand location by controlling the hydrogen concentration in accordance with the user’s requirements. A hydrogen deblending system is be developing to separate hydrogen from the mixture gas at the user-specified concentration. By utilizing a hydrogen separation membrane, this system can continue to maintain the required hydrogen concentration even if the concentration in the gas grid fluctuates. In this paper, methods are investigated to control the permeation gas hydrogen concentration to the target level of 20 % by means of a sweep gas flow rate using our experimental apparatus with a polymer membrane even though the change of feed gas hydrogen concentration. The hydrogen concentration of the permeation gas was controlled by the flow rate of the feed gas and the sweep gas by detecting changes in the hydrogen concentration of the feed gas. The timing of the flow rate change had to be adjusted to take into account the time taken for the feed gas with a changed hydrogen concentration to reach the membrane module. In our experiments, the hydrogen concentration of the permeation gas was below the lower limit of the control range if the timing of the flow adjustment was early, and above the upper limit if the timing was late. In cases where the timing was matched, the hydrogen concentration of the permeation gas could be controlled to 20 % ± 1.0 %. The performance of the proposed transient simulation method based on a plug flow model using the permeance of hydrogen and methane was also evaluated using the experimental data.