# Research on Pure Hydrogen Production Using a Fuel-Processing System Combined with a PSA System
###### Abstract
Therefore, high-purity hydrogen is required as a fuel in PEMFCs, and hydrogen-purification systems must be combined [17; 21; 27; 28; 29], which requires the development of a separation and purification process [30]. Existing technologies include a low-temperature distillation method, a non-porous polymer membrane method, a preferential oxidation (PROX) reaction method and an adsorption method (PSA: Pressure Swing Adsorption, TSA: Temperature Swing Adsorption). The hydrogen separation and purification process using the swing adsorption method is an energy-saving process without a phase transition for the mixture and enables separation and recovery at the same time [31; 32]. In addition, it is a process that enables precise separation at the molecular level through the pore size and surface treatment of the adsorbent, and it has technical advantages when applied to small- to large-scale processes. With the swing adsorption method, CO\({}_{2}\) that cannot be removed from the PROX reactor also can be removed and used as a carbon capture and storage (CCS) method. In addition to these advantages, a PSA system was selected as a hydrogen-purification method, possessing additional advantages of relatively low operating costs, easy operation, and easy automation of the process in the commercialization process [31; 32; 33]. In this study, the PSA system was applied for hydrogen purification to obtain over 99.97% pure hydrogen. The PSA system purifies hydrogen by adsorbing and desorbing substances other than hydrogen, depending on the diffusivity, molecular weight, and density of the gas, by repeating the adsorption and desorption of two or more chambers crossing each other [31; 33]. For hydrogen production, a fuel-processing system was applied. Much research has been conducted on fuel-processing systems and PSA systems, respectively. However, there is not much research on systems combining fuel-processing and PSA systems and economical pure-hydrogen-production methods, especially at the small and medium scale [31; 32]. In this study, we combined two cost-effective systems--the methane steam reforming system and the PSA system--for small- to medium-sized pure hydrogen production and investigated the influence of various thermodynamic parameters on the overall system efficiency using Aspen Plus(r) and Aspen Adsorption(r). The concentration of gas discharged from the fuel-processing system varies depending on the temperature and pressure conditions of the reformer, which affect the hydrogen-purification efficiency of PSA systems. During PSA operation, the pressure of the PSA system was maintained at 9 atm, and the use of a compressor was essential depending on the operating pressure of the fuel-processing system. The combined system was analyzed using the following:  
1. Efficiency analysis according to the temperature and pressure of the fuel-processing system. 2. Purification efficiency analysis according to PSA injection gas composition. 3. Selection of optimal operating conditions through efficiency analysis according to the operating conditions of the fuel-processing and PSA combined system. For optimizing the process of producing hydrogen with a purity of 99.97% or higher by linking the PSA system to the existing fuel-processing process, the overall thermal efficiency and the hydrogen-production yield were analyzed.