# Research on Pure Hydrogen Production Using a Fuel-Processing System Combined with a PSA System
###### Abstract  
Research was conducted to improve the system efficiency of a fuel-processing system combined with a hydrogen-purification system to supply hydrogen to a 10 kW residential building proton-exchange membrane fuel cell (PEMFC). The system consists of a steam-reforming reactor, a water-gas shift reactor, heat exchangers and a pressure swing adsorption (PSA) system, increasing the purity of the produced hydrogen by over 99.97%. Aspen Plus(r) and Aspen adsorption(r) simulators were used to optimize operating conditions by calculating thermal efficiency and hydrogen-production yield under various temperature and pressure conditions in the reformer. To optimize the hydrogen-production system, simulations were performed under conditions of 1 to 10 atm and  
affecting the environment compared to other renewable energy sources. Commonly used types of fuel cells include PEMFCs (Polymer Electrolyte Membrane Fuel Cells), DMFCs (Direct Methanol Fuel Cells), SOFCs (Solid Oxide Fuel Cells), and MCFCs (Molten Carbonate Fuel Cells). Among them, PEMFCs operate at a relatively lower temperature than other types of fuel cells, have a high-power density, have a simple structure with excellent space efficiency, and have power production flexibility [15]. Hydrogen fuel cells are expected to be a next-generation energy source and are expected to be in high demand [16; 17]. Because of these advantages, they are the most commercialized and are mainly used as fuel cells for homes and residential buildings [18]. The growing demand for hydrogen for residential buildings has had a significant impact on the development of hydrogen-production processes for fuel cell systems in residential buildings [1]. Widely used hydrogen-production methods include water electrolysis methods, which electrolyze water to produce hydrogen; the ammonia photolysis method, which irradiates light through a bulb to decompose ammonia into hydrogen and nitrogen; and the hydrocarbon reforming method, which extracts hydrogen from various hydrocarbons such as methanol, ethanol, LNG (Liquefied Natural Gas) and PNG (Pressurized Natural gas). Reforming processes are the most popular hydrogen-production methods and include autothermal reforming, partial oxidation reforming, steam reforming, and ethanol reforming [17; 19; 20; 21]. Among them, the natural gas steam-reforming system has the advantage of relatively high hydrogen production, the lowest unit hydrogen-production cost and stable operation, making it the most commonly used technology for industrial use [17; 22; 23]. As the residual fuel cell system increases, it is needed to maximize the efficiency of the hydrogen-production system [17; 21]. The natural gas steam-reforming system consists of a steam-reforming reactor, a water gas shift (WGS) reactor and a preferential oxidation reactor (PROX). In the steam-reforming process, natural gas and steam react to form hydrogen, along with carbon monoxide and carbon dioxide. Reformate gas is further reacted with water in the water-gas shift reactor and produces additional hydrogen and carbon dioxide from CO and water. After the water-gas shift reaction, the concentration of hydrogen of the product gas would be around 75% and the concentration of CO\({}_{2}\) is around 20%, with a very small amount of CO and unreacted hydrocarbons [12; 23; 24]. If carbon monoxide is introduced to the polymer-exchange membrane fuel cell (PEMFC) along with hydrogen, carbon monoxide reacts with the platinum catalyst of the fuel cell and acts as a poison, reducing the performance and durability of the fuel cell, and the carbon dioxide also acts as a poison in the anode [25; 26]. The allowable concentration of carbon monoxide is 10 ppm in a normal state and 100 ppm in an excessive state. Also, CO\({}_{2}\) is emitted from the steam-reforming process, which needs to be separated and stored or utilized.