Analysis of steam reforming of methane integrated with solar central receiver system
Authors: Ali Haider , Tahir Furqan , Atif Maimoon , AB Baloch Ahmer 
Published: June 2019

Steam reforming is used for the production of hydrogen or other useful products from hydrocarbon fuels such as natural gas. Reforming is the process in which steam at high temperature reacts with the fossil fuel to form Syngas (CO+H2). The steam methane reformer is widely used in industry for the production of hydrogen. It has the advantage that the energy released from the combustion of hydrogen is almost four times as the energy released from the combustion of methane. In the present study, modeling and analysis of the steam methane reformer is carried out while utilizing the energy via solar tower. In the conventional modeling systems, solar based steam reforming is studied only for a single point in time and the dynamic fluctuations in the solar energy is not taken into account. Therefore, the performance metrics calculated are not necessarily representative of the actual performance of the solar reforming cycle since the performance will obviously be effected by the amount of solar input. In the work, herein, a solar steam reformer is modeled by considering the real-time data for Direct Normal Incident (DNI) irradiation for the city of Doha. As very high temperature is required for reforming, a solar central receiver tower is incorporated which can achieve high temperatures as much as 1300°C. The solar steam reformer is integrated into a solar receiver tower, surrounded by a field of heliostats, such that the solar is directly irradiating the solar reformer. The steam reformer and solar receiver tower is modeled and in-house code on Engineering Equation Solver (EES) software is written for performing the simulations. The system is analyze based on an annual performance so that the fluctuation of solar supply is taken into account with the cycle performance. The performance of steam methane reformer is studied for three representative days of the year that is 29th April, 15th May and 11th August. The performance characteristics of the steam methane reformer is analyzed in terms of methane conversion (Methane Conversion = (xCO+ xCO2)/(xCO+ xCO2+xCH4), where x is the molar concentration) and molar concentration, while incorporating the solar energy data. For 29th April, the peak incident energy is observed at around 1300 hours and the maximum methane conversion (Methane Conversion = 1) takes place at same time due to high solar irradiation. As for the molar concentration of different species, a maximum hydrogen presence in the peak solar irradiance, and the minimum amount of steam and methane is observed. CO presence tends to increase as well, at solar peak hours whereas the CO2 presence does not vary much and almost remains constant most of the time. Similar trends is observed for 15th May while as for 11th August due to no overcasting and continuous solar irradiance, a smooth trend of solar irradiance and consequently a smooth trend of methane conversion and molar concentrations is observed. The steam methane reformer with the solar receiver tower is effectively converting the methane during the solar hours of day. The study provides information about the performance characteristics of the steam methane reformer.