Scoping of a commercial micro reformer for the production of hydrogen

• Main Author: Koorts, Waldo Pieter
• Format: Others
• Language: English
• Published: Nelson Mandela Metropolitan University 2016
• Subjects: Hydrogen as fuel; Fuel processors
• Online Access: http://hdl.handle.net/10948/8175

Hydrogen has gained interest as fuel recently as the harmful effects of fossil fuels on the environment can no longer be ignored. Hydrogen, which produces no pollutants, forms the feed for cleaner fuel cells systems currently in use. Fuel cells, although not as economically viable as fossil fuels, have found a foothold in the energy market in various markets like power backup and use in remote locations. Production of hydrogen is still largely done via fossil fuel reforming and this technology has received renewed interest for use with fuel cells in the form of micro- reformers or fuel processors. This study entailed the performance benchmarking of a so called Best-in-Class commercial micro reformer (as available in 2010), the 1 kW WS FLOX Reformer, and was undertaken under the auspices of the national HySA programme. The study’s focus was primarily on reformate output quality (carbon monoxide concentration), and start up time, thermal efficiency and hydrogen output (15 SCLM). The reformer consisted of a combustion section encased in an outer reforming section consisting of three reactors in series, steam reforming, water gas shift and selective methanation. As-provided temperature control is simplified though the use of only one temperature setpoint in the combustion chamber and temperature control in the CO clean up stages obtained through means of heat transfer with incoming water being evaporated. Combustion takes place through flame combustion or by means of the supplier’s patented FLOX (flameless oxidation) combustion. The purchased FLOX Reformer assembly was integrated into a fully automated unit with all balance of plant components as well as microGC and flue gas analysis for measurement of outlet conditions. The FLOX Reformer was tested at multiple combustion temperatures, combustion flowrates, reforming loads and steam-to-carbon ratios to obtain a wide set of benchmark data. From the testing it was found that the reformer was able to produce the necessary 15 SCLM hydrogen with a carbon monoxide purity of less than 10 ppm as required in fuel cells for all testing if the reaction temperatures were within the recommended limits. Intermediary water gas shift analysis showed methane and carbon monoxide conversion in the reforming and water gas shift stages to be identical to thermodynamic equilibrium conversion – 95% and higher for all temperatures. iii Selective methanation conversion obtained was 99%, but not always at equilibrium conversion due to increased selective methanation temperatures, where carbon dioxide methanation was also observed at the higher temperatures. Temperature control through heat exchange with incoming water in the CO removal stages was found to be less than ideal as the temperature inside these stages fluctuated dramatically due to inaccuracies in the water pump and a lagged response to flowrate changes. Startup times of less than an hour was observed for multiple combustion flowrates and the reformer boasts a standby function to reduce this to less than half an hour. The thermal efficiency was independently confirmed and tested and found to be higher than 70 % for flame combustion and on par with other commercially available fuel processors. The suppliers trademark FLOX combustion only reaching 65% due to decreased combustion efficiency.