Process integration and exergy analysis of the autothermal reforming of glycerol using supercritical water

• Published in: Energy (Oxford) 2012-06, Vol.42 (1), p.192-203
• Main Authors: Gutiérrez Ortiz, F.J., Ollero, P., Serrera, A., Galera, S.
• Format: Article
• Language: English
• Subjects: Applied sciences; Autothermal reforming; burning; electric power; Energy; equations; Exact sciences and technology; exergy; Exergy analysis; Glycerol; Hydrogen; Process integration; Supercritical water; temperature
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2012.03.069

The most thermodynamically favorable operating conditions at which glycerol can be converted into hydrogen with maximum hydrogen yield by autothermal reforming using supercritical water were identified in a previous paper. As a second part of the study, a conceptual design based on energy integration and exergy analysis of the whole process has been performed. In the proposed scheme, the huge pressure energy of the gas product just at the outlet of the reforming reactor is converted into electrical power and a fraction of the expanded gas used to provide energy support for the process by burning it in a furnace, if needed. By using the optimal conditions found in the previous work, a severe deficit of energy arises in the process. Thus, both water-to-glycerol and oxygen-to-glycerol mole ratios at which thermoneutral conditions are achieved in the reformer are computed by burning all the product gas from the reformer, both for pure and pretreated crude glycerol, at different reforming and preheating temperatures. The pressure used is 240 atm. The effects of the main operating parameters are investigated by sensitivity analysis to identify optimal conditions to maximize power production under autothermal conditions, evaluating the results by energy and exergy analyses. The computations are made with the aid of AspenPlus™, using the predictive Soave–Redlich–Kwong equation of state as the thermodynamic method in the simulation of the supercritical region. ► A conceptual design of the autothermal reforming of glycerol using supercritical water is established. ► The energy that can be taken out of the process comes from the expansion of the product gas in an expander. ► The effect of the main operating parameters aimed at maximizing electrical power is investigated. ► A sensitivity analysis is conducted both for a pure glycerol feed and pretreated crude glycerol feed. ► The conceptual design includes the energy integration, and the process is assessed by an energy and exergy analysis.