Graphical Representation of Chemical Reactions and Heat Cascade Analysis of Biomass Residue Syngasification to Produce Hydrogen

The production of hydrogen by syngasification of biomass in Brazil provides a significant opportunity to increase the profitability of the sugarcane ethanol industry, as sugarcane biomass residues are available at low cost and in large quantities in the country. Hydrogen makes it possible to produce high-value chemicals from ethanol, whose production from sugarcane is already developed and energy efficient, and H 2 can also be used as a transportation fuel. This article discusses the reaction thermodynamics of syngasification, proposes a C-H–O chart to analyze the chemical reactions, and analyzes the heat cascade through a syngasifier and the downstream operations for producing hydrogen. The proposed C-H–O chart makes it possible (1) to estimate the higher heating value of molecules involved in the syngasification, (2) to visualize the region of carbon deposit, (3) to represent the reactions occurring in a syngasifier and determine whether the enthalpy and entropy changes are positive or negative, and (4) to evaluate the effects of composition, pressure, and temperature on the reaction system. The tool also allows following the progressive changes in stream composition through process operations. For the first time, the heat cascade through each operation of the complete hydrogen-producing syngasification process has been analyzed. Results show that the chemical reactions release enough heat to satisfy all thermal demands of the downstream operations. Overall, purified hydrogen contains around 67% of the higher heating value of inlet biomass. Integrating the process that produces hydrogen with the process of making ethanol from sugarcane, whose bagasse would feed the hydrogen process, leads to a reduction of 20% of the total heat consumption. Graphical Abstract Chemical reactions occurring in an allothermal syngasifier The yellow diamond shows the global composition (mixture of biomass and steam).