Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2018;140(6):062001-062001-10. doi:10.1115/1.4038782.

The aerosols from CO2-depleted flue gas at the National Carbon Capture Center (NCCC) Pilot Solvent Test Unit (PSTU) and Slipstream Solvent Test Unit (SSTU) were measured in real-time using a Dekati Electric Low Pressure Impactor (ELPI+™). The coal-fired flue gas is provided by Alabama Power's Gaston Power Plant Unit 5. The utilization of ELPI+™ for aerosol research in postcombustion CO2 capture is very important due to its quick response time with size classification as low as 6 nm under transient conditions observed at the NCCC. Different process changes have been quantified at the PSTU and SSTU by multiple tests using the ELPI+™. The performance of smooth and sintered collection plates during dynamic process changes has been investigated. Between separate tests, upstream at unit 5, a new baghouse was installed. The aerosols measured at SSTU, before and after the baghouse installation, are compared. PSTU measurements demonstrated sample sensitivity to transient intercooler start-up conditions and dilution gas temperatures. During the tests, the typical concentration ranged from 106 to 107 cm−3. The aerosol's counter median diameter (CMD) for the sintered plates are lower (47–60 nm) compared to the normal plates (89–130 nm). The optical images indicate that sintered plates soak up all of the collected aerosols. The aerosol number concentration showed a significant drop after the baghouse installation. These results are promising and will enable the development of process control strategies to mitigate solvent losses and reduce operation and maintenance expenses.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2018;140(6):062201-062201-5. doi:10.1115/1.4039321.

This study was aimed at comparing the pyrolysis behavior of several selected biomass samples, namely, pine wood, poplar wood, wheat straw, and sugarcane bagasse, with a particular attention to the effect of lignin. Raw samples were first treated using Soxhlet solvent extraction with a 2:1 (v/v) mixture of toluene/ethanol to remove wax. Lignin was then removed by soaking the dewaxed samples in a 1.0 M sodium chlorite solution at 343 K till the solids became white. Fourier transform infrared (FTIR) spectroscopy analysis was applied to characterize the surface functional groups of the samples. The morphology of the samples before and after delignification treatment was analyzed using scanning electron microscope (SEM). The pyrolysis behavior of the raw and treated biomass samples was studied using a thermogravimetric analyzer (TGA) operating in nitrogen at a constant heating rate of 10 K min−1 from room temperature to the final temperature 823 K. The FTIR and SEM results indicated that lignin can be successfully removed from the raw biomass via the chemical treatment used. As expected, the pyrolysis behavior differed significantly among the various raw biomass samples. However, the pyrolysis behavior of the delignified samples showed almost identical thermal behavior although the temperature associated with the maximum rate of pyrolysis was shifted to a lower temperature regime by ca. 50 K. This suggests that the presence of lignin significantly affected the biomass pyrolysis behavior. Thus, the pyrolysis behavior of the biomass cannot be predicted simply from the individual components without considering their interactions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2018;140(6):062204-062204-5. doi:10.1115/1.4039318.

This paper reports an experimental study of the effect of biochar addition and temperature on hydrogen production in the first phase of the two-phase anaerobic digestion (TPAD) of carbohydrates food waste. Anaerobic digestion (AD) experiments using white bread representing carbohydrate food wastes were conducted in bench scale 100 ml reactors. The cultures with biochar addition were placed in the reactors and incubated at different temperatures (18, 35, and 52 °C) over a period of 8 days. The biochar addition ratio was varied from 0 to 18.6 g l−1. The daily volumetric hydrogen production was measured, and the cumulative yield (YH) and daily production rate (RH) of hydrogen were calculated. Both biochar addition and temperature affected hydrogen production significantly. YH and maximum RH increased as the biochar addition ratio increased from 0 to 10 g l−1 then decreased as the biochar addition ratio further increased up to 18.6 g l−1. At different temperatures, YH varied significantly, increasing from 846 ± 18 ml l−1 at 18 °C to 1475 ± 53 ml l−1 at 35 °C and dropped to 1149 ± 26 ml l−1 at 52 °C. The maximum RH also peaked at 35 °C, reaching 858 ± 57.1 ml l−1 day−1. The effect of biochar addition was more profound under mesophilic conditions. The results of this study confirmed the beneficial effect of biochar addition in hydrogen production of carbohydrate food waste in the TPAD process.

Commentary by Dr. Valentin Fuster

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