The modeling and design of large-scale thermochemical reactors are depending on reliable kinetic data. Thermogravimetric analyzer is a common tool for most kinetics studies. However, the test is usually conducted at ambient pressure with slow heating rate based on weight change. Though some analyzers are currently equipped with evolved gas analyzer and can operate under high pressure, there are still many restrictions on the gaseous environment. This kind of advanced analytical instrument is very expensive as well. Moreover, the sample is initially located in the thermogravimetric analyzer and then heated up, which is far from the practical operation. Therefore, the kinetic study using a specific reactor configuration which can simulate the way to transport the feedstock into a hot and pressurized reactor with high heating rate is more attractive and reliable.
A novel inverted batch reactor associated with an instant high pressure feeding system can be a better option for the kinetic study of most thermochemical conversion technologies such as gasification. The new design was inspired by the free fall reactors under atmosphere pressure. The configuration is mainly consisted of a tubular reactor with perforated quartz disc, a pressure-driven feeding system, an inverted magnetically controlled agitation system, a gas collection system with capillary line, and a mass spectrum analyzer. In particular, the outlet flowrate to the gas analyzer is controlled by the capillary line for minimizing the gas loss in the reactor during the analysis. The temperature profile after injecting the sample is very stable.
The real-time concentrations of major product gases such as CH4, CO and CO2 are obtained according to the corresponding intensities on the mass spectrum. Then the gas evolution can be depicted for kinetic measurement. A simplified 1st order kinetic model can be applied, which assumes that the feedstock decomposition is through a series of 1st order parallel reactions and each gas species is generated from an independent, single and molecular reaction with individual activation energy.
In a word, the newly designed inverted system with high pressure feeding capability can simplify the kinetics study and reduce the cost. The configuration is flexible for different modes (open test or closed test) and different thermochemical technologies (e.g. pyrolysis, gasification). Also, the reliable kinetic data can be obtained using the simplified kinetic model.
Fan X1, Liu Z2, Norbeck JM1, Park CS1.Show Affiliations
- Bourns College of Engineering-Center for Environmental Research and Technology (CE-CERT), Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521-0425, United States.
- Department of Civil, Construction and Environmental Engineering, Marquette University, Milwaukee, WI 53233, United States. Electronic address: [email protected]
A newly designed inverted batch reactor equipped with a pressure-driven feeding system was built for investigating the kinetics of syngas during the steam hydrogasification of biomass. The system could instantly load the feedstock into the reactor at high temperature and pressure, which simulated the way to transport the feedstock into a hot and pressurized gasifier. Experiments were conducted from 600°C to 700°C. The inverted reactor showed very high heating rate by enhancing the carbon conversion and syngas production. The kinetic study showed that the rates of CH4, CO and CO2 formation during steam hydrogasification were increased when the gasification temperature went up. Steam hydrogasification had comparatively lower activation energy for CH4 production. The activation energies of CH4, CO and CO2 during steam hydrogasification were 42.8, 51.8 and 14kJ/mol, respectively.
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