K₂CO₃-Catalyzed CO₂ Gasification of Ash-Free Coal: Kinetic Study

Abstract

The kinetics of K 2 CO 3 -catalyzed CO 2 gasification of ash-free coal was investigated with a thermogravimetric analyzer and compared to raw coal and uncatalyzed ash-free coal. At 750 °C, the gasification of ash-free coal dry mixed with 20 wt % K 2 CO 3 was approximately 3 and 60 times faster than the raw coal and ash-free coal without catalyst, respectively. Increasing the amount of catalyst from 20 to 45 wt % increased the gasification rate 3-fold. The gasification rate of ash-free coal containing potassium catalyst strongly depended upon the pretreatment (i.e., heating gas atmosphere and heating time) because it directly affected the degree of catalyst reduction. The catalytic gasification behavior could only be predicted with the extended random pore model, whereas the random pore model and integrated model were essentially equal for fitting the gasification rate for raw and ash-free coal. The activation energy for the catalyzed ash-free coal gasification was approximately 100 kJ mol −1 larger than for raw coal and the uncatalyzed ash-free coal. This increase might be due to the energy required for the potassium (i.e., catalyst) transfer to a new carbon site or caused by the pyrolysis process, because the formed char might have different properties.

Preliminary study on co-gasification behavior of deoiled asphalt with coal and biomass

“…Once this phenomenon is detected, the catalytic effect can be easily explained: The potassium transfers from CC to DOA and causes the catalytic effect. The mechanism can be described as follows [38]:…”

Kinetic study of steam gasification of two mineralogically different lignite chars: An active site/intermediate model

“…ERPM behaved indeed well in denoting a maximum at a lower or higher carbon conversion [12]. Kopyscinski et al [11] further validated the high accuracy of ERPM to fit the uncatalyzed and K 2 CO 3 -catalyzed char gasification of ashfree coal char by comparing with RPM and other models. Despite the above success, the drawback of ERPM is apparent due to the introduction of two more parameters into RPM, c and p, either of which has no chemical meanings.…”

“…It remains a prevalent subject in recent researches [11][12][13]. The part of reason for this situation is that the char gasification kinetics is complicated by a multitude of influencing factors, particularly by the properties of char such as granularity, porosity, compositions and dispersion of minerals in char, and carbon structures [14].…”

Effect of metal content on CO₂ gasification behavior of K- and Fe-loaded bio-chars

“…In this case, the random pore model (RPM) was applied to estimate the CO 2 gasification rates of the chars (Bhatia and Perlmetter, 1980, Gil, et al, 2010, Yuan, et al, 2011. In cases where a drastic increase in the non-dimensional rate is observed at high carbon conversion (X > 0.6) during the CO 2 gasification of metal-loaded chars, the extended random pore model (eRPM) is usually applied to estimate the gasification rates (Tancredi, et al, 1996, Marques, et al, 2002, Zhang, et al, 2008, Kopyscinski, et al, 2013. However, in the present study, no drastic increase was observed even at high carbon conversion because the char particles were isolated each other on a pan in the thermogravimetric analyzer.…”

“…The CO 2 gasification reaction mechanism in the presence of K has been proposed to be as follows (Moulijn, et al, 1984, Kopyscinski, et al, 2013 …”