Kinetic Study of Coal Char Thermal Deactivation

Abstract

As one of the significant properties in char combustion, char reactivity has been widely investigated. However, the previous deactivation kinetic models are unable to predict the char reactivity for different kinds of coals because of (i) the complex components of different coals; (ii) the additional holding process during heat treatment. In this study, the char reactivity under different heating rates was studied by a self-developed two-step fluidized bed reactor. The char deactivation model is proposed and applied in Carbon Burnout Kinetics (CBK). The results show that char tends to a higher reactivity under a high heating rate, and increasing holding time at the terminal temperature would further decrease char reactivity. Predicting results of char deactivation model are close to experiment results, indicating that this model has a good predicting ability. After applying this model to CBK, modified-CBK (M-CBK) has a better predicting performance for different kinds of coals in char combustion.

Effect of CO2 and H2O on Char Properties. Part 2: In Situ and Ex Situ Char in Oxy-Steam Combustion

“…We self-developed the MFB-TIRA to study combustion kinetics of in situ char and ex situ char at different cooling rates. Detailed descriptions can be found in our previous study. , As shown in Figure , MFB-TIRA mainly contains three parts, i.e., a micro drop tube furnace, a micro fluidized bed, and PLC. The micro drop tube furnace was the location for coal pyrolysis.…”

“…The active surface area was obtained by measuring the oxygen chemisorption capacity of the char surface. After oxygen chemisorption, the oxygen complexes, such as CO and CO 2 , were released and measured by mass spectrometry (Ametek Dycor-LC-D 100) during the desorption process . Three different cooling chars were characterized for their physical and chemical structure evolution.…”

“…Detailed descriptions can be found in our previous study. 19,20 As shown in Figure 1, MFB-TIRA mainly contains three parts, i.e., a micro drop tube furnace, a micro fluidized bed, and PLC. The micro drop tube furnace was the location for coal pyrolysis.…”

“…After oxygen chemisorption, the oxygen complexes, such as CO and CO 2 , were released and measured by mass spectrometry (Ametek Dycor-LC-D 100) during the desorption process. 19 Three different cooling chars were characterized for their physical and chemical structure evolution. It should be pointed out that in situ char cannot be collected and characterized.…”

“…Further, char combustion kinetics have been studied over the past decades, and several reaction models have been built. ,− Some of these models have been applied to CFD simulation to predict char combustion rate, which requires kinetic parameters, including activation energy and the pre-exponential factor. Obtaining intrinsic kinetic parameters is a very important issue.…”