Thermal Debinding Kinetics of Gelcast Ceramic Parts via a Modified Independent Parallel Reaction Model in Comparison with the Multiple Normally Distributed Activation Energy Model

Abstract

This work aims to provide useful insights into the thermal debinding kinetics of gelcast ceramic parts, especially for debinding kinetics prediction involving heat preservation. Debinding experiments were conducted in a differential thermogravimetric analyzer at five heating rates (5, 8, 10, 15, and 20 °C/min) in the temperature range of 35–900 °C under an air atmosphere. The conversion (α) and pyrolysis rate (dα/d T ) data were simulated using a modified independent parallel reaction (IPR) model and a multiple normally distributed activation energy model (M-DAEM). Their validity was assessed and compared by checking the agreement between the experimental results and the prediction capability. The results showed that both the modified IPR model and M-DAEM had high predictability for thermal debinding kinetics under linear heating conditions. The fitting quality parameters (Fit) were less than 1.406 and 1.01%, respectively. The activation energies ( E i , i = 1, 2, 3, 4, and 5) calculated by the M-DAEM ranged from 153.312 to 217.171 kJ/mol. The relationships between E i of pseudo components 1 to 5 calculated by the modified IPR model were a function of the conversion rate. The E i values were E 1 (α) = 116.750 + 11.153α – 26.772α 2 + 4.362α 3 kJ/mol, E 2 (α) = 139.595 – 66.162α + 75.702α 2 – 38.041α 3 kJ/mol, E 3 (α) = 190.854 + 135.755α – 214.801α 2 + 116.093α 3 kJ/mol, E 4 (α) = 64.068 + 280.086α – 380.270α 2 + 264.724α 3 kJ/mol, and E 5 (α) = 188.257 – 77.086α + 74.129α 2 – 48.669α 3 kJ/mol, respectively. However, it is noteworthy that the α and dα/d T curves predicted by the modified IPR model with a deviation of less than 8% were better than those predicted by the M-DAEM for the linear thermal debinding process with the holding stage. Accordingly, it is believed that the proposed modified IPR model is suitable for describing the thermal debinding kinetics involving the heat preservation of gelcast green parts.

Predicting Pyrolysis of a Wide Variety of Petroleum Coke Using an Independent Parallel Reaction Model and a Backpropagation Neural Network

“…In addition, it was found that a thermal hysteresis appeared in the DTG curve as the heating rate increased. The peak value of the DTG curves increased and shifted to the high-temperature region, due to the different conversion rates of petroleum coke at different heating rates …”

“…The IPR model has been widely used in pyrolysis fields such as biomass and industrial waste, and relevant studies reported that model predictions agreed well with the experimental data. − The IPR model, also known as the n -pseudocomponent model, means that the pyrolysis process of petroleum coke can be described by several independent parallel first or n th reactions, each of which corresponds to the pyrolysis of different components in petroleum coke. This can be described as follows normald ( m t / m 0 ) normald t = prefix− prefix∑ c i · normald α i normald t goodbreak0em1em⁣ i = 1 , 2 , 3 , ... N normald α i normald t = k i · exp ( − E i R · T ) · false( 1 − α i false) n i where subscript i represents the i th pseudocomponent, and c i is the mass fraction of pseudocomponent i .…”

“…The performance of the IPR model was evaluated by the fitting quality parameter Fit (%) Fit ( % ) = 100 ∑ i = 1 n d false[ α exp , i − α cal , i false] 2 / N normalp where α exp, i and α cal, i represent the experimental data and calculated data, respectively, and N p denotes the number of unknown parameters.…”

“… 34 − 36 The IPR model, also known as the n -pseudocomponent model, means that the pyrolysis process of petroleum coke can be described by several independent parallel first or n th reactions, each of which corresponds to the pyrolysis of different components in petroleum coke. This can be described as follows 37 where subscript i represents the i th pseudocomponent, and c i is the mass fraction of pseudocomponent i .…”

“…The peak value of the DTG curves increased and shifted to the high-temperature region, due to the different conversion rates of petroleum coke at different heating rates. 37 3.2. TG−MS Analysis of Petroleum Coke.…”