Combustion Kinetics Research Articles

A Large-Eddy Simulation study on the effect of fuel configuration and pan distance towards chemical species for under-ventilated compartment fire scenario

A set of numerical analyses was conducted to investigate the effect of fuel location of dual burners in an under-ventilated ISO9705 compartment room. Moreover, the influences of the burner separation displacement on the fire development, the evolution of thermal layers, the distribution of toxic gas species were comprehensively studied. The simulations were conducted using a novel in-house large eddy simulation (LES) based fire field model comprised of subgrid-scale (SGS) turbulence, detailed chemical kinetics of combustion, soot and radiation models. The first part of the simulation focused on 3 different fuel distributions: single centre burner (SCB), single rear burner (SRB) and two distributed burner (TDB). Alternative configurations were considered for dual burners with 4 different distances between the dual burners, to study the influence towards air flow at the doorway, internal temperature profile and major chemical species (i.e. CO/CO2) distributions. The numerical outcome states that fuel distribution has a minor effect on heat release rate and the total CO2 amount but noticeable differences in CO's generation and distribution. Overall, the temperature and gas field predictions were almost identical for all dual burner cases, while significant differences were observed at the rear section of the compartment, especially temperature, CO/CO2vol fraction and soot concentration.

Thermogravimetric analysis of the pyrolysis and combustion kinetics of surface dead combustibles in the Daxing'an Mountains.

In boreal regions, the frequency of forest fires is increasing. In this study, thermogravimetric analysis was used to analyze the pyrolysis kinetics of dead surface combustibles in different forest types within the Daxing’an Mountains, China. The results show that the combustible material load of forest types, the Larix forest (LG) is relatively high. Base on the E of kinetic parameters, the LG, and Quercus forest (QM) forest types had relatively high combustibility values and comprehensive combustibility values for 1-, 10-, and 100-h time lags. According to the obtained P values, the pyrolysis of dead surface fuels with 1-, 10-, and 100-h time lags is relatively difficult in the Larix / Betula mixed forest (L-B) and QM forest types. Therefore, mixed forests of the LG, L-B, and QM tree species can be established as fire-resistant forests to establish a fire barrier, reduce the combustibility of forest stands, and reduce the possibility of forest fires.

An effective method to remove organic sulfur in coal: Effects on the physicochemical properties and combustion kinetics

The present work investigated an effective method to remove organic sulfur in coal utilizing different microorganisms (Nocardia mangyaensis and Pseudomonas putida). The most obvious finding to emerge from the sulfur forms analysis is that the organic sulfur removal of these two bacterial strains on Yunnan bumuga high-sulfur coal were 61.58% and 54.19%, respectively. This result may be confirmed by the Fourier transform infrared spectroscopy (FTIR) analyses that there were obvious decreases of intensity after biotreatment in the CS bond. Besides, the results of X-ray diffraction and X-ray photoelectron spectroscopy showed that major mineralogical phases in the forms of kaolinite and pyrite exist in raw coal. And more than 80% of thiophene and sulfoxide in the raw coal were removed by N. mangyaensis and P. putida. In addition, the results of the thermogravimetric analysis indicated that the combustion performance of biotreated coal samples was better than that of raw coal, and the most probable models to describe the combustion kinetics for biotreated coal and raw coal at different stages were obtained by the Arrhenius method and Coats–Redfern method.

Hydrothermal carbonization of the waste straw: A study of the biomass transient heating behavior and solid products combustion kinetics

In this study, HTC impact on the waste straw fuel properties and waste straw hydrochars combustion kinetics have been presented. HTC experiments were carried out at Parr 4650 250 ml batch reactor, at temperatures of 225, 250, and 275 °C. Each temperature was investigated at 4 residence times: 10, 20, 30, and 40 min. Denoted hydrochars yields were more influenced by temperature than residence time, with different decomposition patterns observed at 275 °C compared to 225 and 250 °C, with final solid yields of 42.0%, 66.9%, and 65.3% at 40 min residence times respectively. The study of the transient HTC period resulted in the determination of the exothermal WS activity with the heat release of the 254.9 ± 48.8 kJ/kg of biomass. LHV values of the obtained hydrochars were 18.7–20.2 MJ/kg, 19.9–22.2 MJ/kg, and 23.1–26.2 MJ/kg for HTC temperatures of 225, 250, and 275 °C respectively. TGA analysis of the hydrochar combustion highlighted significant changes in the kinetic interpretation of the combustion profiles throughout investigated temperature ranges. The influence of residence time was only significant in the case of the 275 °C HTC samples, where a major shift of the combustion reactivity towards higher-temperature char oxidation was denoted. Hydrochars combustion kinetics were modeled with the implementation of Fraser-Suzuki deconvolution, and model-fitting of nth-order Arrhenius equation, with R2 values within 0.98–0.99.

Kinetics of the Catalytic Combustion of Ethanol and Ethyl Acetate with Estimation of Activation Energy and Rate Constants: An Analytical Study

Background: A mathematical model for the combustion of ethanol and ethyl acetate mixtures using Mn9Cu1 (mixture of manganese and copper with a weight ratio of 9:1) catalyst is discussed. The model’s kinetic mechanism is expressed in terms of nonlinear reaction-diffusion equations with common initial and boundary conditions in a finite planar, cylindrical, and spherical geometry. : A Taylor series approach is used to derive general approximate analytical expressions of ethanol, acetaldehyde, and ethyl acetate molar concentrations inside the particle and reactor phase for various values of rate constants, diffusion, and kinetic parameters. The effect of shape factor for the planar, cylindrical, and spherical geometry of dispersed particles was examined for the first time. Activation energy and rate constant at the reference temperature of ethanol, acetaldehyde, and ethyl acetate are also obtained from the rate equations. A direct comparison with numerical simulations confirms the accuracy of the derived analytical results. Objective: Derive general approximate analytical expressions of ethanol, acetaldehyde, and ethyl acetate molar concentrations inside the particle and reactor phase for various parameter values. Methods: We employ the simple and reliable Taylor series method. Results: Semi-analytic expressions of the concentration and bulk concentration of ethanol, ethyl acetate, and acetaldehyde. Conclusion: Approximate analytical expressions of the concentrations of ethanol, acetaldehyde and ethyl acetate were derived for arbitrary catalyst particle (planar, cylindrical and spherical) by using a simple, reliable, and robust method. In addition, the concentration of the species in reactor phase was also reported. The effects of the kinetic parameters, which are influenced by adsorption equilibrium constant, effective diffusivity, activation energy, on concentration, were discussed.

Safety of a rotating detonation engine fed by acetylene – oxygen mixture launching stage

The process of starting the rotating detonation engine initially filled with air in low outer pressure conditions was studied. Such engines can be used for bringing satellites into the Earth orbit. A three-dimensional numerical simulation of an engine combustion chamber with a rotating detonation wave of a cylindrical type with an internal body fed by a hydrogen-oxygen mixture or an acetylene-oxygen mixture was performed. The influence of the lengths of the combustion chamber channel on the stability of the detonation wave and thrust characteristics was considered. An author's computer code was used in simulations, the code was based on a model of multicomponent gas dynamics with chemical transformations and turbulence. The code was tested by comparing it with experiments and analytical solutions for simple cases. To describe the kinetics of acetylene combustion, a simplified chemical scheme of interaction of 10 components was used, without “heavy” radical species: [C2H2, CO, CO2, H2, O2, H2O, OH, O, H, N2]. The influence of the chosen kinetic mechanism in case of hydrogen-oxygen mixture on the simulation results was studied. Various modes of the process in the detonation engine were obtained, including those with a stable detonation wave.

Combustion performance of fine screenings from municipal solid waste: Thermo-kinetic investigation and deep learning modeling via TG-FTIR

The combustion behavior, kinetics, thermodynamics and gas products of fine screenings (FS) classified from municipal solid waste (MSW) in an air atmosphere were explored by TG-FTIR. A deep learning model was established using 1D–CNN–LSTM algorithm to predict thermogravimetric data of FS combustion, with visualization technology (TensorBoard) applied to display the weights and biases in various cells. The thermogravimetric analysis (TG) and differential thermal gravity (DTG) curves indicated that the FS combustion process can be divided into four stages. The average activation energy (Ea) of FS combusted at different stages, exhibited different change tendencies with increasing levels of conversion (α). The highest enthalpy (ΔH) of 206.40 kJ/mol and free Gibbs energy (ΔG) of 55.03 kJ/mol emerged in stage Ⅳ, while the highest changes of entropy (ΔS) of 169.11 J/(mol·K) occurred in stage Ⅱ. The main gas products (CO2, H2O and CO) and functional groups (CO and phenols) were all detected. For the 1D–CNN–LSTM model, the optimal settings for the prediction of thermogravimetric data were a neuron number of 150, dropout of 0.003, epoch number of 200, and batch size of 25. The highest correlation coefficient (R2) of 94.41% was obtained using the optimum model parameters, achieving an excellent prediction performance.

Predictive Combustion Kinetics of OH Radical Reactions with a C5 Unsaturated Alcohol: The Competitive H-Abstraction and OH-Addition Reactions of 2-Methyl-3-buten-2-ol.

2-Methyl-3-buten-2-ol (MBO232) is a potential biofuel and renewable fuel additive. In a combustion environment, the consumption of MBO232 is mainly through the reaction with a OH radical, one of the most important oxidants. Here, we predict the intricate reactions of MBO232 and OH radicals under a broad range of combustion conditions, that is, 230-2500 K and 0.01-1000 atm. The potential energy surfaces of H-abstraction and OH-addition have been investigated at the CCSD(T)/CBS//M06-2X/def2-TZVP level, and the rate constants were calculated via Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) theory. The decomposition reactions of the critical intermediates from the OH-addition reactions have also been studied. Our results show that OH-addition reactions are dominant below 850 K, while H-abstraction reactions, especially the channel-abstracting H atoms from the methyl groups, are more competitive at higher temperatures. We found that it is necessary to discriminate H atoms attached to the same C atom, as their abstraction rates can differ by up to 1 order of magnitude. The calculated results show good agreement with the reported experimental data. We have provided the modified Arrhenius expressions for rate constants of the dominant channels. The kinetic data determined in this work are of much value for constructing the combustion models of MBO232 and understanding the combustion kinetics and mechanism of other unsaturated alcohols.

Study on the Microscopic Mechanism of Spontaneous Combustion and Oxidation Kinetics of Water-Leached Coal

In this article, a series of experiments have been carried out to study the spontaneous combustion and oxidation mechanism of coal after water immersion and investigate its tendency to spontaneous combustion, analyze the difficulty of spontaneous combustion of coal samples under different water immersion conditions, and establish a kinetic model of water immersion coal oxidation (taking the Bulianta 12# coal as a case study). They rely on physical oxidation adsorption, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry, and oil bath heating. SEM has been used to analyze the characteristics of coal pore structure under different water immersion conditions (water-saturated coal samples under different water loss conditions until the coal samples are completely dried); FTIR served to investigate the characteristics of the molecular chemical structure of the coal surface before and after the coal is immersed in water. Through programmed temperature oxidation experiments combined with FTIR analyses and gas chromatographic (GC) analysis of gaseous products, it has been possible to study the changes of molecular structure and gas products on the surface of coal samples at different temperatures and water immersion conditions. The oxidation reaction rate of the 12# coal samples of Shendong Mine’s Bulianta Mine under different water content conditions during the spontaneous combustion process has been quantitatively studied. The difficulty of spontaneous combustion of coal samples has been correspondingly addressed. A kinetic model from the perspective of oxygen consumption has been proposed. Thermogravimetry-differential scanning calorimetry (TG-DSC) has been used to analyze and study the exothermal oxidation process before and after coal immersion. From the perspective of the exothermic intensity of the coal-oxygen reaction, an oxidation kinetic model for immersed coal samples has been developed to qualitatively determine its spontaneous combustion tendency. Results have shown that the increase in the specific surface area increases the risk of spontaneous combustion, and coal samples after soaking and drying have a stronger tendency to spontaneous combustion than raw coal. The moisture content of the coal sample leading to the easiest ignition conditions is 16.05%. Regardless of the moisture content, the critical temperature is maintained at 65–75°C, and the temperature of the left coal in the goaf should be prevented from exceeding this critical value.

Acceleration of Chemical Kinetics Computation with the Learned Intelligent Tabulation (LIT) Method

In this work, a data-driven methodology for modeling combustion kinetics, Learned Intelligent Tabulation (LIT), is presented. LIT aims to accelerate the tabulation of combustion mechanisms via machine learning algorithms such as Deep Neural Networks (DNNs). The high-dimensional composition space is sampled from high-fidelity simulations covering a wide range of initial conditions to train these DNNs. The input data are clustered into subspaces, while each subspace is trained with a DNN regression model targeted to a particular part of the high-dimensional composition space. This localized approach has proven to be more tractable than having a global ANN regression model, which fails to generalize across various composition spaces. The clustering is performed using an unsupervised method, Self-Organizing Map (SOM), which automatically subdivides the space. A dense network comprised of fully connected layers is considered for the regression model, while the network hyper parameters are optimized using Bayesian optimization. A nonlinear transformation of the parameters is used to improve sensitivity to minor species and enhance the prediction of ignition delay. The LIT method is employed to model the chemistry kinetics of zero-dimensional H2–O2 and CH4-air combustion. The data-driven method achieves good agreement with the benchmark method while being cheaper in terms of computational cost. LIT is naturally extensible to different combustion models such as flamelet and PDF transport models.

Optimization of rice husk hydrochar via microwave-assisted hydrothermal carbonization: Fuel properties and combustion kinetics

The optimization of rice husk hydrochar was carried out via microwave-assisted hydrothermal carbonization to find the optimum parameters for hydrochar production. Three optimized hydrochar was selected to find the best properties for solid biofuel application. The percentage difference between predicted and experimental values was below 10% for all optimized hydrochar. Hydrochar B (optimized for maximum high heating value) has the highest fixed carbon (29.86%), lowest volatile matter (54.6%), lowest ash (8.87%) and highest higher heating value (18.9 MJ/kg) compared to raw rice husk, hydrochar A (maximum solid yield) and hydrochar C (maximum solid yield and higher heating value). The result suggests that the optimized hydrochar produced is comparable to lignite and can be used as direct solid biofuel.

Combustion Kinetics of Coal Treated by Microwave Irradiation Combined with Hydrochloric Acid Pickling.

The desulfurization efficiency, combustion properties, combustion kinetics, and structural changes of Kentucky coal under microwave irradiation (MI) combined with hydrochloric acid solution pickling were investigated and compared using a thermogravimetric analyzer coupled to a Fourier transform infrared spectrometer. The results show that the desulfurization rate increases with the concentration of hydrochloric acid solution. The introduction of MI can effectively improve the desulfurization efficiency. After desulfurization, the ignition temperature and burnout temperature of coal samples increase, the combustion index decreases, and the combustion performance deteriorates. The maximum weight loss rate decreases with the increase of the concentration of hydrochloric acid solution, and the activation energy of the coal sample after microwave treatment increases, and the reaction difficulty increases. The infrared analysis results show that MI and hydrochloric acid pickling treatment have little effect on the functional group structure of coal samples.

LES of Reacting Flow in a Hydrogen Jet into Supersonic Crossflow Combustor Using a New Turbulent Combustion Model

Modelling the complete flow physics and chemical kinetics of supersonic combustion is a particularly complex and daunting task that requires significant computational resources. To foster performance evaluation tools for future hypersonic vehicles, developing accurate yet computationally efficient solution methods is of great importance. In this work, a new subgrid combustion model for large eddy simulations is derived and used in a three-dimensional in-house flow solver to provide simulations of experimental scramjet ground tests. In particular, this paper introduces a hybrid model closure with the reaction-rate approach to close the filtered chemical source terms in the governing equations for species mass fractions and total energy. The model developed here makes use of a linear bridging function, depending on the segregation rate of the mixture fraction, between a resolved contribution issued from a perfectly stirred reactor (PSR) estimation, and a subgrid-scale (SGS) contribution where a closure that approximates the Lagrangian trajectory in the composition space is retained. The new model considers the effect of fluctuations of compositions and can be extended to take into account, for example, the fluctuations of temperature. The new approach is tested using a hydrogen-fueled scramjet combustor from circular injector into a Mach 2 vitiated airflow for total pressure and temperature of 0.40 MPa and 1695 K, respectively. The selected operating conditions are representative of the LAPCAT-II dual-mode ramjet/scramjet combustion. Chemistry is described using a four-step reduced mechanism. The results obtained with the present modelling proposal are compared to those issued from numerical simulations performed with the quasi-laminar chemistry or PSR approach. These results do show that, even for a highly resolved computational mesh, the effects of composition fluctuations remain significant, especially in the vicinity of the injection where the SGS fluctuations of the scalar field are non-negligible.

Combustion performance and kinetic modeling of lignite blended with torrefied biomass of different origin

ABSTRACT Biomass materials of different origin were upgraded by torrefaction and blended with lignite. Combustion characteristics, reactivity, and synergistic effects were determined through thermal analysis tests. An independent parallel reactions model was developed to describe combustion kinetics. According to the results, torrefaction delayed ignition and reduced the reactivity of biomass fuels. Blending of lignite with either raw or torrefied materials exhibited some synergy and improved the reactivity of lignite up to two times/fold. The model applied fitted the experimental results accurately. The kinetic parameters of lignite/torrefied biomass blends were closer to the values corresponding to lignite (ΔΕl = 74–235 kJ/mol, ΔΕl/t biomass = 80–223 kJ/mol), pointing to a higher similarity in mechanism of combustion and thermal behavior.

Effect of O2 concentration on combustion behavior and kinetics of coal gangue during oxy‐fuel combustion and oxy‐steam combustion

AbstractIn this work, the effect of O2 concentration on combustion behavior and kinetics of coal gangue during oxy‐fuel combustion and oxy‐steam combustion were studied by non‐isothermal thermogravimetric analysis technology. The results showed that the increase of O2 concentration could improve the combustion performance of coal gangue. The O2/CO2 atmosphere was unfavorable to the combustion of coal gangue compared with the O2/N2 atmosphere. Furthermore, the gasification reaction could accelerate overall carbon consumption in oxy‐steam combustion with 5% O2 concentration; and the presence of H2O could delay the ignition and accelerate burnout at this condition. Kinetic analysis showed that the combustion of coal gangue in O2/N2 and O2/CO2 atmosphere followed the first‐order kinetics under O2 concentrations studied; and the combustion in O2/H2O atmosphere followed the 0.5‐order kinetics at 5% and 10% O2 concentration, while it followed the first‐order kinetics at 21% O2 concentration.

Insight into the Ozone-Assisted Low-Temperature Combustion of Dimethyl Ether by Means of Stabilized Cool Flames.

The low-temperature combustion kinetics of dimethyl ether (DME) were studied by means of stabilized cool flames in a heated stagnation plate burner configuration using ozone-seeded premixed flows of DME/O2. Direct imaging of CH2O* chemiluminescence and laser-induced fluorescence of CH2O were used to determine the flame front positions in a wide range of lean and ultra-lean equivalence ratios and ozone concentrations for two strain rates. The temperature and species mole fraction profiles along the flame were measured by coupling thermocouples, gas chromatography, micro-chromatography, and quadrupole mass spectrometry analysis. A new kinetic model was built on the basis of the Aramco 1.3 model, coupled with a validated submechanism of O3 chemistry, and was updated to improve the agreement with the obtained experimental results and experimental data available in the literature. The main results show the efficiency of the tested model to predict the flame front position and temperature in every tested condition, as well as the importance of reactions typical of atmospheric chemistry in the prediction of cool flame occurrence. The agreement on the fuel and major products is overall good, except for methanol, highlighting some missing kinetic pathways for the DME/O2/O3 system, possibly linked to the direct addition of atomic oxygen on the fuel radical, modifying the product distribution after the cool flame.

Functional Group Characteristics and Pyrolysis/Combustion Performance of Karamay OS Based on FT-IR and TG-DTG Analyses.

Proximate analysis, ultimate analysis, Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetry–differential thermal analysis characterization were carried out on oily sludge (OS) samples OS1–OS5, from Karamay, Xinjiang, China. The Coast–Redfern model (CRm) was used to simulate the pyrolysis and combustion kinetics of oily samples. The results showed that the peak area percentage of benzene ring trisubstitution of OS5, in the range of 700–900 cm–1, is close to 75%, corresponding to its high volatile content. Based on the kinetic analysis by the CRm, it is found that the fitting degree of the five samples is better when the reaction order is selected as n = 2, with R2 close to 1.00 and 2RT/E to 0. Among them, the SN and DW of OS5 are 17.8 × 10–10%2 min–2 °C–3 and 0.10899 × 10–5% min–1 °C–2, respectively, higher than those of other samples, indicating a good combustion performance.

Numerical and Experimental Study on the Impact of Mild Cold Exhaust Gas Recirculation on Exhaust Emissions in a Biodiesel-Fueled Diesel Engine

Abstract This work evaluated the effect of cooled exhaust gas recirculation (EGR) on fuel consumption and pollutant emissions from a diesel engine fueled with B8 (a blend of biodiesel and no. diesel 8:92% by volume), experimentally and numerically. Experiments were carried out on a diesel power generator with varying loads from 5 kW to 35 kW and 10% of cold EGR ratio. Exhaust emissions (e.g., total hydrocarbons (THCs), nitrogen oxides (NOx), carbon monoxide (CO), etc.) were measured and evaluated. The results showed mild EGR and low biodiesel content have minor impact of engine-specific fuel consumption, fuel conversion efficiency, and in-cylinder pressure. Meanwhile, the combination of EGR and biodiesel reduced THC and NOx up to 52% and 59%, which shows promising effect on overcoming the particulate matter–NOx tradeoff from diesel engine. A three-dimensional computational fluid dynamics engine model incorporated with detailed biodiesel combustion kinetics and NOx formation kinetics was validated against measured in-cylinder pressure, temperature, and engine-out nitric oxide emission from diesel engine. This valid model was then employed to investigate the in-cylinder temperature and equivalence ratio distribution that predominate NOx formation. The critical results showed that the reduction of NOx emission by EGR and biodiesel is obtained by a little reduction of the local in-cylinder temperature and, mainly, by creating comparatively rich combusting mixture, which makes the combustion path pass through lower NOx zone in the ϕ–T diagram.

Thermogravimetric analysis of co-combustion between municipal sewage sludge and coal slime: Combustion characteristics, interaction and kinetics

Based on the physical and chemical properties of municipal sewage sludge (SS) and coal slime (CS), the combustion behaviors of SS, CS and their blends were investigated by the thermogravimetric analyzer. The interaction between SS and CS was evaluated, and the combustion reaction rate equations were obtained. The results suggest that during the co-combustion, SS could improve the ignition performance, while CS could enhance the activity in the high temperature zone and improve the slagging characteristics. There was the most significant interaction in 550–600℃, which had a positive effect on the entire combustion process, and the synergy reached its peak when the CS ratio was 40% with synergy index SI=1.53. The combustion of the blend was a multi-step process, which conformed to the nth-order model, and the addition of CS could reduce the apparent activation energy of SS during the entire combustion process.

Combustion Behavior and Kinetics Analysis of Isothermal Oxidized Oils from Fengcheng Extra-Heavy Oil

The low-temperature oxidation (LTO) of heavy oil is of great significance for the combustion front stability, which directly influences the efficiency and safety of in-situ combustion (ISC). To provide feasible heating by artificial ignition before the implementation of ISC in the Xinjiang Fengcheng (FC) oilfields, this paper investigates the oxidation behavior of FC extra-heavy oil and its isothermal oxidized oils. Firstly, FC extra-heavy oil was subjected to isothermal oxidation experiments conducted utilizing an oxidation reactor, and the physical properties of the gaseous products and oxidized oils were analyzed. The combustion behavior of the FC extra-heavy oil and oxidized oils was then studied by non-isothermal thermogravimetry and differential scanning calorimetry. Subsequently, the Friedman and Ozawa–Flynn–Wall methods were adopted to perform kinetic analysis. Oxygen consumption was always greater than the production of CO and CO2, so oxygen addition reactions were the main pathway in heavy oil LTO. H/C decreased to 8.31% from 20.94% when the oxidation temperature rose from 50 °C to 150 °C, which deepened the oxidation degree. The density and viscosity of 200 °C to 350 °C oxidized oils increased at a slower rate, which may be related to the LTO heat effect. The change law of temperature interval, peak temperature, and mass loss of the oxidized oils had a good correlation with the static oxidation temperature. Compared with other oxidized oils, the peak heat flow and enthalpy of 350 °C oxidized oil increased significantly with high-temperature combustion, and were 42.4 mW/mg and 17.77 kJ/mol, respectively. The activation energy of 350 °C oxidized oil began to decrease obviously around a conversion rate of 0.4, which indicates that it was beneficial to coke deposition with stronger activity. Finally, we came up with LTO reaction mechanisms and put forward a reasonable preheating temperature for the application of ISC in FC oilfields.