Properties,combustion behavior,and kinetic triplets of coke produced by low-temperature oxidation and pyrolysis:Implications for heavy oil in-situ combustion

This work aimed at investigating the crucial factor in building and maintaining the combustion front during in-situ combustion(ISC),oxidized coke and pyrolyzed coke.The surface morphologies,elemental contents,and non-isothermal mass losses of the oxidized and pyrolyzed cokes were thoroughly examined.The results indicated that the oxidized coke could be combusted at a lower temperature compared to the pyrolyzed coke due primarily to their differences in the molecular polarity and microstructure.Kinetic triplets of coke combustion were determined using iso-conversional models and one advanced integral master plots method.The activation energy values of the oxidized and pyrolyzed cokes varied in the range of 130-153 k J/mol and 95-120 kJ/mol,respectively.The most appropriate reaction model of combustion of the oxidized and pyrolyzed cokes followed three-dimensional diffusion model(D_(3)) and random nucleation and subsequent growth model(F_(1)),respectively.These observations assisted in building the numerical model of these two types of cokes to simulate the ISC process.

Thermal Kinetics and Decomposition Mechanism of 1-Amino-1,2,3-triazolium Nitrate

The thermal decomposition kinetics of 1-amino-l,2,3-triazolium nitrate（ATZ-NO3） was investigated by non-isothermal TG-DTG at various heating rates（2,5,10,15 and 20 ℃/min）.The results show that the thermal decomposition of ATZ-NO3 consists of two stages corresponding to the losing of nitrate anion,substituent group and the splitting of triazole ring respectively.The kinetic triplets of the two stages were described by a three-step method.First,the differential Kissinger and intergral Ozawa methods were used to calculate the apparent activation energies（E） and pre-exponential factors（A） of the two decomposition stages.Second,two calculation methods（intergral （S）atava-（S）esták and differential Achar methods） were used to obtain several probable decomposition mechanism functions.Third,three judgment methods（average,double-extrapolation and Popescu methods） were used to confirm the most probable decomposition mechanism functions.Both reaction models of the two stages were randominto-nucleation and random-growth mechanisms with n=3/2 for the first stage and n=1/3,m=3 for the second stage.The kinetic equations for the two decomposition stages of ATZ-NO3 may be expressed as da/dt=1013.60·e-128970/RT（1-α）[-1n（1-α）]-1/2 and da/dt=1011.41·e-117370/RT（1-α）[-1n（1-α）]-2/3.The thermodynamic parameters including Gibbs free energy of activation（△G≠）,entropy of activation（△S≠） and enthalpy of activation（△H≠）,for the thermal decomposition reaction were also derived.

Kinetic triplet from low-temperature carburization and carbon deposition reactions

Carbon deposition reaction is unfavorable for smooth operation of blast furnace,while the product of carburization reaction is a superior iron-bearing raw material in non-blast furnace routes.The kinetic triplet of these two reactions was obtained based on non-isothermal kinetic analysis.According to the Sharp–Wentworth method,the activation energy of the carburization reaction is 397.77 kJ/mol,and the activation energies of the carbon depositions on hematite and magnetite are 188.92 and 100.89 kJ/mol,respectively.The carburization reaction is controlled by the Jander mechanism,and the carbon depositions on hematite and magnetite are both controlled by the mechanism of Zhuravlev–Lesokhin–Tempelman.Based on Coats–Redfern method,the activation energies of the above three reactions are 360.65,149.29,and 102.36 kJ/mol,respectively.The carburization reaction is a first-order reaction,while the carbon depositions on hematite and magnetite are both third-order reaction.In particular,the negative activation energy is obtained if considering the anti-Arrhenius circumstance in the Sharp-Wentworth method.Based on above results,it is feasible to adopt non-isothermal kinetic method to study the kinetic triplet of a reaction.According to the obtained activation energies and reaction mechanism functions,the simulated kinetic data are in good agreement with the experimental values even using the negative activation energy.