• Energy Research

Abstract Pyrolysis characteristics of Beizao oil shale in nitrogen were investigated by thermogravimetric analysis coupled with deconvolution procedure. A new method was proposed to separate multistep thermal decomposition process. Kissinger-Kai method was employed to determine the peak positions of main components involved in the complex reaction, and the overlapping peaks were separated by bi-Gaussian function according to the thermal knowledge of sub-reaction. The results showed that four parallel reactions were observed in the whole process, including the decomposition of kerogen, pyrite, carbonate, as well as removal of crystal water from clay minerals. Furthermore, the kinetic parameters of the separated reactions were estimated by traditional model-free and model-fitting methods on the basis of deconvolution analysis, wherein the optimal reaction models were modified with the accommodation function. Eventually, these parameters were optimized to predict the pyrolysis behavior. It was found that the obtained kinetic parameters and four-component reaction models can well characterize the entire pyrolysis process of Beizao oil shale.

AbstractChlorinated polyvinyl chloride (CPVC) is a widely‐used material in various fields with excellent properties. However, CPVC waste is one of the most intractable solids to dispose of. With the development of pyrolysis technology, some advantages have been exhibited, for example, it is flexible to convert solid waste into clean products by pyrolysis, which can be used as energy. Therefore, pyrolysis is considered as an effective method to dispose of solid waste. Especially, kinetic parameters are significant for pyrolysis, which contributes to reactor design and waste management. To better apply the kinetic parameters of CPVC to dispose of waste, thermogravimetric experiments were conducted to obtain the kinetic parameters and establish the reaction mechanism. The Tang, distributed activation energy model, and Advanced Vyazovkin methods were used to calculate the activation energy, and the reaction order was obtained by the Coats‐Redfern method. The results showed that the reaction consisted of two stages, and the average activation energy of the corresponding stage was 153.27 and 290.55 kJ/mol, respectively. However, the abovementioned parameters by traditional methods were not enough to characterize the whole pyrolysis behaviors, then the obtained kinetic parameters were further optimized and extra parameters were computed by the Particle Swarm Optimization algorithm.

Abstract This paper investigates the temperature profile of large scale RP – 5 aviation kerosene pool fire in an open space through a series of large scale experiments of 1 m2, 5 m2, 10 m2, 25 m2 pool sizes. The temperature profile is acquired by thermocouple trees positioned in various distances to the pool centerline, while the ambient wind velocity is captured by four transducers in the experimental field. Results show that the large scale pool fire behaves different to the used small to medium scale experiments. The mass loss rate is in good agreement with Blinov and Khudyakov’s results, but the vertical temperature is much lower than the McCaffery’s results due to the reduced global combustion efficiency as more sooty smoke produced. The three regimes in McCaffery’s model is redefined, correlating well with the vertical temperature profile upon the pool centerline. Gaussian Fit is well proposed for the lateral temperature profile at the pool base level, however as the ambient wind inevitable, the fire plume would be tilted to the downstream direction. Finally, the isothermal diagrams of fire plume for various pool sizes are plotted showing the temperature field of plumes, and also the tilt angle of plumes is presented.

Abstract Thermoplastic polymers are versatile for different fields, and their waste is produced largely. Among the waste treatment methods, pyrolysis is an important method to dispose of thermoplastic polymers waste because of potential energy utilization. Furthermore, accurate pyrolysis kinetic parameters can reflect the pyrolysis process. Therein, reaction order n is an essential factor to characterize reaction kinetics, while the difference between different n values is very small, so the accuracy of n should be paid more attention. To obtain the accurate n value of thermoplastic polymers waste in nitrogen, one representative material called extruded polystyrene (XPS) was studied by using thermogravimetric analysis at five heating rates. The kinetic parameters and thermodynamic parameters were calculated simultaneously, and n was estimated by multiple methods (master plots, model-free, Shuffled Complex Evolution (SCE) and model reconstruction) at heating rates of 10, 30 and 40 K/min. The results showed that XPS waste had important energy potentials, and the n was 2, 2.08, 1.99 and 1.64 for four methods, respectively. Moreover, based on fixed kinetic parameters, the accuracy of n obtained by multiple methods was compared at 3 and 80 K/min not used to estimate kinetic parameters. The accuracy of these methods was: SCE > model reconstruction > model-free > master plots.

Abstract Pyrolysis of beech wood (Fagus sylvatica) was investigated based on thermogravimetric analysis coupled with Fourier transform infrared spectrometry analysis at heating rates from 20 K/min to 60 K/min. The various activation energies were estimated at different conversions by three model-free methods and were in the range of 146.84–174.44 kJ/mol. The peak locations of three main components (hemicellulose, cellulose and lignin) were predicted more exactly by the K-K method. The absorbance spectra corresponding to the three peak locations were basically the same at different heating rates, indicating that the heating rate had little influence on the produced composition. During the whole pyrolysis process, the evolution of gas components (CO, CO2, methane, methanol and formaldehyde) was consistent with the trend of derivative thermogravimetric curves, and possible formation pathways of main gases were tentatively presented. The amount of these five components produced in the order of most to least produced was formaldehyde > CO2 or methanol > methane > CO. In particular, the amount of formaldehyde was almost triple the amount of methanol and ten times the amount of methane at the maximum peak.

Abstract The pyrolysis of lignocellulosic biomass has received extensive attention due to its potential as an alternative and renewable energy source. The chemical reaction kinetic parameters, obtained by micro-scale thermogravimetric experiments and optimized by the Shuffled Complex Evolution method, are one of the key factors to represent the pyrolysis process. The bench-scale Fire Propagation Apparatus experiment with sample size of 0.1 m × 0.1 m is conducted to investigate the scale effect of these parameters during the pyrolysis process in a N2 environment. These optimized parameters are applied to the pyrolysis model based on Gypro considering the three-component parallel reaction mechanism, moisture and volume change to simulate the bench-scale experiment based on FireFOAM coupled with the dynamic mesh technology. Eventually, the predicted results agree well with experimental data, validating the effectiveness of the current parameters. Moreover, the effects of chemical reaction kinetic parameters from different references or models are further analyzed based upon the predicted results.

Abstract The pyrolysis of woody biomass has received extensive attention due to its importance in the thermal chemical conversion and energy utilization. Due to the complexity of actual reaction scheme, the pyrolysis of wood is generally modeled on the basis of apparent kinetic models. In this paper, six classic lumped kinetic models (Models I-VI) were applied and compared with each other to analyze their sensitivity coupled with Shuffled Complex Evolution method based on the measured thermogravimetric data. The optimized kinetic parameters were used to predict the pyrolysis process, and then verify the validity of different reaction kinetic models. The results show that the existence of second tar reaction for one-component mechanism and the refinement of reactant components for multi-component mechanism can be helpful to improve the reasonability of reaction models. Eventually, the simplest global reaction Model I and second tar reaction involved one-component Models III, IV, as well as three-component parallel reaction Model V can achieve the better compatibility of reaction kinetic models and Shuffled Complex Evolution optimization, with the acceptable efficiency to describe the pyrolysis of woody biomass.

Abstract This paper investigates building eave effect of fire-induced ejected plume from a room window and its heat flux imposing upon the facade wall. Based on a 1:8 cubic model and Froude modeling, a series of reduced scale experiments are set up. The window dimensions and total heat release rate due to a room fire are changed during experiments. The eave upon the facade wall, made of noncombustible fiber board is installed horizontally above the window top, varying with different vertical heights (distance of the eave to the window top) and lengths (direction normal to the facade wall). The facade flame height is recorded by a CCD camera, while the heat fluxes imposing upon the facade wall are collected by five water-cooled heat flux gauges. Results show that the ejected flame with horizontal eave can be distinguished into the “free flame stage”, the “flame horizontal spread stage” and the “flame overflow stage”. The visible flame height and heat flux within the “flame overflow stage” are detailed discussed, revealing the physical mechanism of the vertical height and length of the horizontal eave effects. Finally, an implicit correlation in regarding with the visible flame height, the updated flame extension area beneath the horizontal eave as well as the vertical height of the horizontal eave to the window top is established. Taking the horizontal eave conditions into consideration, the heat flux correlation is well corrected and proposed. The results would provide theoretical basis for the fire-induced thermal protection in high buildings.

Abstract Since the horizontal projection upon the building facade are widely used in vertical fire-induced thermal protection, this paper is focused on the temperature decay beneath a horizontal projection of spilled plumes from a compartment window. A series of 1:8 reduced scale experiments were carried out in a cubic compartment. The window dimensions as well as the total heat release rates were variable, whilst the temperature was measured by thermocouples installed beneath a horizontal projection, which was located right attached to the facade wall at the top of the compartment window. The temperature field beneath the horizontal projection was found to be singular to a naturally formed ceiling jet. The elongation of temperature field in the longitudinal direction was observed, which should be attributed to the extra horizontal velocity provided by the window spilled plume, and meanwhile, the horizontal velocity started to take advantage as the flow spreads. Finally, the temperature decay in both longitudinal and transversal directions are well correlated by dimensionless functions. The results would provide crucial references in the realistic interpretation on the thermal and strength performance of building structure in building fire scenarios.