Coats-Redfern Integral Method Research Articles

Synergistic transformation: Kinetic and thermodynamic evaluation of co-pyrolysis for low-rank bituminous coal and polyurethane foam waste

Co-pyrolysis is regarded as a sustainable and ecologically friendly method of improving waste management, pollution control, and renewable energy security. This investigation reports a thermo-kinetic study of low-rank coal-polyurethane foam waste (C-PU) blends through co-pyrolysis and was characterized using a number of techniques such as CHNS-O, GCV, and FTIR. The thermal degradation behavior of C-PU blends during co-pyrolysis via TGA is studied, whereas the degradation process happens in three stages i.e. moisture, devolatilization, and slow degradation of the char in the temperature ranges viz. (25 –140 °C), (140 – 580 °C), and (580 – 900 °C) respectively. Synergistic effects observed may improve product qualities compared to those from separate pyrolysis. The presence of synergistic effects during co-pyrolysis was demonstrated by the positive variation in WL% and DTGmax values. The Coats-Redfern integral method was utilized to investigate the thermo-kinetic parameters of C-PU blends through twelve (12) reaction mechanism models. The activation energy (Ea) for 100C and 100PU was 60.08 kJ/mol and 100.8 kJ/mol via F2 and F3 models, although the optimum blend (50 C-50PU) showed 67.01 kJ/mol and 26.74 kJ/mol via F2 and D3 model in the first and second stage. Thermodynamic characteristics i.e. (∆G) and (∆H) displayed positive values, while (∆S) for each C–PU blend was negative, but the best blend further lowered it. It was found that the fuels could be ranked in the following order 100PU> 50 C-50PU> 100 C based on mean reactivity and pyrolysis factor. The co-pyrolysis of polyurethane foam waste with low-rank coal to develop alternative energy sources has been proposed as a potential method and is critical for designing an effective large-scale reactor system thus understanding the solid-state co-pyrolytic kinetics.

Experimental and kinetic study on pyrolysis and combustion characteristics of pesticide waste liquid

Waste liquid treatment is widely concerned with the deepening of people's awareness of environmental protection, especially for the waste liquid with a high chemical oxygen demand (COD), which also has a high calorific value and makes it possible for the incineration treatment. In this study, the pyrolysis and combustion characteristics of pesticide waste liquid (PWL) are investigated by using thermogravimetric experiment and kinetic analysis, and the effects of different water and salt contents on its pyrolysis and combustion are discussed. The results show that both pyrolysis and combustion processes of the simulated pesticide waste liquid (sPWL) could be divided into two stages. As the water content increases from 0% to 18.5%, the volatilization characteristic index of stage Ⅰ (low temperature) increases by 263.31%, while that of stage Ⅱ (high temperature) decreases by 28.32%, and the water content could promote the pyrolysis and comprehensive combustion performance of the sPWL. As the sodium chloride contents increase from 0% to 1.5%, both the pyrolysis and combustion process of the PWL are enhanced, and the volatile release characteristic index, the ignition temperature and burnout characteristic index increase by 60.77%, 18.74% and 47.95%, respectively. By the means of the Coats-Redfern integral method, the kinetics of the pyrolysis and combustion of the PWL are analyzed, with a linear correlation coefficient of more than 95%. In a whole, a suitable water and sodium chloride content in the pretreatment process is crucial for efficient and low-cost treatment of waste liquid, which can promote the pyrolysis and combustion processes. These results are expected to provide several insightful guidance for the efficient treatment of the waste liquid.

Thermogravimetric characteristics of corn straw and bituminous coal copyrolysis based the ilmenite oxygen carriers

Herein, the co-pyrolysis reaction characteristics of corn straw (CS) and bituminous coal in the presence of ilmenite oxygen carriers (OCs) are investigated via thermogravimetry coupled with mass spectrometry. The results reveal that the participation of OCs weakens the devolatilization intensity of co-pyrolysis. When the CS blending ratio is < 50%, the mixed fuel exhibits positive synergistic effects. The fitting results according to the Coats-Redfern integral method show that the solid-solid interaction between OCs and coke changes the reaction kinetics, enhancing the co-pyrolysis reactivity at the high-temperature zone (750–950 °C). The synergistic effect is most prominent at 30% CS blending ratio with co-pyrolysis activation energy being in the range 26.35–40.57 kJ·mol–1.

Apparent activation energy of mineral in open pit mine based upon the evolution of active functional groups

This study aimed to investigate the mechanism of mineral spontaneous combustion in an open pit. On the study of coal and mineral mixture in open pit mines, as well as through the specific surface area and Search Engine Marketing (SEM) experiments, the specific surface area and aperture characteristics of distribution of open pit coal sample and pit mineral mixture samples were analyzed. Thermal analysis experiments were used to divide the oxidation process was divided into three stages, and the thermal behavior characteristics of experimental samples were characterized. On the basis of the stage division, we explored the transfer law of the key active functional groups of the experimental samples. The apparent activation energy calculation of the key active groups, performed by combining the Achar differential method with the Coats–Redfern integral method, microstructural and oxidation kinetic properties were revealed. The resulted showed that the mixed sample had high ash, the fixed carbon content was reduced, the specific surface area was far lower than the raw coal, the large aperture distribution was slightly higher than the medium hole, the micropore was exceptionally low, the gas adsorption capacity was weaker than the raw coal, the pit coal sample had the exceedingly more active functional groups, easy to react with oxygen, more likely to occur naturally, and its harm was relatively large. The mixed sample contained the highest C–O–C functional group absorbance. The functional groups were mainly influenced by the self-OH content, alkyl side chain, and fatty hydrocarbon in the sample. The main functional groups of the four-like mixture had the highest apparent activation energy, and the two reactions were higher in the low-temperature oxidation phase.

Study on the suppression characteristics and mechanism of ABC powder on pulverized coal explosion based on the analysis of thermal decomposition characteristics and reaction kinetics

This study investigates the inhibitory characteristics and mechanisms of ABC powder on coal powder explosion using a combination of experimental, theoretical, and numerical methods. In a 20 L spherical explosion experimental system, coal powder was mixed with ABC powder at various mass concentrations. The microstructure and major functional groups of the explosion products were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The proportions of the major functional groups were determined through peak fitting analysis. The research findings demonstrate that the introduction of 60 wt% ABC powder into the coal sample led to a significant decrease in the maximum explosion pressure, from 0.683 MPa to 0.454 MPa, indicating a remarkable reduction of 33.38%. Moreover, the inclusion of 70 wt% ABC powder exhibited complete suppression of coal dust explosions. Thermal decomposition characteristics of the mixed system were investigated using a thermogravimetric analyzer, and the Coats-Redfern integral method was employed to analyze the pyrolysis experimental data. The results suggest that the optimal reaction kinetics models for the combustion stage of coal powder and the mixed system are F1 and F2, respectively. Adding ABC powder increases the activation energy by 27.35% and slows down the pyrolysis rate by 37.97%. Furthermore, numerical simulations using CHEMKIN software were conducted to study the inhibitory effect of ABC powder on coal powder explosion. The results demonstrate that the addition of ABC powder significantly reduces the content of O·, H·, and OH·radicals, which are responsible for sustaining explosive chain reactions within the explosion system. By incorporating the findings of this investigation, the present study offers a comprehensive explication of the intricate micro-level mechanisms that underlie the inhibitory properties exerted by ABC powder on coal dust explosions. These results contribute novel scientific and theoretical foundations, yielding profound insights into the prevention and mitigation of calamitous coal dust explosion incidents within coal mining environments.

Evaluation of fuel properties and combustion behaviour of hydrochar derived from hydrothermal carbonisation of agricultural wastes

Biomass energy is an effective way to replace traditional fossil fuels. In this paper, hydrochar fuels were prepared using agricultural wastes (AW) from corn field at different hydrothermal carbonisation (HTC) temperatures. Their physicochemical properties, combustion characteristics, kinetic analysis and tendency of slagging and scaling were systematically investigated. The results showed that hydrochar had the highest energy yield of 68.54% when the HTC temperature was 220 °C. With the increase in HTC temperature, the H/C and O/C atomic ratios of hydrochar decreased, while the porosity increased first and then decreased. The higher HTC temperature was favourable for the formation of aromatic structures and unfavourable for the formation of oxygen-containing functional groups. As the HTC temperature increased, the Ti and Tb of hydrochar gradually moved to higher temperature range. The Coats-Redfern integration method was applied for the kinetic analysis of AW and hydrochar. The slagging and fouling indices of hydrochar were measured and indicated its low slagging and fouling tendencies, which are conducive to improving the heat transfer efficiency of the heat receiving surface.

Study on Thermodynamic Characteristics and Heat Transfer Method of Uncontrolled Fire in Coal Mine Gangue Mountain Spontaneous Combustion Based on System Dynamics.

Coal fire disaster caused by the spontaneous combustion of coal has always been one of the serious problems that threaten the safety of coal mining. In our study, we first solved the dynamic parameters and mechanical functions of coal gangue using the Achar differential method and Coats-Redfern integral method. Then, based on the flow and heat transfer mechanism of hot rod vapor-liquid two-phase flow, combined with coal spontaneous ignition conditions, influencing factors, coal pile spontaneous combustion temperature field structure distribution, etc., the heat transfer process of the hot rod in the coal pile (coal gangue mountain) was analyzed. Results show the average activation energies of the second stage of different types of coal mine gangue. Upon comparing the characteristic parameters of coal gangue in different regions and ages, it is found that 8# coal gangue has better combustion and burn-out characteristics, and its comprehensive combustion characteristics are second only to those of the coal gangue in Datong and higher than those in Panzhihua, Pingdingshan, and Hancheng. The higher the content of volatile matter and fixed carbon in coal gangue, the lower the ash content, and the better the comprehensive combustion performance of the coal gangue. Under the condition of sufficient oxygen supply combustion, the larger the fuel ratio, the better the burnout performance of the coal gangue. The test of the influence of the hot rod on the temperature field distribution inside the coal pile shows that the maximum cooling rate of a single hot rod to the coal pile during the test period is 33.4°C, and the maximum cooling rate reaches 39.6%. The calculated heat dissipation of the 80 h hot rod is 1.0865, 2.1680, and 3.3649 MJ, respectively.

Application of distributed activation energy model and Coats-Redfern integration method in the study of industrial lignin pyrolysis kinetics

Application of distributed activation energy model and Coats-Redfern integration method in the study of industrial lignin pyrolysis kinetics

A new approach to obtain kinetic parameters of corn cob pyrolysis catalyzed with CaO and CaCO3

A new approach is proposed to obtain the kinetic parameters of biomass pyrolysis mixed with calcium catalyst. This approach involves the optimization of least squares (LS) with the Coats-Redfern integral method to avoid mathematical biases that may appear when applying the linear regression approach. The method was applied to the TGA data of pyrolysis of corn cob and corn cob mixed with 20 or 40 % by weight of CaO or CaCO3 under N2 atmosphere at temperatures between 25 and 700 °C. For raw cob, r2 reaches 0.997. For corn cob mixed with 20 % by weight of CaO or CaCO3, r2 reached 0.996–0.998, and for 40 % by weight, r2 reached 0.836–0.957. Applying this method, the activation energy (EA) value of the raw cob pyrolysis is 58.35 kJ mol−1, while the addition of CaO or CaCO3 increases the EA to 69.33 and 66.07 kJ mol−1, respectively. The method is simple to use and allows reliable values of kinetic parameters.

In depth thermokinetic investigation on Co-pyrolysis of low-rank coal and algae consortium blends over CeO2 loaded hydrotalcite (MgNiAl) catalyst

This study investigates the co-pyrolysis behavior of bituminous coal (100%BC), algae consortium (100%AC), and their blends at various blending ratios. The pure and coal-biomass blends were characterized using CHN-S, GCV, and FTIR analysis. Whereas, the co-pyrolysis of blends were performed in a TGA. The deviation between the experimental and calculated values of weight loss (WL%), the residue left (RL%), and the maximum rate of weight loss (wt%/min) was used to calculate the synergistic effects. Kinetic parameters were investigated using the Coats-Redfern integral method through eighteen (18) reaction mechanistic models. The activation energy (Ea) for 100%BC was 85.04 kJ/mol through the F3 model, whilst for 100%AC showed 78.22 kJ/mol using the D3 model. Thermodynamic parameters such as Enthalpy (∆H) and Gibbs free energy (∆G) showed positive values, while Entropy (∆S) was negative for each coal-biomass blend. The catalytic co-pyrolysis of the optimum blend (20BCE-80AC) was studied using CeO2 loaded MgNiAl (CeO2 @MNA) as a multifunctional catalyst. The increased WL% displayed a positive effect toward a higher yield of volatile matter. Ea of the optimum blend in co-pyrolysis was further reduced through catalytic co-pyrolysis and Ea in the first and second stages was 72.48 kJ/mol and 13.76 kJ/mol, while 3 wt% catalyst loading further reduced its Ea in both stages to 67.82 kJ/mol and 41.21 kJ/mol. The use of CeO2 @MNA at 3 wt% loading showed a reduction in the peak devolatilization temperature (Tp) of the optimum blend substantially increasing the reaction rate, and reducing the Ea required for the decomposition process.

Hydrothermal carbonization of petrochemical sludge: The fate of hydrochar and oil components

In this study, the physical and chemical properties, combustion behaviors, kinetics, and the distribution of C, O, N, and S during different hydrothermal carbonization (HTC) temperatures of petrochemical sludge (PS) were investigated. The increase in HTC temperature is favorable to obtain higher organic-dissolved oil (ODO) content and less water-soluble oil (WSO) content. The solid conversion rate of hydrochar reached a maximum of 83.90% and comprehensive combustion performance is the best at 270 °C. The higher heating values (HHVs) value of hydrochar is stable at 21.00 MJ/kg. While the HHVs value range of ODO and WSO are 32.03–38.65 MJ/kg and 13.90–19.83 MJ/kg, respectively. Except for hard to occur WSO combustion stageⅢ, the Coats-Redfern integral method is well suited for kinetic simulations of all stages of hydrochar, WSO, and ODO. The long-chain alkanes, aromatic hydrocarbons, and cycloalkanes attach to the surface of the solid particles to form ODO and further convert to hydrochar via carbonization process. Nitrogen heterocycles, amines, and ketones remain in the feedwater to form WSO. Therefore, Carbon was maximally preserved in hydrochar and ODO, while N and S were removed by migration into WSO.

Synergistic effect of potassium and calcium ions on coal pyrolysis behaviors: Experimental and kinetic model investigations

A low rank coal was first used to investigate the synergistic effect of inherent and loaded potassium and calcium ions on the pyrolysis behaviors. The non-isothermal thermal analysis with higher heating rate to medium pyrolysis temperature was carried out by thermogravimetric analyzer for the selected raw and treated coal samples. Preliminary experiments conducted show that the particle size smaller than 160 mm can eliminate heat and mass transfer effect, and the most of volatile matter was released by heating the raw coal (R-coal) to 750?C. Moreover, the effect of heating rate, inherent and loaded potassium and calcium on moisture evaporation and devolatilization is systematically investigated, and the devolatilization index is introduced to estimate the activity of pyrolysis pr?cess. A comparison among the acid pickling coal (H-coal), acid pickling coal loaded with calcium (H-coal-C), and potassium (H-coal-P) shows that potassium and calcium have improved the inner water holding capacity. Finally, the influence of inherent and loaded potassium and calcium on the kinetic characteristics of volatile matter release stage was studied with Coats-Redfern integral method.

Co-pyrolysis characteristics and kinetics of low metamorphic coal and pine sawdust

Co-pyrolysis experiments with low metamorphic coal (LC) and pine sawdust (PS) were carried out in a fixed-bed pyrolysis reactor. The effect of biomass addition on the yield distribution and composition of the coal pyrolysis products was investigated. The pyrolysis behavior was studied by thermogravimetric analysis. The Coats–Redfern integral and Achar differential methods were used to study the mechanism functions and the kinetic parameters of the pyrolysis process of each sample. The results show that there is a synergistic effect on the co-pyrolysis and it is most pronounced at a PS mixing ratio of 30%, and it results in improved tar and gas yields. Part of the polycyclic aromatic hydrocarbons (PAHs) in the co-pyrolysis tar are converted into phenolic substances with a simple structure, which improves the quality of the tar. At the same time, the alcohols and acids in the PS and LC react to generate a large number of esters. The addition of PS shifted the LC pyrolysis process towards the low temperature region, lowering the pyrolysis temperature of the coal sample and increasing the pyrolysis rate of the sample. The main pyrolysis process of LC conforms to the second-order chemical reaction law with an activation energy of 35.93 kJ mol−1, and the main pyrolysis process of PS conforms to the one-dimensional diffusion parabolic law with an activation energy of 63.84 kJ mol−1, and the main pyrolysis process of LC and PS co-pyrolysis conforms to a second-order chemical reaction law with an activation energy of 86.19 kJ mol−1.

Co-Pyrolysis of Estonian Oil Shale with Polymer Wastes.

Recycling of polymeric wastes is important for both energy recovery and raw material processing. In light of the EU Green Deal, the oil shale industry is looking for new opportunities to use its production potential. As an intermediate stage, the co-pyrolysis of oil shale with waste plastic and tires will be considered acceptable. The article presents the kinetics of pyrolysis of Estonian oil shale, the main polymer components of municipal waste, and their mixtures with oil shale by the thermogravimetric analysis method. The influence of each component separately on the process of sample weight loss during co-pyrolysis was also studied. It is shown that when plastics are added to oil shale, the experimental and calculated data coincide according to the principle of the additive contribution of each component. Kinetic parameters were calculated according to the Coats–Redfern integral method and show that during the co-pyrolysis of mixtures of oil shale with polymer wastes, the value of the activation energy increases in comparison with the pyrolysis of oil shale. Based on the experimental data, it was determined that there is a manifestation of a synergistic effect in the form of an increase in the yield of liquid products during the co-pyrolysis of oil shale and polymer wastes.

Kinetic and thermodynamic analyses of date palm surface fibers pyrolysis using Coats-Redfern method

This study presents the thermo-kinetics and thermodynamic analyses of date palm surface fibers (DPSFs) using thermogravimetric analysis. DPSFs were heated non-isothermally from 20 to 800 OC at a ramp rate of 10 OC/min in nitrogen atmosphere. Thermogravimetric analysis indicated that there have been two stages for pyrolysis of DPSFs. Kinetic and thermodynamic parameters have been calculated for the second stage which is further subdivided into two mass-loss regions. The low-temperature stable components were decomposed in a temperature range of 270–390 OC and high-temperature stable components were degraded in a temperature range of 390–600 OC. The Coats–Redfern integral method was employed with 21 different kinetic models from four major solid-state reaction mechanisms. Among all models, the two diffusion models: Ginstling–Brounshtein and Ginstling diffusion were the best fitted models with highest regression coefficient values (R2 > 0.99) in both mass-loss regions. For mass-loss regions: I (270–390 OC) and II (390–600 OC), the activation energy values were found to be 96–98 and 113–114 kJ/mol, respectively. Thermodynamic parameters (ΔH, ΔG, ΔS) were calculated using kinetic data. The findings reported herein are helpful in characterizing date palm fibers as a source of energy, designing reactors, producing chemicals, and understanding the properties of surface fibers for making composites.

A comparative study on physicochemical properties, pyrolytic behaviour and kinetic parameters of environmentally harmful aquatic weeds for sustainable shellfish aquaculture

Aquatic weeds pose hazards to aquatic ecosystems and particularly the aquatic environment in shellfish aquaculture due to its excessive growth covering entire freshwater bodies, leading to environmental pollution particularly eutrophication intensification, water quality depletion and aquatic organism fatality. In this study, pyrolysis of six aquatic weed types (wild and cultured species of Salvinia sp., Lemna sp. and Spirodella sp.) were investigated to evaluate its potential to reduce and convert the weeds into value-added chemicals. The aquatic weeds demonstrated high fixed carbon (8.7–47.3 wt%), volatile matter content (39.0–76.9 wt%), H/C ratio (1.5–2.0) and higher heating value (6.6–18.8 MJ/kg), representing desirable physicochemical properties for conversion into biofuels. Kinetic analysis via Coats-Redfern integral method obtained different orders for chemical reaction mechanisms (n = 1, 1.5, 2, 3), activation energy (55.94–209.41 kJ/mol) and pre-exponential factor (4.08 × 104-4.20 × 1017 s-1) at different reaction zones (zone 1: 150–268 °C, zone 2: 268–409 °C, zone 3: 409–600 °C). The results provide useful information for design and optimization of the pyrolysis reactor and establishment of the process condition to dispose this environmentally harmful species.

Thermogravimetric Analysis of Coal Semi-Char Co-Firing with Straw in O2/CO2 Mixtures

For coal semi-char as a by-produced of low-temperature pyrolysis, combustion for power generation is one of the effective utilization methods to realize its clean and efficient utilization. However, the coal semi-char combustion process has a difficult ignition, unstable combustion and low burnout rate. The co-firing of the semi-char with biomass under oxy-fuel conditions can improve the combustion behavior and reduce fossil CO2 emissions. In this paper, the combustion behavior of Shenhua coal semi-char (SHC) co-firing with straw (ST) in O2/CO2 mixture is investigated using thermogravimetric analysis. The results show that each curve lays between those of the individual fuels and presents three peaks (i.e., three stages). The thermogravimetric curves of SHC co-firing with ST can be divided into three stages: the volatile combustion of ST, the co-combustion of SHC and ST fixed-carbons and the SHC fixed-carbon combustion and the decomposition of the difficult pyrolytic material of ST. Blending ST into the SHC can significantly decrease the ignition temperature and improve the comprehensive combustion behavior of blended samples. In increasing the proportion of ST from 25 to 100%, the change of the blended ignition temperature is slight, but the burnout temperature decreases greatly. Kinetic parameters of combustion are calculated by using the Coats–Redfern integral method. Compared to that of stage I and stage III, the activation energy of stage II is significantly lower. As increasing blending ratio from 25% to 100%, the activation energy increases at stage I and decreases at stage III. Furthermore, the O2 concentration obviously affects stage III of 50% SHC + 50% ST, and the thermogravimetric curves at this stage are obviously shifted to the lower temperature zone as the O2 concentration increases. The activation energy of 50% SHC + 50% ST increases as the oxygen concentration increases. Besides, the activation energy shows that the combustion characteristics cannot be determined only by the activation energy obtained by the Coats–Redfern method. These findings can provide useful information for semi-char co-firing with biomass.

Co-pyrolysis of waste polyvinyl chloride and oil-based drilling cuttings: Pyrolysis process and product characteristics analysis

Oil-based drill cuttings (OBDC) and waste polyvinyl chloride (waste PVC) both are solid wastes. The pyrolysis/co-pyrolysis characterizations of OBDC, waste PVC and OBDC/waste PVC at varying heating rates were investigated using thermogravimetric analysis (TG/TGA). Coats-Redfern and Kissinger integration methods were employed to fit the TG curve. The optimal fitting effect was obtained with reaction order at 2 and Kissinger integration method was better than Coats-Redfern integration method for co-pyrolysis of OBDC/waste PVC. The practical co-pyrolysis condition was optimized using batch experiment and the optimal condition was as following: final temperature for 600 °C, holding time for 60 min, heating rate at 10 °C/min and ratio of PVC as 10% PO. The gas, solid and liquid phase products of pyrolysis/co-pyrolysis were characterized and analyzed using thermogravimetry-mass spectrometry (TG-MS), gas chromatography-mass spectrometry (GC-MS) and X-ray diffraction (XRD). The gas product of pyrolysis/co-pyrolysis indicated the inhibitory effect on HCl emission due to the positive synergic effect of OBDC and PVC. High pyrolysis temperature was beneficial to increase the content of hydrocarbons, which enhanced the quality of oil recovery. This study indicated that the co-pyrolysis of OBDC and waste PVC is a promising method for waste disposal and oil recovery.

Effect of CaO on catalytic combustion of semi-coke

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

Effects of Algal Biomass Blending on Coal Decomposition Behaviour and Kinetics at Intermediate Pyrolysis Regimes

Co-pyrolysis of coal with biomass is becoming a popular method of reducing the net carbon dioxide emissions associated with the process. In present work, the pyrolysis of coal and algae was studied using thermogravimetric methods and the kinetics were analyzed using the Coats-Redfern integral method. The kinetics were evaluated for 1st and 2nd order reaction models. The effect brought by blending coal with algae on kinetics was studied via the analysis of pyrolysis of different coal-algae blends. The results revealed that the pyrolysis of coal and algae follows 2nd and 1st order kinetics with activation energy evaluated in the range 213.4-241.8 and 108.9-122.8 kJ/mol, respectively. It was observed that for coal-algae blending of 20-40% algae, intermediate pyrolysis, typical heating rates of 50-200 ºC/min was characterized by two distinct stages (ignoring the drying stage) that correspond to the individual decomposition of algae and coal. However, there was an evidence of coal-algae interactions during co-pyrolysis, which made the kinetics of the two distinct stages not to correspond to the kinetics of the individual materials.