Conversion Rate Range Research Articles

Carbothermal reduction of flue gas desulfurization ash through the utilization of waste heat from steel slag: Investigating performance and mechanism

Flue gas desulfurization ash is a significant solid waste generated by the steel industry, leading to environmental pollution. In response to this challenge, this study proposes a novel method for preparing CaS from desulfurized ash through carbothermal reduction using steel slag waste heat. Thermodynamic analysis using FactSage and non-isothermal thermogravimetric testing were conducted to confirm the feasibility of carbothermal reduction. The experiment successfully prepared CaS, with a molar ratio of C to CaSO3 of 1.5 or higher leading to complete reduction. The presence of reducing agent C replaced the decomposition reaction of CaSO3 with reduction, occurring at a temperature 60 K lower. Large scale thermogravimetric analysis experiments demonstrated that as the mass percentage of pulverized coal increased, the reduction reaction of CaSO3 shifted to a lower temperature zone, expanding the temperature range and achieving the theoretical value. Reduction rates of CaSO3 were 43.12 %, 76.9 %, and 99.3 % with ratios of CaSO3 to reducing agent C of 1:0.75, 1:1.5, and 1:3, respectively. Kinetic study results showed that the activation energy of CaSO3 reduction ranged from 90.669 kJ/mol to 136.059 kJ/mol within the conversion rate range of 0.2 to 0.9. When CaSO3 and carbon powder are mixed and subsequently added, the thermochemical decomposition reaction of CaSO3 is inhibited. This inhibition leads to the formation of stable CaS through the reduction of desulfurization ash by carbon.

Product regulation and kinetics for fast pyrolysis of corncob over niobium oxide modified zeolite

Catalytic fast pyrolysis is considered as a promising technology for converting biomass into biofuels. In the present research, a series of NbOx modified ZSM-5 catalysts were developed and applied for the selective fast pyrolysis of corncob into aromatics. Depolymerization and hydrodeoxygenation of lignin constituents as well as the aromatization of polysaccharide fractions were the major source of aromatics. The introduction of niobium oxide into ZSM-5 remarkably enriched the Lewis acids and improved the porous structures. The presence of synergistic effect between acid sites and porous structure of NbOx modified ZSM-5 contributed to the aromatics formation in a certain degree. Under the catalysis of 3Nb/ZSM-5, the optimum aromatic content was 86.4 % at 450 °C with a heating rate of 104 °C/s. In the meantime, 3Nb/ZSM-5 presented good stability and recyclability in the fast pyrolysis of corncob, and over 75 % aromatics was achieved even after 3 cycles. Kinetical study revealed that the Ea value for corncob pyrolysis could be lowered to ∼ 250 kJ/mol with conversion rate range of 0.4–0.7.

Thermal Characteristics and Simulation of Enzymatic Lignin Isolated from Chinese Fir and Birch

Lignin is one of the main components of the plant cell wall, and the thermal properties of in situ biomass lignin are crucial for the multi-scale modeling of biomass properties and the thermodynamic modeling of lignin. In this study, high yields of double enzymatic lignin (DEL) were successfully isolated from softwood Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) and hardwood white birch (Betula platyphylla Suk.) to represent the in situ wood lignin. Their thermal properties, including specific heat capacity, thermal conductivity, thermal stability, and thermal degradation kinetic parameters, were tested and simulated. The results showed that Chinese fir DEL has different chemical structural units and thermal properties than birch DEL. The specific heat capacities of Chinese fir DEL and birch DEL at 20 °C were 1301 and 1468 J/(kg·K), respectively, and their thermal conductivities were 0.30 and 0.32 W/(m·K). Their specific heat capacity and thermal conductivity showed a positive linear relationship over a temperature range of 20–120 °C. Chinese fir DEL had a better thermal stability and a higher carbon residue than birch DEL. The average activation energy and pre-exponential factor changed with the conversion rate, and their relationships were simulated using linear or quadratic equations in the conversion rate range of 0.02–0.60. A second-order reaction function was found to be the best mechanism function for DEL thermal degradation.

Study on the Thermal Stability of Octogen and other Energetic Materials (RDX, TNT, NQ, PBT, TDI and HTPB)

AbstractThe Octogen (HMX) and other energetic materials, such as Hexogen (RDX), Trinitrotoluene (TNT), Nitroguanidine (NQ), Polybutylene terephthalate Glycol Ester (PBT), Toluene Diisocyanate (TDI), and Hydroxy‐Terminated Polybutadiene (HTPB) were subjected to linear heating tests by a Microcalorimeter (C600), to obtain thermal decomposition curves. Based on this data, the thermal stability was studied experimentally and theoretically. The decomposition peak and melting peak of RDX were coupled, and the time to reach the maximum weight loss increased with the increase of heating rates. Within a certain experimental error range, the apparent activation energy calculated by different methods was basically consistent in a larger conversion rate range. The thermal stability of other energetic materials, such as RDX, TNT, NQ, PBT, TDI and HTPB in the mixed system of HMX were explored. The results revealed that HMX had salient thermal stability with RDX, PBT and TDI. However, the thermal stability of HMX mixed with TNT, NQ, HTPB and other substances was poor, which promoted the thermal decomposition of each other, resulting in the decrease of thermal decomposition temperature and further decrease of thermal safety of the mixed system. Therefore, HMX should not be placed in the same place as TNT, NQ and HTPB in the actual application process.

TG-FTIR study on co-combustion of bituminous coal semicoke and lignite

The combustion behaviors and pollutants emission characteristics during co-combustion of bituminous coal semicoke and lignite were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR). Results showed the addition of lignite could lower the ignition and burnout temperature and also enhance the comprehensive combustion performance of blends. High heating rate could improve the combustion intensity and corresponding combustion characteristic indexes. The activation energy analysis by distributed activation energy model (DAEM) and Ozawa–Flynn–Wall (OFW) methods at lignite blend ratio of 40% indicated its distribution was consistent with the combustion process of blends. An obvious activation energy jump occurred at conversion rate range of 0.4–0.55 due to the poor ignition performance of semicoke. The average activation energy obtained by DAEM and OFW methods was 101.69 kJ mol−1 and 109.12 kJ mol−1, respectively. With the increase of lignite blend ratios, CO and CO2 emission gradually decreased. Meanwhile, NO emission increased, while NO2 and SO2 emission ascended after an initial decline. Semicoke had certain suppression effect on NOx and SO2 emission. The minimum NO2 and SO2 emission was obtained at lignite blend ratio of 20%.

The impact of the oil character and quartz sands on the thermal behavior and kinetics of crude oil

Oxidation reaction plays an important role in air flooding. In this paper, three oxidation reaction stages of both light and heavy oils, as well as mixtures of oil and quartz sands are studied at four heating rates by conducting thermogravimetric experiments. Commonly used kinetic methods are modified to estimate kinetics parameters, and a more realistic range of conversion rates is used. The results demonstrate that low temperature oxidation (LTO) dominates for light oil but fuel deposition (FD) and high temperature oxidation (HTO) dominate for heavy oil. The region of transition intervals in both LTO & FD and FD & HTO should be avoided to get more accurate kinetics parameters. Quartz sands are used to provide a large surface area, which result in decreasing the estimated activation energy of LTO for light oil by 15%, whereas the FD and HTO of heavy oil are enhanced by 11.7% and 14.1%, resulting in enhancing oil recovery (EOR). These results improve the understanding of the oxidation of different crude oils over the whole range of temperatures and have broad applicability to improving the design of air injection based on EOR projects.

Thermal characteristics of birch and its cellulose and hemicelluloses isolated by alkaline solution

AbstractCellulose and hemicelluloses were isolated from birch wood using a dilute alkaline solution and then consolidated into pellets as model compounds of cellulose and hemicelluloses in the wood cell wall. The purity of isolated cellulose and hemicelluloses was examined by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The density, thermal diffusivity, heat capacity, and thermal conductivity were experimentally determined for consolidated birch powder, cellulose, and hemicelluloses in over-dry condition. The thermal degradation kinetic parameters of these materials were successfully calculated using a conversion rate step of 0.01, and the relationship with conversion rate was established. The results show that cellulose and hemicelluloses consolidated under 25 MPa had densities of 1362 kg/m3and 1464 kg/m3, respectively. The cell wall of birch powder in the oven-dry state was not collapsed under 25 MPa. The thermal diffusivity of consolidated birch powder, cellulose, and hemicelluloses linearly decreased with temperature, with values of 0.08, 0.15, and 0.20 mm2/s at room temperature, respectively. The specific heat capacity (1104, 1209, and 1305 J/(kg·K) at 22 °C, respectively) and thermal conductivity (0.09, 0.24, and 0.38 W/(m·K) at 22 °C, respectively) linearly increased with temperature, except for those for hemicelluloses which exhibited a nonlinear relationship with temperature above 120 °C, and their linear experimental prediction equations were given. Birch cellulose was more thermally stable than hemicelluloses. The thermal degradation kinetic parameters including activation energy and pre-exponential factor of birch powder, cellulose, and hemicelluloses varied with the conversion rate and calculation methods, with average activation energy in a conversion rate range of 0.02–0.15 of 123.2, 159.0, and 147.2 kJ/mol, respectively (using the Flynn–Wall–Ozawa method), for average natural logarithm pre-exponential factors of 25.0, 33.1, and 28.7 min−1, respectively. Linear and quadratic equations were fitted to describe the relationship between the kinetic parameters and conversion rates. These results give comprehensive thermal properties of the densified cellulose and hemicelluloses isolated from a specific wood.

Kinetics, Thermodynamics, and Volatile Products of Camphorwood Pyrolysis in Inert Atmosphere.

The kinetics, thermodynamics, and volatile products of camphorwood pyrolysis were investigated via thermogravimetry coupled with Fourier transform infrared (FTIR) spectroscopy at multiple heating rates. The kinetic triplets and thermodynamic parameters were estimated via model free combined with the model-fitting approach. The results showed that the pyrolysis of camphorwood in the conversion rate range from 0 to 0.85 might be considered as one-step process. The mean value of the activation energy and pre-exponential factor was 192.63kJ/mol and 2.38 × 1013s-1, respectively. The pyrolysis process (0 ≤ α ≤ 0.85) can be described by the three-dimensional diffusion model g(α) = [(1-α)-1/3 -1]2. Furthermore, the predicted curves of the conversion rate α showed good agreement with the experimental curves. The values of ΔH, ΔG, and ΔS varied little with α and remained positive. In addition, the major gas products released from the camphorwood waste pyrolysis were H2O, methane, CO2, CO, C=O, O-H, C-O-C, and NH3, whose concentration in the order from highest to lowest was C=O > CO2 > O-H > H2O > methane > NH3 > C-O-C > CO. The main conclusions in the present study can provide guidance for the design and optimization of industrial reactor and selection of target biofuels or chemical raw materials.

Pyrolysis Characteristics and Reaction Mechanisms of Pine Needles.

Pyrolysis has been considered as a promising method to utilize biomass by thermal cracking for energy or feedstock. In order to provide guidance for thermochemical process management of pine needle utilization by pyrolysis, the pyrolysis kinetics and reaction mechanism of one typical pine needle are investigated employing thermogravimetric analysis in nitrogen in the present study. Multi kinetics methods including model-free method and model-fitting method are adopted. Results indicate that one peak and three shoulders occur in the reaction rate curves. The maximum reaction rates decrease with the increasing of heating rates, and the average reaction rate of the whole process is 0.0021K-1. The pyrolysis process of pine needles in nitrogen may be divided into four stages in the conversion rate range of 0~0.1, 0.1~0.5, 0.5~0.75, and 0.75~1, which may be mainly resulted by the reaction of the extractives, hemicellulose, cellulose, and lignin, respectively. The reaction mechanisms of stages I, II, and III may be regarded as random nucleation and nuclei growth, but the reaction mechanism of stage IV may be chemical reaction. The average value of activation energy and logarithm of the pre-exponential factor for the whole pyrolysis process is 215.99kJmol-1 and 38.75min-1, respectively.

PYROLYSIS KINETICS OF HULLESS BARLEY STRAW USING THE DISTRIBUTED ACTIVATION ENERGY MODEL (DAEM) BY THE TG/DTA TECHNIQUE AND SEM/XRD CHARACTERIZATIONS FOR HULLESS BARLEY STRAW DERIVED BIOCHAR

Abstract The pyrolysis kinetics of hulless barley straw at different heating rates of 5，10, 15, 20 and 30 oC/min were investigated via thermogravimetry, and the activation energy distribution E and pre-exponential factor k0 were calculated using the Distributed Activation Energy Model (DAEM) from thermogravimetric analysis (TGA) curves, and characterizations of pyrolysis product of biochar were analyzed by techniques of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The pyrolysis process consisted mainly of the dehydration stage (50-150 oC), the active pyrolysis stage (200-400 oC) and the passive pyrolysis stage (400-800 oC). The E ranged from 73.45 to 214.11 kJ/mol within the conversion rate range of 0.10-0.55, and changed from 214.11 to 141.55 kJ/mol within the conversion rate range of 0.55-0.90, and the average value of E was 172.23 kJ/mol. The values of k0 changed greatly with E values at different mass conversion. The wide E and k0 distributions obtained from the kinetic analysis are attributed to the complex chemical reactions of pyrolysis. The structure of biochar was degraded or ruptured due to the increase in temperature. The XRD analysis confirmed that the biochar was amorphous, dominated by disordered graphitic crystallites.

Thermodynamic analysis on mid/low temperature solar methane steam reforming with hydrogen permeation membrane reactors

Hydrogen production by methane reforming reaction in membrane reactors is a promising means of solar energy harvesting and storage. The integration of endothermic methane reforming with selective removal of H2 through hydrogen permeation membrane theoretically enables a near-complete conversion of methane at the temperature of 400 °C or above (normally 800–900 °C) by shifting the equilibrium of reforming reaction. Operation of methane membrane reforming reactors at lower temperatures offers a special advantage of possible combination with solar trough collector on a large scale. However, such advantages are not immediately apparent due to special characteristics of solar thermal technologies and lower conversion rates of methane, which needs further clarification from a thermodynamic perspective. In this work, a numerical model of solar-driven methane reforming reaction in a palladium (Pd) membrane reactor with vacuum pump and compressor is established. Methane reforming and H2 permeation processes are theoretically investigated in a temperature range of 300 °C to 700 °C. An optimal conversion rate range of methane for efficient solar methane membrane reforming is calculated, and the net solar-to-fuel efficiency can reach as high as 38.25% at 400 °C after taking real vacuum pump and compressor efficiencies into account. The findings of this work show feasibility of integrating methane reforming with mid- or low-temperature solar thermal technologies.

Isoconversional kinetics and characteristics of combustion on hydrothermally treated biomass

Pine sawdust and its resulting hydrochars hydrothermally produced at different time were characterized by scanning electron microscope and Fourier transform infrared spectroscopy to indicate the transformation in their morphologies and chemical structure, respectively. Afterwards, a comparative study in relation to the thermal behavior and combustion characteristics for the pine sawdust and the hydrochars was investigated. The relationship between the activation energy and various conversion rates of pine sawdust and hydrochars heated at various heating rates of 10, 20 and 30 °C/min were evaluated by the methods of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The results obtained from the two methods revealed that the activation energies of hydrochars fluctuate within a narrow range when the conversion rate is 0–0.55 and then decrease drastically at the conversion rate range of 0.55–0.95, due to the decomposition of relative reactive compounds. In comparison of the two methods, the average activation energies of hydrochars obtained at 6 h and 12 h using FWO method are 112.63 and 82.83 kJ/mol, respectively, larger than 107.70 and 76.30 kJ/mol using KAS method.

Estimating met demand for alcohol and other drug treatment in Australia.

To estimate the amount of alcohol and other drug (AOD) treatment provided and number of treatment recipients in Australia in 2011-12, and document an approach for future estimates internationally. We combined multiple data sources to estimate the amount of treatment received: administrative data on AOD treatment funded by the Australian and state/territory governments, survey data from treatment providers and programme evaluation data. The various data sources were reconciled, using published studies of treatment activity, to estimate the unique number of treatment recipients. Treatment funded by the Australian and state/territory governments provided by general practitioners, specialist treatment services, hospitals, community- and hospital-based ambulatory mental health-care services and allied health professionals. People receiving AOD treatment in the above settings. Annual quantum of AOD treatment (encounters, episodes, consultations) and the number of unique treatment recipients. In 2011/12 we estimated 1.6 million episodes of care, consultations or encounters, noting that measures of treatment are not comparable. Based on a range of conversion rates to account for people accessing treatment multiple times in that year, we estimated that the number of Australians in receipt of AOD treatment ranged from 202 168 to 232 419. This is an underestimate and subject to error. Using the upper range of the estimate, on average each treatment recipient made 4.7 visits to a general practitioner (GP) or allied health professional providing mental health services for AOD treatment, and had 1.2 treatment episodes with a specialist AOD treatment provider and/or hospital. Between 202 168 and 232 419 Australians are estimated to have received alcohol and other drug treatment in 2011-12. The comprehensive approach used to calculate this estimate, combining multiple independent data sets across treatment settings and programmes, can be replicated in other countries.

Y chromosome haplotype diversity in Mongolic-speaking populations and gene conversion at the duplicated STR DYS385a,b in haplogroup C3-M407.

Y chromosome microsatellite (Y-STR) diversity has been studied in different Mongolic-speaking populations from South Siberia, Mongolia, North-East China and East Europe. The results obtained indicate that the Mongolic-speaking populations clustered into two groups, with one group including populations from eastern part of South Siberia and Central Asia (the Buryats, Barghuts and Khamnigans) and the other group including populations from western part of Central Asia and East Europe (the Mongols and Kalmyks). High frequency of haplogroup C3-M407 (>50%) is present in the Buryats, Barghuts and Khamnigans, whereas in the Mongols and Kalmyks its frequency is much lower. In addition, two allelic combinations in DYS385a,b loci of C3-M407 haplotypes have been observed: the combination 11,18 (as well as 11,17 and 11,19) is frequent in different Mongolic-speaking populations, but the 11,11 branch is present mainly in the Kalmyks and Mongols. Results of locus-specific sequencing suggest that the action of gene conversion is a more likely explanation for origin of homoallelic 11,11 combination. Moreover, analysis of median networks of Y-STR haplotypes demonstrates that at least two gene conversion events can be revealed-one of them has probably occurred among the Mongols, and the other event occurred in the Barghuts. These two events give an average gene conversion rate range of 0.24-7.1 × 10(-3) per generation.

Sputum conversion at the end of 8 weeks among category 1 tuberculosis patients: How reliable are the peripheral laboratory results?

ObjectiveTo assess the quality of week 8 sputum smear AFB microscopy performed by peripheral TB laboratories in Nigeria. MethodA cross-sectional review was performed of all week 8 tuberculosis sputum smear slides reported for the first quarter of 2009 by peripheral laboratories in five States of Nigeria. Each slide was reviewed by two independent external slide readers as external quality check and also crosschecked with fluorescent microscopy. ResultsIn Akwa Ibom, Anambra, Enugu, Kogi and Ogun States, a total of 415, 315, 231, 206 and 428week 8 slides respectively were studied (a grand total of 1595 slides studied). The wide range of conversion rates between the different States as reported by peripheral labs (83.8% in Anambra State to 98.1% in Kogi State) was also observed by the external quality check (68.4% in Kogi State to 88.0% in Akwa Ibom State). In all the States, the studied sputum conversion rates reported by the peripheral labs were significantly higher than values obtained from external quality check and fluorescent microscopy (P=0.000). Conclusion/recommendationThere is a wide range of sputum conversion rates between States, but the conversion rate in each State is significantly higher than those of external quality check possibly indicating many false negative reports by peripheral labs. It is recommended that training and re-training of laboratory persons be continued. Internal and external quality checks should also continue to be practiced in the national TB program.

Pyrolysis kinetic and product analysis of different microalgal biomass by distributed activation energy model and pyrolysis-gas chromatography-mass spectrometry.

To assess the energy potential of different microalgae, Chlorella sorokiniana and Monoraphidium were selected for studying the pyrolytic behavior at different heating rates with the analytical method of thermogravimetric analysis (TG), distributed activation energy model (DAEM) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Results presented that Monoraphidium 3s35 showed superiority for pyrolysis at low heating rate. Calculated by DAEM, during the conversion rate range from 0.1 to 0.7, the activation energies of C. sorokiniana 21 were much lower than that of Monoraphidium 3s35. Both C. sorokiniana 21 and Monoraphidium 3s35 can produce certain amount (up to 20.50%) of alkane compounds, with 9-Octadecyne (C18H34) as the primary compound. Short-chain alkanes (C7-C13) with unsaturated carbon can be released in the pyrolysis at 500°C for both microalgal biomass. It was also observed that the pyrolysis of C. sorokiniana 21 released more alcohol compounds, while Monoraphidium 3s35 produced more saccharides.

Thermogravimetric study and kinetic analysis of fungal pretreated corn stover using the distributed activation energy model

Non-isothermal thermogravimetry/derivative thermogravimetry (TG/DTG) measurements are used to determine pyrolytic characteristics and kinetics of lignocellulose. TG/DTG experiments at different heating rates with corn stover pretreated with monocultures of Irpex lacteus CD2 and Auricularia polytricha AP and their cocultures were conducted. Heating rates had little effect on the pyrolysis process, but the peak of weight loss rate in the DTG curves shifted towards higher temperature with heating rate. The maximum weight loss of biopretreated samples was 1.25-fold higher than that of the control at the three heating rates, and the maximum weight loss rate of the co-culture pretreated samples was intermediate between that of the two mono-cultures. The activation energies of the co-culture pretreated samples were 16–72kJmol−1 lower than that of the mono-culture at the conversion rate range from 10% to 60%. This suggests that co-culture pretreatment can decrease activation energy and accelerate pyrolysis reaction thus reducing energy consumption.

Sticking probability of light hydrocarbons on tungsten

Hydrocarbons were decomposed on the surface of an incandescent tungsten filament in a low pressure flow reactor. The rate of conversion of tungsten to ditungsten carbide W2C was measured by a resistance method. Carbon accumulation on the outer W2C surface was prevented by rapid inward diffusion. The sticking probability γ was defined as the probability that a room temperature hydrocarbon molecule striking the hot W2C surface would undergo complete decomposition to carbon and hydrogen. The value of γ for different hydrocarbons, measured over a 300-fold range of conversion rates, increased in the order: methane<propane≃cyclopropane<neopentane. Mixing of hydrogen gas with the hydrocarbon reactant markedly increased γ. For example, at a filament temperature of 2610°K, γ increased from 6.4 × 10–3(methane only) to 2.6 × 10–2(methane plus hydrogen). This novel effect is explained by carbon patches on the W2C surface. These patches are associated with low values of γ but can be removed by adsorbed hydrogen.