Effects Of Furnace Temperature Research Articles

Effect of furnace temperature and oxygen concentration on combustion and CO/NO emission characteristics of sewage sludge

Addressing the growing energy crisis, the development and utilization of solid waste have become a critical research areas. Sewage sludge, rich in organic matter, can serve as an alternative fuel to coal. This study employs a thermogravimetric analyzer to investigate the combustion characteristics of sewage sludge at heating rates of 10, 20, and 40 °C/min. Additionally, a horizontal tube furnace is utilized to analyze the CO and NO emission characteristics during sewage sludge combustion at varying oxygen concentrations and temperatures. Results indicate that at a constant gas velocity, the primary factor influencing combustion characteristics and CO/NO emissions is the composition difference. Higher furnace temperatures lead to lower CO generation and increased combustion efficiency. The conversion of coke-N to NO rises with increasing temperature. Moreover, higher furnace temperatures decrease the conversion of fuel-N to NO. Increasing oxygen concentration reduces the ignition concentration limit of sewage sludge. The lowest NOx emissions were recorded at an oxygen concentration of 21 vol%. This study provides essential data for reducing coal consumption and enhancing the safe and efficient treatment of sewage sludge.

Investigation on the reaction characteristics and influencing factors of thermal runaway of di-tert-butyl peroxide

Thermal runaway reactions of organic peroxides often cause accidents. To improve the chemical production safety, pressure vessel test studies were conducted on the thermal runaway reaction of di-tert-butyl peroxide (DTBP). The effects of furnace temperature and sample mass on the runaway reaction characteristics were discussed, and the venting phenomenon was captured by high-speed camera. The results indicated that the thermal runaway reaction of DTBP includes thermal decomposition, explosion, and venting. The combined effects of heat release, gas production, and boiling that occur simultaneously increase the complexity of decomposition process. If DTBP is completely vaporized before venting, an explosion is triggered. For the same sample mass, the higher the furnace temperature, the faster the rise in temperature and pressure, and the shorter the decomposition reaction time. For the same furnace temperature, the larger the sample mass, the later the thermal decomposition, and the greater the pressure rise rate after boiling. Furthermore, as the furnace temperature increases and the sample mass decreases, it is more likely to cause an explosion, whereas there are no significant changes in the venting characteristics during the pressure drop process. This work can provide a reference for process safety and risk control of organic peroxides.

An experimental study of the ignition and combustion characteristics of single coal gangue particles under oxy-fuel conditions

The ignition and combustion characteristics of single coal gangue particles under simulated oxy-fuel combustion conditions were experimentally studied. A coal gangue particle was suspended at the tip of a thin wire sample holder and introduced into an electrically heated furnace set at a desired temperature and in a predetermined atmosphere. A high-speed CCD camera was used to record the ignition phenomena and combustion process, which was examined to determine ignition mechanism, ignition delay time and volatile flame duration. The minimum ignition temperature (Ti,min) was also studied. The effect of furnace temperature (750–950 °C), particle size (3–9 mm), O2 concentration (10–30% vol.) and steam addition was examined. Results indicate that the coal gangue ignition followed the homogeneous ignition mechanism under conventional combustion conditions (O2/N2). Under oxy-fuel conditions (O2/CO2), however, the coal gangue particles ignited homogeneously at high temperature but heterogeneously at low temperature. Ignition mechanism changed from heterogeneous to homogeneous ignition with steam addition at low temperature. As the temperature or particle size increased, the volatile matter flames decreased in the brightness and size. Increasing O2 concentration or steam addition resulted in larger and brighter volatile flames. The volatile flame duration became shorter as temperature and particle size increased but longer with increasing concentration of O2 or steam. The Ti,min of particles in O2/N2 atmosphere was 662 °C but increased by 157 °C in O2/CO2 atmosphere at the same O2 concentration and decreased with increasing steam concentration.

Numerical analysis of the carbon containing pellets direct reduction process

In view of the carbon-containing composite pellets direct reduction process in rotary hearth furnace, a mathematical model coupling heterogeneous chemical reaction kinetics, heat and mass transfer of this process was established. The effects of furnace temperature (from 1273.15 K to 1673.15 K) and pellet radius (from 6 mm to 16 mm) on the direct reduction of carbon-containing composite pellets were studied by adopting computational fluid dynamics software. The pellet temperature and composition changes under different operating conditions were analyzed. CO and CO2 fluxes, heat fluxes on the pellet surface were especially studied. Total heat absorption by the pellet, CO and CO2 overflow from the pellet surface together with pellet degree of metallization (DOM) and zinc removal rate (ZRR) were calculated. Results show that with the increasing of furnace temperature or the decreasing of the pellet radius, the temperature difference between pellet surface and its center and the final DOM, ZRR increased. The larger the pellet radius, the smaller the heat absorption, also the smaller CO and CO2 overflow. But heat absorption and CO overflow per unit volume are higher. There is an optimal pellet radius with high CO utilization efficiency. Pellet porosity decreases at first and then increases with reducing time. It is also found that effective thermal conductivity is a major factor limiting the pellets temperature increasing. The reduction sequence of the pellets is Fe2O3→Fe3O4→FeO→Fe.

Comprehensive CFD modelling of reduction behaviour inside coal-based composite pellets

ABSTRACT The direct reduction process of coal-based composite pellet involves a series of physicochemical reactions. This paper reports a 3D unsteady mathematical model for simulation of heat transfer, mass transfer and chemical reactions inside the pellets. In this model, the pellets are assumed to be continuous porous medium composed of fine spherical particles. User-defined functions (UDFs) program in C language are developed to define chemical reactions, parameters and linked to FLUENT. The results predicted by the model are good agreement with experimental data. In addition, temperature, concentration, pressure and flow field inside the pellets are investigated by the model. Finally, the effects of furnace temperature and pellet diameter on the average pellet temperature, average molar concentration of reducing gases and degree of metallization have been simulated. The results show that the reduction rate is influenced more by the average pellet temperature than by average molar concentration of reducing gases.

Effect of Furnace Temperature on the Distribution of Tar during Gasification of Miscanthus

Biomass has been extensively recognised as a clean and sustainable energy source with the highest probability to substitute fossil fuel in the energy market. Its utilisation for energy generation is of particular interest to the world at large because of its potential to reduce global carbon dioxide emission. Concerning these considerations, gasification technology comes to the forefront of biomass conversion to various forms of energy for some reasons. Primarily, gasification offers a high flexibility in utilising different kinds of biomass feedstock to produce a combustible gas, making it more active process than pyrolysis and direct combustion. However, the major challenge associated with thermal gasification of biomass is tars and particulates formation. These compounds compromise the state of syngas, potentially harming end use systems especially those delicate to the quality of gas. In this research, tar sampling and analysis was performed based on a modified standard tar protocol followed by gas chromatography-flame ionisation detector (GC-FID) so as to quantify tar concentration in syngas produced from gasification of Miscanthus. Experiments was carried out at various furnace temperature in the range 350-650 , with temperature enhancement, the abundance of phenolic compounds increases.

Effects of natural and modified calcium-based sorbents on heavy metals of food waste under oxy-fuel combustion

Performance of natural and modified calcium-based sorbents for heavy metals for food waste under oxy-fuel combustion in a lab-scale tubular furnace was carried out. The effects of furnace temperature, sorbents type, and CO2/O2 ratio on adsorption of heavy metals were investigated. Increasing the furnace temperature helped fixing Al in the bottom ash, but increased the volatilization of Zn. The results showed that heavy metals captured by sorbents highly depended on the metals types. Nature and modified CaO had excellent performance for Al capture while CaCO3 could not absorb Al. Neither CaCO3 or CaO could not use as sorbents for the Cr capture. CO2/O2 ratio highly affected the capture of Cr and Zn but had no influence on Al, and the decrease of CO2/O2 ratio would help capturing Cr and Zn. This work contributes to the heavy metals controlled by Ca-based sorbents during municipal solid waste oxy-fuel combustion.

Experimental investigation of synergistic behaviors of lignite and wasted activated sludge during their co-combustion

To explore the feasibility of co-combustion of lignite and wasted activated sludge (WAS) and examine their synergistic effects, combustion of lignite–WAS blend at a mass ratio of 90:10 in a horizontal tube furnace was conducted. Results showed that the synergistic effects occurred between lignite and WAS during their co-combustion because the actual conversion ratio of combustible substances (CR) was higher than the theoretical prediction. Effects of furnace temperature and O2 concentration of inlet atmosphere on CR were also determined. High furnace temperature and O2 concentration of the inlet atmosphere resulted in high CR. In the early combustion stage, the furnace temperature played a major role. In the middle stage, the furnace temperature and O2 concentration of the inlet atmosphere exhibited a combined effect. In the late state, the O2 concentration of the combustion atmosphere played a key role. Scanning electron microscopy (SEM) photos indicated that the micro appearance of solid particles and their changing trends during the combustion of lignite–WAS blend were similar to those of lignite because of the high proportion of lignite (90%) in the blend. However, when compared to the case of lignite, the solid particles of the lignite–WAS blend were smaller, rougher, and looser in structure as the combustion progressed. In the solid combustion products of blend, carbon (C), oxygen (O), and chlorine (Cl) contents exhibited different evolution behaviors. The C content first increased and decreased, the O content first decreased and increased, and the Cl content continuously decreased to zero.

Single Particle Asphaltene Pyrolysis in a Drop-Tube Furnace

Oil sands in the Athabasca and Cold Lake regions of Northern Alberta form Canada’s primary source of energy reserves. Asphaltenes, a significant part of bitumen, are often considered to be the least valuable component of crude oil due to various factors such as difficulty in transporting and processing. Very few studies have been carried out on the pyrolysis of asphaltenes in entrained flow conditions. Single particle investigations are useful since they are conducted in a well-controlled environment allowing for the elimination of complexities arising from particle–particle interactions. Char is an intermediate of the gasification process, and the structural and morphological behavior of char plays a pivotal role in determining the rate of gasification. In this work, the pyrolysis of pulverized asphaltene feedstock was carried out in a tube furnace maintained at atmospheric pressure. The effects of furnace temperature and particle size on char formation and char characteristics were investigated. Chars o...

Evolution of size distribution and morphology of carbon nanoparticles during ethylene pyrolysis

The effects of furnace temperature and residence time on particle size distributions (PSDs) of carbon black, which is a type of carbon nanoparticle, were studied with a scanning mobility particle sizer. Particles were classified according to their mobility diameters by a differential mobility analyzer, followed by thermophoretic sampling by scanning electron microscopy to investigate their carbon black morphologies. PSDs were power-law distributions at short residence times and log-normal distributions at long residence times; these distributions indicate that agglomeration increases with increasing residence time. In addition, few 2.5-nm-sized particles existed above 1540 ± 40 K, while the critical size was 3 nm at 1350 ± 40 K. This finding indicates that the critical size of nuclei changes with temperature. At high temperatures of 1776 and 1676 K, the 100 and 180-nm-sized particles, whose primary particles kept their shape, had very complex morphologies. In contrast, at low temperature at 1570 K, the morphologies of 100 and 180-nm-sized aggregates are relativity simple, and primary particles nearly fused together in those aggregates. These observations indicate that the nucleation rate and fusing behavior change with temperature.

The Relation of Temperature Distribution on Silicon Wafer with Furnace Temperature and Gas Flow during Thermal Dry Oxidation Process

Silicon dioxide film has been used as the gate dielectric material in MOS device technology for decades. The film is normally grown in a diffusion furnace using a dry thermal oxidation process. As the device is scaled down to nanometer dimensions, the SiO2 film uniformity requirement is more stringent than ever. In this paper, the effect of furnace temperature and the flow rate of oxygen gas on wafer temperature distribution was investigated. The result was recorded by using the Infrared Thermometer with Dual Laser Targeting device (IRT5000). We have found that the uniformity of temperature distribution on the wafer is almost directly proportional to the O2 flow rate for the entire furnace temperature range (900 - 1050°C). On the other hand, the effect of O2 flow rate on wafer temperature distributions clearly shows two distinct regions; for furnace temperatures of less than 1000 °C, the higher the O2 flow rate, the better the uniformity. For the furnace temperatures of more than 1000 °C, we did not observe any clear dependency of wafer temperature distribution on O2 flow rate.

Protein-Directed Synthesis of γ-Fe2O3Nanoparticles and Their Magnetic Properties Investigation

In this study, maghemite (γ-Fe2O3) nanoparticles were produced using gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared γ-Fe2O3 nanoparticles were characterized using XRD, FT-IR, TEM, SEM and VSM data. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced gelatin-Fe3O4 nanocomposite were examined to prove the fundamental effect of gelatin; both as a capping agent in the nanoscale synthesis and as the director of the spinel γ-Fe2O3 synthesis among possible Fe 2O3 crystalline structures.

Mathematical simulation of direct reduction process in zinc-bearing pellets

A one-dimensional unsteady mathematical model was established to describe direct reduction in a composite pellet made of metallurgical dust. The model considered heat transfer, mass transfer, and chemical reactions including iron oxide reductions, zinc oxide reduction and carbon gasification, and it was numerically solved by the tridiagonal matrix algorithm (TDMA). In order to verify the model, an experiment was performed, in which the profiles of temperature and zinc removal rate were measured during the reduction process. Results calculated by the mathematical model were in fairly good agreement with experimental data. Finally, the effects of furnace temperature, pellet size, and carbon content were investigated by model calculations. It is found that the pellet temperature curve can be divided into four parts according to heating rate. Also, the zinc removal rate increases with the increase of furnace temperature and the decrease of pellet size, and carbon content in the pellet has little influence on the zinc removal rate.

Mathematical model of the direct reduction of dust composite pellets containing zinc and iron

Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace (RHF) in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.

Experimental Study of Post-Fire Behavior of Steel Fiber Reinforced Ceramsite Concrete Filled Steel Tubes

The axial compressive mechanical behavior of steel fiber reinforced ceramsite concrete filled steel tubes (noted as SFR-CCST) after exposure to fire are experimentally studied. Effect of furnace temperature, dosage of steel fiber in specimens on the post-fire mechanical performance of the specimens after exposure to fire was especially discussed. The results show that all the specimens of SFR-CCST have higher post-fire bearing capacity and better plastic deformation, and there was no obvious descending segment in the load-strain curves of the most specimens after exposure to fire. It was concluded that the furnace temperature applied to the specimens and dosage of steel fiber in the specimens of SFR-CCST has some effect on the post-fire mechanical performance of the ceramsite concrete-filled steel tubes after exposure to fire, and the dosage of steel fiber of 0.5% has the most effect on the post-fire performance of lightweight aggregate concrete filled steel tubes after exposure to fire.

Influence of furnace temperature and residence time on configurations of carbon black

The effects of furnace temperature and residence time on the mean primary particle diameter and aggregate shape of carbon black are investigated by benzene pyrolysis to confirm the factors that control the configuration of carbon black. With a high furnace temperature and short residence time, the mean primary particle diameter decreases and the aggregate shapes are complex; on the other hand, with a low furnace temperature and short residence time, the mean primary particle diameter increases and the aggregate shapes are simple. Moreover, with a high furnace temperature and long residence time, the mean primary particle diameter increases and the aggregate shapes are relatively simple. However, the aggregate shapes remain basically unchanged with increasing residence time. The results of this study suggest that the main factors that control the configurations of carbon black are nucleation, surface growth and sintering of primary particles. Nucleation, which is affected by high-molecular-weight polycyclic aromatic hydrocarbons (PAHs), controls aggregate shapes, while surface growth, which is affected by low-molecular-weight PAHs contributes to the growth of primary particles. The sintering of primary particles controls the simplification of aggregate shape and the growth of primary particles.

Effect of Furnace Temperature on Emission of Nitrous Oxide from Municipal Refuse Incinerators

Effect of Furnace Temperature on Emission of Nitrous Oxide from Municipal Refuse Incinerators

Numerical Prediction of Eutectic Temperature Using a Multi-phase-Field Model

To evaluate the reliability of metal-carbon eutectic systems as fixed points for the next generation of the international temperature scale, the effect of the eutectic microstructure on the temperature at the solid/liquid (s/l) interface during solidification and melting is preliminarily investigated using a multi-phase-field model. First, the effects of furnace temperature, lamellar spacing, and interface energy on the average temperature of the s/l interface are studied in the solidification process. With increased furnace undercooling, the s/l interface temperature was found to decrease. Calculated eutectic microstructures are then adopted as initial conditions for a melting simulation. The interface undercooling during melting is observed to be smaller than that observed during solidification. This difference in interface undercooling is attributed to the solute/solvent concentration profiles in the liquid phase near the s/l interface being different for melting and solidification.

Numerical Simulation for Direct Reduction of Pure Zinc Oxide Pellet Containing Carbon

Based on the equations of mass conservation, energy conservation and chemical reaction rates, a mathematical model of direct reduction for pure zinc oxide pellet containing carbon was built. On the basis of verifying the accuracy of the model by comparing calculated values with experimental results, the effects of furnace temperature, porosity and radius of pellet on the reduction were investigated. The calculated results revealed that the furnace temperature and the radius of pellet have significant effect while porosity has only a little. Thus it can be inferred that the rate-determining step for direct reduction in the pellet containing zinc oxide and carbon is heat transfer.

果樹剪定枝エネルギー利用のための基礎燃焼特性に関する研究

From a viewpoint of environmental preservation and resource protection, the recycling of wastes has been promoting. Expectations to new energy resource are growing by decrease of fossil fuel. Biomass is one of new energies with prevent global warming. This study is an attempt to burn pruned branches of plum trees in order to thermally recycle waste products of fruits agriculture. The devolatilization property of pruned branches of plum trees were observed by the thermogravimerty and differential thermal analysis (TG/DTA) to obtained fundamental data of fuel pyrolysis. The thermogravimetric analyzer was used to measure weight loss and temperature difference. It observed that the weight of pruned branches was decreased under three stages with endothermic reaction during water vaporazation and volatile pyrolysis, and with exothermic reaction during combustion of volatile and fixed carbon. The combustion behavior of pruned branches was observed in the electric furnace, where the video-recording and measurement of pruned branches weight were carried out at sequential steps of the combustion process. It observed that the combustion behavior of pruned branches was similar to woody pellets. The effects of furnace temperature and branch size were examined in order to elucidate the combustion characteristics as fuel, such as ignition delay, burning period, char-combustion time and the change of weight decrease. The results indicated that they are influenced at each step of the combustion processes such as devolatilization, ignition, visible envelope flame combustion and char combustion. Pruned branches showed medium values of characteristic time between of cider and woody pellet, and therefore ume plum pruned branches are considered to be promising alternative fuels.