Increase In Combustion Temperature Research Articles

Combustion behavior, emission characteristics of SO2, SO3 and NO, and in situ control of SO2 and NO during the co-combustion of anthracite and dried sawdust sludge

The combustion behaviors of anthracite and dried sawmill sludge (DSS) were studied using thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). DSS was found to be a promoter for anthracite combustion, the addition of DSS in anthracite decreased the burnout temperature and time. But DSS caused the rapid releases of SO2 and NO in the initial combustion stage. In overall, the increasing of DSS significantly decreased the emission factor of SO2 from 13.42 ± 1.80 to 0.31 ± 0.08 g/kg; while the emission factor of NO was not obviously changed and stable at 0.7–0.8 g/kg in all cases. The oxygen-rich atmosphere was helpful for the rapid and sufficient combustion of blend; the oxygen-lean atmosphere delayed the combustion process and slowed down the releases of SO2 and NO. The increasing combustion temperature improved the anthracite combustion, and the emission factors of SO2 and NO were all increased with the temperature increasing. 900 °C was found to be the best combustion temperature for NO generation. SO3 was detected in the combustion of anthracite under 21% and 30% of O2. Two promising ways for control of SO2 and NO were provided: 1) urea-fuel mixture combustion combined with the post-combustion wet absorption by Na2CO3; 2) post-combustion wet absorption by NaClO/Na2CO3. The removal efficiencies of SO2 and NO could reach 100% and over 95% respectively. The removal products were determined as sulfate, sulfite and nitrate by IC, with no toxic byproducts being produced.

Efficiency enhancement of spark-ignition engines using a Continuous Variable Valve Timing system for load control

In this work, a Continuous Variable Valve Timing (CVVT) system for load control in spark-ignition engines is proposed, analyzed, and compared with a conventional Throttle-controlled Engine. An analytical model for ideal processes is initially developed to study the performance of both cycles during part-load operation. Then, irreversibilites comprising charging dilution effects and heat losses during compression and expansion strokes are considered to approach a more realistic engine operation. At full-load, both cycles reach a maximum efficiency corresponding to that of an Otto cycle. However, a reduction in the efficiency occurs at part-load operation, with the CVVT Engine having a higher efficiency with respect to the Throttled Engine due to its unthrottled load control mechanism, which avoids power consumption caused by friction during air intake. It is found that charge dilution exerts a strong impact in the net power output and efficiency of both cycles. Additional reductions in power output and efficiency are caused by heat losses. At part-load operation, lower temperatures and pressures are reached in the CVVT Engine, which imply lower mechanical stresses that favor engine lifetime. It also represents a potential for additional efficiency enhancement via increasing combustion temperature. Finally, a fuel economy estimation analysis is carried out to provide quantitative assessment about the economic advantage of the proposed CVVT Engine. From this analysis, a fuel economy increment of up to 4.1% is obtained for a CVVT Engine with respect to a Throttled Engine at a 20%–30% load, which is typical of a real vehicle engine operation.

Alteration behavior of mineral structure and hazardous elements during combustion of coal from a power plant at Huainan, Anhui, China

The alteration behavior of minerals and hazardous elements during simulated combustion (100–1200 °C) of a raw coal collected from a power plant were studied. Thermogravimetric analysis indicated that there were mainly four alteration stages during coal combustion. The transformation behavior of mineral phases of raw coal, which were detected by X-ray polycrystalline diffraction (XRD) technique, mainly relied on the combustion temperature. A series of changes were derived from the intensities of mineral (e.g. clays) diffraction peaks when temperature surpassed 600 °C. Mineral phases tended to be simple and collapsed to amorphous glass when temperature reached up to 1200 °C. The characteristics of functional groups for raw coal and high-temperature (1200 °C) ash studied by Fourier transform infrared spectroscopy (FTIR) were in accordance with the result obtained from XRD analysis. The volatilization ratios of Co, Cr, Ni and V increased consistently with the increase of combustion temperature, suggesting these elements were gradually released from the organic matter and inorganic minerals of coal.

Combustion Characteristics of Tight Sandstone

As a promising unconventional energy source, tight sandstone gas has attracted increasing attention. Because of the extremely low porosity/permeability of tight sandstone, large scale exploration and development are still challenging. Recently, high-temperature combustion or pyrolysis has been employed to increase sandstone porosity/permeability. In this study, the sandstone samples obtained from Xinjiang Province in China were heated for 30 min in air atmosphere at temperatures of 350, 500, 700, 800, and 900 °C respectively. The combustion characteristics and property changes of sandstone were investigated. In the beginning, thermal decomposition process of sandstone and gas emission were tested using thermogravimetry combined with Fourier transform infrared spectroscopy. Then, the mineral composition and pore structure of different combusted sandstones were tested and analyzed. Moreover, the effects of combustion temperature on particle size of sandstone were also investigated. Finally, scanning electron microscopy (SEM) technology was performed to study the surface appearance change of sandstone. According to the experiment results, organic matters started releasing at 350–500 °C, and most of the minerals such as carbonate decomposed at 600–870 °C. During the combustion process, carbon dioxide and water vapor were the main product gases. With the increase of combustion temperature, the mean pore diameter increased from 8.0 to 22.6 nm, while the particles size remained almost constant. In addition to the increase of pore size, it can be found from SEM photos that the compact surface of sandstone became smooth and some new pores and small cracks appeared on the surface of sandstone after high-temperature combustion, especially at 900 °C. As a result, high-temperature combustion is one of the feasible methods to improve the porosity/permeability of sandstone.

A Comparative Study of Syngas Production From Two Types of Biomass Feedstocks With Waste Heat Recovery

This paper deals with an integrated biomass system developed for syngas production with waste heat recovery option and analyzes this system thermodynamically using both energy and exergy approaches. Also, an aspenplus simulation model is developed to demonstrate comparative gasification analyses of wood (Birch) and olive waste using Gibbs reactor for syngas production. Gibbs free energy minimization technique is applied to calculate the equilibrium of chemical reactions. In this newly developed model, the heat of the product syngas and the waste heat from the flue gas are recovered through a unique integration of four heat exchangers to produce steam for the gasification process. The sensitivity analyses are performed to observe the variations in the concentration of the methane, carbon monoxide and carbon dioxide in syngas against various operating conditions. Furthermore, the performance of gasifier is indicated through cold gas energy efficiency (CGE) and cold gas exergy efficiency (CGEX). The overall energy and exergy analyses are also conducted, and the comparisons reveal that the biomass composed of olive waste yields high magnitude of overall and cold gas energy efficiencies, whereas wood (Birch) yields high magnitude of overall and cold gas exergy efficiencies. Moreover, the energy of the product syngas is recovered through an expander which enhances energy and exergy efficiencies of the overall system. The present results show that the CGE, CGEX, and overall energetic and exergetic efficiencies follow a decreasing trend with the increase in combustion temperature. The proposed system has superior and unique features as compared to conventional biomass gasification systems.

Study on migration characteristics of heavy metals during oil sludge incineration

ABSTRACTExperimental and simulation studies on the migration characteristics of heavy metals during the incineration of OS were conducted with a tube furnace reactor and thermodynamic equilibrium calculation software FactSage, respectively. The results showed that when the incineration temperature increased from 800°C to 1100°C, the release rates of heavy metals such as Cr, Pb, Cu, Zn and Ni increased gradually and reached the maximum at 1000°C. When the excess air ratio increased from 1.0 to 1.4, the release rates of heavy metals such as Cr, Pb, Cu, Zn and Ni first decreased and then became steady. The content of gaseous hydroxide of Cr and gaseous chlorides of Pb and Cu increased while the chemical forms of Zn and Ni did not change obviously with the increase of combustion temperature or excess air ratio.

Thermodynamic Prediction of the Effect of Excess Air Ratios and Combustion Temperatures on the Equilibrium Phases Formed during Ash Fusion from Coal and Cedar Nut Shells

An analysis of equilibrium phase formation in the ashes from Polish coal and cedar nut shells (CNS) was performed for different combustion conditions in a bubbling fluidized bed boiler. Equilibrium calculations were performed using Factsage 6.3 for five excess air ratio values (λ)—0.7, 0.9, 1.0, 1.2, and 1.6—at a temperature range of 650 ≤ T ≤ 1050 °C. The masses and compositions of ashes synergistically depend on λ and T. An increased combustion temperature results in a decrease in the mass of (i) ashes formed from coal and CNS and (ii) liquid slag (in the case of CNS), resulting from a lower content of K2CO3(l) (the lower the λ, the greater the decrease in K2CO3(l)), and the migration of potassium into the exhaust gas in the form of compounds KCl(g), KOH(g), and K2SO4(g). Ashes from both coal and CNS contain compounds present (i) throughout the whole temperature range, regardless of λ value, e.g., KAlSi2O6(s) and Mg2Al4Si5O18(s), in the case of coal; e.g., Mg2SiO4(s) and MgO(s), in the case of CNS; (ii)...

Experimental study on combustion and pollutants emissions of oil sludge blended with microalgae residue

Experimental study on co-combustion of oil sludge (OS) and microalgae residue (MR) was conducted with a thermogravimetric analyzer and a designed fluidized bed reactor system. Combustion process of OS blended with MR could be divided into four stages, water evaporation, volatiles release and combustion, fixed carbon combustion and minerals decomposition. With MR ratio increasing, combustion performance of the mixture became better. MR addition can help improve the combustion performance of OS. NOx and SO2 concentrations increased firstly and then decreased with the increase of combustion temperature which ranged from 800 to 1100 °C. With the increase of excess air ratio α, NOx and SO2 emissions increased. Generally, NOx and SO2 emissions decreased with MR ratio increased at 800 °C, which is caused by the catalysis effect of ash and heavy metals in OS. OS blended with MR could both improve combustion performance and help reduce NOx and SO2 emissions during OS combustion, which provides an effective approach to massive synergistic disposal of waste resources.

Analysis and Assessment of A Biomass Energy-Based Multigeneration System with Thermoelectric Generators

This study demonstrates comparative energy and exergy analyses of an advanced biomass energy-based integrated multigeneration system with two innovative embodiments of thermoelectric generators. These two systems uniquely integrate the configurations of thermoelectric generators for better performance. System 1 incorporates an integration of the thermoelectric generators at the exhaust of the gas turbine. In system 2, thermoelectric generators are considered at the inlet of organic Rankine cycle 1. The heat rejected at the low temperature interface of the thermoelectric devices generates the electricity through organic Rankine turbine 2. Some of the electricity produced by thermoelectric generators is used to operate an electrolyzer to produce hydrogen. The utilization of thermoelectric device developed in system 2 increases the energetic and exergetic efficiencies of the overall multigeneration system and organic Rankine cycle 1. Also, the net amount of work output by organic Rankine cycle 1 of system 2 is improved greatly. Furthermore, the design configurations of the thermal system and the influence of operating conditions on the energy and exergy efficiencies of the multigeneration system and organic Rankine cycle are investigated for comparative assessments. The present results show that an increase in combustion temperature improves the work rate by turbines and thermoelectric generators appreciably. In addition to this, the overall energetic and exergetic efficiencies of system 1 are found to be 73.4% and 33.3%, respectively, whereas for system 2 these efficiencies are enhanced in the order 74.5% and 34.02%, respectively. The net amount of work output by organic Rankine cycle 1 in embodiment 2 is improved from 8023 kW to 8908 kW. The highest amount of exergy destruction (accounting for 91.5%) occurs in the gas turbine of system 1 followed by organic Rankine cycle 1 (accounting for 6.64%) of system 2. The proposed system has superior and unique features as compared to conventional systems with thermoelectric generation.

Combustion Efficiency and Pollution Risk Analysis Based on Different Type of Coal

Air pollution such as PM2.5 and PM10 has become a serious problem for many cities in China. One of the key factors for the causation of air pollution is the exhausts of coal combustion. The combustion efficiency and emission will be affected by different type of coal. Thus, four raw coals include Gaoping anthracite coal, Tangshan bituminous coal, Liupanshui lean coal, and Indonesia lignite coal are selected for the combustion process simulation and analysis based on Aspen Plus. The results show that the combustion heat of anthracite coal reached the highest level based on same combustion condition. According to the emission results of the selected coal, the combustion temperature just has a little impact on the emission of SOX, while the emission of NOX will increase when the combustion temperature increase. The study may provide a constructive strategy for the selection and utilization of different type of coal for relevant industry.

Experimental Study on Performance, Combustion and Emissions of Diesel Engine with Re-entrant Combustion Chamber of Aluminum Alloy

Internal combustion engines have been in use for more than a century and have undergone tremendous changes in their design, materials used and operating characteristics. Diesel engine is the most efficient type of internal combustion engines. In past few decades research efforts have been focused largely on better engine design from the perspective of reducing pollutants emission without sacrificing performance and fuel economy. Gas motion inside the engine cylinder, which depends on combustion chamber geometry is highly influences the performance of any internal combustion engine. Hence an attempt is made to study the performance, combustion parameters and emission particulates of diesel engine using different designs of combustion chambers of Aluminum alloy, in order to enhance the air swirl. Experiments are conducted on four stroke single cylinder water cooled diesel Engine at constant speed of 1500 rpm at different loads with hemispherical, toroidal and re-entrant toroidal geometries of the combustion chambers. The effect of varied piston bowl geometry on performance & combustion parameters viz. brake thermal efficiency (BTE), Brake specific fuel consumption (BSFC), exhaust gas temperature (EGT), heat release rate (HRR) & cylinder pressure and emission particulates have been investigated and presented in this paper. Results suggest that re-entrant piston bowl geometry has significant impact on performance, combustion characteristics and emission particulates inside the cylinder with varied piston bowl geometry shows that the squish flow effects the turbulence near the TDC during compression stroke. However, there is slight increase in particulates of NOx particulates due to increase in combustion temperature with enhanced air swirl with varied piston bowl geometry.

SHS of pyrochlore-type ceramic matrices for immobilization of actinide-containing nuclear wastes

Mineral-like Y2(Ti1–x Zr x )2O7 ceramic matrices for immobilization of actinide–Zr–RE-containing high-level nuclear wastes (HLW) were prepared by SHS method. In experiments, HLW were modeled by a mixture of CeO2, La2O3, ZrO2, MnO2, and Fe2O3 powders. An increase in the HLW content of green mixture decreased the amount of Y2(Ti1–x Zr x )2O7 in combustion product and increased that of ZrO2, LaTiO3, and CaTiO3; decreased the fractional substitutionality of Zr for Ti; and increased the product porosity. An increase in combustion temperature and suppression of heat sink during SHS reaction did not diminish markedly the porosity of synthesized ceramics.

Ash deposition and sodium migration behaviors during combustion of Zhundong coals in a drop tube furnace

Zhundong coalfield is one super-large coalfield recently discovered in China. However, the utilization of Zhundong coal in power plants has caused serious ash-related issues mainly due to its high-sodium feature. The ash deposition problem on convection heat exchanger surfaces is still particularly difficult to resolve and its mechanism has yet to be fully understood. This study deals with the ash deposition and alkali metal migration behaviors on convection heat exchanger surfaces between 400 and 800 °C during combustion of Zhundong coal using a lab-scale drop tube reactor. Experimental results show that the sodium content in ash deposit of Zhundong coals increases obviously as the deposition temperature decreases from 800 to 600 °C, while it is almost unchanged below 600 °C. The contents of iron and calcium in ash deposits exhibit nonmonotonic variations as the deposit probe temperature varies between 400 and 800 °C. Quartz and calcium sulfate are main crystalline phases in ash deposit of Zhundong coals. Calcium is inclined to present as calcite and lime at low deposition temperature, while high temperature facilitates calcium sulfation. Sodium of crystalline phase is found as albite and sodium sulfate at low deposition temperature. Both condensation of gaseous alkali metals and formation of low-melting minerals were responsible for the ash deposition phenomenon on convection heat exchanger surfaces involved in combustion of Zhundong coal. The sodium content in ash deposit decreases considerably with the increasing combustion temperature while the case of iron variation is opposite due to its low-volatility. In addition, the Na content in ash deposits increases obviously with the access air ratio reduced from 1.2 to 1.05, but the local weakly reducing atmosphere leads to less iron within ash deposits. Clarification of sodium migration and evaluation of ash deposition behaviors during combustion of Zhundong coal is helpful for a better exploration of the functional mechanism of ash deposit and then large-scale utilization of high-sodium coals.

Experimental and numerical investigations on the cyclic variability of an ethanol/diesel dual-fuel engine

Experiments and simulations were used to explore the cyclic variability of an ethanol/diesel dual-fuel engine. The experiments were conducted on a light-duty diesel engine fueled with port injection of ethanol and direct injection of diesel. The influences of engine load, ethanol proportion and diesel injection timing on the cyclic variability were investigated. In-cylinder pressure traces of 150 consecutive cycles were acquired at each test condition. Consequently, cyclic variations of ignition timing (CA5), combustion phasing (CA50), accumulated heat release (Qf) and indicated mean effective pressure (IMEP) were used to quantify the cyclic variability. The experimental results showed that the fluctuations of CA5 and CA50 were very small throughout the premixed ratio sweep for both the light and high loads. However, the cyclic variation of IMEP was increased with the increasing ethanol ratio at both load conditions. And the cyclic variation of IMEP was reduced at the high load. The variations of IMEP and Qf showed similar magnitudes and trends at the test conditions, indicating that the cyclic variation of IMEP was mainly caused by the variation of Qf. Simulations confirmed that the combustion of premixed ethanol showed larger variations to initial in-cylinder temperature fluctuations at the light load, and consequently resulted in higher cyclic variation of Qf. At the high load, the increased combustion temperature enhanced the oxidation of ethanol, which contributed to stabilizing the combustion and reducing the cyclic variations. The cyclic variations increased with retarded diesel injection timing, which was mainly due to the reduced combustion temperature.

Sensitivity of thermal conductivity for Al2O3 nanofluids

Present work deals with synthesis, characterization and the sensitivity study of thermal conductivity of Al2O3 nanofluids in different base fluids with change in concentration and temperature. In this work, the solution combustion synthesis method was used for synthesis and samples were combusted at three different temperatures. It was observed that increase in combustion temperature leads to the increase in particle size. Al2O3 nanoparticles combusted at 1000°C, having average particle size 53nm, were used for preparation of nanofluids in distilled water and ethylene glycol base fluids using two step approach. For change in temperature from 10 to 70°C and concentration variation from 0 to 2vol%; 30 and 31% increase in thermal conductivity was observed for distilled water and ethylene glycol based Al2O3 nanofluids, respectively. Finally, sensitivity analysis for thermal conductivity was also performed. Results of sensitivity analysis revealed that change in thermal conductivity is more sensitive to increase in volume percent at higher concentration.

Ancient Egyptian Blue (CaCuSi4O10) Pigment by Modern Solution Combustion Synthesis Method

<p class="Default"> </p><p class="Default"> The Egyptian blue pigment, CaCuSi<sub>4</sub>O<sub>10</sub>, has been used in ancient Egypt from 3000 BC. This pigment consists of CaCuSi<sub>4</sub>O<sub>10</sub> with variable amounts of wollastonite</p><p>(CaSiO<sub>3</sub>), high amount of Cu oxides, cuprite (Cu<sub>2</sub>O) or tenorite (CuO). It was prepared by melting the high percentage of copper in association with lime and desert sand in the Ancient time. In this work Egyptian blue was produced by solution combustion synthesis (SCS) in homogeneous aqueous solution of composition: cupper and calcium nitrates, sodium silicate and urea. This method permits chemically stable Egyptian blue fast and economic production. The Egyptian blue composition and structure obtained after SCS and calcination were studied by XRD, FTIR and SEM/EDX analysis. Crystallite size and crystal lattice parameters were calculated. An increase in combustion temperature during SHS and calcinations temperature influence Egyptian blue yield and crystallite size, slightly influence parameters of crystal lattice.</p>

Distribution of Clay Minerals in Light Coal Fractions and the Thermal Reaction Products of These Clay Minerals during Combustion in a Drop Tube Furnace

To estimate the contribution of clay minerals in light coal fractions to ash deposition in furnaces, we investigated their distribution and thermal reaction products. The light fractions of two Chinese coals were prepared using a 1.5 g·cm−3 ZnCl2 solution as a density separation medium and were burned in a drop-tube furnace (DTF). The mineral matter in each of the light coal fractions was compared to that of the relevant raw coal. The DTF ash from light coal fractions was analysed using hydrochloric acid separation. The acid-soluble aluminium fractions of DTF ash samples were used to determine changes in the amorphous aluminosilicate products with increasing combustion temperature. The results show that the clay mineral contents in the mineral matter of both light coal fractions were higher than those in the respective raw coals. For the coal with a high ash melting point, clay minerals in the light coal fraction thermally transformed more dehydroxylation products compared with those in the raw coal, possibly contributing to solid-state reactions of ash particles. For the coal with a low ash melting point, clay minerals in the light coal fraction produced more easily-slagging material compared with those in the raw coal, playing an important role in the occurrence of slagging. Additionally, ferrous oxide often produces low-melting substances in coal ash. Due to the similarities of zinc oxide and ferrous oxide in silicate reactions, we also investigated the interactions of clay minerals in light coal fractions with zinc oxide introduced by a zinc chloride solution. The extraneous zinc oxide could react, to a small extent, with clay minerals in the coal during DTF combustion.

Volatilization of Arsenic in Coal during Isothermal Oxy-Fuel Combustion

Arsenic volatilization characteristics of SJS bituminous coal were carried out in a customized isothermal thermogravimetric experimental system at 600–1400 °C under different oxy-fuel atmospheres. The mineralogical and morphological characterization of ash samples were analyzed using XRD and SEM instruments. Different from conventional nonisothermal mass loss curves by TG analyzer, the isothermal mass loss curves of coal did not show a clear process of moisture removal and devolatilization. With the increase of combustion temperature, the isothermal mass loss curve of SJS coal shifted to the left gradually and the burnout time shortened at the same time, whereas the mass loss curves of arsenic showed different tendencies at 900 °C stages. At the 900 °C stage, the volatilization of arsenic was delayed in oxy-fuel condition but with a higher release...

Performance and Flame Visualization of Dicyclopentadiene Rocket Propellants with Metal Hydride Additives

The addition of metal hydride improves the combustion performance of hybrid rocket fuels due to increased combustion temperature and hydrogen addition. However, the flame zone structure sensitivity to the addition of metal hydride has not been directly studied. This paper examines visible solid fuel flame height measurements and confirms these results with chemiluminescence in an optically accessible combustor. In addition, the fuel combustion performance is considered using a traditional hybrid rocket combustor as a comparison to the optical chamber results. This paper investigates dicyclopentadiene as the primary fuel binder in gaseous oxygen flow. is studied as a fuel additive and is compared to aluminum and mechanically activated aluminum-polytetrafluoroethylene. Twenty-five wt % increases the regression rate of dicyclopentadiene by 19% due to increased hydrogen release into the flame zone. Enhanced blowing from the 25 wt % decomposition increases the dicyclopentadiene flame height by 44%. decomposition is rapid with respect to dicyclopentadiene pyrolysis, and as a result particle size reduction from 100–200 to has no appreciable effect on the fuel regression or flame height. The addition of aluminum and aluminum-polytetrafluoroethylene increases the regression rate due to enhanced heat release but does not impact the flame height like .

Influence of small calcium additives on the structure and properties of ML5 (AZ91) alloy

The influence of calcium additives (from 0,1 to 1,0 wt.%) on the phase composition and the solidus temperature of ML5 magnesium alloy was studied. During the alloy crystallization in the presence of aluminum, calcium forms an intermetallic compound with a variable composition containing Al (53,4–57,4 %), Ca (42,6–42,8 %) and Mg (0,002–3,8 %). As the temperature decreases, this compound degenerates to Al 2 Ca combination. The impact of calcium on the number of Mg 17 Al 12 and Al 2 Ca phases as well as its distribution in the structure of the cast and heat-treated ML5 alloy was analyzed. By means of the electron microprobe analysis, it was found that calcium and aluminum were concentrated along the boundaries of the solid magnesium solution. It was shown that satisfactory mechanical properties of magnesium alloys containing calcium could only be acquired by their smelting and casting according to the process preventing metal contamination with rough inclusions. It was found that small calcium additions (up to 1 wt.%) increased combustion temperature and reduced the oxidation of the alloy at elevated temperatures (up to 715 °C). The effect of sulfur hexafluoride on the loss of calcium in flux-free melting was found.