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Energy consumption of fuel-fired industrial furnace accounts for about 23% of the national total energy consumption every year in China. Meanwhile, the reduction of combustion-generated pollutants in furnace has become very important due to the stringent environment laws and policy introduced in the recent years. It is therefore a great challenge for the researchers to simultaneously enhance the fuel efficiency of the furnace while controlling the pollution emission. In this study, a transient 3-D mathematical combustion model coupled with heat transfer and pollution formation model of a walking-beam-type reheating furnace has been developed to simulate the essential combustion, and pollution distribution in the furnace. Based on this model, considering nitrogen oxides formation mechanism, sensitivity study has been carried out to investigate the influence of fuel flow rate, air-fuel ratio on the resultant concentration of nitrogen oxides in the flue gas. The results of present study provide valuable information for improving the thermal efficiency and pollutant control of reheating furnace. [ABSTRACT FROM AUTHOR]

A problem of the technology of blast-furnace smelting connected with the necessity of guaranteeing the uniform distribution of the blast rate along the circumference of blast-furnace hearth remains unsolved up to now. The degree of stable nonuniformity of the blast rate over the circumference of blast-furnace hearth caused, first of all, by the design of the joint of a straight-line air channel and an annular channel can be significantly reduced by realizing two-sided diametrically opposite hot-blast supplies from the straight air channel to the annular channel. [ABSTRACT FROM AUTHOR]

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In small countries like Lithuania with a widespread district heating system, 5–10 MW moving grate biomass furnaces equipped with water boilers and condensing economisers are widely used. Such systems are designed for firing biomass fuels; however, varying fuel moisture, mostly in the range from 30% to 60%, complicates the automated operation. Without manual adjustment of the grate motion mode and other parameters, unstable operation or even extinction of the furnace is possible. To ensure stable furnace operation with moist fuel, the indirect method to estimate the fuel moisture content was developed based on the heat balance of the flue gas condensing economiser. The developed method was implemented into the automatic control unit of the furnace to estimate the moisture content in the feedstock and predictively adjust the furnace parameters for optimal fuel combustion. The indirect method based on the economiser heat balance was experimentally validated in a 6 MW grate-fired furnace fuelled by biomass with moisture contents of 37, 46, 50, 54 and 60%. The analysis shows that the estimated and manually measured values of the fuel moisture content do not differ by more than 3%. This deviation indicates that the indirect fuel moisture calculation method is sufficiently precise and the calculated moisture content varies proportionally to changes in the thermal capacity of the economiser. By smoothing the data using sliding weighted averaging, the oscillations of the fuel moisture content were identified. [ABSTRACT FROM AUTHOR]

Milling and grinding biomass fuels for pulverized combustion in industrial furnaces can be very expensive. This study aims to evaluate the effect of the particle size on the burnout and emissions of particulate matter from the combustion of agricultural residues (wheat straw and rice husk) in a drop tube furnace. Initially, both agricultural residues were crushed and sieved below 1 mm and the resulting particle size distributions formed one size class here named <1000 μm. In addition to this wide size class, three narrow particle size classes were prepared for each residue; namely, size classes 100–200 µm, 400–600 µm and 800–1000 µm. Subsequently, all size classes of both agricultural residues were burnt in a drop tube furnace at 1100 °C. The data reported include profiles of temperature, particle burnout and particulate matter concentration and size distribution measured along the drop tube furnace. The main conclusions from this study are: (i) for both agricultural residues the size class 100–200 µm presents the highest burnout values, followed by the size classes 400–600 µm and 800–1000 µm; (ii) the burnout values for the rice husk are higher than those for the wheat straw, and the total particulate matter emissions are rather similar for both agricultural residues, regardless of the size class; (iii) during the last stages of the combustion of the wheat straw occur particle fragmentation and the size classes 400–600 µm and 800–1000 µm are those that most contribute to this phenomenon, but particle fragmentation was not observed during the combustion of the rice husk; (iv) the wheat straw size classes 100–200 µm, 400–600 µm and <1000 µm present a bimodal particulate matter size distribution, while the class size 800–1000 µm presents a unimodal one, but the rice husk size classes show all a unimodal particulate matter size distribution. [ABSTRACT FROM AUTHOR]

This work presents first-of-a-kind results on the enhanced oil recovery (EOR) by CO 2 stream of oxy-fuel-fired circulating fluidized bed (CFB) boilers for Constant Furnace Size Scenario and Constant Thermal Power Scenario. The CO 2 flow rate, the associated impurities and the furnace thermal properties are investigated. The total mass flow rate of the EOR gas in Constant Furnace Size Scenario for the oxy-fuel case of 70% O 2 concentration becomes more than 2.6 times of the one with 29% O 2 concentration. The oxy-fuel CFB usage for EOR offers the opportunity of reconfigurable manufacturing system (RMS) where the CO 2 production capacity is flexible to market demand. While the increased CO 2 mass flow rates at elevated O 2 concentrations is in favor of Constant Furnace Size Scenario, the mass flow rates of the impurities of O 2 , CO and H 2 O also increase leading to higher costs for gas cleaning before sending the CO 2 stream for EOR injection. The relatively low outgoing CO level in addition to considerably lower furnace CO maxima compared to the other scenario are merits of Constant Thermal Power Scenario. [ABSTRACT FROM AUTHOR]

Electric-arc furnace dust (EAFD) is an industrial waste produced by the volatilization of metals during scrap melting in electric arc furnaces. This waste is classified as Class I – hazardous, because lead and cadmium concentrations are above the limits set in the leaching test. Processes are carried out in many countries to recover the metals contained in EAFD. In Brazil, these processes are usually not conducted in the industry because the low percentage of commercially valuable metals makes it economically unfeasible to recover them. One of the study alternatives is the use of EAFD in civil construction. Studies have shown that EAFD increases the mechanical strength of mortars and Portland cement-based concretes. However, EAFD delayed cement setting time, which can jeopardize its use in construction. Thus, this study aims to evaluate the effect of EAFD when added to fly ash (FA) and rice husk ash (RHA) based geopolymers. Geopolymer mortars were prepared at a ratio of 1:3 (FA + RHA: sand, four different granulations) and added with 0, 10, 15, and 20% EAFD in relation to the mass of FA + RHA. Compressive mechanical strength and leaching tests were carried out at the ages of 7, 28, and 91 days. Microstructural analyses were performed using XRD, FTIR, and SEM/EDS. EAFD did not negatively influence the geopolymerization process. The highest compressive strength results for the mortars containing the waste were found for 20% of EAFD. All mortars, regardless of EAFD content, were classified as non- hazardous Class II at the age of 91 days. [ABSTRACT FROM AUTHOR]

In this work, we focus on the scheduling of multi-crane operations in an iron and steel enterprise for a two-stage batch annealing process. The first stage is the heating process, and the second stage is the cooling process. To start the heating (cooling) stage, a special machine called a furnace (cooler) must be loaded. The real constraints of no-delay machine unloading are defined as follows: once the heating (cooling) is completed, the furnace (cooler) must be unloaded by crane immediately. The goal is to schedule limited machines (furnaces and coolers) operated by multiple cranes to minimize the completion time of the last annealed coil ( makespan ). We formulate a mixed-integer linear programming model to address this problem. Certain feasible properties are identified to avoid crane conflicts and ensure that the machine unloading no-delay constraints are met. Based on these necessary conditions, we then present a heuristic algorithm with running time in connection with the number of cranes, coils and machines. A lower bound to the problem is also developed. Through theoretical analysis, we show the worst-case bound of our heuristic algorithm. The average performances of the solution approaches are computationally evaluated. The computational results show that the proposed heuristic algorithm is capable of generating good quality solutions. [ABSTRACT FROM AUTHOR]

Explosive incidents with harmful consequences continue to occur in boilers and furnaces (heaters) where fossil fuels are burned. Proper designs, proper maintenance, and proper operating procedures have been developed, backed by standards, codes, guidelines, and recommended practices. However, process knowledge (education) and appropriate operating and maintenance procedures (training) remain the essential tools for personnel to understand the circumstances leading to catastrophic consequences and thus be able to enhance the safety conditions of combustion processes. Tackling the root of this problem requires visualizing the associated concepts, rules, and cautions to fully understand the nature of combustion, foresee its hazards, and prevent incident outcomes and consequences. This article is intended to provide colleagues in the field, engineers, technicians, and operators-who, on a daily basis, live in close proximity to the risks of fossil-fired boilers, furnaces, gas turbines, heaters, and processes with flammable mixtures-three basic tools to allow them to visualize, and thus, find it easier to remember, the concepts associated with the hazards of combustion processes by reviewing the knowledge available to prevent explosive incidents. © 2017 American Institute of Chemical Engineers Process Saf Prog 36: 221-236, 2017 [ABSTRACT FROM AUTHOR]

Pulse firing offers significant process and productivity benefits, such as improved temperature uniformity and high heat transfer rates to the product load through maximum system turndown and utilizes the system’s burners at their most efficient firing rates. However, overshoot and undershoot is unavoidable. To minimize these effects, the system operates the burner at an enhanced turndown rate. Faster cycle rates improve temperature uniformity but reduce equipment lifetime. Therefore, a tradeoff exists between furnace temperature uniformity and the cycle rate used by the pulse firing control.This paper proposes models and simulates an advanced technique that improves temperature uniformity while decreasing the cycle time used by the pulse firing control. This provides reliable, safe furnace operating conditions, thereby extending the lifetime of the equipment. After an analysis of a furnace’s combustion system that utilizes the pulse firing method to control the heat demand of the furnace, non-linearities were found in the combustion system. To improve the performance of the temperature control, an error-driven function was coupled to the control strategy to compensate the signal error fed to a proportional–integral–derivative controller. The error-driven function was implemented using a fuzzy system, which improved the temperature uniformity and allowed a 60% duty cycle reduction in comparison with similar combustion systems. [ABSTRACT FROM AUTHOR]

Steam boiler is an integral and important component of steam turbine used for electricity generation. Its design is however complex, time consuming and prone to errors if done manually. In this study, we report the application of computer based approach to design palm kernel shell combusting furnace for generating a desired amount of electricity. Using backward calculation approach, standard design equations were used to size furnace and its components. The equations were coded and solved using C-Sharp programming language. The results showed that to generate 5 kW of electricity from palm kernel shell; 5.5 kW turbines, 3.6 m super heater, 3.2 m riser, furnace of 1.432 m height and 0.45 m3 volume were required having considered power loss due to friction and others. While these results are in good agreement with those calculated manually, human errors are virtually eliminated. In addition, calculations and drafting time were reduced from 5 hrs 47 mins when done manually to about 4 mins when the developed code was used. This code can be used to size boiler for any desired power output. [ABSTRACT FROM AUTHOR]

Moving grate firing systems are widely used for biomass combustion. The characteristics of the fuel bed combustion in moving grate boilers are of practical interest as they are directly related to the release of pollutants and affect the furnace efficiency. Measurements of temperature and gas species concentrations inside the fuel bed are necessary to improve our understanding of the highly complex processes involved in biomass combustion. There have been few experimental studies of the fuel bed of industrial scale grate furnaces. The present study measured temperature and gas species concentrations within a thick burning bed of wet woody biomass, in a 4 MW reciprocating grate boiler. Measurements were carried out under three different operating conditions through ports located in the wall of the furnace using a stainless steel probe incorporating a thermocouple. Temperatures of about 1000 °C were measured close to the grate, indicating intense combustion at the bottom of the fuel bed. The temperature distribution along the bed height showed that different stages of the combustion process take place in horizontally adjacent layers along the grate. Higher flow rates of the primary air resulted in relatively higher CO and lower CO 2 and NO concentrations in the fuel bed. [ABSTRACT FROM AUTHOR]

This paper focuses on revealing flame image characteristics in a pilot-scale air combustion and oxygen-enriched combustion furnace. Changes in flame image parameters were examined according to flame behavior patterns, and 3-D temperature field distribution had been investigated under different air to oxy-fuel combustion conditions. These differences were controlled by regulating operation parameters (the amount of coal, circulating rate of flue gas, and oxygen concentration in primary air and secondary air). The analysis results show that combustion features such as flame length and igniting position can be increased as the increment of coal feeder frequency and flue gas circulation ratio at a certain oxygen concentration scope, but the flame brightness should be weakened. The variation trend of furnace temperature has revealed in quantity that the average temperature in oxy-fuel combustion is less 120 °C than that in air condition. In addition, flame brightness is enhanced as oxygen concentration increases, possibly decreasing the igniting distance, flame length, and combustion intensity in the higher CO2 concentration atmospheres; switch operation from air to oxy-fuel combustion should be stable with the circulation ratio of flue gas at a scope of 0.6–0.8 and about 28% oxygen concentration under oxy-fuel combustion. The flame behavior analysis method proposed here may represent an effective online monitoring and diagnostics tool for application in oxy-fuel combustion systems. [ABSTRACT FROM PUBLISHER]

A fast and furnace-free method of combustion synthesis is employed for the first time to synthesize iron-based superconductors. Using this method, Fe 1.1 Se 1 − x Te x (0 ≤ x ≤ 1) samples can be prepared from self-sustained reactions of element powders in only tens of seconds. The obtained Fe 1.1 Se 1 − x Te x samples show clear zero resistivity and corresponding magnetic susceptibility drop at around 10–14 K. The Fe 1.1 Se 0.33 Te 0.67 sample shows the highest onset T c of about 14 K, and its upper critical field is estimated to be approximately 54T. Compared with conventional solid state reaction for preparing polycrystalline FeSe samples, combustion synthesis exhibits much-reduced time and energy consumption, but offers comparable superconducting properties. It is expected that the combustion synthesis method is available for preparing plenty of iron-based superconductors, and in this direction further work is being in progress. [ABSTRACT FROM AUTHOR]

Co-firing of synthesis gas (syngas) produced from biomass/waste gasification is a promising option for increasing renewable energy production from existing boilers burning fossil fuels. This study presents an experimental approach to utilizing syngas as reburn fuel for NO emissions reduction. In a 65 kW furnace firing natural gas, the reburning characteristics for simulated syngas representing main syngas components, such as CH, CO and H, were evaluated for co-firing ratios up to 20%. The heating value and gas residence time of the syngas were maintained in the reburn zone by adjusting the N concentration. Detailed distribution of temperature, O and NO concentrations within the furnace were measured for the test conditions. The lower stoichiometric ratios of the primary combustion zone by reburning were favorable in reducing NO formation from the main fuel. Among the syngas components, CH was most efficient, exhibiting an immediate decrease in NO concentration after injection through the formation of HCN. CO and H also contributed to the reduction of NO emissions by suppressing further formation of NO in the reburn zone. The NO removal efficiency was diminished by an increase in NO concentrations in the burnout zone. [ABSTRACT FROM AUTHOR]

This paper presents the numerical simulation of gasless combustion of a sample as a combination of thermally coupled flat layers consisting of two different chemical compounds, which represent the model of a chemical furnace. The critical combustion conditions are established, depending on the volume ratio of mixtures in the sample or the content of reaction products. The time, velocity, and combustion modes of the layer composition are determined, depending on the volume content of the mixtures, the thickness, and the number of layers. The combustion wave propagation in view of 'homogenization' of the sample with layer thickness decreasing at a fixed concentration of the components is considered. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The power generation industry throughout the world stands to gain significantly from process improvements and optimization which can potentially lead to cleaner production of cost effective electricity. The efficient operation of lignite-based tangentially-fired combustion systems, as commonly used in Victoria, Australia, depends on critical issues such as ignition and combustion of the fuel, which are largely controlled by burner aerodynamics. The geometry of the burner and the ratio of velocities between the primary and secondary jets play an important role in achieving stable combustion, high burnout of fuel, low production of pollutants and control of fouling. Slot-burners are vertically aligned stacks of rectangular nozzles delivering primary fuel and secondary air jets, and are commonly used in tangentially-fired boilers. To obtain a better understanding of the overall combustion process, it is important to understand the aerodynamics of jet development from these burners. This paper reports an experimental investigation into the aerodynamics of a recessed rectangular slot-burner of the type used in the Yallourn stage-2 tangentially-fired furnace. The 1:15 scale model burner consisted of a central (primary) rectangular fuel nozzle with two secondary rectangular air jets positioned above and below it. The burner jets were at an angle of 60° to the wall and were diffused and mixed in a recess before entering into the measurement vessel. A cross-flow jet was attached to the wall of the vessel to simulate the recirculation similar to tangentially-fired furnaces. Experiments for both single and two-phase flow were performed. For single-phase flow, the air flow was seeded with a fine mist of sugar particles (mean diameter 1 μm) introduced into the primary, secondary and cross-flow ducts. For two-phase flow, solid glass spheres (mean diameter 66 μm, density 2450 kg/m 3 ) were used as the representative of the coal particles and were introduced only at the centre of the primary duct from a bubbling fluidized bed. Experiments were conducted using a primary to cross-flow jet velocity ratio ( φ ) of 1.0 and secondary to primary jet velocity ratios ( ϕ ) of 1.0 and 3.0 as found in real furnaces. Laser Doppler Anemometry (LDA) was used to measure mean and turbulent velocity components in the near field and downstream regions of the jets. The flow pattern inside the recess was very complex and greatly influenced the flow where it entered the measurement vessel. For single-phase flow and ϕ = 1.0, the jets diverged completely from the geometric axis of the burner and attached to the wall. The degree of deflection of the lower secondary jet was slightly more than the primary jet. For ϕ = 3.0, after exiting from the nozzle, the primary jet diffused outwards and mixed with the higher momentum secondary jets in the recess and came out with the secondary jets. For two-phase flow and ϕ = 1.0, in the mixing region between the primary and cross-flow jet, the gas-phase velocities were higher than the particle-phase. Further downstream the peak velocities of the particle-phase slightly deviated and occurred farther from the wall. For ϕ = 3.0, downstream of the nozzle there was a tendency of separation for the gas-phase near the wall while the particle-phase was attached to the wall. [ABSTRACT FROM AUTHOR]

This paper focuses on assessment of the effect of flue gas recirculation (FGR) on heat transfer behavior in 1296t/h supercritical coal-fired circulating fluidized bed (CFB) combustor. The performance test in supercritical CFB combustor with capacity 966 MW th was performed with the low level of flue gas recirculation rate 6.9% into furnace chamber, for 80% unit load at the bed pressure of 7.7 kPa and the ratio of secondary air to the primary air SA/PA = 0.33. Heat transfer behavior in a supercritical CFB furnace between the active heat transfer surfaces (membrane wall and superheater) and bed material has been analyzed for Geldart B particle with Sauter mean diameters of 0.219 and 0.246 mm. Bed material used in the heat transfer experiments had particle density of 2700 kg/m3. A mechanistic heat transfer model based on cluster renewal approach was used in this work. A heat transfer analysis of CFB combustion system with detailed consideration of bed-to-wall heat transfer coefficient distributions along furnace height is investigated. Heat transfer data for FGR test were compared with the data obtained for representative conditions without recycled flue gases back to the furnace through star-up burners. [ABSTRACT FROM AUTHOR]

Long afterglow SrAl 2 O 4 :Eu 2+ ,Dy 3+ nanophosphors were synthesized via a facile but effectual auto-combustion technique followed by post-annealing treatment at elevated temperatures. The influence of various fuels during synthesis and thereafter improvement in the luminescence decay characteristics under various illuminant irradiations of long afterglow nanophosphors have been reported. Extensive studies on structural, morphological and luminescent properties of the as-synthesized afterglow nanophosphors have been presented. Powder X-ray diffraction studies confirm the presence of high-purity, single-phase monoclinic nanophosphors. HRTEM investigations confirm the formation of nanophosphors of particle size less than 50 nm. Photoluminescence emission is attributed to the characteristic d–f transition (4f 6 5d 1 →4f 7 ) of Eu 2+ ions and was positioned at 512 nm. As-synthesized nanophosphors exhibit considerable confinement effects resulting into blue shift in emission maxima as compared to their bulk counterparts. The mechanism underlined for long afterglow has been discussed using trapping–detrapping model. The nanophosphor being multifunctional finds many interesting applications including dark-vision display, energy storage, fingerprint detection, in vivo and in vitro biological staining, etc. [ABSTRACT FROM AUTHOR]

Comparison calibrations comprise by far the majority of all thermometer calibrations, and the improvement of the calibration speed and quality is of significant importance. In general, these calibrations are performed by comparing a thermometer under calibration with a reference thermometer, with both thermometers being placed in a zone of controlled temperature that is in thermal equilibrium. The time invariance of metrological characteristics of temperature regulated zones (gradients, stability, repeatability) adds a significant contribution to the total calibration uncertainty. To improve spatial thermal homogeneity and temporal stability of ordinary equalizing blocks (commonly used in combination with calibration baths and furnaces), a new concept is developed under the name multi-entrance fixed point (MEFP). With the MEFP, performances are improved by utilizing a phase transition of matter, similar to the fixed-point cells that are used for calibration of thermometers at the primary level. While fixed-point cells represent temperature standards alone, the MEFP concept requires the use of a standard thermometer as the calibration reference. This paper discusses the advantages, design possibilities, and performance of the concept and gives results of the investigation of the zinc-filled MEFP cell. The performance of the new MEFP cell was examined by calibrating a thermometer against a standard. Two calibrations were performed in the same furnace, first using an MEFP cell as an ordinary equalizing block (without a phase transition) and then at the melt plateau of zinc. The investigation results confirmed the usefulness of the MEFP concept, as the uncertainty contributions from temperature gradients and the stability of the furnace were decreased by an order of magnitude, in comparison to the ordinary equalizing block. [ABSTRACT FROM AUTHOR]

This paper presents the experimental observations and results of three one-quarter scale composite slab-beam systems, 3.15 m by 3.15 m in plan, and tested in fire conditions. The tests aimed to examine the effects of unprotected interior secondary beams and edge rotational restraint on the behaviour of floor assemblies. The test results show that continuity of reinforcement in the slab over the supporting beams, and the presence of interior beams, can reduce the slab deflection and enhance its load-bearing capacity. Interior beams can be left unprotected without leading to a structural failure. The interior beams play a major role in helping the slab to move from biaxial bending stage to membrane behaviour, enabling the slab to mobilize higher tensile membrane forces. Rotational restraint along the protected edge beams induces intense stress concentration above these beams, resulting in more severe concrete crushing at the four corners and wide cracks over the edge beams. In addition to the experimental study, a numerical model using ABAQUS has been developed to simulate the tests. The numerical predictions agree well with the experimental results, showing that the proposed model is reliable. A shortcoming of the study is that the fire resistance performance of the specimens cannot be compared with those in practical design because a real furnace fire and small-scale fire tests were used due to limits of the furnace. However, the experimental results do provide basic information on the membrane behaviour in fire and also allow analytical methods and numerical models to be validated. [ABSTRACT FROM AUTHOR]

This research is carried out to investigate thrust force and torque during drilling on the developed bio-degradable sandwich composites. Two natural fibers, namely vetiveria zizaniodes (vetiver) and jute, and one synthetic fiber, namely Eglass, are used as reinforcements with vinyl ester resin to form three composite specimens. The fiber compositions in each specimen are varied while the resin composition is kept as a constant. The vetiver fibers are pre-treated with alkali and followed by furnace heating in order to improve its surface properties. The specimens are subjected to a set of 28 drilling operations during which the machining parameters, like speed, feed rate, tool point angle and work sample, are varied between four levels to form a four-factor mixed level D-optimal factorial design. During each drilling operation, the thrust force and torque are measured as responses by using a kistler make drill dynamometer with an accuracy level of 0.01N. The responses are analyzed by using response surface method, and non-linear regression equations are developed. Optimization on the experimental data resulted in selection of a high level of speed of 2000 rpm, low level feed of 0.1 mm/rev, tool angle between 600 to 900 and selection of sample level I as optimized values with a thrust force of 82.47 N and torque of 4.4 Nm. Confirmatory runs are conducted and the responses are again measured. The average error between the developed model and the confirmatory runs is found to be minimal and hence the optimization is highly satisfactory. [ABSTRACT FROM AUTHOR]

Combustion tests in a large-scale laboratory furnace were carried out to assess the feasibility of using biodiesel as a fuel in industrial furnaces. For comparison purposes, petroleum-based diesel was also used as a fuel. Initially, the performance of the commercial air-assisted atomizer used in the combustion tests was scrutinized under non-reacting conditions. Subsequently, flue gas data, including PM (particulate matter), were obtained for various flame conditions to quantify the effects of the atomization quality and excess air on combustion performance. The combustion data was complemented with in-flame temperature measurements for two representative furnace operating conditions. The results reveal that (i) CO emissions from biodiesel and diesel combustion are rather similar and not affected by the atomization quality; (ii) NOx emissions increase slightly as spray quality improves for both liquid fuels, but NOx emissions from biodiesel combustion are always lower than those from diesel combustion; (iii) CO emissions decrease rapidly for both liquid fuels as the excess air level increases up to an O2 concentration in the flue gas of 2%, beyond which they remain unchanged; (iv) NOx emissions increase with an increase in the excess air level for both liquid fuels; (v) the quality of the atomization has a significant impact on PM emissions, with the diesel combustion yielding significantly higher PM emissions than biodiesel combustion; and (vi) diesel combustion originates PM with elements such as Cr, Na, Ni and Pb, while biodiesel combustion produces PM with elements such as Ca, Mg and Fe. [ABSTRACT FROM AUTHOR]

Abstract: The application of proportional–integral–derivative (PID) controllers to chemical processes may not achieve the desired effect due to large time delay, model/plant mismatches, etc, which causes performance deterioration. In view of this, the paper first proposes a new PID controller design based on dynamic matrix control (DMC) optimization and then tests it on the residual oil outlet temperature in an industrial coke furnace. The resulting PID controller shows that it has the superior character of DMC algorithm and, at the same time, the simple structure as a traditional PID controller. Since model predictive control is effective in dealing with long time delays and model/plant mismatches, the control performance under the proposed PID is improved compared with typical PID controllers. [Copyright &y& Elsevier]

The article focuses on the automation of high-purity zirconium production from wastes and recycled materials on industrial equipment at the Chepetskii Mechanical Plant. Topics discussed include iodide refining as a process to obtain purest zirconium, automation of the process on the basis of the SKB-5025 industrial furnace, and choosing best automation software for the process.

Investigation on optimization of pellet shaft furnace based on the combination of genetic algorithm and support vector machine (SVM) is carried out. A SVM classifier model is developed to map the complex nonlinear relationship between operating parameters and the quality indexes of fired pellet, and a genetic algorithm is adapted in the energy optimization with the fitness function based on the SVM classifier model. This method can reduce the energy consumption while maintaining the fired pellet quality stable. The results show that the accuracy of the SVM classifier model is satisfied and the gas consumption can be reduced by 4% per ton of green pellets with this optimization method. [ABSTRACT FROM AUTHOR]

Controlled bench scale pulverized coal combustion studies were performed, demonstrating that inorganic particles play a critical role as carriers of organic species. Two commonly-used aerosol mass spectrometry techniques were applied to characterize fine particle formation during coal combustion. It was found that the organic species in coal combustion aerosols have mass spectra similar to those generated by biomass combustion. Ambient measurements in Shanghai, China confirm the presence of these species in approximately 29-38% of the sampled particles. With the absence of major biomass sources in the Shanghai area, it is suggested that coal combustion may be the main source of these particles. This work indicates there is a significant potential for incorrect apportionment of coal combustion particles to biomass burning sources using widely adopted mass spectrometry techniques. [ABSTRACT FROM AUTHOR]

Abstract: To achieve significant reductions in particularly high NO x emissions and to eliminate severely asymmetric combustion found in down-fired boilers, a multiple-injection and multiple-staging combustion technology was developed in our previous study. Representing great progress in this area, one of two newly-designed down-fired 600 MWe supercritical utility boilers using this technology had a recent trial run before its 168-h test. By phase-Doppler anemometry measurements within a cold 1:40-scaled model of the furnace, gas/particle flow characteristics were compared among various staged-air ratio settings (i.e., 20%, 25%, 30%, and 35%) to establish an appropriate staged-air ratio range for boiler operation. Meanwhile, to validate this first industrial application of the newly developed technology, industrial-size measurements were made at a 550 MWe load during the trial run. Experimental gas/particle flow results uncovered that at the highest setting, a severely asymmetric gas/particle flow field developed in the furnace. For the two lower settings, an essentially symmetric gas/particle flow field appeared. Moreover, gas/particle flow-field symmetries at the 30% setting were generally acceptable. Consequently, a staged-air ratio range of 20–30% is recommended for the boiler. As expected, industrial-size data revealed that excellent furnace performance, characterized by symmetric combustion and low levels of carbon in fly ash (5.1%) and NO x emissions (822 mg/m3 at 6% O2), appeared within the boiler. This was despite combustion optimization and a present lack of industrial-size data at full load. [Copyright &y& Elsevier]

Highlights: [•] Comparison between CFD predictions and in-flame measurements of 3MW oxy-NG tests. [•] Modeling strategies required to diminish the computational time. [•] Inadequacy of fast chemistry approaches to treat the turbulence/chemistry interaction. [•] Strong influence of the spectral model on predictions. [ABSTRACT FROM AUTHOR]

To achieve significant reductions in NOx emissions and to eliminate strongly asymmetric combustion found in down-fired boilers, a deep-air-staging combustion technology was dialed in a down-fired 600 MWe supercritical utility boiler. By performing industrial-sized measurements taken of gas temperatures and species concentrations in the near wing-wall region, carbon in fly ash and NOx emissions at various settings, effects of overfire air (OFA) and staged-air damper openings on combustion characteristics, and NOx emissions within the furnace were experimentally determined. With increasing the OFA damper opening, both fluctuations in NOx emissions and carbon in fly ash were initially slightly over OFA damper openings of 0-40% but then lengthened dramatically in openings of 40-70% (i.e., NOx emissions reduced sharply accompanied by an apparent increase in carbon in fly ash). Decreasing the staged-air declination angle clearly increased the combustible loss but slightly influenced NOx emissions. In comparison with OFA, the staged-air influence on combustion and NOx emissions was clearly weaker. Only at a high OFA damper opening of 50%, the staged-air effect was relatively clear, i.e., enlarging the staged-air damper opening decreased carbon in fly ash and slightly raised NO, emissions. By sharply opening the OFA damper to deepen the air-staging conditions, although NOx emissions could finally reduce to 503 mg/m3 at 6% 02 (i-e., an ultralow NOx level for down-fired furnaces), carbon in fly ash jumped sharply to 15.10%. For economical and environment-friendly boiler operations, an optimal damper opening combination (i.e., 60%, 50%, and 50% for secondary air, staged-air, and OFA damper openings, respectively) was recommended for the furnace, at which carbon in fly ash and NOx emissions attained levels of about 10% and 850 mg/m3 at 6% O2, respectively [ABSTRACT FROM AUTHOR]

Ways of enhancing energy efficiency of tube furnace operation (by improving lining quality, controlling fuel/air/steam ratio, etc.) are described. Methods of removing deposits from the outer surface of the coils in the operating furnace are examined. The operational characteristics of several investigated furnaces are cited. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results from two full-scale furnace tests conducted on two-way concrete slabs supported by composite beams in a three-storey steel-framed building. Each floor of the building consisted of nine panels (three by three) supported by composite beams. In two tests, a corner and an interior panel on the top of the building were heated by two specially designed furnaces respectively. Detailed experimental data in the form of describing slab cracking, the furnace temperatures, temperature distributions within the slab, vertical deflections and horizontal displacements are presented. Comparison of the results for the two tests indicates that the structural fire behaviour of two-way concrete slabs supported by composite beams in a multi-storey steel-framed building is highly dependent on the restraint provided by the adjacent structural members. Observations from the tests indicate that in addition to the extensive cracks formed on the top surface of the heated panels, regular cracks also occurred on the top of the adjacent unheated panels due to structural continuity and the interaction between the concrete slabs and the supporting beams. The test results show that both tested panels had good fire performances even under long duration fire conditions. [Copyright &y& Elsevier]

Abstract: Oxy-fuel combustion technique is a viable option to reduce several types of greenhouse gases (GHGs) emissions from the pulverized coal (PC) combustion systems. In this paper, a computational fluid dynamics (CFD) modelling study has been developed in order to investigate the Victorian brown coal combustion in a 550MW utility boiler under the air-fired (reference case) and three oxy-fuel-fired scenarios. The reference firing case was modelled based on the operating conditions of Loy Yang A power plant located in the state of Victoria, Australia. While Chalmers’ oxy-fuel combustion approach was selected for the present oxy-fuel combustion simulations, which referred to as OF25 (25vol.% O2), OF27 (27vol.% O2), and OF29 (29vol.% O2). User-defined functions (UDFs) were written and incorporated into the CFD code to calculate the following mathematical models: the PC devolatilization, char burnout, multi-step chemical reactions, mass and heat transfer, carbon in fly-ash, and NO x formation/destruction. A level of confidence of the CFD model was achieved validating four different parameters of the conventional combustion case, as well as the previous preliminary CFD studies that conducted on a 100kW unit firing propane and lignite under oxy-fuel combustion environments. The numerical results of OF29 combustion condition were considerably similar to the reference firing results in terms of gas temperature levels and radiative heat transfer relative to the OF25 and OF27 combustion cases. This similarity was due to increasing the residence time of PC in the combustion zone and O2-enriched in feed oxidizer gases. A significant increase in the CO2 concentrations and a noticeable decrease in the NO x formation were observed under all oxy-fuel combustion scenarios. The combustion chemistry was adopted in these investigations in order to capture the effects of O2 concentrations and gas temperatures on the CO/CO2 production rate and equilibrium between H2 and H2O in the combustion zone. Also, the use of O2-enriched atmospheres during oxy-fuel-fired cases was slightly enhanced the carbon burnout rate. These predicted results were reasonably consistent with the experimental investigations and numerical modelling found in the literature. This study of Victorian brown coal oxy-fuel combustion in a large-scale tangentially-fired boiler is important prior to its implementation in real-life. [Copyright &y& Elsevier]

Abstract: A large number of papers reported measures of coal char conversion rate under combustion and gasification conditions. Measures involved a variety of coal and char types, as well as different experimental techniques, ranging from TGA to wire mesh reactors and drop tube furnaces. For oxy-combustion with flue gas recirculation the impact of CO2 on the rate of combustion of char combustion is still controversial. In the present paper the rate of carbon conversion in O2/CO2 mixtures typical of oxyfuel conditions has been investigated by conventional as well as innovative experimental techniques, respectively isothermal/non-isothermal thermogravimetric analysis and reaction in an aerodynamic levitator particle reactor (ALPR). Results show that the ALPR provides reliable results also at values of temperature and oxygen concentration where thermogravimetric analysis fails. Experimental results have been worked out to obtain simple rate expressions for oxy-fuel combustion. Commonly used kinetic laws, however, proved unable to fit the experimental results in the whole range of operating conditions. [Copyright &y& Elsevier]

Abstract: Organic compounds occurring in coal ash of known mineralogy were investigated. Ash came from two domestic furnaces using bituminous coal from the Upper Silesia Coal Basin. Dichloromethane extracts of ash were analyzed with gas chromatography–mass spectrometry (GC–MS) for biomarkers from fuel and formed during combustion. Distributions of aliphatic hydrocarbons, aromatic and polar compounds were researched. Results were compared with those found for power plant coal ash, coal wastes which underwent self-heating and source bituminous coal. It was found that geochemical features of plant coal ash organic matter reflects mainly geochemistry of source bituminous coal. Several groups of biomarkers such as as n-alkanes, steranes and pentacyclic triterpanes show distributions recognizable as coal-deriving what enables to identify source fuel. Values of most biomarker and aromatic hydrocarbon parameters show minor changes due to heat of the combustion process. The most advanced changes are found in distributions of alkylnaphthalenes, pristane, phytane and lighter n-alkanes reflected by values of Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios. Much less extensive changes are seen in distributions of pentacyclic triterpanes which make them the most useful biomarker group for source fuel characterisation. Most of biomarkers are probably present in coal ash in unburnt coal particles occurring in ash due to low temperature in domestic furnaces favoring organic matter preservation. [Copyright &y& Elsevier]

The solution for dynamic modeling of reheating furnaces requires a burner model, which is simultaneously accurate and fast. Based on the fact that radiative heat transfer is the most dominant heat transfer mode in high-temperature processes, the present study develops a simplified flame representation model that can be used for dynamic simulation of heat transfer in reheating furnaces. The first part of the paper investigates, experimen-tally and computationally, gas combustion in an industrial burner. Experiments aim at establishing an experimental database of the burner characteristics. This database is compared with numerical simulations in order to establish a numerical model for the burner. The numerical burner model was solved using a commercial computational fluid dynamics (CFD) software (FLUENT 6.3.26). A selection of results is presented, highlighting the usefulness of CFD as a modeling tool for industrial scale burners. In the second part of the paper, a new approach called the "emissive volume approach" is established. This approach consists of replacing the burner flame by a number of emissive volumes that replicates the radiative effect of the flame. Comparisons with CFD results show a difference smaller than 1% is achieved with the emissive volume approach, while computational time is divided by 40. [ABSTRACT FROM AUTHOR]

Abstract: The discrete ordinates method (DOM) and finite-volume method (FVM) are used extensively to solve the radiative transfer equation (RTE) in furnaces and combusting mixtures due to their balance between numerical efficiency and accuracy. These methods produce a system of coupled partial differential equations which are typically solved using space-marching techniques since they converge rapidly for constant coefficient spatial discretization schemes and non-scattering media. However, space-marching methods lose their effectiveness when applied to scattering media because the intensities in different directions become tightly coupled. When these methods are used in combination with high-resolution limited total-variation-diminishing (TVD) schemes, the additional non-linearities introduced by the flux limiting process can result in excessive iterations for most cases or even convergence failure for scattering media. Space-marching techniques may also not be quite as well-suited for the solution of problems involving complex three-dimensional geometries and/or for use in highly-scalable parallel algorithms. A novel pseudo-time marching algorithm is therefore proposed herein to solve the DOM or FVM equations on multi-block body-fitted meshes using a highly scalable parallel-implicit solution approach in conjunction with high-resolution TVD spatial discretization. Adaptive mesh refinement (AMR) is also employed to properly capture disparate solution scales with a reduced number of grid points. The scheme is assessed in terms of discontinuity-capturing capabilities, spatial and angular solution accuracy, scalability, and serial performance through comparisons to other commonly employed solution techniques. The proposed algorithm is shown to possess excellent parallel scaling characteristics and can be readily applied to problems involving complex geometries. In particular, greater than 85% parallel efficiency is demonstrated for a strong scaling problem on up to 256 processors. Furthermore, a speedup of a factor of at least two was observed over a standard space-marching algorithm using a limited scheme for optically thick scattering media. Although the time-marching approach is approximately four times slower for absorbing media, it vastly outperforms standard solvers when parallel speedup is taken into account. The latter is particularly true for geometrically complex computational domains. [Copyright &y& Elsevier]

Abstract: Combustion in fired heaters, boilers and furnaces often accounts for the major energy consumption on industrial processes. Small improvements in efficiency can result in large reductions in energy consumption, CO2 emissions, and operating costs. This paper will describe some useful low cost modelling techniques based on the zone method to help identify energy saving opportunities on high temperature fuel-fired process plant. The zone method has for many decades, been successfully applied to small batch furnaces through to large steel-reheating furnaces, glass tanks, boilers and fired heaters on petrochemical plant. Zone models can simulate both steady-state furnace operation and more complex transient operation typical of a production environment. These models can be used to predict thermal efficiency and performance, and more importantly, to assist in identifying and predicting energy saving opportunities from such measures as: [•] Improving air/fuel ratio and temperature controls. [•] Improved insulation. [•] Use of oxygen or oxygen enrichment. [•] Air preheating via flue gas heat recovery. [•] Modification to furnace geometry and hearth loading. There is also increasing interest in the application of refractory coatings for increasing surface radiation in fired plant. All of the techniques can yield savings ranging from a few percent upwards and can deliver rapid financial payback, but their evaluation often requires robust and reliable models in order to increase confidence in making financial investment decisions. This paper gives examples of how low cost modelling techniques can be applied to improve confidence in implementing energy efficiency improvements whilst safeguarding manufacturing output and quality. [Copyright &y& Elsevier]

As a major consumer of energy the steel producers are always mentioned as interesting field of investigations. The aim of this paper is to establish the basic relations for a model in order to help to evaluate the parameters of the heat transfer and energy consumption in the case of some metallurgical heating furnaces for billets reheating. Starting from considerations about the burning process of the fuels, the paper establishes connections between the heat exchange coefficients, energy and metallic material saving. Saving energy and lost metal due to the oxidation process, means to have a cleaner environment. A new disposing system of the burners inside the furnace can lead to saving energy and metal. The paper offer also a model to calculate the temperature in the furnace (temperature of the flue gases) taking in consideration the global heat exchange, the technological temperature of the billet in order to evaluate the thermal energy looses. [ABSTRACT FROM AUTHOR]

During kraft recovery boiler operation, situations can be encountered where the furnace temperature is asymmetric when comparing one side of the furnace to the other (i.e., left vs. right). In this paper, computational fluid dynamics (CFD) modeling is applied to study furnace load and liquor spraying as causes for asymmetric furnace temperatures in a 4450 tons dry solids (TDS)/day kraft recovery boiler. The model predictions are compared against validation measurements. Decrease in furnace load is identified as the main cause of the temperature asymmetry. The simulations also suggest that, at decreased load, relatively small differences in the tilts of individual liquor sprays can increase the temperature asymmetry. [ABSTRACT FROM AUTHOR]

As part of an investigation few experiments were conducted to study the enhanced heat transfer rate and increased furnace efficiency in a diesel fired crucible furnace with oscillating combustion. The results of experimental investigations of temperature distribution inside the crucible furnace during oscillating combustion are validated with the numerical simulation CFD code. At first pragmatic study of temperature distribution inside a furnace was carried out with conventional mode of combustion at certain conditions and later transient behavior similar to that is conducted with oscillating combustion mode with the same conditions. There found to be enhanced heat transfer rate, reduced processing time and increased furnace efficiency with visibly clean emissions during the oscillating combustion mode than the conventional combustion mode. In the present paper the temperatures inside the furnace at few designated points measured by suitable K type thermo-couples are compared with the CFD code. The geometric models were created in ANSYS and the configuration was an asymmetric one for computational reason. The experimental and numerical investigations produce similar acceptable results. The presented results show that the 3D transient model appeared to be an effective numerical tool for the simulation of the crucible furnace for melting processes. [ABSTRACT FROM AUTHOR]