Test Furnace Research Articles

An assessment for the viability of recovering heat from a smoke extract system

Over the course of industrial manufacturing, additional heat within the extract systems is usually released into the atmosphere and its intrinsic energy is wasted. This paper investigated a cold abatement smoke extract system for a fire testing wall furnace to determine the viability in recovering heat from the hot smoke. Three scenarios were investigated: 1) the extract system was closed and only 300°C smoke was present; 2) the system took in ambient air around the furnace and heat recovery occurred at 80°C in smoky air; 3) the smoke had been removed from the air and the temperature was 60°C. It was found that there was a significant build-up of soot on Scenarios 1 & 2 with a build-up rate of 0.25 μm/s which totalled 2.7 mm of soot after a three-hour test. The soot had a low heat transfer rate and therefore acted as an insulator on the heat exchanger which reduced the efficiency significantly of it over time. Due to this loss in efficiency, it was more viable to recover heat in Scenario 3 at 60°C in clean air than it was to recover heat at 300°C or 80°C in smoky air. The results show that having clean air was more important than a higher temperature when it came from recovering heat from a cold abatement system for a fire testing furnace. This paper contributes to reveal the possibilities of harnessing the “waste heat” for use in other applications in the vicinity of the manufacturing processes, such as heating water within a central heating plant, domestic hot water or electricity generation, or re-cycled within the industrial plant itself.

Fire dynamics inside a large and open‐plan compartment with exposed timber ceiling and columns: CodeRed #01

SummaryThere is an increasing global demand to build from timber as it is a sustainable and attractive material. One of the key challenges associated with timber buildings is their performance in a fire, in particular, for medium‐ and high‐rise buildings and when timber is exposed. Research on this topic to date has been performed in compartments smaller than 84 m2 which does not capture the fire dynamics of large compartments. This paper presents the first in a series of experiments carried out inside a large, purpose‐built, open‐plan compartment with a floor area of 352 m2. The large‐scale compartment had a fully exposed, unloaded, cross‐laminated timber (CLT) ceiling and glued laminated timber (glulam) columns, made with adhesives that have been tested to not exhibit char fall‐off in fire. At 352 m2 floor area, this is currently the largest compartment fire experiment carried out globally. The compartment characteristics and the arrangement of the wood crib mimicked the previous series of experiments in Poland in a non‐combustible compartment by Rackauskaite et al. (2021). The experiment was instrumented with thermocouples measuring the gas temperature in the compartment, and above two of the openings, as well as the temperature within the timber members. Plate thermometers were also included to measure the heat flux to the ceiling and of the external flaming. Additionally, fixed and drone‐mounted cameras captured the fire. A protected steel column was added to calculate the equivalent fire exposure when compared to a standard fire resistance furnace test. The experiment was allowed to burn out without fire‐fighting intervention. Continuous measurements were taken for 48 h. The wood crib was ignited at one end of the compartment. Flames rapidly spread across the timber ceiling to the other end of the compartment with the rest of the wood crib being involved in the fire at 5 min 36 s from ignition. The total duration of the fire was 22 min 30 s, at which time visible flaming ceased. Significant external flaming was observed through the openings in the order of 3 m in height but varied with position as the fire travelled across the compartment. Analysis of the experimental results and camera footage showed that the presence of the timber structure approximately doubled the heat release rate (HRR) compared to the value expected from the wood crib alone. Smouldering combustion of the timber members continued for hours after the cessation of flaming, burning in several hotspots, resulting in holes through the CLT slab. This paper improves the understanding fire dynamics for open‐plan, exposed timber compartments and has shown that issues such as external flaming, smouldering and the increase in HRR need to be considered when deriving practical design solutions.

Investigation on factors affecting early strength of high-performance concrete by Gaussian Process Regression.

This study aims to investigate the influence of all the mixture components of high-performance concrete (HPC) on its early compressive strength, ranging from 1 to 14 days. To this purpose, a Gaussian Process Regression (GPR) algorithm was first constructed using a database gathered from the available literature. The database included the contents of cement, blast furnace slag (BFS), fly ash (FA), water, superplasticizer, coarse, fine aggregates, and testing age as input variables to predict the output of the problem, which was the early compressive strength. Several standard statistical criteria, such as the Pearson correlation coefficient, root mean square error and mean absolute error, were used to quantify the performance of the GPR model. To analyze the sensitivity and influence of the HPC mixture components, partial dependence plots analysis was conducted with both one-dimensional and two-dimensional. Firstly, the results showed that the GPR performed well in predicting the early strength of HPC. Second, it was determined that the cement content and testing age of HPC were the most sensitive and significant elements affecting the early strength of HPC, followed by the BFS, water, superplasticizer, FA, fine aggregate, and coarse aggregate contents. To put it simply, this research might assist engineers select the appropriate amount of mixture components in the HPC production process to obtain the necessary early compressive strength.

Thermo-mechanical analysis of laminated composites shells exposed to fire

This paper describes the research performed within the scope of H2020 project FIBRESHIP in the development and validation of a thermo-mechanical model to assess the fire performance of composite structures. A one-dimensional thermal model with pyrolysis is used to obtain the temperature profile across the thickness, and later, introduced in the thermo-mechanical model with a quadrilateral shell element approach. The composite constitutive model employed is the so-called Serial/Parallel Rule of Mixtures (SPROM) which has been modified to introduce the effect of the thermal deformation. A set of experimental tests are then used to validate the correctness of the numerical method proposed. The experimental data used to validate the thermal model is the classic Henderson experimental test. The thermo-mechanical coupling is validated against an original vertical furnace test of an FRP ship’s bulkhead, following on the 2010 FTP Code standards. These validations demonstrate the correctness and accuracy of the proposed decoupled thermo-mechanical formulation.

Novel carbon nitride@polydopamine/molybdenum disulfide nanoflame retardant improves fire performance of composite coatings

An effective method to enhance the flame retardant capability of intumescent fire retardant (IFR) coatings by constructed a two-dimensional/two-dimensional (2D/2D) hybrid with good composition and microstructure. Herein, g-C3N4@PDA (CNP) was firstly obtained by loading graphite phase carbon nitride (g-C3N4) with bio-inspired polydopamine (PDA). Subsequently, a novel [email protected] hybrids was successfully prepared by loading molybdenum disulfide onto the CNP surface via a simple one-step hydrothermal method. Then, the obtained [email protected] was added to the IFR coating as a synergist to improve the flame resistance. Results indicated that the addition of 2 wt% [email protected] to the coating effectively accelerated the formation of the char layer and reinforced its thermal insulation properties. The [email protected]/EP sample exhibited the lowest backside temperature (179.6 ℃), the highest expansion ratio (10.53) and the most residual char (30.7%) by fire performance test, furnace test and TGA test. The combustion performance of the IFR coatings was investigated by cone calorimeter, and the results showed that the [email protected] hybrids based composite coating exhibited the lowest heat release rate (HRR), total heat release rate (THR), and total smoke production value (TSP). The mechanism investigations showed that the physical barrier effect and catalytic carbonization produced by [email protected] hybrids during the combustion process are the main reasons for the improved flame retardancy of epoxy coatings.

Determining the optimum fuel concentration for ignition and combustion of semi-coke and bituminous coal blends with rich/lean burner

To burn semi-coke with ultra-low volatile content effectively at a large blending proportion with high volatile bituminous coal using a pulverized fuel (PF) rich/lean burner, the ignition and combustion behaviors of blended fuel of semi-coke and bituminous coal (1:1 by weight) in reducing to oxidizing atmosphere were investigated in a 300 kW pilot-scale test furnace with an arrangement of varying pulverized fuel-rich side stream concentration (Pfc,rich, kg/kg). The results showed that ignition distance of the fuel-rich stream decreased from 339 mm to 159 mm when Pfc,rich increased from 0.37 kg/kg to 0.58 kg/kg, which then increased again to 0.63 kg/kg. The ignition distance for the fuel-lean stream increased monotonically from 332 mm to 383 mm with an increase in the Pfc,rich. The intersection of two streams showed a positive effect on overall ignition when Pfc,rich was varied from 0.49 kg/kg to 0.58 kg/kg, which was mainly attributed to the mean volatile content of blended fuel. A parameter Vindex was introduced to evaluate the effects of quantity of volatiles on the ignition behaviour of blended fuels, and it was found that the volatile effect was more sensitive to the ignition distance than the ignition temperature. The ignition of the fuel-rich stream transformed from the heterogeneous-homogeneous combined mode to the homogeneous mode at Pfc,rich of 0.49 kg/kg. The burnout ratio of blended fuel was highest at Pfc,rich = 0.52 kg/kg and 12.21% higher than that of the ordinary unbiased burner. NO emission was inhibited under rich/lean combustion conditions, and the existence of a strong reducing zone was the key factor for the low conversion ratio of fuel-N to NO. Based on the experimental results, Pfc,rich ranging from 0.52 kg/kg to 0.58 kg/kg was observed to be optimum for rich/lean co-combustion at large proportion of semi-coke in the blends.

Experimental study of fire damage to reinforced concrete tunnel slabs

Fire hazards are a major threat to tunnel structures; however, the existing understanding of the behavior of tunnel linings under fire is limited, which restricts cost-effective and safe design of tunnels for fire. The research work in this paper aims to experimentally evaluate and quantify fire damage to tunnel linings considering a combination of influencing factors. The effects of three parameters on fire damage to the ceiling (typically the most damaged area) of a tunnel lining are studied through five furnace tests on large-scale reinforced concrete slabs. The parameters include: (1) concrete composition - presence/absence of polypropylene fibers, (2) the level of structural restraint (induced using post-tensioned strands), and (3) the fire intensity and duration. These parameters are selected to reflect realistic scenarios and provide a rational basis for evaluating tunnel damage, in terms of crack pattern, spalling, discoloration, non-destructive testing, and deflections during fire and after cooling. This research provides vital experimental data for fire damage assessment of reinforced concrete tunnel linings, and assists in verifying numerical models for analyzing structural performance during both the heating and cooling phases of fire.

Additive Manufacturing of Miniaturized Peak Temperature Monitors for In-Pile Applications.

Passive monitoring techniques have been used for peak temperature measurements during irradiation tests by exploiting the melting point of well-characterized materials. Recent efforts to expand the capabilities of such peak temperature detection instrumentation include the development and testing of additively manufactured (AM) melt wires. In an effort to demonstrate and benchmark the performance and reliability of AM melt wires, we conducted a study to compare prototypical standard melt wires to an AM melt wire capsule, composed of printed aluminum, zinc, and tin melt wires. The lowest melting-point material used was Sn, with a melting point of approximately 230 °C, Zn melts at approximately 420 °C, and the high melting-point material was aluminum, with an approximate melting point of 660 °C. Through differential scanning calorimetry and furnace testing we show that the performance of our AM melt wire capsule was consistent with that of the standard melt-wire capsule, highlighting a path towards miniaturized peak-temperature sensors for in-pile sensor applications.

Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell

Additive manufacturing (AM), for example, directed energy deposition (DED), may allow the processing of self-healing metal–matrix composites (SHMMCs). The sealing of cracks in these SHMMCs would be achieved via the melting of micro-encapsulated low melting point particulates (LMPPs), incorporated into the material during AM, by heat treatment of the part during service. Zn-Al alloys are good candidates to serve as LMPPs, for example, when the matrix of the MMC is made of an aluminum alloy. However, such powders should first be encapsulated by a thermal and diffusion barrier. Here, we propose a sol–gel process for encapsulation of a custom-made ZA-8 (Zn92Al8, wt.%) core powder in a ceramic alumina (Al2O3) shell. We first modify the surface of the ZA-8 powder with (12-phosphonododecyl)phosphonic acid (Di-PA) hydrophobic self-assembled monolayer (SAM) in order to prevent extensive hydrogen evolution and formation of non-uniform and porous oxide/hydroxide surface layers during the sol–gel process. Calcination for 1 h at 500 °C is found to be insufficient for complete boehmite-to-γ(Al2O3) phase transformation. Thermal stability tests in an air-atmosphere furnace at 600 °C for 1 h result in melting, distortion, and sintering into a brittle sponge (aggregate) of the as-atomized powder. In contrast, the core/shell powder is not sintered and preserves its spherical morphology, with no apparent “leaks” of the ZA-8 core alloy out of the ceramic encapsulation.

Silicon oxide encapsulated ZIF-8 loaded on reduced graphene oxide to improve flame retardancy of waterborne epoxy coatings

Herein, the ZIF nanoparticles were firstly anchored uniformly on the reduced graphene oxide (RGO) surface, and then a layer of silica was deposited on the surface to avoid the negative impact of the pores generated by the decomposition of the ZIF nanoparticles on the thermal insulation properties. The effect of reduced graphene oxide/zeolitic imidazolate framework-8@silicon oxide (RGO/ZIF@SiO2) hybrids on the fire performance of the coatings was analyzed by big plate experiments, furnace test, and thermal weight loss test. The results showed that the backside temperature of RGO/ZIF@SiO2 based intumescent fire-retardant coating (IFR) reached the minimum value (173.9 °C) compared to other samples. The expansion characteristics of the coatings were significantly increased by the addition of nanoadditives. By comparison, RGO/ZIF@SiO2/IFR composite coating exhibited the largest expansion height (21.5 mm) and expansion rate (16.28). Moreover, the IFR loaded RGO/ZIF@SiO2 displayed the highest maximum thermal decomposition temperature (Tmax, 371.1 °C) and residual char (29.8%), indicating its best fire resistance properties. The cone calorimeter test results illustrated that RGO/ZIF@SiO2/IFR had the lowest PHRR (482 ± 21 kW/m2), THR (15.57 ± 0.9 MJ/m2), PSPR (0.10 ± 0.01 m2/m2), TSP (2.01 ± 0.11 m2/m2) and CRR (28.8%) values, indicating its best flame retardant and smoke suppression properties.

The Re2Sn2O7 (Re = Nd, Sm, Gd) on the enhancement of fire safety and physical performance of Polyolefin/IFR cable materials

Polyolefin (PO) cables used in confined spaces need to have low smoke, low heat release, low toxic gas release and excellent physical properties. In this work, a series of rare earth stannates Re2Sn2O7 (RES, Re = Nd, Sm, Gd) with high temperature catalytic performance were prepared by hydrothermal method for synergistic flame retardant PO/IFR. The flame retardancy, heat release, smoke density, toxic gas release and physical properties of PO composites were thoroughly studied in detail. The RES could enhance the vertical burning rating and the limiting oxygen index (LOI) of PO/IFR composites. Moreover, the residual char of the thermogravimetric analysis increased from 9.7% to 11.4 wt% after the RES added in PO/IFR system. Interestingly, the PO/IFR system containing Gd2Sn2O7 exhibits the lowest peak heat release rate of 233.7 kW/m2. Excellent flame resistance due to the formation of a complete and compact protective char layer. In addition, the toxic release of PO during combustion is also effectively reduced by introducing the RES. The tube furnace combustion test shows that the emission of carbon oxide (CO) and hydrogen cyanide (HCN) of PO/IFR/Gd2Sn2O7 are the lowest. It can be attributed to the catalytic effect of rare earth elements and the blocking effect of the dense char layer. In addition, compared with the PO/IFR composites, the PO/IFR/RES system demonstrate higher mechanical properties and volume resistivity. Therefore, the addition of RES has a positive effect on improving the physical properties and fire safety properties of the PO/IFR cable composites, especially suitable for using in confined spaces.

Mussel inspired polydopamine@KH560-linked hexagonal boron nitride and CNTs nanoflame retardants improve fire performance of composite coatings

Herein, the excellent properties of one dimension (1D) and two dimension (2D) nanoparticles were fully combined to enhance the thermal stability and flame retardancy of waterborne epoxy intumescent fire retardant (IFR) coatings. Specifically, layered hexagonal boron nitride (h-BN) nanosheet-linked acidified carbon nanotubes (CNTs) hybrids (BP@Si/CNTs) were prepared using polydopamine (PDA) and γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560) as bridging agents. The results of the fire test, furnace test and thermogravimetric analysis indicated that the incorporation of 2 wt% of BP@Si/CNTs hybrids in the IFR coating significantly improved the thermal stability and flame retardancy of the char layer. The backside temperature of the BP@Si/CNTs2.0%/EP sample decreased by 89.3 °C, the expansion rate increased by 11.53, and the residual char increased by 11.05 wt% compared to the control EP. The potential flame retardant mechanism was investigated by residual char analysis. The mechanism investigations indicated that the improved fire resistance of the composite coatings is attributed to the enhancement of the char layer by the physical barrier effect of the h-BN nanosheets and the "skeletal framework" effect of the CNTs during the combustion process.

Numerical prediction on deposition growth and heat transfer characteristics burning high–sodium pulverized coal

In this paper, a transient numerical model, which both considered fly–ash particle deposition and alkali vapor condensation, is proposed to predict the ash deposition propensity on a single heat transfer surface. Four deposition mechanisms are considered comprehensively, named inertial force, thermophoresis force, direct condensation, and heterogeneous nucleation. The condensation behavior caused by high content of AAEM was quantitatively evaluated according to the partial pressure of alkali vapor and the changing saturation pressure. The dynamic mesh technology based on an advisable strategy was performed to reflect the actual shape of fluid–solid interface in deposition process. Furthermore, a resistance network model (RNM) is established to calculate the effective heat transfer coefficient, and the temperature of deposition surface is solved based on the principle of energy conservation, in order to analyze the heat transfer performance of deposition layer. The contribution of each of the four essential mechanisms to tendency of deposition and condensation in different areas is evaluated. The different cases are used to investigate the effects of five typical furnace temperatures and six prime particle sizes on deposition and heat transfer characteristics. The proposed model has been validated and shown to predict deposition rate effectively and heat transfer parameters for ZD coal burned in 300 kW test furnace.

Fire-Resistant Properties of Modified Epoxy Based Intumescent Fire-Retardant Coating: Hybridizing of Oyster Shell Powder with Glass Frit

Fire retardant coatings play vital role in safety of construction nowadays, to delay the fire propagation and provide more time for evacuation. The current research work aimed to study the use of modified siloxane epoxy binder to develop intumescent coating. Polyamide amine was used as a hardener. Three different sets of formulations were developed by using three different fillers, namely the oyster shell powder (OSP), glass frit (GF) and combination of both oyster shell powder and glass frit (OG). All three set of formulation also includes the basic ingredients of intumescent coating. These samples were used to study the synergistic effects of fillers on thermal performance of the coating as well tested for char expansion, heat shielding, char morphology and composition. Fire resistant testing was conducted by using a Bunsen Burner and GF samples had found to have minimum substrate temperature of 175.3°C. The char morphology was analysed via Scanning Electron Microscope (SEM) which confirmed the adhesion between the matrix with fillers. Furnace test was carried out to investigate the char expansion of OSP/GF/OG with the modified siloxane epoxy composition and the maximum expansion was OSP 1% with intumescent factor of 7.78. XRD was conducted to evaluate the residual compounds in the char and FTIR was utilized to analyse the functional group where O-H, C-N, O=C=O and C=C bonds were found in the degradation compounds in the char residual of the coatings.

Cycling Characteristics of Tubular Liquid Antimony Anode Direct Carbon Fuel Cells Prepared by Atmospheric Plasma Spray

Liquid antimony anode direct carbon fuel cell (LAA-DCFC) is a promising technology for efficient conversion of solid carbon fuels. However, the operating process and the regeneration method of the fuel cells with LAAs are different from those with solid anodes and still need to be researched. In the present research, the tubular LAA-DCFC units were fabricated based on stainless steel support by atmospheric plasma spray (APS) technology. The LAA-DCFCs were cycled by furnace control method and “hot plug” method to simulate the normal start-stop and the anode regeneration processes, respectively. No degradation was observed after five temperature cycles of furnace control test, which showed that the phase change process of the LAA has no influence on the sprayed electrolyte and cathode. During the “hot plug” test, the tubular cell was measured in Ar atmosphere and was removed from and put back into the LAA at a speed of 20 mm min-1 and 50℃ min-1. The cell performance recovered once the cell was put back and a degradation of 0.1% cycle-1 was observed. Considering the low frequency of anode regeneration, the degradation rate is relatively acceptable. The environmental air leakage and the floating ash retarded the recovery rate, but have no influence on the degradation degree. The cycling characteristics in the present research proved the long-term operating feasibility of DCFC with LAA.

Feasibility of biogas and oxy-fuel combustion in steam cracking furnaces: Experimental and computational study

This work evaluates the feasibility of biogas air-fuel combustion and natural gas oxy-fuel in steam cracking furnaces. Four cases, namely air-fuel combustion of pure natural gas, 20% CO2, 40% CO2 diluted natural gas, and oxy-fuel combustion of natural gas are investigated both experimentally and numerically. The John Zink Hamworthy Combustion test furnace, representing a section of a steam cracking furnace, is used for experimental studies. A three-dimensional steady-state CFD model is also developed to simulate the test furnace. The simulation results of the air-fuel combustion scenarios are in good agreement with the experimental data, with the maximum and average relative errors of furnace temperature of 3.86% and 1.78%, respectively. The reduction of flame length with increasing CO2 mole fraction in the fuel is observed in both experiments and simulations. It is shown that CO2 dilution has minor effect on the overall heat flux profile, which is beneficial for retrofitting existing furnaces. On the other hand, the oxy-fuel combustion simulation using default EDC model predicts a significant flame lift-off and incident radiative heat flux shift towards the higher elevations which was not observed in the experiments. This can be mainly attributed to the reduced reaction rate in a CO2 and H2O enriched combustion environment. Adjusting the EDC model parameters helps to achieve better agreement between simulation results and experimental data, while additional lab-scale experiments are essential for further validation of the numerical model. Moreover, it is of particular interest to study the optimal mole fraction of O2 in oxy-fuel combustion scenario.

Determination of the Fire-Retardant Efficiency of Magnesite Thermal Insulating Materials to Protect Metal Structures from Fire

This paper presents the results of fire test of an I-beam protected by a combined magnesite plate-magnesite mixture heat-insulating material. It was shown that a composite with an average thickness of 37 mm maintained an average temperature of 380 °C on the metal surface after 150 minutes of fire exposure, not exceeding the critical value of 500 °C. From 60 to 100 minutes of fire testing (furnace temperature of 980-1025 °C), the temperature of the metal did not exceed 100 °C. This was achieved both due to the high thermal insulation properties of the magnesite mixture, and due to gas and vapor release from the hydration products of magnesia cement. The developed fire-retardant material provides the first group of fire-retardant efficiency (150 minutes) and, after the fire test, is characterized by density of 352.4 kg/m3 and compressive strength of 0.85 MPa, which is three times lower than the original.

Characterisation of anode plasma deposited IN718 TBC system after thermal cycle shocking test

ABSTRACT The coating that creates a barrier for high temperatures is called as thermal barrier coating (TBC). Yttria-stabilised Zirconia (7–8YSZ (7–8 wt% Y2O3ZrO2)) is characterised after taking a thermal cycling test in a muffle furnace. The specimen is obtained from IN718, which is a nickel-based super alloy and coated by using anode plasma coating technique. Then, the specimen is allowed to heat in muffle furnace for fatigue testing at 1100°C. The holding time for the specimen is 45 minutes and then it is allowed for air cooling. The testing is done to analyse the microstructure of coating before and after thermal fatigue using various microscopy. The delamination of the TBC from the specimen surface is the outcome of the Thermal Fatigue Testing (TFT). Then, the failed specimen is characterised by various techniques like Scanning Electron Microscopy and Transmission Electron Microscopy for microstructure characterisation and material identification. Mismatching of the thermal expansion coefficients of the substrate and coating material is the reason for the more thermal gradients in between the bond coat and top coat. The spallation originated from the corners of the specimen due to the microvoids after TFT and frequent cooling.

Oxidation behavior of dense Yttrium doped B2-NiAl bulk material fabricated by ball milling self-propagating high-temperature synthesis and densified by spark plasma sintering

The effect of Y additions on the oxidation behavior in furnace cyclic tests and its correlation with thermogravimetric analysis of sintered NiAl alloys is here reported. Part of the samples got an EB-PVD 7YSZ coating on top. Highly ordered B2-NiAl intermetallic powder was obtained by self-propagating high-temperature synthesis (SHS) during ball milling of elemental precursors with Y additions in amounts between 0 and 1.5 at.%. The SHS process was optimized to identify the combination of milling parameters that leads to a sharp increase in the reaction temperature for intermetallic synthesis. The tested samples consisted of NiAl-Y buttons densified by spark plasma sintering (SPS). Furnace cyclic testing of the SPS- buttons at 1100 °C showed high resistance to spallation of the 7YSZ top-coat and a significant decrease in its oxide growth kinetics attributed to Y-additions. Contents below 0.5 at.% Y reduce the oxidation kinetics of NiAl exposed to thermal cycles at 1100 °C, while higher Y contents are favorable for a longer TBC life.

Combustion Using Oxygen-Lancing in a Reheating Furnace.

Fuel economy has been a primary issue in the steel industry because it uses large amounts of energy, such as the gaseous fuel of byproduct gas. Furthermore, reheating throughput capacity has been a key issue because it can improve furnace efficiency, leading to fuel economy. Many attempts have tried improving fuel economy using oxygen in a reheating furnace. Oxygen-lancing technology was developed to increase fuel economy and maintain the same level of NOx concentration simultaneously. Mechanisms that inject oxygen into flames locally causing flame quenching and at the same time suppressing the increase in NOx concentration due to recirculation of reheating furnace-burned gases are key to this study. Various oxygen concentrations for its lancing were used to investigate its effects on furnace temperature and NOx concentration in a test furnace. It was determined that 30% of oxygen was optimal regarding fuel economy and NOx concentrations. Oxygen was injected into the flame using two lancing pipes at 11° in a design capacity of 125 MW. The results showed a 3–5% increase in fuel economy and the same level of NOx concentration in the furnace.