Test Furnace Research Articles

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.

Study of high-temperature oxygen combustion (HiTOx) and its heating performance using a laboratory-scale test furnace

Abstract High-temperature air combustion technology (HiCOT), which uses air preheated by heat recirculation, has had a great impact on reduction of CO2 and NOx emissions from combustion furnaces. In this study, a lab-scale test furnace was developed to examine the novel combustion method termed as high-temperature oxygen combustion, HiTOx. HiTOx uses combustion with a preheated mixture of oxygen and burned gas. Testing was conducted with liquefied petroleum gas. HiTOx has the following three characteristics because nitrogen is excluded from the working gas: (1) in principle, no thermal NOx is generated; (2) combustion gas is almost entirely water vapor and carbon dioxide, providing better heating performance because of its strong gas-phase radiation; and (3) the method has good compatibility with carbon dioxide capture, utilization and storage (CCUS) technologies because carbon dioxide can be separated easily from the combustion gas of HiTOx furnace by condensation of water vapor. Heating performance tests in a lab-scale test furnace were conducted using stainless steel rectangular rods as heating objects. Gas temperature, object temperature, and heat fluxes on the objects were measured. Compared to HiCOT, HiTOx enables stable operation with a lower flow rate of flue gas, better gas temperature uniformity in the furnace, faster heating, and higher heat flux. The heat flux of HiTOx was slightly higher than that of HiCOT (7%) when the furnace temperature was low (973 K) and the temperature difference between the gas and object was large (280 K). On the other hand, the heat flux of HiTOx was much higher than that of HiCOT (22%) when the furnace temperature was high (1323 K) and the temperature difference was small (60 K). Radiative heat transfer at high temperature was greater in HiTOx than in HiCOT at small temperature difference between the gas and object. A furnace body can be greatly downsized by the good radiation performance of combustion gas in HiTOx, resulting in a remarkable improvement in energy-saving performance.

Assessing the combustibility of claddings: A comparative study of the modified cone calorimeter method and cylindrical furnace test

SummaryA cone calorimeter, a standard device to measure the fire reaction properties of materials, is modified in this study to investigate its potential to replace the cylindrical furnace test method to assess the combustibility of cladding materials used in buildings. The modification allows cladding materials to be evaluated under conditions closer to their end‐use configuration than the current testing condition in the cylindrical furnace test. In addition, the modified cone calorimeter method provides more quantitative data on the fire reaction properties of the cladding materials compared to the passed/failed indicator in the cylindrical furnace test. Comparative studies between modified cone calorimeter and cylindrical furnace test results for four types of cladding with different combustibility properties are performed. The surface temperature, time‐to‐ignition, and flaming duration values measured for the claddings using the two test methods are similar, leading to the same classification based on AS 1530.1 standard. Other fire reaction properties of the claddings can be measured using the modified cone calorimeter method, which is not possible with the cylindrical furnace test, including mass loss rate, heat release rate, and smoke production, which are particularly dependent on the formation of a ceramic‐like carbonaceous layer of tested samples.

Conceptual Design for a Blanket Tritium Extraction Test Stand

Future fusion reactors must be able to breed the tritium they will consume. Several breeding and tritium extraction technologies are under investigation internationally. PbLi is of particular interest as a breeder material. A new forced convection PbLi loop, the Tritium Extraction eXperiment (TEX), is being designed and constructed to investigate tritium extraction from PbLi. Specifically, TEX will serve to investigate the extraction efficiency of various vacuum permeator membranes and configurations. The major components of the loop include a moving magnet pump, reverse permeator, furnace test section, analysis chamber, supply tank, and plenum. As significant hazards are present in such experiments, safety is an integral focus of the experimental design.

Polydopamine enwrapped titanium dioxide-assisted dispersion of graphene to strength fire resistance of intumescent waterborne epoxy coating

Herein, polydopamine (PDA) with excellent hydrophilicity and strong adhesion was used to decorate the TiO2 nanoparticles. Then, the obtained PDA modified TiO2 was directly combined with graphene (Gr) through the π-π non covalent interaction to improve the water dispersion stability of hydrophobic Gr. After that, the above hybrids (TPG) was added to the intumescent waterborne epoxy coating to explore its fire protection ability. The fire resistance of the intumescent composite coating was tested by big panel method test, furnace test and thermogravimetric analysis (TGA). And the structure and morphology of the inorganic residual char were analyzed by FT-IR, XPS, SEM and XRD technology. The results showed that the introduction of PDA effectively improved the oxidation resistance of the composite coating, while TiO2 nanoparticles enhanced the stability of the char layer. More importantly, the incorporation of Gr further enhanced the barrier effect of char layer on thermal and mass. The 1.5 % TPG based sample exhibited the maximum expansion rate (8.61), the highest carbon residue (29.7 %) and the best heat insulation property due to the synergistic fire prevention effect of PDA, TiO2 and Gr nanosheets.

Surface modification of multi-scale cuprous oxide with tunable catalytic activity towards toxic fumes and smoke suppression of rigid polyurethane foam

The development of flame retardant rigid polyurethane foam (RPUF) composites with low smoke toxicity emission, as well as excellent mechanical properties remains a huge challenge. Herein, a facile wet chemical approach was proposed for the preparation of cuprous oxide (Cu2O) crystals with different sizes, i.e. approximately 5 nm, 100 nm and 1 μm in lateral size, which were confirmed by X-ray diffraction and transmission electron microscopy. The effect of Cu2O crystals on the combustion behavior of RPUF was evaluated by cone calorimetry and steady state tube furnace tests. Significant reduction in peak carbon monoxide (CO) production rate (by 41.2%, 67.6% and 27.9%) and total smoke production (21.6%, 16.1% and 12.2%) were realized by the incorporation of 2 wt% Cu2O into the RPUF matrix in addition to a slight reduction in peak heat release rate. Notably, nano-sized Cu2O with high specific surface area is beneficial for the complete combustion of RPUF and the conversion of CO to carbon dioxide (CO2), involving the reduction of Cu2+-Cu+-Cu0 by degraded gases and the oxidation of Cu0-Cu+-Cu2+ by oxygen. This work demonstrated that submicron-sized Cu2O is an effective smoke and toxic gases suppressant for RPUF, which is expected to find practical applications in polymeric materials.

Structural response of fire-exposed laminated glass beams under sustained loads; exploratory experiments and FE-Simulations

This paper investigates the structural response of laminated glass beams under combined fire-exposure and sustained in-plane loading. This is done by means of experimental testing and Finite Element (FE) numerical modelling. Firstly, small-scale (1 m long) laminated glass beams are tested under thermal exposure and in-plane loading on a small fire resistance test furnace. From the test results it can be seen that laminated glass beams are able to sustain an imposed in-plane load for a time of 34–51 min before failing according to the limiting rate of deflection as defined in EN 1363–1:2012. It should be noted, however, that the observed failure times are strictly related to the boundary conditions applied in the test, i.e. the magnitude of mechanical loads (in this study a relatively small load of P = 1.15 kN was applied) and the presence of an inherent top zone protection, which may have positively affected the results. Secondly, additional FE thermo-mechanical simulations are performed to further investigate the mechanical response of the laminated glass beams under thermal exposure, with a focus on the effects of the top zone protection and the load magnitude on the performance of the examined laminated glass beams. From the FE study it can be seen that reducing the top zone protection (from 40 mm to 0 mm) results in a reduction in failure time from 45 min to 20 min, while increasing the load with a factor 5 (taking 30 mm top zone protection as a reference) results in a reduction of failure time from 32 to 18 min.

Flame retardant properties of waterborne epoxy intumescent coatings reinforced by polydopamine@KH560/carbon nitride/graphene ternary system

Firstly, the bio-inspired polydopamine (PDA) was coated on the surface of carbon nitride (CN), then used it (CNP) as nano-dispersant to improve the dispersion of graphene (Gr) in water on the basis of π-π interaction. After that, the KH560 was further grafted on the CNPG surface to improve the compatibility between inorganic hybrids and epoxy resin. The results of large plate experiments showed that the backside temperature of composite IFR coating containing CNPG@Si hybrids was significantly lower than that of other samples. Meanwhile, its expansion height after furnace test reached the maximum value (17.8 mm), which was greatly improved compared with the pure epoxy coating. Further, the maximum thermal decomposition temperature and the amount of char residue for the CNPG@Si/EP sample were significantly enhanced through the TGA test result. Besides, CNPG@Si based sample showed the lowest smoke density rating (SDR) due to its excellent smoke suppression performance. From the analysis of the morphology and composition of the char layer for CNPG@Si based sample, it can be seen that the introduction of Gr and CN increased the compactness of the char layer, and silicon network structures remained in the char layer after combustion, which effectively increases its strength and heat insulation effect.

Control of the Pore Structure of Plasma-Sprayed Thermal Barrier Coatings through the Addition of Unmelted Porous YSZ Particles

In this study, a new pore structure control method for plasma-sprayed thermal barrier coatings (TBCs) through the addition of unmelted, porous yttria-stabilized zirconia (YSZ) particles was investigated. Through a unique way of feeding powder, two powder feeders were used simultaneously at different positions of the plasma flame to deposit a composite structure coating in which a conventional plasma-sprayed coating was used as a matrix and unmelted micro-agglomerated YSZ particles were dispersed in the dense conventional coating matrix as second-phase particles. The effects of the distribution and content of second-phase particles on the microstructure, mechanical properties, and lifetime were explored in a furnace cyclic test (24 h) of the composite coating. The mechanical properties and lifetime of the composite coating depend on the content and morphology of the particles embedded in the coating. The lifetime of the composite structure coatings is significantly higher than that of the conventional coatings. By adjusting the spraying parameters, the lifetime of the composite coating prepared under the optimum process is up to 145 days, which is about three times that of the conventional coating. The results of this study provide guidance for the preparation of high-performance composite structure TBCs.

Experimental Study on Delaying the Failure Time of In-Service Cables in Trays by Using Fire-Retardant Coatings

Improving the fire resistance of the key cables connected to firefighting and safety equipment is of great importance. Based on the engineering practice of an oil storage company, this study proposes a modification scheme that entails spraying fire-retardant coatings on the outer surface of a cable tray to delay the failure times of the cables in the tray. To verify the effect, 12 specimens were processed using five kinds of fire-retardant coatings and two kinds of fire-resistant cotton to coat the cable tray. The specimens were installed in the vertical fire resistance test furnace. For the ISO 834 standard fire condition, a fire resistance test was carried out on the specimens. The data for the surface temperature and the insulation resistance of the cables in trays were collected, and the fireproof effect was analyzed. The results showed that compared with the control group, the failure time of the cable could be delayed by 1.57–14.86 times, and the thicker the fire-retardant coatings were, the better the fireproof effect was. In general, the fire protection effect of the fire-retardant coating was better than that of the fire-resistant cotton.

Influence of nozzle height to width ratio on ignition and NOx emission characteristics of semicoke/bituminous coal blends in a 300 kW pulverized coal-fired furnace

To improve the ignition behavior and to reduce the high NOx emissions of blended pulverized fuels (PF) of semicoke (SC), large-scale experiments were conducted in a 300 kW fired furnace at various nozzle settings, i.e., ratios (denoted by hf/b) of the height of the rectangular burner nozzle to its width of 1.65, 2.32, and 3.22. The combustion tests indicate that the flame stability, ignition performance, and fuel burnout ratio were significantly improved at a nozzle setting of hf/b = 2.32. The smaller hf/b delayed ignition and caused the flame to concentrate excessively on the axis of the furnace, while the larger hf/b easily caused the deflection of the pulverized coal flame, and a high-temperature flame zone emerged close to the furnace wall. NOx emissions at the outlet of the primary zone decreased from 447 to 354 mg/m3 (O2 = 6%), and the ignition distance decreased from 420 to 246 mm when the hf/b varied from 1.65 to 3.22. Furthermore, the ratio (denoted by SR/SC) of the strong reduction zone area to the combustion reaction zone area was defined experimentally by the CO concentration to evaluate the reduction zone. The SR/SC rose monotonously, but its restraining effects on NOx formation decreased as hf/b increased. The results suggested that in a test furnace, regulating the nozzle hf/b conditions sharply reduces NOx emissions and improves the combustion efficiency of SC blends possessing an appropriate jet rigidity.

The Combustion Characteristics of Waste Liquor from Renewable Plant-Derived Chemical Polyol Processing

An experimental study was carried out to investigate the combustion characteristics of plant-derived polyol liquor waste using thermogravimetric analyzer and vertical tube furnace tests. The research results showed that the waste liquor combustion reaction comprised four processes: evaporation, pyrolysis, combustion, and inorganic salt reaction, and that a wave peak exists for each process. The pyrolysis process, which is the most violent reaction, exhibited the maximum peak weight-loss rate and weight-loss ratio and had the lowest activation energy and frequency factor. The peak weight-loss rate of inorganic salt reaction process was less than that during the combustion process, but sodium alkali has catalytic effect at high temperature, which makes the activation energy and the frequency factor of inorganic salt reaction process less than that of the combustion process. The ignition temperature of the waste liquor in the vertical tube furnace was lower than the temperature in the thermogravimetric analyzer. The ignition temperature of pyrolysis volatiles measured in a vertical tube furnace was less than 700 °C but the ignition temperature of carbon combustion as measured with TG – DTG was 718 °C. When the temperature inside vertical tube furnace was higher than 800 °C, the waste liquor combustion process becomes almost instantaneous (about 8 s) and is violent, which produces more residual carbon content in the combustion products as a longer holding time is necessary to ensure that the reaction is completed.

Using a radiant heat test facility to study the options for the fire protection of structures involving coiled MBOR basalt fiber material

Introduction. Coiled MBOR basalt fiber material is used to demonstrate the potential of research into the fire protection of structures using a radiant heat test facility. Research methods. A set of high-power halogen lamps is used to simulate a high temperature impact. The heating intensity is adjusted by changing the voltage applied to the lamps, and it is controlled by the thermocouples that record the temperature of the heated surface of a fire proofing material. The studies have proven efficient for various types of fire proofing and various structures. They are especially relevant in providing rational fire protection of polymer composite structures having relatively low thermal resistance (80…120 °С) due to the fact that they are rarely tested in fired furnaces. Results and discussion. Several options of multilayered MBOR-20F fire proofing were tested. Dependences between time, on the one hand, the surface temperature of protected elements (200 × 300 × 20 mm polyurethane plates), and the temperature between the layers of the fire-proofing material, on the other hand, are presented under standard temperature conditions. Fire protection efficiency improvement by PLAZAS fire-resistant adhesive compound, applied between MBOR layers, is demonstrated. This fireproofing method is applicable not only to metal structures. It demonstrates high fireproofing properties and has a strong potential if applied to fireproof polymer composite structures and products. The measurements, taken by thermocouples in the course of a session of tests, can be used to estimate the thermophysical properties of fireproofing materials exposed to high temperatures, which are rare in most cases, although they are necessary for a thermal analysis. It is demonstrated that similar experiments can also be carried out at nonstandard heating temperatures (for example, when the combustion of fossil fuels is imitated). Conclusions. Experiments, conducted using the radiant heat test facility, and thermal engineering calculations allow to accelerate the selection of the optimal fire protection option and identification of the fireproofing thickness. Moreover, this method allows to reasonably minimize the number of costly fired furnace tests using fullscale samples of fireproofed structures and products.

Dynamic simulation on high-temperature corrosion behaviour of tube surface with fouling in utility boiler fired by high-chlorine coal

A dynamic model on high-temperature corrosion with fouling-type ash deposition was established to predict the thickness distribution of corrosion layer and the outer/inner layer of ash deposit. It provides an observation on variation of heat transfer characteristics of the alloy test probe over time. This model involves the combustion characteristics of high-chlorine coal, the process of formation, migration, and deposition of fly ash particles, and the corrosion of alloy test probe. In this study, the dynamic model has been integrated into the numerical simulation of high-chlorine coal combustion in a 50 kW long-period corrosion test furnace. The prediction results show that the amount of fly ash deposition on the windward surface is the most while the least amount appears on the side surface. There is a great correlation between the corrosion layer and the inner layer of ash deposit. Because the inner layer of ash deposit and the alloy substrate are spatially adjacent, the high temperature corrosion process is greatly affected by the growth and property of fly ash deposit layer. The simulation results show that the heat flux of probe surface beneath ash deposit is 2.5 kW/m2 which is 50% of the clean surface (5 kW/m2). The changing pattern of thermal resistance versus time at different positions of the alloy surface is consistent with the variation of thickness of the corrosion layer and ash deposit layer. The windward face has the highest thermal resistance and the least heat flux due to the highest thickness of the corrosion layer and ash deposit layer. With the increase of probe wall temperature, the ratio of thermal resistance of corrosion layer to total heat transfer resistance increases, and the ratio at the side face is larger than that at other locations. And the proportion of the corrosion layer in thermal resistance for alloy TP347H reaches 8% at the probe wall temperature of 973 K.

Coal Particle Devolatilization and Soot Formation in Pulverized Coal Combustion Fields

In this paper, recent developments of the devolatilization model and soot-formation model for the numerical simulations of pulverized-coal combustion fields, and the technology used to measure soot particles in pulverized-coal combustion fields are reviewed. For the development of new models, the validation of the developed models using measurement is necessary to check the accuracy of the models because new models without validation have a possibility to make large errors in simulations. We have developed the tabulated devolatilization process model (TDP model) that can take into account the effect of particle heating rate on the volatile matter amount and the devolatilization-rate parameters. The accuracy of the developed TDP model was validated by using the laser Doppler velocimetry data for the bench-scale coal combustion test furnace. The soot-formation model combined with TDP model for the large eddy simulation (LES) has been also developed. The spatial distributions of both the soot-volume fraction and the polycyclic aromatic hydrocarbons were measured by virtue of laser-induced incandescence (LII) and laser-induced chemiluminescence (PAHs-LIF). The accuracy of the developed soot-formation model was validated by using the measured data.

Possibility of Using Spent Coffee Grounds as a Fuel for Co-Firing Application

The possibility of co-firing spent coffee grounds (SCG) with pulverized coal was investigated with a pilot combustion test facility in terms of pulverization performance, combustion and emission characteristics. A coal and two SCG-coal blends having SCG 5 and 10 wt. % in the blend were used for the tests. The thermal behaviors of fuels tested were also evaluated with a thermogrvimetric analyzer.The pyrolysis and combustion behaviors of SCG were very similar to those of woody biomass. The addition of SCG to coal decreased the activation energy of the blend, and improved the reactivity during pyrolysis and combustion. The pilot mill tests showed that SCG-coal blends, compared to coal, produced the higher pressure difference in the mill, and subsequently resulted in the higher mill power consumption, the less amount of fuel pulverized and the finer particle size distribution. The co-firing of SCG with coal improved the burnout of coal and increased gas temperature in the pilot test furnace, and NOx and SOx emissions were somewhat increased, compared to those in solely burning of coal.

Spectral energy characteristics of radiation in oxy-coal combustion for energy utilization

In this paper, the radiative energy characteristics, especially the spectral distribution characteristics, of the oxy-fuel combustion of pulverized coal are studied from the perspective of radiative energy utilization. Based on a modified tube furnace test platform, the radiative energy flux and spectral distribution of oxy-fuel combustion for three typical Chinese coals under O2/N2 and O2/CO2 atmospheres in the temperature range of 600–1000 °C are measured online using radiative heat flux sensors. In particular, the radiative exergy and its spectral distribution characteristics are analyzed based on the second law of thermodynamics. It is found that the intensity of the radiative energy and exergy increase, as does the proportion of spectral radiation below the wavelength of 4.1 μm, with the increase of the oxygen ratio and combustion temperature under the experimental conditions. In contrast, different atmospheres are found to have little effect on the radiation characteristics. One-dimensional calculation cases of media radiation transfer constructed according to the combustion characteristics can better reveal the proportional characteristics of the spectral radiation. The results provide a reference for research on the cascade conversion and management of photo-thermal energy in fuel combustion.

The mechanisms of controlling FCT life and failure mode of Ni-based EBPVD YSZ thermal barrier coatings via the effects of both substrate elements and reactive element doping

Electron-beam physical vapor deposition (EBPVD) of NiCoCrAlY- and Hf-modified bond coats on (1) selected polycrystalline, directionally solidified, (2) single crystalline substrate alloys and (3) an uncoated NiCrAl bond-coat surrogate substrate, all of them covered with standard EBPVD YSZ topcoats were subjected to cyclic furnace testing (FCT) at 1100 °C. The lifetime and spallation failure upon FCT were evaluated. A typical mixed layer zone (MZ) of alumina and zirconia has formed during topcoat processing above the thermally growing oxide layer. The MZ was investigated by energy-dispersive X-ray spectroscopy after intermediate lifetimes and at the end of life. Chemical composition of the MZ and lifespan data were related to each other thus accounting for rate-determining reactions which could be assigned to either cation- or anion-controlled transport mechanisms. These provide a new approach to address FCT life and failure mode of even complex TBC systems containing reactive elements (e.g. Y and Hf). The cation-controlled processes are accelerated according to their concentration by tetravalent elements of the substrates, while the anion-controlled processes are unaffected by this and only adopt a cation-dominated mode when alloying elements of a low valence (e.g. Ti+) reach a supercritical concentration.

Elevated temperature response of RC beams strengthened with NSM FRP bars bonded with cementitious grout

This paper presents the results of 12 tests on small-scale reinforced concrete beams strengthened in flexure with a single NSM carbon FRP bar. The used FRP bar is a novel commercial bar with high values of glass transition Tg and decomposition Td temperature to improve the performance of the strengthening system at elevated temperature. The FRP is bonded using a cementitious grout rather than an epoxy adhesive. Flexural tests were performed at both ambient and elevated temperatures on both un-strengthened and strengthened beams. Tests at elevated temperature were performed using propane-fired radiant panels, rather than a fire testing furnace, in two heating configurations (localised heating near midspan only and global heating over the entire bonded length of the FRP systems).This paper also shows the results of Dynamic Mechanic Analysis (DMA), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) tests conducted on the CFRP. The results of thermal conductivity tests of CFRP and cementitious grout, and tests conducted to define the mechanical properties of concrete, steel bars, cementitious grout and CFRP bar are discussed herein.The flexural tests demonstrated the grout-bonded NSM CFRP strengthening system’s ability to maintain structural effectiveness at temperatures up to about 600 °C with adequate anchorage. However, similar tests with an epoxy adhesive are needed before the novel system can be confidently stated as being vastly superior to epoxy-adhered NSM systems.

Novel-structured plasma-sprayed thermal barrier coatings with low thermal conductivity, high sintering resistance and high durability

The microstructure of the ceramic topcoat has a great influence on the service performance of thermal barrier coatings (TBCs). In this study, conventional layered-structure TBCs, nanostructured TBCs, and novel-structured TBCs with a unique microstructure were fabricated by air plasma spraying. The relationship between the microstructure and properties of the three different TBCs was analysed. Their thermal insulation ability, sintering resistance, and durability were systematically evaluated. Additionally, their failure modes after being subjected to two kinds of thermal shock tests were analysed. The results revealed that the novel-structured TBCs had remarkably superior performances in all the examined aspects. The thermal conductivity of the novel-structured TBCs was significantly lower than those of the conventional and nanostructured TBCs both in the as-sprayed state and after thermal treatment for 500 h at 1100 °C. The macroscopic elastic modulus of the novel-structured TBCs after sintering at 1300 °C for 100 h was similar to those of the conventional and nanostructured TBCs in the as-sprayed state. During both a burner rig thermal shock test and a furnace cyclic oxidation test, the thermal shock lifetime of the novel-structured TBCs was much longer than those of the conventional and nanostructured TBCs. This study has demonstrated novel-structured plasma-sprayed TBCs with high thermal insulation ability and high durability.