Large Furnace Research Articles

Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+)—μ‐computed tomography approach

SummaryIntumescent coatings have been used for fire protection of steel for decades, but there is still a need for improvement and adaptation. The key parameters of such coatings in a fire scenario are thermal insulation, foaming dynamics, and cohesion. The fire resistance tests, large furnaces applying the standard time temperature (STT) curve, demand coated full‐scale components or intermediate‐scale specimen. The STT Mufu+ (standard time temperature muffle furnace+) approach is presented. It is a recently developed bench‐scale testing method to analyze the performance of intumescent coatings. The STT Mufu+ provides vertical testing of specimens with reduced specimen size according to the STT curve. During the experiment, the foaming process is observed with a high‐temperature endoscope. Characteristics of this technique like reproducibility and resolution are presented and discussed. The STT Mufu+ test is highly efficient in comparison to common tests because of the reduced sample size. Its potential is extended to a superior research tool by combining it with advanced residue analysis (μ‐computed tomography and scanning electron microscopy) and mechanical testing. The benefits of this combination are demonstrated by a case study on 4 intumescent coatings. The evaluation of all collected data is used to create performance‐based rankings of the tested coatings.

Important role of volatile–char interactions in enhancing PM1 emission during the combustion of volatiles from biosolid

A three-stage pyrolysis/combustion reactor was used to demonstrate the importance of volatile–char interactions in inorganic particulate matter (PM) emission from the combustion of biosolid volatiles. It consists of a two-stage quartz reactor (including an inner drop-tube/fixed-bed pyrolyser as Stage I and an outer fixed-bed as Stage II) cascaded into a large drop-tube furnace (DTF, Stage III). The unique reactor design enables the volatiles that are produced in situ from the fast pyrolysis of cellulose, polyethylene or acid-washed biosolid in Stage I to pass through a preloaded bed of slow-pyrolysis biosolid char in Stage II then be immediately combusted (achieving complete combustion) in the DTF as Stage III at 1300°C. Limited by quartz maximum working temperature (in Stages I and II), two temperatures (800 or 1000°C) were considered for preparing the bed of char and generating the in situ volatiles. The results clearly show that volatile–char interactions lead to significant changes in the particle size distributions (PSDs) of PM emitted from the combustion of volatiles produced in situ from cellulose, polyethylene or acid-washed biosolid pyrolysis. The volatile–char interactions increase the yield of PM1 (i.e. PM with aerodynamic diameter<1µm), dominantly PM0.1 (i.e. PM with aerodynamic diameter <0.1µm). The results show that small non-oxygenated reactive species (especially H free radicals) in the fresh volatiles can react with the chars to enhance the release of alkalis (Na and K) as well as P and S in the chars. The released Na, K, P and S can react to form alkali metaphosphate and sulphate which subsequently form PM1 during volatiles combustion. It is also evident that volatile–char interactions convert some of Pb and Cr in the biosolid chars into volatile forms which are released and then contribute to PM1 emission.

Species and temperature predictions in a semi-industrial MILD furnace using a non-adiabatic conditional source-term estimation formulation

A Reynolds-Averaged Navier–Stokes (RANS) simulation of the semi-industrial International Flame Research Foundation (IFRF) furnace is performed using a non-adiabatic Conditional Source-term Estimation (CSE) formulation. This represents the first time that a CSE formulation, which accounts for the effect of radiation on the conditional reaction rates, has been applied to a large scale semi-industrial furnace. The objective of the current study is to assess the capabilities of CSE to accurately reproduce the velocity field, temperature, species concentration and nitrogen oxides (NOx) emission for the IFRF furnace. The flow field is solved using the standard k–ε turbulence model and detailed chemistry is included. NOx emissions are calculated using two different methods. Predicted velocity profiles are in good agreement with the experimental data. The predicted peak temperature occurs closer to the centreline, as compared to the experimental observations, suggesting that the mixing between the fuel jet and vitiated air jet may be overestimated. Good agreement between the species concentrations, including NOx, and the experimental data is observed near the burner exit. Farther downstream, the centreline oxygen concentration is found to be underpredicted. Predicted NOx concentrations are in good agreement with experimental data when calculated using the method of Peters and Weber. The current study indicates that RANS-CSE can accurately predict the main characteristics seen in a semi-industrial IFRF furnace.

Considerations for Scale-Up of Ferronickel Electric Smelting Furnaces

In ferronickel smelting, the selective carbothermic reduction of calcined nickel laterite ores in large electric furnaces yields a crude ferronickel product. The optimal process for nickel laterite smelting requires a fine balance between the metallurgical requirements of the process (feed composition, nickel recovery, energy consumption, product quality) and the capabilities of the feeding, tapping and off-gas systems, and especially of the furnace crucible and electrical system. The scale-up of nickel laterite smelting operations over the last 50 years has seen a tenfold increase in furnace power input. Furnace operations within the industry are examined to identify common trends and some new metrics are proposed which incorporate the combination of electrode power densities and the impact of alloy nickel grade on gas generation rates, and hence local electrode gas fluxes, which may impact on future scale-up of ferronickel furnaces.

Analysis of thermoacoustic instability with corresponding eigenfrequencies in a large scale industrial oil furnace

It has been a serious concern to cope with noise and vibration problems due to thermoacoustic instability in design and operation of large industrial furnaces. In this work Reynolds-averaged Navier-Stokes (RANS) simulation was performed with resulting mean scalar fields provided as an input for acoustic analysis at the Maximum continuous rating (MCR) and 50 % MCR loads. Large Eddy simulation (LES) was performed for a single burner to investigate shear layer oscillations leading to vortex shedding which was suspected to be an excitation source. The Rayleigh parameter was estimated to check mutual correlation and any positive feedback of fluctuating pressure and heat release throughout the single burner domain. The flame transfer function in terms of n and τ was obtained for simplified network analysis from LES results. The peak frequency in turbulence energy spectrum was in good agreement with the measured resonant frequency with positive Rayleigh parameters around the region of shear layer oscillation at the MCR load. No instability was predicted at 50 % MCR load to be consistent with test results, with negative Rayleigh parameters throughout the domain. And the energy spectrum analysis confirms that there is mismatch between the peak frequency and the eigenfrequencies of the furnace at 50 % MCR load.

Electrochemical Aspects of the ESR Process

Current passage in the ESR process is accomplished by at least two Faradaic reaction systems, one at the electrode/slag interface and another at the slag/ingot interface. The nature of these reactions has been investigated and is reported to be a function of the alloy composition, current density and slag composition. In this report, data generated from both DC and line- frequency AC ESR operations is used to relate laboratory investigations on these reactions to results obtained in industrial practice. The operating reaction in the line frequency AC melting of simple alloy steels is found to be principally the reversible anodic oxidation of iron (Fe/Fe2+). In the equivalent DC process there is in addition the cathodic deposition of aluminium, resulting in the formation of substantial amounts of D-type alumina inclusions in the ingot. The Faradaic reactions involve energy exchange which should be taken into account in the process energy balance. They also are likely to change the interface physical characteristics such as interfacial tension. The data is extended to the case of low frequency ESR furnaces in which it is found that the extent of the reactions is strongly dependent on current density. It is concluded that the presence of Faradaic reactions in low frequency furnaces is unlikely to lead to quality problems in the alloys and applications for which these processes are used. This conclusion appears to be supported by industrial practice and leads to a further conclusion that low frequency practices in large ESR furnaces could potentially be replaced by simpler DC systems.

Coupled Heat Transfers in a Refinery Furnace in View of Fouling Prediction

In industrial refinery furnaces, the efficiency of thermal transfer to heat crude oil before distillation is often altered by coke deposition inside the fuel pipes. This leads to increased production and maintenance costs, and requires better understanding and control. Crude oil fouling is a chemical reaction that is, at first order, thermally controlled. In such large furnaces, the predominant heat transfer process is thermal radiation by the hot combustion products, which directly heats the pipes. As radiation fluxes depend on temperature differences, the pipe surface temperature also plays an important role and needs to be predicted with sufficient accuracy. This pipe surface temperature results from the energy balance between thermal radiation, convective heat transfer, and conduction in the solid material of the pipe, meaning that the thermal behavior of the whole system is a coupled radiation–convection–conduction problem. In this work, this coupled problem is solved in a cylindrical furnace, in which the crude oil flowing in vertical pipes is heated. The thermal radiation of combustion gases is modeled using the discrete ordinate method (DOM) with accurate spectral models and is coupled to heat conduction in the pipe to predict its wall temperature. The flame is described with a complex chemistry combustion model. An energy balance confirms that heat transfers are effectively dominated by thermal radiation. Good agreement with available measurements of the radiative heat flux on a real furnace shows that the proposed approach predicts the correct heat transfers to the pipe. This allows an accurate prediction of the temperature field on the pipe surface, which is a key parameter for liquid fouling inside the pipe. This shows that the thermal problem in furnaces can be handled with relatively simple models with good accuracy.

Numerical analysis on effect of furnace scale on heat transfer mechanism of coal particles in pulverized coal combustion field

To investigate the effect of the furnace scale on the heat transfer mechanism of coal particles, numerical simulations of coal combustion fields in three different scale furnaces (915MWth actual large scale boiler, 2.4MWth and 0.76MWth test furnaces) were conducted. High accuracy of simulation methods was validated with the measured data. From the comparison of numerical simulations between three different scale furnaces, it was clarified that the particle residence time with high particle temperature for a small scale furnace is shorter than that for a large scale furnace even if the particle residence time passing the high temperature gas is the same. This is caused by the insufficient heat gain of particles for a small scale furnace due to the lower radiation heat transfer because of the thinner flame thickness in the small furnace. The sphericity of ash particles from small scale furnaces is lower than that for large scale furnaces due to the shorter particle residence time with high particle temperature. These findings should be considered when the usability of coal brands for actual large scale boilers is evaluated by the fly ash properties from a small scale experimental furnace.

Superplastic Forming of a Complex Shape Automotive Component with Optimized Heated Tools

Superplastic forming (SPF) commonly requires industrial presses with an integrated large furnace able to uniformly heat the tools and the blank. In this work the feasibility to form via SPF an automotive component using a different heating approach was investigated. The heat is localized only where it is really needed embedding electric heating elements directly in the forming tools. Preliminary numerical simulations of the heating phase were aimed at calculating the electrical power and at choosing a suitable positioning of the heating elements. Further forming simulations were run to calculate the pressure profile. SPF experiments were finally conducted and sound components were obtained saving energy costs and using a common industrial press with lower investment costs.

An Efficient Simulation Method for Current and Power distribution in 3-Phase Electrical Smelting Furnaces

Abstract: A simplified simulation method for 3-phase AC smelting furnaces is presented and analyzed. The DC potential equation is first solved for three basis problems where the potential is 1 V at the top of one electrode and 0 V at the two others. Then these three solutions are combined, taking the phase shift between the electrodes into account. The method ignores electromagnetic induction. Mathematical analysis shows that this approximation is better the smaller the furnace. Further studies are required to find how well it performs for large furnaces. The method has been tested using COMSOL Multiphysics. Computed results are compared with a pure DC approach. The method is suitable to provide more understanding of AC effects in 3-phase furnaces. When simulation results are compared with full AC computations, effects of the phase shift between the electrodes can be separated from effects due to electromagnetic induction.

Экспериментальные исследования модели МГД-перемешивателя с постоянными магнитами для алюминиевых печей

A m odel experimental set-up was built aiming to ensure achievable similitude to large scale metal melting furnaces, where electromagnetic stirring is required to reduce the melting time and to achieve thermal and compositional uniformity. The widely used three-phase AC current linear travelling magnetic field inductor is substituted by a new energy-saving concept of a Permanent-Magnet (PM) inductor, consisting of a multitude of cylindrical dipoles, which form a Halbach array and are rotated synchronously. The stirrer creates a very unstable time-dependent flow pattern in the liquid metal pool. The turbulent local velocity was measured, delivering experimental data about time-averaged flow and turbulence intensity as well. Spatial components of velocity were measured by ultrasound Doppler anemometry and by a potential difference probe with an incorporated permanent magnet, delivering mutually verifying and complementary data with higher reliability. The experimental data might be used to validate the full three-dimensional numerical simulations of the stirring produced in actual large scale metal melting furnaces Normal 0 false false false RU X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Обычная таблица; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

High-strength glass-ceramic materials synthesized in a large solar furnace

It is shown, that based on Uzbekistan minerals sintered in the Large Solar Furnace, it is possible to obtain ceramic granite material with physicomechanical properties exceeding GOST (State Standard) requirements. The obtained high physicomechanical properties are related to structural formation of multicomponent fine phases based on mullite, wollastonite, and cristobalite.

Investigation of using shrinking method in construction of Institute for Research in Fundamental Sciences Electron Linear Accelerator TW-tube (IPM TW-Linac tube)

Due to Iran's growing need for accelerators in various applications, IPM's electron Linac project has been defined. This accelerator is a 15 MeV energy S-band traveling-wave accelerator which is being designed and constructed based on the klystron that has been built in Iran. Based on the design, operating mode is π /2 and the accelerating chamber consists of two 60cm long tubes with constant impedance and a 30cm long buncher. Amongst all construction methods, shrinking method is selected for construction of IPM's electron Linac tube because it has a simple procedure and there is no need for large vacuum or hydrogen furnaces. In this paper, different aspects of this method are investigated. According to the calculations, linear ratio of frequency alteration to radius change is 787.8 MHz/cm, and the maximum deformation at the tube wall where disks and the tube make contact is 2.7μ m. Applying shrinking method for construction of 8- and 24-cavity tubes results in satisfactory frequency and quality factor. Average deviations of cavities frequency of 8- and 24-cavity tubes to the design values are 0.68 MHz and 1.8 MHz respectively before tune and 0.2 MHz and 0.4 MHz after tune. Accelerating tubes, buncher, and high power couplers of IPM's electron linac are constructed using shrinking method.

Static Characteristics of Aerostatic Thrust Bearings With Multiple Porous Inlet Ports

Aerostatic porous bearings have been applied successfully to various precision devices, such as precision machine tools and precision measuring equipment, to achieve higher accuracy of motion. Recently, large aerostatic porous thrust bearings have been used as essential components in a lithography machine for large liquid crystal display (LCD) glasses. Conventional aerostatic porous bearings are made of porous material that covers the whole of the bearing surface area, requiring a large piece of such material for large bearings. However, making large pieces of porous material requires the use of a large electric furnace, which is a very expensive part of the bearing's manufacturing cost. To overcome this problem, this paper proposes an aerostatic thrust bearing with multiple porous inlet ports. The proposed bearing has a number of small porous inlet ports on the bearing surface, thereby avoiding the need for large electric furnaces. The static characteristics of the proposed bearings are investigated numerically and experimentally. The results show that the proposed aerostatic thrust bearing is potentially very useful for the manufacture of large aerostatic thrust bearings, where it would have advantages over conventional aerostatic porous thrust bearings.

Impact of Radiation Models in Coupled Simulations of Steam Cracking Furnaces and Reactors

As large floor-fired furnaces have many applications in refinery and (petro-) chemical units and about 80% of heat transfer in these furnaces is by radiation, the accurate description of radiative heat transfer is of the most importance for accurate design and optimization. However, the impact of using different radiation models in coupled furnace/reactor simulations has never been evaluated before. Therefore, coupled furnace/reactor simulations of an industrial naphtha cracking furnace with a 130 kt/a capacity have been conducted. Computational fluid dynamics simulations were performed for the furnace side, while the one-dimensional reactor model COILSIM1D was used for the reactor simulations. The Adiabatic, P-1, discrete ordinates model (DOM), and discrete transfer radiation model (DTRM) were evaluated for modeling the radiative heat transfer. The results with DOM and DTRM are very similar both on the furnace and the reactor sides. The flue gas temperature using DOM is higher than when using the P-1 radiation model, resulting in higher incident radiation. Comparing the simulated results of all radiation models to the industrial product yields and run lengths shows that DOM and DTRM outperform the others. As DOM has a broader application range than DTRM, and because the current implementation of DTRM in FLUENT/14.0 cannot be run in parallel yet, DOM is the recommended radiation model for run length simulations of steam cracking furnaces.

ACCURACY OF ANN BASED DAY-AHEAD LOAD FORECASTING IN TURKISH POWER SYSTEM: DEGRADING AND IMPROVING FACTORS

This paper presents development of a day ahead load forecasting (DALF) model for Turkish power system with an artificial neural network (ANN). Effects of special holidays including national and religious days, and hourly random load deviations observed in Turkish power system due to significant arc furnace loads are discussed. Performance of the ANN is investigated in the sense of both DALF performance - in terms of both daily mean absolute percentage error (MAPE) and hourly absolute percentage error (APE) - and hourly secondary reserves required to ensure supply/demand adequacy of the system. The most sensitive cities to DALF in terms of daily city temperature forecasts are ranked in order to reduce the input of the developed ANN and thereby to improve execution of the model. Candidate cities are determined based on both their placement with respect to climatic zones of the country and their contribution to the system load during peak hours. The results show that, although a well-trained ANN could provide very satisfactory daily MAPEs at non-special days, such as ~ 1%, the hourly absolute percentage errors (APE) could be significant due to large random load disturbances, which necessitate special attention during the day ahead allocation of hourly secondary reserves. By limiting the temperature data set with major cities, the input of ANN reduces significantly while not disturbing the MAPEs. Main contributions of the study are; addressing both benefits of the prioritizing the cities in a power system in the sense of their temperature forecast effects on the DALF performance and assessing the performance of DALF in the sense of necessary amount of secondary reserves in power systems which include significant random load deviations (e.g., large arc furnace loads).

Design of Light Moisture Tester and its Application in Tiefa Coal Industry Group

This paper introduces the research and design of a light moisture tester. In the coal quality analysis field, moisture test most of the use of infrared heating pipe heating or drying box to measure, low heating rates, nitrogen through a single mode, before heating furnace uniform nitrogen filled with test conditions and have the test conditions, the same way caused by nitrogen, nitrogen waste. Based on this study, the heating pipe comprises an infrared tube into a light tube, the heating rate is improved; the general nitrogen control size flow switching mode using 2.5min before the experiment, large flow quick heating furnace filled with nitrogen, achieved through experimental conditions drying nitrogen, open a small flow, keep the atmosphere. The improved design of a light moisture meter analysis of water air drying method precision test, analysis of water air drying method accuracy experiments, 6 water - air drying method of precision experiment, 6 water - air drying method accuracy experiments, analysis of water through nitrogen drying method precision experiment, analysis of water. Nitrogen drying method accuracy experiments, Ȼ 6 full water through nitrogen drying method precision experiment, Ȼ 6 full water through nitrogen drying method accuracy experiments, results in line with national standard test, repeatability. Instrument for field application test in Tiefa Coal Industry Group, good test effect.

Analysis of oxy-fuel combustion as an alternative to combustion with air in metal reheating furnaces

Using oxygen instead of air in a burning process is at present being widely discussed as an option to reduce CO2 emissions. One of the possibilities is to maintain the combustion reaction at the same energy release level as burning with air, which reduces fuel consumption and the emission rates of CO2. A thermal simulation was made for metal reheating furnaces, which operate at a temperature in the range of 1150–1250 °C, using natural gas with a 5% excess of oxygen, maintaining fixed values for pressure and combustion temperature. The theoretical results show that it is possible to reduce the consumption of fuel, and this reduction depends on the amount of heat that can be recovered during the air pre-heating process. The analysis was further conducted by considering the 2012 costs of natural gas and oxygen in Brazil. The use of oxygen showed to be economically viable for large furnaces that operate with conventional heat recovering systems (those that provide pre-heated air at temperatures near 400 °C).

Preliminary Design and Simulation of a Turbo Expander for Small Rated Power Organic Rankine Cycle (ORC)

Nowadays, the Organic Rankine Cycle (ORC) system, which operates with organic fluids, is one of the leading technologies for “waste energy recovery”. It works as a conventional Rankine Cycle but, as mentioned, instead of steam/water, an organic fluid is used. This change allows it to convert low temperature heat into electric energy where required. Large numbers of studies have been carried out to identify the most suitable fluids, system parameters and the various configurations. In the present market, most ORC systems are designed and manufactured for the recovery of thermal energy from various sources operating at “large power rating” (exhaust gas turbines, internal combustion engines, geothermal sources, large melting furnaces, biomass, solar, etc.); from which it is possible to produce a large amount of electric energy (30 kW ÷ 300 kW). Such applications for small nominal power sources, as well as the exhaust gases of internal combustion engines (car sedan or town, ships, etc.) or small heat exchangers, are very limited. The few systems that have been designed and built for small scale applications, have, on the other hand, different types of expander (screw, scroll, etc.). These devices are not adapted for placement in small and restricted places like the interior of a conventional car. The aim of this work is to perform the preliminary design of a turbo-expander that meets diverse system requirements such as low pressure, small size and low mass flow rates. The expander must be adaptable to a small ORC system utilizing gas of a diesel engine or small gas turbine as thermal source to produce 2–10 kW of electricity. The temperature and pressure of the exhaust gases, in this case study (400–600 °C and a pressure of 2 bar), imposes a limit on the use of an organic fluid and on the net power that can be produced. In addition to water, fluids such as CO2, R134a and R245fa have been considered. Once the operating fluids has been chosen, the turbine characteristics (dimensions, input and output temperature, pressure ratio, etc.) have been calculated and an attempt to find the “nearly-optimal” combination has been carried out. The detailed design of a radial expander is presented and discussed. A thermo-mechanical performance study was carry out to verify structural tension and possible displacement. On the other hand, preliminary CFD analyses have been performed to verify the effectiveness of the design procedure.

Challenges with Industrialization of Atomic Layer Deposition of Silicon Nitride

Scaling of next generation logic and memory semiconductor devices requires conformal thin films on high aspect ratio features at low deposition temperatures (<500ºC). Atomic layer deposition (ALD) is an ideal method for depositing these films and is currently being used in high volume manufacturing (HVM) to deposit high-k dielectric materials (HfO2, ZrO2, etc.) as well as the more traditional dielectrics silicon oxide (SiO2) and silicon nitride (SiNx). With the notable exception of silicon nitride, all of these films can be deposited at sufficiently low temperatures to satisfy the integration requirements while maintaining reasonable throughput and cost. In the HVM environment, silicon nitride ALD has historically been deposited in large furnaces operating at high temperatures, and although both plasma and thermal deposition of silicon nitride have been reported at low temperatures1-2, translation of these low temperature R&D films into HVM films has been challenging.In this presentation, we discuss some of the challenges faced with addressing the requirements associated with bringing low temperature ALD SiNx into HVM, which include achieving high wafer throughput and low per wafer cost, while simultaneously keeping the resistance of the film to multiple downstream etches and cleans, which may include exposure to hydrofluoric acid (HF). Generic to all ALD processes is the high cost of the precursors relative to traditional chemical vapor deposition (CVD); in the case of SiNx, this is exacerbated by the relative low “reactivity to cost ratio” of available silicon precursors. Cost can partially be addressed with chlorosilane precursors, but the chlorine byproducts create challenges with deposition chamber materials and effluent management. Low reactivity of the silicon precursors poses challenges with respect to process design; the choice of spatial ALD vs. temporal ALD and isobaric vs. non-isobaric deposition sequences affects the final cost and throughput. Lastly, the use of plasmas in ALD poses challenges for achieving isotropic film properties over the complex topography on today’s semiconductor substrates.