Modelling of transient heat transfer in annealing furnaces

This is a study of heat transfer in a lift-off furnace which is employed in the batch annealing of a stack of coils of steel strip. The objective of the project is to investigate the various factors which govern the furnace design and the heat transfer resistances, so as to reduce the time of the annealing cycle, and hence minimize the operating costs. The work involved mathematical modelling of patterns of gas flow and modes of heat transfer. These models are: Heat conduction and its conjectures in the steel coils;Convective heat transfer in the plates separating the coils in the stack and in other parts of the furnace; and Radiative and convective heat transfer in the furnace by using the long furnace model. An important part of the project is the development of numerical methods and computations to solve the transient models. A limited number of temperature measurements was available from experiments on a test coil in an industrial furnace. The mathematical model agreed well with these data. The model has been used to show the following characteristics of annealing furnaces, and to suggest further developments which would lead to significant savings: - The location of the limiting temperature in a coil is nearer to the hollow core than to the outer periphery. - Thermal expansion of the steel tends to open the coils, reduces their thermal conductivity in the radial direction, and hence prolongs the annealing cycle. Increasing the tension in the coils and/or heating from the core would overcome this heat transfer resistance. - The shape and dimensions of the convective channels in the plates have significant effect on heat convection in the stack. An optimal design of a channel is shown to be of a width-to-height ratio equal to 9. - Increasing the cooling rate, by using a fluidized bed instead of the normal shell and tube exchanger, would shorten the cooling time by about 15%, but increase the temperature differential in the stack. - For a specific charge weight, a stack of different-sized coils will have a shorter annealing cycle than one of equally-sized coils, provided that production constraints allow the stacking order to be optimal. - Recycle of hot flue gases to the firing zone of the furnace would produce a. decrease in the thermal efficiency up to 30% but decreases the heating time by about 26%.

Dust recovery practice at blast furnaces; an evaluation of settleable solids formation and recovery at mills in the Ohio Valley and a suggested proceedure [sic] for defining performance of wastewater clarifiers.

"Reference data publication."

Prediction of structural integrity, robustness and service life using advanced finite element methods

Corrosion is a common phenomenon and critical aspects of steel structural application. It affects the daily design, inspection and maintenance in structural engineering, especially for the heavy and complex industrial applications, where the steel structures are subjected to hash corrosive environments in combination of high working stress condition and often in open field and/or under high temperature production environments. In the paper, it presents the actual engineering application of advanced finite element methods in the predication of the structural integrity and robustness at a designed service life for the furnaces of alumina production, which was operated in the high temperature, corrosive environments and rotating with high working stress condition.

Finite element modelling of load bearing steel stud walls under real building fires

Fire safety has become an important part in structural design due to the ever increasing loss of properties and lives during fires. Conventionally the fire rating of load bearing wall systems made of Light gauge Steel Frames (LSF) is determined using fire tests based on the standard time-temperature curve given in ISO 834 (ISO, 1999). The standard time-temperature curve given in ISO 834 (ISO, 1999) originated from the application of wood burning furnaces in the early 1900s. However, modern commercial and residential buildings make use of thermoplastic materials, which mean considerably high fuel loads. Hence a detailed fire research study into the performance of LSF walls was undertaken using the developed real fire curves based on Eurocode parametric curves (ECS, 2002) and Barnett’s BFD curves (Barnett, 2002) using both full scale fire tests and numerical studies. It included LSF walls without any insulation, and the recently developed externally insulated composite panel system. This paper presents the details of the numerical studies and the results. It also includes brief details of the development of real building fire curves and experimental studies.

Fire tests of load bearing steel stud walls exposed to real building fires

Abstract. Fire resistance has become an important part in structural design due to the ever increasing loss of properties and lives every year. Conventionally the fire rating of load bearing Light gauge Steel Frame (LSF) walls is determined using standard fire tests based on the time-temperature curve given in ISO 834 [1]. Full scale fire testing based on this standard time-temperature curve originated from the application of wood burning furnaces in the early 1900s and it is questionable whether it truly represents the fuel loads in modern buildings. Hence a detailed fire research study into the performance of LSF walls was undertaken using real design fires based on Eurocode parametric curves [2] and Barnett’s ‘BFD’ curves [3]. This paper presents the development of these real fire curves and the results of full scale experimental study into the structural and fire behaviour of load bearing LSF stud wall systems.

Improving combustion stability in sugar factory boilers

Reliable operation of a sugar factory boiler station is essential for efficient and timely processing of the cane supply. Sugar factory boilers have to contend with changes in fuel quality caused by variations in performance of the extraction station, different cane varieties and associated agronomic factors along with fluctuations in factory steam demand. These variations can affect the stability of combustion in boiler furnaces leading to reductions in boiler steam output and large furnace pressure fluctuations that can cause serious damage. This paper investigates the causes of unstable combustion, discusses aspects of boiler design that make a boiler more susceptible to unstable combustion and uses modelling to evaluate different options for improving combustion stability.

Dewatering of microalgal culture for biodiesel production : exploring polymer flocculation and tangential flow filtration

Background: Conventional biodiesel production relies on trans-esterification of lipids extracted from vegetable crops. However, the use of valuable vegetable food stocks as raw material for biodiesel production makes it an unfeasibly expensive process. Used cooking oil is a finite resource and requires extra downstream processing, which affects the amount of biodiesel that can be produced and the economics of the process. Lipids extracted from microalgae are considered an alternative raw material for biodiesel production. This is primarily due to the fast growth rate of these species in a simple aquaculture environment. However, the dilute nature of microalgae culture puts a huge economic burden on the dewatering process especially on an industrial scale. This current study explores the performance and economic viability of chemical flocculation and tangential flow filtration (TFF) for the dewatering of Tetraselmis suecicamicroalgae culture. Results: Results show that TFF concentrates the microalgae feedstock up to 148 times by consuming 2.06 kWh m-3 of energy while flocculation consumes 14.81 kWhm-3 to concentrate the microalgae up to 357 times. Economic evaluation demonstrates that even though TFF has higher initial capital investment than polymer flocculation, the payback period for TFF at the upper extreme ofmicroalgae revenue is ∼1.5 years while that of flocculation is ∼3 years. Conclusion: These results illustrate that improved dewatering levels can be achieved more economically by employing TFF. The performances of these two techniques are also compared with other dewatering techniques.

Numerical and Experimental Investigation On The Prevention of Co Deflagration

The exhaust gases from industrial furnaces contain a huge amount of heat and chemical enthalpy. However, it is hard to recover this energy since exhaust gases invariably contain combustible components such as carbon monoxide (CC). If the CO is unexpectedly ignited during the heat recovery process, deflagration or even detonation could occur, with serious consequences such as complete destruction of the equipment. In order to safely utilize the heat energy contained in exhaust gas, danger of its explosion must be fully avoided. The mechanism of gas deflagration and its prevention must therefore be studied. In this paper, we describe a numerical and experimental investigation of the deflagration process in a semi-opened tube. The results show that, upon ignition, a low-pressure wave initially spreads within the tube and then deflagration begins. For the purpose of preventing deflagration, an appropriate amount of nitrogen was injected into the tube at a fixed position. Both simulation and experimental results have shown that the injection of inert gas can successfully interrupt the deflagration process. The peak value of the deflagration pressure can thereby be reduced by around 50%. (C) 2008 Elsevier Ltd. All rights reserved.

Photographic investigations in molecular spectroscopy

The determination of the energy levels and the probabilities of transition between them, by the formal analysis of observed electronic, vibrational, and rotational band structures, forms the direct goal of all investigations of molecular spectra, but the significance of such data lies in the possibility of relating them theoretically to more concrete properties of molecules and the radiation field. From the well developed electronic spectra of diatomic molecules, it has been possible, with the aid of the non-relativistic quantum mechanics, to obtain accurate moments of inertia, molecular potential functions, electronic structures, and detailed information concerning the coupling of spin and orbital angular monenta with the angular momentum of nuclear rotation. The silicon fluori1e molecule has been investigated in this laboratory, and is found to emit bands whose vibrational and rotational structures can be analyzed in this detailed fashion.

Like silicon fluoride, however, the great majority of diatomic molecules are formed only under the unusual conditions of electrical discharge, or in high temperature furnaces, so that although their spectra are of great theoretical interest, the chemist is eager to proceed to a study of polyatomic molecules, in the hope that their more practically interesting structures might also be determined with the accuracy and assurance which characterize the spectroscopic determinations of the constants of diatomic molecules. Some progress has been made in the determination of molecule potential functions from the vibrational term values deduced from Raman and infrared spectra, but in no case can the calculations be carried out with great generality, since the number of known term values is always small compared with the total number of potential constants in even so restricted a potential function as the simple quadratic type. For the determination of nuclear configurations and bond distances, however, a knowledge of the rotational terms is required. The spectra of about twelve of the simpler polyatomic molecules have been subjected to rotational analyses, and a number of bond distances are known with considerable accuracy, yet the number of molecules whose rotational fine structure has been resolved even with the most powerful instruments is small. Consequently, it was felt desirable to investigate the spectra of a number of other promising polyatomic molecules, with the purpose of carrying out complete rotational analyses of all resolvable bands, and ascertaining the value of the unresolved band envelopes in determining the structures of such molecules, in the cases in which resolution is no longer possible. Although many of the compounds investigated absorbed too feebly to be photographed under high dispersion with the present infrared sensitizations, the location and relative intensities of their bands, determined by low dispersion measurements, will be reported in the hope that these compounds may be reinvestigated in the future with improved techniques.

Analyses of patterns of copper and lead mineralisation in human skeletons excavated from an ancient mining and smelting centre in the Jordanian desert

Grattan, J.P., Al-Saad, Z., Gilbertson, D.D., Karaki, L.O., Pyatt, F.B 2005 Analyses of patterns of copper and lead mineralisation in human skeletons excavated from an ancient mining and smelting centre in the Jordanian desert Mineralogical Magazine. 69(5) 653-666.

Ironworking in late medieval Ireland, c. AD. 1200 to 1600

The landscape of late medieval Ireland, like most places in Europe, was characterized by intensified agricultural exploitation, the growth and founding of towns and cities and the construction of large stone edifices, such as castles and monasteries. None of these could have taken place without iron. Axes were needed for clearing woodland, ploughs for turning the soil, saws for wooden buildings and hammers and chisels for the stone ones, all of which could not realistically have been made from any other material. The many battles, waged with ever increasingly sophisticated weaponry, needed a steady supply of iron and steel. During the same period, the European iron industry itself underwent its most fundamental transformation since its inception; at the beginning of the period it was almost exclusively based on small furnaces producing solid blooms and by the turn of the seventeenth century it was largely based on liquid-iron production in blast-furnaces the size of a house. One of the great advantages of studying the archaeology of ironworking is that its main residue, slag, is often produced in copious amounts both during smelting and smithing, is virtually indestructible and has very little secondary use. This means that most sites where ironworking was carried out are readily recognizable as such by the occurrence of this slag. Moreover, visual examination can distinguish between various types of slag, which are often characteristic for the activity from which they derive. The ubiquity of ironworking in the period under study further means that we have large amounts of residues available for study, allowing us to distinguish patterns both inside assemblages and between sites. Disadvantages of the nature of the remains related to ironworking include the poor preservation of the installations used, especially the furnaces, which were often built out of clay and located above ground. Added to this are the many parameters contributing to the formation of the above-mentioned slag, making its composition difficult to connect to a certain technology or activity. Ironworking technology in late medieval Ireland has thus far not been studied in detail. Much of the archaeological literature on the subject is still tainted by the erroneous attribution of the main type of slag, bun-shaped cakes, to smelting activities. The large-scale infrastructure works of the first decade of the twenty-first century have led to an exponential increase in the amount of sites available for study. At the same time, much of the material related to metalworking recovered during these boom-years was subjected to specialist analysis. This has led to a near-complete overhaul of our knowledge of early ironworking in Ireland. Although many of these new insights are quickly seeping into the general literature, no concise overviews on the current understanding of the early Irish ironworking technology have been published to date. The above then presented a unique opportunity to apply these new insights to the extensive body of archaeological data we now possess. The resulting archaeological information was supplemented with, and compared to, that contained in the historical sources relating to Ireland for the same period. This added insights into aspects of the industry often difficult to grasp solely through the archaeological sources, such as the people involved and the trade in iron. Additionally, overviews on several other topics, such as a new distribution map of Irish iron ores and a first analysis of the information on iron smelting and smithing in late medieval western Europe, were compiled to allow this new knowledge on late medieval Irish ironworking to be put into a wider context. Contrary to current views, it appears that it is not smelting technology which differentiates Irish ironworking from the rest of Europe in the late medieval period, but its smithing technology and organisation. The Irish iron-smelting furnaces are generally of the slag-tapping variety, like their other European counterparts. Smithing, on the other hand, is carried out at ground-level until at least the sixteenth century in Ireland, whereas waist-level hearths become the norm further afield from the fourteenth century onwards. Ceramic tuyeres continue to be used as bellows protectors, whereas these are unknown elsewhere on the continent. Moreover, the lack of market centres at different times in late medieval Ireland, led to the appearance of isolated rural forges, a type of site unencountered in other European countries during that period. When these market centres are present, they appear to be the settings where bloom smithing is carried out. In summary, the research below not only offered us the opportunity to give late medieval ironworking the place it deserves in the broader knowledge of Ireland's past, but it also provided both a base for future research within the discipline, as well as a research model applicable to different time periods, geographical areas and, perhaps, different industries..