Tap Hole Research Articles

Research on the Temperature Field and Roast Mechanism of Blast Furnace Tap-Hole Clay

The temperature field of blast furnace tap hole clay was analyzed by using ABAQUS software. Samples taken from the tap-hole clay in depth of 1200mm, 2200mm, 2600mm and 2800mm after roasted for 100 minutes were studied by using XRD and SEM to investigate their roast mechanism and microstructure at different temperatures. The results show that the ore phase of the tap-hole clay in depth of 1200mm remained unchanged but only tar and asphalt appear the carbonation phenomena. There is a large number of SiC crystalline phase appears in depth of 2200mm. At the same time, porosity increases and coke structure is formed. The air permeability is enhanced. In the tap-hole clay of 2600mm～2800mm depth, elongated rod-likeβ-Si3N4 grains obviously increase while the SiC grains decrease. A large number of high-temperature flocculent mullite phase appears and the high-temperature strength of the tap-hole clay is strengthened.

Short‐term Lining Temperature Changes during Tapping in a Blast Furnace

AbstractThe following paper presents a three‐dimensional heat transfer model of the blast furnace hearth. The model has been developed with the objective of studying the short term changes in lining temperature during regular tappings. It is based on the actual conditions of Blast Furnace No. 2 at SSAB Oxelösund in Sweden. The model was evaluated and analysed using thermocouple data from the operating furnace. The study showed that a layer of tap clay around the tap hole had a significant effect on the heat transfer by reducing the heat variations in the lining. More specifically, a layer of 10–15 cm gave the best correlation between calculated and thermocouple data. A simulation was performed where the melt temperature and the tap cycle duration was based on process data from the operating furnace. Moreover, the size of the area subjected to changes due to the regular tappings was defined. It was found to be the region within an angle of 13° from the tap hole, 0.9 m above and 0.8 m below the tap hole.

Submerged steel blowing through equipment tap holes

Results are presented for experimental submerged blowing of steel with a gas–oxygen and gas–air mixture through a special lance installed in a steel tap hole of a melting unit and a furnace-ladle unit.

Numerical Study on Metal/Slag Drainage Rate Deviation during Blast Furnace Tapping

Remarkable deviation of metal fraction in the liquid drained out of blast furnace tap hole has been occasionally observed between the operated tap holes and/or tapping time stages. Introducing the concept of low permeability zone whose wall, due to the difference in two liquid phases' viscosity and/or wettabilitiy to coke particle, allows for metal to permeate freely but for slag not to permeate, the liquid drainage behaviors are examined by furnace hearth mathematical model simulations.The deviation of metal fraction between two operated tap holes is materialized under the hypothesis that furnace heath is divided into two sections by planar vertical low permeability wall (VLPW). While, the variation of time series change in liquid metal fraction during tapping operation is reproduced by hypothesizing the formation of cylindrical low permeability wall (CLPW) which concentrically parts the furnace hearth into center and peripheral area.Since the results of calculation for VLPW or CLPW formation indicate the notable raise of liquid level in furnace which could influence on abrupt increase of blowing pressure, the effectiveness of several operational optimization is assessed, resulting in suggestive conclusion that increasing the initial tap hole diameter is the most effective.

CFD modelling of the effect of furnace crater pressure on the melt and gas flows in the submerged arc furnaces used for silicon production

In this paper the effect of furnace crater pressure on the melt and gas flows inside the submerged arc furnaces used for silicon production is investigated. The multiphase flow model predicts how the gas pressure in the furnace crater zone can affect the metal flows at the furnace bottom, the gas flow pattern inside the charge materials, the metal tapping flow rate and the gas flow rate from the furnace taphole. The model also shows that gas blow out from the tap hole can change the gas flow pattern inside the charge materials all the way to the furnace top.

A New Advisor System to Detect the ‘Tap Hole Whistling and Splashing’ in a Blast Furnace

A New Advisor System to Detect the ‘Tap Hole Whistling and Splashing’ in a Blast Furnace

An Adaptation of Weil's Osteotomy of the Lesser Metatarsal Neck

Weil's osteotomy is a useful technique for the treatment of central metatarsalgia and lesser metatarsophalangeal joint dislocation. In this report, we describe a technical maneuver that involves predrilling and tapping holes that can be used to guide translocation of the capital fragment of the metatarsal. This configures the final hole that will be used for single screw placement to secure the osteotomy in the position of correction. This technical tip is useful in regard to establishing the intraoperative orientation of the osteotomy and screw placement, and enables the use of a single, generic screw for stabilization of the realigned metatarsal.

Analysis of Drainage Rate Variation of Molten Iron and Slag from Blast Furnace during Tapping

Despite its importance in practical blast furnace (BF) operation, the dominant factors to control drainage rate or tapping time have not been well studied. In most cases, short tapping time has been attributed to rapid tap hole diameter enlargement. On the other hand, the experiential tendency about positive correlation between furnace hearth bottom temperature and drainage rate has been widely recognized.In order to examine the dominant factors to control the liquid drainage rate or tapping time at BF, a simulative calculation model is introduced, where the liquid drainage path consists of coke particles packed layer (coke filter) and tapping hole and the overall drainage rate is determined as one of smaller fluid rate in coke filter or tapping hole. For calculating the fluid rate in coke filter, a hypothesis that liquid iron and slag in coke filter is driven toward the tap hole entry point consuming the coke particles, whose extent depends on molten iron C saturation degree and FeO fraction in molten slag, was introduced.The calculation results present good matches with the observed tapping operation. This result can be explained by the two influences of low permeability zone formation or elimination at furnace hearth. Considering the two influences of low permeability zone formation, (1) to lower hearth bottom temperature and (2) to induce low C saturation of pig iron due to short traveling time in liquid pool to tap hole entry point, the simulation result conforms to the above mentioned experiential tendency.

Numerical Study on Metal/Slag Drainage Rate Deviation during Blast Furnace Tapping

Remarkable deviation of metal fraction in the liquid drained out of blast furnace tap hole has been occasionally observed between the operated tap holes and/or tapping time stages. Introducing the concept of low permeability zone whose wall, due to the difference in two liquid phases' viscosity and/or wettabilitiy to coke particle, allows for metal to permeate freely but for slag not to permeate, the liquid drainage behaviors are examined by furnace hearth mathematical model simulations.The deviation of metal fraction between two operated tap holes is materialized under the hypothesis that furnace heath is divided into two sections by planar vertical low permeability wall (VLPW). While, the variation of time series change in liquid metal fraction during tapping operation is reproduced by hypothesizing the formation of cylindrical low permeability wall (CLPW) which concentrically parts the furnace hearth into center and peripheral area.Since the results of calculation for VLPW or CLPW formation indicate the notable raise of liquid level in furnace which could influence on abrupt increase of blowing pressure, the effectiveness of several operational optimization is assessed, resulting in suggestive conclusion that increasing the initial tap hole diameter is the most effective.

The laminar hole pressure for Newtonian fluids

For flows with wall turbulence the hole pressure, PH, was shown empirically by Franklin and Wallace (J Fluid Mech, 42, 33–48, 1970) to depend solely on R+, the Reynolds number constructed from the friction velocity and the hole diameter b. Here this dependence is extended to the laminar regime by numerical simulation of a Newtonian fluid flowing in a plane channel (gap H) with a deep tap hole on one wall. Calculated hole pressures are in good agreement with experimental values, and for two hole sizes are well represented by: (PH−PHS)/τw = √(k2 + c2R+2)−k, where the Stokes hole pressure PHS/τw = s (b/H)3, k, c, s are fitted constants, and τw is the wall shear stress.

Analysis of Drainage Rate Variation of Molten Iron and Slag from Blast Furnace during Tapping

Despite its importance in practical blast furnace (BF) operation, the dominant factors to control drainage rate or tapping time have not been well studied. In most cases, short tapping time has been attributed to rapid tap hole diameter enlargement. On the other hand, the experiential tendency about positive correlation between furnace hearth bottom temperature and drainage rate has been widely recognized.In order to examine the dominant factors to control the liquid drainage rate or tapping time at BF, a simulative calculation model is introduced, where the liquid drainage path consists of coke particles packed layer (coke filter) and tapping hole and the overall drainage rate is determined as one of smaller fluid rate in coke filter or tapping hole. For calculating the fluid rate in coke filter, a hypothesis that liquid iron and slag in coke filter is driven toward the tap hole entry point consuming the coke particles, whose extent depends on molten iron C saturation degree and FeO fraction in molten slag, was introduced.The calculation results present good matches with the observed tapping operation. This result can be explained by the two influences of low permeability zone formation or elimination at furnace hearth. Considering the two influences of low permeability zone formation, (1) to lower hearth bottom temperature and (2) to induce low C saturation of pig iron due to short traveling time in liquid pool to tap hole entry point, the simulation result conforms to the above mentioned experiential tendency.

A Comparison of Pullout Strength for Pedicle Screws of Different Designs

The pullout strengths of various pedicle screw designs are compared using tapped and untapped pilot holes. The objective of this study is to compare the pullout strength of various pedicle screw designs. The designs are compared using tapped and untapped pilot holes. By using several different screw designs, it is possible to gain an understanding of whether there is a correlation between tapping a pilot hole and the ultimate pullout strength. Most bone screws originally developed were intended to be installed in a pretapped pilot hole. This same technology has been carried over to the development of more modern bone screws for use in spinal fixation applications. Many pedicle screws in use today are still intended to be installed in a tapped hole. Preparing the vertebrae and tapping of a pilot hole involve additional trauma to the patient as well as increased operating time. Pedicle screws from various manufacturers are installed in tapped and untapped pilot holes and then loaded to failure. A uniform synthetic material was used to provide a consistent test of each screw design by eliminating variability seen in bone. Tapping pilot holes did not increase the pullout strength of the screws tested in this study. It was observed during testing that tapping some of the holes degraded the material. This degradation led to pullout strengths that were lower than in the untapped case, and generally larger standard deviations. The pullout strength was not increased by tapping for the screws in this study. Screws placed in untapped holes generally had higher pullout strengths and lower standard deviations. The results of this study suggest that tapping does not increase pullout strength in bone with densities near 20 lb/ft3, which correlates with low density cancellous or osteoporotic bone.

Optimising the design of fume extraction hoods using a combination of engineering and CFD modelling

Fume and hygiene hoods are widely used to prevent fugitive emissions from charge ports, tap holes and many other openings in mineral processing and smelting vessels. The highly buoyant nature of the fume combined with often complex geometries make the design of these hoods difficult with traditional engineering tools. However, by combining the traditional engineering approach with computational fluid dynamics (CFD) techniques, a clear understanding of the shortfalls of an existing system can be obtained, and an optimised hood design can be achieved. This paper reports on a combined engineering and CFD analysis of a fume extraction system for a zinc slag fumer charge port. The engineering model revealed that the existing plant components (bag house and fan) were not capable of capturing the required amount of fume, and that the original hood design was flawed. The CFD model was then used to predict the fume capture and emission from the existing hood. CFD model predictions showed that increasing the draft flow rate by an order of magnitude would only give a marginal improvement in fume capture. Using findings of both the models enabled a new fume capture hood to be designed. CFD analysis of the new hood revealed that a significant improvement in fume capture is possible. Construction and installation of the hood has been performed and a 65% reduction in fume emission was achieved, thus significantly mitigating a long-standing emission problem.

高炉レースウェイ深度制御による出銑口深度安定化技術

On facing the high productivity and elongation of life time in blast furnace iron-making, it is essential to protect the peripheral iron flow formed by a free space in the hearth in addition to maintaining the gas and liquid permeability of deadman. Therefore, it is important to stabilize the length of mud (tapping hole length) which is plugged and formed by hole closing refractory (mud materials), but the phenomena of fluctuation of tapping hole length are not clarified. In this paper, variables affecting the tapping hole length including the raceway depth measured by micro wave reflection struck tuyere are discussed under dimension analysis. As the burden weight above the raceway are balanced to upwind gas, the load to the hearth under the raceway is less than that in the furnace center and a high void ratio area or free space is easy to be formed under the raceway. As the result, it is clarified and quantified that the tapping hole length is recovered from shortage of distance by decreasing raceway depth which promotes deadman to sink further into bottom or increase the void ratio of peripheral area in the hearth.

Stabilization of Tapping Hole Length by Controlling Blast Furnace Raceway Depth

On facing the high productivity and elongation of life time in blast furnace iron-making, it is essential to protect the peripheral iron flow formed by a free space in the hearth in addition to maintaining the gas and liquid permeability of deadman. Therefore, it is important to stabilize the length of mud (tapping hole length) which is plugged and formed by hole closing refractory (mud materials), but the phenomena of fluctuation of tapping hole length are not clarified. In this paper, variables affecting the tapping hole length including the raceway depth measured by micro wave reflection struck tuyere are discussed under dimension analysis. As the burden weight above the raceway are balanced to upwind gas, the load to the hearth under the raceway is less than that in the furnace center and a high void ratio area or free space is easy to be formed under the raceway. As the result, it is clarified and quantified that the tapping hole length is recovered from shortage of distance by decreasing raceway depth which promotes deadman to sink further into bottom or increase the void ratio of peripheral area in the hearth.

Simulation of Iron Flow and Heat Transfer in the Hearth of a Blast Furnace

The aim of this research is to numerically simulate iron flow and heat transfer in the hearth of a blast furnace by solving the three-dimensional turbulent Navier-Stokes equation coupled with the transport equation of energy at steady state. Under the effects of conjugate heat transfer and natural convection, a computational fluid dynamic (CFD) was performed to generate flow field in the hearth and temperature distribution in the refractories during the tapping process. The accuracy and computation of the model is validated using operation data from Bluescope Steel’s No. 5 blast furnace. The shear stress and heat flux on the wall were then predicted for the different vertical movements, shapes of the coke zone (deadman), and the lengths of the tap-hole. As shown in the results, it is worth noticed that an increase in the tap hole length causes the peak values of shear stress to shift in the increasing azimuthal direction at a particular plane, and the location of the peak value of shear stress coincides with the location of higher temperature actually measured on the hearth wall, signifying enhanced heat transfer to the wall at location of peak stress.

1998 ice storm impact on sugar bushes of eastern Ontario

In 1998, thirty-four managed sugar bush blocks with 7% to 72% ice-induced crown damage were established in eastern Ontario. All received dolomitic lime (Ca, Mg) and P and K treatments in June 1999. Initial crown damage, fall root starch and sugar levels, sap production and sweetness, sap amino acid concentration, and tap hole closure rate were measured. Syrup production was calculated. Trees with >50% (severe) crown damage had reduced root starch content in 1998 and 2000, but not in 1999. In 2000, root total sugars were lower in trees with >50% crown damage. Sap produced per tap, and sap sweetness were reduced by damage, but not consistently in all years. Sap per tap increased with total crown branches in all three years, but sap sweetness and syrup production only in 1999. Syrup production per tap was consistently reduced in damaged trees in all three years, usually in trees with > 50% damage. The lime and P and K treatments did not significantly affect any of the variables measured. Results suggest that severe ice storm damage to crowns resulted in reduced fall root starch levels and less sap production, and/or sap sweetness, and therefore lowered the syrup producing capacity of sugar maple. Key words: Acer saccharum, ice storm, sap and syrup production, root starch, crown damage

Effects of Particle Free Space on Hearth Drainage Efficiency.

This paper presents an experimental and numerical study of the two-phase flow in a particle packed bed, under conditions related to a blast furnace hearth. In these models, drainage velocities, slag ratio, tapping time, and maximum slag level in hearth are studied. The coke free space formed at tap hole level forms a circumference slag flow and significantly improves the hearth drainage efficiency. When the coke free space surround a part of packed bed, the effect is in proportion to the surrounded packed bed size. Such a nonaxisymmetric coke free space causes the imbalances of tap time and slag ratio.

Development of coal science in the 20th century. Part 2

The heat loss and its distribution are of great importance for the calculation and simulation of COREX process. Based on Baosteel COREX process, a method was applied to measure the heat loss of the furnace shell, the accessory equipments and the cooling water system. Then, a static model was established based on the measured heat loss of COREX process. The results showed that the main heat loss of furnace shells took place at the dome of the COREX melter-gasifier and the reducing gas entrance position of the shaft furnace while the main heat loss caused by cooling water occurred at the tap hole area. And the heat loss caused by cooling water accounts for about 85% of the total heat loss in COREX process. The measured total heat loss for producing every 1 t hot metal was 542. 164 MJ, which accounted for about 92% of the theoretical total heat loss.

Deadman and hearth phenomena in the blast furnace

The deadman and hearth phenomena play key roles in hot metal quality. The condition of the deadman has a strong influence on hot metal temperature and composition. When hot metal can flow freely towards the tap hole and the deadman is a porous coke bed, then conditions are good for desulphurization and carbonization of hot metal. The deadman has also a significant effect on lining wear and campaign length by controlling hot metal flow in the hearth.Particular observations of hearth behaviour have been made during the last six years. Data of blast furnace operation have been studied and compared with hearth condition, hot metal and slag properties. Several methods to control the dead man have been experienced in Koverhar. The best method so far is to use coarse coke with low reactivity and to control burden distribution with movable armour. Response times to hearth control actions are painfully long – four weeks or even more.A set of indications about deadman condition have been collected. Hearth bottom temperatures are used to monitor the location of 1150°C isotherm. Rod tests have been used to sound the dead man hardness and to measure the length of the raceways.Interesting dependence between deadman condition, reduction of iron, hot metal sulphur and carbon and hot metal temperature has been found. This knowledge has been practised resulting in remarkable improvement of hot metal quality and hearth condition.