Specialized metallurgical processes – compositions for use therei – Processes – Process control responsive to sensed condition
Reexamination Certificate
1999-02-19
2001-05-01
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Process control responsive to sensed condition
C075S491000, C075S492000, C266S087000, C266S160000, C266S183000
Reexamination Certificate
active
06224647
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process and device for coating a fusion gasifier with gasifying means and spongy iron.
DESCRIPTION OF THE PRIOR ART
Such a device is previously known from the documents DE 30 34 539 A1 and DE 37 23 137 Cl. The DE 30 34 539 A1 shows a fusion gasifier and a reduction shaft, which is arranged spaced and aligning toward the fusion gasifier. In the lower section of the reduction shaft a plurality of discharge devices being arranged star-like is provided therefrom in form of screw conveyors in a horizontal arrangement perpendicularly through the peripheral wall, which discharge the spongy iron from this lower section of the reduction shaft such that it is dispensed through the respective downpipes instantaneously into the fusion gasifier. For this purpose the downpipes terminate in the head section of the fusion gasifier in a centrical manner about the center line thereof being arranged spaced therefrom and to each other. In close proximity of the inlet connection piece of these downpipes in the gasifier head inlet openings for the gasifying means, preferably coal, are also placed as well as simultaneously the outlets for the reduction gas and crude gas, respectively, produced within the gasifier.
The fusion gasifier is directly connected to the reduction shaft through the downpipes. Hence, a great quantity of dust with such a gasifying gas being not dedusted enters into the reduction shaft through such downpipes. To reduce the total charge of dust into the reduction shaft and to limit the samples resulting therefrom, the main quantity of the gasifying gas is introduced as a reduction gas into the reduction shaft after dedusting inside a hot gas type cyclone dust separator at least 2 m above the screw conveyors of the discharge devices. The discharge in the reduction shaft between the port of the screw conveyors and the reduction gas inlet serves as gas obstruction means, hence the quantity of gasifying gas being not dedusted entering into the reduction shaft through the downpipes is limited. However, the larger the shaft diameter is, the larger this distance has to be. With a reduction shaft diameter of 5 m this distance is already more than 4 m. Because of this the reduction shaft becomes higher and heavier.
As a result of leading the screw conveyors in its radial arrangement into the perpendicularly extending wall portions in the lower section of the reduction shaft, a clearance volume results between the plane defined herewith inside the reduction shaft and the reduction gas inlet arranged thereabove, in which such a spongy iron is not reduced which does not participate in the process cycle which burdens it in an uneconomic manner. This clearance volume necessarily also increases the distance between the reduction shaft and the fusion gasifier arranged below and increases the weight of the reduction shaft as well as the total height of the plant. Another substantial disadvantage of this arrangement is a very low gas resistance of the piling up, which is predetermined by a large cross section of the reduction shaft in this portion, whereby an essential quantity of gas carrying a lot of dust flows from the fusion gasifier through the downpipes into the reduction shaft. Additionally, from this flowing up gasifying gas a great part of fine particles of the discharged spongy iron and calcined aggregates in case in the downpipes is sized and conveyed back to the reduction shaft such that the total charge of dust into the reduction shaft still becomes increased. Particularly disadvantageous coal particles, which pass from the close gasifying means inlets into the downpipes and which contain because of its short residence time in the gasifier a portion of volatile constituents and tar, which in the lower section of the reduction shaft as a binder can result in a bridging and nodulizing as well as an uncontrolled discharge of the screw conveyors.
It was also found that having this arrangement with charging the fusion gasifier, a uniform distribution and mixing between the gasifying means and the spongy iron within the region of the gasifying bed is not insured at least or can not be satisfactorily assured. This inhomogeneous charging becomes disadvantageously apparent in particular in the center of the gasifier and during an unsteady operation of the fusion gasifier with great variations of the gas quantities and the pressure of the plant as well as in front of the single oxygen nozzles, if one of such spongy iron conveyor devices fails and only acid slag from coal ash without spongy iron and aggregates is melted. Further disadvantages of this arrangement are a great wear of the lining in the downpipes and the necessity of emptying the reduction shaft during greater repairs with the conveying devices. Because of this, longer lasting losses of production occur as well as high starting costs. Because of the fact that the conveyor devices are only one-side supported, a further limitation of the size and the effectivity of the general plant is given.
With the device according to the document DE 37 23 137 C1 a plurality of the above mentioned problems are solved or alleviated. The problem of such a still relatively high charge of dust via the pipe connections to the reduction shaft and the following problems associated therewith, which all of the reduction melting processes have to contend with, however, are not yet satisfactorily solved with this device as well. During normal operation a greater portion of dust is indeed separated inside the connection shafts between the discharge devices and the reduction shaft in the piling up such that less dust passes into the reduction shaft, however covering with dust of the piling up within the connection shafts further remains increased, whereby such a piling up in this region relatively easily tends in hanging. With a more highly dusting of the furnace piling up in the reduction gas inlet region, the so called bustle region of the reduction shaft, the pressure difference increases between the fusion gasifier and the lower region of the reduction shaft and accordingly the flowing up quantity of the gasifying gas increases being not dedusted via the connection shafts and, according to the DE 30 34 539 A1 modification, via the downpipes, respectively, toward the reduction shaft. This effect is still increased in that the gasifying gas includes a direct access to the relatively not dedusted piling up in the center of the reduction shaft via the downpipes and connection shafts, respectively, as well as the discharge devices. Hence, the effect of an air separation in the dome cap of the gasifier and in the downpipes, respectively, also becomes stronger and stronger, the dust content of the flowing back gas becomes higher and higher, and the piling up inside the connection shafts as well as in the lower section of the reduction shaft is allowed to be concentrated with this cycle dust, such that due to high friction forces in the piling up very low pressure differences are sufficient to cause hanging of the piling up in the connection shafts and the lower part of the reduction shaft, whereby the well-known phenomenons of chanelling and undisturbed gas flow having a high dust content occur from the fusion gasifier toward the reduction shaft. Such cases happen when too much fine dust is charged with the coal by employing a greater quantity of coal in the coal mixture, which highly disintegrates at high temperatures if extremely high temperatures appear in the gasifier, which result in a greater disintegration of coal as well as with greater disintegration of ore in the reduction shaft and with a failure and partly failure of the dust recirculation. In such cases still more problems can appear by the recirculated dust with the embodiment according to
FIG. 1
of the DE 37 23 137 C1 than with the device according to the DE 30 34 539 A1 since by the addition of gasifying means and coal as well as spongy iron, respectively, via a common dome cap, in which highly lower temperatures are present than within the
Andrews Melvyn
Deutsche Voest-Alpine Industrieanlagenbau GmbH
Marshall & Melhorn LLC
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