Metallurgical apparatus – With control means responsive to sensed condition – With temperature sensor
Reexamination Certificate
1999-08-23
2001-03-06
Kastler, Scott (Department: 1742)
Metallurgical apparatus
With control means responsive to sensed condition
With temperature sensor
C266S178000
Reexamination Certificate
active
06197249
ABSTRACT:
The invention relates to an apparatus for conducting gas through material to be sintered, which material is set in an essentially continuous motion, especially when said gas is used for sintering said material.
Several smelting processes require that the material to be fed into smelting is not too finely divided. Therefore a finely ground material such as a concentrate must first be pelletized and thereafter sintered in order to improve the strength of the pellets. The sintering can be carried out for instance in a conveyor-type furnace where hot gas is blown in the pellet bed in order to sinter the wet pellets. In that case, the gas penetrates only the surface layer of the bed, and the sintering of the bed remains poor. In conveyor-type sintering, there can also be used a belt that is perforated in the lengthwise direction as is described in the SE patent publication 8,704,329. Said publication applies a metal belt which is arranged in between the drawing drum and the folding drum, in the same manner as a conveyor belt. The belt is also provided with several longitudinal perforations that are spaced at given intervals from each other. When using the belt described in the SE publication 8,704,329 for sintering pellets, the pellet bed is fed to a slowly proceeding belt, first to the drying zone, then to the preheating and sintering zone and further to the cooling zone. In these zones, the pellet bed is treated with gas that penetrates the belt owing to the belt perforations. Now the pellet sintering takes place in an even fashion, if changes do not occur for instance in the belt temperature.
Generally the funnels used for controlling the gas flow in a belt sintering furnace are uniform chambers covering the whole zone, and the only way for regulating the process is to manually adjust the speed of rotation according to the temperature of the belt or of the chamber. The temperatures are measured by means of thermoelements that slowly react to the changes in the temperature. Moreover, the thermoelements only measure the temperature of gases penetrating the perforations, and not the temperature of for instance the sintering belt. In the transversal direction, the sintering belt is formed of several perforated areas through which the gases proceed, and therefore the overheating of a single area already leads to a reduction in the gas blowing. If the temperature in this overheated area is remarkably higher than in the rest of the areas, the sintering of the pellets in other areas is very poor, which makes the sintering product extremely non-homogeneous.
When gas flows in a belt sintering furnace are controlled by means of uniform chambers covering the whole zone, and when one temperature on the sintering belt surpasses a so-called alarm cooling temperature, the whole sintering process must be stopped by turning off the gas blowers and burners in the preheating and sintering zones, as well as the blowers in the cooling zones. The speed of the sintering belt cannot be essentially changed, wherefore this type of alarm cooling results, depending on its duration, in a large amount of essentially non-sintered pellets.
The object of the present invention is to eliminate some drawbacks of the prior art and to achieve an improved apparatus which is more reliable in operation for conducting gas through material to be sintered, in which apparatus the gas flow is directed so that the temperature of the member that conveys the material to be sintered can be evened out in the transversal direction of said member. The essential novel features of the invention are apparent from the appended claims.
According to the invention, in order to control a gas flow passing through the material to be sintered, which is set in an essentially continuous motion, the gas is conducted, prior to the material to be sintered, from the gas duct to a control member, so that the gas inlet of the control member is placed centrally with respect to the material to be sintered. The gas inlet also is arranged so that when gas is discharged from the gas duct to the control member, the flow direction is essentially perpendicular to the material to be sintered. The control member extends in its cross-sectional area in the gas flow direction, so that at the gas outlet, the control member extends, with respect to the proceeding direction of the material to be sintered, transversally over the sintering belt serving as the conveying member of the material to be sintered. Now the gas essentially gets into contact with the whole material to be sintered. The form of the control member also is advantageous owing to the fireproof lining. In addition, at the weakest points in the fireproof lining, there can, if necessary, be installed cooling pipes for improving the strength.
According to the invention, the gas collecting member that receives the gases that have passed through the material to be sintered is divided into several parts, so that the collecting member advantageously contains, at least in the transversal direction of the sintering belt, a number of funnel elements corresponding to the number of perforations serving as flow apertures for the penetrating gas. A funnel element is provided with an adjusting member for the gas flowing through the funnel element, and this adjusting member is advantageously controlled by a pyrometer measuring the sintering belt temperature in real time. The temperature measurement can also be carried out by some other similar known method, where it is performed sufficiently rapidly. In order to change the position of the adjusting member according to the temperature, the adjusting member is provided with a pneumatically operating cylinder. Moreover, in the wall of the funnel element, there is attached another gas flow adjusting member operated by a pneumatic cylinder, but this adjusting member is advantageously used only in a so-called emergency cooling. In that case the adjusting member attached in the funnel element wall is opened, and external cooling gas is conducted into the funnel element in order to cool the sintering belt. The adjusting members provided in the funnel element can also be operated electrically or hydraulically without essentially deteriorating the invention.
According to the invention, the temperature-controlled adjusting members connected to the funnel elements operate on the basis of the temperature, so that when the temperature is low, i.e within the range 160-200° C., the adjusting member is completely open, and respectively, when the temperature is too high, i.e. within the range 260-300° C., the adjusting member is closed, thus preventing the flowing of too hot gases and the excessive heating of the sintering belt in the funnel element in question. Because the required temperatures depend for example on the materials to be sintered, the operation of the adjusting member can also be regulated so that a specific low and high temperature range is chosen for each material.
When employing the apparatus according to the invention, the gases passing through the sintering belt can be distributed essentially evenly throughout the whole width of the pellet bed to be sintered. If the temperature at some point of the sintering belt rises, the respective adjusting member controlling this temperature begins to close, thus reducing the gas flow passing through said funnel element. If the temperature rises further and surpasses the so-called emergency cooling temperature, being for instance 30° C. higher than the temperature where the temperature-controlled adjusting member already was closed, the adjusting member provided in the funnel element wall is opened.
By means of the apparatus according to the invention, the flowing of hot gases through material to be sintered can be advantageously controlled, so that the gas flow is distributed essentially evenly throughout the whole width of the sintering belt. At the same time, the apparatus according to the invention essentially reduces the need for emergency cooling caused by an excessive heating of the sintering belt, and thus protects t
Mustikka Lauri
V{umlaut over (aa)}nänen Eero
Kastler Scott
Morgan & Finnegan , LLP
Outokumpu Technology Oy
LandOfFree
Apparatus for conducting gas through material to be sintered does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for conducting gas through material to be sintered, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for conducting gas through material to be sintered will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2486533