Glass manufacturing – Processes – Slag – utilization
Reexamination Certificate
2000-08-01
2001-11-20
Colaianni, Michael (Department: 1731)
Glass manufacturing
Processes
Slag, utilization
C065S020000, C065S021100, C065S141000, C065S142000, C065S128000, C065S130000, C065S329000, C065S330000, C588S251000, C266S201000, C241S016000, C241S038000, C425S007000
Reexamination Certificate
active
06318123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for granulating liquid slag melts, in particular blast furnace slag, wherein the melt is ejected into a cooling chamber via a slag tundish and wherein fluid under pressure, in particular compressed gas, vapor or pressurized water, is injected in the direction of the slag exit in order to eject said liquid slag, as well as a device for carrying out this method.
2. Prior Art
In order to granulate and disintegrate molten slags, it has already been proposed to eject the same into granulation spaces by the aid of vapor or a propellant with further comminution subsequently being effected also in jet mills using propellant jets. Based on slag temperatures of between 1400° and 1600° C., the relatively large temperature difference between the propellant gas stream and the molten slag involves the risk of the formation of more or less large agglomerates as well as the danger of thread formation, which will consequently increase the comminution work and considerably reduce the cooling rate. The proposals made so far were primarily based on the object to accomplish the cooling of the molten slags as rapidly as possible, such proposals having, of course, been impaired by the formation of agglomerates and threads.
According to another unpublished proposal made by the Applicant, the liquid slag was ejected into the granulation space by the aid of combustion offgases in order to reduce the danger of the slag exit opening from the slag tundish to be obstructed by solidifying slag. By such a mode of procedure, the slag particles injected into the granulation space get into a consecutively arranged cooling zone at substantially higher temperatures, which higher temperatures bring about a reduced slag viscosity and a reduced surface tension of the slag droplets such that a finer division of the slag droplets is being obtained as the latter enter the cooling zone. The fine dispersion of slag droplets results in accordingly small droplets having relatively high specific surfaces such that cooling may be achieved in smaller-structured cooling chambers. Yet, the installation of burners in the region of the slag spout of the tundish involves high structural and apparative expenses.
SUMMARY OF THE INVENTION
The invention aims to further reduce, and render adjustable to the respective requirements within wide limits, the particle size of the ejected dispersion when using fluid under pressure for ejecting liquid slags from a slag tundish into a consecutively arranged granulation chamber in which cooling takes place as well. In particular, the invention aims to form such fine-particle slag droplets which, as a result, render feasible to obviate the injection of water as a whole and to effect cooling exclusively by radiation cooling means. To solve this object, the mode of procedure according to the invention essentially consists in that the pressure fluid jet discharges into a throttle pipe which is immersed in the slag bath and whose lower edge is mounted so as to be adjustable in the height direction. By the pressure fluid jet discharging into a throttle pipe which is immersed in the slag bath and whose lower edge is mounted so as to be adjustable in the height direction, it has become feasible to impart on the molten slag streaming in from the slag tundish the form of a thin-walled jacket of a slag jet, wherein the wall thickness of such a tubular slag jet may be substantially influenced by varying the height adjustment of the lower edge of the throttle pipe. Due to the fact that, as a rule, a pressure fluid jet of the appropriate temperature, for instance, formed by hot combustion offgases, compressed gas, vapor or pressurized water is coaxially directed into the axis of this tubular slag jet, particularly fine divisions and dispersions may be provided with particle sizes of below 10 &mgr;m being obtainable. Such fine particles, as a result, will yield microgranulates having a grain size distribution of 10 to 500 &mgr;m, wherein, due to the particularly fine division, it will usually do to exclusively use radiation coolers for solidifying the droplets.
According to a preferred mode of procedure, the throttle pipe space surrounding the pressure fluid jet discharge may be kept under a negative pressure. By that measure an even finer division may be achieved, whereby a pulsating jet may be obtained, in particular, if the supply of ambient air from the throttle pipe entrained by the propellant jet, in turn, is accordingly throttled itself. By appropriately tuning the pressure ratios in the space surrounding the fluid jet and adjusting the height of the lower edge of the throttle pipe accordingly, a controlled oscillation procedure may be triggered with a small amount of air each being sucked in, thus causing oscillation pulses to be generated in the space surrounding the mouth of the fluid jet, which is configured as a negative-pressure chamber. Therefore, pulses are imparted on the slag jet for the formation of droplets with periodic pressure impacts being superimposed, leading to a further comminution of the droplets. The pulse frequency may be tuned to the slag viscosity and the surface tension, wherein said pulse frequency may be influenced by the length of the throttle pipe, the speed of the propellant, the air flow rate, the pressure difference between the negative-pressure chamber and the counter pressure established within the granulation space, the rheology of the slag and, in particular, the surface tension as well as the temperature of the propellant and the choice of the propellant. By suitably selecting these parameters even ultrasonic vibrations aimed at a superfine disintegration with droplet sizes of less than 1 &mgr;m may be formed. To this end, the method advantageously is carried out in a manner that the amount of air sucked into the hollow space of the throttle pipe is dimensioned for the formation of oscillation pulses, wherein, preferably, gas or hot gas is fed to the lance under a pressure of 3 to 7 bars.
The device according to the invention for granulating liquid slag melts, in particular blast furnace slag, in which the melt is ejected into a cooling chamber via a slag tundish and in which fluid under pressure, in particular compressed gas, vapor or pressurized water, is applied or introduced by means of a lance in the direction of the slag exit in order to eject said liquid slag, is essentially characterized in that the lance is surrounded by a height-adjustable throttle pipe whose lower edge is immersed in the slag bath contained in the tundish and forms a throttling cross section between the slag exit and the slag bath. By employing a height-adjustable throttle pipe it is feasible, as mentioned in the beginning, to adapt to the respective requirements the wall thickness of the tubular slag jet formed. In order to induce suitable resonance processes as well as oscillations overlaying said ejection, the configuration advantageously is devised such that the throttle pipe is designed to be closed on its side facing away from the slag bath and is connected with a gas duct, in particular an air duct, via an adjustable and closeable throttle valve. Depending on the position of that throttle valve, a more or less small negative pressure will be maintained within the throttle pipe, wherein the configuration advantageously is devised such that the throttle pipe is designed as a resonance pipe whose length and whose throttling cross section are dimensioned for the sucking in of air aimed at the generation of ultrasonic vibrations.
On account of the extremely small slag droplets obtainable in this manner it may consequently do to exclusively use radiation coolers, the configuration preferably being devised such that at least one radiation cooler and a discharging sluice for granulates are connected to the exit opening of the slag tundish.
A particularly intensive and small-structured granulation chamber in that case is essentially configured in a manner that a first radiation cooler is designed as a h
Colaianni Michael
Joyce Kevin E.
“HolderBank”Financiere Glarus AG
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