Plastic and nonmetallic article shaping or treating: processes – Formation of solid particulate material directly from molten... – By impinging plural liquid masses
Reexamination Certificate
1999-10-18
2001-11-20
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Formation of solid particulate material directly from molten...
By impinging plural liquid masses
C264S012000, C425S006000, C425S007000
Reexamination Certificate
active
06319434
ABSTRACT:
SUMMARY OF THE INVENTION
1. Field of the Invention
The invention relates to a process for granulating and disintegrating molten slags, in particular blast furnace slags, with water, in which a compressed water jet is directed into the slag. The invention also relates to a device for carrying out this process, comprising a slag vessel for molten slag including an outlet opening for the molten slag.
2. Description of the Related Art
A process for granulating and disintegrating molten material is described, for instance, in AT-B 400 140. In that known mode of procedure melt was introduced into a mixing chamber under pressure with compressed water vapor or water vapor mixtures having been nozzled into the mixing chamber. A configuration for realizing that mode of procedure comprised a multicomponent nozzle, wherein a pressure causing the solidified particles to be ejected via a diffuser was built up due to the rapid expansion. The kinetic energy of the particles was utilized for disintegration, to which end, for instance, baffle plates were arranged to follow the diffuser or the exit jet of the diffuser was directed against the exit jet of a further diffuser.
Besides water granulation, also processes in which the slags were spread to a low slag height or thickness and solidified by means of air or compressed air have already been proposed.
By those known processes, granulates having grain sizes of about 2 to 6 mm were obtained provided the plant technological expenditures and, in particular, the size of the plant were not to rise superproportionally. For further comminution of the material various types of mills and, in particular, jet mills have already been proposed. The applicability of jet mills does, however, presuppose that the granulates are available in a pneumatically conveyable form.
Austrian application A 1826/97 has already proposed to convey the molten slag through a slag atomizer where compressed water was fed to the molten slag. The molten slag was caused to leave a pressure-proof chamber in the free fall to get into the region of the slag atomizer, where it was granulated by substantially radially directed compressed water. The thus produced granulates were immediately transported into a counterflow mill along with vapor as well as optionally additional vapor or additional propellants. Also according to such a configuration, the disintegration operation proper was performed within the mill, wherein the molten slag had to be introduced into a vessel closeable in a pressure-proof manner before it could be transferred into the granulating device in a free jet.
SUMMARY OF THE INVENTION
The invention aims at further developing a device of the initially defined kind to the extent that slag handling is substantially facilitated and conventional means will do in the slag-charging region. At the same time, the process according to the invention is aimed to ensure a high disintegration efficiency within a small space for granulation and to produce granulates capable of being ground or further comminuted with less additional energy than would be required for conventional granulates.
To solve this object, the process according to the invention essentially comprising dissolving gases, in particular O
2
, air and/or oxygen inert-gas mixtures, in the slag prior to discharging by the compressed water jet so that iron portions of the slag are quantitatively oxidized, that the slag out through a slag outlet by the pressure of the compressed water and ejecting the slag as the jacket of the compressed water jet. By the slag being available in a slag chute or slag ladle without previous introduction into a pressure-proof vessel, the handling of the slag is substantially facilitated as compared to known proposals, wherein, due to the fact that a compressed water jet is pressed into the slag coaxially with the slag exit from the slag vessel, the water jet immerses in the slag jet over a pressure-depending depth of, for instance, about 0.5 to 1.5 m.
In this manner, kind of a soul” is formed as the water jet penetrates the slag. The evaporation of that “water soul” occurs after at a short delay sufficient for discharging the jet jacketed by solidifying or at least partially solidified slag. Relatively low mechanical demands are set on such a discharge, the emergence of the slag being substantially simpler to realize than with complicated multicomponent nozzles. The exit of the slag jet discharged with a “water soul” is immediately followed by the boiling, as well as the abrupt and explosion-like evaporation, of the water with the kinetics of the intruded water jet overcoming relatively high counter pressures. With the explosion-like widening of the jet at temperatures of about 800 to 1200° C., a high degree of disintegration is ensured by the simultaneous glassy solidification of the granulates.
Blast furnace slag to be granulated generally has a low content of residual pig iron, which is smaller than 0.5% by weight under correct process control. In the event of improper blast furnace operation control, the content of pig iron may, however, rise to as much as 5% by weight. The oxidation of iron portions by oxygen or air reduces the risk of explosions due to the formation of hydrogen gas. A considerably enhanced disintegration effect additionally occurs on account of the solubility of gases in the slag and, in particular, the saturation of the slag with gases. The solubility of gases strongly decreases as the slag temperature drops such that the explosion-like demixing of the dissolved gases due to the falling slag temperature and hence the rapid decrease of the saturation concentration of gases in the molten slag is additionally observed in the region of abrupt cooling by the compressed water jet. The gases thus released from the solidifying slag expand vigorously on account of the relatively high temperatures with an enhanced disintegration of the slag particles being observed. At ambient pressure and 1000° C., approximately 11.2 m
3
air or nitrogen/ton of slag are, for instance, formed by such a release of dissolved air, wherein the internal slag gas pressure presumably may range from some 100 bars to more than 1000 bars. Slag particle sizes all below 0.1 mm are immediately obtained in this manner, wherein, in addition, such a slag on account of its porosity may subsequently be further disintegrated by the abruptly released and originally dissolved gases at less expenditures and less energy consumption.
Advantageously, the process according to the invention is carried out in a manner that the compressed water is introduced at a pressure of from 35 to 160 bars. In this manner, it is ensured that the “water soul” is formed over a length sufficient for the jacketed jet to safely leave the outlet part of the slag vessel or a slag tundish, thereby protecting the outlet part from excessive mechanical stress.
Further enhancement of the disintegration effect and of granulation may be obtained in that the solidified jacket of the slag surrounding the compressed water jet is cut or split by additional compressed water.
Basically, it is feasible by the mode of operation according to the invention to immediately obtain a pneumatically conveyable mixture such that after the expansion of the slag particles a mixture is provided in an expansion vessel by collecting these slag particles together with the expanding gases, which mixture may be directly introduced into gas counterflow mills and could be supplied to further disintegration. The vapor forming may be used as a propellant together with the gases forming by degasification and originally dissolved in the slag. In particular, when using additional compressed water jets for cutting or splitting the jet, also the problem of sealing between a connected expansion vessel and a slag tundish is particularly easy to resolve by a seal being accomplishable in the manner of a pneumatic seal and remaining untight spots as throttle cross sections enabling efficient sealing, taking into account the high pressures prevailing.
The device according to the invent
"Holderbank" Financiere Glarus AG
Joyce Kevin E.
Theisen Mary Lynn
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