Metallurgical apparatus – Means for treating ores or for extracting metals – By means applying heat to work – e.g. – furnace
Patent
1992-12-07
1994-03-01
Kastler, Scott
Metallurgical apparatus
Means for treating ores or for extracting metals
By means applying heat to work, e.g., furnace
266190, F27D 112
Patent
active
052900169
DESCRIPTION:
BRIEF SUMMARY
The invention concerns an arrangement for cooling vessel portions of a furnace, in particular a metallurgical furnace, comprising a cooling box which is fitted into a wall or cover region to be cooled or which forms a wall or cover region and which, towards the interior of the furnace, has a heat exchange plate and, in opposite relationship thereto and spatially distributed, a plurality of spray nozzles for spraying a cooling fluid onto the heat exchange plate, and also an outlet for the cooling fluid.
An arrangement of that kind with a steel plate as the heat exchange plate is known for example from EP 0 044 512 A1 or EP 0 197 137 B1. In the arrangement described in the first-mentioned specification, individual or group-wise control of the spray times of the nozzles means that the amount of cooling fluid which is sprayed against the heat exchange plate is only such that the sprayed cooling fluid is essentially evaporated and thus the enthalpy of evaporation is utilised to give the cooling action. In the other arrangement, the amount of cooling fluid sprayed against the heat exchange plate is such that it still remains substantially in its liquid form. In that case the coolant consumption is substantially higher than in the first-mentioned case.
Besides spray cooling, it is also known for example from DE 26 59 827 B1, DE 28 17 869 B2 and DE 38 20 448 A1, in relation to cooled wall or cover elements for metallurgical furnaces, for the heat to be removed from the heat exchange surface of the cooling elements by way of a forced cooling water flow. Particularly in the case of furnaces in which the heat exchange plate is exposed to strong fluctuations in respect of time and location of the thermal loading involved, such cooling water systems require a substantially larger amount of cooling fluid than spray-cooled systems in order to prevent a film boiling phenomenon, that is to say, the occurrence of thin insulating layers of vapour at locations on the heat exchange surface which are subjected to a heavy thermal loading. That effect would result in damage to the cooling element in that region.
DE 38 20 448 A1 describes inter alia a cooled wall element for metallurgical furnaces, in particular electric arc furnaces, which includes a steel plate which is provided on one side with a plating of copper or a copper alloy and which, on the surface remote from the plating, is fitted with shaped metal members forming coolant ducts. The layer of copper on the side of the wall element which is towards the inside, by virtue of the high level of thermal conductivity of copper, is intended to provide for very rapid transmission of the heat received, uniform distribution of the heat and rapid removal of the heat so as to prevent material damage, even in the event of local overheating occurring. In addition, the layer of copper which is preferably applied in a thickness of between 6 and 10 mm remains ductile and prevents the formation of cracking in the wall of the cooling element.
In the spray cooling systems which are set forth in the opening part of this specification and which are distinguished by a greatly reduced level of coolant consumption in comparison with cooling systems wit a forced cooling fluid flow, there is the problem that the dissipation of heat from the heat exchange plates does not take place uniformly. By virtue of the spatially distributed arrangement of individual spray nozzles and in addition the need which sometimes arises, for reasons of space, for individual nozzles to be arranged inclinedly, so that they only spray the cooling fluid against the heat exchange plate at an inclined angle, the heat exchange plate is acted upon by the coolant in an irregular fashion. The heat exchange plate is cooled to a substantially greater degree at the locations at which the cooling fluid is sprayed thereagainst, than in the regions therebetween. In order to prevent the admissible temperature being exceed at the locations which are less heavily cooled, it is necessary to operate with a larger total amount of coolant
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Ameling et al. "Water-cooled sidewall elements in UHP arc furnaces" Stahl u. Eisen vol. 98 No. 9, pp. 429-434; (Dec. 1978).
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