GB2048444A - Cooling of tuyeres in blast furnaces - Google Patents

Abstract

A tuyere for use in a blast furnace, the tuyere being provided with a plurality of heat pipes (16) for transmitting heat away from the nose portion of a body part (10). In order that the heat pipes (16) can operate efficiently they may be disposed in such a way that they all incline downwardly towards the nose portion of the body part (10). In order that the heat pipes (10) can operate at their maximum heat removal capacity they may be provided with internal ribs which increase their internal surface area. <IMAGE>

Description

SPECIFICATION Cooling of tuyeres in blast furnaces The invention relates to the cooling of tuyeres in blast furnaces and has for its object to provide an improvement therein.

The tuyeres of blast furnaces are nozzles for blasts of air blown into the furnace during its operation to provide the necessary reaction with the coke therein. This generates intense heat for the operation of the furnace. The tuyeres are subjected to very severe operating conditions and it is necessary for heat to be transmitted away from them at a very high rate throughout the operation of the furnace.

For this reason they are invariably made of copper and in the past it has been commonplace to transfer the heat away by the use of water flowing through passages formed in the walls of the tuyeres and extending into their nose portions, that is to say, those portions which project into the furnace environment and which are therefore extremely vulnerable.

Failure of a tuyere does occur from time to time due to molten metal locally burning through the copper at the nose portion and breaking into one or more of the passages carrying cooling water. At such a time the flow of cooling water must be immediately shut off and this then results in the total destruction of the tuyere. This failure is inconvenient for two reasons. Firstly, large quantities of water in the furnace cause cooling of the iron therein and oxidation of the carbon refractories. Secondly, the need for frequent interruption of the furnace operation to enable the replacement of the tuyere to be carried out is both costly and troublesome. The present invention aims to at least alleviate such difficulties which have been encountered in the past.

According to one aspect of the invention, there is provided a tuyere for use in a blast furnace, the tuyere being provided with a plurality of heat pipes (that is to say low pressure, boiling/condensing units) extending generally longitudinally of the tuyere between its wall thickness rearwardly from its nose portion, or alternatively, the tuyere being constituted by the evaporator (heat input) ends of a plurality of hollow segments each of which constitutes a heat pipe. The heat pipes or hollow segments, as the case may be, may be of such a configuration that their internal surface areas are as great as possible and the transfer of heat from the tuyere is thereby facilitated, for example by said heat pipes or hollow segments being internally ribbed, the aspect ratio of the ribs, that is to say their radial depth in relation to their width, prefera bly being at least 2:1.Condenser (heat re moval) sections of the heat pipes or of said hollow segments, as the case may be, may extend outwards from a back face of the tuyere for connection to heat transfer apparatus located remote from said tuyere and wholly outside the furnace in which the tuyere is fitted. Alternatively, the tuyere itself may be formed with a heat exchange chamber through which a flow of cooling water can be maintained, the heat exchange chamber being located between the wall thickness of the tuyere and near its back face, the condenser (heat removal) sections of the heat pipes extending into or through said heat exchange chamber.

According to another aspect of the invention, there is provided a blast furnace with tuyeres which are each provided with a plurality of heat pipes (that is to say low pressure, boiling/condensing units) extending generally longitudinally of the tuyere between its wall thickness and connected to heat transfer apparatus, or alternatively, each tuyere being constituted by a plurality of hollow segments each of which constitutes a heat pipe. The heat pipes or hollow segments, as the case may be, will preferably be of such a configuration that their internal surface areas are as great as possible so that the transfer of heat from the tuyere is thereby facilitated. Preferably, the said heat pipes or hollow segments will be internally ribbed, the aspect ratio of the ribs, that is to say their radial depth in relation to their width preferably being at least 2:1.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a diagrammatic sectional view of a tuyere embodying the invention, Figure 2 is a diagrammatic illustration of a heat pipe, Figure 3 is a sectional view, drawn to a greatly enlarged scale, of a part of a heat pipe which will presently be referred to, Figures 4 and 5 are diagrammatic side and end views which will presently be referred to, Figures 6 and 7 are views similar to Figs. 4 and 5 which will be referred to when describing a possible modification, Figure 8 is a longitudinal section through a different construction of tuyere embodying the invention, and Figure 9 is a sectional view on the line 9-9 in Fig. 8.

Referring now to Fig. 1 of the drawings, the tuyere there illustrated comprises a frusto con ical section copper casting 10 provided with a plurality of heat pipes 1 2 extending generally longitudinally of the tuyere between its wall thickness and projecting from an outer end of the tuyere for connection to heat transfer apparatus generally indicated 1 4. Only two of the heat pipes are shown in Fig. 1, but it will be understood that the heat pipes are closely spaced around the circumference of the tuy ere. The tuyere is shown to extend through the wall of a blast furnace (shown in chaindotted lines).

Each heat pipe is a sealed, low pressure, boiling/condensing tubular unit utilising capillary action for condensate return to an evaporator (heat input) section from a condenser (heat removal) section. Such units are commercially available. A heat pipe is illustrated diagrammatically in Fig. 2 and is shown to include a hollow tube 1 6 with closed ends and a lining material constituting a wick 18.

The tube has been evacuated of air and a quantity of a suitable working fluid has been introduced into the tube before it has been sealed. It will also be seen that, as drawn in Figs. 1 and 2, the heat pipes appear to be of plain cylindrical form. In Fig. 3, which is a much enlarged view of part of the cross section of one of the heat pipes which extend through the tuyere of Fig. 1, it will be seen that these special purpose heat pipes are of such a configuration that their internal surface areas are as great as possible by the provision of internal ribs which extend longitudinally of the heat pipes. The aspect ratio of the ribs, that is to say their radial depth in relation to their width, is approximately 2:1. It will be understood that the internal ribbing of the heat pipes in this way facilitates the transfer of heat from the tuyere.However, it will be understood that such internal ribbing may not always be required and that plain cylindrical heat pipes are adequate for the required heat removal.

The heat transfer apparatus 14, includes a heat exchange chamber 20 located wholly outside the furnace and surrounding the uppermost portion of at least one of the heat pipes, the chamber 20 being provided with flow and return pipes 22 and 24 for the circulation of cooling water through the chamber. However, it will be understood that if the heat pipes extend only within the walls of the body portion of the tuyeres the flow of cooling water may extend through flow channels surrounding the rearward portions of the heat pipes within the body of the tuyere.

Referring to Figs. 4 and 5, these views, which are diagrammatic only, illustrate how the plurality of heat pipes extend generally longitudinally of the tuyere between its wall thickness, the pipes being equally spaced apart at the front end but not equally spaced at the rear end of the tuyere. However, in Figs. 6 and 7, which are views similar to Figs.

3 and 4, there is illustrated a possible modification in which although the heat pipes are equally spaced apart around the front end of the tuyere (that is to say the narrower end which is to extend into a furnace) they are gathered together at the rear end of the tuyere before extending upwards into the heat transfer apparatus. This may be advatageous because it ensures that the euaporator (heat input) section of all the heat pipes, that is to say even the lowermost ones, are downwardly inclined so that the working fluid can return from the condenser (heat removal) sections assisted by gravity along the entire length of each pipe.

Referring now to Figs. 8 and 9, in a rather different construction of tuyere, the doublewalled frusto-conical body part is constituted by the evaporator (heat input) ends of a plurality of hollow segments 26 abutting together side by side, each of said segments constituting a heat pipe. As in the previously described embodiments, the uppermost portions (not shown) of the heat pipes, that is to say, the condenser (heat removal) sections, will be associated with heat transfer apparatus. The tuyere is again shown extending through the wall of a blast furnace (shown in chain-dotted lines). The hollow segments will be provided with internal ribs (not shown) in much the same manner and for the same purpose as those of the heat pipes provided in the tuyere of Fig. 1.

Various modifications may be made without departing from the scope of the invention. In all the embodiments illustrated it will be understood that refractory cladding may be employed to protect the tuyere from damage by sudden high heat fluxes. Although the tuyeres described have been said to be made from copper it will be understood that they could be made from other metals.

Claims (9)

1. A tuyere for use in a blast furnace, the tuyere being provided with a plurality of heat pipes (that is to say low pressure, boiling/condensing units) extending generally longitudinally of the tuyere between its wall thickness rearwardly from its nose portion, or alternatively, the tuyere being constituted by the evaporator (heat input) ends of a plurality of hollow segments each of which constitutes a heat pipe.

2. A tuyere according to claim 1, in which the heat pipes or hollow segments, as the case may be, are of such a configuration that their internal surface areas are as great as possible and the transfer of heat from the tuyere is thereby facilitated.

3. A tuyere according to claim 2, in which the heat pipes or hollow segments are internally ribbed, the aspect ratio of the ribs, that is to say their radial depth in relation to their width, being at least 2:1.

4. A tuyere according to any one of the preceding claims, in which condenser (heat removal) sections of the heat pipes or of said hollow segments, as the case may be, extend outwards from a back face of the tuyere for connection to heat transfer apparatus located romote from said tuyere and wholly outside the furnace in which the tuyere is fitted.

5. A tuyere according to any one of claims 1 to 3 in which the tuyere is formed with a heat exchange chamber through which a flow of cooling water can be maintained, the heat exchange chamber being located between the wall thickness of the tuyere and near its back face, the condenser (heat removal) sections of the heat pipes extending into or through said heat exchange chamber.

6. A blast furnace with tuyeres which are each provided with a plurality of heat pipes (that is to say low pressure, boiling/condensing units) extending generally longitudinally of the tuyere between its wall thickness and connected to heat transfer apparatus, or alternatively, each tuyere being constituted by a plurality of hollow segments each of which constitutes a heat pipe.

7. A blast furnace according to claim 6, in which the heat pipes or hollow segments, as the case may be, are of such a configuration that their internal surface areas are as great as possible so that the transfer of heat from the tuyere is thereby facilitated.

8. A blast furnace according to claim 7, in which the heat pipes or hollow segments are internally ribbed, the aspect ratio of the ribs, that is to say their radial depth in relation to their width being at least 2:1.

9. A tuyere for use in a blast furnace, the tuyere being constructed, arranged and adapted to operate substantially as hereinbefore described, with reference to and as illustrated by Fig. 1, Figs. 1 to 3 in combination, Figs. 4 and 5, Figs. 6 and 7 or Figs. 8 and 9 of the accompanying drawings.