GB2069678A - Process and device for regulating the temperature of the hot air in an installation for the production of hot air - Google Patents

Abstract

The temperature of the hot air (22) emerging from a cowper of an installation for the production of hot air is controlled by mixing cool air from the main supply pipe (16) with the hot air produced in the chamber (34) during the air cycle. A pipe (30) with a regulating valve (32) leads the cool air to valves (26) in the cowper burners (10) and so into the chamber (34). Valves (32 and 26) are regulated to maintain the desired temperature of the hot air output. <IMAGE>

Description

SPECIFICATION Process and device for regulating the tem- perature of the hot air in an installation for the production of hot air The present invention relates to a process and a device for regulating the temperature of the hot air in an installation for the production of hot air, with at least one pair of Cowpers, each cowper comprising, inter alia, a checkerwork shaft mainly occupied by a stack of refractory bricks and provided at its base with an inlet orifice for the cold air and an outlet orifice for the combustion fumes, a hot air outlet orifice being provided at the top of the shaft, and one or more burners mounted either above the checkerwork shaft or in a combustion shaft, and a monitoring device for the temperature of the hot air provided by the installation, this process comprising a combustion period, consisting of the operation of burning a combustible gas in each of the burners, for the purpose of heating the checkerwork shaft, and an air period, consisting of the introduction of cold air at the base of the checkerwork shaft and of the extraction, from the top of the shaft, of the heat which on its passage through the checkerwork has recuperated the heat which was stored in the latter during the combustion period, a certain quantity of cold air being mixed into the hot air, this quantity being regulated in accordance with the temperature detected by the temperature monitoring device in order to ensure that it remains constantly equal to a certain preselected temperature.

It is known that in the case of a blast furnace, for example, the hot air is conveyed into a circular pipe feeding the individual tuyeres through which the hot air is injected into the furnace for the purpose of maintaining the process inside the latter. To enable the operation of the furnace to be faultlessly controlled the temperature of the hot air must be kept constant or must at all events be controllable. Now the hot air produced in an assembly of cowpers of this kind does not have a temperature which remains constant throughout the air period. There may also be a temperature difference between the hot air produced in one of the cowpers and that produced in another. In order to eliminate these hot air temperature fluctuations the present installations comprise a mixing station upstream from the circular pipe and downstream from the cowpers.In this mixing station the hot air is given an addition of that quantity of cold air which is required in order to keep the temperature in the circular pipe constant, this being known as the regulated hot air temperature. If the hot air is to be set to a temperature of 1 250 C, for example, as is the case in the present-day blast furnaces, a temperature of 1400"C must be obtained in the refractory checkerwork, at least in the upper part thereof.

The purpose of the present invention is to provide a new mixing process enabling the hot air production installation to be considerably simplified. For this purpose, the process to which the present invention relates is characterized by the fact that the mixture is effected inside the cowper enclosure. This enables the entire mixing station to be dispensed with.

In one advantageous embodiment the mixture is carried out immediately above the refractory checkerwork, and mixing air being introduced through the burners, both in cases in which these latter are mounted in a combustion shaft and in cases in which they are positioned in the arch of the cowper, immediately above the checkerwork. The mixing air will preferably consist of part of the cold air, the quantity required for the mixing being taken from the main cold air inlet pipe.

The installation for the performance of the process is essentially characterized by an auxiliary pipe connecting at least one of the burners to a main cold air inlet pipe at the base of the checkerwork shaft and by a regulating valve in the said auxiliary pipe, the position of this valve being automatically controlled in accordance with the temperature monitoring device.

Further features and characteristics of the invention will emerge from the description of an embodiment thereof, by reference to the accompanying drawings, wherein Fig. 1a and Fig. 1 b illustrate an example of a cowper without combustion shaft, with burners in the cupola, of the type described in the Luxembourg Patent No 82,176. In should nevertheless be pointed out that the invention is not confined to this specific example.

The cowper shown in the diagram and marked 2 as a whole essentially consists of a checkerwork shaft 4 surmounted by a chamber 6 and separated from the latter by a transverally slab 8 of refractory material. This slab supports a number of burners 10, of which there are four in the example shown, situated inside the chamber 6. The burners 10 are fed with combustible gas through an external circular pipe 1 2 and with combustion air through a central pipe 1 4 connected radially to each of the burners.

The diagram also shows a main pipe 1 6 which conveys the cold air to the base of the cowper. This pipe communicates with the checkerwork shaft 4 via a main gate 1 8 and an auxiliary gate 20. The hot air emerges from the checkerwork shaft via a side opening 22, which can be connected to the circular hot air pipe of a blast furnace.

In the embodiment shown in the diagram a cooling system and pressurization system for the chamber 6 has been adopted, this being analogous to the example shown in Fig. 6 of the aforementioned patent. Fot this purpose the combustion air pipe 14 has first of all been enabled to communicate with the interior of the chamber 6 via a set of valves 24.

An additional set of valves 26 regulates the passage between the pipe 14 and each of the burners 10. The circulation in the chamber 6 is ensured by evacuating the air via a pipe 28 either to the atmosphere or to the base of the checkerwork shaft 4, for the purpose of recycling it with the cold air. During the combustion period, therefore, combustion air is caused to circulate not only in the burners but also around the latter and inside the chamber 6, for cooling purposes.

With a view to the pressurization of the chamber 6 and to enable it to be cooled during the air period an auxiliary cold air pipe 30 is provided, connecting the main pipe 1 6 to the combustion air feed pipe of the burners 10 via the gates 18 and 20. This pipe 30 likewise comprises a regulating valve 32 serving to determine the rate of flow in the pipe 30. For more complete details concerning the operation of the system, particularly the cooling and the pressurization, reference should be made to the patent specification mentioned farther back.

In the present invention the mixing of the hot air and a certain quantity of cold mixing air is effected, for the purpose of retaining a regulated temperature for the hot air. inside the enclosure of the cowper 2 and, in the particular case illustrated in the accompanying diagram, in a chamber 34 formed between the upper surface of the checkerwork shaft 4 and the lower surface of the slab 8 supporting the burners. In this particular case the existence of the pipe 30 can be utilized in order to convey a certain quantity of cold air through the pipe 14 and the burners 10 into the chamber 14. Consequently, both the cooling air of the chamber 6 and the pressurization air of this chamber 6, as well as the mixing air, are formed by a certain quantity of cold air branched off from the main pipe 16.

The operation of regulating the total quantity required for the cooling, pressurization and mixing process is regulated by means of the valve 32. The required proportion between the mixing air on the one hand and the cooling air and equalization air on the other is obtained by means of the two sets of valves 24 and 26. If, for example, the device for monitoring the temperature of the hot air in the circular pipe. this device not being shown, detects an ascending tendency in the temperature of the hot air, the quantity of mixing air has to be increased in order to restore the temperature to the desired level. For this purpose the valve 32 and also the valve 26 will be open.

Independently of this operation, the valve 24 can also be actuated for the purpose of providing the required cooling for the chamber 6.

If on the other hand, the hot air temperature monitoring device detects a descending tendency in the regulated temperature of the hot air, all that is required is to close the valve 32, in order to reduce the rate of flow in the pipe 30 and at the same time reduce the quantity of mixing air. If the reduction of mixing air has to be accompanied by an increase in the quantity of cooling air, in order to provide the necessary cooling for the chamber 6, the valves 24 can be opened to a greater extent and the valves 26 closed to a greater extent without changing the position, of the valve 32.

Needless to say, the operations of the valves are effected automatically in accordance with the indications provided by the hot air temperature monitoring device for the circular pipe, on the one hand, and a further temperature monitoring device in the chamber 6 on the other.

In the case of a conventional cowper with a combustion shaft, whether the latter is separated from or incorporated therein, it is likewise possible to introduce the mixing air through the burner or burners by connecting them via an auxiliary pipe. analogous to the pipe 30, to the main cold air inlet pipe. It is nevertheless obvious that the system proposed by the invention is particularly advantageous in the case of a construction such as that illustrated in the diagram or in the case of other constructional versions proposed in the aforementioned patent specification since use is made of the presence of the cooling circuits and since the mixing operation and the cooling operation can be thus combined together.

In other words, hot air with a regulated temperature is obtained without recourse to any mixing station and without the necessity of any supplementary equipment.

Claims (10)

1. A process for regulating the temperature of the hot air in an installation for the production of hot air, with at least one pair of cowpers, each cowper comprising, inter alia, a checkerwork shaft mainly occupied by a stack of refractory bricks and provided at its base with an inlet orifice for the cold air and an outlet orifice for the combustion fumes, a hot air outlet orifice being provided at the top of the shaft, and one or more burners mounted either above the checkerwork shaft or in a combustion shaft, and a monitoring device for the temperature of the hot air provided by the installation, this process comprising a combustion period, consisting of the operation of burning a combustible gas in each of the burners, for the purpose of heating the checkerwork shaft, and an air period consisting of the introduction of cold air at the base of the checkerwork shaft and of the extraction, from the top of the shaft, of the heat which on its passage through the checkerwork has recuperated the heat which was stored in the latter during the combustion period, a certain quantity of cold air being mixed into the hot air, this quantity being regulated in accordance with the temperature detected by the temperature monitoring device in order to ensure that it remains constantly equal to a certain preselected temperature, wherein said mixture is effected inside the enclosure of the cowper.

2. A process in accordance with claim 1, wherein the mixture is effected immediately above the refractory checkerwork.

3. A process in accordance with either of claims 1 or 2, wherein the mixing air is introduced via the burner or burners.

4. A process in accordance with either of claims 1 to 3, wherein the mixing air is formed by part of the cold air which has branched off from a main cold air inlet pipe at the base of the checkerwork shaft.

5. A device for the performance of the process described in either of claims 1 to 4, comprising an auxiliary pipe connecting at least one of the burners to a main cold air inlet pipe at the base of the checkerwork shaft and a regulating valve mounted in the said auxiliary pipe, the position of this valve being controlled automatically in accordance with the temperature monitoring device.

6. A device in accordance with claim 5, wherein the auxiliary pipe is connected to the burners via a combustion air inlet pipe in which regulating valves are provided.

7. A device in accordance with either of claims 5 or 6, wherein the burners are mounted on a transversal slab above the checkerwork shaft and wherein the mixture is effected in a mixing chamber defined between the slab and the upper surface of the checkerwork.

8. A device in accordance with claim 7, wherein the auxiliary pipe consists of the pipe through which cold air is conveyed as cooling air and pressurization air into the upper part of the cowper above the slab.

9. A process substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

10. A device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.