GB1561119A

GB1561119A - Injection of fuels into tuyeres

Info

Publication number: GB1561119A
Application number: GB210477A
Authority: GB
Original assignee: Esso SA
Current assignee: Esso SA
Priority date: 1976-01-23
Filing date: 1977-01-19
Publication date: 1980-02-13
Also published as: LU76631A1; BE850674A; IT1080423B; FR2339136A1; FR2339136B1

Description

(54) IMPROVEMENTS IN THE INJECTION OF FUELS INTO TUYERES (71) We, ESSO SOCIETE ANONY ME FRANCAISE, a body corporate duly organised under the laws of France, of 6 Avenue A. Prothin, 92 Courbevoie, France, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an improved method and apparatus for the injection of fuel into a tuyere and in particular to a method and apparatus which results in improved combustion of the fuel in the tuyere. The invention is particularly concerned with the injection of fuel into blast furnaces.

In a blast furnace iron ore is reduced and melted by heat generated by the burning of a special metallurgical coke by preheated air injected at the bottom of the furnace.

Generally, the ore and coke are arranged in horizontal layers so that the coke supports as well as heating the iron ore. As the ore is converted to the metal the charge descends in the furnace and is replenished from the top.

The metallurgical coke that is used is expensive and furthermore takes up a considerable volume of the furnace thus limiting the quantity of iron the furnace is capable of producing. Attempts have therefore been made to reduce the quantity of coke used in the furnace and one method has been to achieve some of the heating by the injection of fuel oil into the furnace.

Various lances consisting of a tube ending in an injector have been proposed for the injection of the fuel. For example, lances are known which convey fuel through the wall of a tuyere, atomise the fuel, and deliver the atomised fuel into the tuyere in, or at a very small angle to, the general longitudinal direction of the hot blast flowing through the tuyere into the furnace.

The lances most commonly used are shown diagrammatically in Figures 1, 2, 3 of the accompanying drawings in which Figure 1 illustrates an injector with axial pneumatic atomising, Figures 2-2a illustrate an injector for axial mechanical atomising and Figures 3-3a illustrate another type of injector for axial mechanical atomising.

By reference to Figure 1, it will be seen that the mixture of propellant gas and fuel admitted coaxially furnishes at the downstream end of the lance 1, a fuel jet which is carried along into the hot blast flowing along the tuyere (not shown) in the same direction and the same sense as the hot gas blast.

In the case of figure 2 (figure 2a being the view at the end of the downstream extremity of the rod la), the jet of fuel emerging in the form of a divergent cone through the combined effect of pressure and a mechanical device is sprayed into the hot blast flowing along in the tuyere (not shown).

In the variant illustrated in Figure 3 (figure 3a being a view of the downstream extremity of the lance lib), the fuel jet emerging from the orifice 1c is sprayed under pressure into the hot blast flowing along in the tuyere (not shown).

These known lances, which are known as axial injection lances, have the drawback of furnishing very long flames, which lead to the appearance of carbon black or soot with high rates of fuel injection. This soot tends to clog and choke the distributing circuits, to reduce the combustion yield and to be present in the blast furnace gases and then in the decantation tanks of the gas washing liquor.

It has been proposed to overcome this problem by the radial injection of fuel, or by injecting a fuel/air mixture axially into the furnace. A known injector of the radial injection type is illustrated in figures 4-4a, representing diagrammatically a rod or tube of uniform bore 1d closed at its downstream extremity and provided radially in the vicinity of that extremity, with one or more orifices such as le. The fuel admitted to the rod or tube under pressure forms, at a lesser pressure, at the outlet from these orifices jets of fuel which are sprayed radially in respect of the axis of the tuyere into the hot blast in the tuyere (not shown).

Although this radial injection solves certain difficulties it suffers from the disadvantage that it requires a sufficient rapid delivery of fuel to avoid cracking of the fuel in the rod or tube or in the injector and therefore the choking of the orifices by the coke formed. However, as fuel delivery speed rises it becomes increasingly difficult to obtain a homogenous dispersion of the fuel in the hot blast which leads to incomplete fuel combustion and the production of carbon deposits.

It is an aim of the present invention to provide a means for introducing fuel into the tuyere which overcomes the problems of the current axial and radial systems described above and which leads to improved combustion of the fuel and thus greater efficiency and reduced deposits.

The present invention, in one aspect, provides a process for injecting fuel into a tuyere, comprising atomising the fuel in a fluid, increasing the velocity of the thus atomised fuel and thereafter, without any subsequent decrease in its velocity, injecting the atomised fuel into a gaseous stream in the tuyere, said fuel being injected at an angle between 60 and 1200 to the general longitudinal direction of flow of the gaseous stream in the tuyere.

The fluid in which the fuel is atomised may be a gas or liquid and examples of suitable fluids include air and water.

We have found that the process of this invention allows a homogeneous mixture of fuel and gas containing oxygen, with a high dispersion of the particles of fuel without coalescence to be obtained in the tuyere and that this allows practically total combustion which avoids the formation of coke or soot in either the injection orifices or the gases produced by combustion. An added advantage is that the deflection of the jet injected into the stream of gas in the tuyere prevents impact of the fuel jet on the sides of the tuyere, thus avoiding damage of the walls.

In this preferred construction the injection tube or rod is provided with means for regulating the pressure of the fluid and the fuel to enable alterations to be made as necessary to give the required dispersion of the fuel in the fluid and ejection pressure into the tuyere. It should also be noted that by making use of the invention and by altering the means of regulation, the higher the upstream pressure of the fluid entering the injector - the higher will be the impulsion of that fluid/fuel jet and consequently the penetration and atomising of the fuel in the gaseous stream in the tuyere will be better. This in turn will lead to a shorter flame in the gaseous tuyere stream resulting in more complete combustion so reducing deposits and allowing larger quantities of fuel to be used.

In another aspect the present invention provides an injection lance for use in injecting atomised fuel into a tuyere, which lance comprises a rod or tube closed at one end and provided with (i) one or more atomised fuel outlet orifices arranged radially near to that end, (ii) means for introducing a fuel, (iii) means for introducing a fluid, (iv) means for atomising the fuel in said fluid within said rod or tube, and (v) means upstream of the outlet orifice(s) for permanently increasing the velocity of the atomised fuel; the arrangement of the outlet orifices further being such that when, in use, the closed end of the lance is located substantially axially in a tuyere, atomised fuel will be injected at an angle of between 60 and 1200 to the general longitudinal direction of flow of a hot gaseous stream in the tuyere.

The means for atomising the fuel in the fluid that is used will depend upon the nature of the fluid and the fuel. Examples include static mixers, rotary discs or dishes or, as is preferred, means allowing rapid expansion of the fluid where it meets the fuel. Our preferred lance comprises concentric tubes, the stream of fuel being admitted through the inner tube whilst the fluid is introduced through the outer tube. The two tubes are arranged to communicate shortly before the position of the radial holes. The communicating channel is such that the fluid is accelerated through the channel, preferably to sonic speed, when it contacts and atomises the fuel and the atomised fuel is still further accelerated before passing through the outlet orifices.

The present invention is illustrated but in no way limited by reference to Figures 5 to 11 of the accompanying drawings in which: Figure 5 is a diagrammatic view illustrating the process of the invention.

Figure 6 is an end view of the embodiment shown in Figure 5.

Figure 7 is a longitudinal cross section of one form of injection lance according to the invention.

Figure 8 is a transverse cross section of the lance of Figure 7.

Figures 9 and 10 are sectional views of an injection lance that can be used for carrying out the invention with different position of the extremity of the jet.

Figure 11 is a view along the section A-A of Figures 9 and 10.

Figures 5 and 6 demonstrate the process of the invention. The injection lance 10 admits through orifices arranged radially at its downstream extremity a jet of fuel J atomised in a stream of auxiliary air (as will be seen below) at an angle between 60 and 1200 in relation to the direction V of the flow of the gas in the tuyere 11. The jet J is therefore turned back and deflected by th4e flow V so that the flame F has the shape illustrated in Figures 5 and 6.

Figures 7 and 8 show on a larger scale the configuration of an injection lance according to the invention and how it operates to deliver a jet of fuel as depicted by J in Figures 5 and 6. Air, for instance, is admitted to channel 12 in the rod or tube 10 while the fuel (fuel oil, denoted by FOL on the drawing) is admitted to the inner jet 13 of that tube.

The air passes through the conduit 14 connecting channel 12 to the zone 15 where the fuel emerges from the jet 13. The speed of the air in zone 15 is such that an aerosol 16 of the fuel is generated in zone 15. The velocity of the aerosol is permanently increased by passage through the convergent end portion of zone 15 before ejection from the radial orifice 17 formed at the end of rod 10. The aerosol 16 flows into the flow of hot gas V in the tuyere (not shown) and is carried along with the gas V and further atomised and burnt therein to yield the flame 18.

We prefer that in operation of a device of the type illustrated in Figure 7 the speed of the air flow be at least equal to the speed of sound when it contacts the fuel since we find this gives the desired atomisation of the fuel.

The extent to which the aerosol 16 penetrates the gas flow V and the speed of its deflection depends upon the size of the holes and the pressure at which it is ejected from the rod 10 and the speed of the gas flow. We obtain the optimum situation which prevents coalescence of the fuel by permanently raising the speed of the aerosol up to its outlet into the stream of gas V. We prefer that the speed of the aerosol at the orifice 17 is substantially equal to the speed of sound.

It is also useful to be able to adjust the distance the fuel/fluid aerosol travels within the tube before being injected into the hot gases since where this distance is too great the heat from the hot gas surrounding the tube may crack the fuel possibly blocking the jet.

The detailed construction of two possible lance configurations are shown in cross section in Figures 9 and 10 in which numerals common to Figure 7 refer to common parts. As is shown the inner jet 13 is mounted and retained by the part 19 and the jet tapers towards its end 13 which leads into the zone 15. The zone 15 is contained within the nozzle 20 which has a tapered end 21 which increases the velocity of the aerosol and helps deflect the aerosol into the radial exit holes 17. The nozzle 20 is threaded and removable from the body of the rod 10.

Alternatively and as is illustrated in Figure 10 the nozzle 22 may be an integral part of the rod 10 resulting in a much smaller chamber 15 with the inner jet 13 close to the exit holes 17.

Figure 11 is a cross section through A-A of Figures 9 and 10 showing the configuration of the radial exits 17.

Although the radial exits into the stream of gas are shown to be through radial cylindrical holes it may equally be through conical holes or slots. Furthermore, the injection need not be exactly at right angles to the direction of the gas containing oxygen but may be at an angle of from 60 to 1200.

We prefer that there be at least two radial exits and that the surface area of each exit is at least equal to that of a circular hole of diameter 1.5 millimetres.

The device shown in our Figure 10 is particularly useful when the fuel injection lance passes through a considerable length of the hot blast which is usually at a temperature between 800 to 1400"C. The use of the device of our Figure 10 prevents recirculation of the aerosol within the lance and, if the distance between the end of the jet and the nozzle is adjustable, it is also possible to adjust the speed of the dispersing fluid at the point of its impact with the fuel to be atomised.

WHAT WE CLAIM IS: 1. A process for injecting fuel into a tuyere, comprising atomising the fuel in a fluid, increasing the velocity of the thus atomised fuel and thereafter, without any subsequent decrease in its velocity, injecting the atomised fuel into a gaseous stream in the tuyere. the atomised fuel being injected at an angle of between 60 and 1200 to the general longitudinal direction of flow of the gaseous stream in the tuyere.

2. A process according to claim 1, in which the fluid is a gas.

3. A process according to claim 1 or claim 2, in which the fuel is atomised by contact with a stream of the fluid which is travelling at least the speed of sound.

4. A process according to any one of the preceding claims, in which the atomised fuel is injected into the gaseous stream in the tuyere at a speed at least equal to the speed of sound.

5. A process substantially as hereinbefore described with reference to Figures 5 to 11 of the accompanying drawings.

6. An injection lance for use in injecting

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of Figures 9 and 10. Figures 5 and 6 demonstrate the process of the invention. The injection lance 10 admits through orifices arranged radially at its downstream extremity a jet of fuel J atomised in a stream of auxiliary air (as will be seen below) at an angle between 60 and 1200 in relation to the direction V of the flow of the gas in the tuyere 11. The jet J is therefore turned back and deflected by th4e flow V so that the flame F has the shape illustrated in Figures 5 and 6. Figures 7 and 8 show on a larger scale the configuration of an injection lance according to the invention and how it operates to deliver a jet of fuel as depicted by J in Figures 5 and 6. Air, for instance, is admitted to channel 12 in the rod or tube 10 while the fuel (fuel oil, denoted by FOL on the drawing) is admitted to the inner jet 13 of that tube. The air passes through the conduit 14 connecting channel 12 to the zone 15 where the fuel emerges from the jet 13. The speed of the air in zone 15 is such that an aerosol 16 of the fuel is generated in zone 15. The velocity of the aerosol is permanently increased by passage through the convergent end portion of zone 15 before ejection from the radial orifice 17 formed at the end of rod 10. The aerosol 16 flows into the flow of hot gas V in the tuyere (not shown) and is carried along with the gas V and further atomised and burnt therein to yield the flame 18. We prefer that in operation of a device of the type illustrated in Figure 7 the speed of the air flow be at least equal to the speed of sound when it contacts the fuel since we find this gives the desired atomisation of the fuel. The extent to which the aerosol 16 penetrates the gas flow V and the speed of its deflection depends upon the size of the holes and the pressure at which it is ejected from the rod 10 and the speed of the gas flow. We obtain the optimum situation which prevents coalescence of the fuel by permanently raising the speed of the aerosol up to its outlet into the stream of gas V. We prefer that the speed of the aerosol at the orifice 17 is substantially equal to the speed of sound. It is also useful to be able to adjust the distance the fuel/fluid aerosol travels within the tube before being injected into the hot gases since where this distance is too great the heat from the hot gas surrounding the tube may crack the fuel possibly blocking the jet. The detailed construction of two possible lance configurations are shown in cross section in Figures 9 and 10 in which numerals common to Figure 7 refer to common parts. As is shown the inner jet 13 is mounted and retained by the part 19 and the jet tapers towards its end 13 which leads into the zone 15. The zone 15 is contained within the nozzle 20 which has a tapered end 21 which increases the velocity of the aerosol and helps deflect the aerosol into the radial exit holes 17. The nozzle 20 is threaded and removable from the body of the rod 10. Alternatively and as is illustrated in Figure 10 the nozzle 22 may be an integral part of the rod 10 resulting in a much smaller chamber 15 with the inner jet 13 close to the exit holes 17. Figure 11 is a cross section through A-A of Figures 9 and 10 showing the configuration of the radial exits 17. Although the radial exits into the stream of gas are shown to be through radial cylindrical holes it may equally be through conical holes or slots. Furthermore, the injection need not be exactly at right angles to the direction of the gas containing oxygen but may be at an angle of from 60 to 1200. We prefer that there be at least two radial exits and that the surface area of each exit is at least equal to that of a circular hole of diameter 1.5 millimetres. The device shown in our Figure 10 is particularly useful when the fuel injection lance passes through a considerable length of the hot blast which is usually at a temperature between 800 to 1400"C. The use of the device of our Figure 10 prevents recirculation of the aerosol within the lance and, if the distance between the end of the jet and the nozzle is adjustable, it is also possible to adjust the speed of the dispersing fluid at the point of its impact with the fuel to be atomised. WHAT WE CLAIM IS:

1. A process for injecting fuel into a tuyere, comprising atomising the fuel in a fluid, increasing the velocity of the thus atomised fuel and thereafter, without any subsequent decrease in its velocity, injecting the atomised fuel into a gaseous stream in the tuyere. the atomised fuel being injected at an angle of between 60 and 1200 to the general longitudinal direction of flow of the gaseous stream in the tuyere.

2. A process according to claim 1, in which the fluid is a gas.

6. An injection lance for use in injecting

atomised fuel into a tuyere, which injection lance comprises a rod or tube closed at one end and provided with (i) one or more atomised fuel outlet orifices arranged radially near to that end, (ii) means for introducing a fuel, (iii) means for introducing a fluid, (iv) means for atomising the fuel in said fluid within said rod or tube, and (v) means upstream of the outlet orifice(s) for permanently increasing the velocity of the atomised fuel; the arrangement of the outlet orifices further being such that when, in use, the closed end of the lance is located substantially axially in a tuyere, atomised fuel will be injected at an angle of between 60 and 1200 to the general longitudinal direction of flow of a hot gaseous stream in the tuyere.

7. A device according to claim 6, in which the means for atomising the fuel in the fluid comprises a static mixer.

8. A device according to claim 6, in which the means for atomising the fuel in the fluid comprises means allowing rapid expansion of the fluid where it meets the fuel.

9. A device according to claim 8, comprising two concentric tubes arranged to communicate shortly before the position of the radial orifice or orifices in said rod, the communicating channel being such that the fluid is accelerated through the channel into the zone where it contacts the fuel.

10. A device according to claim 6 substantially as hereinbefore described with reference to Figures 5 to 11 of the accompanying drawings.