GB2138556A

GB2138556A - Apparatus for Burning Fuel and Feeding the Products of Combustion Into a Melt

Info

Publication number: GB2138556A
Application number: GB08310398A
Authority: GB
Inventors: Alexei Mikhailovich Ptitsyn; Nikolai Mikhailovich Korobov; Andrei Evgenievich Bobkov; Boris Petrovich Derevensky; Viktor Pavlovich Belkin; Vladimir Alexandrovich Murkin; Vladimir Grigorievich Brovkin; Gennady Georgievich Paschenko; Vadim Alexandrovich Gustov
Original assignee: GPNII NIKEL KOBALT OLOV PROMY; RYAZANSKY Z PROIZV I OBRABOTKE; SP K BJORO TYAZHELYKH TSVETNYK
Current assignee: GPNII NIKEL KOBALT OLOV PROMY; RYAZANSKY Z PROIZV I OBRABOTKE; SP K BJORO TYAZHELYKH TSVETNYK
Priority date: 1983-04-07
Filing date: 1983-04-18
Publication date: 1984-10-24
Also published as: DE3312563A1; DE3312563C2; GB2138556B; AU1413283A; AU557951B2; GB8310398D0

Abstract

Apparatus for burning fuel comprises a mixing chamber (1) having an inlet (2) through which an oxidizing agent is tangentially introduced into the mixing chamber (1) and a collector (3) with openings (4), (Fig. 2, not shown); for admitting fuel into the chamber (1). The openings (4) in the collector (3) have their axes forming together with the radii of the collector (3) drawn through the centre of each opening (4), at the place of their intersection, an angle of at least 10 degrees. The openings (4) are formed so as to permit the vector of the fuel flow to be counter to the vector of the oxidizing agent flow admitted into the chamber (1) through the inlet (2). A combustion chamber (6), connects mixing chamber (1) to a nozzle (7) the nozzle having ducts (8) for a cooling fluid, at least one pocket (9) disposed between the outer surface of the duct (8) and an inner surface (10) of the nozzle (7). <IMAGE>

Description

SPECIFICATION Apparatus for Burning Fuel and Feeding the Products of Combustion into a Melt The present invention relates to equipment for use in pyro-metallurgical practice, and more particularly, to apparatus for burning fuel and feeding the products of combustion into a melt, generally mounted on smelting units to cause bubbling of the melt and maintaining the latter at a high temperature.

The invention may find wide application in non-ferrous metallurgy for the oxidation smelting of ores and concentrates, and for the fuming of slags containing non-ferrous metals, such as tin and zinc, as well as in the fire refining of biister copper.

For feeding the products of combustion immediately into a pasty reacting mass, for example, into a melt or a bath, it is necessary that the pressure of a gaseous mixture in the zone of burning (in a combustion chamber) be maintained at a level higher than the hydrostatic pressure in the column of the reacting mass. From the above it follows that all the devices intended for burning fuel and feeding the products of combustion into the melt should be made to ensure adequate mixing of the fuel with an oxidizing agent, along with sufficiently high heat resistance in.the zone of burning (due to intensive combustion at elevated pressure). The nozzle of such a device is subjected to especially severe operating conditions as it makes contact with hightemperature products of combustion at one end, and the aggressive reacting mass, or the melt, at the other.

USSR Inventor's Certificate No. 189,143 discloses an apparatus for burning fuel and feeding the products of combustion into a melt, which comprises a chamber for mixing fuel and a gaseous oxidizing agent, and a combustion chamber adapted for burning this mixture and provided with a jacket and a water-cooled nozzle.

The fuel is fed into the mixing chamber from one end along its axis, and the gaseous oxidizing agent is introduced into a combustion-chamber jacket connected in series with the mixing chamber. While passing along the jacket, the oxidizing agent cools the surface of the combustion chamber and then is admitted into the mixing chamber.

In the prior art apparatus it is impossible to control within a wide range the composition of the combustion products relative to a selected content of oxygen. Moreover, by using the oxidizing agent for cooling down the combustion chamber, it is impossible to ensure sufficient removal of heat from the refractory lining of the combustion chamber, which brings about untimely damage to the apparatus as a whole.

U.S.A. Patent 2,833,6433 discloses an apparatus for burning fuel and feeding the products of combustion into a melt, which comprises a chamber for mixing the fuel and an oxidizing agent, this chamber having an inlet through which the oxidizing agent is tangentially introduced, and a collector with ports through which the fuel is admitted into the mixing chamber. It also has a combustion chamber adapted for burning the oxidizing agent and fuel mixture and a nozzle with ducts for a cooling agent.

The process of mixing fuel and oxidizing agent in the aforesaid apparatus is as follows.

The oxidizing agent is tangentially introduced into the mixing chamber so that a flow of the resultant mixture is directed along its walls along a helical path. The fuel is introduced into the mixing chamber radially through openings in the collector surrounding the mixing chamber. By supplying the reagents of the gaseous mixture to the mixing chamber in the manner described above, the flow of fuel is directed perpendicularly to the flow of the reducing agent; this however fails to ensure adequate mixing of the reducing agent with the fuel and thus leads to an excessive amount of free oxygen in the products of combustion. This is undesirable where the process is carried out in a reducing atmosphere, for example, during volatilization of lead, zinc and tin compounds in a fuming furnace.Furthermore, the use of the apparatus as disclosed in the patent referred to above is limited to the processes which are carried out in the oxidizing atmosphere, with the content of free oxygen in the products of combustion being over 4 per cent, by reason of unstable combustion brought about by additional supply of the oxidizing agent.

Moreover, the known apparatus is characterized by substantial losses of heat dissipated from the products of combustion in the course of their passage through the water-cooled nozzle.

What is desired is an apparatus for burning of fuel and feeding the products of combustion into a melt of the type and of such construction that will ensure maximum speed gradients between the flow of the oxidizing agent and that of fuel as well as their adequate mixing so as to ensure stable conditions for the melt to be blown through with the products of combustion while observing specified conditions for oxidation and reduction and maintaining the highest possible temperature with a minimum consumption of fuel.

The invention provides an apparatus for burning fuel and feeding the products of combustion into a melt, which comprises a chamber for mixing the fuel with a gaseous oxidizing agent, having an inlet through which the oxidizing agent is introduced tangentially into the mixing chamber, and a collector with openings through which the fuel is admitted into the mixing chamber brought in communication with a combustion chamber adapted for burning the fuel and gaseous oxidizing agent mixture and ending in a nozzle intended for feeding the products of combustion into the melt and having ducts for the passage of a coolant, wherein the openings in the collector have their axes forming together with the collector radii, drawn through the centre of the openings, at the point of their intersection, an angle of at least 10 degrees, the axes of these openings being so directed that the vector of the fuel flow admitted into the mixing chamber is counter to the vector of the gaseous oxidizing agent flow admitted into the same mixing chamber, the wall of the nozzle having at least one pocket disposed between the outer surface of the duct for a cooling fluid and the nozzle surface and intended to reduce the losses of heat removed from the products of combustion.

Such an apparatus construction makes it possible to reduce the amount of free oxygen in the combustion products from 3-4 vol.% to 1.5-2 vol.%, to increase the temperature of the products of combustion, which permits the time required for the reducing blowing of slag in a fuming furnace to be decreased, on the average, by 5 per cent while maintaining the fuel consumption rates unaltered.

To ensure stable operation of the apparatus with an increased content of oxygen in the products of combustion, supplied to a fuming furnace into the melt, the mixing chamber preferably has an air inlet deepened or arranged along its axis by a distance of at least 0.15 times the chamber length, which makes it possible to reduce the time of the oxidizing blowing of the melt on the average by 35 to 40 per cent.

To keep the high temperature products of combustion fed into the melt through the nozzle cooled by a cooling agent, there is provided in the nozzle interior a shield conforming in shape to the interior space of the nozzle and arranged therein with a gap extending throughout its perimeter.

This makes it possible to step up the technological process or, in other words, to bring down the time required for blowing the melt with the products of combustion under appropriate oxidizing and reducing conditions, which is equivaient to an increase in the production efficiency of the apparatus of about 1 5 per cent.

To ensure a sufficiently long service life of the nozzle along with an increase in the temperature of the combustion products introduced into the melt, the nozzle is preferably made of high chromium iron or steel.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a longitudinal sectional view of apparatus for burning of fuel and feeding the products of combustion into a melt; Fig. 2 is a cross-section on line Il-Il of Fig. 1; Fig. 3 is a cross-section on line Ill-Ill of Fig. 1.

The illustrated apparatus comprises a fuel and gaseous oxidizing agent mixing chamber 1 (Figs.

1 and 2) having an inlet 2 (Figs. 1 and 2) through which an oxidizing agent is tangentially introduced into the chamber 1. In addition, the chamber 1 comprises a collector 3 (Figs. 1 and 2) with openings 4 (Fig. 2) through which the fuel is admitted into the chamber 1. The openings 4 in the collector 3 are preferably formed so that their axes form together with the radii of the collector 4, drawn through the centre of each opening 4 at the point of their intersection, an angle of at least 10 degrees. The openings in question are located or arranged so that the vector of the fuel flow admitted into the mixing chamber 1 is directed counter to the vector of the gaseous oxidizing agent flow admitted through the inlet 2 into the mixing chamber 1.By introducing the initial components of the mixture into the mixing chamber in the above-described manner, it becomes possible to achieve a maximum speed gradient between the flow of fuel and that of the oxidizing agent. Relative speed of the two flows determines the intensity of turbulence at their boundary and, consequently, the intensity with which the components are mixed. Since velocity is a vector quantity, then, at specified absolute values of this parameter, determined by the amount of fuel and that of oxidizing agent, the greatest relative velocity of the flows will be achieved during their counter-movement. The intensity of mixing of the components is the basic factor influencing the combustion efficiency.It is advantageous that the contact of free oxygen in the products of combustion be at a minimum to permit effective operating conditions for the apparatus of the invention. By providing the mixing-chamber 1 with the above-described means for introducing the initial components of the mixture into the chamber 1, it is intended to ensure effective pre-mixing of the components and in this way to reduce the amount of free oxygen.

Through effective mixing of gas and air it becomes possible to achieve stable burning of the fuel-air mixture and thus to improve the process efficiency, and to save fuel and secondary power resources, as well as to ensure stable operation of smelting units.

According to the invention, the chamber 1 has an air inlet 5 (Fig. 1) located or arranged along the axis of the chamber 1 at a distance of not less than 0.15 times the length of the chamber 1. In the case when the inlet 5 is positioned in the chamber 1 by a distance less than 1.0 times the length of the chamber, the stream of air admitted into the chamber through this inlet will spread before its exit from the chamber 1, which may adversely affect hydrodynamic interaction between the flows of the main oxidizing agent and fuel. If the indicated value is above 0.15 times the length of the chamber 1, the outside edge of the inlet 5 will be in the high-temperature zone and will soon burn out.

The mixing chamber 1 is brought into communication with a combustion chamber 6 (Fig. 1) adapted for burning fuel and gaseous oxidizing agent and which ends in a nozzle 7 (Figs.

1 and 3) intended for introducing the products of combustion and the oxidizing agent into the melt.

The nozzle is preferably made of high-chromium iron or steel, whereby its service life is substantially prolonged even with an increase in the temperature of the products of combustion fed into the melt through the nozzle 7. To reduce the removal of heat from the high-temperature combustion products to a cooling fluid circulating along ducts 8 (Figs. 1 and 3), the walls of the nozzle 7 are preferably formed with at least one pocket 9 (Figs. 1 and 2) disposed between the outer surface of the duct 8 and an inner surface 10 (Figs. 1, 3) of the nozzle 7. The number of the pockets 9 may correspond to the number of the ducts 8 for the cooling agent.To reduce the amount of heat removed from the products of combustion due to a close passage of the cooling fluid through the ducts 8, a shield 11, is placed in the interior 9 of the nozzle 7 with a gap relative to the inner surface of the wails of the nozzle 7 throughout its perimeter and conforming in shape to the nozzle interior space. Due to a lower amount of heat dissipated from the products of combustion to the cooling agent the temperature of an inner surface 10 of the nozzle 7 is raised.

The material for the shield 11 is selected so as to prevent its fusion during the process of casting of the nozzle 7 and to preclude wettability of the shield surface with the molten metal from which the nozzle 7 is manufactured. The conditions of non-wettability of the shield 11 with the metal used for casting the nozzle 7 are indispensable for the formation of a gap in the pocket 9 between the shield and the surface of the pocket 9. The provision of the gap ensures substantial heat resistance and makes it possible to bring down the intensity of heat flux passing from the products of combustion to the surface of the nozzle 7.

By varying the number of shields, it is possible to achieve an optimum rate of cooling of the nozzle 7, at which ths heat flux will have a minimum value and the temperature on the inner surface 10 will be the highest possible allowable for the material of the nozzle 7.

The body of the nozzle 7 is made by way of casting a coil pipe, forming the ducts 8 for a cooling agent, with molten iron or steel high in chrome (10 to 30 per cent by weight). A high content of chrome in the cast metal makes it possible to raise the allowable working temperature of the inner surface 10 of the nozzle 7 up to 6000C without any danger to material durability.

In addition, a high content of chrome impairs heat conductivity of the material and substantially increases resistance to the heat flux passing from the products of combustion to the cooling fluid used for cooling the nozzle 7.

The apparatus according to the invention for burning fuel and feeding the products of combustion into the melt is operated in the following manner.

A gaseous oxidizing agent, such as oxygenenriched air at a high temperature, or pure oxygen, is fed along the inlet 2 to be tangentially introduced into the mixing chamber 1. An additional flow of the oxidizing agent is also introduced into the chamber 1 through-the inlet 5.

A gaseous fuel, such as an oil-stream mixture or combustible gas is admitted into the chamber 1 along the collector 3 through the openings 4 as it passes in counter-movement to the flow of the gaseous oxidizing agent. The manner in which the gaseous components are fed into the chamber 1 creates the best possible conditions for their effective intermixing. The resultant mixture of fuel and oxidizing agent is delivered to the combustion chamber 6 wherein it-is ignited (initially by means of an igniter provided in the chamber 6 and which is not designated in the figure) and then is burnt down.As the combustion products formed in the chamber 6 possess reduction potential, which is essential, for example, for the treatment of stanniferous materials in a fuming furnace, the above-mentioned conditions for mixing the gaseous components of the fuel-air mixture permit a minimum amount of free oxygen to be maintained in the products of combustion.

Where it is necessary to obtain the products of combustion with a high content of free oxygen (from 1 to 10 per cent by volume), an additional amount of the gaseous oxidizing agent is introduced through the inlet 5. The reaction between the fuel and the oxidizing agent is stable and proceeds under the same conditions as before, without breaking-away of the flame.

On completion of combustion in the chamber 6, the products of combustion are passed into the nozzle 7 and, on scrubbing over its inner surface 10, are then delivered into the melt, for example, in a fuming furnace.

As the high-temperature gases pass through the nozzle 7, the heat flux is transferred from the inner surface 10 of the nozzle 7 to the ducts 8 for a cooling fluid. Here, owing to the provision of the pocket 9 with the shield 11 mounted therein, additional resistance is created in the way of the heat flux.

From the above it follows that with the apparatus of the invention it becomes possible to bring down the intensity of heat flux from the products of combustion fed into the melt, which results in an increase of temperature of the combustion products fed under the melt by 700C as compared to the prior art apparatus. Such temperature increase makes it possible to reduce the time required for the delivery of combustion products by about 12 minutes, and thus to enhance production efficiency of a fuming furnace by 20 per cent.

While the invention has been described in terms of the preferred embodiment, numerous variations may be made in the apparatus illustrated in the drawings and herein described within the ambit of the invention as set forth in the appended claims.

Claims

1. Apparatus for burning of fuel and feeding the products of combustion into a melt, comprising a chamber for mixing the fuel with a gaseous oxidizing agent, having an inlet through which the oxidizing agent is tangentially introduced into the interior of said chamber and a collector with openings for admitting fuel into the mixing chamber, said openings having their axes forming together with the radii of the collector, drawn through the centre of these openings, at the point of their intersection, an angle of at least 1 0 degrees, with the axes of said openings being directed so that the vector of the fuel flow admitted into the mixing chamber is counter to the vector of the gaseous oxidizing agent flow admitted into the mixing chamber, a combustion chamber communicating with the mixing chamber and adapted for burning the mixture of fuel and oxidizing agent and ending in a nozzle intended for feeding the products of combustion into the melt and having ducts for a cooling fluid, at least one pocket disposed between the outer surface of the duct for a cooling fluid and the inner surface of the nozzle in order to reduce the amount of heat removed from the products of combustion.

2. Apparatus as claimed in claim 1, wherein the mixing chamber has an air inlet deepened along the axis of the mixing chamber by a distance of at least 0.15 times the length of the mixing chamber.

3. Apparatus as claimed in claim 1, and having a shield arranged in the nozzle interior and conforming in shape to the interior space of the nozzle and spaced with a gap therein extending throughout its perimeter.

4. Apparatus as claimed in claim 1, wherein the nozzle is made of high-chromium iron or steel.