FI86470C - GASBRAENNARE. - Google Patents

Abstract

High-velocity gas burners having enhanced flame stability over wide operating ranges are provided by correlating the dimensions of the combustion chamber with other burner dimensions, in particular, the ratio of the combustion chamber diameter (DS), to the flame holder exit diameter (DF), and the ratio of the effective length (LE), of the combustion chamber to the combustion chamber diameter (DS).

Description

1 86470

This invention relates to high speed gas burners with enhanced flame stability. In particular, the invention relates to high speed gas burners in which flame stability is enhanced over a wide range of applications and which are used in melting furnaces and the like.

It is very important for the industry to have 10 burners for efficient heating and defrosting, especially at a time when energy costs are rising and fuel stocks are running low. In this connection, it must be possible to use the burners in furnaces under both low and high operating conditions, while maintaining the production of molten metal products as commercially acceptable, i.e. free from contamination.

Gas burners of the type according to the present invention can be used in a variety of furnaces 20 or units where a high temperature level is required. The present gas burners have been found to be effective in melting furnaces, for example in a vertical melting furnace, which is described and illustrated by means of figures in U.S. Patents 3,199,977 and 3,366,465. The gas burners are placed in each side wall opening and secured in place by bolts which hold the mounting plate of each burner body tightly to the furnace jacket so as to provide a substantially gas-tight attachment.

30 A difficult problem in burner technology, specifically in the use of burners in furnaces, such as those mentioned above. . in the vertical melting furnaces of the U.S. Patents, there has been the formation of a stable flame under a wide range of operating conditions. In the burner according to the present invention, the flame burns both inside and outside the combustion chamber 2 86470, and the shape of the chamber delimits the shape of the flame in the chamber, the flame being substantially conical outside the chamber. Burners typically have an igniter rod in the igniter compartment with a combustion chamber diameter greater than the outlet of the igniter compartment. The flame remains immediately downstream of the igniter and spreads into the non-combustible mixture passing by it. The flame is further maintained by the circular area whose shoulder forms at the junction of the igniter section and the combustion chamber. Thus, two flame fronts are obtained, one spreading out of the igniter bar and the other spreading out of a round, shoulder-type flame holding compartment.

Unfortunately, however, the spread of flame from the round shoulder can be unstable because it forms completely in the shoulder and thus forms a black or cold point in this area of the shoulder. This type of flame is unstable and vibrates and flakes and forms a cold point in this area of the shoulder in the vertical furnace used for smelting copper, where 20 unmelted copper can accumulate. This accumulation of metal in the combustion chamber and / or an unstable flame adversely affects the operation of the furnace, as it forms impurities in the copper in the pen, so that the furnace may have to be closed for cleaning. The instability of the flame is very. V 25 when starting a powerful burner when the oven and burner are cold, but unfortunately it also occurs in "va - *: 1 boiler" operation.

This problem has been very serious in shaft furnace technology in an attempt to design such a furnace, for example a furnace of reasonable capacity, i.e. with a capacity of less than 20 small tons per hour. . (STPH), which can be decelerated in a ratio of 2.1: 1 in the flame. "Deceleration" as used herein means reducing the rate of melting of the furnace by reducing the amount of fuel and oxygen formed in the burners by forming a mixture of 3 86470 man. When the maximum capacity designed for the furnace is 20 STPH and the deceleration ratio is 2.5: 1, the furnace capacity is only about 8 STPH, i.e. 20 / 2.5 = 8. In order for the furnace to work well over such a wide operating range, the burner must keep the flame stable also in the retardation range. If the flame is unstable at low operating speeds, molten copper will become contaminated, metal will accumulate in the combustion chamber, and other problems will also arise.

For example, in low power furnaces, 10 traditionally only one row of burners placed on the circumference of the furnace has been used because the second burner row is thought to provide more melting capacity than needed, causing problems slowing down the furnace melting rate and avoiding metal sinking and cooling in the furnace. In small furnaces, getting the heat evenly distributed from a single row of burners has been a difficult problem. In these single-row furnaces, at maximum heating rates, the metal can easily remain above the burner row, creating metal suspension problems when the indigestible charge does not descend from the large diameter top of the furnace to its smaller diameter lower part. Such a phenomenon creates high oxygen levels and uneven temperatures in the metal and causes the furnace to "whine". In addition, a "cavity phenomenon" arises, meaning the absence of a metal charge at the bottom of the furnace, which: * is due to said uneven heat distribution, and the overheating of refractory materials, large variations in molten metal temperatures and 30 maximum or almost maximum heat input. In double-row furnaces, and also in single-row furnaces, prolonged deceleration can cause the metal to "soften" as the fuel supply decreases, thereby reducing the heat supply and possibly causing the metal to sink to the bottom of the furnace.

4,86470

It is an object of the invention to provide a high speed gas burner with enhanced flame stability over a wide operating range. This object is achieved by a gas burner having a slow-flame capacity of about 2.5: 1 with a stable flame and uniform and complete combustion in this range, comprising a mixing section for combining the oxygen-containing gas stream and the fuel stream, a flame-retaining section having an outlet diameter of D to ignite a mixture of fuel and oxygen and to maintain and enhance combustion of an adjacent combustion chamber, the combustion chamber being formed of a refractory burner plate and having a substantially cylindrical shape and having a diameter of Dg, 15 effective length Lg and a burner plate is characterized in that the burner dimensions are correlated, with a Dg / Dp of about 1.35 to 1.70 and a LE / Dg of about 1.2 to 3.7.

Advantages of the burner according to the invention include, inter alia, prolonging the service life of the tiles and minimizing the contamination of the molten metal caused by the "cold" points in the combustion chamber.

GB Patent 850,907 and the aforementioned U.S. Patent 2,806,517 disclose gas burners in which V 25 has a mixing section, a flame retention section and an adjacent combustion chamber. However, neither publication presents a critical ·; ratios D-./D-, and D ^ / D ^, which are necessary

.... Oi1 Cl O

to improve flame stability. The burners according to these publications: also do not mix air and. 30 fuel in mixing chambers before the combustion chamber, but rather in the combustion chamber.

The "effective length" L · ,,, of the burner according to the invention is the length of the slab cladding measured from the point of intersection of the combustion chamber and the flame retention compartment ("shoulder") to the opposite end of the chamber. The diameter Dg is essentially constant at 5,86470 for the entire chamber portion. The chamber consists of an outer refractory tile cladding, preferably with substantially circular openings at each end for the flue gas inlet (Dp) and outlet (Dg), and is usually made of a suitable high temperature resistant refractory material. The function of the combustion chamber is to burn substantially all of the incoming fuel gas and oxygen-containing gas by continuously maintaining a predetermined temperature at a substantially constant temperature gradient, preferably about 550 ° C, over the effective length of the chamber. Such performance is achieved by designing the chamber based on several important ratios: (1) the ratio of the diameter Dg of the combustion chamber to the diameter Dp of the outlet of the adjacent flame-15 holding compartment is about 1.35 to 1.70, preferably about 1.43; and (2) the ratio of the effective length Lg to the combustion chamber diameter Dg is about 1.2 to about 3.70, preferably about 1.56 or 3.00. In a preferred embodiment, the structure of the burner unit controls the ratio of the total length L_ of the combustion chamber plate to the "effective length" L_ of the chamber, i.e. the length of the chamber plate cladding as measured from the intersection of the combustion chamber and , 00 and! 25 preferably about 1.47.

Although burners with a mixing compartment 50 will now be described, those skilled in the art will appreciate that fuel and air may also be mixed outside the burner and transferred through the ignition compartment or flame retention compartment 51 30 to the combustion chamber 52. The burners now arranged in the same way, . . in other words, they provide a stable flame over a wide operating range.

The burner according to the present invention is suitable for a very low power vertical shaft furnace, i.e. a furnace which melts less than 20 STPH of metal, in particular copper, said furnace comprising a substantially cylindrical chamber with a plurality of circumferential bricks. burners spaced apart in the direction around the lower end of the furnace, each burner being intended to supply a sufficient amount of energy, usually about 0.7 to about 1.8 x 10 3 BTU / hr 10 ^ BTU / hr = 293 kW. These furnaces are designed to ensure an efficient distribution of heat to evenly melt the solid feed feed, i.e. preferably copper cathodes and scrap, without causing the furnace to clog and cool the metal. Larger burners are preferably used for higher power furnaces.

Other burners which guarantee flame stability over a wide operating range are used according to the present invention for energy levels of 50 x 10 6 BTU / hr or higher, preferably about 2 x 10 to about 20 x 10, e.g. x 10 ^ BTU / hr. The recommended range is 0.7 to 10 x 10 3 BTU / hr or 20 to 5 x 106 BTU / hr.

In the drawings, Fig. 1 is an enlarged vertical section showing a burner unit, Fig. 2 is a section of a preferred combustion chamber for use in connection with the invention, *: 1 Fig. 3 shows a shaft melting furnace apparatus, *: 1 Fig. 4 is a vertical section of a furnace, and Fig. 3 “'· Part of the exhaust pipe with some of the burner units and the fuel supply piping excluded.

As can be seen from Figure 1, the burner body 3 comprises a fuel flow of the mixing compartment 50 and oxygen oxygen. . to connect a gas stream (air stream) to provide a uniform flow, and to supply this uniform flow to the flame retention compartment 51. The burner body 35 is also provided with a combustion chamber compartment 52 shown in • · · · · • · ·

7 8 6 4 7 O

in more detail in Figure 2 and is mounted on the flange 53 against the shoulder of the flame holding compartment 51. The igniter rod 58 may be located in the throat and a conventional electric spark plug 59 for igniting said uniform current is mounted on the side of the compartment 51 with the inner end of the spark plug close to the rod 58. The combination of throat and rod 58 is highly preferred to maintain uniform current combustion. for. Compartment 51 is also provided with openings 69 and 70 10 for sampling a uniform stream.

The compartment 50 has a circular manifold portion 60, a sleeve 61, a bend portion 62, an orifice plate 63 and an observation opening 64 provided with a transparent observation portion 65. The sleeve 61 associated with the shoulder 66 and the left end 15 of the compartment 50 cooperates with the circular portion 60 and forming a manifold that feeds the smaller of the two interconnectable streams (usually the fuel stream) from the tubes 36 through the openings 67 into the connecting chamber 68; the size and distribution of the openings 67 on the circumferential portion of the sleeve is selected to control the supply of fuel to the chamber. The greater current enters the chamber 68 from the tube 29 through the opening in the plate 63 and the bend portion 62.

When a burner body is used, the greater of the two interconnected currents is conducted to the burner body 25 through an opening in the bending portion leading to the connecting chamber, and the exact composition of the stream is determined as disclosed in U.S. Patent No. 3,199,977.

Figure 2 shows in detail the preferred structure of the burner combustion chamber 52 when fixed in place on the wall 5 of the refractory furnace. A uniform stream of gaseous fuel and air passes through the flame retaining compartment 51 past the spark plug 58, with the spark plug 59 or one other efficient ignition -: * ·. · the device ignites the mixture, and then enters the burner combustion chamber 52.

β 86470

Preferably, the combustion chamber 52 is substantially completely cylindrical and begins at the "shoulder" 99 formed by the junction of the combustion chamber 52 and the adjacent flame retention compartment 51 and extends to the beginning of the exhaust passage 96 (gauge 5 to 94) where combustible fuel gases enter the furnace and melt the metal charge. The chamber 52 is shown formed of a burner plate 49, preferably made of silicon carbide, and a thin cylindrical shock 90, pre-sized to be uniform, usually about 1/2 "strong, and made of a hard, dense, wear-resistant refractory material, preferably SiCr. capable of withstanding a continuous temperature of 550 ° C. Although the use of a removable SiC sleeve is preferred in the main structure of the invention, similar results can probably be obtained if the entire burner plate structure and sleeve are cast in one piece or the like, provided the structure conforms to the proportions and dimensions described below. the use facilitates the replacement of corroded or worn parts with new ones and also allows for changes in the sizing of the 20 combustion chambers if the operation is to take place at different tonnage levels. "Pre-determined sizing" of a sleeve means a specific, mainly The sleeve is invented axially with respect to the diameter of the chamber hole 92 and is attached, preferably as an oxide joint, to an adjacent support. to the running plate 49.

'; It has been found that the burner can be used in a certain operating range when the burner plate 49 comprising the sleeve 90 is dimensioned to correspond to several important chamber parameters, namely: '·· (1) the ratio of the combustion chamber diameter 95 (Dg) to the flame retention ::: the ratio of the compartment outlet diameter 97 (Dp.) and (2) the "effective length" (L) to the diameter of the sleeve Λ .: 35 when said length is measured along the center line of the chamber from the beginning of the slab to the intersection of a certain plane at the exit surface of the combustion chamber plate 49, to the "effective length" (L_.) 94 of the combustion chamber, i.e.

No soot to the length of the slab cladding as measured from its point of intersection with the flame retardant compartment (shoulder 99) to the end of the sleeve cladding at the outlet of the chamber. The reasons for the significance of these parameters and relationships are not fully known, but the following theories have been presented, although the inventors do not wish to be bound by them.

The function of this structural ratio Dg / Dp is to control the degree of expansion of the fuel mixture as it exits the flame retention compartment and enters the combustion chamber. This continued enlargement allows ignition and flame to settle on the shoulder formed by the flame retention compartment and the combustion chamber compartment. In previous burners, combustion reactions often occurred only about halfway through the chamber, which is believed to be due to a sudden significant increase in the high velocity fuel flow as it entered the combustion chamber. Surprisingly, it has been found that a combustion chamber (Dg / Dp) correctly dimensioned with respect to the igniter compartment can produce and maintain a "stable" flame, whereby the melting capacity of the burner remains optimum and a flame is obtained which melts the metal primarily by a convection mechanism.

! Maintaining a stable flame is therefore highly desirable because a long, unstable flame is characterized by a relatively low rate of combustion of fuel and oxygen. 30 Such an unstable flame causes a greater amount of copper to accumulate in the chamber and an increase in the oxygen content of the copper to undesired levels. Instead, a short, stable flame is a sign of near-complete combustion in the chamber. An additional consequence of incomplete combustion is the considerable variation of the temperature of the refractory plate and also the uneven wear of the refractory structure, which shortens the service life of the plate.

It has been found that the preferred ratio of the diameter of the combustion chamber to the diameter of the outlet of the flame retention compartment 5 (Dg / D 2 is about 1.35 to 1.70 and preferably about 1.40 to 1.45, for example 1.43).

The ratio of the effective length L £ of the combustion chamber to the diameter Dg of the chamber sleeve has also been found to be an important burner performance parameter. This is believed to be due to the fact that this ratio provides a suitable geometry for the combustion chamber, which enhances combustion and keeps the walls hot throughout this length. In this respect, it has been found to depend on the operating energy range (BTU / hr) of the burner, so that generally increasing operating energy ranges require lower ratios. Thus, a range of about 1.2 to 3.7 can be applied to the invention and the best results are obtained when the ratio (Lg / Dg) is about 1.85 to 3.70 and preferably about 2.5 to 3.5, for example 3, 0, for burners smaller than about 10 x 10 4 BTU / hr, for example about 0.5 x 10 4 to 4 x 10 3 BTU / hr. For larger burners, for example larger than about 10 x 10 4 BTU / hr, a ratio of about 1.2 to 1.7, for example about 1.3 to 1.6, is recommended.

The ratio of the total slab length (LT) of the combustion chamber plate (LT) to the "effective length" L_, i.e. (L / L_), mainly determines the length of the sleeve for a given burner; the desired result is obtained. The best results are obtained when the above ratio is about 1.20 to 2.00 with the preferred length of the refractory slab being about 11 "and the length of the SiC sleeve associated with the slab 30 being about 6 to 9", preferably about 7.5 ", where the ratio is 1.47.

Those skilled in the art know that De, D_, L „

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and the absolute values of LT will vary depending on the desired burner size (BTU / hr) provided that the ratios mentioned herein are maintained. In general, the larger the burner 1 ·

11 8647G

The BTU power is, the larger the values D_, D „, L„ and Lm are.

b Γ Ct 1 Another important parameter of the system is the speed at which the combustion gases pass through the chamber. Surprisingly, the best results are obtained when the velocity of the outgoing gases is about twice as high as the gas velocities present in previous burners. This is believed to be due to the results obtained from the correlation of the burner dimensions according to the above ratios and the enhanced combustion of the fuel gases.

Thus, correlating the dimensions of the burner according to the invention to obtain a properly sized combustion chamber has contributed to improved flame stability at a deceleration ratio of about 2.5: 1, whereby impurity levels decrease in molten copper and combustion chamber wear is significantly reduced.

Figures 3 and 4 show a unit with a vertical shaft melting furnace 1, a chute 2 and corresponding pipes for supplying fuel and oxygen-containing gas (air) to a plurality of burners 3 arranged in two circumferential rows. As can be seen from Figure 4, the side walls and the bottom of the furnace 1 are provided with a refractory lining 5 surrounded by a jacket 6 made of a suitable metal, preferably steel, and assembled in a suitable manner by welding to give a gas-tight jacket. The side walls of the furnace have several openings 7 for the burners 3. As shown in Fig. 4, the lower side walls 8 of the furnace are inclined inwards, and the bottom 9 of the furnace is inclined towards the outlet 10 leading to the trough 2.

As shown in Fig. 3, the air coming from the fan 11 enters the control valve 13 at the desired overpressure along the pipe 12, which supplies the air to the manifolds 14, from which it is supplied at the desired overpressure to the different burners 3 by insulated pipes. Gas supplied from a suitable source ·: 1. The ground fuel flows at the desired overpressure along a pipe 15 i2 86 4 70 which is a heater 16 to which heat is supplied to heat the fuel in a suitable manner, for example by a heat exchanger using either electric heating or hot combustion products. The preheated fuel 5 then passes through insulated pipes and control valves 16A to various burners 3, which may also be insulated to prevent heat loss. The burners 3 are located in the openings in the side wall and are held in place by bolts 17 which hold each mounting plate 18 of the burner 10 tightly against the jacket 6, so that a virtually gas-tight fastening is obtained. Such a fixation and the closed structure of the burners together almost completely allow air outside the furnace to enter it through the burner openings. As already mentioned above, a plurality of burners are arranged in the wall of the furnace, each burner being preferably at a predetermined distance from the other burners around the furnace.

Details of an exemplary vertical shaft melting furnace and burner are set forth in U.S. Patent No. 3,199,977, the contents of which are incorporated herein by reference.

A preferred high speed burner structure according to the invention is shown in Figure 2 and has the following dimensions. The burner chamber plates 49 of the burners are square in shape and have a side length of 9 ". The diameter Ds of the sleeve of the burner chamber chamber plate 49 is about 2.5", the outlet diameter D "of the flame compartment 51 is about Γ 1.75 "and the ratio Dg / DF is about 1.43. To burn a uniform gas flow, the burner is equipped with an electric spark plug 30a 59 and a igniter rod 58 which promotes the combustion of a uniform current in the combustion chamber 52. Effective length L_ ·. ·. · measured flame retention from the end of the compartment 51 to the end of the combustion chamber plate 49 is about 7.5 ". The length LT of the slab is about 11 ", where Lm / T_ = 1.47. The ratio of the effective length L„ to the diameter Dg of the sleeve * · X £ jh: 11: 35, i.e. LE / Dg = 3.00. A stable flame is obtained at a retardation ratio of about 2.5: 1 in a vertical melting furnace of the type described in U.S. Patent No. 3,199,977 having a structural melting capacity of about 20 STPH.

In the high power burner of the invention shown in Figure 2, having a power of more than 10 x 10 3 BTU / hr, a sleeve diameter Dg of about 10 1/4 ", an outlet diameter D_ of about 7.5", an effective length L "of about 16" and r L · plate length L_ about 23 3/16 ". The ratio De / D_ is 1.37, L-VD-, 1 or h. O 10 is 1.56 and L 1 / L- is 1.45. The burner provides a stable flame with a deceleration ratio of about 2.5: 1.

Claims (6)

A gas burner having about 2.5: 1 throttling capacity while maintaining a stable flair with uniform and complete combustion in this range, comprising a mixing section for combining a gas stream containing oxygen and a fuel stream, a flame retardant section having an outlet diameter for fuel sealing - the oxygen mixture and a connecting combustion chamber to maintain the combustion and enhance the combustion, the combustion chamber being made of refractory burner plates and of substantially cylindrical shape with a diameter Dg, an effective length Dg, burner plate total length LT, may be characterized in that the burner dimensions are correlated, with Dp / D ^ being about 1.35 - 1.70 and L „/ D„ being about 1.2-brhb 3.7. 2. A burner according to claim 1, characterized in that the dimensions of the combustion chamber of the burner are correlated, with L ^ / L ^ being about 1.2 - 2.0. 3. A burner as claimed in claim 1 or 2, characterized in that D „/ D„ is about 1.40 - 1.45. b Γ 4. A burner according to claim 1 or 2, characterized in that L L / D. Is about 1.85 - 3.7. L · b 5. A burner according to claim 1 or 2, characterized in that L 2 / D- is about 1.2 - 1.7. '1 b b Burner according to any of the preceding claims, characterized in that the combustion chamber is located axially along a common center line with the connecting flame-retaining section. · 1 • ·