JPH0559322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heating a burner and enclosure. In detail, the operation of a tank for melting selected ores to obtain molten glass (hereinafter referred to as a glass tank), a burner for heating a kiln, etc. (hereinafter collectively referred to as an enclosure), and liquid fuel. For example, it relates to a burner itself that uses gas as a medium for atomizing heavy oil.

It is known in the art to supply oxygen-enriched gas (commercially pure oxygen or oxygen-enriched air) to a flame to improve the efficiency of combustion of liquid fuels. The conventional method is to inject a combustion gas with a high oxygen content into the flame from below. Many aspects of this and other techniques for supplying oxygen-enriched gas to a flame are known in the literature. (e.g. “Use of oxygen in glass melting furnaces”)
Glass Technology Vol. 14, No. 6, December 1973, pp. 171-181)
Briefly, these advantages are increased frame temperature and improved heat transfer from the frame to the perimeter wall by radiation and convection. These benefits are due in part to the faster rate at which free radicals are generated in the flame. This phenomenon of increasing the rate at which free radicals are formed increases the rate of group reassociation in the low-temperature part of the flame or the part of the outer peripheral wall outside the flame, and
This results in an increased release of separation latent heat that promotes heat transfer by convection. Using a high oxygen content gas aids in complete combustion of the fuel gas and also allows for a reduction in the need for secondary air to the flame.

The above-mentioned paper by Messrs. Miller and Lloyd describes the operating life of a preheating device or recuperator attached to a glass tank in order to preheat secondary air using gas with a high oxygen content when the device ages. It is said to be extended. Recently, there has been an interest in increasing the amount of glass produced per unit heat of glass and other materials to be melted by using a gas with a high oxygen content, from the perspective of saving fuel rather than increasing the amount of production. .

Another phenomenon of supplying oxygen-rich gas to the flame is that the length of the flame is shortened. The shortening of such a form when an oxygen-enriched gas is used as an atomizing agent, as shown in Figure 1 of the paper by Miller and Lloyd, promotes other techniques for adding oxygen-enriched gases as an atomizing agent. This especially occurs.

Recently, when heavy oil is used, the use of gas with a high oxygen content as an atomizer has been reconsidered. There are two advantages to using oxygen-enriched gas as the atomization medium. First, the need for lances required under downward flame injection or the need for relatively complex oxy-fuel burners and high equipment costs is avoided. Secondly, there is no need to compress the air normally used as the atomization medium, which immediately leads to cost savings.

Despite the recommendations of Messrs. Miller and Lloyd, experiments using commercially available pure oxygen as the atomization medium significantly reduced fuel costs. However, these experiments were conducted in enclosures where there was no need to avoid shortening the flame length when oxygen was used in place of compressed air, so there was no negative effect of the shortened flame length.

In many cases, it is necessary to avoid shortening the length of the flame or changing the shape of the flame. An example is a cross-heated glass tank. In this tank, the burner fire is directed approximately perpendicular to the flow of molten glass. In this tank, the shorter the length of the flame, the less uniform and insufficient heating of the glass occurs, and the part of the glass material furthest from the burner remains cooler than the other parts of the glass. Become. If the heating is uneven, some ores may remain unmelted or refined, or they may harden and leave scratches in the glass.

Conventionally, it has been taught that adding oxygen-rich gas to a flame, especially when it is used as an atomizing medium, shortens the length of the flame, but according to the present invention, the length of the flame can be reduced without shortening the length of the flame. It became possible to use gas with a high oxygen content. As a result, a highly combustible flame was obtained and the heat exchange rate increased significantly. This has been made possible by appropriately selecting the flow rate and speed at which oxygen gas and liquid fuel as atomizing media are ejected from the burner, and the flow rate at which secondary air is applied to the burner flame.

According to this invention, the liquid fuel is atomized using ordinary air as an atomization medium to promote its combustion and heat the enclosure, and excess secondary air is supplied to the enclosure to form an elementary atmosphere. In a method of operating a burner for liquid fuel in which the length of the flame is prevented from becoming shorter than a predetermined length, a gas with a high oxygen content is used as an atomizing medium instead of the air, and the supply flow rate of the gas and fuel is adjusted. , speed, mixed atomization momentum, and supply flow rate of secondary air are selected appropriately to achieve stable combustion of the desired length and with a higher flame temperature than when normal air is used as the atomization medium. A method of operating a burner is provided that includes generating a flame.

The method of this invention is suitable for application to a burner using heavy oil using a normal pressure atomizer. A normal pressure atomizer is one in which the atomizing medium gas is supplied under a pressure of 20 to 50 psig, and thus the fuel is also supplied at this pressure. Conventionally, ordinary air has been used as the atomizing medium, but in the present invention, an oxygen-enriched gas is used instead of ordinary air.

By using such a burner and fuel, the temperature of the flame can be increased by increasing the flow rate of oxygen molecules provided to the flame via the atomizing medium. The increase in flow rate is approximately
It is in the range of 200 to 300%. Therefore, if substantially pure oxygen (e.g., greater than 99% purity) is selected as the oxygen-enriched gas, the flow rate supplied as the atomization medium in place of regular air may actually be reduced. become. Preferably, pure oxygen is supplied at a flow rate of 2 to 3% of the air flow rate required for complete theoretical combustion of heavy oil.

As used herein, "oxygen-enriched gas" refers to pure oxygen or a mixture containing at least 22% and typically 25% oxygen, as well as "oxygen-enriched air". .

When the flow rate of molecular oxygen to the flame through the atomizing medium exceeds the above-mentioned values, the temperature of the flame becomes extreme and tends to create "hot spots" within the enclosure.

Heavy oil burners with normal pressure atomizers result in fuel cost savings of 10-15%, ie 10-15% fuel liquid savings. Such percentage fuel savings occur when substantially pure oxygen is used instead of normal air as the atomization medium.
Preferably, the amount of atomizing gas is also reduced by 40 to 50%. Preferably, the flow rate of the secondary air is then reduced sufficiently to reduce the oxygen concentration of the enclosure atmosphere to 3% by volume or less.

The atomization momentum (i.e. the momentum required for atomization) is reduced by a substantial reduction in the ratio of the atomization medium feed flow rate to the fuel feed flow rate (notwithstanding a 10-15% reduction in the fuel feed flow rate). ) will be substantially reduced. This results in less complete atomization of the liquid fuel, ie, the formation of larger fuel particles, than when conventional air is used as the atomization medium. Although the larger atomization particles slightly compensate for the tendency for shorter flame lengths when oxygen-enriched gases are used in place of regular air, virtually pure oxygen gas is the atomization medium. Simply adjusting the flow rate of the atomizing medium or fuel, or even reducing the flow rate of the secondary air, cannot prevent the phenomenon of shortened flame length. The use of substantially pure oxygen gas therefore requires a narrow supply path for the atomizing medium to the atomizing chamber or zone of the burner, and that the burner is converted as described above. It has been found necessary to narrow the injection holes or orifices through which the atomized fuel atomization medium mixture leaves the burner. This 2
By narrowing the fluid flow path, the rate at which the atomized fuel and oxygen-enriched gas mixture is injected from the burner is increased.

Burners with normal pressure atomizers have a body sometimes known as a spud. The body is provided with passages for fuel and atomizing medium and a cap engaged with the body and having injection holes. The body and the cap define an atomization chamber or zone therebetween and are dimensioned to define a narrow flow path for the atomization medium leading to such atomization chamber. When substantially pure oxygen is used as the atomizing medium, the fit of the cap on the spud is further adjusted to further narrow the flow path. When substantially pure oxygen is used as the atomizing agent instead of air, the cross-sectional area of the passage is reduced by about two-thirds. This increases the velocity, and therefore the momentum, with which the atomizing medium is delivered to the atomizing chamber or zone, making it possible to use oxygen-enriched gases as the atomizing medium at lower flow rates. The loss in momentum due to this will be fully compensated for. In practice, it is preferable not to rely on such compensation when switching the burner from using air as the atomizing medium to using substantially pure oxygen gas. In other words, m and v are respectively the mass flow rate and velocity when the atomizing medium of air enters the atomizing chamber, and m ₂ or v ₂ are the atomizing medium of oxygen-rich gas entering the atomizing chamber. It is preferable that m is larger than m ₂ , v ₂ is larger than v, and (m×v) is larger than (m ₂ ×v ₂ ), where the mass flow rate and velocity are .

When converting a burner with a normal pressure atomizer to use substantially pure oxygen as the atomizing medium instead of normal air, the cross-sectional area of the exit hole of the cap is reduced by about 25%.

One benefit of increasing the velocity at which the oxygen-enriched gas and atomized fuel mixture is injected from the burner is that flame lift (i.e.
The gap between the tip of the burner and the starting point of the flame is
This means that after switching from normal air to a gas with a high oxygen content, the burner is prevented from decreasing. The higher the temperature, the lower the flame lift may erode the refractory blocks around the burner. Furthermore, the molten refractories flow into the molten glass, where they solidify and remain as impurities. The refractory blocks referred to here are usually used to attach heating burners to cross-heating glass tanks and the like.

Typically, in the operation of cross-heated glass tanks, each burner is adapted to uniformly heat the contents of the tank from one end of the tank to the other (in which case the atomizing medium is conventional air). For this purpose, it is necessary to carefully determine the shape of the flame generated by the burner. In particular, if the flame is too short, the heating of the molten glass at the other end of the tank will be insufficient, whereas if the flame is too long, the wall of the tank facing the burner may be damaged. By using an oxygen-enriched gas as the atomizing medium under the method of the invention, the disadvantages of distortions in the shape of the flame, especially changes in its length, are avoided. The length of the flame remains constant, i.e. at least 4/4 of the width of the tank.
It is preferable to maintain it so that it extends up to 5 and does not reach the opposing wall.

In switching the burner to change the atomization medium from normal air to an oxygen-enriched gas, the foregoing discussion has assumed that the fuel itself and its viscosity remain unchanged. It is the viscosity of the fuel that determines the amount of energy required to atomize the fuel. For commercial use, heavy oil is heated to reduce its viscosity before entering the burner. Even in that case, to atomize heavy oil, use a normal pressure atomizer (approximately
Pressures of 20 to 80 psig) had to be used (at least when melting glass). According to the present invention, it has become possible to burn heavy oil even in a burner equipped with an extremely low-pressure atomizer by using gas with a high oxygen content instead of air. Low pressure herein refers to the use of atomizing media at pressures of 10 psi or less.

The invention further provides a method for burning heavy oil in a burner equipped with a low-pressure gas atomizer using oxygen-enriched gas as the atomization medium. The oxygen-enriched gas is preferably substantially pure and needs to be supplied in the amount of 20 to 30% of the oxygen required for complete combustion of the fuel. "Heavy fuel oil" as used herein refers to fuel oil having a viscosity of at least 3500 SR (Second Drop No. 1).

The invention also includes within its scope a burner for carrying out the method defined above. next,
The method and burner according to the invention will be described in detail with reference to the additional drawings.

The glass melting furnace 2 is provided with a hopper 4 for supplying glass material ore to one end of the tank 6. The ore is melted by a plurality of burners 8. A combustion gas port 10 is provided above the burner 8 . Only one burner is shown in FIG. The molten glass flows out from the tank 6 through the weir 12.

As shown in FIG. 1, four ports 10 are provided on one side of the tank 6, and the remaining four ports are provided on the opposite side. The furnace 2 is provided with a set of regenerators 14 . One of them communicates with four ports along one end of the furnace, and the other regenerator 14 communicates with four other ports along the other side of the tank 6, and the regenerator 14 communicates with four other ports along the other side of the tank 6. The vessels each have an air inlet 15 and an air outlet 17, ie, a heated gas outlet. Outlet 17 communicates with chimney 18 through an inversion. One of the burners 8 has the structure shown in FIG.

20 is a main body portion, and 23 is an auxiliary cap.
The body 20 consists of a solid cylindrical body 24 with an integrally formed projecting head 26. A central channel 28 passes through the cylinder 24 and the head 26 to connect the body 2.
It is formed coaxially with the axis of 0. Twelve channels 30 (only two of which are shown in the drawings) are formed in the cylindrical body 24 surrounding the central channel 28. A pipe 32 for fuel oil is held in the central channel 28 in a fluid-tight manner. The pipe 32 is provided coaxially with and inside the atomizing medium pipe 34. Cap 22 is fluid-tightly engaged with cylinder 24 and pipe 34. The end face 36 of the head 26 of the main body has a central flat part 38 and a tapered part 4 on the outer periphery.
It consists of 0. The inner surface of the cap 22 is formed into a concave shape corresponding to the tapered portion 40, and an atomization chamber 46 is formed between the outlet hole of the central passage 28 and an orifice 48 formed in the cap 22 and coaxial with the central passage 28. A narrow flow path 6 is formed leading to.

A swirl plate 50 is engaged between the end of the fuel supply pipe 32 and the inner wall of the central passage 28 to impart swirling motion to the fuel oil entering the atomization chamber 46 during operation. In the operation of the burner shown in FIG.
Also, atomizing media are respectively supplied to the pipes 34 under the same pressure. The fuel oil passes through the central passage 28 and is given swirling motion by the swirl plate 50. This point has been well known for a long time. It exits the central passage 28 and enters the atomization chamber 46, where it collides with the atomization medium that has entered the same chamber via the pipe 34, flow path 30, and flow path 44, and is atomized. The supply pressure of the atomizing medium and the cross-sectional width of the flow path 44 determine the flow rate and velocity at which the atomizing medium enters the atomizing chamber 46 . A momentum sufficient to atomize the fuel oil is appropriately determined, and fuel particles dispersed in the atomizing medium are injected from the orifice 48 and ignited to form a flame. It should be noted that not all of the oxygen molecules required for combustion are provided by the atomizing medium. As shown in FIG. 1, most of the air required for combustion is supplied from preheater 14 through port 10.

In FIG. 3, a plurality of burners 8 are provided below the port 10. The burner 8 is partially supported by a refractory block 60, and the refractory block 60 is formed with a flow passage 62 whose inner diameter is narrowed at the center, and the end of the burner is thrust into the inside of the passage 62 to reach the narrowest part. It terminates at a point close to 64. The positional relationship between the refractory block 60 and the outlet side of the port 10 is such that the viscosity is sufficient so that the "lift" of the flame during operation (the gas between the tip of the burner and the beginning of the flame) will not damage the refractory block 60. It is considered that there is.

Returning to FIG. 1, a description will be given of how the preheating device 14 and burner 8 melt the glass. Both burner 8 and preheater 14 are operated continuously in two cycles. That is, the burner and preheating device on each side of the tank 6 are operated alternately. In the first cycle, the burner on one side is ignited and secondary air is supplied from the preheater on that same side, which is preheated while passing through the preheater. The hot combustion gases heat the preheater on the opposite side. On entering the next cycle, the burner is internally cooled by air, while the hot combustion gases from the tank 6 enter the port 10 on the side of the currently lit burner and then into the preheater to heat the device. In this way, the raw glass is alternately but continuously heated by the burner group on the west side. It is important that the flame from the burner spreads sufficiently from one side of the tank to the other side so that even the parts furthest from the burner are heated. Heat from the burner is transferred to the glass by convection and radiation.

It is necessary to prevent combustion from occurring within the preheater 14 and the ports 10 at the same time as to prevent uneven heating of the raw material. Furthermore, it is important to prevent soot from accumulating in the preheating device. Therefore, several points should be considered regarding the supply of the atomizing medium.

According to conventional methods, it is desirable to minimize the amount of air as an atomizing medium in order to conserve the power consumption required to compress the air. Furthermore, the primary air that is directly supplied to the burner 8 without passing through a preheating device has a pressure substantially equal to atmospheric pressure, unlike secondary air, and therefore has a negative effect of cooling the flame. However, if there is too little atomization medium air, the fuel oil particles will become too large and cause incomplete combustion, resulting in soot and incomplete combustion gases being accumulated in the preheating device.

Furthermore, there are limits to the speed at which the air atomized fuel mixture is injected from the injection orifice 48 (see FIG. 2) of the burner 8. If it were to be injected too quickly, there would not be enough time for complete combustion to occur before the gas reaches the opposite port of the currently lit burner. Therefore, even if there is the necessary momentum to achieve a sufficient amount of atomization, the speed of the atomizing medium will limit the degree of atomization.

In fact, when air is used as the atomization medium, it is necessary to supply an amount that can cover 4 to 8% of the total amount of air required for combustion of the atomized fuel oil. Furthermore, it is necessary to supply secondary air in excess of that required for combustion. If a typical flame temperature of 1725°C is obtained, the temperature of the combustion gases entering the port 10 opposite the currently lit burner will be approximately 1300-1400°C. These high-temperature gases raise the temperature of the preheating device on the port 10 side, and the air within the device is preheated to about 600 to 800° C. in preparation for the next cycle. The time length of each cycle is appropriately determined to be sufficient to preheat the secondary air.

Simply substituting regular air for pure oxygen or oxygen-enriched gas as the atomizing medium will only shorten or flatten the flame, resulting in the material being heated by the burner in the tank. There is a risk that it will be insufficient in dry areas.

Furthermore, the "lifting force" of the flame decreases and burns out the surrounding fireproof walls, and a local heating phenomenon occurs in which the flame becomes more uneven, causing the tank 6 and preheating device 14 to burn out.
will also be burnt out. In addition, these problems cannot be solved simply by adjusting the flow rates of oxygen, secondary air, and fuel oil, which only leads to incomplete combustion of the fuel.

According to the invention, the rate at which the atomizing medium is supplied to the atomizing chamber 46 of each burner 8 is proportional to the rate at which the mixture of atomized fuel oil and atomizing medium is injected from the injection hole 48 of the burner. is increased. The necessary adjustment of the burner 8 is carried out experimentally. In order to use pure oxygen instead of ordinary air as the atomizing medium, the oxygen supply flow rate is suitably selected between 40 and 60% of the flow rate for air. This allows the amount of fuel oil per unit weight of glass to be reduced. Fuel consumption can be reduced by 10-15% and therefore the fuel oil supply flow to each burner can be reduced by 10-15%. It was confirmed that there was no change in the length or shape of the flame even under such a flow rate. However, in this case, even if the cap 22 is tightened, the main body 2
It is necessary to approach the 0 side and narrow the diameter of the flow path 44 by about 2/3 to reduce the cross-sectional area of the orifice 48 by about 25%.

The atomization momentum of the oxygen and the rate at which the fuel oil and oxygen mixture is injected from the burner will be adjusted as a result, but the length, shape, and lift of the flame will remain unchanged. and can generate a stable flame. The overall oxygen atomization momentum is reduced due to the increased velocity of the atomization medium due to the smaller diameter of the flow path 44. As a result, the atomization of the fuel oil is somewhat relaxed and the particles become coarser, but this prevents the length of the flame from becoming shorter. The supply flow rate of secondary air is also reduced.

As a result of the reduced cross-sectional area of the orifice 48, the rate at which the oxygen and fuel oil mixture is injected from the burner 8 is increased. This keeps the flame length constant. In this case, the particles become coarser, but the increase in injection speed compensates for the faster combustion speed due to the use of oxygen instead of air.

While the length, shape, and lift of the flame remain unchanged, there are many advantages to using oxygen in place of air as the atomizing medium. The temperature of the flame is
The heat generated by the increase in temperature from 150 to 250°C and the formation of free radicals as a result of the high flame temperature improves the efficiency of heat transfer by convection. Furthermore, there is no need to provide excessive amounts of secondary air. (i.e.
The minimum amount required for stoichiometric combustion is ensured. )
The tank 6 will be able to operate at a 2-3% level of atmospheric oxygen instead of the conventional 4-6% level. Since a high preheating temperature can be obtained, the efficiency of the preheating device is improved. The amount of carbon monoxide and hydrogen in the combustion products is reduced.

Preferably all burners should be converted to use oxygen-enriched gas as the atomizing medium in place of normal air. However, in some cases only the desired numbers may be converted. In this case, it is inevitable that the effect will be less. Gases with high oxygen content, such as gases containing 50 to 95% oxygen, may be used in place of pure oxygen, but
The higher the purity of oxygen, the greater the effect. Burners must be made of materials that do not pose a problem when using oxygen. If the type of burner that uses air as the atomizing medium is not made of such a material, the port portion will need to be replaced with a port portion made of a suitable material.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional perspective view of a cross-heating type glass melting furnace, Figure 2 is a longitudinal cross-sectional view of a burner equipped with a normal pressure atomizer, and Figure 3 is a view of the injection holes of the burner shown in Figure 1. FIG. 3 is a partially sectional side view.

Claims (1)

Claims: 1. For liquid fuels that use an atomizing medium to atomize the liquid fuel and that typically use air and heat in an enclosure to help support combustion of the fuel. A method of operating a burner in which an excess of secondary air is supplied to an enclosure to form an oxygen-containing atmosphere thereby forming a stable, substantially completely burned flame of at least a predetermined length. , in which case oxygen or an oxygen-enriched gas is used in place of air as the atomizing medium, thereby producing a stable fully combusted flame of a predetermined length or substantially longer and using air as the atomizing medium. 1. A method of operating a burner for liquid fuel, characterized in that a higher flame temperature is obtained than would otherwise be obtained. 2 The enclosure is a cross-heated glass tank and the flame is at least 4/5 of the width of the tank.
2. A method as claimed in claim 1, in which the method extends up to 100 meters and does not collide with the opposing wall. 3. The method according to claim 1 or 2, wherein the fuel is heavy oil and the burner is equipped with a normal pressure atomizer. 4 Claim 1 in which the atmosphere in the enclosure contains oxygen in an amount not exceeding 3% (by volume)
The method according to any one of Items 3 to 3. 5. The burner has a body part having a flow passage for an atomizing medium for the fuel and a cap having an orifice engaging the body part and allowing the mixture of fuel and atomizing medium to leave the burner. , the body portion and the cap are dimensioned to define an atomization chamber or zone between them, the confined passage for the atomization agent being
The position of its cap in relation to its body reduces the cross-sectional area of its confined passage, such as extending into the atomization chamber or zone, and before using oxygen-enriched gas instead of air as the atomization agent. 5. A method as claimed in any one of claims 1 to 4, wherein the orifice area is reduced. 6 Let m be the mass flow rate of the atomizing agent entering the atomizing chamber before using the oxygen-enriched gas instead of air, and let its velocity be v
and when the mass flow rate and velocity after using oxygen-enriched gas as the atomization medium instead of the air are m ₂ and v ₂ respectively, m is larger than m ₂ and v ₂ is larger than v,
6. The method according to claim 5, wherein (m×v) is greater than (m ₂ ×v ₂ ). 7. The method of claim 5 or 6, wherein the cross-sectional area of the confined flow path is reduced by at least about two-thirds. 8. The method of any of claims 5-7, wherein the area of the orifice is reduced by at least about 25%. 9. A method according to any of claims 5 to 8, wherein the flow rate at which secondary air is supplied to the enclosure is reduced when the atomization medium is switched. 10. A method according to any one of claims 1 to 9, wherein the lift force of the frame does not decrease upon switching of the atomizing medium. 11. The method according to claim 1, wherein the burner is equipped with a low-pressure gas atomizer. 12. The method of claim 11, wherein the oxygen-rich gas is substantially pure oxygen. 13 Claim 1 in which the atomizing medium is supplied with 20 to 30% of the amount of oxygen required for complete combustion of the fuel oil
The method according to item 1 or item 12.