JPH0743096B2 - Burner for fine powder solid fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention is used in an electric furnace for melting steel scrap,
Alternatively, it relates to a burner for fine powder solid fuel used for melting metals such as aluminum and copper.

[Prior Art] As a burner for melting steel scrap, aluminum, copper, etc., a stable flame of about 2000 ° C. or more is required as a flame characteristic because of the required melting capacity.
However, the combustion speed of pulverized coal itself is much slower than gas fuels such as C ₃ H ₈ and CH ₄ , as well as liquid fuels such as heavy oil, and the flame temperature is low. Therefore, when the temperature in the vicinity of the burner in the furnace is low, the radiant heat from the surroundings is also small, a stable flame cannot be obtained by combustion of only pulverized coal, and it may extinguish, so the conventional burner for the above purpose is LPG, Burners that use a gaseous fuel such as natural gas or a liquid fuel such as heavy oil as a fuel have been used, and when pulverized coal has been used as a fuel, a co-firing type burner with these fluid fuels has been used. However, in order to obtain a high-temperature stable flame, it is necessary to increase the mixing ratio of liquid fuel or gas fuel, so the usage ratio of pulverized coal, which is cheap, is reduced, and the energy cost is increased as a whole.

FIG. 2 shows an example of a burner of a mixed combustion type of pulverized coal and liquid fuel which has been conventionally used. This burner is composed of concentric circular cylinders with six end faces, and in order from the center to the outside, the center pipe is the liquid fuel supply conduit 31, the periphery of which is the combustion-supporting gas supply conduit for liquid fuel combustion 32, and the pulverized coal outside it. A supply conduit 33, a combustion-supporting gas supply conduit 34 around the supply conduit 33, and a cooling water jacket 35 outside the supply conduit 33. A liquid fuel spray nozzle 36 is attached to the tip of the liquid fuel supply conduit 31, and the liquid fuel supplied through the conduit 31 is ejected from the nozzle 36. At the tip of the liquid-fuel combustion combustion-supporting gas supply conduit 32, a liquid-fuel combustion combustion-supporting gas ejection nozzle forming ring 37 is formed.
Is attached, the combustion supporting gas for liquid fuel combustion is ejected from an annular ejection port 38 formed by the outer periphery of the liquid fuel spray nozzle 36 and the combustion supporting gas ejection nozzle forming ring 37, Mix to produce a primary flame. Reference numeral 39 denotes a main combustion chamber forming cylinder, and the cylinder 39 and the liquid fuel spray nozzle 36
Further, the main combustion chamber 40 is formed by the tip of the combustion-supporting gas supply conduit 32 for liquid fuel combustion and the tip of the pulverized coal supply conduit 33.
A pulverized coal ejection port 41 supplied by the pulverized coal supply conduit 33 is further opened on the rear surface of the main combustion chamber 40, and a part of the pulverized coal combustion-supporting gas is ejected to the outer periphery thereof. The jet port 42 is opened, and the pulverized coal and the combustion-supporting gas jetted from the jet ports 41, 42 are mixed and burned by being assisted by the primary flame of the liquid fuel to form a secondary flame. In front of the main combustion chamber 40, there is a sub-combustion chamber 43 formed in front of the combustion-supporting gas supply conduit 34 and the main combustion chamber 40, and the combustion-supporting gas ejected from the outer periphery of the main combustion chamber forming cylinder 39. The primary flame and the secondary flame are surrounded by the gas and completely burned. As described above, the conventional burner is a mixed burning system in which the flame of liquid fuel and the flame of fine powder are mixed together to form a combustion flame.

[Problems to be solved by the invention]

As described above, in a melting burner used in an electric furnace for melting steel scrap, an aluminum melting furnace, a copper reflex furnace, etc., even when used in a place where the temperature near the burner in the furnace is low, a stable flame at high temperature is obtained. There has never been a burner for forming fine powder, which has a sufficient melting ability. The present invention is a fine powder burner that can be sufficiently used for such applications, and uses only gas or liquid fuel for preheating the combustion-supporting gas, and the main combustion flame is pulverized coal flame. The purpose is to provide a burner for fuel.

[Means for solving problems]

The present invention has been made in view of the above-described object, and a combustion chamber that mixes and burns a gaseous fuel or a liquid fuel with a combustion-supporting gas, and a gas curtain with the combustion-supporting gas that surrounds the combustion chamber and is to be preheated. And a main combustion chamber that mixes and burns the produced high temperature combustion-supporting gas and fine powder solid fuel. A burner for fine powder solid fuel (first invention), which is a burner for fine powder solid fuel, which melts metal such as steel scrap, aluminum, and copper using a fine powder solid fuel combustion flame. A main combustion chamber that mixes and combusts fine powdered solid fuel with each other, and a conduit that supplies fine solid fuel to the main combustion chamber, and a gaseous fuel or a liquid fuel is used as a combustion-supporting gas around the conduit. Mixed A fine powder solid characterized by comprising a plurality of combustion-supporting gas preheating devices for obtaining a high-temperature combustion-supporting gas by mixing a combustion product gas obtained by combustion with the combustion-supporting gas for combustion of the fine powder solid Burner for fuel (second invention)
Is.

[Work]

As described above, the present invention is a burner for fine powder solid fuel in which a preheating device for combustion-supporting gas is incorporated in the burner body, and the preheating device is a gaseous fuel such as propane or methane in the combustion-supporting gas atmosphere, or kerosene, A liquid fuel such as heavy oil is burned to obtain a high-temperature combustion product gas, which is mixed with a combustion-supporting gas to form a high-temperature combustion-supporting gas. The high-temperature combustion-supporting gas and pulverized coal are provided at the burner tip. Pulverized coal as the main fuel by mixing and burning in the main combustion chamber
A stable flame having a flame temperature of

〔Example〕

FIG. 1 is a view showing a vertical cross section of a pulverized coal burner which is an embodiment of the present invention. In the figure, 1 is a burner body, 2 is a pulverized coal supply conduit, 3 is a gas or liquid fuel introduction pipe for preheating combustion-supporting gas, 4 is a gas or liquid fuel supply branch pipe, 5a ... 5n
Is a combustion-supporting gas preheating gas or liquid fuel supply conduit, 6 is a combustion-supporting gas introduction pipe, 7 is a combustion-supporting gas supply conduit, and 8 is the conduit 2 and a conduit arranged so that their cross sections are concentric The combustion-supporting gas flow passages formed by 7; 9a ... 9n are combustion-supporting gas preheating devices provided around the pulverized coal supply conduit 2;
... 10n is a combustion chamber provided in each preheating device, 11 is a preheating combustion-supporting gas nozzle for ejecting combustion-supporting gas into each combustion chamber 10a ... 10n, 12 is a combustion-supporting gas preheating flame, Nozzles for a combustion-supporting gas curtain 13 for ejecting combustion-supporting gas so that a gas curtain is formed surrounding each of the combustion chambers 10a ... 10n, 14
Is a mixed portion of the high temperature combustion product gas and the room temperature combustion supporting gas, 15 is a pulverized coal combustion nozzle forming body, 16a and 16b are high temperature combustion supporting gas nozzles, 17 is the main combustion chamber, 18 is pulverized coal combustion flame jet , 19 is a pulverized coal combustion flame. Nozzles 16a, 16 for high temperature combustion supporting gas
Each b is composed of a plurality of small holes or slits formed in the direction of converging to one point (P and Q) in the direction of the pulverized coal combustion flame jet 18 on the central axis of the burner body 1. The nozzles may be provided not only in two groups 16a and 16b but also in three groups or four groups.

Reference numeral 20 denotes a heat insulating layer, which is provided over the entire outer circumference of the combustion-supporting gas supply conduit 7 to prevent loss of heat generated by the preheating devices 9a ... 9n.

Reference numeral 21 denotes a cooling water jacket, which is provided to prevent the burner tip portion, that is, mainly the pulverized coal combustion nozzle forming body 15, from being overheated and damaged by radiant heat from the pulverized coal combustion flame 19 and the furnace.

Further, a is pulverized coal, b is a combustion-supporting gas, c is a gas or liquid fuel, d is a combustion-supporting gas for preheating, e is a combustion-supporting gas for a gas curtain, and f is a flow of high-temperature-supporting gas. Show.

The pulverized coal, which is the main fuel in this burner, is supplied with the pulverized coal supply conduit 2 together with the carrier gas such as carbon monoxide or argon.
Will be introduced to. On the other hand, the gaseous fuel or the liquid fuel for preheating the combustion-supporting gas is introduced from the gaseous or liquid fuel introduction pipe 3, passes through the branch pipe 4, and the gaseous or liquid fuel supply conduit 5a ...
It is supplied to 5n, reaches the combustion-supporting gas preheating device 9a ... 9n, and is introduced into the combustion chambers 10a ... 10n of the device 9a. In addition, the combustion-supporting gas is introduced through the combustion-supporting gas introduction pipe 6, reaches the combustion-supporting gas preheating device 9a ... 9n through the combustion-supporting gas supply passage 8, and part of the combustion-supporting gas is a combustion-supporting gas nozzle for preheating. Combustion chamber 10a from 11 ...
… Introduced in 10n. In the combustion chambers 10a ... 10n, the gas or liquid fuel supplied through the supply conduits 5a ... 5n is mixed and combusted to form a flame 12 for combustion-supporting gas. The remaining portion of the combustion-supporting gas passes through a combustion-supporting gas curtain nozzle 13 provided around each combustion chamber, and surrounds each combustion chamber 10a ... 10n to form a gas curtain, which is used for preheating the combustion-supporting gas. flame
Heat transfer from 12 to the combustion-supporting gas supply conduit 7 is prevented to protect the heat transfer tube 7, and heat loss is minimized.

The high temperature combustion generated gas due to the flame generated in each combustion chamber 10a ... 10n and the combustion-supporting gas forming the gas curtain are mixed in the mixing section 14 to become the high-temperature combustion-supporting gas, and the high-temperature combustion-supporting gas nozzle 16a , 16b and then to the main combustion chamber 17. On the other hand, the pulverized coal introduced together with the carrier gas through the pulverized coal supply conduit 2 is similarly ejected into the main combustion chamber 17 and the nozzle
16a, 16b is mixed with the high temperature combustion-supporting gas and burned, then pulverized coal combustion flame is ejected from the ejection port 18, pulverized coal combustion flame
Forming 19. In the main combustion chamber 17, since the combustion-supporting gas has a high temperature, the combustion continues stably, and the flame temperature is about 2000 to 24.
A stable flame of 00 ℃ is obtained.

〔The invention's effect〕

The present invention is a burner which uses the pulverized coal as a main fuel and which has the combustion-supporting gas preheating device configured as described above, and has a flame temperature of 20
A pulverized coal combustion flame of 00 to 2400 ° C can be obtained in a stable state, and the energy cost is lower than that of a co-firing burner with gas or liquid fuel, and a burner with a compact structure can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the burner for pulverized coal solid fuel of the present invention, and FIG. 2 is a vertical cross-sectional view of a conventional burner of a mixed burning system of pulverized coal and liquid fuel. 1 ... Burner body, 2 ... Pulverized coal supply conduit, 3 ... Combustion gas preheating gas or liquid fuel introduction pipe, 4 ... Gas or liquid fuel supply branch pipe, 5a ... 5n ... Gas Or liquid fuel supply conduit, 6 ... combustion supporting gas supply conduit, 8 ...
Combustible gas flow path, 9a ... 9n ... Combustible gas preheater, 10
a …… 10n …… Combustion chamber, 11 …… Supporting combustion gas nozzle for preheating,
13 …… Nozzles for supporting gas curtain, 16a, 16b …… Nozzles for high temperature supporting gas, 17 …… Main combustion chamber

Claims (5)

[Claims] 1. A combustion chamber for mixing a gaseous fuel or a liquid fuel with a combustion-supporting gas for combustion, and a combustion-supporting gas nozzle for surrounding the combustion chamber and forming a gas curtain with the combustion-supporting gas to be preheated. And a main combustion chamber for mixing and burning the generated high temperature combustion-supporting gas and fine powder solid fuel, and a burner for fine powder solid fuel. 2. The burner for finely divided solid fuel according to claim 1, wherein the combustion-supporting gas is oxygen. 3. The burner for finely divided solid fuel according to claim 1, wherein the combustion-supporting gas is oxygen-enriched air. 4. The burner for finely divided solid fuel according to claim 1, wherein the combustion-supporting gas is air. 5. A burner for fine powder solid fuel, which melts metal such as steel scrap, aluminum and copper by using fine powder solid fuel combustion flame, and burns by mixing combustion supporting gas for fine powder solid combustion and fine powder solid fuel. And a main combustion chamber for supplying fine powdered solid fuel to the main combustion chamber, and combustion obtained by mixing a gaseous fuel or a liquid fuel with a combustion-supporting gas and burning the gas around the conduit. A burner for a fine powder solid fuel, comprising a plurality of combustion-supporting gas preheating devices for obtaining a high-temperature combustion-supporting gas by mixing the generated gas and the combustion-supporting gas for burning a fine powder solid.