JPS6012126A - Calcinating method and furnace therefor - Google Patents

Abstract

PURPOSE:To enhance the combustion efficiency of gaseous fuel, by providing a fuel supplying pipe for blowing the gaseous fuel in the vicinity of the outlet of the gas extracting duct of a calcination furnace while introducing hot air and the gaseous fuel into a calcination region in a preliminarily prepared state. CONSTITUTION:Preheated cement is supplied into a calcination furnace 5 of cement from a stock material chute 4d while air is supplied thereinto from an air duct 6 through an air dispersing plate 6f and heated air generated in a cooler is supplied from a gas extracting duct 6b. One or a plurality of fuel supply pipes 6j are provided to said gas extracting pipe 6b so as to be positioned in the vicinity of the outlet thereof to supply natural gas and, after this natural gas is mixed with heated air in the gas extractin duct 6b, the gaseous mixture is sent to the calcination region of the calcination furnace 5 to perform the calcination of cement.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calcination method in a cement or limestone sintering apparatus and an improvement to a calcination furnace for carrying out this method.

The gt diagram shows a conventionally commonly used cement firing device. This cement firing equipment includes a suspension preheater (floating preheater) 1, a calcining furnace 5, a four-tally kiln 7, a 29, a 77-channel 10 air supply for the 2, an exhaust gas conduit t t for the suspension preheater 1, and an IDF.
(fil17) It is composed of 12 (J).

Suspension preheater 1 C, usually 4K, CD cyclone 2a, 2b, 2c, 26 and pipe line 5 connecting each other 5 a #5 b #5 c y 5 el
and are connected by raw material chutes 4a, 4b, 4c, and 46 and arranged vertically. . Exhaust gas with a high temperature of about C (0□ Rockiness: 1
~3%] to preheat the cement raw material. In addition, all these systems are operated under suction by the IDF 12.

The calcining furnace 5 includes a fluidizing air supply blower 6a.

Fluidizing air duct) 6'x Cooler 9 to about 700C (Bleed air duct for supplying hot summer air) 6 b.

It consists of a raw material shoe from the cyclone 20) 4d, a fuel supply pipe (burner) 6d1 into which pulverized coal or heavy oil is normally blown, and an exhaust gas duct 6θ. This device is 6d
Burning the fuel from 6a and 6d with air from 4
Heat the cement raw material entering from d to 750-850C,
The limestone in the cement raw material is temporarily tJ1. c) It is related to decarburization. The cement raw material and exhaust gas decarboxylated in the calcining furnace 5 pass through 6e, are combined with the four-tally kiln exhaust gas in the pipe 3d, and are transported to the cyclone 2d.
After solid-gas separation, only the cement raw material is supplied to the tally kiln through 46.

The four-tally kiln 7 heats the cement raw material until 1150t7&1 summer using the combustion heat of the fuel supplied from the burner 8, reacts it, and converts it into clinker. The cooler 9 is a cooling device for clinker discharged from the rotary kiln 7, and cools the clinker to 150 to 250C with air from an air supply fan 10 for the cooler 2.

Note that a part of the air heated by the cooler 29 is transferred to the bleed air duct 6.
b is supplied to the calcining furnace 5.

FIG. 2 shows a conventional calcining furnace 5. At the bottom of the calciner body 5, there are a number of nozzles (an air dispersion plate 6f consisting of an open tube, and a raw material shoe on the upper side wall) 4d, several M fuel supply pipes 6d, and further above these 11114i. It has one to four bleed ducts 6b arranged in the circumferential direction of the furnace.

Below the air distribution plate 6f is a fluidizing air duct) 6
a.

The air chamber 'is has a powder discharge pipe 6b near the center of the air distribution plate 6f, and a discharge valve 61 at its lower end. FIG. 3 shows a cross section along the line A--m in FIG. 2.

Normally, in the calciner 5, about 10 to 20% of the air amount required for combustion of the fuel supplied from the fluidizing air duct) is supplied from the calcination furnace 5.
From da, the remaining total air is supplied from the extraction duct 6b. In addition, the amount of NOx generated in the calcining furnace is low because the temperature inside the calcining furnace 5 is kept at a low temperature of 800 to 850 C due to the decarboxylation reaction of the cement raw material, and because of the catalytic action of the cement raw material itself. Low, 100-500 for coal fuel
It is about ppm. When the fuel used in such a calciner is heavy oil or pulverized coal, a fuel supply pipe (burner) is installed on the wall of the main body gJJ. Because the solid fuel is spread through the layers, and the solid fuel is fluidized and diffused, even if the mixing with the air near the supply port 3 is somewhat poor, it can be completely burned in the calciner, so no particular inconvenience will occur. .

However, when gas fuel, for example natural gas whose main component is methane, is used as a fuel, the ignition temperature of methane is lower than that of coal or heavy oil. Since the mixture of fuel and branch gas (oxygen) is a gas-gas mixture, compared to the case of liquid or solid fuel, the dispersion mixing of the exciter layer circle is not good, and sufficient mixing cannot be achieved. It is said that complete combustion in the calciner is not possible and combustion occurs in the downstream cyclone 26, etc., and as a result, the temperature of the exhaust gas from the eggplant preheater 1 rises, causing an increase in fuel consumption. There is a high possibility that this will cause inconvenience.

SUMMARY OF THE INVENTION An object of the present invention is to provide a calcination method for performing pre-metal combustion when gas is used as fuel in the calcination of cement or limestone, and a calcination r for carrying out the same.

The mold of the present invention can be removed by installing one or more burners in the vicinity of the outlet of the bleed duct, rather than in the case of conventional solid or liquid fuels, where the burner is installed in one or more stages near the outlet of the bleed duct. Increase the heating efficiency with the air from the calcination furnace 7.
The objective is to improve combustion performance by making uniformity of the cross-section of the Leeboard.

FIG. 4 shows a calcining furnace 5 to which the present invention is applied. The symbols used are the same as those in Figure 2 and Figure i5, and the calciner body 5
The bottom of the furnace has an air distribution plate 6f consisting of a large number of nozzles, and the upper side wall thereof has a raw material chute 411. Furthermore, there are 1 to 4 air extraction ducts 6b disposed on the upper wall 110 of the furnace in the direction of the furnace main body. Below the total air distribution plate 6f, there is a fluidization duct) 6a, a nitrogen chamber 6g% air distribution plate 6
A powder discharge pipe 6h is located near the center of f.

It has a discharge valve 61 at its lower end. Figure 5 shows the fourth
The 8-8UT plane of the figure is shown. At this time, at the outlet of the bleed duct 6b (near the connecting part with the calciner body), a plurality of fuel supply pipes (burners) 6j are provided in each bleed duct 6b in the circumferential direction, passing through the side wall 6k of the bleed duct. The tip of the burner is installed so that it hardly protrudes into the bleed duct.

In order to complete the combustion of gas fuel, such as natural gas whose main component is methane, in the calciner, it is most important to mix it with air as well as possible in the lower part of the calciner. . This requires that the gas ejected from the burner be mixed with the combustion air as quickly as possible, and for this it is necessary to ensure that the fuel gas jet from the burner passes through an area where the velocity relative to the air flow is high. .

If a burner is provided on the side wall near the outlet of the bleed duct as in the present invention, compared to a case where a burner is provided on the side wall of the calcination furnace body, after mixing in the bleed duct, the inside of the calcination furnace body Because it mixes in two stages, mixing again with air, it mixes with air more quickly (
, more thorough mixing can be achieved. The side wall near the outlet of the bleed duct and the calciner body [from the burner position on the wall,
FIG. 6 shows data comparing the mixing states of the same cross section inside the main body after each tracer gas was injected.

Figure 6 U) shows the tracer concentration distribution in the case of the present invention, and Figure 6 (B) shows the tracer concentration distribution in the case where a separate burner is provided on the reactor water side wall as in a conventional reactor, where σ is the cross-sectional average 1. The standard deviation in the case of 0 is shown. It is clear from this result that mixing is better when the burner is provided on the side wall near the outlet of the bleed duct.

Furthermore, the tip of the burner hardly protrudes from the inner surface of the bleed duct, thereby reducing the risk of local overheating of the duct due to direct contact of the frame with the bleed duct facing the burner.

In other words, when the burner protrudes into the bleed duct, the distance between the burner tip and the opposing wall becomes shorter, so if the flame is long, it will lick the opposing wall, causing damage to the wall due to local overheating. This is because it may cause burnout. In addition, in the case of a small-diameter furnace, the fuel pipe is opened at a position close to the cross section where the bleed duct opens into the calciner. 4. The method of mounting the burner is not limited to the methods shown in FIGS. 4 and 5, but also includes mounting methods such as horizontal and vertical directions.

As mentioned above, in the present invention, one or more fuel gas supply pipes (burners) are provided on the side wall near the outlet of the bleed duct, but when multiple burners are provided, the nozzle axes of them are gathered at one point. If the combustion gas is concentrated at one point, a large amount of high-temperature combustion gas will be locally present, and the mixing of the combustion gas and the bleed air will be worse than if it were not concentrated at one point. This is because if the performance of the calciner deteriorates or if local high-temperature gas comes into contact with the raw material, the raw material will overheat, melt, and adhere to the furnace wall, making operation difficult.

According to the present invention, it is possible to prevent the burnout of the duct in the calciner and the adhesion of high-temperature raw materials at the opening of the calciner, which cause decarboxylation reactions, which are often seen in conventional seizo. , it can improve the mixing of gas fuel. □

[Brief explanation of drawings]

FIG. 1 shows a cement firing apparatus commonly used in the past, FIG. 2 shows a conventional calcining furnace, and FIG. 3 shows a cross section taken along the line AA in FIG. 2. FIG. 4 shows the calcining furnace of the present invention, and FIG. 5 shows the B-8 cross section in FIG. 4, respectively. Figure 6 shows the gas mixing state when tracer gas is introduced at the lower part of the free board of the calciner main body. This shows the case where a burner is installed on the side wall of the main body.Sub-agent 1) Mei-Fuku agent Ryo Hagiwara - Oni 2 figure t4FF4 !, Cemen l-MFl 兇5 figure (8-8 cross section of Kabuto figure 4) ＼cement Seri r1 Light 6 diagram (a) (b)

Claims (1)

[Claims] In a calcining method in which a gaseous fuel such as natural gas is blown into a cement raw material or limestone heated to a temperature of t71t or preheated to cause a decarboxylation reaction, a bleed air supply for supplying hot air to a calcining area is used. A calcination method characterized in that the hot air and the gaseous fuel are premixed in a duct and introduced into a calcination area. In a calcining furnace in which a gaseous fuel such as natural gas is injected into 7i temperature or preheated basket raw materials or limestone to cause a decarboxylation reaction, there is a hot air pattern on the side wall of the calciner body. A calciner characterized in that one or more fuel supply pipes for blowing the gaseous fuel are provided near the outlet of an air bleed duct for supplying the gas to the calciner.