JPS6065751A - Calcining furnace for cement raw material powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calciner for cement raw powder disposed between a raw material preheating device and a tCt forming furnace. The cement raw materials are highly calcined by burning the supplied fuel while suppressing the generation of oxides), and if necessary, the NO contained in the furnace exhaust gas is removed.
By effectively denitrating x, the amount of NOx emitted from the raw material preheating device is reduced, and at the same time, the formation of coatings due to the heating part in the calcination furnace is eliminated, making it possible to operate more stably. The present invention relates to an improvement of a calciner for cement raw material 1'5], and provides a structure for supplying fuel and preheating raw materials to the calciner, which is particularly suitable for pulverized coal fuel.

A modern cement calcining apparatus is constructed by disposing a calcining furnace having an independent heat source between the raw material preheating device 0 and the calcining furnace. FIG. 1 is a linear system diagram showing the steps of preheating, calcination, firing, and cooling of cement raw material powder. In the figure, solid arrows indicate the flow of hot air, and dashed arrows indicate the flow of the raw material powder. The outline of the device is as follows: 1. A raw material preheating device configured by arranging powder separators such as cyclones in multiple stages. Calcining furnace 2. The cement raw material powder supplied from the raw material input chute 5 sequentially descends through each of the first to fourth cyclones C, -c, and the other, the firing furnace 3 and the clinker cooler 4. High-temperature exhaust gas from the calcining furnace 2 is passed through the induced draft fan 7
Since it is sucked by a and rises inside the raw material preheating device 1,
Heat exchange between the raw material powder and the high temperature gas is repeated within the duct 8 and within the cyclones C and -c. The preheated raw material powder is placed under the raw material preheating device (from the second stage Φ-cycle controller C).
4 into the calcining furnace 2 through the chute 14. On the other hand, combustion occurs in the calciner 2 by high-temperature secondary combustion air introduced from the clinker cooler 4 and fuel supplied from the burner 6d together with the primary combustion air, and the combustion heat and sintering or exhaust gas are The raw material powder is calcined by receiving the heat. The calcined raw material powder is sent to the calciner 2 together with the combustion gas.
After entering the lowest stage cyclone C5 and being separated,
Fuel enters the firing furnace 3 through the chute and is supplied from the burner 6 installed at the lower end of the firing furnace 3.
%, it undergoes the necessary heat treatment in the firing Iy33 to become clinker, and then is cooled in the cooling tJl14. Air for cooling the clinker is supplied by the forced air blower 10, and a part of the air heated by exchanging heat with the clinker is distributed and introduced into the calcining furnace 2 and the firing furnace 3 as described above. Excess air is discharged through the dust collector 9 by an induced draft fan. Then, the clinker from the clinker cooler 4 and the dust collector ta9 is carried out to the next process by the container 11.

Figure 2-1 is a conceptual diagram showing in more detail the structure near the calciner in Figure 1. Using these figures, the structure and function of the calciner when pulverized coal is used as fuel is explained as follows. That's right.

That is, in this configuration example, the calcining furnace 2 has a cylindrical vertical shape, and the constricted part 2
It is composed of a lower combustion chamber 21 and an upper mixing chamber 2 which communicate with each other with the border c as the boundary. 2
J is connected to the firing furnace 3 via the inlet end fiffi12. Further, a bleed air duct 13 that guides high temperature bleed air from the clinker cooler 4 as secondary air for combustion is opened and connected to the lower side wall of the combustion chamber 2a in the radial or tangential direction, and the ceiling wall of the bleed air duct 13 is connected to the lower side wall of the combustion chamber 2a. Combustion chamber 2 of calciner 2
．． There is a combustion chamber 2 in the vicinity where it joins the side wall. A burner 6, 1 is installed that blows pulverized coal together with primary air toward the high-temperature bleed air flowing into the combustion chamber 2a. The preheated material input shoe 1-14 from C1 is connected to the mixing chamber 2. The combustion gas outlet 2e is the lowest stage cyclone C5 of the raw material preheating device 1.
It is connected to the.

When using these devices, the preheated raw material from the cyclone C4 at the second stage from the bottom of the +m raw material preheating device 1 is supplied into the combustion chamber 2n of the calciner 2 through the input chute 14, and is passed through the inlet end 12 into the combustion chamber 2n. Exhaust gas from the firing furnace 3 flowing upward through the combustion chamber 2a from below mixes and stirs the combustion chamber 2a to form a spouted bed. High-temperature bleed air from the clinker cooler 4 is introduced into the spouted bed as secondary combustion air through the bleed duct 13.
The burner 68 installed on one side of the inlet to the combustion chamber 2a
Pulverized coal as a P material is supplied together with primary air for combustion through the jet, and trowel combustion is performed using a jet stream jτ41. The raw material 15) fed through the preheated raw material chute 14 toward the combustion zone formed in the combustion chamber 24 absorbs the combustion heat of these fuels and the sensible heat of the sintering furnace exhaust gas to advance the calcination reaction. The combustion gas is introduced into the mixing chamber 2 through the constriction part 2c, but is stirred and mixed by the diffusion effect due to acceleration and deceleration when passing through the constriction part 2c and the turbulent flow generated in the mixing chamber 2c. is promoted, the combustible components contained in the combustion gas are completely combusted in the mixing chamber 2, the raw material powder is sufficiently calcined, and then the raw material preheater W is passed through the 2° opening.
It is designed to be discharged to the lowest stage cyclone C5 of No. 1.

When burning fuel in such a calciner, the burner 6a
Although it is intended that a good combustion state can be obtained by attaching the unit facing the high-temperature bleed air flowing into the combustion chamber 2a, combustion is carried out in a spouted bed and the second stage from the bottom of the raw material preheating device 1 is installed. All of the preheated raw material from cyclone C4 is directed toward the combustion zone formed in the combustion chamber 2a, and the combustion temperature in the combustion zone is therefore maintained relatively low, so that the combustion rate of the fuel increases. It is slow and has not yet achieved sufficient combustion performance.

In addition, the lower opening 2 of the calcining furnace 2. The exhaust gas from the kiln 3 that rises and flows from the burner 6t contains a large amount of NOx that was originally present during the combustion of the fuel supplied from the burner 6t in the kiln 3.
is contained, and a reducing gas atmosphere is formed in H15 inside the inverted cone-shaped part 2f by using fuel supplied through the burner 6° installed on the side wall of the inverted cone-shaped part 2f of the calciner 2. In some cases, denitrification is carried out, and it is known that the cement raw material powder forming the jet stream effectively acts as a denitrification catalyst. These raw material powders are a part of the raw material powder supplied into the combustion chamber 2a from the preheated raw material chute 14 and flowed down to the inverted cone-shaped part 2f. Depending on the operating condition, if the velocity of the secondary combustion air introduced through the bleed air duct 13 is high or if the combustion air is directed toward the combustion zone formed within the lower opening 2.
If the velocity of the firing furnace exhaust gas introduced from J is high, a dense spouted layer of raw material powder cannot be formed inside the inverted conical part 2f, and not only will a sufficient denitrification effect not be obtained, but also The combustion of the high-temperature exhaust gas or the fuel supplied from the burner 6c forms a localized overheated area in the lower part of the calciner, causing a coating of Ijj (material powder) on the wall of the calciner, which causes operational problems. There are cases.

The present invention solves the above-mentioned problems of the prior art, and improves the combustibility of fuel by appropriately adjusting the temperature of the combustion atmosphere in the combustion zone formed in the combustion chamber. This method effectively denitrates NO contained in the calciner and at the same time eliminates the formation of coating of the raw material powder at the bottom of the calciner, enabling more stable operation of the calciner. It is intended to provide a supply and distribution structure for preheating raw materials.

However, in the present invention, the preheated raw material is supplied to the combustion zone formed in the calciner by supplying fuel to the high-temperature bleed air from the cooler flowing into the calciner. The arrangement structure of the preheating raw material chute that can adjust and supply only a part of the preheated raw material is provided, and furthermore, the preheated raw material other than the one supplied to the combustion zone is transferred to the calciner exhaust gas flowing from the bottom of the calciner. The gist lies in the arrangement structure in which the branched preheated raw material chute for directional supply is connected to or near the inverted cone-shaped portion at the bottom of the calciner.

The present invention will be described in detail below based on the drawings, but the drawings show specific examples of implementation, and the present invention is not limited to these illustrated examples. Even if the configuration or a part of the design is changed, the same implementation is possible.

FIG. 3 is a conceptual diagram showing the structure of the vicinity of the calcining furnace in one embodiment of the calcining furnace for cement raw material powder according to the present invention,
Basic structure of the calcining furnace 2, method of introducing exhaust gas from the calcining furnace 3 into the calcining furnace 2, method of introducing secondary air for high temperature combustion from the extraction duct I/13, combustion gas in the calcining furnace 2 The flow of steps and the method for discharging the combustion gas from the calciner 2 are the same as those of the conventional apparatus shown in FIG. 2 described above.

An example of the embodiment of the present invention will be described in detail based on FIG. 3. In the charcoal supply pipe 6a as a fuel supply device, the ceiling wall of the extraction duct I/13 is connected to the side wall of the calciner 2. Nearby, the preheated raw material chute 14 from the cyclone C4 in the second stage from the bottom of the raw material preheating device y71 is installed to face the high temperature bleed air flowing into the combustion chamber 2a. Two preheated raw material chutes 14. , i4b, and one branch chute 14. is connected to the pulverized coal supply pipe 6a, so that a part of the preheated raw material is supplied into the calciner together with the fuel, and the other branch chute 14I is connected to the pulverized coal supply pipe 6a in the cross section of the calciner 2. At or near the inverted cone-shaped portion 2f of the calcining furnace 2 at a distance in the circumferential direction from the location where the supply pipe 6d is provided,
It is arranged to face the exhaust gas from the firing furnace 3 rising and flowing in from below.

In addition, in this example, the pulverized coal supplied from the pulverized coal supply pipe 6a is conveyed through the piping 17 by a pneumatic conveying device,
Separated by a primary collector 18 such as a cyclone and a secondary collector 19 such as a filtration dust collector, and directly or by gravity.
The material is charged into the calcining furnace 2 via a storage pot (not shown).

Further, a fuel supply pipe 6e is installed in the inverted cone-shaped portion 2I to supply a portion of fuel as necessary, and solid fuel, liquid fuel, etc. of the same type or different type as the fuel supplied from the fuel supply pipe 6- is installed. It is now being supplied.

Because of this configuration, the pulverized coal supplied from the fuel supply pipe 6a toward the high-temperature bleed air flowing into the combustion chamber 2a forms a combustion zone at the tip of the fuel supply pipe 6J in the combustion chamber 2a,
A part of the preheated raw material is supplied to the combustion zone together with the pulverized coal through the raw material shoe 14a and the pulverized coal supply pipe 6J. At this time, if the atmospheric temperature in the combustion zone of the fuel decreases, the combustibility of the fuel decreases, and conversely, if the temperature of this combustion zone increases, the amount of NOx generated tends to increase, so NOx is supplied to the combustion zone. The amount of the pre-p5 raw material is adjusted by the distribution valve 15, and the structure is such that the temperature of the combustion atmosphere in the combustion zone can be optimally adjusted.

Here, the NOx generated in the combustion zone is 1100°C.
Since the amount of gas generated decreases significantly below the atmospheric temperature of 100%, it is desirable to suppress the atmospheric temperature in the fuel combustion zone to this level. By measuring the CO content as a representative component of NOx and unburned gas in the air and adjusting the distribution valve 15 based on this, the amount of NOx generated can be easily controlled in consideration of combustibility, and the operating conditions can be adjusted. Even if the amount of NOx fluctuates, it is possible to always keep the NOx generation amount stable and low. In addition, according to the configuration of the illustrated example in which a part of the preheated raw material is supplied to the calciner together with the fuel, the raw material powder rapidly absorbs the combustion f; However, the present invention is not limited to the illustrated example;
The preheated raw material may be supplied directed to the combustion zone, and the fuel may be separately supplied as in the conventional example shown in FIG.

Next, the other part of the preheating raw material is supplied from the inverted conical part 2I of the calciner 2 or its vicinity through the branch shoe 14b, away from the location where the fuel supply pipe 6J is disposed in the cross section of the calciner. , the injected gas is directed toward the exhaust gas from the firing furnace 3 that rises and flows in from below, so regardless of the operating conditions such as the firing furnace exhaust gas velocity, a dense spouted bed of raw material powder is always flowed into the inverted cone-shaped part. 2f, a reducing gas atmosphere is created inside the inverted cone-shaped portion 21 by the fuel supplied from the fuel supply device 6e, and the NOx-containing firing furnace exhaust gas passing through the core portion is denitrified. In some cases, the raw material powder acts sufficiently and effectively as a denitrification catalyst to promote the denitrification reaction. A-Not only does it cause heat, but also the high temperature exhaust gas from the calciner 3 or the combustion heat of the fuel supplied from the fuel supply device (6e) causes a localized overheated area in the lower part of the calciner, causing it to reach the wall of the calciner +ll11. It is possible to avoid a situation where a coating of the raw material powder is formed and the operation is hindered.

In these calciner structures, the cross-sectional shape of the calciner, the number of bleed ducts, the number and arrangement of fuel (Jli supply devices), etc. can be freely selected according to the purpose.
The effect can be further enhanced by combining with other methods related to suppression of Ox generation or denitrification.

The present invention is constructed as described above, and when supplying the preheated raw material from the second-stage end separator from the bottom of the raw material preheating device to the calciner, the preheated 13% charge is adjusted and divided. By using them for their respective purposes, the combustibility of the fuel in the calciner can be improved, and at the same time, the generation of NOx can be suppressed or controlled, and local overheating in the calciner can be eliminated. This enabled even more stable operation.

[Brief explanation of drawings]

Figure 1 shows the conventional cement clinker manufacturing process.
FIG. 2 is a conceptual diagram of the vicinity of the calcining furnace in FIG. 1, and FIG. 3 is a conceptual diagram showing the configuration of the vicinity of the calcining furnace according to an embodiment of the present invention. (Explanation of symbols) l...Material preheating device 2...Calcination furnace 2a...Combustion chamber 2T...Mixing chamber 21...Inverted conical portion 3...Calcination furnace 4... - Clinker cooler 6...Fuel supply device 13...Bleed air duct 14...Preheated raw material chute 14a, 146...Branch chute 15...Distribution valve 16...Branch member. Applicant: Kobe Steel, Ltd. Agent Patent Attorney: Takeyu Honjo Figure 1 Figure 2

Claims (2)

[Claims] (1) Placed between the raw material preheating device and the firing furnace, the lower end is constricted into an inverted conical shape and connected to the firing furnace via the inlet end cover, and the upper end or the vicinity thereof is connected to the powder at the lowest stage of the raw material preheating device. A bleed air duct from the clinker cooler connected to the separator and on the side wall,
In the calciner for cement raw powder powder connected to the fuel supply device and the preheating ring from the second-stage powder separator from the bottom of the raw material preheating device] high-temperature bleed air from the cooler that flows into the calciner. A fuel supply device is arranged near the joint between the side wall of the calciner and the ceiling wall of the bleed duct, and the preheated raw material chute is branched, and one preheated raw material chute is connected to the calciner from the fuel supply device. It is connected to the calciner to supply a part of the preheating raw material toward the combustion zone formed by the fuel supplied into the furnace, and the other preheating raw material shoe i is connected across the cross section of the calciner. A calcining furnace for cement raw material powder, characterized in that a distribution valve for adjusting the amount of preheated raw material supplied toward the combustion zone is installed at a branch part of the preheated raw material chute. (2) In order to supply preheated raw materials other than those directed toward the combustion zone toward the calciner exhaust gas rising and flowing from below the calciner, the other branched preheating raw material chute is connected to the lower width of the calciner. 1. The calcining furnace for cement l-raw material powder according to claim 1, characterized in that the calcining furnace is connected to or near the inverted cone-shaped part of the RFID.