JPH11130489A - Removing method of harmful material from cement firing device and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove harmful materials such as alkali chlorine, sulfur, heavy metals and the like discharged from a rotary kiln system cement firing device, to suppress the generation of the coating on an air bleed duct, a kiln inlet hood and other parts, to prevent the direct falling of raw materials to the tail end of the kiln to perform a stable operation and to attain the decrease of raw material loss and heat loss. SOLUTION: A part of a kiln waste gas is bled from the kiln inlet hood 14 in the rotary kiln system cement firing device and after the bled waste gas is cooled to 600-800 deg.C by blowing out and supplying a cooling air to a bleeding and pulling out part 22, the cooled waste gas is introduced into a cyclone 32 to separate and collect coarse dust, the collected coarse dust is introduced into the kiln inlet hood 14 by circulation and at the same time, a part of the cyclone waste gas is introduced into the kiln inlet hood 14 by circulation and the remaining cyclone waste gas is introduced into a dust collector 44 to remove a fine dust after heat is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for efficiently removing harmful substances such as alkali, chlorine, sulfur and heavy metals from a rotary kiln type cement firing apparatus.

[0002]

2. Description of the Related Art Alkali (N
a ₂ O, K ₂ O), chlorine compounds (NaCl, KCl, C
aCl ₂ ), sulfate compounds (Na ₂ SO ₄ , K ₂ SO ₄ ,
CaSO ₄ ), carbonate compounds (Na ₂ CO ₃ , K ₂ C)
Low melting point materials such as O ₃ ) are heated in the kiln and volatilized (gasified). These enter the suspension preheater or the calciner and the suspension preheater together with the kiln exhaust gas, where they condense and solidify and enter the kiln again with the powder, and volatilize again to the suspension preheater or the calciner and the suspension preheater. Cycle phenomena such as alkali and chlorine occur between the flow, the kiln and the suspension preheater, or between the calciner and the suspension preheater.

When alkalis, chlorine, and the like volatilized from successive raw materials are added to the cycle and their concentration exceeds a certain limit value, when they are condensed and solidified by a suspension preheater or the like, these low melting point substances form a paste. It plays the role of agglomeration of raw material powder, coaching on furnace wall, and clogging of cyclone that constitutes suspension preheater,
It may cause the kiln operation to be hindered. Especially recently,
Industrial waste, sludge, municipal solid waste, etc. are reused as part of raw materials for cement firing or fuel, and in this case, harmful substances such as alkali, chlorine, sulfur, and heavy metals are contained in the firing equipment. Substances are accumulated, and problems such as coaching trouble and product quality deterioration often occur more often than before.

[0004] To solve these problems, conventionally, alkali,
A so-called alkali bypass method is known in which a part of a volatile gas such as chlorine is extracted and extracted to the outside of the system, and various methods and apparatuses as described below have been proposed. Some problem was unresolved. That is, as a problem of the prior art, (1) coaching occurs in the bleed duct. (2) Raw material (dust) loss is large. (3) High heat loss. (4) Raw materials fall directly into the bottom of the kiln, making stable operation impossible. However, any of the conventional alkali bypass systems is practically (1) to
At least one of (4) has not been resolved.

As one example of the alkali bypass system, Japanese Patent Application Laid-Open No. 49-69758 discloses a method in which a kiln exhaust gas is partially bypassed, alkali is solidified to 10 to 20 μm or less by water injection, and the first separator is used for 10 to 20 μm. A method and apparatus for reducing the alkali content of cement clinker by water spraying in which the above-mentioned dust is separated and returned to a firing device and dust having a size of less than 10 to 20 μm is separated by a second separator is described. Also, Japanese Patent Application Laid-Open No. 54-11132 discloses that a part of the kiln exhaust gas is discharged as a bypass to the outside of the system to remove alkalis and the like, and the air from the cooling device is supplied to the kiln butt in response to a change in the bypass amount. A cement firing method and apparatus which are supplied to secure the kiln bottom flow rate are described.

In Japanese Patent Application Laid-Open No. 54-138022, air is supplied to the entire amount of kiln exhaust gas, cooled to 800 ° C. or less, introduced into a cyclone, and dust is collected by the cyclone and returned to the kiln. A cement firing method is described in which cyclone exhaust gas is introduced into a heat exchanger to recover heat, then dust is removed by an electric dust collector, discharged, and dust is discarded. Also, Japanese Patent Application Laid-Open No. 62-252349 discloses that air is supplied to a part of
After cooling to 00 ° C, a method for treating cement kiln exhaust gas is described, in which dust of about 10 µm or more is separated into a classifier, returned to the kiln, and the cyclone exhaust gas is heat-exchanged by a boiler, and fine powder is removed by a dust collector. Have been. Further, Japanese Patent Application Laid-Open No. 2-116649 discloses that when a part of the kiln exhaust gas is extracted as a bypass, a bypass pipe extracting portion has a double structure, and air is blown between the inner pipe and the outer pipe. A method and an apparatus for preventing scale adhesion of a cement sintering apparatus in which scale adhesion in a bypass pipe is prevented by flowing into an inner pipe are described.

[0007]

Problems to be Solved by the Invention
In the method described in Japanese Patent Publication No. 8 (1994), the temperature inside the extraction duct is high, so that coaching occurs in the extraction duct, and since water is sprayed, the heat loss is large. Since the amount of gas flowing in is reduced, there is a problem that the raw material falls directly to the kiln butt, that is, the kiln entrance hood. In the method described in Japanese Patent Application Laid-Open No. 54-11132, a part of the combustion air is bypassed to the bottom of the kiln, so that the combustibility in the calciner deteriorates and the temperature in the bleed duct is high. Coaching occurs in the bleed air duct, and dust collected by a dust collector provided in the bypass line is discarded. Therefore, there is a problem that a large amount of raw material (dust) is lost and a large amount of heat is lost.

In the system described in Japanese Patent Application Laid-Open No. 54-138021, the classification performance of a normal cyclone at large and high temperatures is not good, so that the raw material (dust) loss tends to increase. In addition, coaching occurs in the bleed air duct, and furthermore, the entire amount of kiln exhaust gas is extracted, so that there is a problem that heat loss is large and the amount of combustion in the calciner increases. Further, in the method described in Japanese Patent Application Laid-Open No. 62-252349, the loss of raw material (dust) tends to increase due to poor classification performance in a large cyclone and high temperature in a normal cyclone. When the exhaust gas is bled and the amount of gas flowing into the raw material preheating system is reduced by that amount, the raw material falls directly to the kiln bottom. Further, Japanese Patent Laid-Open No. 2-11
In the system described in Japanese Patent No. 6649, a method is adopted in which the inner pipe of the double pipe is shortened to prevent the introduced air from flowing out to the suspension pre-heater side. Flows to the side,
There is a large heat loss, and when the exhaust gas is bled, the amount of gas flowing into the raw material preheating system is reduced by that amount, so that there is a problem that the raw material falls directly to the kiln tail.

The present invention has been made in view of the above points, and an object of the present invention is to suppress the occurrence of coaching in a bleed duct and other parts, to perform a stable operation, and to reduce the loss of raw material and heat. It is an object of the present invention to provide a method and an apparatus capable of reducing a loss and obtaining a high-quality cement clinker having a low harmful substance content.

[0010]

In order to achieve the above-mentioned object, a method for removing harmful substances from a cement burning apparatus according to the present invention comprises a method of removing part of kiln exhaust gas from a kiln inlet hood in a rotary kiln type cement burning apparatus. After extracting and cooling air is blown out and supplied to a bleed extraction unit to cool the bleed exhaust gas to a range of 600 to 800 ° C., the cooling exhaust gas is introduced into a cyclone to collect and collect coarse dust. The collected coarse-grained dust is circulated and introduced into the kiln inlet hood, and a part of the cyclone exhaust gas is circulated and introduced into the kiln inlet hood. It is configured to remove dust (see FIGS. 1 and 6).
In this case, since the vapor of harmful substances such as alkalis flows in the upper part of the kiln in the rotary kiln, it is preferable to extract a part of the kiln exhaust gas from the kiln side portion of the kiln inlet hood (FIGS. 1 and 1). 6). In addition, the temperature of the cooling exhaust gas was set to 600
An appropriate temperature is determined within the range of ８００800 ° C. 600
If the temperature is lower than ℃, heat loss increases, and if it exceeds 800 ° C, condensation of volatile harmful substances decreases. In addition, 600-8
In the range of 00 ° C., most of the volatile harmful components condense.

In the above method, it is preferable that the bleed-out portion is made an air-cooled box structure and cooling air is blown out into the bleed-out gas from a number of air outlets to uniformly cool the entire surface of the bleed-out portion. 2 to 4). As the cyclone, it is preferable to use one or a plurality of cyclones that can collect coarse dust having a particle size of about 10 μm or more in parallel. In addition, a part of the kiln exhaust gas circulated into the kiln inlet hood is made approximately the same as the amount of air extracted from the kiln inlet hood, and the remainder of the cyclone exhaust gas discharged outside the system is made approximately the same as the amount of cooling air. Is preferred.

An apparatus for removing harmful substances from a cement firing apparatus according to the present invention includes a suspension preheater or a raw material preheating system including a suspension preheater and a calciner.
In a cement sintering apparatus including a rotary kiln for firing preheated raw materials and a clinker cooler for cooling the fired clinker, a bleed extraction unit for bleeding a part of exhaust gas is provided to a kiln side portion of a kiln inlet hood. A cooling air supply pipe is connected to the bleed air extraction unit, and the bleed air extraction unit is connected to the bleed air extraction unit via a bleed exhaust gas conduit.
A plurality of cyclones or a plurality of parallel cyclones are connected, a bottom of the cyclone and a kiln inlet hood are connected via a collection dust collection pipe, an exhaust gas outlet conduit of the cyclone is branched, and one cyclone exhaust gas conduit is connected to a kiln inlet. It is connected to a hood, and a heat exchanger or a cooler and a dust collector are provided in series in the other cyclone exhaust gas conduit (see FIGS. 1 and 6).

[0013] In the above apparatus, it is preferable that the bleed air extraction unit has an air-cooled box structure composed of a double pipe having a large number of air ejection holes in the inner pipe (see FIGS. 2 to 4). In addition, as a cyclone, for example, an exhaust gas inlet for introducing exhaust gas in a tangential direction is provided at an upper portion, and a substantially inverted conical body is continuously provided at a lower portion of a cylindrical body having an exhaust gas discharge pipe at a central portion of an upper surface. consecutively provided an enlarged wall portion at the bottom of the inverted conical body further consecutively provided a substantially inverted conical barrel in the expanded wall portion, the inner diameter d of the substantially inverted cone body of the lower end inner diameter D ₁ and the exhaust gas discharge pipe D ₁ ≧ d, and D ₂ = (0.8 to 1.D) between the inner diameter D of the cylindrical body and the inner diameter D ₂ of the lower end of the enlarged wall.
It is preferable to use a high-efficiency cyclone having a relationship of 0) × D (see FIG. 5).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications. FIG. 1 shows an apparatus for removing harmful substances from a cement firing apparatus according to a first embodiment of the present invention, which includes a new suspension preheater (NSP method) having a suspension preheater and a calciner. Reference numeral 10 denotes a suspension preheater, which includes a plurality (four in FIG. 1 as an example) of cyclones C ₁ , C ₂ , C ₃ , and C ₄ . The suspension preheater 10 and the calciner 1
2 constitutes a raw material preheating system. 13 is an exhaust gas fan. The lower end of the calciner 12 is connected to one end of a rotary kiln 16 via a kiln inlet hood 14, and the other end of the rotary kiln 16 is connected to an air-cooled clinker cooler 18. 19 is a high-temperature air pipe, 20 is a kiln burner.

An extraction section 22 for extracting a part of the exhaust gas is provided at a portion of the kiln inlet hood 14 on the kiln side, and the extraction section 22 is provided with a cooling air supply pipe 2.
4 are connected. 26 is a cooling air supply fan, 2
Reference numeral 8 denotes a cooling air flow control valve (for example, a damper). Further, a cyclone 32 is connected to the bleed gas extraction unit 22 via a bleed exhaust gas conduit (alkali bypass pipe) 30, and the bottom of the cyclone 32 and the inside of the kiln inlet hood 14 are connected via a collection dust collection tube 34. It is connected. The exhaust gas outlet conduit 36 of this cyclone 32 is branched into two, one cyclone exhaust gas conduit 38 is connected to, for example, the anti-kiln side of the kiln inlet hood 14, and the other cyclone exhaust gas conduit 40 has a heat exchanger 42. And an electric dust collector 44 are provided in series. Note that, instead of the heat exchanger 42, a cooler that sprays water to lower the temperature of exhaust gas, for example, a stabilizer, may be provided. 46 is an exhaust gas fan, 48 is an exhaust gas flow control valve (for example, a damper), 50 is an exhaust gas circulation fan, and 52 is an exhaust gas circulating flow control valve (for example, a damper).

FIG. 2 shows an example of the bleed-out section 22, and FIG. 3 shows an example of a cross section taken along line AA in FIG. The bleed air extraction part 22 is provided with a large number of air ejection holes 7 in the inner pipe 70.
It is formed in an air-cooled box structure consisting of a double tube having two. 74 is an outer tube, 76 is an air inlet, and 78 is an air cooling box. In this case, as shown in FIG.
6 is connected in the tangential direction of the outer tube 74, and the air ejection holes 72 are preferably provided in an oblique direction so that the exhaust gas flow becomes a swirling flow. With this configuration, the inner pipe 70 can be more efficiently used.
And the bleed air can be cooled. FIG. 4 shows another example of the bleed extraction unit 22a. This bleed extraction unit 22a
Has a plug damper 80 provided in an inner tube 70. Other numbers indicate the same members as those in FIG. When the amount of harmful substances such as alkalis in the raw material is small, it is not necessary to perform bleeding. In such a case, the plug damper 80 is moved to the closed position (the position shown by a chain line in FIG. 4) to reduce the bleeding amount. Set to zero.

A plurality of cyclones 32 may be installed in parallel. In this case, since the diameter of the cyclone is smaller than that in the case where one cyclone is installed, finer dust can be collected. As the cyclone 32, for example,
It is preferable to use a high-efficiency cyclone as described in Japanese Utility Model Publication No. 7-46357. As shown in FIG. 5, the high-efficiency cyclone has an exhaust gas inlet 82 for introducing exhaust gas in a tangential direction on the upper side, and a substantially inverted cylinder body 86 having an exhaust gas discharge pipe 84 in the center of the upper surface. A conical body 88 is continuously provided, and the substantially inverted conical body 88 is provided.
Lower the continuously provided an enlarged wall portion 90 of the further, inner diameter d of the enlargement wall portions 90 continuously provided a substantially inverted conical barrel 92, an inverted conical body 88 substantially lower inner diameter D ₁ and the exhaust gas discharge pipe 84 Is D ₁ ≧ d
D ₂ = (0.8-1.0) × D between the inner diameter D of the cylindrical body 86 and the inner diameter D ₂ of the lower end of the enlarged wall 90.
Are configured to have the following relationship. By using a cyclone having such a structure, 10 to 20
Dust of about μm or more can be collected efficiently.

In the cement sintering apparatus configured as described above, the exhaust gas from the rotary kiln 16 is introduced into the calciner 12 and the suspension preheater 10 through the kiln inlet hood 14, and these are sequentially turned into a raw material flow. The gas passes through the opposite direction to preheat the raw material, and the exhaust gas fan 13
Is discharged out of the system. The preheated raw material is supplied from the preheated raw material introduction pipe 15 to the kiln inlet hood 14. The high-temperature air from the air-cooled clinker cooler 18 is introduced into the calciner 12 through the high-temperature air pipe 19 and used as combustion air for the calciner. In this case, the exhaust gas from the rotary kiln 16 usually has a temperature of about 1100 ° C., and contains raw material dust and atomized or vaporized alkali and chlorine compounds. The alkali or the like in the atomized or vaporized state flows in the upper part of the rotary kiln 16, so that a part of the kiln exhaust gas is extracted from the kiln side portion of the kiln inlet hood 14 and the extraction part 2
2, cooling air is supplied from many air ejection holes 72, for example,
Spouts at a flow rate of 20-30 m / s and removes bleed exhaust gas
Cool to a temperature set in the range of ８００800 ° C. (depending on the components in the raw material).

As described above, the extracted exhaust gas is 600 to 800
Cools rapidly to ° C. In this case, the alkali vapor or the like solidifies into extremely small particles, and the alkali vapor or the like adheres and solidifies to the raw material dust. Most of harmful substances such as alkali are contained in dust having a particle size of 10 to 20 μm or less. The exhaust gas cooled to 600 to 800 ° C. is introduced into the cyclone 32, and coarse dust is separated and collected. In this case, the particle size is about 10 to 20 μm or more, preferably
A cyclone capable of collecting coarse dust of about 0 μm or more is used. Since the collected coarse-grained dust is mostly composed of the raw material dust having a small alkali content, it is returned into the kiln inlet hood 14. Further, a part of the cyclone exhaust gas is returned to the kiln inlet hood 14. In this case, it is preferable to return the kiln entrance hood 14 to the part on the opposite side to the kiln. The remainder of the cyclone exhaust gas is transferred to a heat exchanger 4
2 and heat recovery, and then into an electric precipitator 44 to remove fine dust having a size of 10 to 20 μm or less, which is mainly composed of an alkali or the like, and then discharge the dust outside the system. The heat exchanger 4
In the case where a cooler such as a stabilizer is provided instead of 2, the cooled exhaust gas is introduced into the electric dust collector 44 without performing heat recovery.

The amount of air extracted from the kiln inlet hood 14 is preferably 0 to 0.5 times the kiln exhaust gas. When the content of harmful substances such as alkali in the raw material is small, for example, when the industrial waste is not mixed with the raw material, or when the raw material having a small content of alkali or the like is used, the kiln exhaust gas is extracted. No need. 0 to above
0 of 0.5 corresponds to such a case. Then, it is preferable that the amount of part of the cyclone exhaust gas returned to the kiln inlet hood 14, that is, the amount of circulation is equal to the amount of extracted air. In this way, even if the amount of extracted gas fluctuates, the same amount of circulating gas as this amount of extracted gas enters the kiln inlet hood 14, so that the amount of gas flowing to the calciner 12 does not fluctuate and stable operation is performed. Can be continued. The amount of cooling air supplied to the bleed air extraction unit 22 is 1.0 to
It is about 0.5 times. In this case, 1.0 times is the amount of air when cooling to 600 ° C, and 0.5 times is the amount of air when cooling to 800 ° C. As described above, when controlling the amount of extracted air and the amount of circulation to be equal, the amount of cooling air and the amount of exhaust gas extracted from the electric precipitator 44 out of the system are necessarily equal.

FIG. 6 shows an apparatus for removing harmful substances from a cement burning apparatus according to a second embodiment of the present invention.
This embodiment is a case of an SP system in which a calciner is omitted and a raw material preheating system is constituted only by the suspension preheater 10. In the SP method without the calcining furnace, the upper limit of the amount of extracted air is about 0.3 times the amount of kiln exhaust gas. Other configurations and operations are the same as those in the first embodiment.

[0022]

As described above, the present invention has the following effects. (1) From a rotary kiln type cement firing device,
Harmful substances such as alkali, chlorine, sulfur, and heavy metals can be efficiently removed, and a high-quality cement clinker can be obtained. Also, bleed air duct, kiln inlet hood,
It is possible to suppress the occurrence of coaching in other parts, prevent the raw material from directly dropping into the kiln bottom, perform a stable operation, and reduce raw material loss and heat loss. (2) Since the cooling air is ejected and supplied to the bleed air extraction unit, the cooling of the bleed air extraction unit and the cooling of the extracted kiln exhaust gas can be efficiently performed. In particular, when the bleed air extraction unit has an air-cooled box structure and the cooling air is blown out from a large number of air outlets, the bleed air extraction unit is uniformly cooled over the entire surface, and almost all of the air is effectively used for cooling the bleed air. You. (3) Since dust is collected at a relatively high temperature by one or more cyclones and returned to the kiln inlet hood, heat loss and material loss are reduced. (4) Since a part of the cyclone exhaust gas is circulated and collected to the kiln inlet hood, the fluctuation of the amount of gas injected into the calciner is reduced. In particular, when the same amount of extracted gas as the kiln exhaust gas from the cyclone exhaust gas is circulated and collected in the kiln inlet hood, the amount of gas injected into the calciner always depends on the change in the extracted gas amount (bypass rate). It becomes constant and stable operation can be continued.

[Brief description of the drawings]

FIG. 1 shows an apparatus for removing harmful substances from a cement burning apparatus according to a first embodiment of the present invention, which is a new suspension preheater (NSP) system in which a suspension preheater and a calciner constitute a raw material preheating system. It is a schematic block diagram.

FIG. 2 is an explanatory cross-sectional view showing an example around a bleed air extraction unit in FIG. 1;

FIG. 3 is an explanatory sectional view taken along line AA in FIG. 2;

FIG. 4 is an explanatory cross-sectional view showing another example around the bleed air extraction unit in FIG. 1;

FIG. 5 is an elevational view showing an example of the cyclone in FIG. 1;

FIG. 6 is a schematic configuration diagram showing an apparatus for removing harmful substances from a cement burning apparatus according to a second embodiment of the present invention, which is of a suspension preheater (SP) type.

[Explanation of symbols]

C _{1 to} C ₄ cyclone 10 suspension preheater 12 calciner 13 exhaust gas fan 14 kiln inlet hood 15 preheating raw material introduction pipe 16 rotary kiln 18 clinker cooler 19 high temperature air pipe 20 kiln burner 22, 22a bleed air extraction section 24 cooling air supply pipe 26 Cooling air supply fan 28 Cooling air flow rate control valve 30 Bleed exhaust gas conduit (alkaline bypass pipe) 32 Cyclone 34 Collection dust collection tube 36 Exhaust gas outlet conduit 38, 40 Cyclone exhaust gas conduit 42 Heat exchanger 44 Electric precipitator 46 Exhaust gas fan 48 Exhaust gas flow control valve 50 Exhaust gas circulation fan 52 Exhaust gas circulation flow control valve 70 Inner pipe 72 Air outlet 74 Outer pipe 76 Air inlet 78 Air cooling box 80 Plug damper 82 Exhaust gas inlet 84 Exhaust gas exhaust pipe 86 Cylindrical body 88 Abbreviation Inverted conical body 90 Enlarged wall 92 Approximately inverted conical body

Claims (8)

[Claims] In a rotary kiln type cement firing apparatus, a part of kiln exhaust gas is bled from a kiln inlet hood, and cooling air is blown and supplied to a bleed extraction part to reduce the bleed exhaust gas to a range of 600 to 800 ° C. After cooling, this cooling exhaust gas is introduced into a cyclone to separate and collect coarse dust, and the collected coarse dust is circulated and introduced into the kiln inlet hood, and a part of the cyclone exhaust gas is introduced into the kiln inlet hood. A method for removing harmful substances from a cement sintering apparatus, comprising circulating and collecting or cooling the remainder of cyclone exhaust gas, and then introducing the dust into a dust collector to remove fine dust. 2. The method for removing harmful substances from a cement firing apparatus according to claim 1, wherein a part of the kiln exhaust gas is extracted from a kiln side portion of the kiln inlet hood. 3. The cement according to claim 1 or 2, wherein the bleed-out portion has an air-cooled box structure, and cooling air is blown into the bleed-out gas from a number of air outlets to uniformly cool the entire surface of the bleed-out portion. A method for removing harmful substances from a firing device. 4. A harmful effect from the cement firing apparatus according to claim 1, wherein one or more cyclones capable of collecting coarse dust having a particle size of about 10 μm or more are connected in parallel. How to remove the substance. 5. A part of the kiln exhaust gas circulated and introduced into the kiln inlet hood is substantially equal to the amount of bleed air extracted from the kiln inlet hood, and the remainder of the cyclone exhaust gas discharged out of the system is substantially equal to the amount of cooling air. The method for removing harmful substances from a cement firing apparatus according to any one of claims 1 to 4, wherein the same amount is used. 6. A raw material preheating system including a suspension preheater or a suspension preheater and a calciner,
In a cement sintering device consisting of a rotary kiln for firing preheated raw materials and a clinker cooler for cooling the fired clinker, a bleed extraction unit for bleeding a part of exhaust gas is provided at a kiln side portion of a kiln inlet hood. A cooling air supply pipe is connected to the bleed air extraction unit, and one or a plurality of parallel cyclones are connected to the bleed air extraction unit via a bleed exhaust gas conduit, and the bottom of the cyclone and the kiln inlet hood are connected to each other. The cyclone exhaust gas outlet pipe is connected through a collection dust collection pipe, the cyclone exhaust gas outlet pipe is branched, one cyclone exhaust gas pipe is connected to the kiln inlet hood, and the other cyclone exhaust gas pipe is connected with a heat exchanger or a cooler and a dust collector. An apparatus for removing harmful substances from a cement burning apparatus, which is provided in series. 7. The apparatus for removing harmful substances from a cement firing apparatus according to claim 6, wherein the bleed-out unit has an air-cooled box structure comprising a double pipe having a large number of air ejection holes in an inner pipe. 8. A cyclone has an exhaust gas inlet for introducing exhaust gas in a tangential direction at an upper portion, and a substantially inverted conical body is continuously connected to a lower portion of a cylindrical body having an exhaust gas discharge pipe at a central portion of an upper surface. An enlarged wall portion is continuously provided at a lower portion of the substantially inverted conical body, and a substantially inverted conical body portion is continuously provided on the enlarged wall portion.
The inner diameter d of the substantially inverted cone body of the lower end inner diameter D ₁ and the exhaust gas discharge pipe
Has a relationship of D ₁ ≧ d, and D ₂ = (0.8 to 1.0) × between the inner diameter D of the cylindrical body and the lower end inner diameter D ₂ of the enlarged wall portion.
The apparatus for removing harmful substances from a cement burning apparatus according to claim 6 or 7, wherein the apparatus is a high-efficiency cyclone having a relationship of D.