JPH0432792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a firing device for cement raw material powder.

“Prior Art” Traditionally, this type of firing apparatus typically
A device is known that includes a raw material preheating device that preheats raw material powder prior to firing, and a firing furnace that fires the preheated raw material powder. Such firing apparatuses have been increasingly used in recent years because they consume less fuel for firing and are suitable for mass production.

Here, in order to explain a conventional firing apparatus, FIG. 3 shows an overall system diagram of an example of a conventional cement raw material firing apparatus. In the figure, the flow of raw material powder is shown by broken line arrows, and the flow of hot gas is shown by solid line arrows.

This device mainly includes a preheating device 1 consisting of powder collectors C ₁ to _{C 4} such as cyclones for preheating raw material powder arranged vertically, a firing furnace 3 such as a rotary kiln for clinker firing, and a clinker. It is composed of a cooling device 4.

In such a cement raw material firing apparatus, the raw material powder input from the input chute 5 sequentially descends through the preheating cyclones C ₁ to _{C 3} , during which time it is sucked by the exhaust gas induction fan 8 and passes through the duct 7 . After being gradually preheated by the rising hot gas, it is fed to the lowermost separation cyclone C ₄ and then introduced into the kiln 3 via the raw material chute 15 and the connection housing 12 .

High-temperature air supplied from the clinker cooling device 4 and firing fuel sent from the burner 6b are introduced into the firing furnace 3, and the clinker that has been fired at high temperature is passed through the clinker cooling device 4. is discharged.

Incidentally, cement raw materials and fuel contain various impurities such as alkali (K, _Na ), chlorine (Cl), and sulfur (S) (for example, K ₂ SO ₄ ,
(Na ₂ SO ₄ , KCl, NaCl, etc.). These compounds accumulate through repeated evaporation and condensation in the firing apparatus including the raw material preheating apparatus 1 and the firing furnace 3, and eventually form a large amount of coating on the duct 7 of the raw material preheating apparatus 1 and the inner wall surface of each cyclone _C1 to _C4 . These impurities may be generated and cause problems in operation, or the above impurities may be mixed into the cement clinker, reducing the quality of the product.

Therefore, conventionally, as a means for discharging the above-mentioned harmful compounds out of the system, a bypass conduit 16 is connected to the inlet end cover 12 of the firing furnace 3, as shown in FIG. While a part of the exhaust gas from the firing furnace 3 is sucked in by the bypass gas exhaust fan 20, a bypass gas cooling device 17 is disposed in the middle of the bypass conduit 16, and the cooling device 17
In addition, harmful compounds are condensed by drawing cold air from a quench blower 18, and then dust contained in the bypass gas is removed by a dust collector 19.

``Problems that the invention attempts to solve'' However, in such a bypass method,
The amount of bypass gas discharged is determined by the amount of impurities contained in raw materials and fuel, the quality of the required product, etc., but originally it is not possible to bypass the exhaust gas of the kiln and discharge it outside the system. It involves relatively large heat loss.

In addition, the bypass gas quenching device rapidly cools the high-temperature bypass gas to thermally protect the subsequent dust collection and exhaust equipment and prevent coating from adhering to the inside of the bypass conduit. This serves to condense some of the impurities contained in the dust into ultra-fine atomized particles, which then pass through the dust collector and are released into the atmosphere. However, since most of the impurities adhere to the dust surface and condense, the dust collected by the dust collector still contains a relatively large amount of impurities. Therefore, it cannot be re-supplied to the firing apparatus, nor can it be easily disposed of due to environmental pollution, resulting in extremely unpleasant problems.

Moreover, if this dust were to be dumped, the production volume of the calcination equipment would be reduced accordingly, and the main component of this dust would be calcium oxide (CaO), which has already undergone a considerable decarboxylation reaction. Therefore, discarding this waste not only reduces the yield of the product but also doubles the heat loss associated with the bypass.

“Objective of the Invention” Therefore, the main object of the present invention is to prevent the operation from occurring during the firing process of raw material powder.
Another object of the present invention is to provide a firing device for cement raw material powder that can efficiently remove harmful compounds that degrade the quality of the product (clinker).

In other words, the dust extracted from the cement raw material firing equipment along with gaseous substances containing harmful compounds can be reused as raw material powder, so the product yield is high, and the raw material powder prevents heat loss when the dust is discarded. The purpose is to provide a firing device for
Furthermore, it is an object of the present invention to provide a firing device for cement raw material powder that can eliminate environmental pollution caused by dumping of dust.

"Means for Solving the Problems" In order to achieve the above object, the main means adopted by the present invention includes a preheating device for preheating raw material powder, and a firing furnace for firing the preheated raw material powder. In the firing equipment for cement raw material powder,
a dust heating furnace that is connected to the firing furnace via a gas introduction part and that appropriately introduces and heats the gaseous material generated in the firing furnace together with dust; and a dust heating furnace that is connected to the outlet side of the dust heating furnace and that Equipped with a dust separator that circulates the dust heat-treated by the heating furnace to the preheating device or the firing furnace,
A gas cooling device and a dust collector are sequentially disposed on the downstream side of the dust separator when viewed in the gas flow direction, and the dust discharged from the dust collector is transferred to the dust heating furnace via a dust conveying means. In addition, in a cement raw material powder firing apparatus comprising a preheating device for preheating raw material powder and a firing furnace for firing the preheated raw material powder, a gas introduction part is provided in the firing furnace. a dust heating furnace that is connected to the outlet side of the dust heating furnace and that heats the gaseous material generated in the firing furnace by appropriately introducing it together with dust; and a dust separator that allows the dust to flow back to the preheating device or the firing furnace, and on the downstream side of the dust separator when viewed in the flow direction of the gas,
A gas cooling device, a dust preheating device, and a dust collector are arranged in this order, and the dust discharged from the dust collector is transported to the dust heating furnace through the dust preheating device via a dust transport means. be.

"Operation" The bypass dust accompanying the gaseous material extracted from the calcination equipment passes through the dust heating furnace and is separated from the gaseous material by the dust separator attached to the heating furnace. The remaining dust is collected by a dust collector via a gas cooling device, and then
The dust is again introduced into the furnace. When the dust is heated to a high temperature in the dust heating furnace, some of the impurities (hazardous compounds) that have condensed and adhered to the dust surface are reevaporated, and then the dust is removed from the gaseous body in the dust separator. Separated. The separated dust is returned to the firing device and reused as raw material powder.

At this time, the sensible heat of the gaseous body discharged from the firing device is effectively used to heat the dust, thereby improving the thermal economy.

"Effects of the Invention" According to the present invention, in the firing treatment process of raw material powder, it is possible to efficiently remove harmful compounds that hinder operations and reduce the quality of products, and Dust can be reused as raw material powder.

Moreover, heat loss when the dust is discarded can be prevented, and furthermore, environmental pollution caused by dumping the dust can be eliminated.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

"Example" FIG. 1 is a diagrammatic system diagram of a cement raw material powder firing apparatus according to an embodiment of the present invention, and FIG. 2 is a diagrammatic diagram of a cement raw material powder firing apparatus according to another embodiment of the present invention. It is a graphical system diagram.

It should be noted that the following examples are only specific examples of the present invention, and the technical scope of the present invention is not limited by these examples.

Further, the same reference numerals will be used to describe elements common to those of the conventional raw material powder firing apparatus shown in FIG. 3.

In FIG. 1, a cement raw material powder firing apparatus S is connected to a dust heating furnace 26. The dust heating furnace 26 has a bypass gas inlet 20 at the bottom,
For example, it is equipped with a fuel supply device 22 consisting of a burner or the like, and is equipped with a dust separator 24 at the upper part. Among these, the bypass gas inlet 20 is connected to the bypass conduit 16 provided in the inlet end cover 12 of the firing furnace 3, and the fuel supply device 22 heats the inside of the dust heating furnace 26 to a high temperature state. A well-known fluidized bed type or spouted bed type is suitable for such a dust heating furnace 26, and the dust collected in the subsequent dust collector 28, for example, contains a conveyor 29a and a lift 29b. The dust is circulated and supplied via a dust transport device 29.

Note that the bypass conduit 16 is provided with a gas cooling device 17 connected to a quenching blower 18, as in the conventional device (see FIG. 3), and bypass gas introduced from the firing furnace 3 to the dust heating furnace 26 is installed in the bypass conduit 16. is cooled to a predetermined temperature. Gas cooling device 1 in this case
7 is for preventing coating of raw material powder from occurring in the bypass conduit 16, and the temperature of the bypass gas cooled here is 800°C.
℃~900℃ is suitable.

On the other hand, the dust separator 24 is connected to the dust heating furnace 26
Inside, the dust from which impurities (harmful compounds) have been removed is separated and refluxed to the firing furnace 3 again, and the bypass gas discharged from the dust heating furnace 26 is sent toward the subsequent dust collector 28.
As such a dust separator 24, a cyclone type separator is used in the figure. Therefore,
A dust discharge port 24a of the dust separator 24 is connected to the inlet end cover 12 of the firing furnace 3, and a bypass gas discharge port 24b of the dust separator 24 is connected to the dust collector 28 side. Note that a gas cooling device 30 is provided between the dust separator 24 and the dust collector 28 to rapidly cool the conveyed bypass gas on the front side of the dust collector. This cooling device 30 is selected from a water withdrawal type or a cold air type. Thereby, harmful compounds that are impurities in the bypass gas are condensed into a mist and easily pass through the dust collector 28.

In this case, in order to effectively evaporate the impurities in the dust within the dust heating furnace 26, it is desirable to make the inside of the dust heating furnace 26 as high as possible. However, if the temperature inside the dust heating furnace 26 is set too high, the dust separator 24 may suffer heat loss or become clogged with dust, for example. . Therefore, the temperature of the bypass gas sent from the dust heating furnace 26 to the dust separator 24 needs to be maintained at about 1000°C or less.

Therefore, if the temperature of the dust heating furnace 26 becomes too high, the raw material powder that has been preheated to an appropriate temperature in the raw material preheating device 1 may be supplied to the vicinity of the exit of the dust heating furnace 26. , it is necessary to adjust the temperature of the bypass gas introduced into the dust separator 24 to the above temperature. In addition, when supplying the dust collected by the dust collector 28 to the dust heating furnace 26, it is harmful to direct the dust toward the high temperature area formed in the dust heating furnace 26 due to combustion of fuel. Extremely effective in evaporating compounds.

In addition, as the dust collector 28, it is desirable to use a type suitable for passing a mist, such as an electric precipitator or a Multi-Cron. In particular, in the case of an electrostatic precipitator, the temperature of the bypass gas cooled in the gas cooling device 30 is set at around 200° C., thereby improving the permeability of the mist.

Incidentally, the dust collected by the dust collector 28 is
There is no need for the entire amount to be circulated and supplied to the dust heating furnace 26, and if a portion is discarded, discarding the collected dust 28a on the gas outlet side of the dust collector 28 will increase the concentration of harmful compounds. It is effective. The dust collector 28 is composed of a primary dust collector and a secondary dust collector arranged in series, and the dust collected by the primary dust collector is circulated and supplied to the dust heating furnace 26.
A similar effect can be obtained by discarding the collected dust 28a in the secondary dust collector, and in this case, the amount of discarded dust can be adjusted by providing a means for adjusting the amount of dust collected in the primary dust collector.

Next, with reference to FIG. 1, the functions of the cement raw material powder firing apparatus having the above configuration will be explained. First, the bypass gas extracted from the firing furnace 3 is introduced into the dust heating furnace 26 while being cooled by the gas cooling device 17 as necessary. The bypass gas introduced into the dust heating furnace 26 is supplied with fuel by the fuel supply device 22, and the dust that is accompanied by the bypass gas and flows in from the firing furnace 3 side and the subsequent dust collector 28 are further supplied with fuel. Dust that is circulated and supplied via the transport device 29 as appropriate is supplied and heated. At this time,
Combustion air necessary for supplementary fuel is supplied to the dust heating furnace 26 as needed.

In this way, the impurities contained in the dust are
The dust is heated in a heating furnace 26 and partially volatilized into the bypass gas. The bypass gas containing impurities that has been volatilized into a gaseous state is then
It is introduced into the adjacent dust separator 24. Here, the dust with reduced impurities is separated and refluxed to the firing furnace 3 side.

On the other hand, the bypass gas discharged from the dust separator 24 and containing vaporous impurities is sent toward the gas cooling device 30, where it is rapidly cooled. Through this rapid cooling process,
Impurities in the bypass gas are condensed into a mist and are discharged outside the system without being collected by the subsequent dust collector 28.

However, some of the vaporous impurities are condensed on the surface of fine dust that was not separated and collected by the dust separator 24, and such impurities are collected together with the dust by the dust collector 28. dust collector 28
from the dust heating furnace 2 via the dust conveying device 29
6.

Thus, some of the impurities in the bypass gas are
So to speak, the dust heating furnace 26 →
The gas circulates from the gas cooling device 30 to the dust collector 28 to the dust heating furnace 26, but this also passes through the dust collector 28 and is discharged out of the system.

Next, referring to FIG. 2, another embodiment of the present invention will be described. The apparatus of this embodiment is a case in which a calcining furnace is included in the raw material preheating apparatus shown in FIG. 3 described above.

The calcining furnace 35 is connected to the bleed air duct 13 from the cooling device 4.
This is the part where combustion is caused by high-temperature secondary combustion air introduced through the burner 6a and fuel supplied from the burner _6a together with the primary combustion air, and the combustion heat and the heat of the furnace exhaust gas are combined. As a result, the raw material powder supplied from the cyclone _C3 through the raw material chute 14 is calcined. In the firing furnace 3,
As described above, the calcined raw material powder, fuel, and combustion air are introduced, and clinker is fired in the same manner as described in FIG. 3.

The device S' of the embodiment provided for the raw material preheating device 1' having such a configuration is as follows.
This embodiment differs from the embodiment shown in FIG. 1 in the following points.
First, a dust heating furnace 26' is formed in the inlet end cover 12 of the firing furnace 3 via a distribution chamber 38 provided with its own burner _6c for adjusting the temperature of the firing furnace exhaust gas. . This dust heating furnace 2
6' is the same as that used in the embodiment device S in FIG. In this case, the distribution chamber 38 is a part where the exhaust gas from the combustion furnace 3 is once introduced before being supplied to the dust heating furnace 26' as a bypass gas, and a part of the combustion furnace exhaust gas is transferred to the raw material preheating device 26'. It is connected to the calcining furnace 35 via a hot gas conduit 41 in order to supply hot gas for preheating to the ' side.

The calcining furnace 35 is also connected via a chute to a dust separator 24' installed in the dust heating furnace 26', and the heated dust sent from the dust separator 24' is transferred to the calcining furnace 35. will be introduced in After the heated dust is sufficiently mixed with the above-mentioned preheated raw material powder, it is returned to the firing furnace 3 from the separation cyclone _C4 .

Another difference is that an air-cooled gas quenching device 17' is provided downstream of the dust separator 24' when viewed in the flow direction of the bypass gas. In addition, this quenching device 17' and a subsequent dust collector 28
A re-preheating device 39 for the dust transported from the dust collector 28 to the dust heating furnace 26' is provided between the dust collector 28 and the dust collector 28.
is arranged, and the sensible heat of the gas after quenching is effectively utilized by the quenching device 17'. The temperature of the bypass gas after quenching should be as high as possible within a range that can atomize vaporized impurities; for example,
The temperature is selected to be around 400℃~500℃. Furthermore, if the exhaust gas from the re-preheating device 39 is too high for the dust collector 28, a gas cooling device is also provided in the duct on the inlet side of the dust collector 28.

Next, the dust collector 28 and the re-preheating device 3
A dust storage tank 40 is provided in a chute 40' that connects the dust storage tank 9 with the dust storage tank 40, in which the collected dust is once stored and then quantitatively cut out and sent to the dust reheating device 39.

Therefore, in the apparatus of the embodiment shown in FIG. 2 having such a configuration, the raw material preheating device 1' including the calciner 35 can be operated without problems even when the exhaust gas from the calciner 3 is not introduced. Therefore, it is extremely suitable when the amount of bypass gas is large.

For example, if a damper (not shown) is provided in the hot gas conduit 41 connecting the distribution chamber 38 and the calcining furnace 35 of this embodiment apparatus S' and the damper is fully opened, the exhaust gas from the calcining furnace 3 is the dust heating furnace 26'
When the damper is fully opened, the entire amount of the exhaust gas is supplied to the dust heating furnace 26' side, and the so-called bypass rate of the calciner exhaust gas is reduced. It can be adjusted to a desired degree over a wide range.

In addition, since the bypass dust is supplied from the dust separator 24' to the calcining furnace 35, and is sufficiently mixed with the preheated raw material powder, it is supplied to the calcining furnace 3, so that the operation of the calcining furnace 3 is controlled by bypass. Another advantage is that it is not disturbed by the circulating supply of dust.

Further, the bypass dust collected by the dust collector 28 is preheated by the bypass gas discharged from the dust separator 24' toward the dust collector 28, and then supplied to the dust heating furnace 26'. Therefore, the sensible heat of the bypass gas is utilized even more effectively.

In the above description, the types and configurations of the dust heating furnace, dust separator, dust collector, dust preheating device, and gas cooling device can be freely selected.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic system diagram of a cement raw powder firing apparatus according to an embodiment of the present invention, and FIG. 2 is a diagrammatic system diagram of a cement raw material powder firing apparatus according to another embodiment of the present invention. , FIG. 3 is a diagrammatic system diagram of a conventional cement raw material powder firing apparatus which is the background of this invention. (Explanation of symbols), S, S'... Cement raw material powder firing device, 1, 1'... Raw material preheating device, 3...
Firing furnace, 12... Inlet end cover, 16... Bypass conduit, 17, 17'... Gas cooling device, 24, 2
4'...Dust separator, 26, 26'...Dust heating furnace, 28...Dust collector, 29...Dust transport device, 30...Gas cooling device, 35...Calcination furnace, 38...Distribution chamber , C ₁ ~ C ₄ ... Cyclone.

Claims (1)

[Scope of Claims] 1. A cement raw material powder firing apparatus comprising a preheating device for preheating raw material powder, and a firing furnace for firing the preheated raw material powder, which is connected to the firing furnace via a gas introduction part. and a dust heating furnace which introduces and heats the gaseous material generated in the firing furnace together with the dust, and a dust heating furnace which is connected to the outlet side of the dust heating furnace and which heats the dust heated by the dust heating furnace. a dust separator for circulating the gas back into the preheating device or the firing furnace; a gas cooling device and a dust collector are sequentially disposed on the downstream side of the dust separator when viewed in the flow direction of the gas; A cement raw material powder firing apparatus in which dust discharged from a dust collector is conveyed to the dust heating furnace via a dust conveying means. 2. A cement raw material powder firing apparatus comprising a preheating device for preheating raw material powder and a firing furnace for firing the preheated raw material powder, which is connected to the firing furnace through a gas introduction part, and is connected to the firing furnace through a gas introduction part, and a dust heating furnace which introduces and heats the gaseous material generated in the dust together with the dust; and a dust heating furnace that is connected to the outlet side of the dust heating furnace and heats the dust heated by the dust heating furnace to the preheating device or the calcination device. and a dust separator for circulating gas back into the furnace, and a gas cooling device, a dust preheating device, and a dust collector are arranged in this order on the downstream side of the dust separator when viewed in the flow direction of the gas, and the dust collector A cement raw material powder sintering apparatus in which dust discharged from a cement raw material powder is conveyed to the dust heating furnace through the dust preheating device via a dust conveying means.