JPS5857382B2 - Cement firing equipment including calcining furnace for cement raw materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement firing apparatus including a calcination furnace for cement raw materials.

The rotary kiln with a raw material preheater has been improved, and a calcination furnace with an independent heat source has been installed between the raw material preheater and the rotary kiln. Cement firing equipment is widely known and is designed to reduce the size of the equipment and reduce various basic units by using a calcining furnace with high heat transfer efficiency instead of using a rotary kiln with low heat transfer efficiency, and is already very effective. Many inventions have been made.

Some of these devices have already been put into practical use.

Such cement firing equipment uses a cyclone alone, or a so-called co-current preheater that combines several stages of cyclones and vortex chambers, as a raw material preheater, and has various equipment characteristics depending on the method of the calcining furnace. These calciners can be separated according to the type of airflow used and their structure.

That is, they are divided into those that utilize swirling flow, those that utilize a spouted bed, those that utilize a spouted bed and swirling flow, and those that utilize a fluidized bed.

Compared to a kiln with a raw material preheater, cement firing using these cement firing devices reduces the size of the rotary kiln and reduces the heat load inside the kiln, resulting in lower equipment costs, lower unit consumption of refractory bricks, and lower nitrogen pollution. Oxide (NO
Various benefits can be expected, such as a reduction in the amount of x) generated.
Nevertheless, various drawbacks are found as shown below.

(1) In general, in calciners, especially in calciners other than the fluidized bed type, the residence time of raw materials and fuel is short, and in many calciners, the kiln exhaust gas is mixed with high-temperature air extracted from the clinker cooler. Since the fuel is combusted at a relatively low oxygen concentration in the gas, the fuel is not completely combusted in the furnace, and combustion continues even in the second or third cyclone counting from the lowest or lowest stage. Coating troubles may occur in the cyclones or the conduits between the cyclones, or the capacity of the raw material preheater may not be large enough to absorb the retained heat of the combustion gas generated at those locations into the raw material.
The temperature of the gas discharged from the raw material preheater is raised, and the heat removed from the exhaust gas is increased.

The amount of increase in the removed heat is large, and the heat consumption of the entire firing apparatus may be greater than that of the raw material preheater kiln.

(2) These cement firing devices usually use a rotary kiln, a so-called co-current preheater that combines several stages of cyclones, or a vortex chamber, or a calcining system in which raw materials are suspended in an air stream and calcined using the heat of fuel combustion. It consists of a furnace and a cyclone that separates the raw material from the calciner exhaust gas accompanied by the calcined raw material.

Therefore, the pressure loss of the entire cement firing device is the sum of the pressure losses of these individual devices.

Preheaters require fairly high pressure drops.

In addition, many calcining furnaces are of the type that disperses the raw material in an upward air current and calcinates it while lifting it. The gas flow rate must be increased considerably, which not only reduces the calcination time and fuel combustion time in the calcination furnace, but also increases the pressure drop, as mentioned above.

In addition, the pressure loss of the cyclone for separating the calcined raw materials is added, and the overall pressure loss becomes quite high.

As a result, the amount of electricity used by the exhaust gas induction fan is quite large, and although the kiln has the advantage of reducing drive power by making the kiln smaller, the amount of electricity used by the entire firing device is not necessarily lower than that of a kiln with a raw material preheater. No.

Note that when a fluidized bed furnace is used as the calcining furnace, the pressure loss is particularly high, and furthermore, the amount of electric power consumed increases.

(3) Cement raw materials contain some alkali and chlorine, but these components are concentrated in the dust between the kiln and the calciner, or between the calciner and the preheater, due to the effects of volatilization and condensation. be done.

If these components increase, the melting point of the dust will drop, and the dust will weld in the duct between the kiln and calciner, or between the cyclone of the preheater, causing coaching problems and lowering the draft, making it impossible to operate. Sometimes.

Therefore, the content of alkali and chlorine in the raw materials used is limited.

This invention relates to a cement firing device that improves the drawbacks of the above-mentioned prior art. It includes a countercurrent preheater that swirls calciner exhaust gas upward from the bottom and feeds raw materials from the top, and a clinker cooler at the top. The main part of the extracted high-temperature air is introduced by swirling, the remaining mixed gas of rotary kiln exhaust gas and high-temperature air is introduced by swirling from the lower part, and the raw material to be calcined is input from the upper part, the fuel is combusted, and the raw material and combustion gas are combined. A calciner is combined with a calciner that exchanges heat in countercurrent flow, and an exhaust gas conduit and a calciner exhaust gas conduit are installed at the center of the upper end of the countercurrent preheater and the calciner, respectively, and raw materials and The raw material discharged from the countercurrent preheater is input, and after parallel flow heat exchange, the raw material is separated in the upper separation cyclone and the lower separation cyclone, and as described above, the raw material is transferred to the upper end of the countercurrent preheater and calciner, respectively. When solid fuel is used as well as liquid fuel, it is completely combusted in the lower part of the calciner, calciner exhaust gas pipe, or countercurrent preheater, which has a long residence time. The heat retained in the combustion gas is fully absorbed by the raw material in the preheater with a large heat exchange capacity, lowering the temperature of the preheater exhaust gas, increasing the calcining rate of the raw material in the rotary kiln to almost 100%, and reducing fuel consumption. It is an object of the present invention to provide a cement firing apparatus that can reduce the overall pressure loss and further reduce the amount of nitrogen oxide emissions sufficiently.

Next, a cement firing apparatus including a cement raw material calcining furnace of the present invention will be explained with reference to drawings shown in embodiments.

1 is an exhaust fan for all exhaust gas flow, 2 is an upper separation cyclone, 3 is an exhaust gas conduit, 4 is a countercurrent preheater,
9 is a lower separation cyclone, 13 is a calciner, 16 is a rotary kiln, and 18 is a clinker cooler.

The countercurrent preheater 4 includes a cylindrical vertical main body 4a and an inverted conical raw material discharge chamber 4b formed at the lower part of the main body 4a.

The lower part of the main body 4a is communicated with the upper end of the lower separation cyclone 9 via the exhaust gas conduit 1.

As shown in FIG. 2, the exhaust gas conduit I is connected tangentially to the main body 4a.

Further, the raw material discharge chamber 4b is communicated with the calciner exhaust gas conduit 8 through a preheated raw material supply pipe 10.

The upper end of the counterflow type preheater 4 is connected via the exhaust gas conduit 3 to the inlet pipes 3a of the plurality of upper separation cyclones 2 provided around the exhaust gas conduit 3.

The lower end of the upper separation cyclone 2 is communicated with the upper part of the main body 4a of the countercurrent preheater 4 through a conduit 2a.

The upper end of the upper separation cyclone 2 is connected to the suction side of the exhaust fan 1 via an exhaust gas discharge pipe 19.

5 is a dispersion cone for uniformly dispersing the raw material within the main body 4a, and 6 is a raw material supply pipe.

The lower end of the lower separation cyclone 9 is connected to a raw material supply pipe 11 provided at the upper part of the main body 13a of the calciner 13 via a conduit 9a.
connected to.

The calcining furnace 13 includes a vertically cylindrical main body 13a and a main body 13.
It is composed of an inverted conical raw material discharge chamber 13b formed at the lower part of the chamber a.

A combustion air introduction pipe 15 connects the clinker cooler 18 and the upper part of the main body 13a of the calciner 13.

The combustion air introduction pipes 15 are each tangentially connected to the main body 13a of the countercurrent plate baking furnace 13, as shown in FIG.

20 is a damper provided in the combustion air introduction pipe, and 12a
is a burner provided at the upper part of the countercurrent plate baking furnace 13.

14 is a kiln exhaust gas conduit that connects the exhaust gas discharge side of the rotary kiln 16 and the main body 13a of the countercurrent plate baking furnace 13.

21 is a combustion air branch pipe that connects the kiln exhaust gas conduit 14 and the combustion air introduction pipe 15.

Reference numeral 22 denotes a raw material introduction pipe for introducing cement raw material from the lower end (cement raw material discharge port) of the lower chamber 13b of the countercurrent plate baking furnace 13 to the raw material receiving side of the rotary kiln 16.

23 is a damper provided in the combustion air branch pipe.

Reference numeral 11 denotes a burner provided in the rotary kiln 16. Since the cement firing apparatus of the present invention is configured as described above, the following operations can be performed.

A part or all of the cement raw material is supplied from a feeder (not shown) into the exhaust gas conduit 3 through a raw material supply pipe 6.

The cement raw material dispersed in the exhaust gas conduit 3 is heated (cocurrent heat exchange) by the exhaust gas discharged from the countercurrent preheater 4, and is passed through the inlet pipe 3a together with the exhaust gas by the exhaust fan 1. Then, it is sucked into the upper separation cyclone 2.

Exhaust gas containing cement raw materials is passed through the upper separation cyclone 2.
It is separated into cement raw material and waste heat gas inside.

The separated cement raw material is supplied to the upper part of the main body 4a of the countercurrent preheater 4 through the conduit 2a.

The cement raw material supplied into the main body 4a of the counter-current preheater 4 is affected by the dispersion cone 5 and the swirling flow of gas rising from the lower part of the counter-current preheater 4 (thus, the cement raw material is uniformly distributed throughout the main body 4a). distributed in

When the cement raw material descends within the main body 4a of the countercurrent preheater 4, it is heated countercurrently with the exhaust gas swirling upward within the main body 4a via the exhaust gas conduit 7, and is heat-treated to the extent that a portion thereof is calcined. receive.

Thereafter, the cement raw material is separated from the exhaust gas by centrifugal force, discharged from the raw material discharge chamber 4b through the preheated raw material supply pipe 10, and supplied into the calciner exhaust gas conduit 8.

The cement raw material supplied into the calciner exhaust gas conduit 8 is heated by the exhaust gas discharged from the calciner 13, and while being partially calcined, it is transferred to the lower separation cyclone together with the exhaust gas by the exhaust fan 1. 9.

Exhaust gas containing cement raw materials is sent to the lower separation cyclone 9.
It is separated into cement raw material and waste heat gas inside.

The separated raw materials are put into the upper end of the main body 13a of the calciner 13.

In addition, the main part of the high temperature air extracted from the clinker cooler 18 is swirled into the upper part of the main body 13a of the calciner 13 through the combustion air introduction pipe 15, and a vortex layer of high temperature air is formed, where the fuel is combusted by the burner 12a. At the same time, a mixed gas of the kiln exhaust heat gas and the remainder of the high-temperature air is swirled into the lower part of the main body 13a of the calciner 13 through the kiln exhaust gas conduit 14 and the combustion air branch pipe 21, and the mixture gas is introduced into the lower part of the main body 13a of the calcining furnace 13. The burner 12b also burns fuel.

Therefore, the raw material charged into the upper end of the main body 13a of the calciner 13 is uniformly distributed in the vortex layer by the action of the swirling flow of high-temperature air at the upper part of the furnace main body 13a, and immediately absorbs the combustion heat of the fuel. A large portion is calcined.

Thereafter, the raw material descends inside the furnace body 13a, and gradually increases its calcination rate while exchanging heat countercurrently with the mixed gas of the kiln exhaust heat gas swirling upward from the lower part and the combustion gas from the lower burner 13a. When reaching the lower end of the main body 13a, the calcination rate reaches approximately 100%, the material is separated by centrifugal force, and is fed into the rotary kiln 16 from the material discharge chamber 13b via the material introduction pipe 12.

The clinker fired in the rotary kiln 15 is taken out, cooled in a clinker cooler 18, and sent to the next process.

Next, the flow of combustion gas will be explained.

The kiln exhaust gas is mixed with a portion of the high-temperature air extracted from the clinker cooler 18 and flows into the kiln exhaust gas conduit 1 as a swirling flow.
4 and the combustion air branch 21 into the lower part of the body 13a of the calciner 13, where the kiln exhaust gas conduit 1
The fuel is combusted by the lower burner 12b provided at the upper part of the combustion chamber 4, and the combustion gas rises while swirling and exchanges heat with the raw material in a countercurrent manner.

Further, the remainder (main portion) of the high-temperature air is swirled into the upper part of the furnace body 13a through the combustion air introduction pipe 15, and is combusted by the upper burner 12a.

The combustion gas is mixed with the combustion gas from the lower part of the calciner exhaust gas conduit 8. The swirling flow is induced into the lower part of the main body 4a of the countercurrent preheater 4 via the lower separation cyclone 9 and the exhaust gas conduit 1.

The exhaust gas introduced into the countercurrent preheater main body 4a swirls upward while exchanging heat countercurrently with the cement raw material within the main body 4a.

Note that in the calciner 4, the residence time of gas is long, and the main combustion of the fuel takes place in a place where the oxygen concentration is high, so the fuel is almost completely combusted, but if a fuel with a slow combustion rate is used, etc. If incompletely burned substances of the fuel remain in the furnace, they are completely combusted in the calciner exhaust gas conduit 8 or at the latest in the lower part of the main body 4a of the countercurrent preheater 4, which has a long residence time.

Thereafter, the exhaust gas passes through the exhaust gas conduit 3, passes through the upper separation cyclone 2, and is discharged out of the system by the exhaust fan 1.

The cement sintering apparatus including the cement/Q material calcination furnace of the present invention is constructed as described above, and is operated as described above according to the construction, so that the following effects can be achieved.

(1) In the calcining furnace 13 of the cement firing apparatus of the present invention, as described above, the raw material charged into the upper end of the main body 13a is uniformly dispersed by the swirling flow of high-temperature air introduced into the upper part. The upper stage burner 12a installed there absorbs the fuel combustion heat, and a considerable part of it descends in the calcined furnace body 13a, and is further mixed with the mixed gas of combustion gas and kiln exhaust gas produced by the lower stage burner 12b. The raw material is discharged from the separated raw material discharge chamber 13b through countercurrent heat exchange.

That is, the flow of the raw material and the gas are countercurrent in the calciner 13, and there is no need for the gas flow to lift the raw material as in many conventional calciners, so the gas velocity and the raw material velocity can be controlled. Therefore, the heat exchange volume can be made sufficiently large, and the residence time of raw materials and gas can be several times that of many conventional calciners.

Further, the combustion of fuel by the upper stage burner 12a is performed in a place where the oxygen concentration is relatively high due to the swirling flow of high temperature air, and the unburned portion of the fuel by the lower stage burner 12b can also be re-burned by the swirling flow of high temperature air in the upper stage.

Therefore, in the calcining furnace 13, not only the fuel is almost completely combusted, but also the heat exchange efficiency is increased, and the calcining rate of the raw material entering the kiln can be increased to approximately 100%.

Furthermore, the exhaust gas discharged from the calciner 13 undergoes parallel flow heat exchange with the raw material in the calciner exhaust gas conduit 8, countercurrent heat exchange in the countercurrent preheater 4, and cocurrent heat exchange in the exhaust gas conduit 3. Particularly, the countercurrent preheater 4 has a large internal volume and a long residence time.

Therefore, the heat exchange capacity and volume of the raw material preheater section above the calcining furnace 13 is very large.

Therefore, even if unburned fuel remains in the calciner 13, it will be completely combusted in the calciner exhaust gas conduit 8, or at the latest in the lower part of the main body 4a of the countercurrent preheater 4, and will be discharged from the calciner 13. The heat retained in the hot gas is sufficiently absorbed by the raw material, and the temperature of the gas finally discharged from the upper separation cyclone 2 is sufficiently lowered, and of course, the temperature is lower than the exhaust gas temperature of conventional cement firing equipment of this type. The temperature of the exhaust gas is lower than that of a kiln with a raw material preheater, and the amount of fuel used in the entire cement firing equipment can be reduced compared to a kiln with a raw material preheater.

(2) For the reasons stated above, the cement firing apparatus of the present invention is particularly suitable when solid fuel is used as the calcining fuel.

Even if a solid fuel such as coal with a slow combustion rate is used in the calciner 9, it will be almost completely combusted in the furnace with a long residence time, but the unburned fuel will be stored in the lower part of the main body 4a of the countercurrent preheater 4 or there. Complete combustion occurs at the previous location.

Therefore, solid fuel can be used without causing inconveniences such as coaching troubles and increased heat consumption due to a decrease in the combustion rate of the fuel in the calciner, which are seen in conventional devices of this type.

Further, according to the cement firing apparatus of the present invention, the total fuel used in the rotary kiln 16 and the calcining furnace 13 is 100%
It is possible to use it as a solid fuel, and furthermore, low-rank coal, coal, a part of industrial waste, etc. can also be used as a fuel for calcining.

(3) As the preheating and calcining device of the cement firing apparatus of this invention, only the upper and lower separated cyclones are used as cyclones with high pressure loss, and the countercurrent preheater 4 and calciner 13 are both countercurrent. Since the gas flow does not have to lift the raw powder and the gas velocity is low, the pressure loss is quite low.

Therefore, it is necessary to use a four-stage cyclone and a parallel flow type gas flow to lift the raw material powder, as seen in conventional cement firing equipment of this type, compared to equipment consisting of a calciner with a high gas velocity. If so, the pressure drop will be considerably lower.

For example, the pressure loss of a conventional cement firing equipment is 700 I
While it is about 500 Aq for the same scale device of the present invention, it is about 500 Aq.

(4) Since the combustion in the calciner 13 of the cement firing apparatus of the present invention is low-temperature combustion, less nitrogen oxides (NOx), which are pollutants, are generated.

Further, in the lower part of the calciner 14, reducing combustion air is generated in the combustion by the burner 12b, and reducing incompletely combusted substances are generated, and these substances are immediately mixed with the kiln exhaust heat gas introduced as a swirling flow. Decomposes nitrogen oxides contained in kiln exhaust gas and turns them into harmless nitrogen gas.

Therefore, the amount of nitrogen oxides in the exhaust gas finally discharged from the cement firing apparatus can be considerably reduced, which brings about favorable results in terms of pollution control.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of a cement firing apparatus including a calcining furnace for cement raw materials according to the present invention, and Fig. 2 is an A-A in Fig. 1.
Cross-sectional view, Figure 3 is a BB cross-sectional view of Figure 1, Figure 4 is a cross-sectional view of Figure 1.
It is a CC sectional view of the figure. 1 is an exhaust fan, 2 is an upper separation cyclone, 3 is an exhaust gas pipe, 4 is a countercurrent preheater, 4a is the main body of the countercurrent preheater, 4b
is the raw material discharge chamber of the countercurrent preheater, 5 is the dispersion cone of the countercurrent preheater, 6 is the raw material supply pipe, 1 is the exhaust gas pipe, 8 is the calciner exhaust gas pipe, 9 is the lower separation cyclone, 10 is the preheating A raw material supply pipe, 11 is a raw material supply receiving pipe, 12a is an upper burner of the calciner, 12b is a lower burner of the calciner, 13 is a countercurrent type plate baking furnace, 13a is the main body of the countercurrent type plate baking furnace, 13b 14 is a kiln exhaust gas conduit, 15 is a combustion air introduction pipe, 16 is a rotary kiln, 18 is a tarinka cooler, 19 is an exhaust gas discharge pipe, 20 is a damper of the combustion air introduction pipe, 21 is a combustion air branch pipe, 22 is a raw material introduction pipe, 2
3 is a damper for the combustion air branch pipe.

Claims (1)

[Claims] 1. A calcining furnace with an independent heat source is installed between the rotary kiln and a countercurrent preheater that preheats the raw material, and the upper end of the main body of the countercurrent preheater is connected to the inlet pipe of the upper separation cyclone via an exhaust gas pipe. The lower part of the main body is connected to the gas outlet pipe of the lower separation cyclone through the exhaust gas inlet pipe connected tangentially to the main body, and the lower part of the main body is connected to the gas outlet pipe of the lower separation cyclone, and the lower part of the main body is connected to the calciner exhaust gas conduit provided at the upper end of the main body of the calciner. In a cement firing apparatus, in which the inlet pipe of the lower separation cyclone is connected to the inlet pipe, and the raw material discharge ports of the upper separation cyclone and the lower separation cyclone are communicated with the upper end of the main body of the countercurrent preheater and the upper end of the main body of the calciner, respectively. The raw material discharge chamber of the counter-current preheater and the calciner exhaust gas conduit are connected by a preheated raw material supply pipe, and the calciner has a shape that is a combination of a cylinder and a cone. The upper part of the body of the calciner is connected tangentially to the body through a combustion air introduction pipe, and the exhaust gas discharge side of the lorry kiln and the lower part of the body of the calciner are connected to the body through a kiln exhaust gas conduit. The kiln exhaust gas conduit and the combustion air introduction pipe are connected tangentially, and the combustion air introduction branch pipe is used to connect the kiln exhaust gas conduit and the combustion air introduction branch pipe, so that the raw material is not calcined while exchanging heat countercurrently with the combustion gun in the calcining furnace. 1. A cement firing apparatus including a calcination furnace for cement raw materials, characterized in that a calcination raw material is separated and a raw material discharge chamber of the calcination furnace is connected to a raw material feed end of a rotary kiln.