JPS5913460B2 - 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 calcining furnace for cement raw materials, which improves the conventional rotary kiln with a preheating device for cement raw materials, and improves the calcining furnace for raw materials that require the largest amount of heat. Instead of performing calcination in a rotary kiln with low heat transfer efficiency as in conventional equipment of this kind, calcination is performed in a calcination furnace with high heat transfer efficiency, in an attempt to downsize the equipment and reduce various basic units. .

A large number of inventions have been made regarding such cement firing devices, and some of these devices have already been put into practical use.

All of the devices that have been put into practical use are combinations of cyclones or vortex chambers, and various devices are characterized by the type of calciner.

These calcining furnaces can be classified 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 preheating device, cement firing using these cement firing devices reduces the size of the rotary kiln and reduces the heat load inside the kiln, reducing equipment costs, reducing the unit consumption of refractory bricks, and reducing the pollution component nitrogen. Oxide (N
Although various benefits such as a reduction in the amount of Ox) generated can be expected, there are still various drawbacks as shown below.

(1) In general, in a calciner, especially in a calciner other than a fluidized bed type, the residence time of the raw fuel is short, and therefore the fuel does not burn completely in the furnace, resulting in 3
Combustion may continue in the second cyclone, causing coaching troubles in those cyclones or in the pipes between them, or increasing the temperature of the gas discharged from the top cyclone, causing waste heat gas retention in the cement firing equipment. and increase heat.

The amount of increase in heat removed is equal to or may be greater than the amount of reduction in heat consumption due to kiln miniaturization using this method.

Such problems are especially serious when solid fuels such as coal are used, and often make the use of solid fuels almost impossible.

This is because the combustion time of solid fuel is longer than that of liquid fuel.

(2) These cement firing devices usually consist of a rotary kiln, a preheater combined with a four-stage cyclone, or a whirlpool chamber, and a calcining furnace, and the pressure loss of the entire cement baking device is the same as that of each of these individual devices. This is the total pressure loss, but in addition to the preheater power, which requires a fairly high pressure loss, the pressure loss of the calciner is added, and on top of that, the high temperature combustion air extracted from the cooler and the kiln exhaust gas A pressure loss is added to the restriction provided in the kiln exhaust gas duct to maintain the pressure balance between the two, resulting in a considerably high overall pressure loss.

As a result, the amount of electricity used in the exhaust gas induction fan is quite large, and although the kiln has the advantage of reducing driving 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 material preheating device. No.

When a fluidized bed furnace is used as a calcining furnace, the pressure loss is particularly high, and the amount of electricity used is also increased.

(3) Cement raw materials contain some alkali and chlorine, but these components volatilize and condense in the circulating dust between the kiln and the calciner or between the calciner and the preheater. It is concentrated by

When these components increase, the melting point of the dust decreases,
Dust may be deposited in the duct between the kiln and the calcination furnace or between the cyclones of the preheater, causing coating trouble and lowering the draft, making it impossible to operate.

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

The present invention improves the above-mentioned drawbacks of the prior art, and even when using solid fuel as well as liquid fuel, the fuel is completely combusted in the lower part of the calciner and countercurrent preheater, and coating etc. This prevents various troubles, lowers the temperature of the gas discharged from the counterflow preheater, reduces fuel consumption, and balances the pressures of the kiln exhaust gas system and cooler oil/air system, reducing overall pressure loss. Cement firing equipment that has low and high heat transfer efficiency in the counter-current preheater and calciner, increases the calcining rate of raw materials to almost 100%, and can extremely reduce nitrogen oxide emissions. This is what we are trying to provide.

Next, a cement firing apparatus including a cement raw material calcining furnace of the present invention will be described with reference to drawings showing 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,
8 is a lower separation cyclone, 9 is a calciner, 15 is a rotary kiln, and 17 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 bottom of the main body 4a.

The lower part of the main body 4a is communicated with a lower separation cyclone 8 via a calciner exhaust gas conduit 7.

As shown in FIG. 2, the calciner exhaust gas conduit 7 is connected tangentially to the main body 4a.

Further, the raw material discharge chamber 4b is communicated with a kiln exhaust gas supply pipe, which will be described below, via a raw material discharge pipe 18.

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

The lower end of the upper separation cyclone 2 communicates 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 calcining furnace 9 is composed of two chambers, upper and lower.
a. The lower part is defined as a lower chamber 9b, and a constricted part 9c is provided between the upper chamber 9a and the lower chamber 9b.

The immediate lower end of the lower chamber 9b and the exhaust gas inlet of the lower separation cyclone 8 are communicated through an exhaust gas conduit 11.

12 is a combustion air introduction pipe connecting the clinker cooler 17 and the upper chamber 9a.

As shown in FIG. 3, the combustion air introduction pipe 12 communicates tangentially with the upper chamber 9a.

13 is a kiln exhaust gas supply pipe connecting the uppermost end of the upper chamber 9a of the calciner 9 and the exhaust gas discharge side of the rotary kiln 15;
4 is a preheating raw material supply pipe attached to the kiln exhaust gas supply pipe 13.

The kiln exhaust gas supply pipe 13 is connected to the upper chamber 9 as shown in FIG.
It is connected tangentially to a.

The preheating raw material supply pipe 14 includes a raw material discharge pipe 1 of the countercurrent preheater 4.
8 are connected.

10 is a burner provided in the calcining furnace 9, and 16 is a burner provided in the rotary kiln.

Further, 20 is a raw material feeding pipe for feeding cement raw material from the lower end of the lower separation cyclone 8 to the raw material receiving side of the rotary kiln 15.

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 pipe 3 is heated by the exhaust gas discharged from the countercurrent preheater 4, and
The raw material introduction pipe 3 along with the exhaust heat gas is induced by the exhaust fan 1.
a and is sucked into the upper separation cyclone 2.

Exhaust gas containing cement raw materials is passed through the upper separation cyclone 2.
Inside, the cement raw material and waste heat gas are separated, and the separated cement raw material is supplied to the upper part of the countercurrent preheater 4 through the conduit 2a.

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

Then, as the cement raw material descends within the main body 4a of the countercurrent preheater 4, it is heated countercurrently with the exhaust heat gas that is induced to rise within the main body 4a through the calciner exhaust gas conduit 7, and is partially calcined. Heat treated to a certain degree.

Thereafter, the cement raw material is separated from the exhaust gas by centrifugal force, discharged from the raw material discharge chamber 4b through the raw material discharge pipe 18, and supplied into the kiln exhaust gas supply pipe 13 via the preheated raw material supply pipe 14.

The cement raw material supplied to the kiln exhaust gas supply pipe 13 is
It is dispersed in the exhaust gas stream discharged from the lorry kiln 15, and immediately absorbs the heat of the high-temperature exhaust gas to increase the calcining rate of the raw material and lower the exhaust gas temperature to 800°C, together with the exhaust gas. The upper chamber 9 of the calcining furnace 9 becomes a swirling flow.
Enter a.

Further, high-temperature air for combustion is also introduced into the upper chamber 9a as a swirling flow from the clinker cooler 17 via the combustion air introduction pipe 12, and a vortex layer is formed by these gases.

The burner 10 burns fuel within this swirl bed,
The main part of calcination of cement raw material is accomplished.

The incompletely burned fuel and cement raw material are sucked into the lower chamber 9b while swirling together with the exhaust gas.

Further, since a constricted portion 9c is formed between the two chambers 9a and 9b, the fuel and cement raw material introduced from the upper chamber 9a into the lower chamber 9b are introduced at an increased speed.

In the lower chamber 9b, the fuel is almost completely combusted and the raw material is completely calcined.

The cement raw material that has been almost completely calcined in the calcining furnace 9 is guided along with the exhaust gas to the lower separation cyclone 8 through the exhaust gas pipe 11, where the exhaust gas and the cement raw material are separated and almost 100% calcined. The resulting cement raw material is supplied to the rotary kiln 15 via the raw material feed pipe 20, and the final clinker firing is performed by burning fuel in the burner 16.

The clinker fired in the rotary kiln 15 is taken out, cooled in the clinker cooler 17, and sent to the next process.

On the other hand, to describe the flow of combustion gas, kiln exhaust gas is accompanied by cement raw materials and enters the upper chamber 9a of the calciner 9 through the kiln exhaust gas supply pipe 13 as a swirling flow, and high-temperature air extracted from the clinker cooler 17 is supplied to the upper chamber 9a as a swirling flow through the combustion air introduction pipe 12.

A vortex bed is formed in this upper chamber 9a, main combustion of the fuel is performed, and most of the calcining of the raw material is performed.

The exhaust gas containing incompletely burned fuel is introduced into the lower chamber 9b while swirling, and secondary combustion of the incompletely burned fuel is performed in the lower chamber 9b.

Thereafter, the raw material enters the lower separation cyclone 8 to separate the calcining raw material, and then is introduced into the lower part of the main body 4a of the countercurrent preheater 4 as a swirling flow through the calciner exhaust gas conduit 7.

The final secondary combustion of the fuel is performed in the countercurrent preheater 4, and the exhaust gas swirls upward while exchanging heat countercurrently with the cement raw material, passes through the exhaust gas conduit 3, and passes through the upper separation cyclone 2. , are discharged out of the system by the exhaust fan 1.

Since the cement firing apparatus including the cement raw material calcining furnace of the present invention is constructed as described above and operated as described above, it is possible to achieve the following effects.

(1) Upper chamber 9 of the calcining furnace 9 of the cement firing apparatus of the present invention
Fuel and high-temperature combustion air are supplied to a, the fuel is combusted there, and the incompletely combusted material is transferred to the calciner 9.
It burns in the lower chamber 9b.

Even if the incompletely combusted material is not completely combusted there, it passes through the lower stage separation cyclone 8, which has a large internal volume.
The gas rise rate is low, the residence time of raw material and waste heat gas is very long, and it enters the countercurrent preheater 4, which has a simple structure, and is completely combusted in the lower part. There are no problems such as coaching troubles in the upper cyclone than the lower cyclone or in the duct between the cyclones, or an increase in heat consumption due to an increase in the temperature of the gas discharged from the preheater.

In addition, the cement raw material is supplied to the exhaust gas pipe 3 of the countercurrent preheater 4, passes through the upper separation cyclone 2, and then enters the countercurrent preheater 4, where it undergoes countercurrent heat exchange with the exhaust gas. Alternatively, after preheating and partial calcination are performed by absorption of the secondary combustion heat of the calciner fuel, it is separated and fed into the kiln exhaust gas supply pipe 13, where it is further heated by the sensible heat of the high temperature kiln exhaust gas. Part is calcined.

Thereafter, the raw material enters the upper chamber 9a of the calciner 9, where the main combustion of the fuel takes place, and after finishing most of the calcining in the swirl bed, it enters the lower chamber, where the final Calcination is performed, the product is separated by a lower stage separation cyclone 8, and then fed into a rotary kiln 15.

As explained above, in the cement firing apparatus of the present invention, the combustion of the fuel and the calcination of the raw materials are performed in several stages, so the combustion of the fuel and the calcination of the raw materials are performed at relatively low temperatures. There is no local heating, and various troubles such as coating troubles in various parts of the cement firing device do not occur, and the raw material calcination rate can be increased to almost 100%.

(2) The cement firing apparatus of the present invention is particularly suitable when solid fuel is used as the calcining fuel for the reason shown in item (2) above.

When a solid fuel such as coal with a slow combustion rate is used in the calciner 9, the fuel is combusted in the upper chamber 9a, but a portion of the fuel is incompletely combusted and gasified, and the gasified fuel is transferred to the calciner. It is burned in the lower chamber 9b, and the unburned content passes through the lower stage separation cyclone 8 and is transferred to the countercurrent preheater 4 with a large internal volume.
and complete combustion occurs at the bottom.

Therefore, there are no inconveniences such as coaching troubles or increased heat consumption due to a decrease in the combustion rate of solid fuel in the calciner, which are seen in conventional equipment of this type, and the system can operate under the same operating conditions as when using liquid fuel. Solid fuel can be used.

In addition, since the calcination furnace 9 of the cement firing apparatus of the present invention is of the downflow type, there is no need to lift the raw material unlike in the case of upflow, and the gas flow rate can be considerably reduced. It is also possible to make the equivalent diameter larger than that of the furnace, and the residence time can be increased, and from this point of view as well, it is suitable for the apparatus of the present invention to use solid fuel as the calcining fuel.

Therefore, according to the cement firing apparatus of the present invention, the total fuel used in the rotary kiln 15 and the calcining furnace 9 is 100%
% solid fuel is also possible.

Furthermore, low-grade coal, bottlings, and a portion of industrial waste can also be used as fuel for the calciner.

(3) The cement firing device of the present invention can be used as a preheater;
Apart from the lower stage separation cyclone, no cyclone with high pressure loss is used, and a vertical countercurrent preheater with low pressure loss is used for the main part of preheating the raw material.

In addition, the calcining furnace has a downward flow type of gas and raw material flow, so there is no need to lift the raw material, and the gas flow rate can be lowered, so that pressure loss can be kept low.

Therefore, the pressure loss of the entire device can be considerably reduced; for example, while the pressure loss of a conventional cement firing device of this type is about 700 mmAq, it is about 500 mmAq of the same scale of the device of the present invention.

In addition, since the raw material taken out from the countercurrent preheater 4 is input into the kiln exhaust gas supply pipe 13, a pressure loss occurs due to the lifting of the raw material by the kiln exhaust gas, and the pressure in the kiln exhaust gas system and clinker cooler extraction system increases. It is possible to balance the kiln exhaust gas supply pipe 13 without providing an orifice, and to avoid problems such as coaching in the supply pipe 13.

(4) In the calcining furnace 9 of the cement firing apparatus of the present invention, the combustion of fuel is performed at a low temperature, so that the new generation of nitrogen oxides NOx in the furnace is almost 77%.

In addition, in the upper chamber 9a of the calciner 9, the fuel is combusted in a relatively low oxygen concentration airflow of a mixed gas of high temperature air and kiln exhaust gas. These substances immediately mix with the kiln exhaust gas, decompose the nitrogen oxide NOx contained in the kiln exhaust gas using the raw material as a catalyst, and convert it into harmless nitrogen gas.

Therefore, the amount of nitrogen oxides in the exhaust gas finally discharged from the countercurrent preheater can be significantly reduced.
It brings about favorable results in terms of pollution control.

Reducing substances that are not used in the decomposition reaction of nitrogen oxides are completely combusted at low temperatures in the lower chamber 9b of the calciner, the lower separation cyclone 8, and the countercurrent preheater 4, so there is no problem. do not have.

(5) Since the preheater of the cement firing apparatus of the present invention is of a vertical countercurrent type, the installation area of the entire apparatus is small, and equipment costs can be reduced.

Furthermore, when the raw material taken out from the countercurrent preheater 4 is introduced into the kiln exhaust gas supply pipe 13, the raw material is dispersed in the exhaust gas and then introduced into the calciner 9, so the position of the countercurrent preheater 4 can be lowered, and the height of the entire device can be kept low.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a cement firing apparatus including a calcining furnace for cement raw materials according to the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 is a view of Fig. 1 from B-B. This is a diagram. 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, 6 is the raw material supply pipe, 7 is the calciner exhaust gas conduit, 8 is the lower separation cyclone, 9 is the calciner, 9a is the upper chamber of the calciner, 9b is the calciner Lower chamber of the furnace, 10
is the burner of the calciner, 11 is the exhaust gas pipe, 12 is the combustion air introduction pipe, 13 is the kiln exhaust gas supply pipe, 14 is the preheating material supply pipe, 15 is the rotary kiln, 16 is the burner of the rotary kiln, 17 is the clinker cooler , 18 is a raw material discharge pipe;
19 is an exhaust gas discharge pipe, and 20 is a raw material feed pipe.

Claims (1)

[Claims] 1. A calcining furnace having an independent heat source is provided 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 an upper separation cyclone via an exhaust gas pipe. In addition, the lower part of the main body is connected to the lower separation cyclone through a calciner exhaust gas pipe connected tangentially to the main body, and the raw material discharge ports of the upper separation cyclone and the lower separation cyclone are connected to countercurrent preheaters. In a cement firing device that communicates with the upper end of the body of the calciner and the raw material feed side of the rotary kiln, the upper chamber of the calciner is divided into an upper chamber and a lower chamber by an intermediate constriction part, and the exhaust gas exhaust end of the rotary kiln. A raw material discharge pipe communicates between the kiln exhaust gas supply pipe, which is connected tangentially to the upper chamber, and the raw material discharge chamber of the countercurrent preheater, and also communicates with the upper chamber of the calciner. and the clinker cooler are communicated by a combustion air introduction pipe, the combustion air introduction pipe is connected tangentially to the upper chamber, and the lower chamber of the calciner and the lower separation cyclone are communicated by an exhaust gas conduit. A cement firing device including a calcining furnace for cement raw materials, characterized by: