JPH058135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cement clinker cooling device, and more particularly, to a cooling device for cement clinker, which is used to cool high-temperature cement clinker discharged from a cement clinker baking device, such as a rotary kiln. related to a device for

Prior Art Conventionally, this type of cooling device has been of the so-called cross-flow type, in which cooling air is passed orthogonally through a layer of high-temperature cement clinker formed on a built-in ventilation grid to cool the cement clinker. are known. Such a cooling device has high heat exchange efficiency and can cool cement clinker to a sufficiently low temperature, so it is often used as subsequent equipment to a cement clinker firing device. Such a cooling device is typically disclosed in Japanese Utility Model Application No. 59-193832, which is an earlier application of the present applicant.

FIG. 2 shows a typical example of such a cooling device. In FIG. 2, a cement clinker (hereinafter referred to as clinker)
A cooling device 4 is arranged. Clinker, which has been fired at high temperature in the rotary kiln 1 by the combustion heat of fuel supplied from the burner 3, is supplied to the cooling device 4 through the firing port cover 2.

Such a cooling device 4 comprises a ventilation grid 5, for example a swinging grid or a moving grid. Clinker 6 deposited in layers on the air permeable grid 5 is transported in a substantially horizontal direction toward the discharge end. At this time, the clinker 6 is cooled by cooling air sent from the forced air blower 7 into the wind box 8 provided below the ventilation grid 5 during the transfer process. In this case, the cooling air flows orthogonally through the layered clinker 6 which is in a high temperature state from below. Then, the cooled clinker 6 is
The material is discharged from the chute 10 provided at the discharge end 20 to the conveyor 12 and carried out to the next process.

On the other hand, a part of the high-temperature air heated by heat exchange with the clinker 6 is transferred from the inlet side upper chamber 9a to the firing port cover 2 in the upper space 9 of the ventilation grid 5.
The air is recovered as combustion air in the rotary kiln 1. In some cases, another part of this high-temperature air may be used for combustion necessary for a calciner (not shown) constituting the clinker firing apparatus from a high-temperature air outlet 21 provided in the upper air 9. Recovered as secondary air.

The remainder of the heated air is then stored in the upper space 9.
Excess low-temperature side air is sucked into the induced draft fan 16 from the exhaust outlet 23 provided near the upper chamber 9b on the exit side, and is sent to the chimney 1 via the dust collector 15.
It is discharged at 7.

In such cross-flow cooling systems, the amount of cooling air forced into the interior of the system to cool the clinker is typically 2.4 to 2.7 Nm ³ per kg clinker. On the other hand, the fuel consumption in modern clinker firing equipment equipped with raw material preheating equipment etc. is per 1 kg of clinker.
700 to 800kcal, and the secondary combustion air taken out from the cooling device for combustion of this fuel is 0.8
or 0.9Nm ³ /Kg clinker. Therefore, in such a cooling device, there is a surplus of heated air after heat exchange that hits the clinker at 1.6 to 1.8 Nm ³ /Kg. The surplus air in this air distribution is
As shown in the figure, the accompanying clinker dust is removed through a dust collector 15 and then released into the atmosphere.

Incidentally, as a dust collector used for such a purpose, a Multichron type dust collector or the like has been used conventionally, but recently, due to the need to reduce environmental pollution, an electric dust collector is often used.

At this time, the dust collection characteristics of the electrostatic precipitator are generally related to the charging characteristics of the clinker dust to be collected. That is, when the electrical resistivity value of clinker dust exceeds a certain level, for example, 2 to 5×10 ¹¹ Ω·cm, the collection performance of the electrostatic precipitator deteriorates extremely.

For example, in the case of air distribution as described above, where only secondary air for combustion is recovered to the clinker burning device, the temperature of the low-temperature side air discharged from the exhaust outlet 23 (Fig. 2) of the cooling device is Although it depends on the conditions, it is usually about 210 to 230°C. The electrical specific resistance value of clinker dust in this temperature range is relatively low, as shown in Figure 3, and an electrostatic precipitator with the above characteristics has a relatively high dust collection efficiency. can be maintained.

Problems with the Prior Art By the way, coal is often used as a firing fuel in recent years. At this time, in order to dry the moisture-containing coal, a part of the high-temperature air obtained by the cooling device is transferred to a high-temperature air tank provided in the middle of the upper space 9, as shown by the two-dot chain arrow in FIG. The air may be supplied to the coal crusher 18 (heat utilization equipment) through the air outlet 22.

By the way, the air used to dry the coal is usually 400 to 450, depending on the moisture content of the coal.
0.2 to 0.3 Nm ³ /Kg clinker of heated air is required at a temperature of °C.

In such a case, in addition to the secondary combustion air supplied to the clinker burning device, such a cooling device
Heated air for other heat utilization equipment will also be extracted from the hot air. Therefore, if we look at the surplus air released into the atmosphere through the electrostatic precipitator, the quantity will be reduced accordingly, and the temperature will also be lowered.

In other words, in the case where only secondary air for combustion is supplied to the clinker burning equipment under the above air distribution, the temperature of the surplus air discharged from the cooling equipment is generally 210 to 230°C, whereas If the drying air is also taken out from the high temperature air area, the temperature of the excess air will drop to 160 to 190°C.

In this case, the temperature of the surplus air discharged from the exhaust outlet 23 (Fig. 2) approaches a high temperature range, for example, 130 to 170°C, when the electrical resistivity value of clinker dust is high, as can be seen from Fig. 3. , problems arise in that the collection efficiency of the electrostatic precipitator decreases, or that an electrostatic precipitator with a large dust collection area is required.

In addition to using the high-temperature air of the cooling device for drying coal as described above, it can also be used as a heat source for drying auxiliary raw materials for cement production, or when the amount of fuel required for clinker firing equipment is large. A similar problem occurs when a large amount of high-temperature air is recovered from the device to heat utilization equipment including a sintering device.

OBJECTS OF THE INVENTION Therefore, the main object of the present invention is to provide a cooling device for cement clinker that improves the dust collection efficiency of an electrostatic precipitator by using the electrostatic precipitator in a temperature range where the electric specific resistance value of clinker dust is reduced. It is to provide.

Structure of the Invention In order to achieve the above object, the main means adopted by the present invention is to cool the high temperature cement clinker disposed subsequent to the kiln and discharged from the kiln by heat exchange with cooling air. , in a cement clinker cooling device configured to recover a portion of the heated high-temperature air to a heat utilization facility including the kiln, the cooling device includes a cooling device downstream of the high-temperature air recovery section when viewed in the flow direction of the cement clinker; At least two discharge means are provided on the side for discharging excess air which has become relatively low temperature with respect to the high temperature recovered air, and each of these at least two discharge means is equipped with a separate electrostatic precipitator, and A temperature range in which one of the at least two discharge means provided on the upstream side is higher than a temperature range in which the electrical resistivity value of clinker dust discharged along with the surplus air is equal to or higher than a predetermined value. The other discharge means provided on the downstream side is communicated with a temperature region lower than a temperature region in which the electrical resistance value of the clinker dust is set to a predetermined value or more.

Effect Even if the temperature of the surplus air discharged from the low-temperature side of the cooling device is in the region where the electrical resistivity value of the clinker dust contained therein is at its maximum, the surplus air is discharged. By extracting surplus air from appropriately separated points in the flow direction of the cement clinker, for example, the temperature of the surplus air taken out from the upstream side is set to a temperature range that maximizes the electrical resistivity value of the accompanying clinker dust. The temperature of the surplus air taken out from the downstream side can be set to a temperature lower than the temperature range in which the electric resistivity value of the accompanying clinker dust is maximized. Therefore, each surplus air is set at a temperature at which the electrical resistivity value of the clinker dust contained therein is considerably lower than the maximum value.

Effects of the Invention According to the present invention, since the electric specific resistance value of clinker dust can be set low, the dust collection efficiency in an electrostatic precipitator can be improved and the electrostatic precipitator can be operated efficiently.

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.

Embodiment FIG. 1 is a schematic vertical sectional view of a cement clinker cooling device according to an embodiment of the present invention.

Note that the following example is only one specific example of the present invention, and the technical scope of the present invention is not limited by this example. Further, the same reference numerals will be used to describe the same elements as those of the conventional cement clinker cooling device shown in FIG.

In Fig. 1, the cooling device 4' adopts the conventional cooling device 4 (see Fig. 2) described above as its basic structure, and directs high-temperature air to a firing furnace (not shown) (part of the firing equipment). Secondary air for combustion is recovered from the outlet 21, and another high temperature air outlet 2
2 through which a portion of the heated air is taken off for drying the coal in the coal crusher 18. Parts that are particularly different from the conventional example will be explained below.

The cooling device 4' includes a cooling device 4 located downstream of the high-temperature air outlet 22, in the vicinity and above the upper chamber 9b on the outlet side of the cooling device 4', when looking at the flow direction of the cement clinker 6. A high-temperature side exhaust outlet 24 and a low-temperature side exhaust outlet 25 are sequentially formed along the longitudinal direction of . Both outlets 24 and 25 are equipped with electric dust collectors 15a and 15b separately via appropriate exhaust ducts 31 and 32, respectively.
Induced ventilation fan 16a, 1 for each dust collector 15a, 15b
6b is provided.

That is, the high-temperature side exhaust outlet 24 communicates with the upper chamber of the cooling device located in a higher temperature range than the temperature range with which the low-temperature side exhaust outlet 25 communicates, and the low-temperature side exhaust outlet 25 communicates with the high-temperature side exhaust outlet 24. It communicates with the upper chamber of the cooling device, which is in a lower temperature region than the temperature region with which it communicated.

Therefore, for example, in the cooling device 4', secondary air for combustion is recovered from the high temperature air outlet 21 to the calciner (not shown) under the same conditions as in the case of the cooling device 4 explained in FIG. 2 above. , and when the air for drying coal is taken out from the high-temperature air outlet 22 to the coal crushing device 18, the temperature of the entire surplus air is determined by the electric specific resistance value of the clinker dust, which is determined by the collection efficiency of the electrostatic precipitator. For example, even if the temperature is in a temperature range that lowers the If the surplus air is distributed in Nm ³ at a ratio of about 2:1, the surplus air on the high temperature side sent to the electrostatic precipitator 15a will be taken out at about 220 to 250°C, and the electric specific resistance value of the clinker dust will be equal to or higher than a predetermined value. In addition, the surplus air on the low temperature side is taken out at about 110°C, and the temperature becomes lower than the temperature range in which the electrical resistivity value of clinker dust exceeds a predetermined value.
The electrical resistivity value of the clinker dust in 5b is suppressed to a sufficiently low value.

In addition, when the surplus air exhausted is distributed to the high temperature side and the low temperature side as described above, it is necessary to reduce the electrical resistivity value of the clinker dust in the surplus air exhausted on the high temperature side to below the above-mentioned predetermined value. is relatively easy, but it may be difficult to lower the air specific resistance value of clinker dust in the excess air exhausted on the low temperature side.

In this case, the exhaust duct 32 for discharging surplus air on the low temperature side is provided with, for example, a cold air suction port 26, and low temperature outside air is appropriately mixed in through the damper 27 as appropriate. Thereby, the temperature of the surplus air exhausted from the low temperature side exhaust outlet 25 can be reliably lowered. Furthermore, the distribution ratio of the excess exhaust gas on the low temperature side can also be increased by means of mixing low temperature outside air.

Furthermore, if the surplus air discharged from the high-temperature side exhaust outlet 24 is larger in actual air volume than the surplus air discharged from the low-temperature side exhaust outlet 25, the high-temperature side exhaust outlet 24 may be equipped with The electrostatic precipitator used may be divided into multiple units.

By the way, the electrical resistivity value of clinker dust is
It can vary considerably depending on the type of clinker dust and the water vapor content in the excess air, and in addition, the temperature range where the electrical resistivity reaches its maximum also varies depending on individual factors. It is desirable that the distribution ratio of the excess air discharged from the side exhaust outlet and the amount of cold air sucked are optimally selected according to the amount and temperature of the surplus air discharged, the charging characteristics of the clinker dust, etc.

In the above explanation, we will not only refer to the types of firing furnaces and cross-flow cooling equipment, but also the types of heat utilization equipment including firing equipment, the form of recovery of high-temperature air from the cooling equipment to the equipment, and the cooling equipment for excess air. There are no particular restrictions on the presence or absence of recirculation, and the type and structure of the electrostatic precipitator.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a cement clinker cooling device according to an embodiment of the present invention, FIG. 2 is a schematic vertical cross-sectional view of a cement clinker cooling device that is the background of this invention, and FIG. 3 is a vertical axis It is a characteristic diagram of the electrical resistivity of clinker dust, in which the electrical resistivity (Ω·cm) of clinker dust is plotted on the horizontal axis, and the temperature of the clinker dust is plotted on the horizontal axis. (Explanation of symbols), 1...Kilning furnace, 4, 4'...Cooling device, 5...Ventilation grid, 6...Cement clinker, 7...Forced air blower, 9...Upper space, 1
5, 15a, 15b...electrostatic precipitator, 16, 16
a, 16b... Suction ventilator, 18... Coal crusher, 21, 22... High temperature air outlet, 23... Exhaust outlet, 24... High temperature side exhaust outlet, 25...
Low-temperature side exhaust outlet, 26...cold air inlet.

Claims (1)

[Claims] 1. A cement clinker disposed subsequent to a kiln, which cools high-temperature cement clinker discharged from the kiln by heat exchange with cooling air, and directs a portion of the heated high-temperature air to the kiln. In a cooling device for cement clinker that is collected into a heat utilization facility including At least two exhaust means are provided for exhausting the surplus air that has become low temperature, and each of these at least two exhaust means is equipped with a separate electrostatic precipitator, and the at least two exhaust means are provided on the upstream side. one of the discharge means is connected to a temperature region higher than a temperature region in which the electric resistivity value of clinker dust discharged together with the surplus air is equal to or higher than a predetermined value, and the other discharge means provided on the downstream side A cooling device for cement clinker, wherein the means is connected to a temperature region lower than a temperature region in which the electrical resistivity value of the clinker duct is set to a predetermined value or more. 2. The cement clinker cooling device according to claim 1, wherein the discharge means on the downstream side is equipped with cold air suction means when viewed in the flow direction of the cement clinker.