JPS5919899B2 - Cooling method for sintered material discharged from rotary furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling sintered material escaping from a rotary furnace.

Due to the stricter pollution control laws, waste heat utilization equipment in the cement industry was increasingly combined with expensive dust removal equipment, which led to the development of special technologies.

Therefore, in recent years, secondary cooling devices have been used advantageously in large heat-saving rotary furnaces.
This is because, in contrast to the thermally advantageous grid cooling system, this cooling system only incorporates the amount of cooling air that is required for combustion as secondary air in any case. It is.

In this case, together with poor heat recovery, the clinker escapes the cooling equipment at significantly high temperatures, i.e. 150-300 °C, which leads to difficulties when post-processing the clinker, above all when grinding cement. It was decided to invite.

In fact, a so-called evaporative cooling device is installed on the waste gas side of such a heat-saving rotary furnace with a flash preheating device, and this device cools the waste gas of the heat exchange device to about 320°C.
to about 120° C. and enriched in this case with water vapor, thereby reducing the effective gas volume and dust resistance and improving the separation conditions.

Such evaporative cooling devices are quite expensive, because of the large volumes and therefore the long residence times.
Care must be taken to ensure that all the water that is sprayed in is evaporated and does not, for example, condense on the walls or flow downwards as slag together with dust.

It is easy to transfer and entrain the clinker's low-value residual heat, which is below about 400°C, into a large volume of air using a long residence time, and at the same time remove the resulting difficulty of dust removal by water evaporation. However, this method is used, with the exception of the cement industry, only in two variants.

On the other hand, large secondary cooling devices are cooled by occasionally spraying or injecting water into the outlet if the clinker escape temperature is too high (ZKGl 978 Vol. 1,
(See page 45).

However, this method requires that the steam lowers the secondary temperature, requires additional heat for heating in the combustion section of the rotary furnace, thus cooling the sintering zone, and that the steam leaves the device at exhaust gas temperature. This has the disadvantage of causing increased heat loss and therefore increased heat loss.

On the other hand, the clinker is cooled by spraying or injecting the water after it has escaped the cooling device into the conveying device.

The water vapor generated in this case mostly condenses in the immediate environment and combines with the entrained clinker dust, resulting in unclean scorching and mineral deposits that reduce the operational safety factor.

Furthermore, from West German Patent Publication No. 2412695, pressurized water is injected into the hottest part of the clinker cooling device,
Thereby, proposals are known to agglomerate the clinker or, if desired, to crush it.

However, in this case, there is an inherent cooling effect as an unintended side effect that is disadvantageous from a thermodynamic point of view.

The object of the invention is to remove the largely worthless residual heat of the clinker by means of steam without the disadvantages mentioned above.

This problem is solved by the method described in claim 1.

According to this, the water that evaporates in the back cooling section of the cooling device for cooling the sintered product can be transferred, on the one hand, without fear of condensation and, on the other hand, without loss of useful process heat, and therefore under bypass of the rotary furnace. It is supplied to a dust removal section, in which case the dust removal conditions are further improved.

In a further development of the invention according to claims 2 to 4, only rotary furnace gas is used, in particular partially or completely, to obtain a mixture consisting of gas and steam. and the sinter is cooled even in a water bath.

In the following, the method according to the invention will be explained in more detail with reference to the exemplary embodiments of the drawings.

FIG. 1 shows an installation with a rotary furnace 1 with a rear-mounted grate cooling device 2 and a front-mounted oil heating device 3 for powdered raw materials.

After the rotary furnace gas escapes the preheating device 3, it passes through the waste gas cooling device 4 and is led to the electric collection device 5 before escaping into the open air.

The grate cooling device 2 is supplied with air for cooling the clinker falling from the rotary furnace 1 into the grate cooling device 2, which in this case is preheated and enters the rotary furnace 1 and is exposed to the heat from the burner 6. is introduced into the combustion process together with

The grid cooling device 2 has a rear cooling section 2a into which air is also introduced as a carrier gas; furthermore, water W is introduced into the rear cooling section 2a, which together with the air flows into the end of the clinker. cooling.

In this case, a mixture of air and water vapor WD is formed, which is discharged upwards and is conducted via line 7 with rotary furnace gas AG into line 8 leading from waste gas cooling device 4 to electric vehicle collection device 5.

In this case, for example, the following values are obtained: Rear cooling section 2
At a, the clinker reaches a temperature of 90°C after it is discharged from the rotary furnace 1 at approximately 400°C.

The rear cooling section 2a is partitioned so that water vapor generated on the grid by spraying water W can be simultaneously carried out together with a predetermined amount of preheated air.

400 with 0.1 kg of water and 0.2 Nm' of cooling air
clinker (hereinafter referred to as kl).

) with a temperature of 90 °C and a water saturation of 9 to 0.39 kg of water/1 part of air, with a dew point of 75 °C, This results in a sufficiently low waste air to avoid condensation during transport to the electric vehicle collection device 5.

The advantage in this case is that the amount of waste air typically generated in the grid cooling system 2 is approximately 1.2 to 1.4 Nm' and 9k1. is humid air 0
．． 3Nm'/kgk1. , i.e. an additional waste gas loss of approximately 50 J/ky of air is avoided when the water vapor is entrained through the rotary furnace.

According to FIG. 2, no air is introduced into the rear cooling section 2a of the grate cooling device 2, but a portion of the rotary furnace gas leaving the preheating device 3 is introduced, more specifically via the conduit 9. In this variant, air is not used as carrier gas, but a rotary furnace gas is used.

Since this rotary furnace gas generally has a significantly higher temperature than air, it is necessary to additionally evaporate water W in order to cool the mixture to the optimum dust removal temperature.

The advantage of this variant is that not only does the additional cooling air for the clinker not increase the waste gas volume, but the volume of hot waste gas is further reduced by being cooled;
The rear cooling section 2a then assumes the function of a part of the waste gas cooling device 4.

The description in FIG. 2 makes clear the temperatures that can be obtained.

As shown in FIG. 3, when the total amount of gas AG for each rotary furnace is cooled by this method, the amount of gas flowing through the rear cooling section 2a increases by about 2 to 3 times its effective volume.

Similarly, the amount of water W that can evaporate increases. For this reason, the waste gas cooling device designated by 4 in FIG. 1 can be completely omitted.

Figure 3 shows some of the temperature values that can be obtained.

With a view to increasing the amount of water, another variant is obtained, as shown in FIG. The wet clinker is then fed via a conveying device 13 via a conduit 12 to a drying drum 11 through which rotary kiln gas flows.

Particularly in the case of a water bath, water is only cooled superficially when water is sprayed, and large clinker chunks, which are the main cause of damage to the Bora belt conveyor that transports clinker in a saporary manner, are also completely cooled. be done.

In principle, the advantage of the process according to the invention is that the removal of residual heat, which is of little value, is carried out by evaporating water, if necessary in the clinker or in the rotary furnace gas, and that the condensation of this water vapor is carried out in the conveying air. or by using a rotary furnace separate gas, and in particular (compared to the small amount in the device according to FIG. 1) no additional amount of air has to be introduced into the device. As a result, the difficulties of dedusting for this purpose are eliminated and the conditioning of the waste gas for electrostatic extraction is improved or costs are saved by eliminating the evaporative cooler (waste gas cooler). Is Rukoto.

Significant economic improvements in such rotary furnace installations are therefore possible.

[Brief explanation of the drawing]

1, 2, 3, and 4 are system diagrams showing embodiments of the method according to the present invention. 1... Rotary furnace, 2... Grid cooling device, 3... Preheating device, 4... Waste gas cooling device, 5... ...Electric dust suction device, 6...
Burner, 11...Rotating drum, 13...
...Transportation device.

Claims (1)

[Claims] 1. Cooling the sintered material, in particular cement clinker, escaping from the rotary furnace in a cooling device in which the residual heat of the sintered material is removed by evaporation of water, in which case the clinker is cooled. The water vapor produced in the rear cooling section 2a of the cooling device 2 is absorbed by a hot carrier gas, the amount of hot carrier gas being such that the mixture of water vapor and carrier gas is cooled without condensation. , and finally, in the method of supplying the mixture to the dust removal device 5, the mixture is supplied to the dust removal device by bypassing the rotary furnace. . 21 parts of the rotary furnace waste gas are used in the mixture, whereas the remaining rotary furnace waste gas is fed to the waste gas cooling device 4, and the mixture is added to the rotary furnace waste gas of the remaining amount after the waste gas cooling device. A method for cooling a sintered material escaping from a rotary furnace according to claim 1, wherein the sintered material is mixed into a gas. 3. Claim 1, characterized in that all rotary furnace waste gases are used in the mixture with a corresponding increase in the amount of water to be evaporated, and the mixture is fed directly to the dedusting device 5.
A method for cooling sintered material escaping from a rotary furnace as described in item (2). 4. The sintered material to be cooled is sprinkled with water or introduced into a water bath, in which it is completely cooled and subsequently dried in a drying device 11 through which rotary furnace waste gas flows, in which case the rotary furnace waste gases flow through it. 4. Process for cooling sinter escaping from a rotary furnace according to claim 3, characterized in that the gas dries the clinker, is itself cooled and enriched with water vapor.