CS214541B1 - Appliance for preheating and calcination of powder materials - Google Patents

Abstract

The invention relates to a device for preheating and curing the powdery materials, in particular cement raw meal before its sintering in another aggregate, most often in a rotary kiln, in a dry firing process cement clinker. The gas supply duct from the rotary kiln is guided along the exchanger shaft upwards above the manhole level, then vertically downward and arch to the exchanger shaft into which it is tangential, the bottom wall obliquely down at an angle of 10 to 30 ° from the horizontal planes and top wall horizontally or obliquely upward, 0 to 15 ° bd horizontal planes.

Description

BACKGROUND OF THE INVENTION The present invention relates to an apparatus for preheating and forging of pulverulent materials, in particular cement raw meal before sintering in another aggregate, most commonly in a rotary kiln, in a dry method of firing cement clinker.

The gas inlet duct from the rotary kiln is routed along the exchanger shaft upwards above the level of the inlet to the shaft, then vertically downward and arched to the exchanger shaft into which it opens tangentially, the bottom wall obliquely down at 10-30 ° from the horizontal and the top wall horizontally or obliquely upwards at an angle of 0 to 15 ° bd of the horizontal plane.

21-4541

The invention relates to a device for preheating and calcining pulverulent materials, in particular. cement raw meal, before its sintering in another aggregate, most often in rotary pee, in the dry way of firing cement clinker.

Already in the industry, a countercurrent shaft exchanger for preheating and partial calcination of cement raw meal has been routinely used in industrial practice prior to entering the short rotary kiln, where the thermal calcination process completes and sinters.

Recently, it has been possible to increase the degree of calcination carried out in the exchanger and thereby to increase the specific power of the rotary kiln by separating the preheated feedstock, part being introduced into the recirculation circuit formed by the gas supply channel and exchanger, and part being introduced into the rotary kiln. the fuel is not combusted in the recirculation circuit at the lower desired degree of calcination and the fuel is combusted at the higher desired degree of calcination.

In recent years there has been a need for better use of fuel. Therefore, all possibilities are investigated to improve the thermal economy of individual equipment, including the shaft countercurrent exchanger, both in the basic application, where artificially controlled recirculation between the gas supply channel is not used, and in applications with recirculation if the fuel does not burn here. eventually incinerates.

By studying the problem it was found that the detail of the tangential inlet of the gas inlet duct into the ^! The exchanger shaft, where the channel is led from the transition piece of the rotary furnace upwards and arched to the exchanger shaft, is not suitable from the viewpoint of heat economy of the exchanger shaft especially for the following reasons:

The gases coming from the furnace always contain a considerable amount of raw material drift. When using recirculation to increase the degree of calcination, whether the fuel is combusted or not combusted, the recirculating raw material can also be considered as a drift entering the gas inlet of the exchanger. This drift has practically a gas temperature and, depending on its amount, more or less influences the heat content of the medium in the gas supply channel.

Due to the centrifugal force, the particles of the fly as they pass through the channel arch adhere to the outer wall of the arch and are thus thrown together with the gases into the exchanger shaft. Here, the gases are mixed, drifted and preheated, the temperatures practically equal to a value approximately equal to the temperature of the preheated raw material, which is practically measured as the "temperature at the bottom of the shaft".

From the point of view of preheating the raw material, it is desirable that this temperature be as high as possible. However, in view of the level of all temperatures in the exchanger and thus also the temperature of the exhaust gases after the exchange with the exchanger, it is desirable that this temperature be as low as possible.

The object of the present invention is to eliminate this inconsistency, to raise the temperature of the preheated feedstock, to increase the degree of calcination thereof and to reduce the level of all the gas temperatures in the exchanger, and thus the waste gas temperature, thereby improving thermal economy by the simplest means.

SUMMARY OF THE INVENTION The gas inlet duct from the rotary kiln extends along the exchanger shaft upwards above the level of the orifice into the shaft, then vertically downward and arched to the exchanger shaft into which it runs tangentially through the bottom wall at an oblique angle. up to 30 ° from the horizontal and the top wall horizontally or obliquely upwards at an angle of 0 to 15 ° from the horizontal.

The apparatus according to the invention is shown schematically in FIG. 1 in an application to a conventional shaft countercurrent exchanger, in FIG. 2 in an application to an exchanger with increased precalcination by recirculating the raw material without additional heating and in FIG. 3 with additional heating.

The device in Fig. 1 consists of a shaft exchanger 1 formed by a cylindrical shaft 2 terminated at the bottom by a conical hopper 3. The cylindrical shaft 2 in the upper part passes into a pipeline 4, which is distributed to cyclones 5, which are connected a gas line 6 extending to a smoke fan (not shown). The cyclones 5 in their lower part are interconnected by the raw material line 7 with the flaps 8 with the upper part of the cylindrical shaft 2, where a shatter cone 9 is located under the outlets of the raw material line 7.

The raw material feed line 12 for processing is connected to the pipe 4.

The shaft exchanger 1 is connected to the rotary kiln 10 by a gas supply duct 11 which, before it enters the exchanger shaft 2, is guided upwards above the orifice level, then vertically downwards and further guided in an arc towards the exchanger shaft 2 into which it is connected tangentially through the bottom wall obliquely down at an angle α = 10 to 30 ° from the horizontal and the top wall horizontally or obliquely up at an angle β = 0 - 15 ° from the horizontal. The conical hopper 3 is also connected to the rotary kiln 10 via a duct 18 with a flap valve 19.

The device of Fig. 2 differs from the device of Fig. 1 in that the conical hopper 3 is connected to a raw material distributor 13 from which the raw material pipe 14 is routed to the rotary kiln 10 and the recirculation pipe 15 upstream of the gas inlet duct 11. .

The apparatus of Fig. 3 differs from the apparatus of Fig. 2 in that the gas inlet duct 11 is provided with fuel burners 17 in one or more horizontal planes. 2 and 3 of the apparatus or pipes 15 of the recirculation apparatus described in FIGS. 2 and 3 are provided, at their point of entry, with shattering elements 18 of sheet metal or lining.

The apparatus of FIG. 1 operates as follows:

The hot flue gases from the rotary kiln 10 'are passed through the gas inlet duct 11 and the shaft exchanger 1 by means of a smoke fan.

Due to the tangential inlet of the gas inlet duct 11 into the cylinder shaft 2, the gases rotate over the entire height of the cylinder shaft 2. They then proceed through line 4 to cyclones 3, a gas exhaust line 6 and a smoke fan to a dust collector or for further use.

The raw material to be preheated and calcined is conveyed by the raw material feed line 12 to the line 4 where it is shattered on the shredding element 16, dispersed in the gases, dried and partially preheated and carried to the cyclone 5 where it is separated. It is fed through the raw material pipes 7 with flaps 8 into the upper part of the cylindrical shaft 2, where it splits on the splitting cone 9 and disperses into the stream of rotating gases. At the start of operation, it is carried back to the cyclones 5, it returns to the cylindrical shaft 2, but after a few moments the recirculation circuit described is so overloaded that from the point where the gas carrying capacity is the lowest and In the shaft 2, the raw material begins to advance through the cylindrical shaft 2 while rotating upstream of the rotating gases, thereby preheating and partially calcining in a counter-current manner.

The drift of the raw material from the rotary kiln 10, which is introduced into the shaft 2 by hot flue gases through the gas inlet duct 11, separates in its arc before it enters the shaft 2 by centrifugal force and slides down its bottom inclined wall directly into the conical hopper 3 the raw material coming from the shaft mainly in the absence of gases and, on the other hand, the dehumidified gases proceed substantially horizontally; or

Claims (3)

A device for preheating and calcining pulverulent materials consisting of a cylindrical shaft, cyclones in its upper part, a conical hopper in its lower part, a gas supply channel from the rotary furnace to the bottom of the shaft tangentially, in the pipeline below the conical hopper with the downstream piping to the rotary kiln and the recirculation piping leading to the gas inlet duct, alternatively inclined up along the horizontal or slightly inclined upper wall of the gas inlet duct 11, tangentially to the shaft 2 where they transfer their heat directly to the feed 2 mostly without drift. The preheated feedstock, including the gaseous entrainment, is collected in the conical hopper 3, from where it is fed via a duct 18 with a flap valve 19 to a rotary kiln 10 for further processing. The device of FIG. 2 works similarly with the difference that the raw material that is collected in the conical hopper 3. it enters the feedstock distributor 13 where it divides with a ratio setting of, for example, 40 ° / o £ 60%. 60% of the feedstock is distributed through the feedstock pipeline 14 to a rotary kiln. 10, 40% through the recirculation line 15 to the bottom of the gas inlet duct 11 where it splits on the shredding element 16, disperses in the gas stream and is carried back by the gases back into the shaft 2. This controlled circulation increases the degree of calcination of feedstock but recirculating feedstock in the gases in the gas inlet duct 11 as a drift; therefore, the amount of drift is higher than normal operation, so that the significance of the above-described separation of drift from gases is more thermodynamically significant. The device of FIG. 3 works similarly to the apparatus of FIG. 2 except that the feedstock distributor 13 adjusts the feedstock to furnace to recirculation ratio of, for example, 25% and 75%, and burns the fuel supplied by the burners 17 in the gas inlet duct 11. This operation allows a high degree of calcination of the feedstock, but the amount of feedstock in the gas supply duct 11 which appears to be a drift is several times higher than the above-described operating conditions, so that the significance of the drift-gas separation described above is even more thermodynamically. With the introduction of the invention, the temperature of the preheated feedstock is increased and the degree of calcination is increased by reducing the temperature of the gases in the shaft countercurrent exchanger, which makes it possible to reduce the heat consumption after firing. of the invention with a fuel burner in the gas inlet duct characterized in that the gas inlet duct (11) from the rotary kiln (10) extends along the shaft (2) of the exchanger (1) upwards above the level of the orifice into the shaft (2) then vertically down and by an arc to the exchanger shaft (2) into which it extends tangentially, through the bottom wall at an angle of 10 to 30 ° from the horizontal and the top wall horizontally or at an angle of 0 to 15 ° from the horizontal.