JPS595008B2 - Method and apparatus for firing fine powder or granular materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a process in which a fine powder or granular material, in particular a lime-containing material such as, but not limited to, a cement raw material, is coupled to a kiln in which the raw material is fired and to the rear of the kiln. a cooler connected to the front of the kiln for cooling the product fired in the kiln by means of cooling atmospheric air; and at least one preheater for preheating (i.e. preheating and preheat calcination) the fresh raw material by heat exchange with the kiln plant.

Calcination refers to the expulsion of gases such as carbon dioxide by an endothermic reaction.

Hereinafter, "plant" refers to the type described above.

In known kiln plants of this type, rotary kilns are usually used as kilns, but other types of kilns can also be used.

In a combined kiln plant, the process carried out in its own kiln, regardless of the kiln type, is limited as much as possible to the sintering of the material before it is sent to a cooler for cooling before further processing. It is preferable to do so.

It is particularly necessary to carry out maximum preheating in a preheater or maximum cooling in a cooler connected to the preheater or calcination mold, but this method increases the dimensions of these heat exchangers considerably.

When using the heat of used cooling air for preheating, the hot used cooling air must be conveyed from one end of the kiln to the other, and heat loss is unavoidable. It requires a large and efficient cooler, a large preheater, and an associated exhaust fan.

Furthermore, if the material undergoes precalcination in a calciner connected to a preheater, large dust collectors and large exhaust fans are required due to the large amount of smoke generated by combustion of the fuel in the calciner.

It is also desirable to improve the capacity of such kiln plants, while at the same time improving the capacity of at least some of the preheaters, calciners, coolers, smoke gas fans and dust collectors without increasing the power consumption of the plant. It is preferable to make the dimensions of the object as small as possible.

According to the invention, in the method of combusting fine powder or granular raw material in a kiln plant as described above, a first raw material stream is preheated in a preheater, and a Preheating another feed stream by heat, and then subjecting said two preheated feed streams to a firing or final preheating treatment together, preferably when both feed streams have undergone the same degree of heat treatment. They are combined to undergo firing.

The preheating treatment that the two feed streams undergo in the preheater and cooler is essentially only preheating, as the two feed streams are joined just before being introduced into the kiln and together undergo first calcination and then firing.

However, the preheating treatment that the second feed stream undergoes in the cooler involves both preheating and at least partial calcination.

The two feed streams may be combined in a calcination mold connected to a preheater, in which they are locally heated in the presence of oxygen contained in the spent cooling air from the cooler. Burning the supplied fuel generates heat to calcinate the raw material.

Alternately to the method described above, a first feed stream is at least partially calcined in a calcination mold connected to a preheater, and then a second feed stream is similarly calcined and preheated in a cooler. The first downstream of the calcination mold
Preferably, the raw material stream is combined with the raw material stream.

Preferably, the second feed stream is conveyed to join the first feed stream suspended in spent cooling air from the cooler.

The second feed stream may represent 5-40% of the total feed sent to the kiln plant.

The second feed stream may be suspended in atmospheric air before entering the cooler.

In the cooler, the atmospheric air in which the feedstock is suspended may be mixed with atmospheric air supplied to the cooler for cooling the final product.

At least a portion of the thus mixed air stream comprises heated, used, and cooled air that is passed through a preheater and a second preheated feed stream from the cooler to join the first feed stream.
It acts as a carrier for transporting the raw material flow.

Instead of suspending the second feed stream in atmospheric air before entering the cooler, it is first mixed with the kiln product, processed with this product in the cooler, and subsequently separated from the kiln product. It may also be suspended in cooled air.

If the feedstock is transferred to the hot section of the cooler or into the precooling zone of the kiln itself near the kiln outlet, this feedstock is mixed with the product of the kiln in the hot section of the cooler and is simultaneously preheated and It may be at least partially calcined and subsequently separated from the products of the kiln, suspended in the cooling air, and then subjected to further processing within the plant.

When the raw material is sent to the low-temperature section of the cooler and mixed with the kiln product therein, it is separated from the kiln product after preheating, floats in the cooling air, and passes through the high-temperature section of the cooler with the air. The kiln product may be at least partially calcined by heat generated from the kiln product.

Most of the used cooling air from the cooler is sent to the preheater and used for both preheating and calcination of the first feed stream, so the remaining used cooling air is sent to the kiln. The heat required to carry out the sintering within the kiln cannot be generated because it is insufficient to promote the combustion of the fuel being used.

Therefore, it is necessary to send extra air into the kiln.

This excess atmosphere may be preheated by indirect heat exchange with the gas from the kiln in a heat exchanger of known type.

The present invention is a kiln plant implementing a novel process, comprising: a kiln; a cooler connected to the kiln for cooling the kiln product with atmospheric air; at least one feed preheater for preheating a continuous feed stream; and means for directing a second continuous feed stream to and through a cooler; and for use with a second feedstock suspended within the cooler. means for blowing the already cooled air into the preheater to enable at least a major portion of the second feedstock to be combined with the first feedstock.

The preheater may be connected to a calcination mold that delivers a continuous flow of preheated raw material.

The preheated second feed stream from the cooler is conveyed by pipes leading from the cooler to the lower part of the preheater where they are combined before sending the first and second feed streams together to the kiln. at least a major part of the calcination (sintering) is carried out in the cooler, or the first and second feed streams are conveyed by a pipe connected to the lower end of the preheater or leading to the calciner to partially divide both the first and second feed streams. It is advisable to calcine it completely before sending it to the kiln.

The cooler may be provided with means for liberating the second feedstock into the atmospheric air and conveying the suspended feedstock to the cooler.

Alternatively, the plant includes means for mixing the second feed stream with the product of the kiln and for separating the product of the kiln and the feed after processing the feed with the product in the cooler and placing the feed in cooling air. A means for levitation may be provided.

The above-mentioned mixing means may, for example, feed the raw material to the cooler and the entire width of the product of the kiln in the cooler, or the entire width of the movable shoe of a grate-type cooler, or added in the cooler or cooling tubes. The full width of a rotating cooler or cooling tube that creates a turbulent flow of the kiln product with the raw material, or of a conveyor that feeds the raw material into the kiln product at the bottom of the fixed casing between the outlet end of the kiln and the inlet end of the cooler. It may consist of a suitable structure of a vibro which distributes the raw material over the entire width or a combination of two or more of the above devices.

This cooler may be a grate type cooler or a model rotary cooler.

A planetary cooler may be added to the latter rotary cooler, and a cooling tube may be provided around the outlet of the model rotary cooler to rotate with it.

Additionally, each planetary cooling tube may be provided with means for conveying the second feedstock together with atmospheric air, so that the feedstock suspended in air is primarily passed through the tube and further into the model cooler.

The main feature of the invention is that not only the feedstock is sent to the preheater, as is known, but also a separate second feedstock is sent to the cooler.

The heat generated from the kiln product is then used in a cooler while it is available, providing the following benefits:

The size of the cooler can be reduced since the preheating and preferably partial calcination of the feedstock in the cooler consumes some amount of heat that previously had to be removed by means of a large cooling surface.

Used cooling air can be sent to the preheater at a low temperature, reducing heat loss.

The preheater can be small because it preheats only a portion of the amount of feedstock fed to the plant and only enough gas is needed for that purpose.

When part of the raw material is partially calcined in a cooler before it is sent to a calcining mold connected to a preheater or to a kiln, the calcining mold can be made smaller and therefore the calcination mold fuel consumption can be reduced.

Finally, the smoke gas fan and dust collector can be made smaller as the smoke gases implementing the method can be reduced.

Balancing the amount of material fed into the preheater and cooler, respectively, and the amount of smoke gas generated in the calcination mold, which is related to the heat consumption of the preheater during prefiring, and the amount of material fed into the preheater and the cooler, respectively. Overall fuel consumption of the plant is reduced by 10-12% compared to similar plants that had to send
This is clear from various calculations.

Various embodiments of a kiln plant according to the present invention will be described below with reference to the accompanying drawings.

The plant shown in FIG. 1 has a rotary kiln 1, a cooler 2, a preheater 3, a calcination mold 4, and a heat exchanger 5, the ends of which are connected by fixed casings 1' and 1. ” is surrounded by

Fuel is sent to the calcination type burner 6 and the kiln burner 7.

The casing 1' connects the kiln 1 and the cooler 2, and the casing 1'' connects the kiln 1 and the heat exchanger 5.

A part of the fine powder or granular raw material is sent to the preheater through the pipe 14 and a part is sent to the cooler 2 through the pipe 8, and is input into the plant.

First of all, the first feedstock from the pipe 14 to the preheater is preheated and partially calcined in this preheater by the smoke generated in the calcination mold 4.

The smoke used at this time is sucked up from this preheater by the fan 13.

After being preheated, the material passes through the calcination mold 4 and is sent to the kiln 1 through the lowermost stage of this preheater and the descending pipe 2'.

The second feedstock to the cooler 2 is blown into the cooler from the outlet end of the cooler through the pipe 8 together with atmospheric air from the pipe 9.

This feed is suspended by the air flow over the product in the cooler and passes through the cooler in countercurrent to the kiln product, where it is partially calcined by heat from the kiln product.

The raw material treated in this way is sent from the cooler directly to the calcination mold 4 through the casing 1' and the pipe 12, together with the preheated and mostly spent cooling air to be utilized in the calcination mold 4.

The remaining used cooling air sent from the cooler is insufficient to promote combustion of the fuel sent to the kiln and therefore cannot generate the amount of heat necessary to effectuate sintering.

Therefore, an extra amount of atmospheric air must be sent to the kiln.

This operation is carried out by a fan 15 through a pipe 15, and the air is preheated indirectly by a heat exchanger together with the exhaust gas from the kiln.

The materials derived from both the first co-feed and the second feedstock are thoroughly calcined together in the calcination mold 4 before the entire amount of material is sent to the kiln 1.

In this way, the calcination process is divided into the calcination mold 4 and the cooler 2,
At the same time, by improving the utilization of the heat generated in the cooler, an arbitrary reduction in the dimensions of the cooler 2, the calcination mold 4 and the preheater 3 is possible.

This method allows the smoke gas generated in the calcination mold 4 to meet the conditions of preheating the material in the preheater 3, so that all the smoke gas generated in the kiln passes through the casing 1''. The secondary air is passed through a pipe 15 to the kiln and the smoke gases are passed through a fan to preheat the secondary air. 11, they are removed one after another.

Such a method improves the thermal economy of the entire plant.

FIG. 2 shows a cooler 2 in the form of a grate-type cooler 23 for partially calcining the finely powdered or granular material fed.

The cooler 22 is connected to the rotary kiln 21 through a fixed casing 2z.

This kiln is provided with a burner 23, and the cooler is provided with air injection means 25.
Cooling air 26 flows from the cooler through the grate 24 of the cooler.

The feed mixed with air is blown through pipe 28 into the outlet end of the cooler.

This mixing of raw material and air takes place in pipe 28, and the raw material is then sent to pipe 28 through another pipe 29.

The feedstock is captured in a flow of cooling air 26 within the cooler.

This cooling air stream 26, after passing between the kiln product 27 distributed on the grate of the cooler,
℃ and the raw material is kept suspended above the product of the kiln.

As a result, a partial calcination of the raw material takes place and the raw material is sent one after another through the pipe 30 to the calcination mold together with the air preheated in the cooler.

The secondary air pipe 15 shown in FIG. 1 has been removed from FIG. 2 for clarity.

The cooler shown in FIG. 3 is a horizontal hole rotary cooler 32 which partially burns the fine powder or granular material that is also supplied.

This cooler is connected via a fixed casing 37 to a rotary kiln 31, which has a burner 23 and a pipe 15 for conveying excess secondary air into the kiln.

The second feedstock sent to the plant is from pipe 40,
into the air stream passing through the pipe 33;
3 into the outlet end of the cooler.

The cooling air sent into the cooler from the pipe 34 carries the raw material suspended in the air stream above the kiln product 35, which is transported into the cooler 32 during rotation of the cooler. Stirred at the bottom.

The cooling air has a temperature of about 850 while passing through this cooler.
The raw materials that are heated to ℃ and suspended in this cooling air are
Partially calcined, preheated cooling air is passed successively through pipe 38 into the calcination mold.

The smoke gases from the kiln are sent to a heat exchanger as described in connection with FIG.

Reference number 36 is a device for conveying the clinker provided after the cooler, and 39 is a quenching device for pre-cooling the clinker within the fixed casing.

FIG. 4 shows a modification of the embodiment of FIG. 3, in which a side-hole rotary cooler 32 is equipped with a planetary cooler consisting of a number of cooling tubes 45 arranged at equal intervals around the outlet end of the cooler. is added, and this cooling tube is a model cooler 32
It is fixed to the cooler and rotates together with this cooler.

A stationary casing 50 collects the kiln product 49 after it has passed through the cooler.

At the lower end of the outlet casing is provided an outlet 51 with a rotary valve gate, and at the upper end is provided a pipe 46 for blowing air into the cooling tube.

The second feedstock is passed through pipe 47 into the air stream and the feed suspended in air stream 48 enters through casing 50 and above kiln product 49 in cooling tube 45 .

The air in the cooling tube is heated to about 850° C. by heat from the kiln product to effect partial calcination of the feedstock.

The mixed stream 48 flows countercurrently to the kiln product into a schematic cooler 3.
2, where partial calcination and preheating are continued.
The material and preheated cooling air from the inlet end of this model cooler 32 sequentially enter the calcination mold as described in connection with FIGS. 1 and 3.

Number 52 is a dam ring for properly draining the kiln product from the model cooler into the cooling tube 45.

The embodiments of FIGS. 5 and 6 are shown in FIGS.
This embodiment is the same as the embodiment shown in FIG. 2 except for the following.

In FIG. 5, the feedstock is fed into the kiln product in a precooling zone at the exit end of the kiln and conveyed with the kiln product to a portion of the hopper of the cooler.

The feedstock is preheated and partially calcined by heat from the kiln product while passing through the cooler.

The feedstock is separated from the kiln product, suspended in the cooling air 26 and sent along with the spent cooling air through pipes 30 to the calcination mold.

In the embodiment shown in FIG. 6, the feedstock is passed through the vibro 2 into the kiln product in the cooler of the cooler and is mixed with this product.

The feedstock is thus preheated and separated from the kiln product one after another, suspended in the cooling air 26, and partially calcined while passing with the air through the hot section of the cooler.

The embodiments of FIGS. 7 and 8 are shown in FIGS.
This embodiment is the same as the embodiment shown in FIG. 3 except for the following.

The two structures shown in FIGS. 7 and 8 do not differ from the structures in FIGS. 5 and 6 except that the cooler is a side hole rotary cooler and not a grate cooler. and the cooling air is sent to the plant through pipes 34 and fans 39.

The embodiment shown in FIG. 9 corresponds to the embodiment shown in FIG.
The raw material that is not previously suspended in the airflow is passed through the pipe 66 (
(Compare with pipes 46 and 47 in Figure 4) Cooling tube 4
The difference is that it is fed directly into the product of the kiln in 5 and that the raw material is passed through the outlet opening of the tube and into the tube.

Figure 10 shows a separate plant for mixing raw materials and kiln products in a plant consisting of a rotary cooler, a stationary casing, and a side-hole rotary cooler corresponding to the plant shown in Figure 3 and transporting the raw materials to a cooling zone. We will show you how.

The raw material is passed through a pipe 67 to a conveyor, such as a worm conveyor 68, and is conveyed to the bottom of the stationary casing, which is connected to the kiln 32 and rotary cooler 32.

As the feedstock enters the bottom of the can 7/7'', it mixes with the kiln product which passes through the casing and descends into the cooler.

In the latter, the feedstock is preheated and partially calcined by heat from the kiln product before being separated from the kiln product as described in Figures 3 and 7 and placed in cooling air. Float.

[Brief explanation of the drawing]

Figure 1 is a flow sheet for a rotary kiln plant. FIG. 2 shows a grate-type cooler for partial calcination of pulverulent or granular raw materials. FIG. 3 shows a side hole rotary cooler for partial calcination of raw materials. Figure 4 shows a side hole rotary cooler with the addition of a planetary cooler to partially calcinate the feedstock in both coolers. FIG. 5 shows a grate-type cooler connected to the rear of the kiln which feeds the raw material to a portion of the hopper of the cooler and mixes with the product of the kiln. FIG. 6 shows a grate-type cooler similar to that shown in FIG. 5, but which transports the feedstock to the cold section of the cooler and mixes it with the product of the kiln. FIGS. 7 and 8 show a similar device to FIGS. 5 and 6, except that the cooler is a side hole rotary cooler. FIG. 9 shows a schematic rotary cooler with the addition of a planetary cooler, into which feedstock is fed and mixed with the product of the kiln. FIG. 10 shows another device for transferring raw materials to the hot section of a model rotary cooler. 1...Rotary kiln, 2...Cooler, 3...Preheater, 4...Calcination mold.

Claims (1)

[Claims] 1. A kiln for firing fine powder or granular material, a cooler connected to the rear of the kiln and for cooling the product fired in the kiln with cooling atmospheric air, and a kiln. at least one preheating device connected in front of the cooler for preheating the new feedstock before entering the kiln by heat exchange with used cooling air from the cooler, the first feedstock stream The second step is preheating with a preheater.
A kiln plant in which a raw material stream is preheated in a cooler by heat generated from a fired product in the cooler, and the preheated raw material streams are merged and fired together or are fired after a final preheating treatment. A method of firing fine powder or granular materials. 2. The method of claim 1, wherein the two preheated feed streams are combined when they have undergone substantially the same degree of heat treatment. 3 Claim 1 or 2 in which the raw material contains lime
The method described in section. 4. A method according to any one of claims 1 to 3, wherein the preheating step to which the second feed stream is subjected in the cooler comprises both a preheating step and an at least partial calcination step. 5 The two feed streams are combined in a calciner connected to a preheater, within which they are locally added in the presence of oxygen contained in the spent cooling air from the cooler. 5. A method as claimed in any one of claims 1 to 4, in which the heat for calcining the raw material is generated by burning the fuel. 6. Conveying the second feed stream to join the first feed stream suspended in spent cooling air from the cooler, as claimed in any one of claims 1 to 5. the method of. 7. The second feed stream is first mixed with the kiln product and treated with the product in a cooler, and then separated from the kiln product and suspended in cooling air. The method according to any one of paragraph 6. 8 A second feed stream is mixed with the kiln product in the hot section of the cooler by sending it to the hot section of the cooler or to the precooling zone of the kiln, and is simultaneously preheated and at least partially calcined before kiln production. The method according to claim 7, wherein the method is separated from objects and suspended in cooling air. 9 A second feed stream is sent to the cooler where it is preheated by mixing with the kiln product in the cooler and is then separated from this kiln product and is suspended in the cooling air and transported with this air to the hot section of the cooler. 8. A method as claimed in claim 7, in which the product is at least partially calcined by the heat generated from the product of a kiln passing through the cooler. 10. A method as claimed in any one of claims 1 to 6, in which the feedstock in the second feedstream is suspended in atmospheric air before it enters the cooler. 11 A major portion of the feedstock forming the second feedstream is passed through a cooler while suspended in an atmospheric airflow, such that one component of the atmospheric airflow causes the second feedstream to flow into the cooler. Atmospheric air is used as a carrier to send
The other component is the atmospheric air initially used in the refrigeration to cool the product, the heated used cooling air and preheating treatment in which at least a portion of the atmospheric air stream is subsequently passed through a preheater. 11. The method of claim 10, further comprising carrier means operative to carry the preheated second feed stream onto the preheated first feed stream. 12. A method according to any one of claims 1 to 11, wherein the feedstock in the second feedstream accounts for 5 to 40 parts of the total feedstock sent to the kiln plant. 13 a kiln, a cooler coupled to the kiln to cool the kiln product by atmospheric air, at least one feed heater coupled to the kiln pressure for preheating the first continuous feed stream; means for directing the continuous feedstock through the cooler and blowing the spent cooling air along with the suspended second feedstock into the preheater and combining a majority of the second feedstock with the first feedstock; A kiln plant characterized in that it consists of means for causing. 14 in which at least the majority of the calcination (sintering) takes place within the kiln itself, the means for blowing spent cooling air into the preheater comprising a pipe leading to the lower part of the preheater;
14. The kiln plant of claim 13, wherein the and second feed streams are combined before they both enter the kiln. 15 a calciner is connected to the lower end of the preheater, and means for blowing spent cooling air into the preheater includes a pipe leading to the calciner, before the first and second feed streams enter the kiln. 14. A kiln plant as claimed in claim 13, in which both are partially and completely calcined. 16. According to any one of claims 13 to 15, the cooler is provided with means for suspending a fresh second feed stream in atmospheric air and conveying this feed while in suspension to the cooler. Kiln plant listed. 17 means for mixing the second feed stream with the product of the kiln;
Claims 13 to 16 include means for separating the feedstock from the kiln product after processing the feedstock in a cooler with the product and suspending the feedstock in cooling air.
A kiln plant according to any one of the clauses. 18. A kiln plant according to any one of claims 13 to 17, wherein the cooler is a grate type cooler. 19. A kiln plant according to any one of claims 13 to 17, wherein the cooler is a side hole rotary cooler. A planetary cooler is added to the 20-lateral rotary cooler, and the cooling tube of this planetary cooler is arranged around the outlet end of the model cooler, and rotates with the model cooler. The cooler is provided with means for sending a second stream of raw material along with atmospheric air into each of the planetary cooling tubes, and the raw material sent into the cooling tubes flows through these tubes while being primarily suspended in the air. 20. A kiln plant according to claim 19, wherein the kiln plant passes through the air and enters the model cooler while still suspended in atmospheric air. 21 A planetary type cooler is added to the horizontal hole rotary cooler,
The cooling tubes of the planetary cooler are arranged around the outlet end of the pattern cooler and rotate with the pattern cooler, and the second feed stream and the kiln product are separated from each other within the respective cooling tubes. and means for separating the raw material from the kiln product and suspending it in the cooling air before the raw material is introduced into the side hole rotary cooler, the cooler being provided with Kiln plant as described in section.