JPS629547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides several steps of heat treatment of the raw powder with a rotary tube furnace and a waste gas stream from the calcination furnace prior to deoxidation in a calcination furnace and subsequent firing in a rotary tube furnace. Preheating is carried out in two parallel waste gas channels in exchange, with the raw powder stream being alternately passed through a heat exchange stage arranged just before the calciner and connected to the waste gas stream from the rotary tube furnace. The present invention relates to a method and an apparatus for producing cement by guiding from one waste gas line heat exchange stage to another waste gas line heat exchange stage.

In order to improve the deoxidation in the calciner by reducing the partial pressure of carbon dioxide on the one hand, and on the other hand to improve the preheating of the raw material powder before entering the calciner, the rotary tube furnace is used in the calciner. The waste gas streams from the rotary tube furnace and calciner are fed into two mutually separate, multi-stage heat exchangers, supplying heated cooling air when cooling the already calcined cement clinker rather than the waste gas. It is known (German Patent Publication no. 2931590) to introduce the raw powder into parallel waste gas paths (German Patent Publication No. 2931590), in which case the flow of raw powder is alternately carried from one waste gas path heat exchange stage to another waste gas path. The heat exchange stage is then guided to the calciner. With this method, the rotary tube furnace waste gases cannot have a detrimental effect on the deoxidation of the raw powder in the calciner. Furthermore, the flow of raw material powder, before entering the calciner,
Since the waste gas temperature of the rotary tube furnace is higher than the waste gas temperature of the calciner, a higher preheating temperature is obtained than if the waste gas were introduced in a single stream.

In the case of this known process, the raw powder must be charged to the heat exchanger in two metered streams, inter alia, in order to ensure approximately the same temperature ratio of the two waste gas streams at the end of the cooling of the heat exchanger. That is a disadvantage. These raw powder sub-streams are actually recombined and introduced and removed together between the heat exchange stages of the two waste gas paths, but such a feeding of the raw powder requires increased outlay. Additionally, separate blowers are used in each waste gas line for different waste gas temperatures and pressures. Finally, since suitably high waste gas volumes occur in the calciner, another disadvantage arises of having to design the heat exchange units of the two waste gas channels differently. Furthermore, the scorching dust content contained in the waste gas of rotary tube furnaces requires special measures to avoid scorching in the heat exchange stages and conduits.

It is therefore an object of the present invention to avoid the above-mentioned disadvantages and to
The object of the present invention is to improve the method for producing cement as described above in such a way that the cost of the equipment is significantly reduced and the risk of burning of the dust contained in the rotary tube furnace waste gas is largely avoided.

The present invention solves the problem set by transferring a portion of the hot waste gas stream of the calciner to the hot waste gas stream from the rotary tube furnace before or in a heat exchange stage arranged immediately before the calciner. This can be solved by mixing in the stage.

By mixing a portion of the waste gas stream from the calcination furnace with the waste gas stream from the rotary tube furnace, it is possible to firstly ensure that the two waste gas paths have the same amount of waste gas; This makes it possible to use the same heat exchange unit for the two waste gas paths and thus to have identical temperature conditions in the waste gas paths. This ensures that, under otherwise equal conditions, the exit temperature of the waste gas stream depends on the mass ratio of raw powder to waste gas and that the entire raw powder flow is sent undivided to the heat exchange unit of the heat exchanger. This not only reduces the cost of the equipment but also improves thermal efficiency. In order to achieve well-matched temperature conditions in the two waste gas paths, it is also possible to use a common blower for the two waste gas paths. Furthermore, dilution in terms of dust content in the rotary tube furnace waste gas is achieved by mixing a portion of the calciner-waste gas stream into the waste gas stream from the rotary tube furnace, which The risk of sticking is sufficiently reduced.

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One particularly advantageous method of ensuring matching temperature conditions in the two waste gas paths is, in another embodiment of the invention, to transfer a portion of the hot waste gas stream from the rotary tube furnace to the calciner. This can be obtained by feeding the waste gas stream to the calciner before its incorporation. This method results in the presence of a mixed waste gas stream even in the calciner, which significantly reduces the dust content. Furthermore, if variations in the operation of the rotary tube furnace cause changes in the amount of waste gas and the temperature of the waste gas in the rotary tube furnace, the flow of waste gas from the rotary tube furnace that is supplied to the calcination furnace may be appropriately adjusted. This makes it possible to guarantee constant conditions for the preheating and preliminary deoxidation of the raw flour. In this case, only a partial stream of the rotary tube furnace waste gas is fed to the calciner and the main part of the gas stream fed to the calciner advantageously consists of preheated air, so that the rotary tube for the calcination process The adverse effects of reactor waste gas are not significant in practice.

In order to be able to utilize the high temperature of the rotary tube furnace waste gas for high preheating of the raw material powder, the raw material powder is mixed with the waste gas stream of the rotary tube furnace before it is mixed with the waste gas stream of the calciner. The hot waste gas stream from the rotary tube furnace can be fed upstream of a heat exchange stage arranged immediately before the calciner. Furthermore, due to the mixed stream having a low temperature compared to the rotary tube furnace waste gas, the raw powder is guided in the flow direction of the raw powder to the last heat exchange stage before it reaches the calciner.

When the raw powder is preheated in two parallel waste gas channels in several steps of heat exchange with the waste gas stream from the calciner before deoxidation in the calciner and subsequent calcination in the rotary tube furnace. , the raw powder stream is placed just before the calciner,
The heat exchange stages connected to the waste gas stream from the calciner are guided alternately from the heat exchange stages of one waste gas line to the heat exchange stages of another waste gas line. In this case, in another embodiment of the invention, the hot waste gas stream from the rotary tube furnace is fed with raw powder before a heat exchange stage arranged immediately before the calciner, and then the waste gas stream When mixed with the waste gas stream in the calciner,
A partial stream of the raw powder is conveyed together with a waste gas stream from the calciner to a heat exchange stage arranged immediately before the calciner, from which the raw material already led through the calciner is conveyed. The flour reaches the calciner together with the remaining raw flour, so that the residence time of this material and thus the degree of deoxidation is extended. This means that the size of the rotary tube furnace can be reduced for a higher degree of deoxidation in the calciner, or the size of the calciner can be reduced for the same degree of deacidification. . Since, as is well known, the deoxidation depends in particular on the particle size of the raw flour, a corresponding view suggests that, inter alia, by circulating the coarse fraction of the raw flour, the coarse and fine fractions can be reduced. It can be achieved that they have the same degree of deoxidation when they reach the rotary tube furnace.

The apparatus according to the present invention has a rotary tube furnace for firing deoxidized raw material powder and a calcination furnace adjacent to the rotary tube furnace, and a multistage heat exchanger is connected in front of the furnace, and the calcination furnace is provided with a multistage heat exchanger. The exchange units are each connected in series in two parallel waste gas lines connected to the waste gas pipes of the calciner, and the powder discharge pipe of the heat exchange unit in one waste gas line is connected to the waste gas line in the other waste gas line. They are alternately connected to the waste gas inlet pipes of the heat exchange unit. The calciner has an outlet pipe for the raw material powder and a part of the waste gas flow in the tangential direction in the central part of the height divided into three equal parts, and a discharge pipe directly in front of the upper part of the height divided into three equal parts. The waste gas pipe of the rotary furnace is connected to the calciner above the discharge pipe. This makes it possible to ensure a rapid mixing of the rotary tube furnace waste gas stream with the part stream of the calciner that does not contain raw material, which is especially true in the direction of flow of the raw material from the last two. This is particularly important if the discharge pipe of the second heat exchanger unit opens into the waste gas line of the rotary tube furnace upstream of the calciner in the flow direction of the rotary tube furnace waste gas. The raw powder, which is carried into the upper region of the calciner by the rotary tube furnace waste gas, can therefore mix intimately with the waste gas stream already outside the last heat exchanger unit, so that the heat transfer and thus the Thermal efficiency is improved.

Next, the present invention will be explained in detail with reference to the drawings.

The raw material powder, which is indicated by dotted lines in the system diagram, is supplied via an inlet pipe 1 to a heat exchanger in several stages, which is connected to a rotary tube furnace 2 in which the preheated and calcined raw material powder is fired. Waste gas from and rotary tube furnace 2
It is heated by waste gas from a calcination furnace 3 placed in front of the calcination furnace. According to FIG. 1, this heat exchanger is
It has two parallel waste gas channels 4 and 5, which are formed on one side by heat exchange units 4a, 4b, 4c, 4d configured as cyclones and on the other side by heat exchange units 5a. , 5b, 5c.

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As can be seen from the system diagram, which shows the waste gas flow in solid lines, the waste gas lines 4 and 5 are connected to the waste gas pipe 6 of the rotary tube furnace 2 and to the waste gas pipe 7 of the calciner 3. . The raw material powder is heated in stages by the waste gas from the rotary tube furnace 2 and the calciner 3, in which case it is alternately introduced between the heat exchange units of the two waste gas channels 4 and 5. and transported. This is because the outgoing pipes 8 of the heat exchange units of all the waste gas paths are connected to the inlet pipes 9 of different waste gas paths and the heat exchange unit 4a (the outgoing pipes 10 of this heat exchange unit are connected to the calciner 3). This is because it is connected even to the opening (which is open). The raw powder deoxidized in the calciner 3 is carried out of the calciner by a waste gas stream and fed to a separator 11 in which the raw powder is separated from the waste gas stream and is subsequently passed through a rotary tube. It is carried into the furnace 2. The additional heat required for deoxidation is produced by burning the fuel in a calciner, in which case the combustion air is provided by a cooler 12 arranged after the rotary tube furnace 2. A portion of the heated cooling air from the rotary tube furnace 2 is used, and the raw material powder to be calcined into cement clinker in the rotary tube furnace 2 is cooled in this cooler. Another part of the cooling air from the cooler 12 is supplied to the rotary tube furnace 2 as combustion air.

In contrast to the known device, in the device according to FIG. 1 for carrying out the method of the invention, the waste gas line 7 of the calciner 3 and the waste gas line 6 of the rotary tube furnace 2 are connected via a branch pipe 13. This branch pipe has a control valve 14 that adjusts the amount of passage. Since the branch pipe 13 is located in front of the separator 11 with respect to the flow of the raw material powder, a part of the raw material powder that has already undergone the deoxidation process in the calciner 3 is , is carried into the waste gas stream from the rotary tube furnace and reaches a heat exchange unit 4a located immediately before the calciner. Therefore, this raw material powder is circulated and supplied to the calciner 3 again, so that the residence time in the calciner 3 and thus the degree of deoxidation are increased accordingly. If it is not desirable to circulate part of the raw powder in this way, the branch pipe 13 can be arranged in the waste gas pipe 7 of the calciner 3 after the separator 11. In this case, only the advantage of mixing a part of the waste gas stream from the calciner into the rotary tube furnace waste gas is used, which means that only about 2/3 of the waste gas stream from the calciner is mixed into the rotary tube furnace waste gas. belongs to the rotary tube furnace waste gas, so the amounts of waste gas in the two waste gas paths 4 and 5 can be made the same.

Thus achieved, two waste gas channels 4 and 5
With matching conditions, the two waste gas lines 4 and 5
The same heat exchange unit is obtained for both, so that this heat exchange unit can be connected to a common waste gas blower 15.

Reducing the burnable dust content of the rotary tube furnace waste gas by incorporating a portion of the waste gas stream from the calcination furnace 3 into the rotary tube furnace waste gas is another of the described waste gas guides. This is one advantage. This effect also has the added benefit of being able to feed the hot rotary tube furnace waste gas to the calciner upstream of the branch pipe 13 between the waste gas pipe 6 of the rotary tube furnace 2 and the calciner 3 in the flow direction. It can be enlarged by providing a connecting pipe 16. Rotary tube furnace 2 fed to calcination furnace 3
The amount of waste gas from the exhaust gas can be selected again using the control valve 14 as necessary. The connecting pipe 16 is
A waste gas mixture flow is also ensured for the calciner 5, with this waste gas mixture flowing through the two waste gas channels 4.
and 5 further improve the agreement in terms of operating conditions.

Of course, if in special cases a part of the rotary tube furnace waste gas has to be discharged due to too high a hazardous substance load, the flue gas from the calciner 3 can be transferred to the connecting pipe 1.
6 to the rotary tube furnace 2.

In the device according to the invention shown in FIG. 2, the calciner 3 has a tangential discharge pipe 7a in the average area above the narrowing 17, by means of which the flow of the raw powder is directed into the waste gas stream. The waste gas stream from the calciner is fed into the waste gas line 5, and the separated raw material powder is sent to the rotary tube furnace 2.
It is distinguished from the device according to FIG. 1 by reaching . The rotary tube furnace waste gas is transferred to the penultimate heat exchange unit 5a in the flow direction (see Fig. 1).
The exhaust pipe 7 is connected to the waste gas pipe 6 through which the discharge pipe 8 opens.
a is guided into the calciner 3, in which a rapid and intimate mixing of the calciner waste gas with the powder-free substream takes place. The mixed waste gas stream together with the raw powder is then fed by the waste gas pipe 7b to the last heat exchange unit 4a arranged immediately before the calciner. In a particularly advantageous manner, therefore, the appreciable waste heat of the waste gas stream can be utilized.

Uniform waste gas flow to the two heat exchangers 4 and 5
In order to ensure distribution, a portion of the rotary tube furnace waste gas can again be fed directly to the calciner 3 via the branch pipe 16. For regulating the individual gas flows, corresponding regulating devices are of course provided, but they are not shown for reasons of clarity.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of an apparatus for carrying out the method of the invention, and FIG. 2 is a system diagram likewise showing a structurally alternative embodiment of the apparatus according to the invention. 1... Raw material powder delivery pipe, 2... Rotary tube furnace, 3... Calciner, 4... Waste gas path, 4a, 4b, 4c, 4d... Heat exchange unit, 5... Waste gas path, 5a, 5b, 5c
...Heat exchange unit, 6, 7, 7a, 7b... Waste gas pipe, 8... Raw material powder delivery pipe, 9... Waste gas introduction pipe, 10
...Raw material powder delivery pipe, 11...Separator, 12...Cooler,
13... Branch pipe, 14... Control valve, 15... Waste gas blower, 16... Connection pipe. 〓〓〓〓〓

Claims (1)

[Scope of Claims] 1. The raw material powder is heated in several steps with the waste gas stream from the rotary tube furnace 2 and the calcination furnace 3 before deoxidation in the calcination furnace 3 and subsequent calcination in the rotary tube furnace 2. The raw powder stream is preheated in exchange in two parallel waste gas channels 4, 5, the flow of raw powder being passed through a heat exchange stage arranged immediately before the calciner 3 and connected to the waste gas stream from the rotary tube furnace 2. (Heat exchange unit 4
In a method for producing cement by conducting the heat exchange stages of one waste gas line (4 or 5) alternately up to a) into the heat exchange stages of another waste gas line (5 or 4), A portion of the hot waste gas stream of the furnace 3 is transferred to the hot waste gas stream from the rotary tube furnace 2 before or in a heat exchange stage (heat exchange unit 4a) arranged immediately before the calciner 3. A method of producing cement characterized by mixing. 2. Process according to claim 1, characterized in that a portion of the hot waste gas stream from the rotary tube furnace 2 is fed to the calciner 3 before being mixed with the waste gas stream from the calciner 3. 3 The hot waste gas branch from the calcination furnace 3 is transferred to the rotary tube furnace 2.
3. A method as claimed in claim 1 or 2, in which the waste gas stream from the calcination furnace is fed to the waste gas stream from the calcination furnace prior to the separation of the raw powder from the waste gas of the calciner. 4 the raw powder is passed through two parallel waste gas channels 4 in several steps of heat exchange with the waste gas stream from the calcination furnace 3 before deoxidation in the calcination furnace 3 and subsequent calcination in the rotary tube furnace 2; 5, the flow of the raw powder is alternately passed up to the heat exchange stage (heat exchange unit 4a) arranged immediately before the calciner 3 and connected to the waste gas stream from the calciner 3.
In a method for producing cement, raw powder is placed just before the calciner 3 by guiding it from a heat exchange stage of one waste gas path (4 or 5) to a heat exchange stage of another waste gas path (5 or 4). The hot waste gas stream from the rotary tube furnace 2 is fed before a heat exchange stage (heat exchange unit 4a) arranged in the calcination furnace 3.
A method for producing cement, characterized in that it is mixed with its waste gas stream at. 5 It has a rotary tube furnace 2 for firing the deoxidized raw material powder and a calcination furnace 3 adjacent to the rotary tube furnace 2, and a multi-stage heat exchanger is connected in front of the furnace, and the heat exchange unit 4a, 4b, 4c, 4d; 5a, 5b, 5c
are connected in series in two parallel waste gas channels 4, 5 connected to the waste gas pipes 7a, b of the calcination furnace 3, respectively, and the raw material of the heat exchange unit in one of the waste gas channels (4 or 5) is connected in series. The powder discharge pipe 8 is connected to the other waste gas path (5
or 4) waste gas introduction pipe 9 of the heat exchange unit
In the cement manufacturing apparatus, the calciner 3 has a discharge pipe 7a for the raw material powder and a part of the waste gas flow in the tangential direction in the central part of the calciner 3 which divides its height into three equal parts, A waste gas pipe 7b connected to the heat exchange unit 4a arranged directly in front is provided at the upper part of the height divided into three parts, and the waste gas pipe 6 of the rotary tube furnace 2 is provided.
is connected to a calciner 3 above a discharge pipe 7a.