JP2011051850A - System and method for treating cement kiln extraction gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and the like for treating a cement kiln extraction gas capable of obtaining plaster of high purity without incurring increase of operation cost while maintaining stable operation. <P>SOLUTION: The system 1 for treating the cement kiln extraction gas and the like includes: a wet dust collector 6 wet collecting dust F which is contained in a gas G1 extracted from a portion of a combustion gas from a kiln exhaust gas flow path from an end of a cement kiln 2 to a lowermost cyclone of a preheater; a density measuring device 10 measuring density of a slurry S3 obtained by the wet dust collector 6; a density adjusting means 16 adjusting the density of the slurry S3 measured by the density measuring device 10 so as to be in a prescribed range; and the like. A wet classifier 11 wet classifying a slurry S2 whose density is adjusted in a prescribed range and a route 14 for returning a coarse slurry S5 separated by the wet classifier 11 to the wet dust collector 6 may be provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cement kiln extraction gas processing system and a processing method, and in particular, wet collection of dust contained in extraction gas extracted from a kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone of the preheater. It is related with the system etc. which do.

  Focusing on chlorine, sulfur, alkali, etc., which causes problems such as blockage of preheaters in cement manufacturing facilities, from the bottom of the kiln of the cement kiln to the bottom cyclone From the kiln exhaust gas flow path, a chlorine bypass facility for extracting chlorine while extracting a part of the combustion gas while cooling is used.

  As shown in FIG. 3, this chlorine bypass facility includes a probe 73 that bleeds while cooling a part of the combustion gas from the kiln bottom of the cement kiln 72, a cooling fan 74 that supplies cold air A to the probe 73, and a probe 73. The cyclone 75 that separates the dust coarse powder C contained in the combustion gas G1 extracted in step 1, the wet dust collector 76 that wet-collects the fine powder F contained in the exhaust gas G2 of the cyclone 75, and the slurry S2 discharged from the wet dust collector 76 The solid-liquid separator 77 for obtaining the gypsum G and the salt water SW by solid-liquid separation, the induction fan 78 for attracting the exhaust gas G3 from the wet dust collector 76, and the like.

  In addition, the wet dust collector 76 includes a scrubber 76a that cools the exhaust gas G2 containing fine powder F in contact with moisture in the slurry S1, a circulating liquid tank 76b that receives the slurry from the scrubber 76a and supplies the slurry to the scrubber 76a, And a cleaning tower 76c for spraying industrial water.

In the above configuration, when a part of the combustion gas in the cement kiln 72 is extracted while being cooled by the probe 73, crystals of a chlorine compound are generated. At that time, since chlorine is unevenly distributed on the fine powder F side of the dust contained in the extracted exhaust gas G1, the coarse powder C classified by the cyclone 75 is returned to the cement kiln system, and the fine powder F and the exhaust gas G2 having a high chlorine content. Is guided to the wet dust collector 76 and cooled by the moisture of the slurry S1 supplied from the circulating liquid tank 76b. Further, slaked lime (Ca (OH) ₂ ) is added to the circulating liquid tank 76b and reacted with SO ₂ contained in the exhaust gas G2 to generate gypsum. Then, the fine powder F in the exhaust gas G2 is collected by the wet dust collector 76, the dust collection dust slurry S2 is separated into the gypsum G and the salt water SW containing KCl by the solid-liquid separator 77, and the gypsum G is recovered. The separated salt water SW is added to the cement pulverization process, or discharged into sewage or the ocean after the water treatment (for example, see Patent Document 1).

JP 2009-35450 A

However, in the chlorine bypass facility 71, the amount of dust (fine powder F) brought into the wet dust collector 76 and the SO ₂ concentration in the exhaust gas G2 supplied to the wet dust collector 76 are not constant. Therefore, it is difficult to keep the slurry concentration in the circulating liquid tank 76b constant by increasing or decreasing the amount of dust brought in or by changing the amount of slaked lime added according to the SO ₂ concentration.

  Here, if the slurry concentration in the circulating liquid tank 76b is too high, deposits increase in the circulating liquid tank 76b, the discharge pump 79 is blocked, the circulating pump 80 stops due to overload, or the scrubber 76a. There are concerns such as obstruction.

  On the other hand, if the slurry concentration in the circulating liquid tank 76b is too low, the formation of the cake layer discharged from the solid-liquid separator 77 becomes insufficient, causing the efficiency of the solid-liquid separator 77 to decrease, and the operating cost increases. There was a problem. There is also a problem that suspended matter (SS) in salt water separated by the solid-liquid separator 77 increases.

Furthermore, in the chlorine bypass facility 71, the slurry discharged from the circulating liquid tank 76b contains slaked lime that has not reacted with SO ₂ , so the purity of the gypsum discharged from the solid-liquid separator 77 is high. There was also a problem of a drop.

  Accordingly, the present invention has been made in view of the above-mentioned problems of the prior art, and is a cement capable of obtaining high-purity gypsum without causing an increase in operating cost while maintaining stable operation. An object of the present invention is to provide a kiln extraction gas processing system and the like.

  In order to achieve the above object, the present invention is a cement kiln extraction gas processing system, in which a part of combustion gas is extracted from a kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone of the preheater. A wet dust collector that wet-collects dust contained in gas, a density measuring device that measures the density of the slurry obtained by the wet dust collector, and the density of the slurry measured by the density measuring device is within a predetermined range. And density adjusting means for adjusting as described above.

  According to the present invention, the density adjusting means adjusts the density of the slurry obtained by the wet dust collector to be within a predetermined range, so that the properties of the slurry can be stabilized, and the stable operation of the wet dust collector. Can be maintained.

Further, the cement kiln extraction gas processing system includes a wet classifier that wet-classifies the slurry whose density is adjusted within a predetermined range by the density adjusting unit, and the coarse slurry separated by the wet classifier. And a route back to the wet dust collector. By returning the coarse powder obtained by wet classification of the slurry in the wet classifier to the wet dust collector, unreacted slaked lime can be returned to the wet classifier and reacted with SO _2, and the purity of the resulting gypsum can be increased. The amount of slaked lime can be reduced.

  The cement kiln extraction gas processing system includes a first supply device that supplies the slurry obtained by the wet dust collector to the density measuring device, and supplies the slurry obtained by the wet dust collector to the wet classifier. And a water supply device for supplying water to the slurry in the wet dust collector, the density measuring device measures the density of the slurry supplied by the first supply device, and the density The adjusting means adjusts the amount of slurry supplied to the wet classifier by the second supply device based on the measured density, stops the supply of the slurry, or uses the water supply device to The amount of water supplied to the wet dust collector can be adjusted, or the water supply can be stopped. As a result, the density of the slurry in the wet dust collector can be adjusted with a simple configuration, preventing an increase in deposits in the wet dust collector and stoppage due to overloading of the second supply device, and maintaining stable operation. In addition, the water content of the slurry in the wet dust collector can be prevented from becoming too high, and the efficiency of the subsequent solid-liquid separator can be prevented from decreasing.

  Further, the present invention provides a cement kiln extraction gas for extracting a part of combustion gas from a kiln exhaust gas passage from the bottom of the kiln of the cement kiln to the lowermost cyclone of the preheater, and collecting dust contained in the extraction gas in a wet manner In this processing method, the density of the slurry obtained by the wet dust collection is measured, and the measured density is adjusted to be within a predetermined range. According to the present invention, similar to the above-described invention, the properties of the slurry can be stabilized, and wet dust collection can be performed stably.

  In the cement kiln bleed gas processing method, the predetermined range of the density may be 1.01 or more and 1.10 or less. Thereby, solid content in the slurry obtained by wet dust collection can be adjusted in a suitable range of 5 mass% or more and 20 mass% or less.

  In the above cement kiln extraction gas processing method, the slurry adjusted so that the density is within a predetermined range can be wet-classified, and the coarse slurry obtained by the wet classification can be used for the wet dust collection. . Thereby, wet classification can be performed stably and efficiently, the purity of the resulting gypsum can be increased, and the amount of slaked lime used can be reduced.

  In the method for treating a cement kiln extraction gas, the classification point of the wet classification can be 10 μm or more and 40 μm or less. Thus, a slurry having a high slaked lime content can be used for wet dust collection, and the purity of the resulting gypsum can be increased more efficiently and the amount of slaked lime used can be reduced.

  As described above, according to the present invention, it is possible to provide a cement kiln bleed gas treatment system and the like that can maintain stable operation, increase operating costs, and obtain high-purity gypsum. .

1 is an overall configuration diagram showing an embodiment of a cement kiln extraction gas processing system according to the present invention. It is a graph which shows the relationship between the density of the slurry in the circulating liquid tank of the wet dust collector of the extraction gas processing apparatus of a cement kiln, and the solid content rate of a slurry. It is a whole block diagram which shows an example of the processing system of the conventional cement kiln extraction gas.

  Next, an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an embodiment of a cement kiln extraction gas processing system according to the present invention. This processing system 1 includes a probe 3 for extracting a part of combustion gas from the bottom of a kiln 2 while cooling it. , A cooling fan 4 that supplies cold air A to the probe 3, a cyclone 5 that separates coarse dust C contained in the combustion gas G1 extracted by the probe 3, and a fine powder F contained in the exhaust gas G2 discharged from the cyclone 5. Wet-type dust collector 6 for wet-dust collection, wet-classifier 11 for wet-classifying slurry S2 discharged from wet-type dust collector 6, tank 12 for storing fine-particle slurry S4 discharged from wet-classifier 11, and wet-classifier 11 and the route 14 for returning the coarse-grain slurry S5 discharged to the wet dust collector 6 and the slurry S6 supplied from the tank 12 to solid-liquid separation, and gypsum G and salt water S A solid-liquid separator 13 to obtain the bets composed of induced draft fan 9 or the like to attract an exhaust gas G3 from the wet dust collector 6.

  In addition, the wet dust collector 6 includes a scrubber 6a that cools the exhaust gas G2 containing the fine powder F in contact with moisture in the slurry S1, a circulating liquid tank 6b that receives the slurry from the scrubber 6a and supplies the slurry to the scrubber 6a, And a cleaning tower 6c for spraying the construction water W from a water supply device (not shown).

  Further, the wet dust collector 6 includes a circulation pump 15 that circulates the slurry S1 between the circulating liquid tank 6b and the scrubber 6a, and a density measuring device 10 that measures the density of the slurry in the circulating liquid tank 6b using γ rays. A supply pump (first supply device) 17 for supplying the slurry in the circulating liquid tank 6b to the density measuring device 10, and a discharge pump (second pump) for supplying the slurry S2 from the circulating liquid tank 6b to the wet classifier 11 Supply device) 16.

  The wet classifier 11 is provided to wet-classify the slurry S2 discharged from the wet dust collector 6, and the wet classifier 11 is a wet centrifugal classifier such as a wet cyclone, and has a classification point of 10 μm to 40 μm. Something of a degree can be used.

  Next, the operation of the extraction gas processing apparatus 1 having the above configuration will be described with reference to FIGS.

A part of the combustion gas of the cement kiln 2 is extracted while being cooled by the probe 3, the extracted combustion gas G1 is classified by the cyclone 5, the coarse powder C is returned to the cement kiln system, and the fine powder F having a high chlorine content and The exhaust gas G2 is guided to the wet dust collector 6 and cooled by the moisture of the slurry S1 supplied from the circulating liquid tank 6b in the scrubber 6a, and the fine powder F is wet collected. Further, slaked lime is added to the circulating liquid tank 6b and reacted with SO ₂ contained in the exhaust gas G2 to generate gypsum.

  A part of the slurry (slurry S3) in the circulating liquid tank 6b is supplied to the density measuring device 10 by the supply pump 17, and the density of the slurry S3 is measured. The relationship between the measured density of the slurry S3 and the solid content in the slurry S3 is as shown in FIG.

  Here, according to experiments conducted by the present inventors, when the solid content contained in the slurry is in the range of 5% or more and 20% or less, deposits increase in the circulating liquid tank 6b, or the discharge pump 16 The slurry S2 discharged from the circulating liquid tank 6b can be maintained without causing problems such as blocking, circulation pump 15 stopping due to overload, and scrubber 6a blocking. It has been confirmed that the operation efficiency of the solid-liquid separator 13 in the subsequent stage is not lowered because the concentration of the liquid is too low.

  Therefore, the density of the slurry S3 measured by the density measuring device 10 is adjusted to be 1.01 or more and 1.10 or less. Specifically, when the density of the slurry S3 is less than 1.01, the operation of the discharge pump 16 is stopped or the number of revolutions is decreased to keep the supply amount to the wet classifier 11 low, or the water supply device Operations such as stopping the addition of the working water W from the (not shown) to the washing tower 6c and reducing the amount of the working water W added are performed. On the other hand, when the density of the slurry S3 exceeds 1.10, the amount of the working water W added to the cleaning tower 6c is increased.

Next, the slurry S2 in the above density range is supplied from the circulating liquid tank 6b to the wet classifier 11 through the discharge pump 16. Here, the slurry S2 supplied to the wet classifier 11 contains slaked lime that has settled in the circulating liquid tank 6b without reacting with SO ₂ contained in the exhaust gas G2, but is shown in Table 1. As shown, the particle size of the slurry in which gypsum and slaked lime are mixed is small compared to the particle size of only the slaked lime slurry, especially when compared with coarse particles when the passing particle size is 10 to 40 μm. It can be seen that the proportion of slurry is quite large. Therefore, by setting the classification point of the wet classifier 11 to 10 μm or more and 40 μm or less, the slurry containing a large amount of slaked lime can be separated on the coarse slurry side, and this coarse slurry S5 is circulated through the route 14 to the circulating liquid tank By returning to 6b and reacting again with SO ₂ to produce gypsum, the purity of gypsum recovered by the solid-liquid separator 13 can be increased. In addition, the amount of slaked lime added to the wet dust collector 6 can be reduced.

  On the other hand, the fine slurry S4 containing a large amount of gypsum separated by the wet classifier 11 is temporarily stored in the tank 12, and then supplied to the solid-liquid separator 13, and separated into gypsum G and salt water SW containing KCl. Then, the gypsum G is recovered, and the separated salt water SW is added to the cement pulverization step, or is discharged to sewage or the ocean after the water treatment.

In the above embodiment, the wet classifier 11 and the route 14 are provided, and the coarse slurry S5 is returned to the circulating liquid tank 6b via the route 14 to react with SO ₂ again to produce gypsum. Although the purity of the gypsum recovered by the separator 13 is increased, when gypsum having a desired purity is obtained, the slurry S2 is discharged from the circulating liquid tank 6b without using the wet classifier 11 and the route 14. After being stored in the tank 12 as it is via 16, the solid-liquid separator 13 performs solid-liquid separation to obtain gypsum G and salt water SW.

  In the above embodiment, a part of the combustion gas is extracted from the kiln bottom of the cement kiln 2, but extracted from the kiln exhaust gas passage from the kiln bottom of the cement kiln 2 to the lowermost cyclone of the preheater. The gas can also be processed as described above.

  Furthermore, in the said embodiment, although the cyclone 5 is arrange | positioned between the probe 3 and the wet dust collector 6, you may introduce extraction gas into the wet dust collector 6 directly from the probe 3 without providing the cyclone 5. FIG.

DESCRIPTION OF SYMBOLS 1 Cement kiln extraction gas processing system 2 Cement kiln 3 Probe 4 Cooling fan 5 Cyclone 6 Wet dust collector 6a Scrubber 6b Circulating liquid tank 6c Washing tower 9 Induction fan 10 Slurry density measuring device 11 Wet classifier 12 Tank 13 Solid-liquid separator 14 (Return coarse slurry to wet dust collector) Route 15 Circulation pump 16 Discharge pump 17 Supply pump A Cold air C Coarse powder F Fine powder G Gypsum G1 Combustion gas G2, G3 Exhaust gas S1-S3, S6 Slurry S4 Fine particle slurry S5 Coarse slurry SW Salt water W Industrial water

Claims (7)

A wet dust collector that wet-collects dust contained in the gas extracted from the kiln exhaust gas passage from the kiln bottom of the cement kiln to the lowermost cyclone of the preheater,
A density measuring device for measuring the density of the slurry obtained by the wet dust collector;
A cement kiln bleed gas processing system, comprising: density adjusting means for adjusting the density of the slurry measured by the density measuring device to be within a predetermined range. A wet classifier that wet-classifies the slurry whose density is adjusted within a predetermined range by the density adjusting means;
The cement kiln bleed gas processing system according to claim 1, further comprising a route for returning the coarse slurry separated by the wet classifier to the wet dust collector. A first supply device for supplying the slurry obtained by the wet dust collector to the density measuring device;
A second supply device for supplying the slurry obtained by the wet dust collector to the wet classifier;
A water supply device for supplying water to the slurry in the wet dust collector,
The density measuring device measures the density of the slurry supplied by the first supply device, and the density adjusting unit is connected to the wet classifier by the second supply device based on the measured density. The amount of slurry to be supplied is adjusted, the supply of the slurry is stopped, or the amount of water supplied to the wet dust collector is adjusted by the water supply device, or the supply of water is stopped. The cement kiln bleed gas processing system according to claim 2. A cement kiln extraction gas treatment method in which a part of the combustion gas is extracted from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone of the preheater, and the dust contained in the extraction gas is wet-collected. ,
Measure the density of the slurry obtained by the wet dust collection,
A method for treating a cement kiln bleed gas, wherein the measured density is adjusted to be within a predetermined range.   5. The cement kiln extraction gas processing method according to claim 4, wherein the predetermined range of the density is 1.01 or more and 1.10 or less. The slurry adjusted so that the density is within a predetermined range is wet-classified,
6. The method for treating a cement kiln bleed gas according to claim 4 or 5, wherein the coarse slurry obtained by the wet classification is used for the wet dust collection.   The method for treating a cement kiln extraction gas according to claim 6, wherein a classification point of the wet classification is set to 10 µm or more and 40 µm or less.

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