JP5661151B2 - Cement kiln extraction gas processing method and processing system - Google Patents

Description

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

  Further, the wet dust collector 76 has 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 circulates the slurry S1 between the scrubber 76a, and the working water W. And a cleaning tower 76c for spraying.

  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 the chlorine is unevenly distributed on the fine powder F side of the dust contained in the extracted combustion gas G1, the coarse powder C classified by the cyclone 75 is returned to the cement kiln system, and the fine powder F and exhaust gas having a high chlorine content. G2 is guided to the wet dust collector 76, and is cooled by moisture of the slurry S1 supplied from the circulating liquid tank 76b. Then, the fine powder F in the exhaust gas G <b> 2 is collected by the wet dust collector 76.

Further, in this chlorine bypass facility 71, quick lime (CaO) contained in fine powder F in the extracted exhaust gas G2 reacts with water in the wet dust collector 76 to generate slaked lime (Ca (OH) ₂ ), It has a desulfurization function that reacts with sulfur dioxide (SO ₂ ) in the exhaust gas G2 to generate gypsum. In addition, when the quantity of the slaked lime derived from the said quicklime is insufficient, slaked lime is added to the circulating liquid tank 76b.

  On the other hand, in order to prevent scale troubles in the flow path of the slurry S1 supplied to the scrubber 76a and to reduce the amount of chemicals used in the water treatment facility at the subsequent stage, the pH of the circulating liquid in the circulating liquid tank 76b is set to 4-6. It is preferable to adjust to the front and back, so when the pH value of the circulating fluid in the circulating fluid tank 76b is excessively increased, the classification point of the cyclone 75 is changed to reduce the CaO concentration in the fine powder F, If necessary, sulfuric acid is added to the circulating liquid tank 76b.

  Finally, the 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, and the separated salt water SW is added to the cement pulverization process or after the water treatment. It is discharged into sewage or the ocean and processed (for example, see Patent Document 1).

JP 2009-35450 A

However, in the treatment method described in Patent Document 1, the pH value of the circulating liquid in the circulating liquid tank 76b is ensured while ensuring the amount of slaked lime (Ca (OH) ₂ ) in the wet dust collector in order to maintain the desulfurization function. Need to be managed around 4-6. Therefore, in many cases, the pH value cannot be adjusted by adjusting the classification point of the cyclone 75. In this case, the amount of sulfuric acid or slaked lime added to the circulating liquid tank 76b is increased, and the drug cost is increased accordingly. This has led to a problem that the operating cost increases.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and is used when processing the extraction gas from the kiln exhaust gas passage from the bottom of the cement kiln to the lowermost cyclone of the preheater. The purpose of this is to reduce the operating cost.

In order to achieve the above object, the present invention is a method for treating a cement kiln extraction gas, wherein a part of the combustion gas is extracted from a kiln exhaust gas passage from the bottom of the cement kiln to the bottom cyclone, Separating the coarse dust of dust in the extracted gas, measuring the SO ₂ concentration in the gas after separating the coarse powder, wet collecting dust fine dust in the gas after separating the coarse powder, When the SO ₂ concentration is lower than a predetermined range, a combustible material and / or a waste material containing a sulfur content is charged into the cement kiln.

And according to the present invention, since the SO ₂ concentration in the gas after separating the coarse powder is adjusted to a predetermined range using a combustible material, a chemical such as sulfuric acid for adjusting the pH of the slurry is unnecessary. Or the amount of medicine used can be kept low, and the operating cost can be reduced. In addition, the amount of combustible material and waste can be increased while adjusting the SO ₂ concentration.

In the above cement kiln extraction gas treatment method, the SO ₂ concentration in the gas after separating the coarse powder can be adjusted to be not less than 300 ppm and not more than 10,000 ppm with the standard oxygen concentration being 18%.

Further, the present invention is a cement kiln extraction gas processing system, a probe for extracting a part of combustion gas from a kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone, A classifier for separating coarse dust particles, a densitometer for measuring the SO ₂ concentration in the gas after separating the coarse particles, and wet dust collecting dust fine particles in the gas after separating the coarse particles. A wet dust collector for dusting, and an input means for supplying a combustible material and / or a waste containing a sulfur content to the cement kiln when the SO ₂ concentration measured by the densitometer is lower than a predetermined range. Features. According to the present invention, similar to the above-described invention, it is possible to eliminate the need for a chemical for adjusting the pH of the slurry obtained by the wet dust collector, to suppress the usage amount of the chemical, and to reduce the operating cost. In addition, the amount of combustible material and waste can be increased while adjusting the SO ₂ concentration.

  As described above, according to the present invention, it is possible to reduce the operating cost when processing the extracted gas extracted from the kiln exhaust gas passage from the bottom of the kiln of the cement kiln to the lowermost cyclone of the preheater. .

It is a flowchart which shows one Embodiment of the processing system of the cement kiln extraction gas concerning this invention. Is a graph showing transition of SO ₂ concentration in the chlorine bypass the exhaust gas before and after introducing combustibles to kiln of the cement kiln. It is a flowchart which shows an example of the processing system of the conventional cement kiln extraction gas.

  Next, embodiments 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. A wet-type dust collector 6 that collects wet dust, a solid-liquid separator 8 that obtains gypsum G and salt water SW by solid-liquid separation of the slurry S2 discharged from the wet dust collector 6, and an exhaust gas G3 from the wet dust collector 6 An induction fan 9, an SO ₂ concentration meter 13 for measuring the concentration of SO ₂ contained in the exhaust gas G 2, a pH meter 14 for measuring the pH value of the slurry S 1 circulating in the wet dust collector 6, etc. Made.

  The wet dust collector 6 includes a scrubber 6a that cools the exhaust gas G2 containing fine powder F in contact with moisture in the slurry S1, a circulating liquid tank 6b that circulates the slurry S1 between the scrubber 6a, a circulating pump 11, and a circulating liquid. A discharge pump 12 that discharges the slurry S2 in the tank 6b and supplies the slurry S2 to the solid-liquid separator 8 and a cleaning tower 6c that sprays the working water W from a water supply device (not shown) are provided.

  Next, the operation of the processing system 1 having the above configuration will be described with reference to FIG.

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 as necessary, and reacted with SO ₂ contained in the exhaust gas G2, thereby generating gypsum while desulfurizing.

  The slurry S2 discharged from the wet dust collector 6 is supplied to the solid-liquid separator 8 and separated into gypsum G and salt water SW containing KCl. The gypsum G is recovered and the separated salt water SW is used in the cement grinding process. Add or discharge to sewage or ocean after water treatment.

Here, the SO ₂ concentration meter 13 measures the concentration of SO ₂ contained in the exhaust gas G2 from the cyclone 5, and the pH meter 14 measures the pH value of the slurry S1 circulating in the wet dust collector 6. Then, the measured value of the SO ₂ concentration by the SO ₂ concentration meter 13 is 300 ppm to 10000 ppm with the standard oxygen concentration being 18%, and the measured value of the pH by the pH meter 14 is 4-6. Adjust as follows.

If SO ₂ concentration measured by the SO ₂ concentration meter 13 is lower than the above range, and when the pH value measured by the pH meter 14 is higher than the above range, in FIG. 1, introducing combustible material into the cement kiln 2 . Here, this combustible can be used as coke, coal tar pitch, tire, coal, anthracite, bituminous coal, lignite, lignite, graphite, flame retardant plastic, phenol resin, furan resin, thermosetting resin, cellulose, charcoal, waste toner. , Mixed coke, fine coke, electrode scrap, activated coke, carbide, heavy oil ash and one or more selected from the group consisting of unburned carbon contained in fly ash. Moreover, waste containing sulfur content may be thrown into the cement kiln 2.

Fig. 2 shows the transition of the SO ₂ concentration in the exhaust gas G3 of the cement kiln bleed gas treatment system 1 when 0.6 t / h of coke is introduced as a combustible material into the kiln bottom of the cement kiln 2 with a clinker production of 85 t / h. Indicates. As shown in the figure, it can be seen that the SO ₂ concentration in the exhaust gas G3 changes from 500 to 2000 ppm before the coke is charged, but increases significantly to about 3000 to 6000 ppm after the coke is charged.

As described above, in this embodiment, for adjusting the SO ₂ concentration in the exhaust gas G2 after separating the coarse powder C in a predetermined range, for adjusting the pH of the slurry S1 such as sulfuric acid or slaked lime The medicine can be made unnecessary and the amount of the medicine used can be reduced.

  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.

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 8 Solid-liquid separator 9 Induction fan 11 Circulating pump 12 Discharge pump 13 SO ₂ Concentration meter 14 pH meter A Cold air C Coarse powder F Fine powder G Gypsum G1 Combustion gas G2, G3 Exhaust gas S1, S2 Slurry SW Salt water W Industrial water

Claims (3)

A part of the combustion gas is extracted from the kiln exhaust gas flow path from the kiln bottom of the cement kiln to the bottom cyclone,
Separating coarse dust particles in the extracted gas;
Measure the SO ₂ concentration in the gas after separating the coarse powder,
Wet dust collection of fine dust in the gas after separating the coarse powder,
When the SO ₂ concentration is lower than a predetermined range, a cement kiln bleed gas treatment method is characterized in that a combustible material and / or a waste containing a sulfur content is introduced into the cement kiln. _2. The cement kiln bleed gas according to claim 1, wherein the SO ₂ concentration in the gas after separating the coarse powder is adjusted to be not less than 300 ppm and not more than 10,000 ppm with a standard oxygen concentration of 18%. Processing method. A probe for extracting a part of the combustion gas from the kiln exhaust gas passage from the bottom of the kiln of the cement kiln to the lowermost cyclone,
A classifier for separating coarse dust particles in the extracted gas;
A densitometer for measuring the SO ₂ concentration in the gas after separating the coarse powder;
A wet dust collector that wet-collects fine dust particles in the gas after separating the coarse powder;
Cement kiln bleeder, comprising: a charging means for charging a combustible material and / or a waste containing a sulfur content to the cement kiln when the SO ₂ concentration measured by the densitometer is lower than a predetermined range. Gas processing system.

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