JP5279665B2 - Cement kiln extraction gas processing system and processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent caking of an adhering matter in an inside of a wet dust collector to attain stable continuous operation when a cement kiln extraction gas is treated using the wet dust collector. <P>SOLUTION: In a system 1 for treating the cement kiln extraction gas wherein dust contained in an extraction gas G1 extracted from a kiln exhaust gas flow path from an end of a cement kiln 2 to a lowermost cyclone of a preheater is wet collected by the wet dust collector 6, an anticaking agent containing a carboxylic acid, a dicarboxylic acid or a hydroxycarboxylic acid is added to a scrubber 6a of the wet dust collector 6. The added amount of the carboxylic acid or the like is preferably 0.5 to 3 mole equivalent to a carried sulfur content. <P>COPYRIGHT: (C)2011,JPO&amp;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 relates to the system etc.

  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 has a probe 43 for extracting air while cooling a part of the combustion gas from the kiln exhaust gas passage from the bottom of the cement kiln 42 to the lowermost cyclone (not shown). A cooling fan 44 that supplies cold air to the probe 43, a cyclone 45 that separates coarse dust particles contained in the combustion gas extracted by the probe 43, and a wet dust collector that wet-collects fine particles contained in the exhaust gas of the cyclone 45 46, a solid-liquid separator 47 for solid-liquid separation of the slurry discharged from the wet dust collector 46 to obtain gypsum and salt water, and a clean gas discharged from the wet dust collector 46 (hereinafter referred to as “exhaust gas of the wet dust collector”). And so on).

  Further, the wet dust collector 46 sprays the industrial water with a scrubber 46a that cools the extraction gas containing fine powder in contact with moisture in the slurry, a circulating liquid tank 46b that circulates the dust collection dust slurry between the scrubber 46a, and Cleaning tower 46c.

  In the above configuration, when a part of the combustion gas of the cement kiln 42 is extracted while being cooled by the probe 43, a crystal of a chlorine compound is generated. At that time, since chlorine is unevenly distributed on the fine powder side of the dust contained in the extracted exhaust gas, the coarse powder classified by the cyclone 45 is returned to the cement kiln system, and fine powder and gas having a high chlorine content are supplied to the wet dust collector 46. Then, it is cooled by the moisture of the slurry supplied from the circulating liquid tank 46b. Then, the fine powder in the gas is collected by the wet dust collector 46, the dust collection slurry is separated into gypsum and salt water containing KCl by the solid-liquid separator 47, the gypsum is recovered, and the separated salt water is cemented. It adds to a grinding | pulverization process, or it discharges to a sewage or the ocean after a water treatment, and processes (for example, refer patent document 1).

JP 2004-331474 A

  The scrubber 46a of the wet dust collector 46 is a device that gives a specific flow to the exhaust gas supplied from the cyclone 45 and the slurry circulated from the circulating liquid tank 46b and efficiently contacts them. A plurality of guide vanes for controlling the flow of exhaust gas and slurry are disposed.

On the other hand, the exhaust gas from the cyclone 45 contains sulfur (SO ₂ ), and the fine powder in the exhaust gas contains quick lime (CaO), which is one of the main cement raw materials. In addition, slaked lime is added as appropriate to remove sulfur and keep the pH constant. For this reason, in the wet dust collector 46, the sulfur content and the calcium content react to become gypsum (CaSO ₄ .2H ₂ O). On the other hand, due to the concentration of the gypsum component in the scrubber 46a and the reaction between the slurry adhering to the guide blade and the sulfur content, solidification is generated in the guide blade.

  As a result, there is a problem that the pressure loss increases and the performance decreases such as desulfurization and dust removal, and the scrubber 46a needs to be periodically cleaned, resulting in a decrease in operating efficiency. It should be noted that by controlling the pH of the slurry, it is possible to suppress the growth of consolidation, but it has not been possible to avoid the occurrence of consolidation, and it was not always perfect.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and prevents the adhesion of deposits in the wet dust collector when processing the cement kiln extraction gas using the wet dust collector. An object of the present invention is to provide a processing system capable of stable continuous operation.

  In order to achieve the above object, the present invention provides a cement kiln for collecting dust contained in extraction gas extracted from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone of a preheater by a wet dust collector. In the extraction gas processing system, carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is added in the wet dust collector or upstream of the wet dust collector.

  According to the present invention, the calcium content contained in the bleed gas or dust reacts with the carboxylic acid added to the inside or upstream of the wet dust collector, so that calcium carbonate with high solubility is temporarily generated. In addition, it is possible to prevent caking of deposits in the wet dust collector, and to obtain gypsum without deteriorating the performance of removing sulfur, thereby enabling stable continuous operation.

  In the cement kiln extraction gas treatment system, the carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is formic acid, acetic acid, propionic acid, butyric acid, butanoic acid, valeric acid, benzoic acid, phthalic acid, terephthalic acid, salicylic acid, pyruvic acid. , Lactic acid, malic acid or citric acid can be used.

  In the cement kiln extraction gas processing system, the amount of the carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid added can be 0.5 molar equivalent or more and 3 molar equivalent or less with respect to the introduced sulfur content. According to this, it is possible to avoid adverse effects on cement quality while preventing caking of deposits in the wet dust collector.

  The present invention also relates to a method for treating a cement kiln extraction gas, in which the dust contained in the extraction gas extracted from the kiln exhaust gas flow path from the bottom of the cement kiln to the bottom cyclone of the preheater is wet collected by a wet dust collector. Then, carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is added in the wet dust collector or upstream of the wet dust collector. According to the present invention, as in the case of the above-described invention, it is possible to prevent the deposits in the wet dust collector from being consolidated, and a stable continuous operation is possible.

  As described above, according to the present invention, when a cement kiln extraction gas is processed using a wet dust collector, it is possible to prevent caking of deposits in the wet dust collector and to enable stable continuous operation. .

It is a flowchart which shows one Embodiment of the processing system of the cement kiln extraction gas concerning this invention. It is a graph which shows the test example of the setting characteristic of cement, (a) shows the test example at the time of adding a calcium formate to a cement, (b) shows the test example at the time of adding a formic acid to a cement. It is a flowchart which shows 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. The processing system 1 includes a kiln extending from the bottom of the cement kiln 2 to the lowermost cyclone (not shown) of the preheater. A probe 3 for extracting while cooling a part of the combustion gas from the exhaust gas flow path, a cooling fan 4 for supplying cold air to the probe 3, and a cyclone 5 as a classifier for separating the coarse powder D1 contained in the extracted gas G1. And solid-liquid for obtaining a gypsum and a filtrate (salt water) by solid-liquid separation of the wet dust collector 6 that wet-collects the fine powder D2 contained in the exhaust gas G2 of the cyclone 5 and the slurry S discharged from the wet dust collector 6 The separator 7 and the induction fan 8 for attracting the exhaust gas G3 of the wet dust collector 6 are configured.

The wet dust collector 6 dissolves water-soluble components (mainly chlorine compounds) contained in the exhaust gas G2 of the cyclone 5, or sulfur (SO ₂ ), quick lime (CaO) and slaked lime (Ca (OH) ₂ ) in the exhaust gas G2. It is provided for the purpose of producing gypsum (CaSO ₄ .2H ₂ O). This wet dust collector 6 has a scrubber 6a that cools gas, removes sulfur, and removes dust by bringing the exhaust gas G2 into contact with moisture in the slurry S, and a circulation for receiving the slurry from the scrubber 6a and supplying it to the scrubber 6a. It is comprised from the liquid tank 6b and the washing tower 6c which sprays industrial water. In addition, a pump 6d for circulating the slurry S is disposed between the scrubber 6a and the circulating liquid tank 6b, and the pH value of the circulating slurry S is adjusted to pH 4 to 6 in the circulating liquid tank 6b. For this purpose, a sulfuric acid storage tank 6e and a slaked lime storage tank 6f are attached.

  In the present embodiment, an anti-caking agent containing carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is added to the inlet portion of the scrubber 6a of the wet dust collector 6, and a plurality of guide vanes (inside the scrubber 6a ( Prevents solidification of deposits on the not shown. Here, as carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, butanoic acid, valeric acid, benzoic acid, phthalic acid, terephthalic acid, salicylic acid, pyruvic acid, lactic acid, malic acid or citric acid An acid can be used.

  Next, operation | movement of the processing system 1 of the cement kiln extraction gas which has the said structure is demonstrated, referring FIG.

  From the kiln exhaust gas flow path from the kiln bottom of the cement kiln 2 to the lowest cyclone, part of the combustion gas is extracted by the probe 3 and at the same time, the extracted gas extracted by the cooling fan 4 is cooled by the melting point of the chlorine compound. Cool to: Next, in the cyclone 5, the extracted gas G1 exhausted from the probe 3 is separated into the coarse powder D1 and the exhaust gas G2 containing the fine powder D2, and the coarse powder D1 is returned to the cement kiln system.

On the other hand, the exhaust gas G2 of the cyclone 5 is introduced into the wet dust collector 6, and an anti-caking agent containing carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is added to the scrubber 6a of the wet dust collector 6. As a result, in the scrubber 6a, quick lime contained in the fine powder D2 in the exhaust gas G2 reacts with water to produce slaked lime (Ca (OH) ₂ ), and this slaked lime and the carboxylic acid contained in the anti-caking agent (2RCOOH) reacts as follows to produce calcium carboxylate.
Ca (OH) ₂ + 2RCOOH → (RCOO) ₂ Ca
(R is, H, a CH _3, CH ₃ CH _2, etc.)

This prevents the slaked lime from reacting with the sulfur content (SO ₂ ) in the exhaust gas G2 to become gypsum (CaSO ₄ · 2H ₂ O) inside the scrubber 6a of the wet dust collector 6, while the calcium carboxylate Since it has high water solubility, it is possible to avoid the caking of the guide vanes in the scrubber 6a.

When calcium carboxylate enters the circulating liquid tank 6b, it reacts with the sulfur dissolved in the slurry S in the circulating liquid tank 6b and sulfuric acid (H ₂ SO ₄ ) supplied from the sulfuric acid storage tank 6e as follows. , Gypsum is produced.
(RCOO) 2Ca + H ₂ SO ₄ → CaSO ₄ + 2RCOOH

  The slurry S containing gypsum is solid-liquid separated by the solid-liquid separator 7 and separated into a cake containing gypsum and a salt water (filtrate) containing KCl. In addition, since carboxylic acid (2RCOOH) is dissolved in the slurry S, the slurry S flows along with the slurry S into the solid-liquid separator 7 and is mixed into each of the cake and the filtrate.

  The gypsum contained in the cake can be collected separately and then put into a cement mill or the like and pulverized with a clinker to be used as part of the cement. In that case, carboxylic acid is mixed into the cement as a result. I will let you. However, as shown in FIG. 2, the carboxylic acid acts so as to shorten the setting time of the cement, so from the viewpoint of cement quality, it is preferable to suppress the amount of carboxylic acid (anti-caking agent) added. .

  Here, FIG. 2 (a), (b) shows the test example of the setting characteristic of the cement when calcium formate ((HCOO) 2Ca) and formic acid (HCOOH) are added to the cement. The “addition amount of calcium formate” and “addition amount of formic acid” are the content ratio of calcium formate and the like to the cement. Further, “start” in the figure corresponds to the time when the setting of the cement starts, and “end” corresponds to the time when the setting is completed. From these figures, it can be seen that when calcium formate or formic acid is added, the setting start time of the cement is shortened or the period until the setting is completed is shortened. In particular, when formic acid is added, the influence appears remarkably.

Therefore, the amount of carboxylic acid added in the wet dust collection step is adjusted to 0.5 mole equivalent or more and 3 mole equivalent or less with respect to the introduced sulfur content, and the mixing into the cement is appropriately adjusted. As a result, it is possible to avoid adverse effects on the cement quality while preventing the guide vanes in the scrubber 6a from being consolidated. Here, the sulfur content brought in is the amount of sulfur obtained from the product of the amount of exhaust gas introduced into the wet dust collector and the concentration of SO ₂ contained in the exhaust gas, and the concentration and amount of supplied sulfuric acid. .

  On the other hand, the filtrate of the solid-liquid separator 7 is separately drained and discharged into sewage or the like, or returned to the scrubber 6a of the wet dust collector 6 for reuse. In addition, when reusing, it is necessary to adjust to the sum of the addition amount which also considered the carboxylic acid contained in a filtrate, for example, the amount of newly added carboxylic acid, and the amount of carboxylic acid contained in reuse water. Moreover, it is possible to put into a cement mill or the like and pulverize it with a clinker within the allowable range of cement quality, in particular, an acceleration of setting due to chlorine content or carboxylic acid contamination.

  In the above embodiment, an anti-caking agent is added to the inlet portion of the scrubber 6a of the wet dust collector 6, but the exhaust gas pipe 5a connected to the intermediate portion of the scrubber 6a and the inlet portion of the scrubber 6a (see FIG. 1). Etc. may be added.

  In the above embodiment, after the coarse powder D1 is classified by the cyclone 5, the exhaust gas G2 containing the fine powder D2 is introduced into the wet dust collector 6. However, the extracted gas G1 extracted by the probe 3 without the cyclone 5 being provided. May be introduced directly into the wet dust collector 6.

DESCRIPTION OF SYMBOLS 1 Cement kiln extraction gas processing system 2 Cement kiln 3 Probe 4 Cooling fan 5 Cyclone 5a Exhaust gas line 6 Wet dust collector 6a Scrubber 6b Circulating liquid tank 6c Cleaning tower 6d Pump 6e Sulfuric acid storage tank 6f Slaked lime storage tank 7 Solid-liquid separator 8 Induction fan

Claims (4)

A cement kiln bleed gas treatment system that wet-collects dust contained in the bleed gas 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 with a wet dust collector,
A cement kiln bleed gas treatment system, wherein carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is added in the wet dust collector or upstream of the wet dust collector.   The carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is formic acid, acetic acid, propionic acid, butyric acid, butanoic acid, valeric acid, benzoic acid, phthalic acid, terephthalic acid, salicylic acid, pyruvic acid, lactic acid, malic acid or citric acid. The cement kiln bleed gas processing system according to claim 1.   The cement kiln according to claim 1 or 2, wherein the addition amount of the carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid is 0.5 molar equivalent or more and 3 molar equivalent or less with respect to the introduced sulfur content. Extraction gas processing system. A method for treating a cement kiln bleed gas, wherein the dust contained in the bleed gas extracted from the kiln exhaust gas flow path from the kiln bottom of the cement kiln to the lowermost cyclone of the preheater is wet collected by a wet dust collector,
A method for treating a cement kiln bleed gas, comprising adding carboxylic acid, dicarboxylic acid or hydroxycarboxylic acid in the wet dust collector or upstream of the wet dust collector.

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