JP2019064857A - Method of treating cement kiln extraction gas - Google Patents

Abstract

To provide a method and a device of treating exhaust, capable of effectively decreasing the content of volatile mercury contained in exhaust from a cement production facility to reduce the running cost of a heating device that heats collected dust to evaporate mercury contained therein.SOLUTION: The method of treating cement kiln extraction gas, i.e., a method of extracting a portion of combustion exhaust from a cement kiln exhaust passage extending from the tail of a cement kiln to the lowest stage of a calcination furnace to recover dust present in the extraction gas to discharge it to the outside of the cement kiln, comprises a step of branching a portion of extraction gas prior to introducing the extracted gas into a classifier, a step of allowing the branched extraction gas to bypass a classifying cyclone into which un-branched extraction gas is introduced for separating fine powder and coarse powder, and to merge with the gas containing fine powder dust discharged from the classifying cyclone, a step of cooling the merged gas by a heat exchanger, and a step of recovering fine powder dust using a bag filter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for treating cement kiln bleed gas, and more particularly, to a method for bleeding a part of combustion gas from exhaust gas of cement production equipment to remove chlorine and sulfur trioxide contained in the bleed gas. The present invention relates to a method of treating extracted gas in a desalination bypass system.

In the manufacture of cement, a large amount of waste is used as a substitute for raw materials and fuels.
As a result, the amount of chlorine taken into the kiln increases, and in order to ensure the quality of the cement and the stability of the operation, the gas is extracted from the fuel end including the raw material to the outside and cooled, thereby reducing the chlorine concentration. Chlorine bypass equipment, which removes high dust from the system, has been introduced into operation in many cement kilns.

  If a lot of chlorine and sulfur trioxide are contained in the system of cement manufacturing process, low melting point substance adheres to the bottom cyclone or calciner furnace wall surface, and the coating adheres with the substance as nucleus, and the flow path becomes thin. Or there is a problem that operational problems such as blocking due to dropping off of the coach occur frequently.

  As a method for treating chlorine bypass exhaust gas, for example, in order to treat chlorine bypass exhaust gas while suppressing the influence on the amount of cement clinker production, fuel consumption and power consumption as disclosed in JP-A-2013-180941 (Patent Document 1), In the chlorine bypass system where the combustion gas G is extracted by the probe 3 from the kiln exhaust gas flow path from the bottom of the cement kiln 2 to the lowermost cyclone and cooled by low temperature gas, dust from the extraction gas G2 (chlorine bypass dust D2) Chlorine bypass exhaust gas provided with a second cooler 10 for cooling the dust collector outlet exhaust gas (exhaust gas G3) after collecting the particles, and a circulation route 12 for returning extracted gas (exhaust gas G5) cooled by the second cooler to the probe The processor 1 of is described.

  In addition, as a method of adjusting the chlorine concentration of bypass dust, it is possible to adjust the chlorine concentration of bypass dust recovered from kiln exhaust gas in the bypass device and method of kiln exhaust gas in JP-A-2000-146458 (patent document 2) The apparatus and method for adjusting the chlorine concentration of bypass dust are described. Specifically, dust contained in the exhaust gas extracted from the kiln 11 through the probe 13 is converted into coarse dust and bypass dust by the cyclone 14 The classified coarse dust is recovered from the lower end portion of the cyclone 14 and enters the coarse dust post-adding device 21, and the exhaust gas containing bypass dust is discharged from the cyclone 14 and sent to the cooler 15 to A part is added from the coarse dust post addition apparatus 21 into the exhaust gas containing bypass dust, and the rest is added again. Returned to the kiln system, it is described that the mixing portion of the lower coarse powder dust chlorine concentration to a high bypass dust chlorine concentration.

However, in any of the above-mentioned conventional methods, when the chlorine concentration of the fine powder dust is 25% or more, the hygroscopicity of the bypass dust increases and the adhesion is increased, so that the handling property becomes worse, and the bypass Handling becomes difficult, for example, the transportability of dust deteriorates, and there is a problem in extraction from the silo.
In addition, in the conventional method, handling is improved by mixing limestone and raw material before cement firing with the fine powder to be collected, but the amount of extracted chlorine increases while the amount of dust to be collected increases. There was a problem of not doing.

  In the chlorine bypass facility, dust is classified into coarse powder and fine powder from the extracted gas, and fine powder dust concentrated with chlorine etc. is discharged out of the system, but the smaller the particle size, the higher the chlorine concentration On the other hand, the amount of fine powder generation decreases. In addition, since the classification point of the classifier can not be easily changed, it is difficult to change the classification point of the classifier, which has been set once, to an optimal classification point in accordance with the decrease in the amount of fine powder generated. Furthermore, although it is more efficient to recover chlorine by collecting dust with a smaller particle size, in this case, the concentration of chlorine in the dust is high, and it is known that there are major obstacles in dust handling.

Not only chlorine, but also sulfur trioxide is a substance that forms a coating in a cement manufacturing apparatus and becomes an operation inhibiting factor, and it is desirable that it can be discharged out of the system. The uneven distribution of content is not as remarkable as chlorine, and is proportional to the amount of dust.
However, if all the extracted air is discharged as dust, the amount of dust also increases, and as a result, problems occur in dust processing.

  Furthermore, the contained sulfate compounds can not be removed in large quantities, but will accumulate in the cement kiln system. When the amount of extraction is optimized so that a large amount of sulfate compound can be removed, the heat gas is extracted, which causes a heat loss, which is not preferable.

On the other hand, depending on the ratio of the amount of chlorine and sulfuric acid taken into the system of the cement manufacturing process, it is considered that there is an optimum point in the chlorine bypass method.
By operating the bypass facility at such an optimal point, it is expected that the degree of concentration of chlorine and sulfate compounds will be appropriate, the cement production operation will be stable, and the quality of cement to be produced will also be stable.

JP, 2013-180941, A JP 2000-146458 A

  Therefore, an object of the present invention is to solve the above-mentioned problems and extract a part of combustion gas from the exhaust gas of cement production equipment to efficiently remove sulfur trioxide as well as chlorine contained in the extract gas. It is an object of the present invention to provide a method for treating the bleed gas of a desalting bypass facility.

  The present inventors bypass the classification cyclone and process it without introducing a part of the extraction gas before being introduced into the classification cyclone for classifying dust in the extraction gas into the classification cyclone, etc. As a result, the inventors have found that the above objects can be achieved, and have reached the present invention.

  According to the first aspect of the present invention, a part of the combustion exhaust gas is extracted from the cement kiln exhaust gas flow path from the butt of the cement kiln to the lowermost stage of the calciner to recover the dust in the extracted gas. In the method of discharging out of the cement kiln system, a part of the extracted gas is branched before introducing the extracted gas into the classifier, and the branched extracted gas is introduced with the extracted gas which has not been branched, to be fine powder. The classification cyclone separated into coarse powder is bypassed and combined with the gas containing fine powder dust discharged from the classification cyclone, then the combined gas is cooled by a heat exchanger, and then it is subjected to bag filtration A method of treating cement kiln bleed gas comprising collecting fine powder dust.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the bypass ratio of the branch extraction gas for bypassing the classification cyclone is 25 to 75% (volume%) of the extraction gas. It is a processing method of a kiln extraction gas.

  In the invention according to claim 3, in the invention according to claim 1 or 2, the fine dust collected from the bag filter and the dust collected by being cooled by the heat exchanger are introduced into a dust bin, Cement kiln extraction gas characterized in that the chlorine content or sulfur trioxide content of dust in the dust bin is measured, and the bypass ratio of the branch extraction gas bypassing the classification cyclone is varied according to the measured value. Processing method.

  The invention according to claim 4 is characterized in that, in the invention according to any one of claims 1 to 3, the extraction rate for extracting a part of the combustion exhaust gas is 0.8 to 10% (volume%). To process the cement kiln bleed gas

According to the method of the present invention, sulfur trioxide can be efficiently removed together with chlorine contained in the extracted gas, and the concentrations of chlorine and sulfur trioxide in the cement kiln system can be reduced. .
In addition, the contents of chlorine and sulfur trioxide in the exhaust gas can be reduced, the occurrence of coating in the demineralization bypass facility can be suppressed, and the dust transportability becomes good, and the cement production facility It is also possible to suppress the occurrence of internal coaching.

It is a figure which represents the demineralization bypass installation typically, and shows the processing method of the cement kiln extraction gas of this invention. When the extraction rate is 1.3% (volume%) and the treatment method of the present invention is performed, the chlorine concentration contained in the dust in the dust bin 10 and the bypass ratio of the branched extraction gas bypassing the classification cyclone FIG. 8 is a diagram showing the relationship and the relationship between the concentration of sulfur trioxide contained in the dust in the dust bin 10 and the bypass ratio of the branched extraction gas bypassing the classification cyclone. When the extraction rate is 2.6% (volume%) and the treatment method of the present invention is carried out, the chlorine concentration contained in the dust in the dust bin 10 and the bypass ratio of the branched extraction gas bypassing the classification cyclone FIG. 8 is a diagram showing the relationship and the relationship between the concentration of sulfur trioxide contained in the dust in the dust bin 10 and the bypass ratio of the branched extraction gas bypassing the classification cyclone. When the extraction rate is 5.0% (volume%) and the treatment method of the present invention is performed, the chlorine concentration contained in the dust in the dust bin 10 and the bypass ratio of the branched extraction gas bypassing the classification cyclone FIG. 8 is a diagram showing the relationship and the relationship between the concentration of sulfur trioxide contained in the dust in the dust bin 10 and the bypass ratio of the branched extraction gas bypassing the classification cyclone. The extraction amount of chlorine and sulfur trioxide (kg / day) and the amount of extraction dust (kg / day) when the treatment method of the present invention is carried out at an extraction rate of 1.3% (volume%), It is a figure which shows the relationship with a bypass rate. The extraction amount of chlorine and sulfur trioxide (kg / day) and the amount of extraction dust (kg / day) when the extraction rate is 2.6% (volume%) and the treatment method of the present invention is performed, It is a figure which shows the relationship with a bypass rate. The extraction amount of chlorine and sulfur trioxide components (kg / day) and the amount of extraction dust (kg / day) when the extraction rate is 5.0% (volume%) and the treatment method of the present invention is performed, It is a figure which shows the relationship with a bypass rate.

  The invention will be illustrated using the following preferred examples, without being limited thereto.

  In the method for treating cement kiln extract gas according to the present invention, a portion of the combustion exhaust gas is extracted from the cement kiln exhaust gas flow path from the end of the cement kiln to the bottom of the calciner and dust in the extract gas is extracted. In the method of recovering and discharging the cement kiln system out of the cement kiln system, a portion of the bleed gas is branched before introducing the extracted gas into the classifier, and the branched bleed And bypass the classification cyclone, which is separated into fine powder and coarse powder, and combine with the gas containing fine powder dust discharged from the classification cyclone, and then the combined gas is cooled by a heat exchanger, Next is a method for treating cement kiln bleed gas, wherein fine dust is recovered by a bag filter.

  According to the present invention, the contents of chlorine and sulfur trioxide in the exhaust gas can be reduced, and the occurrence of coating in the desalination bypass facility and the cement production facility can be suppressed.

Next, the processing method of the present invention will be described with reference to FIG.
FIG. 1 shows a process according to the present invention for efficiently removing the chlorine and nitrogen trioxide contained in the extracted gas by means of a demineralizing bypass facility with the extracted gas extracted from the combustion gas flowing in the cement kiln exhaust gas flow path. It is a figure showing the method typically and A is a desalting bypass installation.
The solid line indicates the flow of dust, and the broken line indicates the flow of bleed gas.
Specifically, first, the probe 3 is provided in the cement kiln exhaust gas flow path between the lower end of the calciner 2 from the butt of the cement kiln 1, and from the cement kiln exhaust gas flow path via the probe 3 , Bleed some of the exhaust gas.

When the extraction rate is increased, the amount of generated dust to be collected increases, but in such a case, the processing of the collected dust is difficult and the cost increases.
Accordingly, it is desirable that the extraction rate be about 0.8 to 10.0% (volume%), preferably about 1.3 to 5.0%, of the combustion gas flowing through the kiln exhaust gas flow path.

The extracted exhaust gas (hereinafter referred to as extraction gas) is introduced into the classification cyclone 5 in order to classify dust contained in the extraction gas, but before being introduced into the classification cyclone, part of the extraction gas is branched Let
A part of the branched bleed gas is not introduced into the classification cyclone 4 and causes the classification cyclone 4 to bypass.

Extracted gases other than some of the branched extract gas are introduced into the classification cyclone 4 and the contained dust is separated into the coarse powder D1 and the fine powder.
The classification point of the coarse powder and the fine powder is not particularly limited, but usually, the classification point is around 10 μm.
However, the volume of air passing through the classification cyclone 4 is reduced because a part of the extracted gas is branched and bypassed. Therefore, the classification point of the classification cyclone 4 becomes coarse, and the chlorine concentration of the recovered fine dust becomes low. In order to recover fine powder dust with high chlorine concentration, it is better to classify the coarse powder and fine powder classifiers with high efficiency. However, if the chlorine concentration is increased, the amount of collected fine powder dust is small, the chlorine concentration is high, the handling is very bad, and the dust can not be discharged.
Generally, since chlorine and sulfur trioxide are contained in a large amount in fine dust, coarse dust separated by the classification cyclone 4 is recovered and returned to the cement kiln system.
The coarse powder dust returned into the cement system can be mixed, for example, in a cement raw material silo (not shown) and used as a cement raw material.

A part of the coarse powder D1 collected by the classification cyclone 4 can be merged with the exhaust gas containing fine powder dust discharged from the classification cyclone 4 by the coarse powder branching damper 5 as necessary.
As a result, the coarse powder dust and the chlorine in the fine powder dust are brought into contact with each other to make the coarse powder dust adhere to chlorine, which facilitates handling and suppresses the coating.

Further, the branched extracted gas which is not introduced into the classification cyclone 4 and bypasses the classification cyclone 4 is merged with the exhaust gas containing the fine powder discharged from the classification cyclone 4.
Thereby, the fine powder dust containing a large amount of chlorine and the like contained in the exhaust gas is brought into contact with the dust in the bypassed branch extraction gas, and the chlorine in the fine powder adheres to the dust in the bypassed branch extraction gas. Handling will be easier and will reduce coaching

Next, a gas obtained by combining an exhaust gas containing fine powder dust discharged from the classification cyclone 4 and the branched extracted gas is introduced into the heat exchanger 8 and cooled.
Air is introduced into the heat exchanger 8 via the cooling fan 7 (−−−) and circulated, and the combined exhaust gas is cooled to, for example, about 150 to 200 ° C.

The exhaust gas cooled by the heat exchanger 8 is introduced into the bag filter 9, the dust such as fine powder dust is collected, and the collected dust is stored in the dust bin 10, so that chlorine and sulfur trioxide can be efficiently obtained. It becomes possible to remove. For the recovery of the fine powder dust, the dust recovered from the bag filter 9 is the main route.
The recovered dust is stored in the dust bin 10, which makes it possible to efficiently remove chlorine and sulfur trioxide.

  In addition, a part of dust may adhere to the heat exchanger 8 in the heat exchanger 8, and the dust adhering to the heat exchanger 8 is collected and stored in the dust bin 10.

The exhaust gas from the bag filter 9 from which chlorine and sulfur trioxide have been removed is discharged via the bag fan 11.
By adjusting the bag fan 11, it is possible to adjust the extraction rate of the exhaust gas from the cement kiln.

In addition, the dust collected from the bag filter 9 and the heat exchanger 8 is stored in the dust bin 10, and the chlorine concentration of the dust in the dust bin 10 and the concentration of sulfur trioxide are measured (not shown). Accordingly, the bypass damper 6 is adjusted to determine the ratio of the branch extraction gas bypassing the classification cyclone 4 in the extraction gas from the cement kiln.
For example, if it is desirable to reduce the concentration of chlorine in the collected dust bin 10 and the measured concentration of sulfur trioxide in the dust bin 10 and if problems such as difficulty in handling the dust occur, it is desirable to reduce these concentrations. Adjust to perform operations to increase the rate. As a result, the concentration of chlorine and the concentration of sulfur trioxide in the collected dust decrease, and the amount of collected dust increases.
In addition, adjusting the bypass ratio within the range of 25 to 75% (volume%), preferably 30 to 60% (volume%) of the extracted gas more effectively exerts the above-mentioned effect of the present invention. It is desirable because it can.

As an example, the extraction ratio for extracting a part of the cement kiln exhaust gas from the bottom of the cement kiln 1 of the desalination bypass facility A shown in FIG. The processing method of the present invention was carried out at 6 vol% and 5.0 vol%.
0% in volume ratio while adjusting bypass ratio of branch extraction gas which bypasses classification cyclone 4 (does not introduce) in desalting bypass facility A for part of extraction gas of each extraction ratio with bypass damper 6 , 25%, 50%, 75% and 100% (volume%), respectively, to carry out the treatment method of the present invention.
Measure the chlorine content (% by mass) and the sulfur trioxide content (% by mass) contained in the dust in the dust bin 10, bypass ratio and chlorine content (%), bypass ratio and sulfur trioxide content ( The relationship with%) is shown in Table 1 and FIGS.

In addition, when the above-mentioned extraction rate is 1.3%, 2.6%, 5.0% (volume%) in volume ratio, the extraction amount of chlorine and sulfur trioxide components (kg / day) and extraction dust generation The relationship between the amount (kg / day) and the bypass rate is shown in Table 1 and FIGS.
The amount of chlorine extracted (kg / day) refers to the amount of dust generated (kg / day) × the chlorine content of daily dust contained in the dust bin.

From the above figures 2 to 7, since the chlorine removal efficiency does not necessarily increase even if the bypass rate is 75% (volume%) or more, the bypass rate is 25 to 75% (volume%). It turns out that it is good to.
Also, it can be seen that sulfur trioxide can be largely removed when the bypass ratio is increased, but by setting the bypass ratio to 25 to 75% (volume%) in volume ratio, simultaneous removal with chlorine is efficiently performed It becomes possible.

  The method for treating cement kiln bleed gas according to the present invention can be effectively applied for removing chlorine and sulfur trioxide in the exhaust gas from a cement kiln, and therefore, can be effectively applied to cement manufacturing equipment.

A · · · desalting bypass facility 1 · · · cement kiln 2 · · · calcining furnace 3 · · · desalting probe 4 · · · classification cyclone 5 · · · coarse powder branch damper 6 · · ... Bypass damper 7 ... ... Cooling fan 8 ... ... Heat exchanger 9 ... ... Bag filter 10 ... Dust bin 11 ... Bug fan

Claims (4)

  A portion of the combustion exhaust gas is extracted from the cement kiln exhaust gas flow path from the butt of the cement kiln to the lowermost stage of the calciner, and the dust in the extracted gas is recovered and discharged out of the cement kiln system. In the method, a part of the extracted gas is branched before introducing the extracted gas into the classifier, and the branched extracted gas is separated into fine powder and coarse powder by introducing unextracted extract gas. After bypassing the classification cyclone and combining with the gas containing the fine powder dust discharged from the classification cyclone, the combined gas is cooled by a heat exchanger, and then the fine powder dust is recovered by a bag filter. Method for treating cement kiln bleed gas characterized by   2. A method according to claim 1, wherein the bypassing ratio of the branch extraction gas for bypassing the classification cyclone is 25 to 75% (volume%) of the extraction gas.   In the invention according to claim 1 or 2, the fine powder dust recovered from the bag filter and the dust recovered from the heat exchanger are introduced into a dust bin, and the chlorine content of the dust in the dust bin or the sulfur trioxide containing What is claimed is: 1. A method of treating cement kiln bleed gas comprising: measuring an amount; and varying a bypass ratio of a branch bleed gas bypassing a classification cyclone according to the measured value.   The method according to any one of claims 1 to 3, wherein the extraction rate for extracting a part of the combustion exhaust gas is 0.8 to 10% (volume%). .

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