JP2003277106A - Method and apparatus for treating exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating exhaust gas capable of effectively recovering a low-melting point compound from the exhaust gas from a cement calcination plant. <P>SOLUTION: The exhaust gas from the cement calcination plant is partly extracted and the low-melting compound is recovered. The temperature state of the extracted exhaust gas is regulated to 1,100 to 1,500°C and thereafter the extracted exhaust gas is rapidly cooled down to 120 to 600°C, by which the low-melting point compound is recovered. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas treatment method and apparatus. More specifically, the present invention relates to a method and an apparatus for extracting and treating a part of exhaust gas of a cement burning device.

[0002]

2. Description of the Related Art Conventionally, a bypass is provided to remove low melting point compounds such as sodium chloride (NaCl), potassium chloride (KCl), heavy metal chlorides, and sodium sulfate, potassium sulfate, and heavy metal sulfates, and cement firing is performed. A part of the exhaust gas is extracted from the device. The extracted cement kiln exhaust gas is subjected to solid-gas separation by a cyclone, and dust with a relatively large particle size containing calcium is recovered. The collected dust is returned to the cement kiln. Further, dust having a relatively small particle size is removed through a filter means such as a bag filter. This dust contains a low melting point compound. Then, the exhaust gas is returned to the cement burning device.

However, the bleeding operation is usually performed on the raw material feeding side (inlet hood) of the cement rotary kiln, and the temperature of the extracted bleeding cement kiln exhaust gas is 800 to 900 ° C. Therefore, for the purpose of recovering the low melting point compound, a sufficient temperature was not maintained.

That is, this temperature range is between the melting point and the boiling point of sodium chloride, potassium chloride and the like, and in this temperature range, a considerable part of the low melting point compound to be recovered has a relatively small particle size in the exhaust gas. It has moved to the side of dust containing large calcium components. In this case, the low melting point compound cannot be effectively recovered, and improvement has been desired.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an exhaust gas treatment method and device capable of effectively recovering a low-melting point compound from the exhaust gas of a cement calcination device. The purpose is to

[0006]

In order to achieve the above object, the present invention provides an exhaust gas treatment method for extracting a low melting point compound by extracting a part of the exhaust gas of a cement calcination device,
It is characterized in that the temperature of the extracted exhaust gas is adjusted to 1100 to 1500 ° C., and then the extracted exhaust gas is cooled to 120 to 600 ° C., and the low melting point compound is recovered. In the exhaust gas treatment method according to the present invention, it is preferable that the solid content in the extracted exhaust gas is separated and the solid content is returned to the cement firing device. The exhaust gas treatment method according to the present invention, as an embodiment thereof, uses a bleed line 110 provided at a connecting portion of a cement kiln having two or more stages.
It is preferable to extract the exhaust gas at 0 to 1500 ° C. to recover the low melting point compound. As another embodiment, the exhaust gas treatment method according to the present invention uses the extracted exhaust gas described above.
It is preferable to raise the temperature to 00 to 1500 ° C. to recover the low melting point compound.

Further, in another aspect of the present invention, there is provided an exhaust gas treatment apparatus, which is an exhaust gas treatment apparatus for extracting a part of exhaust gas from a cement calcination device to recover a low melting point compound, and a temperature state of the extracted exhaust gas is 1100. ~ 1500 ℃
And means for cooling the extracted exhaust gas,
It is characterized by including a means for controlling the temperature to 600 ° C. and a means for recovering the low melting point compound. The exhaust gas treatment apparatus according to the present invention preferably includes means for separating the solid content in the extracted exhaust gas and returning the solid content to the cement firing apparatus. As an embodiment of the exhaust gas treating apparatus according to the present invention, the temperature state of the extracted exhaust gas is set to 1100 to 150.
The means for maintaining the temperature at 0 ° C. includes a cement kiln configured in two or more stages, a connecting portion between the cement kilns, and an extraction line provided at the connecting portion. Further, the exhaust gas treating apparatus according to the present invention preferably includes, as another embodiment, a temperature raising means for raising the temperature of the extracted exhaust gas to 1100 to 1500 ° C.

In the present specification, the term "recovery" means, in addition to the meaning generally understood by those skilled in the art, "separation only", "removal only", or "separated" or "removed" is valuable. It also includes obtaining as a compound. In the present specification, the “low melting point compound” includes sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, chlorides and sulfates of heavy metals, and the like. In the present specification, the "cement burning device" means
This refers to the system of the entire firing equipment, including peripheral equipment such as cement kilns such as rotary kilns for firing cement and cyclones, calcination furnaces (preheaters), and clinker coolers. "Part of the extracted gas" means that in a normal firing device,
This is because, in principle, it is impossible in principle to extract all of the cement because it is mainly used for burning the cement and it is linked to peripheral equipment such as a calcining furnace. However, it does not eliminate the case where "all" is extracted when possible or necessary.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings,
Embodiments of an exhaust gas treatment method and apparatus according to the present invention will be described. FIG. 1 shows an embodiment of a cement calcination device for carrying out an exhaust gas treatment method and device according to the present invention.
It is a conceptual diagram which shows the outline.

Cement firing apparatus 1 according to this embodiment
00 is the main component equipment for cement firing,
The rotary kiln 102, the calcination furnace 104, the suspension preheater 106, and the clinker cooler 108 are provided.
The entire length of the rotary kiln 102 is substantially the same as a normal one. However, it is divided into two at approximately the center. As a result, the left and right kilns 110 and 112 are divided. And these left and right kilns 110, 11
2 are connected by a connecting portion 114 so that the firing atmosphere is continuous. The connecting portion 114 constitutes a so-called fixed joint.

In this embodiment, a bleed line 116 is provided at this connecting portion 114. The extraction line 116 is connected to the bag filter 120 via the cyclone 118 immediately above the connecting portion 114, and exits the bag filter 120.
It is connected to the raw material input part 122. Bug filter 120
Is connected to the heavy metal recovery device 126 and the alkali salt recovery device 128 from the lower recovery port 124. The two-stage rotary kiln 102 and the low melting point compound recovery device after the extraction line 116 constitute an embodiment of the exhaust gas treatment device according to the present invention.

Next, an embodiment of the exhaust gas treating method according to the present invention will be described by explaining the operation of the cement burning apparatus 100 including the embodiment of the exhaust gas treating apparatus according to the present invention. In the present embodiment, the cement raw material is fed into the suspension preheater 106 in the upper raw material feeding section 1
Put in 22. Cement raw materials are generally limestone,
It is a mixture of clay, iron raw materials and the like in an appropriate ratio. However, it is not limited to such raw materials as long as it is not against the object of the present invention. The suspension preheater 106 preheats the cement raw material. Then, the cement raw material is preheated and then calcined in the calcining furnace 104.
In the calcining furnace 104, the burner 130 calcinates the cement raw material.

The calcined cement raw material reaches the rotary kiln 102. The right kiln 112 of the rotary kiln 102 includes a burner 132. This burner 1
A main fuel such as heavy oil or pulverized coal is fed to 32 and burned to burn the cement raw material. Rotary kiln 10
The cement clinker discharged from No. 2 enters the clinker cooler 108 and is cooled by the cooling air 134.

On the other hand, in the present embodiment, part of the exhaust gas is extracted by an extraction device such as an extraction probe (not shown) provided in the connecting portion 114. Extracted exhaust gas is 1100
It is set to be extracted in a temperature state of up to 1500 ° C. Generally, it is preferable to extract air from the side of the burner 132 within a range of 1/10 to 2/3 as viewed from the entire length of the rotary kiln 102. In addition, during this period, the cement raw material which is the object to be treated includes a region where the temperature rises from about 900 ° C. to about 1400 ° C., and the low melting point compound volatilizes vigorously in this region. The low melting point compound is not contained in the exhaust gas on the burner side of this volatilization region. Therefore, it is preferable to extract air from the volatilization region on the inlet hood side and from a position where the gas temperature is sufficiently high. The exhaust gas treating apparatus of the present embodiment is characterized by including the above-mentioned extraction means. The extracted exhaust gas reaches the cyclone 118 from the extraction line 116. Here, solid-gas separation is performed, and solid content (dust)
Are returned to the rotary kiln 102. Here, the low melting point compound is vaporized and contained in the gas component under the above temperature. Therefore, the returned dust contains almost no low melting point compound. The gas component is sent to the bag filter 120. Cooling air is sent at a position 136 in front of the bag filter 120 to extract the bleed gas from 120-
Cool to 600 ° C. As a result, the low melting point compound is deposited. Examples of the low melting point compound include potassium, sodium, and chlorides and sulfates of metals such as copper, zinc, and lead.

The deposited low melting point compound is the bag filter 1
Separated at 20. The separated low melting point compound is recovered from the lower recovery port 124 and sent to the heavy metal recovery device 126. As the heavy metal recovery device 126, a device commonly used by those skilled in the art such as a wet refining device can be adopted. For example, the collected dust-like low melting point compound is washed with water, acid / alkali elution, sulfide precipitation and the like are appropriately combined and fractionated as a metal refining raw material containing a zinc component, a copper component and a lead component. Further, the filtrate and the washing water after the heavy metals are collected are sent to the alkaline salt collecting device 128.

The alkali salt recovery device 128 can recover the alkali metal salt by various methods.
For example, the filtrate and washing water are boiled to a supersaturated state,
Then, it can be recovered by a method such as cooling and precipitation. At this time, it is also possible to separate potassium chloride and sodium chloride depending on the difference in dissolution characteristics. Therefore, for example, potassium chloride that can be reused as fertilizer can be recovered.

The gas component of the extracted exhaust gas passing through the bag filter 120 is returned to the raw material charging section 122 again. When the temperature of this gas is 350 ° C. or higher, it contributes to increase the efficiency of the entire apparatus.

The cement burning apparatus 100 is equipped with a waste heat recovery boiler 138, recovers the waste heat of the exhaust gas, and then exhausts the exhaust gas from the chimney 142 through the bag filter 140.

In the exhaust gas treatment method and apparatus described in the present embodiment, the exhaust gas is extracted in the relatively high temperature range as described above. In this high temperature state, the low melting point compound exists in the gas component of the extracted exhaust gas, and the low melting point compound can be effectively recovered.

Next, FIG. 2 is a conceptual diagram showing the outline of another embodiment of the cement burning apparatus for carrying out the exhaust gas treating method and apparatus according to the present invention. In this embodiment, as an embodiment of the exhaust gas treating apparatus according to the present invention, a part of the exhaust gas is extracted from the raw material feeding side (inlet hood) of the rotary kiln 102 and then heated.

That is, the cement calcination apparatus 200 according to this embodiment includes a rotary kiln 102, a calcination furnace 104, a suspension preheater 106, a clinker cooler 108, etc. as main components for cement calcination. 1 is the same as that of the cement burning apparatus 100 of FIG. 1, and the elements shown in FIG. 2 with the same reference numerals have substantially the same functions and functions as in FIG. However, the rotary kiln 102 does not necessarily have to be divided into multiple stages.

The exhaust gas treating apparatus according to this embodiment is
Heating device 202, cyclone 204, bag filter 20
6, heavy metal recovery device 208, alkali salt recovery device 210
Is equipped with. In order to carry out the exhaust gas treatment method according to the present invention using this exhaust gas treatment device, first, the extracted exhaust gas is sent to the heating device 202. The extraction operation is performed using an extraction device such as an extraction probe (not shown). The extracted exhaust gas is usually in the temperature range of 800 to 900 ° C. In the heating device 202, this is heated to a temperature of 1100 to 1500 ° C. As the fuel of the heating device 202, it is preferable to use flammable substances having a chlorine content of 500 ppm or less, such as tires, waste plastics such as polypropylene, polyethylene and polystyrene, in addition to heavy oil and coal. By heating in this way, the low-melting-point compound is vaporized from the dust side mainly composed of the calcium component and transferred to the gas component.

The exhaust gas is then sent to cyclone 204. Here, solid-gas separation is performed, and the dust is returned to the firing step. Here, the low melting point compound is contained in the gas component. Therefore, the returned dust contains almost no low melting point compound. Examples of the low melting point compound include potassium, sodium, and chlorides and sulfates of metals such as copper, zinc, and lead. The extracted exhaust gas containing the low melting point compound is sent to the bag filter 206. Before this,
A cooling gas is fed and cooled to a temperature of 120 to 600 ° C. Then, the low melting point compound is separated by the bag filter 206. The separated low melting point compound is used for the lower recovery port 2
It collects from 12, and sends to the heavy metal recovery apparatus 208. As the heavy metal recovery device 208, a device commonly used by those skilled in the art such as a wet refining device can be adopted. For example, the collected dust-like low melting point compound is washed with water, acid / alkali elution, sulfide precipitation and the like are appropriately combined and fractionated as a metal refining raw material containing a zinc component, a copper component and a lead component. Further, the filtrate and the washing water after collecting the heavy metals are sent to the alkaline salt collecting device 210.

The alkali salt recovery device 210 can recover the alkali metal salt by various methods.
For example, the filtrate and washing water are boiled to a supersaturated state,
Then, it can be recovered by a method such as cooling and precipitation. At this time, it is also possible to separate potassium chloride and sodium chloride depending on the difference in dissolution characteristics. Therefore, for example, potassium chloride that can be reused as fertilizer can be recovered.

The gas component of the extracted exhaust gas that has passed through the bag filter 206 is returned to the raw material charging section 122 again. When the temperature of this gas is 350 ° C. or higher, it contributes to increase the efficiency of the entire apparatus.

Other Embodiments Although the exhaust gas treating method and apparatus according to the present invention have been described with reference to the embodiments shown in FIGS. 1 and 2, the present invention is not limited to these embodiments, and those skilled in the art can understand the present invention. All modifications, changes and additions within the scope of the technical idea of the present invention which is obvious are included in the present invention. For example, a cement firing furnace
Although the rotary kiln is used in the embodiment of FIG. 1, other types of firing furnaces such as a moving bed such as a vertical kiln or a fluidized bed type firing furnace may be used. Further, the present invention can be practiced even in a cement calcination device that does not include a calcining furnace and / or a suspension preheater. In addition, instead of heating with the heating device of FIG.
The temperature may be raised to 00 to 1500 to extract air.

[0027]

As is apparent from the above, according to the present invention, there is provided an exhaust gas treatment method and device capable of effectively recovering a low melting point compound from the exhaust gas of a cement burning device.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating an outline of an embodiment of a cement calcination device including an exhaust gas treatment device according to the present invention.

FIG. 2 is a conceptual diagram for explaining the outline of another embodiment of the cement firing apparatus including the exhaust gas treatment apparatus according to the present invention.

[Explanation of symbols]

100 cement burning equipment 102 rotary kiln 104 Calciner 106 Suspension preheater 108 Clinker Cooler 114 connection 116 Extraction line 118 cyclone 120 bug filters 122 Raw Material Input Section 124 Lower recovery port 126 Metal Recovery Device 128 Alkaline salt recovery device 130 burners 132 burner 138 Waste heat recovery boiler 140 Bug Filter 142 chimney 200 Cement firing equipment 202 heating device 204 cyclone 206 Bug Filter 208 Heavy metal recovery equipment 210 Alkaline salt recovery device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Taku Nakano             2-4-2 Daisaku, Sakura City, Chiba Prefecture             Central Research Institute, Mento Co., Ltd. F-term (reference) 4D002 AA01 AA18 AC05 BA12 BA13                       CA13 FA01 GA01 GB03

Claims (8)

[Claims] 1. In an exhaust gas treatment method for extracting a part of exhaust gas from a cement calcination device to recover a low melting point compound, the temperature state of the extracted exhaust gas is set to 1100 to 1500 ° C., and then the extracted exhaust gas is cooled. , 120-600
And a low melting point compound is recovered, and the exhaust gas treatment method is characterized by including: 2. The method for treating exhaust gas according to claim 1, further comprising separating a solid content in the extracted exhaust gas and returning the solid content to the cement burning device. 3. From an extraction line provided at a connecting portion of a cement kiln having two or more stages, from 1100 to 1500
The exhaust gas treatment method according to claim 1 or 2, wherein the exhaust gas at a temperature of 0 ° C is extracted to recover the low melting point compound. 4. The extracted flue gas is 1100 to 1500 ° C.
The exhaust gas treatment method according to claim 1 or 2, wherein the low melting point compound is recovered by raising the temperature. 5. An exhaust gas treatment device for extracting a part of exhaust gas from a cement calcination device to recover a low melting point compound, and a means for adjusting the temperature state of the extracted exhaust gas to 1100 to 1500 ° C., and the extracted exhaust gas. Cool, 120-6
An exhaust gas treatment apparatus comprising: means for controlling the temperature to 00 ° C. and means for recovering a low melting point compound. 6. The exhaust gas treating apparatus according to claim 5, further comprising means for separating a solid content in the extracted exhaust gas and returning the solid content to the cement firing apparatus. 7. The temperature state of the extracted exhaust gas is set to 1100 to
The means for controlling the temperature to 1500 ° C. includes a cement kiln configured in two or more stages, a connecting portion between the cement kilns, and an extraction line provided in the connecting portion. Exhaust gas treatment equipment. 8. The extracted flue gas is 1100 to 1500 ° C.
The exhaust gas treatment method according to claim 5 or 6, further comprising a temperature raising means for raising the temperature.