JP4105466B2 - Cement kiln extraction gas processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating a cement kiln bleed gas, and more particularly, to a method for treating a cement kiln bleed gas for removing chlorine and sulfur by extracting a part of combustion gas from the vicinity of an inlet hood of the cement kiln.
[0002]
[Prior art]
In the past, attention has been paid to the fact that chlorine is a particular problem among chlorine, sulfur, alkali, etc. that cause problems such as clogging of preheaters in cement production facilities. Chlorine bypass equipment is used to bleed out the part to remove chlorine.
[0003]
In this chlorine bypass facility, for example, as described in International Patent Application PCT / JP96 / 03545 (International Publication Number: WO 97/21638), chlorine is unevenly distributed on the fine powder side of dust generated by cooling the extracted exhaust gas. Therefore, the dust is separated into coarse powder and fine powder by a classifier, the coarse powder is returned to the cement kiln system, and the fine powder (chlorine bypass dust) containing potassium chloride (KCl) etc. is recovered and cemented. It was added to the grinding mill system.
[0004]
However, in recent years, recycling of waste by converting it into cement raw material or fuel has been promoted, and as the amount of waste processed increases, the amount of chlorine, sulfur, alkali and other volatile components brought into the cement kiln also increases. The amount of bypass dust is also increasing. For this reason, all of the chlorine bypass dust could not be used in the cement crushing process and was washed with water. However, the amount of chlorine bypass dust generated is expected to increase further in the future, so the development of an effective method for its use is expected. Was demanded.
[0005]
From this point of view, in the cement raw material processing method described in JP-A-11-100233, chlorine-containing waste that has been conventionally washed with water is desalted and effectively used as a cement raw material. Water is added to the effluent to elute and filter out the chlorine in the waste, and the resulting desalted cake is used as a raw material for cement, and the wastewater is purified to prevent the use of chlorine bypass dust. We are trying to use it.
[0006]
[Problems to be solved by the invention]
However, in the cement raw material treatment method described in JP-A-11-100233, when desalting the chlorine bypass dust, etc., the bulk specific gravity is extremely low and the large capacity for storing a large amount of dust that is difficult to handle. A tank, a quantitative feeder, etc. were required, and there was a problem that the equipment cost increased.
[0007]
When performing chlorine bypass, some of the combustion gas extracted from the vicinity of the cement kiln inlet hood contains sulfur, so the extracted gas cannot be discharged out of the system as it is, and is attached to the cement kiln. It was necessary to return to a dried raw material or pulverization process.
[0008]
Therefore, the present invention has been made in view of the problems in the conventional method for treating a cement kiln bleed gas, and can reduce the equipment cost. The combustion gas extracted from the vicinity of the inlet hood of the cement kiln can be reduced. It is an object of the present invention to provide a method for treating a cement kiln bleed gas capable of removing contained sulfur and effectively utilizing it.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is a method for treating a cement kiln extraction gas, wherein a part of the combustion gas is removed from the kiln exhaust gas flow path from the bottom of the cement kiln to the bottom cyclone. Extracting and separating coarse dust particles in the extracted gas, introducing the extracted gas containing fine powder into a magnesium hydroxide slurry absorption desulfurization apparatus, and desulfurizing the extracted gas containing fine powder while cooling with water .
[0010]
And according to invention of Claim 1, in order to desulfurize extraction gas containing fine powder using a magnesium hydroxide slurry absorption method desulfurization apparatus while water-cooling, the slurry containing chlorine content is processed as it is as a waste water treatment / desalination apparatus. The water washing equipment that has been used when desalinating chlorine bypass dust in the past can be dispensed with, and the equipment cost can be reduced, and sulfur dioxide (SO ₂ ) in the combustion gas can be reduced. Gypsum can be recovered by reacting with magnesium hydroxide (Mg (OH) ₂ ) and slaked lime (Ca (OH) ₂ ) for desulfurization.
[0011]
The invention according to claim 2 is the processing method of the cement kiln bleed gas according to claim 1, wherein the solid content of the absorption liquid from the magnesium hydroxide slurry absorption desulfurization apparatus is concentrated and added to the cement grinding mill system. It is characterized by doing.
[0012]
According to the invention described in claim 2, since the absorbent is added to the cement grinding mill system, the gypsum contained in the absorbent can be effectively used in the cement manufacturing factory.
[0013]
According to a third aspect of the present invention, there is provided the cement kiln extraction gas processing method according to the first or second aspect, wherein the gypsum separated and by-produced from the absorbent of the magnesium hydroxide slurry absorption desulfurization apparatus is used as a cement grinding mill. It is characterized by being added to the system.
[0014]
According to the invention described in claim 3, by using gypsum separated and by-produced from the absorbent of the magnesium hydroxide slurry absorption desulfurization apparatus in a cement grinding mill system, effective utilization of gypsum in a cement manufacturing plant Can be achieved.
[0015]
According to a fourth aspect of the present invention, in the method for treating a cement kiln bleed gas according to any one of the first to third aspects, the waste liquid after separating gypsum from the absorbent of the magnesium hydroxide slurry absorption desulfurization apparatus is used. And added to a cement grinding mill system.
[0016]
According to invention of Claim 4, in order to process the waste liquid after isolate | separating gypsum from the absorption liquid of a magnesium hydroxide slurry absorption method desulfurization apparatus by a cement grinding mill type | system | group, the water discharged | emitted out of a cement manufacturing factory is made as much as possible. Less water can be used effectively.
[0017]
According to a fifth aspect of the present invention, in the method for treating a cement kiln extraction gas according to the third or fourth aspect, the waste liquid after separating gypsum from the absorbent of the magnesium hydroxide slurry absorption desulfurization apparatus is desalted. The wastewater after desalting is sent to the apparatus and used as circulating water as water used in the extraction gas treatment system.
[0018]
According to the fifth aspect of the present invention, when chlorine is desalted, water can be circulated and used in the magnesium hydroxide slurry absorption desulfurization apparatus, the desalination apparatus, and the extraction gas treatment system. Water can be effectively used by reducing the amount of water discharged as much as possible.
[0019]
Invention of Claim 6 is the extraction method extracted from the kiln exhaust gas flow path from the kiln bottom of the said cement kiln to a bottom cyclone in the processing method of the cement kiln extraction gas in any one of Claim 1 thru | or 5. The coarse powder separated from the gas is reacted with water to produce slaked lime, which is used for metathesis of a magnesium hydroxide slurry absorption desulfurization apparatus.
[0020]
According to the sixth aspect of the invention, the sulfur content in the extraction gas can be removed using the coarse powder separated from the extraction gas, and recovered as gypsum.
[0021]
A seventh aspect of the present invention is the cement kiln extraction gas treatment method according to any one of the first to sixth aspects, wherein the calcined raw material of the cement kiln is reacted with water to produce slaked lime, and magnesium hydroxide It is used for metathesis of slurry absorption method desulfurization equipment.
[0022]
According to the seventh aspect of the invention, the sulfur content in the extraction gas can be removed using the calcined raw material of the cement kiln and recovered as gypsum.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Next, a specific example of an embodiment of a method for treating a cement kiln extraction gas according to the present invention will be described with reference to the drawings.
[0024]
FIG. 1 shows an embodiment of a method for treating a cement kiln bleed gas according to the present invention. This treatment apparatus 1 is provided with a magnesium hydroxide slurry absorption desulfurization apparatus, and mainly includes a cyclone 5 and The absorption tower 7, the septic tank 13, the filtration / separation device 18, the oxidation tower 19, the liquid cyclone 21, the drainage desalination device 25, and the like.
[0025]
The extracted gas from the kiln exhaust gas flow path from the kiln bottom of the cement kiln 2 to the bottom cyclone is cooled by the cold air from the cooling fan 4 in the probe 3 and then introduced into the cyclone 5, where coarse powder, fine powder and gas And separated. The fine powder and gas are cooled by water supplied from the water supply device 24 in the pre-cooling tower 6 and supplied to the absorption tower 7. In the absorption tower 7, the chlorine content such as KCl contained in the fine powder is maintained as it is, and the slurry containing the fine powder is circulated by the pump 12 while being absorbed by the pump 9 from the magnesium hydroxide tank 8. It reacts with water and magnesium hydroxide supplied via the liquid adjustment tank 10 and the pump 11, and as shown below, sulfur (SO ₂ ) is recovered as magnesium sulfate (MgSO ₄ ). The exhaust gas from the absorption tower 7 is exhausted to the atmosphere via the fan 22 and the damper 23.
SO ₂ + H ₂ O → H ₂ SO ₃
H ₂ SO ₃ + Mg (OH) ₂ → MgSO ₃ + 2H ₂ O
MgSO ₃ + SO ₂ + H ₂ O → Mg (HSO ₃ ) ₂
Mg (HSO ₃ ) ₂ → Mg (OH) ₂ + H ₂ SO ₃ + H ₂ O
Mg (HSO ₃ ) ₂ + Mg (OH) ₂ → 2MgSO ₃ + 2H ₂ O
H ₂ SO ₄ + Mg (OH) ₂ → MgSO ₄ + 2H ₂ O
MgSO ₃ + 1 / 2O ₂ → MgSO ₄
[0026]
On the other hand, the slurry containing a chlorine component such as KCl discharged from the absorption tower 7 is supplied to the liquid cyclone 21, and the collected portion of the liquid cyclone 21 is supplied to the filtration separation device 18, thereby supplying the slurry to the filtration separation device 18. While reducing the load, reduce the magnesium content in the collected fraction and increase the gypsum content. The concentrated slurry collected by the liquid cyclone 21 is filtered by the filtration / separation device 18, and then industrial salt is recovered by the drainage demineralizer 25. The wastewater can be circulated and used in the septic tank 13 or the like. On the other hand, the supernatant of the hydrocyclone 21 is supplied to the absorption tower 7 and the oxidation tower 19 via the pump 12.
[0027]
A part of the supernatant of the liquid cyclone 21 sent to the oxidation tower 19 via the pump 12 contains magnesium sulfate (MgSO ₄ ) and sulfuric acid (H ₂ SO ₄ ) in the oxidation tower 19 as shown below. appear.
MgSO ₃ + 1 / 2O ₂ → MgSO ₄
Mg (HSO ₃ ) ₂ + O ₂ → MgSO ₄ + H ₂ SO ₄
[0028]
On the other hand, the coarse powder separated by the cyclone 5 is introduced into the slaked tank 13, and quick lime (CaO) in the coarse powder reacts with water to become slaked lime (Ca (OH) ₂ ) and is stored in the slaked lime tank 14. . The slaked lime in the slaked lime tank 14 is sent to the double decomposition tank 16 by the pump 15.
[0029]
In the metathesis tank 16, the slaked lime reacts with magnesium sulfate discharged from the oxidation tower 19 via the pump 20, and gypsum and magnesium hydroxide are generated as shown below.
MgSO ₄ + Ca (OH) ₂ + 2H ₂ O → CaSO ₄ .2H ₂ O + Mg (OH) ₂
[0030]
The gypsum and magnesium hydroxide generated in the metathesis tank 16 are guided to the absorption liquid adjusting tank 10 via the pump 17 and then supplied as an absorption liquid to the absorption tower 7 via the pump 11. Along with what is replenished in the magnesium hydroxide tank 8, it is used for desulfurization. On the other hand, gypsum is discharged from the absorption tower 7 and then supplied to the filtration / separation device 18 via the liquid cyclone 21, filtered and recovered.
[0031]
In addition, the gypsum collected in the said Example can also be used with the cement grinding mill attached to the cement kiln 2, and can aim at the effective utilization of gypsum within a cement manufacturing factory.
[0032]
Further, as described above, the chlorine content containing KCl may be recovered as an industrial salt, and a part or all of the filtered salt water is directly put into a cement crushing mill attached to the cement kiln 2 for processing. It is also possible to do.
[0033]
Further, a part or the whole amount of gypsum and magnesium hydroxide as the absorption liquid is not returned to the absorption tower 7, but the solid content of the absorption liquid is concentrated in the liquid cyclone 21 to a cement grinding mill attached to the cement kiln 2. You may throw it in for processing. However, when concentrating the solid content of the filtered salt water or absorbent and putting it into a cement grinding mill, care must be taken not to exceed the upper limit of 200 ppm of the chlorine concentration in the cement specified in JIS. is there.
[0034]
Further, gypsum is separated from the absorption liquid and added to a cement grinding mill or the like, and the waste liquid after separation of the gypsum is sent to the drainage demineralizer 25. Can be supplied to the water supply device 24 to be used as coarse powder water, supplied to the water supply device 24 to be used as gas cooling water, or supplied to the absorption liquid adjustment tank 10 to be used for adjusting the water content of the absorption liquid. .
[0035]
Furthermore, in the above embodiment, as a slaked lime source, a coarse powder separated from the extracted gas extracted from the kiln exhaust gas passage from the kiln bottom of the cement kiln to the bottom cyclone was used with water, A kiln calcined raw material obtained by reacting with water can also be used.
[0036]
【The invention's effect】
As described above, according to the cement kiln extraction gas processing method according to the present invention, it is possible to reduce the equipment cost when desalinating chlorine bypass dust, and the combustion extracted from the vicinity of the cement kiln inlet hood It is possible to effectively use by removing sulfur contained in the gas.
[Brief description of the drawings]
FIG. 1 is a flowchart showing one embodiment of a method for treating a cement kiln bleed gas according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing apparatus 2 Cement kiln 3 Probe 4 Cooling fan 5 Cyclone 6 Precooling tower 7 Absorption tower 8 Magnesium hydroxide tank 9 Pump 10 Absorption liquid adjustment tank 11 Pump 12 Pump 13 Summing tank 14 Slaked lime tank 15 Pump 16 Metathesis tank 17 Pump 18 Filtration separation device 19 Oxidizing tower 20 Pump 21 Hydrocyclone 22 Fan 23 Damper 24 Water supply device 25 Drainage desalination device

Claims (7)

A part of combustion gas is extracted from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone, coarse dust particles in the extracted gas are separated, and the extracted gas containing fine powder is absorbed with magnesium hydroxide slurry. It was introduced into the desulfurization apparatus, the processing method of the cement kiln extracted gas, which comprises desulfurizing while water cooling the extracted gas containing the fine powder.   The method for treating a cement kiln extraction gas according to claim 1, wherein the solid content of the absorption liquid from the magnesium hydroxide slurry absorption desulfurization apparatus is concentrated and added to a cement grinding mill system.   The method for treating a cement kiln bleed gas according to claim 1 or 2, wherein gypsum separated and by-produced from the absorption liquid of the magnesium hydroxide slurry absorption desulfurization apparatus is added to a cement grinding mill system.   4. The cement kiln bleed gas according to claim 1, wherein the waste liquid after separating gypsum from the absorption liquid of the magnesium hydroxide slurry absorption method desulfurization apparatus is added to a cement grinding mill system. 5. Processing method.   The waste liquid after separation of gypsum from the absorption liquid of the magnesium hydroxide slurry absorption method desulfurization apparatus is sent to the desalination apparatus, and the drained water after the desalination is used as circulating water for use in the extraction gas treatment system. The processing method of the cement kiln extraction gas of Claim 3 or 4 characterized by these.   The coarse powder separated from the extracted gas extracted from the kiln exhaust gas flow path from the kiln bottom of the cement kiln to the bottom cyclone is reacted with water to produce slaked lime, and used for metathesis of the magnesium hydroxide slurry absorption desulfurization unit The processing method of the cement kiln bleed gas according to any one of claims 1 to 5.   The cement kiln bleed gas according to any one of claims 1 to 6, wherein the calcination raw material of the cement kiln is reacted with water to produce slaked lime and used for metathesis of a magnesium hydroxide slurry absorption desulfurization apparatus. Processing method.

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