JP2000313643A - Production of cement feedstock and cement clinker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize both bottom ash and sludge by preparing a cement feedstock from them which are discharged from circulating fluidized bed boilers. SOLUTION: The subject cement feedstock is obtained by utilizing both bottom ash and sludge; wherein the bottom ash is pref. such one as to be discharged from circulating fluidized bed boilers which used limestone as desulfurizing medium, while the sludge is pref. such one as to result from dredging and/or construction activities; the mixing ratio for them is pref. such that the water content of the resultant mixture is 0.5-30 wt.%, esp. 1-10 wt.%; when bottom ash substantially free from water is mixed, the water content of the resultant mixture can be reduced even if sludge resulting from dredging and/or construction activities is high in water content, improving the handleability of the mixture; when bottom ash containing quicklime (CaO) is used, the quicklime reacts with water, effecting improving dehydration efficiency and participating the quicklime as part of the objective cement feedstock, thereby enabling the amount of limestone to be reduced; thus, significance of enabling wastes to be utilized as a resource in the form of a cement feedstock through their mixing together is extremely high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for effectively utilizing sludge such as dredged sludge and construction sludge as resources.
In particular, the present invention relates to effective utilization of sludge as a part of cement raw material in a cement firing step.

[0002]

2. Description of the Related Art Several proposals have been made as techniques for treating sludge in a cement manufacturing plant. For example, in Japanese Patent Application Laid-Open No. 3-98700, a dewatering step of mixing sewage sludge and quicklime to dewater the sewage sludge; A sewage sludge recycling system has been proposed, which includes a cement clinker firing step of firing together with a cement raw material, and a gas treatment step of introducing gas generated in the dehydration step to the cement clinker firing step.

In Japanese Patent Application Laid-Open No. 8-276199,
There has been proposed a sludge treatment method characterized in that hydrated sludge is directly introduced into a kiln bottom portion of a dry kiln or a calciner and incinerated. Also, in Japanese Patent Application Laid-Open No. Hei 10-192896, a storage tank for storing organic sludge, and the organic sludge in the storage tank are fed from the lower part of a preheater for cement material calcination in a firing step of a cement production plant. There has been proposed a sludge treatment facility provided with a sludge introduction device for introducing a dry cement kiln to a kiln bottom of a cement cement kiln for firing cement raw materials.

[0004] Further, in Japanese Laid-10-194800 discloses a calcined cement raw material by a preheater in NO _x reduction method in the exhaust gas generated when firing a dry cement kiln, from the bottom of the preheater N of exhaust gas of cement kiln that introduces organic sludge containing ammonia up to the kiln bottom of the dry cement kiln
_Ox reduction methods have been proposed.

[0005] The technique proposed in Japanese Patent Application Laid-Open No. 3-98700 discloses a method of mixing sewage sludge with quicklime before the sewage sludge is put into a cement kiln and calcined together with other cement raw materials. While dehydration is performed, Japanese Patent Application Laid-Open No. 8-276199 and Japanese Patent Application Laid-Open
The technology proposed in Japanese Patent Application Laid-Open No. 192896 and Japanese Patent Application Laid-Open No. Hei 10-194800 is intended to put sewage sludge into a kiln end portion of a dry kiln as it is, without performing pretreatment.

[0006] In the former technique, sewage sludge is mixed and treated with quick lime.
Useful effects such as improved handling are expected,
Since expensive quicklime is used, the processing cost is high.
In addition, when used as a cement raw material, weak points such as the necessity of adjusting some components are also assumed. In the latter technology, sewage sludge is introduced and incinerated in the kiln bottom of a dry kiln without any pretreatment, so equipment and treatment costs are considered to be lower, but the components have already been adjusted. Since the sewage sludge component and the water content are added separately and added to the cement raw material in a concentrated manner, variations in the components and water content of the sewage sludge may promote variations in the cement clinker component, which is an intermediate product of cement production. In order to avoid this, a method such as dispersing and charging is conceivable. However, sewage sludge generally has a high viscosity, and thus has a drawback that a special device such as an injection device is required. Furthermore, there is a problem in handling such as poor handling. In addition to these, consolidation is likely to occur in the kiln butt, which is likely to hinder stable operation of the kiln.

[0007] In addition, the above-mentioned proposed technology is called sludge,
This is a so-called sewage sludge. For this reason, it is unknown whether it can be applied to sludge such as dredged sludge and construction sludge. By the way, in recent years, it has become difficult to treat not only sewage sludge but also sludge such as dredged sludge and construction sludge by landfill disposal and the like, and development of new treatment methods and further resource utilization are required.

Further, not only sludge such as the above-mentioned dredged sludge and construction sludge but also bottom ash discharged from a circulating fluidized-bed boiler is required to be treated and further recycled. That is, there is a cement manufacturing plant provided with a circulating fluidized-bed boiler as a power generation facility. In such a factory, a large amount of bottom ash is discharged from the circulating fluidized-bed boiler device. For this reason, it is difficult to treat a large amount of bottom ash. And it is not only a mere process but also a resource.

Accordingly, a first object of the present invention is to provide a technique capable of effectively utilizing sludge, particularly sludge such as dredged sludge and construction sludge. A second problem to be solved by the present invention is to provide a technique capable of effectively utilizing bottom ash discharged from a circulating fluidized bed boiler device.

[0010]

The first and second objects are attained by a cement raw material comprising bottom ash discharged from a circulating fluidized bed boiler and sludge.

Particularly, the present invention is solved by a cement raw material characterized by including bottom ash discharged from a circulating fluidized-bed boiler apparatus using limestone as a desulfurization medium and sludge. When using bottom ash and sludge (particularly, dredged sludge and construction sludge) as cement raw materials, the mixing ratio of bottom ash and sludge is such that the water content of the mixture is 0.5 to 30 wt% (particularly 1 wt% or more). 10w
t% or less. It is preferable that bottom ash and sludge are mixed so that That is, by using such a water content, the handleability can be improved, and the variation in the quality of the obtained cement product can be reduced.

In the present invention, the bottom ash discharged from a circulating fluidized-bed boiler using limestone as a desulfurization medium in the bottom ash is preferable because the bottom ash contains quicklime. This is because the dehydration efficiency is improved. That is, the bottom ash discharged from the circulating fluidized-bed boiler apparatus of the present invention has a water content of substantially 0%, and is a so-called "puffy" feeling. Therefore, such a substantially water content of 0%
By mixing bottom ash, even if it is dredged sludge or construction sludge having a high water content, the water content can be relatively reduced. And when handling this as a cement raw material, handleability improves.

[0013] In particular, when a bottom ash containing quicklime (CaO) is used, the quicklime reacts with water,
Dehydration efficiency is improved. Moreover, limestone used as a desulfurization medium is normally used as a part of a raw material in a cement plant, and even if quick lime in bottom ash is added as a part of a cement raw material, there is no problem. Rather, the limestone raw material is replenished, and the amount of limestone originally used as a cement raw material can be reduced, which is very convenient.

Further, the first and second problems are solved by a method for producing a cement clinker, which comprises introducing the above cement raw material into a cement firing system and firing it together with other cement raw materials. Further, the problem is solved by a method for producing a cement clinker, which comprises mixing iron oxide, silica, clay, limestone and the above-mentioned cement raw materials and firing the mixture.

According to the present invention, dredged sludge or construction sludge can be recycled as a cement raw material, and its social significance is extremely high. In the above description, sludge is described as dredged sludge or construction sludge, but, for example, sewage sludge generated in a sewage treatment facility, manure sludge generated in a manure treatment facility, and organic matter generated from various other treatment facilities. It can also be applied to sludge containing sludge. That is, even in the case of such sludge, when bottom ash discharged from the circulating fluidized bed boiler apparatus, particularly bottom ash discharged from the circulating fluidized bed boiler apparatus using limestone as a desulfurization medium, is used. The water content of the mixture becomes suitable for handling as a cement raw material, and the handleability is improved. Moreover, all of them are wastes that were difficult to treat, and by mixing wastes and wastes,
It can be recycled as a raw material for cement, and its social significance is extremely high.

In particular, the bottom ash used in the present invention is:
Since it is discharged from a circulating fluidized-bed boiler device in a cement manufacturing plant equipped with an in-house power generation facility, it is not transported from another source, and does not require transportation costs, which is extremely convenient. Any means may be used for mixing bottom ash discharged from the circulating fluidized-bed boiler, particularly bottom ash discharged from the circulating fluidized-bed boiler using limestone as a desulfurization medium, and sludge. For example, they may be mixed by a shovel, or a mixer such as a pro-share mixer may be used.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A cement raw material according to the present invention comprises bottom ash discharged from a circulating fluidized-bed boiler (particularly, bottom ash discharged from a circulating fluidized-bed boiler using limestone as a desulfurization medium). Sludge (especially, dredging sludge and construction sludge). When using bottom ash and sludge (particularly, dredged sludge and construction sludge) as a cement raw material, the mixture of bottom ash and sludge has a water content of 0.5 to 30 wt% (particularly 1 wt% or more).
10 wt% or less. ) Is mixed with the bottom ash and the sludge. The bottom ash discharged from the circulating fluidized-bed boiler of the present invention has a water content of substantially 0%. Sludge such as dredged sludge and construction sludge generally has a water content of 15 wt% or more.

The method for producing a cement clinker according to the present invention is a method in which the above cement raw material is introduced into a cement firing system and fired together with other cement raw materials. Alternatively, it is a method in which iron oxide, silica, clay, limestone, and the above cement raw materials are mixed and fired. This will be further described below. FIG.
1 is a schematic view of a cement clinker firing plant.

In FIG. 1, reference numeral 1 denotes a circulating fluidized-bed boiler in a private power generation facility provided in a cement manufacturing plant (cement clinker firing plant). Here, coal or the like is burned as a fuel, and limestone is used as a desulfurization medium. Bottom ash containing quicklime is discharged from the circulating fluidized bed boiler device 1. The amount of bottom ash discharged is about 10 t / day when the power generation is 23 to 25 MW.

In addition, about the discharged bottom ash,
When the component analysis was attempted, SiO ₂ was 19.5 wt%,
8.6 wt% of Al ₂ O _{3 and} 2.6 wt% of Fe ₂ O ₃
%, 49.1 wt% of CaO, 0.6 wt% of MgO,
SO ₃ is 7.0wt%, other 10.0wt%, Ig.
Loss was 2.6% by weight. The water content is 0 wt
%Met.

2 is a cement manufacturing plant (cement clean
This is a sludge storage site provided within the sintering plant. This dirty
In the mud storage site 2, construction sludge and dredging are performed using a
Sludge is brought in. By the way, it is carried in by a dump truck
Tried to analyze the components of the construction sludge
Treatment, SiO_TwoIs 65.9 wt%, Al_TwoO_ThreeIs 14.1
wt%, Fe_TwoO _ThreeIs 4.8 wt% and CaO is 1.8 w
t%, MgO 2.3 wt%, SO_ThreeIs 0.3 wt%,
Others 5.7 wt%, Ig. Loss is 5.1wt%
there were. The water content was 15.1% by weight.

The bottom ash from the circulating fluidized-bed boiler 1 and the construction sludge from the sludge storage 2 are mixed by a mixer 3.
Mixed by Since the mixing ratio varies depending on the water content of the sludge, it cannot be uniquely determined. However, when the mixture is used as a cement raw material, the water content in the mixture is 0.5 to 30 wt% (particularly, 1 wt% or more). (Less than 10 wt%). In the present embodiment, bottom ash: sludge = 1: 1 to 5 (weight ratio)
At a rate of

Incidentally, in the case of bottom ash: sludge = 1: 5, the water content immediately after mixing was determined by calculation.
It was 6 wt%, and the water content after being allowed to stand for 24 hours after mixing was 10.8 wt%. Therefore, the dehydration efficiency ([moisture content before leaving-moisture content after leaving] / moisture content before leaving × 100) was 14.3%. In the case of bottom ash: sludge = 1: 3, the water content immediately after mixing was calculated to be 11.3 wt%, and the water content after mixing and standing for 24 hours was 9.9.
It was 4 wt%. Therefore, the dehydration efficiency ([moisture content before leaving-moisture content after leaving] / moisture content before leaving × 100) is 16.8.
%Met.

In the case of bottom ash: sludge = 1: 1, the water content immediately after mixing was calculated to be 7.8 wt%, and the water content after mixing and standing for 24 hours was 5%. 0.8 wt%. Therefore, the dehydration efficiency ([moisture content before leaving-moisture content after leaving]) / moisture content before leaving ×
100) was 23.7%. As can be seen from this, it is found that mixing the bottom ash with the sludge lowers the water content. In particular, it can be seen that dehydration is effectively performed by the presence of quicklime (CaO) in the bottom ash.

After being sufficiently mixed by the mixer 3, it is taken out and temporarily stored in the storage 4. Cement raw materials, for example, iron oxide, are stored in a storage 5, silica is stored in a storage 6, clay is stored in a storage 7, and limestone is stored in a storage 8. Then, a desired amount of each raw material is taken out of the storages 4, 5, 6, 7, and 8 into a raw material pulverizer 9 and pulverized. After that, the raw material is supplied to a suspension preheater 10 composed of a plurality of stages of cyclones. It is charged and reaches a rotary kiln 11 through a calciner (there may be no calciner).
The exhaust gas from the rotary kiln 11 moves from the lowermost cyclone of the calciner and the suspension preheater 10 to the upper cyclone. Then, the cement raw material is heated, and quicklime is generated by decarboxylation. Since these cement clinker sintering facilities and sintering steps are well known, further explanation is omitted.

That is, in the present embodiment, the basic technical idea is the same as that of the conventional cement clinker firing technology except that a mixture of bottom ash and construction sludge is used as one of the cement raw materials. . Then, since the bottom ash and the construction sludge were mixed, the mixture could be recycled as a cement raw material. In this regard, the present invention has great significance. In other words, there is great significance in that resources that have been conventionally troubled as waste can be recycled by mixing with each other.

In the above embodiment, the mixture of bottom ash and construction sludge is supplied to the suspension preheater 10.
Is introduced into the uppermost cyclone, but may be introduced directly into the cement firing system on the way to the rotary kiln 11. Further, the rotary kiln 11 may be introduced into the inside of the kiln from the bottom. For example, a screw type introducing means may be attached to the kiln tail of the rotary kiln 11 so that a mixture of bottom ash and construction sludge may be introduced into the rotary kiln 11 from the kiln tail.

Further, not only construction sludge but also dredged sludge may be mixed with bottom ash. Further, a mixture of construction sludge and dredged sludge may be used. That is, even such sludge can be effectively used as a raw material for cement by mixing it with bottom ash. That is, since the construction sludge and / or the dredged sludge were mixed with the bottom ash, when these sludges were introduced into the cement burning system, a good handling treatment was possible,
There is no problem in the stable operation of cement clinker firing.

In particular, sludge is not directly injected as it is, but rather, sludge is mixed with bottom ash. This mixture is in the form of powder and granules, and is not viscous like sludge. Easy handling when loading. For example, when the sludge is introduced into a kiln or the like, a spraying device for dispersing the sludge, which is required when sludge is directly introduced, is not required.

Furthermore, since it is mixed with bottom ash discharged from a circulating fluidized-bed boiler using limestone as a desulfurization medium, it is easy to make it uniform as a cement raw material.
Less variation in cement clinker components. Furthermore, since bottom ash can be obtained at the cement manufacturing plant where the sludge is to be effectively used (treated), there is no need to separately transfer special quicklime to the cement manufacturing plant, and the cost is low in this respect as well. become.

[0031]

Effect of the Invention Sludge, particularly sludge such as dredged sludge and construction sludge, is effectively used. Despite the use of sludge, cement of stable quality can be obtained. Excellent handleability. Cost is low. No complicated management is required.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of a cement manufacturing plant in which the present invention is implemented.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circulating fluidized-bed boiler apparatus 2 Sludge storage place 3 Mixer 4,5,6,7,8 Storage 9 Raw material crusher 10 Suspension preheater 11 Rotary kiln

Continuing on the front page (72) Inventor Ken Hirano, Kochi City, Kochi City, Higashi 25 Pacific Ocean Cement Co., Ltd. Tosa Plant F term (reference) 4D059 AA09 BB14 BF15 CA14 CC04 DA04 DA12 DA22 DA54 DA60 EB01

Claims (5)

[Claims] 1. A cement raw material comprising bottom ash discharged from a circulating fluidized-bed boiler and sludge. 2. A cement raw material comprising: bottom ash discharged from a circulating fluidized-bed boiler using limestone as a desulfurization medium; and sludge. 3. The cement raw material according to claim 1, wherein the bottom ash and the sludge are mixed so that the water content of the mixture of the bottom ash and the sludge is 0.5 to 30% by weight. . 4. The cement raw material according to claim 1, wherein the sludge is dredged sludge and / or construction sludge. 5. A method for producing a cement clinker, comprising introducing a cement raw material according to any one of claims 1 to 4 into a cement firing system and firing it together with another cement raw material.