JPH05331829A - Surplus soil improving method using shell incineration lime produced out of shell adhering to intake pipe for power station - Google Patents

Abstract

PURPOSE:To lower cost for surplus soil improvement by making use of shell incineration ashes as a lime constituent of improving agent, which are obtained through the incineration of raw shells collected from the wall of an intake pipe at a specified temperature. CONSTITUTION:A sort of shells on the wall of an intake pipe for a power station is peeled off and recovered so as to be dewatered. It is then incinerated at 700 to 900 deg.C in a rotary kiln and the like so as to be formed into shell incineration quick lime powder. It is formed into shell incineration slaked lime with the quantity of water added as specified so as to be formed into a condition suitable for handling and storing, and slaked lime is added to surplus soil and mixed to be used for reclamation and the like as improved soil. Furthermore, shell incineration ashes are combined with coal ashes and desulfurizing gypsum to accelerate borazon reaction. This constitution thereby enables cost for surplus soil improvement to be lowered because incineration ashes are utilized, enables a space for filling raw shells to be eliminated, enables energy cost to be lowered because of incineration at low temperatures, and also enables mixing properties to be enhanced because shell incineration slaked lime is coarse in grain size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for improving residual soil,
In particular, the present invention relates to a method for improving the residual soil using incinerated ash containing lime as a main component, which is obtained by collecting and incinerating raw shellfish attached to intake channels of thermal power plants and nuclear power plants.

[0002]

2. Description of the Related Art In recent years,
Since it is difficult to secure a disposal site for surplus soil, and collecting sand for backfilling may lead to environmental damage, there are active moves to recycle surplus soil as an alternative to sand. The flow of recycling the residual soil is as shown in Fig. 1. First, of the residual soil generated from each civil engineering work site, it is not suitable as a backfill material 1
Is improved as the backfilling improved soil 3 having a certain quality characteristic by adding, mixing, depositing and curing the improving material 2 such as quick lime in the residual soil improving plant. In addition, the "remaining soil" in this specification refers to the earth and sand not used as a material in the said site among earth and sand discharged by excavation work. Currently, industrial quick lime is often used as a residual soil improving material, and the addition amount thereof is about 3 to 5% in terms of the dry soil weight ratio.
The improvement of the residual soil by lime is to improve the physical and chemical properties of the soil by utilizing the reaction with the soil. In the case of quick lime, (1) dehydration by water absorption exothermic reaction, (2) particle size by ion exchange reaction Improvement, (3) consolidation by pozzolanic reaction,
(4) It is said that the residual soil is improved by the carbonation reaction and the like.

By the way, in thermal power and nuclear power plants,
Seawater is introduced and used as cooling water for the condenser of the power generation facility via the intake channel, but raw shellfish such as mussels grow and adhere to the bottom and side surfaces of the channel, increasing water flow resistance, or part of it. Since the raw shellfish that separates and flows out adheres to the cooling pipe of the power plant and causes a problem, it is necessary to regularly strip and remove the raw shellfish. Annual removal and recovery of raw shellfish adhering to this intake channel is 1,000 per thermal power plant.
It is about t / year, and a huge amount of raw shellfish is removed.
A lot of raw shellfish is being landfilled. With regard to landfill disposal, securing landfill sites and measures against spoilage and offensive odors at their deposits are issues.

[0004]

[Means for Solving the Problems] In view of the above circumstances, the present inventors have earnestly studied to promote effective use of raw shellfish attached to thermal power / nuclear power plant intake channels and reduce the amount of raw shellfish landfill disposal. Invented the invention. That is, the present invention is
(1) Addition and mixing of raw shellfish, which has been stripped and collected from the intake channel wall of thermal power and nuclear power plants, as a lime component of the residual soil improving material, to form improved soil. Characteristic method for improving residual soil using incinerated lime adhering to power plant intake channel, and (2) Shell incinerated ash powder obtained by incinerating raw shellfish stripped and recovered from power station intake channel wall, coal ash, and desulfurization gypsum It is a method for improving the residual soil using the incineration lime from the power plant intake channel, which comprises adding and mixing the mixture consisting of and as the residual soil improving material to the residual soil to mix with the residual soil.
Here, the shell cremation lime means shell ash mainly composed of quick lime or slaked lime.

The present invention will be described in detail with reference to preferable conditions and the like. Raw shellfish stripped and collected from the intake channel wall of a thermal power / nuclear power station is, for example, (1) in the intake channel cleaning work, the intake port of the power station, the intake channel. Obtained by scraping and collecting the mussels attached to the bottom and side walls of the road, then (2) draining, (3) 700-900 ° C for 1-2 hours in a rotary kiln, etc. Incinerate. Through the above steps, shellfish incineration quicklime powder can be obtained. Here, the incineration quicklime powder of shellfish refers to the incineration ash of shellfish whose main component is quicklime. In addition, shellfish incineration quicklime is
Like industrial quicklime, it has high reactivity and is good as a residual soil improvement material, but it has the risk of suddenly becoming hot when it comes into contact with water. It is preferable that a certain amount of water (about 30% of shell-burned quick lime) is mixed with a mixer to form shell-burned slaked lime, which has good handleability and storage stability. Shellfish incineration slaked lime
The quick lime component in the incinerated ash is slaked lime.

[0006] The incineration temperature of the raw shellfish is usually 700 ° C to 9 ° C.
A temperature of 00 ° C. is sufficient. As a result, shellfish, sea life and organic substances contained at the time of collection are dissipated, and shell-burned quicklime, which is mostly quicklime, is obtained. The obtained shellfish incineration quicklime is a coarse-grained ash that retains the shape of the shell. When mixed with water, shellfish incineration slaked lime can be obtained as a fine white powder. The chemical composition and physical properties of the shell incineration ash obtained as described above are as shown in Table 1. The composition and properties of coal ash and desulfurized gypsum are also described.

[0007]

[Table 1]

The residual soil improving material according to the present invention can be added to and mixed with the residual soil by adding the shell incineration ash obtained as described above to the improved soil, and further, it is a mixture type residual soil improving material containing coal ash and desulfurized gypsum. You can also do it. As the coal ash used for the production of the mixture type residual soil improving material, it is possible to use a large amount of by-product from the thermal power plant, and use desulfurized gypsum that is a large amount of by-product in the exhaust gas treatment of the thermal power plant. You can Therefore, the residual soil improving material mixture according to the present invention can be produced by using the by-products of thermal power plants, nuclear power plants, etc. as raw materials. When the residual soil has a large amount of water, it is necessary to increase the amount of the residual soil improving material according to the present invention in proportion to the amount of the residual soil. However, the ratio M / W between the weight of the improving material (M) and the water content in the residual soil (W) is There is a linear relationship between the strength of the improved soil and the strength increases as M / W increases. M / W = a / ω (where a: improvement material addition rate (%),
ω: Remaining soil water content ratio (%)), the uniaxial compressive strength of the improved soil can be kept constant if M / W is kept constant even if the water content ratio changes. The addition amount of the improving material may be adjusted according to the ratio. Usually, the amount of the incineration quicklime to be added according to the present invention is about 3 to 5% by weight ratio to dry soil, which is about the same as industrial quicklime. In the case of incinerated slaked lime, the amount added increases to some extent.

In the mixture type residual soil improving material according to the present invention, when coal ash (fly ash) is combined with power plant shell burned quick lime or shell burned slaked lime, Ca ²⁺ is increased, and the coal ash content increases. The pozzolanic reaction is promoted, and the improvement effect by the hydration hardening of coal ash is expected. Further, when combined with desulfurized gypsum, SO ₄ ²⁻ increases, so that it is expected that the pozzolanic reaction is further promoted. Since desulfurized gypsum contains about 3% of water in addition to water of crystallization, when used in combination, it is necessary to dry and then blend, which requires a drying step.

[0011]

EXAMPLES Next, the present invention will be specifically described by way of examples. Improved soil was manufactured by adding to and mixing with the residual soil shown in Table 2 alone or in combination with the coal ash or desulfurized gypsum according to the example of the present invention. The properties of the sample residual soil used in this example are as shown in Table 2, with a water content ratio of 83.5% and a clay content.
It has a particle size of 40%, sand content 24% and silt content 36%.

[0012]

[Table 2]

The above-mentioned shellfish incineration ash powder was manufactured according to the following steps. ． Recovery of shellfish from the intake channel →. Draining →. Incinerating raw shellfish in a rotary kiln (700-900 ° C, 1-2 hours) →. Generation and storage of shellfish incineration quicklime →. Water mix →
． Generation and storage of incinerated slaked lime

In the above, the mussels adhering to the intake of the power plant, the bottom of the intake channel, and the side wall are stripped and collected by scraping, and subsequently, in (1) to (7), the raw shells are drained and supplied to the rotary kiln. ~ 900 ° C
Then, the mixture is heated for 1 to 2 hours to collect shellfish incineration quicklime powder. Furthermore, water is sprinkled on this to make slaked lime by incineration.

The physical properties and chemical compositions of the obtained shellfish incineration quicklime and shellfish incineration slaked lime are shown in Table 1.

Further, in FIG. 2, the above shellfish incineration quicklime (L) is used.
The result (10 days of age) of the residual soil improvement test using the mixture type residual soil improving material obtained by adding coal ash (F) and desulfurized gypsum (G) in various mixing ratios is shown in FIG. The addition ratio of the improving material is 12% based on the weight ratio of dry soil. The numbers in the figure show the uniaxial compressive strength of the improved soil, and some contour lines show the uniaxial compressive strength contour lines of ² , 5, 10, 15, 18 kgf / cm ² . As can be seen from the figure, the general composition showing a uniaxial compressive strength of 10 kgf / cm ² or more after 10 days of age consists of shell-burned quicklime 50-100%, coal ash 0-45%, desulfurized gypsum 0-20%. Further, the general composition showing 15 kg / cm ² or more is 70 to 100% of shell-burning quicklime, 0 to 30% of coal ash, 0 of desulfurization gypsum.
.About.20%.

Obtained shell-and-burnt quicklime, shell-and-burnt lime, coal ash (F) and desulfurization gypsum (G) and shell-and-burnt quicklime (L)
The combined material (F: G: L = 2: 1: 7) of No. 1 was added to and mixed with the above-mentioned residual soil of the sample to obtain the improved soil.
Shown in. The quality standards for the improved soil (Tokyo) are as shown in Table 3, but according to the method of the present invention, the improved soil satisfying the same standard could be easily produced.

[0018]

[Table 3]

[0019]

As is apparent from the above description,
According to the invention: In conventional thermal and nuclear power plants, the incineration ash can be effectively used as a residual soil improvement material without landfill disposal of a huge amount of raw shellfish that grows and adheres to the bottom and sides of the intake channel, resulting in a reduction in residual soil improvement cost and a reduction in raw shellfish. The problem of land reclamation site is also solved. ． The lime produced from the raw shellfish attached to the intake of the power plant produces highly active lime despite incineration at a relatively low temperature, resulting in a low energy cost. Further, the shellfish incineration quicklime powder has a coarse particle size, so that it has good compatibility with the residual soil as a residual soil improving material and can be easily mixed homogeneously. Therefore, the required minimum amount is sufficient. In addition, dust is unlikely to rise during mixing. ． All of the mixture type residual soil improving materials can be produced by-products obtained from thermal power plants and nuclear power plants, and the obtained residual soil improving materials can be used to easily produce improved soil satisfying the conditions required as backfill materials. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the flow of recycling the residual soil.

FIG. 2 is a triangular coordinate graph showing the results of the residual soil improvement test using a mixture type residual soil improving material.

[Fig. 3] Graph of the test results obtained by adding and mixing the residual soil improving material to the sample residual soil to obtain improved soil.

[Explanation of symbols]

 1: Bad residual soil 2: Improved material 3: Improved soil F: Coal ash G: Desulfurized gypsum L: Shell incineration quicklime

Claims (3)

[Claims] 1. A shell soil incineration ash powder obtained by incinerating raw shellfish stripped and collected from the intake wall of a thermal power / nuclear power plant is added to and mixed with the residual soil as a lime component of the residual soil improving material to form improved soil. A method for improving residual soil using incinerated lime attached to a power plant intake canal. 2. A mixture of shell incineration ash powder obtained by incinerating raw shellfish stripped and collected from the intake wall of a thermal power / nuclear power plant, coal ash, and desulfurized gypsum is added and mixed to the residual soil. A method for improving residual soil using incinerated lime attached to a water intake of a power plant, which is characterized as improved soil. 3. A shell incineration ash powder obtained by incinerating raw shellfish stripped and collected from the intake channel wall of a thermal power / nuclear power plant at 700 ° C. to 900 ° C. is used.
A method for improving the residual soil using the incinerated lime that adheres to the water intake of the power plant described above.