JP2768147B2 - Remaining soil improvement method using incinerated lime from shellfish attached to power plant intake channel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 residual soil using incinerated ash mainly composed of lime obtained by collecting raw shellfish attached to intake channels of thermal power plants and nuclear power plants and incinerating them.

[0002]

2. Description of the Related Art In recent years,
Due to the difficulty in securing a landfill site and the possibility that collecting sand for backfill may lead to environmental destruction, there is a growing movement to recycle the soil as a substitute for mountain sand. The flow of recycle of surplus soil is as shown in Fig. 1. First, of the surplus soil generated from each civil engineering work site, unsatisfactory surplus soil 1 that is not suitable as backfill material.
In a remnant soil improvement plant, an improving material 2 such as quick lime is added, mixed, deposited, and cured to improve as a backfill improved soil 3 having a certain quality characteristic. In the present specification, “remaining soil” refers to earth and sand that is not used as a material at the site among earth and sand discharged by excavation work. At present, industrial quicklime is often used as a soil improvement material, and its addition amount is about 3 to 5% by weight based on dry soil.
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 and exothermic reaction, and (2) particle size by ion exchange reaction Improvement, (3) solidification by pozzolanic reaction,
(4) It is said that the residual soil is improved by a carbonation reaction or the like.

[0003] In thermal and nuclear power plants,
Seawater is introduced and used through the intake channel as cooling water for the condenser of the power generation facility, but raw shells such as mussels grow and adhere to the bottom and sides of the channel, increasing the water flow resistance, or In order to cause such a problem that the raw shells that have separated and flowed out adhere to and block the power plant cooling pipes, it is necessary to periodically strip and remove the raw shells. The annual removal and recovery of raw shellfish attached to this intake channel is 1,000 per thermal power plant.
t / year, a huge amount of raw shells are removed,
Many of the raw shellfish are being landfilled. As for landfill disposal, securing landfill sites and countermeasures against off-flavors in the areas where they are deposited are issues.

[0004]

Means for Solving the Problems In view of the above circumstances, the present inventors have conducted intensive research to promote the effective use of raw shellfish attached to the intake of thermal and nuclear power plants and to reduce the amount of raw shellfish landfill disposal. Invented the invention. That is, the present invention
(1) Adding and mixing shellfish incineration ash powder obtained by incineration of raw shellfish stripped and recovered from the intake channel wall of thermal power and nuclear power plants as a lime component of remaining soil improvement material, and mixing it with the remaining soil to obtain improved soil. A method for improving soil remnants using incinerated lime of a shell attached to a power plant intake channel, and (2) a shell incinerated ash powder obtained by burning raw shellfish stripped and recovered from a power plant intake channel wall, coal ash, and desulfurized gypsum A method for improving the residual soil using incinerated lime from a shellfish attached to a power plant intake, characterized in that a mixture consisting of
Here, the shellfish incineration lime refers to shellfish incineration ash mainly composed of quicklime or slaked lime.

The present invention will be described in detail with reference to preferred conditions and the like. Raw shellfish stripped and recovered from the intake channel wall of a thermal / nuclear power plant can be used, for example, in (1) Intake channel cleaning and intake of a power plant in intake channel cleaning work. It is obtained by depriving and collecting the purple mussels attached to the bottom and side walls of the road, and then (2) draining the water, and (3) raw shellfish in a rotary kiln or the like at 700 to 900 ° C. for 1 to 2 hours. Incinerate. Through the above steps, it is possible to obtain shellfish incinerated quicklime powder. Here, the shellfish incinerated lime powder refers to shellfish incinerated ash whose main component is quicklime. In addition, shellfish incinerated quicklime is
Like industrial quicklime, it has high reactivity and is good as a soil remediation material.However, it has the danger of suddenly rising to high temperature when it comes into contact with water. An amount of water (about 30% of the shellfish incinerated lime) is preferably mixed with water by a mixer to form shellfish incinerated lime, and the handleability and storage stability are preferably improved. Shellfish incinerated lime is
It means that the quicklime component in the incinerated ash has become slaked lime.

[0006] The incineration temperature of the raw shellfish is usually from 700 ° C to 9 ° C.
00 ° C. is sufficient, whereby shellfish and sea creatures and organic impurities contained at the time of collection are dissipated, and shellfish incinerated lime which is mostly quicklime is obtained. The resulting shellfish incinerated quicklime is ash with a large amount of coarse particles that leave the shape of a shell. There is a characteristic that when mixed with water, the incinerated slaked lime can be obtained as fine white powder. The chemical composition and physical properties of the shellfish ash obtained as described above are as shown in Table 1. In addition, each composition and property of coal ash and desulfurized gypsum were also described.

[0007]

[Table 1]

[0008] The reclaimed soil improving material according to the present invention can be added to and mixed with the reclaimed soil by the shellfish incineration ash obtained as described above alone, and can be used as a mixed type reclaimed soil improving material further provided with coal ash and desulfurized gypsum. You can also. As the coal ash used in the production of the mixture-type residual soil improvement material, it is possible to use a large amount of by-products from thermal power plants, and desulfurized gypsum that produces a large amount of by-products in thermal power plant exhaust gas treatment Can be. Therefore, all of the mixture for improving the residual soil in the present invention can be produced using by-products such as thermal and nuclear power plants as raw materials. When the residual soil has a large amount of water, the amount of the additive for improving the residual soil according to the present invention must be increased in proportion thereto. However, the ratio M / W of the weight of the improver (M) to the water content (W) of the residual soil is required. There is a linear relationship between the strength of the improved soil and the strength increases as the M / W increases. M / W = a / ω (where, a: improvement material addition rate (%),
ω: residual soil moisture content (%)), the unconfined compressive strength of the improved soil can be kept constant by keeping M / W constant even if the moisture content fluctuates. What is necessary is just to adjust the addition amount of an improving material according to a ratio. Usually, the addition amount of the shellfish incinerated quick lime according to the present invention is about 3 to 5% by weight to dry soil, which is about the same as that of industrial quick lime. In the case of shellfish incinerated lime, the amount to be added increases.

[0010] In the mixture-type surplus soil improving material of the present invention, when coal ash (fly ash) is combined with shell lime incinerated in a power plant or slaked lime in shell ash, Ca ²⁺ increases, and coal ash increases. Pozzolanic reaction is promoted, and the effect of improvement by hydration hardening of coal ash is expected. Further, when desulfurized gypsum is combined, the amount of SO ₄ ²⁻ increases, so that it is expected that the pozzolanic reaction is further promoted. In addition, since desulfurization gypsum contains about 3% of water in addition to water of crystallization, when used in combination, it is necessary to dry and then blend, and a drying step is required.

[0011]

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

[0012]

[Table 2]

The shellfish incineration ash powder was produced according to the following steps. . Collection of shellfish from intake channel →. Drain → Raw shellfish is incinerated in a rotary kiln (700-900 ° C, 1-2 hours) →. Formation and storage of incinerated lime from shellfish →. Add water →
. Formation and storage of incinerated lime in shellfish

In the above, the mussels on the water intake, the bottom of the water intake channel, and the side wall of the power plant are deprived and collected by scraping. Subsequently, in step (1), the raw mussels are drained and supplied to the rotary kiln. ~ 900 ° C
Then, heat for 1 to 2 hours to collect incinerated quicklime powder. In addition, water is sprinkled on this to make shellfish incinerated lime.

The physical properties and chemical composition of the obtained shellfish incinerated quicklime and shellfish incinerated lime are as shown in Table 1.

FIG. 2 shows the shellfish incinerated quicklime (L).
The results of a soil remediation test (10 days old) using a mixture-type remnant soil improving material obtained by adding coal ash (F) and desulfurized gypsum (G) in various mixing ratios are shown below. The rate of addition of the modifier is 12% by weight to dry soil. The numbers in the figure indicate the uniaxial compressive strength of the improved soil, and some contour lines indicate the contour lines of the respective uniaxial compressive strengths of ² , 5, 10, 15, and 18 kgf / cm ² . As can be seen from the figure, the schematic composition showing a uniaxial compressive strength of 10 kgf / cm ² or more at a material age of 10 days consists of 50-100% shellfish incinerated lime, 0-45% coal ash, and 0-20% desulfurized gypsum. In addition, the rough composition showing 15 kg / cm ² or more is 70-100% of shellfish incinerated lime, 0-30% of coal ash, and 0 of desulfurization gypsum.
-20%.

The obtained shellfish incinerated quicklime, shellfish incinerated slaked lime, coal ash (F) and desulfurized gypsum (G) and shellfish incinerated quicklime (L)
FIG. 3 shows a test result in which a combination material (F: G: L = 2: 1: 7) was added to and mixed with the above-mentioned residual soil to obtain an improved soil.
Shown in The quality standard of the improved soil (Tokyo) is as shown in Table 3. According to the method of the present invention, an improved soil satisfying the same standard could be easily produced.

[0018]

[Table 3]

[0019]

As is apparent from the above description,
According to the present invention, In conventional thermal and nuclear power plants, the incinerated ash can be effectively used as a soil remediation material without having to landfill and dispose of a huge amount of raw shells that grow and adhere to the bottom and sides of the intake channel. The problem of securing land for landfill is also solved. . The lime produced from raw shellfish attached to the power plant intake can be obtained with high activity lime despite relatively low temperature incineration and low energy cost. Further, since the shellfish incinerated lime powder has a coarse particle size, it has a good mixability with the remaining soil as a material for improving the remaining soil, and can be easily and homogeneously mixed. Also, dust does not easily form during mixing. . All of the mixture-type soil improvement materials can be manufactured from by-products obtained from thermal and nuclear power plants, and the obtained soil improvement materials can easily be used to produce improved soil that satisfies the requirements for backfill materials. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a flow of recycling of surplus soil.

FIG. 2 is a triangular coordinate graph of a result of a residual soil improvement test performed using a mixture type residual soil improvement material.

FIG. 3 is a graph of a test result in which an improved soil was obtained by adding and mixing a remaining soil improving material to a sample remaining soil.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E02D 3/00 E02F 7/00

Claims (3)

(57) [Claims] Claims: 1. Incinerated shellfish incineration ash powder obtained by incinerating raw shellfish stripped and recovered from the intake channel wall of a thermal or nuclear power plant as a lime component of a soil improvement material, and mixed with the remaining soil to form an improved soil. A method for improving residual soil using incinerated lime from shellfish attached to a power plant intake channel. 2. A mixture of shellfish incineration ash powder obtained by incinerating raw shellfish stripped and recovered from the intake channel wall of a thermal and nuclear power plant, coal ash, and desulfurized gypsum is added to and mixed with the remaining soil. A method for improving residual soil using incinerated lime from shellfish attached to a power plant intake, which is characterized as improved soil. 3. The shellfish incinerated ash powder obtained by incinerating raw shellfish stripped and recovered from the intake channel wall of a thermal or nuclear power plant at 700 ° C. to 900 ° C.
A method for improving residual soil using incinerated lime from shellfish attached to a power plant intake channel described in the paragraph.