JPH04202034A - Aging treatment of steel making slag - Google Patents

Abstract

PURPOSE:To stabilize the expansion fracture property of steel making slag in a short period of time and to reduce the cost of the aging treatment by subjecting the steel making slag to the natural aging treatment under an atm. pressure, then to the steam aging treatment. CONSTITUTION:A steam injection pipe 3 is laid on the base of a slag treating tank 1 formed with the base and side walls of concrete, and the steel making slag 6 is formed thereon via a crushed stone layer 5 of prescribed grain sizes. The surface thereof is coated with a vinyl sheet 7. This slag layer 6 is subjected to the natural aging treatment for 1 to 3 months and, thereafter, steam is supplied from the injection pipe 3 and the slag layer is subjected to the steam aging treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aging treatment method for preventing the expansion and destruction of steelmaking slag used as a road material. The present invention relates to a steelmaking slag aging treatment method that stabilizes the expansion fracture properties of slag in a short period of time and reduces aging treatment costs.

BACKGROUND OF THE INVENTION Since steelmaking slag is crystalline and hard, it is suitable as a roadbed material if it is crushed after cooling and adjusted to a predetermined particle size. However, in the case of steelmaking slag, some of the quicklime used during smelting remains unreacted (unsludged lime).
Free lime), which has the property of hydrating and expanding when it reacts with water, makes it difficult to use steelmaking slag immediately after production as a roadbed material.

As a countermeasure against this problem, - For boat fishing, aging is a process in which crushed slag is piled up in the atmosphere, and the unslaged lime undergoes a natural hydration reaction to stabilize its expansion and fracture properties before use. was. However, this method requires a period of at least six months to stabilize the expansion and fracture properties, requires a vast aging yard, is inefficient, and requires labor such as lot management. was there.

In view of this situation, various methods have been developed to shorten the aging period, and one of the representative methods is an aging treatment method using water vapor. This method uses the heat of steam and excess moisture to promote the water utilization reaction of unsludged lime in steelmaking slag.
The aging period is approximately one week.

Problems to be Solved by the Invention However, although the aging treatment method for steelmaking slag using steam has a great effect of promoting the water utilization reaction of free lime in the steelmaking slag, the manufacturing cost of the steam used is high;
When considering the economic efficiency of this aging treatment, it is necessary to reduce the amount of steam used as much as possible. however,
Conventionally, the amount of steam used has not been controlled in consideration of the economic efficiency of aging treatment, and the reality is that the cost of aging treatment of steelmaking slag is high.

In view of the above-mentioned circumstances, the present invention seeks to propose a method for aging treatment of steelmaking slag with the aim of shortening the aging treatment period and reducing costs.

Means for Solving the Problems This invention focuses on the phenomenon of grain refinement of slag lumps due to aging, and accelerates the water utilization reaction of steam aging in a short period of time, as a method for simultaneously shortening the aging treatment period and reducing treatment costs. This paper proposes a method for aging steelmaking slag, which consists of a first step of natural aging under atmospheric pressure and a second step of steam aging under atmospheric pressure.

Function: As mentioned above, steam aging of steelmaking slag can be aged in a much shorter period of time than natural aging, and slag with stable quality can be obtained. The free lime in the slag reacts with water and expands, causing cracks in the slag mass, and the steam that enters through the cracks further reacts with the free lime inside, causing the crack to expand.The phenomenon is repeated and stabilized.

At this time, the slag lumps often crack and become finer, but even in natural aging, a phenomenon is observed in which the grains become significantly finer within 1 to 3 months after the start of aging, and then become stable.

In other words, in both natural aging and steam aging, once the slag lump is cracked and becomes finer, the free lime existing inside the slag lump comes to the surface, promoting the water utilization reaction of the free lime and making it stable. become

This invention effectively utilizes the aging phenomenon of slag lumps, and steam aging is carried out when the slag grains become finer due to natural aging and the free lime inside the slag lumps comes out to the surface. This makes it possible to reduce the amount of steam used and achieve stability at low cost and in a short period of time.

Table 1 shows the results of investigating the change in particle size due to natural aging of converter slag that has been crushed to 25 mm or less and adjusted in particle size.As aging progresses, the amount of lumpy slag with a particle size of 13 to 25 mm decreases. Dog listening, 2.
An increase of 5 mm or less is observed, and particle sizes of 5 to 13 mm and 2.5 to 5 mm are hardly observed. This is because particles with a particle size of 13 to 25 mm are finely divided into 13 mm or less due to the free lime irrigation reaction, but 5 to 13 mm.
, 1111 grains also occur in the 2.5-5mm ones =
5- This is considered to be the reason for this phenomenon.

Table 1 From Table 1 above, it can be said that in the case of converter slag, grain refinement is almost complete by three months after the start of natural aging, and the reaction of free lime existing at or near the slag surface is progressing. .

Therefore, if steam aging is performed on the granulated slag in this state, free lime can be stabilized in a much shorter time than when steam aging is performed from the beginning. , the amount of steam used can be significantly reduced compared to conventional steam aging treatment alone.

In addition, in the case of only natural aging treatment, the knee zinc treatment takes more than 6 months, requiring a vast site and lot management, but in the case of this invention, the natural aging period is 1 to 3 months, so this problem is solved.

As mentioned above, by combining short-term natural aging treatment and steam aging treatment, quality-stable slag road material can be produced in a period longer than steam aging alone but much shorter than natural aging. This not only makes it possible to reduce the amount of steam used, but also reduces costs by reducing the amount of steam used.

Embodiment Figures 1 and 2 schematically illustrate the Nijin equipment for carrying out the method of this invention. Here, a rectangular steelmaking slag processing tank with one side of the side wall as a gate for importing and exporting slag is shown. This will be explained by taking as an example a steam aging facility equipped with steam piping.

In the figure, (1) is a slag treatment tank whose bottom and side walls are made of concrete, etc., (2) is a steam supply main pipe, (3) is a steam injection pipe, (4) is a steam flow rate control valve, and (5) is a crushed stone layer,
(6) is a steelmaking slag layer, and (7) is a heat-retaining vinyl sheet.

That is, in the above equipment, a steam injection pipe (3) is installed on the bottom of a slag treatment tank (1) whose bottom and side walls are made of a structure (made of concrete, iron plate) that prevents steam from leaking. This is a method for steam aging by forming a steelmaking slag layer (6) through a crushed stone layer (5) of a predetermined grain size on top of the steel, and the crushed stone layer (5) is provided to ensure stable steam permeability. It is.

The results of actually aging converter slag using the above aging equipment are shown below.

In this example, unaged converter slag 3001-n whose particle size was adjusted to 25 mm or less was first naturally aged for two months, and then steam aged.

Table 2 shows the water immersion expansion test conducted on the slag before and after steam aging (80"C16Hr/day,
The results show that by first performing natural aging for two months, the amount of water immersion expansion decreased from 3.67% before aging to 1,69% after aging, approximately 172%. It was confirmed that the hydration reaction of free lime present near the surface of the converter slag was progressing.

In addition, the particle size distribution at this time showed a decrease in lumpy slag with a particle size of 13 to 25 mm, and an increase in fine slag with a particle size of 2.5 mm or less, confirming that the slag became finer due to the hydration reaction of free lime. Ta.

Next, the unaged converter slag and the converter slag that had been naturally aged for two months were steam aged, and the changes in water immersion expansion over time were investigated from the time when the slag temperature rose to 100 °C. The results are shown in Figure 3.

In Figure 3, A is a naturally aged product that has been steam aged for two months (the present invention), B is an unaged product that has been steam aged (conventional method), and C is an unaged low expansion slag product (comparative example). It is.

From the results in Table 1 and Figure 3, the converter slag that has been subjected to natural aging treatment and then steam aging treatment has less water immersion expansion and is more stable than those that have only been subjected to steam aging treatment. In addition, if the water immersion expansion after steam aging is the same, for example, naturally aged converter slag will be 0.5% or less after 10 hours of steam aging, whereas if only steam aging is performed, it will be 0.5% or less. It turns out that it takes 26 hours for this to happen.

Therefore, compared to 53 kg/T for steam aging only, the unit steam consumption for the present invention, which combines natural aging and steam aging, was 40 kg/T, reducing steam costs by approximately 25%.

In addition, the water immersion expansion amount when the slag temperature reaches 100°C and is held for 40 hours and the steam is stopped in the case of only steam aging treatment and in the aging treatment that combines natural aging and steam aging of this invention. are 0.37% and 0.09%, respectively, values that fully satisfy the standard value of 51.5% for road subgrade materials (asphalt pavement guidelines).

As explained in detail below, this invention method effectively utilizes the phenomenon of slag grain refinement caused by short-term natural aging to bring out the effect of steam aging to carry out aging treatment. This has the advantage of being able to reduce the amount used, stabilize the quality in a short period of time, and obtain high-quality slag that can be used as a roadbed material at a low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing an example of aging treatment equipment for carrying out the method of this invention, FIG. 2 is a longitudinal sectional front view taken along the line ■-■ in FIG. It is a figure which shows the change with time of the amount of immersion expansion. 1. Slag treatment tank 2... Steam supply main pipe 3. Steam injection pipe 4. Steam flow control valve 5... Crushed stone layer 6... Steelmaking slag layer Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Press 1 ) Longevity ・、：：（、、、、−
1”':l,!1

Claims (1)

[Claims] A method for aging steelmaking slag, which comprises a first step of performing natural aging treatment under atmospheric pressure, and a second step of performing steam aging treatment under atmospheric pressure.