JPH04202033A - Aging treatment of steel making slag - Google Patents

Abstract

PURPOSE:To decrease the amt. of the steam to be used and to stabilize the expansion fracture property of steel making slag in a short period of time by controlling the amt. of the superheated steam to be used according to the voids of the steel making slag to be treated. CONSTITUTION:A crushed stone layer 7 is laid on a steam injection pipe 3 provided in the bottom of a slag treating tank 1 made of concrete and the steel making slag layer 8 to be treated is provided thereon and is coated with a vinyl sheet 9. The voids of the steel making slag layer 8 are calculated by a void calculator 5 and an optimum steam ejection rate is computed from the voids by a steam ejection rate computer 6. A solenoid valve 4 is controlled according to this value to supply the superheated steam via a steam supply main 2 and the injection pipe 3, by which the slag layer 8 is subjected to the aging treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aging treatment method for preventing expansion and destruction of steel slag used as a road material, and more specifically, it relates to an aging treatment method for preventing expansion and destruction of steel slag used as a road material. The present invention relates to a steelmaking slag aging treatment method for stabilizing the expansion fracture properties of steelmaking slag in a short period of time by effectively using steam without waste.

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 6 months to stabilize the expansion and fracture properties, requires a vast aging yard, is inefficient, and requires labor such as lot management. There was a problem.

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 water to promote the water utilization reaction of unsludged lime in steelmaking slag. Specifically, methods for reacting steam and steelmaking slag include a method of forming a steelmaking slag layer on a high-temperature steam pipe from which steam spews out, and a method of placing steelmaking slag in a hopper and spouting steam from the bottom of the hopper. be.

Problems to be Solved by the Invention However, although the method of aging steelmaking slag using steam has a great effect of promoting the hydration reaction of unsludged lime in the steelmaking slag, the manufacturing cost of the steam used is high; When considering the economic efficiency of 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 that can reduce the aging period of steelmaking slag by effectively using steam without waste, in order to reduce the cost of aging treatment using steam. It is.

Means for Solving the Problems The gist of the present invention is to use superheated steam as the steam when aging steelmaking slag using steam under atmospheric pressure, and to adjust the aging of the superheated steam according to the porosity of the slag to be treated. This is an aging processing method that controls usage.

There are two types of working steam: saturated steam and superheated steam, and the temperature changes at a certain level under constant pressure. For example, at 10 atm, 1
Steam below 79°C is saturated steam, and steam above this is superheated steam.

The biggest difference between these steams is their enthalpy.

Table 1 shows an example of enthalpy under 10 atmospheres, and the temperature is 17
Saturated steam at 0° C. and superheated steam at a temperature of 180° C. differ in temperature by only 10° C., whereas the enthalpy of superheated steam is approximately four times higher. High enthalpy means that steam has high energy, and as shown in Table 2, the thermal properties of steelmaking slag are those with high specific heat and low thermal conductivity, so-called materials that are difficult to heat. It can be said that it is suitable for heating.

For example, the amount of steam required to heat steelmaking slag from 20°C to 100°C under atmospheric pressure using the steam shown in Table 1 is 212 kg of saturated steam and 27 kg of superheated steam.
kg (calculated assuming zero heat loss).

Table 1 Furthermore, the porosity of steelmaking slag is as shown in equation (1) below, and varies depending on the grain size.

T: Unit volume weight (kg/l) Q: Water absorption rate of slag (%) Ds Surface dry specific gravity of varnish slag, that is, slag with a high porosity has a high vapor aeration rate, while slag with a low porosity has a high aeration rate. The speed is small. Therefore, the amount of steam used varies depending on the porosity, and even with the same porosity, it varies depending on the steam ejection speed.

In other words, the optimum jetting speed that reduces the amount of steam used differs depending on the porosity of the slag.

Figure 1 illustrates the relationship between steam ejection speed, steam aeration rate in the slag layer, and steam consumption rate in the case of converter slag. It becomes 150m/sec.

In addition, Figure 2 illustrates the relationship between the porosity of converter slag, the optimum steam injection rate, and the steam consumption unit, and shows that the optimum injection rate of steam that minimizes the amount of steam used differs depending on the porosity of the slag. I understand.

Therefore, in the present invention, the slag porosity that minimizes the amount of superheated steam used is determined, and the steelmaking slag is aged at the optimal steam flow rate.

In addition, as a method of controlling the steam flow rate, a method can be adopted in which a solenoid valve is used as an on-off valve of a steam pipe and the valve opening degree is electrically controlled.

Embodiment Figures 3 and 4 schematically illustrate aging equipment for carrying out the method of this invention. It is a figure (1
) is a slag treatment tank made of concrete, (2) is a steam supply main pipe, (3) is a steam injection pipe, (4) is a solenoid valve for regulating steam flow rate, (5) is a porosity calculator, (6) is (7) is a crushed stone layer, (8) is a steelmaking slag layer, and (9) is a vinyl sheet.

That is, the above-mentioned equipment calculates the porosity of the steelmaking slag layer (8), calculates the optimum steam jetting speed from this porosity, and controls the solenoid valve (4) according to the calculated value. be.

In addition, in the above equipment, the crushed stone layer (7) was provided between the steam injection pipe (3) and the steelmaking slag layer (8) to simplify the loading and unloading of slag and to ensure stable steam ventilation. This is to ensure uniform diffusion of steam into the steelmaking slag layer. Further, if necessary, a structure may be adopted in which a heat insulating material or the like is attached to the inner circumferential wall or outer circumferential wall of the slag treatment tank (1) to prevent heat loss of the steam.

Converter slag was steam aged at 300 T/time using the above aging equipment. In this example, superheated steam (200° C., 9 atm) was used as the steam.

Further, the porosity of the slag layer was 41.7%, and the steam ejection speed was 147 m/see.

For comparison, normal saturated steam (1
The same converter slag was steam aged using a temperature of 1.8 atm (00°C, 1.8 atm).

As a result, the amount of steam required to raise the temperature of converter slag from room temperature to 100°C (steam aerated through the slag layer) was 153 tons (510 kg/T) of saturated steam; Then, 16 tons of superheated steam (53 kg/T
- Slag) and steam consumption were significantly reduced.

Further, Table 3 shows the results of investigating the amount of water immersion expansion of converter slag subjected to steam aging according to the method of the present invention. As is clear from the results in Table 3, the amount of expansion is 0.3% or less, and it can be fully used as a roadbed material.

*Asphalt Paving Guidelines Standards゛≦1.5 As explained in detail about the invention, this invention is a method of aging treatment using superheated steam with high enthalpy and controlling the amount of steam used according to the slag porosity. As a result, the amount of steam used can be significantly reduced, reducing aging treatment costs, and the expansion of slag can be significantly reduced, producing high-quality slag that can be used as roadbed material. It has a great effect on the aging treatment of steelmaking slag.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between steam ejection speed, steam slag aeration rate, and steam consumption rate in the case of converter slag, and Figure 2
The figure is a diagram showing the relationship between the porosity of converter slag, the optimum steam ejection speed, and the steam consumption unit; Figure 3 is a schematic plan view showing an example of aging treatment equipment for carrying out the method of the present invention; Figure 4 is a longitudinal sectional front view taken along line IV-IV in FIG. 3; 1...Slag treatment tank 2...Steam supply main pipe 3...
Steam injection pipe 4 Solenoid valve 5...Porosity calculator 6...Steam injection rate calculation controller 7...Crushed stone layer 8/Steelmaking slag layer Applicant: Sumitomo Metal Industries, Ltd. ) Wave ``Katsukari Katsumi (ru ka) m city merchant EJt excretion Y (09 sea) men 款冑υ 71 minato W brainsou (↓ 4 me) Fusaku Soracho mae) Zhang ■

Claims (1)

[Claims] A method for aging steelmaking slag using steam under atmospheric pressure, characterized in that superheated steam is used as the steam, and the amount of superheated steam used is controlled according to the porosity of the slag to be treated. Aging treatment method.