JPH10182196A - Production of rigid granulated blast furnace slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce a rigid granulated blast furnace slag by specifying conditions of the flow rate of spray water/flow rate of a molten blast furnace slag (weight ratio) and water temperature in a granulating tank. SOLUTION: A rigid granulated blast furnace slag is produced under conditions of >=30 value of the flow rate of spray water/flow rate of a molten blast furnace slag (weight ratio) and <95 deg.C water temperature in a granulating tank in a step for granulating the molten blast furnace slag and producing the granulated blast furnace slag. Although the slag in an intactly granulated state does not satisfy >=1.45kg/L unit volume mass which is the JIS standard, the unit volume mass of the granulated slag having >=1.35kg/L is surely improved to >=1.45kg/L unit volume mass by crushing the granulated slag and regulating the grain size thereof. Thereby, the granulated slag may be produced under granulating conditions of >=1.35kg/L unit volume mass of the slag. For that purpose, the ratio of the flow rate of the spray water/flow rate of the molten blast furnace slag is initially regulated to >=30 and the water temperature in the granulating tank is regulated to <95 deg.C. This is because the amount of generated steam is large when spraying water and cooling the slag and the amount of the present closed pores after the cooling is increased to reduce the bone-dry specific gravity (apparent density) and further the unit volume mass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing hard granulated blast furnace slag from molten blast furnace slag.

[0002]

2. Description of the Related Art Blast furnace slag is generated in Japan alone at about 23 million tons per year, of which more than 60%, more than 14 million tons, were obtained by directly spraying water onto molten slag and rapidly cooling it. It is used as granulated slag. Granulated slag is classified into soft granulated slag for cement raw materials and hard granulated slag for fine aggregate for concrete according to its properties.

The required characteristics of hard granulated slag for fine aggregate for concrete are specified in JIS A 5011. As shown in FIG. 8, a general method for producing soft granulated slag is to install a blowing box 4 at the tip of a slag gutter 21 of a blast furnace 1 and to flow molten slag 3 into the blowing box 4 while blowing water. 2 is a method of spraying the molten slag 3 from a nozzle installed in the blowing box 4 to rapidly cool and solidify it.

The produced granulated slag is shipped separately from water. One example of a separation method is a distributor 9 inside a cylindrical filter 8 as shown in FIG.
And is stored in the product tank hopper 15 via the belt conveyor 10 after draining. The separated water is sent from the hot water tank 7 below the filter 8 to the cooling tower 13,
Water for the granulation by pump 17 again
Used as

[0005] Soft granulated slag for cement raw materials which can be produced by the above-mentioned method for producing soft granulated slag is mainly composed of soft water granulated slag because it has a low unit mass and absolute dry weight and does not satisfy the above-mentioned standards. It must be produced separately from crushed slag. Conventionally, as a method for producing hard granulated blast furnace slag, a method has been employed in which slag discharged from a blast furnace is once put into a slag pot and then granulated.

According to this method, when the slag is received in the slag pot or when the slag pot is transported to the water granulation equipment, the slag temperature is lowered. Granulated slag is obtained. However, although this method is a method to obtain hard granulated blast furnace slag,
If there is already soft granulated slag production equipment on the blast furnace equipment side,
Having such a new hard blast furnace granulated slag production facility complicates the facility and imposes a heavy burden on the economy.

In this method, it is an essential condition for producing hard granulated blast furnace slag by receiving slag in a slag pot and reducing the slag temperature. The slag that can be effectively used as hard blast furnace granulated slag has a low yield of about 50 to 70% of the slag received and removes solidified slag attached to the pot bottom. Has the problem that it takes a lot of time.

Further, other methods for obtaining hard granulated blast furnace slag include slag temperature reduction during granulation, addition of a nucleating agent, and blowing of oxygen. The method is not suitable for mass production and has not been adopted on a commercial scale. Japanese Patent Application Laid-Open Nos. 55-136150 and 55-1361 disclose a method for producing hard granulated blast furnace slag with equipment having a blow box installed at the tip of a slag gutter of a blast furnace cast floor.
In Japanese Patent Publication No. 51, the ratio of the amount of blown water to the amount of slag for granulation is specified to be 8 to 12, and the amount of water / slag in the subsequent granulation tank is set to 10 or more, or the water granulation tank is A method is disclosed in which the water temperature is reduced to 70 ° C. or lower.

Japanese Patent Application Laid-Open No. Sho 59-121140 discloses a method of adjusting the blowing water flow rate from a nozzle hole of a blowing box to 13 to 20 m / s. The present inventors varied the slag flow rate and the blowing water volume, and investigated the relationship between the unit volume and mass of the granulated slag to be produced. As a result, good results were not always obtained under the conditions specified in the above-mentioned conventional technique. .

That is, the ratio of the amount of blowing water to the amount of slag is 8 to
Even if the amount of water in the granulation tank / the amount of slag is set to 10 or more as 12, hard granulated slag can be obtained only at the initial timing of granulation production, and the ratio of the amount of blown water to the amount of slag is 8
Even if you try to keep the water temperature of the granulation tank below 70 ° C as ~ 12,
The water temperature quickly rose to 70 ° C or higher, and it could not be adopted unless facilities for cooling blown water were installed.

In the method of adjusting the flow rate of the blowing water in the range of 13 to 20 m / s, if the flow rate of the blowing water is reduced, hard granulated blast furnace slag cannot be produced even if the flow rate is increased. It was not a reliable method. At present, as a method for producing hard blast furnace granulated slag, a method is employed in which soft granulated slag is produced by using a soft granulated slag production facility, and a method that selects hard granulated slag that meets the conditions of the hard granulated slag is employed. ing.

One method is to take several samples each time tapping is performed, measure the specific gravity of the sample, and convert the high specific gravity to a hard granulated blast furnace slag.
There is a disadvantage that hard granulated slag of a required production amount cannot be produced systematically because it is only after the subsequent inspection that hard granulated slag or soft granulated slag is determined. As another method, in the blast furnace, the amount of discharged slag is small from the start of slag to a certain time, and the slag temperature when supplied to the granulated slag production equipment is low, so that the specific gravity is relatively high. Since granulated slag can be produced, a method of separating and sorting granulated slag from hardened granulated slag made from slag discharged during a certain period of time from the start of slag removal is also employed.

However, in the blast furnace, the outflow situation of the slag changes for each tapping, so that the time during which the granulated slag having a high specific gravity can be manufactured changes, and as described above, a certain time after the start of the slagging. When separating granulated slag from the slag discharged in between as hard blast furnace granulated slag, the specific gravity of the granulated slag immediately after separation is too low, and the slag that has passed the time is hard blast furnace slag. Poor separation efficiency, which can result in crushed slag, poses a problem.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing hard granulated blast furnace slag which can be efficiently and mass-produced in a granulated slag manufacturing facility directly connected to a blast furnace.

[0015]

A first aspect of the present invention is a process for granulating molten blast furnace slag to produce granulated slag.
Hard blast furnace granulated slag characterized by producing hard granulated slag under the condition that the value of blowing water flow rate / melted blast furnace slag flow rate (weight ratio) is 30 or more and the water temperature in the granulated tank is less than 95 ° C. It is a manufacturing method of.

A second invention is to granulate molten blast furnace slag,
In the process of manufacturing granulated slag, the flow rate of blown water and the production amount of granulated slag are measured, and the flow rate of molten blast furnace slag is determined from the production amount of granulated slag. The method for producing hard granulated blast furnace slag according to claim 1, wherein the granulated blast furnace slag is manufactured with a value of 30 or more.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The operating conditions of a general soft granulated slag production facility and the change over time of the unit mass of the granulated slag were investigated.
The unit mass of the granulated slag in the early stage of tapping was high, but the unit mass in the latter half of tapping tended to decrease with time.

FIG. 1 shows an example of the operating conditions and changes over time of the granulated slag. The data collection items are slag temperature, blowing water temperature, granulation tank temperature, slag flow rate, unit mass, and water / slag ratio (ratio of blowing water flow rate and slag flow rate). Here, the slag flow rate is the amount of water corrected from the weighed value of the granulated slag by the weighing device attached to the belt conveyor that transports the granulated slag from the filter to the product hopper, and the slag is transported to the product tank after draining. Samples were collected every 5 to 10 minutes on the way, and after drying, the mass per unit volume was measured.
In the early stage of tapping, the slag temperature is low and the slag flow rate is low.

In the condition as it is after granulation, the hard blast furnace granulated slag has a unit mass of JIS standard of 1.45 kg / l or more.
There is nothing that satisfies the requirements, but by crushing and adjusting the particle size, those with 1.35 kg / l or more surely have a unit volume mass of 1.45 kg.
/ l or more. Therefore, the production conditions for granulation are:
The unit volume mass may be 1.35 kg / l or more. In the case of FIG. 1, if slag having a unit mass of ≧ 1.35 kg / l or more can be made into hard blast furnace granulated slag, the hard blast furnace slag can be formed from the start of tapping for about 120 minutes. The relationship between the blowing water flow rate / melting blast furnace slag flow rate (hereinafter referred to as water / slag ratio) and the unit volume mass at the timing of blowing the collected granulated slag is as shown in FIG.
It was found that when the slag ratio was ≧ 30, the mass per unit volume was ≧ 1.35 kg / l.

If the water temperature is sufficiently low, such as 50 to 60 ° C. or less, the slag can be cooled by increasing the water temperature even if the water / slag ratio is about 10, but the water temperature becomes high and the slag becomes 70 ° C.
Under the above high conditions, the water temperature reaches 100 ° C. immediately after blowing, and steam is generated. As the generation of steam increases, as shown in FIG. 3, the amount of bubbles in the granulated slag increases, and the mass per unit volume decreases. In actual water granulation equipment, blowing water is circulated and used.
It is difficult to control the temperature below 50-60 ° C, especially at the end of tapping and continuous water granulation, and in summer, the blowing water temperature will be 70 ° C or more. Under such conditions, a water / slag ratio ≧ 30 is required as a condition under which hard blast furnace granulation is always obtained.

As can be seen from FIG. 2, the water / slag ratio is 30
If this is the case, the unit volume mass will be approximately 1.35 kg / l or more, and since the effect of the water / slag ratio is small, it is not necessary to aim for a very large water / slag ratio. However, since the slag flow rate increases in the latter half of tapping, if the blowing water flow rate is increased in accordance with the increase in the slag flow rate and the water / slag ratio can be maintained at 30 or more, the yield of hard granulated slag can be improved. Therefore,
If the blowing water amount is controlled according to the slag flow rate, the whole tapping period can be made into hard granulated slag, and each production amount can be controlled according to the demand of hard granulated slag and soft granulated slag.

Even if the water / slag ratio is 30 or more, when the water temperature in the granulation tank reaches 95 ° C. or more, the unit mass decreases as shown in FIG. The reason is as follows. The unit mass of the granulated blast furnace slag, that is, the bulk specific gravity, is determined by two factors. One is the amount of closed pores in the granulated slag, and the other is due to the particle size distribution and appearance properties.
The amount of closed pores determines the absolute density (apparent density), which is the density of the granulated slag itself. According to the conventional research results, a mixed gas of hydrogen gas and nitrogen gas is known to exist in the closed pores. According to the measurement results of the present inventors, it was found that the compound was present at a ratio of H ₂ : N ₂ = 3: 1. It is considered that the formation of the closed pores was caused by the fact that water that had come into contact with the slag during cooling became water vapor and was dissolved in the slag and reacted with dissolved nitrogen in the slag. From this fact, in a granulation tank in which water and slag are present together with water immediately after granulation, under conditions where the water temperature has already reached 95 ° C or higher, a large amount of steam is generated during blown cooling, and Since the abundance of the closed pores increases, the absolute specific gravity decreases, and the mass per unit volume decreases. Therefore, at least the water temperature in the granulator should not reach 95 ° C.

[0023]

FIG. 4 shows an outline of a granulated slag producing apparatus used in the present invention. The blown water 2 is sprayed on the molten slag 3 falling in the blowing box 4 to granulate the water, and then the cooled and solidified slag enters the granulating tank 5 together with the water. Then, after the granulated slag and water are separated by the cylindrical filter 8, the granulated slag is separated from the product tank hopper 15.
Transport by belt conveyor 10 until A weighing device 14 is provided in the middle of the belt conveyor, and continuously measures the granulated slag production amount. Since the granulated slag on the belt conveyor contains water, the amount obtained by subtracting the amount of water is the molten slag flow rate.

The amount of water in the granulated slag may be measured using a moisture meter or the like along the path from the filter 8 to the product tank hopper 15, or the amount of water in the granulated slag after draining by the above-described draining device may be measured. Since the water content ratio does not change so much even if the production amount or blowing water volume of the granulated water is changed, the water content ratio after draining is measured in advance to determine a correction value, and the water granulated slag production amount is determined. A correction for subtracting a fixed amount of water may be performed.

In the case of this equipment, it takes about 3 minutes for the slag to reach the weighing device 14 after the slag is granulated by the blow making box 4. The value obtained by correcting the moisture with the correction value determined by measuring is the molten slag flow rate three minutes ago. In addition, this equipment has a product tank hopper 15
Are arranged in two tanks, and by operating the switching damper 16, the granulated slag transported by the belt conveyor can be sorted.

Blast furnace output 7800-8000t / day, slag ratio approx.
The method of the present invention was carried out during operation at 320 kg / t and tapping temperature of 1495 to 1505 ° C. Water granulation was performed under the conditions of blowing water amounts of 50 m ³ / min and 60 m ³ / min. After tapping, water is blown, and water granulation is started when slag starts to flow. About 20 tons after the start of granulation, there are many impurities such as ingots and flakes remaining in the gutter, so the switching damper 16 is manually operated and put into the hopper on the soft granulated slag side of the product tank hopper. After flowing about 20 tons, the damper was switched to the hard granulated slag side.

Since the flow rate of the molten slag increases with the elapse of time after the start of slagging, when the flow rate of the molten slag reaches an average of 1.7 t / min when the blown water flow rate is 50 m ³ / min, the flow rate of the blown water is 60 m ³ / min. ^{At 3} / min, the average molten slag flow rate is 2.0t / min
When it became, the changeover damper was switched and put into the product tank hopper on the soft granulated slag side. Since the flow rate of the molten slag is obtained by correcting from the weighed value of the weighing device on the belt conveyor, the fluctuation is as large as ± 0.5 t / min, but the control device 20 takes the time average and switches the damper when the above criterion is reached. Was performed.

When the temperature in the granulating tank reaches 95 ° C. before the molten slag flow rate reaches the above-mentioned standard, the switching damper is switched at that point and the molten granulated slag is charged into the product hopper on the soft granulated slag side. . 5 or more samples were taken from each of the hard granulated slag and the soft granulated slag extracted from the separate product tank hoppers.
It became like. The unit mass of hard granulated slag is 1.35
~ 1.45 kg / l, unit weight of soft granulated slag is 1.15 ~ 1.
It was 38 kg / l. This granulated slag is crushed and granulated with a crusher as shown in Fig. 6, and all the hard granulated slag has a unit volume mass of 1.45 kg / l, which is the standard for fine aggregate for concrete.
Was satisfied.

FIG. 7 shows an example of the particle size distribution of the hard granulated slag, which is coarser than the standard before crushing and graining. As a result, the particle size was within the range of the hard granulated blast furnace slag shown by the dotted line.

[0030]

According to the method of the present invention, the existing granulated slag manufacturing equipment for cement is used without newly installing a hard blast furnace granulated slag facility, and without changing the operating conditions of the blast furnace. In addition, hard granulated slag that passes the fine aggregate standard for concrete can be separated and manufactured.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing time-dependent changes in water granulation production conditions and the unit mass of granulated slag during tapping.

FIG. 2 is a graph showing a relationship between a water / slag ratio and a unit mass per unit volume.

FIG. 3 is a graph showing a relationship between a unit volume mass and a granulation tank temperature.

FIG. 4 is a layout diagram of a granulated slag manufacturing apparatus used in the present invention.

FIG. 5 is a graph showing a unit volume mass of granulated blast furnace slag.

FIG. 6 is a graph showing a unit volume mass before and after crushing / granulation.

FIG. 7 is a graph showing the particle size distribution of hard granulated slag.

FIG. 8 is an explanatory view showing an example of a general hard granulated slag manufacturing apparatus.

[Explanation of symbols]

 1 Blast Furnace 2 Blow Making Water 3 Melting Slag 4 Blow Making Box 5 Granulator 6 Chimney 7 Hot Water Tank 8 Filter 9 Distributor 10 Belt Conveyor 11 Thermometer 12 Cold Water Tank 13 Cooling Tower 14 Weighing Device 15 Product Tank Hopper 16 Switching Damper 17 Pump 18 Valve 19 Steam 20 Control device 21 Slug gutter

Claims (2)

[Claims] In the process of granulating a molten blast furnace slag to produce a granulated slag, the value of blowing water flow rate / molten blast furnace slag flow rate (weight ratio) is 30 or more, and the water temperature in the granulating tank is 95 ° C. A method for producing hard granulated blast furnace slag, comprising producing hard granulated slag under the following conditions. 2. A process for granulating a molten blast furnace slag to produce granulated slag, measuring a blowing water flow rate and a granulated slag production amount, obtaining a molten blast furnace slag flow rate from the granulated slag production amount, 2. The method for producing a hard granulated blast furnace slag according to claim 1, wherein the value of the ratio of the flow rate of water production to the flow rate of the molten blast furnace slag (weight ratio) is 30 or more to produce the hard granulated slag.