JPH0249376B2 - - Google Patents

Description

[Detailed description of the invention]

Dust and sludge (hereinafter referred to as dust) generally generated from steel factories include zinc oxide, lead oxide,
Since it contains toxic heavy metals such as cadmium oxide and far exceeds the disposal standards for industrial waste, it is a pollution problem to dispose of it as it is, and it is difficult to dispose of it, and it costs a lot of money to dispose of it. It takes. On the other hand, slag generated in large quantities from steel factories is discharged as high-temperature slag, and although it has a large amount of thermal energy, it is left unused and wasted to cool. The present inventors paid attention to these problems and invented a treatment method that utilizes the sensible heat of the molten slag to turn dust into molten slag and remove and recover harmful heavy metals. As shown in Japanese Patent Publication No. 51-145528, an application has already been filed, and as an improved method, prior to converting the dust into slag, preliminary roasting is performed and the dust is heated during slag in a high temperature state. A method of reacting with the above has been filed as Japanese Patent Application No. 58-236755. The present invention enables the roasting of dust in these dust processing methods to be carried out efficiently with simpler equipment.The gist of the present invention is to mix a small amount of coke powder with dust and roast it into briquettes or pellets. After the slag is agglomerated, it is filled into a pallet-shaped roasting box with ventilation holes on the bottom to a layer thickness of 200 mm to 600 mm, and placed on top of the high-temperature slag discharged from the steelmaking furnace in the roasting box. The dust on the bottom is ignited, and after ignition, the roaster is left in a place where the smoke from the roasting can be collected and the dust can be collected and roasted through natural ventilation. The method of the present application will be described in detail below based on explanatory diagrams.
Figure 1 shows the structure of the dust roasting box. 1 is the roasting box body, 2 is the bottom with grid-like ventilation holes, and 3 is removable partitions inserted vertically at 500 mm intervals. The board shows a 200mm agglomerated material 4 made by mixing dust with coke powder, etc.
It is filled to a layer thickness of ~600 mm, and the heat source from below ignites the soul compound at the bottom, which is then roasted using natural ventilation. However, if the packed layer thickness is thinner, the dust roasting after ignition is reduced. If the firing temperature is insufficient and the packed layer thickness is too thick, the roasting time will be significantly delayed and at the same time the dust roasting temperature will become too high, causing a sintering phenomenon, which is undesirable. The temperature for roasting the dust is preferably about 900 to 1000°C, which reduces and volatilizes harmful heavy metals but does not cause sintering. When roasting with natural ventilation, it is appropriate to set the packed layer thickness to 200 mm to 600 mm. be. Partition plate 3 is roasting box 1
It is not necessary for small-sized cases with a side of 500 mm or less, but for large-sized cases, it serves to evenly roast the packed agglomerate 4, and the ventilation resistance of the packed bed can be adjusted appropriately. It has the effect of creating a wide filling layer, and must be placed vertically at intervals of 500mm.
However, the spacing between the partition plates has a correlation with the packed layer thickness.
The method of the present invention is characterized in that the larger the packed layer thickness, the narrower the distance between the partition plates, and the roasting time and roasting temperature are controlled by these adjustments. Note that iron is sufficient as the material for the roasting box and partition plate, but this does not preclude lining with refractory material or colorizing treatment. Figure 2 shows the dust treatment process when the method of the present invention is used in the preliminary roasting process, in which a roasting box 1 filled with dust agglomerates 4 is placed on top of the slag 14 that has undergone the dust charging process. The ignited roasting box 5 is left in a hood 9 connected to a dust collector and roasted by natural ventilation. to complete. The dust agglomerates 4 ignited at the bottom are moved to the upper part of the combustion layer 6 by natural ventilation, and the whole is roasted to a red-hot high temperature. At this time, the inside of the packed bed 7 becomes high temperature and is heated by coke powder. A reducing atmosphere is created, and oxides of harmful heavy metals such as Zn, Pb, and Cd are reduced and volatilized and collected in a dust collector as white smoke. When the roasting is left until the roasting is completed, a large number of roasting boxes may be stacked on top of each other, but in this case, consideration must be given to not impeding ventilation from below. Next, some of the harmful heavy metals are removed through the above roasting process, and the dust agglomerates are heated to a high temperature.
The molten slag is transferred to a hopper 8 for charging the slag, and is charged into the slag 12 discharged from the steelmaking furnace 10 and moved into the dust collection hood 11 while still at a high temperature, and then heated by a bubbling lance 13 using high-pressure gas. As the mixture is stirred, it is completely converted into slag. Through this treatment reaction, some harmful heavy metals remaining after roasting are completely volatilized and collected and collected, completing the dust pollution-free treatment. Examples will be described below. <Example> 100 parts by weight of ordinary steel electric furnace dust, 15 parts by weight of coke powder, and 5 parts by weight of bentonite were kneaded to make charcoal-like briquettes,
It was charged into a 1000 mm deep iron roasting box with a depth of 700 mm so that the packed layer thickness was 500 mm, and the result was placed on about 3 tons of electric furnace slag (surface temperature 600℃) and roasted. When a cross-shaped partition plate is inserted in the direction (the distance between the main body and the partition plate is 500 mm),
A comparison with the case without the partition plate shows the following results.

[Table] This shows that when using a partition plate, the roasting time is short and even roasting is possible. In addition, the results of an analytical comparison of changes in the amount of heavy metal components in the dust due to roasting are as shown in the table below, and the removal rate of heavy metal components is also higher when using the partition plate, indicating good results.

[Table] As explained above, the method of the present invention uses steelmaking dust,
This process can be carried out by simply preparing a simple roasting box to make sludge non-polluting, and can be applied in small-scale factories as a low-cost method of non-polluting processing. The effect is that it has great significance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a roasting box used in the present invention, and FIG. 2 is a schematic diagram showing the steps of the method of the present invention.

Claims (1)

[Scope of Claims] 1 Dust and sludge containing harmful heavy metals generated during steelmaking operations are kneaded with a single carbon fuel consisting of coke powder or a mixed fuel with liquid fuel added to form briquettes or pellets. After the formation, the torrefaction box with ventilation holes at the bottom is filled with a layer thickness of 200 mm to 600 mm, the dust and sludge are ignited by a heat source from below, and the torrefaction box is placed in a dust collector. Connect it and leave it in the hood,
A method of roasting dust and sludge, which is characterized by roasting with natural ventilation to reduce and volatilize the heavy metals contained. 2. The dust according to claim 1, characterized in that the agglomerated product of dust and sludge is roasted by inserting a partition plate vertically into the roasting box.
Suratji roasting method.