JPS6115929A - Method for burning steel-making dust and sludge - Google Patents

Abstract

PURPOSE:To eliminate the pollution at low cost by kneading the dust generated in steel making and contg. harmful heavy metals, etc. with a carbonaceous fuel to form a briquette, and burning the briquette in a combustion box with a vent at the bottom under specified conditions to reduce and volatilize the metals. CONSTITUTION:A carbonaceous fuel such as coke powder is added to dust and sludge contg. harmful heavy metals, etc. and generated in a steel making operation, and the mixture is kneaded to form a briquette 4, which is packed into a combustion box body 1 equipped with a bottom surface part 2 and a partition plate 3 in 200-600mm. thickness. The box body 1 is placed on slag 14 wherein dust is already charged, and burnt with the sensible heat of the slag under natural ventilation. The harmful heavy metals are reduced and volatilized, and recovered. The briquette 4 from which a part of the heavy metals is removed is transferred into a hopper 8, charged into molten slag 12 discharged from a steel-making furnace 10 while keeping the briquette at high temps., agitated by the bubbling 13 of a high-pressure gas, and completely slagged into the molten slag.

Description

[Detailed Description of the Invention] Dust and sludge (hereinafter referred to as dust) generally generated from steel factories contain hazardous heavy metals such as zinc oxide, lead oxide, and cadmium oxide, and furthermore, they significantly exceed the disposal standards for industrial waste. In order to overcome this problem, it is a pollution problem to dispose of it as it is, and it is difficult to dispose of it, and a large amount of money is required to dispose of it. ' On the other hand, slag generated in large quantities from steel factories is discharged as high-temperature slag, and although it contains a large amount of thermal energy, it is left to cool unusedly.

The present inventors paid attention to these problems and invented a treatment method for converting dust into molten slag in slag using the sensible heat of slag and removing and recovering harmful heavy metals. ,
Patent Application No. 50-69268 has already been filed, and as an improvement on the method, a patent has been granted for a method in which the dust is pre-roasted and reacted with the hot dust in the slag before being converted into slag. 5g-, 236755.

It is a method that can be carried out more efficiently using simpler equipment than the conventional roasting method. Afterwards, a pallet-shaped roasting box with ventilation holes on the bottom is filled with a layer thickness of about 200 mm to 600III11, and the roasting box is placed on top of the high-temperature slag discharged from the steelmaking furnace. The dust is ignited, and after ignition, the roasting process is carried out through natural ventilation by leaving it in a place where the smoke from the roasting can be collected and collected.

The method of the present application will be described in detail below based on explanatory diagrams.

Figure 1 shows the structure of the dust torrefaction box. (1) is the torrefaction box body, (2) is the bottom part with grid-like ventilation holes, and (3) is the vertical part at intervals of approximately 500 rnrn. It shows a removable partition plate that is inserted in the direction of
It is filled to a layer thickness of 0 mm to 600 mm, and a heat source from below ignites the soul compound at the bottom, which is then roasted with 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 be too high, causing a sintering phenomenon, which is undesirable.

The roasting temperature of the dust is such that harmful heavy metals are reduced and volatilized, and when roasted with natural ventilation, the packed layer thickness is approximately 200 mm.
It is appropriate to set it as mm - 600Iam. Partition plate (
3) The - side of the roasting box (1) is approximately 50011II1
It is not necessary in small cases of 1 or less, but in large cases it works to uniformly roast the filled soul compound (4), and has the effect of appropriately adjusting the ventilation resistance of the packed bed. , and should be inserted perpendicularly to the wide packed bed at intervals of about 50011 Im. However, the spacing between the partition plates is correlated with the thickness of the packed bed, and the larger the thickness of the packed bed, the narrower the gap between the partition plates. There are characteristics of the method.

It is sufficient that the roasting box and the partition plates are made of iron, but this does not preclude them from being lined with a refractory material or calorized.

Figure 2 shows the dust treatment process when the present method is used in the preliminary roasting process. (14) Place it on top and leave it for about 30 minutes to ignite the dust particles at the bottom of the roasting box by the sensible heat of the slag, and connect the ignited roasting box (5) to a dust collector. The dust particles (4) ignited at the bottom move upward through the combustion layer (8) due to natural ventilation, and are roasted to a red-hot temperature as a whole, but at this time, the inside of the packed layer (7) becomes high temperature. At the same time, a reducing atmosphere is created due to coke powder, and oxides such as Zn5PbXCd, which are harmful heavy metals, 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 by the above roasting process,
The dust particles, which have reached a high temperature as a whole, are transferred to a hopper (8) for charging molten slag, and the molten slag (12) is discharged from the steelmaking furnace (10) and moved into a dust collection hood (11). Inside,
The slag is poured into the slag at a high temperature and stirred by bubbling (13) using high-pressure gas, and is completely converted into slag.

Through this processing reaction, some harmful heavy metals that remain after roasting are completely volatilized and s! 1 is 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 briquettes9, 1000 rn in length and 1000 rn in width.
The result was charged into an iron roasting box with a depth of 700 mrn so that the packed layer thickness was 50 mrn, and was placed on electric furnace slag (surface temperature 600°C) of about 3 m and left to roast. A comparison between a case in which a cross-shaped partition plate (the distance between the main body and the partition plate is 5001 ntn) in the vertical direction and a case without a partition plate is as follows.

This shows that when the partition plate is used, 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.

As explained above, the method of the present invention can be carried out by simply preparing a simple roasting box for the purpose of decontaminating steelmaking dust and sludge, and can be done at low cost. This method can be applied in small-scale factories and has great industrial 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)

[Claims] 1. Briquettes, etc. are produced by kneading dust and sludge containing harmful heavy metals generated during steelmaking operations with a single carbon fuel such as coke powder or a mixed fuel with liquid fuel added. After the pellets are formed, they are packed in a roasting box with ventilation holes at the bottom to a layer thickness of approximately 200 mm to 600 mm, and the dust and sludge are ignited by a heat source from below. A method of roasting dust and sludge, which is characterized by leaving a roasting box in a hood connected to a dust collector and roasting with natural ventilation to reduce and volatilize the heavy metals contained. 2. It is characterized by inserting a partition plate vertically into the roasting box to roast dust and sludge.
A method for roasting dust and sludge according to claim 1.