JPH01310290A - Furnace constructing structure for rotary furnace - Google Patents

Abstract

PURPOSE:To permit the loading of bulk material in a high density near the discharging end of the material without accumulating powder material in the furnace by providing a comb-type dam at the discharging end of the material in a rotary furnace. CONSTITUTION:A comb-type dam 3 having notches 4 is provided in order to maintain a loading factor at a predetermined value without stagnating powder material at the lower part of a material layer near the discharging end of the material. The area ratio and the number of the notched parts 4 are different depending on the properties of material to be processed, however, 1 to 10% of the area of the dam supposed to have no notch and 4 to 10 pieces are optimum. When a pellet, having the diameter of 10 to 20mm and including the ores of chrome and coke, is reduced and roasted practically, a relation between the height H of the dam and a packing factor alpha should preferably satisfy the relation of {(the inner diameter of furnace D - the height of dam H)/(the inner diameter of furnace D)}<2> 1 - packing factor alpha.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a furnace construction structure for a rotary furnace, and more specifically, to a furnace construction structure near the discharge end of a rotary furnace for increasing the filling rate of raw materials. be.

[Conventional technology]

A rotary kiln has a cylindrical furnace body installed at an angle, and as the furnace body rotates, the charged raw material inside the furnace is heated and moves forward. Therefore, the raw materials are well mixed and there is little variation in the product, so it is suitable for mass production in the ceramic industry such as cement, limestone, alumina, magnesha, etc.
Widely used in metallurgical fields such as nickel and chromium.

In general, the residence time of raw materials in a rotary furnace is determined by the angle of repose of the raw materials, the rotation conditions of the furnace, etc. Adjusted by number.

As shown in FIG. 5, the construction of the raw material discharge end of a typical rotary furnace is made of standard-shaped bricks and is flat.

In this case, the residence time of the raw material in the furnace is, for example, Zablot
It is given by the equation of on7 or the equation of Sulivan (see "Process Kiln" edited by Japan Powder Industry Technology Association, Nikkan Kogyo Shimbun Co., column 2.65).

Increasing the filling rate can be achieved to some extent by adjusting each of the above factors.

Furthermore, as shown in FIG. 6, it is common practice to provide a bottle as a furnace structure at the raw material discharge end. However, as shown in Fig. 6, increasing the height of the entire circumferential direction causes small-sized raw materials to sink to the bottom of the raw material layer, and fine-grained raw materials accumulate near the weir, making it less effective in improving the filling rate. Does not perform well. Especially when using bulk raw materials such as granules such as metallurgical raw materials, the particle size distribution of the raw materials also has a wide range.
In addition, mixing of powder raw materials is unavoidable, and when trying to increase the reduction rate by increasing the residence time in the furnace of raw materials with a large particle size,
The filling rate near the raw material discharge end becomes a problem.

[Problem to be solved by the invention]

When using a rotary furnace as a metallurgical reduction device.

Since heat transfer to the raw material is carried out by radiation heat transfer and conductive heat transfer from the inner wall of the rotary furnace, it goes without saying that in order to increase the reduction rate, it is advantageous to make the residence time as long as possible with a high filling rate. However, in the conventional flat raw material discharge end structure as shown in Figure 5, the raw material is discharged at an angle of repose, so the filling rate near the discharge end decreases, and therefore the filling rate in the high temperature zone near the discharge port decreases. The residence time becomes short, making it impossible to achieve a high reduction rate.

In addition, with conventional weirs where the entire raw material discharge end is raised,
Powdered raw materials remain at the bottom of the raw material bed, impeding conductive heat transfer from the inner wall of the furnace to the raw materials, and not only does the reduction rate not improve.
The temperature of the powdered raw material gradually rises, and eventually it starts to adhere to the inner wall, causing a dam ring to gradually grow, which not only causes the weir to lose its effectiveness, but also eventually becomes inoperable. It had

[Means to solve the problem]

The present invention provides a comb-shaped weir 3 having notches 4 as shown in FIG. 1 as a method for maintaining the filling rate at a predetermined value without causing the powder raw material to stagnate in the lower part of the raw material layer near the raw material discharge end. method was adopted.

In Figure 1, the area ratio and number of the notched portions 40 vary depending on the properties of the raw material to be processed, but they are approximately 1 to 10% of the area of the poetry weir without notches, and the number is 4 to '+0.
It is appropriate to set the number to 1. If the area ratio of the cutout portion is too large, it will not function as a weir, and if it is too small, powder raw materials will accumulate in the furnace.

Also, if there are too many notches, the cross-sectional area of each piece will become too small, making it impossible to smoothly discharge the product.
It is desirable that the number be 0 or less.

Specifically, a case where coke-filled pellets of chrome ore having a diameter of 10 to 20 cm is reduced and roasted will be explained as an example.

The pellet size is 10-20 layers 1, and the dust generated by transfer in the furnace is 1+u+ or less. Therefore 10
Pellets larger than mm should be kept in the furnace for as long as possible.
We want to increase the reduction rate, and on the other hand, we want to discharge powdered raw materials such as dust out of the furnace as quickly as possible.

Under the above circumstances, as a result of examining various weir shapes, it was found that the relationship between the weir height H and the filling rate α is as shown in Figure 7, and it is best to satisfy the following relationship.

For example, in a rotary furnace with an inner diameter of 1.35 m1k, the filling rate is 40%.
If this is desired, the appropriate height H of the weir is Hζ0.3m.

If there is no bottle, the repose angle of the pellets is 30 degrees, so the filling rate can only be about 7%, but the effect of providing the weir is significant.

Next, the notch width d was set to 10+w layer width, which is the lower limit of pellet size control, as shown in FIG. 1(b).

Eight notches were provided in the circumferential direction of the weir. In this case, the ratio of the notch area to the total area is about 2.4%. Figure 2 shows the appearance of the furnace structure at the top.

The shape of the notch may be a concave shape as shown in FIG. 1(b), or may be a 7-shaped shape as shown in FIG. 3(a). When configured in a figure 7 shape, only the fine dust-like raw material at the bottom of the raw material layer can be discharged to the outside of the furnace. Furthermore, as shown in Fig. 3(b), the notch width d1 outside the raw material layer may be smaller than the notch width d2 outside the furnace (dl<d2). There is less chance that raw materials will get stuck in the notches, and the filter effect will be better exhibited.

It is sufficient that the width (W) of the weir is 100 to 200 mm. The weir is usually constructed by making the terminal refractories of the rotary furnace from deformed refractories.

[Effect]

As explained above, by configuring the refractory at the raw material discharge end of the rotary furnace, the dust generated by the abrasion of the raw material is discharged outside the furnace, but the raw material with large particle size is stopped by the weir, and the high temperature at the end of the furnace is Since it can be allowed to stay in the tank for a long time, the reduction reaction can be further accelerated.

〔Example〕

Bentonite and water are added to chromium ore and coke powder that have been finely ground to 200 mesh passes or more than 80%, and granulated into pellets with a diameter of 0 to 15 m11. After drying,
Solid phase reduction was carried out using an indirect heating rotary furnace with the structure shown in the figure. As shown in Fig. 4(b), the restrained heating type rotary furnace has 6
The combustion chamber and reaction chamber are separated by a ceramic shielding plate.

At the raw material discharge end, there is a height of 30 mm as shown in Figure 2.
Six comb-shaped weirs with a width of 10mm and a thickness of 100mm were installed.

Charge raw materials in 1. Reduction treatment was performed at a rate of Bt/h.

The maximum heating temperature was 1430° C., and the target reduction rate was 96.5% or more for chromium reduction and 98.0% or more for iron reduction. The amount of kerosene required at this time was 243 kg/h.

For comparison, when using an indirect heating type rotary kiln similar to the example shown in FIG. The amount of kerosene required was only 1.4 tons, and the amount of kerosene required was 255 kg/h. From this result, 1. When using the furnace construction structure of the present invention, the filling rate in the high temperature section increases.

It can be seen that the residence time becomes longer and the reduction is further promoted. As a result, processing capacity increased by 14%, and kerosene consumption per unit increased by 30%.
This means that kg/ton of pellets can be reduced.

〔effect〕

According to the present invention, it is possible to densely pack the bulk raw material near the raw material discharge end without depositing the powder raw material in the furnace, and the residence time of the raw material in the high temperature zone can be increased. This can be particularly effective in indirectly heated rotary furnaces.

By using the present invention, it has become possible to reduce ores that are difficult to reduce, such as chromium ore, by indirect heating on a commercial production basis.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the furnace construction structure of the rotary furnace of the present invention, (a)
is a cross section parallel to the rotation axis, and (b) is a cross section perpendicular to the rotation axis. FIG. 2 is a diagram showing the appearance of the furnace construction structure of the upper part of the present invention. FIG. 3 is a diagram showing another embodiment of the present invention, in which (a) shows a cross section perpendicular to the rotation axis, and (b) shows the external appearance. Figure 4 is a diagram showing the structure of an indirect heating rotary furnace used in an example of the present invention, (a) is a cross section parallel to the rotation axis, (b)
is the cross section perpendicular to the axis of rotation. FIG. 5 is a diagram showing the construction structure of a conventional rotary furnace, in which (a) is a cross section parallel to the rotation axis, and (b) is a cross section perpendicular to the rotation axis. FIG. 6 is a diagram showing another example of the construction structure of a conventional rotary furnace, in which (a) is a cross section parallel to the rotation axis, and (b) is a cross section perpendicular to the rotation axis. FIG. 7 is a diagram showing the relationship between the height of the weir and the raw material filling rate. 1... Iron skin 2... Firebrick 3... Weir 4...
・Notch 5...Reaction chamber 6...
... Heating chamber 7 ... Support ring 8 ...
... Roller tire 9 ... Smoke exhaust box
10... Burner 11... Burner 12... Combustion furnace 13... Flue 14... Shielding plate 15...
...Exhaust hole 16...Raw material discharge hole 1
7... Raw material discharge chute 18... End plate 19... Raw material input pipe 20, old... Rotary furnace body 21-, - +-6 4 Figure 1 (CL) (b) Figure 3 (b) Figure 4 Figure 5 (Q) (b) Figure 6

Claims (3)

[Claims] (1) A construction structure for a rotary furnace characterized by providing a comb-shaped weir at the raw material discharge end of the rotary furnace. (2) The construction structure of a rotary furnace according to claim 1, wherein the rotary furnace is of an indirect heating type. (3) The furnace construction structure for a rotary furnace according to claim 1 or 2, wherein the cut of the comb-shaped weir is narrower toward the inside of the rotary furnace.