JPS606692B2 - Firing method and furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to, for example, a method for firing magnetic iron oxide or lime, and a firing furnace.

[Purpose of the invention]

One object of the present invention is to disclose a method for calcining magnetic iron oxide using a vertical kiln with high thermal efficiency, and to provide a vertical furnace apparatus that does not cause defects that degrade the product during calcining.

Conventionally, when a rotary kiln is used for calcining magnetic iron oxide, the fuel consumption rate is 130 to 180 x 1 pk per ton of product.
It was cal.

In a rotary kiln, the specific sensible heat generated by the exhaust gas is large, and there is a large amount of heat dissipated from the furnace wall and leakage of air, so the basic unit is large. In the case of a rigid reactor, the fuel consumption rate in a small reactor is 20n/day.
It is 0 to 100×1 pkcal, and it has been found that the fuel consumption rate when scaled up to an actual state of 12 bn/day can be reduced to about 40×1 pkcal.

Currently, the quality of calcined magnetic iron oxide produced in hard furnaces is said to be slightly inferior to that produced in rotary kilns.

However, the vertical furnace of the present invention is of a natural fall type, and is used for drying and heating in the vertical furnace.

There are four cooling zones, that is, four steps. The material to be fired becomes a product through the above four steps. In the preliminary production of magnetic iron oxide, a rapid mixing short flame burner is used because the generation of reducing gas has a negative effect on the quality of the product.
○Use a two-stage combustion method to prevent the occurrence of x.

Further, the descent or advancement of the magnetic iron oxide in the furnace is performed by its own weight, and the discharge machine that causes the descent is a screw feeder whose rotation speed can be controlled.

In order to prevent blockage due to particles in the exhaust header, six suction holes are provided, and each suction hole has an inner cylinder attached to it.

To prevent bridging of the drying zone, increase the air volume so that the generated water vapor is rapidly sucked through the exhaust suction hole.

Moreover, by making the flow in the furnace active, the occurrence of bridging in the firing zone is prevented, and the phenomenon of expansion due to rising temperature of the raw material and fusion of the surface due to high temperature is prevented from occurring. The temperature of the hot gas in the firing zone is set to 1,200 to 13,000 C, which is lower than the melting temperature of magnetic iron oxide, which is 150,000, and the combustion gas is divided into a large amount of cocurrent flow and a small amount of countercurrent flow.

In order to keep the flame temperature in the combustion zone above 120,000, the side walls are wrapped with insulating bricks to prevent heat radiation and prevent the firing temperature in the furnace from decreasing. When the air ratio is set to 1.0, bridging tends to occur and the resulting fused material was examined by X-ray diffraction and was found to be ferrous oxide, which was determined to be due to the generation of reducing gas. Therefore, the air ratio is set to 1.05.
Control so that it does not fall below.

The combustion gas is divided into upper and lower parts so that the highest temperature point is slightly below the burner, and the furnace is designed to gradually become wider to prevent bridging from occurring. [Successful technology] Takenaka Corporation, one of the applicants of the present application, is the owner of the Samurai Gansho 51-1
58030 (Special Seki Sho 53-80400), filed a patent application for ``amorphous ferrite firing furnace''.

According to the claims, the content is a vertical furnace consisting of the following four constituent elements. 1. A cylindrical furnace body lined with refractory material is installed so as not to rotate in the vertical direction. 2. A fuel nozzle is installed in a penetrating tank around a predetermined height position on the same wall of the furnace body. An amorphous ferrite firing furnace comprising a cooling air nozzle installed in a penetrating shield, and a rotary table for receiving ferrite equipped with a rotationally driven scraping plate installed at a predetermined distance below the closed bottom end of the furnace body. A vertical furnace is used, which is taller than a vertical furnace, and drying, child heating, baking, and cooling zones are provided in the furnace.While the former is a countercurrent type, the present invention is a countercurrent type, mainly cocurrent flow. The firing furnace has a tapered structure with a small diameter at the top and a large diameter at the bottom to prevent the formation of bridges.

For taking out, instead of a rotary table, a screw type taking out means is provided which allows the amount taken out to be adjusted, and the raw material to be fired is fed by its own weight. [Configuration of the Invention] A magnetic iron oxide calcining furnace according to the present invention will be explained with reference to FIG. 1 showing an embodiment thereof.

This calcining furnace has a height of about ah, a warhead conical shape with an inner diameter of about 80 cm at the top and an inner diameter of 160 cm at the bottom.

Its inner peripheral wall is well protected with fireproof and heat insulating materials.
Supply means 2 for granulated magnetic iron oxide material at the top of the furnace
will be established. The supply means 2 is composed of, for example, a hopper and a supply pipe, and is a supply system in which when the material in the furnace falls downward, it naturally falls from above to below due to its own weight, and is successively replenished. Several gas burners 8, 8', . . . are provided on the inner circumferential wall of the furnace 1 at a suitable height position approximately in the middle, that is, at a position 5 at a height of about four skins.

Each of these gas burners 8 has a gas fuel supply pipe 0 and a wind box 9, and the ejection end thereof has a heat-resistant structure. Position 5 is maintained at a positive pressure of about 5 columns of water, and the fuel and air vigorously jetted out from gas burners 8, 8', . . . create a flame that reaches the center of the furnace. Suction pipes 14, 14', . . . are provided on the inner circumferential wall of the furnace 1 at a suitable position, for example, at a height of about 2 skins, at a height 6 of the furnace 1, with the suction ends of the suction pipes having a heat-resistant structure.

These suction pipes are put together by an annular pipe 15, and the annular pipe 15
is connected to a suction pipe of a blower 17 having a regulating valve 16. The control valve 16 can be adjusted to maintain a negative pressure of about one column of water at location 6 within the furnace. Since location 6 in the furnace is under negative pressure of about 1 column of water, most of the flame and hot combustion gases blown into location 5 in the furnace flow downward.

The hot combustion gases flow parallel to the descending material to be fired,
The temperature between position 5 and position 6 is maintained at an appropriate temperature of, for example, about 1,200 degrees Celsius, and a calcination reaction is carried out. position 5 and position 6
In between is the firing zone. Several cooling air injection holes 11, 11', . . . are provided in the furnace peripheral wall at a position 7 near the bottom of the furnace 1.

These cooling air jet holes 11 are connected to an annular pipe 12, and the annular pipe 12 is connected to a cooling air supply pipe having a control valve 13. Therefore, an appropriate amount of cooling air is blown into the furnace from the bottom position 7, flows upward, exchanges heat with the fired product, becomes high-temperature air, and then enters the suction pipe 14 at position 6.
is taken out of the furnace along with the firing gas. Between positions 6 and 7 is a cooling zone. A textbook blowout pipe 19 is installed around the furnace at a suitable upper part of the furnace 1, for example, at a height position 4 of about 6.
19'... is provided.

These ejection pipes 19 are connected to an annular pipe 20, and the annular pipe 20 is connected to the delivery pipe 18 of the blower 17 mentioned above. Therefore, a mixed gas of high-temperature combustion gas and high-temperature air is ejected from the ejection pipe 19. position 4
is maintained at the front of the ship, approximately IW in the water column. At this position 4, a relatively high temperature and a considerable amount of mercury gas is vigorously jetted out by the jetting pipe 19. Textbook discharge pipes 21, 21 are installed on the furnace peripheral wall at a position near the top of the furnace 1, that is, at a position 3 at a height of about 8 skins of the furnace 1.
'... is provided.

These discharge pipes 21 are combined into an annular pipe 22, which is connected to a suction pipe of a blower 24 having a regulating valve 23. Adjust the control valve 23 to set position 3 in the furnace.
can be maintained above a negative pressure of about 20 bars of water. Since position 3 in the furnace has a negative pressure of approximately 2 mm water column and position 4 has a positive pressure of approximately 1 mm water column, the mixed gas injected at position 41 actively rises through the material layer. By the time it reaches position 3 in the furnace, it exchanges heat with the raw material and reaches a fairly low temperature before being discharged through the discharge pipe 21.

The material is sufficiently dried and heated sufficiently from position 3 to position 4.

The area between positions 3 and 4 is a drying zone, and the area between positions 4 and 5 is a preheating zone. A product removal means 26 is provided at the bottom of the furnace 1.

The take-out means 26 is, for example, a screw conveyor,
It is possible to continuously take out a constant amount of pre-fired magnetic iron oxide that has already been fired and cooled to a reasonably low temperature by cooling air. In addition, due to this ejection, the raw materials are lowered into the furnace and the raw materials are supplied by their own weight falling from the supply means 2 at the top of the furnace, and the automatic supply and automatic fall of these materials are carried out to the extent that the firing furnace 1 is as described above. Because it is tapered, and because the inside of the furnace is activated by providing suction at three locations and two locations, it is possible to descend smoothly without causing bridging, and to perform the desired firing. The injection of the flame by the burner 8 and the injection of the mixed gas by the ejection pipe 19 are performed so that the pressure in the furnace at the positions 5 and 4 becomes the water column IQ skin and the water column 5 willow, respectively.
All of these jets can reach the center of the furnace. Figure 2 shows the pressure in each layer in the furnace and the air flow in the furnace in the calcining furnace for magnetic iron oxide in Figure 1, and Figure 3 shows the temperature in the calcining furnace for magnetic iron oxide in Figure 1. Show the distribution.

In the graph of FIG. 3, the vertical axis represents the height of the furnace, and the horizontal axis represents the temperature inside the furnace, indicating the temperature at each height within the pre-calcination furnace. In this graph, the area from position 3 to position 4 is the drying zone, the area from position 4 to position 5 is the child heating/heating zone, and the area from position 5 to position 6 is the firing reaction zone. In the furnace and firing method of the present invention, the firing temperature is maintained at a constant temperature of approximately 1200° C. in this zone, so that the firing reaction takes place completely. position 6 to position 7
This is a cooling zone. [Effects of the Invention] In the firing method and firing furnace of the present invention, firing can be performed with a relatively small amount of gas fuel, thermal energy is used effectively, and fuel costs can be significantly reduced.

Furthermore, the speed of the material descending within the furnace can be easily adjusted by adjusting the speed of the removal means. The temperature and pressure at each height in the furnace can be easily adjusted by each control valve. The above has described a vertical furnace that uses as a raw material the granules of about 12 sides of barium ferrite matrix feed e203, which is magnetic iron oxide, and freezes it. It can be used as a dry distillation furnace for dry distillation of gas, and can also be used for producing calcined limestone cement, as well as for other uses.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a temporary firing furnace for magnetic iron oxide according to the present invention. Figure 2 is a graph showing the pressure in the furnace and the flow of gas in the furnace in the calcining furnace shown in Figure 1, and Figure 3 is a graph showing the temperature distribution in the furnace in the calcining furnace shown in Figure 1. be. 1
2 is a temporary firing furnace for magnetic iron oxide, 2 is a supply means, 3 is a pseudo gas extraction position near the top of the furnace, 4 is a blowing position for a mixture of combustion gas and air, 5 is a gas burner mounting position, and 6 is a suction pipe mounting device. , 7 is the cooling air blowing position, 8 is the burner, 9 is the wind box, 1
0 is a gas fuel supply pipe, 11' is a cooling air outlet, 12 is
1 is an annular pipe, 13 is a control valve, 14 is a suction pipe, 15 is an annular pipe, 16 is a control valve, 17 is a blower, 18 is a delivery pipe, 1
9 is a mixed gas ejection pipe, 20 is an annular pipe, 21 is a discharge pipe, 2
2 is an annular pipe, 23 is a control valve, 24 is a blower, 25 is a delivery pipe, and 26 is a take-out means. Figure 2 Figure 3

Claims (1)

[Claims] 1. A vertical furnace 1 in which the inner diameter of the furnace increases from the top to the bottom.
The majority of the flame and combustion gas from several gas burners 8, 8'... installed on the peripheral wall of the furnace at an appropriate position 5 in the middle of the furnace is directed downward in the same direction as the advancing direction of the material to be fired. The material to be fired is sintered between positions 5 and 6 by flowing in the direction of the negative pressure section position 6, and several cooling air jet holes are provided in the furnace peripheral wall at position 7 near the bottom of the furnace. 11
, 11'... are caused to flow upward toward the negative pressure section position 6 to cool the fired material from position 6 to position 7. Suction pipes 14, 14', etc. are provided, and the mixed gas of combustion gas and air sucked by these suction pipes is transferred to several mixed gas pipes installed on the furnace peripheral wall at position 5 and position 4 at an intermediate height between position 3 near the top. Gas is ejected from the ejection pipes 19, 19'..., and several exhaust pipes 21, 21'... are provided on the furnace peripheral wall at position 3, and the gas is sucked through these exhaust pipes to create a negative pressure section, and the gas is discharged near position 4. The material to be fired fed from the top is dried and preheated, and the fired product is taken out by the take-out means 26 provided at the bottom of the furnace, so that the material is successively replenished by its own weight from the supply means 2 provided at the top of the furnace. This is the firing method. 2 Vertical furnace 1 whose inner diameter is large from the top to the bottom
A supply means 2 for the material to be fired is provided at the top of the furnace 1, and several gas burners 8, 8'... are provided on the furnace peripheral wall at a suitable height position 5 in the middle of the furnace 1. Several cooling air jet holes 11, 11'... are provided on the furnace peripheral wall at position 7 near the bottom of the furnace, and several cooling air jet holes 11, 11'... are provided on the furnace peripheral wall at position 6, which is at an intermediate height between positions 5 and 7, to suck combustion gas and air. Several mixed gas ejection pipes 19, 19'... are provided on the furnace peripheral wall at an intermediate height position 4 between the burner position 5 and the position 3 near the top of the furnace. A firing furnace is provided with several discharge pipes 21, 21', .