JP2000344526A - Roasting furnace for producing iron oxide, and production of iron oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roasting furnace for always producing iron oxide having stabilized quality even if the state of a swirling gas flow in the furnace is changed, and to provide the method for producing the iron oxide. SOLUTION: In this roasting furnace for producing iron oxide, which is provided with a heat source gas blowing port provided on the furnace wall of the cylindrical furnace and for forming the swirling gas flow in the furnace and a spray header 3 inserted into the inside of the furnace vertically from the ceiling of the furnace and having a nozzle for spraying a iron chloride aq. solution at the tip, the spray header is freely rotatable around the vertical axis and a nozzle position changing means is provided so that the tip part 15 of the spray header is inclined of capable of being inclined from the vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roasting furnace for producing iron oxide and a method for producing iron oxide, and more particularly, to a roasting furnace for producing iron oxide capable of changing a spraying direction of an aqueous solution of iron chloride as a raw material. And a technique for producing iron oxide using the roasting furnace.

[0002]

2. Description of the Related Art Generally, a roasting apparatus as shown in FIG. 7 is used for oxidizing and roasting an aqueous solution of iron chloride to produce iron oxide and recover hydrochloric acid. The main device in this facility is a roasting furnace 1 as shown in FIG. The roasting furnace shown in FIG. 7 or FIG. 8 is a so-called Lusna type furnace in which a cone-shaped cylinder is connected to a lower part of a cylindrical body, and an iron chloride aqueous solution 6 is supplied from a ceiling 2 of the furnace. One spray header 3 is inserted into the furnace, and a blowing device 4 for blowing a flame and / or a heated gas (hereinafter, referred to as a heat source gas 12) as a heat source into the furnace to form a swirling gas flow 13. And a heat source gas injection port 5 is provided. An iron chloride aqueous solution 6 (usually, waste acid generated in a pickling process of a steel sheet is often used) 6 as a material to be heated is sprayed into a furnace through a nozzle at a tip of a spray header 3. Heat is exchanged in advance with the high-temperature exhaust gas 7 (hydrogen chloride gas, steam, etc.) from the roasting furnace 1 in the washing tower 10 to concentrate iron chloride, and then spray. On the other hand, the high temperature exhaust gas 7 generated in the furnace is
After being recovered by the cyclone 9, the iron oxide discharged along with the high-temperature exhaust gas 7 is guided to the washing tower 10. The number of the spray headers 3 for supplying the aqueous iron chloride solution 6 is not limited to one, but is usually about three, and is fixed and supported on the ceiling 2 of the furnace.

In the roasting furnace 1, the sprayed iron chloride aqueous solution 6 is heated and oxidized and roasted to generate solid iron oxide and hydrogen chloride gas according to the following reaction formula.

[0004] FeCl ₂ + H ₂ O + ／ O ₂ → → F
e ₂ O ₃ + 2HCl FeCl ₃ + 3 / 2H ₂ O → 1 / 2Fe ₂ O ₃ + 3HCl As shown in FIG. 8, the generated iron oxide 11 falls by its own weight near the center of the roasting furnace 1, Some fall along the inner wall of the furnace 1.

[0005] The iron oxide 11 produced in such a roasting furnace is
Mainly used as a raw material for ferrite production. In this case, the iron oxide 11 is required to have a low concentration of impurities such as chlorine and certain powder characteristics. The powder characteristics are evaluated based on the particle diameter of the iron oxide 11 (measured by the air permeation method or the BET method), the molding (filling) density when molding, and the like. It depends on the roasting situation. That is, at the time of roasting, there are the following factors (1) to (3) which affect the powder characteristics of the iron oxide 11, and by controlling these factors, the powder characteristics of the iron oxide 11 are determined. For this reason, research on technology for controlling such factors during roasting has been conducted more actively than before, and many technologies have been disclosed.

(1) Diameter of spray droplets (2) Temperature of heat source gas (3) Speed of heat source gas in furnace (combustion air ratio) For example, Japanese Patent Application Laid-Open No. 61-086425 discloses a spray attached to a furnace. The number of headers and nozzles is changed, and JP-A-6-048740 discloses a method in which the pressure of a pump used for spraying is changed to adjust the diameter of a spray droplet of an aqueous solution of iron chloride to an appropriate size. Proposes technology to control iron oxide quality. In addition, a technique has been proposed in which the ratio of fuel to air in the blowing device (referred to as a combustion air ratio) and the blowing speed are variously changed to control iron oxide quality (Japanese Patent Application Laid-Open No. 7-041320).

However, the techniques described in the above publications can control the powder characteristics of the iron oxide 11 in a state where the state of the swirling gas flow 13 is stable. Has no description. In the actual operation, if iron oxide or the like adheres to the vicinity of the inlet 5 of the heat source gas 12, the flow of the swirling gas flow 13 is disturbed, and the quality of the iron oxide changes, which may make it difficult to control the quality. .

[0008]

SUMMARY OF THE INVENTION In view of the foregoing, the present invention has been made in consideration of the above circumstances, and therefore, it is possible to always produce iron oxide of stable quality even if the state of the swirling gas flow in the roasting furnace changes. An object of the present invention is to provide a furnace and a method for producing iron oxide.

[0009]

Means for Solving the Problems The inventor has conducted intensive studies in order to achieve the above object, and has embodied the results in the present invention.

That is, the present invention provides a heat source gas injection port provided on a furnace wall of a cylindrical furnace for forming a swirling gas flow in the furnace, and a vertically inserted iron chloride aqueous solution from a ceiling of the furnace. In a roasting furnace for producing iron oxide, comprising: a spray header having a nozzle at the tip for spraying the inside of the furnace.
The spray header is rotatable about a vertical axis,
Further, a roasting furnace for producing iron oxide is characterized in that a tip portion of the spray header is inclined from a vertical direction or provided with a nozzle position changing means capable of tilting.

In this case, it is preferable that the spray header can be moved up and down freely.

Further, the present invention provides a method for producing iron oxide, comprising oxidizing and roasting iron chloride by bringing a swirling gas stream formed in the furnace into contact with an aqueous solution of iron chloride sprayed into the furnace.
An iron oxide production method characterized by measuring the temperature of exhaust gas generated by oxidizing roasting, and changing the spray direction of an aqueous solution of iron chloride so that the measured value matches a target value.

According to the present invention, even if the state of the swirling gas flow in the furnace changes, an aqueous solution of iron chloride is sprayed to a position optimal for roasting, so that iron oxide of stable quality can be produced. become able to.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below, taking into account the circumstances leading to the invention.

First, the inventor examined the cause of the change in the powder characteristics of the iron oxide 11 due to the change in the state of the swirling gas flow 13. As a result, the ambient temperature and the state of the swirling gas flow (flow velocity, path, etc.) change in the area where the aqueous iron chloride solution 6 is roasted (the area where the aqueous iron chloride solution is sprayed, hereinafter referred to as the roasting area). Thus, it was expected that the powder characteristics would change because the heat load on the aqueous iron chloride solution 6 would be different. Then, when the state of the swirling gas flow 13 changes,
The idea was to move the roasting zone to an appropriate location and apply the same heat load as before the change.

To embody such an idea, the inventor:
Various studies have been made on the means of moving the roasting zone, and the spray direction of the aqueous solution of iron chloride 6 has been changed freely. That is, the spray header 3 to which the nozzle is attached is rotatable about a vertical axis, and the nozzle provided at the tip of the spray header 3 is connected to the furnace 1.
In all radial directions. The mechanism may be any known mechanism, but a practical example is shown in FIG.
Shown in That is, the spray header 3 provided with the nozzle 14 is connected and supported by a worm gear 16,
The gear 16 is rotated. Thereby, the nozzle 14 can rotate in the furnace continuously or intermittently. In the present invention, the shape of the nozzle 14 used is
There is no particular limitation. However, since it is preferable that the spraying area is wider to some extent, it is preferable that the iron chloride aqueous solution 6 can be sprayed radially. Further, in the present invention, the rotation driving force of the worm gear 16 may be automated so as to be remotely operated in the instrument room.

Further, in the present invention, the spray header 3
As shown in FIG. 1, the distal end portion 15 is inclined from the vertical direction. This inclination angle α is preferably 5 to 20 °. Since the roasting reaction is usually completed within 5 m below the nozzle 14, if it is less than 5 °, the spray header 3
This is because, even if is rotated, it is possible to spray only into a narrow area. On the other hand, if it exceeds 20 °, the nozzle 14 is too directed toward the furnace wall, and the iron chloride may reach the furnace wall without being roasted.

In addition, in the present invention, a structure in which the central axis of the nozzle 14 can be tilted (referred to as nozzle position changing means) may be adopted. For example, as shown in FIG. 3, a connecting portion 18 such as a universal joint is provided at the tip portion 15 of the spray header 3, and the tip portion 15 can be tilted by pulling the tip portion 15 with a wire 19.

In addition, in the present invention, the spray header 3 may be movable up and down. Thereby, even if the appropriate spraying area changes in the height direction of the roasting furnace 1, it is easy to cope with it. A known mechanism such as a wire suspension system or a cylinder system can be used for the elevating means.

Next, a method of adjusting the spray area of the aqueous iron chloride solution 6 according to the change in the state of the swirling gas flow 13 will be described. In actual operation, it is difficult to measure the direction, the flow velocity distribution, and the temperature distribution of the swirling gas flow 13, and it is difficult to clearly determine the state change of the swirling gas flow 13. Therefore, a change in state of the swirling gas flow 13 is determined by determining the heat load on the oxidized and roasted iron oxide 11. The heat of the heat source gas 12 supplied to the roasting furnace 1 is as follows:
Except for heat release outside the system, it is consumed in the roasting reaction. Since the heat radiation outside the system is substantially constant, the heat load on the iron oxide 11 corresponds to the heat amount of the heat source gas 12 minus the heat amount of the exhaust gas. In other words, if the heat quantity of the exhaust gas 7 is made constant under the condition that the supply heat quantity is made constant,
The heat load also becomes constant. Therefore, the spray area may be adjusted by making full use of the position changing means of the nozzle 14 so that such a state is maintained. For this reason, in the present invention, a thermometer 17 is installed in the exhaust gas passage 8 of the furnace (see FIG. 8) so that the temperature of the exhaust gas 7 can be constantly monitored in the instrument room, and the temperature of the exhaust gas 7 reaches a predetermined target temperature. Thus, the operation of moving the nozzle 14 is performed to adjust the position.

When the swirling gas flow passes near the center of the roasting furnace, the probability of contact with the aqueous solution of iron chloride decreases, and the temperature of the exhaust gas tends to increase because the heat source is not used for the oxidizing roasting reaction. For this reason, when the temperature of the exhaust gas becomes higher than the target value, it is preferable to spray the aqueous solution of iron chloride toward the center of the roasting furnace. If the heat source is excessively used in the oxidative roasting reaction and the exhaust gas temperature becomes lower than the target value, overburning occurs and the particle size of iron oxide increases. When the temperature of the exhaust gas becomes lower than the target value, it is preferable to spray an aqueous solution of iron chloride toward the furnace wall in order to shorten the contact time with the heat source.

[0022]

EXAMPLE Using a roasting furnace 1 according to the present invention, an iron oxide 11 was produced from a waste acid 6 containing iron chloride as a raw material. The roasting furnace 1 has a hollow cylindrical body and a size of 6.
5m, height 14.9m. The heat source gas 12 is
Four coke gas (C gas) burners (blowing devices) were arranged in the circumferential direction at a height of 4.2 m from the furnace bottom and supplied. The gas burner is installed so that the supplied gas forms a swirling gas flow in the furnace. Exhaust gas 7 from the furnace is discharged from the furnace top, and a thermocouple type thermometer 17 is installed in the exhaust gas passage 8. The supply of the waste acid into the furnace is carried out via three spray headers 3, which are supported from the furnace ceiling 2 by the pivoting means shown in FIG. The nozzle 14 attached to each spray header 3 was arranged so that the tip position was 4 m below the inner surface of the ceiling of the furnace. Each nozzle 14 has the same shape, and the inclination angle of the nozzle is 10 ° from the vertical direction.

The operation was performed by an operator rotating each spray header 3 appropriately so that the temperature of the exhaust gas 7 was kept constant at 410 ° C. FIG. 4 shows the change over time in the temperature. Next, results of operation (comparative operation) without rotating the nozzle 14 based on the temperature of the exhaust gas 7 on different days in the same roasting furnace 1 are also shown in FIG. It is clear from FIG. 4 that the roasting furnace and the manufacturing method according to the present invention performed a stable operation. The powder characteristic values of the iron oxide sampled during these operations are shown in FIGS. It is clear that the powder properties (particle diameter, compaction density) of the iron oxide 11 obtained by the practice of the present invention are superior to those of the comparative operation.

[0024]

As described above, even if the state of the swirling gas flow in the roasting furnace changes, the manufacturing method of the present invention in which the spraying direction of the aqueous solution of iron chloride is changed enables the use of iron oxide of stable quality. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a tilt state of a nozzle according to the present invention.

FIG. 2 is a view showing an example of a rotating means of a spray header according to the present invention.

FIG. 3 is a diagram illustrating an example of a method of tilting a nozzle according to the present invention.

FIG. 4 is a diagram showing a change over time of the exhaust gas temperature in the operation according to the present invention and the comparative operation.

FIG. 5 is a diagram showing the change over time in the particle size of iron oxide obtained by the operation according to the present invention and the comparative operation.

FIG. 6 is a graph showing the change over time of the iron oxide molding density obtained in the operation according to the present invention and the comparative operation.

FIG. 7 is a diagram showing a general process of producing iron oxide from an aqueous solution of iron chloride.

FIG. 8 is a longitudinal sectional view showing the shape of a roasting furnace used in the above steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Roasting furnace 2 Ceiling 3 Spray header 4 Injection device 5 Injection port 6 Iron chloride aqueous solution (waste acid) 7 Exhaust gas 8 Exhaust gas passage 9 Cyclone 10 Cleaning tower 11 Iron oxide 12 Heat source gas 13 Swirling gas flow 14 Nozzle 15 Spray header tip 16 worm gear 17 thermometer 18 connecting part 19 wire

Claims (2)

[Claims] 1. A heat source gas injection port provided on a furnace wall of a cylindrical furnace for forming a swirling gas flow in the furnace, and vertically inserted into the furnace from a ceiling of the furnace, and an aqueous solution of iron chloride is introduced into the furnace. In a roasting furnace for manufacturing iron oxide, comprising: a spray header having a nozzle for spraying at a tip thereof, wherein the spray header is rotatable around a vertical axis,
A roasting furnace for producing iron oxide, wherein a tip portion of the spray header is inclined from a vertical direction or provided with a nozzle position changing means capable of tilting. 2. A method for producing iron oxide by oxidizing and roasting iron chloride by bringing a swirling gas stream formed in the furnace into contact with an aqueous solution of iron chloride sprayed into the furnace. A method for producing iron oxide, comprising: measuring a temperature of exhaust gas thus discharged, and changing a spray direction of the aqueous solution of iron chloride so that the measured value matches a target value.