JP2022180818A - Method for operating rotary kiln - Google Patents

Abstract

To reduce fuel cost in a rotary kiln whose interior is heated by combustion heat of a fossil fuel such as fuel oil and dust coal while avoiding excessive advance of reduction treatment in a reduction furnace on a downstream side of the rotary kiln.SOLUTION: A method for operating a rotary kiln 1 which is a heating furnace configured to heat the interior thereof by combustion heat of a fossil fuel, and in which a reduction furnace that carries out reduction treatment is connected on a downstream process side. A part of the fossil fuel loaded into the rotary kiln 1 is replaced with RPF.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of operating a rotary kiln. More specifically, the present invention relates to a method for operating a rotary kiln, which can be preferably applied to the operation of a rotary kiln for drying nickel oxide ore as a raw material in ferronickel smelting.

In the smelting of ferronickel, which is an alloy of iron and nickel, the nickel oxide ore used as a raw material is an ore containing about 1% by weight or more and 3% by weight or less of nickel. Since this ore contains about 20% by weight or more and 25% by weight or less of water, before being pulverized and charged into an electric furnace to be reduced and melted, the water is removed. drying process is carried out.

In ferronickel smelting, this drying treatment is usually carried out by calcining the ore using a rotary kiln to remove moisture from the ore and to promote partial reduction. The ore stays in the rotary kiln for about 2 hours or more and 3 hours or less, and then sequentially charged into the electric furnace.

In the above drying process, the heat source for removing the moisture in the ore and partially reducing the ore is mainly heavy oil or pulverized coal that is burned by the burner installed at the discharge end of the rotary kiln. The heat of combustion of fossil fuels and the heat of combustion of coal charged into the rotary kiln are used.

The above coal is usually charged from the charging end of the rotary kiln. However, in order to reduce the amount of expensive heavy oil and pulverized coal used, in recent years, an operation method has been implemented in which coal is charged from a reductant (fuel) supply port provided in the middle of the rotary kiln instead of from the charging end. (see Patent Document 1).

In the above operation method, by charging the coal from the middle of the rotary kiln, the coal is supplied to the high-temperature part of the rotary kiln, and the volatile matter contained in the coal can be burned more efficiently than before. However, the amount of volatile matter contained in coal is limited, and the amount of reduction in the amount of heavy oil and pulverized coal used has been limited.

Another conventional method for reducing the amount of heavy oil and pulverized coal used is to mix wood pellets with coal and charge it into a rotary kiln (see Patent Document 2). However, wood pellets contain a large proportion of fixed carbon that contributes as a reducing agent, from 16% to 23%. On the other hand, there have been cases where the degree of reduction in the electric furnace in which the reduction treatment is performed is excessively increased, making it impossible to properly maintain the quality of the final product.

JP 2014-141719 A JP 2011-225903 A

The present invention reduces fuel costs while avoiding excessive progress of reduction treatment in a reduction furnace on the downstream side of a rotary kiln in which the interior is heated by the combustion heat of fossil fuels such as heavy oil and pulverized coal. for the purpose.

The present inventors have found that in a rotary kiln in which a reducing furnace is further connected downstream, some of the fossil fuels such as heavy oil and pulverized coal that are input as heat sources are replaced with wood pellets, which have been the main alternative fuel in the past. , "RPF (refused derived paper and plastics densified fuel)", the present invention has been completed. The present invention specifically provides the following.

(1) A method of operating a rotary kiln, which is a heating furnace that heats the inside by combustion heat of fossil fuel, and is a heating furnace in which a reducing furnace that performs reduction treatment is connected to the downstream process side, A method of operating a rotary kiln, wherein RPF replaces part of the fossil fuel to be fed into the rotary kiln.

According to the rotary kiln operation method of (1), in a rotary kiln that heats the inside by combustion heat of fossil fuels such as heavy oil and pulverized coal, excessive progress of reduction processing in the reduction furnace downstream of the rotary kiln is avoided. while reducing fuel costs.

(2) The rotary kiln is a rotary kiln that dries the material to be fired and performs partial reduction treatment with a reducing agent, wherein the amount of fixed carbon in the RPF charged into the rotary kiln and the fixed amount of the reducing agent other than the RPF The method of operating a rotary kiln according to (1), wherein the total amount of fixed carbon necessary for the reduction treatment performed in the rotary kiln and the reducing furnace is adjusted.

According to the method of operating a rotary kiln in (2), in the method of operating a rotary kiln described in (1), the amount of fixed carbon contained in "RPF" is excessive or insufficient to maintain an appropriate degree of reduction. By optimizing without, fuel costs can be reduced while maintaining an appropriate degree of reduction in more strictly downstream processes.

(3) The method of operating a rotary kiln according to (1) or (2), wherein the RPF input amount is adjusted so that the effective utilization rate of the RPF is 80% or more.

According to the method of operating a rotary kiln in (3), in the method of operating a rotary kiln described in (1) or (2), the heat amount of "RPF" is excessive or insufficient to the amount necessary to maintain an appropriate furnace temperature. By optimizing without, fuel costs can be reduced while more closely maintaining proper furnace temperatures.

(4) The method of operating a rotary kiln according to (2), wherein the RPF is charged into the rotary kiln in a state of being mixed with the reducing agent other than the RPF.

According to the operation method of the rotary kiln of (4), "RPF" can be burned more efficiently, so more fossil fuel can be saved while maintaining the required heat quantity.

(5) The method of operating a rotary kiln according to any one of (1) to (4), wherein the rotary kiln is a rotary kiln that dries nickel oxide ore as a raw material and performs partial reduction treatment in ferronickel smelting. .

According to the rotary kiln operating method of (5), the above-mentioned effects of the rotary kiln operating method of any one of (1) to (4) are obtained, and the raw material cost is reduced in the production of ferronickel smelting. can contribute to the improvement of economic efficiency.

According to the present invention, in a rotary kiln that heats the inside by combustion heat of fossil fuel such as heavy oil and pulverized coal, fuel cost is reduced while avoiding excessive progress of reduction treatment in the reduction furnace downstream of the rotary kiln. can be reduced.

In the overall process of ferronickel smelting, using a drying/reducing rotary kiln installed on the upstream side of a reducing furnace (electric furnace), an example of an embodiment of the method for operating a rotary kiln of the present invention is as follows: It is a figure shown typically. FIG. 2 is another example of a rotary kiln in which the present invention can be implemented in a preferred embodiment, and is a cross-sectional configuration diagram of a rotary kiln having a scoop feeder for charging coal.

Hereinafter, specific embodiments of the "method for operating a rotary kiln" of the present invention will be described. It should be noted that the present invention is not limited to the following embodiments, and can be implemented in forms and modes other than those described below without departing from the scope of the present invention.

The "rotary kiln operating method" of the present invention is a heating furnace that heats the inside by combustion heat of fossil fuel such as heavy oil and pulverized coal, and a reducing furnace that performs reduction treatment is connected to the downstream process side. It is a process that can be widely implemented in various rotary kilns. The "heating furnace that heats the interior with the heat of combustion of fossil fuels" may be any heating furnace intended to dry the charged material, but the drying process and the partial reduction process are combined. It is preferable that the heating furnace is intended to be used for heating.

In this specification, "a heating furnace in which a reducing furnace for performing reduction treatment is connected to the downstream process side" means that the high-temperature discharge from the heating furnace (rotary kiln) installed on the upstream process side is It means that both facilities are installed so as to operate in conjunction with each other in a mode in which they are put into a "reducing furnace" installed on the downstream side. For example, even if a heating furnace such as a rotary kiln and a reducing furnace such as an electric furnace, which operate in conjunction with each other in the above-described manner, are connected via a conveying device such as a belt conveyor, it is natural that the "reducing furnace that performs reduction treatment is a heating furnace connected to the downstream process side, and is the object of implementation of the present invention.

As a preferable implementation target of such a "method for operating a rotary kiln" of the present invention, in the "whole process of ferronickel smelting" described in detail below, it is installed upstream of a reducing furnace (electric furnace), Mention may be made of "drying-reducing rotary kilns" for drying and partial reduction of the ore.

<Overall process of ferronickel smelting>
The "whole process of ferronickel smelting" is a metal smelting process that uses nickel oxide ore (nickel oxide ore) as a raw material and includes at least a "partial reduction step" and a "melting reduction step" as essential steps. This process can produce ferronickel with a nickel grade of about 20% by weight. In this process, if necessary, a drying step preceding the partial reduction step and a desulfurization step following the melting reduction step are also carried out.

In the above-mentioned "whole process of ferronickel smelting", the nickel oxide ore (nickel oxide ore) used as a raw material has, for example, a Ni grade of 2.1% by weight or more and 2.5% by weight or less in terms of dry ore. , Fe grade 11 wt% to 23 wt%, MgO grade 20 wt% to 28 wt%, _SiO2 grade 29 wt% to 39 wt%, CaO grade less than 0.5 wt%, ignition loss 10 wt% Garnierite ore with a content of 15% by weight or more is preferably used.

[Partial Reduction Step]
The partial reduction step is a step of completely removing moisture (attached water, crystal moisture) in the nickel oxide ore and producing a partially reduced nickel oxide ore (nickel oxide calcine). In the partial reduction step, a reducing agent (coal) is added, these are put into a rotary kiln for drying and reduction, and fired at a firing temperature of about 800 ° C to 900 ° C to completely remove moisture and partially Apply reduction treatment. The firing is carried out by heating the inside of the rotary kiln with combustion heat of fossil fuels such as heavy oil and pulverized coal.

As shown in FIG. 1, combustion heat of fossil fuel such as heavy oil and pulverized coal fired by a burner 14 provided at the discharge end 13 of the rotary kiln 1 is used for the above drying and partial reduction treatment. The ore that has been dried and partially reduced is turned into calcined ore, discharged from the discharge end 13, and conveyed to a reducing furnace such as an electric furnace that is connected to the downstream side by a conveying means.

By performing such a partial reduction process according to the "method for operating a rotary kiln" of the present invention, while avoiding excessive progress of the reduction treatment in the electric furnace in which the subsequent melting reduction process is performed. , fuel costs can be reduced.

[Melting Reduction Step]
The melting reduction process is a process in which the nickel oxide ore produced in the partial reduction process is put into an electric furnace and melted and reduced in the furnace to produce ferronickel (metal) and slag. The ferronickel molten body produced in this step is mainly composed of iron and contains nickel with a grade of about 16% by weight or more and 25% by weight or less depending on the set amount of the carbonaceous reducing agent. Although illustration of the electric furnace is omitted, as a specific example of the electric furnace for melting reduction, a known "three-phase AC electrode type circular electric furnace" can be mentioned.

<Rotary kiln operation method>
The ``operation method of a rotary kiln'' of the present invention includes, for example, a ``drying/reducing rotary kiln'' used in the above-mentioned ``whole process of ferronickel smelting'', and a ``reducing furnace for performing reduction treatment connected to the downstream process side. A method of operating a rotary kiln, which is mainly characterized by replacing part of the above-mentioned fossil fuel put into the rotary kiln with "RPF (Refuse derived paper and plastics densified fuel)" in the rotary kiln which is a "heating furnace". .

[RPF]
"RPF" is an abbreviation for "Refused derived paper and plastics densified fuel", which is an industrial waste-based solid fuel formed by mixing waste paper, waste plastics, and wood waste. The carbon content (hereinafter also referred to as "fixed carbon") after volatile content is removed is about 5% or more and 10% or less, which is lower than that of wood pellets, and the fuel is rich in volatile content compared to wood pellets. It has become.

Therefore, by using "RPF" as a fuel, it is possible to burn its abundant volatile matter, obtain combustion heat substantially equivalent to that of coal, and efficiently raise the temperature inside the rotary kiln. In addition, when using "RPF" as fuel, unlike conventional alternative fuels such as "wood pellets", it is necessary to consider the risk of introducing excessive "fixed carbon" into the downstream reduction furnace. Since there is almost no wood pellets, a larger amount can be put into the upstream rotary kiln. Therefore, "RPF" can effectively reduce the amount of fossil fuels such as heavy oil and pulverized coal used in "a heating furnace in which a reducing furnace for performing reduction treatment is connected to the downstream process side".

In addition, in the "method for operating a rotary kiln" of the present invention, the amount of "RPF" input to the rotary kiln is the fixed carbon amount of "RPF" and the fixed carbon amount of the reducing agent other than RPF (coal in this example). It is preferable to adjust the total so that the amount of fixed carbon required for the reduction of the ore is obtained. Therefore, when it is desired to increase the input amount of "RPF", the input amount of reducing agents other than RPF (coal in this example) must be decreased by an amount corresponding to the increased fixed carbon amount of "RPF". Just do it.

However, if the input amount of "RPF" is increased beyond a certain limit, it may become difficult to effectively utilize the combustion heat of "RPF". Therefore, it is preferable to adjust the input amount of "RPF" within a range in which the combustion heat of "RPF" is effectively utilized. In this specification, the degree to which the combustion heat of the "RPF" is effectively utilized is evaluated by the "RPF effective utilization rate" defined by the following formula (1). This "RPF effective utilization rate" is defined as the ratio of the combustion heat generated by the fuel (heavy oil + pulverized coal) reduced by the input "RPF" to the combustion heat generated by the input "RPF".

(RPF effective utilization rate)
= (heat amount of reduced fuel (heavy oil + pulverized coal))/(heat amount of RPF input) (1)

As described above, in the "method for operating a rotary kiln" of the present invention, the amount of "RPF" to be fed into the rotary kiln is maintained constant while the total amount of fixed carbon content of the RPF and other reducing agents fed into the rotary kiln is kept constant. In addition, it is preferable to adjust the input amount within a range such that the above "RPF effective utilization rate" is 80% or more.

In the "method for operating a rotary kiln" of the present invention, the optimum value of the input amount of "RPF" to the rotary kiln is the reduction amount of heavy oil and pulverized coal with respect to the input amount of "RPF", and the relationship with the "RPF effective utilization rate". It can be specifically specified by a method such as conducting a test to determine the sex. As a specific example of adjusting the input amount of "RPF" to a rotary kiln, for example, in a rotary kiln with a total length of 100 m, when sintering 50 t / h of ore, the input amount into the rotary kiln is By adjusting the input amount of both to 0.25 t/h and the input amount of coal as a reducing agent to 5.0 t/h, the "RPF effective utilization rate" can be 93.4%. . Also, in a similar rotary kiln, by adjusting the input amount of "RPF" so that the input amount of "RPF" is 0.5 t/h and the input amount of coal is 4.9 t/h, the "RPF effective utilization rate" can be 86.2%. In this way, under the condition of firing 50t/h of ore in a rotary kiln with a total length of 100m, which is also a standard operating condition in the "whole process of ferronickel smelting", the amount of RPF input is 0.25 wt/hr or more and 1.0 wt/hr or less, preferably 0.25 wt/hr or more and 0.5 wt/hr or less, the advantageous effects of the present invention can be enjoyed and the product quality can be maintained. while reducing fuel costs.

"RPF" is usually distributed as cylindrical pellets. In the "method for operating a rotary kiln" of the present invention, the pellets having the above shape preferably have a diameter of 15 mm or more and 40 mm or less, a length of 10 mm or more and 110 mm or less, and a density of 0.3 to 0.4 cm ³ . In addition, it is more preferable that the pellets having the above shape are balanced in overall shape so that the larger the diameter, the shorter the length. As an example, when the pellet has a diameter of 15 mm or more and less than 25 mm, the length is preferably 60 mm or more and 110 mm or less, and when the diameter is 25 mm or more and 40 mm or less, the length is 10 mm or more and less than 60 mm. is more preferable. By adjusting the shape and size of the pellets in this manner, the size of the "RPF" can be averaged for more efficient combustion.

[Injection of fuel (reducing agent) into rotary kiln]
The rotary kiln 1 shown in FIG. 1 is a "drying/reducing rotary kiln" which is an example of a rotary kiln that can be suitably operated according to the "whole process of ferronickel smelting" described above. When the "method for operating a rotary kiln" of the present invention is implemented in this rotary kiln 1, "RPF" and "reducing agent other than RPF such as coal", preferably a mixture thereof (hereinafter collectively referred to as " A reducing agent (also referred to as "reducing agent r") is introduced from a charging end 11 of the rotary kiln 1 or from a reducing agent (fuel) supply port 12 provided near the intermediate position of the conveying path of the rotary kiln. In the rotary kiln operation method of the present invention, by burning the "RPF" charged in this way in the rotary kiln 1, the combustion heat of the "RPF" is actively used for calcining the ore. This process makes it possible to reduce the amount of fossil fuels such as heavy oil and pulverized coal used as fuel.

[Rotary kiln]
A rotary kiln 1, which is a preferred embodiment of the present invention, is a large cylindrical rotary heating furnace, as shown in FIG. Further, the rotary kiln 1 is inclined downward from its charging end 11 toward its discharging end 13 . In the rotary kiln 1 , raw material ore is charged from a charging end 11 , and the ore moves toward a discharging end 13 in a rotating body portion. In the rotary kiln 1, a heating burner 14 such as a heavy oil burner is usually installed on the discharge end 13 side, and the combustion heat of the fossil fuel burned by the burner 14 flows in the opposite direction to the ore. to heat the ore countercurrently. Further, as shown in FIG. 1, in the rotary kiln 1, a granular reducing agent r and the like cut out from a hopper 2 in a fixed amount are fed to the rotary kiln 1 from a reducing agent (fuel) supply port 12 via a charging conveyor 3. is put into

The size of the rotary kiln 1 is not particularly limited, but as a drying/reduction rotary kiln used in ferronickel smelting, a rotary kiln with an inner diameter of about 4.5 m or more and 6.5 m or less and a total length of about 100 m or more and 150 m or less is preferably used. ing. In a rotary kiln with an inner diameter of less than 4.5 m or a total length of less than 100 m, it is difficult to secure sufficient time for drying the ore in the rotary kiln and performing partial reduction treatment. There is a concern that processing cannot be performed. On the other hand, a rotary kiln with an inner diameter of more than 6.5 m or a total length of more than 150 m is not preferable from an economical point of view because the cost of equipment investment for installing the rotary kiln and the cost of maintaining it increase.

The temperature inside the rotary kiln 1 is not particularly limited, but the ore temperature at the discharge end 13 is approximately 700° C. or higher and 900° C. or lower, and the exhaust gas temperature at the charging end 11 is approximately 250° C. or higher and 400° C. or lower. It is preferable to keep By maintaining the temperature above each lower limit temperature, the volatile matter and fixed carbon in the charged reducing agent r can be sufficiently burned. Further, by maintaining the temperature below the upper limit temperature, it is possible to prevent the inner wall of the rotary kiln 1 from forming bumps.

Also, the rotation speed of the rotary kiln 1 is not particularly limited, but it is preferable to set the rotation speed to about 0.5 rpm or more and 1.5 rpm or less. When the rotation speed of the rotary kiln 1 is less than 0.5 rpm, the stirring force inside the rotary kiln 1 is weak, and the introduced reducing agent r slowly slides in the circumferential direction while being buried in the ore used as the raw material. while gradually moving from the charging end 11 side to the discharging end 13 side. In such a case, the contact between the surface of the reducing agent r and the air inside the rotary kiln 1 becomes insufficient, and there is a concern that it becomes difficult to burn the volatile matter and fixed carbon in the introduced reducing agent r. On the other hand, when the rotation speed of the rotary kiln exceeds 1.5 rpm, the stirring force inside the rotary kiln 1 becomes strong, and the raw material ore charged into the rotary kiln 1 rises up in the rotary kiln 1 and is charged together with the exhaust gas as dust. There is a concern that the yield of the calcined ore that is discharged from the end 11 and obtained from the discharge end 13 will decrease.

FIG. 2 is another example of a rotary kiln in which the present invention can be implemented in a preferred embodiment, and is a rotary kiln having a scoop feeder 17 for feeding "RPF" and "reducing agents other than RPF such as coal". It is a cross-sectional block diagram. The scoop feeder 17 is provided in the rotary kiln 1A in the middle of the ore moving direction (longitudinal direction of the rotary kiln main body). As shown in FIG. 2, the rotary kiln 1A is composed of a rotating body portion 15 and an outer shell 16 covering the body portion 15. A scoop feeder 17 is provided at a predetermined position of the body portion 15. .

A rotary kiln 1A having a scoop feeder 17 is charged with ore o as a raw material into a body portion 15, and the ore o moves from a charging end 11 to a discharging end 13 as the body portion 15 rotates. . Further, in this rotary kiln 1A, a space portion 16R is formed by the body portion 15 and the outer shell 16. Through the reducing agent (fuel) supply port 12A provided in the outer shell 16, the space portion 16R A reducing agent r is charged therein.

The scoop feeder 17 is formed of, for example, an L-shaped tube, and scoops up the reducing agent r with a tip portion 171 having an L-shaped curved portion, and feeds it into the tube forming an L-shaped straight portion 172 . It is supplied to the inside of the body portion 15 by passing it through. More specifically, the scoop feeder 17 is fixed to the body portion 15 at a predetermined location, and a tip portion 171 having an L-shaped curved portion is a space formed by the body portion 15 and the outer shell 16 . Located within 16R. In this scoop feeder 17, as the body portion 15 to which the scoop feeder 17 is fixed rotates, the reducing agent r charged in the space portion 16R is scooped up through the tip portion 171 and taken into the scoop feeder 17. be When the scoop feeder 17 is positioned above the body portion 15 as the body portion 15 rotates, the action of gravity causes the reducing agent r taken into the scoop feeder 17 to form an L-shaped straight line. It is supplied to the inside of the body portion 15 through the tube that constitutes the portion 172 .

In the rotary kiln 1 (1A), the installation position of the reducing agent (fuel) supply port 12 (12A) in the ore moving direction (longitudinal direction of the main body of the rotary kiln) is such that the temperature inside the rotary kiln main body is 900°C or higher and 1200°C. It is preferable to set the position immediately above or in the vicinity of the position where the distance is less than or equal to the degree. By charging the reducing agent r from this position in the rotary kiln 1A, the volatile matter of the reducing agent r and the fixed carbon can be efficiently burned.

In addition, the installation position of the reducing agent (fuel) supply port 12 (12A) is, among the above-described positions, particularly "a position separated by a length of 2/10 of the total length of the rotary kiln from the discharge end 13". More preferably, it is positioned at a distance of 5/10 of the total length of the rotary kiln from the end 13. If the position where the reducing agent r is introduced is closer to the discharge end 13 than "the position separated from the discharge end 13 by 2/10 of the total length of the rotary kiln", the introduced reducing agent r will If the residence time is shortened, the temperature rise time will be insufficient, and there is a concern that it will be difficult to burn the volatile matter and fixed carbon in the RPF. On the other hand, when the charging end 11 is closer to the charging end 11 than "the position separated from the discharging end 13 by a length of 5/10 of the total length of the rotary kiln", the reducing agent r is introduced into the rotary kiln 1 at a location where the temperature is low. Therefore, the reducing agent r is dispersed in the ore layer from which water is not completely removed, and the surface is covered with water-containing ore. This is because even if it is warmed, the reducing agent r cannot sufficiently come into contact with the air, and there is a concern that it will be difficult to sufficiently burn the volatile matter and fixed carbon in the RPF.

As an example, in the case of the rotary kiln 1 having a total length of 100 m, the ore charged from the charging end 11 moves gradually toward the discharge end 13 and moves about 200 ℃, and heated to 900 to 1200 ℃ while reaching 80 m. In such a rotary kiln 1, assuming that the scoop feeder 17 is provided at a position 50 m from the charging end 11, feeding via this scoop feeder 17 will result in a 50 m to 80 m , the region heated to 900° C. or more and 1200° C. or less can be expanded.

EXAMPLES The present invention will be described in more detail below with reference to examples of test operations, but the present invention is not limited to the following examples.

[Example 1]
In ferronickel smelting, a rotary kiln (rotary kiln for drying/reduction) having an inner diameter of 4.8 m and a length of 105 m was used to perform sintering and drying treatment of ore. In this baking and drying treatment, a reducing agent composed of "RPF" and coal was used as the reducing agent. Injecting the reducing agent into the rotary kiln rotating at a rotation speed of 1.5 rpm is performed by pre-mixing "RPF" and coal, and then placing it at a position 2/10 of the total length away from the discharge end of the rotary kiln. Feeding was done via a provided scoop feeder. Here, the "RPF" used for charging has a diameter of 30 mm, a length of 10 to 40 mm, and a density of 0.4 g/ ^cm3 . .25 t/h, and the amount of coal input was 5.0 t/h.

The heating power of the burner was adjusted so that the ore temperature at the discharge end of the rotary kiln was 800° C. or higher and 900° C. or lower, and the above operation was continued. The amounts of heavy oil and pulverized coal used in the burner were 80 L/h for heavy oil and 3.4 t/h for pulverized coal.

Next, after the ore is dried and reduced according to the above procedure to obtain calcined ore, the obtained calcined ore is charged into an electric furnace, and is reduced and melted by supplying an electric power of 500 kwh/dry-ton. produced ferronickel. When the iron grade in the slag generated in this process was checked, the iron grade was 7% or more and 9% or less, which is within the control target value range.

[Example 2]
A test operation was performed in the same manner as in Example 1, except that the input amount of "RPF" was 1 t/h and the input amount of coal was 4.8 t/h. The amounts of heavy oil and pulverized coal used in the burner were 42 L/h for heavy oil and 2.97 t/h for pulverized coal. When the iron grade in the slag generated in the electric furnace was checked, the iron grade was 7% or more and 9% or less, which is within the control target value range.

[Comparative Example 1]
A test operation was performed in the same manner as in Example 1, except that "RPF" was not used and only coal was used as a reducing agent, and the input amount was set to 5.1 t/h. The amounts of heavy oil and pulverized coal used in the burner were 94 L/h for heavy oil and 3.57 t/h for pulverized coal. When the iron grade in the slag generated in the electric furnace was checked, the iron grade was 7% or more and 9% or less, which is within the control target value range.

In Example 1 and Example 2 using a reducing agent containing "RPF", compared with Comparative Example 1 not using "RPF", in Example 1, the amount of heavy oil used was 14 L / h, pulverized coal was reduced by 0.17 t/h, and in Example 2, the amount of heavy oil used was reduced by 52 L/h, and the amount of pulverized coal used was reduced by 0.60 t/h. In addition, the iron grade in the slag changes within the range of 7% or more and 9% or less, and there is no change in the degree of reduction due to substituting "RPF" for a part of the reducing agent that also acts as a heat source. I didn't. From the above, it was confirmed that the rotary kiln operation method of the present invention is a process that can suppress the increase in the degree of reduction in the electric furnace and reduce the amount of heavy oil and pulverized coal used as fuel.

1 rotary kiln 11 charge end 12, 12A reducing agent (fuel) supply port 13 discharge end 14 burner 15 body portion 16 outer shell 16R space portion 17 scoop feeder 171 tip portion 172 straight portion 2 hopper 3 feeding conveyor

Claims (5)

A method of operating a rotary kiln, which is a heating furnace that heats the inside by combustion heat of fossil fuel, and is a heating furnace in which a reducing furnace that performs reduction treatment is connected to the downstream process side,
Replacing a part of the fossil fuel put into the rotary kiln with RPF,
How to operate a rotary kiln. The rotary kiln is a rotary kiln that dries the object to be fired and performs partial reduction treatment with a reducing agent,
Adjust so that the total amount of the fixed carbon amount of the RPF and the fixed carbon amount of the reducing agent other than the RPF to be put into the rotary kiln is the fixed carbon amount necessary for the reduction treatment performed in the rotary kiln and the reduction furnace. has been
The operating method of the rotary kiln according to claim 1. adjusting the input amount of the RPF so that the effective utilization rate of the RPF is 80% or more;
The operating method of the rotary kiln according to claim 1 or 2. The RPF is charged into the rotary kiln in a state of being mixed with the reducing agent other than the RPF.
The operating method of the rotary kiln according to claim 2. The rotary kiln is a rotary kiln that dries nickel oxide ore as a raw material and performs partial reduction treatment in ferronickel smelting,
A method for operating a rotary kiln according to any one of claims 1 to 4.

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