Method for producing dried or fired product using rotary kiln, and method for producing crude zinc oxide

Abstract

To provide a method for producing a dried product or a fired product, in a process executed using a rotary kiln provided with a burner for heating using heavy oil or the like as a fuel and a rotary heating furnace body driven by electric power, more economically than the conventional case by optimizing the input of a fuel to be put into the burner while maintaining the production quantity of the dried product or the fired product.SOLUTION: A method for producing a dried product or a fired product is executed using a rotary kiln 1 comprising a burner 30 and a rotary heating furnace body 10 driven by electric power and has: an estimated production quantity per unit time calculation step of calculating an estimated production quantity per unit time of the rotary kiln 1 from a regression equation of the drive power and the production quantity per unit time of the rotary kiln 1; and a fuel input adjustment step of executing an adjustment making the input of a fuel into the burner 30 closer to the estimated production quantity per unit time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a dried product or a fired product using a rotary kiln, and a method for producing crude zinc oxide using this method. More specifically, the present invention relates to a rotary kiln comprising a burner for heating using heavy oil or the like as a fuel and a rotary heating furnace body driven by electricity, and by optimizing the fuel input amount to the burner, it relates to a method for producing a dried product or a fired product capable of improving the economic efficiency of the production of the dried product or the fired product, and a method for producing crude zinc oxide using this method.

Background Art

[0002] For example, when implementing various non-ferrous metal smelting processes, as an industrial heating furnace for performing drying, firing, or both treatments of raw materials and intermediate products (in this specification, these treatments are also collectively referred to as "firing treatment"), a cylindrical furnace with a total length of about 30 m, which comprises a rotary heating furnace body driven by electricity and a burner using heavy oil or the like as a fuel, is widely used (see Patent Document 1).

[0003] When performing the "firing treatment" of the input using the above-mentioned rotary kiln, in order to allow sufficient drying or firing to proceed in the furnace, it is necessary to supply sufficient fuel to maintain a predetermined furnace temperature. However, on the other hand, regarding the fuel cost of heavy oil or the like input to the heating burner, it is required to minimize this and improve the economic efficiency of the "firing treatment" using the rotary kiln. In order to meet such requirements, conventionally, while confirming the "quality of the obtained dried product / fired product", the fuel input amount has been adjusted by means corresponding to their changes.

[0004] As a technique for adjusting the fuel input amount to the burner of a rotary kiln, there is known an operation method of controlling the heavy oil amount and the air amount supplied to the burner for the purpose of maintaining the CO concentration in the discharged gas and the temperature inside the rotary kiln within a predetermined range (see Patent Document 2). However, this technique does not give particular consideration to improving the fuel use efficiency. In the process of performing a firing process using a rotary kiln, with respect to the technique of improving the economic efficiency of the operation by suppressing the fuel input amount to the necessary and sufficient minimum while maintaining the production amount of the product, the above-mentioned means (the means corresponding to the change in the quality of the obtained dried product / fired product) is still insufficient, and furthermore, it has been required to increase the fuel use efficiency and improve the economic efficiency of the operation.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to enable the production of a dried product or a fired product to be performed more economically than before by optimizing the fuel input amount to be input to a burner while maintaining the production amount of the dried product or the fired product in a process performed using a rotary kiln including a heating burner using heavy oil or the like as fuel and a rotary heating furnace body driven by electricity.

Means for Solving the Problems

[0007] The inventors of the present invention have conceived that the above problems can be solved by substituting the real-time "production amount per unit time", which should be used as an index for adjusting the input amount of fuel input to the burner of the rotary kiln, with the "estimated production amount per unit time" calculated from the regression formula between the driving power of the rotary kiln and the production amount per unit time, and have completed the present invention. Specifically, the present invention provides the following.

[0008] (1) A method for producing a dried product or a fired product, which is carried out using a rotary kiln including a burner and a rotary heating furnace body driven by electricity, wherein an estimated production amount per unit time of the rotary kiln is calculated from a regression formula between the driving power of the rotary kiln and the production amount per unit time, and a fuel input amount adjustment step of adjusting the fuel input amount to the burner to be close to the product of the estimated production amount per unit time and the fuel unit consumption. A method for producing a dried product or a fired product, comprising:

[0009] According to the method for producing a dried product or a fired product according to (1), in the step of using a rotary kiln including a heating burner using heavy oil or the like as fuel and a rotary heating furnace body driven by electricity, while maintaining the production amount of the dried product or the fired product, by optimizing the fuel input amount input to the burner, the production of the dried product or the fired product can be carried out more economically than before.

[0010] (2) The method for producing a dried product or a fired product according to (1), wherein the regression formula is a formula obtained by classifying the relationship between the driving power of the rotary kiln and the production amount per unit time according to the rotation speed of the rotary kiln.

[0011] According to the method for producing a dried product or a fired product according to (2), in the production method according to (1), the amount of fuel input to the burner can be optimized with higher accuracy, and the economic efficiency of the production of the dried product or the fired product can be further improved.

[0012] A method for producing crude zinc oxide, wherein the drying and heating step of obtaining crude zinc oxide sinter by firing a crude zinc oxide cake is carried out by the method for producing a dried product or a fired product described in (1) or (2).

[0013] According to the method for producing crude zinc oxide in (3), it is possible to contribute to the reduction of the production cost of crude zinc oxide sinter by enjoying the above effects of the production methods in (1) or (2).

Effects of the Invention

[0014] According to the present invention, in the step carried out using a rotary kiln comprising a burner for heating using fuel such as heavy oil and a rotary heating furnace body driven by electricity, while maintaining the production amount of the dried product or the fired product, by optimizing the input amount of the fuel input to the burner, it is possible to make the production of the dried product or the fired product more economical than before.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] Hereinafter, a preferred embodiment of the method for manufacturing a dried product or a fired product of the present invention will be described. However, the present invention is not limited to the following embodiments.

[0017] <Method for manufacturing a fired product> The manufacturing method of the present invention, that is, "a method for manufacturing a dried product or a fired product using a rotary kiln equipped with a burner and a rotary heating furnace body driven by electricity (also referred to as the'method for manufacturing a fired product' in this specification)", for example, in the manufacturing process of roasting crude zinc oxide (also referred to as 'crude zinc oxide roasting' in this specification) performed in the flow shown in FIG. 2, it is a manufacturing method that can be preferably used as a method for performing a drying and heating step (FIG. 2: S30) of firing intermediate products such as crude zinc oxide and secondary raw materials using a rotary kiln.

[0018] Here, in the drying and heating step, that is, the step of performing "firing treatment" using a rotary kiln, in order to suppress the fuel input amount to the minimum necessary and sufficient amount and improve the economic efficiency of the operation, for each plant where the operation is carried out, it is possible to assume in advance the "fuel consumption per unit production amount", which is the necessary fuel input amount per unit production amount, and the real-time "production amount per unit time" of the rotary kiln in the plant. Making the fuel input amount input to the rotary kiln match the theoretically necessary and optimal fuel input amount, which is the product of these two values, is an ideal adjustment in terms of economic efficiency.

[0019] However, in a rotary kiln where the input material progresses over about 1 to 3 hours in a cylindrical furnace with a total length of about 30 m, among the above-mentioned quantities that can be indicators for adjusting the fuel input amount, it is almost impossible in reality to directly measure and grasp the real-time "production amount per unit time".

[0020] Therefore, in the "method for manufacturing a fired product" of the present invention, instead of obtaining the real-time "production amount per unit time" which is extremely difficult to grasp as described above, two new steps are provided, namely, a "step for calculating the estimated production amount per unit time" of the rotary kiln by calculating the "estimated production amount per unit time" of the rotary kiln from the "regression equation between the driving power of the rotary kiln and the production amount per unit time", and a "step for adjusting the fuel input amount" for adjusting the actual fuel input amount to be close to this management target value by using the product of the "estimated production amount per unit time" and the "fuel unit" as the management target value are carried out as essential steps.

[0021] [Rotary kiln] FIG. 1 is a schematic cross-sectional view showing the overall configuration of a rotary kiln capable of manufacturing a dried product or a fired product using the "method for manufacturing a fired product" of the present invention. The "method for manufacturing a fired product" of the present invention can be widely applied to various processes carried out using a rotary kiln 1 including a rotary heating furnace body 10 driven by electricity and a burner 30 for burning a fuel such as heavy oil to heat the inside of the furnace as shown in the figure.

[0022] As shown in FIG. 1, the rotary kiln 1 is a rotary heating furnace including a rotary heating furnace body 10 which is a hollow cylindrical furnace, a kiln body support portion (not shown) for rotatably supporting the rotary heating furnace body 10 (rotation in the R direction in the figure as an example), a fixed hood 20 covering one end of the rotary heating furnace body 10, a burner 30 for burning a fuel such as heavy oil supplied from a fuel supply pipe 31 and radiating a flame 32 for heating the inside of the rotary heating furnace body 10, and a drive gear 40 for driving and rotating the rotary heating furnace body 10 by electricity.

[0023] Further, in the rotary kiln 1, the rotary heating furnace body 10 is, as an example, a cylindrical furnace with an overall length of about several meters or more and 100 meters or less. During use, it is installed so as to have an inclination of 3 to 4% with respect to the horizontal plane in the direction in which the object to be processed moves from the loading port 11 of the object to be processed toward the discharge port 12 of the object to be processed. Further, the rotary kiln 1 may be provided with a dam 13 having a height of 2% or more with respect to the inner diameter of the rotary kiln at the inner peripheral portion near the discharge port 12. The dam 13 is provided mainly for the purpose of extending the residence time of the object to be processed.

[0024] In the rotary kiln 1 having the above-described configuration, as shown in FIG. 1, the inside of the rotary heating furnace body 10 is heated to a high temperature by the burner 30, and while the rotary heating furnace body 10 is rotated in the R direction by the drive gear 40, the object to be processed is carried in from the loading port 11 in the a direction. The object to be processed moves along the inclination of the inside of the rotary heating furnace body 10 heated to a high temperature while being stirred, and moves toward the discharge port 12, and the high-temperature fired product is discharged from the discharge port 12 in the b direction.

[0025] The "method for manufacturing a fired product" of the present invention, among the above-described rotary kilns, particularly when employed in a large-sized rotary kiln in which the overall length of the rotary heating furnace body is 20 m or more, preferably 30 m or more, the effect of improving economic efficiency becomes particularly remarkable.

[0026] [Estimated production amount calculation step per unit time] Hereinafter, the details of the "estimated production amount calculation step per unit time", which is the first essential step in the "method for manufacturing a fired product" of the present invention, will be described.

[0027] In this specification, the "estimated production amount per unit time" is an estimated value of the production amount per unit time in a rotary kiln, which is used as an alternative index for the "production amount per unit time" in the rotary kiln. In the "method for manufacturing a fired product" of the present invention, in the step of calculating the estimated production amount per unit time, the real-time "estimated production amount per unit time" is calculated from the regression equation between the driving power of the rotary kiln and the production amount per unit time. Since the driving power of the rotary kiln can be continuously measured in real time, it is possible to always grasp the "estimated production amount per unit time" that varies every moment in real time during the driving of the rotary kiln.

[0028] (Regression equation between the driving power of the rotary kiln and the production amount per unit time) The "regression equation between the driving power of the rotary kiln and the production amount per unit time" (also simply referred to as the "regression equation" in this specification) can be obtained from the scatter diagram of the driving power for rotating the rotary heating furnace body 10 of the rotary kiln 1 and the production amount per unit time. FIG. 3 is an example of such a scatter diagram. The production amount shown in the figure is the value indexed with the reference value set to 100, and the driving power is the value indexed with the reference value set to 10. The values of the production amount and the driving power in FIG. 4 are the same. In addition, as samples of the combined values of power and production amount necessary for creating such a scatter diagram, the power value and the production amount value at that time collected in the control room of the rotary kiln can be used.

[0029] Furthermore, regarding the correlation between the driving power for rotating the rotary heating furnace body 10 of the rotary kiln 1 and the production amount per unit time, generally, in a rotary kiln for drying and firing a metal oxide dehydration cake, when the daily production capacity is 0.5 t or more and 1.3 t or less per unit volume in the rotary heating furnace body of the rotary kiln, it is known that there is a strong correlation between the driving power of the rotary kiln and the production amount per unit time. Therefore, under such operating conditions, the "estimated production amount per unit time" can be calculated from the above-mentioned "regression equation" with particularly high accuracy.

[0030] Furthermore, it is more preferable that the above-mentioned "regression equation" is an equation obtained by classifying the relationship between the driving power of the rotary kiln and the production amount per unit time according to the rotational speed of the rotary kiln. By creating a scatter diagram (see Fig. 4) classified by the rotational speed of the rotary kiln, which affects the driving power, and using the "regression equation" obtained from the classified scatter diagram, the "estimated production amount per unit time" can be calculated with higher accuracy.

[0031] In addition, in the scatter diagram of Fig. 4, in the range where the rotational speed of the rotary kiln is 0.4 rpm or more and less than 0.6 rpm (which is the normal rotational speed range of the rotary kiln), the driving power of the rotary kiln and the production amount per unit time show a strong correlation. Therefore, when the rotary kiln is driven at a rotational speed within this range, the "estimated production amount per unit time" can be calculated with high accuracy from the "regression equation".

[0032] On the other hand, in the range where the rotational speed of the rotary kiln is 0.6 rpm or more, which is outside the normal rotational speed range, the variation becomes large and the correlation between the driving power and the production amount per unit time weakens. This is presumably because when the rotational speed is above a certain level, the state inside the furnace is such that factors other than the rotational speed, such as sticking of the melt, have a relatively large influence on the driving power. Therefore, when the correlation is expected to weaken, such as when the rotational speed of the rotary kiln is 0.6 rpm or more, it is preferable to use the conventional method in combination with the present invention, that is, to determine the fuel consumption while checking the quality of the obtained dried or fired product according to the amount of raw material charged, or to temporarily switch to the conventional method as needed.

[0033] [Fuel input amount adjustment step] Next, the details of the "fuel input amount adjustment step", which is the second essential step in the "method for manufacturing a fired product" of the present invention, will be described. In this step, the product of the "estimated production amount per unit time" obtained in the above-described "estimated production amount per unit time calculation step" and the "fuel unit consumption" (production estimation amount per unit time × fuel unit consumption) is set as the management target value, and the fuel input amount to the burner 30 is adjusted to approach or preferably match this value.

[0034] Here, the "fuel unit consumption" is a value determined in advance according to the basic performance and operating conditions of the actually used rotary kiln. Based on the operating results of the rotary kiln, for example, when the fuel is heavy oil, it is obtained by the formula (heavy oil unit consumption = heavy oil usage amount / production amount), that is, it is determined as the amount of heavy oil actually required per unit production amount.

[0035] As described above, in the "estimated production amount per unit time calculation step", during the driving of the rotary kiln, the "estimated production amount per unit time" that varies moment by moment can always be grasped in real time. Therefore, an optimal management target value for the fuel input amount in real time can be set from the grasped "estimated production amount per unit time" and the "fuel unit consumption" which is given basic data.

[0036] <Method for manufacturing crude zinc oxide sinter>[ As described above in detail, the "method for manufacturing a dried product or a fired product" of the present invention can preferably be used as a method for carrying out a drying and heating step S30 of drying and heating a crude zinc oxide dehydration cake (also referred to as a "crude zinc oxide cake" in this specification) and a secondary raw material to obtain a crude zinc oxide sinter in a manufacturing plant for crude zinc oxide sinter by the Waelz process.

[0037] As shown in Fig. 2, the above-mentioned "method for producing crude zinc oxide sinter" includes a reduction roasting step S10 of obtaining crude zinc oxide by reduction roasting primary raw materials such as steel dust, a wet process S20 of separating and removing chlorine, fluorine, etc. from the crude zinc oxide dust obtained in the reduction roasting step S10 to obtain a crude zinc oxide cake, and a drying and heating step S30, which are sequentially performed. In the above overall process, primary raw materials containing zinc, such as steel dust, are charged into the reduction roasting step S10, which is an upstream process. Separately, secondary raw materials containing zinc may be directly charged into the drying and heating step S30, which is a downstream process.

[0038] [Reduction Roasting Step] The reduction roasting step S10 is a step of obtaining crude zinc oxide dust by reduction roasting primary raw materials containing zinc. The reduction roasting treatment is performed by a reduction roasting rotary kiln (RRK). In this RRK body, the steel dust is reduction roasted, and the metal zinc reduced and volatilized thereby is re-oxidized in the exhaust gas to become powdery zinc oxide.

[0039] [Wet Process] The wet process S20 is a step of obtaining a crude zinc oxide cake by removing water-soluble impurities from the crude zinc oxide dust containing zinc oxide recovered in the reduction roasting step S10 by wet treatment. In the wet process S20, the slurry with sufficiently removed impurities is dehydrated by a vacuum suction type dehydrator or the like to become a crude zinc oxide cake containing zinc oxide.

[0040] [Drying and Heating Step] The drying and heating step S30 is a step that can enjoy the effect of improving economic efficiency by being carried out according to the "method for manufacturing a dried or fired product" of the present invention. This step is a step of obtaining crude zinc oxide sinter by firing the crude zinc oxide cake obtained in the wet step S20. The firing treatment is carried out by a drying and heating rotary kiln (DRK) as shown in FIG. 1. In the drying and heating step S30, the crude zinc oxide cake is charged into the DRK and fired to further reduce the concentrations of chlorine, fluorine, etc., to obtain crude zinc oxide sinter. Regarding the heating temperature in the drying and heating step S30, it is preferable to maintain and manage so that the temperature of the sinter when discharged from the DRK is 800°C or higher and 1150°C or lower.

[0041] Conventionally, the adjustment of the fuel (heavy oil) input amount to the rotary kiln in this drying and heating step has generally been carried out in accordance with the amount of raw materials and the like charged into the same step as described above. However, as shown in FIG. 2, in the drying and heating step S30, in addition to the crude zinc oxide cake obtained in the upstream wet step, variously shaped secondary raw materials are also charged. Since the total amount and composition ratio of these charged materials vary complicatedly due to various factors, it has been difficult to supply the optimal heavy oil amount based on these values. On the other hand, according to the "method for manufacturing a dried or fired product" of the present invention, the heavy oil input amount can be adjusted to the optimal amount with high accuracy.

Example

[0042] In the production of crude zinc oxide carried out in the flow shown in FIG. 2, a test operation was carried out as follows to verify the effect of improving economic efficiency by carrying out the drying and heating step according to the "method for manufacturing a dried or fired product" of the present invention. The rotary kiln for carrying out the drying and heating step is a rotary heating furnace body driven by a burner and electricity, and the total length of the rotary heating furnace body is 31 m and the furnace content volume is 191 m 3 A rotary kiln for drying and heating was used.

[0043] [Example] In the production of the above-mentioned crude zinc oxide, the drying and heating step was changed in the process so as to be carried out by the "method for producing a dried product or a fired product" of the present invention, and the test operation was continued for about one month. Specifically, regarding the regression equation between the driving power of the rotary kiln and the production amount per unit time, regression equations were used for each layer according to the rotation speed of the rotary kiln, that is, every 0.1 rpm of the rotation speed. The driving power of the rotary kiln measured in real time was applied to this regression equation to calculate the estimated production amount per unit time, and the operation was continued in such a manner that the input amount of heavy oil was adjusted with this value and the amount of heavy oil calculated from the heavy oil unit as the target control value. The X-Rs control chart of the heavy oil unit during the test operation period of about one month (N = 26) is shown in FIG. 5. From FIG. 5, it can be confirmed that both the X control chart and the Rs control chart are within the control limits during the period of about one month. Note that the heavy oil unit shown in FIG. 3 shows the value indexed with the reference value being 50. The same applies to the values of the heavy oil unit in the following figures.

[0044] [Comparative Example] In the production of crude zinc oxide under the same conditions as in the example, the adjustment of the input amount of heavy oil to the rotary kiln in the drying and heating step was carried out by a conventional method of adjusting according to the charging amount into the rotary kiln, not according to the method of the present invention, and the X-Rs control chart of the heavy oil unit when operating for one year is shown in FIG. 6.

[0045] When comparing the heavy oil units of the example and the comparative example, the variation in the heavy oil unit has become smaller, and by implementing the present invention, a reduction effect of 6.9% in the heavy oil unit could be obtained. From the above results, it can be seen that the "method for producing a dried product or a fired product" of the present invention is a production method that can economically produce a dried product or a fired product while optimizing the amount of fuel input to the burner in a rotary kiln equipped with a heating burner using heavy oil or the like as fuel and a rotary heating furnace body driven by electricity.

Explanation of Signs

[0046] 1 Rotary kiln 10 Rotary heating furnace body 11 Inlet 12 Outlet 13 Dam 20 Fixed Hood 30 Burner 31 Fuel Supply Pipe 32 Flame 40 Driving Gear S10 Reduction Roasting Process S20 Wet Process S30 Drying and Heating Process

Claims

1. A method for producing a dried product or a fired product, which is carried out using a rotary kiln comprising a burner and a rotary heating furnace body driven by electricity, a step of calculating an estimated production amount per unit time of the rotary kiln from a regression equation between the driving power of the rotary kiln and the production amount per unit time; a fuel input amount adjustment step of adjusting the fuel input amount to the burner to be close to the product of the estimated production amount per unit time and the fuel unit consumption; characterized by comprising: A method for producing a dried product or a fired product.

2. The regression equation is an equation obtained by classifying the relationship between the driving power of the rotary kiln and the production amount per unit time according to the rotation speed of the rotary kiln. The method for producing a dried product or a fired product according to Claim 1.

3. A drying and heating step of obtaining crude zinc oxide sinter by firing a crude zinc oxide cake is carried out by the method for producing a dried product or a fired product according to Claim 1 or 2. A method for producing crude zinc oxide.

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