JP6447423B2 - Method for producing zinc oxide ore - Google Patents

Description

  The present invention relates to a method for producing zinc oxide ore. More specifically, the zinc-containing steel dust and zinc-containing steel dust pellets generated in the steel manufacturing process are reduced, volatilized, or the rough zinc oxide dust obtained by wet purification of the crude zinc oxide dust. The present invention relates to a method for producing zinc oxide ore from zinc dust.

  Conventionally, zinc oxide ore obtained by separating and removing impurities from a zinc-containing ore such as crude zinc oxide has been widely used as a raw material for zinc bullion in a zinc smelter.

  Crude zinc oxide is a by-product generated from steelmaking furnaces such as blast furnaces and electric furnaces in the steel industry, for example, and reduced roasting into steel dust and steel dust pellets that contain a relatively large amount of zinc in addition to iron components. It can be obtained by processing. This reduction roasting treatment of steel dust is generally performed by reduction roasting (so-called Welts method) using a rotary kiln. Zinc contained in steel dust reduced and roasted by this method is reduced and volatilized in a rotary kiln for reduction roasting and recovered as crude zinc oxide dust.

  Naturally, the halogen concentration in the final product zinc is required to be extremely low. Further, in order to use zinc oxide ore as a raw material for zinc smelting by the ISP smelting method or the like, it is necessary to reduce the halogen concentration of zinc oxide ore to a value allowed in each smelting process. In order to reduce the halogen concentration of zinc oxide ore, as a method of separating and removing halogen from the reduced zinc oxide after reduction roasting, the halogen is volatilized and separated by baking in a rotary kiln for drying and heating (patent) Reference 1).

  In general, a rotary kiln for drying and heating is based on a system in which a material ore is fired by heating the inside of a furnace by jetting a flame from an oil burner. However, in such a heating method using an oil burner, in order to sufficiently raise the firing temperature and secure the necessary halogen removal rate, increasing the flame strength by increasing the amount of fuel and air to be ejected, The oil frame spreads accordingly, in other words, the cross-sectional area of the burner frame increases. Then, the spread flame directly hits a part of the wall surface in the kiln and is in an excessively heated state locally. In this state, zinc oxide ore melts at a specific location on the discharge end side in the kiln, and deposits in the furnace called coaching, ring, beco, etc. (hereinafter collectively referred to as “coaching”) are generated, Will grow. If the growth of the coaching proceeds beyond an allowable range, the raw material becomes an obstacle when moving in the rotary kiln, and there is a problem that the operation is finally stopped for maintenance work.

  For example, as a means for suppressing the generation of such coaching, the weight of the steelmaking dust charged to increase the softening / melting point of the charge and to prevent the charge from adhering to the inner wall of the kiln. A method of adding 3% or more of MgO is disclosed (see Patent Document 2).

  However, when it is assumed that the technique described in Patent Document 2 is applied not to the reduction kiln rotary kiln but to the drying / heating rotary kiln that is the target equipment of the present invention, the charging side in the drying / heating rotary kiln The pellets of the crude zinc oxide dust granulated in step 1 are dried and heated while moving from the charging side to the discharging side, and once in a semi-molten state by the firing reaction on the discharging side, the oxide sintered body However, since the melting point of zinc oxide ore is increased, this firing reaction is not sufficiently performed, and good pellets cannot be obtained. In addition, when zinc oxide ore containing MgO is treated by a dry smelting method such as an ISP smelting method, the treated MgO is distributed to slag, which is an important factor in blast furnace operation. The slag composition and slag melting point will also change, and the adverse effect on the operation of the blast furnace is very large.

  On the other hand, many techniques for suppressing an overheating state that causes the generation of coaching have been proposed. For example, in a rotary kiln for ferronickel smelting, the rotary kiln for appropriately controlling the length and diameter of the burner frame, the rotary kiln burner, and the operation method of the rotary kiln (see Patent Document 3), the frame in the rotary kiln Rotary kiln burner capable of controlling the length and shape thereof, improving combustion efficiency, reducing power cost used for primary air and obtaining an efficient heat flow distribution, and a method of blowing pulverized coal into the burner (See Patent Document 4).

  However, the methods described in Patent Documents 3 and 4 are all directed to a process involving combustion of pulverized coal whose combustion speed is much slower than that of gaseous fuel or liquid fuel. Each of these prior arts is a process proposed from the viewpoint of how to increase the burning rate of pulverized coal or burn out the pulverized coal. On the other hand, this invention makes the application object the process of burning the liquid fuel which is excellent in combustibility unlike pulverized coal. Therefore, the technical problems of the methods described in Patent Documents 3 and 4 are different from those of the present invention, and application to a process involving combustion of liquid fuel to which the present invention is applied is not effective.

JP-A-9-125169 JP-A-5-132723 Japanese Patent Laying-Open No. 2015-25152 Japanese Patent Laid-Open No. 10-300021

  In the production of zinc oxide ore, the present invention suppresses the generation and growth of coating in a rotary kiln for drying and heating to avoid a decrease in productivity while maintaining a high halogen removal rate in the furnace. An object of the present invention is to provide a production method capable of producing high-grade zinc oxide ore with high productivity.

  In the rotary kiln used in the drying and heating process, the present inventors optimize the spread of the flame ejected from the oil burner, for example, by appropriately changing the discharge angle or the like of the portion that ejects or ejects oil or air. As a result, the present inventors have found that the above problems can be solved, and have completed the present invention. Specifically, the present invention provides the following.

(1) A method for producing zinc oxide ore comprising a step of drying and heating to make zinc oxide ore by firing crude zinc oxide dust using a rotary kiln, wherein the rotary kiln comprises an oil burner at the discharge end, The oil burner has a substantially cylindrical shape, and sequentially discharges oil and spray air from the central portion, a swirling flow blowing portion that blows primary air that is a swirling flow, and blows secondary air that is a straight flow. A straight flow outlet is an oil burner formed concentrically in this order,
The control temperature range of the outer surface temperature of the rotary kiln at a specific distance from the discharge end of the rotary kiln is determined, and the shape of the oil burner is changed so that the outer surface temperature is within the control temperature range By doing so, the spread of the flame spouted from this oil burner is optimized, The manufacturing method of the zinc oxide ore characterized by the above-mentioned.

  (2) In the rotary kiln, the shape of a nozzle installed at the tip position of the discharge part of the oil burner is a shape that allows an oil spray diffusion angle to be 15 ° to 30 °, and the swirl flow The swirl vane portion constituting the blowout portion is composed of a plurality of blades having substantially the same angle of 40 ° to 60 ° with respect to the longitudinal center line of the oil burner, and the straight flow blowout portion is It is formed as a gap between the outer periphery of the swirl vane portion and the inner periphery of the burner tile, and is any one of the shape of the nozzle, the shape of the swirl flow outlet, and the shape of the straight flow outlet Or the manufacturing method of the zinc oxide ore as described in (1) which optimizes the spreading of the flame spouted from the said oil burner by changing suitably everything suitably.

  (3) The outer surface temperature of the rotary kiln at a position separated from the discharge end of the rotary kiln by one-sixth of the total length of the rotary kiln is separated from the discharge end by one-third of the total length of the rotary kiln. Any one or all of the shape of the nozzle, the shape of the swirling flow blowing portion, and the shape of the straight flow blowing portion are appropriately and appropriately adjusted so that the outer surface temperature is within a range of ± 20 ° C. The zinc oxide ore production method according to (1) or (2), wherein the spread of the flame is optimized by changing.

  (4) The outer surface temperature of the rotary kiln at a position separated from the discharge end of the rotary kiln by one-sixth of the total length of the rotary kiln is the temperature of zinc oxide ore discharged from the rotary kiln, The nozzle so that the thickness of the kimono and the thermal conductivity, the thickness and thermal conductivity of the refractory in the rotary kiln, and the outside air temperature are less than + 50 ° C. The flame spread is optimized by appropriately changing any one or all of the shape, the shape of the swirl flow outlet, and the shape of the rectilinear flow outlet (1). ) Or the method for producing zinc oxide ore according to (2).

  (5) The shape of the nozzle, the shape of the swirl flow outlet, and the straight flow so that the outer surface temperature of the rotary kiln at a position of 5 m or more and 10 m or less from the discharge end of the rotary kiln is 250 ° C. or less. The method for producing a zinc oxide ore according to (1) or (2), wherein the spread of the flame is optimized by appropriately changing any or all of the shapes of the blowout portions as appropriate. .

  (6) A rotary kiln for producing zinc oxide ore having an oil burner at the discharge end, the oil burner having a substantially cylindrical shape, a discharge unit for discharging oil and spraying air sequentially from the center, a swivel An oil burner in which a swirl flow blow-out portion for blowing out primary air as a flow and a straight-flow blow-out portion for blowing out secondary air as a straight flow are concentrically formed in this order and are arranged at the tip of the discharge portion The shape of the nozzle is such that the oil spray diffusion angle is not less than 15 ° and not more than 30 °, and the swirl vane portion constituting the swirl flow blowing portion is 40 with respect to the longitudinal center line of the oil burner. It is composed of a plurality of blades having substantially the same angle of not less than 60 ° and not more than 60 °, and the straight flow outlet is formed as a gap between the outer periphery of the swirl blade and the inner periphery of the burner tile. Rotary kiln made.

  According to the present invention, in the production of zinc oxide ore, the generation and growth of coating in a rotary kiln for drying and heating is suppressed to avoid a decrease in productivity, and the high halogen removal rate in the furnace is also achieved. It is possible to provide a production method capable of maintaining and producing high-grade zinc oxide ore with high productivity.

It is sectional drawing which shows typically the structure by the side of the discharge end about the rotary kiln used for the manufacturing method of this invention. It is sectional drawing which shows the structure typically about the oil burner of the rotary kiln of FIG. It is a side view which shows typically an example of the shape of the nozzle of the oil burner of FIG. 2, and the angle of the burner frame ejected from the said nozzle. It is a front view which shows an example of the swirl | vortex flow blowing part of the oil burner of FIG. It is a graph which shows the temperature distribution of the outer surface of the rotary kiln for drying heating with respect to the distance from the discharge end of a kiln before and behind implementation of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<Method for producing zinc oxide ore>
The zinc oxide ore production method of the present invention is ejected from an oil burner of a rotary kiln (hereinafter, also simply referred to as “rotary kiln” or “DRK”) used in the “dry heating step” described in detail below. By appropriately controlling the spread of the generated flame, the growth of the coaching in the DRK furnace is suppressed to avoid a decrease in productivity while maintaining a high halogen removal rate in the furnace. This is a production method capable of producing high-grade zinc oxide ore with high productivity.

  The method for producing zinc oxide ore according to the present invention is a method for producing the effects described above by applying this to the drying and heating step in a general overall process for producing zinc oxide ore. The general overall process of zinc oxide ore production is a reduction roasting process in which zinc containing ore such as steel dust is reduced and roasted to obtain crude zinc oxide, and the halogen components are separated and removed from the crude zinc oxide obtained in the same process. Thus, an overall process including at least a wet process for obtaining a crude zinc oxide cake and a dry heating process for obtaining a zinc oxide ore by drying and heating the crude zinc oxide cake obtained in the same process is assumed.

[Reduction roasting process]
In the reduction roasting process, the raw material etc. which pelletized steel dust with the reducing material previously are reduced and roasted by the rotary kiln (RRK) for reduction roasting. In this step, the raw material pellets are continuously charged into the RRK together with limestone and the like. The raw material derived from steel dust is reduced and roasted in the RRK furnace, and the volatilized metallic zinc is re-oxidized in the furnace to powdery zinc oxide. Powdered zinc oxide is introduced into the dust collector together with the exhaust gas from the RRK, captured, and recovered as crude zinc oxide.

[Wet process]
In the wet process following the reduction roasting process, impurities such as fluorine contained in the crude zinc oxide obtained in the reduction roasting process are separated and extracted into the treatment liquid, and further impurities from the crude zinc oxide by solid-liquid separation treatment. Is removed by a water washing method to obtain a crude zinc oxide cake. More specifically, in a state where halogen-based impurities such as fluorine are removed in the treatment liquid, the treatment liquid in which the impurities are distributed is removed from the slurry by solid-liquid separation. As a result, the crude zinc oxide slurry becomes a higher concentration crude zinc oxide cake.

[Dry heating process]
In the drying and heating process, the crude zinc oxide cake obtained in the wet process is put into a rotary kiln (DRK) for drying and heating and baked to produce high-grade zinc oxide ore while further reducing the halogen concentration. Perform dry processing.

  The moisture content of the crude zinc oxide cake to be treated in this step is generally 20% by mass or more and 30% by mass or less. Further, the general composition of the crude zinc oxide cake is as follows: zinc is 61 mass% or more and 68 mass% or less, lead is 7 mass% or more and 10 mass% or less, chlorine is 0.3 mass% or more and 0.9 mass% or less, Fluorine is 0.2% by mass or more and 1.5% by mass or less (both are based on dry amount). Such a crude zinc oxide cake is put into the DRK by a quantitative charging device such as a screw feeder in the form of a water-containing cake.

The exhaust gas generated by the DRK is sucked from the charging end side, removed through a wet exhaust gas cleaning facility and a wet electric dust collector, and discharged from the chimney through a fan or other exhaust fan. The amount of exhaust gas sucked from the charging end side is generally 9000 Nm ³ / h or more and 11000 Nm ³ / h or less. The crude zinc oxide cake charged into the DRK is granulated into pellets at the charging end inside a rotary kiln having a length of about 30 m, then dried, heated, and baked at the discharge end.

  The firing temperature in the drying and heating step is 900 ° C. or more and 1200 ° C. or less at the zinc oxide ore temperature. The discharged ore temperature is continuously measured and monitored with a radiation thermometer. Here, it is preferable to maintain and manage the firing temperature so that the zinc oxide ore temperature is in the range of 1050 ° C. to 1150 ° C. The DRK is provided with an oil burner on the discharge end side for discharging zinc oxide ore, and is heated by direct fire from the discharge end side. The firing temperature can be adjusted by the amount of heavy oil supplied to the oil burner. By monitoring the discharged zinc oxide ore temperature, the amount of oil, for example, heavy oil, used in the oil burner is generally adjusted in the range of 400 L / h to 700 L / h.

  In the drying and heating step, the size of the zinc oxide ore discharged from the DRK is generally 1 mm or more and 6 mm or less, and the general composition thereof is 60% by mass to 70% by mass of zinc and 3% by mass or more of lead. 5% by mass or less, chlorine is 0.5% by mass or more and 1.5% by mass or less, and fluorine is about 0.6% by mass or less (both are based on dry amount). The fluorine content may be further controlled to be 0.05% by mass or less depending on the application. In addition, the yield of zinc oxide ore in a general zinc oxide production process is about 6 t / h or more and 10 t / h or less.

(Rotary kiln (DRK) for drying and heating)
Here, the rotary kiln for dry heating according to the present invention used in the implementation of the method for producing zinc oxide ore of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing a configuration on the discharge end side which is a technical feature of a rotary kiln 1 which is a typical example of a rotary kiln for drying and heating according to the present invention.

  The rotary kiln 1 rotates to a kiln body 10 that is a hollow cylindrical kiln, a fixed hood 30 that covers one end of the kiln body, an oil burner 40 that blows hot air to heat the inside of the kiln body 10, and the kiln body 10. It is a rotary heating furnace provided with a drive gear (not shown) for transmitting force.

  In the rotary kiln 1, the inside of the kiln main body 10 is heated to a high temperature by the oil burner 40, and the crude zinc oxide cake is subjected to a heat drying process while rotating the kiln main body 10 by the drive gear. The crude zinc oxide cake moves along the inside of the kiln body 10 toward the discharge end 11 while being stirred and roasted along the inclination of the kiln body 10. As discharged. The kiln main body 10 is made of steel, and a refractory layer is formed on the inner side by a regular refractory (brick) or an irregular refractory (castable) with a thickness of about 25 mm to 30 mm. In general, the outer diameter is 3.3 m, the length is 30 m, and the exterior is about 25 mm thick. In this invention, the rotary kiln provided with the kiln main body from 2 m to 4 m in inner diameter and 20 m to 50 m in length is assumed as the applicable range.

  As shown in FIG. 2, the oil burner 40 is provided with a burner body 44 and a swirl vane portion 45 inside a substantially cylindrical burner tile 46, and converts combustion air into a core airflow and an external airflow. It is a burner in which a multi-layer cavity structure capable of diversion is formed. Specifically, this multi-layered cavity configuration is a discharge unit 41 that discharges oil and air for spraying sequentially from the center, a swirl flow blowing unit 42 that blows primary air a2 that is a swirl flow, and a straight flow. A straight flow outlet 43 for blowing the secondary air a3 is formed concentrically in this order. The discharge part 41 is mainly formed by the burner main body 44, and a nozzle 441 is installed at the front end portion of the burner main body 44, that is, at the front end position of the discharge part 41. The swirl flow outlet 42 is mainly formed by swirl vanes 45. The straight flow outlet 43 is formed as a gap between the outer periphery of the swirl vane 45 and the inner periphery of the burner tile 46.

  In the oil burner 40, the oil sprayed from the nozzle 441 at the tip of the burner body 44 and the combustion air are mixed to cause a combustion reaction, and the burner frame 50 is rotated in the manner shown schematically in FIG. Formed inside. In the oil burner 40, the nozzle 441 disposed at the tip of the burner body 44 preferably has a shape that allows the oil spray diffusion angle to be in the range of 15 ° to 30 °. Here, the “oil spray diffusion angle” in this specification refers to an angle as indicated by θ in FIG. 3, and refers to the sum of the angle of elevation and depression of the oil spray. . For example, the oil spray diffusion angle is 15 ° in total of the elevation angle and the depression angle, that is, +7.5 degrees and −7.5 degrees, and the oil and the spray air have a diameter of 7 mm or more and 9 mm or less. An oil burner provided with a nozzle 441 that blows out from about four small holes 442 can be given as an example of a preferable oil burner that the rotary kiln 1 used in the practice of the present invention should have.

  In the oil burner 40, the swirl vane portion 45 (see FIG. 4) constituting the swirl flow blowout portion 42 that blows the combustion air a <b> 1 as the primary air a <b> 2 that is a swirl flow is the center tip in the longitudinal direction of the oil burner 40. The blades 451 are arranged at substantially the same angle of 40 ° or more and 60 ° or less. For example, an oil burner having a swirl vane portion in which the swirl vane portion 45 is composed of 16 plates having substantially the same angle of 50 ° with respect to the longitudinal center line of the oil burner 40 is implemented in the present invention. It can mention as an example of the preferable oil burner which the rotary kiln 1 to be used should provide.

  Further, in the oil burner 40, the straight flow outlet 43 that blows out the combustion air a1 as secondary air that is a straight flow is between the outer periphery of the swirl vane portion 45 and the inner periphery of the burner tile 46 as described above. It is formed as a void. For example, an oil burner provided with a straight flow outlet formed as a substantially concentric circular gap of 10 mm to 15 mm on the outer peripheral portion of the swirl blade 45 is a preferable oil burner to be provided in the rotary kiln 1 used in the practice of the present invention. As an example.

  In the oil burner 40 having the above-described configuration, the combustion air a <b> 1 is introduced between the burner tile 46 and the burner body 44. As shown in FIG. 2, the combustion air a <b> 1 is divided into air that passes through the swirl flow blowing portion 42 near the center of the oil burner 40 and air that passes through the straight flow blowing portion 43 near the outer peripheral portion. The The air passing through the swirl flow outlet 42 is turned into a swirl flow a2 by the swirl blade 45. Then, the air passing through the straight flow outlet 43 is blown into the kiln main body 10 as the straight flow a3 without passing through the swirl blade 45.

  The rotary kiln 1 is provided with the oil burner 40 having the above-described configuration, thereby improving the straightness of the burner frame 50. By making the rotary kiln 1 into a long and narrow frame, it is possible to suppress the lifting of the burner frame 50. Thereby, it can suppress that the burner flame | frame 50 directly hits the inner wall of the kiln main body 10, and generation | occurrence | production of the coaching resulting from the excessive heating of the said inner wall can be suppressed.

(Coaching detection and control method)
Details of the coaching detection and control method will be described below. As described above, when the coaching is generated, the in-furnace environment is getting worse and it is almost impossible to improve. Therefore, the most important point in management is how to detect the sign of coaching and prevent the generation of coaching. In view of this point, in the method for producing zinc oxide ore of the present invention, the position separated by a specific distance from the discharge end of the rotary kiln is defined as a specific location for management, and the management temperature range of this specific location is determined to determine the outer surface temperature. To monitor. Then, the monitoring result is appropriately fed back to the adjustment of the oil burner of the rotary kiln. Specifically, any or all of the shape of the nozzle 441, the shape of the swirling flow blow-out portion 42, and the shape of the straight flow blow-out portion 43 arranged at the tip position of the discharge portion 41 of the oil burner 40, Change as appropriate. By this method, the burner frame 50 ejected from the oil burner 40, that is, the spread of the flame can be optimized as appropriate, and the generation of the coaching can be detected at an early stage, or the growth can be suppressed. A specific example of a preferred embodiment of the method for monitoring the surface temperature will be described below.

  As a first method of detecting and controlling the coaching, the outer surface temperature of the rotary kiln 1 at a position separated from the discharge end 11 of the rotary kiln 1 by one sixth of the entire length of the rotary kiln 1 is The shape of the nozzle 441 of the oil burner 40, the shape of the swirling flow outlet 42, so that the outer surface temperature of the rotary kiln 1 at a position separated by one third of the full length of 1 is within a range of ± 20 ° C. And the method of optimizing the spread of a flame can be mentioned by changing suitably one or all of the shape of the straight flow blow-out part 43 suitably.

  As a second method of detecting and controlling the coaching, the outer surface temperature of the rotary kiln at a position separated from the discharge end 11 of the rotary kiln 1 by one-sixth of the total length of the rotary kiln 1 is discharged from the rotary kiln 1. From the temperature of zinc oxide ore, the thickness and thermal conductivity of deposits in the rotary kiln 1, the thickness and thermal conductivity of refractories in the rotary kiln 1, and the outside air temperature Appropriately change any or all of the shape of the nozzle 441 of the oil burner 40, the shape of the swirling flow outlet 42, and the shape of the straight flow outlet 43 so as to be less than the estimated value + 50 ° C. A method for optimizing the spread of the flame can be mentioned.

  As a third method of detecting and controlling the coaching, the nozzle of the oil burner 40 is set so that the outer surface temperature of the rotary kiln 1 at a position of 5 m or more and 10 m or less from the discharge end 11 of the rotary kiln 1 is 250 ° C. or less. A method for optimizing the spread of the flame can be exemplified by appropriately changing any one or all of the shape of 441, the shape of the swirling flow blowing portion 42, and the shape of the straight flow blowing portion 43. .

  In the first method, the position separated from the discharge end 11 of the rotary kiln 1 by one-sixth of the total length of the rotary kiln 1 means the position of the tip of the burner frame 50, and from the discharge end 11 of the rotary kiln 1. The position separated by one third of the total length of the rotary kiln 1 is a position where the outer surface of the rotary kiln 1 begins to be heated by the charged material in the furnace. Therefore, the outer surface temperature of the rotary kiln 1 at “a position separated from the discharge end 11 of the rotary kiln 1 by one-sixth of the total length of the rotary kiln 1”, and “3 of the total length of the rotary kiln 1 from the discharge end 11 of the rotary kiln 1”. If the outer surface temperature of the rotary kiln 1 at a position separated by a fraction of a length is substantially the same, it is assumed that the burner frame 50 does not directly contact the inner wall of the kiln body 10.

  In the second method, the zinc oxide ore temperature is 900 ° C. or more and 1200 ° C. or less, while the temperature of the burner frame 50 is 1400 ° C. or more and 1500 ° C. or less, and is estimated from the zinc oxide ore temperature. If the temperature exceeds the outer surface temperature of the rotary kiln being + 50 ° C. as a threshold, it is determined that the burner frame 50 is in contact with the inner wall of the kiln body 10.

  In the third method, each temperature value or the like as a criterion is more specifically quantified. Further, the spread of the flame can be adjusted by changing the shape of the nozzle 441, the shape of the swirl blade 45, and the shape (gap width, etc.) of the straight flow outlet 43. By changing the shape of the nozzle at the tip of the discharge portion 41 of the oil burner 40, the diffusion angle of the oil spray, that is, the spread of the burner frame 50 can be adjusted. Further, if the shape of the swirl vane portion 45 and the clearance width of the straight flow outlet 43 are changed, the pressure loss between the air flow passing through the swirl vane portion 45 and the air flow straightly traveling around the outer periphery of the swirl vane portion 45 will be described. And the flow rate ratio between the swirling flow a2 and the straight flow a3 can be adjusted. Thereby, the spread of the burner frame can be adjusted.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

As shown below, a test operation for verifying the effect of the present invention was performed using the rotary kilns of Comparative Example, Example 2, and Example 1 in which the configuration of the oil burner portion was sequentially improved. As a rotary kiln for test operation, the outer diameter of the kiln main body is 3.3 m, the same length is 30 m, and the outer thickness of the kiln main body is 25 mm. In addition, a refractory layer formed of a regular refractory (brick) and an irregular refractory (castable) with a thickness of 25 to 30 mm was used.
(Comparative Example 1)
Assuming a rotary kiln before improvement, the DRK according to the present invention does not have a configuration for diverting combustion air to the core and the outside, and a DRK in which an oil burner that blows only a swirl flow is installed is Comparative Example 1. DRK. The shape of the nozzle was adjusted so that the oil spray diffusion angle was 60 °.
(Example 2)
Next, the DRK of the present invention, that is, the DRK using the oil burner in which the three-layer outlets of the discharge part, the swirl flow outlet part, and the straight flow outlet part are formed concentrically in order from the center part. 2 ”DRK. The diffusion angle of the oil spray was kept at 60 ° as in Comparative Example 1.
Example 1
Regarding the DRK in Example 2, the DRK in which the shape of the nozzle at the tip of the oil discharge part of the oil burner was further changed to a shape in which the oil spray diffusion angle was 30 ° was designated as the DRK in Example 1.

The test operation using DRK of each Example or Comparative Example was performed under the following conditions.
In each test operation using DRK of each example, the outer surface temperature of the rotary kiln was measured in the range of 1 m to 10 m from the discharge end of the rotary kiln. The amount of heavy oil used in the oil burner was adjusted in the range of 400 to 700 L / h so that the firing temperature was in the range of 1050 to 1150 ° C. at the zinc oxide ore temperature. The combustion air flow rate was also adjusted according to the amount of heavy oil used so that the air-fuel ratio was constant. The yield of zinc oxide ore was 6 to 10 t / h. The temperature was measured once every 8 hours for 20 days after 2 days from the start of operation. An infrared thermometer was used for the measurement.

  FIG. 3 is a diagram showing the outer surface temperature of the kiln with respect to the distance from the discharge end of the kiln, and plots the data of the average value for 20 days at the position at each distance from the discharge end. In FIG. 3, the one where the outer surface temperature of the kiln is lower represents that the lifting of the burner frame can be suppressed.

  Table 1 below shows the stop time rate resulting from the occurrence of coaching before improvement (comparative example) and after improvement (Examples 1 and 2), with 100 before improvement. The investigation period is about 12 months before improvement, about 9 months after separation of combustion air, and about 7 months after atomization of the atomized air. It can be seen that the outage due to coaching has been greatly reduced by the practice of the present invention.

  From FIG. 3 and Table 1, according to the production of zinc oxide ore of the present invention, the growth of the coating is maintained while maintaining a sufficient furnace temperature for achieving a high halogen removal rate in the rotary kiln for drying and heating. It can be seen that this is a production method that can suppress the decrease in productivity, that is, can produce high-grade zinc oxide ore with high productivity.

DESCRIPTION OF SYMBOLS 1 Rotary kiln 10 Kiln main body 11 Discharge end 30 Fixed hood 40 Oil burner 41 Discharge part 42 Swirling flow blowing part 43 Straight flow blowing part 44 Burner main body 441 Nozzle 442 Small hole 45 Swirling blade part 451 Blade 46 Burner tile 50 Burner frame 60 Burned material

Claims (6)

A method for producing zinc oxide ore, comprising a step of drying and heating zinc oxide ore by firing crude zinc oxide dust using a rotary kiln,
The rotary kiln has an oil burner at the discharge end,
The oil burner has a substantially cylindrical shape, and sequentially discharges oil and spray air from the central portion, a swirling flow blowing portion that blows primary air that is a swirling flow, and blows secondary air that is a straight flow. A straight flow outlet is an oil burner formed concentrically in this order,
The control temperature range of the outer surface temperature of the rotary kiln at a specific distance from the discharge end of the rotary kiln is determined, and the shape of the oil burner is changed so that the outer surface temperature is within the control temperature range By doing so, the spread of the flame spouted from this oil burner is optimized, The manufacturing method of the zinc oxide ore characterized by the above-mentioned. The rotary kiln is
The shape of the nozzle installed at the tip position of the discharge part of the oil burner is a shape that allows the oil spray diffusion angle to be 15 ° to 30 °,
The swirl vane portion constituting the swirl flow blowout portion is composed of a plurality of blades having substantially the same angle of 40 ° to 60 ° with respect to the longitudinal center line of the oil burner,
The straight flow outlet is formed as a gap between the outer periphery of the swirl vane and the inner periphery of the burner tile;
Optimizing the spread of the flame ejected from the oil burner by appropriately changing any one or all of the shape of the nozzle, the shape of the swirling flow blowing portion, and the shape of the straight flow blowing portion. The method for producing a zinc oxide ore according to claim 1. The outer surface temperature of the rotary kiln at a position separated from the discharge end of the rotary kiln by one-sixth of the total length of the rotary kiln is at a position separated from the discharge end by one-third of the total length of the rotary kiln. Any or all of the shape of the nozzle, the shape of the swirling flow outlet, and the shape of the straight flow outlet are appropriately changed so as to be in the range of the outer surface temperature ± 20 ° C. The method for producing zinc oxide ore according to claim 2 , wherein the spread of the flame is optimized. The outer surface temperature of the rotary kiln at a position one-sixth the length of the rotary kiln from the discharge end of the rotary kiln is the temperature of the zinc oxide ore discharged from the rotary kiln, the thickness of the deposit in the rotary kiln. The shape of the nozzle so that the estimated value of the outer surface temperature of the rotary kiln derived from the heat calculation is less than + 50 ° C. from the thickness and heat conductivity of the refractory in the rotary kiln and the outside air temperature, the shape of the swirling flow blowing unit, and any or all of the shape of the straight flow blowing unit, by appropriately changed appropriately, according to claim 2, characterized in that to optimize the spread of the flame Method for producing zinc oxide ore. The shape of the nozzle, the shape of the swirl flow outlet, and the straight flow outlet of the rotary kiln so that the outer surface temperature of the rotary kiln at a position of 5 m to 10 m from the discharge end of the rotary kiln is 250 ° C. or lower. The method for producing zinc oxide ore according to claim 2 , wherein the spread of the flame is optimized by appropriately changing any or all of the shapes appropriately. A rotary kiln for producing zinc oxide ore with an oil burner at the discharge end,
The oil burner has a substantially cylindrical shape, and sequentially discharges oil and spray air from the central portion, a swirling flow blowing portion that blows primary air that is a swirling flow, and blows secondary air that is a straight flow. A straight flow outlet is an oil burner formed concentrically in this order,
The shape of the nozzle arranged at the tip position of the discharge part is a shape in which the diffusion angle of oil spray is 15 ° or more and 30 ° or less,
The swirl vane portion constituting the swirl flow blowout portion is composed of a plurality of blades having substantially the same angle of 40 ° to 60 ° with respect to the longitudinal center line of the oil burner,
The rotary kiln in which the straight flow outlet is formed as a gap between the outer periphery of the swirl vane and the inner periphery of the burner tile.

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