JP5708380B2 - Gas seal structure and gas seal method for rotary kiln - Google Patents

Description

  The present invention relates to a gas seal structure of a rotary kiln and a gas seal method using the same.

  Valuable metals including zinc exist in so-called steel dust generated in a steelmaking electric furnace or the like. As a method for separating zinc from this dust, for example, there is a reduction roasting method using a rotary kiln represented by the Welts kiln process. The Welts kiln process is a method of reducing and volatilizing zinc and recovering it as an oxide by roasting steel dust in a reducing atmosphere using a rotary kiln.

  Generally, a kiln for roasting requires airtightness to prevent leakage of gas in the furnace, but in a rotary kiln that is a rotary heating furnace, the rotating kiln main body and the end side of the kiln main body are connected. In the sliding portion that becomes a contact point with the fixed hood to be covered, a slight gap is inevitably formed due to the structure. Therefore, a seal structure for preventing gas leakage from the gap is required. Further, since the kiln body used at a high temperature undergoes appropriate expansion in the longitudinal direction, a seal structure capable of absorbing or avoiding such expansion or contraction has also been demanded.

  As such a seal structure, a labyrinth seal that ensures a pressure difference between the furnace pressure and the furnace pressure due to pressure loss due to the labyrinth structure, a gland seal that uses a gland packing for the sliding part, and a lip type that uses a lip packing for the sliding part A seal or the like has been proposed (see Patent Document 1).

  However, the labyrinth seal is likely to leak, and in the case of a gland seal, a lip seal, etc., the sealing performance of the sliding part depends greatly on the nature of the packing. Under severe conditions such as a rotary furnace with a high temperature treatment of 1000 ° C or higher, there is no packing that satisfies all of heat resistance, wear resistance, and elasticity, so it has appropriate elasticity and excellent sealing performance. However, there is no choice but to select a packing that deteriorates quickly or to select a packing that is durable but poorly sealed. In any case, internal gas cannot be stably shut down and internal gas leakage cannot be sufficiently prevented. .

  As a seal structure that can solve the above problems of the labyrinth structure or a structure using some packing, an inert gas such as nitrogen gas is injected into the seal portion to form an air wall with a high-pressure inert gas, and the internal gas is There is a gas seal structure to shut off. Since this seal structure requires a large amount of inert gas and is expensive, application to a rotary kiln was small, but the amount of necessary inert gas was reduced as in the seal structure described in Patent Document 2. Things have also been proposed.

Japanese Utility Model Publication No. 60-28396 Japanese Patent Application Laid-Open No. 8-14569

  However, the seal structure described in Patent Document 2 still requires a certain amount of inert gas, and at a lower cost, blocks leakage of internal gas to the outside of the furnace. There has been a demand for a gas seal structure that can be used.

  In general, in the case of a rotary furnace in a reducing atmosphere, explosion may occur if air enters the furnace. In the Weltz kiln process, air for reaction or transportation of volatile zinc from the inlet side of the rotary kiln. At the same time, re-oxidation is carried out during air flow. Therefore, there is no problem even if outside air is introduced into the seal portion instead of an inert gas. The present inventors set the gas seal structure of the rotary kiln to a structure in which the outside air is introduced into the seal space formed between the sliding portions provided in a double manner by an outside air introduction mechanism that introduces the outside air. Therefore, in a certain process in which oxygen for reaction is introduced into the furnace, as represented by the Weltz kiln process, it is possible to stably prevent leakage of internal gas without requiring an inert gas. I found.

  Further, the present inventors have found that the gas seal structure of the rotary kiln having the above structure also has an effect of cooling the rotary kiln body exposed to a high heat load, and improves the durability of the rotary kiln. The invention has been completed. More specifically, the present invention provides the following.

  (1) A gas seal structure of a rotary kiln, which is formed between a cylindrical kiln main body, a fixed hood that covers one end of the kiln main body, an outer periphery of one end of the kiln main body, and the fixed hood. A first sliding portion and a second sliding portion that are arranged in order from one end side of the kiln main body on the inner peripheral surface of the fixed hood, and the kiln. A seal space formed by a space surrounded by a body-side sliding portion disposed on an outer peripheral surface of the main body, an inner peripheral surface of the fixed hood, and an outside air introduction mechanism for introducing outside air into the seal space; The rotary kiln is configured so that the outside air introduced by the outside air introduction mechanism flows into the fixed hood portion through the first sliding portion through the seal space. The gas sea Structure.

  (2) The gas seal structure according to (1), which is used in a Wertz kiln process.

  (3) A gas seal method for a rotary kiln with the gas seal structure according to (1) or (2), wherein outside air is introduced from the outside air introduction mechanism to block leakage of gas in the rotary kiln, and The rotary kiln gas sealing method is characterized in that the kiln main body is cooled by causing the introduced outside air to enter the fixed hood.

  (4) The gas sealing method of the rotary kiln according to (3), wherein a blowing speed of the outside air flowing from the first sliding portion into the fixed hood is an average flow velocity of 3.0 m / s or more. Gas seal method for rotary kiln.

  The gas seal structure of the rotary kiln is a gas seal structure that introduces outside air into the seal space formed between the sliding parts provided in double by the outside air introduction mechanism that introduces outside air, and the outside air is more positive. The structure was introduced into the furnace. Accordingly, it is possible to provide a gas seal structure that can prevent leakage of internal gas stably and at low cost without requiring an inert gas. Further, the durability of the rotary kiln can be improved by the cooling effect by the outside air.

It is a cross-sectional schematic diagram which shows the whole structure and usage mode of a rotary kiln. It is a cross-sectional schematic diagram which shows the structure of the gas seal structure of the rotary kiln of this invention. It is a graph which shows the result of having measured the thickness loss amount of the kiln main body accompanying the operation days progress about the rotary kiln provided with the gas seal structure of the rotary kiln of this invention.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to the following embodiment at all.

<Rotary kiln>
First, with reference to FIG. 1, the overall configuration and usage of a rotary kiln that is an embodiment of the gas seal structure of the present invention will be described. As shown in FIG. 1, the rotary kiln 1 includes a kiln main body 10 that is a hollow cylindrical kiln, a kiln support portion (not shown) that rotatably supports the kiln main body 10 in the R direction in the drawing, and one end portion of the kiln main body. A fixed hood 20 that covers the outside, an outside air introduction mechanism 40 having a function of introducing outside air into the fixed hood 20, a burner 50 that blows hot air to heat the inside of the kiln body 10, and a drive gear that transmits rotational force to the kiln body 10 60 is a rotary heating furnace. In addition, when the kiln main body 10 is in use, the to-be-roasted object moves from the inlet 11 that is the inlet of the to-be-roasted object toward the outlet 12 that is the discharge port of the to-be-roasted object, and moves 3 to 3 in the horizontal plane. Installed with 4% slope.

  In the rotary kiln 1, the inside of the kiln main body 10 is heated to a high temperature by the burner 50, and steel dust and the like are carried in from the inlet 11 in the a direction while rotating the kiln main body 10 in the R direction by the drive gear 60. Steel dust or the like moves in the kiln main body 10 toward the direction of the outlet 12 while being stirred and roasted along the inclination of the kiln main body 10, and a high-temperature fired product is discharged in the direction b from the outlet 12. The

<Gas seal structure of rotary kiln>
Next, the details of the gas seal structure 2 of the rotary kiln of the present invention will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view showing the configuration of the gas seal structure 2 of the rotary kiln of the present invention.

  The gas seal structure 2 of the rotary kiln of the present invention includes a kiln main body 10, a fixed hood 20, a first sliding portion 31A and a second sliding portion 31B interposed between the kiln main body 10 and the fixed hood 20, and a main body side slide. It is comprised by the seal | sticker part 30 comprised by the moving part 32, and the external air introduction mechanism 40. It is a space surrounded by the inside of the seal portion 30, that is, the first sliding portion 31 </ b> A and the second sliding portion 31 </ b> B, the outer peripheral surface on one end side of the kiln body 10, and the inner peripheral surface of the fixed hood 20. A seal space 33 is formed. An outside air introduction port 21 for introducing outside air is provided at a position on the seal space 33 of the fixed hood 20, and an outside air introduction mechanism 40 including an air fan or the like is connected to the outside air introduction port 21. . An environmental dust collection hood 22 is provided on the outer surface side of the second sliding portion 31 </ b> B in the fixed hood 20.

  The first sliding portion 31A and the second sliding portion 31B (hereinafter collectively referred to as the sliding portion 31) are a pair of circumferentially arranged in order from one end side of the kiln body 10 of the fixed hood 20. It is a sliding part. From the viewpoint of enhancing the sealing capability, the sliding portion 31 is preferably a circular one that is formed in a ring shape so as to cover the entire outer periphery of the kiln body 10. However, the pair of circumferential sliding portions in the gas seal structure of the rotary kiln of the present invention is not limited to this. If the sliding part 31 is formed in a part necessary for preventing leakage of internal gas along the outer periphery of the kiln body 10, it is not formed in a complete annular connection and is not formed in the kiln body 10. There may be a portion on the outer periphery in which the sliding portion 31 is not formed. For example, it may be possible to maintain a practically sufficient sealing ability by using the upper half of the outer periphery of the kiln body 10 where the sliding portion 31 is likely to become a high temperature internal gas leakage path. Even a semicircular shape formed so as to cover substantially the upper half of the outer periphery of the main body 10 is within the scope of the present invention. The sliding part 31 can be formed of a ceramic heat resistant cloth. The main body side sliding portion 32 is a plate-like member formed on the outer peripheral surface of the kiln main body 10 at a position directly below the sliding portion 31 in the vicinity of one end side of the main body of the kiln main body 10. The main body side sliding portion 32 can be formed of a metal plate material, and a stainless steel slip plate can be preferably used. In addition, as shown in FIG. 2, the main body side sliding part 32 is preferably formed wider than the width between the first sliding part 31A and the second sliding part 31B. Thereby, it can prevent that the interruption | blocking capability of internal gas falls by expansion | swelling or shrinkage | contraction of a kiln main body. The seal portion 30 is formed so as to slide in a state in which the sliding portion 31 and the main body side sliding portion 32 are in contact with each other when the kiln main body 10 is rotated, but due to its structure, the seal space 33 is completely airtight. It is difficult to ensure the property, and a slight gap is generated between the sliding portion 31 and the main body side sliding portion 32. The gas seal structure of the present invention actively uses such a gap, and actively flows out the outside air into the furnace through the gap, thereby blocking leakage of internal gas and further cooling the kiln body 10. However, the durability is improved. In addition, since the seal portion 30 is configured on a surface irrelevant to the expansion and contraction of the kiln main body 10, the internal gas leakage blocking ability is not reduced by the expansion and contraction of the kiln main body 10.

  The outside air introduction mechanism 40 is an air passage for introducing outside air into the seal space 33, and includes an air conditioner 41 that can introduce outside air such as an air fan or an air pump. The outside air introduction mechanism 40 is not particularly limited as long as the outside air 70A around the rotary kiln 1 can be introduced into the seal space 33 as it is, and a device including an air conditioner 41 such as a known fan device or an air pump can be appropriately applied. it can. Further, the outside air introduction mechanism 40 has at least an average flow rate of 1.0 m / s with respect to the blowing speed of the outside air 70B blown out from the gap between the first sliding portion 31A and the main body side sliding portion 32 toward the inside of the fixed hood 20. As mentioned above, it is preferable that there is an ability to ensure an average flow velocity of 3.0 m / s or more. Details of a specific example of such an outside air introduction mechanism 40 will be described in a later embodiment.

  The outside air 70A introduced from the outside air introduction mechanism 40 is introduced into the seal space 33 that is an incomplete airtight space. Although the seal space 33 is imperfect but also has a certain airtightness, the pressure inside the seal space 33 becomes higher than the pressure outside the seal space 33 due to the introduction of outside air. When the atmospheric pressure inside the seal space 33 reaches a certain pressure, the introduced outside air 70A is directed from the first sliding portion 31A side toward the inside of the fixed hood 20 (outside air 70B) or from the second sliding portion 31B side. The dust flows out into the dust collection hood 22 (outside air 70C). Then, the outside air 70 </ b> B that flows out toward the inside of the fixed hood 20 flows into the kiln main body 10. On the other hand, the hood outflow gas 80A generated in the fixed hood 20 or the like is caused by the fluctuation in atmospheric pressure accompanying the fall and discharge of the high-temperature fired product in the fixed hood 20, the upward air flow in the hood, the subtle fluctuation in atmospheric pressure in the kiln, and the like. It moves to the vicinity of the moving part 31A. However, the outflow gas 80A in the hood is pushed back into the hood by the outside air 70B, and the outflow gas 80A in the hood can be prevented from leaking from the gap of the first sliding portion 31A. The outflow gas 80A in the hood pushed back into the hood is guided to the exhaust gas treatment facility by the exhaust gas suction fan, for example, through the inside of the kiln together with the in-furnace gas 80.

  Here, the portion near the outlet 12 of the rotary kiln 1 has an atmospheric temperature of about 1200 ° C., and high-temperature oxidation of the kiln shell surface in contact with the internal gas has been a problem. Since the outside air 70B also has an effect of cooling the vicinity of the outlet 12 of the kiln body 10 exposed to a high temperature heat load, the durability of the rotary kiln 1 is enhanced by the cooling effect as will be described in detail later in the embodiments. Can do.

<Gas sealing method of rotary kiln>
The gas sealing method for a rotary kiln according to the present invention will be described with reference to FIG.

  The rotary kiln gas sealing method of the present invention is a gas sealing method in the rotary kiln 1 having the rotary kiln gas sealing structure of the present invention described above. Unlike gas seals using inert gas that have been applied to reduction roasting furnaces, the introduction of outside air to the seals has made it possible to significantly reduce costs, and the outside air has been actively introduced into the furnace. Introducing the seal 30 in order to block the leakage of internal gas and simultaneously improve the durability of the kiln main body 10 by cooling the kiln main body 10. Since it is configured, it is a feature of the present invention that the internal gas leakage blocking ability is not reduced by expansion and contraction of the kiln body 10.

  With respect to the flow rate of the outside air introduced into the seal space 33, a flow rate is required to keep the internal pressure of the seal space 33 higher by about 0.5 to 1.0 kPa than the pressure inside the furnace. By maintaining such an internal pressure, leakage of the outflow gas 80A in the hood from the gap of the sliding portion 31 to the outside can be blocked. Details of a specific example of the flow rate of outside air will be described in a later embodiment. It is preferable to secure an average flow rate of 3.5 m / s or more for the blowing speed of the outside air from the first sliding portion 31A side toward the inside of the fixed hood 20 by appropriately adjusting the flow rate of the outside air. Leakage of the outflow gas 80A in the hood from the gap of the sliding portion 31 to the outside can be blocked by the airflow from the outside air 70B flowing out toward the inside of the fixed hood 20 and the air pressure inside the seal space 33.

  Moreover, since the gas sealing method of the rotary kiln of the present invention is a method of positively introducing outside air into the furnace, the kiln body 10 can be cooled by the outside air 70B. Thereby, durability of the kiln main body 10 can be improved notably.

  As mentioned above, although the gas sealing method of the rotary kiln of the present invention has been described for the case where the sliding portion 31 is provided on the outlet 12 side of the kiln main body 10, the present method is not limited to this, for example, the kiln main body 10 The same applies to the case where the sliding portion 31 is provided on the inlet 11 side.

  The gas seal structure and the gas seal method of the present invention were adopted on the outlet side of the rotary kiln by the Welts kiln method in which steelmaking dust was reduced and roasted. Moreover, the rotary kiln which employ | adopted the labyrinth seal which is a conventionally well-known sealing means was made into the comparative example.

  About the rotary kiln of an Example, the structure similar to the gas seal structure 2 shown in FIG. 2 demonstrated above is employ | adopted about the exit side of a rotary kiln, and a stainless steel slip is used for a sliding part as a main body side sliding part. A plate was installed, and a ceramic heat-resistant cloth was installed as the first sliding portion and the second sliding portion so as to sufficiently contact the slip plate.

And outside air was introduce | transduced into the seal space of width 700mm and height 500mm sealed by the sliding part, the kiln main body outer peripheral surface, and the fixed hood inner surface. In addition, the diameter in the outer peripheral surface of a kiln main body is 3.6 m, and the gas seal structure was provided in the circumferential shape so that the perimeter of the outer periphery of a kiln main body might be covered. At this time, the flow rate was adjusted with a fan installed as an outside air introduction mechanism so that the pressure in the seal space could be maintained at 1.5 kPa, and outside air of about 8000 to 12000 m ³ / h was introduced. Between the lower ends of the first sliding portion and the second sliding portion and the outer periphery of the kiln main body, an average gap of about 35 mm is finally formed around the entire circumference due to distortion of the kiln main body and deformation or wear of the ceramic heat resistant cloth. It was vacant. In this case, the outside air flowed in the furnace and the environmental dust collection side at an average flow velocity of 3.5 m / s, and it was sufficiently effective in blocking the internal gas.

  In a rotary kiln of a comparative example employing a labyrinth seal which is a conventionally known sealing means, the furnace pressure was maintained at −0.1 to −0.2 kPa, but the internal gas was collected in the environmental dust collection hood surrounding the labyrinth structure. Flows in, and dust accumulates and adheres to the gap of the seal ring forming the labyrinth to promote high temperature corrosion, or the dust adheres to the gap and the seal ring competes and eventually the weld breaks, Such a situation occurred within several months after the repair.

  About each rotary kiln of an Example and a comparative example, the thickness loss amount of the fixed point of the kiln main body exit side vicinity part accompanying operation days progress was measured. About the comparative example, the average value of the said measured value about two rotary kilns was made into the comparison object as a result value. The results are shown in FIG.

  In the rotary kiln of the example, a significant decrease in the high-temperature corrosion rate is recognized rather than a decrease in the temperature at the periphery of the outlet side due to the intake of outside air. Conventionally, it has been reduced by about 5 mm in 0.5 years, but after remodeling, it has been improved by 80% to about 1 mm in 0.5 years. No corrosion tendency was detected for the seal part. As a result, it has been necessary to replace the furnace end portion after 10 years, but it is expected that the period until the furnace end replacement can be extended to about five times as long as the present invention is implemented. Conventionally, it has been necessary to take measures for gas leakage every three months. However, after improvement of the gas seal structure according to the present invention, there is no gas leakage and the surrounding environment is greatly improved. It was.

DESCRIPTION OF SYMBOLS 1 Rotary kiln 10 Kiln main body 11 Inlet 12 Outlet 2 Gas seal structure 20 Fixed hood 21 Outside air inlet 22 Environmental dust collection hood 30 Seal part 31 Sliding part 31A First sliding part 31B Second sliding part 32 Main body side sliding Part 33 Seal space 40 Outside air introduction mechanism 41 Air conditioning equipment 50 Burner 60 Drive gear 70A-C Outside air 80 Furnace gas 80A Outflow gas in hood

Claims (1)

A gas sealing method for a rotary kiln used in a Welts kiln process ,
A cylindrical kiln body,
A fixed hood that covers one end of the kiln body;
An outer periphery of one end of the kiln main body, and a seal portion formed between the fixed hood,
The seal portion is disposed on an inner peripheral surface of the fixed hood in order from a circumferential first sliding portion and a second sliding portion that are sequentially disposed from one end side of the kiln main body, and an outer peripheral surface of the kiln main body. A seal space formed by a space surrounded by a main body side sliding portion and an inner peripheral surface of the fixed hood, and an outside air introduction mechanism for introducing outside air into the seal space,
The outside air introduced by the outside air introduction mechanism passes through the seal space and flows into the fixed hood through the first sliding part at a blowing speed of an average flow rate of 3.0 m / s or more. By introducing the outside air from the outside air introduction mechanism by the gas seal structure that has been cut off, leakage of the gas in the rotary kiln is blocked, and further, the introduced outside air flows into the fixed hood, thereby A rotary kiln gas sealing method , characterized in that a main body is cooled , and a blow-out speed of the outside air flowing into the fixed hood from the first sliding portion is an average flow velocity of 3.0 m / s or more.

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