JP2017032231A - Rotary kiln - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parallel flow heating type rotary kiln capable of heating and processing while controlling a material within a predetermined temperature range, even when variation occurs in a property of the material, a supply amount and the like.SOLUTION: A parallel flow heating type rotary kiln 1 which adopts exhaust gas temperature control includes material temperature sensors 22a to 22c for detecting material temperature flowing down in a kiln, in a kiln body 2, and also includes material temperature/burner air ratio controller 24 for adjusting a burner air ratio by increasing/decreasing a secondary air amount which is supplied to a burner 5, based on a material temperature value detected by the material temperature sensors 22a to 22c. Then, a burner combustion amount is adjusted by the exhaust gas temperature control capable of controlling the material temperature at the exhaust gas temperature or lower, and in the case where sudden change occurs in the material temperature, the secondary air amount to the burner 5 is increased/decreased according to the change amount accordingly. Thus, flame temperature is adjusted irrespective of the burner combustion amount by adjusting the burner air ratio, and thereby, the material temperature deviating from a predetermined temperature range is suppressed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotary kiln that heat-treats various materials to a predetermined temperature, and more particularly to a co-current heating type rotary kiln in which the material supplied into the kiln body and the flow direction of hot air are in the same direction.

  When heat-treating various materials, rotary kilns that have excellent heating efficiency and can be continuously fed are often used. For example, waste gypsum in the form of dihydrate gypsum that is generated in large quantities due to the dismantling of buildings, etc. The board is crushed into powder particles, and this is put into the kiln main body of the rotary kiln and heated to a predetermined temperature with a high-temperature combustion gas supplied from a burner to produce half-hydrate gypsum, type II anhydrous gypsum, etc. They are rearranged and recycled as soil-solidifying material or cement raw material.

By the way, when using type II anhydrous gypsum obtained from waste gypsum as a raw material for cement, etc., heat treatment at a relatively high temperature of about 900 ° C. or more may be required to adjust its fluidity, specific surface area, etc. . However, when waste gypsum is heated to about 1100 ° C, which is slightly higher than the above temperature, it decomposes and generates sulfur oxides (SO ₃ ) that cause corrosion such as chimneys and bag filters, or melts. In the rotary kiln, the waste gypsum supplied into the kiln body has a relatively narrow temperature range of about 900 to 1100 ° C because it may cause problems such as adhesion and growth on the inner peripheral wall of the kiln and the discharge hopper. Temperature control performance that can be heat-treated while maintaining the inside is required.

  On the other hand, as shown in Patent Document 1 (Japanese Patent Application No. 2015-102224), the present applicant is derived from a high-temperature heat treatment kiln of a co-current heating method provided with a burner for supplying hot air, and the high-temperature heat treatment kiln. A low-temperature heat treatment kiln of a co-current heating method that heats powder particles with exhaust gas, and equipped with an exhaust gas temperature sensor on the exit side of each kiln, and the exhaust gas temperature value detected by the exhaust gas temperature sensor Has been filed for the heat treatment device for the granular material with exhaust gas temperature control that adjusts the burner combustion amount based on this, and according to this device, the kiln just before the kiln discharge, although inferior to the countercurrent heating method in terms of heating efficiency A co-current heating system that can suppress the influence of radiant heat from the burner flame formed in the main body and control the heating temperature of the granular material to at least about the exhaust gas temperature or less. By adopting the tally kiln, for example, as described above, the exhaust gas temperature is maintained at about 1000 to 1200 ° C. even when the type II anhydrous gypsum suitable for the raw material of cement is regenerated from waste gypsum. If the burner combustion amount is adjusted by controlling the exhaust gas temperature, the waste gypsum can be heat-treated in the above temperature range of about 900 to 1100 ° C., which is slightly lower than that, and desired without causing thermal decomposition or melting. Recyclable to type II anhydrous gypsum with the following properties:

Japanese Patent Application No. 2015-102224

  However, even when a co-current heating type rotary kiln with exhaust gas temperature control is adopted as in the above-mentioned conventional device, a large variation occurs in the properties and supply amount of the material supplied into the kiln, for example, If waste gypsum with a low water content is supplied or the supply amount of waste gypsum is reduced, the exhaust gas temperature control cannot control the material temperature very severely. Or may be heated to such a high temperature as to cause melting.

  In view of the above-described points, an object of the present invention is to provide a co-current heating type rotary kiln capable of performing heat treatment while controlling the material within a predetermined temperature range even if the property or supply amount of the material varies.

  As a result of intensive studies to solve the above problems, the present applicant has determined that the burner flame temperature also changes if the burner air ratio (combustion air amount) changes even if the amount of fuel supplied to the burner during combustion is constant. For example, if the burner air ratio is increased (increasing the amount of combustion air), the flame temperature can be decreased by that amount, whereas if the air ratio is decreased (increasing the amount of combustion air) The flame temperature can be increased by that amount (according to burner combustion test data conducted by the present inventors, when the fuel supply amount to the burner is constant and the burner air ratio is 1.1, the burner flame is When the air ratio is 1.3, the flame temperature is about 1500 ° C., and when the air ratio is 1.5, the flame temperature is about 1200 ° C.), and the material temperature is supplied from the burner. Hot air temperature Focusing on the fact that it is greatly influenced not only by the temperature of the flame (radiant heat from the burner flame) formed in the kiln body in the burner, for example, the influence of the radiant heat from the burner flame just before the kiln discharge The temperature of the material flowing down in the kiln is measured and the temperature change is monitored while adopting the rotary kiln of the exhaust gas temperature control and the co-current heating method that can control the material temperature to some extent below the exhaust gas temperature. If the material temperature in the kiln suddenly increases due to material fluctuations or the amount of supply, etc., the amount of combustion air to the burner is forcibly increased. By increasing the burner air ratio, the burner flame temperature alone can be quickly reduced regardless of the burner combustion amount, which effectively suppresses the temperature rise of the material. It is believed that it would be possible to prevent the inconvenience that would be heated more than necessary, and have reached the present invention.

  That is, in the rotary kiln according to the first aspect of the present invention, a hot air supply burner and a material supply means are provided at one end of a kiln main body that is rotatably and tiltably supported via a hot hopper, while a cold is provided at the other end. An exhaust duct for exhaust gas exhaust and a material discharge port are provided via a hopper, the exhaust duct is provided with an exhaust gas temperature sensor for detecting exhaust gas temperature, and a burner is based on the exhaust gas temperature value detected by the exhaust gas temperature sensor. In the rotary kiln of a cocurrent heating system configured to adjust the combustion amount, the kiln main body is provided with a material temperature sensor for detecting a material temperature flowing down in the kiln main body, and the material temperature detected by the material temperature sensor A material temperature / burner air ratio controller for adjusting the burner air ratio by increasing or decreasing the amount of combustion air supplied to the burner based on the value It is a symptom.

  The rotary kiln according to claim 2 further includes a static pressure sensor for detecting a static pressure in the kiln main body at a corner portion of the hot hopper provided with the burner, and a static pressure value detected by the static pressure sensor is increased. It is characterized by a static pressure / exhaust air volume controller that adjusts the exhaust air volume of exhaust gas so as to suppress the amount of air entering the kiln main body as much as possible while maintaining it slightly lower than the atmospheric pressure.

  The rotary kiln according to claim 3 includes a transmitter that wirelessly transmits signal data of a material temperature value detected by a material temperature sensor to the kiln main body that is a rotating body, and a signal transmitted from the transmitter. A wireless receiver configured to receive the data in a non-contact manner apart from the kiln body, and configured to output the material temperature value signal data received by the receiver to the material temperature / burner air ratio controller It is characterized by having a telemeter device.

  According to the rotary kiln according to claim 1 of the present invention, in the rotary kiln of the cocurrent heating system that employs exhaust gas temperature control, the kiln main body is provided with a material temperature sensor that detects the material temperature flowing down the kiln main body, Equipped with a material temperature / burner air ratio controller that adjusts the air ratio by increasing or decreasing the amount of combustion air supplied to the burner based on the material temperature value detected by the material temperature sensor. While adjusting the burner combustion amount with controllable exhaust gas temperature control, measure the temperature of the material flowing down in the kiln body and monitor the temperature change, along with fluctuations in the properties of the supply material, supply amount, etc. When a sudden change occurs in the material temperature in the kiln body, the burner air ratio is adjusted by appropriately increasing or decreasing the amount of combustion air to the burner according to the change amount. The burner flame temperature can be quickly adjusted regardless of the amount of burner burned, thereby preventing problems such as the material being heated to an unnecessarily high temperature or insufficient heating, and the material in the kiln body is kept at a predetermined temperature. Heat treatment can be performed while controlling the range.

  Further, according to the rotary kiln according to claim 2, a static pressure sensor for detecting a static pressure in the kiln main body is provided at a corner portion of the hot hopper provided with the burner, and a static pressure value detected by the static pressure sensor. Because it is equipped with a static pressure / exhaust air volume controller that adjusts the exhaust air flow rate so that the air pressure is kept slightly lower than the atmospheric pressure, the amount of air entering the kiln main body, which is a disturbance factor, can be suppressed and used for combustion in the burner. Correlation between the amount of air and the burner air ratio can be increased, whereby the burner air ratio can be accurately adjusted so that the burner flame temperature matches the material temperature flowing down in the kiln body.

  According to the rotary kiln according to claim 3, the kiln main body is provided with a transmitter that wirelessly transmits the signal data of the material temperature value detected by the material temperature sensor, while the signal data transmitted from the transmitter is received. Since the receiver for receiving is separated from the kiln main body, and the radio telemeter device configured to output the signal data of the material temperature value received by the receiver to the material temperature / burner air ratio controller is provided. The material temperature data detected by the material temperature sensor provided on the kiln main body, which is a rotating body, can be transferred to the material temperature / burner air ratio controller side with a relatively simple device configuration without requiring complicated wiring. It is useful in terms of uptake, cost and maintenance.

It is a schematic explanatory drawing which shows one Example of the rotary kiln which concerns on this invention.

  The rotary kiln according to the present invention includes a material supply means and a hot air supply burner via a hot hopper at one end of a substantially cylindrical kiln body that is rotatably and tiltably supported. On the other hand, the other end of the kiln main body is provided with a material discharge port and an exhaust duct for exhaust gas exhaust via a cold hopper, and the material flow direction and the hot air flow direction from the burner The exhaust gas temperature sensor for detecting the exhaust gas temperature is provided in the middle of the exhaust duct, and the burner combustion amount is determined based on the exhaust gas temperature value detected by the exhaust gas temperature sensor. The exhaust gas temperature control to adjust is adopted. Further, the end of the exhaust duct is connected to the chimney via a dust collector that captures dust in the exhaust gas, a main damper for adjusting the amount of exhaust air, an air exhauster, and the like on the downstream side of the exhaust duct.

  Further, the kiln main body is provided with at least one material temperature sensor such as a thermocouple so that the temperature of the material flowing down in the kiln main body can be detected, and is detected by the material temperature sensor. A material temperature / burner air ratio controller that adjusts the burner air ratio by increasing or decreasing the amount of combustion air supplied to the burner based on the material temperature value. Since the kiln body is a rotating body, the kiln body is equipped with a transmitter that wirelessly transmits signal data of the material temperature value detected by the material temperature sensor on the kiln body side, while the transmitter transmitted from the transmitter A receiver for receiving signal data in a non-contact manner is installed on the ground surface, for example, separated from the kiln body, and the material temperature value signal data received by the receiver is used as the material temperature / burner air ratio controller. A wireless telemeter device configured to output sequentially is employed.

  In the material temperature / burner air ratio controller, for example, if the material temperature value in the kiln body detected by the material temperature sensor is higher than a predetermined material temperature setting value (setting range) set in advance, the difference value The amount of combustion air supplied to the burner according to the amount is forcibly increased to increase the burner air ratio, so that only the burner flame temperature can be quickly reduced regardless of the burner combustion amount, and the rise in material temperature can be suppressed. On the other hand, if the material temperature value in the kiln body detected by the material temperature sensor is lower than a predetermined material temperature setting value (setting range) set in advance, the material is supplied to the burner according to the difference value amount. The combustion air volume can be forcibly reduced to reduce the burner air ratio, so that only the burner flame temperature can be quickly raised regardless of the burner combustion volume to suppress the decrease in material temperature. They are programming in.

  Note that the amount of increase (decrease) in the combustion air amount (air ratio) relative to the amount of difference between the material temperature value and the material temperature set value is based on the test results and the like by performing a test operation or the like in advance. For example, if the amount of combustion air is increased (decreased) to decrease (increase) the burner flame temperature with respect to the difference value, the temperature increase (decrease) of the material can be increased. It is possible to derive a relational expression such as whether the material temperature at the time of discharging the kiln can be corrected so as to be close to the target temperature, and determine based on the relational expression etc. If it is an urgent avoidance to avoid exceeding the temperature range, allow a certain amount of margin to sufficiently reduce the burner flame temperature when the material temperature value exceeds the material temperature set value Predetermined amount (constant amount) The combustion air (air ratio) may be increased.

  In addition, the material temperature sensor attached to the kiln main body only needs to be corrected so that the difference value between the material temperature value and the material temperature set value appears to some extent clearly, and the material temperature falls within the target temperature before the material is discharged. In order to ensure time, for example, one may be provided in the vicinity of the center in the length direction of the kiln body, but if a plurality are provided at predetermined intervals along the length direction of the kiln body. The temperature change rate, temperature distribution, etc. of the material flowing down the kiln can be grasped, and if the amount of combustion air supplied to the burner is adjusted accordingly, precise temperature control with more margins becomes possible. .

  As a means for increasing / decreasing the amount of combustion air supplied to the burner, it may be directly increased / decreased by a burner fan provided in the burner body, but for example, a secondary air is supplied near the burner along the burner flame. If a secondary air supply fan is provided separately and the amount of combustion air is increased or decreased by increasing or decreasing the amount of secondary air supplied from the secondary air supply fan, the amount of combustion air can be adjusted to adjust the burner flame temperature. Even when increasing or decreasing, the burner itself can continue to supply the primary air amount from the burner fan to such an extent that a stable combustion state can be maintained (for example, about 1.1 to 1.2 in air ratio) The amount of combustion air can be adjusted without difficulty, which is more preferable.

  In addition, a static pressure sensor for detecting the static pressure in the kiln main body is provided at the corner of the hot hopper provided with the burner, and the static pressure value detected by the static pressure sensor is maintained slightly lower than the atmospheric pressure. Equipped with a static pressure / exhaust air volume controller that controls the exhaust air volume of exhaust gas by adjusting the opening of the main damper (or the rotational speed of the exhaust fan), and burns through the gap between the kiln body, hot hopper, and cold hopper While preventing gas, dust, water vapor, etc. from jetting out, the amount of air entering the kiln body, which is a disturbance factor, is suppressed as much as possible to increase the correlation between the amount of combustion air supplied to the burner and the burner air ratio, The burner air ratio can be adjusted with high accuracy so that the burner flame temperature matches the material temperature inside the kiln.

  When an appropriate material is heat-treated at a predetermined temperature in the rotary kiln having the above-described configuration, the material temperature sensor is adjusted while adjusting the burner combustion amount by the exhaust gas temperature control capable of controlling the material temperature below the exhaust gas temperature. The material temperature flowing down in the kiln main body is continuously detected and the temperature change is monitored. And, for example, when a large variation occurs in the properties or supply amount of the supply material, and the material temperature value flowing down in the kiln main body deviates from a preset predetermined material temperature set value, the material temperature / burner air The ratio controller adjusts the burner air ratio by appropriately increasing or decreasing the amount of combustion air supplied to the burner in accordance with the amount of difference between the material temperature value and the material temperature set value. At this time, by adjusting the burner air ratio, only the burner flame temperature (radiant heat amount) can be adjusted regardless of the burner combustion amount, thereby quickly correcting the material temperature in the kiln body to a predetermined temperature range. Can do.

  In this way, when various materials are heat-treated in a predetermined temperature range in a co-current heating type rotary kiln, the burner combustion amount is adjusted by exhaust gas temperature control that can control the material temperature below the exhaust gas temperature. Because the material temperature and the rapid change in material temperature due to fluctuations in the supply amount, etc., it was made possible to respond quickly by adjusting the burner flame temperature. It is possible to prevent problems such as thermal decomposition and melting from occurring. In addition, it can be installed relatively easily and inexpensively by simply adding a material temperature sensor, a material temperature / burner air ratio controller, etc. to the existing rotary kiln, and it is easy to adopt regardless of the size of the rotary kiln. is there.

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

  In the figure, reference numeral 1 denotes a rotary kiln that heats an appropriate material to a predetermined temperature, and rotates a substantially cylindrical kiln body 2 that is rotatably supported at a predetermined speed by a drive motor (not shown). In addition, a heat-resistant caster 3 such as refractory bricks or ceramics having no scraping function is provided around the inner wall surface of the kiln main body 2 to protect the inner wall surface of the kiln from high-temperature hot air. One end of the kiln body 2 is provided with a burner 5 for supplying hot air via a hot hopper 4 and a belt conveyor 6 which is a material supply means, while the other end of the kiln body 2 is provided with a cold. An exhaust duct 8 for discharging exhaust gas and a material discharge port 9 are provided via a hopper 7, and a parallel flow heating method is adopted in which the flow direction of hot air supplied from the burner 5 is the same as the flow direction of the material. .

  Downstream of the exhaust duct 8, an exhaust duct 8 is disposed via a cooling tower 10 that cools the exhaust gas, a bag filter 11 that is a dust collector for capturing dust in the exhaust gas, a main damper 12 for adjusting the amount of exhaust air, and an exhaust device 13. The end is connected to the chimney 14. An exhaust gas temperature sensor 15 for detecting the exhaust gas temperature is provided in the middle of the exhaust duct 8, and the exhaust gas temperature for adjusting the combustion amount of the burner 5 based on the exhaust gas temperature value detected by the exhaust gas temperature sensor 15. / A burner combustion amount controller 16 is provided.

  In the exhaust gas temperature / burner combustion amount controller 16, a control motor 17 is used to control the difference between the exhaust gas temperature value detected by the exhaust gas temperature sensor 15 and an appropriate preset exhaust gas temperature set value. The opening of the fuel supply valve 18, that is, the amount of fuel supplied is adjusted to control the burner combustion amount, and the opening of the air flow adjustment damper 21 of the burner fan 20 is controlled via the control motor 19 in accordance with this burner combustion amount. The amount of combustion air (primary air amount) is adjusted to adjust. The burner fan 20 is set to be supplied with a combustion air amount of, for example, about 1.2 in terms of an air ratio with respect to the fuel supply amount so that the burner 5 can stably burn. Keep it.

  The kiln body 2 is provided with a plurality of material temperature sensors 22a to 22c such as thermocouples for detecting the material temperature flowing down in the kiln body 2 at predetermined intervals along the length direction of the kiln body 2. The temperature measuring part at the tip of the material temperature sensors 22a to 22c is passed through a caster 3 provided around the inner wall surface of the kiln body 2 so as to slightly protrude toward the inside of the kiln body 2, and a predetermined laminar pressure is applied inside the kiln body 2. The temperature of the heating material flowing down while forming can be directly measured. In addition, although only one material temperature sensor may be installed with respect to the kiln main body 2, by providing a plurality of material temperature sensors at predetermined intervals along the length direction of the kiln main body 2 as described above, It is preferable that the temperature change rate and temperature distribution of the material flowing down can be grasped in detail, and precise control with a margin can be performed in controlling the material temperature described later. Reference numeral 23 in the figure denotes a flame temperature sensor for confirming the temperature of the burner flame F formed in the kiln main body 2 by the burner 5, and the temperature measuring part at the tip thereof is close to where the burner flame F is formed. I ’m here.

  24 in the figure is a material temperature for adjusting the burner air ratio by increasing or decreasing the amount of combustion air (secondary air amount) supplied to the burner 5 based on the material temperature value detected by the material temperature sensors 22a to 22c. / Burner air ratio controller, which is connected via the inverter 25 based on the difference value between the material temperature value detected by the material temperature sensors 22a to 22c and a preset appropriate material temperature setting value. The rotational speed of the air supply fan 26 is appropriately adjusted, and the burner air ratio is adjusted by increasing / decreasing the amount of secondary air blown out in the vicinity of the burner flame F formed in the kiln main body 2 by the burner 5, and the burner combustion amount Regardless of, the flame temperature is controlled to be a predetermined temperature.

  For example, if the material temperature value at each measurement point in the kiln main body 2 detected by each material temperature sensor 22a to 22c is higher (or lower) than an appropriate material temperature set value set in advance for each measurement point. In accordance with the difference value, the rotational speed of the secondary air supply fan 26 is increased (decreased) to increase (decrease) the amount of secondary air to increase (decrease) the burner air ratio, thereby reducing the burner flame temperature. Programming is performed so that the temperature can be quickly lowered (increased) to prevent the material temperature from rising (decreasing). When adjustment is performed to reduce the combustion air amount (secondary air amount), for example, secondary air corresponding to about 0.1 is supplied from the secondary air supply fan 26 in terms of air ratio in advance. It is good to keep.

  In addition, since a plurality of material temperature sensors are provided along the length direction of the kiln body 2, the temperature change rate and temperature distribution of the material can be grasped from the material temperature values detected by the material temperature sensors 22a to 22c. These data may be added to the burner flame temperature control. For example, when the secondary air amount is increased in accordance with the amount of difference between the material temperature value and the material temperature set value, the material temperature change rate (temperature increase rate) is determined to be relatively large. The rate of change in temperature (temperature increase rate) is relatively large even if the secondary air volume is increased or the material temperature value is within the material temperature setting value (setting range). It is possible to control the temperature with more margins, such as preventing the material temperature value from deviating from the material temperature setting value by deliberately increasing the secondary air amount. Become.

  As the amount of increase (decrease) in the secondary air amount relative to the difference value amount between the material temperature value and the material temperature set value, for example, how much the secondary air amount is increased (decreased) relative to the difference value amount. If the burner flame temperature is lowered (increased), the temperature rise (decrease) of the material can be suppressed and the material temperature at the time of discharge from the material discharge port 9 can be corrected so as to be close to the target temperature. It is preferable to derive a formula or the like in advance by a test operation or the like and determine it appropriately based on the relational formula or the like. At this time, when the temperature of the burner flame F is detected by the flame temperature sensor 23 and the burner flame temperature value is fed back to the control, control with higher accuracy becomes possible.

  Further, a transmitter 27 that takes in each signal data such as the material temperature value detected by the material temperature sensors 22a to 22c and 23 and the temperature value of the burner flame F and transmits it wirelessly on the surface of the kiln main body 2 that is a rotating body. On the other hand, a receiver 28 for receiving the signal data transmitted from the transmitter 27 in a non-contact manner is installed on the ground surface separated from the kiln body 2. And a radio telemeter device 29 configured to sequentially output the received signal data such as the material temperature value to the material temperature / burner air ratio controller 24. In addition, as a material temperature sensor with which the kiln main body 2 is equipped, it can replace with the thermocouple described in the present Example, but can also employ | adopt the radiation thermometer etc. which can detect material temperature by non-contact, but the kiln main body 2 is filled. Considering the possibility of measurement error due to the influence of dust, water vapor, etc., it is more preferable to directly measure the material temperature with a thermocouple or the like as in this embodiment.

  Further, a static pressure sensor 30 for detecting the static pressure in the kiln main body 2 is provided at the corner of the hot hopper 4 provided with the burner 5, and the static pressure value detected by the static pressure sensor 30 is slightly higher than the atmospheric pressure. A static pressure / exhaust air volume controller 31 that controls the exhaust air volume of the exhaust gas by adjusting the opening degree of the main damper 12 (or the rotational speed of the exhaust fan 13) so as to maintain a low, for example, about −10 to −20 Pa. The combustion gas, dust, water vapor, etc. in the kiln main body 2 are not ejected from the gaps between the kiln main body 2 and the hot hopper 4 and the cold hopper 7, but the kiln main body 2 becomes a disturbance factor. Increase the correlation between the amount of combustion air supplied to the burner 5 and the burner air ratio while suppressing the amount of intrusion air as much as possible, and accurately set the burner air ratio so that the burner flame temperature matches the material temperature inside the kiln body 2. Adjustment It is aimed to function as such.

  When the type of anhydrous gypsum suitable for the raw material of cement is regenerated from waste gypsum, for example, in the cocurrent heating type rotary kiln 1 having the above configuration, first, the waste gypsum is heated to about 1000 ° C. In the exhaust gas temperature / burner combustion amount controller 16, an exhaust gas temperature set value of about 1100 ° C., which is slightly higher than 1000 ° C., is set and registered in the exhaust gas temperature / burner combustion amount controller 16. The air ratio controller 24 has a target temperature value of waste gypsum in the kiln body 2 such as 400 to 600 ° C., 600 to 800 ° C., and 800 to 1000 ° C. for each material temperature sensor 22a, 22b, and 22c. The material temperature set value is set in advance, and each material temperature set value and the material temperature value detected by each material temperature sensor 22a, 22b, 22c. As secondary air quantity is increased in accordance with the difference value amount, for example setting the adjustment value of about 0.1 / 50 ° C. at the burner air ratio conversion.

  If waste gypsum is supplied into the kiln main body 2 by a predetermined amount while adjusting the burner combustion amount by exhaust gas temperature control in this state, the waste gypsum is moved into the kiln main body 2 while flowing down the kiln main body 2. It is gradually heated by being exposed to the radiant heat from the burner flame F formed and the high-temperature hot air supplied from the burner 2, and the target temperature value of about 1000 ° C. from the material outlet 9 at the downstream end of the kiln body 2. It is sequentially discharged as type II anhydrous gypsum that has been heat-treated.

  On the other hand, the waste gypsum's properties, supply amount, etc. greatly fluctuate.For example, waste gypsum with low moisture content is supplied or waste gypsum supply amount decreases, and the temperature of the waste gypsum increases rapidly. When the material temperature value in the kiln main body 2 detected by the sensors 22a, 22b, and 22c exceeds the material temperature set value, the material temperature / burner air ratio controller 24 determines the material temperature value and the material Depending on the amount of difference from the temperature set value, for example, if the amount of difference is about 100 ° C., the secondary air amount is increased by about 0.2 in terms of burner air ratio (total burner The rotational speed of the secondary air supply fan 26 is adjusted so that the air ratio is about 1.4.

  At this time, although the burner combustion amount is adjusted by the exhaust gas temperature control, it is possible to forcibly reduce only the burner flame temperature (radiant heat amount) regardless of the burner combustion amount by increasing the combustion air amount. (For example, according to the combustion test conducted by the present inventors, when the burner air ratio was increased from 1.2 to 1.4, the burner flame temperature could be reduced by about 300 ° C.). Can effectively suppress the waste gypsum flowing down in the kiln body 2 from being heated more than necessary, and the temperature of the waste gypsum at the time of discharge from the material discharge port 9 is about the target temperature value. It can be stored in the vicinity of 1000 ° C.

  In this way, when a material such as waste gypsum is heat-treated in a predetermined temperature range with a rotary kiln of a cocurrent heating system, while adjusting the burner combustion amount by exhaust gas temperature control that can control the material temperature below the exhaust gas temperature The material temperature in the kiln is continuously measured and the temperature change is monitored, and the material temperature in the kiln changes suddenly due to fluctuations in the material properties, supply amount, etc. When the temperature range is likely to be exceeded, the burner air ratio is increased to forcibly reduce the burner flame temperature, while when the material temperature is likely to fall below the target temperature range, the burner air ratio is decreased to forcibly increase the burner flame temperature. By doing so, it is possible to quickly correct the material temperature to the target temperature range, and the material is heated to an unnecessarily high temperature, or the heating becomes insufficient It is possible to prevent in advance.

  In the present embodiment, the case where the rotary kiln 1 of the present invention is used for the heat regeneration treatment of waste gypsum has been described. However, the present invention is not limited to this application, and various types can be used without departing from the gist of the present invention. For example, even when soil contaminated with heavy metals is heat treated at a high temperature to remove heavy metals for purification treatment, if the temperature is slightly higher than the purification temperature, There is a concern of melting, and a relatively severe temperature control performance is required as in the case of heat regeneration treatment of waste gypsum. Even in such a case, according to the rotary kiln 1 of the present invention, heat treatment is preferably performed. Can do.

DESCRIPTION OF SYMBOLS 1 ... Rotary kiln 2 ... Kiln main body 4 ... Hot hopper 5 ... Burner 6 ... Belt conveyor (material supply means) 7 ... Cold hopper 8 ... Exhaust duct 9 ... Material discharge port 15 ... Exhaust gas temperature sensor 16 ... Exhaust gas temperature / burner combustion amount control 22a, 22b, 22c ... Material temperature sensor 24 ... Material temperature / burner air ratio controller
26 ... Secondary air supply fan 27 ... Transmitter 28 ... Receiver 29 ... Telemeter device 30 ... Static pressure sensor 31 ... Static pressure / exhaust air flow controller

Claims (3)

  One end of a kiln main body that is rotatably supported is provided with a burner for supplying hot air via a hot hopper and a material supply means, while an exhaust duct for discharging exhaust gas and a material discharge port via a cold hopper at the other end. The exhaust duct is provided with an exhaust gas temperature sensor for detecting the exhaust gas temperature, and a co-current heating system configured to adjust the burner combustion amount based on the exhaust gas temperature value detected by the exhaust gas temperature sensor. In the rotary kiln, the kiln main body is provided with a material temperature sensor for detecting a material temperature flowing down in the kiln main body, and an amount of combustion air supplied to the burner based on a material temperature value detected by the material temperature sensor A rotary kiln comprising a material temperature / burner air ratio controller that adjusts the burner air ratio by increasing / decreasing the ratio.   The rotary kiln according to claim 1, further comprising a static pressure sensor for detecting a static pressure in the kiln main body at a corner portion of the hot hopper provided with the burner, and a static pressure value detected by the static pressure sensor from an atmospheric pressure. A rotary kiln equipped with a static pressure / exhaust air volume controller that adjusts the exhaust air volume of exhaust gas so that the amount of air entering the kiln main body can be suppressed as much as possible while keeping it slightly low.   The rotary kiln according to claim 1 or 2, further comprising a transmitter that wirelessly transmits signal data of a material temperature value detected by a material temperature sensor to the kiln main body that is a rotating body, and a signal transmitted from the transmitter. A wireless receiver configured to receive the data in a non-contact manner apart from the kiln body, and configured to output the material temperature value signal data received by the receiver to the material temperature / burner air ratio controller A rotary kiln equipped with a telemeter device.

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