JP5235308B2 - Externally heated rotary kiln - Google Patents

Description

  The present invention relates to an externally heated rotary kiln used for a carbonization furnace, a pyrolysis furnace, a heat treatment furnace, or the like.

  An externally heated rotary kiln is provided with an outer cylinder around a rotary kiln (kiln inner cylinder) that rotates about an axis, and a heated gas is circulated through the outer cylinder to heat the rotary kiln from the outside, and the processed material is rotated inside the kiln. Heat treatment is performed while being transferred in the direction, and it is also called an indirect heating type because it has a configuration in which the heated gas does not come into contact with the workpiece, and is widely used in carbonization furnaces, pyrolysis furnaces, heat treatment furnaces, drying furnaces, etc. It's being used.

  Utilizing the above characteristics of an external heat type rotary kiln, it has been studied to thermally decompose organic waste such as sewage sludge into fuel. In other words, organic waste is introduced into the externally heated rotary kiln, and pyrolysis gas and carbides are recovered by pyrolysis under low oxygen without mixing heated gas, and these are used as fuel gas and solid fuel. In the case of fuel gasification, the heating temperature is set as high as possible to efficiently gasify the organic substance. On the other hand, when aiming at solid fuel conversion, it is necessary to terminate pyrolysis at a lower temperature than when gasifying and to leave a combustible component in the carbide. For this reason, temperature management inside the kiln becomes important.

  As a method of controlling the temperature inside the rotary kiln that rotates around the axis, a pipe is arranged along the axis of the kiln, and the output of the heating coil or heating is based on the temperature detected by the temperature sensor mounted inside the pipe. There are a method for controlling the thermal power of the gas combustion apparatus (see Patent Document 1) and a method for controlling the amount of combustion air based on the detected temperature of a thermocouple provided at the discharge port of the kiln (see Patent Document 3). However, since these are all configured to measure the gas temperature inside the rotary kiln, they do not necessarily reflect the carbonization temperature of the processed material, and changes in the balance of radiation and convection inside the kiln and deposits on the temperature sensor In addition, the organic waste such as sewage sludge has a large variation in the inlet properties such as the treatment amount and the water amount, and it is difficult to stably control the carbonization temperature.

JP 11-2111040 A JP 2002-174415 A Japanese Patent No. 2903045

  The present invention has been made in view of such a situation, and the purpose thereof is to accurately measure the temperature inside the rotary kiln rotating around the axis with a correlation with the temperature of the processed material, and to increase the heating temperature. It is to provide an externally heated rotary kiln that enables stable control of the heat.

  In order to solve the above-described problems of the prior art, the present invention includes a kiln inner cylinder that rotates around an axis, and an outer cylinder that circulates a heated gas around the kiln inner cylinder, and the inside of the kiln inner cylinder. In an external heating type rotary kiln that performs heat treatment while transferring a processed material in the axial direction, the kiln inner cylinder is rotatably supported at a movable side end portion and a fixed side end portion that are movable in the axial direction. Thermal elongation measuring means for measuring the amount of thermal elongation in the axial direction of the cylinder, and a plurality of non-contact type thermometers for measuring the shell temperature at a plurality of positions in the axial direction of the inner cylinder of the kiln from the peripheral wall portion of the outer cylinder. Prepared.

  In a preferred aspect of the present invention, the thermal elongation measuring means includes total thermal elongation measuring means for measuring the total thermal elongation in the axial direction of the kiln inner cylinder. Further, the thermal elongation amount measuring means includes at least one partial thermal elongation amount measuring means for measuring the thermal elongation amount in the axially intermediate portion of the kiln inner cylinder from the peripheral wall portion of the outer cylinder.

  In another aspect of the externally heated rotary kiln according to the present invention, the outer cylinder is divided into a plurality of zones in the axial direction, and the non-contact type thermometer is disposed in each of the zones. The apparatus further includes heating gas amount adjusting means for adjusting the gas flow rate, and temperature control means for controlling the heating gas amount adjusting means based on a measured value of the shell temperature in each zone. In a preferred embodiment, the thermal elongation measuring means includes zone thermal elongation measuring means for measuring the thermal elongation in each zone from the peripheral wall portion of the outer cylinder. In a further preferred aspect, the heating gas amount adjusting means adjusts the total flow rate of the heating gas distribution means for distributing the heating gas of one system to the respective parts at a predetermined flow rate ratio, and the heating gas distribution means. Heating gas total flow rate adjusting means.

  According to the externally heated rotary kiln according to the present invention, a means for measuring the amount of thermal expansion in the axial direction of the kiln inner cylinder, and a plurality of shell temperatures at a plurality of axial positions of the kiln inner cylinder from the peripheral wall portion of the outer cylinder. Because it is equipped with a non-contact type thermometer, the thermal expansion rate obtained from the measured value of the thermal elongation measurement means is divided by the linear expansion coefficient of the kiln inner cylinder material to change the radiation and convection inside the kiln. In addition, it is possible to detect an accurate kiln shell temperature (converted shell temperature) that eliminates measurement errors due to deposits on the kiln inner cylinder or the temperature sensor.

  Moreover, since the kiln shell temperature is the temperature of the part in direct contact with the processed material inside the kiln, it has a high correlation with the thermal decomposition temperature of the processed material, and reflects the heating situation well. By performing temperature control based on this, it is possible to stably control the heating temperature. As a result, when the externally heated rotary kiln according to the present invention is used in, for example, a carbonization furnace for obtaining fuel carbide from organic waste, an appropriate temperature corresponding to the desired combustible residual rate is obtained. Therefore, it is possible to stably obtain a high quality carbonized fuel.

  Moreover, by comparing the converted shell temperature based on the amount of thermal elongation with the average shell temperature of a non-contact type thermometer, it is possible to detect the adhesion of ash to the outer surface of the kiln inner cylinder and the corrosion status of the kiln inner cylinder. When the temperature difference is equal to or greater than a predetermined value, an operation method in which compressed air is injected onto the outer surface of the kiln inner cylinder to remove ash adhering to the outer surface of the kiln inner cylinder, or the temperature An operation method that outputs a signal that prompts maintenance of the kiln inner cylinder when the difference continues for a predetermined time, and further, the average shell temperature is calibrated using emissivity according to the temperature difference, and the rotary kiln is operated as it is. A continuous driving method is possible.

  The outer cylinder is divided into a plurality of zones in the axial direction, the non-contact thermometer is disposed in each zone, and a heating gas amount adjusting means for adjusting the heating gas flow rate in each zone; In an aspect further comprising temperature control means for controlling the heating gas amount adjusting means based on the measured value of the shell temperature of each zone, the temperature varies depending on the zone based on the measured value of the shell temperature of each zone. Can be controlled to shell temperature. In addition, the temperature control of each zone is combined with the calibration of the control temperature range based on the comparison between the converted shell temperature based on the amount of thermal elongation and the average shell temperature of the non-contact thermometer, so that more reliable temperature control is possible. It becomes possible, and high-quality heat treatment can be performed.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.
FIG. 1 shows an embodiment in which an externally heated rotary kiln 1 according to the present invention is implemented as a carbonization furnace. In the figure, the rotary kiln 1 is provided with an inner cylinder 11 (kiln shell) and an outer cylinder 12 (muffle) through which heated gas is circulated. The inner cylinder 11 is supported so as to be rotatable about an axis at a movable side end 13 and a fixed side end 14 that are movable in the axial direction. A screw conveyor 10 is provided for charging the product, and a chute 15 for discharging the processed product is provided at the fixed side end portion 14 constituting the outlet portion of the inner cylinder 11.

  More specifically, the movable side end 13 of the inner cylinder 11 is provided with an annular frame 131 that rotatably supports the inner cylinder 11, and both sides of the annular frame 131 can swing from the installation surface 130. It is rotatably supported by the upper end part of the supporting member 132 erected. The distance between the fulcrums of the support member 132 is set to be sufficiently larger than the thermal expansion amount of the kiln inner cylinder 11 described in detail later, and the vertical movement of the movable side end 13 accompanying the swinging of the support member 132 is sufficiently small. It is suppressed.

  Further, the movable side end 13 and the fixed side end 14 of the inner cylinder 11 form an air seal between the respective rotating portions (11) and the non-rotating portions (13, 14). An expansion 133 that absorbs the displacement of the movable side end 13 in the axial direction is provided at a connection portion between the end 13 and the screw conveyor 10.

  The movable side end 13 of the inner cylinder 11 is provided with a measuring means 114 that measures the thermal expansion amount of the entire heating portion of the inner cylinder 11, that is, the total thermal elongation amount D. The measuring means 114 measures the displacement of the index P provided at the movable side end 13 of the inner cylinder 11 with a scale fixed to the installation site of the rotary kiln 1, and the displacement of the index P is measured. It may be a position sensor that measures by electromagnetic means such as a differential transformer. In addition, instead of a sensor that detects continuous displacement, it is possible to provide a feeler that detects that a predetermined displacement has been set in advance, or to detect displacement using a laser distance meter.

  The inner wall portion of the inner cylinder 11 is provided with a plurality of fins (or spirals, not shown) arranged in an inclined manner with respect to the circumferential direction, and the inner cylinder 11 is rotated at a predetermined speed by a driving source (not shown). By being driven and rotated by a number, it is possible to transfer the processed material introduced from the inlet side to the outlet side while heating. In addition, instead of providing the fins, the inner cylinder 11 may be supported so as to be rotatable about an axis slightly inclined with respect to the horizontal, and the workpiece may be transferred to the outlet side by the inclination and rotation of the inner cylinder 11. is there.

  The outer cylinder 12 is fixed to an installation site via a support member (not shown) in a state in which the inner cylinder 11 is allowed to rotate and move in the axial direction and a seal is secured with the inner cylinder 11. The entire inner surface of the outer cylinder 12 is covered with a heat insulating material, and as shown in FIG. 2, one side of the inner space (the side of the inner cylinder 11) is partitioned over the entire length by a partition wall 120. A heating gas introduction part 121 is defined below the formed part, and a heating gas delivery part 122 is defined on the upper side, and a heating gas flow path from the introduction part 121 to the delivery part 122 is formed. Yes. The introduction part 121 of the outer cylinder 12 communicates with the supply pipe 20 for the heated gas fed from the heated gas combustion furnace 2, while the delivery part 122 of the outer cylinder 12 is connected via the heated gas delivery pipe 21. The heated gas amount adjusting damper 3 and the induction fan 4 are communicated with each other.

  Three inspection windows 123 are provided at an upper portion of the outer cylinder 12 so as to be separated from each other in the axial direction. Each inspection window 123 has a partial displacement of the inner cylinder 11, that is, a partial thermal expansion amount D1, Measuring means 124 for measuring D2 and D3 is provided. The measuring means 124 is composed of a scope or an imaging device disposed in the inspection window 123 of the outer cylinder 12 so as to face the indices P1, P2, and P3 provided on the outer peripheral surface of the inner cylinder 11, and is an index for the measurement position. The displacement of P1, P2, and P3 is measured with a scale installed in the field of view of the scope, or is measured based on the position on the image obtained by the imaging device.

  Further, six windows 125 are provided apart from each other in the axial direction at a position near the delivery portion 122 at the upper part of the outer cylinder 12, and each window 125 is provided on the outer peripheral surface of the inner cylinder 11 rotating around the axis. A non-contact thermometer 126 that measures the kiln shell temperatures T11 to T32 (Tn) is provided. As the non-contact type thermometer 126, a radiation thermometer can be used. In that case, since the combustion gas containing soot is used as the heating gas flowing inside the outer cylinder 12 as will be described later, the response wavelength of the radiation thermometer is not affected by soot and combustion gas. It is preferred to use infrared wavelengths. A two-color thermometer in the vicinity of 1.0 μm is also preferable because it is less affected by combustion gas and dust, and even when the outer surface of the inner cylinder 11 is corroded, it is less susceptible to emissivity.

  Next, based on the said embodiment, the operating method in the case of using the external heating type rotary kiln 1 as a carbonization furnace which heats and decomposes organic wastes, such as sewage sludge, will be demonstrated.

  In the outer cylinder 12 of the rotary kiln 1, heated gas is supplied from the heated gas combustion furnace 2 by the attracting action of the attracting fan 4, and the inner cylinder 11 positioned in the outer cylinder 12 is surrounded by the heated gas. Is heated from. The heating power of the heated gas combustion furnace 2 is kept constant, and the temperature of the heated gas fed from the heated gas combustion furnace 2 is maintained at a predetermined high temperature, but the processed material introduced into the kiln inner cylinder 11 The amount of heat required for heating the inner cylinder 11 varies depending on the load variation such as the properties, the processing amount, and the moisture amount.

  Therefore, based on the control logic shown in FIG. 3 so that the kiln shell temperatures T11 to T32 (Tn) measured by the non-contact thermometers 126 installed at six locations in the axial direction are maintained in a predetermined temperature range. The temperature control means 5 controls the opening degree of the heated gas amount adjusting damper 3 and the rotational speed of the induction fan 4.

  In FIG. 3, the kiln shell temperatures T11 to T32 at each of the six measurement points are selected by the selection switch 50 at any one place or any plurality of places (up to six places), and when one of these places is selected. Uses the selected kiln shell temperature as a process value, and when a plurality of locations are selected, the average value of the kiln shell temperature is set as a process value by the averaging process 51 so that the process value PV is maintained at the set value SV. PID control is performed.

  That is, the proportional operation (P operation) proportional to the deviation between the process value PV and the set value SV of the kiln shell temperature after the delay processing 52, the integral operation (I operation) proportional to the duration of the deviation, and the change rate of the deviation The output of the PID control combined with the differential operation (D operation) is inverted 53 to obtain an opening command, and the opening adjustment of the heating gas amount adjusting damper 3 is performed. Further, the opening command to the heating gas amount adjusting damper 3 is set as a process value in the rotational speed control of the induction fan 4 through the delay process 54, and PID control is performed so that the process value PV is maintained at the set value SV. The output is inverted 55 so that the rotational speed command of the attracting fan 4 is set, and the rotational speed of the attracting fan 4 is adjusted.

  In this way, the basic temperature control is performed by adjusting the opening degree of the heating gas amount adjusting damper 3, and the opening degree of the heating gas amount adjusting damper 3 is maintained within a predetermined range by adjusting the rotation speed of the induction fan 4. By performing the backup control, it is possible to perform stable control with respect to fluctuations in the inlet load. Further, in the above control, by setting the delay process 54 in the rotational speed control of the induction fan 4 larger than the delay process 52 in the opening adjustment of the heating gas amount adjusting damper 3, it is possible to prevent a short-term temperature change. If the rotational speed control of the induction fan 4 is not operated, only the opening degree adjustment of the heated gas amount adjusting damper 3 is supported, and the rotational speed control of the induction fan 4 is adapted to a long-term temperature change. Stable temperature control can be performed.

  A dryer (not shown) is disposed on the upstream side of the rotary kiln 1 whose temperature is controlled as described above, and the dried sludge 71 that has been agitated and dried by this dryer and adjusted to a predetermined amount of water is a screw. It is introduced into the inner cylinder 11 of the rotary kiln 1 by the conveyor 10. The dried sludge 71 introduced into the inner cylinder 11 is heated while being transported toward the outlet side as the inner cylinder 11 rotates, so that first the remaining moisture evaporates, and the organic component of the organic component is removed along with the completion of moisture evaporation. Pyrolysis proceeds, carbonized while generating pyrolysis gas, and discharged from the chute 15 as a carbide 72 (solid fuel) having a predetermined carbonization degree.

  On the other hand, the pyrolysis gas 73 generated by the pyrolysis is introduced from a chute 15 into a dry gas combustion furnace (not shown) and combusted together with combustion air exchanged heat in the auxiliary fuel or the heated gas delivery pipe 21, and the combustion gas. A part of this is circulated to the heated gas combustion furnace 2, burned with auxiliary fuel in the heated gas combustion furnace 2, and used for heating the rotary kiln 1. By the way, since the said heating gas is combustion gas, it contains soot, ash, etc. If this ash adheres to the outer peripheral surface of the inner cylinder 11, it will be temperature T11-T32 (Tn) measured with the non-contact-type thermometer 126. ) And the actual kiln shell temperature may cause an error.

  Therefore, an average value of the kiln shell temperature (converted shell temperature) is obtained based on the measured value of the total thermal elongation D by the measuring means 114 provided at the movable side end 13 of the inner cylinder 11, and this value and the kiln shell described above are obtained. By comparing the average values (Tn) of the temperatures T11 to T32, it is possible to detect the state of ash adhesion to the kiln shell.

That is, when the total thermal elongation D (mm, = ΔL) of the kiln inner cylinder 11, the heating part length L (m) of the kiln inner cylinder 11, and the linear expansion coefficient α (mm / m · ° C.) of the kiln material are converted. The shell temperature Ts (° C.) is obtained by dividing the total thermal elongation D / L (ΔL / L) by the linear expansion coefficient α of the kiln material,
Ts = D / αL
And the difference between the converted shell temperature Ts and the average shell temperature Tn ΔT = (D / αL) −Tn
Is equal to or greater than the set value or when the state continues for a predetermined time, it is determined that ash has adhered to the kiln shell, and the nozzle 127 (FIG. 2) provided on the outer cylinder 12 Compressed air can be sprayed onto the outer surface to remove ash, or a signal that prompts maintenance of the kiln inner cylinder 11 can be output.

  Furthermore, when ash adheres to the kiln shell, the average shell temperature Tn based on the non-contact thermometer 126 is lower than the converted shell temperature Ts based on the total thermal elongation of the kiln inner cylinder 11, but the rotary kiln 1 does not immediately disturb the operation of itself, so when the temperature difference ΔT exceeds the set value (or when the state continues for a predetermined time), the non-contact thermometer The average shell temperature is calibrated using emissivity, etc., and the amount of heated gas flowing through the outer cylinder 12 of the heated gas amount adjusting damper 3 or the induction fan 4 is controlled using the calibrated average shell temperature, and the rotary kiln 1 is operated as it is. Can be continued.

  Moreover, based on the measured value of the measurement means 124 which measures the partial thermal expansion amounts D1-D3 of the inner cylinder 11, the kiln shell temperature (converted partial shell temperature) of the said part is calculated | required, and this value and the non-contact-type thermometer 126 are obtained. By comparing the kiln shell temperatures T11 to T32 based on the above (in the example shown in FIG. 1, the average value T1 of T11 and T12, the average value T2 of T21 and T22, the average value T3 of T31 and T32) It is possible to detect an error in measured values for each of the eleven portions P1, P2, and P3 and the ash adhesion state. Of the partial thermal elongation amounts D1 to D3, D2 and D3 need to use values obtained by subtracting the partial thermal elongation amounts D1 and D2 on the fixed-side end portion 14 side from the actually measured displacement amount. is there.

  Such a measuring means 124 for the partial thermal expansion amounts D1, D2, and D3 of the inner cylinder 11 is advantageous when implemented in a rotary kiln 41 having a plurality of zones with different heating temperatures in the axial direction, as shown in FIG. It is. Hereinafter, the rotary kiln 41 of 2nd Embodiment is demonstrated with drawing. In addition, since the rotary kiln 41 of 2nd Embodiment is the same as that of the rotary kiln 1 of 1st Embodiment in basic structure, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  In FIG. 4, the rotary kiln 41 is divided into three zones Z1 to Z3 by partition walls 42 and 43, and the heated gas is distributed and supplied from the heated gas combustion furnace 2 to the zones Z1 to Z3. In addition, heating gas amount adjusting dampers 31 to 33 for adjusting the heating gas flow rates of the zones Z1 to Z3 are provided.

  Further, the rotary kiln 41 is provided with one partial thermal elongation measuring means 124 (D1 to D3) and two non-contact thermometers 126 (T11 to T32) in each zone Z1 to Z3. Based on the measured values T1 to T3 of the kiln shell temperature of each zone Z1 to Z3 (average value T1 of T11 and T12, average value T2 of T21 and T22, average value T3 of T31 and T32), each heating gas amount adjusting damper By controlling the opening degree of 31 to 33, the amount of heated gas flowing through each zone Z1 to Z3 can be adjusted, and the kiln shell temperature of each zone Z1 to Z3 can be maintained at different set temperatures.

  Based on the partial thermal elongation amounts D1 to D3 of the zones Z1 to Z3, the converted shell temperatures Ts1 to Ts3 of the zones Z1 to Z3 (D1 / αL1 to D3 / αL3, where L1 to L3 are zone lengths). By comparing this value with the measured values T1 to T3 of the kiln shell temperature of each zone Z1 to Z3, and obtaining the temperature differences ΔT1 to ΔT3, the temperature error and ash adhesion for each zone Z1 to Z3 The situation can be detected. At this time, it goes without saying that the above-described method of comparing the converted shell temperature Ts from the total thermal elongation D and the average value of the kiln shell temperatures T11 to T32 may be performed in parallel.

  In addition, the kiln shell temperature T3 (average value of T31 and T32) of any zone, for example, the outlet zone Z3 located on the most downstream side, with the heating gas amount adjusting dampers 31 to 33 being held at a predetermined ratio. ) Can be maintained in a predetermined temperature range so that the rotational speed of the induction fan 4 can be controlled. In this case, the partial thermal elongation measuring means 124 may be provided only in the exit zone Z3.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various deformation | transformation and change are possible based on the technical idea of this invention. For example, in the above embodiment, the rotary kiln provided with the six non-contact thermometers 126 and the three partial thermal elongation measuring means 124 in the axial direction is shown, but the number of these can be set as appropriate. Moreover, in 2nd Embodiment, although the rotary kiln provided with three zones which differ in kiln shell temperature in an axial direction was shown, the number of zones may be other than this and the length of each zone may differ.

It is sectional drawing which shows the outline of the external heating type rotary kiln of 1st Embodiment of this invention. It is AA sectional drawing of FIG. It is a figure which shows control of an external heating type rotary kiln. It is sectional drawing which shows the outline of the external heating type rotary kiln of 2nd Embodiment of this invention.

DESCRIPTION OF SYMBOLS 1,41 Rotary kiln 2 Heated gas combustion furnace 3, 31, 32, 33 Heated gas amount adjustment damper 4 Induction fan (heating gas amount adjusting means)
5 Temperature control means 10 Screw conveyor 11 Inner cylinder (kiln shell)
12 outer cylinder (muffle)
13 Movable side end 14 Fixed side end 15 Chute 114 Measuring means (total thermal elongation measuring means)
124 Measuring means (partial thermal elongation measuring means)
126 Non-contact type thermometer D Total thermal elongation D1, D2, D3 Partial thermal elongation T11, T12, T21, T22, T31, T32 Kiln shell temperature P, P1, P2, P3 Index

Claims (6)

  An external heat that includes a kiln inner cylinder that rotates around an axis and an outer cylinder that circulates a heating gas around the kiln inner cylinder, and that performs heat treatment while transferring a processed material in the axial direction inside the kiln inner cylinder. In the rotary kiln, the kiln inner cylinder is rotatably supported at the movable side end and the fixed side end movable in the axial direction, and measures the amount of thermal elongation in the axial direction of the kiln inner cylinder. An external heating rotary kiln comprising means and a plurality of non-contact thermometers that measure shell temperatures at a plurality of positions in the axial direction of the kiln inner cylinder from a peripheral wall portion of the outer cylinder.   2. The external heating rotary kiln according to claim 1, wherein the thermal elongation measuring unit includes a total thermal elongation measuring unit that measures a total thermal elongation in the axial direction of the kiln inner cylinder.   The thermal elongation measurement means includes at least one partial thermal elongation measurement means for measuring a thermal elongation amount in an axial intermediate portion of the kiln inner cylinder from a peripheral wall portion of the outer cylinder. Item 2. An externally heated rotary kiln according to Item 1.   The outer cylinder is divided into a plurality of zones in the axial direction, the non-contact type thermometer is disposed in each zone, and a heating gas amount adjusting means for adjusting a heating gas flow rate in each zone; The external heating type rotary kiln according to claim 1, further comprising temperature control means for controlling the heating gas amount adjusting means based on a measured value of a shell temperature of the zone.   5. The externally heated rotary kiln according to claim 4, wherein the thermal elongation measuring unit includes a zone thermal elongation measuring unit that measures a thermal elongation amount in each zone from a peripheral wall portion of the outer cylinder.   The heating gas amount adjusting means adjusts the total flow rate of the heating gas for adjusting the total flow rate of the heating gas of the one system, and the heating gas distribution means for distributing the heating gas of one system to the respective parts at a predetermined flow rate ratio. The externally heated rotary kiln according to claim 4 or 5, characterized by comprising: means.

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