JP2009204265A - Rotary kiln type sludge dryer and its safety stop method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary kiln type sludge dryer and its safety stop method for preventing spontaneous ignition within the dryer during stop of sludge drying operation of the dryer and safely performing a stop process without causing failure also of other equipment such as a heat exchanger installed at a rear stage. <P>SOLUTION: After stop of sludge drying operation of the dryer, based on a detection signal of either of inlet side temperature of a rotating drum, a CO concentration inside the drum or thermal expansion amount (linear expansion amount) in the axial direction of an agitating shaft 102 or the rotating drum, presence/absence of spontaneous ignition within the rotating drum is monitored, and either one of filling of nitrogen to inside of the rotating drum or input of water spray or dehydrated sludge is performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotary kiln-type sludge drying apparatus and a safety stop method thereof, and prevents spontaneous ignition in the drying apparatus when the drying apparatus stops the sludge drying operation, and further includes a heat exchanger and the like installed at a subsequent stage. TECHNICAL FIELD The present invention relates to a rotary kiln-type sludge drying apparatus capable of preventing damage and ignition of equipment and a method for safely stopping the apparatus.

  In a system equipped with a dryer, a high-temperature combustion gas for drying the object to be processed is generated, and the object to be processed is directly or indirectly heated by introducing the combustion gas into the dryer. It is dried. In such a system, at the time of a normal stop or an emergency stop when an abnormality occurs, the supply of the object to be processed is stopped first. However, if the combustion gas flows in without the object to be processed being supplied into the dryer, However, there is a risk that the dryer body will be damaged due to the high temperature atmosphere, or that the dried product remaining in the machine will be exposed to combustion gas, resulting in overdrying and generation of flammable gas, and explosion after the dryer. In addition, the overdried product itself may spontaneously ignite and there is a risk of serious damage to peripheral equipment.

In order to avoid such a problem, conventionally, the suction damper of the circulation fan that supplies the combustion gas into the dryer is stopped to block the combustion gas flowing into the dryer.
As a similar configuration, Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-195278) describes a method for introducing hot air into a dryer when the burner flame of a hot stove generating combustion gas disappears at the time of operation. A configuration for stopping the operation of the combustion fan is disclosed.

  However, in recent years, in order to improve the thermal efficiency, a heat exchanger may be installed at the rear stage of the dryer. As described in Patent Document 1, the combustion gas of the deodorization furnace is used as the high temperature side gas introduced into the heat exchanger. In the case of a system using dry exhaust gas from a dryer as the low temperature side gas, when the dryer stops and the dry exhaust gas on the low temperature side is not supplied, the heat exchanger suddenly rises in temperature and the heat exchanger There was a risk of damage or fire. Therefore, in such a system, it is dangerous to shut off the dry exhaust gas on the low temperature side.

In order to solve such a problem, the present patent applicant provides a heat treatment system including a dryer described in Patent Document 2 (Japanese Patent Application No. 2006-326254) and an operation method thereof. Specifically, a combustion furnace in which a dry exhaust gas outlet side of a dryer and a heat exchanger are connected via a dry exhaust gas discharge line, and combustion gas is generated by burning dry exhaust gas heated at the heat exchanger. A combustion gas inlet side of the dryer is connected via a combustion gas supply line, and the heat exchanger is configured so that at least a part of the dry exhaust gas and the combustion gas is introduced and performs heat exchange therebetween. In the heat treatment system equipped with a dryer,
Provided on the dry exhaust gas discharge line is a shut-off damper that is kept open during steady operation and is switched off when the dryer is stopped, and is inactive when the dryer is stopped on the combustion gas supply line An inert gas supply means for supplying gas is provided.

  According to Patent Document 2, a shut-off damper is provided on the dry exhaust gas discharge line on the dryer outlet side, and the shut-off damper is closed when stopped to prevent high-temperature superheated gas from being supplied into the dryer. Thereby, it is possible to prevent the dryer from being heated to a high temperature, and it is possible to prevent damage to the dryer body and ignition of the dried processed product remaining in the dryer. Furthermore, it is possible to prevent a large amount of flammable gas from being generated due to overdrying, and to prevent the risk of explosion at a later stage. Furthermore, since the shut-off damper is installed in the low-temperature dry exhaust gas discharge line, use in a high-temperature atmosphere can be avoided, and the damper can have high reliability and low material cost. In addition, since the inert gas is supplied to the dryer inlet side at the time of stoppage, it is possible to prevent the oxygen concentration in the dryer from increasing due to leaked oxygen. An interlock that closes the shut-off damper may be provided depending on the stop condition of the system.

JP 2005-195278 A Japanese Patent Application No. 2006-326254

As mentioned above, problems with systems equipped with dryers include high temperatures inside the dryer when the dryer is stopped, damage to the dryer body, ignition due to overdrying of the workpiece, and explosion due to generation of flammable gases. There was a danger of.
As a countermeasure, there is a method of shutting off the combustion gas used for drying as described in Patent Document 1, but a heat exchanger is provided on the rear side of the dryer, and dry exhaust gas is used as a low-temperature side gas. In such a case, the heat exchanger is heated to a high temperature due to the circulation of the dry exhaust gas, and the heat exchanger may be damaged or ignited.

On the other hand, in the method described in Patent Document 2, it is possible to prevent the dryer from becoming high temperature, and it is possible to prevent damage to the dryer body and ignition of the dried processed material remaining in the dryer. However, if a shut-off damper is provided on the dry exhaust gas discharge line on the dryer outlet side and the shut-off damper is closed during stoppage to prevent high-temperature superheated gas from being supplied into the dryer, some of the gas may have a low pressure inlet. There is a possibility that a reverse flow will occur.
In addition, during normal operation, the condition inside the dryer is monitored at the outlet temperature of the dryer, but after the hot air supply to the dryer is stopped in the stop process, there is a possibility that the situation inside the dryer cannot be fully grasped only by the outlet side temperature. There is.
Therefore, in view of the above-mentioned problems of the prior art, the present invention prevents spontaneous ignition in the drying device when the drying operation of the drying device is stopped, and also in other devices such as a heat exchanger installed in the subsequent stage. It is an object of the present invention to provide a rotary kiln-type sludge drying apparatus and a safe stopping method thereof that can safely perform a stopping process without causing a problem.

Therefore, in order to solve such a problem, the present invention provides a sludge inlet and a combustion gas inlet used for drying sludge on the rotary kiln main body inlet side provided with a sludge stirring shaft inserted along the axial direction of the rotating drum. On the other hand, in the safety stop method of the rotary kiln type sludge drying apparatus provided with the dried product discharge port on the main body outlet side and the dried exhaust gas outlet for discharging the dried exhaust gas generated by the sludge drying,
After the sludge drying operation of the drying apparatus is stopped, based on detection signals of the temperature at the rotary drum inlet side, the CO concentration in the drum, and the thermal expansion amount (linear expansion amount) in the axial direction of the stirring shaft or the rotary drum. Then, the presence or absence of spontaneous ignition in the rotating drum is monitored, and any one of nitrogen sealing, water spraying, or dewatered sludge charging into the rotating drum is performed.

  According to the present invention, after the sludge drying operation is stopped, the detection signal is detected by detecting any of the temperature at the inlet side of the rotating drum, the CO concentration in the drum, and the thermal expansion amount in the axial direction of the stirring shaft or the rotating drum. The presence or absence of spontaneous ignition in the drum can be monitored. As a result, any one of nitrogen sealing, water spraying, and dewatered sludge charging into the rotating drum can be performed, and a measure for suppressing the temperature rise in the drying apparatus can be appropriately performed. Therefore, the heat loss of the drying apparatus can be prevented, and furthermore, the stopping process can be safely performed without causing any trouble in other equipment such as a heat exchanger installed in the subsequent stage.

Further, in the safety stop method of the rotary kiln-type sludge drying apparatus according to the above, wherein the detection signal for the spontaneous combustion monitoring is the rotary drum inlet side temperature,
The selection of either or both of water spray and dehydrated sludge is determined based on the rate of change in temperature rise of the rotary drum inlet side temperature.
Water spraying is effective when the temperature of the rotary drum inlet side temperature is abrupt, but there is a risk of sudden generation of water vapor. If there is such a fear, additional dehydrated sludge with a high water content is added. A treatment is selected according to the temperature rise of the rotary drum inlet side temperature.
In this way, by selecting a measure that suppresses the temperature rise in the drying device based on the rate of change in the temperature at the inlet side of the rotating drum of the drying device, it is possible to prevent spontaneous ignition in the rotating drum and to prevent the sudden evaporation of moisture. This can prevent sludge and reduce the temperature of sludge products.
Further, the sludge drying operation of the drying device is stopped by the sludge input stop from the sludge input, the combustion gas introduction stop from the combustion gas inlet, and the rotation drum drive stop.

In addition, as an invention of the apparatus, a sludge inlet and a combustion gas inlet used for drying sludge are provided on the rotary kiln main body inlet side provided with a sludge agitation shaft inserted along the axis of the rotating drum. In the rotary kiln type sludge drying device provided with the treated product discharge port and the dry exhaust gas outlet for discharging the dry exhaust gas generated by the sludge drying,
After the sludge drying operation of the drying apparatus is stopped, based on detection signals of the temperature at the rotary drum inlet side, the CO concentration in the drum, and the thermal expansion amount (linear expansion amount) in the axial direction of the stirring shaft or the rotary drum. Spontaneous ignition monitoring means for monitoring the presence or absence of spontaneous ignition in the rotating drum,
And a flame extinguishing means for performing any one of nitrogen filling, water spraying and dewatering sludge charging based on the monitoring result of the monitoring means.

Furthermore, in the rotary kiln-type sludge drying apparatus according to the above, wherein the monitoring signal is the rotary drum inlet side temperature,
It is characterized in that a controller is provided in which selection of either or both of water spraying and dewatered sludge charging is determined based on a rate of change in temperature of the rotary drum inlet side temperature.
This has the same effect as the method invention described above.

As described above, according to the present invention, after the sludge drying operation is stopped, as the detection signal, any one of the temperature at the rotary drum inlet side, the CO concentration in the drum, and the thermal expansion amount in the axial direction of the stirring shaft or the rotary drum is detected. Thus, the presence or absence of spontaneous ignition in the rotating drum can be monitored. Thus, any one of nitrogen sealing, water spraying or dewatered sludge charging into the rotating drum can be performed, and a measure for suppressing the temperature rise in the drying apparatus can be appropriately performed, and spontaneous ignition can be prevented. . Moreover, the heat loss of the drying apparatus can be prevented, and furthermore, the stopping process can be safely performed without causing any trouble in other equipment such as a heat exchanger installed in the subsequent stage.
In addition, by selecting a measure that suppresses the temperature rise in the drying device based on the rate of change in the temperature at the inlet side of the rotating drum of the drying device, it prevents spontaneous ignition in the rotating drum and reduces the risk of sudden moisture evaporation. It can prevent and lower the sludge product temperature.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is a basic configuration diagram of a heat treatment system provided with a conventional rotary kiln type sludge drying device, FIG. 2 is a configuration diagram of a rotary kiln type sludge drying device according to Example 1, and FIG. 3 is a stirring shaft of the drying device when the drying device is stopped. FIG. 4 is a diagram showing a change with time in elongation, and FIG. 4 is a configuration diagram of a rotary kiln-type sludge drying apparatus according to Example 2.
Here, sludge is sewage sludge, pulp sludge, manure sludge, livestock sludge, and the like, and dehydrated sludge is particularly preferably used.
The term “when the drying apparatus is stopped” means that the sludge is stopped from the sludge inlet, the combustion gas is stopped from the combustion gas inlet, and the rotation drum is stopped. In addition, the emergency stop at the time of abnormality is included.

  As shown in FIG. 1, the conventional heat treatment system burns and burns a dryer 1 that dries sludge, a cyclone 2 that collects dry exhaust gas discharged from the dryer 1, and a dry exhaust gas that passes through the cyclone 2. A dryer combustion furnace 3 for generating gas, a circulating gas preheater 4 for exchanging heat between the dried exhaust gas from the dryer 1 and the combustion gas from the dryer combustion furnace 3, and the circulating gas preheater 4 And an exhaust gas treatment line 5 for treating the cooled combustion gas.

  The dryer 1 may have any structure as long as the sludge is dried, but a direct heating dryer is particularly preferable. As an example, there is a rotary kiln type dryer as shown in FIG. This is inserted into the kiln main body 101 in a state where the stirring shaft 102 is eccentric, and the stirring shaft 102 is provided with a plurality of paddles 103. A sludge inlet is formed on one side of the kiln main body 101, and a dried product discharge outlet is formed on the other side. The kiln main body 101 has a combustion gas inlet for introducing a combustion gas used for drying sludge. In addition, a dry exhaust gas outlet is provided for discharging dry exhaust gas generated by sludge drying. The sludge introduced into the kiln body is brought into contact with the combustion gas while being transferred through the kiln by the stirring shaft 102 rotating at a high speed and the kiln body 101 rotating at a low speed in the opposite direction to the stirring shaft 102. It is dried by. When sewage sludge is used as the sludge, a rotary kiln dryer having the above-described configuration is suitable. This is because there is a region where the viscosity increases depending on the water content of the sewage sludge, and therefore, the sludge can be prevented from sticking to the kiln body 101 by rotating the stirring shaft 102 at a high speed.

The dryer combustion furnace 3 is a device for burning dry exhaust gas containing a combustible gas, and supplementary fuel is supplied as necessary.
In the circulating gas preheater 4, the dry exhaust gas from the dryer 1 is introduced into the low temperature side gas inlet, and at least a part of the combustion gas from the dryer combustion furnace 3 is introduced into the high temperature side gas inlet. It is a device for exchanging heat with gas, and aims to cool the combustion gas as the dry exhaust gas rises in temperature. The circulating gas preheater 4 is a gas-gas heat exchanger without phase change. In principle, the cooled combustion gas is fed to the exhaust gas treatment line 5 on the rear stage side.

The exhaust gas treatment line 5 includes at least an acid gas removal device 501. The acidic gas removal device 501 is a device that removes acidic gas such as SO _x and HCl, and examples thereof include a scrubber and a bag filter.
The scrubber removes acid gas by spraying cleaning water containing an alkaline agent such as caustic soda. At this time, the exhaust gas temperature can also be lowered. Since the scrubber is suitable for removal of SO _x , sewage sludge containing a large amount of SO _{x in the} combustion gas is preferable as a treatment target.

Here, the gas flow in the system will be described. In addition, the temperature described here is one Example, and is not limited to these.
The 200 ° C. dry exhaust gas discharged from the dryer 1 is guided to the cyclone 2 through the dry gas discharge line 31, collected in the cyclone 2, and then passed through the dry exhaust gas discharge line 32 to circulate gas preheater. 4 is sent. At this time, at least a part of the dry exhaust gas is fed to the combustion gas inlet side of the dryer via the circulation gas line 38. A damper 46 is installed on the circulating gas line 38, and the combustion gas temperature for drying is adjusted by adjusting the circulating gas flow rate.

  The exhaust gas heated up to 550 ° C. by the circulating gas preheater 4 is supplied to the dryer combustion furnace 3 through the gas feed line 34, and is deodorized by the dryer combustion furnace 3. The high-temperature combustion gas at 950 ° C. generated in the dryer combustion furnace 3 is supplied to the dryer 1 through the combustion gas supply line 35 as a combustion gas used for drying at least a part thereof, and the rest is sent as gas. It is led to the circulating gas preheater 4 through the supply line 36 and cooled. The cooled combustion gas is discharged from the circulating gas preheater 4 and supplied to the exhaust gas treatment line 5.

A circulation fan 44 is installed on the dry gas discharge line 32 so that the gas flow as described above is formed. At this time, as a general rule, the motor rotation speed of the circulation fan 44 is step-controlled so that the output of the damper 43 on the fan suction port side is 15 to 30%.
A damper 43 is installed on the dry exhaust gas discharge line 32 and upstream of the circulation fan 44. The opening degree of the damper 43 is controlled based on the exhaust gas temperature and flow rate at the outlet of the dry exhaust gas of the dryer 1 to adjust the flow rate of the dry exhaust gas. Similarly, the rotational speed of the attracting fan may be appropriately adjusted based on the exhaust gas temperature and flow rate at the outlet of the dry exhaust gas.

  In the heat treatment system having the configuration shown in FIG. 1, there is a concern that the dryer main body may be damaged if high-temperature combustion gas is supplied into the dryer when the dryer 1 is stopped. Moreover, when the dried processed material remaining in the dryer 1 is exposed to a high-temperature heating gas, it becomes over-dried, and a combustible gas is generated, and there is a risk of explosion at a later stage. Moreover, the overdried product itself may ignite and there is a risk of serious damage to peripheral equipment.

Therefore, a shut-off damper 41 that shuts off the dry exhaust gas is provided on the dry gas discharge line 32 on the downstream side of the dryer 1 and upstream of the circulation fan 44. The shutoff damper 41 is kept open during steady operation, but is closed when the dryer 1 is stopped to shut off the flow of dry exhaust gas. An interlock for closing the shutoff damper 41 may be provided depending on the stop condition of the system.
An inert gas supply means is provided on the combustion gas supply line 35. This inert gas supply means is preferably a nitrogen gas supply means. The nitrogen gas supply means includes a nitrogen gas supply line 50 and a shut-off damper 51 provided on the nitrogen gas supply line 50. The shut-off damper 51 is kept closed during steady operation, but when the dryer 1 is stopped, the shut-off damper 51 is switched to open to supply nitrogen gas.

  In addition, it is preferable to provide second inert gas supply means for supplying an inert gas to the inlet side and the outlet side of the shutoff damper 41 on the dry exhaust gas discharge line 32. The second inert gas supply means is also preferably a nitrogen gas supply means. In this case, the second inert gas supply means includes a nitrogen gas supply line 53 and a shut-off damper 54 provided on the nitrogen gas supply line. The shut-off damper 54 is kept closed during normal operation, but when the dryer 1 is stopped, the shut-off damper 54 is switched to open to supply nitrogen gas.

  Further, a combustion gas return line 37 for introducing the combustion gas downstream from the acid gas removing device 501 to the circulating gas preheater 4 when the dryer is stopped, and a shut-off damper 42 located on the combustion gas return line 37 are provided. It is preferable. The shut-off damper 42 is kept closed during steady operation, and the shut-off damper 42 is switched to open when the dryer is stopped to supply low-temperature and low oxygen concentration combustion gas to the circulating gas preheater 4.

With reference to FIG. 2, the rotary kiln type sludge drying apparatus which concerns on Example 1 is demonstrated. In addition, Example 1 and Example 2 are based on the heat processing system of FIG. 1 mentioned above, The detailed description is abbreviate | omitted about the structure similar to FIG.
In FIG. 2, the rotary kiln type sludge drying apparatus is an apparatus mainly including a dryer 1 for drying dewatered sludge, and uses a rotary kiln type dryer. The dryer 1 is inserted into the kiln main body 101 with the stirring shaft 102 being eccentric, and the stirring shaft 102 is provided with a plurality of paddles 103. A sludge inlet is formed on one side of the kiln main body 101, and a dried product discharge outlet is formed on the other side. The kiln main body 101 has a combustion gas inlet for introducing a combustion gas used for drying sludge. In addition, a dry exhaust gas outlet is provided for discharging dry exhaust gas generated by sludge drying. The sludge introduced into the kiln body is brought into contact with the combustion gas while being transferred through the kiln by the stirring shaft 102 rotating at a high speed and the kiln body 101 rotating at a low speed in the opposite direction to the stirring shaft 102. It is dried by. The dry exhaust gas is led from the dry exhaust gas outlet to the cyclone 2 (FIG. 1) via the dry gas discharge line 31.
An inert gas supply means is provided on the combustion gas supply line 35. This inert gas supply means is preferably a nitrogen gas supply means. The nitrogen gas supply means includes a nitrogen gas supply line 50 and a shut-off damper 51 provided on the nitrogen gas supply line 50. The shut-off damper 51 is kept closed during steady operation, but when the dryer 1 is stopped, the shut-off damper 51 is switched to open to supply nitrogen gas.

Further, the dryer 1 includes a dryer inlet thermometer 12 that detects the temperature of the rotary drum inlet (dryer inlet temperature), and a dryer outlet that detects the temperature of the rotary drum outlet (dryer outlet temperature). A thermometer (not shown), a CO concentration meter 13 for detecting the CO concentration in the dryer, and a stirring shaft elongation measuring device 14 for measuring the thermal elongation of the stirring shaft 102 are provided. In addition, the dryer inlet part thermometer 12 can detect the temperature inside a dryer by installing a thermometer inside the combustion gas inlet of the fixed end surface of a dryer inlet part. Moreover, although it can be installed either on the outer side or on the inner side of the rotary drum entrance, if it is installed on the inner side of the rotary drum, there is a concern about the influence of sludge in the drum, so the outer side of the drum is preferable. When the supply of hot air to the dryer is stopped and the drying device is stopped, it is not possible to grasp the situation inside the dryer with the outlet side temperature alone, so the inlet side temperature is measured and the situation inside the dryer or the presence of spontaneous ignition is monitored. To do.
Moreover, although the thermal elongation of the stirring shaft 102 is monitored by the stirring shaft elongation measuring device 14, the thermal elongation of the rotating drum may be monitored. Visual monitoring may also be used.

  Here, FIG. 3 shows the change with time of the stirring axis elongation of the drying apparatus when the drying apparatus is stopped. As shown in FIG. 3, it can be seen that when the drying apparatus is stopped, the stirring shaft elongation decreases as the temperature in the dryer decreases. As described above, monitoring the thermal elongation of the stirring shaft together with the dryer inlet temperature and the dryer outlet temperature is effective for detecting the temperature rise in the dryer and the presence or absence of spontaneous ignition.

  In FIG. 2, when the drying apparatus stops the sludge drying operation by stopping the sludge input from the sludge inlet, shutting off the shut-off damper 41 and stopping the introduction of the combustion gas from the combustion gas inlet, and stopping the driving of the rotating drum, When the temperature of the dried sludge is high, the dried sludge in the dryer may spontaneously ignite. Therefore, in order to detect spontaneous ignition, the presence or absence of spontaneous ignition is monitored by measuring the temperature on the inlet side of the rotary drum, the CO concentration in the dryer, and the thermal elongation. When spontaneous ignition is detected, for example, an alarm (not shown) is issued, and nitrogen gas is supplied into the dryer 1 or sprayed with water. Water spray is an effective means when the temperature rise of the rotary drum inlet side temperature is abrupt. However, when water is sprayed in a high-temperature dryer, there is a risk that water vapor is rapidly generated.

Therefore, when there is a risk of sudden generation of water vapor, additional dehydrated sludge with a high water content is added. By additionally adding dehydrated sludge having a high water content, the temperature in the dryer can be lowered without rapid water evaporation, and the sludge product temperature can be lowered. In addition, the dewatered sludge thrown at this time is normal temperature. It is also possible to add both water spray and dewatered sludge based on the temperature rise of the inlet side temperature of the rotating drum.
In this way, by selecting a measure that suppresses the temperature rise in the drying device based on the rate of change in the temperature at the inlet side of the rotating drum of the drying device, it is possible to prevent spontaneous ignition in the rotating drum and to prevent the sudden evaporation of moisture. This can prevent sludge and reduce the temperature of sludge products. This can prevent heat loss of the drying apparatus, and also leads to prevention of malfunctions of equipment such as a heat exchanger installed in the subsequent stage.

Next, with reference to FIG. 4, the rotary kiln type sludge drying apparatus which concerns on Example 2 is demonstrated. Detailed description of the same configuration as that of the first embodiment is omitted.
In FIG. 4, the rotary kiln type sludge drying apparatus is an apparatus mainly including a dryer 1 for drying dewatered sludge, and uses a rotary kiln type dryer. The dryer 1 is inserted into the kiln body with the stirring shaft 102 being eccentric, and the stirring shaft 102 is provided with a plurality of paddles. A sludge inlet is formed on one side of the kiln main body and a dried product discharge outlet is formed on the other side. The kiln main body has a combustion gas inlet for introducing a combustion gas used for drying sludge, and a sludge. A dry exhaust gas outlet is provided for exhausting the dry exhaust gas generated by the drying. The sludge thrown into the kiln main body is brought into contact with the combustion gas while being transferred through the kiln by the stirring shaft 102 rotating at a high speed and the kiln main body rotating at a low speed in the opposite direction to the stirring shaft 102. Dried. The dry exhaust gas is led from the dry exhaust gas outlet to the cyclone 2 (FIG. 1) via the dry gas discharge line 31.
An inert gas supply means is provided on the combustion gas supply line 35. This inert gas supply means is preferably a nitrogen gas supply means. The nitrogen gas supply means includes a nitrogen gas supply line 50 and a shut-off damper 51 provided on the nitrogen gas supply line 50. The shut-off damper 51 is kept closed during steady operation, but when the dryer 1 is stopped, the shut-off damper 51 is switched to open to supply nitrogen gas.

Further, the dryer 1 includes a dryer inlet thermometer 12 that detects the temperature of the rotary drum inlet (dryer inlet temperature), and a dryer outlet that detects the temperature of the rotary drum outlet (dryer outlet temperature). A thermometer (not shown), a CO concentration meter 13 for detecting the CO concentration in the dryer, and a stirring shaft elongation measuring device 14 for measuring the thermal elongation of the stirring shaft 102 are provided. In addition, the dryer inlet part thermometer 12 can detect the temperature inside a dryer by installing a thermometer inside the combustion gas inlet of the fixed end surface of a dryer inlet part. Moreover, although it can be installed either on the outer side or on the inner side of the rotary drum entrance, if it is installed on the inner side of the rotary drum, there is a concern about the influence of sludge in the drum, so the outer side of the drum is preferable. When the supply of hot air to the dryer is stopped and the drying device is stopped, it is not possible to grasp the situation inside the dryer with the outlet side temperature alone, so the inlet side temperature is measured and the situation inside the dryer or the presence of spontaneous ignition is monitored. To do.
Further, as in the first embodiment, the thermal elongation of the stirring shaft 102 is monitored by the stirring shaft elongation measuring device 14, but the thermal elongation of the rotating drum may be monitored. Visual monitoring may also be used.

  Similarly to Example 1, in order to detect spontaneous ignition, the temperature on the rotary drum inlet side, the CO concentration in the dryer, and the thermal elongation are measured to monitor the presence or absence of spontaneous ignition. When spontaneous ignition is detected, for example, an alarm (not shown) is issued, and nitrogen gas is supplied into the dryer 1 or sprayed with water. In addition, when there is a possibility that water vapor is suddenly generated, dehydrated sludge having a high water content is additionally added. Further, both water spray and dewatered sludge can be added based on the temperature rise of the rotary drum inlet side temperature.

In FIG. 4, in addition to the above-described configuration, a controller 15 that determines whether or not to spray water spray or dehydrated sludge based on the temperature rise of the rotary drum inlet side temperature, and the controller 15 in the dryer 1 A motor 16 for controlling the amount of water sprayed, a pump 17 for spraying water into the dryer 1, a motor 19 for controlling the amount of dewatered sludge in the dryer 1 by the controller 15, and turning the motor 19 ON / OFF The screw feeder 20 is used to feed sludge into the dryer 1.
The controller 15 determines either or both of water spraying and dewatered sludge charging based on the temperature rise of the rotary drum inlet side temperature. By selecting a measure to suppress the temperature rise, it is possible to prevent spontaneous ignition in the rotating drum and to prevent the risk of rapid water evaporation and to reduce the sludge product temperature.

  According to the present invention, the rotary kiln-type sludge drying apparatus and the safety stop method thereof prevent spontaneous ignition in the drying apparatus when the drying apparatus stops the sludge drying operation, and further include a heat exchanger installed in the subsequent stage. It is useful as a rotary kiln type sludge drying apparatus and its safe stopping method that can prevent other equipment from being damaged and ignited.

It is a basic block diagram of the heat processing system provided with the conventional rotary kiln type sludge drying apparatus. It is a block diagram of the rotary kiln type sludge drying apparatus which concerns on Example 1. FIG. It is a figure which shows the stirring axis elongation time-dependent change of a drying apparatus at the time of a drying apparatus stop. It is a block diagram of the rotary kiln type sludge drying apparatus which concerns on Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dryer 2 Cyclone 3 Dryer combustion furnace 4 Circulating gas preheater 5 Exhaust gas treatment line 12 Dryer inlet thermometer 13 CO concentration meter 14 Stirring shaft elongation measuring device 15 Controller 31 Dry exhaust gas discharge line 35 Combustion gas supply line 38 Drying Exhaust gas circulation line 41 Blocking damper 50, 53 Nitrogen gas supply line 102 Stirring shaft

Claims (5)

A rotary kiln with a sludge agitation shaft inserted along the axis of the rotating drum is provided with a sludge inlet on the main body inlet side and a combustion gas inlet used for drying sludge, while a dried product outlet on the main body outlet side, and sludge. In the safety stop method of the rotary kiln type sludge drying device provided with the dry exhaust gas outlet for discharging the dry exhaust gas generated by the drying of
After the sludge drying operation of the drying apparatus is stopped, based on detection signals of the temperature at the rotary drum inlet side, the CO concentration in the drum, and the thermal expansion amount (linear expansion amount) in the axial direction of the stirring shaft or the rotary drum. The rotary kiln-type sludge drying apparatus is safely stopped by monitoring the presence or absence of spontaneous ignition in the rotary drum and performing any one of nitrogen filling, water spraying and dewatered sludge charging into the rotary drum. Method. In the safe stop method of the rotary kiln type sludge drying device according to claim 1, wherein the detection signal for monitoring the spontaneous ignition is the temperature at the inlet side of the rotary drum.
A method for safely stopping a rotary kiln-type sludge drying apparatus, wherein the selection of either or both of water spray and dewatered sludge is determined based on the rate of change in temperature of the rotary drum inlet side temperature.   2. The rotary kiln type according to claim 1, wherein the sludge drying operation of the drying device is stopped by the sludge input stop from the sludge input, the combustion gas introduction stop from the combustion gas inlet, and the rotation drum drive stop. Safe stop method for sludge drying equipment. A rotary kiln with a sludge agitation shaft inserted along the axis of the rotating drum is provided with a sludge inlet on the main body inlet side and a combustion gas inlet used for drying sludge, while a dried product outlet on the main body outlet side, and sludge. In the rotary kiln type sludge drying apparatus provided with the dry exhaust gas outlet for discharging the dry exhaust gas generated by the drying of
After the sludge drying operation of the drying apparatus is stopped, based on detection signals of the temperature at the rotary drum inlet side, the CO concentration in the drum, and the thermal expansion amount (linear expansion amount) in the axial direction of the stirring shaft or the rotary drum. Spontaneous ignition monitoring means for monitoring the presence or absence of spontaneous ignition in the rotating drum,
A rotary kiln-type sludge drying apparatus, comprising: flame extinguishing means for performing any one of nitrogen filling, water spraying, and dewatered sludge charging based on a monitoring result of the monitoring means. In the rotary kiln type sludge drying apparatus according to claim 4, wherein the monitoring signal is the rotary drum inlet side temperature.
A rotary kiln-type sludge drying apparatus comprising a controller in which selection of either or both of water spray and dewatered sludge is determined based on a rate of change in temperature of the rotary drum inlet side temperature.

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