JP4920388B2 - Heat treatment system equipped with a dryer and its operating method - Google Patents

Description

  The present invention prevents damage and ignition due to high temperature in the dryer when the operation is stopped in a system equipped with a dryer, and also damage and ignition of other equipment such as a heat exchanger installed in the subsequent stage. The present invention relates to a heat treatment system including a dryer that can be prevented and an operation method thereof.

  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, May cause damage to the main body of the dryer or exposure of the dried product remaining in the machine to the combustion gas, resulting in overdrying and generation of flammable gas that may explode later in the dryer. In addition, the overdried product itself may 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.

  Further, as a technique for preventing the ignition of the dryer, a method described in Patent Document 2 (Japanese Patent Laid-Open No. 9-138069) has been proposed. As shown in FIG. 4, in this drying facility, the combustion gas generated in the hot stove 201 is supplied to the dryer 202 by the drying fan 203, and the garbage is dried by the combustion gas. The dried exhaust gas discharged from the dryer 202 is heated by the heat exchanger 204 and then burned and deodorized by the deodorizing furnace 205. The combustion gas from the deodorizing furnace 205 is cooled by exchanging heat with dry exhaust gas in the heat exchanger 204 and then circulated in the hot stove 201. In this facility, a damper 210 is provided between the hot stove 201 and the dryer 202, and a bypass 211 is provided to connect the drying fan 203 and the hot air inlet of the dryer 202 without using the hot stove 201, During unstable operation in which the pressure and temperature change rapidly, the damper 210 is closed and the damper 212 is opened, and a drying path is formed in a state where the oxygen concentration is low by forming a circulation path that does not pass through the hot stove 201 and does not allow outside air to enter. The machine is configured to cool.

JP 2005-195278 A Japanese Patent Laid-Open No. 9-138069

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, the gas flow supplied to the heat exchanger 204 can be secured by providing the bypass 211. However, the damper 210 provided immediately after the hot stove 201 is configured to prevent inflow of combustion gas from the hot stove 201 to the dryer 202, and the damper 210 is easily damaged because it is exposed to the combustion gas atmosphere. Since distortion tends to occur, the reliability is low, and it is difficult to reliably block the combustion gas.
Therefore, in view of the problems of the prior art described above, the present invention reliably prevents the dryer from being damaged and ignited when the operation is stopped, and also has a problem with other devices such as a heat exchanger provided at the rear stage of the dryer. It aims at providing the heat processing system provided with the dryer which can perform a stop process safely, without generating, and its operating method.

Therefore, in order to solve such problems, the present invention connects the dry exhaust gas outlet side of the dryer and the heat exchanger via the dry exhaust gas discharge line, and burns the dry exhaust gas heated by the heat exchanger. A combustion furnace for generating combustion gas and a combustion gas inlet side of the dryer are connected via a combustion gas supply line, and at least a part of the dry exhaust gas and the combustion gas is introduced into the heat exchanger. In a heat treatment system equipped with a dryer that performs heat exchange between them,
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 a gas is provided.

  According to the present invention, the cutoff damper is provided on the dry exhaust gas discharge line on the outlet side of the dryer, and the cutoff damper is closed at the time of stoppage, thereby preventing 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.

In addition, an exhaust gas treatment line including an acid gas removal device for removing acid gas from the combustion gas cooled in the heat exchanger,
Combustion gas return line connected to the dry gas discharge line from the downstream side of the acid gas removal device of the exhaust gas treatment line, and the combustion gas return line are provided on the combustion gas return line. A shut-off damper that is switched to open when the machine is stopped is provided, and combustion gas having a low temperature and a low oxygen concentration is supplied to the heat exchanger when the dryer is stopped.

  Thus, by introducing the combustion gas downstream from the acid gas removal device into the heat exchanger when the dryer is stopped, the combustion gas having a low temperature and a low oxygen concentration can be supplied to the heat exchanger. Overheating of the exchanger can be prevented. By preventing overheating of the heat exchanger, it is possible to provide a highly safe system without risk of equipment damage, ignition, and dust explosion. Furthermore, since this combustion gas is a clean gas after removing the acid gas, it is possible to prevent corrosion in the system including the heat exchanger. According to this configuration, the system operation can be continued without stopping the dryer circulation fan, and the system stop process can be performed safely without affecting other devices.

Further, a second inert gas supply means for supplying an inert gas to the inlet side and the outlet side of the shut-off damper provided on the dry exhaust gas discharge line is provided.
In this way, after closing the shut-off damper, an inert gas is sealed on the inlet side and the outlet side of the shut-off damper, thereby preventing ignition of flammable fine particles due to leaked oxygen and heat generated in the heat storage of the dryer. Purge can be performed.

And a carbonization furnace that carbonizes the dried product discharged from the dryer, and a pyrolysis gas discharge line that supplies the pyrolysis gas discharged from the carbonization furnace to the combustion furnace. To do.
Furthermore, a melting furnace for melting the dried product discharged from the dryer, and a pyrolysis gas discharge line for supplying the pyrolysis gas discharged from the melting furnace to the combustion furnace is provided. And
Thus, the present invention can be suitably applied to a system including a carbonization furnace or a melting furnace.

Further, as an invention of the operation method, the combustion gas generated in the combustion furnace is introduced from the combustion gas inlet of the dryer, the dry exhaust gas discharged from the drying exhaust gas outlet of the dryer is introduced into the heat exchanger, and In the operation method of the heat treatment system in which a part of the combustion gas generated in the combustion furnace is introduced into the heat exchanger and heat exchange is performed between the dry exhaust gas and the combustion gas.
A shut-off damper is provided on the dry exhaust gas discharge line connected to the heat exchanger from the dry exhaust gas outlet of the dryer, and the shut-off damper is maintained in an open state during normal operation,
When the dryer is stopped, the shut-off damper is switched to close to shut off the dry exhaust gas, and an inert gas is supplied to the combustion gas inlet side of the dryer.

Furthermore, when the dryer is stopped, a low temperature and low oxygen concentration combustion gas after removing acid gas from the combustion gas cooled by the heat exchanger is introduced into the heat exchanger as an alternative to the dry exhaust gas. It was made to do.
Furthermore, when the dryer is stopped, an inert gas is supplied to the inlet side and the outlet side of the shut-off damper.

As described above, according to the present invention, by providing a shut-off damper on the drying exhaust gas outlet side of the dryer, the heat source to the dryer can be shut off immediately when the dryer is stopped, and the dryer is heated to a high temperature. It is possible to prevent damage to the dryer body and ignition of the dried processed material 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.
In addition, by providing inert gas supply means on the inlet side of the dryer and on the inlet side and outlet side of the shut-off damper, it is generated due to prevention of ignition of flammable fine particles due to leaked oxygen and heat storage of the dryer when the dryer is stopped. Steam purge can be performed.
Further, by introducing the combustion gas downstream from the acid gas removal device into the heat exchanger when the dryer is stopped, the combustion gas having a low temperature and a low oxygen concentration can be supplied to the heat exchanger. Overheating can be prevented, and a highly safe system without the risk of equipment damage, ignition, and dust explosion can be obtained.

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.
FIG. 1 is a basic configuration diagram of a heat treatment system including a dryer according to the first embodiment, FIG. 2 is a configuration diagram of a heat treatment system including a dryer and a carbonization furnace according to the second embodiment, and FIG. It is a block diagram of the heat processing system provided with the dryer and the melting furnace.
The heat treatment system of the present embodiment is a highly safe system that prevents damage and ignition of equipment including the dryer and the heat exchanger without increasing the temperature inside the dryer even when the dryer is stopped. Here, the time of stop includes a normal stop during steady operation and an emergency stop during an abnormality.

With reference to FIG. 1, the basic configuration of the system according to the present embodiment will be described.
This system includes a dryer 1 that dries an object to be processed, a cyclone 2 that collects dry exhaust gas discharged from the dryer 1, and a dryer combustion that generates combustion gas by burning the dry exhaust gas that has passed through the cyclone 2. The furnace 3, the circulating gas preheater 4 that exchanges heat between the dried exhaust gas from the dryer 1 and the combustion gas from the dryer combustion furnace 3, and the combustion gas cooled by the circulating gas preheater 4 The exhaust gas treatment line 5 to be treated is provided.

  The dryer 1 may be any one as long as it has a structure for drying an object to be processed, 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 rotating shaft 102 is eccentric, and the rotating shaft 102 is provided with a plurality of paddles 103. A workpiece input port is formed on one side of the kiln body 101 and a dried product discharge port is formed on the other side, and combustion gas used for drying the workpiece is introduced into the kiln body 101. A combustion gas inlet and a dry exhaust gas outlet for discharging a dry exhaust gas generated by drying the workpiece are provided. An object to be processed put into the kiln body is brought into contact with the combustion gas while being transferred through the kiln by the rotating shaft 102 rotating at a high speed and the kiln body 101 rotating at a low speed in the opposite direction to the rotating shaft 102. To be dried. When using sewage sludge as an object to be treated, a rotary kiln dryer having the above-described configuration is suitable. This is because there is a region where the clay becomes higher depending on the moisture content of the sewage sludge, and thus the sludge can be prevented from sticking to the kiln body 101 by rotating the rotating shaft 102 at a high speed.

The dryer combustion furnace 11 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.
On the other hand, the bag filter removes acidic gas mainly composed of HCl by spraying slaked lime on the exhaust gas inlet side. When installing a bag filter, it is necessary to install a temperature reducing tower upstream from the bag filter to lower the bag filter inlet temperature to a predetermined temperature. Since the bag filter is suitable for removal of HCl, waste such as general waste containing a large amount of HCl 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 so as to adjust 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 system having the configuration as in the present embodiment, there is a concern that the dryer 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, as a characteristic configuration of the present embodiment, 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 this embodiment, 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.

According to the present embodiment, by installing the shut-off damper 41 in the dry exhaust gas discharge line 32, the heat source to the dryer 1 can be shut off immediately when the dryer 1 is stopped. Further, the above operation can prevent the dryer 1 from being damaged, the generation of combustible gas due to the excessive drying of the dried processed product, and the ignition of the processed product.
Further, by installing the shut-off damper 41 on the dry gas discharge line 32 upstream of the circulation fan 44, only the dryer 1 can be stopped without stopping the circulation fan 44 when the dryer 1 is stopped.
Furthermore, by stopping the dryer 1 and continuing the operation of only the circulation fan 44, the influence on other devices can be reduced and the entire system can be safely stopped.
Furthermore, after closing the shut-off damper 41 on the downstream side of the dryer, nitrogen gas is sealed on the inlet and outlet sides of the shut-off damper 41 to prevent ignition of combustible fine particles due to leaked oxygen and to store heat in the dryer 1. The generated steam can be purged.

  Furthermore, in this embodiment, when the dryer is stopped, the combustion gas return line 37 that introduces the combustion gas downstream from the acidic gas removal device 501 to the circulating gas preheater 4 and the cutoff located on the combustion gas return line 37 A damper 42 is preferably provided. Then, 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 combustion gas having a low temperature and a low oxygen concentration to the circulating gas preheater 4. Thereby, the overheating of the circulating gas preheater 4 can be prevented. By preventing overheating of the circulating gas preheater 4, it is possible to provide a highly safe system free from the risk of equipment damage, ignition, and dust explosion. Furthermore, since this combustion gas is a clean gas after removing the acid gas, it is possible to prevent corrosion in the system including the circulating gas preheater 4. According to this configuration, the system operation can be continued without stopping the circulation fan 44, and the system stop process can be safely performed without affecting other devices.

With reference to FIG. 2, it demonstrates per whole structure of the heat processing system provided with the heat exchanger and the carbonization furnace. In this embodiment, as an example, a case where sewage sludge is treated is described. In the following second and third embodiments, detailed description of the same configurations as those of the first embodiment will be omitted.
In FIG. 2, the configuration of this system includes a direct heating dryer 1 that dries dehydrated sludge, a carbonization furnace 6 that carbonizes the dried sludge discharged from the dryer 1, and thermal decomposition generated in the carbonization furnace 6. The apparatus includes various furnaces including a dryer combustion furnace 3 that combusts gas and a carbonization furnace combustion furnace 10 that generates combustion gas to be supplied to the carbonization furnace 6, and heat from exhaust gas used to heat the carbonization furnace 6. Various heat exchangers comprising an air preheater 7 for recovery, a circulating gas preheater 4 for recovering heat from the combustion gas generated in the dryer combustion furnace 3, and a white smoke preventer 12 are provided. The exhaust gas treatment line 5 for treating the exhaust gas generated in the system is provided, and the exhaust gas treatment line 5 has a flue gas treatment tower 502 and a wet electrostatic precipitator 503.

The flow of this system will be described together with the specific configuration of each device. In addition, the temperature, pressure, and moisture content described here are one example, and are not limited thereto.
The direct heating dryer 1 is supplied with dewatered sludge obtained by dewatering sewage sludge. Dehydrated sludge has a moisture content of about 80%. At the same time, a combustion gas of 850 ° C. is introduced into the dryer 1. This combustion gas is produced by mixing the 950 ° C. combustion gas produced in the dryer combustion furnace 3 with the dry exhaust gas discharged from the dryer 1.
In the dryer 1, the dewatered sludge is dried until it has a moisture content of 25% and discharged. The dry exhaust gas generated in the dryer 1 is a dry exhaust gas containing dust. After the dried exhaust gas is collected by the cyclone 2, a part of the exhaust gas is branched and sent to the combustion gas side introduced into the dryer 1 through the circulation gas line 38, and the other dried exhaust gas passes through the gas supply line 32. To the circulating gas preheater 4.

The dried sludge discharged from the dryer 1 is supplied to the carbonization furnace 6. In the figure, the carbonization furnace 6 shows an indirect heating type rotary kiln, but it may have other configurations. A combustion gas at 1100 ° C. is introduced into the jacket of the indirectly heated carbonization furnace 6. This combustion gas is produced by supplying a part of the combustion gas at 950 ° C. generated in the dryer combustion furnace 3 to the carbonization furnace combustion furnace 10 together with air and burning them using auxiliary fuel. .
The dried sludge heated in the reducing atmosphere by the combustion gas is carbonized, and the generated carbide is fed to the carbide hopper through the carbide cooling conveyor 8 and the humidifier 9.
The combustion gas used for carbonization is discharged from the jacket of the carbonization furnace at 670 ° C. and supplied to the air preheater 7. In the air preheater 7, the combustion gas discharged from the carbonization furnace 6 and the combustion air at normal temperature are subjected to heat exchange, and the combustion gas is cooled and the combustion air is heated. The heated combustion air is introduced into the dryer combustion furnace 3 (not shown), and the cooled combustion gas is sent to the exhaust gas treatment line 5.

  On the other hand, the pyrolysis gas generated in the carbonization furnace 6 is led to the dryer combustion furnace 3 through the pyrolysis gas discharge line 25, and the dryer combustion is performed together with the dry exhaust gas heated by the circulating gas preheater 4. It is burned with auxiliary fuel in the furnace 3 to produce 950 ° C. combustion gas. The combustion gas generated here is branched into three systems, one system is guided to the dryer 1 and used as a heat source for drying, and the other system is guided to the carbonization furnace combustion furnace 10 and further heated to be carbonized. Used as a heat source for the furnace, the remaining one system is sent to the exhaust gas treatment line 5 at the subsequent stage.

Of the combustion gas generated in the dryer combustion furnace 3, the system sent to the exhaust gas treatment line 5 is first introduced into the circulating gas preheater 4. The circulating gas preheater 4 has the same configuration as that of the first embodiment described above. The combustion gas from the dryer combustion furnace 3 and the dry exhaust gas from the dryer 1 are introduced, and heat exchange is performed between them. Is done. The dried exhaust gas heated by heat exchange is supplied to the dryer combustion furnace 3.
The combustion gas cooled by the circulating gas preheater 4 is subjected to heat exchange with the white smoke prevention air by the white smoke preventer 12 and further cooled, and then the acid gas is removed by the flue gas treatment tower 502. After being collected by the wet electrostatic precipitator 503, it is released into the atmosphere from the chimney. The white smoke prevention air heated by the white smoke preventer 12 is introduced immediately before the chimney and used to raise the temperature of the exhaust gas.

  An induction fan 46 and a circulation fan 44 are installed on the exhaust gas treatment line 5 between the flue gas treatment tower 502 and the electrostatic precipitator 503 and on the dry exhaust gas circulation line 32 between the dryer 1 and the circulating gas preheater 4, respectively. The induction fan 46 and the circulation fan 44 form a gas flow as described above. The induction fan 46 and the circulation fan 44 make the dryer combustion furnace 3 the starting point, the dryer combustion furnace 3 is -50 Pa, the cyclone 2 outlet is -2000 Pa, the circulation fan 44 inlet side is -2500 Pa, and the induction fan 46 outlet is 1000 Pa. It has become. That is, from the dryer combustion furnace 3 to the dryer 1 and the circulation fan 44 is a negative pressure system line, and similarly from the dryer combustion furnace 3 to the circulation gas preheater 4 and the induction fan 46 is a negative pressure system line. On the other hand, from the induction fan 46 to the chimney is a positive pressure system line.

Further, as a characteristic configuration of the present embodiment, a shut-off damper 41 for shutting off the dry exhaust gas is provided on the dry gas discharge line 32 connected from the dryer 1 to the circulating gas preheater 4 as in the first embodiment. Yes. The shut-off damper 41 is kept open during steady operation, but is shut off when the dryer 1 is stopped to shut off the flow of dry exhaust gas.
The combustion gas supply line 35 connected from the dryer combustion furnace 3 to the dryer 1 is provided with an inert gas supply means including a nitrogen gas supply line 50 and a shut-off damper 51. The shut-off damper 51 is kept closed during steady operation, and is switched to open to supply nitrogen gas when the dryer 1 is stopped.
Furthermore, a 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 is provided, and the second inert gas supply means is a nitrogen gas. A supply line 53 and a shut-off damper 54 are included. The shut-off damper 54 is kept closed during steady operation, and the shut-off damper 54 is switched to open to supply nitrogen gas when the dryer 1 is stopped.

Furthermore, a combustion gas return line 37 that branches at least a part of the combustion gas downstream from the flue gas treatment tower 502 and downstream from the induction fan 46 and connects to the dry exhaust gas discharge line 32 is provided. A damper 42 is provided on the combustion gas return line 37 and is kept closed during steady operation. A damper 43 is provided on the dry exhaust gas discharge line 32 and is kept open during steady operation. As a result, dry exhaust gas is supplied to the circulating gas preheater 4 during steady operation.
When the system is stopped, the damper 43 on the dry exhaust gas discharge line 32 is switched to close, and the damper 42 on the combustion gas return line 37 is switched to open. Thereby, the positive pressure combustion gas is smoothly supplied to the circulating gas preheater 4.
By adopting the configuration of the present embodiment, the same effect as that of the first embodiment can be obtained even in the heat treatment system including the carbonization furnace 6.

With reference to FIG. 3, the overall configuration of a heat treatment system including a heat exchanger using dry exhaust gas and a melting furnace will be described. In the present embodiment, a case where waste is treated as an example will be described.
In FIG. 3, the configuration of the present system includes a direct heating dryer 1 for drying waste, a melting furnace 60 for melting dry waste discharged from the dryer 1, and pyrolysis gas generated in the melting furnace 60. And a recirculating gas preheater 4 for recovering heat from the combustion gas generated in the drier combustor 3 and a white smoke preventer 12. It has various heat exchangers. The exhaust gas treatment line 5 for treating the exhaust gas generated in the system is provided, and the exhaust gas treatment line 5 has a flue gas treatment tower 502 and a wet electrostatic precipitator 503.

In the present embodiment, the dry waste dried in the dryer 1 is melted in the melting furnace 60, and the slag discharged from the melting furnace 60 is fed to the slag hopper via the slag conveyor 61. The pyrolysis gas discharged from the melting furnace 60 is supplied to the dryer combustion furnace 3 through the pyrolysis gas discharge line 26.
The dry exhaust gas generated in the dryer 1 is collected by the cyclone 2 and then guided to the circulating gas preheater 4 through the dry exhaust gas discharge line 32. After performing heat exchange between the high-temperature side combustion gas from the dryer combustion furnace 3 and the low-temperature side dry exhaust gas in the circulating gas preheater 4, the dry exhaust gas is introduced into the dryer combustion furnace 3, Combustion is performed by supplying auxiliary fuel together with the pyrolysis gas from the melting furnace 60.
The combustion gas discharged from the dryer combustion furnace 3 is branched into three systems, part of which is introduced as combustion air of the melting furnace 60 through the gas supply line 39, and the other part of the combustion gas is supplied through the combustion gas supply line 35. Then, it is guided to the dryer 1 and used as a heat source for drying, and the rest is sent to the exhaust gas treatment line 5 through the gas supply line 36.

Similarly to the second embodiment, a shut-off damper 41 for shutting off the dry exhaust gas is provided on the dry gas discharge line 32 connected from the dryer 1 to the circulating gas preheater 4. The shut-off damper 41 is kept open during steady operation, but is shut off when the dryer 1 is stopped to shut off the flow of dry exhaust gas.
The combustion gas supply line 35 connected from the dryer combustion furnace 3 to the dryer 1 is provided with an inert gas supply means including a nitrogen gas supply line 50 and a shut-off damper 51. The shut-off damper 51 is kept closed during steady operation, and is switched to open to supply nitrogen gas when the dryer 1 is stopped.
Furthermore, a 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 is provided, and the second inert gas supply means is a nitrogen gas. A supply line 53 and a shut-off damper 54 are included. The shut-off damper 54 is kept closed during steady operation, and the shut-off damper 54 is switched to open to supply nitrogen gas when the dryer 1 is stopped.

Further, a combustion gas return line 37 that branches at least part of the combustion gas downstream from the flue gas treatment tower 502 and downstream from the induction fan 46 and connects to the dry exhaust gas discharge line 32 is provided. A damper 42 is provided on the combustion gas return line 37 and is kept closed during steady operation. A damper 43 is provided on the dry exhaust gas discharge line 32 and is kept open during steady operation. As a result, dry exhaust gas is supplied to the circulating gas preheater 4 during steady operation.
When the system is stopped, the damper 43 on the dry exhaust gas discharge line 32 is switched to close, and the damper 42 on the combustion gas return line 37 is switched to open. Thereby, the positive pressure combustion gas is smoothly supplied to the circulating gas preheater 4.
By adopting the configuration of the present embodiment, the same effect as that of the first embodiment can be obtained even in the heat treatment system including the melting furnace 60.

1 is a basic configuration diagram of a heat treatment system including a dryer according to Example 1. FIG. It is a block diagram of the heat processing system provided with the dryer and carbonization furnace which concern on Example 2. FIG. It is a block diagram of the heat processing system provided with the dryer and melting furnace which concern on Example 3. FIG. It is a block diagram of the conventional waste drying equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dryer 2 Cyclone 3 Dryer combustion furnace 4 Circulating gas preheater 5 Exhaust gas treatment line 6 Carbonization furnace 7 Air preheater 10 Carbonization furnace combustion furnace 25, 26 Pyrolysis gas discharge line 31, 32 Dry exhaust gas discharge line 35 Combustion gas supply Line 37 Combustion gas return line 38 Dry exhaust gas circulation line 41, 42, 51, 54 Shut-off damper 44 Circulation fan 46 Induction fan 50, 53 Nitrogen gas supply line 60 Melting furnace 501 Acid gas removal device 502 Smoke treatment tower

Claims (8)

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 the dry exhaust gas heated at the heat exchanger is burned to generate combustion gas, and the dryer A dryer connected to the combustion gas inlet side of the combustion gas supply line, wherein the heat exchanger introduces at least a part of the dry exhaust gas and the combustion gas and exchanges heat between them. In the heat treatment system with
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 A heat treatment system provided with a dryer, characterized in that an inert gas supply means for supplying gas is provided. An exhaust gas treatment line including an acid gas removal device for removing acid gas from the combustion gas cooled in the heat exchanger;
Combustion gas return line connected to the dry gas discharge line from the downstream side of the acid gas removal device of the exhaust gas treatment line, and the combustion gas return line are provided on the combustion gas return line. A shut-off damper that is switched to open when the machine is stopped is provided, and low temperature and low oxygen concentration combustion gas is supplied to the heat exchanger when the dryer is stopped. Heat treatment system equipped with a dryer.   3. The drying according to claim 1, further comprising second inert gas supply means for supplying an inert gas to an inlet side and an outlet side of the shut-off damper provided on the dry exhaust gas discharge line. Heat treatment system equipped with a machine.   A carbonization furnace that carbonizes the dried processed product discharged from the dryer, and a pyrolysis gas discharge line that supplies the pyrolysis gas discharged from the carbonization furnace to the combustion furnace. Item 4. A heat treatment system comprising the dryer according to any one of Items 1 to 3.   A melting furnace that melts the dried processed product discharged from the dryer, and a pyrolysis gas discharge line that supplies the pyrolysis gas discharged from the melting furnace to the combustion furnace. Item 4. A heat treatment system comprising the dryer according to any one of Items 1 to 3. Combustion gas generated in the combustion furnace is introduced from the combustion gas inlet of the dryer, dry exhaust gas discharged from the drying exhaust gas outlet of the dryer is introduced into the heat exchanger, and combustion gas generated in the combustion furnace In the operation method of the heat treatment system in which a part of is introduced into the heat exchanger and heat exchange is performed between the dry exhaust gas and the combustion gas,
A shut-off damper is provided on the dry exhaust gas discharge line connected to the heat exchanger from the dry exhaust gas outlet of the dryer, and the shut-off damper is maintained in an open state during normal operation,
When the dryer is stopped, the shut-off damper is switched to close to shut off the dry exhaust gas, and the inert gas is supplied to the combustion gas inlet side of the dryer. .   When the dryer is stopped, the low temperature and low oxygen concentration combustion gas after removing the acidic gas from the combustion gas cooled by the heat exchanger is introduced into the heat exchanger as an alternative to the dry exhaust gas. The operation method of the heat treatment system according to claim 6, wherein the heat treatment system is operated.   The operation method of the heat treatment system according to claim 6, wherein an inert gas is supplied to an inlet side and an outlet side of the shut-off damper when the dryer is stopped.

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