JP2013087985A - Radiant tube burner, and operation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiant tube burner and an operation method therefor, which can properly prevent an unburned component, which is included in a combustion exhaust gas circulated from an exhaust region to a combustion region, from burning in a circulation passage.SOLUTION: The radiant tube burner 1 includes a combustion tube 8 in which a fuel is burned with supplied combustion air A to generate a combustion exhaust gas G, a heater tube 9 which is placed in a furnace S and releases the exhaust heat of the incoming combustion exhaust gas from the combustion tube 8, an exhaust tube 10 which discharges the combustion exhaust gas flowing out of the heater tube 9, and a circulation path 6 which is placed in the furnace S and communicatively connects the exhaust tube 10 to the combustion tube 8 to cause part of the combustion exhaust gas G to circulate therein. A supply path 7 for jetting control air C with a temperature lower than that of the combustion exhaust gas is connected to the circulation path 6.

Description

  The present invention relates to a radiant tube burner capable of appropriately suppressing unburned components contained in combustion exhaust gas circulated from an exhaust region to a combustion region in a circulation path and an operating method thereof.

  Conventionally, as a radiant tube burner, for example, as disclosed in “Recuperator” of Patent Document 1, a circulation path is provided between an exhaust side (exhaust region) and a burner side (combustion region) of a radiant tube. A circulation type radiant tube burner is known in which the exhaust gas on the exhaust side is sucked through the circulation path by the kinetic energy of the high-temperature combustion exhaust gas from the side and recirculated to the burner side.

  Such a circulation type radiant tube burner recombusts the combustion exhaust gas sucked to the burner side, so that the amount of exhausted NOx is suppressed. However, if unburned components are contained in the sucked combustion exhaust gas, unburned components may be burned in the circulation path, which may cause damage to the circulation path.

  For this reason, for example, as disclosed in “Hot-air circulation type radiant tube device” of Patent Document 2, the communication path is arranged in the furnace, so that the unburned portion burns in the communication path. It is known that it is constructed so as not to cause a rapid temperature change that damages the substrate.

JP 2000-146118 A JP 2000-283416 A

  If the circulation path is arranged in the furnace as in Patent Document 2, it is possible to suppress a rapid temperature change due to the combustion of unburned components contained in the combustion exhaust gas, but it is not possible to suppress the occurrence of combustion. There was still a problem that the circulation path might be damaged.

  The present invention has been devised in view of the above-described conventional problems, and can appropriately suppress unburned components contained in the combustion exhaust gas circulated from the exhaust region to the combustion region in the circulation path. An object is to provide a radiant tube burner and an operation method thereof.

  The radiant tube burner according to the present invention includes a combustion region that is combusted with supplied combustion air to generate combustion exhaust gas, and a heat dissipation region that is disposed in the furnace and dissipates the exhaust heat of the combustion exhaust gas flowing from the combustion region. A radiant tube having an exhaust region for exhausting the combustion exhaust gas flowing out from the heat dissipation region, and a circulation path that is disposed in the furnace and communicates the exhaust region with the combustion region to circulate a part of the combustion exhaust gas. A burner, characterized in that a supply path for ejecting control air having a temperature lower than that of combustion exhaust gas is connected to the circulation path.

  The exhaust region is provided with a recuperator that preheats combustion air to be supplied to the combustion region with combustion exhaust gas, and the supply path ejects a part of the combustion air as control air. It is connected to the downstream side.

  The supply path is provided with a shut-off device for shutting off the flow of control air.

  A method of operating a radiant tube burner according to the present invention is characterized in that the above-mentioned radiant tube burner is used and the amount of control air is adjusted according to the furnace temperature and supplied to the circulation path.

  Using the radiant tube burner, the control air amount is adjusted in accordance with the amount of NOx discharged and supplied to the circulation path.

  The radiant tube burner is used to cut off the supply of control air to the circulation path when the furnace temperature of the furnace rises.

  In the radiant tube burner and the operation method thereof according to the present invention, damage to the circulation path is appropriately suppressed by appropriately suppressing unburned components contained in the combustion exhaust gas circulated from the exhaust area to the combustion area in the circulation path. Can be prevented.

It is a schematic block diagram which shows suitable embodiment of the radiant tube burner which concerns on this invention. It is a schematic block diagram which shows the modification of the radiant tube burner which concerns on this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a radiant tube burner and an operation method thereof according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic configuration diagram of a radiant tube burner 1 according to the present embodiment.

  The radiant tube burner 1 of the present embodiment includes a radiant tube 2 configured in an approximately U-shaped outer shape, a nozzle 3 that is provided in one end of the radiant tube 2, and a radiant tube 2. A recuperator 4 provided in the other end portion for preheating the combustion air A by exhaust heat of the combustion exhaust gas G and a combustion air A provided in the radiant tube 2 and preheated by the recuperator 4 are supplied to the periphery of the nozzle 3. A duct-like air supply passage 5 and a circulatory path 6 provided in the radiant tube 2 and communicating between the vicinity of the nozzle 3 and the vicinity of the recuperator 4, and a control air to be described later are connected to the circulation path 6. And a pipe-shaped supply path 7 for supplying C by jetting it to the circulation path 6.

  The radiant tube 2 constituting the radiant tube burner 1 has a combustion tube portion 8 which is a combustion region in sequence, with one end portion provided with a nozzle 3 as a start end and the other end portion provided with a recuperator 4 as an end portion. The heater tube 9 that is a heat radiating region and the exhaust tube 10 that is an exhaust region are provided in series.

  The heater tube portion 9 protrudes inward from the furnace wall 11a of the furnace 11 where the radiant tube burner 1 is provided, and is disposed in the furnace S. An exhaust port 10 a of the exhaust pipe portion 10 extends through the furnace wall 11 a to the outside of the furnace 11 and is connected to the exhaust duct 12.

  In the combustion pipe portion 8, combustion exhaust gas G is generated by the combustion action of the fuel ejected from the nozzle 3 and the combustion air A supplied from the air supply passage 5. The combustion exhaust gas G flows from the combustion tube portion 8 into the heater tube portion 9. The heater tube portion 9 radiates the exhaust heat of the inflowing combustion exhaust gas G and exhibits a heater function. The combustion exhaust gas G that has heated the heater pipe portion 9 flows toward the exhaust pipe portion 10. The exhaust pipe part 10 circulates the combustion exhaust gas G flowing out from the heater pipe part 9 toward the exhaust port 10 a and exhausts it to the exhaust duct 12.

  The entire recuperator 4 is provided by being inserted into the exhaust pipe portion 10 from the exhaust port 10a side, and preheats the combustion air A with the combustion exhaust gas G flowing through the exhaust pipe portion 10 by heat exchange.

  The recuperator 4 is provided in the exhaust pipe portion 10 along the pipe axis direction, and opposes the combustion exhaust gas G flowing toward the exhaust port 10a and the combustion air A supplied from the blower 13 as a combustion air source. The outer pipe 14 is a flow, the opening 15a through which the combustion air A flows from the outer pipe 14 is provided in the outer pipe 14 along the pipe axis direction, and connected to the air supply passage 5 for combustion. And an inner pipe 15 for supplying the combustion air A to the pipe section 8, and a double pipe structure.

  Between the recuperator 4 and the exhaust pipe portion 10 that accommodates it, a heat exchange channel 16 is formed along the length direction, and the exhaust gas G is exchanged with the combustion air A while being exhausted. It is distributed toward 10a.

  Connected to the outer pipe 14 is a combustion pneumatic feeding pipe 17 that pumps the combustion air A fed from the blower 13. An air supply passage 5 that communicates with the combustion tube portion 8 is connected to the inner tube 15, and the air supply passage 5 is disposed outside the furnace 11. The combustion air A is preheated by the combustion exhaust gas G while circulating in the outer pipe 14, flows into the inner pipe 15 from the opening 15 a, is sent out from the inner pipe 15 to the air supply passage 5, and goes to the combustion pipe section 8. Supplied.

  The air supply passage 5 is provided with a supply path 7 branched from the air supply path 5, and the supply path 7 is connected to the circulation path 6. The circulation path 6 is disposed in the furnace S, communicates the exhaust pipe portion 10 and the combustion pipe portion 8, and allows a part of the combustion exhaust gas G to flow into the combustion pipe portion 8. The supply path 7 supplies control air C having a temperature lower than that of the combustion exhaust gas G to the circulation path 6 with an ejection action. The supply path 7 generates an ejector effect that sucks the combustion exhaust gas G from the exhaust pipe portion 10 into the circulation path 6 by the jetting action of the control air C.

  The action of ejecting the control air C from the supply path 7 can be obtained by a generally known technique for increasing the gas flow rate, such as providing an ejection nozzle. In the present embodiment, the supply path 7 is branched from the air supply passage 5 downstream of the recuperator 4 outside the furnace 11. Thereby, the supply path 7 supplies a part of the combustion air A preheated by the recuperator 4 to the circulation path 6 as control air C.

  In the circulation path 6, in combination with the ejector effect, upstream of the connection position of the supply path 7 in the flow direction of the combustion exhaust gas G, the flow velocity of the combustion exhaust gas G flowing through the circulation path 6 is increased to increase the combustion exhaust gas G. The diameter-reduced portion 18 for circulating the gas toward the combustion tube portion 8 is formed. The tip 7a of the supply path 7 is bent toward the flow direction of the combustion exhaust gas G in order to further facilitate the flow of the control air C into the circulation path 6.

  The combustion exhaust gas G flowing into the circulation path 6 is mixed with the control air C from the supply path 7 and circulated to the combustion pipe portion 8. The reduced diameter portion 18 functions as a baffle that prevents the flow of the combustion exhaust gas G from the exhaust pipe portion 10 to the combustion pipe portion 8 when the control air C does not flow from the supply path 7. In addition, when smoothing the supply of the control air C from the air supply passage 5 to the supply path 7, a throttle 19 may be provided on the downstream side of the branch position of the supply path 7.

  The supply path 7 is provided with a flow rate adjusting valve 20 for adjusting the flow rate of the control air C to the circulation path 6 and a shut-off valve 21 for blocking the supply of the control air C to the circulation path 6. The control air C flowing in the supply path 7 is preheated although it is at a lower temperature than the combustion exhaust gas G. When the flow rate adjusting valve 20 is opened and controlled to increase the flow rate of the control air C, the circulation amount of the combustion exhaust gas G is increased, and at the same time, the low temperature control is performed for the combustion exhaust gas G including unburned components. The amount of air C is increased, and unburned combustible combustion is suppressed from occurring in the circulation path 6. Further, since the control air C having a temperature lower than that of the combustion exhaust gas G is supplied in a large amount to the combustion pipe portion 8, the amount of NOx in the combustion exhaust gas G is also reduced.

  When the flow control valve 20 is throttled to reduce the flow rate of the control air C, the amount of the combustion exhaust gas G circulated is reduced, and at the same time, the amount of the low-temperature control air C with respect to the combustion exhaust gas G is reduced. The flame temperature in the combustion pipe part 8 becomes high, and the combustion temperature rises. When the supply of the control air C is stopped by the shutoff valve 21, combustion is performed only by the combustion air A from the air supply passage 5, and a combustion operation by a normal high temperature flame is ensured.

  The flow rate adjusting valve 20 and the shutoff valve 21 are input with a signal from the temperature sensor 22 that detects the furnace temperature and a signal from the NOx sensor 23 that detects the NOx concentration in the combustion exhaust gas G discharged from the exhaust duct 12. The operation is controlled by the controller 24.

  Next, an operation method of the radiant tube burner 1 according to the present embodiment will be described. When starting the radiant tube burner 1, the shutoff valve 21 is closed by the controller 24. As a result, the circulation of the combustion exhaust gas G and the introduction of the control air C are stopped, and the combustion air A preheated by the recuperator 4 is supplied to the combustion pipe portion 8 as quickly as the normal radiant tube burner 1 and promptly. And a high-temperature combustion flame is produced | generated smoothly and favorable start-up performance is ensured.

  After the start of operation, the shutoff valve 21 is opened by the controller 24. When the NOx sensor 23 detects that the amount of NOx in the combustion exhaust gas G is large, the controller 24 increases the opening amount of the flow rate adjustment valve 20 and preheats the recuperator 4 via the supply path 7. A large amount of control air C flows into the circulation path 6.

  By introducing the control air C through the supply path 7, a large amount of combustion exhaust gas G is circulated from the exhaust pipe portion 10 to the combustion pipe portion 8. By mixing the control air C with the combustion exhaust gas G, the temperature of the combustion exhaust gas G circulated to the combustion pipe portion 8 is lowered, the combustion temperature is lowered, and the NOx amount is reduced.

  On the other hand, when the amount of NOx is small, a controller is used to reduce the amount of control air C supplied and the amount of combustion exhaust gas G sent by the suction action of the control air C through the supply path 7 for high temperature combustion. 24, the opening amount of the flow regulating valve 20 is decreased.

  On the other hand, when the temperature sensor 22 detects that the furnace temperature is low, the controller 24 decreases the opening amount of the flow rate adjustment valve 20. Thereby, inflow of the control air C and the combustion exhaust gas G into the combustion pipe portion 8 is suppressed, and high-temperature combustion is ensured. When it is detected that the furnace temperature is high, the controller 24 increases the opening amount of the flow rate adjusting valve 20 and increases the supply amount of the control air C and the combustion exhaust gas G to the circulation path 6. Thereby, the furnace temperature is lowered.

  There is a correlation between the NOx amount and the combustion temperature, that is, the furnace temperature, that the combustion temperature is high when the NOx amount is large and the combustion temperature is low when the NOx amount is small. By controlling with the controller 24 based on the detected value, the control for suppressing the NOx amount to the set value or less is achieved.

  During normal operation of the radiant tube burner 1, the control air C having a temperature lower than that of the combustion exhaust gas G is continuously supplied to the circulation path 6. Combustion is suppressed.

  As described above, in the radiant tube burner and the operation method thereof according to the present embodiment, the operation of the radiant tube burner 1 is left to the gas flow by the control air C ejected to the circulation path 6 so as to exert the ejector effect. It can be controlled accurately rather than simply.

  In the radiant tube burner and its operating method according to the present embodiment described above, the control air C having a temperature lower than that of the combustion exhaust gas G is jetted to the circulation path 6 via the supply path 7. It can suppress that the unburned part contained in is combusted within the circulation path 6, and can prevent the circulation path 6 from being damaged.

  By jetting the control air C to the circulation path 6, the combustion temperature in the combustion pipe section 8 can be lowered by the control air C and the suctioned exhaust gas G, and the amount of NOx emission can be reduced. Can do.

  Since the control air C ejected to the circulation path 6 is a part of the combustion air A preheated by the recuperator 4, the combustion temperature in the combustion pipe portion 8 becomes too low, and the furnace temperature becomes too low. Can be prevented. In other words, the temperature of the control air C can be raised by using the recuperator 4 that preheats the combustion air A supplied to the combustion pipe section 8, and there is no need to provide an additional heating device. The structure of 1 can be simplified and the equipment cost and running cost can be reduced.

  The flow rate adjusting valve 20 can adjust the ejection amount of the control air C in accordance with the furnace temperature and the amount of NOx, thereby controlling the combustion temperature and optimizing the operation of the radiant tube burner 1. .

  Since the shutoff valve 21 blocks the injection of the control air C to the circulation path 6 when the temperature in the furnace rises, such as when the operation is started up, the combustion exhaust gas G is circulated to the combustion pipe section 8. Therefore, the temperature in the furnace can be raised smoothly in a short time, and the rising performance of the radiant tube burner 1 can be improved.

  A plurality of radiant tube burners 1 according to the present embodiment may be installed for one furnace 11, and the combustion pneumatic feed pipe 17 and the exhaust duct 12 may be shared for these radiant tube burners 1.

  In such a case, the combustion state of each radiant tube burner 1, specifically, the supply amount of combustion air A and the discharge amount of combustion exhaust gas G affect the operation of other radiant tube burners 1. become. For example, when the supply amount of the combustion air A to any one of the radiant tube burners 1 increases, the supply amount of the combustion air A decreases in the other radiant tube burners 1 and the operation state becomes unstable. turn into.

  In the present embodiment, since each radiant tube burner 1 is provided with the shut-off valve 21 and the flow rate adjusting valve 20, each radiant tube burner 1 can be individually controlled for combustion, and these operations are performed. The state can be stabilized.

  When the control air C is ejected from the supply path 7 by the reduced diameter portion 18, the flow rate of the combustion exhaust gas G flowing through the circulation path 6 is combined with the ejector effect of the supply path 7 that ejects the control air C. The speed can be increased, and the combustion exhaust gas G can be smoothly circulated toward the combustion pipe portion 8. Further, the reduced diameter portion 18 functions as a baffle when the control air C is not ejected, and can suppress the combustion exhaust gas G from flowing to the combustion pipe portion 8 via the circulation path 6.

  FIG. 2 shows a modification of the above embodiment. This modification differs from the above embodiment in that the supply path 7 is branched from the air supply path 5 and connected to the circulation path 6 so that the blower 13 and the circulation path 6 are connected and controlled. This is because the working air C is introduced from the blower 13 into the circulation path 6. In this case, it is preferable to provide a heating device 25 for preheating the control air C in the supply path 7.

  In this modification, since the control air C having a high dynamic pressure is jetted directly from the blower 13 to the circulation path 6, the combustion air A supplied from the recuperator 4 to the combustion pipe portion 8 is used. In comparison, the combustion exhaust gas G can be efficiently sucked into the circulation path 6.

  In the above embodiment, the case where the circulation path 6 is installed in the furnace S has been described. However, if the configuration of the present invention is used, combustion does not occur inside the circulation path 6 and damage can be prevented. 6 can also be installed outside the furnace 11. In this way, the structure of the furnace S can be simplified.

DESCRIPTION OF SYMBOLS 1 Radiant tube burner 2 Radiant tube 3 Nozzle 4 Recuperator 5 Air supply path 6 Circulation path 7 Supply path 7a Tip of supply path 8 Combustion pipe part 9 Heater pipe part 10 Exhaust pipe part 10a Exhaust port 11 Furnace 11a Furnace wall 12 Exhaust duct 13 Blower 14 Outer pipe 15 Inner pipe 15a Opening 16 Heat exchange flow path 17 Combustion pneumatic feeding pipe 18 Reduced diameter part 19 Throttle 20 Flow control valve 21 Shut-off valve 22 Temperature sensor 23 NOx sensor 24 Controller 25 Heating device A Combustion air C Control air (lower temperature than combustion exhaust gas)
G Combustion exhaust gas S Furnace

Claims (6)

Combustion region that generates combustion exhaust gas by burning with supplied combustion air, a heat dissipation region that is disposed in the furnace and dissipates exhaust heat of the combustion exhaust gas flowing in from the combustion region, and combustion that flows out of the heat dissipation region A radiant tube burner having an exhaust region for exhausting exhaust gas, and a circulation path disposed in the furnace and allowing the exhaust region to communicate with the combustion region and circulate a part of the combustion exhaust gas,
A radiant tube burner, wherein a supply path for ejecting control air having a temperature lower than that of combustion exhaust gas is connected to the circulation path.   The exhaust region is provided with a recuperator that preheats combustion air to be supplied to the combustion region with combustion exhaust gas, and the supply path ejects a part of the combustion air as control air. The radiant tube burner according to claim 1, wherein the radiant tube burner is connected to a downstream side.   The radiant tube burner according to claim 1, wherein the supply path is provided with a shut-off device that shuts off the flow of control air.   A method for operating a radiant tube burner, characterized in that the radiant tube burner according to any one of claims 1 to 3 is used and the amount of control air is adjusted according to the furnace temperature and supplied to the circulation path.   The radiant tube burner according to any one of claims 1 to 3, wherein the amount of control air is adjusted according to the amount of NOx discharged and supplied to the circulation path. How to drive a radiant tube burner.   The radiant tube burner according to any one of claims 1 to 3, wherein supply of control air to the circulation path is interrupted when the furnace temperature of the furnace rises. The operation method of the radiant tube burner of Claim 5.

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