Combustion device

Abstract

To provide a combustion device capable of precisely adjusting an air ratio.SOLUTION: A combustion device 10 for mixing and combusting fuel gas and combustion air includes a fuel gas pipe 2 for supplying the fuel gas, an air pipe 5 for supplying the combustion air, an exhaust gas pipe 7 for discharging combustion exhaust gas generated by mixing and combusting the fuel gas and the combustion air, and a control device 8 for controlling the combustion device 10. An exhaust pipe 56 having an inner diameter smaller than the inner diameter of the air pipe 5 is connected to the air pipe 5, the exhaust pipe 56 is provided with a regulating valve 57 for regulating the discharge amount of the combustion air, and the control device 8 regulates the opening degree of the regulating valve 57 so as to obtain an appropriate combustion air amount by the excess-air-ratio setter 72 based on the detection result of the oxygen concentration sensor 71.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion device that mixes fuel gas and combustion air and burns the mixture. [Background technology]

[0002] Conventionally, in a combustion device that mixes and burns fuel gas and combustion air, it is necessary to properly adjust the air ratio to perform combustion appropriately. For this reason, as shown in Patent Documents 1 to 3, a flow control valve is provided to adjust the flow rates of the fuel gas and combustion air, and a pressure equalizing valve is provided in the fuel gas supply line and an air control valve is provided in the combustion air supply line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-160123 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-274670 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-157620 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when controlling flow rate using a flow control valve, for example, if the fuel gas is ammonia, the amount of air is nearly four times the volume of the ammonia gas, which makes the flow control valve large and makes it difficult to precisely adjust the air ratio.Furthermore, when controlling pressure using a pressure equalizing valve, the air pressure changes depending on the air temperature, making it similarly difficult to precisely adjust the air ratio.

[0005] Therefore, an object of the present invention is to provide a combustion device that allows precise adjustment of the air ratio. [Means for solving the problem]

[0006] The present invention is a combustion device that mixes fuel gas and combustion air and burns the mixture, a fuel gas pipe for supplying fuel gas; an air pipe for supplying combustion air; an exhaust gas pipe for discharging combustion exhaust gas obtained by mixing and burning fuel gas and combustion air; a control device for controlling the combustion device, an oxygen concentration sensor that detects the oxygen concentration of the combustion exhaust gas is provided in the exhaust gas pipe; an exhaust pipe having an inner diameter smaller than an inner diameter of the air pipe is connected to the air pipe, and an adjustment valve for adjusting the amount of combustion air discharged is provided in the exhaust pipe; The control device adjusts the opening of the regulating valve so that an appropriate amount of combustion air is obtained by an air ratio setting device based on the detection result of the oxygen concentration sensor.

[0007] According to the above configuration, an exhaust pipe having an inner diameter smaller than that of the air pipe is connected to the air pipe, a regulating valve is provided in the exhaust pipe to adjust the amount of combustion air discharged, and the control device adjusts the opening of the regulating valve so that an appropriate amount of combustion air is obtained using an air ratio setter based on the detection result of the oxygen concentration sensor. In other words, by providing a regulating valve in the exhaust pipe and adjusting the amount of combustion air supplied with the regulating valve based on the oxygen concentration of the combustion exhaust gas, precise adjustment of the air ratio can be achieved. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a combustion device that allows precise adjustment of the air ratio. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a combustion device according to an embodiment of the present invention. [Figure 2] FIG. 4 is a schematic diagram of a combustion device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) Fig. 1 is a schematic diagram of a combustion device 10 according to an embodiment of the present invention. As shown in Fig. 1, the combustion device 10 is a combustion device that mixes fuel gas and combustion air and burns them, such as a radiant tube type combustion device 10. The radiant tube type combustion device 10 includes a cylindrical radiant tube 11, which is heated from the inside, and the material to be treated placed in a furnace F is heated by radiant heat from the outer circumferential surface of the radiant tube 11.

[0011] In the radiant tube combustion apparatus 10 of this embodiment, a W-shaped radiant tube 11 is used, and the main body 12 of the W-shaped radiant tube 11 is placed inside the furnace F. Both ends of the radiant tube 11 extend to the outside of the furnace F through the furnace wall F1. Note that the radiant tube 11 is not limited to a W-shape, and may have a U-shape, I-shape, or other shape.

[0012] A burner 3 is provided at one end of the radiant tube 11, which burns the fuel gas supplied from the fuel gas pipe 2 with combustion air. The burner 3 generates combustion exhaust gas by burning the fuel gas using the combustion air, and heats the radiant tube 11 from the inside using the combustion exhaust gas flowing through the radiant tube 11.

[0013] A heat exchanger 4 is provided at the other end of the radiant tube 11. The heat exchanger 4 heats the combustion air by exchanging heat between the combustion exhaust gas that has heated the radiant tube 11 and the combustion air supplied from the air pipe 5. The combustion air heated by the heat exchanger 4 is supplied through the combustion air supply pipe 6 to one end of the radiant tube 11, where the burner 3 is provided. The burner 3 burns the fuel gas supplied from the fuel gas pipe 2 with the combustion air heated by the heat exchanger 4, thereby generating combustion exhaust gas. The combustion exhaust gas flows through the main body 12 of the radiant tube 11 and toward the heat exchanger 4.

[0014] The combustion exhaust gas that has exchanged heat with the combustion air supplied from the air pipe 5 in the heat exchanger 4 is discharged to the outside through the exhaust gas pipe 7. The exhaust gas pipe 7 is provided with an oxygen concentration sensor 71 that detects the oxygen concentration of the combustion exhaust gas flowing through the exhaust gas pipe 7. Data on the oxygen concentration of the combustion exhaust gas detected by the oxygen concentration sensor 71 is sent to an air ratio setter 72, which controls the amount of combustion air to achieve an appropriate air ratio based on the oxygen concentration data of the combustion exhaust gas and the detection result of a temperature sensor F2 that measures the temperature inside the furnace F.

[0015] The fuel gas pipe 2 is provided with a fuel gas regulating valve 21 (fuel gas supply mechanism) that regulates the supply of fuel gas to the burner 3. The fuel gas regulating valve 21 is a flow rate regulating valve, and the amount of fuel gas supplied is regulated by adjusting its opening. In the fuel gas pipe 2, a flow rate orifice 22 is provided upstream of the fuel gas regulating valve 21, and the flow rate through the fuel gas pipe 2 is adjusted to be constant.

[0016] When a plurality of radiant tubes 11 are provided in the radiant tube combustion apparatus 10, the fuel gas piping 2 is configured so that fuel gas is supplied to each radiant tube 11 from a branching section 23 downstream of the fuel gas regulating valve 21. An on-off valve 24 that regulates the fuel gas supplied to each radiant tube 11 is provided downstream of the branching section 23. A pressure gauge 25 that measures the pressure in each fuel gas piping 2 is provided downstream of the on-off valve 24.

[0017] The air piping 5 is provided with an air regulating valve 51 (air supply mechanism) that adjusts the supply of combustion air to the heat exchanger 4. The air regulating valve 51 is a flow rate control valve, and by adjusting its opening, the amount of combustion air supplied is adjusted. In the air piping 5, a flow rate orifice 52 is provided upstream of the air regulating valve 51, and the flow rate through the air piping 5 is adjusted to be constant.

[0018] In the radiant tube combustion apparatus 10, when multiple radiant tubes 11 are provided, the air piping 5 is configured so that combustion air is supplied to each radiant tube 11 from a branching section 53 downstream of the air regulating valve 51. An on-off valve 54 that adjusts the combustion air supplied to each radiant tube 11 is provided downstream of the branching section 53. A pressure gauge 55 that measures the pressure in each air piping 5 is provided downstream of the on-off valve 54.

[0019] An exhaust pipe 56 having an inner diameter smaller than that of the air pipe 5 is connected to the air pipe 5 downstream of the branching portion 53 and upstream of the on-off valve 54. The exhaust pipe 56 is a pipe that exhausts the combustion air in the air pipe 5 to the outside, and is provided with an adjustment valve 57 that adjusts the amount of combustion air exhausted. The exhaust pipe 56 is connected to an exhaust gas pipe 7, and the fuel air in the air pipe 5 is exhausted to the outside via the exhaust gas pipe 7. The exhaust pipe 56 is connected to the exhaust gas pipe 7 downstream of the oxygen concentration sensor 71 in the combustion exhaust gas direction.

[0020] The radiant tube combustion apparatus 10 is equipped with a control device 8 that controls the combustion apparatus 10. The control device 8 adjusts the opening of the fuel gas regulating valve 21 and the air regulating valve 51 so that the combustion in each radiant tube 11 has an appropriate air ratio. The control device 8 also adjusts the opening of the regulating valve 57 based on the detection result of an oxygen concentration sensor 71 that detects the oxygen concentration of the combustion exhaust gas flowing through the exhaust gas piping 7 so that the air ratio set by the air ratio setter 72 is achieved, thereby adjusting the amount of combustion air supplied from the air piping 5 (the amount of combustion air discharged from the exhaust pipe 56).

[0021] The combustion device 10 having the above-described configuration can achieve the following effects.

[0022] (1) An exhaust pipe 56 having an inner diameter smaller than that of the air pipe 5 is connected to the air pipe 5, and a control valve 57 for adjusting the amount of combustion air discharged is provided in the exhaust pipe 56. The control device 8 adjusts the opening of the control valve 57 so that an appropriate amount of combustion air is provided by an air ratio setter 72 based on the detection result of an oxygen concentration sensor 71, thereby enabling more precise air ratio control than conventional adjustments made solely by the opening of the air control valve 51.

[0023] The operation of the regulating valve 57 is such that if the air ratio becomes lower than the set value, the opening of the regulating valve 57 is reduced to reduce the amount of combustion air discharged (bleed), and if the air ratio becomes higher than the set value, the opening of the regulating valve 57 is increased to increase the amount of combustion air discharged. At this time, the inner diameter of the exhaust pipe 56 is smaller than that of the air pipe 5, so the air flow rate flowing through the exhaust pipe 56 is less than that of the air pipe 5, and this small air flow rate is adjusted by the regulating valve 57, so that more fine adjustment can be made overall than by adjusting only the opening of the air regulating valve 51.

[0024] (2) The fuel gas pipe 2 is provided with a fuel gas regulating valve 21, which is a fuel gas supply mechanism that regulates the supply of fuel gas, and the air pipe 5 is provided with an air regulating valve 51, which is an air supply mechanism that regulates the supply of combustion air. The fuel gas pipes 2, air pipes 5, and exhaust gas pipes 7 are provided in multiple pairs, and a regulating valve 57 is provided in each exhaust pipe 56 connected to the air pipes 5. Therefore, it is possible to provide a combustion device 10 that performs precise air ratio control in units of the fuel gas pipes 2, air pipes 5, and exhaust gas pipes 7 that are provided as pairs.

[0025] (3) In a combustion device 10 in which multiple pairs of fuel gas pipes 2, air pipes 5, and exhaust gas pipes 7 are provided, the fuel gas regulating valve 21 regulates the amount of fuel gas supplied to the multiple fuel gas pipes 2, and the air regulating valve 51 regulates the amount of combustion air supplied to the multiple air pipes 5, so that the number of fuel gas regulating valves 21 and air regulating valves 51 can be reduced without arranging them in each radiant tube 11, thereby reducing the cost of the combustion device 10. Meanwhile, even in this case, a regulating valve 57 is provided in each exhaust pipe 56, so precise air ratio control can be performed.

[0026] (4) In the fuel gas piping 2, by supplying fuel gas to each radiant tube 11 from the branching portion 23 downstream of the fuel gas regulating valve 21, a configuration can be achieved in which one fuel gas regulating valve 21 adjusts the amount of fuel gas supplied to multiple fuel gas piping 2 branching off from the branching portion 23.

[0027] (5) In the air piping 5, by supplying combustion air to each radiant tube 11 from a branching section 53 downstream of the air regulating valve 51, a configuration can be achieved in which a single air regulating valve 51 adjusts the amount of combustion air supplied to multiple air piping 5 branching from the branching section 53.

[0028] (Another embodiment) In the above embodiment, the fuel gas may include ammonia.

[0029] 2 is a schematic diagram of a combustion device 10 according to another embodiment of the present invention. This embodiment differs from the above-described embodiment in that, since the fuel gas contains ammonia, an ammonia concentration sensor is provided to detect the ammonia concentration in the combustion exhaust gas, and control is performed from that perspective. The other configurations are the same as those of the above-described embodiment. Therefore, in the description of this embodiment, the same components as those in the above-described embodiment are denoted by the same reference numerals, and detailed description of those components will be omitted.

[0030] The exhaust gas pipe 7 is provided with an ammonia concentration sensor 73 that detects the ammonia concentration (unburned ammonia concentration) of the combustion exhaust gas flowing through the exhaust gas pipe 7. The ammonia concentration sensor 73 is located downstream of the oxygen concentration sensor 71 in the combustion exhaust gas direction and upstream of the connection point to the exhaust pipe 56. Based on the ammonia concentration of the combustion exhaust gas detected by the ammonia concentration sensor 73, the control device 8 controls the combustion device 10 to reduce the unburned ammonia in the combustion exhaust gas. Specifically, when the control device 8 detects that the detection result of the ammonia concentration sensor 73 exceeds a predetermined first concentration, the control device 8 closes the adjustment valve 57. Closing the adjustment valve 57 prevents the supplied combustion air from being discharged to the outside, increases the amount of combustion air supplied to the heat exchanger 4, and reduces the generation of unburned ammonia. Here, the first concentration is, for example, 25 ppm.

[0031] Furthermore, when the control device 8 detects that the detection result of the ammonia concentration sensor 73 has exceeded a second concentration that exceeds the first concentration, it closes the on-off valve 24 provided in the fuel gas pipe 2. Closing the on-off valve 24 prevents fuel gas from being supplied from the fuel gas pipe 2 to the burner 3, and combustion in the burner 3 stops. Stopping combustion in the burner 3 prevents the emission of combustion exhaust gas with a high ammonia concentration. Here, the second concentration is, for example, 1000 ppm.

[0032] The combustion device 10 having the above-described configuration can achieve the following effects.

[0033] (1) When the ammonia concentration in the combustion exhaust gas is higher than a predetermined value (for example, 25 ppm), the unburned ammonia can be reduced by closing the regulating valve 57 and increasing the amount of combustion air supplied.

[0034] (2) When the ammonia concentration in the combustion exhaust gas exceeds a predetermined threshold value (for example, 1000 ppm), the on-off valve 24 is closed, the supply of fuel gas to the burner 3 is stopped, and combustion is stopped, thereby preventing the release of combustion exhaust gas with a high ammonia concentration.

[0035] In the above embodiment and other embodiments, the combustion device 10 is a radiant tube type combustion device, but the present invention is not limited to radiant tube type combustion devices and can be applied to any combustion device that mixes fuel gas and combustion air and burns them.

[0036] In the above embodiment and other embodiments, the fuel gas supply mechanism is a fuel gas regulating valve 21, and the air supply mechanism is an air regulating valve 51. The fuel gas regulating valve 21 is a flow rate regulating valve that regulates the amount of fuel gas supplied, but the fuel gas supply mechanism is not limited to a flow rate regulating valve, and fuel gas may be supplied by pressure regulation using an equalizing valve or ON-OFF control using a shutoff valve. Furthermore, the air regulating valve 51 is a flow rate regulating valve that regulates the amount of combustion air supplied, but the air supply mechanism is not limited to a flow rate regulating valve, and combustion air may be supplied by regulation using a control valve or ON-OFF control using a shutoff valve.

[0037] In the above embodiment and other embodiments, the exhaust pipe 56 is connected to the exhaust gas pipe 7, and the fuel air in the air pipe 5 is exhausted to the outside via the exhaust gas pipe 7, but the exhaust pipe 56 may be open to the outside, and the combustion air may be exhausted directly to the outside from the exhaust pipe 56.

[0038] The present invention and embodiments can be summarized as follows.

[0039] (1) One embodiment of the present invention is a combustion device that mixes fuel gas and combustion air and burns the mixture, a fuel gas pipe for supplying fuel gas; an air pipe for supplying combustion air; an exhaust gas pipe for discharging combustion exhaust gas obtained by mixing and burning fuel gas and combustion air; a control device for controlling the combustion device, an oxygen concentration sensor that detects the oxygen concentration of the combustion exhaust gas is provided in the exhaust gas pipe; an exhaust pipe having an inner diameter smaller than an inner diameter of the air pipe is connected to the air pipe, and an adjustment valve for adjusting the amount of combustion air discharged is provided in the exhaust pipe; The control device adjusts the opening of the regulating valve so that an appropriate amount of combustion air is obtained by an air ratio setting device based on the detection result of the oxygen concentration sensor.

[0040] According to the above configuration (1), by providing a control valve in the exhaust pipe and adjusting the amount of combustion air supplied by the control valve based on the oxygen concentration of the combustion exhaust gas, it is possible to provide a combustion device that performs more precise air ratio control than the conventional method of adjusting only by the opening of the air control valve 51.

[0041] (2) In the configuration (1), the fuel gas pipe is provided with a fuel gas supply mechanism that adjusts the supply of fuel gas, The air piping is provided with an air supply mechanism that adjusts the supply of combustion air, The fuel gas pipe, the air pipe, and the exhaust gas pipe are provided in pairs, and The adjusting valve is provided in each of the exhaust pipes connected to the air pipe.

[0042] According to the configuration (2), in a combustion apparatus in which a plurality of pairs of fuel gas pipes, air pipes, and exhaust gas pipes are provided, an adjustment valve is provided in each exhaust pipe connected to the air pipes, so that a combustion apparatus can be provided in which precise air ratio control is performed for each pair of fuel gas pipes, air pipes, and exhaust gas pipes.

[0043] (3) In the configuration (2), the fuel gas supply mechanism is a fuel gas regulating valve that regulates the supply flow rate of the fuel gas, the air supply mechanism is an air regulating valve that adjusts the supply flow rate of combustion air, the fuel gas regulating valve is configured to regulate the amount of fuel gas supplied to the plurality of fuel gas pipes, The air regulating valve is configured to regulate the amount of combustion air supplied to the plurality of air pipes.

[0044] According to the configuration (3), in a combustion apparatus in which a plurality of pairs of fuel gas pipes, air pipes, and exhaust gas pipes are provided, the fuel gas regulating valve regulates the amount of fuel gas supplied to the plurality of fuel gas pipes, and the air regulating valve regulates the amount of combustion air supplied to the plurality of air pipes, so that the number of fuel gas regulating valves and air regulating valves can be reduced, thereby reducing the cost of the combustion apparatus. Even in this case, since a regulating valve is provided in each exhaust pipe, precise air ratio control can be performed.

[0045] (4) In any one of the above configurations (1) to (3), the fuel gas contains ammonia.

[0046] According to the configuration (4), by including ammonia in the fuel gas, it is possible to contribute to reducing CO2 generated from the combustion device. Furthermore, by performing precise air ratio control, it is possible to suppress the generation of NOx while reducing unburned ammonia.

[0047] (5) In the configuration (4), an ammonia concentration sensor that detects the ammonia concentration of the combustion exhaust gas is provided in the exhaust gas pipe, The control device is configured to close the regulating valve when it detects that the detection result of the ammonia concentration sensor exceeds a first concentration that is a predetermined concentration.

[0048] According to the above configuration (5), when the ammonia concentration in the combustion exhaust gas is higher than a predetermined value, the amount of unburned ammonia can be reduced by increasing the supply amount of combustion air.

[0049] (6) In the configuration (5), when the control device detects that the detection result of the ammonia concentration sensor has exceeded a second concentration that exceeds the first concentration, the control device closes the on-off valve provided in the fuel gas piping.

[0050] According to the configuration (6), when the ammonia concentration in the combustion exhaust gas exceeds a predetermined threshold, the supply of fuel gas is stopped and combustion is stopped, thereby making it possible to prevent the release of combustion exhaust gas with a high ammonia concentration.

[0051] Various modifications and variations may be made without departing from the spirit and scope of the present invention as set forth in the following claims. [Industrial Applicability]

[0052] The present invention can provide a combustion apparatus that allows precise adjustment of the air ratio, and is therefore of great industrial utility. [Explanation of symbols]

[0053] 10 Combustion equipment 11 Radiant tube 12 Main body 2 Fuel gas piping 21 fuel gas regulating valve 22 flow orifice 23 Branching section 24 On-off valve 25 Pressure gauge 3 Burner 4 Heat exchanger 5 Air piping 51 air regulating valve 52 flow orifice 53 Branching section 54 On-off valve 55 Pressure gauge 56 Exhaust pipe 57 Regulating valve 6 Combustion air supply pipe 7 Exhaust gas piping 71 Oxygen concentration sensor 72 Air ratio setting device 73 Ammonia concentration sensor 8 Control Device F Furnace F1 furnace wall F2 temperature sensor

Claims

1. A combustion device that mixes and burns fuel gas and combustion air, a fuel gas pipe for supplying fuel gas; an air pipe for supplying combustion air; an exhaust gas pipe for discharging combustion exhaust gas obtained by mixing and burning fuel gas and combustion air; a control device for controlling the combustion device, an oxygen concentration sensor that detects the oxygen concentration of the combustion exhaust gas is provided in the exhaust gas pipe; an exhaust pipe having an inner diameter smaller than an inner diameter of the air pipe is connected to the air pipe, and an adjustment valve is provided in the exhaust pipe to adjust the amount of combustion air discharged; The control device adjusts the opening of the regulating valve based on the detection result of the oxygen concentration sensor so that an appropriate amount of combustion air is obtained by an air ratio setter.

2. the fuel gas pipe is provided with a fuel gas supply mechanism that adjusts the supply of fuel gas, The air piping is provided with an air supply mechanism that adjusts the supply of combustion air, The fuel gas pipe, the air pipe, and the exhaust gas pipe are provided in pairs, and 2. The combustion apparatus according to claim 1, wherein the adjusting valve is provided in each of the exhaust pipes connected to the air pipe.

3. the fuel gas supply mechanism is a fuel gas regulating valve that regulates the supply flow rate of the fuel gas, the air supply mechanism is an air regulating valve that adjusts the supply flow rate of combustion air, the fuel gas regulating valve is configured to regulate the amount of fuel gas supplied to the plurality of fuel gas pipes, 3. The combustion apparatus according to claim 2, wherein the air regulating valve regulates the amount of combustion air supplied to the plurality of air pipes.

4. 4. The combustion device according to claim 1, wherein the fuel gas contains ammonia.

5. an ammonia concentration sensor that detects the ammonia concentration of the combustion exhaust gas is provided in the exhaust gas piping; 5. The combustion apparatus according to claim 4, wherein the control device closes the regulating valve when the control device detects that the detection result of the ammonia concentration sensor exceeds a first concentration that is a predetermined concentration.

6. 6. The combustion apparatus according to claim 5, wherein the control device closes an on-off valve provided in the fuel gas pipe when detecting that the detection result of the ammonia concentration sensor has exceeded a second concentration that is greater than the first concentration.

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