JP3286901B2 - Combustion control method for regenerative burner furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method for a regenerative burner furnace installed in a furnace using a combustion reaction as a heat source and other heat equipment, and more particularly to a switching control of the combustion.

[0002]

2. Description of the Related Art In recent years, as a combustion apparatus for improving the thermal efficiency of industrial furnaces such as a metal heating furnace and a heat treatment furnace, Japanese Patent Application Laid-Open No. Sho 62-947 has been proposed.
No. 03, Japanese Patent Application Laid-Open No. 2-10002, etc., a first burner and a second burner are paired, and a pair or a plurality of pairs of burners are arranged in one combustion chamber. Each burner has a heat storage body through which combustion air and combustion exhaust gas pass, and the first burner group and the second burner group are alternately burned, and the burner passes through the heat storage body of the burner when not burning. A regenerative burner has been proposed which repeats a cycle in which heat of combustion exhaust gas is transferred and stored in the regenerator, and combustion air passing through the heat stored in the regenerator is removed and preheated (heated) during combustion. I have.

[0003]

Problems to be Solved by the Invention
The outline of a furnace in which a regenerative burner is arranged will be described with reference to Japanese Patent Application Laid-Open Publication No. HEI 10-202733 as an example. FIG. 8 is a system diagram showing a regenerative burner disclosed in the publication. In the figure, 110 is a regenerative burner,
112 is a furnace, 114 is a burner, 116 is a combustion air / exhaust passage, 118 is a regenerator, 120 is a combustion blower, 121 is a fan inlet, 122 is an air valve, 124 is an exhaust valve, 126
Is a connection, and 127 is a control valve. 4 and 5 are explanatory diagrams showing the operation.

[0004] The regenerative burner 110 is configured such that the fluid in the pipe from the heat storage body 118 to the four-way switching valve (the device for switching between the combustion air and the flue gas flow path, the air valve 122 and the exhaust valve 124) is switched every time combustion is switched. It is replaced by combustion air and flue gas. In particular, when performing complete combustion with an air ratio of 1 or more, when the combustion air starts to flow, first, the heat storage body 1
Since the combustion exhaust gas remaining in the pipe between the heat storage body 18 and the heat storage body 118 to the four-way switching valve flows into the burner 114,
When the four-way switching valve injects fuel to the burner 114 at the same time as the completion of the flow path switching at the time of combustion switching, the heat storage element 118 and the heat storage
The fuel is injected into the flue gas containing almost no oxygen remaining in the pipe from 18 to the four-way switching valve, and while the remaining flue gas flows into the burner, the fuel is incompletely burned and unburned. Combustion gases will be emitted.

[0005] Therefore, the combustion side burner 114 at the time of combustion switching.
After the four-way switching valve completes the change of the flow path, the fuel is supplied to the heat storage body 118 by flowing only the combustion air without supplying the fuel for several seconds.
And exhausts the combustion exhaust gas remaining in the pipe between the heat storage body 118 and the four-way switching valve (referred to as “exhaust gas purge”).
After that, fuel is injected (injected).

The fuel gas remaining in the pipe between the fuel solenoid valve and the fuel nozzle causes residual fuel to be ejected from the fuel nozzle into the furnace due to residual pressure even when the solenoid valve is closed. In consideration of this, the operation of shutting off the fuel solenoid valve several seconds before the combustion switching is performed.

FIG. 7 shows the burner operation of the entire furnace when the individual burner operation shown in FIG. 6 is combined with the furnace shown in FIG. 3 based on the above-described concept. The furnace shown in FIG. 3 has two zones, five pairs in one zone and three pairs of regenerative burners in two zones. Each burner switches the combustion in 30 seconds and exhaust gas →
The air replacement time T _pa is 2 seconds, and the remaining fuel discharge time T _pg is 2 seconds. Further, in each zone, if all the burners ignite and extinguish the burners at the same time, the furnace pressure fluctuates greatly due to the ignition shock. In the case of one zone, five pairs are arranged in 30 seconds of combustion switching. The fire extinguishing of the burner is delayed in units of 6 seconds for each burner. Similarly, in the case of two zones, three pairs are arranged in 30 seconds of combustion switching, so the fire extinguishing of the burners is delayed in units of 10 seconds for each burner. The operation to make it happen. FIG. 7 shows the combustion operation of the entire furnace.

When the conventional combustion switching system as described above is used, there are the following problems. As shown in FIG. 7, in one zone, the number of open fuel solenoid valves 20 as shown in FIG.
It can be seen that it changes in the second cycle. Further, in the two zones, it can be seen that the number of open fuel solenoid valves 20 changes from three to two in a cycle of 6 seconds to 4 seconds. Further, considering the entire furnace, it can be seen that the number of open fuel solenoid valves 20 changes cyclically at intervals of several seconds between six and eight.

Generally, in the case of a furnace having a plurality of zones, since the combustion amount is controlled for each zone, there are fuel flow control valves 21 and 22 as shown in FIG. The fuel flow rate control valves 21 and 22 function by controlling the amount of heat required for each predetermined zone by controlling the fuel flow rate, and control the furnace temperature to a target value with respect to the determination of the amount of heat input. And those that control the temperature of the object to be heated to a target value, etc., and vary depending on the type of furnace. Normally, in the case of a conventional furnace in which the heat load of the furnace is constant and the burner does not perform switching combustion, the amount of fuel to be injected into the zone is constant, so that the fuel flow control valves 21 and 22 are stable at a constant opening. Flow control can be performed. However, when the combustion control of the furnace as shown in FIG. 7 is performed, as described above, the fuel solenoid valve 2
Since the pressure loss of the fuel system in the zone changes every few seconds even when the heat load is constant due to the change in the number of open zeros, the fuel flow control valves 21 and 22 always supply a fixed amount of fuel. In order to absorb the pressure loss change of the fuel system of the zone, the opening and closing operation of the valve is repeated as much as possible.

As a result, there is a problem that the fuel pressure fluctuation before each burner in each zone becomes large and the combustion becomes unstable. In some cases, there is a problem that the fuel pressure in the entire furnace fluctuates and combustion is not stable in the entire furnace. In addition, there is a problem that a piping capacity, that is, a piping size is increased so as to be able to cope with pressure fluctuations, or a flow regulating valve that opens and closes quickly is required, so that equipment costs rise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to provide a regenerative burner furnace that can burn each burner stably even when the burners are switched and burned in a short time (in units of seconds). A method for controlling combustion is provided.

[0012]

According to the present invention, there is provided a combustion control method for a regenerative burner furnace according to the present invention (claim 1), wherein a plurality of pairs of regenerative burners are arranged in one zone. Where T _pa is the replacement time from air to air, T _{pg is the} fuel purge time due to residual fuel pressure before switching to combustion, N is the number of burner pairs in the zone, and T _c is the fuel ejection time of one regenerative burner. _c = (N−1) × (T _pa + T _pg ) (1) The fuel injection time from one regenerative burner is determined based on the relationship (1), and the regenerative burner is controlled based on the fuel injection time.

Further, another combustion control method for a regenerative burner furnace according to the present invention (Claim 2) is a method for controlling a combustion in which a plurality of pairs of regenerative burners are arranged in one zone. Where T _pa , the fuel purge time due to the residual fuel pressure before combustion switching is T _pg , the number of burner pairs in the zone is N, and the combustion switching time of the regenerative burner is CT, CT = N × (T _pa + T _pg ) ... The combustion switching time of one regenerative burner is determined based on the relationship (2),
The regenerative burner is controlled based on the combustion switching time.

According to another aspect of the present invention, there is provided a method for controlling combustion of a regenerative burner furnace, wherein the regenerative burner is arranged and includes at least two zones. The replacement time of the exhaust gas from the air-exhaust system of the regenerative burner in the above zones to air is T _pa , the fuel purge time by the residual fuel pressure before switching to combustion is T _pg, and T _pa and T _pg of the corresponding zone are equivalent. and then, if the total Banapea number of the relevant zones and N, 1 single fuel jetting time of regenerative burners and T _c, 1 in relation to _{= T c (N-1)} × (T pa + T pg) ... (3) The fuel injection time from one of the regenerative burners is determined, and the regenerative burner is controlled based on the fuel injection time.

According to another aspect of the present invention, there is provided a method for controlling combustion of a regenerative burner furnace, wherein a regenerative burner is provided and the furnace has a plurality of zones constituted by regenerative burners. The replacement time of the exhaust gas from the air-exhaust system of the regenerative burner in the above zones to air is T _pa , the fuel purge time by the residual fuel pressure before switching to combustion is T _pg, and T _pa and T _pg of the corresponding zone are equivalent. and then, the total Banapea applicable number of zones N, if the combustion mode switching time of regenerative burner was CT, CT = N × (T pa + T pg) ... (4) combustion switching time of one regenerative burner in relation And determine
The regenerative burner is controlled based on the combustion switching time.

According to another aspect of the present invention, there is provided a combustion control method for a regenerative burner furnace in which the switching of the regenerative burner does not occur in two or more burner pairs at the same timing. To do.

According to another aspect of the present invention, there is provided a combustion control method for a regenerative burner furnace, wherein at least one radiant tube burner is used for the regenerative burner.

The inventors of the present invention have conducted various studies in the stage where the regenerative burner furnace was designed and manufactured and started operation, in view of the above problems, and as a result, the present invention has been achieved.
In other words, the number of open fuel solenoid valves in the management zone fluctuates every few seconds, and the fuel system pressure loss in the zone fluctuates synchronously. Along with this, as a result of various studies, it was found that keeping the number of open fuel solenoid valves in the control zone constant at all times is a basic principle to solve the above-mentioned problem.

As described above, in a regenerative burner that repeats point fire extinguishing, exhaust gas-air replacement and residual fuel discharge are basic operations that cannot be avoided as safety measures due to the configuration of the regenerative burner system every time a point fire extinguishes. This exhaust gas-air replacement time T _pa
By making the total time of the remaining fuel discharge time _Tpg equal to the fuel solenoid valve delay time of each burner arranged in the control zone, the combustion control in accordance with the basic principle can be performed. That is, the replacement time of the exhaust gas of the air-exhaust system with the air is T _pa , the fuel purge time by the residual fuel pressure before the combustion switching is T _pg , the number of burner pairs in the zone is N, and the fuel injection time of one regenerative burner. the Agego that the T _c, the combustion control in accordance with the basic principles by determining the fuel injection time from _{T c = (N-1)} × (T pa + T pg) 1 single regenerative burner in relation It becomes possible. Therefore, when the combustion switching time of a pair of regenerative burners is considered as CT in accordance with the basic principle, it is necessary to maintain the following relationship: CT = N × (T _pa + T _pg ).

If the furnace has a configuration in which a large number of burner pairs can be secured in the management zone, the combustion switching control may be performed in zone units in accordance with the basic principle described above. 50% above air - necessary to double the burner capacity will be devoted to the fuel purge time T _pg by replacement time T _pa and combustion before switching fuel residual pressure from the exhaust gas of the exhaust gas system to the air comes out. Accordingly, by considering a plurality of zones collectively as a management zone and achieving the above-described basic principle, it is possible to prevent the regenerative burner from becoming enormous and to avoid a rise in equipment costs.

In order to suppress the fluctuation of the fuel gas source pressure in the furnace, it is effective to reduce the number of burners for which the furnace is switched to the minimum. That is, the switching of the regenerative burners arranged in the furnace does not occur in two or more burner pairs at the same timing (time), so that it is possible to suppress the fluctuation of the fuel gas source pressure of the furnace. As described above, the basic principle is that in a radiant tube furnace composed of many small burners, such as a continuous annealing furnace, reducing the fuel gas pressure fluctuation of the furnace is an important item for ensuring the combustion stability of the burner. ,
It is effective in reducing misfire and unburned loss of the main burner.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An example in which the present invention is applied to a furnace 10 provided with a regenerative burner shown in FIG. 3 will be described. The furnace 10 of FIG. 3 is divided into two zones. One zone has 10 pairs of 5-storage burners 1-1-A and 1-1.
.. 1-5-B are arranged, and two pairs of regenerative burners 2-1-A, 2-1-B,.
-B is arranged. Each burner is provided with a fuel solenoid valve 20 for controlling fuel injection, a combustion air solenoid valve 30 for controlling combustion air injection, and an exhaust gas solenoid valve 40 for controlling furnace atmosphere, that is, suction of combustion exhaust gas. I have. Furthermore, a pilot burner (not shown) and associated equipment piping are arranged in each burner as an ignition source.

In each zone, fuel flow regulating valves 21 and 22 for controlling the amount of heat input, and combustion air flow regulating valves 31 and 32 for controlling the amount of combustion air supplied corresponding to the supplied fuel,
Exhaust gas flow control valves 41 and 42 are arranged to control the amount of exhaust gas suction, and control the temperature of the exhaust gas while controlling the temperature inside the furnace to control the amount of fuel input and the air ratio to control the ratio of fuel to air. The furnace is operated by controlling the furnace pressure. When balancing the sensible heat of exhaust gas emission from the heat storage body and the sensible heat of air absorption for combustion, a method in which part of the combustion exhaust gas is directly discharged to the outside of the furnace may be adopted in the furnace. There is no problem even if the present invention is applied. In the present embodiment, as the fuel, natural gas that can be pumped at the supply pressure itself is applied, but the present invention can be applied to any fuel such as other gas fuel, liquid fuel such as heavy oil, and solid fuel such as pulverized coal. It is. The atmosphere of the fuel air is pressure-fed from the combustion air blower 33, and the combustion exhaust gas is attracted by the exhaust gas inducing fan 43 and is emitted to the atmosphere from the chimney.

FIG. 1 is a diagram showing the operation of the regenerative burner of the entire furnace according to the first embodiment of the present invention in chronological order.
Each operation of the storage burner will be described with reference to FIG. 1
In zone, air - the replacement time T _pa from the exhaust gas of the exhaust gas system to the air for 2 seconds, the fuel purge time T _pg by the fuel residual pressure before combustion changeover and 2 seconds, Banapea number in one zone is 5 pairs Therefore, the fuel injection time _Tc of one burner per zone is 16 seconds according to the above equation (1). Therefore, the combustion switching time CT of the pair of burners is equal to the above (2).
It is 20 seconds according to the formula. As a result, four fuel solenoid valves in one zone are always kept open.

Further, in the second zone, air - and from the exhaust gas of the exhaust gas system 5 seconds replacement time T _pa to the air, the fuel purge time T _pg by the fuel residual pressure before combustion changeover and 5 seconds, 1
Since the number of burner pairs in the zone is three, the fuel ejection time _Tc of one burner in one zone is 20 seconds according to the above equation (1). Therefore, the combustion switching time CT of the pair of burners is 30 seconds according to the above equation (2). As a result, the two fuel solenoid valves in one zone are always kept open. Therefore, in the entire furnace, the six solenoid valves are always kept open.

(Embodiment 2) FIG. 2 is a diagram showing the operation of the regenerative burner of the entire furnace according to Embodiment 2 of the present invention in time series. explain. The present embodiment is an example in which the combustion switching timing control is performed by using two zones, one zone and two zones, as one management zone. The replacement time _Tpa from the exhaust gas to the air in the air-exhaust gas system is 2 seconds, and the combustion switching timing is 2 seconds. the fuel purge time T _pg by switching before the fuel residual pressure was 2 seconds, the Banapea number in the management zone are 8 pairs, by the above equation (3), fuel injection time T _c of the management zone one burner 28 seconds. Therefore, the combustion switching time CT of the pair of burners is 32 seconds according to the above equation (4). In the whole furnace, seven fuel solenoid valves are always kept open, and in each zone, the variation in the number of solenoid valves opened is suppressed as compared with the example of FIG. Control became possible.

[0027]

As described above, according to the present invention, since the number of open fuel solenoid valves of the regenerative burner in the control zone is controlled to be always constant, the fuel pressure fluctuation before the burner is controlled. Therefore, it is not necessary to increase the pipe capacity, that is, the pipe size, or to dispose a flow regulating valve that opens and closes promptly, and the fuel pressure in front of each burner in each zone and the entire furnace is not required. Fluctuations disappear,
Combustion control of a furnace capable of stable combustion has become possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing, in chronological order, the operation of a regenerative burner of an entire furnace according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing an operation of a regenerative burner of the entire furnace according to Embodiment 2 of the present invention in chronological order.

FIG. 3 is a diagram showing an outline of a furnace in which a regenerative burner is arranged.

FIG. 4 is a diagram showing the operation of each device of a pair of regenerative burners.

FIG. 5 is a diagram showing operation contents of a pair of regenerative burners.

FIG. 6 is a diagram showing an operation example of a pair of regenerative burners.

FIG. 7 is a diagram showing operation contents of a burner of the entire furnace according to the conventional technique.

FIG. 8 is a diagram showing a configuration of a conventional regenerative burner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Furnace 20 Solenoid valve arranged individually for burner before burner 21 1Z Fuel flow regulating valve 22 2Z fuel flow regulating valve 30 Combustion air solenoid valve arranged individually for burner before burner 31 1Z Combustion air flow regulating valve 32 2Z Combustion Air flow control valve 33 Combustion air blower 40 Exhaust gas solenoid valve arranged individually for burner in front of burner 41 1Z combustion exhaust gas suction flow control valve 42 2Z combustion exhaust gas suction flow control valve 43 Combustion exhaust gas inducing fan

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kento Sasaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Hirokazu Katsushima 2-1-1 53, Shirite, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture No. Japan Furnace Industry Co., Ltd. (72) Inventor Toshiaki Hasegawa 2-53-1, Shirite, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture In-house Furnace Industry Co., Ltd. (72) Inventor Yasuhiro Takahashi 21-7 Yamashima, Imago-cho, Ichinomiya-shi, Aichi Prefecture (56) References JP-A-6-200329 (JP, A) JP-A-62-294703 (JP, A) JP-A-2-10002 (JP, A) JP-A-10-185180 (JP, A) JP-A-10-17926 (JP, A) JP-A-10-185178 (JP, A) JP-A-7-280258 (JP , A) Special Flat 7-218142 (JP, A) JP flat 7-97619 (JP, A) JP flat 6-200321 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) C21D 1 / 52 C21D 11/00 101

Claims (6)

(57) [Claims] 1. In a furnace in which a plurality of pairs of regenerative burners are arranged in one zone, the replacement time of the air-exhaust gas from the exhaust gas of the air-exhaust gas system to the air is T _pa , and the fuel purge time by the residual fuel pressure before the combustion switching is T. _pg , the number of burner pairs in the zone is N, 1
Assuming that the fuel ejection time of one regenerative burner is _Tc , the fuel ejection time from one regenerative burner is determined in the relationship of _Tc = (N-1) * ( _Tpa + _Tpg ), and the fuel ejection is performed. A combustion control method for a regenerative burner furnace, wherein the regenerative burner is controlled based on time. 2. In a furnace in which a plurality of pairs of regenerative burners are arranged in one zone, the replacement time of the air-exhaust gas from the exhaust gas of the air-exhaust gas system to the air is T _pa , and the fuel purge time by the residual fuel pressure before the combustion switching is T. _pg, the Banapea number in a zone N, regenerative If the combustion mode switching time was CT burner, determine the _{CT = N × (T pa +} T pg) combustion switching time of one regenerative burner in relation,
A combustion control method for a regenerative burner furnace, wherein the regenerative burner is controlled based on the fuel switching time. 3. In a furnace having a plurality of zones each including a regenerative burner and including a regenerative burner, a replacement time of at least two or more zones of the regenerative burners from the exhaust gas of the air-exhaust gas to the air is reduced. T _pa , the fuel purge time due to the residual fuel pressure before combustion switching is T _pg , T _pa and T _pg in the corresponding zone are the same value, the total number of burner pairs in the zone is N, and the fuel injection time of one regenerative burner is N When _Tc is set, the fuel injection time from one regenerative burner is determined in the relationship of _Tc = (N-1) * ( _Tpa + _Tpg ), and the regenerative burner is controlled based on the fuel injection time. Combustion control method for a regenerative burner furnace. 4. In a furnace having a plurality of zones each including a regenerative burner and comprising a regenerative burner, the time required for replacing the regenerative burners of at least two or more zones with the air from the exhaust gas of the air-exhaust gas system to the air is reduced. T _pa , the fuel purge time due to the residual fuel pressure before switching to combustion is T _pg , T _pa and T _pg in the zone are the same, N is the total number of burner pairs in the zone, and CT is the combustion switching time of the regenerative burner. In this case, the combustion switching time of one regenerative burner is determined in the relationship of CT = N × (T _pa + T _pg ),
A combustion control method for a regenerative burner furnace, comprising controlling combustion of a regenerative burner based on the combustion switching time. 5. The combustion control method for a regenerative burner furnace according to claim 1, wherein switching of the regenerative burner does not occur in two or more burner pairs at the same timing. 6. The combustion control method for a regenerative burner furnace according to claim 1, wherein at least one radiant tube burner is used for the regenerative burner.