JP4158313B2 - Combustion method with regenerative burner - Google Patents

Description

【００２２】
〔条件２〕
一次燃料ガス供給量Ｇ１と二次燃料ガス供給量Ｇ２の比率Ｇ１／Ｇ２を４０／６０（一定）とし、一次燃料ガスに予混合する予混合用空気Ａの量を変えたときの、炉内雰囲気中のすす濃度を測定した結果を、表２に実施例５〜８および比較例３として示す。なお、すす濃度の測定法および評価は前記実施例と同じである。
【００２３】
【表２】

【００２４】
表１および表２の結果から、一次燃料ガス供給量Ｇ１と二次燃料ガス供給量Ｇ２の比率、および一次燃料ガスに予混合する予混合用空気の量がこの発明の限定範囲内にある各実施例においては、比較例に対して、すすが少なく着火性も安定した燃焼がおこなわれていることが判る。
【００２５】
【発明の効果】
以上説明したようにこの発明によれば、燃焼側の蓄熱バーナにおいて空気比１．０未満で燃料ガスの燃焼をおこなった場合でも、一次燃料ノズルに供給される一次燃料ガスに、燃焼用空気の一部を予混合することにより、一次燃料ガスと燃焼用空気の混合・接触が良好となり、すすの発生がほとんどない高速燃焼がおこなわれ、この燃焼による高温燃焼ガスにより二次燃料ガスもすすの発生の少ない状態で燃焼するので、燃焼に伴うすすの発生を抑制でき、排気側の蓄熱体や炉内へのすすの付着堆積を防止でき蓄熱体の熱交換効率の低下を防止できるとともに、排ガス中のすすを除去するための再燃焼装置を設ける必要もなくなる。
【図面の簡単な説明】
【図１】この発明の実施の形態の一例を示す蓄熱式バーナをそなえた加熱炉の配管系統図である。
【符号の説明】
１ａ，１ｂ…蓄熱式バーナ、２…ケーシング、４…燃焼ガス吐出口、５…給排気管接続部、６…蓄熱体、７…空気供給路、８…一次燃料ノズル、９…二次燃料ノズル、１１…燃料ガス供給管、１２…分岐管、１３…分岐管、１６…給気管、１６ａ…枝管、１７〜１９…開閉弁。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion method using a regenerative burner.
[0002]
[Prior art]
At least a pair of regenerative burners that are a combination of a burner and a regenerator, and a pair of regenerative burners are switched between the combustion side and the exhaust side at a predetermined switching cycle time, and the combustion gas of the regenerative burner on the combustion side is exhausted The furnace that is discharged through the heat storage body of the regenerative burner of this type has excellent thermal efficiency because the recovered heat of the combustion gas by the heat storage body can be effectively used for preheating the combustion air after switching, heating furnace and other various industrial furnaces Has come to be used as a lot.
[0003]
In the above regenerative burner, the combustion air is preheated to a high temperature, so the flame temperature rises and the nitrogen oxide (NOx) concentration increases. The primary fuel gas is injected from the primary fuel nozzle into the combustion air heated by passing through the heat accumulator, and the primary fuel gas is burned into the primary combustion nozzle, and the secondary fuel gas is directly injected into the furnace from the secondary fuel nozzle that opens toward the inside of the furnace. There are two-stage combustion types in which secondary combustion is performed by injection.
[0004]
However, if the above two-stage combustion type regenerative burner is used for combustion with less than 1.0 air to maintain the inside of the furnace in a non-oxidizing atmosphere, soot is likely to be generated. The heat storage efficiency of this type of regenerative burner is reduced and heat exchange efficiency is reduced, or it adheres to each part of the furnace and the material to be treated, or part of it is released into the atmosphere as soot and smoke. In order to prevent this, various problems such as the necessity of providing a reburning device separately arise.
[0005]
[Problems to be solved by the invention]
The present invention is intended to solve the above-mentioned conventional problems. Combustion by a regenerative burner capable of suppressing the generation of soot even when fuel gas is burned at an air ratio of less than 1.0 in a regenerative burner on the combustion side. Is to provide a method.
[0006]
[Means for Solving the Problems]
In the combustion method using the regenerative burner according to the present invention, a heat storage body is accommodated in a casing having a combustion gas discharge port at one end and a supply / exhaust pipe connection at the other end, and the heat storage body and the combustion gas discharge. At least a pair of regenerative burners provided with a primary fuel nozzle that opens into an air supply passage formed between the outlet and a secondary fuel nozzle that opens to the inside of the furnace in the vicinity of the combustion gas discharge port is provided in the furnace body. The regenerative burner which alternately switches the pair of regenerative burners between the combustion side and the exhaust side, and the combustion regenerative burner burns at an air ratio of less than 1.0 and maintains the inside of the furnace in a non-oxidizing atmosphere. The ratio of the primary fuel gas supply amount G1 to the primary fuel nozzle and the secondary fuel gas supply amount G2 to the secondary fuel nozzle is within the range of G1 / G2 = 30/70 to 50/50. And keep it on In addition, 5 to 20% of the combustion air is premixed with the primary fuel gas supplied to the primary fuel nozzle and blown into the air supply path as a premixed gas, and the remaining portion of the combustion air is transferred to the heat storage body. It supplies to the said air supply path via.
[0007]
In the present invention, the amount of premixed air premixed with the primary fuel gas and the ratio between the primary fuel gas supply amount G1 and the secondary fuel gas supply amount G2 are determined based on the knowledge obtained by the inventors as a result of earnest research. Although limited, the reason for the limitation will be described below.
[0008]
That is, it was confirmed that by mixing a part of the combustion air into the primary fuel gas as premixing air, the mixing of the primary fuel gas and the combustion air is promoted and the generation of soot is suppressed. Therefore, the amount of the premixing air is limited to 5 to 20% of the combustion air (total amount). If the amount of the premixing air is less than 5%, the soot preventing effect is insufficient. Moreover, since the quantity of the combustion air which passes a thermal storage body reduces, so that this numerical value is large, it leads to the fall of thermal efficiency, Therefore It is unpreferable from the point of the said thermal efficiency to set it as a numerical value exceeding 20%. The amount of this premixing air is more preferably 10 to 15% of the combustion air, and by setting it to 10% or more, the suppression of soot generation is further assured and should be 15% or less. This is because a decrease in thermal efficiency can be suppressed.
[0009]
In addition, it was confirmed that the effect of suppressing soot generation differs depending on the ratio G1 / G2 of the primary fuel gas supply amount G1 and the secondary fuel gas supply amount G2, that is, the mixed combustion ratio of the primary fuel gas and the secondary fuel gas. The range of G1 / G2 was limited to 30 / 70-50 / 50. When the ratio G1 / G2 exceeds 50/50, soot is likely to be generated. When the ratio G1 / G2 is less than 30/70, the primary combustion gas discharged from the combustion gas discharge port into the furnace has low seeding effect, and the secondary This is because it becomes difficult to ignite the fuel gas. The ratio (mixed firing ratio) G1 / G2 is more preferably 35/65 to 45/55, and by setting it to 45/55 or less, the suppression of soot generation is further ensured, and 35/65 or more. This is because the secondary fuel gas can be burned more reliably without being influenced by the type of fuel gas.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention will be described below with reference to the example shown in FIG. In FIG. 1, 1a and 1b are a pair of regenerative burners having the same structure, and the casing 2 has a combustion gas discharge port 4 at one end, which is an attachment side to the furnace body 3, and the other end. An air supply / exhaust pipe connection portion 5 is provided, and a heat storage body 6 made of breathable ceramics is accommodated in the vicinity of the air supply / exhaust pipe connection portion 5, and 7 is a connection between the heat storage body 6 and the combustion gas discharge port 4. It is the air supply path formed in the middle. Reference numeral 8 denotes a primary fuel nozzle that opens to the air supply path 7, and 9 denotes a secondary fuel nozzle that opens to the inside of the furnace in the vicinity of the combustion gas discharge port 4.
[0011]
A fuel gas supply pipe 11 is connected to a fuel gas supply source (not shown). The branch pipe 12 is connected to the primary fuel nozzle 8, and the branch pipe 13 is connected to the secondary fuel nozzle 9. The branch pipe 16a of the supply pipe 16 connected to the air supply blower 15 is connected to a portion near the primary fuel nozzle 8 of the branch pipe 12, and the primary fuel gas from the branch pipe 12 is preliminarily supplied from the branch pipe 16a. The mixing air A is mixed and supplied to the primary fuel nozzle 8 as a premixed gas. You may provide mixers, such as a venturi mixer, in the connection part of this branch pipe 12 and branch pipe 16a. Reference numerals 17 to 19 denote on-off valves. Although a pilot burner for ignition is provided in the vicinity of the premixed gas outlet 8a of the primary fuel nozzle 8, its illustration is omitted.
[0012]
Further, in this example, a three-way valve type directional switching valve 21 is built in the supply / exhaust pipe connecting portion 5, and an air supply port 22 and an exhaust port 23 provided on a casing end wall bent at a right angle are illustrated. It is opened and closed by a plate-like valve element fixed to a valve shaft that is rotated by a solenoid that is not operated, and one of the air supply port 22 and the exhaust port 23 is opened and the other is closed. The air supply port 22 is connected to the air supply pipe 16, the exhaust port 23 is connected to the exhaust pipe 24, and the exhaust pipe 24 is connected to the exhaust fan 25.
[0013]
In a furnace equipped with the above-described burner combustion system, in order to heat a material to be processed (not shown) in a non-oxidizing atmosphere in the heating chamber 30 in the furnace body 3, the regenerative burners 1a and 1b are on the combustion side as in the prior art. The combustion gas is burned by alternately switching to the exhaust side. FIG. 1 shows the state where the regenerative burner 1a is switched to the combustion side, and the flow direction of air and gas in this switched state is shown by arrows. It is.
[0014]
As shown in the figure, in the regenerative burner 1a, the directional switching valve 21 is opened, the open / close valves 17 to 19 are opened, and the total amount of fuel gas supplied from the fuel gas supply pipe 11 is set. Then, combustion air (a part of which is used for premixing as will be described later) having an air amount smaller than the theoretical air amount (for example, theoretical air amount × 0.9) is supplied from the air supply pipe 16. Combustion is performed at less than 1.0, and the inside of the heating chamber 30 is maintained in a non-oxidizing atmosphere. At this time, the combustion air fed from the air supply port 22 is preheated when passing through the heat accumulator 6 that is stored during use as an exhaust side in the previous step. On the other hand, in the regenerative burner 1b on the exhaust side, the direction switching valve 21 is opened, the open / close valves 17 to 19 are closed, and the combustion gas flowing through the heating chamber 30 is exhausted through the exhaust pipe 24. When the heat storage body 6 is heated by the passage of the combustion gas, the temperature rises.
[0015]
The fuel gas supplied from the fuel gas supply pipe 11 is divided into a primary fuel gas passing through the branch pipe 12 and a secondary fuel gas passing through the branch pipe 13, and the ratio of the supply amount (mixed combustion ratio) G1 / G2 Is maintained within the range of 30/70 to 50/50. Further, 5 to 20% of the total amount of combustion air supplied from the supply pipe 16 is branched as premixing air A by the branch pipe 16a and premixed with the primary fuel gas, and the premixed gas is supplied from the primary fuel nozzle 8. As a result, the primary fuel gas is diffused and mixed well in the remaining combustion air that has been heated through the heat storage body 6 and is completely burned in excess air, soothe high temperature. The secondary fuel gas ejected from the combustion gas discharge port 4 into the heating chamber 30 as a combustion gas (primary flame) and injected into the heating chamber 30 from the secondary fuel nozzle 9 remains in the high-temperature combustion gas. Secondary combustion occurs by contact with air, and soot generation is suppressed to a small amount.
[0016]
The flow rates of the primary fuel gas and the secondary fuel gas and the flow rate of the premixing air A are set by adjusting or selecting the opening degree of the on-off valves 17 to 19 as well as the branch pipes 12, 13 and This can be done by setting a throttle valve or a flow control valve (not shown) provided in the branch pipe 16a to a predetermined opening.
[0017]
When the above combustion and exhaust are performed for a predetermined time (for example, 30 seconds), the regenerative burner 1b is switched to the combustion side and the regenerative burner 1a is switched to the exhaust side. This switching is performed by opening and closing the direction switching valve 21 and the on-off valves 17 to 19 of each heat storage burner in the opposite manner to the case of FIG. In the same manner as described above, in the regenerative burner 1b, the fuel gas is combusted at an air ratio of less than 1.0, and in the regenerative burner 1a, the combustion gas is exhausted to raise the temperature of the heat accumulator 6, and thereafter the combustion is performed in the same manner. Switch between the exhaust side and the exhaust side.
[0018]
The present invention is not limited to the above example. For example, the number of primary fuel nozzles 8 and secondary fuel nozzles 9, the angle of inclination with respect to the central axis (air flow direction for fuel) of the air flow passage 7, etc. The specific structure of the casing 2 and the means for switching the supply / exhaust to the air supply port 22 and the exhaust port 23 may be other than those described above. In FIG. 1, a pair of regenerative burners 1a and 1b are provided on opposite side walls of the furnace body 3, but may be provided by shifting the position vertically on one side wall. The present invention can also be applied to the case where the above heat storage burner is provided in the furnace body.
[0019]
【Example】
Examples of the present invention and comparative examples will be described below. In the apparatus of FIG. 1, butane gas as fuel gas was burned at an air ratio of 0.9. Under the following two conditions, combustion / exhaust switching of the regenerative burners 1a and 1b is performed once every 30 seconds, soot concentration in the furnace atmosphere, secondary fuel gas ignitability, etc. Was measured.
[0020]
[Condition 1]
The amount of premixed air A premixed with the primary fuel gas is 13.5% (constant) of the total amount of combustion air, and the ratio G1 / G2 between the primary fuel gas supply amount G1 and the secondary fuel gas supply amount G2 Table 1 shows the results of measuring the soot concentration and the ignitability when V is changed as Examples 1 to 4 and Comparative Examples 1 and 2. The measurement method of the soot concentration and the evaluation of the soot concentration and the ignitability in the table are as follows.
□ Soot concentration: The smoke spot test method using a smoke tester manufactured by Bacharach Instrument Co. in the United States divided the blackness of the dust spot on the filter paper that sucked the soot in the exhaust gas from the furnace into 10 stages. The corresponding concentration number was recorded for each measurement in comparison with the smoke scale, and displayed with the following marks according to the variation range of the concentration number in 50 measurements.
A: Concentration numbers 0 to 1
○: Concentration number 1-2
X: Concentration number 3 or more □ Ignition property: The results of measuring the number of times of good ignition for 360 switching injections of the secondary fuel gas in the regenerative burners 1a, 1b are indicated by the following marks.
◎: Good ignition frequency = 360 times ○: Good ignition frequency = 354 times ×: Good ignition frequency = 313 times
[Table 1]

[0022]
[Condition 2]
When the ratio G1 / G2 between the primary fuel gas supply amount G1 and the secondary fuel gas supply amount G2 is 40/60 (constant) and the amount of premixing air A premixed with the primary fuel gas is changed, The results of measuring the soot concentration in the atmosphere are shown in Table 2 as Examples 5 to 8 and Comparative Example 3. In addition, the measurement method and evaluation of soot concentration are the same as the said Example.
[0023]
[Table 2]

[0024]
From the results of Table 1 and Table 2, the ratio of the primary fuel gas supply amount G1 and the secondary fuel gas supply amount G2 and the amount of premixing air premixed with the primary fuel gas are within the limited range of the present invention. In the examples, it can be seen that combustion with less soot and stable ignitability is performed as compared with the comparative example.
[0025]
【The invention's effect】
As described above, according to the present invention, even when the combustion gas is burned at the combustion-side heat storage burner at an air ratio of less than 1.0, the primary fuel gas supplied to the primary fuel nozzle is not subjected to combustion air. By premixing a part, the primary fuel gas and the combustion air are mixed and contacted well, and high-speed combustion with little soot is performed, and the secondary fuel gas is also sooted by the high-temperature combustion gas from this combustion. Because it burns in a state where there is little generation, soot generation due to combustion can be suppressed, soot accumulation on the exhaust side and furnace can be prevented, heat exchange efficiency of the heat storage body can be prevented from decreasing, and exhaust gas There is no need to provide a reburning device for removing the soot inside.
[Brief description of the drawings]
FIG. 1 is a piping system diagram of a heating furnace provided with a regenerative burner showing an example of an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a, 1b ... Thermal storage burner, 2 ... Casing, 4 ... Combustion gas discharge port, 5 ... Supply / exhaust pipe connection part, 6 ... Thermal storage body, 7 ... Air supply path, 8 ... Primary fuel nozzle, 9 ... Secondary fuel nozzle , 11 ... Fuel gas supply pipe, 12 ... Branch pipe, 13 ... Branch pipe, 16 ... Air supply pipe, 16a ... Branch pipe, 17-19 ... Open / close valve.

Claims (1)

A heat storage body is accommodated in a casing having a combustion gas discharge port at one end and a supply / exhaust pipe connection portion at the other end, and an air supply path formed between the heat storage body and the combustion gas discharge port. At least one pair of regenerative burners having a primary fuel nozzle that opens and a secondary fuel nozzle that opens to the inside of the furnace in the vicinity of the combustion gas discharge port is provided in the furnace body, and both regenerative burners that make a pair are on the combustion side. In the combustion method using a regenerative burner in which the combustion side regenerative burner performs combustion at an air ratio of less than 1.0 and maintains the inside of the furnace in a non-oxidizing atmosphere, The ratio of the primary fuel gas supply amount G1 to the secondary fuel gas supply amount G2 to the secondary fuel nozzle is maintained within the range of G1 / G2 = 30/70 to 50/50, and 20% of the primary Premixed with the primary fuel gas supplied to the fuel nozzle and blown into the air supply path as a premixed gas, and supplies the remainder of the combustion air to the air supply path via the heat storage body. A combustion method using a regenerative burner.

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