JP4009989B2 - Heating furnace operating method with narrow pitch heat storage burner group - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of operating a heating furnace provided with a regenerative burner group arranged at a narrow pitch, and in particular, a medium to high temperature at which the temperature at the center of the furnace increases due to interference between staggered flames at the center of the furnace. The present invention relates to a method of operating a heating furnace provided with a narrow-pitch regenerative burner group capable of suppressing the occurrence of distribution.
[0002]
[Prior art]
In recent years, as a method of heating an object to be heated such as a metal piece, a regenerative alternating combustion burner system excellent in energy saving has been adopted. A regenerative alternating combustion burner system burns a pair of burners alternately, recovers the heat of the flue gas through a non-combustion burner at a high temperature, and uses it as a preheating source for combustion air. Thermal efficiency is very high compared to the burner system.
[0003]
FIG. 4 is a block diagram showing such a regenerative type alternating combustion burner system. In the heating furnace X, at least a pair of combustion burners 111 and 112 are installed facing each other in the furnace width direction. The combustion burners 111 and 112 are provided with fuel cutoff valves 1 and 11, exhaust gas cutoff valves 2 and 22, air cutoff valves 3 and 33, and heat storage bodies 4 and 44, respectively. The combustion air piping system, the exhaust gas piping system, and the fuel piping system are provided with flow control valves 5, 6, and 7, respectively.
[0004]
In such a case, when one combustion burner 111 is in a combustion state, the fuel cutoff valve 1 is open, the exhaust gas cutoff valve 2 is closed, the air cutoff valve 3 is open, and the combustion air is a ceramic that can withstand high temperatures. It is preheated via the heat storage body 4 made of metal, supplied into the furnace, mixed with fuel and burned. Most of the generated exhaust gas is sucked into the other non-combustion burner 112 in the heat storage state, and the heat of the exhaust gas is recovered by the heat storage body 44 through the non-combustion burner 112 at a high temperature and exhausted outside the system.
[0005]
In a heating furnace equipped with a conventional regenerative alternating combustion burner system, for example, a continuous heating furnace having a plurality of zones, a plurality of regenerative burners are usually arranged in each zone in the furnace length direction. The regenerative burner group is installed on the left and right furnace walls of the heating furnace so as to face each other. And each regenerative burner individually sucks the gas in the furnace and stores the sensible heat in the regenerator (heat storage state) at a certain time, and gives the stored sensible heat to the combustion air at another time. The preheated air is obtained and burned (combustion state), so-called regenerative combustion is repeated. For this reason, high-temperature preheated air can be obtained by efficiently recovering the sensible heat of the high-temperature combustion exhaust gas. Therefore, since a large energy saving effect can be obtained when used in a heating furnace, the application has been rapidly expanded in recent years.
[0006]
On the other hand, the regenerative burner has a problem in that the amount of NOx generated increases because high-temperature preheated air is obtained and burned as described above, and a combustion method called a high-temperature air combustion that increases the flame volume is adopted. For this reason, in a heating furnace equipped with a regenerative alternating combustion burner system, switching combustion control is generally performed so that they do not face each other. Specifically, for example, as shown in FIG. 5, a furnace operation method is used in which the regenerative burner groups installed on the left and right furnace walls facing each other are staggered. That is, the burners 112, 121, 132, 141 burn at a certain time, and the burners 111, 122, 131, 142 store heat (state (A) in FIG. 5). After a certain period of time, the burners 112, 121, 132, 141 are now stored, and the burners 111, 122, 131, 142 are combusted (state (B) in FIG. 5). This is repeated to realize heat storage combustion.
[0007]
[Problems to be solved by the invention]
By the way, when installing a regenerative burner by partially remodeling an existing heating furnace (for example, remodeling a specific zone of a continuous heating furnace), the distance between adjacent burners in the furnace length direction (this) (Hereinafter referred to as burner pitch) may have to be narrowed. In that case, the flame of the burner which staggers as shown in FIG. 5 interferes at the center of the furnace. The furnace width direction temperature distribution is a so-called medium-high temperature distribution in which the temperature in the center of the furnace width direction is high. When constructing a new facility, by designing the burner pitch so that it can take an appropriate distance or more, it is possible to prevent the occurrence of staggered burner flame interference and to flatten the furnace width direction temperature distribution.
[0008]
In other words, if the burner pitch must be narrowed by remodeling the existing heating furnace, and if the burner pitch is the same fuel flow rate as that which can be taken more than the appropriate distance, the furnace width direction average temperature from the furnace width direction at this time The temperature in the center increases and the temperature on the left and right furnace walls decreases. For this reason, insufficient heating of the article to be heated occurs.
[0009]
This temperature decrease problem on the left and right furnace walls can be solved by increasing the fuel flow rate rather than a burner pitch that can be taken over an appropriate distance. In this case, however, not only is energy wasted, but the furnace The temperature of the central portion in the width direction becomes too high, and a new problem arises that the quality of the heated object cannot be avoided due to excessive heating.
[0010]
Note that the problem of flame interference due to a narrow pitch can be completely eliminated by adopting a furnace operation method in which all the regenerative burners on the same furnace wall in the zone are grouped into one group and switched left and right. However, in this case, it is necessary to switch a large number of regenerative burners at the same time, and the flow rate fluctuation at the time of switching between the supply and exhaust pipes increases, deviates from the control range of the flow control valve, and appropriate flow control (combustion) Control) becomes impossible.
[0011]
The technical problem of the present invention is to be able to suppress the occurrence of medium-high temperature distribution even when the burner pitch is small and to flatten the furnace width direction temperature distribution.
[0013]
[Means for Solving the Problems]
The method of operating a heating furnace provided with the narrow pitch heat storage type burner group of the present invention comprises a pair of burners opposed in the furnace width direction that are alternately burned, and the heat of the combustion exhaust gas remains at a high temperature through the non-combustion burner. At least four or more sets of regenerative alternating combustion burner systems that are recovered in step 1 and used as a preheating source for combustion air are arranged in the furnace length direction within a certain zone, and each burner group adjacent in the furnace length direction in the zone. mutual furnace length direction pitch P, to chamber width WF, Upon P <0.18 * set to a WF was formed by heating furnace furnace operation of each burner in the zone adjacent the same furnace on the walls The burner group is divided into a plurality of burner groups each including at least two burners. In the same burner group, all the burners are simultaneously burned or stored. When the burner group is in the combustion state, the other burner group opposite to the burner group is in the heat storage state, and the burner group adjacent to the one burner group in the furnace length direction is in the heat storage state, and the other burner group and Rochow as burner group adjacent to the direction is the combustion state, is characterized by burning or heat accumulation each bar burner groups alternately.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for operating a heating furnace including a narrow-pitch regenerative burner group according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. 1 is an explanatory view showing the furnace operation method of a heating furnace according to the present embodiment, FIG. 2 is a graph comparing the furnace width direction temperature distribution caused by the furnace operation method of the conventional example, the vertical axis gas temperature ( ° C), and the horizontal axis represents the furnace width direction distance (m). FIG. 3 is a diagram schematically showing the state of a flame formed by a regenerative burner. In addition, in each figure, the same code | symbol is attached | subjected to the part corresponded to a prior art example.
[0015]
According to the observation by the present inventors, the flame formed by the regenerative burner is diffusely burned with a spread angle of approximately 20 °. Therefore, the condition that the flame of the staggered burner does not interfere at the center of the furnace width is that when the furnace width is WF (unit: m) and the burner pitch is P (unit: m),
P> 2 * tan (10 °) * (WF / 2) (1)
Since tan (10 °) ≈0.176, equation (1) can be rewritten as follows.
P> 0.18 * WF …………………………………………………………………………………………………… (2)
[0016]
That is, if the burner pitch P can be set so as to satisfy the expression (2), the interference of the burner flame that staggers can be prevented. However, in the actual design of the heating furnace, there are cases where the expression (2) cannot be satisfied. For example, when the heating furnace is partially modified and four sets of regenerative burners 111, 112, 121, 122, 131, 132, 141, 142 are installed in the furnace length direction in the zone as shown in FIG. There are cases where the burner pitch has to be narrowed due to the arrangement constraints. In such a case, the burner pitch P of each regenerative burner installed in the part (zone) to be modified is set so that P <0.18 * WF with respect to the furnace width WF.
[0017]
When operating the heating furnace having such a narrow pitch heat storage type burner group, as shown in FIG. 1, the burners 111 and 121 on the left furnace wall in the zone are group A1, and the burners 131 and 141 are group A2. The burners 112 and 122 on the right furnace wall are group B1, and the burners 132 and 142 are group B2, and combustion control is performed in units of groups. That is, in FIG. 1, the groups A1 and B2 burn at a certain time, and the groups A2 and B1 store heat (state (A) in FIG. 1). After a certain period of time, the groups A1 and B2 store heat and the groups A2 and B1 burn (state (B) in FIG. 1). This is repeated to realize heat storage combustion. Thereby, the flame interference location in a furnace width center part can be reduced, and temperature distribution generation | occurrence | production of the middle-high temperature direction can be reduced.
[0018]
Fig. 2 shows the gas temperature distribution in the furnace width direction when group combustion is performed by the operation method of the present invention in a heating furnace having a furnace width of 10 m, and the gas temperature distribution in the furnace width direction when staggered combustion is performed by the conventional operation method. It shows in comparison with 2. In FIG. 2, a line plotted by a square (□) indicates the gas temperature distribution in the furnace width direction when the burner pitch is 1.4 m and group combustion is performed by the furnace operating method of the present invention (FIG. 1). A line plotted by Δ indicates the gas temperature distribution in the furnace width direction when the burner pitch is 1.4 m at the same fuel flow rate as in the present invention (FIG. 5), plotted by black circles (●). The lines shown indicate that the fuel flow rate is increased from that of the two examples (□ and Δ lines), and the temperature on the left and right furnace walls is the same as that of the present invention (□ lines). The line indicating the furnace temperature direction gas temperature distribution plotted with white circles (◯) when staggered with a pitch of 1.4 m (FIG. 5) indicates the fuel flow rate per unit furnace length (□ The burner pitch is set to 1.8m and staggered combustion (Fig. 5) The chamber width direction gas temperature distribution in the case, respectively.
[0019]
As is clear from FIG. 2, according to the furnace operating method of the present invention (square line), the medium-high temperature in the center portion in the furnace width direction is 20 ° C. despite the narrow burner pitch of 1.4 m. The object to be heated can be heated almost uniformly.
[0020]
In the example of the line △, the temperature at the center in the furnace width direction is 60 ° C. higher than the average temperature in the furnace width direction, the temperature on the left and right furnace walls is lower than the average temperature in the furnace width direction, and the heating of the object to be heated is insufficient Occurs. The average temperature in the furnace width direction in this example was substantially the same as that in the furnace operating method of the present invention (example of the square line).
[0021]
In the example of line ●, not only is energy wasted, but the temperature in the center of the furnace width direction is 80 ° C. higher than the average temperature in the furnace width direction by the furnace operating method of the present invention, Quality deterioration is inevitable.
[0022]
In the example of the circle, the burner pitch is set to an appropriate distance of 1.8 m or more, so a substantially flat temperature distribution is formed in the furnace width direction, which is not inferior to that by the furnace operating method of the present invention. It was.
[0023]
【The invention's effect】
As described above, according to the present invention, a pair of burners opposed in the furnace width direction are alternately burned, and the heat of the combustion exhaust gas is recovered by the heat accumulator while being kept at a high temperature through the non-combustion burner. At least four or more sets of regenerative alternating combustion burner systems used for the source are arranged in the furnace length direction in a certain zone, and the furnace length direction pitch P between each burner set adjacent in the furnace length direction in the zone is set. , to oven width WF, Upon P <0.18 * set to a WF was formed by heating furnace furnace operation of each burner in the zone of the burner adjacent the same furnace on the walls of at least two or more of an It is divided into a plurality of burner groups, and all burners in the same burner group are burned or stored at the same time, and when burning these burner groups, one opposing burner group is in a combustion state Sometimes, the burner group adjacent to the one burner group in the furnace length direction is in a heat storage state so that the other burner group opposed to these is in the heat storage state, and is adjacent to the other burner group in the furnace length direction. as burner group is combustion state, since the respective bar burner groups were as burning or thermal storage alternately, even though the burner pitch is narrow pitch, reducing the flame interference location in Rohaba central portion As a result, generation of a large temperature distribution in the furnace width direction as in the prior art is eliminated, and the temperature distribution in the furnace width direction becomes flat. As a result, the object to be heated can be heated almost uniformly, and waste of heating energy due to excessive heating of the object to be heated can be prevented, and variations in the quality of the object to be heated can be eliminated. became. In addition, all regenerative burners on the same furnace wall in the zone are combined into one group, and there is no large flow rate fluctuation when switching between supply and exhaust pipes as in the furnace operation method that switches between left and right. (Combustion control) became possible.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a method for operating a heating furnace provided with a narrow-pitch regenerative burner group according to the present invention.
FIG. 2 is a graph showing a furnace width direction temperature distribution obtained by the furnace operating method of the present invention in comparison with a conventional example.
FIG. 3 is a schematic view of a flame formed by a regenerative burner.
FIG. 4 is a configuration diagram of a regenerative alternating combustion burner system.
FIG. 5 is an explanatory diagram of a conventional furnace operating method.
[Explanation of symbols]
WF Furnace width P Burner pitch X Heating furnace (zone)
111-142 Regenerative Burner 4,44 Thermal Storage A1, A2, B1, B2 Group (Burner Group)

Claims (1)

A regenerative alternating combustion burner system in which a pair of burners facing each other in the furnace width direction are alternately burned and the heat of the combustion exhaust gas is recovered as a high-temperature heat storage body through a non-combustion burner and used as a preheating source of combustion air, At least four or more sets in a zone are arranged in the furnace length direction, and the furnace length direction pitch P between each burner set adjacent in the furnace length direction in the zone is P <0.18 * WF with respect to the furnace width WF. Upon furnace operation of the furnace formed by setting so that,
Each burner in the zone is divided into a plurality of burner groups each including at least two burners adjacent to each other on the same furnace wall, and all the burners in the same burner group are burned or stored simultaneously. In the combustion of these burner groups, when one of the opposed burner groups is in a combustion state, the other burner group opposed to these burner groups is in a heat storage state, and in addition to the one burner group in the furnace length direction. pitch group adjacent burner becomes heat storage state, the other burner group and Rochow burner group adjacent to the direction such that the combustion state, which is characterized in that burning or thermal storage of each bar burner group alternately A method of operating a heating furnace provided with a regenerative burner group.

Images