JPS638384B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating furnace, and in particular to a heating furnace for chemical equipment, which has a novel structure in which the relative arrangement of heat transfer tubes and burners has been improved and improved. .

Heating furnaces used in various chemical equipment, etc. not only have a compact shape and size, but also improve thermal efficiency and
Not only _is there a constant need for improvements and enhancements in terms of lifespan, but in recent years, consideration has been given to preventing environmental pollution and the requirements for pollution control have become increasingly _strict . ) The reality is that regulations on the amount of waste generated are becoming extremely strict.
It is generally widely known that the amount of NO _x generated increases as the temperature in the combustion section increases, and from this point of view, improvements and improvements to the combustion section including burners, heat transfer tubes, etc. in heating furnaces have been made. This was something that was strongly desired.

Figure 1 shows an example of the structure of a heat exchanger tube coil that has been widely used in the past. The fluid to be heated flows in from an inlet header 1 and flows out from an outlet header 2. The inlet header 1, the outlet header 2, and the heat exchanger tubes 3 constitute a set of heat exchanger tube coils 4 in a configuration in which fluid is heated. Figure 2 shows a plan view of a furnace in which a large number of heat transfer tube coils 4 including the inlet header 1, outlet header 2, and heat transfer tubes 3 as described above are arranged together with burners 5, and the burners 5 are placed in the center of the furnace. A plurality of heat exchanger tube coils 4 are arranged, and the heat exchanger tube coils 4 are arranged on a side wall portion 6 made of a firewall refractory material. In such a configuration, only one side of the heat exchanger tube coil 4 facing the burner 5 is heated strongly.

On the other hand, FIG. 4 is a plan view showing another configuration of the furnace part of a heat transfer furnace according to the prior art, in which a heat transfer tube coil 4 including a heat transfer tube 3 is arranged in the center of the furnace, while a burner 5 is The heat exchanger tube coil 4 is placed in close proximity to a side wall 6 made of fireproof material, and a pair of burners 5, 5 sandwich the heat exchanger tube coil 4 therebetween. It will be heated from

In each of the above configurations, in the case of single-sided heating of heat transfer tubes, burners can be installed in the center of the furnace, and heat transfer tubes can be placed on both sides of the burner, so the number of burners can be twice as many as in the case of double-sided heating. This allows heat transfer tubes to be placed. Therefore, the entire device can be made compact, and it is often used in small heating furnaces, boilers, etc. where the temperature of the fluid to be heated is relatively low. On the other hand, in the case of such a single-sided heating structure, as shown in FIG. The situation is represented by curves 8 and 9. As shown in FIG. 4, the heat exchanger tube 3 has a portion that directly receives the radiant heat from the burner 5 side, and a portion that is in the shadow from the radiant heat on the side wall portion 6 side made of a refractory material. This results in a large difference in tube wall temperature. Therefore, as the peak temperature during use increases, the temperature difference between the two parts becomes larger, and the amount of thermal expansion in the two parts also differs greatly, causing thermal stress, which causes When used for a long time, creep deformation occurred, and there were even cases where the heat exchanger tube 3 was bent into an arched shape.

On the other hand, the above tube wall temperature distribution in the case of double-sided heating as shown in FIG. 3 is as shown in FIG. 5. The curve 9 showing this shows a symmetrical temperature distribution extending with respect to the direction 7 of radiated heat, and the difference in thermal expansion is small compared to the case of single-sided heating. It is currently being used as a large heating furnace, etc.

On the other hand, regarding the generation of _NOx , it is generally known that the higher the temperature of the combustion part, the greater the amount of NOx generated. The temperature level in the combustion part is greatly influenced by the surrounding conditions of the flame, such as the heat absorption surface of the heat exchanger tube 3, the reflective surface such as the side wall part 6 of the furnace, and even the flame of the adjacent burner. It is known that it is greatly affected by the interference effect of From this point of view, the single-sided heating described above,
When double-sided heating is considered, single-sided heating as shown in FIG. 2 is characterized by the presence of heat exchanger tubes 3 on both sides of the flame that include heat-absorbing surfaces whose temperature is lower than that of the flame. On the other hand, in the case of double-sided heating shown in Figure 3, there is an endothermic surface only on one side of the flame.
The part on the opposite side is the furnace wall, that is, the side wall part, and the high temperature radiant heat is reflected, creating a high temperature environment around the flame, which is a more disadvantageous situation in terms of NO _x generation than in the case of single-sided heating. Also, from the perspective of the burners 5 arranged in the longitudinal direction, they cannot interfere with each other, and from this point of view,
In either case of single-sided heating or double-sided heating, it is unavoidable that the situation is disadvantageous when it comes to reducing NO _x .

The heating furnace of the present invention was proposed with the aim of solving the problems seen in the prior art described in detail above, and is compact in shape and size and generates less NOx. The present invention provides a heating furnace with an improved new structure.

In the heating furnace with the improved new structure of the present invention, in the arrangement of the heat transfer tube coil and the burner in the furnace section, the inlet side of the heated fluid of the heat transfer tube coil is heated on one side, while the high temperature part on the outlet side is heated. It is characterized by being arranged so that both sides are heated, and having a structure in which each burner is surrounded by the heat exchanger tube coil. The specific structure of the heating furnace according to the present invention will be described in further detail below with reference to the accompanying drawings. Note that in FIG. 6 below, the same reference numerals as in the description of FIGS. 1 to 5 above indicate the same members and mechanisms.

FIG. 6 is a plan view showing an example of a specific structure of the main part of the heating furnace according to the present invention. In FIG. 6, a furnace section, which is a main part of the heating furnace, is surrounded by a side wall section 6 made of a refractory material, and a plurality of burners 5 are arranged inside the side wall section 6. Each heat exchanger tube 3 includes an inlet header 1 and an outlet header 2, and constitutes a set of heat exchanger tube coils 4. In the set of heat exchanger tube coils 4, the fluid to be heated is introduced from the inlet header 1, and the heat exchanger tube 3 and flows out from the outlet header 2, the heated fluid naturally has a low temperature at the inlet header 1 and a high temperature at the outlet header 2. Therefore, considering the influence on the flame temperature of the burner 5, the effect of radiated heat on the tube wall of the heat transfer tube 3, and the generation of thermal expansion difference or thermal stress associated with this, the relatively low temperature part on the inlet header 1 side is It is arranged along the side wall 6 to provide single-sided heating, and on the other hand, the relatively high temperature portions on the outlet header 2 side are bent from the opposing side wall 6 at almost right angles in the direction of the burner 5 at the center of the furnace. The outlet header 2 is arranged in the center where the burner 5 is located, so that it is heated from both sides by the burners 5, which are opposed to each other in the longitudinal direction.

By arranging the heat transfer tube coils 4 as described above, it is possible to effectively reduce the size of the furnace section, especially its length, and furthermore, each of the plurality of burners arranged in the longitudinal direction can be effectively reduced. They are separated from each other by heat pipes 3.
In other words, all of the plurality of burners are individually arranged, and the flames between adjacent burners are effectively suppressed from interfering with each other.

To explain in more detail the effects obtained by the heating furnace with the improved new structure of the present invention, it has a single-sided heating structure compared to the conventional structure in which the number of heat transfer tubes is the same. In addition to solving the problem of thermal stress that occurs in In other words, compared to the conventional heating furnace furnace section with a single-sided heating structure, it is possible to further reduce the volume by about 20%, that is, to make it more compact. Therefore, not only is it possible to save and reduce the weight of the necessary structural materials such as furnace materials, casing structural materials, and steel frames, but also the site area has been reduced.
The economical effects associated with the installation of the heating furnace of the present invention are extremely large, such as the large effects obtained in terms of installation.

On the other hand, looking at the effect of suppressing NO _x , by configuring the burner flame to be surrounded by a heat transfer tube, that is, a heat absorption surface, the temperature of the combustion section is lowered and the amount of NO _x generated at the furnace outlet can be effectively reduced. It became possible to suppress it. Specifically, NO _x generation is reduced by approximately 10% compared to a conventional single-sided heating structure, in which endothermic surfaces are placed on both sides of the burner, and by approximately 25% compared to a double-sided heating structure. It was evaluated that there was a mutual fruit.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of a general structure of a heat exchanger tube coil, Fig. 2 is a plan view showing an example of a single-sided heating structure for the furnace part of a heating furnace according to the prior art, and Fig. 3 is also based on the prior art. Fig. 4 is an explanatory diagram showing the tube wall temperature distribution of one heat exchanger tube, in the case of single-sided heating, and Fig. 5 is the same in the case of double-sided heating. The explanatory diagram shown in FIG. 6 is a plan view showing the configuration of the main part of the heating furnace according to the present invention. Explanation of symbols, 1... Inlet header, 2... Outlet header, 3... Heat exchanger tube, 4... Heat exchanger tube coil, 5...
...Burner, 6...Side wall part.

Claims (1)

[Claims] 1. A heating furnace consisting of a plurality of sets of heat exchanger tube coils including an inlet header and an outlet header for heating fluid, a plurality of burners that heat the heat exchanger tube coils, and a side wall portion surrounding the heat exchanger tube coils and burners. Each inlet header portion is provided close to the side wall portion for single-sided heating, while the outlet header portion is placed in the center between each burner for double-sided heating, and each burner is surrounded by the heat exchanger tube coil. A heating furnace characterized by: