JPH01127807A - Solid fuel combustion equipment - Google Patents

Abstract

PURPOSE:To reduce oxygen concentrations at a furnace outlet port part and to prevent coal particles from short-passing to a flue duct by providing an exhaust gas feeding means between a burner which uses high fuel ratio coal as its main fuel and the furnace outlet port. CONSTITUTION:Pulverized coal charged from a burner 2 and air for combustion are reacted on each other in a furnace to form a flame 11. The flame 11, after once reaching as deep as the bottom of the furnace, turns upward to be blown off toward a flue duct 12. An exhaust gas for combustion is extracted out of the flue duct 12 by an exhaust gas-circulating fan 5 and separated into a system 16, wherein the exhaust gas is fed into the interior of the furnace through a recirculation gas feeding port 13 disposed at the lower part of a furnace hopper 14, and into a system 17, wherein the exhaust gas is fed into an exhaust gas feeding port 3 located between the burner 2 and the flue duct 12 at the uppermost part of the furnace. In the case where the exhaust gas is thus fed into the portion between the burner and a furnace outlet port to form an air curtain, the furnace outlet port is sealed with the exhaust gas so that coal particles from the burner do not short-pass to the flue duct. Thus, the burner flame is directed toward the bottom of the furnace, and the coal particles may be sufficiently and effectively utilized with the flame in respect to the capacity of the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid fuel combustion device, and particularly to a boiler device for burning high fuel ratio coal suitable for reducing unburned content in exhaust gas.

[Conventional technology]

As a combustion method for charcoal with a so-called high fuel ratio (fixed carbon/volatile content), which has a low volatile content even though it is a solid fuel, there is a furnace shape called a wing furnace, in which the burner is installed downward in the furnace, and an arch firing. There are many combustion methods that are used.

The shape of this furnace 1 is shown in FIG. 4, and when compared with the conventional furnace shape shown in FIG. 3, the depth of the furnace is slightly deeper for the same furnace volume.

In FIGS. 3 and 4, the arrow τ is the locus of coal particles from the burner 2, and indicates the residence time to the furnace outlet IA.

In addition, 12 is a flue. Comparing Figures 3 and 4, τ. 1〉τ. Therefore, the arch firing ring shown in FIG. 4 is clearly more advantageous in terms of particle residence time in the furnace. This is because an increase in the residence time of particles in the furnace leads to a reduction in unburned particles.

However, simply turning burner 2 downward will cause the flue 1
2, a phenomenon occurs in which coal particles pass through the flue 12 as shown in 1. This is shown in Figure 4,
τ1<τ0°, and the advantage of configuring the burner 2 downward is almost eliminated.

As a measure to prevent a short pass of coal particles, a method of introducing after air 15 between the burner 2 and the flue 12, as shown in FIG. 5, can be considered.

This corresponds to an air curtain that prevents coal particles from the burner 2 from passing directly into the flue 12.

However, in this method, since highly concentrated oxygen (after air 15) is blown in near the flue 12, a phenomenon occurs in which the air, which is an oxidizing agent, also directly passes through the flue 12.

According to this method of injecting after air, the amount of coal particles short-passing is reduced, but because the oxygen partial pressure at the furnace outlet increases, the heat generation in the furnace decreases, and the temperature at the furnace outlet decreases. There were problems such as an increase in Furthermore, in this method, chemical reactions also proceed in the convection heat transfer section, but since the heat exchanger rapidly cools down, a reduction in unburned content cannot be expected.

An object of the present invention is to provide a solid fuel combustion device that reduces the oxygen concentration at the furnace outlet and prevents coal particles from the burner from making a short pass toward the flue.

[Problem that the invention seeks to solve]

The present invention is a combustion apparatus in which a burner whose main fuel is high fuel ratio coal is arranged downward with respect to the furnace, characterized in that a means for supplying exhaust gas is provided between the burner and the furnace outlet. do.

[Effect]

When exhaust gas is injected between the burner and the furnace outlet to form an air curtain, the exhaust gas has an oxygen concentration of less than 10% and is almost inert to coal fuel, so it tends to pass through the flue as a short path. Even if something happens, the heat generation rate inside the furnace will not decrease. Therefore, it is possible to seal the coal particles from the burner with the exhaust gas so that they do not make a short path to the flue, and to direct the burner flame toward the bottom of the furnace, making it possible to fully utilize the flame effectively with respect to the furnace volume.

〔Example〕

FIG. 1 is a schematic system diagram of a boiler apparatus showing one embodiment of the present invention. Coal fuel is stored in a coal bunker 8 and quantitatively supplied to the mill 7, where the pulverized coal is sent to the burner 2 through a pulverized coal transport pipe 9. On the other hand, the combustion air is pressurized by the forced draft fan 4, preheated by the exhaust gas in the heat exchanger 6, and then sent to the burner 2 as combustion air through the combustion air piping 10. Pulverized coal fuel and combustion air are mixed in a burner 2, and are introduced from the burner 2 toward the bottom of the furnace 1.

On the other hand, pulverized coal introduced from burner 2 and combustion air react in the furnace to form flame 11. After reaching the bottom of the -degree furnace, the flame 11 turns around and is discharged into the flue 12.

The combustion exhaust gas is passed through the flue 12 by the exhaust gas circulation fan 5.
Exhaust gas is extracted from the furnace and sent to the inside of the furnace from the recirculation gas inlet 13 located in the furnace hopper 14, and to the exhaust gas inlet 3 located between the burner 2 and the flue 12 at the top of the furnace. It is divided into 17 systems.

In the present invention, exhaust gas is introduced into the furnace from an intermediate point between the burner 2 and the flue 12, but in this case, the direction of input of the exhaust gas may be parallel to the direction of the burner 2 or directed toward the burner 2. do.

Next, an example of the arrangement of the exhaust gas inlet 3 is shown in Fig. 2.The exhaust gas inlet 3 may be arranged parallel to the burner 2 group as shown in the figure to form a slit, or it may be arranged in a slit shape corresponding to the burner 2 so that it has more than the number of burners. Preferably, several exhaust gas inlets 3 are provided between the burner 2 and the flue 12.

Figure 6 shows the relationship between the oxygen concentration in the exhaust gas and the combustion gas temperature at the furnace outlet when exhaust gas or air is introduced into the furnace from the exhaust gas inlet 3 located between the burner 2 and the flue 12. This is what is shown.

It can be seen that when the oxygen concentration of the exhaust gas is lowered to 21%, that is, the oxygen concentration from air to 3% (combustion air in the furnace is constant), the furnace outlet gas temperature decreases accordingly. This means that the amount of short paths of coal particles due to the exhaust gas from the exhaust gas inlet 3 is reduced, and the amount of heat generated and the amount of heat absorbed inside the furnace are increased.

On the other hand, FIG. 7 shows the relationship between the exhaust gas injection amount and the furnace effective utilization rate. Here, the effective utilization rate of the furnace is defined as the ratio of the volume of the flame (generating heat due to re-reactive gas) to the volume of the furnace. From FIG. 7, it can be seen that the effective utilization rate of the furnace increases as the exhaust gas injection amount increases.

FIG. 8 shows the relationship between the amount of exhaust gas blown from the furnace outlet and the unburned content in the ash. Coal A in Figure 8 is coal with a fuel ratio (fixed carbon in coal/volatile content) of 2 or more, coal with a fuel ratio of around 1, and coal has a slightly higher unburned content in ash. However, no matter which type of coal is burned, there is an optimum value for the exhaust gas injection amount (input amount) that minimizes the unburned content in the ash.

It can be seen that between the case where the amount of exhaust gas blown is 0 and the case where exhaust gas is blown in, it is clear that injecting exhaust gas is more effective in reducing the unburned content in the ash. However, if the amount of exhaust gas input is too large, there is a tendency for the unburned content in the ash to increase (especially for A coal). This is thought to be because the amount of gas in the furnace increases due to the sealing effect and mixing effect of the exhaust gas input, which reduces the residence time of coal particles in the furnace, resulting in a significant increase in unburned content.

Another embodiment of the invention is shown in FIG. In this embodiment, in addition to the conventional air curtain system, the exhaust gas inlet 3 is injected between the after-air inlet 15 and the flue 12 in the form of a screen. The air curtain from the after-air inlet 15 has a two-stage combustion effect, that is, it reduces the amount of combustion air from the burner port of the burner 2 and slows down the velocity of coal particles and mixing with the combustion air, thereby improving the flame. The purpose is to stabilize and reduce NOx. In the case of high fuel ratio coal, the main purpose is to stabilize the flame holding of the burner 2. The effects of this embodiment include stabilizing the flame, reducing unburnt combustion, and further reducing NOx.

Furthermore, FIG. 1θ shows the gas flow in the furnace when the angle of the burner 2 is set slightly downward with respect to the furnace. In this case, the main flow of the gas in the furnace rises along the side wall where the burner 2 is arranged, but in such a flow, a large number of coal particles make a short pass to the flue 12, so the exhaust gas inlet The sealing effect by the exhaust gas from 3 becomes even more effective. Furthermore, although FIG. 11 shows the case of single-sided combustion, similar effects can be expected in this case as well. .

〔Effect of the invention〕

According to the present invention, it is possible to prevent pulverized coal from short-circuiting into the flue, and the residence time in the furnace is increased, so coal with a relatively low combustion rate, such as high fuel ratio coal, can be It can be burned with high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of a boiler device showing an embodiment of the present invention, and FIG. Fig. 3 is a side view of the furnace showing particle trajectories from the burners in a conventional opposed combustion furnace; Fig. 4 is a side view showing particle trajectories from the main burner in a conventional arch-firing type furnace; The figure is a conceptual diagram when seal air is introduced into an arch-firing type furnace. Figure 6 shows the furnace outlet gas temperature and the 02 partial pressure of the blown gas when exhaust gas is circulated in the seal air. - A diagram showing the relationship, Figure 7 is a diagram showing the relationship between the amount of exhaust gas injected and the effective utilization rate of the furnace, Figure 8 is a diagram showing the relationship between the amount of exhaust gas injected and the unburned content in the ash, Figure 9 , FIG. 10, and FIG. 11 are conceptual diagrams of a boiler device showing other embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Furnace, 2... Burner, 3... Exhaust gas inlet, 6... Heat exchanger, 7... Mill, 8... Coal bunker, 9... Pulverized coal transport pipe, 10 ... Combustion air piping, 11... Flame, 12... Flue, 13... GR
Input port, 14...hopper, 15...after air. Agent Patent Attorney Takenaga Kawakita Fig. 5 Fig. 6 Partial pressure of blown gas (%) Fig. 7 Fig. 8 Amount of exhaust gas blown

Claims (2)

[Claims] (1) A combustion device in which a burner whose main fuel is high fuel ratio coal is arranged downward with respect to the furnace, characterized in that a means for supplying exhaust gas is provided between the burner and the furnace outlet. Solid fuel combustion equipment. (2) A solid fuel combustion device according to claim 1, characterized in that the exhaust gas injection nozzle is arranged in a slit shape or in a plurality in the width direction of the furnace.