JPH0593515A - Water tube boiler - Google Patents

Abstract

PURPOSE:To transfer the combustion energy to water, etc., in high efficiency and reduce thereby the volume of a furnace and, at the same time, reduce the proportion of unburned fuel and lower NOx. CONSTITUTION:A group of water tubes 6 that make direct contact with the flame 5 that is blown into a furnace 4 from a burner 2 are disposed to improve the heat transfer and, at the same time, lower the temperature of the flame. The proportion of unburned fuel that increases as the temperature of the flame falls is removed by an unburned proportion removal device 8 that is provided in the downstream side of the flow 3 of the combustion gas. This unburned proportion removal device 8 consists of a group of pipes that have a construction that porous ceramics 12 is wound round an air blow-in tube 11 that has many small holes, and air 14 is blown in through the small holes and the unburned proportion is burned near the surfaces of the ceramics 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion device for transferring combustion heat energy to a heat medium such as water, and more particularly to a water tube type boiler.

[0002]

2. Description of the Related Art Generally, in a water tube type boiler, a furnace (combustion chamber) occupies most of the volume of the boiler. That is, conventionally, the structure is such that the entire flame blown into the furnace is surrounded by the water pipe wall, and the combustion method in which the heat generated from the three-dimensional flame is two-dimensionally mainly radiated to the water pipe wall is used. Has become. Therefore, the heat load is limited to the order of 100,000 kcal / m ² h, and miniaturization of the furnace is the most important issue in terms of boiler cost.

[0003]

As described above, in the conventional boiler combustion system, the entire huge flame is surrounded by the water tube wall of the furnace, and the heat load of the furnace is 100,000 kcal /
The order is m ² h. This is a method of recovering combustion heat from a three-dimensional flame two-dimensionally as radiant heat to the inner surface of the furnace wall, so that the outer surface of the furnace wall does not contribute to heat transfer, and This is because it is difficult to increase the heat load of the furnace because the heat flux can be unbalanced. That is, in the conventional radiant heat recovery method,
There was a limit to the further miniaturization of the furnace.

Further, in order to reduce NOx, attempts have been made to increase the residence time of the fuel in the furnace by keeping the flame temperature low and swirling the fuel in the conventional boiler. It was one of the causes of increasing the furnace volume.

The present invention has been made in order to solve the problems of the prior art, and it is possible to efficiently transfer combustion energy to a heat medium such as water, thereby reducing the volume of the furnace. At the same time, it is an object of the present invention to provide a water tube type boiler that can achieve low unburned content and low NOx.

[0006]

In order to solve the above-mentioned problems, a water tube type boiler according to the present invention comprises a burner for burning fuel, a furnace for flowing combustion gas blown from the burner in a certain direction, A water pipe group having at least a large number of water pipes which are arranged on the upstream side of the combustion gas flow in the furnace and which are in direct contact with the flame, and a water pipe group which is arranged on the downstream side of the combustion gas flow in the furnace, and is not blown into the combustion gas by blowing air. And an unburned component removing device for burning and removing the burned component.

[0007]

According to the above means, the water pipe group is arranged on the upstream side of the combustion gas flowing in a certain direction in the furnace, that is, on the initial flame side blown from the burner. The heat transfer can be performed. That is, the water tube group directly receives two forms of heat transfer, that is, radiation from the flame and heat conduction. Therefore, the heat transfer is significantly improved as compared with the conventional one, the load on the furnace is increased, and the flame temperature is further lowered to easily cope with the reduction of NOx. The air ratio in the furnace in which the water pipe group is arranged is preferably suppressed to 1 or less.

Further, the unburned matter removing device may be configured to blow air as a porous structure in which porous plates or wire nets are bundled, for example, whereby the unburned matter increases with a decrease in flame temperature. Can be dealt with. For example,
The temperature in the furnace can be maintained at about 1000 ° C., and air can be blown into the furnace to complete the combustion. In this case, it is possible to prevent clogging of the structure by blowing air from the tube group of the porous structure into the furnace. The shape of the porous structure may be flat and parallel or perpendicular to the wall surface of the furnace. This can be set according to the type of furnace.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a plan sectional view schematically showing an overall configuration of a water tube type boiler according to this embodiment, and FIG. 2 is a diagram showing a part of FIG. 1 in detail.

According to the present embodiment, as shown in FIG. 1, a water tube type boiler 1 has a plurality of burners 2 for burning fuel by obtaining oxygen in the air and burning it, and a combustion gas 3 blown from these burners 2. 4 for flowing the water in a certain direction, a water tube group 6 composed of a large number of water tubes 6A arranged directly upstream of the combustion gas flow in the furnace 4, and a large number of water tubes 7A not in direct contact with the flame 5. Water tube group 7 consisting of, and furnace 4
Is disposed on the downstream side of the combustion gas flow inside, and is disposed on the downstream side of the unburned-content removing device 8 for burning and removing the unburned-content in the combustion gas 3 by blowing air. A water pipe group 9 including a large number of water pipes 9A is provided.

As shown in detail in FIG. 2, the unburned matter removing device 8 comprises a tube group having a structure in which a porous ceramic 12 is wound around an air blowing tube 11 having a large number of pores 10. , The air 1 for completing the combustion of the unburned matter 13 in the combustion gas 3 through each of the pores 10 of the air blowing pipe 11.
4 is blown in to burn the unburned matter 13 near the surface of the ceramic 12.

In FIG. 1, a plurality of burners 2 arranged at the same level are installed in a plurality of stages in a direction perpendicular to the paper surface of FIG. Further, the water pipes 6A, 7A, 9A of the water pipe groups 6, 7, 9 and the air blowing pipes 11 of the unburned component removing device 8 are arranged so as to extend in a direction perpendicular to the paper surface of FIG.

Next, a specific example will be described. Liquefied natural gas, which is the fuel, has an air ratio of 0.6 due to the multiple-stage burners 2.
Burned with a low air content of ~ 0.9, the flame 5 is a water tube group 6
Enters the region 4A upstream of the furnace 4 in which is arranged. Burner 2
The distance from the base to the water pipe 6A of the water pipe group 6 located closest to the burner is 10 cm, and the gap between the pipes is 5 cm. The flame 5 is burned in a flow form along the surface of each water pipe 6A of the water pipe group 6. When the average temperature of the gas phase in this region 4A was examined, it was 900 to 1200 ° C., the NOx concentration in the combustion gas 3 that passed therethrough was 10 ppm, and the calorific value of the combustion gas 3 was 1000 to 3000 kc.
It was al / Nm ² .

The calorific value of liquefied natural gas is about 10,000 kc
Since it is al / Nm ^2, it is about 7 based on the amount of heat in the furnace 4.
This means that 0 to 90% of the fuel has burned. Combustion gas 3
Is then the next region 4 of the furnace 4 in which the water tube group 7 is arranged.
Enter B and heat is absorbed here as well. The gap between the tubes of the water tube group 7 was also set to 5 cm, but the amount of water was adjusted so that the temperature of the combustion gas 3 passing through the water tube group 7 was 500 to 800 ° C.

Thereafter, the combustion gas 3 containing the unburned matter 13 is
It enters the region 4C of the furnace 4 in which the unburned component removing device 8 is arranged.
Air 14 for burning the unburned component 13 is blown from each of the pores 10 of the air blowing pipe 11 of the unburned component removing device 8, and the vicinity of the surface of the porous ceramic 12 wound around the air blowing pipe 11. The unburned component 13 is burned. Then, in this region 4C, the temperature becomes about 900 ° C. due to heat generation due to the combustion of the unburned component 13. This is because the porous ceramic 12 is red-heated and has the effect of storing heat in the region 4C as radiant heat. Further, since the air 14 blows from the inside of the porous ceramic 12 toward the outside, the porous ceramic is not clogged.

The air ratio of the entire furnace 4 is 1.0.
When the air flow rates of the burner 2 and the unburned-content removing device 8 were finely adjusted to 6
Could be 0.5% or less. The temperature of the combustion gas 3 is about 800 ° C., and heat recovery is also performed by the downstream water pipe group 9 as an economizer.

According to the present embodiment described above, since heat transfer occurs on the surface of each water pipe 6A of the water pipe group 6, it is possible to perform the heat transfer in an amount proportional to the volume of the furnace 4, and to compare with the conventional structure. High efficiency is achieved. Moreover, by controlling the density of the water tube group 6, the flow rate of water as a heat medium, and the ratio of air to fuel, the temperature of the combustion region 4A can be controlled to a region (around 1000 ° C.) in which NOx generation can be suppressed. ..

Further, by setting the interval between the water tubes 6A of the water tube group 6 to be several cm or more, the temperature of the combustion region 4A is lowered due to heat recovery of the water tube group 6 and the unburned component is increased due to the concentration gradient near the tube wall. However, it can be burned and removed by the unburned matter removing device 8 provided on the downstream side of the combustion gas flow in the furnace 4. Then, since the radiant heat of combustion by the unburned-content removing device 8 reaches the upstream side, it is possible to improve the thermal efficiency by feedback.

[0019]

As described above, according to the present invention, a group of water tubes that directly contact the flame blown into the furnace from the burner is arranged, and two types of heat transfer of radiation and heat conduction from the flame are arranged. Since the water tube group is directly received, the heat transfer is greatly improved, the furnace load can be 10 times or more compared with the conventional boiler, and the furnace can be made compact, and the flame temperature can be reduced to about 1000 ° C. As a result, low NOx combustion becomes possible, and the unburned component that increases as the flame temperature decreases can be removed by the unburned component removal device arranged in the downstream of the combustion gas flow. It

[Brief description of drawings]

FIG. 1 is a plan sectional view schematically showing an overall configuration of a water tube type boiler according to an embodiment of the present invention.

FIG. 2 is a diagram showing a part of FIG. 1 in detail.

[Explanation of symbols]

 1 Water Tube Boiler 2 Burner 3 Combustion Gas 4 Furnace 5 Flame 6 Water Tube Group 6A Water Tube 7 Water Tube Group 7A Water Tube 8 Unburned Gas Removal Device 9 Water Tube Group 9A Water Tube 10 Pore 11 Air Blow Tube 12 Porous Ceramic 13 Unburned Part 14 Air

Claims (1)

[Claims] 1. A burner for burning fuel, and a furnace for flowing combustion gas blown from the burner in a certain direction.
A water pipe group having at least a large number of water pipes which are arranged on the upstream side of the combustion gas flow in the furnace and which are in direct contact with the flame, and a water pipe group which is arranged on the downstream side of the combustion gas flow in the furnace, and is not blown into the combustion gas by blowing air. A water tube type boiler, comprising: an unburned component removing device for burning and removing a burned component.