JPS6096813A - Low nox type high efficiency burning device - Google Patents

Abstract

PURPOSE:To retain the NOX reducing efficiency at high level, and maintain the thermal efficiency at high level by a method wherein a main burning area to be loaded mainly the thermal load and a reduction area to be performed the reduction of generated NOX are simultaneously formed. CONSTITUTION:The diffusion flow of a finely powdered coal 11 and secondary air A are mixed rapidly in the vicinity of a burner throat 50, a rapid burning is performed under high efficiency, then a main burning area 111 is formed, the thermal load of a burning device is maintained in said area 11. Meanwhile, a high speed fluid 101 is injected through a fluid injecting pipe 100, a reduction substance generation area 112 containing a large amount of reduction properties intermediate product is formed by the remainder of a finely powdered coal flow in the central part of the main burning area 111. Thereby, the NOX reducing efficiency is retained at high level, also the thermal efficiency is maintained at high level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion device capable of reducing nitrogen oxides (hereinafter referred to as 1NOX).

NOx contained in combustion exhaust gas emitted from large combustion equipment such as manual boilers is important from the perspective of preventing environmental pollution, as the amount of NOx emitted is larger than that in automobile exhaust gas, even if the concentration is low. Moreover, it requires urgent countermeasures.

As is well known, recent fuel demand issues have led to the construction or modification of coal-fired boilers. Coal contains approximately 10 times more organic nitrogen than heavy oil, and naturally this is easily converted into NOx through combustion, and due to the environmental issues mentioned above, more advanced treatment technologies than ever have been developed. is required.

The simplest and most reliable technology for treating NOx is to install a denitrification device in the exhaust gas flow path, but as the capacity of combustion equipment increases, the denitrification device itself becomes extremely large, making it difficult to secure land. This is also uneconomical. Therefore, the most ideal method is to treat raw coal or improve its combustion, such as removing nitrogen from coal (denitrification). This denitrification and combustion improvement has come to be expected to be quite effective in principle, based on the results of recent research at home and abroad. Particularly in combustion technology, the mechanism of LtNOx production and extinction has gradually become clearer.In the past, combustion efficiency had to be sacrificed to simply suppress the production of NOx, but recently, combustion As the reaction progresses, N
Based on research results that focused on the non-competitive nature of the Ox extinction reaction, this is also being developed into a technology that effectively utilizes this.

FIG. 1 shows a conventional low NOx burner for pulverized coal combustion, and FIG. 5 does not show flowchart 1 of combustion by this burner. In both figures, a pulverized coal stream 11 (a mixture of pulverized coal and primary air) is fed into the furnace through a pulverized coal supply pipe 1° to form an initial combustion zone 22.

On the other hand, secondary air A and tertiary air A are injected into the furnace so as to surround this initial combustion zone 22, and as a result, these airs flow in a layered manner in the initial combustion zone forming part, and this initial combustion zone has a low 0□ Perform combustion. As a result, reducing intermediate products are formed in the initial combustion zone to reduce NOx in the gas phase, and downstream of this initial combustion zone, each air is mixed and the unburned matter generated in low 02 combustion is combusted. That's what I do. In other words, in this type of burner, the flame and air are well separated on the upstream side of the flame, and on the downstream side after gas phase reduction, secondary and tertiary air and two-stage combustion are performed. In addition to these requirements, good mixing with the second-stage combustion air is required. However, in conventional burners, it is not always possible to perform these separations and mixes well, and if separation is done well, mixing on the downstream side will be poor, resulting in an increase in the amount of unburned substances emitted, and vice versa. If an attempt is made to improve the mixing, a problem arises in that the formation of a reducing atmosphere becomes insufficient and the NOx reduction rate decreases. Furthermore, in conventional combustion apparatuses, the flame that bears the heat load has a low '1 jof due to the initial low 02 combustion, so it has not been possible to increase the thermal efficiency very much.

This invention was constructed in view of the above-mentioned problems,
An object of the present invention is to provide a combustion device that can significantly reduce NOx and also has high thermal efficiency.

In short, this invention connects the fuel injection port to the ejector tl"J
The device 6 is constructed so as to form a concentration of the fuel flow injected into the furnace, increase the heat load of the combustion device 178, and at the same time perform good gas phase reduction of NOx.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a first embodiment of the invention. Although pulverized coal will be used as an example of fuel for the illustrated device, this device is not limited to combustion of pulverized coal. Reference numeral 10 denotes a pulverized coal supply pipe which is a fuel injection pipe, and the opening inside the furnace is a diffusion section Oa whose diameter is gradually increased toward the opening end. 110 is this diffusion section 1
This is a contracting flow member placed within 0a so that its center substantially coincides with the burner axis. The flow contracting member 110 has an annular planar shape with an injection port 110a in the center, and its cross section is approximately triangular so that it gradually becomes thicker toward the furnace side end, as shown in the figure. It is.

Next, reference numeral 100 denotes a fluid injection pipe arranged so as to be located approximately on the same axis as the pulverized coal supply pipe 10, and its nozzle portion is located in the vicinity of the injection port 110a of the above-mentioned flow contraction member 110. .

The combustion state of the apparatus having the above configuration will be explained with reference to FIG.

The pulverized coal flow 11, which is a mixed fluid of primary air and pulverized coal, is injected into the furnace through the pulverized coal supply pipe 10, but most of the pulverized coal flow is from the flow contraction member 110 and the diffusion section 10a. It is diffused and injected into the furnace through the annular space that is formed. On the other hand, the secondary air A2 supplied to the wind box 40 is given a swirling force by the secondary air swirler 20 and is injected into the furnace from the burner throat 50. As a result, the diffusion flow of the pulverized coal and the secondary air rapidly mix in the vicinity of the burner throat, resulting in highly efficient rapid combustion, forming the main combustion zone 111, which takes charge of the heat load of the combustion device.

On the other hand, the fluid lj from the two-person pipe 100 (is the high-speed fluid 101 (
For example, inert gas such as combustion phase gas) is injected, and the pulverized coal σ
The remainder of 1ε is caused by the ejection of this fluid, which forms the contraction part 4'A'10
injection fil] into the furnace via lOa. This pulverized coal does not diffuse into the furnace, and the alpha partial pressure of the high-velocity fluid is low, so the center of the main combustion zone 111, that is, the burner axis 101,
A reducing substance producing region 11.2 containing a large amount of reducing intermediate products is formed in the furnace centered on the extension line of . In this reducing substance generation region 112, for example, radicals such as .NH2 and .ON and intermediate products having reducing properties such as CO are generated in considerable numbers.

Next, the outer circumference of the reducing material producing region 112 and the main combustion region 111, which was rapidly destroyed by IIA and burned, caused the reducing material producing region 12
A negative pressure section is formed downstream of the main combustion zone 11, into which flames and high-temperature gases flow into the main combustion zone. The gas-phase reduction region 113 of NOx is formed.The gas-phase reduction of NOx in this gas-phase reduction region can be expressed as follows using the example of NOx, which accounts for the majority of NOx. Become.

No-1-, NI (2--YNt + H, O...
(1) No +・ON −→N 10 co = −(2) N
o 10 Co −→l/2N2 + Co x = (3)
Note that since the above reduction reaction is completed in a short time of several hundredths of a second, the effect on combustion does not pose a practical problem. Further, the remainder of the secondary air A2 that was not mixed in the main combustion zone Ill flows into the downstream of the gas phase reduction zone 113, so that the unburned matter is combusted by this secondary air A2. However, the combustion β “6
If the entire device performs two-stage combustion, the unburned matter will be more completely combusted.

Next, FIG. 3 shows a modification of the apparatus shown in FIG. 2. In this case, the burner throw) 50 is
The secondary air A passing through the space between the burner throat 50 and the burner throat 50 is formed gently corresponding to 0a, that is, the surface of the burner throat is formed into a curved surface.
This makes the injection of No. 2 smoother.

FIG. 4 shows yet another actual JAM example. In the case of this embodiment, (1) a passage through which tertiary air passes is formed on the outer periphery of the secondary air passage, and a secondary air and tertiary air flow is formed on the outer periphery of the ecological area 11; It is something.

The combustion device of this embodiment is suitable for modifying an existing combustion device that injects both secondary air and tertiary air! 1. l
It is effective for I.

By implementing this invention, it is possible to simultaneously form a main combustion zone that bears the heat load as raw material and a return zone that reduces the generated NOx, thereby maintaining a high NOx reduction rate and increasing thermal efficiency. can be maintained.

4- Figure 1rlj (7) I! j in, explanation 1st
The figure is a sectional view of a conventional combustion device, FIG. 2 is a sectional view of a combustion device according to the sixth invention, FIG. 3 is a second embodiment, and FIG. 4 is a third embodiment. Cross-sectional view of the combustion device shown, No. 5
FIG. 6 is a flow chart showing the operating state of the combustion device shown in FIG. 1, and FIG. 6 is a flow chart showing the operating state of the combustion device shown in FIG.

10...Pulverized coal supply pipe 10a... Diffusion part 100...Fluid injection pipe 110... Contract flow member 110a... Injection port Ill... Main combustion zone 112...Reducing substance generation area 113... Gas phase reduction area

Claims (1)

[Claims] 1. An ejector portion is formed at the furnace-side opening of the fuel injection pipe, and a fluid injection pipe whose center axis is approximately equal to that of the fuel injection pipe is arranged inside the fuel injection pipe. A reducing material producing region is formed around the inner extension of the burner axis, a high humidity main combustion region is formed around this reducing material producing region, and air is provided downstream of the reducing material producing region. A low NOx type high efficiency combustion device characterized by being configured to form a phase reduction region. 2. The ejector section is composed of a diffusion section formed at the tip of the fuel injection pipe in such a shape that the diameter gradually expands toward the opening end, and an annular flow contraction member disposed within the diffusion section. A low NOx type high-efficiency combustion device according to claim 1, characterized in that: 3. The low NOx type high efficiency combustion device according to claim 2, characterized in that the nozzle portion of the fluid injection tS is located at the injection port of the flow contraction member.