JPS5835308A - Combustion method preventing resonance and its apparatus - Google Patents

Abstract

PURPOSE:To certainly prevent resonance during combustion is on a burner, by composing the burner, with a plurality of fuel spray tubes being equipped, in order to perform a combustion which shows a vibrational change in the rate of heat generation, which is different from an acoustical mode of vibration, which occurs in a combustion furnace, such as an industrial furnace. CONSTITUTION:A heavy oil burner 12a, to which end a flame holder 12 is fitted, is installed in the center part of a burner 8. The primary air is fed into the burner 12a from tubes 12b which encircle the burner 12a, and the secondary air is fed into the burner, passing through the secondary vanes 11. A plurality of fuel spray tubes 3 are annularly arranged to the outer circumference of tubular bodies 11a, encircling the secondary vanes 11. In this case, there are two types of fuel spray tube 3. One is that to which a gas nozzle 13, having a main fuel spray hole 6 which performs both main- hole fuel spray 6' and auxiliary-hole fuel spray 7', and an auxiliary fuel spray hole 7, are equipped. The other is that to which a gas nozzle 13'', having a main fuel spray hole 6 which performs a main-hole fuel spray 6'' only, is equipped. Both types are arranged alternately. With such an arrangement, the pattern of change of the rate of heat generation is made complicated, so that the burner is prevented from resonance during combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion method and apparatus for preventing resonance vibrations that may occur in a boiler furnace or the like.

BACKGROUND OF THE INVENTION Boilers and industrial furnaces that use fossil fuels are being converted to natural gas or coal fuels due to a shortage of petroleum fuels. In particular, natural gas has extremely low sulfur content, 5Ox.
(sulfur oxides) and nitrogen oxides (NOx).
) is attracting attention as a clean energy source because it can be easily prevented. However, natural gas, by its nature, forms short flames, which creates a new problem of generating resonance vibrations in the furnace, and a solution to this problem is desired.

In general, a combustion furnace is a hollow cube with a rectangular cross section as shown in FIG. 1, and a horizontal type of combustion furnace is a cylindrical horizontal industrial furnace as shown in FIG. In this case, the mode of air column pressure vibration is:
Acoustic vibrations from the first to the zeroth orders are generated with the fixed wall at the maximum amplitude part (abdomen) of the euphonic vibrations.

For the boiler shown in Figure 1, width (W), depth (D) and height H
), both ends are closed as shown in Figure 3, and the industrial furnace shown in Figure 2 has one end closed in the cylinder length L) direction as shown in Figure 4. It has become.

As shown in FIG. 5, the natural gas supply device to the burner 8a is constructed by a pipe line that branches from a pipe line 3a via a fuel gas flow rate adjustment valve 1as and a fuel gas cutoff valve 2a, and supplies the natural gas to the burner via a gas population valve 4a. 8a is supplied with natural gas. Code 5a
, 6a is a gas vent valve, and 7a is a gas vent pipe.

FIG. 6 is a sectional view including the axis of the burner 8a, and FIG. 7 is a view taken along line AA (front view) of FIG.

A burner 8a is attached to a burner throat 5 on the wood pipe wall 14 of the furnace 1.
It is installed coaxially with the furnace 1 with its nozzle facing the furnace 1. Heavy oil located at the center of burner 8a/< -+ 12
A flame holding plate 12 is attached to the end of a, and the cylinder 1 surrounding it
Primary air is supplied from 2b, and secondary air 10 is supplied via secondary vane 11.

A plurality of gas elements (fuel spray pipes) 3 (eight in the figure) are located coaxially with the throat 5 on the outer periphery of the cylindrical body 11a surrounding the secondary vane 11. A gas nozzle 13 is attached to the front end of this gas element 3. The gas nozzle 13 is provided with a main fuel spray hole 6 and an auxiliary fuel spray hole 7,
As shown in Fig. 7, main hole fuel spray 6', sub hole fuel spray γ
' gushes out. The sub-hole fuel spray is carried out by the impeller 12 as shown in the figure.
It burns in such a way as to surround it, and a flame holding area 4 is formed by the combustion air flow. Both are main fuel spray 6' and auxiliary fuel spray 7'.
The gas nozzles 13 are provided so that the relative positions of the spraying directions with respect to the flame stabilizing plate 12 are the same. When gas is combusted in such a gas burner 8a, the combustion takes place in a substantially constant shape, that is, the oscillatory heat generation rate changes in a substantially constant manner.

The pressure fluctuation inside the furnace due to its combustion is shown in column 1 of attached Table 1.
The result will be something like the diagram of the "waveform characteristics" of pressure fluctuation shown in the "Stability" column. The relationship between the pressure amplitude and frequency shows a frequency distribution with three average peaks.

However, when this waveform characteristic approximates the unique vibrational vibration mode (waveform and frequency) of the furnace, r,
The waveform characteristics change in the order of n and m, and as shown in (2), a so-called resonant vibration with one large pressure amplitude occurs in the frequency characteristics, eventually leading to damage to the furnace.

The conditions for the development of resonance vibration are as follows: (1) The necessary condition is that the temperature should be at the point where the amplitude of the pressure vibration is maximum, the so-called pressure antinode (near ml).

(2) A sufficient condition is that pressure fluctuations and heat generation fluctuations are synchronized.

However, the requirement 1) cannot be avoided because the burner is attached to the wall of the water pipe which is closed on one side due to the structure of the combustion furnace such as a boiler. Therefore, it is necessary to prevent the condition (2) from being satisfied in order to prevent resonance vibration.

The purpose of this invention is to propose a method and apparatus for arranging fuel spray pipes so as not to satisfy such sufficient conditions, and to perform combustion in a manner that does not form a combustion mode that causes resonance vibration. The present invention is characterized by a resonance vibration prevention combustion method for supplying fuel to a burner having a plurality of fuel spray pipes so as to perform combustion with an oscillatory change in heat generation rate different from the acoustic vibration mode of the combustion furnace. shall be.

Furthermore, the present invention provides a resonance vibration prevention combustion device in which a plurality of sets of fuel spray pipes each consisting of two or more fuel spray pipes with nozzles having different fuel spray directions and fuel spray amounts are arranged along the inner periphery of a burner throat. It is characterized by

An apparatus for carrying out this invention will be explained with reference to FIGS. 8 to 11. In addition, the reference numerals attached in Figures 8 and 9 indicate No. 6.
The same parts as those in the figures and FIG. 7 indicate the same members. In the burner 8 according to the embodiment of the present invention, the fuel spray pipe 3 is a gas nozzle 13 having a main fuel spray hole 6 and an auxiliary fuel spray hole 7.
There are two types: one equipped with a gas nozzle 13r having only the main fuel spray hole 6, and one equipped with a gas nozzle 13r having only the main fuel spray hole 6. Along the inner circumference of the burner throat 5, as shown in FIG. A plurality of sets (four sets in FIG. 9) are provided with a fuel spray pipe equipped with a fuel spray pipe.

That is, the gas nozzles 13 and 13' are arranged alternately along the inner periphery of the burner throat. When such a combination is used, the pattern of heat generation rate change is ql as shown in Figure 11.
The three forms of <qt become a composite form, resulting in a complex waveform, which causes the heat generation rate to change in a waveform different from the unique acoustic vibration mode of the furnace, resulting in resonance vibration of the furnace. There is no.

Further, as shown in No. 101J, the gas nozzle A1 has only the main fuel spray hole 6 or the main fuel spray hole 6 and the auxiliary fuel spray hole 7, the gas nozzle B has only the main fuel spray hole 6, and the gas nozzle CI has only the auxiliary fuel spray holes 7, and a plurality of sets (three in the illustrated example) of A1B1c may be arranged along the inner periphery of the burner throat. In this case, the direction of gas ejection from the main fuel nozzle hole may be changed to <6At 6s and αA, αB in the tangential direction of the inner circumference, as shown in the figure.

Further, the amount of fuel supplied may be changed for each gas nozzle.

The ratio of the amount of fuel jetted from the auxiliary fuel nozzle to the amount of fuel jetted from the main fuel nozzle is usually 0.1 to 0.5.

FIG. 12 shows the relationship between the vibration index (%) and the two-stage combustion ratio, where the A curve shows the conventional burner and the N curve shows the burner according to the present invention. Here, the vibration index is a measure that detects fluctuations in the furnace draft, performs frequency analysis, and indicates the proportion of resonant component frequencies that resonate with the natural frequency of the air column of the furnace. The ratio refers to the ratio between the amount of fuel supplied to the second-stage burner and the amount of fuel supplied to the first-stage burner. The experimental furnace used in the experiment was 2 m deep, had 2 burners, used LPG as fuel, and had a combustion rate of 7.5 mN/hr.

The condition is that the excess air ratio is 10%.

The results of this experiment also confirmed that the vibration index of the burner according to the present invention was always lower than that of the conventional burner.

Furthermore, as a result of installing the burner according to the present invention in an actual boiler in operation, it was confirmed that it is highly effective in preventing the occurrence of resonance vibrations.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a boiler furnace, Figure 2 is a perspective view of an industrial furnace, and Figure 3 is the natural vibration pattern of the air column for each of the depth D1 furnace width W and furnace height H in Figure 1. Fig. 4 is the natural vibration pattern of the air column corresponding to Fig. 2, Fig. 5 is a schematic perspective view of the gas fuel piping, Fig. 6 is a side sectional view of a conventional burner, and Fig. 7 is A of Fig. 6. -A main view, FIG. 8 is a side sectional view of the burner according to the present invention, FIG. 9 is a B-B main view of FIG. 8, and FIG. 10 is a front view of the burner showing another embodiment of the present invention. FIG. 11 is a diagram of changes in heat generation rate and time diagram in the case of implementing the present invention, and FIG. 12 is a diagram showing the relationship between the vibration index and the two-stage combustion ratio. 1...Furnace 3...Fuel spray pipe 6...Main fuel spray hole 7...Auxiliary fuel spray hole 8.8a...Burner 13...Gas nozzle Fig. 2 Fig. 4 3; ≧S

Claims (1)

[Claims] 1. The present invention is characterized in that fuel is supplied to a burner having a plurality of fuel spray pipes so as to perform combustion with an oscillatory heat generation rate change different from the acoustic vibration mode of the combustion furnace. Resonance vibration prevention combustion method 02, a resonance characterized in that a plurality of sets of fuel spray pipes each consisting of two or more fuel spray pipes with nozzles having different fuel spray directions and fuel spray amounts are arranged along the inner periphery of the burner throat. Anti-vibration combustion device. 3. A patent characterized in that fuel spray pipes with nozzles having only main fuel spray holes and fuel spray pipes with nozzles having main fuel spray holes and auxiliary fuel spray holes are arranged alternately along the inner periphery of the burner throat. A resonance vibration prevention combustion device according to claim 1.