JPS6183812A - Atomizer for slurry fuel - Google Patents

Abstract

PURPOSE:To decrease unburnt content in ash without increasing the concentration of NOx in exhaust gas, and to increase combustion efficiency of coal-water mixture (CWM), by controlling the flow rate of spray medium contacting with coal-water slurry below 9% at the gas-fluid ratio. CONSTITUTION:Coal-water mixture, CWM6 is boiled as its pressure is reduced immediately after it is injected into a furnace from an atomizer nozzle 7. There is a little time lag before CWM6 injected from the nozzle 7 is atomized and then is diffused. Therefore atomization ban be taken place continuously without delay by spraying a very little quantity, below 9% at the gas-fluid ratio of steam from a steam feed pipe 15 in the center of a burner. The CWM6 is sufficiently heated, boiled and atomized before it reaches the atomizer nozzle 7 by supplying such a small quantity of injection medium to the CWM6, because a heating jacket is provided around a feed pipe 17. There exists not such a tendency that NOx is suddenly decreased nearly above 0.5% at the gas-fluid ratio being accompanied with the increase of gas-fluid ratio as is seen in conventional atomizers, and unburnt content is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an atomizer device for slurry fuel, and more particularly to a burner atomizer device that is suitable for promoting atomized combustion of coal-water slurry fuel.

(Prior Technology) Since the oil crisis, as a measure to conserve resources, there has been a shift from heavy oil, which was the main fuel for conventional thermal power generation, to coal and LNG. Furthermore, in order to improve the handling of coal, which is a solid fuel, recent efforts are underway to develop a technology that mixes water or oil with coal to form a slurry for easier handling. A typical example of this coal-water slurry is COMCCoal.
and Qil Mixture) and CWM (
Coal and Water Mixture
).

Among these, CWM uses only water and a small amount of surfactant in addition to coal, and has the following features compared to COM.

a) It is a highly concentrated slurry with a coal concentration of 65% or more, and boiler efficiency can be increased by suppressing moisture as much as possible.

b) It can be handled as a non-Newtonian fluid even at room temperature, and there is no need to heat piping like C heavy oil or COM.

C) By not using expensive oil whose price is unstable, it can be expected to be a fuel that can be stably supplied to boilers.

As described above, CWM is a slurry of solid fuel, and can be said to be a fuel that is extremely easy to handle compared to coal and COM.

However, since CWM itself uses coal (pulverized coal) as fuel, the nitrogen content (Fu e
Therefore, during combustion, Fuel N
Since a large amount of Ox is generated and water is used for slurrying, the temperature decreases due to moisture evaporation near the burner, which lowers the combustion efficiency compared to pulverized coal combustion and reduces unburned content in the ash. The disadvantage is that it tends to increase.

Therefore, the results of burning CWM using a conventionally used burner will be described below.

First, Figure 5 shows the burner used for CWM combustion.

An atomizer (burner tip) 4 with an impeller 2 is attached to the tip of the burner gun 12.

Detailed views of this burner chip are shown in FIGS. 6 and 7. Further, FIGS. 6A and 6B are plan views taken in the direction A of FIGS. 6 and 7, respectively.

That is, FIG. 7 shows an internal mixing type atomizer, which has a chamber 15 in which the fuel (CWM') 6 and the spray medium 5 are mixed, and has a spray nozzle 7 in front of the chamber 15.

On the other hand, the atomizer shown in FIG. 7 is of the so-called intermediate mixing type, in which the CWM and the spray medium are mixed in the flow path that enters the spray nozzle 7. In FIG. 5, the atomized CWM is
The flame 8 is diffused by the swirled combustion air and forms a flame 8 in front of the impeller 2. The combustion characteristics of an atomizer are determined by the average spray particle diameter, and in the case of CWM, it has been experimentally confirmed that this average spray particle diameter is approximately determined by the mass flow rate ratio (gas-liquid ratio) of the spray medium and CWM.

Therefore, for the atomizers shown in FIGS. 6 and 7, the average atomized particle size is approximately the same under the same gas-liquid ratio. The combustion characteristics of the conventional burner tips shown in FIGS. 6 and 7 are shown by broken lines (white circle plots) in FIGS. 3 and 4. That is, according to the conventional burner chip, when the gas-liquid ratio is increased, atomization is promoted, so that a phenomenon is observed in which NOx increases and unburned content decreases.

However, when the gas-liquid ratio exceeds 0.25, NOx rapidly increases.
decreases, while unburned content increases.

This is considered to be because, although atomization was promoted, the mass flow rate of the atomizing medium increased, so that the fuel injection speed in the axial direction exceeded the combustion speed of the CWM atomized particles. In other words, it has been found that even if the gas-liquid ratio is increased too much, a flame blow-off phenomenon occurs and the combustion efficiency decreases.

(Problems to be Solved by the Invention) The purpose of the present invention is to eliminate the drawbacks of the prior art described above, and
In WM combustion, C
An object of the present invention is to provide a WM burner device.

(Means for Solving the Problems) In short, the present invention has a supply channel for coal-water slurry and a supply channel for water vapor, which is a spraying medium for the slurry, and the coal-water slurry is supplied with water vapor. In an atomizer device for slurry fuel that mixes and jets it from a spray nozzle, the coal-
A heating jacket is provided around the water slurry supply flow path,
Further, the present invention is characterized in that means is provided for controlling the flow rate of the spray medium that comes into contact with the coal-water slurry to a gas-liquid ratio (steam flow rate/coal-water slurry flow rate ratio) of 9% or less.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a CWM atomizer according to the present invention, and FIG. 1A is a plan view of the CWM atomizer in the direction of view A.

This device includes a tapered water vapor 10 supply channel 15 provided at the center of the burner, a CWM 6 supply channel 17 provided in an annular shape around the same, and similarly tapered.
It is mainly composed of a nozzle 7 through which the CWM 6 and water vapor 10 come into contact with each other at the tip of the supply channel, mix and eject the mixture, and a heating jacket 19 provided around the outer periphery of the CWM supply channel 6. The heating jacket 19 has a return line 19A into which water vapor 1o flows and which forms a U-shaped flow path at its tip.

Immediately after CWM6 is introduced into the furnace through the spray nozzle 7, it is depressurized and boils, causing bubbles to grow rapidly and becoming atomized. Since there is a time delay, atomization can be carried out continuously and without delay by spraying a very small amount of steam with a gas-liquid ratio of 9% or less from the steam supply pipe 15 in the center of the burner. . For this reason, the atomization of CWM is
A sufficient effect can be achieved with an extremely small gas-liquid ratio compared to conventional methods. Although water vapor was used as the spray medium from the viewpoint of practicality, air, other gases, and mixed gases thereof may also be used.

The water vapor 10 supplied to the center of the burner has a gas-liquid ratio of approximately 9
% or less (based on weight, the same applies hereinafter). The lower limit is not particularly limited, but may be any amount effective as a spray medium. Even by supplying such a small amount of atomizing medium, since the CWM 6 has a heating jacket around the supply pipe 17, the CWM is sufficiently heated before reaching the atomizing nozzle 7, and is sufficiently boiled and atomized outside the furnace. Can be done. In addition, there are no disadvantages such as the temporal change in the boiling atomization of CWM or the narrowing of the spray angle as in the conventional method, and it is possible to obtain a good spray state. The steam return line 19A of the heating jacket contains drain after heat exchange, so it is either disposed of through a steam trap or discharged through a drain piping to the condenser.

The combustion characteristics of the atomizer according to the above embodiment are shown in solid lines (black circle plots) in FIGS. 3 and 4.

When the atomizer according to the present invention is used, there is no tendency for NOx to suddenly decrease at a gas-liquid ratio of about 0.5 or more and unburned matter to increase as the gas-liquid ratio increases, as in the conventional type. This is considered to be because the flow rate of the atomizing medium in the atomizer of the present invention is, for example, about half that of the conventional atomizer in order to obtain the same average atomized particle diameter, and the stability of the flame is improved.

Furthermore, the unburned content in the ash is lower in the atomizer according to the present invention despite having the same NOx value.

This is thought to be because boiling atomization is promoted by water vapor and stabilized over time, and also because the spray angle is expanded compared to the conventional type and a good flame is formed.

Furthermore, as shown in Fig. 5, in the conventional burner chip, the gas-liquid ratio is about 9% or less, and the unburned content in the ash increases rapidly, whereas in the atomizer according to the present invention, the unburned content in the ash is about 4% or less. The fuel can be retained, and the amount of unburned content has been significantly reduced. In the embodiment shown in FIG. 1, the control method for heating the CWM 6 includes boiling water in the CWM supply pipe 17.
The so-called paper lock phenomenon may occur, and in this case, the spray becomes unstable over time, so the amount of heat supplied to the outer heating jacket, that is, the steam supply pressure, is changed depending on the flow rate of the CWM, and the amount of heat transferred is It is preferable to control the

Next, FIG. 2 is a sectional view of an atomizer showing another embodiment of the present invention, and FIG. 2A is a plan view of the atomizer in the direction of view A. This embodiment is the same as the atomizer shown in Fig. 1 in that it dispenses the same boiling atomization with water vapor, but in order to particularly control the spray pattern, there is a CWM supply channel 17A in the center of the burner. A heating jacket 19 is provided on the outside through which water vapor 10 passes, and a diffuser cone 1 is provided at the outlet of the tip nozzle of the CWM supply channel.
3A, and a water vapor supply pipe 20 for supplying water vapor 10 as an atomizing medium in the form of a swirling flow to the diffuser cone 13A.

In the apparatus configured as described above, the CWM 6 is supplied into the furnace from the supply passage 17A in the center of the burner through the spray nozzle and the diffuser cone 13;
At A, the CWM is heated by the surrounding heating jacket, and further from the heating jacket 19 to the steam supply channel 20.
The water vapor 10 supplied through the diffuser cone 13 promotes atomization of the CWM. That is, a part of the water vapor 10 supplied to the heating jacket 19 is supplied to promote stable boiling of the particles after boiling and atomization, and to spread the spray particle pattern in the diffuser cone 13. In this way, spray pattern 1
1 is enlarged as shown by the arrow in FIG.

(Effects of the Invention) According to the present invention, the combustibility and ignitability near the burner, which are problematic in the combustibility of CWM, are significantly improved, combustion is possible at a low air ratio, and NOx is suppressed. The effect is also improved. Furthermore, since the combustibility is significantly improved, it can be effectively applied to CWM combustion using high fuel ratio coal (fuel ratio = solid carbon/volatile matter), which has poor combustibility.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a CWM fuel atomizer showing one embodiment of the present invention, FIG. 1A is a plan view taken in the direction of view A in FIG. FIG. 2A is a plan view of the CWM fuel atomizer shown in the A-view direction, and FIGS. 3 and 4 show the ratio of NOx and unburned content in the ash to the gas-liquid ratio in the present invention and the conventional atomizer. 5 is a cross-sectional view showing the structure of a general CWM burner, and FIGS. 6 and 7 are cross-sectional views of the burner chip used in the device shown in FIG. 5, and FIG. 6A and FIG. FIG. 7A is a plan view in the direction A of FIG. 6 and FIG. 7, respectively. 4... Atomizer (burner chip), 5... Spraying medium (water vapor), 6... CWM, ? ...spray nozzle,
lO...Water vapor, 13...Diffuser cone,
15... CWM supply channel, 17... Steam supply channel, 19... Heating jacket, 19A... Return line. Agent Patent Attorney Takeshi Kawakita Figure 1 Figure 1A Figure 3 Gas-liquid Jt, Wg/W! (-) Fig. 4: Decline wglWj (-) Fig. 5, Fig. 6, Fig. 6A, Fig. 7, Fig. 7A

Claims (5)

[Claims] (1) An atomizer for slurry fuel that has a supply channel for coal-water slurry and a supply channel for water vapor, which is a spraying medium for the slurry, and mixes the coal-water slurry with steam and sprays the mixture from a spray nozzle. In the apparatus, a heating jacket is provided around the supply channel of the coal-water slurry, and the vapor-liquid ratio (steam flow rate/coal-water slurry flow rate ratio) of the spray medium in contact with the coal-water slurry is 9%. An atomizer device for slurry fuel, characterized in that it is provided with means for controlling: (2) In claim 1, the coal-water slurry supply channel is located at the center of the burner, and the steam supply channel is located at the outer periphery of the coal-water slurry supply channel, and the spray An atomizer device for slurry fuel, characterized in that the atomizer device for slurry fuel is disposed at a nozzle inlet so that water vapor forms a swirling flow from the outer circumferential side of the coal-water slurry flowing through the center of the burner and mixes in contact therewith. (3) In claim 1, the coal-water slurry supply channel is provided on the outer circumferential side of the burner, and the water vapor supply channel as the spray medium is located at the center of the burner, and the spray nozzle inlet An atomizer device for slurry fuel, characterized in that both flow paths are arranged so that these flow paths mix and come into contact with each other. (4) An atomizer device for slurry fuel according to any one of claims 1 to 3, wherein the heating jacket is comprised of a water vapor supply and return pipe. (5) In any one of claims 1 to 4, there is provided means for controlling the amount of heat supplied to the heating jacket with respect to the flow rate of the coal-water slurry in order to adjust the temperature of the coal-water slurry. An atomizer device for slurry fuel characterized by: