JPS5934246B2 - Method for treating ammonia-containing substances in a fluidized bed combustion furnace - Google Patents

Description

Detailed Description of the Invention The present invention collects ammonia-containing substances such as collected ash (hereinafter referred to as EP ash) collected by a dust collector installed in the exhaust gas flow path of a combustion device such as a boiler in a power plant. The present invention relates to a method of combustion treatment.

In recent years, the amount of unburned carbon in boilers at power plants has increased due to the adoption of two-stage combustion methods and other low-02 combustion methods to reduce nitrogen oxides (hereinafter referred to as NOx) in exhaust gas. .

In addition, by spraying a reducing agent such as ammonia (NH3) to remove NOx and sulfur oxides (SOx) from exhaust gas, the amount of ammonium sulfate ((NH4)2SO4) as an ammonia-containing substance in the collected ash can be reduced. This is causing the problem of increasing numbers of people.

Therefore, it is necessary to combust EP ash containing ammonium sulfate in a combustion furnace, but during this process, the ammonium sulfate melts during the decomposition process, and in the case of a fluidized bed furnace, it adheres to the fluidized medium and the furnace wall, causing various problems in the operation of the furnace. This poses some difficult problems.

Also, depending on the operating conditions of the furnace, NOx may be generated due to oxidation of NH3.
During the combustion process, NOx in the exhaust gas must be treated.

The object of the present invention is to propose a treatment method that does not generate NOx when ammonia component-containing substances are burned in a fluidized bed combustion furnace.

In short, this invention is a method for combustion treatment of an ammonia component-containing substance in a fluidized bed combustion furnace, in which nitrogen oxides generated in the bed are combined with ammonia generated by the decomposition of the substance to be combusted and NOx generated by the decomposition of the ammonia. The method is characterized in that the empty column near the top surface of the fluidized bed is filled with flames generated by combustion of fuel supplied separately from the ammonia component-containing substance, and the ammonia component-containing substance is reacted and removed.

The structure of a conventional fluidized bed combustion furnace will be explained with reference to FIG.

A fluidized medium such as sand is housed in a fluidized bed combustion furnace 1, and a perforated plate 3
A fluidized bed 2 is formed above.

EP ash, which is an ammonia-containing substance of the incinerated material, is supplied into the fluidized bed 2 from a nozzle 4 .

The fluidized medium is heated by a starter burner 5, and is combusted within the bed when fuel is supplied from an auxiliary burner 6.

In this case, when EP ash or the like contains ammonium sulfate as an ammonia-containing substance, acidic ammonium sulfate is produced during the oxidation process, which is integrated with sand to form agglomerates, making combustion in a fluidized bed difficult.

On the other hand, it adheres to the furnace walls and gas passages, causing accumulation and increasing the ventilation resistance of exhaust gas.

In addition, the temperature in the empty column γ is determined by the temperature of the fluidized bed 2,
Depending on the conditions, exhaust gas containing a considerable amount of NOx may be emitted when EP ash or the like is incinerated.

This kind of thing had not been confirmed in previous experiments in which the temperature inside the bed was kept high in a small-diameter experimental reactor.

This invention proposes a means to eliminate these drawbacks based on operational experience and observation of a practical reactor.

An apparatus according to the present invention will be explained with reference to the drawings.

The fluidized bed combustion furnace 8 has a perforated plate 9 at the bottom of the furnace having a large number of air holes for swirling to form a swirling spouted bed of fluidized media.
Air for swirling and combustion is supplied to an air nozzle 10, an air chamber 11. It is supplied to the swirling spouted bed via the perforated plate 9.

The jet air is supplied into the swirling spout bed 26 from the jet air nozzle 25 via the pipe 12 connected to the center of the perforated plate 9 .

The EP ash is fed into the swirling spouted bed 26 via the feed nozzle 13 .

The end of the supply nozzle 13 is cooled by cooling water supplied from a cooling water supply pipe 14.

When EP ash containing ammonium sulfate is supplied to such a swirling spouted bed, the ammonium sulfate decomposes to produce acidic ammonium sulfate and NH3 at 270 to 380°C, and to NH3 and SO2 at 380 to 490°C.

Also, at 500 to 680℃, this NH3 is oxidized and becomes NOx.
On the other hand, it was found that at temperatures above 680 to 700°C, NOx reacts with the remaining NH3 and undergoes gas phase reduction in which it decomposes into N2 and N20.

In addition, the temperature in the fluidized bed proposed by the inventor is approximately 580 to 60.
When the temperature is kept at 0°C and the empty column is kept as is, there is a large chance that NH3 produced by the decomposition of ammonium sulfate will be oxidized and produce NOx, which must be prevented.

Therefore, when burning an ammonia component-containing substance in a fluidized bed, the temperature inside the swirling spouted bed is set to approximately 580 to 600°C, ammonium sulfate, etc. are decomposed to mainly generate NH3, and the temperature in the upper cavity 15 of the swirling spouted bed is 690°C. The purpose is to effectively use the NH3 generated in the fluidized bed by maintaining the temperature at ~710°C or higher and sufficiently decomposing it into N2 and water vapor in the presence of NH3 and NOx.

In general, in a fluidized bed furnace, it is necessary to maintain the temperature inside the bed higher than the ignition temperature of the material to be incinerated to continue combustion, but on the other hand, raising the temperature inside the bed in order to achieve faster processing results in even more NOx This results in the undesirable problem of causing

However, when burning ammonia-containing substances, the generation of NOx is unavoidable as described above, but at the same time, NH3 is also generated due to the decomposition of the incinerated material, and in this invention, these two gases are reacted. The idea is to carry out so-called gas-phase reduction and turn it into a harmless gas.

To this end, it is necessary to increase the atmospheric temperature near the top surface of the fluidized bed to suit the gas phase reduction in order to enhance the NOx removal effect.

In order to increase the atmospheric temperature, the upper surface of the fluidized bed is covered and filled with flame, which causes a sufficient reaction between NOx and NH3 to produce N2 and N2.
The idea is to make the exhaust gas harmless.

In the practical furnace test, an in-bed burner was installed in the bed and N3 was
I tried to decompose it down to N20, but it was not desirable.

In an embodiment according to the present invention, a plurality of burners are arranged as sky burners as shown in FIGS. 2 and 3.

In this case, the plurality of burners include a set of horizontal sky tower burners 17a whose axes are oriented horizontally, and a plurality of diagonal sky tower burners 17 whose axes are oriented diagonally downward.
b are provided as a set located at equal intervals.

When this is done, the thickness of the flame on the upper surface of the fluidized bed becomes thick in the empty column, and the flame fills the upper surface of the fluidized bed with the flame, so that the gas phase reduction of NOx and NH3 is promoted.

The intervals between these burners do not necessarily have to be equal, and may be appropriately arranged in consideration of the relationship between the auxiliary burner 18 DEG EP ash supply nozzle 13.

In one example, a favorable flame was formed when the angle α of the axis of the oblique sky tower burner 17b with respect to the horizontal was approximately 30°.

This is determined by the relative position between the nozzle installation position and the upper surface of the fluidized bed, and the length of the flame.

In addition, from the viewpoint of flame film formation, it is also effective to adopt a burner tip in which a plurality of fuel spray nozzle holes 19 of the burner nozzle are arranged in a row, as shown in FIG. 4, to form a flat flame. be.

The temperature inside the swirling spout bed is measured by a thermometer-side transmitter installed at the T1 location, and the sky temperature is measured at the T2 location, and a plurality of in-bed auxiliary combustion burners 21 are provided to supply fuel to the husband's burners. It is preferable to control the amount, combustion air amount, EP ash supply amount, etc.

By carrying out this invention, there is no need to provide a separate reducing agent supply device, and the NH3 gas generated in the fluidized bed combustion furnace can be used effectively, and the temperature in the empty column can be reduced between NOx and NH3 gas.
By creating conditions suitable for reaction decomposition, the NOx value in the exhaust gas discharged from the fluidized bed combustion furnace can be significantly reduced, and the operation control of the equipment can be easily controlled. be.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the structure of a conventional fluidized bed combustion furnace, FIG. 2 is a vertical cross-sectional view of a fluidized bed combustion furnace according to the present invention, and FIG. 3 is a cross-sectional view taken along line A-A in FIG. 4 is a BB view of the burner chip 17b in FIG. 3. 8...Fluidized bed combustion furnace, 15...Bed upper sky column section, 17a...Horizontal sky tower burner, 17b.
...Diagonal sky tower burner, 19...Fuel spray nozzle v77 α...Angle of inclination.

Claims (1)

[Claims] 1. In a method of combustion treatment of an ammonia component-containing substance in a fluidized bed combustion furnace, the inside of the fluidized bed is maintained at a temperature range in which ammonia gas is generated by decomposition of the ammonia component-containing substance, and the empty column is heated to absorb the generated ammonia gas. In order to maintain the temperature in a temperature range suitable for gas-phase reduction treatment in which nitrogen oxides generated by partial oxidation react with the remaining ammonia gas, the empty column near the top surface of the fluidized bed is supplied separately from the ammonia component-containing substance. 1. A method for treating an ammonia component-containing substance in a fluidized bed combustion furnace, the method comprising filling the furnace with flame generated by combustion of fuel.