JPS5995315A - Nox removing boiler - Google Patents

Abstract

PURPOSE:To remove NOX in combustion gas without wasting energy in the titled boiler, by mounting an injection nozzle of ammonia gas between a gas mixing chamber and a catalytic chamber and providing a damper within a bypass duct. CONSTITUTION:A temperature of combustion gas is lowered through heat exchange between the combustion gas and water in a heating evaporating tube 13, a sulfide is generated by reacting ammonia spouting out into the combustion gas to SOX in the combustion gas and a catalyst is made to inactivate by adhering to the surface of the catalyst. When the temperature of the combustion gas is risen excessively, NOX is increased by reacting the ammonia poured into the combustion gas to oxygen contained in the combustion gas. It becomes important, hereupon, to keep the temperature of the combustion gas available prior to its inflow into a denitration chamber 3 at 300 deg.C- 400 deg.C. When the temperature of the gas is lowered due to a decrease of a load, it is detected by a gas temperature sensor 19 through a control signal of which an opening of a flow adjusting damper 16 is adjusted, part of the combustion gas streamed into a vapor generation chamber 2 is streamed into the damper 16 without passing through the circumference of the heating evaporating tube 13, being mixed with the combustion gas passed through the circumference of the heating evaporating tube 13 within a gas mixing chamber 14 and then the combustion gas is adjusted at a fixed temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a NOx removal boiler for removing NOX contained in exhaust gas.

When fossil fuels such as heavy oil and coal are burned, the nitrogen contained in the fuel and nitrogen combines with acids to form N.

Or it becomes NOx.

The generation rate of NOX varies depending on combustion conditions, but in large boilers such as those used in thermal power plants, it is 150 to 30% when using gas.
0 ppm, 500-1000 ppm for coal
.

In the case of heavy oil, it is said to be 250 to 400 ppm. When NOx is released into the atmosphere, it causes oxidant pollution, so in May 1972, the Central Pollution Control Council set the permissible value for N02 at an hourly daily average of 0.02 ppm or less. The report includes the goal of achieving this strict standard within 95 years of production.

However, the reality is that the development of flue gas denitrification equipment has been delayed, and very few have been put into practical use. It's just working. The main reason for this is that the denitrification equipment is bulky and complicated, requires extensive equipment installation, and requires a large amount of money to operate and maintain the equipment. Therefore, for most boilers except these super large boilers, the NOx countermeasure (1
) Lower temperature combustion at the expense of boiler efficiency. (2) Switch to low NOx fuel such as gas. (3) They simply took measures such as lowering the operating rate of boilers to operate within the framework of total volume regulations. Due to these circumstances, the reality is that the above-mentioned report is far from being achieved.

On the other hand, some specific devices use an afterburner to heat the combustion gas after heat exchange and adjust the temperature immediately before blowing the combustion gas into the denitrification device, since the generation of NOx has a large effect on the exhaust gas temperature. Not only does it require fuel for the process, but it also requires heating the air supplied to the afterburner, which results in a loss of energy, so it can never be considered an effective method.

The present invention solves the above problems and provides a boiler that can effectively remove NOX from combustion gas without wasting energy. Embodiments of the present invention will be described below with reference to the drawings. In the figure, the boiler of the present invention includes a combustion chamber 1,
It includes a steam generation chamber 2 by heat exchange, a deoxidation catalyst reaction chamber (hereinafter simply referred to as a denitrification chamber) 6, and an exhaust chamber 4. The combustion chamber 1, the steam generation chamber 2, and the exhaust chamber 6 are divided into rows in the casing 5, and the combustion chamber 1 and the steam generation chamber 2 are separated by a partition wall 6.
The steam generation chamber 2 and the exhaust chamber 4 are separated by a partition wall 8. On the other hand, a cylindrical part 9 is provided on the upper surface of the casing 5 to communicate between the steam generation chamber 2 and the exhaust chamber 4. The inside of the cylindrical part 9 is partitioned by the rising part 8a of the partition wall 8, It forms a curved passage. This cylindrical part 9 is made of a heat insulating material, and its head is removable, or its outer periphery is covered with a heat insulating material to keep the inside warm. A burner 10 is installed at one end of the combustion chamber 1 facing the communication hole 7, and the piping of a fuel oil pump 11 is connected to the burner 10.

A heating evaporation pipe 16 connected to a water supply pump 12 is wound in multiple layers and housed in the steam generation chamber 2, and the combustion gas flowing into the hollow part at the center of the volume I of the heating evaporation pipe 16 through the communication hole 7 is stored. A flow path is formed to flow out toward the gas mixing chamber 14 within the curved passage. Also, the hollow part 2a at the center of the winding layer of the heating evaporation tube 16
Correspondingly, a bypass passage 15 is formed in the partition wall 8 with one end opened into the steam generation chamber 2 and the other end opened into the downstream side of the steam generation chamber 2, that is, into the gas mixing chamber 14. A flow rate adjustment damper 16 is interposed therein.

A part of the bent passage serves as the denitrification chamber 3, and bundles of cylindrical catalysts 17 and 17 are installed parallel to the gas flow direction in the passages on both sides of the rising portion 8a of the partition wall 8. accommodate. It is necessary to use a catalyst 17 that does not become deactivated even when it is brought into contact with a gas containing a large amount of SOx or dust. According to experiments, good results were obtained using a material whose main component was iron oxide. Immediately before this denitration chamber B, an ammonia gas jet nozzle 18 is installed, and a temperature sensor 19 that senses the temperature of the combustion gas flowing out from the gas mixing chamber 14 and controls the opening degree of the damper 16, and a temperature sensor 19 that controls the opening degree of the damper 16, and Ammonia gas jet nozzle 1 detects low temperature
Emergency shutoff valve 2o installed in the ammonia gas supply pipe P1 of No. 8
A low temperature sensor 21 is installed for controlling the opening and closing of each.

The exhaust chamber 4 is provided with an exhaust port 22 for combustion gas. This exhaust chamber 4 also serves as a preheating chamber for the air supplied to the burner 16 or the water supplied to the steam generation chamber 2. In the embodiment, an example is shown in which the exhaust chamber 4 is used as an air preheating chamber, and an air supply pipe 26 is installed in the exhaust chamber 4, and the piping is connected to the burner 10 via a blower 24. In the figure, reference numeral 25 denotes an ammonia control valve provided in the middle of the ammonia supply pipe Pl, which is operated by a signal sent from the fuel flow meter 26. Further, the ammonia emergency shutoff valve 20 is installed in the supply pipe P downstream of the ammonia control valve 25, and receives a signal from the low temperature sensor 21 and closes when the combustion gas is low, so that the ammonia gas is ejected. It is intended to stop. Ammonia gas is released by opening the ammonia control valve 25 only when the combustion gas temperature in the gas mixing chamber 14 is high.
i The fireflies necessary to reduce NOX are supplied.

In the embodiment, fuel oil is pumped into the burner 10 by driving the fuel oil pump 11 and ignited. Combustion gas generated by combustion of the fuel enters the steam generation chamber 2 from the combustion chamber 1 through the communication hole 7, flows around the heating evaporation pipe 16, flows out into the gas mixing chamber 14, and then passes through the denitrification chamber 6. After that, it is released into the outside air through the exhaust chamber 4. The water pumped up by the water supply pump 12 undergoes heating and evaporation -1-? 13, and the air is sent out into the delivery path P2. Here, the temperature of the combustion gas decreases due to heat exchange between the combustion gas and the water in the heating evaporation tube 16. When the temperature of the scum decreases, the ammonia ejected into the combustion gas reacts with SOX in the gas, producing sulfides, which adhere to the surface of the catalyst and deactivate the catalyst, as described below. occurs.

If the gas temperature is too high, the injected ammonia will react with the gas in the gas and increase NOx. In any case, it is a very important requirement to keep the gas temperature 1i constant, specifically at 300° C. to 400° C., before it flows into the denitrification chamber 6 yen.

Therefore, the invention was to keep the temperature of the combustion L gas constant (600℃ ~ 4℃).
00°C), the gas temperature at the outlet of the steam generation chamber 2 (inside the gas mixing chamber 14) at the maximum load of the boiler is adjusted to within 411 degrees of 300° to 4CO°C. That is, when the load decreases and the gas temperature decreases, the temperature at that time is detected by the gas temperature sensor 19, and the opening degree of the flow rate adjustment damper 16 is adjusted according to the control signal, and the gas flows into the steam generation chamber 2. A part of the combustion gas that has been heated flows into the damper 16 without passing through the periphery of the heating evaporation tube 13, directly flows into the gas mixing chamber 14, and is mixed with the combustion gas that has passed through the circumferential surface of the heating evaporation tube 16. The combustion gases are mixed in the mixing chamber 14 and brought to a constant temperature. The combustion gas is then sent into the denitrification chamber filter, but prior to this, it is supplied with ammonia gas. Ammonia gas is efficiently diffused through the production nozzle 18, so only a small space is needed for diffusion.The reduction reaction between NOx and ammonia in the denitrification chamber filter (c) is very delicate, especially In the case of a gas containing a large amount of sulfur oxides, the sulfides adhere to the surface of the catalyst as described above, causing deactivation and blockage of the catalyst.To prevent this, ammonia is It is necessary to inject an appropriate amount necessary to reduce the ammonia gas, and to immediately stop the supply of ammonia gas when the combustion gas is at a low temperature. The temperature inside the gas mixing chamber 14 is detected by the low temperature detector 21, and when the temperature drops, the ammonia emergency shut-off valve 20 is activated by the horizontal thin signal.
is closed. The combustion gas sent into the denitrification chamber 6 comes into contact with the catalyst 17, and NOx and ammonia in the gas react to remove NOx. The Masumoto reaction between ammonia and NOx can easily occur if the conditions are met. However, the catalyst is relatively weak against thermal stress, so heat up the boiler slowly over time, and to prevent sulfide buildup, use kerosene or other fuel with low S content as fuel during heating. This is desirable. The temperature of the combustion gas flowing out from the denitrification chamber is still high.In the F air chamber 4, heat exchange occurs between the combustion exhaust gas and the air in the supply air nozzle 26, and the air supplied to the burner 10 is heated. The exhaust gas, which has been preheated and has a low temperature due to the heat energy taken away from the supply air, is released into the air through the exhaust port 22. Needless to say, it can be used to preheat feed water to a boiler.

According to the present invention, without using afterburners and other large-scale equipment, a part of the combustion gas is used as the first one and sent into the denitrification chamber, keeping the temperature of the 1J exhaust gas constant. The catalytic function can be effectively used to reduce heavy oil C,
Using low-quality fuel such as coal, it is possible to efficiently remove NOX from the combustion gas. According to the present invention, a denitrification efficiency of 95% can be easily achieved, and it is possible to reduce the quality of the fuel and is not affected by the increase in NOx caused by combustion in the cylinder, reducing NOx in the exhaust gas.
It is possible to reduce the amount of Q to a minimum, and has the effect of contributing greatly to environmental improvement.

The main specifications and actual measurements of the Fuzuki example of the present invention are shown below.

○Boiler steam amount: 10 tons/hour, steam pressure: 10 to 9/hour
era O Fuel used: C heavy oil (S component 60%) ○ Combustion temperature 1200℃, boiler (temperature inside the passageway: 1
000℃ ○Denitrification chamber temperature 1st: 350℃ ○1JC air temperature (preheating) population temperature: 650℃, exit temperature wave 100℃ ○Absorbent: ammonia gas ○Denitrification efficiency = 95% (denitrification house population 1111280 pp
rn, exit 1 rule 15ppm)

[Brief explanation of the drawing]

The drawing is a sectional view showing an embodiment of the boiler of the present invention. 1... Combustion chamber, 2... Steam generation chamber...
- Catalytic reaction chamber for denitrification (denitrification chamber) 14... Gas mixing chamber, 15... Bypass passage 16... Flow rate adjustment damper 18... Ammonia jet nozzle 19... Temperature sensor

Claims (1)

[Claims] (i) In a boiler equipped with a catalytic reaction chamber for denitrification,
A gas mixing chamber is provided on the upstream side of the catalytic reaction chamber to mix the combustion gas that has passed through the steam generation chamber that heats the fluid from the gas combustion chamber and the combustion gas that directly flows into the gas combustion chamber through the bypass passage, An ammonia gas jetting nozzle is installed between the gas mixing chamber and the denitrification catalyst reaction chamber,
The NOx removal boiler is further characterized in that the bypass passage is equipped with a flow rate adjustment damper that controls the flow area of the gas flow according to temperature changes in the gas mixing chamber.