JP2003001058A - Method of operating ammonia forming apparatus and method of operating denitration apparatus in boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely form ammonia when an ammonia forming apparatus is started, to surely denitrate when a denitration apparatus is started and to prevent the effluence of ammonia from a boiler. SOLUTION: A method of operating the ammonia forming apparatus 8 for forming ammonia by heating an aqueous urea solution comprises controlling the supplying amount of the aqueous urea solution according to the operation conditions of the ammonia forming apparatus 8 mentioned above. A method of operating the denitration apparatus 7 in the boiler 1, equipped with an ammonia forming apparatus 8 for forming ammonia by heating the aqueous urea solution, an ammonia feeding means 9 provided at the outlet part of a gas passage 5 of the boiler 1 and a denitration catalyst 10 provided at the downstream side of the ammonia feeding means 9, comprises controlling the supplying amount of the aqueous urea solution to the ammonia forming apparatus 8 mentioned above, based on the operation conditions of the ammonia forming apparatus 8 and the temperature of the denitration catalyst 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating an ammonia generator and a method of operating a denitration device in a boiler.

[0002]

2. Description of the Related Art In recent years, even the boilers have been further reduced in NOx.
There is a demand for higher efficiency, and a denitration device is used as one of the countermeasures. This denitration device is configured to reduce the NOx in the exhaust gas by introducing ammonia as a reducing agent into the exhaust gas from the boiler and promoting the NOx reduction reaction by the ammonia using the denitration catalyst. .

Ammonia used in the denitration device is
It is generated by heating urea water using an ammonia generator. This ammonia generator is provided with a heating unit including a urea water flow passage and heating means. Then, in the heating section, ammonia is generated by heating the urea water flowing in the flow passage by the heating means.

In the denitration apparatus, when ammonia is added when the temperature of the denitration catalyst is low, such as when the boiler starts burning, ammonia and NO
There was a case where NO did not react with x and NOx was emitted as it was. Moreover, if ammonia and NOx do not react, there is a problem that ammonia will flow out from the boiler.

Further, in the ammonia generator, when urea water is supplied to the ammonia generator when the operating condition is not appropriate, water is evaporated from the urea water and urea is crystallized, or urea water is crystallized. The intermediate product in the process of producing ammonia from the solution remains as it is, and the flow passage is clogged. As described above, when the flow passage is clogged, ammonia cannot be generated, and thus the NOx reduction device cannot reduce NOx.

[0006]

The first problem to be solved by the present invention is to reliably generate ammonia at the time of starting the ammonia generator. A second problem is to perform reliable denitration and prevent the outflow of ammonia from the boiler when the denitration device is started.

[0007]

The present invention has been made to solve the above problems, and the invention according to claim 1 is a method for operating an ammonia generator for heating urea water to generate ammonia. The supply of urea water is controlled according to the operating condition of the ammonia generator.

Further, in the invention according to claim 2, the ammonia generator for heating the urea water to generate ammonia, the ammonia feeding means provided at the gas passage outlet of the boiler, and the downstream side of the ammonia feeding means. A method for operating a denitration device in a boiler comprising a denitration catalyst provided in, wherein the supply of urea water to the ammonia generation device is controlled based on the operating conditions of the ammonia generation device and the temperature of the denitration catalyst. It is characterized by that.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. First, a method of operating the ammonia generator according to the present invention will be described. This operation method is an operation method for solving the first problem, and is preferably carried out in an ammonia generation device for generating ammonia from urea water, particularly in an ammonia generation device used for a denitration device in a boiler or the like. You can

The ammonia generator is equipped with a heating unit for heating urea water. The heating unit is composed of a urea water flow passage and a heating means for the flow passage. An electric heater can be used as the heating means. Further, the ammonia generator includes a supply means for supplying urea water and a carrier gas for carrying ammonia generated from the urea water. Air can be used as the carrier gas. That is, the ammonia generator supplies urea water together with the carrier gas to the heating unit, and heats the urea water flowing in the flow passage together with the carrier gas to a temperature equal to or higher than a predetermined temperature by the heating means. To generate.

Now, the method of operating the ammonia generator is a method of controlling the supply of urea water according to the operating condition of the ammonia generator. That is, this operating method is an operating method in which the supply of the urea water to the ammonia generating device is started when the operating condition is in a state suitable for the production of ammonia when the ammonia generating device is started. is there.

Here, the operating status of the ammonia generator is the heating status of the heating section and the supply status of the carrier gas. First, with the heating situation of the heating unit,
This is a situation in which the heating portion is heated to a temperature equal to or higher than a predetermined temperature at which ammonia can be generated without being clogged. Therefore, the predetermined temperature is
The temperature is a temperature at which ammonia can be generated without crystallizing urea or leaving an intermediate product in the process of generating ammonia from aqueous urea as it is. And
The heating condition of the heating unit can be detected based on any one of the temperature of the flow passage, the temperature of the heating unit, and the temperature of the ammonia supply line in the ammonia generator.

The condition of supplying the carrier gas is a condition in which the carrier gas is supplied to the heating unit at a predetermined flow rate. The supply state of the carrier gas can be detected based on either the pressure in the flow passage or the flow rate of the carrier gas in the flow passage.

Therefore, in this operating method, when the ammonia generator is started, the heating portion is at the predetermined temperature or higher, and the carrier gas is supplied from the supply means at the predetermined flow rate, the urea is supplied. Start water supply. Then, since the carrier gas is supplied, urea water can be prevented from staying in the heating unit, and the urea water can be reliably supplied to the heating unit. Moreover, since the heating section is at the predetermined temperature or higher,
Ammonia can be produced without crystallizing the urea water supplied to the heating unit or generating an unnecessary intermediate product. Then, this ammonia can be supplied to the denitration device by a carrier gas.

Next, a method of operating the denitration device in the boiler using the ammonia generator will be described.
This operating method is an operating method for solving the second problem. The boiler is, for example, a multi-tube boiler, and the can body thereof forms, for example, a combustion chamber inside the annular heat transfer tube row, and forms an annular gas passage outside the annular heat transfer tube row. It is configured to connect a flue to the gas passage.

The denitration device comprises an ammonia generator,
It is composed of an ammonia charging means and a denitration catalyst. The ammonia generation device is an ammonia generation device having the same configuration as described above, and is an ammonia generation device that generates ammonia from urea water. The ammonia charging means is, for example, a jet nozzle and is provided at the outlet of the gas passage. That is, the ammonia charging means is configured to eject ammonia from the ammonia generator into the combustion gas in the gas passage. The denitration catalyst is a catalyst having a function of promoting the NOx reduction reaction by ammonia, and is provided in the flue. Therefore, in the denitration device, when the combustion gas mixed with ammonia at the outlet of the gas passage flows into the denitration catalyst as exhaust gas,
NOx is quickly decomposed into nitrogen and water by the denitration catalyst.

Now, the operating method of the denitration apparatus is an operating method of controlling the supply of urea water to the heating section based on the operating status of the ammonia generator and the temperature of the denitration catalyst. Here, the operation status of the ammonia generator is the heating status of the heating unit and the supply status of the carrier gas to the heating unit, and can be detected in the same manner as described above. The temperature of the denitration catalyst can be detected based on the temperature of the denitration catalyst itself, or can be detected based on the temperature of the exhaust gas on the downstream side or the upstream side of the denitration catalyst.

The temperature of the denitration catalyst is equal to or higher than a predetermined temperature, that is, a temperature at which the reduction reaction rate of the denitration catalyst is sufficiently increased (so-called catalyst activation temperature), and the operation condition of the ammonia generator is ammonia generation. In a state suitable for the above, the supply of urea water to the ammonia generator is started. Then, ammonia can be surely supplied from the ammonia generator to the ammonia charging means, and ammonia and NOx can be surely reacted in the denitration catalyst.
Therefore, according to this operating method, denitration can be reliably performed, and ammonia can be surely prevented from flowing out from the boiler.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a denitration device in a boiler for carrying out the present invention, and FIG. 2 is a vertical cross-sectional explanatory diagram showing an example of the configuration of the ammonia generation device of FIG. Here, in the following description, the operation method of the ammonia generation device will be described in the description of the operation method of the denitration device in the boiler.

First, a denitration device in a boiler embodying the present invention will be described with reference to FIG. In FIG. 1, the boiler 1 includes an upper pipe header (not shown) and a lower pipe header (not shown). A plurality of heat transfer tubes 2, 2, ... Are arranged between the two tube headers. Each of these heat transfer tubes 2 is formed as an annular heat transfer tube row (the reference numeral is omitted) by being arranged in an annular shape between the two tube headers. The upper end and the lower end of each heat transfer tube 2 are respectively connected to the upper header and the lower header. A burner 3 is attached to the upper part of the boiler 1, and a combustion chamber 4 is provided inside the annular heat transfer tube array. An annular gas passage 5 is provided outside the annular heat transfer tube array. Further, a flue 6 communicating with the gas passage 5 is connected to the side wall of the boiler 1.

Next, the denitration device 7 of the boiler 1 will be described. This denitration device 7 is an ammonia generation device 8
And an ammonia feeding means 9 and a denitration catalyst 10.

First, the ammonia generator 8 is means for generating ammonia by heating urea water. A urea water supply line 11 and an ammonia supply line 12 are connected to the ammonia generator 8. A first control valve 13, a urea water supply pump 14, and a urea water tank 15 are connected to the urea water supply line 11 from the ammonia generator 8 side. The ammonia supply line 12 is connected to the ammonia feeding means 9
It is connected to the.

Further, an air supply line 16 for supplying urea water and air as a carrier gas for carrying ammonia generated from the urea water is connected to the ammonia generator 8. This air supply line 16
Is provided with a second control valve 17.

The ammonia charging means 9 is a means for charging ammonia from the ammonia generator 8 to the combustion gas in the gas passage 5. A plurality of (six in this embodiment) jet nozzles 18, 1 provided at the outlet of the gas passage 5 are provided as the ammonia feeding means 9.
It is equipped with 8, ...

The denitration catalyst 10 is an N-based catalyst for ammonia.
It is a catalyst having a function of promoting the reduction reaction of Ox.
The denitration catalyst 10 is provided in the flue 6.

The detailed structure of the ammonia generator 8 will be described with reference to FIG. The ammonia generator 8 is provided with a urea water introduction part 19, a urea water flow passage 20, and a urea water heating part 21.

A urea water introducing nozzle 22 is provided in a downward direction inside the introducing portion 19, and the urea water supplying line 11 is connected to the urea water introducing nozzle 22. Further, the air supply line 16 is connected to a side surface of the introducing portion 19, and the flow passage 20 is connected to a lower portion of the introducing portion 19.

The flow passage 20 is provided with a spiral flow path (hereinafter referred to as "spiral portion") 23 in the middle thereof. The spiral portion 23 is formed by inserting the screw-shaped member 25 inside the tubular member 24. The ammonia supply line 1 is provided on the downstream side of the flow passage 20.
2 is connected.

The heating section 21 is configured to heat the urea in the spiral section 23. That is, the heating part 21 is composed of the heating means 26 provided inside the screw-shaped member 25 and the spiral part 23. The heating means 26 is an electric heater.

Next, the control configuration of the boiler 1 and the denitration device 7 will be described. First, the boiler 1 is provided with a first pressure detecting means 27. The first pressure detecting means 27 and the burner 3 have signal lines 28,
Each of them is connected to the controller 29 via 28. Then, the controller 29 controls the burner 3 based on the vapor pressure in the boiler 1 detected by the first pressure detecting means 27.

Next, in the denitration apparatus 7, the ammonia supply line 12 is provided with a first temperature detecting means 30, and the flue 6 is provided with a second temperature detection device 30 on the downstream side of the denitration catalyst 10. A temperature detecting means 31 is provided. Further, in the ammonia generator 8, a third temperature detecting means 32 is provided in the space between the spiral portion 23 and the heating means 26. Further, the air supply line 16 is provided with a second pressure detecting means 33 downstream of the second control valve 17. The detecting means 30 to 33 are connected to the controller 29 via signal lines 28, 28, ....

The urea water supply pump 14, the control valves 13, 17 and the heating means 26 are connected to the signal line 2
, 28 are connected to the controller 29, respectively. Then, the controller 29 controls the supply of the urea water to the ammonia generator 8 by controlling the first control valve 13 and the urea water supply pump 14, respectively. Further, the controller 29 controls the second control valve 17 to control the supply of air to the ammonia generator 8.

Further, based on the surface temperature of the heating means 26 detected by the third temperature detecting means 32, the controller 29 controls the surface temperature of the heating means 26 to be about 500 ° C., for example. The amount of electric power supplied to the heating means 26 is adjusted. At this time, the temperature in the heating unit 21 is set to a predetermined temperature (for example, a temperature at which urea can be produced without crystallizing urea or leaving an intermediate product in the process of producing ammonia from urea water as it is). It is in a state of being heated to 180 ° C to 450 ° C.

Next, a method of operating the denitration device 7 will be described together with the control contents of the controller 29. First, in the denitration device 7, before the boiler 1 is started, the operation of the ammonia generation device 8 is started. That is, the controller 29 controls the heating means 2
6, the second control valve 17 is opened, and the supply of air to the ammonia generator 8 is started. Then, the temperature in the heating unit 21 rises, so that the air flowing in the heating unit 21 is heated in the heating unit 21 and then flows into the ammonia supply line 12.

Then, the controller 29 activates the boiler 1 after a lapse of a predetermined time from the activation of the ammonia generator 8. Then, due to the operation of the burner 3, a gas during combustion reaction, that is, a combustion gas in a flame state is generated in the combustion chamber 4. The combustion reaction of the combustion gas in the flame state is almost completed in the combustion chamber 4, and the combustion gas flows into the gas passage 5. Then, the combustion gas flows through the gas passage 5 and then is discharged to the outside through the flue 6 as exhaust gas. Due to this exhaust gas, the temperature of the denitration catalyst 10 rises.

After the ammonia generator 8 is started, the controller 29 controls the operating condition of the ammonia generator 8 and the temperature of the denitration catalyst 10 based on the detection values from the detection means 30 to 33. Monitor.

Then, the controller 29 determines whether or not the temperature inside the heating section 21 has risen to the predetermined temperature, based on the temperature detection value from the first temperature detecting means 30. Further, the controller 29 determines whether or not a predetermined flow rate of air is being supplied to the heating section 21 based on the pressure detection value from the second pressure detection means 33. Further, the controller 29 causes the temperature of the denitration catalyst 10 to sufficiently increase the reduction reaction rate in the denitration catalyst 10 based on the temperature detection value from the second temperature detection means 31 (so-called catalyst activation temperature). To see if it has risen to.

The controller 29 controls the heating unit 2
When it is determined that the temperature inside 1 has risen to the predetermined temperature, a predetermined flow rate of air has been supplied to the heating unit 21, and the denitration catalyst 10 has risen to the catalyst activation temperature, the urea water supply pump 14 is turned on. While operating, the first control valve 13 is opened. Then, the urea water in the urea water tank 15 is supplied to the introduction part 19. The urea water is reliably conveyed by the air from the air supply line 16 to the heating unit 21 without staying in the introduction unit 19 or the flow passage 20. Since the urea water transported to the heating unit 21 is heated to the predetermined temperature or higher, ammonia can be generated in the heating unit 21 without causing clogging. Then, this ammonia is supplied to the ammonia feeding means 9 together with air through the ammonia supply line 12.

The ammonia supplied to the ammonia feeding means 9 is ejected from each of the ejection nozzles 18 and mixes with the combustion gas at the outlet of the gas passage 5. Then, the combustion gas mixed with ammonia reaches the denitration catalyst 10 as exhaust gas. Since the denitration catalyst 10 is heated to the catalyst activation temperature as described above,
Ammonia and NOx can be reliably reacted. Therefore, NOx is rapidly decomposed into nitrogen and water, and NOx in the exhaust gas is reduced. Moreover, as described above, since ammonia and NOx can be reliably reacted, it is possible to reliably prevent unreacted ammonia from flowing out of the boiler 1.

[0040]

According to the present invention, it is possible to prevent clogging and reliably generate ammonia when the ammonia generator is started. Further, according to the present invention, it is possible to perform reliable denitration at the time of starting the denitration device and to reliably prevent the outflow of ammonia from the boiler.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a denitration device in a boiler for carrying out the present invention.

FIG. 2 is a vertical cross-sectional explanatory view showing an example of the configuration of the ammonia generator of FIG.

[Explanation of symbols]

1 boiler 7 Denitration equipment 8 Ammonia generator 5 gas passages 9 Ammonia charging means 10 DeNOx catalyst

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Masuda             7 Horie-cho, Matsuyama City, Ehime Prefecture Miura Co., Ltd.             In the laboratory (72) Inventor Ishi ▲ Saki ▼ Nobuyuki             7 Horie-cho, Matsuyama City, Ehime Prefecture Miura Industrial Co., Ltd.             In the company (72) Inventor Yukihiro Isshiki             7 Horie-cho, Matsuyama City, Ehime Prefecture Miura Industrial Co., Ltd.             In the company F-term (reference) 4D002 AA12 AB01 AC01 BA06 DA07                       EA06                 4D048 AA06 AB02 AC04 DA01 DA02                       DA06 DA10 DA13

Claims (2)

[Claims] 1. A method of operating an ammonia generator 8 for heating urea water to generate ammonia, wherein the supply of urea water is controlled in accordance with the operating condition of the ammonia generator 8. Ammonia generator operating method. 2. Ammonia generator 8 for heating urea water to generate ammonia, ammonia feeding means 9 provided at the outlet of gas passage 5 of boiler 1, and denitrification provided downstream of this ammonia feeding means 9. A method for operating a denitration device 7 in a boiler 1 comprising a catalyst 10, wherein urea water is supplied to the ammonia production device 8 based on an operating condition of the ammonia production device 8 and a temperature of the denitration catalyst 10. A method for operating a denitration device in a boiler, which is characterized by controlling.