JP2007330837A - Denitration device and denitration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a denitration device and a denitration method, wherein it is possible to stably atomize even when a required amount of a reducing agent is little, and as a result, a desired stable denitration performance is attained. <P>SOLUTION: This denitration device is provided with: a generator 1; a reducing agent injector 2 injecting a reducing agent into a passage of exhaust gas of the generator 1; a denitration reactor 3 decomposing NOx in the exhaust gas of the generator 1 using the reducing agent; a dilution water supply means 4 mixing dilution water into the reducing agent to keep the injection flow above a given flow rate, when the injection flow of the reducing agent by the reducing agent injector 2 is less than the given flow; and an exhaust gas boiler 5 recovering exhaust heat from the exhaust gas. When the injection flow of the reducing agent is less than a given flow, a controller 18 controls a mixing amount of dilution water to keep the flow of mixed liquid of urea water with dilution water constant at the given flow. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a denitration apparatus and a denitration method for reducing nitrogen oxides in exhaust gas while using ammonia water or urea water as a reducing agent. In particular, the present invention relates to a denitration apparatus and a denitration method that enable stable spraying even when the required amount of the reducing agent is small.

As disclosed in Patent Document 1 below, a reducing agent such as urea water is ejected to an exhaust gas by an injection nozzle, and the exhaust gas mixed with the reducing agent is passed through a catalytic reactor, so that nitrogen in the exhaust gas is discharged. A denitration apparatus for reducing oxides is known.
JP 2005-133628 A

  However, when the combustion equipment (engine), which is a nitrogen oxide emission source, is relatively small or has a low NOx removal rate, the required flow rate of the reducing agent is very small (for example, several ml / min). In such a case, the flow rate of the reducing agent injected by the injection nozzle becomes unstable and the denitration rate is not stable. In the first place, when the flow rate of the reducing agent was very small, stable spraying was impossible at the reducing agent injection nozzle.

  The problem to be solved by the present invention is to provide a denitration apparatus and a denitration method that can achieve stable spraying and achieve a stable desired denitration performance even if the necessary amount of the reducing agent is very small. is there.

  The present invention has been made to solve the above-mentioned problems. The invention according to claim 1 is directed to a reducing agent injector for injecting a nitrogen oxide reducing agent into exhaust gas, and the reducing agent injector using the reducing agent injector. A denitration reactor having a denitration catalyst for reducing nitrogen oxides in the exhaust gas, and diluting water to the reducing agent so that the inflow rate by the reducing agent injector is not less than a predetermined amount. A denitration apparatus comprising a dilution water supply means for supplying.

  According to the first aspect of the present invention, when the required amount of the reducing agent is less than the predetermined amount, the inflow flow rate by the reducing agent injector is not less than the predetermined amount by mixing the dilution water into the reducing agent by the dilution water supply means. Maintained. Thereby, the stable injection | pouring of the reducing agent to waste gas is possible, and the stable desired denitration performance can be achieved.

  According to a second aspect of the present invention, there is provided a reducing agent injector for injecting a nitrogen oxide reducing agent into exhaust gas, and an exhaust gas into which the reducing agent is injected by the reducing agent injector, and the nitrogen oxide in the exhaust gas. A denitration reactor having a denitration catalyst for reducing the amount, a diluting water supply means capable of mixing dilution water into the reducing agent to the ejection part of the reducing agent injector, and an injection flow rate of the reducing agent by the reducing agent injector And a control means for controlling the amount of dilution water mixed by the dilution water supply means so that the inflow rate by the reducing agent injector is not less than a predetermined value.

  According to the second aspect of the present invention, the inflow flow rate by the reducing agent injector is always maintained at a predetermined level or more by controlling the amount of dilution water mixed into the reducing agent by the control means. Thereby, the stable injection | pouring of the reducing agent to waste gas is possible, and the stable desired denitration performance can be achieved.

  Furthermore, the invention described in claim 3 is a method of reducing nitrogen oxide in exhaust gas with a denitration catalyst while injecting a reducing agent into exhaust gas, and the injection amount of the reducing agent is less than a predetermined amount. In this case, the denitration method is characterized in that the diluting water is mixed and injected so that the inflow rate by the reducing agent injector is not less than a predetermined value.

  According to the third aspect of the present invention, when the required amount of the reducing agent is less than the predetermined amount, the reducing agent injection flow rate is maintained at a predetermined level or more by mixing the reducing water with the reducing agent. Thereby, the stable injection | pouring of the reducing agent to waste gas is possible, and the stable desired denitration performance can be achieved.

  According to the denitration apparatus and the denitration method of the present invention, even if the necessary amount of the reducing agent is a very small amount, it is possible to achieve stable spraying by mixing the dilution water and ensuring the minimum flow rate, and thus the stable desired amount. Denitration performance can be achieved.

Next, an embodiment of the present invention will be described.
The denitration apparatus and denitration method of this embodiment are used to remove nitrogen oxides (hereinafter referred to as NOx) from exhaust gas. In particular, the denitration apparatus and the denitration method of the present embodiment are suitably applied to a cogeneration system including a generator having combustion equipment and an exhaust gas boiler that recovers exhaust heat of exhaust gas discharged from the combustion equipment.

  The denitration apparatus of the present embodiment includes a generator having combustion equipment, a reducing agent injector for injecting a reducing agent into exhaust gas discharged from the combustion equipment, and a denitration reactor provided on the downstream side of the reducing agent injector. With. Further, dilution water supply means for mixing dilution water into the reducing agent to the ejection part of the reducing agent injector, and the amount of dilution water mixed so as to ensure a predetermined flow rate at the ejection part of the reducing agent injector And a controller. By the way, an exhaust gas boiler for recovering exhaust heat of exhaust gas discharged from the combustion equipment can be provided on the downstream side of the denitration apparatus.

  In the present embodiment, the generator includes combustion equipment such as a gas engine, a gas turbine, and a diesel engine.

  The exhaust gas boiler may be either a steam boiler or a hot water boiler, and may be of any type and form as long as it recovers the heat of the exhaust gas discharged from the combustion equipment.

  The denitration reactor may be of any type as long as it promotes the reaction between a liquid reducing agent such as urea water or ammonia water and NOx in the exhaust gas. The installation position of the denitration reactor is in the exhaust gas passage between the combustion device and the exhaust gas boiler, in the exhaust gas passage formed in the exhaust gas boiler, and in the exhaust gas passage through which the exhaust gas discharged from the exhaust gas boiler flows. Any of them may be used. In this case, since the exhaust gas temperature varies depending on the installation position of the denitration reactor, the amount of catalyst that can be treated using the NOx decomposition catalyst suitable for the exhaust gas temperature is used.

  In addition, the reducing agent injector includes at least a nozzle serving as a jetting portion for injecting the reducing agent to the upstream side of the denitration reactor, and a reducing agent supply means for supplying the reducing agent to the nozzle. In the present embodiment, the first pump is used as the reducing agent supply means for supplying the reducing agent. Control of the amount of reducing agent injected by the reducing agent injector is performed by controlling the number of strokes of the first pump.

  The dilution water supply means mixes the dilution water into the reducing agent on the downstream side of the first pump of the reducing agent injector. Various means can be applied as the means for supplying the dilution water, but in the present embodiment, the second pump is used as the dilution water supply means.

  In the present embodiment, the nozzle, the first pump, and the second pump are not limited to those having a specific configuration.

  In the present embodiment, the reducing agent is injected from the reducing agent injector with respect to the exhaust gas discharged from the combustion device. This reducing agent reacts with NOx in the exhaust gas in the denitration reactor, and NOx is decomposed into nitrogen and water. The injection flow rate of the reducing agent is determined according to the amount of power generated by the generator, or determined according to the NOx concentration detected by the NOx sensor.

  When the injection flow rate of the reducing agent is determined according to the power generation amount of the generator, a signal of the power generation amount of the generator is input to the controller. The controller controls the injection flow rate of the reducing agent by the reducing agent injector as an injection flow rate according to the power generation amount of the generator. The injection flow rate is derived by a function generator as a function of the power generation amount, or the injection flow rate for the power generation amount is stored as a table in the memory of the controller for use.

  In addition, when the injection flow rate of the reducing agent is very small and the injection flow rate is less than the predetermined flow rate when the reducing agent is sprayed from the nozzle, the controller controls the dilution flow so that the inflow flow rate becomes a predetermined flow rate or a predetermined flow rate or higher. Diluted water is mixed into the reducing agent by the water supply means. The predetermined flow rate can be variously set according to circumstances, but in the present embodiment, the predetermined flow rate is set to a minimum flow rate that can be stably sprayed from the nozzle.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic structural view showing an embodiment of the denitration apparatus of the present invention.

  As shown in this figure, the denitration apparatus of this embodiment includes a generator 1, a reducing agent injector 2 for injecting a reducing agent into the exhaust gas passage of the generator 1, and a generator 1 using the reducing agent. When the denitration reactor 3 for decomposing NOx in the exhaust gas and the flow rate of the reducing agent injected by the reducing agent injector 2 are less than the predetermined flow rate, the diluting water is mixed into the reducing agent so that the inflow rate is equal to or higher than the predetermined flow rate. A water supply means 4 and an exhaust gas boiler 5 for recovering exhaust heat from the exhaust gas are provided in the main part.

  The generator 1 includes a gas engine 6 and a power generation unit 7 as combustion equipment. The gas engine 6 includes an intake passage 8. The gas engine 6 and the exhaust gas boiler 5 are connected by a first exhaust gas passage 9, and the exhaust gas discharged from the gas engine 6 is sent to the exhaust gas boiler 5 through the first exhaust gas passage 9. Further, the exhaust gas boiler 5 has a second exhaust gas passage 10 for releasing the exhaust gas after heat recovery to the atmosphere.

  The reducing agent injector 2 includes an injection nozzle 11 for spraying a reducing agent into the first exhaust gas passage 9, a reducing agent storage tank 13 connected to the injection nozzle 11 by a reducing agent channel 12, and a reducing agent channel 12. And a first pump 14 that supplies the reducing agent from the reducing agent storage tank 13 to the injection nozzle 11. In this embodiment, urea water is used as the reducing agent.

  In the middle of the reducing agent flow path 12, one end of the dilution water flow path 15 is connected downstream of the first pump 14. A dilution water storage tank 16 is provided at the other end of the dilution water channel 15. A second pump 17 that supplies dilution water from the dilution water storage tank 16 to the reducing agent passage 12 is provided in the middle of the dilution water passage 15.

  In the present embodiment, the first pump 14 and the second pump 17 are each an electromagnetic pump as a displacement metering pump. The first pump 14 and the second pump 17 are controlled by a controller 18.

  The denitration reactor 3 is provided in the first exhaust gas passage 9 downstream from the reducing agent injector 2. The denitration reactor 3 has a denitration catalyst and has a function of promoting the reaction between urea water and NOx in the exhaust gas temperature range of about 400 ° C. to 450 ° C. and decomposing NOx into nitrogen and water.

  In the denitration apparatus of this embodiment having such a configuration, the exhaust gas discharged from the gas engine 6 is sent to the denitration reactor 3 via the first exhaust gas passage 9. At this time, urea water is sprayed from the injection nozzle 11 of the reducing agent injector 2 into the first exhaust gas passage 9. Air is supplied to the injection nozzle 11 from a compressor (not shown), and urea water is sprayed by the action of this air. In the denitration reactor 3, urea water is used to decompose NOx in the exhaust gas into nitrogen and water. Further, the exhaust gas is sent to the exhaust gas boiler 5 through the first exhaust gas passage 9.

  In this embodiment, the urea water injection flow rate is determined according to the power generation amount of the generator 1, and the controller 18 controls based on the output signal of the engine 6. Specifically, as shown in FIG. 2, the reducing agent injection flow rate is predetermined in accordance with the output signal of the engine 6. The controller 18 operates the first pump 14 to inject urea water at a predetermined injection flow rate according to the output signal of the engine 6.

  And when the injection | pouring flow rate of a reducing agent is less than a predetermined flow rate, dilution water is mixed in a reducing agent. In this embodiment, the predetermined flow rate is set to the lowest flow rate that is stably sprayed from the injection nozzle 11.

  When the injection flow rate of the reducing agent according to the output signal of the engine 6 becomes less than the predetermined flow rate, the controller 18 operates the second pump 17 to mix the diluted water into the reducing agent. And it sprays from the injection | pouring nozzle 11 by making the flow volume of the liquid mixture of urea water and dilution water into a predetermined flow volume.

  That is, in this embodiment, when the reducing agent injection flow rate according to the output signal of the engine 6 is less than the predetermined flow rate, the inflow flow rate of the mixed solution of urea water and dilution water is constant at the predetermined flow rate. The controller 18 controls the amount of dilution water mixed in. When the reducing agent injection flow rate according to the output signal of the engine 6 is equal to or higher than the predetermined flow rate, the controller 18 stops the second pump 17 to stop the supply of the dilution water, and only the reducing agent is sprayed. .

  In this way, the controller 18 acquires the output signal of the engine 6 and determines the reducing agent injection flow rate corresponding to this output signal. Next, the controller 18 determines whether or not the determined injection flow rate is equal to or higher than the predetermined flow rate. If the determined flow rate is equal to or higher than the predetermined flow rate, the controller 18 operates the first pump 14 to inject the reducing agent at the flow rate. On the other hand, when the reducing agent injection flow rate is less than the predetermined flow rate, the first pump 14 is operated to inject the reducing agent at the determined flow rate, and the predetermined flow rate and the determined reducing agent injection flow rate The diluted water corresponding to the difference is mixed into the reducing agent by operating the second pump 17 to inject the inflow flow rate. And the controller 18 acquires the output signal of the engine 6 again, and repeats the same process.

  As described above, in this embodiment, when the injection flow rate of the reducing agent is less than the predetermined flow rate, dilution water is mixed into the reducing agent, and the inflow flow rate of the mixed liquid sprayed from the injection nozzle is set to the predetermined flow rate. Thus, it is possible to stably spray from the injection nozzle 11, and stable denitration is performed.

  The denitration apparatus and the denitration method of the present invention are not limited to the configuration of the above embodiment, and can be changed as appropriate. In the above embodiment, when the injection flow rate of the reducing agent is less than the predetermined flow rate, control is performed so that the mixing amount of the dilution water is reduced as the injection flow rate of the urea water increases, and the inflow flow rate of the mixed liquid is set to the predetermined flow rate. However, the mixture liquid may be sprayed at a predetermined flow rate or more by increasing the mixing amount of the dilution water.

It is a schematic structure figure showing one example of a denitration device of the present invention. It is a figure which shows the relationship between the electric power generation amount of an engine, and the injection flow rate of a reducing agent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generator 2 Reducing agent injector 3 Denitration reactor 4 Dilution water supply means 9 First exhaust gas passage 11 Injection nozzle 12 Reducing agent passage 15 Dilution water passage 18 Controller

Claims (3)

A reducing agent injector for injecting a nitrogen oxide reducing agent into the exhaust gas;
A denitration reactor having a denitration catalyst through which the exhaust gas into which the reducing agent is injected is passed by the reducing agent injector and reducing nitrogen oxides in the exhaust gas;
A denitration apparatus comprising: dilution water supply means for supplying dilution water to the reducing agent so that an injection flow rate by the reducing agent injector is not less than a predetermined value. A reducing agent injector for injecting a nitrogen oxide reducing agent into the exhaust gas;
A denitration reactor having a denitration catalyst through which the exhaust gas into which the reducing agent is injected is passed by the reducing agent injector and reducing nitrogen oxides in the exhaust gas;
Dilution water supply means capable of mixing dilution water into the reducing agent to the ejection part of the reducing agent injector;
Control means for controlling the amount of dilution water mixed by the dilution water supply means so that the inflow flow rate by the reducing agent injector is not less than a predetermined amount when the injection flow rate of the reducing agent by the reducing agent injector is less than a predetermined value. Denitration equipment characterized by. A method of reducing nitrogen oxides in exhaust gas with a denitration catalyst while injecting a reducing agent into the exhaust gas,
When the amount of reducing agent injected is less than a predetermined amount, the denitration method is characterized by mixing and injecting dilution water so that the flow rate of the inflow by the reducing agent injector is not less than a predetermined amount.

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