JP4352452B2 - Cogeneration system - Google Patents

Description

  The present invention relates to a cogeneration system (also referred to as a combined heat and power system) including a generator having combustion equipment and an exhaust gas boiler that recovers exhaust heat of exhaust gas discharged from the combustion equipment.

  Generally, in a cogeneration system, a reducing agent such as urea water is injected into the exhaust gas of the combustion equipment, and this reducing agent is reacted with NOx in exhaust gas on a catalytic reactor, and NOx is converted into nitrogen and water. By decomposing, NOx outflow from the exhaust gas boiler is prevented. In such a conventional cogeneration system, since the injection amount of the reducing agent is controlled using the output of the generator as a variable, the NOx concentration before denitration is affected by seasonal fluctuations, so that the reducing agent injection amount is accurate. There was a problem that it was difficult to follow the actual amount of NOx generated.

  In order to solve this problem, it has been proposed to correct the reducing agent injection amount (see Patent Document 1). This correction method is as follows. The NOx concentration during rated operation of the generator is measured, and a correction value is obtained by multiplying the difference between the measured concentration and the NOx concentration under a specific condition by a fixed constant determined by the generator. Is added to the reducing agent injection amount to correct.

JP 2003-126652 A

  The present invention relates to a further improvement of the invention described in Patent Document 1, and it is an object of the present invention to correct the injection amount of the reducing agent with high accuracy even when the NOx concentration changes due to seasonal fluctuations.

  The present invention has been made to solve the above-described problems, and the invention according to claim 1 is directed to a generator having a combustion device and an exhaust gas boiler for recovering exhaust heat of exhaust gas discharged from the combustion device. A catalytic reactor provided downstream of the combustion device, a reducing agent injector for injecting a reducing agent into the exhaust gas upstream of the catalytic reactor, a NOx concentration detecting means for detecting NOx concentration of the exhaust gas, The reducing agent injection amount is controlled by the injection amount obtained by multiplying the reducing agent injection amount determined according to the power generation amount of the generator by a correction factor a of a value that changes with respect to the NOx concentration detected by the NOx concentration detecting means. And a controller.

  According to the first aspect of the present invention, since the correction factor a is multiplied by the reducing agent injection amount as a value that changes in accordance with the NOx concentration detected by the NOx concentration detecting means, NOx that is discharged due to seasonal fluctuations. Even if the concentration changes, the reducing agent injection amount is corrected in accordance with the change in the NOx concentration.

  The invention according to claim 2 is a generator having a combustion device, an exhaust gas boiler for recovering exhaust heat of exhaust gas discharged from the combustion device, a catalytic reactor provided downstream of the combustion device, A reducing agent injector for injecting a reducing agent into the exhaust gas upstream of the catalytic reactor, an exhaust gas flow rate detecting means for detecting an exhaust gas flow rate, and an exhaust gas flow rate relative to a reducing agent injection amount determined according to the power generation amount of the generator And a controller for controlling the reducing agent injection amount to the injection amount obtained by multiplying the correction rate b of the value changing with respect to the exhaust gas flow rate detected by the detection means.

  According to the second aspect of the invention, the correction factor b is multiplied by the reducing agent injection amount as a value that changes according to the exhaust gas flow rate detected by the exhaust gas flow rate detection means. Even so, the reducing agent injection amount is corrected in accordance with the change in the NOx concentration.

  The invention described in claim 3 includes a generator having a combustion device, an exhaust gas boiler for recovering exhaust heat of exhaust gas discharged from the combustion device, a catalyst reactor provided downstream of the combustion device, and the catalyst According to the reducing agent injector for injecting the reducing agent into the exhaust gas upstream of the reactor, the NOx concentration detecting means for detecting the NOx concentration of the exhaust gas, the exhaust gas flow rate detecting means for detecting the exhaust gas flow rate, and the power generation amount of the generator The correction rate a of the value that changes according to the NOx concentration detected by the NOx concentration detection means and the value that changes with respect to the exhaust gas flow rate detected by the exhaust gas flow rate detection means And a controller for controlling the reducing agent injection amount by the injection amount multiplied by the rate b.

  According to the third aspect of the present invention, the correction rate a is a value that varies depending on the NOx concentration detected by the NOx concentration detection means, and the correction rate b varies depending on the exhaust gas flow rate detected by the exhaust gas flow rate detection means. Since both the correction factors a and b are multiplied by the reducing agent injection amount as a value, the reducing agent injection amount is corrected in accordance with changes in the NOx concentration and exhaust gas flow rate due to seasonal fluctuations.

  According to the present invention, the amount of reducing agent injected can be accurately controlled with respect to changes in NOx concentration and / or exhaust gas flow rate due to seasonal fluctuations.

(Embodiment 1)
Next, an embodiment of the present invention will be described. The embodiment of the present invention is applied to a cogeneration system including a generator having a combustion device and an exhaust gas boiler that recovers exhaust heat of exhaust gas discharged from the combustion device.

(Embodiment 1)
First, the first embodiment will be described. The first embodiment includes a generator having a combustion device, an exhaust gas boiler that recovers exhaust heat of exhaust gas discharged from the combustion device, a catalytic reactor provided on the downstream side of the combustion device, and the catalytic reaction Reducing agent injector for injecting reducing agent into the exhaust gas upstream of the reactor, NOx concentration detecting means for detecting NOx concentration in the exhaust gas upstream of the catalytic reactor, and reducing agent injection determined according to the amount of power generated by the generator And a controller for controlling the reducing agent injection amount by an injection amount obtained by multiplying the amount by a correction factor a of a value changing with respect to the NOx concentration detected by the NOx concentration detecting means.

  In the first embodiment, a reducing agent is injected from the reducing agent injector into the exhaust gas discharged from the combustion device. This reducing agent reacts with NOx in the exhaust gas in the catalytic reactor, and NOx is decomposed into nitrogen and water. The injection amount of the reducing agent is controlled by the controller based on the reducing agent injection amount determined according to the power generation amount of the generator. When the NOx concentration changes due to seasonal variation, the injection amount is corrected by multiplying by a correction rate a of a value that changes according to the NOx concentration detected by the NOx concentration detecting means.

  In the first embodiment, the generator preferably has a gas engine having a large NOx concentration change due to seasonal variation as a combustion device, but has a combustion device such as a gas turbine or a diesel engine. Can do.

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

  The catalytic reactor may be of any type as long as it promotes the reaction between a reducing agent such as urea water, ammonia and ammonium bicarbonate and NOx in the exhaust gas. The installation position of the catalytic reactor is in an exhaust gas passage between the combustion device and the exhaust gas boiler, in an exhaust gas passage formed in the exhaust gas boiler, an exhaust gas passage in which 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, a treatable amount of catalyst is used using a NOx decomposition catalyst suitable for the exhaust gas temperature.

  The reducing agent injector includes at least a nozzle for injecting the reducing agent upstream of the catalytic reactor and a pump for supplying the reducing agent to the nozzle. In this embodiment, the nozzle and the pump are not limited to a specific configuration. Control of the amount of reducing agent injected by the reducing agent injector is performed by controlling the number of strokes of the pump.

  The NOx concentration detector is not limited to a specific configuration as long as it detects the NOx concentration in the exhaust gas upstream of the catalyst reactor, and a known sensor is used.

  The controller receives a power generation amount signal from the generator and a detection signal from the NOx concentration detector, and a reducing agent injection amount G by the reducing agent injector corresponds to a power generation amount P of the generator. Control is performed based on one injection amount G1, and correction control is performed so that a second injection amount G2 = G1 × a obtained by multiplying the base value G1 by a correction factor a. The first injection amount G1 is derived by a function generator as a function of the power generation amount P, or the injection amount for the power generation amount is stored in a memory of the controller as a table and used. The correction factor a is a value that varies (is different) according to the concentration detected by the NOx concentration detector. The correction factor a is used by storing a correction value for the detected density in the controller as a table.

The correction factor a is preferably a value proportional to the ratio of the actual NOx reduction amount △ GC against plan NOx concentration reduction amount △ GP. Wherein the planning NOx reduction amount △ GP, which is a value obtained by subtracting the target NOx concentration GP0 (NOx concentration to reduce target) after the catalytic reactor pass from the NOx concentration GP1 under certain conditions (plan). Further, said actual NOx reduction amount △ GC, which is a value obtained by subtracting the target NOx concentration GP0 from the NOx concentration GC1 detected by the concentration detector. That is, the correction factor a is expressed by the following equation.

  a = ΔGC / ΔGP = (GC1-GP0) / (GP1-GP0)

  By setting the correction rate a in this way, it is possible to correct the injection amount with high accuracy in consideration of the actual NOx concentration and the target NOx concentration.

Further, when the reducing agent is urea water, the correction factor a preferably takes into account a correction factor c that takes into account the decomposition rate of urea water into ammonia estimated from the planned NOx reduction amount or the actual NOx reduction amount. Value. Specifically, the correction rate is obtained by multiplying the correction rate a by the correction coefficient c. The correction coefficient c is a coefficient for taking into account that the decomposition rate of urea water decreases as the denitration rate increases and the exhaust gas temperature decreases. The denitration rate and the exhaust gas temperature independently affect the decomposition rate. If the correction coefficient based on the denitration rate is c1, and the correction coefficient based on the exhaust gas temperature is c2, it is expressed as c = c1 × c2. When the denitration rate is equal to or higher than the predetermined value or the exhaust gas temperature is equal to or lower than the predetermined value, c is set to 1 or higher. This correction coefficient c is a value that varies with the amount of NOx removal.
A table or approximate expression is stored in the memory of the controller and used.

  As described above, according to the first embodiment, when the NOx concentration changes due to seasonal variation, the injection amount of the reducing agent is corrected in consideration of the actual NOx concentration change. As a result, highly accurate reducing agent injection amount control can be performed even if the NOx concentration changes due to seasonal fluctuations.

  The present invention is not limited to the first embodiment, and includes the following second to third embodiments.

(Embodiment 2)
The second embodiment includes a generator having a combustion device, an exhaust gas boiler that recovers exhaust heat of exhaust gas discharged from the combustion device, a catalytic reactor provided on the downstream side of the combustion device, and the catalytic reaction A reducing agent injector for injecting the reducing agent into the exhaust gas upstream of the generator, an exhaust gas flow rate detecting means for detecting the exhaust gas flow rate, and the exhaust gas flow rate detecting means for a reducing agent injection amount determined according to the power generation amount of the generator And a controller for controlling the injection amount of the reducing agent by the injection amount obtained by multiplying the correction rate b of the value changing with respect to the exhaust gas flow rate detected by the above.

  In the second embodiment, the difference from the first embodiment is that the reducing agent injection amount based on the exhaust gas flow rate by the exhaust gas flow rate detecting means is used instead of performing the reducing agent injection amount correction based on the NOx concentration by the NOx concentration detecting means. Correction is performed. Hereinafter, only portions different from those of the first embodiment will be described, but description of the same portions will be omitted.

  In the second embodiment, when the exhaust gas flow rate changes due to seasonal variations, the injection amount is corrected by multiplying the correction rate b by a value that changes with respect to the exhaust gas flow rate detected by the exhaust gas flow rate detection means. This embodiment is particularly suitable for a gas turbine having a large change in exhaust gas flow rate due to seasonal variations.

  Preferably, the exhaust gas flow rate detecting means estimates and determines an exhaust gas flow rate with respect to a power generation amount of the generator based on an intake air temperature of the generator. This is based on the fact that the exhaust gas flow rate changes due to the change in the intake air temperature. The manner of the change is obtained in advance by experiment, and this is stored in the memory of the controller in the form of an approximate expression. To use. Further, the relationship between the exhaust gas flow rate and the pressure loss can be stored and used in the form of a table.

  The exhaust gas flow rate detecting means is not limited to the one based on the intake air temperature, and can be obtained by estimating the exhaust gas flow rate with respect to the power generation amount based on the gas pressure loss (pressure loss) in the exhaust gas passage. . This is based on the fact that the pressure loss is proportional to the square of the exhaust gas flow rate. A proportionality constant is obtained in advance by experiments, and this is stored in the memory of the controller in the form of an approximate expression or table. .

  As described above, according to the second embodiment, when the exhaust gas flow rate changes due to a change in the load on the generator, the injection amount of the reducing agent is corrected in consideration of the actual change in the exhaust gas flow rate. Is called. As a result, highly accurate reducing agent injection amount control can be performed even if the exhaust gas flow rate changes due to seasonal variations.

(Embodiment 3)
The third embodiment includes a generator having a combustion device, an exhaust gas boiler for recovering exhaust heat of exhaust gas discharged from the combustion device, a catalyst reactor provided downstream of the combustion device, and the catalyst reactor A reducing agent injector for injecting a reducing agent into exhaust gas on the upstream side, NOx concentration detecting means for detecting NOx concentration in the exhaust gas upstream of the catalytic reactor, exhaust gas flow rate detecting means for detecting exhaust gas flow rate, and the generator With respect to the reducing agent injection amount determined according to the power generation amount, the correction rate a of a value that changes with respect to the NOx concentration detected by the NOx concentration detection means and the exhaust gas flow rate detected by the exhaust gas flow rate detection means And a controller for controlling the reducing agent injection amount by an injection amount obtained by multiplying the correction value b of the changing value.

  In the third embodiment, the difference from the first embodiment is that the exhaust gas flow rate by the exhaust gas flow rate detection means of the second embodiment in addition to the reducing agent injection amount correction based on the NOx concentration by the NOx concentration detection means. Is performed to correct the reducing agent injection amount. Hereinafter, only parts different from the first embodiment and the second embodiment will be described.

  In the third embodiment, when the NOx concentration changes due to seasonal fluctuations and the exhaust gas flow rate changes, the reducing agent injection amount is a correction rate a of a value that changes depending on the NOx concentration detected by the NOx concentration detecting means. And an injection amount obtained by multiplying the correction rate b of a value that varies depending on the exhaust gas flow rate detected by the exhaust gas flow rate detection means.

  As described above, according to the third embodiment, when the NOx concentration and the exhaust gas flow rate change due to seasonal variation, the injection amount of the reducing agent is corrected in consideration of the actual NOx concentration and the exhaust gas flow rate change. . As a result, even when the NOx concentration and the exhaust gas flow rate change due to seasonal fluctuations, it is possible to perform the reducing agent injection amount control with high accuracy.

  Further, the first, second, and third embodiments include the following denitration method embodiments 4, 5, and 6, respectively.

(Embodiment 4)
The fourth embodiment is a denitration method realized by the first embodiment, in which a reducing agent is injected into the exhaust gas discharged from the combustion equipment of the generator, and NOx in the exhaust gas is decomposed by the denitration reactor. In the exhaust gas denitration method of the cogeneration system, the reducing agent injection amount determined according to the power generation amount of the generator is multiplied by a correction factor a of a value that changes with respect to the exhaust gas NOx concentration upstream of the denitration reactor. It is characterized in that the reducing agent injection amount is controlled to the injected amount.

(Embodiment 5)
The fifth embodiment is a denitration method realized by the second embodiment, in which a reducing agent is injected into the exhaust gas discharged from the combustion equipment of the generator, and NOx in the exhaust gas is decomposed by the denitration reactor. In the exhaust gas denitration method of the cogeneration system, the reducing agent injection amount is set to the injection amount obtained by multiplying the reducing agent injection amount determined according to the power generation amount of the generator by a correction factor b of a value that varies with the exhaust gas flow rate. It is characterized by control.

(Embodiment 6)
The sixth embodiment is a denitration method realized by the third embodiment, in which a reducing agent is injected into the exhaust gas discharged from the combustion equipment of the generator, and NOx in the exhaust gas is decomposed by the denitration reactor. In the exhaust gas denitration method of the cogeneration system, the correction factor a and the exhaust gas of the value changing with respect to the exhaust gas NOx concentration upstream of the denitration reactor with respect to the reducing agent injection amount determined according to the power generation amount of the generator It is characterized in that the injection amount of the reducing agent is controlled by the injection amount obtained by multiplying the correction rate b of the value changing with respect to the flow rate.

  A specific example 1 of the present invention corresponding to the first embodiment will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the first embodiment, and FIG. 2 is an electrical block circuit diagram of the first embodiment.

The first embodiment is a cogeneration system, and the main components are a generator 1,
An exhaust gas boiler 2 that recovers exhaust heat from the exhaust gas of the generator 1, a catalytic reactor 3 that decomposes NOx in the exhaust gas using urea water as a reducing agent, and a reducing agent injector 4 that injects urea water.

  The generator 1 includes a gas engine 5 and a power generation unit 6 as combustion equipment. The gas engine 5 includes an intake passage 7.

  The catalytic reactor 3 is provided in a first exhaust gas passage 8 between the gas engine 5 and the exhaust gas boiler 2. The catalytic reactor 3 has a function of promoting the reaction of urea water and NOx and decomposing NOx into nitrogen and water in an exhaust gas temperature range of about 400 ° C. to 450 ° C.

  The reducing agent injector 4 is connected to the injection nozzle 9 via the reducing agent flow path 10 and is a capacity metering pump that supplies the injection nozzle 9 from a reducing agent storage tank (not shown). The electromagnetic pump 11 is provided.

  The exhaust gas boiler 2 has a second exhaust gas passage 12 for releasing the exhaust gas after heat recovery to the atmosphere.

The pump 11 is controlled by a controller 13. The controller 13 generates the detected concentration signal GC1 of the NOx concentration sensor 14 as the NOx concentration detection means of the exhaust gas in the first exhaust gas passage 8 upstream of the catalyst reactor 3 and the power generation amount signal P of the generator 1. The pump 11 is controlled so that the second injection amount G2 of the reducing agent represented by the following equation is obtained.
G2 = G1 × a ………………… Formula 1
However, a = ΔGC / ΔGP = (GC1-GP0) / (GP1-GP0)
ΔGP: Planned NOx concentration reduction amount, ΔGC: Actual NOx reduction amount GP1: NOx concentration under specific conditions, GP0: Target NOx concentration GC1: NOx concentration detected by NOx concentration sensor 14

  The control of the reducing agent injection amount by the controller 13 is realized by the processing block diagram of FIG. In FIG. 2, the power generation amount signal P of the generator 1 is input to the ratio calculation circuit 15 to generate a first injection amount signal G1 that changes in accordance with the power generation amount P. The power generation amount signal P is also input to the function generation circuit 16 to generate the NOx concentration signal GP1 under the specific condition.

  On the other hand, the NOx concentration signal GC1 detected by the NOx concentration sensor 14 is input to the subtraction circuit 17, and the signal of ΔGC is output. The signal ΔGC is input to the first correction factor calculation circuit 18 where the correction factor a is generated and input to the multiplication circuit 19. The multiplication circuit 19 calculates G1 × a and outputs a second injection amount signal G2 of reducing agent for controlling the pump 11. The second injection amount signal G2 is transmitted to a pump control unit (not shown) constituting a part of the controller 13, and controls the injection amount by the pump 11.

  Next, the operation of the first embodiment having the above configuration will be described. The concentration of NOx discharged from the combustion device 5 changes due to seasonal variation. The change does not change so that the difference from the GC1 becomes uniform (a constant value) with respect to the load of the generator 1, that is, the change in the power generation amount P.

  When the NOx concentration changes in this way, the change is grasped as ΔGC, and is output from the first correction factor calculation circuit 18 as a = ΔGC / ΔGP. In addition, since the correction factor a is corrected by multiplying G1, there is an effect that it is corrected by acting in the same manner on the load change range of the generator 1.

  A specific example 2 of the present invention corresponding to the third embodiment will be described below in detail with reference to the drawings. FIG. 3 is a schematic configuration diagram of the second embodiment, and FIG. 4 is an electrical block circuit diagram of the second embodiment.

  In the second embodiment, only the configuration different from that of the first embodiment will be described, and the same components are denoted by the same reference numerals and omitted.

  The second embodiment is different from the first embodiment in that an exhaust gas flow rate detecting means is provided, and the reducing agent injection amount G is corrected using the correction rate a and the correction rate b based on the detected exhaust gas flow rate F. . Specifically, the second injection amount G2 is set to G1 × a × b. The correction factor b is as described in the second embodiment.

  Specifically, the different portions will be described. In FIG. 3, the temperature sensor 20 constituting a part of the exhaust gas flow rate detection means detects the intake air temperature in the intake passage 7 of the combustion device 5 or before the inflow. Provided.

  In FIG. 4, a second correction factor calculation circuit 21 for calculating the correction factor b is provided, and the multiplication circuit 19 is configured to multiply the signal G1 by the correction factor a and the correction factor b.

  The operation of the second embodiment having the above configuration will be described. The NOx concentration and the exhaust gas flow rate discharged from the combustion device 5 change due to seasonal fluctuations. This NOx concentration change does not change uniformly (so that it becomes a constant value) with respect to the GC1 with respect to the load of the generator 1, that is, the change in the power generation amount P.

  When the NOx concentration changes in this way, the change is grasped as ΔGC, and is output from the first correction factor calculation circuit 18 as a = ΔGC / ΔGP. Further, when the exhaust gas flow rate changes, the change is grasped as a change of b and is output from the second correction factor calculation circuit 21. In addition, since the correction factors a and b are corrected by multiplying G1, there is an effect of being corrected by acting similarly on the load change range of the generator 1.

It is explanatory drawing which shows schematic structure of Example 1 of this invention. It is explanatory drawing which shows the block-like circuit structure of the Example 1. FIG. It is explanatory drawing which shows schematic structure of Example 2 of this invention. It is explanatory drawing which shows the block-like circuit structure of the Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generator 2 Exhaust gas boiler 3 Denitration reactor 4 Reductant injector 5 Combustion equipment 14 NOx concentration sensor 20 Temperature sensor

Claims (3)

  A generator 1 having a combustion device 5, an exhaust gas boiler 2 for recovering exhaust heat of exhaust gas discharged from the combustion device 5, a catalyst reactor 3 provided on the downstream side of the combustion device 5, and the catalyst reactor 3 For the reducing agent injector 4 for injecting the reducing agent into the exhaust gas on the upstream side, the NOx concentration detecting means 14 for detecting the NOx concentration of the exhaust gas, and the reducing agent injection amount determined according to the power generation amount of the generator 1, A cogeneration system comprising: a controller 13 for controlling a reducing agent injection amount by an injection amount obtained by multiplying a correction factor a of a value that changes with respect to the NOx concentration detected by the NOx concentration detecting means 14.   A generator 1 having a combustion device 5, an exhaust gas boiler 2 for recovering exhaust heat of exhaust gas discharged from the combustion device 5, a catalyst reactor 3 provided on the downstream side of the combustion device 5, and the catalyst reactor 3 The reducing agent injector 4 for injecting the reducing agent into the exhaust gas on the upstream side, the exhaust gas flow rate detecting means 20 for detecting the exhaust gas flow rate, and the reducing agent injection amount determined according to the power generation amount of the generator 1, the exhaust gas A cogeneration system comprising a controller 13 for controlling the amount of reducing agent injected to the amount of injection multiplied by a correction factor b of a value that changes with respect to the exhaust gas flow rate detected by the flow rate detection means 20. A generator 1 having a combustion device 5, an exhaust gas boiler 2 for recovering exhaust heat of exhaust gas discharged from the combustion device 5, a catalyst reactor 3 provided on the downstream side of the combustion device 5, and the catalyst reactor 3 The reducing agent injector 4 for injecting the reducing agent into the exhaust gas on the upstream side, the NOx concentration detecting means 14 for detecting the NOx concentration of the exhaust gas, the exhaust gas flow rate detecting means 20 for detecting the exhaust gas flow rate, and the power generation amount of the generator 1 For the reducing agent injection amount determined according to the above, the correction rate a of a value that changes with respect to the NOx concentration detected by the NOx concentration detecting means 14 and the exhaust gas flow rate detected by the exhaust gas flow rate detecting means 20 change. A cogeneration system comprising: a controller 13 for controlling the injection amount of the reducing agent by the injection amount obtained by multiplying the correction rate b of the value to be corrected.

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