JP2012180765A - Exhaust emission control device of gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a thermal efficiency of an engine and an exhaust gas cleaning performance by efficiently adsorbing a methane component discharged as an unburnt component and recirculating to the engine in the gas engine using fuel gas containing methane as a principal ingredient.SOLUTION: The exhaust emission control device of the gas engine using the fuel gas containing methane as the principal ingredient is provided with a main exhaust gas passage 11, a bypass exhaust gas passage 15, a branch control valve 17, a methane adsorption catalysts 21, 23, an exhaust gas cooling means 19 for cooling to an exhaust gas temperature suitable for methane adsorption, a discharge gas heating means 29 for heating up to a temperature suitable for methane desorption, an inlet side control valve 37, a circulation passage 33, an outlet side control valve 39 and a controller 41 for controlling the exhaust gas cooling means 19, a discharge gas heating means 29, the inlet side control valve 37, the discharge side control valve 39 and the branch control valve 17 to switch the adsorption and desorption of a first system methane adsorption catalyst 21 and a second system methane adsorption catalyst 23 to and from each other.

Description

  The present invention relates to an exhaust gas purification apparatus for a gas engine, and more particularly to an exhaust gas purification apparatus for a gas engine that uses a fuel gas containing methane as a main component.

  In recent years, gas pumps that use natural gas (city gas) and coal mine methane generated from coal mines as the main component, and a gas engine that uses fuel as a fuel, have a power generation system and a heat pump system that performs cooling and heating. Due to its nature, it is spreading rapidly.

  In general, the premixed gas of fuel and air introduced into the combustion chamber does not completely burn out in the combustion chamber, but the cylinder ceiling in the combustion chamber, the wall surface of the cylinder liner, the vicinity of the piston ring, and the air supply port In addition, unburned gas remains as residual gas in the exhaust port and is discharged as unburned components without burning.

  On the other hand, as a technique for reducing discharge of unburned components to the atmosphere, a technique for adsorbing with an adsorbent and a technique for using an oxidation catalyst as a post-treatment are known. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-227635) is known. In the publication, an exhaust passage switching device that switches an exhaust gas passage to one of a main exhaust passage and a bypass passage, and an unburned component in exhaust gas that is disposed in the main exhaust passage and led to the main exhaust passage are adsorbed. In addition, the HC adsorbent for desorbing the adsorbed unburned components and the exhaust gas flow path are switched to the main exhaust passage when the unburned components in the exhaust gas are adsorbed to the HC adsorbent, and adsorbed from the HC adsorbent. Switch to bypass exhaust passage when unburned components are desorbed, and switch to main exhaust passage when unburned components are removed from the HC adsorbent. Configuration comprising a control means for controlling the road switching device, a is shown.

JP 2002-227635 A

However, the technique described in Patent Document 1 is once adsorbed to the HC adsorbent as described above, and the adsorbed HC is desorbed when the adsorbent is at a high temperature and recirculated to the engine via the EGR pipe. The engine is supposed to be burned.
For this reason, while the HC adsorbent is performing the desorption operation, the HC adsorbent does not have an adsorption function, and the exhaust gas is exhausted through the bypass exhaust passage, and also during the adsorption operation. Since the desorption operation cannot be performed, the HC component adsorbed by the HC adsorbent is not recirculated to the engine.

  Therefore, in view of the above problems, the present invention is a gas engine using a fuel gas containing methane as a main component, and efficiently adsorbs the methane component discharged as an unburned component and recirculates it to the engine. The purpose is to improve thermal efficiency and exhaust gas purification performance.

  Accordingly, the present invention has been made to solve such a problem. The present invention relates to a main exhaust gas connected to the gas engine in an exhaust gas purification apparatus for a gas engine using a fuel gas containing methane as a main component. A bypass exhaust gas passage that branches off from the main exhaust gas passage and rejoins the main exhaust gas passage, a branch control valve that controls the flow of exhaust gas from the main exhaust gas passage to the bypass exhaust gas passage, and the bypass exhaust gas passage A plurality of methane adsorption catalysts arranged in parallel to adsorb methane components in the exhaust gas, exhaust gas cooling means for cooling the exhaust gas flowing into the methane adsorption catalyst to an exhaust gas temperature suitable for adsorption of the methane components, and passing through the methane adsorption catalyst The release gas for desorbing the methane component adsorbed on the methane adsorption catalyst is heated to a temperature suitable for desorption. The discharge gas heating means and the plurality of methane adsorption catalysts are composed of two systems, and an inlet side control valve for switching between inflow and shutoff of exhaust gas to the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst A circulation passage for circulating the gas discharged from the outlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst to the supply air passage of the engine, and the first system methane adsorption catalyst and the second system An outlet-side control valve for switching the gas discharged from each outlet of the methane adsorption catalyst of the system to the bypass exhaust gas passage or the circulation passage, and the exhaust gas cooling means, the discharge gas heating means, the inlet The side control valve, the outlet side control valve, and the branch control valve to adsorb and desorb the methane adsorption catalyst of the first system and the methane adsorption catalyst of the second system. A controller changing, characterized by comprising a.

  According to this invention, the exhaust gas containing unburned fuel methane is passed through one (first system) of a plurality of methane adsorption catalysts (for example, zeolite) consisting of two systems to adsorb and collect the methane component. In order to increase the methane adsorption capacity during this adsorption, it is necessary to control the exhaust gas temperature to be low (in the case of zeolite, 100 ° C. or lower), and for that purpose, control is performed using exhaust gas cooling means.

In the other (second system) methane adsorption catalyst, methane is desorbed when methane has been adsorbed. In order to improve the methane desorption property during the desorption, it is necessary to control the emission gas temperature to be high (400 ° C. or more in the case of zeolite). For this purpose, the emission gas heating means is used for control.
Thus, the adsorption to the methane adsorption catalyst (for example, zeolite) and the desorption from the methane adsorption catalyst can be effectively performed using the exhaust gas cooling means and the emission gas heating means.

The methane component desorbed and released into the circulation passage is returned to the engine air supply passage and used as fuel.
Therefore, the thermal efficiency of the gas engine can be improved by utilizing the unburned component methane that has been discharged without combustion in the past, and the exhaust gas purification function can also be obtained by the effect of reducing the unburned component emission amount.

In the present invention, the exhaust gas cooling means and the exhaust gas heating means are preferably configured as follows.
(1) The exhaust gas cooling means is constituted by an exhaust gas cooler that cools the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst. It is good to comprise by the air supply pressurized by the compressor of a feeder, and the heater means provided in the methane adsorption catalyst of the 1st system, and the methane adsorption catalyst of the 2nd system.

  Thus, since the temperature of the exhaust gas flowing into the methane adsorption catalyst is controlled by the exhaust gas cooler, the exhaust gas temperature suitable for adsorption can be reliably controlled. In addition, because the desorption gas used for the desorption is pressurized by the turbocharger compressor, it burns like EGR (exhaust gas recirculation device) even if the desorbed methane gas is returned to the engine air supply passage. Since the temperature does not decrease, methane gas can be recirculated even in an engine not equipped with EGR. Further, since the temperature of the exhaust gas flowing into the methane adsorption catalyst into the heater means is controlled, the exhaust gas temperature suitable for desorption can be reliably controlled.

(2) The exhaust gas cooling means supplies the exhaust gas flowing into the respective inlets of the methane adsorption catalyst of the first system and the methane adsorption catalyst of the second system to the supply gas cooled by the supply air cooler provided in the supply air passage. The emission gas heating means is constituted by introducing exhaust gas from the engine outlet to respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst. Good.

In this way, exhaust gas cooler that cools the exhaust gas is not required because the exhaust gas temperature is lowered by using the supply air cooled by the supply air cooler so that the temperature becomes suitable for adsorption, and the system is simplified. The
Further, since the exhaust gas heating means also guides high-temperature exhaust gas discharged from the engine outlet, an apparatus such as a heater means becomes unnecessary, and the system is simplified. Further, since the methane is desorbed from the methane adsorption catalyst using the exhaust gas and recirculated to the supply passage, the exhaust gas also returns to the supply passage, so that an EGR function is obtained and an NOx reduction effect due to a decrease in the combustion temperature is obtained.

(3) The exhaust gas cooling means supplies the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst into a supply air cooled by an air supply cooler provided in an air supply passage. The discharge gas heating means is a heater provided in the supply air pressurized by the compressor of the supercharger, the first system methane adsorption catalyst and the second system methane adsorption catalyst. And means.

  According to such a configuration, since the supply air cooler is used as described above, the exhaust gas cooler for cooling the exhaust gas is not required, and the system is simplified. Moreover, since the emission gas heating means is provided with a heater means, temperature adjustment is facilitated.

(4) The exhaust gas cooling means is constituted by an exhaust gas cooler that cools the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst. The exhaust gas from the engine outlet may be guided to the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst.

Thus, since the temperature of the exhaust gas flowing into the methane adsorption catalyst by the exhaust gas cooler is controlled, the exhaust gas temperature suitable for adsorption can be reliably controlled.
Further, since it is not necessary to provide a heater means as a discharge gas heating means, the system is simplified. Furthermore, the EGR function can be obtained as described above.

  In the present invention, preferably, the circulation passage is returned to the upstream side of the compressor of the supercharger provided in the air supply passage. When the circulation passage is returned to the upstream side of the compressor of the supercharger in this way, the supply side Since the pressure is lower than that on the exhaust side, a circulation flow to the supply passage is likely to occur. The circulation passage may be returned to the upstream side of the supply air cooler provided on the downstream side of the compressor of the supercharger provided in the supply air passage, and thus returned to the upstream side of the supply air cooler. Therefore, it is possible to cool the circulating flow by using the air supply cooler, so that it is not necessary to provide a cooler in the circulation passage, and the system can be simplified.

In the present invention, it is preferable that the control device includes a methane adsorption limit determination unit that determines a methane adsorption limit based on a time when exhaust gas having a temperature suitable for adsorbing a methane component passes through the methane adsorption catalyst. It is good to have.
Thus, by determining that the adsorption limit of the zeolite as the methane adsorption catalyst has been reached based on the time (operation time) that has passed through the target catalyst, the adsorption limit of the target catalyst can be accurately determined. At this time, the influence of the engine load and the influence of the methane concentration may be determined by weighting.

In the present invention, it is preferable that the control device includes a methane desorption completion determination unit that determines completion of methane emission based on a time when a release gas having a temperature suitable for desorption of a methane component passes through the methane adsorption catalyst. It is good to have.
Thus, by determining based on the time (operation time) that has passed through the methane adsorption catalyst, it is possible to accurately determine the end of desorption of the target catalyst. At this time, the influence of the passing exhaust gas temperature may be weighted for determination.

In the present invention, it is preferable that the gas engine is an engine for power generation, and the control device cuts off the flow of exhaust gas to the bypass exhaust gas passage until a rated rotational speed of a predetermined rotational speed is reached after starting. .
In this way, in the gas engine for generators, the flow of exhaust gas from the main exhaust gas passage to the bypass exhaust gas passage is blocked by the branch control valve until the rated operation at a fixed rotation speed is reached from the start, and the methane adsorption catalyst An increase in exhaust pressure can be prevented to improve startability and ensure stability during low-speed operation.

  According to the present invention, exhaust gas containing unburned fuel methane discharged from a gas engine is passed through one system of two methane adsorption catalysts (zeolites) to adsorb and collect methane components. In the other methane adsorption catalyst, methane is desorbed when methane has been adsorbed. In this way, adsorption and desorption are switched using the two systems of methane adsorption catalyst, and the released methane component is returned again to the engine air supply passage and used as fuel. This makes it possible to improve the thermal efficiency of the gas engine by utilizing unburned component methane that has been discharged without combustion in the past, and to reduce the amount of unburned component emission, and to improve the exhaust gas purification function.

1 is an overall configuration diagram of an exhaust gas purifying apparatus for a gas engine showing a first embodiment of the present invention. The control flowchart at the time of methane adsorption | suction of 1st Embodiment is shown. The control flowchart at the time of methane desorption of 1st Embodiment is shown. It is explanatory drawing which shows opening and closing of the gas valve at the time of the 1st methane adsorption catalyst in 1st Embodiment adsorb | sucking, and the 2nd methane adsorption catalyst desorption. It is a whole block diagram of the exhaust gas purification apparatus of the gas engine which shows 2nd Embodiment. The control flowchart at the time of methane adsorption | suction of 2nd Embodiment is shown. The control flowchart at the time of methane desorption of 2nd Embodiment is shown. It is a whole block diagram of the exhaust gas purification apparatus of the gas engine which shows 3rd Embodiment. It is a whole block diagram of the exhaust gas purification apparatus of the gas engine which shows 4th Embodiment. It is a whole block diagram of the exhaust gas purification apparatus of the gas engine which shows 5th Embodiment. It is a whole block diagram of the exhaust gas purification apparatus of the gas engine which shows 6th Embodiment.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specifically described. Only.

(First embodiment)
With reference to FIG. 1, the overall configuration of the exhaust gas purification apparatus for a gas engine according to the first embodiment of the present invention will be described. In the figure, a gas engine 1 is an engine for a generator, and a generator 3 to be directly connected is attached to the engine 1.

As fuel gas, fuel gas mainly composed of methane such as natural gas (city gas), coal mine methane gas generated from the coal mine, or biogas such as landfill gas is flowed from the supply passage 5. It is like that.
The air supply passage 5 is provided with a supercharger 7 including an exhaust turbine 7a and a compressor 7b, and supplies an air supply gas to an air supply inlet of each combustion chamber. An air supply cooler 9 is provided on the downstream side of the compressor 7 b of the supercharger 7.

  A main exhaust gas passage 11 is connected to the exhaust outlet of the engine 1, an exhaust turbine 7 a of the supercharger 7 is provided, and an exhaust heat recovery device 13 is installed downstream thereof. This exhaust heat recovery device 13 uses exhaust heat to generate and use steam and the like. A bypass exhaust gas passage 15 branched from the main exhaust gas passage 11 and joined again to the main exhaust gas passage 11 is provided on the downstream side of the exhaust heat recovery device 13. Further, a branch control valve 17 that controls the flow of exhaust gas from the main exhaust gas passage 11 to the bypass exhaust gas passage 15 is provided.

  In the bypass exhaust gas passage 15, an exhaust gas cooler (exhaust gas cooling means) 19, a first methane adsorption catalyst (first system methane adsorption catalyst) 21 that adsorbs methane components in the exhaust gas in parallel downstream thereof, and a second A methane adsorption catalyst (second system methane adsorption catalyst) 23 is provided. In each of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, moisture removal catalysts 25 and 27 for removing moisture in the exhaust gas and facilitating adsorption of methane components are respectively adjacent to the upstream side. Is provided.

The first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 are each provided with a heater 29 for heating the adsorption catalyst.
The first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 are not limited to two adsorption catalysts, and a plurality of adsorption catalysts may be provided to be divided into two systems and used as one region and the other region.

  In addition, the first emission gas connected to the compressor 7b outlet of the supercharger 7 is connected to the inlet of each of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 so as to join and mix with the bypass exhaust gas passage 15. A passage 31 is provided, and the high-temperature supply air pressurized by the compressor 7b is guided as a discharge gas when desorbing methane adsorbed on the methane adsorption catalyst. The heater 29 and the first discharge gas passage 31 constitute discharge gas heating means.

The first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 are made of, for example, zeolite, and those of Na-A type zeolite (pore diameter 4 mm) and Na-X type zeolite (pore diameter 3.8 mm) are suitable.
The water removal catalysts 25 and 27 are also made of, for example, zeolite, and KA type zeolite (pore diameter 3 mm) and silica gel (pore diameter 2.8 mm) are suitable.
In addition to zeolite, there are molecular sieve carbon, mesoporous silicate and the like as methane adsorption catalysts.

  The adsorption performance of the methane component is enhanced in the temperature range where the exhaust gas temperature is lower than about 100 ° C., and the desorption property is enhanced in the temperature range higher than about 400 ° C. during desorption. For this reason, cooling control is performed with a target of about 100 ° C. when the exhaust gas temperature flowing into the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 is adsorbed. In order to lower the temperature further than 100 ° C, it is necessary to improve the performance of the cooler, and there are problems such as an increase in cost and an increase in the size of the system. .

  In addition, the heating temperature of the released gas at the time of desorption of the methane component is also set to about 400 ° C. for the purpose of increasing the cost accompanying the increase in the capacity of the heater 29 and increasing the size of the system. The gas temperature is controlled.

The respective outlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 are connected to a circulation passage 33 for circulating the released gas to the supply passage 5 of the gas engine 1 and a return side of the bypass exhaust gas passage 15. . The circulation passage 33 is provided with a reflux cooler 35 for cooling the circulation flow.
In the first embodiment, the circulation passage 33 is returned to the upstream side of the compressor 7b of the supercharger 7, and by returning to the upstream side of the compressor 7b in this way, the upstream side of the compressor 7b is in a lower pressure state than the downstream side. Therefore, a circulation flow to the supply passage 5 is likely to occur.

  An inlet-side control valve 37 is provided for switching between inflow and shutoff of exhaust gas to the respective inlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, or switching inflow and shutoff of released gas at the time of desorption of methane components. . As shown in FIG. 1, the inlet side control valve 37 includes gas valves VC11, VC12, VC21, and VC22.

  Further, the exhaust gas from the respective outlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 flows out and shuts down to the bypass exhaust gas passage 15, or the effluent gas flows out to the circulation passage 33 when the methane component is desorbed. An outlet-side control valve 39 that switches between shut-off is provided. As shown in FIG. 1, the outlet side control valve 39 includes gas valves VC13, VC14, VC23, and VC24.

Next, the control device 41 that performs opening / closing control of the inlet side control valve 37 and the outlet side control valve 39 will be described.
The supply air temperature T _a1 from the supply air temperature sensor 43 that detects the supply air temperature at the supply air inlet portion of the gas engine 1, the supply air pressure P _a1 from the supply air pressure sensor 45 that detects the supply air pressure, the first methane The first inlet temperature T ₁₁ from the first inlet temperature sensor 47 that detects the gas temperature flowing into the adsorption catalyst 21, and the second inlet from the second inlet temperature sensor 49 that detects the gas temperature flowing into the second methane adsorption catalyst 23. Inlet temperature T ₂₁ , outlet gas temperature T ₃ from outlet temperature sensor 51 that detects the gas temperature flowing out from first methane adsorption catalyst 21 and second methane adsorption catalyst 23, and methane concentration in exhaust gas flowing into both methane adsorption catalysts detecting the exhaust Gasumetan discharge Gasumetan concentration C ₁ from the density sensor _53, the desorption of methane from the released Gasumetan concentration sensor 55 for detecting the methane concentration in the gas after desorption Signal of the scan concentration C ₂ are input.

  Further, the control device 41 mainly includes an exhaust gas cooling control means 57 that controls exhaust gas at a temperature suitable for adsorbing methane components, and methane that determines a methane adsorption limit based on the time that has passed through the methane adsorption catalyst. Based on the adsorption limit determination means 59, the emission gas heating control means 61 for controlling the emission gas at a temperature suitable for desorbing the methane component, and the time when the emission gas at the time of desorption of the methane component passes through the methane adsorption catalyst. Methane desorption completion judging means 63 for judging completion of methane emission.

Further, based on the desorbed methane gas concentration C ₂ of the desorbed methane gas circulated to the supply passage 5 side, the fuel amount of the gas engine 1 is corrected and controlled, that is, the supply gas amount by the amount of gas corresponding to the circulated methane gas concentration C _2. Therefore, the fuel control means 65 for correcting the amount of fuel to control the amount of fuel to the gas engine 1 is provided.

The control device 41 is based on the detection signals from the sensors, the branch control valve 17, the gas valves VC11, VC12, VC21, VC22 of the inlet side control valve 37, and the gas valves VC13, VC14 of the outlet side control valve 39, While controlling opening and closing of VC23 and VC24, the amount of gas fuel is controlled.
In a predetermined time after starting, or in a predetermined low engine speed range or low load range, the branch control valve 17 is controlled to flow to the bypass exhaust gas passage 15 side in order to avoid unstable operation due to an increase in exhaust pressure loss. After starting, the adsorption and desorption control by the methane adsorption catalyst is performed after reaching the stable operation region of constant rotation.

Control during methane adsorption will be described with reference to the flowchart of FIG.
In step S1, the methane adsorption catalyst for performing the adsorption operation is selected from the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, and the opening / closing control of the gas valve is performed according to the selected catalyst. As shown in FIG. 4, when the first methane adsorption catalyst 21 is selected as the adsorption catalyst, the gas valve shown in FIG. 4A is opened and closed. When the second methane adsorption catalyst 23 is selected as the adsorption catalyst, the gas valve shown in FIG. 4B is opened and closed. As shown in FIGS. 4A and 4B, the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 are controlled so as to alternately switch between adsorption and desorption.

In step S2, the temperature of the exhaust gas flowing into the selected methane adsorption catalyst is detected by the first inlet temperature sensor 47 or the second inlet temperature sensor 49. Then, in step S3, it determines second inlet temperature T ₂₁ of the exhaust gas flowing into the first inlet temperature T ₁₁ or the second methane adsorption catalyst 23 of the exhaust gas flowing into the first methane adsorption catalyst 21 whether substantially 100 ° C. To do. In the case of NO, the amount of cooling water in the exhaust gas cooler 19 is adjusted in step S4 so as to be approximately 100 ° C.

Next, in step S5, the adsorption operation time of the target methane adsorption catalyst is integrated. That is, the cumulative passage time when the exhaust gas temperature is approximately 100 ° C. is calculated. In step S6, it is determined by comparing whether or not the integrated value has reached a preset limit time. If it has reached, it becomes NO, the methane adsorption catalyst is switched to another catalyst in step S7, another adsorption catalyst is selected in step 1, and the same procedure as described above is repeated.
At the same time, in step S8, the operation of releasing methane from the target methane adsorption catalyst that has reached the limit is performed. This discharge operation will be described later.

  On the other hand, if it is before the limit time in step S6, the adsorption operation is continued with the target methane adsorption catalyst in step S9, and the process returns to step 1 to continue the adsorption.

  In the integration of the operation time of the target catalyst in step S5, the influence of the engine load is weighted rather than the mere operation time, and when the load is large, the amount of fuel increases, and a large amount of unburned methane components are discharged accordingly. By calculating the operation time weighted according to the load size (“engine load” × “engine operation time”), it is possible to determine the amount of adsorption with higher accuracy.

Additionally, by weighting the influence of the measured value C ₁ of the exhaust Gasumetan concentration sensor 53, and weighted according to the strength of the concentrations for unburnt methane component is also often discharged accordingly if-enriched operation By calculating the time (“concentration measurement value” × “engine operation time”), it is possible to determine the adsorption amount with higher accuracy.
Also, a combination of the measured value C ₁ of the engine load and the exhaust gas methane concentration sensor 53 described above, may be a ( "engine load" × "density measurement," × "engine operating time"), further, the bypass exhaust gas passage The exhaust gas flow rate flowing into the first methane adsorption catalyst 21 or the second methane adsorption catalyst 23 through 15 is detected by a flow meter (not shown), and the flow rate and the measured value C _{1 of} the exhaust gas methane concentration sensor 53 are used in combination. (“Exhaust gas flow rate” × “concentration measurement value” × “engine operating time”).
In this way, the amount of adsorption can be determined more accurately by correcting the engine operating time by using the engine load and concentration together, or using the exhaust gas flow rate and concentration together.

Next, the control at the time of discharge | release of methane in the control apparatus 41 is demonstrated with reference to the flowchart of FIG.
In step S11, the methane adsorption catalyst to be desorbed is selected from the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, and the opening / closing control of the gas valve is performed according to the selected catalyst. In step S12, specifically, when the target catalyst is the first methane adsorption catalyst 21, the gas valve VC12 is opened, and when the target catalyst is the second methane adsorption catalyst 23, the gas valve VC22 is opened and the release operation is performed. Start.

In step S 13, the outlet gas temperature T ₃ of the catalyst is detected by the outlet temperature sensor 51. Then, in step S15, the outlet gas temperature _{T 3} is determined whether substantially 400 ° C.. In the case of NO, in step S16, the heating amount of the heater 29 is adjusted so as to be approximately 400 ° C.

Next, in step S17, the desorption operation time of the target methane adsorption catalyst is integrated. In other words, the outlet gas temperature T ₃ of the catalyst is to calculate the cumulative transit time in the case of substantially 400 ° C. or higher. In step S18, it is determined by comparing whether or not the integrated value has reached a preset processing completion time.

  When it has reached, it becomes NO, and in step S20, the gas valve VC12 (VC22) is closed to block the inflow of the released gas. At the same time, in step S21, the process waits until the adsorption operation with another catalyst reaches the adsorption limit. When the other catalyst reaches the adsorption limit, in step S22, the gas valves VC11 to VC24 are set so that the target catalyst that has been desorbed can be adsorbed with methane.

In the operation of the time integration of the subject catalyst in the step S17, not just the operating time, in step S14, the methane desorption using a time corrected according to the detected value of the outlet temperature sensor 51 of the outlet gas temperature T ₃ of the catalyst An integrated value of the operation time at the time may be calculated.
In this way, the weighting of the influence of the outlet temperature is corrected so that the operation time is increased because the desorption amount increases when the temperature is higher than 400 ° C.
This is because, when the processing completion time set in advance is set, it is a time calculated from a theoretically calculated value of the operation completion time due to the passage of the emitted gas at 400 ° C. or a necessary time captured by experiments. By correcting by up and down with respect to 400 ° C., the desorption completion can be determined with higher accuracy.

In addition, regarding the integration of the operation time at the time of methane desorption of the target catalyst in the step S17, a flow meter (not shown) is provided in the first discharge gas passage 31 or the circulation flow passage 33, and a detected value from the flow meter, by correcting the operation time by using the detection value of the discharge Gasumetan concentration C ₃ detected by the release Gasumetan concentration sensor 55 provided downstream of the catalyst, the ( "detected flow" × "density" × "operating time") It may be calculated, so that the desorption completion can be determined with higher accuracy.

Further, instead of the determination based on the step S14, S17, the operation time calculated by S18, by detecting the release Gasumetan concentration C ₂ by the release Gasumetan concentration sensor 55 provided downstream of the catalyst, the concentration is preset It may be determined whether or not the threshold concentration is below. That is, if the detected concentration is equal to or lower than the threshold concentration, it is determined that the desorption is completed. In this case, since the methane concentration is directly detected and the determination is made only by the concentration, the completion of desorption can be determined more easily and accurately than the determination based on the operation time.

  As described above, according to the first embodiment, the exhaust gas containing unburned fuel methane is passed through the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, and the exhaust gas cooler 19 is used to reduce the exhaust gas. The first methane adsorption catalyst 21 and the second methane adsorption catalyst 21 are controlled by controlling the temperature to approximately 100 ° C. at which the methane adsorption capacity is increased and by using the heater 29 to control the temperature of the emitted gas to approximately 400 ° C. at which the methane desorption property is enhanced. Adsorption on the 2-methane adsorption catalyst 23 and desorption from these catalysts can be performed effectively.

Then, the desorbed methane component is returned to the engine air supply passage 5 again through the circulation passage 33 and used as fuel, so that the unburned component methane that has been conventionally discharged without combustion is utilized. Thus, it is possible to improve the thermal efficiency of the gas engine 1 and the exhaust gas purification performance.
In particular, the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 are alternately adsorbed and desorbed alternately. While the adsorption operation is performed on the one hand, the desorption operation is performed on the other hand, and the exhaust gas is always one of the adsorption catalysts. The methane component from the adsorption catalyst is always returned to the intake passage 5 of the engine without being released into the atmosphere. For this reason, the discharge | emission amount to the atmosphere of the unburned component methane is reduced effectively, and an exhaust gas purification function improves with improvement in thermal efficiency.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS.
In the first embodiment, as shown in FIG. 1, an exhaust gas cooler 19 is provided as exhaust gas cooling means, and an air supply after being pressurized by the compressor 7b of the supercharger 7 and a heater 29 are provided as emission gas heating means. However, the second embodiment is characterized in that the exhaust gas cooling means and the emission gas heating means are configured without using the exhaust gas cooler 19 and the heater 29, and the whole system is simplified.

  As shown in FIG. 5, an air supply bypass passage 70 is provided so that the outlet of the air supply cooler 9 communicates with the downstream side of the exhaust heat recovery device 13 and the upstream side of the branch portion with the bypass exhaust gas passage 15. . Exhaust gas cooling means for cooling the exhaust gas is formed by guiding the supply air cooled by the supply air cooler 9 through the supply air bypass passage 70 and combining it with the exhaust gas.

  Further, a second emission gas passage 72 is provided so as to communicate the exhaust gas outlet of the gas engine 1 with the inlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23. The second exhaust gas passage 72 guides high-temperature exhaust gas from the gas engine 1 to constitute a discharge gas heating means.

As shown in FIG. 5, the control device 74 mainly includes an exhaust gas cooling control means 76 that controls exhaust gas at a temperature suitable for adsorbing methane components, and a methane adsorption limit based on the time that has passed through the methane adsorption catalyst. Methane adsorption limit determination means 78 for determining the methane desorption completion determination means 80 for determining the completion of methane release based on the time when the released gas at the time of desorption of the methane component has passed through the methane adsorption catalyst, and the supply passage 5 side. Based on the desorbed methane gas concentration C ₂ of the circulated desorbed methane gas (see the first embodiment), the fuel control unit 65 of the gas engine that corrects and controls the fuel amount of the gas engine 1 is provided.

Then, a discharge gas temperature T _e from the discharge gas temperature sensor 82 for detecting the exhaust gas temperature of the second discharge gas passage 72, the exhaust gas temperature T ₁ of the from the exhaust gas temperature sensor 84 for detecting the temperature of exhaust gas flowing through the bypass exhaust gas passage 15 On the basis of this, the supply bypass valve VA provided in the supply bypass passage 70, the release gas valve VE provided in the second release gas passage 72, the gas valves VC11 to VC24, and the branch control valve 17 are opened and closed. Control.
Regarding the other configuration, the same components as those in the first embodiment are denoted by the same reference numerals.

Control during methane adsorption will be described with reference to the flowchart of FIG.
The selection of the methane adsorption catalyst in step S1 is the same as in the first embodiment. In the first embodiment, the temperature of the treated exhaust gas in step S2 is detected at the inlet of each methane adsorption catalyst. However, in the second embodiment, the exhaust gas temperature sensor 84 is set at 1 in the bypass exhaust gas passage 15. Detected at a location. This simplifies the system.

Step S3 is the same as in the first embodiment, and it is determined whether the temperature of the exhaust gas flowing into the selected methane adsorption catalyst is approximately 100 ° C. In step S31, the temperature is adjusted to approximately 100 ° C., but this adjustment is performed by opening the air supply bypass valve VA. That is, since the supply air bypass gas is cooled by the supply air cooler 9, the supply air bypass gas 70 is adjusted by adjusting the supply air amount mixed with the exhaust gas.
Subsequent processing is the same as in the first embodiment.

Next, the control at the time of releasing methane will be described with reference to the flowchart of FIG.
Step S11 is the same as that in the first embodiment, and a methane adsorption catalyst to be desorbed is selected from the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, and the gas valve of the gas valve is selected according to the selected catalyst. Open / close control is performed.

In step S41, the discharge gas valve VE is opened. In step S42, it detects the discharge gas temperature _{T e} by the release gas temperature sensor 82. In step S44, integration of the desorption operation time of the target methane adsorption catalyst is started. In the first embodiment, the calculation is made as the cumulative passage time when the temperature is approximately 400 ° C. or higher. However, in the second embodiment, since the exhaust gas is used as a discharge gas, the accumulated time is often 400 ° C. or higher. In step S44, the integration is performed after the release gas valve VE is opened.

However, in step S43, the passage time is corrected according to the emission gas temperature, and this is reflected in the determination of the processing completion time. That is, since the desorption amount increases when the discharge gas temperature is higher than 400 ° C., the accumulated time is corrected so as to increase the operation time.
In step S45, it is determined by comparing whether or not the integrated value has reached a preset processing completion time.

  If it has reached, NO is determined, and in step S46, the discharge gas valve VE is closed to block the inflow of exhaust gas as the discharge gas. At the same time, in step S21, the process waits until the adsorption operation with another catalyst reaches the adsorption limit. The subsequent steps are the same as in the first embodiment.

  According to the above second embodiment, the exhaust gas cooler 19 and the heater 29 of the first embodiment are not used, and the outlet that connects the outlet of the supply air cooler 9 and the upstream side from the branch portion of the bypass exhaust gas passage 15 is communicated. The exhaust gas cooling means is constituted by the air bypass passage 70, and further, a second emission gas passage 72 that communicates the exhaust gas outlet of the gas engine 1 and the inlet of the methane adsorption catalyst is provided, and the high-temperature exhaust gas from the engine 1 is used. Since the emission gas heating means is configured, the entire system configuration can be simplified.

  Further, since methane is desorbed from the methane adsorption catalyst using the exhaust gas and recirculated to the supply passage 5, the exhaust gas also returns to the supply passage 5, so that an EGR function is obtained and a NOx reduction effect due to a decrease in combustion temperature is also obtained. It is done. Other effects are the same as those of the first embodiment.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG.
The third embodiment is a modification of the second embodiment shown in FIG. 5, in which the recirculation cooler 35 is omitted to cool the circulation flow provided in the circulation passage 33, and the others are the same as those of the second embodiment. It is the same configuration.

  As shown in FIG. 8, the connection position of the circulation passage 33 to the air supply passage 5 is the inlet side of the air supply cooler 9. Accordingly, the system can be simplified by causing the supply air cooler 9 to cool the discharged gas passing through the circulation passage 33.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG.
In the second and third embodiments described above, as shown in FIG. 5, the exhaust gas cooling means is configured by the supply air bypass passage 70 without using the exhaust gas cooler 19 and the heater 29, and the exhaust gas outlet of the gas engine 1, the methane The second emission gas passage 72 communicating with the inlet of the adsorption catalyst is provided, and the emission gas heating means is configured using the high temperature exhaust gas from the engine 1.
On the other hand, in the following fourth and fifth embodiments, the exhaust gas heating means by the heater 29 and the first discharge gas passage 31 is left, and the exhaust gas cooling means by the exhaust gas cooler 19 is constituted by the air supply bypass passage 70. It is.

Such a common effect in the fourth and fifth embodiments is constituted by the high-temperature air supply after being pressurized by the compressor 7b of the supercharger 7 and the heater 29 without using exhaust gas as the emission gas heating means. Since the exhaust gas is not exhaust gas, the EGR function cannot be obtained, and therefore, the system can be applied as a system configuration for an engine specification not equipped with EGR.
Further, since the heating control by the heater 29 is performed, the temperature control of the released gas can be performed with high accuracy.

  In the fourth embodiment, as shown in FIG. 9, the outlet of the air supply cooler 9 is connected to the downstream side of the exhaust heat recovery device 13 and the upstream side of the branch portion with the bypass exhaust gas passage 15. An air supply bypass passage 70 is provided. An exhaust gas cooling means for cooling the exhaust gas is constituted by guiding the supply air cooled by the supply air cooler 9 by this supply air bypass passage 70 and combining it with the exhaust gas. An air supply bypass valve VA is provided in the air supply bypass passage 70.

  Although not shown, the control device of the fourth embodiment replaces the exhaust gas cooling by the exhaust gas cooler 19 of the control device 41 of the first embodiment shown in FIG. That is, the adjustment of the cooling water amount of the exhaust gas cooler in step S4 in the flowchart of FIG. 2 is replaced with the adjustment of the supply air bypass valve VA.

  The first discharge gas passage 31 is connected to the respective inlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23, and the high-temperature air supply gas pressurized by the compressor 7b is desorbed from the methane adsorption catalyst. Sometimes it is led as a release gas. This release control is the same as in the first embodiment.

  According to the fourth embodiment described above, since the supply air supplied by the first discharge gas passage 31 connected to the outlet of the compressor 7b of the supercharger 7 is heated by the heater 29, the exhaust gas is not circulated and the EGR function is achieved. Since it cannot be obtained, it can be applied as a system configuration for engine specifications without EGR. Further, since the heating control by the heater 29 is performed, the temperature control of the released gas can be performed with high accuracy.

(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIG.
The fifth embodiment is a modification of the fourth embodiment shown in FIG. 9, and the system is further simplified by sharing the supply air bypass passage 70 and the first discharge gas passage 31 shown in FIG. Is. The other configuration is the same as that of the fourth embodiment.

As shown in FIG. 10, a common gas passage 90 is provided by branching from the outlet of the air supply cooler 9, and the common gas passage 90 is branched halfway, and one of them is an air supply bypass provided with an air supply bypass valve VA. The passage 90 a is connected to the main exhaust gas passage 11, and the other is connected to the inlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 as a shared discharge gas passage 90 b.
As described above, the common gas passage 90 can be used as a passage configuration in which the supply air bypass passage 70 and the first discharge gas passage 31 shown in FIG. 9 are made common, and the system can be further simplified.

(Sixth embodiment)
Next, a sixth embodiment will be described with reference to FIG.
In the fourth and fifth embodiments described above, as shown in FIG. 9, emission gas heating means is provided by a heater 29 and a first emission gas passage 31, and exhaust gas cooling is performed by an air supply bypass passage 70 instead of the exhaust gas cooler 19. Constituted the means.
In the sixth embodiment, conversely, an exhaust gas cooler 19 is provided as the emission gas heating means, and the exhaust gas from the outlet of the gas engine 1 is used instead of the heater 29 and the first emission gas passage 31 as the emission gas heating means. A second discharge gas passage 72 that leads to the inlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 is provided.

  That is, as shown in FIG. 11, the second emission gas passage 72 is provided so that the exhaust gas outlet of the engine 1 and the inlets of the first methane adsorption catalyst 21 and the second methane adsorption catalyst 23 communicate with each other. The second exhaust gas passage 72 guides and uses high-temperature exhaust gas from the engine 1 to constitute an exhaust gas heating means.

Since the emission gas heating means is constituted by the heat of the exhaust gas from the engine 1, an apparatus such as the heater 29 (see FIG. 9) is not required, and methane released by the exhaust gas recirculates, so that an EGR function is obtained. .
Moreover, since the exhaust gas temperature adsorbed by the exhaust gas cooler 19 is controlled, the exhaust gas temperature can be accurately controlled to an appropriate temperature (approximately 100 ° C.), so that the adsorption performance is improved.

  According to the present invention, in a gas engine using a fuel gas containing methane as a main component, the methane component discharged as an unburned component is efficiently adsorbed and recycled to the engine to improve the thermal efficiency of the engine and the exhaust gas. Since the purification performance can be improved, it is suitable for use in an exhaust gas purification device of a gas engine.

1 Engine (gas engine)
3 Generator 5 Supply passage 7 Supercharger 7b Compressor 7a Exhaust turbine 9 Supply cooler 11 Main exhaust passage 15 Bypass exhaust passage 17 Branch control valve 19 Exhaust cooler 21 First methane adsorption catalyst (first system methane adsorption catalyst)
23 Second methane adsorption catalyst (second system methane adsorption catalyst)
29 Heater (heater means)
31 First emission gas passage 33 Circulation passage 37 Inlet side control valve 39 Outlet side control valve 41, 74 Controller 59, 78 Methane adsorption limit judgment means 63, 80 Methane desorption completion judgment means 72 Second emission gas passage

Claims (10)

In a gas engine exhaust gas purification apparatus using fuel gas containing methane as a main component,
A main exhaust gas passage connected to the gas engine;
A bypass exhaust gas passage branched from the main exhaust gas passage and rejoining the main exhaust gas passage;
A branch control valve for controlling the flow of exhaust gas from the main exhaust gas passage to the bypass exhaust gas passage;
A methane adsorption catalyst that is arranged in parallel in the bypass exhaust gas passage and adsorbs a methane component in the exhaust gas;
Exhaust gas cooling means for cooling the exhaust gas flowing into the methane adsorption catalyst to an exhaust gas temperature suitable for adsorption of methane components;
A discharge gas heating means for heating a discharge gas that passes through the methane adsorption catalyst and desorbs a methane component adsorbed on the methane adsorption catalyst to a temperature suitable for desorption;
The plurality of methane adsorption catalysts are composed of two systems, and an inlet side control valve that switches inflow and shutoff of exhaust gas to the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst;
A circulation passage for circulating gas discharged from the outlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst to the supply passage of the engine;
An outlet-side control valve that switches the gas discharged from the respective outlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst between outflow and shut-off to the bypass exhaust gas passage or the circulation passage;
The exhaust gas cooling means, the discharge gas heating means, the inlet side control valve, the outlet side control valve, and the branch control valve are controlled so that the methane adsorption catalyst of the first system and the methane adsorption catalyst of the second system are controlled. A control device for switching between adsorption and desorption;
An exhaust gas purification apparatus for a gas engine, comprising:   The exhaust gas cooling means is constituted by an exhaust gas cooler that cools the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst, and the emission gas heating means is a supercharger 2. The gas engine according to claim 1, comprising a supply air pressurized by a compressor and heater means provided in the first system methane adsorption catalyst and the second system methane adsorption catalyst. Exhaust gas purification device.   The exhaust gas cooling means mixes the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst with the supply air cooled by the supply air cooler provided in the supply air passage. The emission gas heating means is configured to guide exhaust gas from the engine outlet to the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst. The exhaust gas purification apparatus for a gas engine according to claim 1.   The exhaust gas cooling means mixes the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst with the supply air cooled by the supply air cooler provided in the supply air passage. The discharge gas heating means is constituted by supply air pressurized by a compressor of a supercharger and heater means provided in the first system methane adsorption catalyst and the second system methane adsorption catalyst. The exhaust gas purification apparatus for a gas engine according to claim 1, wherein the exhaust gas purification apparatus is configured.   The exhaust gas cooling means is constituted by an exhaust gas cooler that cools the exhaust gas flowing into the respective inlets of the first system methane adsorption catalyst and the second system methane adsorption catalyst, and the emission gas heating means is the first system 2. The exhaust gas purification apparatus for a gas engine according to claim 1, wherein exhaust gas from the engine outlet is guided to respective inlets of the methane adsorption catalyst of the second system and the methane adsorption catalyst of the second system.   The exhaust gas purification apparatus for a gas engine according to claim 1, wherein the circulation passage is returned to the upstream side of a compressor of a supercharger provided in the air supply passage.   The exhaust gas purification apparatus for a gas engine according to claim 1, wherein the circulation passage is returned to the upstream side of a supply air cooler provided on the downstream side of the compressor of the supercharger provided in the supply air passage.   The control device includes methane adsorption limit determination means for determining a methane adsorption limit based on a time when exhaust gas having a temperature suitable for adsorbing a methane component passes through a methane adsorption catalyst. Item 2. An exhaust gas purifying apparatus for a gas engine according to Item 1.   The control device includes methane desorption completion determining means for determining completion of methane emission based on a time when a discharge gas having a temperature suitable for desorbing a methane component passes through the methane adsorption catalyst. The exhaust gas purification apparatus for a gas engine according to claim 1.   The said gas engine consists of an engine for electric power generation, and the said control apparatus interrupts | blocks the flow of the exhaust gas to the said bypass exhaust gas path until it reaches the rated rotation speed of fixed rotation speed from starting. An exhaust gas purification device for a gas engine as described.

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