JP6168965B2 - Mixed combustion system and fuel gas mixing unit - Google Patents

Description

  The present invention includes a combustion device that operates by burning fuel gas, and a mixing mechanism that mixes biogas with the main fuel gas to generate fuel gas and supplies the generated fuel gas to the combustion device. The present invention relates to a mixed combustion system and a fuel gas mixing unit configured as a mixing mechanism unit.

In recent years, biogas generated on-site is appropriately mixed with main fuel gas such as natural gas to generate fuel gas, and the fuel gas is supplied to a combustion device such as a generator driving engine for combustion. Has been proposed (see, for example, Patent Documents 1 and 2).
This type of co-firing system is connected to a main pipeline that leads the main fuel gas taken from the main fuel gas inflow section connected to the main fuel gas supply source such as a gas conduit to the fuel gas outflow section, and a biogas storage tank. A mixing mechanism for supplying the fuel gas flowing out from the fuel gas outflow portion to the combustion apparatus, and a biogas pipe for guiding the biogas taken in from the biogas inflow portion to the biogas introduction hole arranged in the main pipe Is provided.
And according to this mixed combustion system, utilization of the biogas which can be obtained cheaply can be promoted, and the operating cost of the combustion apparatus can be reduced.

In the mixing mechanism part of the mixed combustion system, it is necessary to stabilize the mixing ratio of the biogas with respect to the main fuel gas in the fuel gas supplied to the combustion device in order to enjoy the effect of reducing the operation cost while ensuring the stable operation of the combustion device. is there.
That is, if the mixing ratio of the biogas is too large, the calorific value of the biogas is unstable, and the operation of the combustion apparatus becomes unstable. On the other hand, if the mixing ratio of the biogas is too small, it is not possible to fully enjoy the effect of reducing the operating cost of the combustion apparatus by using inexpensive biogas.

Therefore, in the mixing mechanism part of the conventional mixed combustion system, a control valve whose opening degree can be controlled by an electrical signal from the combustion apparatus control part for controlling the operation of the combustion apparatus is installed in the biogas conduit through which the biogas flows. The combustion device control unit is configured to control the opening of the control valve based on the output of the combustion device.
That is, when the output of the combustion device increases and the supply amount of the main fuel gas to the combustion device increases, the combustion device control unit adjusts the opening degree of the control valve provided in the biogas conduit. Expanding to increase the amount of biogas mixed into the main fuel gas as the supply amount of the main fuel gas increases, and conversely, the output of the combustion device decreases and the main fuel to the combustion device decreases. When the amount of gas supply decreases, the opening degree of the control valve provided in the biogas pipeline is reduced, and the biogas to the main fuel gas is reduced in accordance with the decrease of the main fuel gas supply amount. The amount of mixing is reduced, which stabilizes the mixing ratio of the biogas to the main fuel gas.

  In addition, in order to promote the use of biogas using an existing combustion device that operates only with natural gas, the above-described mixing mechanism is unitized as a fuel gas mixing unit, and fuel gas mixing is performed in the existing combustion device. It is being considered to be able to build a mixed firing system simply by equipping the unit.

JP 2011-157860 A JP 2011-214491 A

As described above, in the mixing mechanism part of the conventional mixed combustion system, it is necessary to control the opening degree of the control valve provided in the biogas conduit, so that an electrical signal is transmitted between the mixing mechanism part side and the combustion apparatus side. It is necessary to provide a communication interface for inputting / outputting. In particular, when the mixing mechanism is unitized as a fuel gas mixing unit and installed in an existing combustion apparatus, a complicated and expensive modification may be required to provide the communication interface.
The present invention has been made paying attention to such a point, and an object of the present invention is to provide a mixed-combustion system and a fuel-gas mixing unit configured as a mixing mechanism provided in the mixed-combustion system. Without the need for a communication interface between the main unit and the main fuel gas in the fuel gas supplied to the combustion device, maintaining a stable mixing ratio to ensure stable operation of the combustion device. It is in the point of providing the technology which can enjoy the reduction effect of this.

In order to achieve this object, the mixed combustion system according to the present invention comprises:
A combustion apparatus that operates by burning fuel gas and whose output is controlled by adjusting the supply amount of the fuel gas;
A main pipe that leads main fuel gas taken from the main fuel gas inflow part to the fuel gas outflow part, and a biogas pipe that leads biogas taken from the biogas inflow part to the biogas introduction hole that opens to the main pipe, And a mixing mechanism that supplies fuel gas flowing out from the fuel gas outlet to the combustion device,
Its feature configuration is
The mixing mechanism section is
A check valve that is disposed upstream of the biogas introduction hole in the main pipeline, and prevents a gas flow toward the main fuel gas inflow portion in the main pipeline;
A pressure equalizing valve that is disposed in the biogas conduit and whose opening varies so as to maintain a pressure balance between the pressure equalizing section and the outlet side;
The pressure loss adding portion is disposed between the check valve and the biogas introduction hole in the main pipeline and adds a pressure loss to the gas flow in the main pipeline .

According to the mixed combustion system having this characteristic configuration, the check valve is disposed between the biogas introduction hole and the main fuel gas inflow portion, and the gas flow toward the main fuel gas inflow portion in the main pipeline is prevented. Therefore, it is possible to prevent the biogas flowing into the main pipeline from the biogas introduction hole from flowing backward to the main fuel gas supply side such as a gas conduit via the main fuel gas inflow portion.
Further, in the check valve disposed between the biogas introduction hole and the main fuel gas inflow portion, the flow of the main combustion gas toward the fuel gas outflow portion is allowed and the flow of the main fuel gas is reduced. Pressure loss corresponding to the flow rate is added. Therefore, the pressure near the biogas introduction hole in the main pipeline decreases as the flow rate of the main fuel gas increases, and the pressure on the outlet side of the pressure equalizing valve in the biogas pipeline communicating with the biogas introduction hole is the same. To drop.
Then, in the pressure equalizing valve arranged in the biogas conduit, the pressure balance with respect to the pressure of the pressure equalizing section maintained substantially uniform is maintained with respect to the outlet side pressure that decreases as the flow rate of the main fuel gas increases. As shown, the degree of opening automatically changes so as to increase as the flow rate of the main fuel gas increases. Therefore, the flow rate of the biogas mixed with the main fuel gas flowing through the main pipeline from the pressure equalizing valve through the biogas introduction hole automatically changes with a tendency to increase as the flow rate of the main fuel gas increases. It will be.
Therefore, according to the mixed combustion system according to the present invention including such a mixing mechanism unit, the main fuel gas in the fuel gas supplied to the combustion device without performing communication regarding the output of the combustion device and the like with the combustion device side. As a result, it is possible to enjoy the effect of reducing the operating cost while ensuring the stable operation of the combustion apparatus.
In addition, according to the mixed combustion system having this characteristic configuration, a relatively large pressure loss is added to the flow of the main fuel gas flowing through the main pipeline by the pressure loss addition unit in addition to the check valve. The pressure on the outlet side of the pressure equalizing valve in the biogas conduit communicating with the biogas introduction hole on the downstream side thereof decreases relatively with the increase in the flow rate of the main fuel gas. Then, as the flow rate of the main fuel gas in the main pipeline increases, the pressure difference on the outlet side with respect to the pressure equalizing portion in the pressure equalizing valve arranged in the biogas pipeline relatively expands.
Therefore, the opening of the pressure equalizing valve arranged in the biogas conduit through which the biogas flows accurately fluctuates with changes in the flow rate of the main fuel gas, and as a result, the mixing ratio of the biogas to the main fuel gas is more stable. Will be maintained.

A further characteristic configuration of the mixed firing system according to the present invention is as follows.
The pressure equalizing portion of the pressure equalizing valve is connected to the upstream side of the check valve in the main pipeline.

According to the mixed combustion system having this characteristic configuration, the pressure equalizing section of the pressure equalizing valve is connected to the upstream side of the check valve in the main line maintained relatively stably and at a high pressure, so that it is supplied to the combustion device. The mixing ratio of the biogas to the main fuel gas in the fuel gas can be maintained more stably.
That is, the pressure on the upstream side of the check valve in the main line is stabilized by communicating with a main fuel gas supply source such as a gas conduit whose pressure is controlled at that point. Furthermore, the pressure on the upstream side of the check valve in the main line is the bio-pressure communicating with the biogas introduction hole on the downstream side of the check valve due to the pressure loss that the check valve adds to the flow of the main fuel gas. It becomes a relatively high state with respect to the outlet side pressure of the pressure equalizing valve in the gas pipeline.
And, in the pressure equalizing valve arranged in the biogas pipe, the pressure in the pressure equalizing section connected to the upstream side of the check valve in the main pipe is relatively stably maintained at a high pressure. Since the pressure difference between the part and the outlet side becomes relatively large, the change in the outlet side pressure accompanying the change in the flow rate of the main fuel gas can be clearly understood as a change in the relatively large pressure difference.
Therefore, the opening of the pressure equalizing valve disposed in the biogas conduit through which the biogas flows accurately fluctuates as the flow rate of the main fuel gas changes. As a result, the biogas is mixed with the main fuel gas. The rate is kept more stable.

A further characteristic configuration of the mixed firing system according to the present invention is as follows.
It is the point provided with the adjustment valve which is arrange | positioned between the said pressure equalization valve and the said biogas introduction hole in the said biogas pipe line, and an opening degree can be adjusted.

  According to the mixed combustion system having this characteristic configuration, by adjusting the opening of the regulating valve disposed between the pressure equalizing valve and the biogas introduction hole in the biogas pipe, the main pipe is connected via the biogas introduction hole. The flow rate of the biogas mixed with the main fuel gas flowing through the channel can be adjusted, and as a result, the biogas with respect to the main fuel gas maintained stable by the pressure equalizing valve arranged in the biogas conduit The mixing ratio can be adjusted to a desired mixing ratio.

A further characteristic configuration of the mixed firing system according to the present invention is as follows.
A switching valve capable of intermittently supplying biogas from the biogas supply source to the biogas inflow section,
The combustion apparatus closes the switching valve and supplies only the main fuel gas to the combustion apparatus for combustion, and opens the switching valve to open the switching apparatus with the main fuel gas and the biogas. This is because the combustion mode can be switched between the mixed combustion mode in which the mixed gas is supplied and combusted.

According to the mixed combustion system having this characteristic configuration, the combustion mode of the combustion device can be switched between the exclusive combustion mode and the mixed combustion mode only by opening and closing the switching valve disposed on the biogas supply source side. .
That is, by opening the switching valve, the supply of biogas from the biogas supply source to the biogas conduit of the mixing mechanism is continued, and the main fuel mixed at a stable mixing rate in the mixing mechanism A mixed gas of the gas and the auxiliary fuel gas flows out from the fuel gas outflow portion. Therefore, an operation in a so-called mixed combustion mode in which the mixed gas is supplied to the combustion device and burned is executed. On the other hand, by closing the switching valve, the supply of biogas from the biogas supply source to the biogas conduit of the mixing mechanism unit is stopped, and the main fuel gas is directly discharged from the fuel gas outflow unit in the mixing mechanism unit. leak. Therefore, the operation in the so-called exclusive combustion mode in which the main fuel gas is supplied to the combustion device and burned is executed.
Furthermore, when there is a large amount of biogas stored at the biogas supplier, the combustion mode of the combustion device is switched to the mixed combustion mode in order to actively use the biogas. When the amount of stored gas is small, priority is given to securing the amount of biogas stored at the biogas supplier, and the combustion mode of the combustion device is switched to the exclusive combustion mode, so that the combustion mode is automatically switched according to the situation. You may comprise.

A further characteristic configuration of the mixed firing system according to the present invention is as follows.
The combustion apparatus is a gas engine for driving a generator.

  According to the mixed combustion system having this characteristic configuration, even when the combustion device is a gas engine for driving a generator, the mixing ratio of biogas to the main fuel gas in the fuel gas supplied to the gas engine is stabilized as described above. Therefore, the stable operation of the gas engine can be ensured to stably supply the generated power, and the effect of reducing the power generation cost by promoting the use of biogas can be enjoyed.

A further characteristic configuration of the mixed firing system according to the present invention is as follows.
The venturi-type mixer is provided in which the biogas introduction hole is provided in a constricted portion that is arranged in the main pipeline and reduces the diameter of the main pipeline.

According to the mixed combustion system having this characteristic configuration, the throttle section is provided by providing a venturi mixer having a throttle section that reduces the diameter of the main pipe path in the main pipe path, and providing a biogas introduction hole in the throttle section of the venturi mixer. As the suction energy is generated by the velocity energy of the main fuel gas that passes through the biogas and the biogas is attracted from the biogas introduction hole, the pressure on the outlet side of the pressure equalizing valve in the biogas conduit communicating with the biogas introduction hole Is further reduced. Then, as the flow rate of the main fuel gas in the main pipeline increases, the pressure difference on the outlet side with respect to the pressure equalizing portion in the pressure equalizing valve arranged in the biogas pipeline relatively expands.
Therefore, the opening of the pressure equalizing valve arranged in the biogas conduit through which the biogas flows accurately fluctuates with changes in the flow rate of the main fuel gas, and as a result, the mixing ratio of the biogas to the main fuel gas is more stable. Will be maintained.

In order to achieve this object, the fuel gas mixing unit according to the present invention comprises:
It is equipped with a combustion device that operates by burning fuel gas and whose output is controlled by adjusting the supply amount of the fuel gas,
A main pipe that leads main fuel gas taken from the main fuel gas inflow part to the fuel gas outflow part, and a biogas pipe that leads biogas taken from the biogas inflow part to the biogas introduction hole that opens to the main pipe, A fuel gas mixing unit for supplying fuel gas flowing out from the fuel gas outflow portion to the combustion device,
Its feature configuration is
It exists in the point comprised by unitizing the said mixing mechanism part which comprises the mixed combustion system which concerns on this invention demonstrated until now.

  According to the fuel gas mixing unit having this characteristic configuration, since it is configured as a mixing mechanism provided in the mixed combustion system according to the present invention described so far, it is complicated and expensive to provide a communication interface with the combustion apparatus side. It is possible to equip the combustion apparatus without requiring any modification, and furthermore, by installing the combustion apparatus in this way, the biogas of the main fuel gas in the fuel gas supplied to the combustion apparatus can be provided. By maintaining the mixing ratio stable, it is possible to enjoy the effect of reducing operating costs while ensuring stable operation of the combustion apparatus.

Schematic configuration diagram of the mixed combustion system and fuel gas mixing unit of the first embodiment Schematic configuration diagram of mixed combustion system and fuel gas mixing unit of second embodiment

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIG.
A mixed combustion system 100 shown in FIG. 1 includes a gas engine 30 (an example of a combustion device) for driving a generator 31, and a control device 35 including a computer that controls the operation of the gas engine 30. The fuel gas G is generated by mixing the biofuel G2 with the main fuel gas G1 which is the natural gas city gas 13A in a form equipped with the engine 30, and the generated fuel gas G is supplied to the gas engine 30. A fuel gas mixing unit 10 configured as a mixing mechanism unit is provided.
In this embodiment, the natural gas city gas 13A is used as the main fuel gas G1, but other fuel gas that can be stably supplied to the gas engine 30, such as LPG (liquefied petroleum gas), for example. May be used as the main fuel gas G1.

  Although not shown in detail, the gas engine 30 is operated by burning a mixture of fuel gas G and combustion air in a combustion chamber, and outputs rotational power for rotating the generator 31 in general. It is configured as a typical internal combustion engine. Further, the output of the gas engine 30 is controlled by the control device 35 by adjusting the supply amount of the fuel gas G by adjusting the opening of the throttle valve. Specifically, the output of the gas engine 30 is measured as the generated power of the generator 31, and the control device 35 is configured so that the generated power is maintained at the target generated power set according to the power demand or the like. The amount of fuel gas G supplied to the gas engine 30 is adjusted.

(Fuel gas mixing unit)
Next, the detailed configuration of the fuel gas mixing unit 10 will be described.
The fuel gas mixing unit 10 does not require a communication interface with the control device 35 on the gas engine 30 side, and the mixing ratio of the biogas G2 to the main fuel gas G1 in the fuel gas G supplied to the gas engine 30. Is maintained and the stable operation of the gas engine 30 is ensured, and the operation cost of the gas engine 30, that is, the effect of reducing the power generation cost is enjoyed.

Specifically, the fuel gas mixing unit 10 is connected to a main fuel gas inlet 11 connected to a gas conduit 1 serving as a main fuel gas supply source as a pipe interface with the outside. A biogas inflow part 17 to which a biogas supply pipe 4 communicating with the biogas storage tank 3 as a supply source is connected, and a fuel gas outflow part to which a fuel gas supply pipe 29 for supplying the fuel gas G to the gas engine 30 is connected. 15, and other communication interfaces for performing electrical communication are not particularly provided.
Then, the fuel gas mixing unit 10 includes a main pipe 12 that guides the main fuel gas G1 taken from the main fuel gas inlet 11 to the fuel gas outlet 15 and a biogas G2 taken from the biogas inlet 17 to the main pipe 12. And a biogas conduit 18 that leads to the biogas introduction hole 21, which functions as a mixing mechanism that supplies the fuel gas G flowing out from the fuel gas outlet 15 to the gas engine 30.
The end of the biogas pipe 18 on the side of the biogas introduction hole 21 and the main pipe 12 are connected by a simple joint such as a T-type joint.
A check valve 13, an orifice 14 (an example of a pressure loss adding portion), and a biogas introduction hole 21 are disposed in the main pipeline 12 in order from the upstream side, while the biogas pipeline 18 The pressure equalizing valve 19 and the regulating valve 20 are arranged in order from the upstream side.

The check valve 13 disposed on the upstream side of the biogas introduction hole 21 in the main pipeline 12 operates to block the gas flow toward the main fuel gas inflow portion 11 in the main pipeline 12.
Therefore, the operation of the gas engine 30 is stopped and the supply of the fuel gas G to the gas engine 30 is stopped, so that the pressure of the biogas introduction hole 21 in the main pipeline 12 is higher than the pressure of the main fuel gas inflow portion 11. Even in this case, the gas flow toward the main fuel gas inflow portion 11 in the main pipeline 12 is blocked, and the biogas G2 flowing into the main pipeline 12 from the biogas introduction hole 21 passes through the main fuel gas inflow portion 11 as a gas conduit. Backflow to the 1 side is prevented.

Further, as the check valve 13, a swing type valve in which the valve body does not remain in the flow path when fully opened can be used, but in this embodiment, the disc type in which the valve body remains in the flow path when fully opened. Things are provided.
Therefore, the check valve 13 operates to open the valve body so as to allow the gas flow toward the fuel gas outflow portion 15 in the main pipeline 12, but the gas remains when the valve body remains in the flow path. A relatively large pressure loss is added to the flow.
Therefore, the pressure in the vicinity of the biogas introduction hole 21 in the main pipe line 12 decreases with a tendency to decrease as the flow rate of the main fuel gas G1 increases, and the pressure equalizing valve in the biogas pipe line 18 communicating with the biogas introduction hole 21. Similarly, the outlet side pressure P2 which is the pressure on the outlet side of 19 decreases as the flow rate of the main fuel gas G1 increases.

On the other hand, the pressure equalizing valve 19 arranged in the biogas pipe 18 is connected to the pressure equalizing section pressure P1 which is a pressure introduced through the pressure equalizing path 19a as a pressure equalizing section, and the outlet side (that is, in the biogas pipe 18). It is configured as a general pressure equalizing valve whose opening degree is automatically adjusted so that the pressure balance with the outlet side pressure P2, which is the pressure immediately downstream of the pressure equalizing valve 19, is maintained at a desired pressure balance. ing. Specifically, the pressure equalizing valve 19 operates so as to increase the flow rate of the biogas G2 flowing through the pressure equalizing valve 19 as the outlet side pressure P2 decreases with the pressure equalizing section pressure P1 as a reference. .
That is, in the pressure equalizing valve 19, the opening degree of the outlet side pressure P2 that decreases as the flow rate of the main fuel gas G1 decreases is maintained so that the pressure balance with respect to the pressure equalizing section pressure P1 that is kept substantially uniform is maintained. However, it automatically changes so as to increase as the flow rate of the main fuel gas G1 increases. Therefore, the flow rate of the biogas G2 mixed with the main fuel gas G1 flowing through the main pipeline 12 from the pressure equalizing valve 19 through the biogas introduction hole 21 increases as the flow rate of the main fuel gas G1 in the main pipeline 12 increases. As a result, the fuel gas G supplied to the gas engine 30 is automatically changed, and as a result, the mixing ratio of the biogas to the main fuel gas G1 is kept stable.

Further, the pressure equalizing passage 19 a of the pressure equalizing valve 19 is connected to a location upstream of the check valve 13 in the main pipeline 12. Further, the upstream side of the main pipe 12 with respect to the check valve 13 communicates with the gas conduit 1 subjected to pressure control via the main fuel gas supply pipe 2, so that the pressure at that point is compared. It becomes stable in a high state.
Therefore, the pressure equalizing part pressure P1 introduced to the pressure equalizing valve 19 through the pressure equalizing passage 19a is maintained relatively stably at a high pressure.

Then, in the pressure equalizing valve 19, the pressure difference between the pressure equalizing section pressure P1 and the outlet side pressure P2 becomes relatively large, and the change in the outlet side pressure P2 accompanying the change in the flow rate of the main fuel gas G1 is a relatively large change in pressure difference. Will be clearly understood.
As a result, the opening degree of the pressure equalizing valve 19 disposed in the biogas conduit 18 through which the biogas G2 flows is accurately changed with the flow rate change of the main fuel gas G1, so that the bio for the main fuel gas G1 is changed. The mixing ratio of the gas G2 is kept more stable.

In the main pipeline 12, the orifice 14 is disposed between the check valve 13 and the biogas introduction hole 21, and functions as a pressure loss addition unit that adds pressure loss to the gas flow in the main pipeline 12.
This type of orifice 14 is configured as a general orifice having a pair of flanges respectively connected to the upstream and downstream flow paths and sandwiching an orifice plate having a smaller aperture than the flow path. Has been.
By arranging such an orifice 14 in addition to the check valve 13 in the main line 12, a relatively large pressure loss is added to the flow of the main fuel gas G1 flowing through the main line 12. become. Therefore, the outlet side pressure P2 of the pressure equalizing valve 19 in the biogas pipe line 18 communicating with the biogas introduction hole 21 on the downstream side can be further greatly reduced.
The pressure loss adding portion may be other than the orifice 14 as long as it adds pressure loss to the gas flow in the main pipe 12. Further, when the pressure loss applied by the check valve 13 is relatively large and the outlet side pressure P2 of the pressure equalizing valve 19 can be sufficiently reduced only by providing the check valve 13, the orifice 14 is used. It can be omitted.

On the other hand, the regulating valve 20 disposed between the pressure equalizing valve 19 and the biogas introduction hole 21 in the biogas conduit 18 is configured by a general needle valve or the like whose opening degree can be adjusted.
That is, the flow rate of the biogas G2 mixed with the main fuel gas G1 flowing through the main pipeline 12 through the biogas introduction hole 21 can be adjusted by manually adjusting the opening of the adjustment valve 20. it can. Therefore, by adjusting the opening degree of the regulating valve 20, the mixing ratio of the biogas G2 to the main fuel gas G1 maintained stably by the pressure equalizing valve 19 arranged in the biogas pipe 18 is, for example, 10%. It can be adjusted to a desired mixing ratio.
If there is no need to adjust the mixing ratio of the biogas G2 with respect to the main fuel gas G1, the adjusting valve 20 can be omitted, and furthermore, an orifice provided in the biogas pipe 18 or a biogas introduction The mixing ratio of the biogas G2 with respect to the main fuel gas G1 can be set to a desired mixing ratio by setting the diameter of the hole 21 to an appropriate one.

(Combustion mode switching control)
Next, the combustion mode switching control executed by the control device 35 will be described.
The biogas supply pipe 4 is provided with a switching valve 6 capable of intermittently supplying the biogas G2 from the biogas storage tank 3 to the biogas inflow portion 17 of the fuel gas mixing unit 10.
The switching valve 6 is composed of an electromagnetically driven on / off valve, and the control device 35 performs opening / closing control of the switching valve 6 to change the combustion mode of the gas engine 30 into a mono-combustion mode and a co-firing mode described later. And can be switched between.
The exclusive combustion mode is a combustion mode in which the switching valve 6 is closed and only the main fuel gas G1 is supplied to the gas engine 30 for combustion. That is, by closing the switching valve 6, the supply of the biogas G2 to the biogas conduit 18 of the fuel gas mixing unit 10 is stopped. Therefore, only the main fuel gas G1 supplied to the main pipeline 12 flows out from the fuel gas outflow portion 15, and the main fuel gas G1 is supplied as fuel gas G to the gas engine 30 and combusted.
On the other hand, the mixed combustion mode is a combustion mode in which the switching valve 6 is opened and a gas mixture obtained by mixing the main fuel gas G1 and the biogas G2 is supplied to the gas engine 30 and burned. That is, by opening the switching valve 6, the supply of the biogas G2 to the biogas line 18 of the fuel gas mixing unit 10 is continued. Therefore, the biogas G2 is mixed with the main fuel gas G1 supplied to the main pipe line 12 from the biogas introduction hole 21 at an appropriate and stable mixing ratio, and the mixed gas is used as the fuel gas G as a gas engine. 30 is supplied and combusted.

Then, the control device 35 sets the combustion mode of the gas engine 30 between the exclusive combustion mode and the mixed combustion mode based on the storage amount of the biogas G2 in the biogas storage tank 3 in order to appropriately use the biogas G2. The combustion mode switching control for switching is executed.
Specifically, a pressure sensor 5 that measures the supply pressure of the biogas G2 is provided on the outlet side of the biogas storage tank 3, that is, on the upstream side of the switching valve 6 of the biogas supply pipe 4. When the supply pressure of the biogas G2 detected by the pressure sensor 5 is lower than the set pressure, the control device 35 to which the detection result of the pressure sensor 5 is input has a biogas storage amount in the biogas storage tank 3. If the supply pressure of the biogas G2 detected by the pressure sensor 5 is higher than the set pressure, the biogas storage amount in the biogas storage tank 3 is greater than the allowable amount. In the determination to determine that the amount of biogas G2 stored in the biogas storage tank 3 is determined.
When the control device 35 determines that the amount of stored biogas is greater than or equal to the allowable amount, the control device 35 switches the combustion mode of the gas engine 30 to the mixed combustion mode in order to actively use the biogas G2. When the amount of stored biogas is below the allowable amount, combustion is performed in a mode in which the combustion mode of the gas engine 30 is switched to the exclusive combustion mode with priority given to securing the stored amount of the biogas G2 in the biogas storage tank 3. Mode switching control can be executed.
In addition, when the storage amount of the biogas G2 in the biogas storage tank 3 is always sufficient and the supply pressure of the biogas G2 is always equal to or higher than the set pressure, the combustion mode switching control based on the biogas storage amount is performed. May be omitted.

Furthermore, the control device 35 switches the combustion mode of the gas engine 30 between the exclusive combustion mode and the mixed combustion mode based on the startup state of the gas engine 30 in order to start the gas engine 30 stably and quickly. Execute.
Specifically, the control device 35 switches the combustion mode of the gas engine 30 to the exclusive combustion mode regardless of the amount of the stored biogas G2 until the gas engine 30 is started and the warm-up is completed. Do not drive in Then, only the main fuel gas G1 whose calorific value is stably maintained at a higher level than that of the biogas G2 is supplied to the gas engine 30 as the fuel gas G, so that the gas engine 30 is stabilized. And warming up after startup can be promoted.
Then, after the warming up of the gas engine 30 is completed, the control device 35 allows the switching of the combustion mode of the gas engine 30 to the mixed combustion mode. Then, the combustion mode of the gas engine 30 is switched and controlled based on the storage amount of the biogas G2 as described above, so that the biogas G2 is appropriately used.

In addition, since the calorific value of the biogas G2 is lower than the main fuel gas G1 which is the natural gas city gas 13A, a mixed gas of the main fuel gas G1 and the biogas G2 is supplied to the gas engine 30 as the fuel gas G. In the mixed combustion mode, the output of the gas engine 30 may be reduced.
However, since the control device 35 is configured to control the output of the gas engine 30 by adjusting the supply amount of the fuel gas G, the fuel gas G to the gas engine 30 when the gas engine 30 is operated in the mixed combustion mode. As a result, the output of the gas engine 30 is maintained at a desired output.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG.
In the following description, the same components as those in the first embodiment may be given the same reference numerals in the drawings and the description may be omitted.
Compared with the mixed combustion system 100 (see FIG. 1) described above, the mixed combustion system 200 shown in FIG. 2 has a configuration near the connection point of the biogas conduit 18 to the main conduit 12 and the pressure equalizing passage 19a of the pressure equalizing valve 19. The only difference is the connection destination.

First, the configuration in the vicinity of the location where the biogas pipe 18 is connected to the main pipe 12 will be described.
A Venturi mixer 40 is disposed downstream of the check valve 13 in the main pipeline 12.
The venturi mixer 40 includes a throttle portion 42 that reduces the diameter of the main pipeline 12, and the throttle portion 42 is provided with a biogas introduction hole 41 that is a downstream end portion of the biogas pipeline 18. .
That is, in this Venturi mixer 40, the main fuel gas G1 flowing through the main pipeline 12 passes through the throttle portion 42 at a high speed, and a suction force is generated in the biogas introduction hole 41 by the velocity energy of the main fuel gas G1. Therefore, the biogas G2 in the biogas pipeline 18 is attracted to the main pipeline 12 through the biogas introduction hole 41.
Then, the outlet-side pressure P2 of the pressure equalizing valve 19 in the biogas pipe line 18 communicating with the biogas introduction hole 41 is further reduced as compared with the case of the first embodiment described above, and further, the reduction width. Depends on the flow rate of the main fuel gas G1 in the main pipeline 12.
Therefore, in the pressure equalizing valve 19 arranged in the biogas pipe 18, the pressure difference of the outlet side pressure P2 with respect to the pressure equalizing section pressure P1 is further greatly increased, and the outlet side accompanying the flow rate change of the main fuel gas G1. The change in the pressure P2 can be clearly understood as a change in a larger pressure difference.
Further, the throttle portion 42 of the Venturi mixer 40 adds a relatively large pressure loss to the gas flow in the main pipe 12.
Therefore, in the fuel gas mixing unit 10 of the present embodiment, the orifice 14 (see FIG. 1) for adding a pressure loss to the gas flow in the main pipe 12 is omitted.

Next, the connection destination of the pressure equalizing passage 19a of the pressure equalizing valve 19 will be described.
A pressure equalizing passage 19 a of the pressure equalizing valve 19 is connected to a downstream side location of the venturi mixer 40 in the main pipeline 12.
The downstream side of the venturi mixer 40 in the main line 12 has a lower pressure than the upstream side of the check valve in the main line 12, but the fuel after passing through the throttle 42 of the venturi mixer 40. Since the gas G flows, the pressure is relatively stable.
Therefore, in the pressure equalizing valve 19, the opening degree is increased as the outlet side pressure P2 decreases with the relatively stable pressure equalizing portion pressure P1 introduced through the pressure equalizing passage 19a as a reference. Can be operated to increase the flow rate of biogas G2.

  The present invention relates to a combustion apparatus that operates by burning fuel gas and whose output is controlled by adjusting the supply amount of the fuel gas, and a main pipe that guides the main fuel gas taken from the main fuel gas inflow section to the fuel gas outflow section And a biogas pipe that guides the biogas taken from the biogas inflow section to a biogas introduction hole that opens to the main pipe, and supplies the fuel gas flowing out from the fuel gas outflow section to the combustion device Can be suitably used as a mixed combustion system including a mixing mechanism unit that performs the above operation and a combustion device control unit that controls the operation of the combustion device, and a fuel gas mixing unit configured as a mixing mechanism unit provided in the mixed combustion system It is.

3: Biogas storage tank (biogas supplier)
6: Switching valve 10: Fuel gas mixing unit 11: Main fuel gas inflow part 12: Main pipe line 13: Check valve 14: Orifice (pressure loss adding part)
15: Fuel gas outflow part 17: Biogas inflow part 18: Biogas pipe line 19: Pressure equalizing valve 19a: Pressure equalizing path (pressure equalizing part)
20: Regulating valve 21: Biogas introduction hole 30: Gas engine (combustion device)
31: Generator 35: Control device 40: Venturi mixer 41: Biogas introduction hole 42: Throttle part 100: Mixed combustion system 200: Mixed combustion system G: Fuel gas G1: Main fuel gas G2: Biogas P1: Pressure equalizing part pressure P2: Outlet side pressure

Claims (7)

A combustion apparatus that operates by burning fuel gas and whose output is controlled by adjusting the supply amount of the fuel gas;
A main pipe that leads main fuel gas taken from the main fuel gas inflow part to the fuel gas outflow part, and a biogas pipe that leads biogas taken from the biogas inflow part to the biogas introduction hole that opens to the main pipe, And a mixing mechanism that supplies fuel gas flowing out from the fuel gas outlet to the combustion device,
The mixing mechanism section is
A check valve that is disposed upstream of the biogas introduction hole in the main pipeline, and prevents a gas flow toward the main fuel gas inflow portion in the main pipeline;
A pressure equalizing valve that is disposed in the biogas conduit and whose opening varies so as to maintain a pressure balance between the pressure equalizing section and the outlet side;
A mixed combustion system that includes a pressure loss addition unit that is disposed between the check valve and the biogas introduction hole in the main pipeline and adds a pressure loss to the gas flow in the main pipeline .   The mixed combustion system according to claim 1, wherein a pressure equalizing portion of the pressure equalizing valve is connected to an upstream side of the check valve in the main pipeline. Wherein disposed between the pressure equalizing valve in the biogas pipe to the bio-gas inlet, co-combustion system according to claim 1 or 2 with the opening adjustable control valve. A switching valve capable of intermittently supplying biogas from the biogas supply source to the biogas inflow section,
The combustion apparatus closes the switching valve and supplies only the main fuel gas to the combustion apparatus for combustion, and opens the switching valve to open the switching apparatus with the main fuel gas and the biogas. The mixed combustion system according to any one of claims 1 to 3 , wherein the combustion mode is configured to be switchable between a mixed combustion mode in which a mixed gas obtained by mixing a mixture is supplied and combusted. The mixed combustion system according to any one of claims 1 to 4 , wherein the combustion device is a gas engine for driving a generator. The mixed combustion system according to any one of claims 1 to 5 , further comprising a Venturi mixer disposed in the main pipeline and provided with the biogas introduction hole in a constricted portion that reduces the diameter of the main pipeline. It is equipped with a combustion device that operates by burning fuel gas and whose output is controlled by adjusting the supply amount of the fuel gas,
A main pipe that leads main fuel gas taken from the main fuel gas inflow part to the fuel gas outflow part, and a biogas pipe that leads biogas taken from the biogas inflow part to the biogas introduction hole that opens to the main pipe, A fuel gas mixing unit for supplying fuel gas flowing out from the fuel gas outflow portion to the combustion device,
The fuel gas mixing unit comprised by unitizing the said mixing mechanism part which comprises the mixed combustion system of any one of Claims 1-6 .

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