JP3713221B2 - Heat source reuse system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat source reuse system for reusing heat energy contained in exhaust gas from a heat engine such as an engine or a gas turbine that is used as a drive source of a generator in, for example, a self-supporting distributed power supply facility, In particular, the present invention relates to a heat source reuse system that is suitable when the internal pressure of a heat engine is low.
[0002]
[Prior art]
Regarding a heat source reuse system or a cogeneration system that reuses heat energy contained in exhaust gas from a heat engine, there are a method of directly using the heat energy of the exhaust gas and a method of using it indirectly. The latter indirect utilization method is an exhaust recombustion method that uses the thermal energy of exhaust gas to raise the temperature of fuel combustion air, and the recycle efficiency can be nearly doubled compared to the direct utilization method. For this reason, the exhaust gas reburning type has become mainstream recently.
[0003]
As for the exhaust gas reburning type, examples disclosed in, for example, “Osaka Gas Technical REPORT Exhaust Gas Reburning Burner”, Japanese Patent Application Laid-Open No. 10-196933 or Japanese Patent Application Laid-Open No. 9-236201 are known. Examples disclosed in Japanese Patent Laid-Open Nos. 10-47078, 9-287415, 2000-45710, and the like are also known. In particular, the example of FIG. 2 in Japanese Patent Laid-Open No. 10-196933 and the example of FIG. 2 in Japanese Patent Laid-Open No. 9-236201 are one typical structure in the conventional exhaust reburning type.
[0004]
In other words, in the conventional exhaust gas reheat type heat source reuse system, a combustor is provided for use of exhaust gas, and exhaust gas from a heat engine used as a drive source for a generator or the like is used to raise the temperature of combustion air in the combustor. By making use of it, the heat energy contained in the exhaust gas can be reused. In such an exhaust gas utilization mode, the oxygen content of the exhaust gas is, for example, about 13 to 15%, which is lower than that of normal air. Therefore, it is necessary to send fresh air together with the exhaust gas to the combustor. The conventional general structure for the mixed supply of exhaust gas and fresh air is described in Japanese Patent Application Laid-Open No. 10-196933, Japanese Patent Application Laid-Open No. 9-236201, and Japanese Patent Application No. 2000-207751. The fresh air is pressurized by a forced air blower, and the pressurized fresh air is mixed with exhaust gas and sent to the combustor.
[0005]
[Problems to be solved by the invention]
In the conventional exhaust reheat type heat source reuse system as described above, there is a problem that the back pressure of the heat engine, which is an exhaust gas source, increases due to the pressurization by the forced air blower. It can be said that the increase in the back pressure caused by the forced air blower does not have a bad influence if the internal pressure of the heat engine is sufficiently large.
However, it is a gas turbine with an output level of, for example, 300 kw or less, which is expected to be used more and more in relatively small private power generation facilities in the future. In the case of a heat engine generally called a micro gas turbine, The pressure is very low compared to the boosting capacity of a normal forced draft fan. For this reason, there is a possibility that the efficiency of the heat engine is greatly adversely affected by the increase of the back pressure by the forced draft fan.
[0006]
Japanese Laid-Open Patent Publication No. 10-196933 discloses that a fan for pumping exhaust gas from a heat engine is provided. The purpose of this pressure-feeding fan is to eliminate the induction fan that was provided in the conventional system for exhaust after use of exhaust gas, but as a result, it prevents the back pressure of the heat engine from increasing. It also works.
However, in this technology, exhaust gas is pumped by a pumping fan and then mixed with fresh air. Therefore, the pumping fan is directly exposed to a very high temperature of several hundred degrees Celsius accompanied by exhaust gas from a heat engine. Will be. This becomes a heavy burden when selecting and designing the material of the pressure feeding fan, and as a result, it can impair the stable operation of the system and lead to an increase in the cost of the system.
[0007]
Japanese Patent Application No. 2000-207751 discloses a heat source reuse system provided with a boosting unit that sucks while mixing exhaust gas from a heat engine and fresh air, and pressurizes the mixed gas to supply it to a combustor. Is described.
However, in this system, the intake air pressure is increased by adding fresh air to the entire exhaust gas, which requires a large intake fan, leading to an increase in system cost, and the exhaust gas amount from the heat engine and the capacity of the combustor of the heat source reuse system. Is fixed, and there is a restriction such as fixing the thermoelectric ratio of the cogeneration system.
[0008]
The present invention has been made against the background of the conventional situation as described above, and can perform mixed supply of exhaust gas and fresh air without increasing the back pressure with respect to the heat engine that is the exhaust gas source, and from the heat engine. The purpose of the present invention is to provide an exhaust gas reburning heat source reuse system that can do this without being directly affected by the high temperature in the exhaust gas.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an exhaust gas reheat type heat source reuse system of the present invention is a heat source reuse system provided with a combustor that uses exhaust gas from a heat engine to raise the temperature of combustion air. A suction boosting means is provided that sucks while mixing with fresh air and boosts the mixed gas of the exhaust gas and the fresh air and supplies it to the combustor.
[0010]
In order to achieve the above object, an exhaust gas reheat type heat source reuse system of the present invention is a heat source reuse system including a combustor that uses exhaust gas from a heat engine to raise the temperature of combustion air, and the exhaust gas from the heat engine. A part of the gas is sucked and used to raise the temperature of the combustion air, and the remaining exhaust gas is directly reburned in the combustion chamber of the combustor.
[0011]
In order to achieve the above object, the exhaust reburning heat source reuse system of the present invention is provided with an adjusting damper for adjusting the mixing ratio of exhaust gas and fresh air.
[0012]
In order to achieve the above object, the exhaust reheat type heat source reuse system of the present invention is provided with suction boosting means close to the combustor.
[0013]
In order to achieve the above object, the exhaust reburning heat source reuse system of the present invention is provided with an auxiliary outside air inlet for sucking fresh air instead of exhaust gas from the heat engine as combustion air for the combustor.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a flowchart of a heat source reuse system according to the first embodiment. The heat source reuse system according to the present embodiment is an example of reusing exhaust gas from a self-supporting distributed power supply facility used as, for example, a private power generation facility. A power generation facility serving as an exhaust gas source (exhaust heat source) includes a generator (not shown) and a gas turbine 1 that is a heat engine for driving the generator.
[0015]
On the other hand, the main part of the heat source reuse system includes a first exhaust duct 2 connected to the gas turbine 1, a first air guide path 3 connecting one end to the exhaust duct 2, and the other end of the first air guide path 3. An intake fan 4 which is a suction pressure-increasing means connected to the second intake passage 4, a second air passage 5 connected to one end of the intake fan 4, a combustor 6 connected to the second air guide passage 5, and a heat exchange connected to the combustor 6. And a second exhaust duct 8 connected to the boiler 7.
[0016]
The exhaust gas Ge from the gas turbine 1 discharged through the first exhaust duct 2 is guided to the first air guide path 3 by the suction force of the intake fan 4. At that time, fresh air Gf is also sucked and supplied from the open end of the first exhaust duct 2 to the atmosphere side and mixed with the exhaust gas Ge. In this case, since the gas turbine 1 has an internal pressure higher than the atmospheric pressure, the exhaust gas Ge is first sucked preferentially, and the suction amount of the intake fan 4 exceeds the exhaust amount from the gas turbine 1. Fresh air Gf is sucked in a certain amount for the range.
[0017]
Therefore, the mixing ratio of the exhaust gas Ge and the fresh air Gf is determined according to the suction capacity of the intake fan 4. The suction capacity of the intake fan 4 can be adjusted by changing the opening degree of the flow control damper 9 provided in the first air guide path 3 close to the intake fan 4, and the impeller in the intake fan 4. Although it can also be adjusted by changing the rotation speed, it is usually adjusted by the flow rate control damper 9. However, the suction capacity actually required by the intake fan 4 is determined by the amount of air required by the combustor 6. Therefore, normally, the suction capacity of the intake fan 4 is fixedly set so that the amount of air (oxygen amount) required according to the specifications of the combustor 6 can be supplied. For this reason, the mixing ratio of the exhaust gas Ge and the fresh air Gf is also fixed.
[0018]
The mixed gas of the exhaust gas Ge and the fresh air Gf is pressurized to a predetermined pressure or higher by the intake fan 4 and supplied to the combustor 6 through the second air guide path 5. Here, the predetermined pressure is determined by the specifications of the combustor 6. The combustor 6 is supplied with a fuel F such as gas or oil through a fuel supply pipe 11, and the fuel F burns under the mixed gas supplied as described above. The exhaust gas from the combustor 6 is finally discharged into the atmosphere from the second exhaust duct 8.
[0019]
The heat energy generated by this combustion is used as a heat source for the boiler 7. The boiler 7 will take the form according to the utilization purpose of heat energy. For example, if heat energy is used to obtain steam or hot water, it becomes a form for generating steam or hot water. For example, if heat energy is used for refrigerant regeneration of an absorption chiller / heater, It will take the form of a high-temperature regenerator of an absorption chiller / heater.
[0020]
In the heat source reuse system according to the present invention, the exhaust gas from the gas turbine 1 is sucked and boosted by the intake fan 4 and supplied to the combustor 6 as described above. Therefore, the back pressure of the gas turbine 1 is not increased when the mixed gas is supplied to the combustor 6 while being pressurized. Therefore, the gas turbine 1 is a so-called micro gas turbine having an output level of, for example, 300 kW or less, and even when the internal pressure is very low, exhaust heat can be used without reducing the efficiency of the gas turbine 1. Become.
[0021]
In the present invention, the exhaust gas is mixed with fresh air and then sucked and pressurized by the intake fan 4. For this reason, the temperature of the gas passing through the intake fan 4 decreases according to the ratio at which fresh air taken from the atmosphere is mixed with the exhaust gas. For example, as usual, when the mixing ratio of fresh air is 50% or higher, the temperature of the mixed gas passing through the intake fan 4 should be 150 ° C. or lower even if the temperature of the exhaust gas is about 300 ° C., for example. Can do.
[0022]
This is very practically significant compared to a configuration in which only exhaust gas is sucked by a fan as in the above-mentioned JP-A-10-196933 and a very high temperature gas such as 300 ° C. passes through the fan as it is. There are certain advantages. Specifically, each member of the intake fan 4 can be configured with a relatively low level of heat-resistant material, and the intake fan 4 can be designed without requiring a very high heat-resistant design. Cost reduction can be achieved.
[0023]
FIG. 2 is a flowchart of the heat source reuse system according to the second embodiment. In the present embodiment, the outside air intake amount adjusting damper 21 is provided in the first exhaust duct 2, the cutoff damper 22 is provided in the first air guide path 3, and the first air guide path 3. This is basically the same as that of the first embodiment except that the auxiliary outside air inlet 24 with the outside air intake amount adjusting damper 23 is connected to the outside. In the case of the present embodiment in which the first exhaust duct 2 is provided with the outside air intake amount adjusting damper 21, the mixing ratio of the exhaust gas Ge and the fresh air Gf can be adjusted by the outside air intake amount adjusting damper 21.
[0024]
Specifically, by controlling the outside air intake amount adjusting damper 21, the intake resistance of the fresh air Gf can be adjusted, whereby the intake amount of the fresh air Gf can be changed, and thereby the exhaust gas Ge and the fresh air Gf can be changed. The mixing ratio of can be changed. The outside air intake amount adjustment damper 21 is controlled according to the state of the exhaust gas Ge from the gas turbine 1.
[0025]
Information on the state of the exhaust gas Ge can be obtained from the control device of the gas turbine 1, and a dedicated exhaust gas monitoring means may be provided if necessary. Such an adjustment function is useful for stably operating the combustor 6 even when the operating state of the gas turbine 1 changes, and the fresh air Gf according to the amount of oxygen contained in the exhaust gas Ge from the gas turbine 1. By minimizing the amount of mixing, it is useful for increasing the utilization efficiency of exhaust gas.
[0026]
The blocking damper 22 is used when it is necessary to stop the suction of the exhaust gas Ge for some reason. When the combustor 6 is operated in a state where the suction of the exhaust gas Ge is stopped, only fresh air Gf is sucked from the auxiliary outside air inlet 24 and supplied to the combustor 6. In this case, the intake amount of the fresh air Gf is adjusted by the outside air intake amount adjustment damper 23 in accordance with a request from the combustor 6. Such a function is also useful for improving the stability of the heat source reuse system main body portion against fluctuations in the operating state of the gas turbine 1.
[0027]
FIG. 3 is a flowchart of the heat source reuse system according to the third embodiment. The present embodiment is the same as the second embodiment except that the intake fan 4 is directly connected to the combustor 6. That is, in this embodiment, the second air guide path 5 in the first embodiment and the second embodiment is omitted. With this configuration, the entire system can be reduced in size.
[0028]
FIG. 4 is a flowchart of the heat source reuse system according to the fourth embodiment. In this embodiment, the second exhaust duct 2 is provided with an outside air intake amount adjustment damper 21, the second air guide path 15 is provided in parallel with the first air guide path 3, The cutoff damper 22 is provided at the inlet of the air guide path 3, and the outside air is sucked into the first air guide path 3 on the downstream side of the branch point between the first air guide path 3 and the second air guide path 15. This is basically the same as in the third embodiment except that the auxiliary outside air inlet 24 with the amount adjusting damper 23 is connected, and the downstream side of the second air guide path 15 is connected to the combustor 6. Connected directly.
[0029]
When the exhaust heat is reused, the cutoff damper 22 provided in the first air guide path 3 is opened, the outside air intake amount adjusting damper 21 provided in the first air guide path 3 is closed, and the first exhaust duct 2 is The exhaust gas Ge discharged from the gas turbine 1 is branched into the first air passage 3 and the second air passage 15.
On the other hand, fuel F such as gas or oil is supplied to the combustor 6 through the fuel supply pipe 11, and the amount of air necessary for combustion of this fuel is adjusted by the cutoff damper 22 and supplied to the combustor 6. The
[0030]
Therefore, the amount of exhaust gas sucked in the first air passage 3 is determined by the amount of air required by the combustor 6, and the remaining exhaust gas is guided from the second air passage 15 to the combustion chamber of the combustor 6. It is burned and then heated and reburned by the combustion flame.
The exhaust gas from the combustor 6 is finally released into the atmosphere from the second exhaust duct 8, and the heat energy generated by this combustion is used as a heat source for the boiler 7. The boiler 7 will take the form according to the utilization purpose of heat energy.
For example, if heat energy is used to obtain steam and hot water, it becomes a form for generating steam and hot water, for example, if heat energy is used for refrigerant regeneration of an absorption chiller / heater, It will take the form of a high-temperature regenerator for an absorption chiller / heater.
[0031]
The first air passage 3 is provided with an auxiliary outside air introduction port 24 with an outside air intake amount adjusting damper 23, and an intake fan is provided according to the oxygen content of exhaust gas from the gas turbine 1 and the heat resistance specification of the intake fan 4. 4, the mixing ratio of the exhaust gas sucked into fresh air and the fresh air can be adjusted by controlling the outside air suction amount adjusting damper 23.
[0032]
On the other hand, when the heat source reuse system is operated independently without using the exhaust heat of the exhaust gas discharged from the gas turbine 1 for some reason, the cutoff damper provided at the inlet of the first air guide path 3 22 is closed, the outside air intake amount adjustment damper 21 is opened, and the exhaust gas Ge inflow into the first air guide path 3 and the second air guide path 15 is blocked.
When the combustor 6 is operated in a state where the exhaust of the exhaust gas from the gas turbine 1 is cut off, the intake fan 4 sucks fresh air Gf from the auxiliary outside air inlet 24 and supplies it to the combustor 6. The intake amount of the air Gf is supplied to the combustor 6 with fresh air Gf adjusted by the outside air intake amount adjustment damper 23 in accordance with a request in the combustor 6.
Such an independent operation function is also useful for improving the stability of the heat source reuse system and the cogeneration system as a whole against fluctuations in the operating state of the gas turbine 1.
[0033]
When only the power generation is performed by the gas turbine 1 and the exhaust gas exhaust heat is not reused, the shut-off damper 22 provided at the inlet of the first air guide path 3 is closed and the outside air intake amount adjusting damper 21 is opened. Thus, the exhaust gas Ge from the gas turbine 1 is discharged from the first exhaust duct 2 to the atmosphere via the outside air intake amount adjustment damper 21. Even if the shut-off damper 22 is in the fully closed position at this time, in order to prevent a small amount of exhaust gas from leaking and causing abnormal heating of the boiler 7 and corrosion due to condensation on the heat transfer surface, While the turbine 1 is in operation, the intake fan 4 is always operated, and fresh air Gf is sucked from the auxiliary outside air introduction port 24 and supplied into the boiler 7, so that the inside air is always replaced with outside air, and temperature rise and condensation are caused. To prevent.
[0034]
【The invention's effect】
As described above, according to the present invention, there is provided suction boosting means for sucking and boosting the exhaust gas from the heat engine while mixing it with fresh air. This can be performed without increasing the back pressure on the heat engine and without directly affecting the suction pressure increasing means by the high temperature exhaust gas from the heat engine. For this reason, it becomes possible to reuse exhaust gas with high efficiency without reducing the efficiency of a heat engine having a low internal pressure, for example, a so-called micro gas turbine.
[0035]
In addition, a part of the exhaust gas from the heat engine is sucked and used to raise the temperature of the combustion air, and the remaining exhaust gas is directly reburned in the combustion chamber of the combustor. Compared to what is used, a small intake fan can be used, and the capacity of the combustor can be freely selected according to the required capacity of a boiler or the like that uses exhaust heat, so that the cost of the entire system can be reduced.
[0036]
In addition, the combustion air for the combustor is provided with an auxiliary outside air inlet that sucks fresh air instead of exhaust gas from the heat engine. Loss can be reduced, and even when the heat engine is stopped for any reason, the heat source reuse system can be operated independently by supplying outside air to the combustor by the intake fan.
[Brief description of the drawings]
FIG. 1 is a flow diagram of a heat source reuse system according to a first embodiment of the present invention.
FIG. 2 is a flow diagram of a heat source reuse system according to a second embodiment of the present invention.
FIG. 3 is a flow diagram of a heat source reuse system according to a third embodiment of the present invention.
FIG. 4 is a flow diagram of a heat source reuse system according to a fourth embodiment of the present invention.
[Explanation of symbols]
1 Gas turbine (heat engine)
4 Intake fan (suction boosting means)
6 Combustor 21 Outside air intake adjustment damper (adjustment damper)
24 Auxiliary outside air inlet Ge Exhaust gas Gf Fresh air

Claims (5)

In a heat source reuse system including a combustor that uses exhaust gas from a heat engine to raise the temperature of combustion air, the exhaust gas from the heat engine is sucked while being mixed with fresh air, and the exhaust gas and the fresh air The heat source reuse system is provided with suction boosting means for boosting and supplying the mixed gas to the combustor. In a heat source reuse system including a combustor that uses exhaust gas from a heat engine to raise the temperature of combustion air, a part of the exhaust gas from the heat engine is sucked and used to raise the temperature of combustion air, The heat source reuse system, wherein the remaining exhaust gas is directly reburned in the combustion chamber of the combustor. The heat source reuse system according to claim 1 or 2, wherein an adjustment damper for adjusting a mixing ratio of the exhaust gas and the fresh air is provided. The heat source reuse system according to any one of claims 1 to 3, wherein the suction pressure raising means is provided in the vicinity of the combustor. The heat source reuse system according to claim 2, wherein an auxiliary outside air inlet that sucks fresh air instead of exhaust gas from the heat engine is provided as combustion air of the combustor.

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