JPH11218005A - Combined power generation system utilizing waster as fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of an externally heating system waste utilizing combined power generation, without using additional fuels such as natural gas under current restrictions on raw materials. SOLUTION: The combined power generation system is provided with an exhaust gas source 1, an open cycle regenerative type gas turbine 3 in which exhaust gas from the exhaust gas source 1 and compressed air are heat-exchanged and externally heated by an outside air heater 2, a high temperature air preheater 13 for waste burning air, a steam boiler 4 arranged in the downstream of the outside air heater 2 and the high temperature preheater 13, and an air preheater 5 for waste burning air, arranged in the downstream of the steam boiler 4. Then, a feed water heater 8 for heating condensed water 7 of a steam turbine 6 consuming stream generated from the steam turbine 4 by means of the exhaust air at the outlet of a regenerator of the gas turbine, is provided to evaporate-heat ammonia-water mixed fluid 10 of a kalina cycle 20 by means of temperature-reduced exhaust air 9 to generate electricity by means of an ammonia-water mixed fluid steam turbine 12, and to supply a part of exhaust air in the downstream of the heat exchanger to the air preheater 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste fuel whose power is recovered by an externally heated gas turbine, a steam turbine, and an ammonia-water mixed fluid turbine for exchanging heat between high-temperature corrosive combustion gas and air. It relates to a combined power generation system.

[0002]

2. Description of the Related Art In a power generation system using water-steam in waste power generation, since the exhaust gas has severe corrosiveness, the steam temperature is suppressed to 300 ° C. or less as compared with solid fuel power generation such as coal. Was. recent years,
Higher efficiency of waste power generation has been promoted by the Global Warming Prevention Action Plan, and steam conditions of 4 MPa and 400 ° C. have been put to practical use. On the other hand, gasification and melting furnaces for the purpose of reducing dioxin emission in waste combustion, reducing fly ash volume by melting incinerated ash, and making it harmless have also been put into practical use. High temperature.

As a high-efficiency power generation system for solid fuel,
Combustion gasification of solid fuel, gas turbine power generation,
There is a combined power generation that performs steam turbine power generation using the exhaust gas of a gas turbine as a heat source. Due to advances in gas turbine technology, 2
In the first century, the combined power generation efficiency using natural gas as fuel is expected to exceed 60%. In waste power generation, a combined gasification power generation system with an output of 30 MW and a power generation efficiency of 44% or more is about to be put into practical use.
However, the current waste gasification is a method of producing gaseous fuel in a pressurized state, and the waste fuel needs to be converted into RDF to a size that can be introduced from a lock hopper and supplied to a gasification furnace. Gasification also requires the treatment of wastewater from oxygen plants and wet gas scrubbing.

As a method for introducing a combined cycle to waste power generation, there is an externally heated gas turbine by exchanging heat between exhaust gas and compressed air.
The present application is to raise the power generation efficiency to the same level as waste gasification combined cycle power generation by raising the air heating temperature to 1150 ° C at the inlet of the latest commercial gas turbine in a normal pressure gasification and melting furnace that reaches ℃. People apply for Japanese Patent Application 8-3
No. 1412, "Combined power generation using waste as fuel". This method requires a high-temperature and high-pressure ceramic heat exchanger, and materials and structures that can withstand a combustion gas at 1350 ° C. in a waste gasification and melting furnace containing a large amount of steam and hydrogen chloride have not been put into practical use.

[0005] As a method for improving the efficiency of coal power generation, research on an externally heated gas turbine has been conducted in the United States and Europe. The temperature of the heated air is set to 1000 ° C or lower, and the turbine inlet temperature is set to 1150 by additional combustion of natural gas. ℃. A method of increasing the power generation efficiency by additionally heating natural gas from the outside is effective when natural gas can be obtained at low cost and the facility can be located near the pipeline, but there is a problem in economics.

[0006] The applicant of the present application discloses in Japanese Patent Application No. 9-214064 "combined power generation system using waste as fuel," a combination of an externally heated gas turbine having an air heating temperature of 742 ° C and a carina cycle, and an output scale of about 20 MW. Has proposed a system with a power generation efficiency of 35%. The problem with this system is that the air-air heat exchange is lower than the conventional air-steam heat exchange heat transfer area in order to keep the air temperature at the gas turbine compressor outlet below the bag filter inlet temperature of the gasification and melting furnace. Approximately three times, so that the cost of the heat exchanger increases.

[0007] The applicant proposed 10 MPa, 540 proposed in Japanese Patent Application No. 9-296313 "Waste combustion power generation system".
Since the method of obtaining steam at a temperature of 35 ° C. yields a power generation efficiency of 35%, the externally-heated combined power generation with a power generation efficiency of 35% has lost its superiority in performance.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and does not use an additional fuel such as natural gas and is limited by the limitations of current materials. It is an object of the present invention to provide a combined power generation system using waste as a fuel, which can improve the efficiency of the externally heated waste combined power generation. Another object of the present invention is to provide a combined power generation system that can reduce the heat transfer area of an air heater and improve economic efficiency.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides an exhaust gas source using waste as fuel and an external air heater for exchanging heat between the exhaust gas from the exhaust gas source and compressed air. An open-cycle regenerative gas turbine, a high-temperature air preheater for waste combustion air, a steam boiler disposed downstream of the external air heater and the high-temperature air preheater, and a downstream side of the steam boiler. In a waste heat recovery system comprising an air preheater for waste combustion air, a feedwater heater for heating condensate of a steam turbine consuming steam generated from a steam boiler with exhaust air at an outlet of the gas turbine regenerator. The ammonia-water mixed fluid of the carina cycle is evaporated and heated by the heat exchanger using the cooled exhaust air, the power is generated by the ammonia-water mixed fluid steam turbine, and the exhaust air downstream of the heat exchanger is provided. It is characterized in supplying a part of the air preheater.

The combined power generation system of the present invention comprises a reheat regeneration steam turbine, an external heating type open cycle regeneration type gas turbine, a feed heater for the steam turbine using gas turbine exhaust air as a heat source, and a temperature of 200 ° C. or less. It consists of an ammonia-water mixed fluid carina cycle using gas turbine exhaust air as a heat source, and waste combustion exhaust gas is heated by a gas turbine external heater, a steam boiler, and a combustion air preheater of a gasification and melting furnace. Collected.

[0011] The air at the compressor outlet of the gas turbine is heated by a regenerator installed in the exhaust gas of the gas turbine, is heated through waste combustion exhaust gas and an air heater, and is recovered in power by an expansion turbine of the gas turbine. Is done. The outlet air temperature of the gas turbine regenerator is about 30 ° C. higher than the compressor outlet air temperature, and this air is used as a heat source to heat the feed water of the reheat regenerative steam turbine. Led to. Due to the exhaust heat of the gas turbine,
Since the boiler feedwater temperature rises, the amount of boiler evaporation increases.

The superheating of steam at 400 ° C. or higher is performed by using a clean high-temperature gasification / melting furnace combustion air independent of a boiler, and the combustion air is heated by a ceramic bayonet type air heater. By being replaced. This method has been proposed by the present applicant in Japanese Patent Application No. 9-296313, entitled "Waste combustion power generation method". The steam superheated to 500 ° C is recovered by a high-pressure steam turbine, and the steam on the back pressure side is returned to the boiler and reheated to 400 ° C. High efficiency is obtained by using a radial type turbine for the high pressure steam turbine. The reheated steam is superheated to 500 ° C. by the high-temperature combustion air, guided to a low-pressure steam turbine, and recovered for power. The combustion air is the gasification and melting furnace 2
Since it is used as secondary air, the secondary air sensible heat is recovered in the boiler.

The air cooled by the feed water heater serves as a heat source for evaporating and superheating the ammonia-water mixed fluid in the carina cycle, and is powered by an ammonia-steam turbine. When the air temperature is 200 ° C. or less, the ammonia-water mixed fluid in which non-isothermal evaporation occurs can recover heat to a lower temperature than steam recovery. The air temperature at the outlet of the ammonia-water mixed fluid heat exchanger becomes 70 ° C., and a part of the air is led to the air preheater in the boiler as combustion air of the gasification and melting furnace. The sensible heat at the outside air temperature and the air temperature of 70 ° C. is a part of the sensible heat of the gas turbine exhaust gas, and a part of the heat obtained from the gas turbine external heater is recovered by the boiler.

According to the present invention described above, the sensible heat of the exhaust air passing through the regenerator of the externally heated gas turbine is used for heating the feed water of the steam turbine cycle, and the power is recovered in the carina cycle. Finally, since sensible heat is used as combustion air, the amount of boiler evaporation increases. Gas turbines, even at turbine inlet temperatures of 750 ° C, increase compressor and expansion turbine efficiencies to levels used in modern gas turbines and increase the heat transfer area of the regenerator to an economically acceptable limit. Then, it can be set to the same level as the cycle efficiency of the steam turbine. Residual heat other than that the exhaust heat of the gas turbine exhaust is reused as heat input of the steam turbine cycle,
Power is recovered in the Kalina cycle, and the exhaust heat of the gas turbine is used effectively.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a combined cycle power generation system according to the present invention. The combined cycle power generation system includes a corrosive exhaust gas source 1 using waste as a fuel, an open cycle regenerative gas turbine 3 that is externally heated by an external air heater 2 that exchanges heat between the exhaust gas from the exhaust gas source 1 and compressed air, A high-temperature air preheater 13 for the air for burning matter, a steam boiler 4 arranged on the downstream side of the external air heater 2 and the high-temperature air preheater 13
And an air preheater 5 for waste combustion air in the downstream. In this embodiment, the corrosive exhaust gas source 1
Has a configuration in which refuse fuel is partially burned in a gasification furnace 50 to be gasified, and the generated unburned gas, char, and the like are burned in a swirling melting furnace 60 at a high temperature.

The combined power generation system includes a feed water heater 8 for heating the condensate 7 of the steam turbine 6 that consumes the steam generated from the steam boiler 4 with the exhaust air at the outlet of the gas turbine regenerator. , The ammonia-water mixed fluid 10 of the carina cycle 20 is evaporated and heated by the heat exchanger 11, the ammonia-water mixed fluid steam turbine 12 generates electric power, and a part of the exhaust air downstream of the heat exchanger 11 is preheated by air. To the vessel 5.

In the combined power generation system, a gas turbine external air heater 30 comprising a metallic radiant heat transfer section coated with a refractory material is disposed in a vertical duct in which corrosive exhaust gas flows upward. The external air heater 2 is constituted by a gas turbine external air heater having a convection heat transfer portion composed of a metal tube covered with a protective tube made of silicon carbide fiber in a downward flow portion where the exhaust gas temperature is lowered. I have.
The high-temperature air preheater 13 is composed of a ceramic bayonet-type high-temperature air preheater suspended from the exhaust gas duct ceiling.

In the combined power generation system having the above configuration,
The corrosive exhaust gas source 1 is high-temperature exhaust gas from a waste incinerator. There is a waste gasification melting incinerator of 331 tons / day,
The description will be made on the assumption that the exhaust gas amount is 110 t / h and the exhaust gas temperature is 1350 ° C. The numerical values given here are merely examples, and the present invention is not limited to these.

In the open cycle gas turbine 3 having the regenerator 31, the inlet temperature to the axial compressor 32 is 15 ° C., the inlet air flow rate is 302 t / h, and the compressor outlet pressure is 0.43M.
Pa · abs, rotation speed 4700 rpm, adiabatic efficiency 90
%, The outlet temperature is 175 ° C, and the required power of the compressor is 1
It is assumed to be 3.6 MW.

The outlet air of the compressor is heated to 453 ° C. by the regenerator 31 having a temperature efficiency of 90% and guided to the external air heater 2 in the exhaust gas duct 40. Exhaust gas temperature 1000
In the range from ℃ to 600 ℃, the compressed air is heated from 453 ℃ to 636 ℃. The type of the heat exchanger in the external heater 2 is a convection type, and a double pipe having a ceramic protection pipe mounted on the outside of a metal pipe is used. Silicon carbide-based ceramics have no oxidative corrosion if the surface temperature is 1000 ° C. or less. When the silicon carbide ceramics uses a composite material made of silicon carbide fiber with excellent thermal shock resistance, the protective tube thickness is 1 m
m, and the heat transfer loss of the protection tube can be reduced.

The surface temperature of the ceramic is 500.degree. C., which is a temperature range higher than around 400.degree. At the exhaust gas temperature of 770 ° C., the growth of deposits on the surface of the bayonet-type ceramics heating tube in the waste incineration facility having an air preheating temperature of 300 ° C. was caused by the exhaust gas temperature of 55 ° C.
Compared to the adhesion of molten salt to the stainless steel tube of a waste incinerator having a superheated steam temperature of 400 ° C. at 0 ° C., the heat transfer performance deterioration due to the adhering matter is much less. In order to prevent the molten salt from adhering and growing, the flow rate of the exhaust gas to the heat transfer tube is preferably 8 m / s or less, and the tube pitch is preferably 110 mm or more.

The compressed air leaving the convection air heater 2 is heated from 653 ° C. to 750 ° C. by the radiant air heater 30 in a region where the temperature of the exhaust gas ranges from 1350 ° C. to 1100 ° C. The radiant air heater 30 is obtained by forming a radiant chamber in a duct in which exhaust gas from the gasification and melting furnace is directed upward. The radiation wall is covered with a refractory material so that the metal tube does not come into direct contact with the exhaust gas. The refractory material has thermal resistance, and the surface temperature of the metal tube is set to 860 ° C. or lower, which is the allowable temperature of high-temperature stainless steel.
The material of the refractory material is preferably a zirconia-chromium-based material that is less oxidatively degraded even in an exhaust gas at 1350 ° C.

Radiant air heater 30 and convection air heater 2
Is a bent duct that changes the flow direction from upward to downward, and a high-temperature air preheater 13 for the gasification and melting furnace combustion air is installed on the ceiling. The high-temperature air preheater 13 is installed in a region where the exhaust gas temperature ranges from 1100 ° C. to 1000 ° C., and heats preheated air at 200 ° C. to 625 ° C. 62
The preheated air of 5 ° C. is supplied to the independent superheater 61 and the independent reheater 62.
And the superheated steam of 400 ° C. is heated to 500 ° C.
The preheated air cooled to 50 ° C. is used as secondary air in a gasification and melting furnace.

The expansion turbine 33 of the gas turbine 3 has an inlet pressure of 0.402 MPa · abs, an inlet temperature of 750 ° C., an outlet pressure of 0.106 MPa · abs, and a rotation speed of 3000 r.
pm, turbine insulation efficiency 89%, outlet temperature 48
At 3 ° C., the recovery power is 24.9 MW. If the output turbine of a commercial two-shaft gas turbine is diverted to the air expansion turbine 33, high efficiency can be obtained. Subtracting compressor power, reduction gear loss, and generator loss from the expansion turbine output gives a gas turbine power generation of 10.4 MW.

The exhaust air of the gas turbine 3 has a temperature efficiency of 90.
48% in the regenerator 31 with the
The temperature is lowered from 3 ° C to 205 ° C. The 205 ° C. exhaust air is guided to the feed water heater 8 of the steam turbine, and raises the feed water temperature of the condensate 7 from 110 ° C. to 185 ° C. Increasing the feedwater temperature increases the amount of boiler evaporation, and the steam turbine output increases as compared to the case where the temperature is increased by the extracted steam from the steam turbine.

The exhaust air 9 that has passed through the feed water heater 8 is 17
It has a temperature of 9 ° C. and serves as a heat source for evaporating and superheating the ammonia-water mixed fluid 10 of the carina cycle 20. The ammonia-water mixed fluid 10 is subjected to non-isothermal evaporation, and the exhaust air is heat-recovered to 70 ° C. by the carina heat exchanger 11.
Assuming that the cycle efficiency of the carina cycle 20 when the heat source temperature is 179 ° C. is 15%, the amount of recovered power generation is 1.4 MW.
Becomes Serina fin tubes are used for the carina heat exchanger 11, and the mixed fluid is 80% ammonia and 20% water.
Is used.

The gas turbine exhaust air passing through the carina heat exchanger 11 has a sensible heat of 70 ° C.
About 30% of / h is recycled to the flowing air and combustion air of the gasification and melting furnace. The temperature of the gas turbine exhaust air is increased by the air preheater 5 installed before the bag filter 45 of the gasification and melting furnace, and heat is recovered as boiler sensible heat input.

Exhaust heat of the gasification and melting furnace becomes heat input of the steam turbine cycle except for a gas turbine external heater which becomes heat input of the gas turbine cycle. The sensible heat from the high-temperature air preheater 2 and the air preheater 5 is absorbed by the boiler drum by the water cooling wall of the exhaust gas duct. 10 of the steam turbine cycle
MPa · abs, high-pressure steam at 500 ° C is 28.9 t / h
With an exhaust pressure of 2.0 MPa · abs and an outlet steam temperature of 30
When the temperature is set to 5 ° C., the power generation amount of the high-pressure steam turbine becomes 2.5 MW. When the steam amount is relatively small, high efficiency can be obtained by using a high-speed rotating radial turbine.

The steam leaving the high-pressure steam turbine is reheated to a permissible temperature of the metal pipe of 400 ° C. by a reheater in the exhaust gas duct. The steam is reheated to 500 ° C. by the 625 ° C. preheated air of the hot air preheater 2. The exhaust pressure of the low-pressure steam turbine was set to 5 kPa · abs, and the deaerator 46 was set to 0.219MPa.
When a / abs and 3.5 t / h steam are extracted, the power generation amount of the low-pressure steam turbine becomes 6.8 MW. An axial flow turbine is used for the low-pressure steam turbine type.

Assuming that the boiler efficiency of the gasification and melting furnace is 88%, the heat input based on the lower calorific value of the waste is 56.2 MWth, which corresponds to the total power generation of the gas turbine, carina cycle turbine, and steam turbine of 21.5 MW. 38.3%
was gotten.

[0031]

As described above, the present invention has the following effects. 1) Without the use of additional fuel such as natural gas, the efficiency of the externally-heated waste combined power generation can be improved and the heat transfer area of the air heater can be reduced in the current material constraints, Economy can be improved. 2) The total power generation end efficiency is 38% when the lower heat value of waste fuel is used as the heat input value. This is 10MPa, 540 ° C
The power generation efficiency of the steam turbine cycle exceeds 35%. Assuming that the cycle efficiency of the steam turbine is the same, if the cycle efficiency of the gas turbine with the regenerator is equal to or more than the cycle efficiency of the steam turbine, the efficiency surely increases by the amount of the exhaust heat of the exhaust gas of the gas turbine. 3) Since the temperature of the air heated by the exhaust gas is raised in the regenerator, the amount of heat transfer of the external heater is reduced and the heat transfer area can be reduced as compared with the case where there is no regenerator.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a combined cycle power generation system according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust gas source 2 External air heater 3 Open cycle regenerative gas turbine 4 Steam boiler 5 Air preheater 6 Steam turbine 7 Condensate 8 Feedwater heater 9 Exhaust air 10 Ammonia-water mixed fluid 11 Carina heat exchanger 12 Ammonia-water Mixed fluid steam turbine 13 High temperature air preheater 20 Carina cycle 30 Radiation type air heater 40 Exhaust gas duct 50 Gasifier 61 Superheater 62 Regenerator

Continued on the front page (51) Int.Cl. ⁶ Identification code FI // F02C 1/04 F02C 1/04 (72) Inventor Kosuke Taguchi 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation ( 72) Inventor Yutaka Mori 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation

Claims (4)

[Claims] 1. An exhaust gas source using waste as fuel, an open cycle regenerative gas turbine externally heated by an external air heater for exchanging heat between exhaust gas from the exhaust gas source and compressed air, and a waste combustion air source. Exhaust heat provided with a high-temperature air preheater, a steam boiler disposed downstream of the external air heater and the high-temperature air preheater, and an air preheater for waste combustion air downstream of the steam boiler A recovery system, comprising: a feedwater heater for heating condensate of a steam turbine that consumes steam generated from a steam boiler with exhaust air at an outlet of the gas turbine regenerator, and ammonia-water of a carina cycle is provided by the cooled exhaust air. Evaporating and heating the mixed fluid with a heat exchanger, generating electricity with an ammonia-water mixed fluid steam turbine,
A combined power generation system using waste as fuel, wherein a part of the exhaust air downstream of the heat exchanger is supplied to the air preheater. 2. A gas turbine external air heater comprising a metallic radiant heat transfer portion coated with a refractory material is disposed in a vertical duct in which exhaust gas from the exhaust gas source flows upward. A combined power generation system using the waste according to 1 as a fuel. 3. A combined power generation system using waste as a fuel according to claim 1, wherein said high-temperature air preheater comprises a ceramic bayonet-type high-temperature air preheater suspended from an exhaust gas duct ceiling. . 4. The gas turbine external air heater having a convection heat transfer section comprising a metal pipe covered with a protective pipe made of silicon carbide fiber in a downward flow section where the temperature of exhaust gas is lowered. 2. The method according to claim 1, wherein
A combined power generation system using the waste described in the description as a fuel.