JPH09112213A - Boiler facility for recovering waste heat from gas turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler facility for recovering waste heat from a gas turbine, in which unburnt gas discharged from a vent and a drain from a fuel gas supply line is stored in a gas holder and is then fed into a waste heat recovering boiler. SOLUTION: A boiler facility for recovering waste heat from a gas turbine 25 comprises a fuel gas supply line 30 incorporating components for purifying fuel gas fed into a gas turbine 25 and a waste heat recovering boiler 32, drain tanks 9, 14 receiving removed impurities, vent pipes 6, 16 for discharging fuel gas from drain tanks 9, 14, a nitrogen gas supply line 17 and a fuel gas vent pipe 19 incorporated in the supply line 30, and a gas holder 43 having an inlet side connected thereto with the vent pipe 19. A heat recovering boiler 32 is connected to the outlet of an exhaust gas duct 26 of the turbine 25 and an outlet pipe 42 of the gas holder 43 is connected to the fuel gas supply line 30 connected to the boiler 32.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas turbine and an exhaust heat recovery boiler facility.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional gas turbine exhaust heat recovery boiler facility. The low pressure fuel gas supply line 1
On the upstream side of the compressor suction separator 3 of the gas compressor 2, before branching to the boiler fuel gas supply line 30 and entering the exhaust heat recovery boiler 32, impurities are removed by the boiler suction separator 31. On the other hand, the natural gas from which impurities have been removed by the compressor suction separator is pressurized by the gas compressor and guided to the compressor discharge separator 4 by the high-pressure fuel gas supply line 5, where impurities discharged from the compressor are removed. To do. When impurities are accumulated to a certain level at the bottom of each separator, they are discharged to the drain tank 9 manually or automatically. At this time, the natural gas is discharged together with the impurities, so that the natural gas is sent to the flare stack 7 through the vent pipe 6. Natural gas is supplied to the high pressure fuel gas supply line through the combustor 8 of the gas turbine 25.
Prior to entering, the knockout drum 10 removes impurities. When the impurities are accumulated to some extent, they are discharged to the drain tank 14.

As the fuel supplied to the gas turbine, liquefied gas is also used in addition to natural gas. First, the vaporizer 11 is used.
Is vaporized into fuel gas, which is heated by the heater 12 to remove water and liquefied gas by the mist separator 13 and then supplied to the combustor. If impurities are accumulated to some extent in the mistreparator, the liquefied gas is vaporized by being discharged to the drain tank 14 and depressurized to become fuel gas. When the impurities are discharged from the knockout drum 10, natural gas also comes out at the same time, so the drain tank 14 to the vent pipe 16
And sent to the flare stack.

Before disassembling each device or pipe for inspection or repair, it is necessary to replace the residual gas in each fuel supply line with nitrogen gas. In this method, the vent valve 15 provided on the downstream side of each fuel supply line is opened, the residual gas is sent to the flare stack through the vent pipe 19, and each line is reduced to atmospheric pressure. Next, the nitrogen gas stop valve 18 of the nitrogen gas supply line 17 provided on the upstream side of each line is opened, and nitrogen gas is discharged to each line, thereby expelling the residual gas to the flare stack and replacing it with nitrogen gas. In the flare stack, when a small amount of combustible gas is emitted from the tip, it is emitted to the atmosphere and diffused, and when a large amount is emitted, it is burned at the tip.

As a method for treating unburned gas, there is Japanese Patent Laid-Open No. 57-87529, which is similarly sent to a flare stack and burned.

[0006]

The above-mentioned prior art has a problem that valuable flammable gas is not effectively utilized but is released from the flare stack to the atmosphere.

An object of the present invention is to effectively utilize the unburned gas which is wastefully consumed by being sent from the drain and vent to the flare stack.

[0008]

According to the present invention, a gas holder is provided in place of the flare stack to store unburned gas, and the gas pressure in the gas holder is higher than atmospheric pressure. Therefore, the discharge side is connected to the exhaust heat recovery boiler. If so, the energy can be effectively used.

The embodiment of the present invention is an apparatus in which the exhaust heat recovery boiler is provided with an auxiliary combustion device in addition to the energy of the exhaust gas of the gas turbine to generate more steam, and which uses natural gas as the fuel. If part or all of the natural gas to be sent to the auxiliary burner is sent from the gas holder of the present invention, energy saving equipment can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows an embodiment in which an exhaust heat recovery boiler has an auxiliary combustion device. Holder inlet pipe 4 of gas holder 40
A vent pipe 6, a vent pipe 16, and a vent pipe 19 are connected to the device 1. The pressure of the gas flowing into the gas holder balances the weight of the holder floating roof 43, but is set to the pressure of the boiler fuel gas supply line 30. If the pressure in the gas holder is high, there is a risk of backflow to each vent pipe, so a holder inlet check valve 44 is provided. The exhaust heat recovery boiler 32 is connected to the exhaust duct 26 of the gas turbine and generates steam at an exhaust gas temperature of about 500 ° C. When it is desired to increase the amount of steam generated, the auxiliary heat recovery device 33 is installed in the exhaust heat recovery boiler.
Is installed to supply natural gas from the boiler fuel gas supply line. This auxiliary combustion device has an advantage that steam can be generated even while the gas turbine is stopped. In order to supply gas from the gas holder to the auxiliary combustion apparatus, the holder outlet pipe 42 is connected to the boiler fuel gas supply line via the holder outlet check valve 45 and the holder outlet stop valve 46. When half the gas on the fuel gas supply line side is used, the gas supply line valve 34 is half-opened and the holder outlet stop valve 46 is half-opened. When supplying all of the gas on the gas holder side, fully close the gas supply line valve and fully open the holder outlet stop valve.

Next, an embodiment in which the exhaust heat recovery boiler is not equipped with a supplementary heat device will be described with reference to FIG. The natural gas stored in the gas holder opens the holder outlet stop valve, closes the low pressure fuel gas supply line stop valve 20, is guided to the low pressure fuel gas supply line by the holder outlet pipe, and removes dust with the compressor suction separator. It is removed, pressurized with a gas compressor and fed to the gas turbine. However, the gas in the gas holder may also contain nitrogen gas, which has insufficient calorific value, so the liquefied gas of the vaporizer is also activated.
Send fuel gas to the gas turbine. As a result, the output of the gas turbine and the evaporation amount in the exhaust heat recovery boiler do not decrease, and operation can be performed.

[0012]

According to the present invention, it is possible to effectively use energy by recovering fuel which was conventionally wasted and burned in the exhaust heat recovery boiler to generate steam. This reduces plant thermal efficiency by consuming less fuel,
Greatly improved.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a gas turbine exhaust heat recovery boiler facility with an auxiliary combustion device according to an embodiment of the present invention.

FIG. 2 is a system diagram showing a gas turbine exhaust heat recovery boiler facility without an auxiliary combustion device, which is an embodiment of the present invention.

FIG. 3 is a system diagram showing a conventional gas turbine exhaust heat recovery boiler facility.

[Explanation of symbols]

6, 16, 19 ... Vent pipe, 9, 14 ... Drain tank,
25 ... Gas turbine, 30 ... Boiler fuel gas supply line, 32 ... Exhaust heat recovery boiler, 42 ... Holder outlet pipe, 43
… Gas holder.

Claims (3)

[Claims] 1. A fuel gas supply line equipped with a device for cleaning fuel gas supplied to a gas turbine and an exhaust heat recovery boiler, a drain tank for receiving removed impurities, and a fuel gas in the drain tank. A facility equipped with a vent pipe for discharging, wherein the vent pipe is connected to an inlet pipe of a gas holder, a gas turbine exhaust heat recovery boiler facility. 2. A fuel gas supply line equipped with a device for cleaning the fuel gas supplied to the gas turbine and the exhaust heat recovery boiler, and a facility equipped with a nitrogen gas supply line and a fuel gas vent pipe in the fuel gas supply line. In the gas turbine exhaust heat recovery boiler facility, the fuel gas vent pipe is connected to an inlet pipe of a gas holder. 3. A facility having a fuel gas supply line for connecting an exhaust heat recovery boiler to an exhaust gas duct outlet of a gas turbine and supplying a fuel gas to the exhaust heat recovery boiler,
A gas turbine exhaust heat recovery boiler facility, wherein an outlet pipe of a gas holder is connected to the fuel gas supply line.