JPH10238369A - Gasification generating plant and operating method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the NOx exhaust concentration in a plant where a combustion state of a combuster can be switched from the oil combustion to the gas combustion, by using both of steam injection and nitrogen injection in a combustion part, in the gas mono-fuel combustion after the combustion state is switched from the oil to the gas. SOLUTION: A gasification generating plant comprises a gasification furnace 51, a gas refining device (desulfurizer 52, dedusting device 53), a gas turbine (compresser 1, combuster 2, turbine 3), an oxygen manufacturing device 59, an exhaust heat recovering boiler 58, a steam turbine 57, and a generator 56. At the starting, the gas turbine is operated by using the gas oil 105 supplied from a gas oil tank 64. Then the fuel 100 is burned in the gasification furnace 51 while receiving the supply of oxygen 61, and the oil combustion is switched to the gas combustion by a fuel device 2, when the gasified gas is produced. When the combustion reaches the gas mono-fuel combustion state, nitrogen is injected to the combuster 2, and then the steam generated in the exhaust heat recovering boiler 58 is injected to the combuster 2, to reduce NOx.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasification power plant and a method of operating the same, and more particularly, to a case where a combustion state of a combustor is switched from oil combustion to gas combustion, and gasified gas is used as a main fuel during gas combustion. The present invention relates to a gasification power plant that drives a gas turbine to generate power.

[0002]

2. Description of the Related Art A combined power generation plant for gasifying and generating electricity by oxygen oxidation is being studied at present, as compared with an air oxidation system in which heavy oil or coal is gasified by air oxidation. In this case, in the gas obtained by the oxygen oxidation method, the main combustible components in the fuel are hydrogen and carbon monoxide,
Since the combustion speed of the gas is about three times faster than that of natural gas, it is said that it is difficult to reduce NOx by premix combustion performed in a natural gas-fired combustor.

Therefore, there is an urgent need for a low NOx combustion method using nitrogen obtained in a plant. At that time, it is conceivable to mix the supplied nitrogen into the fuel and reduce the calorific value to reduce NOx. However, in this case, since the supply pressure from the gasifier is high, the nitrogen to be mixed is considerably increased in pressure. And there are problems such as a reduction in plant efficiency.

[0004] As a method of gasifying coal with oxygen and supplying nitrogen obtained in the plant to a combustor, there is a method described in Japanese Utility Model Laid-Open No. 57-168735, for example. This fuel is limited to coal, so the oxygen separated from the oxygen production equipment is extracted as an oxidizing agent necessary for gasification, and a part of the remaining nitrogen is supplied to the combustor, This is to reduce the emission concentration of the emitted nitrogen oxides (NOx).

[0005]

In a gasification furnace in a gasification power plant, when a fuel such as coal or heavy oil is gasified by air oxidation, the calorific value of the supplied gas is about 800 to 1000 kcal / Nm3. It becomes a low calorie gas. In this case, in the gas turbine combustor,
At the time of gas combustion, the emission concentration of the unburned portion may increase depending on the load range (particularly, partial load) of the gas turbine, and combustion may be unstable depending on a large variation in the calorific value of the fuel.

Accordingly, recently, a gasification system using oxygen oxidation is being studied. In this method, air extracted from a gas turbine is separated into oxygen and nitrogen by an oxygen separator, and the separated oxygen is supplied to a gasification furnace as an oxidizing agent for gasification. The calorific value of the supplied gas is a medium calorie gas of about 2500 kcal / Nm3.

[0007] The characteristics of this gas are that the main combustible components in the fuel are hydrogen and carbon monoxide, and that the hydrogen content is 25% or more.
The combustion rate is several times faster than low calorie gas and natural gas including 40%, and the adiabatic flame temperature in the stoichiometric mixture ratio of fuel and air is about 2 times higher than that of natural gas burning.
00 deg may be increased.

From the above, it is extremely difficult to reduce NOx by premixed combustion due to the nature of the gas having a high combustion rate, and low NOx using nitrogen separated from the oxygen production apparatus.
The x combustion method is considered to be an effective means. However,
With the increase in the combustion temperature of the gas turbine, it is difficult to achieve a sufficient reduction in NOx with only the amount of nitrogen obtained by separation from the oxygen production equipment of the plant.

It is also conceivable that nitrogen obtained from the plant is mixed with fuel to reduce the calorific value of the fuel, thereby lowering the flame temperature and reducing NOx. Since the gas pressure is about 1.9 times higher than the compressor discharge air pressure, mixing nitrogen into fuel has the problem of increasing the pressure to a considerable pressure. In this case, it is inevitable that the efficiency of the entire plant is reduced. Therefore, it is necessary to consider a method for reducing NOx other than the above.

The present invention has been made in view of the above, and an object of the present invention is to provide a gasification and power generation plant of this type which can sufficiently reduce the NOx emission concentration without lowering the efficiency of the whole plant. It is in.

[0011]

That is, the present invention relates to a gas generator which operates by switching the combustion state of a combustor from oil combustion to gas combustion and drives a gas turbine using gasified gas as a main fuel during gas combustion to generate power. In the operating method of the gasification power plant, in the gas burning state after switching the combustion state from oil to gas, the combustion unit is operated while using both steam injection and nitrogen injection in combination with the intended purpose. It is to achieve.

In this case, the steam to be supplied to the combustion section is extracted from an exhaust heat recovery boiler of a combined cycle power plant combining a gas turbine and a steam turbine or from a steam system after cooling a furnace wall of a gasification furnace. It is designed to be extracted.

The present invention also relates to a gasification power generation plant which operates by switching the combustion state of a combustor from oil combustion to gas combustion and drives a gas turbine using gasified gas as a main fuel during gas combustion to generate power. The plant is provided with a steam injection device for injecting steam into the combustion portion and a nitrogen injection device for injecting nitrogen in a gas-only state after switching the combustion state from oil to gas.

In this case, the injection nozzle of the steam injection device is disposed near the inflow air inlet of the swirler for holding the flame, and the injection nozzle of the nitrogen injection device has the same radial direction as the air injection hole of the fuel nozzle. They are alternately arranged at respective positions, or a plurality of them are arranged on the outer peripheral side of the air injection holes. In addition, the injection nozzle of the nitrogen injection device is circumferentially attached to a fuel nozzle portion for holding a flame composed of oil, gas, and air injection holes and a side wall portion of an outer cylinder that is a pressure vessel of the combustor. A plurality of fuel cells are arranged so that a part of the supplied total nitrogen amount is injected into a combustion region from an end face of the fuel nozzle, and the remaining part is injected into combustion air.

That is, according to the gasification power plant thus formed and the operation method thereof, a low N
In order to operate both the steam injection for Ox and the nitrogen injection that can be supplied at the time of gas firing, and the gas firing after switching of the combustion state from oil to gas, both are used. In this case, the NOx concentration that could not be reduced can be further reduced. These are mainly focused on reducing the peak temperature range of the optimum mixing portion of gas and air present in the combustion region, which is a characteristic of diffusion combustion, by injecting and mixing nitrogen or steam as an inert gas. It has been put.

According to the present invention, steam supplied to a gas turbine combustor is extracted from an exhaust heat recovery boiler in a combined cycle, and from a steam system after cooling a furnace wall of a gasifier in a simple cycle. By supplying a sufficient amount of steam and supplying the steam to the combustor, the output of the gas turbine also increases, so that the efficiency of the entire plant is not reduced.

Further, the steam injection nozzle is arranged near the inlet of the air nozzle of the fuel nozzle composed of an oil nozzle, a gas and an air swirler, and the nitrogen injection nozzle is arranged in the same radial direction as the air nozzle of the fuel nozzle. , Or a plurality of them are arranged on the outer peripheral side of the air injection holes, so that NOx reduction can be achieved within the operating load range of the gas turbine without impairing combustion stability.

By arranging the steam injection nozzle near the inlet of the air injection hole and mixing it in the combustion air, it is effective in reducing the peak temperature region. On the other hand, in a dual type fuel nozzle including an oil nozzle, a gas, and an air injection hole, the arrangement of the oil nozzle and the gas nozzle is generally determined according to the amount of combustion of each fuel. In the present invention, the oil nozzle is disposed at the radial center of the fuel nozzle, and the gas and air injection holes are formed on the outer peripheral side.

At this time, when the nitrogen to be injected is formed on the inner peripheral side of the air injection hole, the mixing is delayed in oil combustion because the radial distance between the supplied air and oil is long.
With respect to gas combustion, the supply of oxygen required for combustion is insufficient, so that unburned components are likely to increase or unstable combustion is likely to occur. For this reason, it is necessary to arrange the nitrogen injection position at a position where supply of oxygen necessary for oil and gas combustion is not interrupted.
In the present invention, in order to avoid them, the air holes are arranged alternately at the same radial position, or the nitrogen holes are provided on the outer peripheral side of the air holes. With such an arrangement, NOx can be reduced without causing unstable combustion during nitrogen injection.

Further, according to the present invention, on the side wall of the combustor outer cylinder,
A plurality of, for example, four or more nitrogen injection nozzles for mixing nitrogen into combustion air are provided in the circumferential direction at four or more positions. In addition, since the nozzles are used together with the nitrogen injection injected from the end face of the fuel nozzle, NOx can be reduced without deteriorating combustion stability. Can be reduced. In the oxygen separator, when nitrogen (maximum amount that can be supplied to the combustor) obtained when air is separated is injected from the end face of the fuel nozzle, the concentration distribution on the end face of the fuel nozzle (radial direction of the injection hole outlet) is considered. Then, there is a region where the supply of nitrogen is locally reduced.

On the other hand, when the entire amount of nitrogen is mixed into the combustion air, unstable combustion is likely to occur due to a decrease in the oxygen concentration in the combustion air, that is, a lack of oxygen. For this reason, it is necessary to mix nitrogen into the air while ensuring the oxygen concentration in the combustion air to such an extent that combustion instability does not occur. In the present invention,
The fuel nozzle and the nitrogen injection system mixed into the air from the outer cylinder side wall are used together, and the nitrogen injected from the fuel nozzle is arranged at a position where the supply of oxygen during oil and gas combustion is not shut off.
Also, the region where the nitrogen concentration is locally low on the nozzle end surface is caused by nitrogen mixed into the combustion air from the outer cylinder side wall.
I can make up for it. Further, since a plurality of nitrogen injection nozzles provided on the outer cylinder side wall are arranged in the circumferential direction, the nitrogen concentration in the annular portion on the outer periphery of the liner can be made uniform.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows heavy oil gasification or coal gasification in which fuel such as heavy oil or coal is gasified by oxygen oxidation, the gas is burned to drive a gas turbine, and power is generated by a generator coupled to the gas turbine. The system of the integrated gasification combined cycle plant is shown.

Here, the case of the integrated coal gasification combined cycle power plant will be described below. This plant includes a gasifier 51, a gas purifier (desulfurizer 52, dust remover 53),
A gas turbine (compressor 1, combustor 2, turbine 3), an oxygen production device 59, an exhaust heat recovery boiler 58, a steam turbine 57, a generator, and the like are provided.

One of the features of this plant is that the gasifier 51
Is a cycle in which the oxidant 104 necessary for the air is extracted from the gas turbine (compressor 1, combustor 2, turbine 3). At the time of startup, the gas turbine driven by external power or the like supplies light oil 105 sent from the light oil tank 64.
Is ignited in the combustor 2 using the fuel as a fuel, and after the gas turbine speeds up, the self-sustaining operation is started. After reaching the no-load rated rotation speed of the gas turbine, the gas turbine gradually starts to take load by incorporating the generator 56.

On the other hand, the oxidizing agent required for the gasification furnace 51 is obtained by separating the bleed air 104 extracted from the backup compressor 60 or the gas turbine into oxygen 61 and nitrogen 62 by the oxygen production device 59, 61 is a gasification furnace 51
And the nitrogen 62 is supplied to the gas turbine combustor 2.

In the gasification furnace 51, the fuel 100 is burned by the supply of oxygen 61, and the gasification gas 101 can be supplied as the gasification furnace load increases. Gasifier 51
Immediately after the start-up, since the temperature and the calorific value of the generated gas 101 are extremely low, the gasified gas 101 is processed in the gas processing furnace 54 until the load increases (the calorific value increases). Therefore, until the load on the gasifier 51 increases, the gas turbine combustor 2 burns with light oil.

In the light oil combustion state of the gas turbine combustor 2, steam 103 is generated by the exhaust heat recovery boiler 58 using the gas 108 exhausted from the turbine 3. Utilizing the steam 103, the steam turbine 57 is also driven, and the output increases.

In the combustor 2, the generated steam 103
And the steam 103 is injected into the combustor by the steam injection device to reduce the emission amount of NOx. Then, after the load of the gasifier 51 increases and the predetermined gas 101 can be supplied to the combustor 2, in the combustor 2, the fuel is switched from oil combustion to coal gas combustion.

After the fuel switching operation is completed and the state of gas combustion is reached, nitrogen 102 is injected into the combustor 2 by the nitrogen injection device. Since the combustion temperature increases with an increase in the gas flow rate, the steam 103 generated in the exhaust heat recovery boiler 58 is injected into the combustor simultaneously with the nitrogen injection to reduce the NOx emission concentration.

Next, an embodiment of the simple cycle will be described with reference to FIG. Here, a system in which the system of the exhaust heat recovery boiler and the steam turbine in FIG. 1 is not provided, that is, a case of a power generation system using a so-called gas turbine alone.

The operation method of the whole plant is the same as described above. In this system, since there is no steam turbine system, the low N
The steam 103, which is a means of Ox, is extracted from a steam system generated after the pressure of the pure water 109 is increased and the wall of the gasification furnace 51 is cooled.

Next, steam and nitrogen injection positions in the combustor will be described with reference to FIG. This figure is a partially enlarged view of the combustor head. This combustor head configuration includes a combustor outer cylinder 206 as a pressure vessel, a liner 208 as a combustion chamber, a flow sleeve 207 for cooling the liner 208, and a fuel nozzle for holding a flame.

The fuel nozzles are arranged at the axial center of the combustor (at the center in the radial direction and at the head of the combustor). Gas injection holes 202 for performing gas combustion,
An air injection hole (swirler) for supplying the combustion air 106 and a nitrogen injection hole 204 for injecting nitrogen (an example in which a nitrogen injection nozzle is arranged on the outer peripheral side of the air injection hole). The gas, air and nitrogen orifices each have a swirl angle to hold the flame and promote mixing.

The air 106 sent from the compressor is supplied into the liner from the combustion air holes provided in the liner 208, which is a combustion chamber, like 106A and 106B. The swirler air 106C is the remaining air after the combustion air is branched into the liner. Light oil 105 is supplied to light oil nozzle 201, and light oil combustion is performed. Thereafter, as the load increases, the steam 103 is supplied from the steam injection nozzle 205 disposed near the fuel nozzle to the combustion air 106.
C is injected and mixed to reduce the emission concentration of NOx.

On the other hand, after the coal gas 101 can be supplied to the combustor, the fuel switching operation from oil to gas is started while gradually decreasing the light oil flow rate 105 and increasing the flow rate of the coal gas 101 accordingly. I do. After the fuel switching is completed and the state of gas combustion is reached, the nitrogen 102 is injected into the combustor through the nitrogen injection hole 204. In addition, as the load increases, both nitrogen injection and steam injection are used.

FIG. 4 shows a structure in which the nitrogen injection system is distributed to the fuel nozzle and the outer cylinder side wall. After switching the combustion state from the oil-only combustion to the gas-only combustion, the steam 103 is injected and mixed into the air 106C from the steam injection nozzle 205 disposed near the fuel nozzle. Almost at the same time, the nitrogen 102 is distributed to a nitrogen injection hole 204 provided in the fuel nozzle and a nitrogen injection nozzle 204A provided in the combustor outer cylinder 206, and the nitrogen 102 injected from the nitrogen injection nozzle 204A is It mixes with the combustion air 106 and a part is supplied into the liner 208 like 106B.

Thus, the combustion air 106 contains nitrogen 1
By mixing 02, it is possible to reduce the peak temperature generated during diffusion combustion. This is because when the air 204 and the gas 203 of the fuel nozzle are mixed near the nozzle,
It aims at lowering the peak temperature and is achieved by reducing the oxygen concentration ratio in the air. In the structure shown in FIGS. 3 and 4, the same effect can be obtained when the position of the nitrogen injection hole 204 injected from the fuel nozzle is provided at the same radial position as the air injection hole 203.

FIG. 5 shows N when nitrogen is injected into the combustor.
The graph shows the Ox concentration and the effect of reducing the NOx concentration when steam is added thereto. It can be seen that, compared to the NOx concentration of only nitrogen injection, the reduction effect is increased by further adding steam.

As described above, in the gasification power plant formed as described above, the nitrogen separated from the oxygen producing apparatus and the steam injection supplied during the oil combustion of the gas turbine combustor are used during the gas combustion. Since the injection is performed in combination, the NOx emission concentration can be significantly reduced as compared with the conventionally considered only nitrogen injection, and further, the nitrogen injection position is set in the same radial direction as the air injection hole of the fuel nozzle, Further consideration was given to the provision on the outer peripheral side, so that by increasing the nitrogen supply amount, it is possible to eliminate the phenomenon that the combustion becomes unstable during gas combustion.

[0040]

As described above, according to the present invention, it is possible to obtain this kind of gasification power plant in which the NOx emission concentration can be sufficiently reduced without lowering the efficiency of the whole plant.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing one embodiment of a gasification power plant of the present invention.

FIG. 2 is an overall system diagram showing another embodiment of the gasification power plant of the present invention.

FIG. 3 is a partially enlarged view showing an embodiment of a combustor head in the gasification power plant of the present invention.

FIG. 4 is a partially enlarged view showing another embodiment of the combustor head in the gasification power plant of the present invention.

FIG. 5 is a characteristic diagram showing the effect of reducing NOx in the gasification power plant of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Combustor, 3 ... Turbine, 51 ... Gasifier, 52 ... Desulfurizer, 53 ... Dust remover, 56 ... Generator
57: steam turbine, 58: waste heat recovery boiler, 59: oxygen production device, 60: backup compressor, 64: light oil tank, 101: gas, 102: nitrogen, 103: steam,
105 ... light oil, 108 ... combustion gas, 201 ... oil nozzle,
202: gas injection hole, 203: air injection hole, 204: nitrogen injection hole, 204A: nitrogen injection nozzle, 205: steam injection nozzle, 206: outer cylinder, 208: liner.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI F02C 7/16 F02C 7/16 Z F23C 11/00 ZAB F23C 11/00 ZAB 316 316 331 331 334 334 F23R 3/20 F23R 3 / 20 3/28 3/28 (72) Inventor Kazumi Iwai 3-2-2, Sachimachi, Hitachi City, Ibaraki Prefecture Within Hitachi Engineering Services Co., Ltd.

Claims (5)

[Claims] 1. A method for operating a gasification power generation plant that switches a combustion state of a combustor from oil combustion to gas combustion and drives a gas turbine by using gasified gas as a main fuel during gas combustion to generate power. A method for operating a gasification power plant, wherein the gasification power plant is operated while using both steam injection and nitrogen injection in a combustion section in a gas only combustion state after switching a combustion state from oil to gas. 2. The steam supplied to the combustion section is extracted from an exhaust heat recovery boiler of a combined cycle power plant combining a gas turbine and a steam turbine, or extracted from a steam system after cooling a furnace wall of a gasification furnace. Claim 1 which is steam
An operation method of the gasification power plant according to the above. 3. A gasification power generation plant that operates by switching a combustion state of a combustor from oil combustion to gas combustion and drives a gas turbine using gasified gas as a main fuel during gas combustion to generate power. A gasification power plant comprising a steam injection device for injecting steam into a combustion portion and a nitrogen injection device for injecting nitrogen into a combustion portion in a gas-only combustion state after switching a combustion state from oil to gas. 4. An injection nozzle of the steam injection device is arranged near an inflow air inlet of a swirler for holding a flame, and an injection nozzle of the nitrogen injection device is located at the same radial position as an air injection hole of a fuel nozzle. Are placed alternately,
4. The gasification power plant according to claim 3, wherein a plurality of the gasification power generation plants are arranged on the outer peripheral side of the air injection holes. 5. An injection nozzle of the nitrogen injection device, wherein oil,
Total number of nitrogen supplied along with a fuel nozzle for holding a flame composed of gas and air injection holes and a plurality of circumferentially arranged on the side wall of an outer cylinder which is a pressure vessel of a combustor 5. The gasification power plant according to claim 3, wherein a part of the fuel gas is injected into the combustion area from an end face of the fuel nozzle, and the remaining part is injected into the combustion air. 6.