CN113958413B - A gas-steam combined cycle intake fuel coupling heating system and method - Google Patents

Abstract

The invention discloses a gas-steam combined cycle air inlet fuel coupling heating system and a method, wherein a gas-steam combined cycle waste heat recovery boiler side system comprises a heater, and the heater is arranged in front of a gas turbine filtering module and a cooling module; in a cross flow system formed by a hot water channel for recovering waste heat, an air inlet plate-fin channel and a natural gas pipe row, hot water transfers heat to air and natural gas through a partition plate and fins, and the hot water channel, the three air inlet air channels and the natural gas pipe are arranged in a staggered mode. The intake air of the intake channel is sent into the heater by the air pump, and the natural gas is sent into the heater to absorb heat and raise temperature and then is sent into the combustion chamber. The invention is beneficial to improving the combined cycle efficiency of the unit during partial load operation, thereby meeting the requirements of optimizing the thermal performance of the unit under different atmospheric temperatures and load conditions and improving the technical economy of the combined cycle generator unit.

Description

A gas-steam combined cycle intake fuel coupling heating system and method

Technical Field

The present invention belongs to the technical field of gas-steam combined cycle in the energy and power industry, and in particular relates to a gas-steam combined cycle intake fuel coupling heating system and method.

Background Art

At present, in order to reduce the occupied space, the compressor air intake and fuel air intake systems of gas-steam combined cycle gas turbines are developing in the direction of compactness and efficiency. Generally speaking, cooling the intake air can improve the efficiency of the gas turbine and the full load output of the combined cycle. However, due to the influence of power generation costs, natural gas sources and the access to the grid of new energy, gas-steam combined cycle units are mostly responsible for peak load regulation and operate at partial load, which greatly increases the heat consumption and reduces the performance. In provinces with more gas turbines in China, the load rate of the gas turbine is 50% to 80%. In this range, when the load rate of the gas turbine is 50%, the heat consumption of the gas turbine increases by about 30%.

On the one hand, practice shows that for gas turbine combined cycle units that operate at partial load for a long time, heating the intake air can effectively improve the thermal efficiency of the combined cycle unit, and using hot water generated by low-grade waste heat boilers as the heating heat source for the intake air can save costs. The shell and tube heater commonly used in this process has low efficiency, non-compact structure, requires a large heat exchange area, occupies a large volume, and is difficult to arrange in space; there are a large number of coils or flat tubes, and it is inconvenient to repair and maintain large-sized heaters during actual use; when the combined cycle unit is operating at partial load, the flow rate of the intake air and fuel is reduced, the turbulent intensity of the fluid heat exchange is weakened, and there is a problem of uneven heat exchange on the circulation surface. The plate-fin heater is a heat exchange equipment with high heat transfer efficiency, compact structure, light weight and strong adaptability, and is a new development direction.

On the other hand, in the gas-steam combined cycle, preheating natural gas can improve the quality of natural gas, reduce the amount of fuel, and improve the efficiency of the gas turbine. At present, the natural gas heaters of domestic gas-steam combined cycle units generally use electric heating and water bath methods to ensure the minimum temperature of natural gas, but the cost and maintenance costs increase. The hot water recovered from the flue gas of the waste heat boiler can be used to transport heat to the gas turbine side, which can save costs. In order to prevent leakage and explosion, hot air is generally not used as a medium for heat exchange with natural gas, and traditional water-gas heat exchangers cannot be used, because it is not safe to circulate hot water in the inner tube and transport fuel in the outer shell. If the inner tube of the tubular shell and tube heater transports natural gas and the outer shell circulates hot water, it can meet the operating pressure on the natural gas side while having intermediate medium separation, which is a new development direction.

Summary of the invention

In order to overcome the above technical problems, the present invention provides a gas-steam combined cycle intake fuel coupling heating system and method, which helps to improve the combined cycle efficiency when the unit is running at partial load, thereby meeting the requirements for optimizing the thermal performance of the unit under different atmospheric temperatures and load conditions, and improving the technical and economic performance of the combined cycle power generation unit. The unit is required to provide a set of thermal solutions for heating the intake air-fuel, based on a plate-fin-tube-shell coupled heater that simultaneously heats the intake air and fuel natural gas of the gas turbine. The air and fuel coupled heater allows three fluids to exchange heat simultaneously, optimizes the design process of coupling the two thermal sources of the combined cycle, is safer, and can effectively improve the combined cycle performance under a certain load.

In order to achieve the above object, the technical solution adopted by the present invention is:

A gas-steam combined cycle inlet fuel coupling heating system, comprising a heater 12 and a gas-steam combined cycle waste heat recovery boiler side system, wherein the gas-steam combined cycle waste heat recovery boiler side system comprises a waste heat boiler 21, a flue gas-water heater 23 is installed at the outlet of a flue 22 at the tail of the waste heat boiler 21, and a baffle 25 is arranged at the outlet of the flue 22 to adjust the waste heat flue gas flow participating in the heat exchange of the flue gas-water heater, and soft water is extracted from a water recovery pipeline 24, and heat is absorbed in the flue gas-water heater 23, and then the heated hot water is transported to a hot water accumulator 26, and then transported to the heater 12 through a water pump 27 and a valve 28 through a pipeline 3, and the heater 12 is arranged before an original gas turbine filter module 16 and a cooling module 17;

The intake air of the intake channel 1 is delivered to the heater 12 by the vacuum pump, and the natural gas is delivered to the heater 12 through the fuel inlet pipe 6. After absorbing heat and heating up, it is delivered to the combustion chamber 19 through the fuel outlet pipe 7. The outlet pipe 7 is sheathed with an outer tube 13 at the part connecting the heater 12 and the combustion chamber 19, and the outer tube 13 delivers hot water.

The heater 12 includes a hot water flow channel 5, which is U-shaped. Hot water-air baffle plates 9 are arranged in the middle and on both sides of the U-shape of the hot water flow channel 5. Stainless steel air inlet fins 2 are placed flatly between the hot water-air baffle plates 9 to form a plate-fin unit. A hot water inlet delivery pipe 3 is arranged on one side of the top of the U-shaped hot water flow channel 5, and a hot water outlet drainage pipe 4 is arranged on the other side. A fuel inlet pipe 6 and a fuel outlet pipe 7 are arranged at the bottom of the hot water flow channel 5, and the fuel inlet pipe 6 and the fuel outlet pipe 7 are U-shaped.

The cold and hot fluids in the air inlet channel 1 and the hot water flow channel 5 flow orthogonally in adjacent plate-fin units, and heat is transferred from the hot water flow channel 5 to the air inlet fins 2 and the soft water-air baffle 9.

The hot and cold fluids in the fuel inlet pipe 6 , the fuel outlet pipe 7 and the hot water flow channel 5 flow in opposite directions in the adjacent shell-and-tube flow channels, and the heat is transferred from the hot water flow channel 5 to the fuel inlet pipe 6 and the fuel outlet pipe 7 .

The hot water-air baffle plates 9 are arranged straight and evenly, and are brazed and welded firmly by the side sealing heads 11 .

The stainless steel air inlet fin 2 is brazed into one piece with the outer partition plate 8 on the side of the fin, and the stainless steel air inlet fin 2 is provided with an air inlet channel 1 in the vertical direction.

A return baffle 10 is provided between the U-shaped hot water flow channel 5 and the hot water-air baffle sheet 9 in the middle to ensure that the hot water wraps around the return portion of the natural gas inner pipe.

The heater 12 is enclosed by an aluminum box.

The heater 12 is divided into a short side and a field side. The short side is located at the top and bottom of the U-shaped hot water flow channel 5. The intake air flow of the intake flow channel 1 is along the short side of the heater 12, and the flow of the hot water flow channel 5 is along the long side of the heater.

The heater 12 is connected to the filter module 16 through the riveted expansion 14, and a temperature measuring point 15 is arranged on the riveted expansion. According to the required intake air heating temperature, the heater 12 can be installed on the basis of the heater 12 through the riveted expansion 14.

An operating method of a gas-steam combined cycle inlet fuel coupled heating system comprises the following steps;

When the gas-steam combined cycle unit is operated at a partial operating condition, or the temperature of the natural gas that needs to be regulated may not meet the prescribed requirements, the heater 12 can preheat the intake air and the fuel natural gas;

When the gas-steam combined cycle is running at full load, in order to ensure the output of the gas turbine, the valve 28 and the water pump 27 after the hot water accumulator should be closed, and the heater 12 does not work at this time;

If the gas turbine output needs to be increased, the valve 28 and the water pump 27 are closed, and the conventional compressor inlet cooling module 17 is turned on, using spray cooling or compressed natural gas cooling energy from the LNG unit;

In summer, when the intake air and fuel temperatures are already high, the heating of the intake air should be reduced. At this time, the angle of the flue gas baffle 25 of the tail flue of the waste heat boiler should be electrically adjusted to block part of the flue gas and reduce the heat transported by the hot water pipe 3;

In order to prevent the intake air 1 from freezing under severe winter conditions, the flue gas damper 25, the hot water valve 28, and the water pump 27 should be fully opened, and the heat accumulator 26 should be electrically heated to increase the hot water temperature;

Alternatively, the soft water return 24 is adjusted to reduce the mass flow rate of soft water provided to control the increase in intake air and fuel temperature.

In summary, the intake air temperature can be adjusted by cooling or heating switching based on the current atmospheric temperature, unit load and operating objectives.

Beneficial effects of the present invention:

The present invention is used for full load and partial working conditions of gas-steam combined cycle. In the cross-flow system formed by the hot water channel for recovering waste heat, the intake air plate-fin channel and the natural gas pipe row, the hot water transfers heat to the air and natural gas through the partition and the fin, and the hot water channel overlaps with the three intake air channels and the natural gas pipe.

The unique advantages of coupled heaters are as follows:

The plate-fin heater has a smaller heat transfer area, heat transfer volume, and energy consumption than traditional heaters. It has a higher heat transfer coefficient and heat transfer efficiency. It does not require sealing elements such as gaskets to manufacture, and there is no internal leakage defect at all.

The inner tube of the tubular shell and tube heater transmits natural gas, and the outer shell circulates hot water. While being able to meet the operating pressure on the natural gas side, it has the function of intermediate medium separation, completely avoiding the risk of leakage and explosion caused by natural gas heating;

Therefore, the coupled heater system of the present invention is simple, compact, occupies a small space, has high heat exchange efficiency, meets the requirements of combined cycle partial load operation, has high safety, and is easy to operate and maintain;

Obviously, using the same heater for both air and natural gas simplifies the system configuration.

Because the intake air and fuel absorb the waste heat energy of the boiler exhaust, this part of energy enters the combined cycle system to do work, the energy carried by natural gas and air increases, and the fuel required by the unit decreases.

The advantages of the heater provided by the present invention in the gas-steam combined cycle system are as follows:

Under partial load conditions of the combined cycle, as the intake air temperature increases, the load rate of the gas turbine increases and the power generation efficiency of the gas turbine increases.

As the temperature of fuel natural gas increases, the efficiency of combined cycle power generation can be improved and the heat consumption of gas turbines can be reduced.

Heating the intake air also prevents problems such as ice and wet blockage of the gas turbine's intake components during winter.

When the gas-steam combined cycle is running at full load, or when the intake air and fuel temperatures are already high under summer conditions, the heater provided by the present invention can be closed at any time because of the hot water heat storage tank and the flue gas valve, without affecting the conventional compressor intake air cooling module.

It saves the traditional device of using factory electricity to heat natural gas, and has good economic efficiency.

At partial load, compressor intake heating is used to increase the load rate of the gas turbine operation. In combination with intake guide vane adjustment, the low-load limit range for stable combustion can also be widened.

The heat from the exhaust gas is used to heat soft water. The temperature of the flue gas is generally around 100°C. The water temperature heated by the waste heat under normal operating conditions is 90°C. The hot soft water is then transported to the heater on the gas turbine island side. Taking into account the heat dissipation loss, the system of the present invention can heat the compressor intake air and fuel natural gas to 80°C.

In summary, this shell and tube-plate-fin coupled heater system and method for recovering low-grade waste heat to heat intake air and fuel natural gas helps to improve the combined cycle efficiency when the unit is operating at partial load, thereby meeting the requirements for optimizing the thermal performance of the unit under different atmospheric temperatures and load conditions, and improving the technical and economic performance of the combined cycle power generation unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an intake-fuel coupled heater according to the present invention.

FIG. 2 is a schematic diagram of a system of a heating device combined with a combined cycle according to the present invention.

DETAILED DESCRIPTION

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the plate-fin-tube shell coupled heater 12 in the present invention is mainly composed of four rows of air inlet channels 1, a hot water inlet delivery pipe 3 and a hot water outlet drainage pipe 4, a natural gas inlet pipe 6 and an outlet pipe 7, an outer partition 8, a soft water-air partition 9, a return partition 10, and a head 11.

The specific features of each part of the heater 12 are:

The cold and hot fluids in the inlet flow channel 1 and the hot water flow channel 5 flow orthogonally in the adjacent plate-fin units, and the heat is transferred from the hot water flow channel 5 to the inlet fin 2 and the soft water-air baffle 9;

The hot and cold fluids in the fuel pipes 6, 7 and the hot water flow channel 5 flow in opposite directions in the adjacent shell-and-tube flow channels, and the heat is transferred from the hot water flow channel 5 to the natural gas pipes 6 and 7;

The hot and cold alternating baffles in the heater are made of stainless steel, and the hot water-air baffles 9 are arranged straight and evenly, and are brazed and welded firmly by the side heads 11;

Each row of air inlet channels 1 is arranged with fins, using 30 pieces of stainless steel air inlet fins 2, which are placed flat between the hot water-air flat baffles 9 and brazed into one piece with the outer baffles 8 on the side of the fins; the return baffle 10 ensures that the hot water wraps the return part of the natural gas inner pipe;

The whole heater 12 is enclosed by an aluminum box, and has good heat preservation performance.

In the above heat exchanger 12, the coupling mode of the three fluids of air, natural gas and hot water is as follows:

The flow path of the intake air intake channel 1 is along the short side of the heater, and the resistance on the intake side of the plate fin is designed to be as small as possible during design;

The hot water flow channel 5 is U-shaped along the long side of the heater. The hot water is input from the inlet delivery pipe 3 on the same side of the heater by a water supply pump and discharged from the hot water outlet drain pipe 4. The recovery device recovers the soft water.

The natural gas inner pipe is arranged in the hot water flow channel 5, and is input from the fuel inlet pipe 6 and output from the fuel outlet pipe 7 on the same side in a U shape. The outlet pipe 7 is sheathed with an outer pipe 13 at the part connecting the heater 12 and the combustion chamber 19, and the outer pipe 13 transports hot water;

There are temperature and pressure measuring instruments at the inlets and outlets of the three fluids.

As shown in FIG. 2 , the present invention provides a corresponding waste heat recovery system for a waste heat boiler based on the above-mentioned gas-air heater 12 , which is applied to a gas-steam combined cycle.

The technical features of the heater 12 on the gas-steam combined cycle gas turbine boiler side are as follows:

A flue gas-water heating pipe row 23 is installed in the tail flue 22 of the waste heat boiler 21, and a hinged baffle 25 is arranged on the flue gas side thereof;

The smoke baffle 25 can rotate to block part of the smoke at the tail end of the flue and adjust the waste heat smoke flow rate participating in the heat exchange of the smoke-water heating pipe row 23;

Soft water is extracted from the water recovery pipe 24, and heat is absorbed in the flue gas-water heat exchange pipe row 23, and then the heated hot water is transported to the hot water heat accumulator 26, and then transported to the heater 12 of the present invention through the pipe 3 via the water pump 27 and the valve 28;

The flow of hot water participating in air intake and fuel heating can be adjusted by adjusting the opening of valve 28, and the valve can be closed when necessary.

The technical features of the heater 12 on the island side of the gas-steam combined cycle gas turbine are as follows:

The heater 12 is arranged before the original gas turbine filter module 16 and the cooling module 17;

The intake air 1 is delivered into the plate-fin-tube-shell coupled heater box by an air extraction pump. Since the size of the heater 12 is larger than the original gas turbine air inlet size, a riveted expansion port 14 needs to be installed;

Arrange temperature measuring point 15 on the riveted expansion to monitor the intake air temperature;

According to the actual required heating temperature of the combined cycle unit, the heater 12 can be installed on the basis of the heater 12 by riveting the expansion opening 14 .

The heater intake air absorbs heat and heats up in the flow channel 1 before entering the compressor 18 through the expansion port 14 for compression, and the air with a higher pressure and temperature enters the combustion chamber 19;

Natural gas is fed into the heater through the fuel inlet pipe 6, and after absorbing heat and heating up, it is transported to the combustion chamber 19 through the fuel outlet pipe 7;

The air and fuel having a relatively high pressure and temperature are mixed and burned, and the high-temperature and high-pressure combustion gas discharged enters the turbine 20 to perform work.

Working principle of the present invention:

When the gas turbine is running at partial load, the compressor intake flow rate is changed by adjusting the opening of the compressor intake guide vane, maintaining the gas turbine pre-turbine temperature at a higher temperature, and ensuring the operating efficiency of the gas turbine. The compressor intake guide vane opening is automatically controlled by the gas turbine unit, so these parameters and the unit load affect each other. Therefore, the specific implementation of the comprehensive optimization plan and the detailed technical plan should be formulated according to the actual operating parameters of the unit and the on-site installation space:

When the gas-steam combined cycle unit is operated at a partial operating condition, or the temperature of the natural gas that needs to be regulated may not meet the prescribed requirements, the heater 12 can preheat the intake air and the fuel natural gas;

When the gas-steam combined cycle is running at full load, in order to ensure the output of the gas turbine, the valve 28 and the water pump 27 after the hot water accumulator should be closed, and the heater 12 does not work at this time;

If the gas turbine output needs to be increased, the valve 28 and the water pump 27 are closed, and the conventional compressor inlet cooling module 17 is turned on, using spray cooling or compressed natural gas cooling energy from the LNG unit;

In summer, when the intake air and fuel temperatures are already high, the heating of the intake air should be reduced. At this time, the angle of the flue gas baffle 25 of the tail flue of the waste heat boiler should be electrically adjusted to block part of the flue gas and reduce the heat transported by the hot water pipe 3;

In order to prevent the intake air 1 from freezing under severe winter conditions, the flue gas damper 25, the hot water valve 28, and the water pump 27 should be fully opened, and the heat accumulator 26 should be electrically heated to increase the hot water temperature;

The soft water return 24 can also be adjusted to reduce the mass flow rate of soft water provided to control the increase in intake air and fuel temperature.

The present invention applies an efficient and compact plate-fin-tube shell coupling heater to the gas turbine intake-fuel heating system, and the water side of the heater is provided by the waste heat of the tail flue of the waste heat boiler. Due to the large difference in pressure and temperature between the gas side and the air side, the volume flow rates of the gas side and the air side differ greatly, so different sizes of tubular gas flow channels and plate air flow channels are designed to achieve higher heat exchange efficiency. The inner tube of the fuel natural gas shell and tube heater adopts a smooth flat tube, and the interior of the intake air plate-fin heater is finned. Convection heat transfer and heat conduction are coupled together to enhance heat exchange. The intake air temperature can be adjusted by cooling or heating switching according to the current atmospheric temperature, unit load and operation target.

Claims (7)

1. A gas-steam combined cycle inlet fuel coupled heating system, characterized in that it comprises a heater (12) and a gas-steam combined cycle waste heat recovery boiler side system, the gas-steam combined cycle waste heat recovery boiler side system comprising a waste heat boiler (21), a flue gas-water heater (23) is installed at the outlet of a flue (22) at the tail of the waste heat boiler (21), and a baffle (25) is arranged on the flue gas side of the flue (22) to adjust the flow rate of waste heat flue gas involved in heat exchange, draw soft water from a water recovery pipeline (24), absorb heat in the flue gas-water heater (23), and then transport the heated hot water into a hot water heat accumulator (26), and then transport the heated hot water to the heater (12) through a water pump (27) and a valve (28) through a hot water inlet transport pipe (3), and the heater (12) is arranged before a filter module (16) and a cooling module (17); The intake air of the intake passage (1) is delivered to the heater (12) by an air pump, and the natural gas is delivered to the heater (12) through a fuel inlet pipe (6), and after absorbing heat and heating up, is delivered to the combustion chamber (19) through a fuel outlet pipe (7). The outlet pipe (7) is provided with an outer pipe (13) at a portion connecting the heater (12) and the combustion chamber (19), and the outer pipe (13) delivers hot water; The heater (12) comprises a hot water flow channel (5), the hot water flow channel (5) is in a U-shape, a hot water-air baffle sheet (9) is arranged in the middle and on both sides of the U-shape of the hot water flow channel (5), a stainless steel air inlet fin (2) is placed flatly between the hot water-air baffle sheets (9) to form a plate-fin unit body, a hot water inlet delivery pipe (3) is arranged on one side of the top of the U-shaped hot water flow channel (5), and a hot water outlet drainage pipe (4) is arranged on the other side, and a fuel inlet pipe (6) and a fuel outlet pipe (7) are arranged at the bottom of the hot water flow channel (5), and the fuel inlet pipe (6) and the fuel outlet pipe (7) are in a U-shape; The cold and hot fluids in the air inlet channel (1) and the hot water flow channel (5) flow orthogonally in adjacent plate-fin units, and heat is transferred from the hot water flow channel (5) to the air inlet fins (2) and the soft water-air baffle plate (9); The hot and cold fluids in the fuel inlet pipe (6), the fuel outlet pipe (7) and the hot water flow channel (5) flow in opposite directions in adjacent shell-and-tube flow channels, and heat is transferred from the hot water flow channel (5) to the fuel inlet pipe (6) and the fuel outlet pipe (7). 2. A gas-steam combined cycle intake fuel coupled heating system according to claim 1, characterized in that the hot water-air baffle plates (9) are arranged straight and evenly, and are brazed firmly by side heads (11). 3. A gas-steam combined cycle intake fuel coupled heating system according to claim 1, characterized in that the stainless steel intake duct fin (2) is brazed into one with the outer partition (8) on the side of the fin, and the stainless steel intake duct fin (2) is provided with an intake channel (1) in the vertical direction. 4. A gas-steam combined cycle intake fuel coupled heating system according to claim 1, characterized in that a return baffle (10) is provided between the U-shaped hot water flow channel (5) and the middle hot water-air baffle plate (9) to ensure that hot water wraps around the return portion of the natural gas inner pipe. 5. A gas-steam combined cycle intake fuel coupled heating system according to claim 1, characterized in that the heater (12) is enclosed by an aluminum box; The heater (12) is divided into a short side and a field side, the short sides are located at the top and bottom of the U-shaped hot water flow channel (5), the intake air flow of the intake channel (1) is along the short side of the heater (12), and the flow of the hot water flow channel (5) is along the long side of the heater. 6. A gas-steam combined cycle intake fuel coupled heating system according to claim 1, characterized in that the heater (12) is connected to the filter module (16) through a riveted expansion (14), a temperature measuring point (15) is arranged on the riveted expansion, and according to the required intake heating temperature, the heater (12) can be installed on the basis of the heater (12) through the riveted expansion (14). 7. An operating method of a gas-steam combined cycle intake fuel coupled heating system according to any one of claims 1 to 6, characterized in that it comprises the following steps; When the gas-steam combined cycle unit is operated at a partial operating condition, or the temperature of the natural gas to be regulated may not meet the prescribed requirements, the heater (12) can preheat the intake air and the fuel natural gas; When the gas-steam combined cycle is running at full load, in order to ensure the output of the gas turbine, the valve (28) and the water pump (27) after the hot water accumulator should be closed, and the heater (12) will not work at this time; If it is necessary to increase the gas turbine output, the valve (28) and the water pump (27) are closed and the conventional compressor inlet air cooling module (17) is turned on to use spray cooling or compressed natural gas cooling energy of the LNG unit; In summer, when the intake air and fuel temperatures are already high, the heating of the intake air should be reduced. At this time, the angle of the flue gas baffle (25) at the tail flue of the waste heat boiler should be electrically adjusted to block part of the flue gas and reduce the heat delivered by the hot water inlet delivery pipe (3); In order to prevent the intake air 1 from freezing under severe winter conditions, the flue gas damper (25), the hot water valve (28), and the water pump (27) should be fully opened, and the heat storage device (26) should be electrically heated to increase the hot water temperature; Alternatively, the soft water return (24) is adjusted to reduce the mass flow rate of the soft water provided, so as to control the increase in the intake air and fuel temperature.