CN100402814C - A flue gas low-temperature end heat utilization system for combined cooling, heating and power supply of natural gas - Google Patents

Abstract

The invention relates to a flue gas low-temperature end heat utilization system for natural gas cooling, heating and power cogeneration and its operation method. The heat utilization system includes a gas-fired power generation device, a waste heat boiler, an absorption refrigeration device, and a heating and water supply device; and the heating and water supply device includes Direct air-water heat exchanger, the body of the heat exchanger is equipped with a shower device for breaking water droplets, and the water droplets in the shower device pass through the space to form a flue gas channel; the flue gas outlet of the waste heat boiler passes through the direct The air-water heat exchanger is connected with the chimney, and the inlet and outlet pipes of the direct air-water heat exchanger are connected in series to the pipe for domestic hot water or heating; the steam pipe of the waste heat boiler is also branched to a gas-fired power generation The reinjection steam pipe of the combustion chamber of the device is connected with a decompression device in series on the reinjection steam pipe. The heat transfer equipment of the low-temperature heat utilization system of the present invention is simple and cheap, can improve the thermal efficiency of the system, can provide domestic hot water at extremely low cost, and greatly improves the economic benefit of the system.

Description

A flue gas low-temperature end heat utilization system for combined cooling, heating and power supply of natural gas

【Technical field】

The invention relates to power generation and thermal equipment, and more specifically, the invention relates to a direct heat exchange system for efficiently utilizing low-temperature waste heat from exhaust gas of a natural gas cogeneration device and domestic hot water.

【Background technique】

With the implementation of the energy strategy of vigorously developing and introducing natural gas resources and optimizing the energy structure in my country, the combined cooling, heating and power system of gas turbines using natural gas as the primary energy is developing rapidly in my country. Ordinary gas turbine combined heat, power and cooling system includes gas turbine generator set, waste heat boiler, steam turbine or absorption refrigeration device; the final flue gas discharge temperature of the system is usually around 130°C, and this part of the flue gas still accounts for about 10% of the total heat energy of the fuel. Thermal utilization potential, not recycling is a huge waste.

At the same time, with the continuous improvement of people's living standards, domestic hot water consumes more and more energy. The relevant statistical data are shown in the table below:

Table 1-Proportion of each part of my country's building energy consumption

Composition of building energy consumption Heating and air conditioning hot water supply electrical cooking The proportion of each part 65% 15% 14% 6%

It can be seen from Table 1 above that the proportion of hot water supply in building energy consumption ranks second only to heating and air conditioning energy consumption.

Domestic hot water belongs to low-grade energy, and the final temperature of bath water is only about 40°C, and its energy level coefficient is about 0.1. However, judging from the current energy supply mode, electric water heaters and gas-fired water heaters are mainly used for urban domestic hot water supply. Some hotels and collective dormitories use coal-fired and oil-fired boilers. They are all high-grade energy sources, and the energy level coefficient is 1.0. It is a huge waste to use such high-level energy to heat the low-level heat sink.

Obviously, the natural gas combined cooling, heating and power system is an important way to efficiently meet the increasing demand for cooling, heating and electricity in building energy consumption. And if the low-grade flue gas heat energy generated by the system can be used as the heat source of domestic hot water at the same time, the energy utilization efficiency and economic benefits of the cogeneration system can be further improved.

However, most of the current gas turbine combined cooling, heating and power systems only consider the energy needs of power supply, heating, and air conditioning; including domestic hot water supply, they do not use the waste heat of flue gas below 130°C, but use steam or 130°C above the flue gas heat. This is because the current heat utilization of low-temperature flue gas usually adopts the method of partition heat exchange, and its transfer coefficient is generally lower than 80W/(m ² ℃). Therefore, a large number of steel pipe heating surfaces need to be arranged when recovering low-temperature flue gas waste heat, which not only consumes a large amount of steel, but also has high flue gas flow resistance; the economic benefit is not large.

At present, in terms of technical improvement of the gas turbine combined cooling, heating and power system, there is a Chinese application document 93116724.8 which discloses a numerically controlled gas turbine combined heating and cooling system, which includes a core engine, a power supply mechanism, and a heating component. The digitally controlled gas turbine combined heating and cooling equipment also includes high and low pressure generators, high and low temperature heat exchangers, condensation chambers, absorption chambers and circulation pumps, regenerative circulation pumps, evaporation chambers and circulation pumps, cooling water serpentine pipes, refrigeration transmission The absorption refrigeration unit composed of thermal medium coils has a refrigerant regeneration heat exchanger in the waste heat boiler. It is said that this equipment uses a gas engine as a power source, and the electric energy output is obtained through a generator, and the gas containing waste heat is heated to regenerate the refrigerant to pump heat to obtain a cooling output. Using the heating medium to output heat can make full use of the output energy of the gas engine.

In this regard, there is also Chinese application document 93116725.6 which discloses a gas turbine combined heating and cooling equipment. It has a core engine, power supply mechanism, heating components. It also includes high and low pressure generators, high and low temperature heat exchangers, condensation chambers, absorption chambers and circulation pumps, regenerative circulation pumps, evaporation chambers and circulation pumps, cooling water coils, refrigeration heat transfer working medium coils The absorption refrigeration unit has a refrigerant regeneration heat exchanger in the waste heat boiler. It is said that this equipment uses a gas engine as a power source, and the electric energy output is obtained through a generator, and the gas power with waste heat is included. The heat regenerative refrigerant pumps heat to obtain refrigeration output. Use the heating medium to output heat and make full use of the output energy of the gas engine. The above two patent application documents do not mention the temperature of flue gas discharged from the system after passing through the waste heat boiler.

In this regard, Chinese application document 01117061.1 discloses a heat and power supply system and its operation method. The system includes: a regenerative gas turbine and an absorption refrigerator for recovering the waste heat in the exhaust gas of the gas turbine. The system has an inlet cooling device, which includes an injection device for injecting cold water from the absorption chiller into the intake port of the regenerative gas turbine and an injection device for humidification by injecting hot water from the regenerator into the compressor delivery port of the regenerative gas turbine functioning humidifier. Cooling with cold water and humidification with hot water jets according to the operating status. It is said that the system can increase the output of electricity. The patent application document also does not mention the temperature of the flue gas discharged from the system through the regenerator of the absorption refrigerator.

In this regard, another Chinese application document 03109715.4 discloses a heat pump cogeneration system powered by a gas turbine, which involves the use of the gas turbine and the improvement of its structure. It is composed of gas turbine, absorption heat pump device, condensing heat exchanger and generator. The mechanical energy output by the gas internal combustion engine is connected to the generator, and its characteristics are: the flue gas discharged from the gas turbine is connected to the flue gas inlet of the condensing heat exchanger through the generator of the absorption heat pump device and exhausted from the flue gas outlet. The water outlet of the condensing heat exchanger is connected with the water inlet of the evaporator of the absorption heat pump device. The water outlet of the evaporator of the absorption heat pump device is connected with the water inlet of the condensing heat exchanger. The condenser and absorber of the absorption heat pump device are connected in series/parallel with the heating return water to the heating water supply circuit. It is said that the system can make full use of the energy of the heating system of the gas turbine, greatly improve energy utilization efficiency and reduce environmental pollution. Although the patent application document mentions that the exhaust gas temperature from the system through the condensing heat exchanger is about 30°C, the document does not fully disclose the technical measures taken to achieve such a low exhaust gas temperature, because if the traditional To achieve the above-mentioned low-temperature smoke exhaust by partition wall heat exchange, a huge amount of steel is required, which has no engineering practical value at all.

It can also be seen from the above examples that the current combined cooling, heating and power supply equipment system either does not consider the joint supply of domestic hot water supply, or uses the traditional partition wall waste heat boiler to provide hot water, which is bound to be left out due to poor technical and economic performance. abandon.

【Content of invention】

In view of the above-mentioned shortcomings of the prior art, the technical purpose of the present invention is to provide a natural gas cooling system with simple and cheap heat transfer equipment, which can further improve the thermal efficiency and economic benefits of the system and provide domestic hot water at a very low cost. The flue gas low-temperature end heat utilization system and its operation method for combined heat and power supply.

For this reason, one of the technical solutions of the present invention is a flue gas low-temperature end heat utilization system for natural gas combined cooling, heating and power supply. The heat utilization system includes a gas-fired power generation device, a waste heat boiler, an absorption refrigeration device, and a heating water supply device; The gas-fired power generation device includes a compressor, a combustion chamber and a generator; the inlet of the compressor is connected to the atmosphere, and its outlet is connected to the inlet of the combustion chamber; the inlet of the combustion chamber is also connected to the gas nozzle; the waste heat boiler It includes flue gas inlet, flue gas outlet, condensed water inlet and steam outlet. The flue gas inlet of the waste heat boiler is connected to the exhaust outlet of the gas-fired power generation device, and its steam outlet is connected to the absorption refrigeration device and the heating The water supply device is connected, and the heating water supply device also includes a direct air-water heat exchanger, the body of the direct air-water heat exchanger is provided with a shower device for breaking water droplets, and the water droplets in the shower device The flue gas channel is formed through the space; the flue gas outlet of the waste heat boiler communicates with the chimney through the flue gas pipe of the direct air-water heat exchanger, and the inlet and outlet pipes of the direct air-water heat exchanger are connected in series On pipelines for domestic hot water or heating.

The structural improvement of the present invention is based on the investigation of the influence of flue gas on various sanitary indicators of domestic hot water at first, and it is found that: after natural gas is liquefied, it basically does not contain sulfur (generally not more than 10ppm); even if the exhaust gas temperature is reduced Low temperature corrosion will not occur below 40°C. The difference between the composition of hot water obtained from natural gas boiler exhaust and cold water and raw water is only that the content of free _CO2 increases and the content of oxygen decreases, while the increase of _CO2 content is beneficial to the removal of bacteria from human skin; the heated water is still transparent It is colorless and odorless, fully in line with hygienic standards, and can be used for various domestic hot water supply. The above conclusions have been confirmed by authoritative research institutions.

Based on the above knowledge, the present invention develops a unique approach and develops a direct air-water heat exchanger to achieve the purpose of providing domestic hot water at low cost. The shower device for broken water droplets installed inside the body of the heat exchanger has a space for water droplets to pass through, and the water droplets in the shower device pass through the space to form a flue gas channel; the flue gas is in contact with the broken water droplets countercurrently or downstream As for heat transfer, the heat exchanger of the present invention adopts a brand-new concept structure to realize the heat transfer mode between the low-temperature flue gas and the water medium. It cancels the smoke pipe and the partition wall on the solid wall surface, and does not need to pass through the intermediary of the solid heat transfer surface. Instead, it relies on direct contact between water and flue gas for heat exchange: in the flue gas channel, a sprinkler device with broken water droplets is used to divide the large group of water media into water droplets with appropriate descending speed and flow rate, which are uniform and controllable, and form a water droplet field. The size of water droplets in the droplet landing field is moderate, neither will it be carried out by low-temperature flue gas, nor will the heat transfer efficiency be poor due to insufficient heating due to too fast falling and large particle size. Uniform water droplets will generate a large dynamic heat transfer specific surface area in direct contact with low-temperature flue gas in the reverse flow, thereby greatly increasing heat transfer efficiency, and will not form excessive resistance to low-temperature flue gas, ensuring Heat transfer is sufficiently and stably performed. Moreover, since the air-water heat exchanger of the present invention makes the water drop waterfall directly contact the low-temperature flue gas, it can absorb the latent heat of condensation of the water vapor in the flue gas, thereby greatly reducing the exhaust gas temperature, and finally passes through the hot water arranged at the lower part of the body. The collection of tanks and outlet pipes results in a high-enthalpy water medium. Its direct contact heat transfer coefficient can be as high as 1000W/(m ² ℃). The heat exchanger and the heat exchange method developed by the present invention can greatly reduce the volume of the air-water heat exchanger, reduce the engineering cost, improve the heat exchange efficiency, and recover the low-temperature flue gas waste heat generated by the combined cooling, heating and power system in the possible in engineering applications. Experiments have proved that the direct air-water heat exchanger of the present invention is an ideal device and method for recovering the waste heat of low-temperature flue gas in combined cooling, heating and power generation systems. Obviously, installing a direct contact heat exchanger behind the traditional waste heat boiler to generate domestic hot water will further improve the thermal efficiency of the system, and provide domestic hot water at a very low cost, which can greatly improve the economic benefits of the system (roughly estimated net benefits can be increased by 10%).

Further research found a new problem: Usually, the temperature of domestic hot water that people need is 45°C, and theoretically, the temperature to which water can be heated during the direct heat exchange process between flue gas and water will not exceed the temperature of the flue gas. The wet bulb temperature of the gas at the inlet, when the water is heated to the wet bulb temperature of the flue gas at the inlet, the water temperature will not rise again, but can only be vaporized into steam, that is, the hot water has reached the heating limit temperature. The wet bulb temperature of the flue gas at the inlet depends on the partial pressure of water vapor in the flue gas, so the limit water temperature at the outlet is different under different partial pressures of water vapor. Because a general gas turbine uses excess air as a co-substance, the partial pressure of water vapor in the exhaust is very low, about 4.5%, and the maximum temperature of the heated hot water at this time is calculated to be 45°C. However, in a centralized domestic hot water supply system, in order to store heat and reduce the need for pipe network investment, a hot water temperature slightly higher than 45°C but lower than 120°C is required, such as 60°C, which means that the flue gas needs to be higher. water vapor partial pressure. To heat up to 60 degrees, steam must be reinjected; but for internal combustion engines, this problem does not exist.

The simulation calculation results show that the limit temperature to which the cold water can be heated increases with the increase of the steam reinjection rate. If the concentration of water vapor in the flue gas is 4.5%, the limit temperature at which the cold water can be heated is 45 degrees. If this temperature is exceeded, the phenomenon of "dry tower" will appear (that is, the hot water starts to evaporate); if the water is to be heated When the temperature reaches 60 degrees, water vapor needs to be reinjected into the gas turbine, and the reinjection rate reaches 12% so that the partial pressure of water vapor in the flue gas reaches 15%. The water can be heated to 60 degrees. (If the steam is not reinjected, the hot water can be further heated from 45 degrees to 60 degrees by installing a steam heater.) Therefore, the simulation calculation results show that the use of steam reinjection is the best way to increase the temperature of the hot water outlet and reduce the system investment. important measure.

The simulation calculation results also show that at different inlet water temperatures, if the output hot water temperature reaches the required 60°C, the NO _X content in the hot water will be negligible, and will show a downward trend with the increase of steam reinjection, which is completely in line with the requirements of domestic hot water. Hygienic standard; _CO Concentration increases slightly with the raising of reinjection rate, but concentration is also very low, has no influence on water quality, can prove that the structural improvement of the system of the present invention has sufficient feasibility and relevant technology at this point Advantages, and consistent with relevant conclusions of authoritative research institutions.

It can also be seen from the simulation calculation results that the structural improvement of reinjection steam can also reduce the generation of NOx and save the power consumption of the compressor at the same time. The reason is very simple, because injecting steam into the combustion chamber of the gas turbine can properly reduce the combustion temperature, reduce the generation of NOx, and is beneficial to environmental protection. Steam reinjection can also reduce the amount of air entering the gas turbine, save part of the compression work, or appropriately increase the output of the gas turbine; making the operation of the unit more flexible. For this reason, the structural improvement of the system of the present invention includes two optional system structures: the gas-fired power generation device is an internal combustion engine type power generation device, and steam reinjection facilities may not be provided at this time; or the gas-fired power generation device is a gas turbine type power generation device. At this time, a steam reinjection pipe leading to the combustion chamber is provided on the steam main pipe of the waste heat boiler, and a decompression device is connected in series on the steam reinjection pipe.

The difference between the present invention and the traditional Cheng's cycle is that the steam reinjection amount of the latter is extremely large, which is almost the same as the air intake of the compressor, so the configuration of the unit, that is, the capacity ratio of the compressor to the power turbine, is special. However, the steam reinjection rate of the present invention is only about 10%; it can be completely used in gas turbines of general design.

At present, there is no report on the combined cooling, heating and power generation method found in the relevant literature. But the advantages of this approach are unquestionable.

All in all, the theoretical analysis and preliminary trial prove that: compared with the common gas turbine cogeneration system, the system flow of the new cogeneration project of the present invention has the following main advantages:

(1) Waste heat boiler steel consumption is small and efficiency is improved:

Because the exhaust gas temperature behind the waste heat boiler is low and the heat transfer temperature difference is small, if a traditional shell-and-tube heat exchanger is used, the required heating surface will be very large, so the consumption of steel will be large. In the present invention, a contact hot water heater is installed at the tail, and the heat transfer coefficient is much higher than that of a common heat exchanger because the flue gas is in direct contact with water. Therefore, the heating surface can be greatly reduced, and the steel consumption is reduced by more than 5 times.

(2) Reduce the equipment cost, corrosion and operation cost of the tail induced draft fan:

Because after passing through the contact hot water heater, the temperature of the flue gas has dropped below 40 degrees. At this time, it is impossible to discharge the flue gas by relying on the draft force generated by the temperature difference between the inside and outside of the chimney. Therefore, the present invention adopts a positive pressure ventilation method, that is, without an induced draft fan, and overcomes the resistance of the waste heat boiler, the contact hot water heater, the rear connecting flue, and the chimney by increasing the exhaust pressure of the gas turbine, and finally discharges the flue gas into the atmosphere. At this time, the chimney can be properly lowered as needed. (At this point the chimney has not much suction)

(3) Steam reinjection measures improve the flexibility and economy of system operation:

A part of the low-pressure steam extracted from the steam turbine is re-injected into the combustion chamber of the gas turbine, which can effectively increase the outlet temperature of hot water, reduce NOx emissions, and prolong the service life of the unit. Its other advantage is to increase the power generation output of the gas turbine. For a simple gas turbine combined cooling, heating and power system, when the terminal heat load is reduced, the excess steam can be reinjected to increase the power generation, which can significantly improve the flexibility and economy of system operation. ; In different seasons, according to the different needs of water temperature and water volume, control the amount of reinjection steam. Compared with the general gas turbine combined cycle cogeneration system, although the power generation increased by steam reinjection is slightly lower than that of the steam turbine, and the back pressure of the gas turbine is slightly higher due to the small chimney suction, the power generation is slightly reduced, but it can Save steam turbine investment and gain greater benefits by recovering a large amount of low-temperature waste heat. If the system uses an internal combustion engine instead of a gas turbine, there is no steam reinjection problem because of the high partial pressure of water vapor in the flue gas.

In order to further realize the basic advantages of the direct air-water heat exchanger of the present invention, the present invention adopts the following more specific improvement measures: the direct air-water heat exchanger includes a body on which an inlet pipe, an outlet pipe and The flue gas outlet is provided with a flue gas inlet on the side wall of the body, and a flue gas channel is arranged in the body; a flue gas flow equalization device is arranged in the axial direction of the flue gas inlet inside the body, and the flow equalization device It includes a flue gas flap with a cross-section bent upward; the flue gas channel includes a channel passing through the flue gas flap and the space inside the body above the flue gas flap. A grid bar array type shower device; the mouth of the water inlet pipe and the gas outlet are both arranged above the shower device, a hot water tank for collecting water droplets is installed under the gas flap, and the outlet The mouth of the water pipe is arranged at the bottom of the hot water tank. The air-water heat exchanger of the present invention is ingenious and ingenious, and adopts the structure that a flow equalizing device is installed in the axial direction of the flue gas inlet, and the flue gas flaps are installed to disperse and guide the low-temperature flue gas upward to contact with the falling water droplets , to overcome the problem that the heat transfer interface between flue gas and water is too small; it has been proved by experiments that the thermal efficiency of the air-water heat exchanger of the present invention can be as high as more than 98%, and the temperature rise speed is very fast after starting up; Furnace and/or flue pipe and other solid heating surfaces, the weight of the air-water heat exchanger of the present invention is only 1/5 of the same heat load partition wall heat exchanger; The long-term use efficiency of the heater will not decrease, no water treatment process and equipment are required, the maintenance work and cost are greatly simplified, and the safety and reliability of operation are greatly increased. The effective life of the air-water heat exchanger of the present invention can be expected to be as long as 20 to 30 years .

In order to further improve the flue gas low-temperature heat utilization system of the combined cooling, heating and power supply of the present invention, ensure system operation stability, and improve heat energy utilization efficiency, the present invention takes the following measures: the system also includes a steam turbine power generation device, and the steam turbine power generation device It includes a steam turbine, a generator, a condenser, and a deaerator; the steam turbine is connected in series on the pipeline between the steam outlet of the waste heat boiler, the absorption refrigeration device and the heating water supply device.

The heating water supply device includes a steam heater, the low-pressure steam outlet of the steam turbine communicates with the steam pipe inlet of the steam heater, and a pair of water pipe ports of the steam heater are connected in series to the direct air-water heat exchange Between the outlet pipe of the appliance and the domestic hot water pipe. The low-pressure steam outlet of the steam turbine is provided with a steam branch pipe leading to the steam nozzle of the deaerator.

In order to further utilize the cooling capacity of liquefied natural gas to reduce the energy consumption of the flue gas low-temperature heat utilization system of the combined cooling, heating and power supply of the present invention, and improve the efficiency of the compressor, the present invention takes the following measures: there is a gap between the inlet of the compressor and the atmosphere. An air cooler is connected in series, and the refrigerant pipe system of the air cooler is connected in series between the gas pipe port and the combustion chamber.

In order to achieve the technical purpose of the present invention, another related technical solution of the present invention is an operation method of a flue gas low-temperature end heat utilization system for natural gas combined cooling, heating and power supply. The heat utilization system operated by this method includes a gas-fired power generation device, waste heat Boiler, absorption refrigeration device, heating water supply device; the gas-fired power generation device includes a compressor, a combustion chamber, a gas turbine and a generator; the inlet of the compressor is connected to the atmosphere, and its outlet is connected to the inlet of the combustion chamber. The inlet of the combustion chamber is also connected to the gas pipe port; the waste heat boiler includes a flue gas inlet, a flue gas outlet, a condensed water inlet and a steam outlet, and the flue gas inlet of the waste heat boiler is connected to the exhaust gas of the gas-fired power generation device. The steam outlet is connected to the absorption refrigeration device and the heating water supply device through a steam pipe, and the heating water supply device also includes a direct air-water heat exchanger, and the body of the direct air-water heat exchanger A shower device for broken water droplets is installed inside, and the water droplets in the shower device pass through the space to form a flue gas channel; the flue gas outlet of the waste heat boiler is connected to the chimney through the flue gas pipe of the direct gas-water heat exchanger The inlet and outlet pipes of the direct air-water heat exchanger are connected in series to the pipes for domestic hot water or heat supply; the steam pipe of the waste heat boiler is also branched with a re-injection pipe leading to the combustion chamber A steam pipe, on which a steam reinjection pipe is connected in series with a decompression device, is characterized in that the method includes controlling the decompression device so that the ratio of the waste heat boiler to reinject steam into the combustion chamber through the reinjection steam pipe can be Adjust within the range of 0% to 12% (W/W). The method of the present invention can make the flue gas temperature at the flue gas outlet of the direct air-water heat exchanger reach below 50°C. The so-called steam reinjection rate is the amount of steam relative to the total amount of air entering the system from the compressor.

In a word, the structural improvement of the present invention has the advantages of simple implementation, effective and low cost.

Below, the technical solution of the present invention will be further described in conjunction with specific embodiments and accompanying drawings.

【Description of drawings】

Fig. 1 is a schematic structural diagram of a traditional gas turbine cogeneration system.

Fig. 2 is a structural schematic diagram of an embodiment of the flue gas low-temperature heat utilization system for cogeneration of cooling, heating and power of the present invention.

Fig. 3 is a schematic structural view of an embodiment of the direct air-water heat exchanger of the present invention.

Traditional gas turbine cogeneration system structure:

As shown in Figure 1, a traditional gas turbine cogeneration system of heat, power and cooling is shown. The flue gas low-temperature end heat utilization system of natural gas combined cooling, heating and power supply includes a gas-fired power generation device, a waste heat boiler, an absorption refrigeration device, and a heating and water supply device; Wherein the gas-fired power generation device comprises a gas compressor 11, a combustion chamber 12, a generator 13, and a gas turbine 14; the inlet of the gas compressor 11 is connected with the atmosphere, and its outlet is connected with the inlet of the combustion chamber 12; the inlet of the combustion chamber 12 is also connected with the natural gas nozzle The waste heat boiler 21 includes a flue gas inlet, a flue gas outlet, a condensed water inlet and a steam outlet. The flue gas inlet of the waste heat boiler 21 is connected to the exhaust outlet of the gas turbine 14 in the gas-fired power generation device, and its 21 steam outlets pass through the steam pipe , the steam turbine 31 is connected with the absorption refrigeration unit 41 and the steam heater 51 as a heating water supply device, and the system includes a steam turbine power generation device, which includes a steam turbine 31, a generator (not shown), a condenser 32, The deaerator 33 ; the steam turbine 31 is connected in series on the pipeline between the steam outlet of the waste heat boiler 21 and the absorption refrigeration device 41 and the steam heater 51 . The system outputs electric energy to the user through two generators including the generator 13 , outputs refrigerant to the user through the absorption refrigeration device 41 , and outputs domestic hot water to the user through the steam heater 51 , and the residual flue gas is discharged from the chimney 6 .

【Detailed ways】

Figure 2 shows the structure of a preferred embodiment of the flue gas low-temperature heat utilization system of combined cooling, heating and power supply of the present invention. The heat utilization system includes a gas-fired power generation device, a waste heat boiler, an absorption refrigeration device, and a heating water supply device; The gas-fired power generation device described includes a compressor 11, a combustion chamber 12, a generator 13, and a gas turbine 14; the inlet of the gas compressor 11 is connected to the atmosphere, and its outlet 11 is connected to the inlet of the combustion chamber 12; the inlet of the combustion chamber 12 is also connected to the natural gas The nozzles are connected; the waste heat boiler 21 includes a flue gas inlet, a flue gas outlet, a condensed water inlet and a steam outlet. The steam path and pipeline of the steam pipe and the steam turbine 31 are connected with the absorption refrigerating device 41 and the steam heater 51 as the heating water supply device; and the heating water supply device also includes a direct air-water heat exchanger 52, which directly A shower device 526 for crushing water droplets is arranged inside the body of the air-water heat exchanger 52, and the space between the shower devices 526 forms a flue gas channel; the flue gas outlet of the waste heat boiler 21 passes through the direct air-water The flue gas pipeline of the heat exchanger 52 is connected with the chimney 6, and the inlet and outlet pipes of the direct air-water heat exchanger 52 are connected in series to the pipeline for domestic hot water or heat supply; the steam pipeline of the waste heat boiler 21 is also branched There is a reinjection steam pipe leading to the combustion chamber 12, and a decompression device 22 is connected in series on the reinjection steam pipe.

The gas-fired power generation device is a gas turbine type power generation device or an internal combustion engine type power generation device.

The system includes a steam turbine power generation device, which includes a steam turbine 31, a generator (not shown), a condenser 32, and a deaerator 33; the steam turbine 31 is connected in series with the steam outlet of the waste heat boiler 21 and the absorption refrigeration device 41 and the pipeline between the steam heater 51. The low-pressure steam outlet of the steam turbine 31 is provided with a steam branch pipe leading to the hot water nozzle of the deaerator.

The heating water supply device includes a steam heater 51, the low-pressure steam outlet of the steam turbine 31 communicates with the steam pipe inlet of the steam heater 51, and a pair of water pipe ports of the steam heater 51 are connected in series with the direct air-water heat exchanger 52. Between the outlet pipe and the domestic hot water pipe.

An air cooler 10 is also connected in series between the inlet of the compressor 11 and the atmosphere, and the refrigerant pipe system of the air cooler 10 is connected in series between the liquefied natural gas nozzle and the combustion chamber 12 .

As shown in Figure 3, the structure of the embodiment of the direct air-water heat exchanger is shown. A flue gas inlet 524 is opened on the side wall of the 520, and a flue gas channel is arranged in the body 520; a flue gas flow equalization device is arranged in the axial direction of the flue gas inlet 524 inside the body 520, and the flow equalization device includes The flue gas folded plate 525 whose section is bent upward; the flue gas channel includes the passage through the flue gas folded plate 525 and the space inside the body above the flue gas folded plate 525, and a broken water droplet is arranged in the space of the body 520 above the flue gas folded plate 525. The shower device 526; the mouth of the water inlet pipe 521 and the smoke outlet 523 are both arranged above the shower device 526, and an array of defogging plates 528 is also arranged between the smoke outlet 523 and the shower device 526, and the smoke deflects The bottom of the plate 525 is provided with a hot water tank 527 for collecting water droplets. The nozzle of the water outlet pipe 522 is arranged at the bottom of the hot water tank 527, and the nozzle of the water outlet pipe 522 is externally connected with a water delivery pump 529 and a water delivery pipe. In addition, an overflow nozzle 530 is provided on the top of the hot water tank 527,

Among them, scheme 1 represents a traditional cogeneration system with an exhaust gas temperature of 120 degrees; scheme 2 represents a cogeneration system according to an embodiment of the present invention with an exhaust gas temperature of 40 degrees (without reinjection of steam).

The present embodiment adopts one 40 small gas turbines 14 . The output power of the gas turbine 14 under normal conditions is 3428kW (intake temperature 20 degrees), and the high-temperature flue gas generated enters the waste heat boiler 21 to generate about 9t/h of steam. The exhaust gas volume of the waste heat boiler 21 is about 7×104m ³ /h (exhaust gas temperature 120 degrees).

Calculated on the basis of 4000 hours of operation per year: the depreciation fee is calculated at 10% per year.

The actual measurement proves that: adopting the scheme 2 of the present invention can save 1.53 million yuan of operating expenses every year, and the investment is only increased by 53,000 yuan, which can be completely ignored. Therefore, it has great advantages and is recommended to be used first.

Further investigate the technical economy of the embodiment of the cogeneration system of the present invention under the condition of steam reinjection: compared with the gas turbine combined cycle, the power generation of the steam turbine 31 is reduced after the steam reinjection cycle is adopted, but the amount of hot water produced at the same time increased, and the power generation of the gas turbine 14 has also increased, and the investment of the steam turbine 31 can be saved at the same time. Therefore, how economical the steam reinjection cycle is, a quantitative analysis is given below, also taking the above small unit as an example:

Table 2 - Economic comparison under different reinjection rates

Steam reinjection rate (%) 0 4% 6% 8% 12% Amount of hot water produced (t/h) (converted to 40°C) 53 64 69 75 82 Theoretically less power generation of the system (kW) 0 139 152 164 177 Reduced hourly electricity fee income (0.55 yuan/kwh) 0 77 84 90 97 Hourly hot water income (calculated at 8 yuan/t) 424 512 552 600 656 hourly economic benefits 424 yuan 435 yuan 468 yuan 510 yuan 559 yuan Total economic benefits (calculated based on 4000 hours of operation per year) 1.7 million yuan 1.74 million yuan 1.87 million yuan 2.04 million yuan 2.24 million yuan

It is not difficult to see from the above table that with the increase of steam reinjection, the total economic benefit increases significantly. Therefore, steam reinjection is an important measure to improve the economic benefits of the system. However, in order to ensure the stable operation of the gas turbine 14, the amount of reinjection should not be too large. According to experience, the reinjection rate is best not to exceed 10%. After comprehensive consideration, the steam reinjection rate recommended in this paper is about 8%, which is more appropriate. At this time, the overall economic benefit has increased a lot, and the outlet temperature of hot water has reached 56°C, which can basically meet the requirements of bathing and long-distance transportation. Therefore, this paper believes that it is beneficial to inject a small amount of steam into the combustion chamber 12, which can improve the overall economic benefits of the system, reduce the emission rate of NOx, prolong the service life of the unit, and increase the outlet temperature of hot water to meet long-distance transportation. needs, but the reinjection rate should not exceed 8%.

Claims (6)

1. the flue gas low-temperature end heat utilization system of a rock gas supply of cooling, heating and electrical powers, this heat utilization system comprises fuel gas generation device, exhaust heat boiler, absorption type refrigerating unit, heating water supply installation; Described fuel gas generation device comprises gas compressor (11), firing chamber (12) and generator (13); The inlet of described gas compressor (11) is connected with atmosphere, and its outlet links to each other with the inlet of firing chamber (12), and the inlet of described firing chamber (12) also is connected with the combustion gas mouth of pipe; Described exhaust heat boiler (21) comprises flue gas inlet, smoke outlet, condensed water import and steam (vapor) outlet, the flue gas inlet of this exhaust heat boiler (21) is communicated with the exhaust outlet of described fuel gas generation device, its steam (vapor) outlet is connected with the heating water supply installation with described absorption type refrigerating unit (41) by steam transmitting pipe, it is characterized in that: described heating water supply installation comprises direct-type air-water heat exchanger (52), body (520) inside of described direct-type air-water heat exchanger (52) is provided with the gondola water faucet device (526) of broken water droplet, and the space of passing through of water droplet constitutes flue gas channel again in this gondola water faucet device (526); The smoke outlet of described exhaust heat boiler (21) is connected with chimney (6) by the fume pipe of this direct-type air-water heat exchanger (52), and the inlet tube and outlet tube of described direct-type air-water heat exchanger (52) is connected on the pipeline into domestic hot-water or heat supply; The body (520) of described direct-type air-water heat exchanger (52) is provided with intake pipe (521), outlet pipe (522) and smoke outlet (523), offers flue gas inlet (524) on the sidewall of described body (520), and body is provided with flue gas channel in (520); Body (520) inner over against this flue gas inlet (524) axially be provided with the flue gas flow equalizing device, this current equalizer comprises cross section bending flue gas flap (525) upwards; Described flue gas channel comprises the passage and top body (520) volume inside thereof of passing through described flue gas flap (525), is provided with the gondola water faucet device (526) of grid bar array formula in body (520) space of described flue gas flap (525) top; The mouth of pipe of described intake pipe (521) and smoke outlet (523) all are arranged on the top of described gondola water faucet device (526), described flue gas flap (525) below is provided with the hot water tank (527) that compiles water droplet, and the mouth of pipe of described outlet pipe (522) is arranged on the bottom of described hot water tank (527).

2. the flue gas low-temperature end heat utilization system of rock gas supply of cooling, heating and electrical powers as claimed in claim 1 is characterized in that: described fuel gas generation device is an internal-combustion engine formula electricity generating device; Perhaps described fuel gas generation device is gas turbine (a 14) formula electricity generating device, and the steam transmitting pipe of described exhaust heat boiler (21) also branch offer a re-injection steam pipe that leads to described firing chamber (12), on this re-injection steam pipe, be in series with decompressor (22).

3. the flue gas low-temperature end heat utilization system of rock gas supply of cooling, heating and electrical powers as claimed in claim 1 or 2, it is characterized in that: described system also comprises the steam turbine electricity generating device, and this steam turbine electricity generating device comprises steam turbine (31), generator, condenser (32), oxygen-eliminating device (33); This steam turbine (31) is connected on the steam (vapor) outlet and the pipeline between described absorption type refrigerating unit (41) and the heating water supply installation of described exhaust heat boiler (21).

4. the flue gas low-temperature end heat utilization system of rock gas supply of cooling, heating and electrical powers as claimed in claim 3 is characterized in that: the low pressure steam outlet of described steam turbine (31) offers a steam branch pipe and leads to described oxygen-eliminating device (33) the steam mouth of pipe.

5. the flue gas low-temperature end heat utilization system of rock gas supply of cooling, heating and electrical powers as claimed in claim 3, it is characterized in that: described heating water supply installation comprises steam heater (51), the low pressure steam outlet of described steam turbine (31) is connected with the steam tube import of this steam heater (51), and a pair of hose nozzle of this steam heater (51) is connected between the outlet pipe and domestic hot-water's pipeline of described direct-type air-water heat exchanger (52).

6. the flue gas low-temperature end heat utilization system of rock gas supply of cooling, heating and electrical powers as claimed in claim 1 or 2, it is characterized in that: also be in series with air-cooler (10) between the inlet of described gas compressor (11) and the atmosphere, the refrigerant piping of this air-cooler (10) is connected between the described combustion gas mouth of pipe and described firing chamber (12).

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