Diesel generating set medium-temperature tail gas waste heat recovery system and process

Abstract

The invention relates to a medium-temperature tail gas waste heat recovery system and process for a diesel generating set. The problems of tail gas expansion noise and tail gas thermal pollution are solved. The system comprises a diesel generating set (4), a high-temperature fan (5), a waste heat boiler (21), a deaerator (8), a middle water tank (12), a condensing steam turbine (15), a condenser (17) and a cooling tower (19), the diesel generating set (4) formed by connecting diesel generators (2) in parallel is communicated with the waste heat boiler (21), the waste heat boiler (21) is provided with a tail gas discharge port (6) and is communicated with the condensing steam turbine (15), and the condensing steam turbine (15) is provided with a tail gas discharge port (6). The condensing steam turbine (15) drives the generator (16) to do work and generate electricity, the condensing steam turbine (15) is communicated with the condenser (17), the condenser (17) is communicated with the cooling tower (19), circulating water (18) circulates between the condenser (17) and the cooling tower (19), the condenser (17) is simultaneously communicated with the middle water tank (12), the middle water tank (12) is further respectively communicated with the cooling tower (19) and the deaerator (8), and the deaerator (8) is communicated with the waste heat boiler (21). According to the invention, the construction cost is low while the reliability is realized.

Description

Technical Field

[0001] The present invention relates to a waste heat recovery system, and in particular to a system and process for recovering waste heat from medium-temperature tail gas of a diesel generator set. Background Art

[0002] The main principle of a diesel generator set is that diesel combustion in the cylinder generates heat energy, gas expansion drives the piston movement to convert heat energy into mechanical energy, and the rotating crankshaft reversely drags the generator through the coupling to convert mechanical energy into electrical energy. However, at this stage, the working efficiency of diesel engines is generally less than 50%, and a large amount of heat energy is discharged into the environment with the exhaust gas. The presence of nitrogen oxides in high-temperature exhaust gas will seriously pollute the environment. High-temperature exhaust gas will also directly cause environmental thermal pollution. The expansion of high-temperature exhaust gas will indirectly cause noise pollution, which seriously affects the occupational health of operators. In order to utilize the large amount of heat energy contained in the exhaust heat of diesel generators, reduce pollutants in exhaust gas, and reduce exhaust thermal pollution and noise pollution. CN103318850A proposes a low-temperature waste heat recovery system for pyrite and smelting flue gas acid-making devices. The purpose of the invention is to use the DWHS absorption tower to absorb acid to produce low-temperature steam. Its system structure and purpose are different from the present invention. CN114654995A proposes a hybrid refrigerated truck waste heat recovery system that recovers waste heat from jacket water and exhaust gas to generate the required cooling capacity and electrical energy for the refrigerated truck. Its system structure and purpose differ from the present invention. CN216617643U proposes an exhaust muffler, which utilizes a novel structure and has a different purpose from the present invention. CN216638962U proposes a diesel engine exhaust waste heat utilization device for heating seawater in the desalination industry. Its novel structure and purpose differ from the present invention. Summary of the Invention

[0003] The purpose of the present invention is to construct a diesel generator set exhaust gas waste heat utilization system based on the current situation that the traditional generator set medium-temperature exhaust gas waste heat system cannot simultaneously meet the needs of exhaust gas treatment, power generation, and domestic hot water supply. The system utilizes the waste heat in the diesel generator set exhaust gas and provides electricity and domestic hot water at the same time, fundamentally solving the problems of exhaust gas expansion noise and exhaust gas thermal pollution.

[0004] Compared with existing technologies, this invention is suitable for diesel generator set applications such as industrial plants and emergency power supply, and is suitable for diesel generator set renovation and expansion, with relatively low new construction and renovation costs. It can be retrofitted to recover exhaust heat from diesel generator sets without changing the original process.

[0005] The present invention is achieved by the following technical solutions:

[0006] A diesel generator set medium temperature exhaust waste heat recovery system, comprising a diesel generator set 4, a high temperature fan 5, a waste heat boiler 21, a deaerator 8, an intermediate water tank 12, a condensing steam turbine 15, a condenser 17 and a cooling tower 19.

[0007] The diesel generator set 4 formed by the diesel generators 2 in parallel is connected in series with a high-temperature fan 5. The high-temperature fan 5 is connected to the waste heat boiler 21. The waste heat boiler 21 is provided with an exhaust gas discharge port 6. The waste heat boiler 21 is connected to the condensing steam turbine 15. The condensing steam turbine 15 drives the generator 16 to generate power. The condensing steam turbine 15 is connected to the condenser 17. The condenser 17 is connected to the cooling tower 19. The circulating water 18 circulates between the condenser 17 and the cooling tower 19. The condenser 17 is also connected to the intermediate water tank 12. The intermediate water tank 12 is also connected to the cooling tower 19 and the deaerator 8 respectively. The deaerator 8 is connected to the waste heat boiler 21.

[0008] Cooling towers are either closed cooling towers or open cooling towers.

[0009] A process for recovering waste heat from medium-temperature exhaust gas from a diesel generator set includes the following process steps:

[0010] Step S0: Start the desalted water system to produce water, store water in the intermediate water tank and boiler, and start the circulating water system;

[0011] Step S1: The diesel generator set is started and the high-temperature fan is turned on as needed;

[0012] Step S2: The tail gas is heated by a waste heat boiler to heat the desalted water to generate low-pressure steam;

[0013] Step S3: After the low-pressure steam parameters meet the turbine work requirements, the steam main vent valve opening is reduced;

[0014] Step S4: Start the condensing steam turbine to generate power, and after it stabilizes, it can be connected to the grid for power generation;

[0015] Step S5: A portion of the heated circulating water can be drawn out as domestic hot water according to the demand for domestic hot water.

[0016] The system of the present invention can provide additional electricity and hot water supply, which can improve the operating economy of diesel generator sets in remote areas. The present invention uses water as the working medium, which is easy to obtain, and the components of the diesel medium-temperature exhaust waste heat power generation system are mature in manufacturing, which has reliability and low construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The invention relates to a medium-temperature exhaust waste heat recovery system for a diesel generator set;

[0018] In the figure, diesel engine 1, diesel generator 2, diesel generator exhaust manifold 3, diesel generator set 4, high-temperature fan 5, exhaust outlet 6, desalted water after deoxidation 7, deaerator 8, desalted water makeup 9, desalted water 10, condensed water for condensing steam turbine 11, intermediate water tank 12, low-pressure steam 13, exhaust main pipe 14, condensing steam turbine 15, steam turbine generator 16, condenser 17, cooling water 18, cooling tower 19, domestic hot water 20, waste heat boiler 21;

[0019] Figure 2 This is a working embodiment of the medium-temperature exhaust waste heat recovery system of the diesel generator set of the present invention. DETAILED DESCRIPTION

[0020] Figure 1 The present invention relates to a medium-temperature exhaust heat recovery system for diesel generator sets, comprising a diesel generator set 4, a high-temperature fan 5, a waste heat boiler 21, a deaerator 8, an intermediate water tank 12, a condensing steam turbine 15, a condenser 17, and a cooling tower 19. The need for a high-temperature fan is determined based on the number of diesel generators being recovered and the exhaust back pressure. If the piping layout has a minimal impact on exhaust back pressure, a high-temperature fan is not selected; otherwise, a high-temperature fan is selected. The cooling tower is selected based on whether domestic hot water is required, either an open or closed cooling tower. A closed cooling tower is preferred when domestic hot water is required; otherwise, an open cooling tower is preferred.

[0021] The process layout consists of diesel generators 2 connected in parallel through a diesel generator set exhaust manifold 3 to form a diesel generator set 4. Diesel generator set 4 is connected in series with a high-temperature fan 5, which enters a waste heat boiler 21 through an exhaust main pipe 14. The cooled exhaust gas is discharged into the environment or further treated through an exhaust outlet 6. Desalted water 10 from an intermediate water tank 12 is pumped into a deaerator 8 to remove oxygen and heat it to produce deoxygenated desalted water 7. After heat exchange in a waste heat boiler 21, low-pressure steam 13 is generated. Part of this low-pressure steam 13 is used to remove oxygen in the deaerator 8, while the remaining part is used to drive a condensing steam turbine 15. The turbine 15 drives a generator 16 to generate electricity. Exhaust steam from the turbine enters a condenser 17, where it condenses into condensed water. The condensed condensing water 11 returns to the intermediate water tank 12. Circulating water 18 circulates between the condenser 17 and the cooling tower 19. Based on hot water demand, some domestic hot water 20 is provided, and desalted water 9 is replenished in the intermediate water tank 12.

[0022] The waste heat recovery process of medium-temperature exhaust gas from diesel generator sets mainly includes the following process flows:

[0023] Step S0: Start the desalted water system to produce water, store water in the intermediate water tank and boiler, and start the circulating water system;

[0024] Step S1: The diesel generator set is started and the high-temperature fan is turned on as needed;

[0025] Step S2: The tail gas is heated by a waste heat boiler to heat desalted water to generate low-pressure steam.

[0026] Step S3: After the low-pressure steam parameters meet the turbine work requirements, the steam main vent valve opening is reduced.

[0027] Step S4: Start the condensing steam turbine to generate power, and after it stabilizes, it can be connected to the grid for power generation.

[0028] Step S5: A portion of the heated circulating water can be drawn out as domestic hot water according to the demand for domestic hot water.

[0029] Step S6: replenish desalted water according to the water level of the intermediate water tank, and replenish circulating water according to the water level of the circulating water pool.

[0030] Example:

[0031] Figure 2 This is a working example of a medium-temperature exhaust heat recovery system for a diesel generator set, which mainly includes the following steps:

[0032] Step S0: Start the desalted water system to produce water, store water in the intermediate water tank and boiler, and start the circulating water system;

[0033] Step S1: The diesel generator set is started, and the high-temperature fan is activated as needed. In this embodiment, multiple diesel engine models are considered to operate together, with exhaust temperatures of 477.78°C and 462.78°C, respectively. The total theoretical exhaust volume is 53.15 kg / s, and the total rated power of the generator set is 36.75 MW. This patent uses a practical example, in which the total output power of the generator set is 17 MW.

[0034] Step S2: The tail gas is passed through a waste heat boiler to heat desalinated water, generating low-pressure steam. The low-pressure steam parameters are 0.65 MPa and 275°C. This low-pressure steam has two main functions: driving the steam turbine to produce power and deoxidizing and heating the desalinated water in the deaerator. The total boiler evaporation capacity is approximately 25.31 t / hr, with the deaerator consuming 2.81 t / hr and the turbine using approximately 22.5 t / hr.

[0035] Step S3: After the low-pressure steam parameters meet the turbine work requirements, the steam main vent valve opening is reduced;

[0036] Step S4: Start the condensing steam turbine to work, and after it stabilizes, it can be connected to the grid for power generation. The mechanical efficiency of the condensing steam turbine is about 0.97, the generator efficiency is about 0.94, the exhaust steam dryness is 0.95, the vacuum degree is 0.8KPa, and according to the amount of low-pressure steam, it can generate about 1.47MW of power. The main energy consumption of the system is the boiler feed water pump and the circulating water pump. According to the circulating water and boiler pressure, it can be seen that the circulating water pump consumes about 79.28kW. Considering that the power consumption of the auxiliary equipment of the steam turbine in this power range is generally around 150kW to 200kW, it can be seen that the static output power is about 1.1MW;

[0037] Step S5: A portion of the heated circulating water can be drawn out as domestic hot water according to domestic hot water demand;

[0038] Step S6: replenish desalted water according to the water level of the intermediate water tank, and replenish circulating water according to the water level of the circulating water pool.

[0039] This invention proposes a diesel generator exhaust waste heat power generation system. This system utilizes exhaust waste heat through the Rankine cycle to generate electricity and provide domestic hot water, achieving combined heat and power generation for the diesel generator set. The system achieves an exhaust waste heat recovery efficiency of ≥6.5%. For example, based on a 17MW generator set (fuel consumption rate of 213g / kWh) operating for 3,650 hours per year, this system can save 855 tons of diesel fuel annually.

[0040] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art to which the present invention relates, if equivalent substitutions or obvious modifications are made without departing from the concept of the present invention and the performance or use is the same, they should be deemed to fall within the scope of protection defined by the claims submitted by the present invention.

Claims

1. A medium-temperature exhaust waste heat recovery system for a diesel generator set, characterized by: The invention comprises a diesel generator set (4), a high-temperature fan (5), a waste heat boiler (21), a deaerator (8), an intermediate water tank (12), a condensing steam turbine (15), a condenser (17) and a cooling tower (19), wherein the diesel generator set (4) formed by connecting the diesel generators (2) in parallel is connected to the waste heat boiler (21), the waste heat boiler (21) is provided with an exhaust gas discharge port (6), the waste heat boiler (21) is connected to the condensing steam turbine (15), and the condensing steam turbine The machine (15) drives the generator (16) to generate power. The condensing steam turbine (15) is connected to the condenser (17). The condenser (17) is connected to the cooling tower (19). Circulating water (18) circulates between the condenser (17) and the cooling tower (19). The condenser (17) is also connected to the intermediate water tank (12). The intermediate water tank (12) is also connected to the cooling tower (19) and the deaerator (8). The deaerator (8) is connected to the waste heat boiler (21).

2. A diesel generator set medium-temperature exhaust waste heat recovery system according to claim 1, characterized in that: It also includes a high-temperature fan (5), a diesel generator set (4) connected in series with the high-temperature fan (5), and the high-temperature fan (5) is connected to the waste heat boiler (21).

3. A medium-temperature exhaust waste heat recovery system for a diesel generator set according to claim 1 or 2, characterized in that: Cooling towers are either closed cooling towers or open cooling towers.

4. A process for recovering waste heat from medium-temperature tail gas of a diesel generator set, characterized by: Including the following process: Step S0: Start the desalted water system to produce water, store water in the intermediate water tank and boiler, and start the circulating water system; Step S1: The diesel generator set is started and the high-temperature fan is turned on as needed; Step S2: The tail gas is heated by a waste heat boiler to heat the desalted water to generate low-pressure steam; Step S3: After the low-pressure steam parameters meet the turbine work requirements, the steam main vent valve opening is reduced; Step S4: Start the condensing steam turbine to generate power, and after it stabilizes, it can be connected to the grid for power generation; Step S5: A portion of the heated circulating water can be drawn out as domestic hot water according to the demand for domestic hot water.

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