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

Abstract

The invention relates to an organic Rankine waste heat recovery system and process for medium-temperature tail gas of a diesel generating set. The problems of tail gas expansion noise, tail gas thermal pollution and pollutant pollution are solved. The system comprises a diesel generating set, a high-temperature fan, a heat conduction oil heat exchanger, an evaporator, a high-low temperature organic working medium heat exchanger, a condenser, a cooling tower, an expansion machine and an expansion machine generator, the diesel generating set is communicated with the high-temperature fan, the high-temperature fan discharges tail gas into the heat conduction oil heat exchanger, and the heat conduction oil heat exchanger is communicated with the evaporator through a heat conduction oil main pipe. The evaporator is communicated with an expansion machine through an organic steam circulating main pipe, the expansion machine is connected with an expansion machine generator, the expansion machine is communicated with a high-low temperature organic working medium heat exchanger, one end of the high-low temperature organic working medium heat exchanger is communicated with the evaporator, the other end of the high-low temperature organic working medium heat exchanger is communicated with a condenser, and the condenser is communicated with a cooling tower. The waste heat in the tail gas of the diesel generating set is utilized, so that the comprehensive fuel consumption rate of the diesel generating set is improved.

Description

Technical Field

[0001] The invention relates to an organic Rankine waste heat recovery system for medium-temperature tail gas of a diesel generator set, belonging to the technical field of heat recovery. Background Art

[0002] Diesel generator sets achieve energy conversion through the thermodynamic cycle of an internal combustion engine: diesel combustion in the cylinder releases chemical energy, the high-temperature combustion gas expands, pushing the piston to complete the power stroke, and the crankshaft's rotational mechanical energy is transmitted to the generator through the coupling, ultimately converting it into electrical energy. According to the second law of thermodynamics, the energy conversion efficiency of current diesel engines is generally less than 50%, and approximately 50%-60% of the input energy is released as exhaust waste heat, resulting in three environmental effects: (1) Energy loss: A large amount of heat energy is discharged into the environment with the exhaust; (2) Atmospheric pollution: The high-temperature exhaust gas contains a large amount of harmful gases such as NOx and SOx; (3) Acoustic pollution: The thermal expansion and exhaust pulsation of the exhaust generate a large amount of high-frequency noise. CN103318850A proposes a low-temperature waste heat recovery system for pyrite and smelting flue gas acid production equipment. The purpose of the invention is to use a DWHS absorption tower to absorb acid to produce low-temperature steam. The system structure and purpose of the system are different from those of 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 has a different structure and purpose from the present invention. CN216638962U proposes a diesel engine exhaust waste heat utilization device for heating seawater in the desalination industry, which has a different structure and purpose from the present invention. Summary of the Invention

[0003] The purpose of the present invention is to construct a diesel generator set exhaust organic Rankine waste heat utilization system based on a traditional generator set, to utilize the waste heat in the diesel generator set exhaust, thereby improving the comprehensive fuel consumption rate of the diesel generator set and fundamentally solving the problems of exhaust gas expansion noise, exhaust gas thermal pollution, and pollutant 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 medium-temperature exhaust gas organic Rankine waste heat recovery system for a diesel generator set includes a parallel diesel generator set, a high-temperature fan, a thermal oil heat exchanger, an evaporator, a high- and low-temperature organic working medium heat exchanger, a condenser, a cooling tower, an expander and an expander generator. The diesel generator set is connected to the high-temperature fan through an exhaust main pipe. The high-temperature fan discharges the exhaust gas into the thermal oil heat exchanger. The thermal oil heat exchanger is connected to the evaporator through a thermal oil main pipe. The evaporator is connected to the expander through an organic steam circulation main pipe. The expander is connected to the expander generator. The expander is connected to the high- and low-temperature organic working medium heat exchanger. One end of the high- and low-temperature organic working medium heat exchanger is connected to the evaporator and the other end is connected to the condenser. The condenser is connected to the cooling tower.

[0007] The expander is a screw expander, and the expander has two stages.

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

[0009] A process for recovering organic Rankine waste heat from medium-temperature exhaust gas of 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: starting the thermal oil circulation pump to heat the thermal oil;

[0013] Step S3: After the organic medium steam parameters meet the work requirements of the expander, the opening of the organic steam circulation main bypass pipe is reduced;

[0014] Step S4: Start the first and second expanders to work, and after stabilization, they 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 domestic hot water demand;

[0016] 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.

[0017] The advantages of this invention lie in the fact that no existing organic Rankine waste heat recovery system for diesel-generator medium-temperature exhaust can simultaneously meet the needs of exhaust gas treatment and power generation. The proposed organic Rankine waste heat recovery system for diesel-generator medium-temperature exhaust gas essentially eliminates the noise and heat pollution caused by exhaust gas discharge, while also providing additional electricity and hot water supply, improving the operating economy of diesel generator sets in remote areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the heat recovery system of the present invention;

[0019] In the figure, diesel engine 1, diesel generator set 2, diesel generator exhaust manifold 3, high-temperature fan 4, thermal oil heat exchanger 5, evaporator 6, high and low temperature organic working medium heat exchanger 7, condenser 8, cooling tower 9, secondary expander 10, secondary expander generator 11, primary expander 12, primary expander generator 13, thermal oil main pipe 14, exhaust main pipe 15, organic steam circulation main pipe 16, circulating water main pipe 17;

[0020] Figure 2 It is a schematic diagram of the implementation of the heat recovery system of the present invention. DETAILED DESCRIPTION

[0021] like Figure 1 As shown, the present invention is a system for recovering waste heat from medium-temperature exhaust gas from a diesel generator set, comprising a diesel engine 1, a diesel generator set 2, a diesel generator exhaust manifold 3, a high-temperature fan 4, a thermal oil heat exchanger 5, an evaporator 6, a high- and low-temperature organic working medium heat exchanger 7, a condenser 8, a cooling tower 9, a secondary expander 10, a secondary expander generator 11, a primary expander 12, and a primary expander generator 13. Whether the high-temperature fan 4 is required is determined by the number of diesel generators being recovered and the exhaust back pressure. If the piping layout has a minimal impact on the exhaust back pressure, a high-temperature fan is not required; otherwise, a high-temperature fan is selected. Cooling tower 9 is selected as either an open or closed cooling tower depending on whether domestic hot water is required. A closed cooling tower is preferred when domestic hot water is required; otherwise, an open cooling tower is preferred.

[0022] The process layout consists of a diesel generator 1 connected in parallel to a diesel generator set 2 via a diesel generator exhaust manifold 3. The diesel generator set 2 then passes exhaust gas from the diesel generator set to a high-temperature fan 4 via an exhaust main 15. The high-temperature fan 4 then discharges the exhaust gas into a thermal oil heat exchanger 5, where the medium-temperature exhaust gas exchanges heat with the thermal oil. The thermal oil heat exchanger 5 is connected to the evaporator 6 via a thermal oil main 14. The thermal oil is circulated through the evaporator 6 and the thermal oil heat exchanger 5 via the thermal oil heat exchanger 5 circulation pump, evaporating the organic medium in the evaporator into organic vapor. The organic vapor, through an organic vapor circulation main 16, drives the first-stage expander 12 to perform work, which in turn drives the generator 13 to convert mechanical energy into electrical energy. After passing through the first-stage expander 12, the organic vapor enters the second-stage expander 10 to perform work. The second-stage expander 10 drives the generator 11 to rotate and converts mechanical energy into electrical energy. The exhaust gas enters the high-low temperature organic working medium heat exchanger 7 to exchange heat with the organic matter passing through the condenser 8. The organic medium preliminarily heated by the high-low temperature organic working medium heat exchanger 7 is evaporated into organic vapor through the pumping evaporator 6 and enters the next working cycle. The condenser 8 is connected to the cooling tower 9 through the circulating water main pipe 17.

[0023] The organic Rankine waste heat recovery process for the medium-temperature tail gas of a diesel generator set according to the present invention mainly includes the following process flow:

[0024] 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;

[0025] Step S1: The diesel generator set is started and the high-temperature fan is turned on as needed;

[0026] Step S2: starting the thermal oil circulation pump to heat the thermal oil;

[0027] Step S3: After the organic medium steam parameters meet the work requirements of the expander, the opening of the organic steam circulation main bypass pipe is reduced;

[0028] Step S4: Start the first and second expanders to work, and after stabilization, they can be connected to the grid for power generation;

[0029] Step S5: A portion of the heated circulating water can be drawn out as domestic hot water according to domestic hot water demand;

[0030] 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.

[0031] Example:

[0032] like Figure 2 The figure shows an example of the process of the organic Rankine waste heat recovery system for the medium-temperature exhaust gas of a diesel generator set according to the present invention, which mainly includes the following steps:

[0033] 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;

[0034] Step S1: The diesel generator set starts, and the high-temperature fan is activated as needed. This embodiment considers multiple diesel engine models operating simultaneously, 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, where the total output power of the generator set is 17 MW.

[0035] Step S2: The exhaust gas passes through a thermal oil heat exchanger to heat the thermal oil, generating organic vapor in the evaporator. In this example, R123 is used as the organic medium. The choice of organic medium should be based on market conditions and equipment capabilities. The organic medium vapor parameters are 2.1 MPa and 150°C. The condensing temperature is approximately 32.5°C, and the condensing pressure is 0.12 MPa. In this case, the evaporation rate of the R123 organic medium is approximately 87.90 kg / s.

[0036] Step S3: After the organic medium steam parameters meet the expander's work requirements, the opening of the organic steam main bypass valve is reduced. In this case, a screw expander is selected. Because screw expanders have a specific expansion ratio (4-8), a two-stage expander structure is used.

[0037] Step S4: Start the two-stage expander to generate power. Once stable, it can be connected to the grid for power generation. Based on the R123 circulation rate, it can generate approximately 2.06 MW of power. The system's main energy consumers are the working fluid pump and the circulating water pump. Based on the circulating water flow rate, the circulating water pump consumes approximately 82.6 kW of power, and the working fluid pump consumes 71.84 kW of power. Considering that the power consumption of the expander auxiliary equipment in this power range is generally around 150 kW to 200 kW, the static output power is approximately 1.5 MW.

[0038] 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.

[0039] This invention proposes a diesel generator set exhaust gas organic Rankine waste heat power generation system. This system utilizes exhaust waste heat through the Rankine cycle process to generate electricity, reducing costs and increasing efficiency for diesel generator sets. The system achieves an exhaust heat recovery efficiency of ≥8.8%. 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 1,166 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. An organic Rankine waste heat recovery system for medium-temperature exhaust gas from a diesel generator set, characterized by: It includes parallel diesel generator sets, thermal oil heat exchangers, evaporators, high and low temperature organic working medium heat exchangers, condensers, cooling towers, expanders and expander generators. The diesel generator sets are connected to the thermal oil heat exchangers through exhaust main pipes. The thermal oil heat exchangers are connected to the evaporators through thermal oil main pipes. The evaporators are connected to the expanders through organic steam circulation main pipes. The expanders are connected to the expander generators. The expanders are connected to the high and low temperature organic working medium heat exchangers. One end of the high and low temperature organic working medium heat exchanger is connected to the evaporator and the other end is connected to the condenser. The condenser is connected to the cooling tower.

2. The organic Rankine waste heat recovery system for medium-temperature exhaust gas from a diesel generator set according to claim 1 is characterized by: It also includes a high-temperature fan. The diesel generator set is connected to the high-temperature fan through an exhaust main pipe, and the high-temperature fan discharges the exhaust gas into the thermal oil heat exchanger.

3. The organic Rankine waste heat recovery system for medium-temperature exhaust gas from a diesel generator set according to claim 1 or 2, characterized in that: The expander is a screw expander, and the expander has two stages.

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

5. A process for recovering organic Rankine waste heat from medium-temperature exhaust gas from 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: starting the thermal oil circulation pump to heat the thermal oil; Step S3: After the organic medium steam parameters meet the work requirements of the expander, the opening of the organic steam circulation main bypass pipe is reduced; Step S4: Start the first and second expanders to work, and after stabilization, they 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 domestic hot water demand; 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.

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