Engine exhaust energy recovery and after-treatment purification system and control method

Abstract

This invention discloses an engine exhaust energy recovery and aftertreatment purification system and control method. It includes an engine, a turbocharger, an electric heater, an evaporator, a turbine, a reheater, a condenser, a water pump, a reservoir, and an aftertreatment unit. The evaporator at the engine exhaust treatment path is connected to a front exhaust pipe, an electric heater, and a turbocharger at its front end, for receiving exhaust gas from the engine and heating it at low temperatures. Its rear end is connected to a rear exhaust pipe for discharging the exhaust gas, and the rear exhaust pipe is connected to the aftertreatment unit. The evaporator is sequentially connected to the turbine, condenser, reservoir, water pump, and reheater. A first temperature sensor is installed on the front exhaust pipe, and a second temperature sensor is installed on the rear exhaust pipe. This invention improves the purification function of the aftertreatment unit at low temperatures and reduces energy waste at high temperatures, thereby increasing heat conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of engine exhaust energy recovery and purification technology, specifically relating to an engine exhaust energy recovery and after-treatment purification system and control method. Background Technology

[0002] The reheat cycle involves reheating steam that has already performed some work in the high-pressure cylinder of a steam turbine into the boiler's reheater, raising the steam temperature back to its initial temperature. This steam is then returned to the intermediate and low-pressure cylinders of the turbine to continue performing work, with the final exhaust steam being discharged into the condenser. This cycle improves the thermal efficiency of the Rankine cycle. Waste heat recovery utilizes thermal energy to achieve useful functions. In many cases, waste heat recovery avoids or reduces the need for additional fuel energy input. The peak BTE efficiency of large diesel engines is between 40% and 50%, meaning that over 50-60% of fuel energy is wasted primarily as heat. Hot exhaust gases and cooling circuits account for the largest share of this wasted heat energy, approximately 35% and 10% of the total fuel energy input, respectively. This waste heat can be partially recovered through a reheat cycle, converting the heat energy in the exhaust gases and engine coolant flow into usable mechanical or electrical energy. The main components of diesel internal combustion engine exhaust gases are NO. X For PM, the corresponding traditional exhaust gas treatment device is DOC+DPF+mixer-SCR+ASC device.

[0003] Existing technologies have the following drawbacks: Existing waste heat recovery methods utilizing the Rankine cycle have low cycle thermal efficiency. While reheat cycles can improve cycle thermal efficiency, they are not integrated with aftertreatment. Due to high costs, commercial application is uncertain. A problem with traditional exhaust gas treatment devices is their low conversion efficiency at low exhaust temperatures. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide an engine exhaust energy recovery and after-treatment purification system and control method.

[0005] The technical solution adopted in this invention is: an engine exhaust energy recovery and after-treatment purification system, including an engine, a turbocharger, an electric heater, an evaporator, a turbine, a reheater, a condenser, a water pump, a liquid receiver, and an after-treatment unit. The evaporator at the engine exhaust treatment path is connected to a front exhaust pipe, an electric heater, and a turbocharger at its front end to receive exhaust gas from the engine and heat it at low temperatures. Its rear end is connected to a rear exhaust pipe to discharge the exhaust gas. The rear exhaust pipe is connected to the after-treatment unit. The evaporator is sequentially connected to a turbine, a condenser, a liquid receiver, a water pump, and a reheater. A first temperature sensor is provided on the front exhaust pipe, and a second temperature sensor is provided on the rear exhaust pipe. A bypass pipe is provided between the front and rear exhaust pipes. A first throttle valve is provided at the front end of the bypass pipe, and a second throttle valve is provided at the front end of the evaporator.

[0006] It also includes an ECU, which is used to activate the electric heater, close the second throttle valve, and open the first throttle valve when the temperature of the first temperature sensor is below 200°C, allowing the exhaust gas to bypass the evaporator and pass directly through the bypass pipe to the after-processor for exhaust pollutants; when the temperature of the first temperature sensor is above 200°C but below 300°C, it activates the electric heater, closes the second throttle valve, and opens the first throttle valve, allowing the exhaust gas to bypass the evaporator and pass directly through the bypass pipe to the after-processor for exhaust pollutants; when the temperature of the first temperature sensor is above 300°C, it activates the electric heater, closes the first throttle valve, and opens the second throttle valve, allowing the exhaust gas to flow through the reheat device for waste heat recovery via reheat circulation before passing through the after-processor for exhaust pollutants.

[0007] The after-processor includes a DOC, a DPF, a mixer, a first SCR carrier module, a second SCR carrier module, a third temperature sensor, and a fourth temperature sensor. The DOC is used to oxidize exhaust products such as HC and CO and increase exhaust temperature. The DPF is used to filter particulate matter. The SCR carrier module is used to catalytically reduce nitrogen oxides. The mixer is located above the SCR carrier module and is used to mix exhaust gas and urea to achieve uniformity and improve SCR conversion efficiency.

[0008] The third temperature sensor is located at the front end of the first SCR carrier module.

[0009] The fourth temperature sensor is located at the rear end of the second SCR carrier module.

[0010] The reheater is connected to the EGR via a gas supply pipe.

[0011] The evaporator is equipped with a liquid delivery connector and a liquid receiving connector, which are sequentially connected to a turbine, a condenser, a water pump, a liquid storage tank, and a reheater.

[0012] The liquid delivery connector is connected to the condenser via a first water supply pipe and a second water return pipe, and the liquid delivery connector is connected to the reheater via the first water return pipe.

[0013] The storage tank is connected to the water pump via a second water supply pipe, and the water pump is connected to the liquid receiving connector via a third water supply pipe.

[0014] The turbine output is connected to the electric heater via a first circuit and a second circuit, and then to the battery.

[0015] A control method for an engine exhaust energy recovery and after-treatment purification system includes the following steps: When the temperature of a first temperature sensor is below 200°C, the electric heater is turned on, the second throttle valve is closed, and the first throttle valve is opened, allowing exhaust gas to bypass the evaporator and directly pass through a bypass pipe to the after-treatment unit for exhaust pollutant processing; when the temperature of the first temperature sensor is above 200°C but below 300°C, the electric heater is turned off, the second throttle valve is closed, and the first throttle valve is opened, allowing exhaust gas to bypass the evaporator and directly pass through the after-treatment unit for exhaust pollutant processing; when the temperature of the first temperature sensor is above 300°C, the electric heater is turned off, the first throttle valve is closed, and the second throttle valve is opened, allowing exhaust gas to flow through a reheat device for waste heat recovery via reheat circulation before passing through the after-treatment unit for exhaust pollutant processing.

[0016] The water pump pressurizes the water in the reservoir and delivers it to the evaporator. Engine exhaust gas reaches the evaporator through the front exhaust pipe. In the evaporator, the exhaust gas heats the water at a constant pressure, turning it into water vapor. The water vapor in the evaporator enters the turbine through the liquid delivery joint to expand and do work. The water vapor converts heat into electrical energy in the turbine and stores the electrical energy in the battery to power the electric heater at low temperatures. When the water vapor expands to a certain intermediate pressure in the turbine, it exits the turbine and is introduced into the reheater to use the waste heat from the EGR to reheat the steam. Then it enters the turbine to do work again. The water vapor after energy conversion enters the condenser, where it releases heat at isobaric pressure to become saturated water. It then returns to the reservoir through the condenser, completing one reheat cycle.

[0017] When engine exhaust temperatures are low, an EHC (Electric Heater) is used to heat the gases exiting the engine, improving the conversion efficiency of the aftertreatment system. When engine exhaust temperatures are high and EGR energy is high, some energy is lost. This waste heat can be partially recovered through a reheat cycle, converting the heat energy in the exhaust gas and engine coolant into usable electrical energy. The reheater is used to improve the efficiency of the thermal cycle. The electrical energy is stored in a battery to power the EHC (Electric Heater) at low temperatures.

[0018] This invention improves the purification function of after-treatment at low temperatures and reduces energy waste at high temperatures, thereby increasing heat conversion efficiency. This invention can be applied to diesel engines, including but not limited to dual-fuel or multi-fuel engines such as diesel engines, ammonia fuel engines, and other fuels.

[0019] The waste heat recovery device of this invention recovers engine exhaust gas energy and EGR energy, and improves the cycle thermal efficiency by introducing steam into the reheater through reheat cycle to increase the steam temperature, dryness and pressure, thereby improving waste heat recovery efficiency and reducing the load on water pump and condenser.

[0020] This invention integrates a waste heat recovery device and an after-treatment system. It heats engine exhaust through an EHC (electric heater), making full use of exhaust energy and purifying exhaust gases, improving after-treatment conversion efficiency, and the overall system is efficient and compact.

[0021] This invention utilizes exhaust energy for reheat cycle to generate electricity and stores the electrical energy in a battery for use in EHC at low temperatures. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the control method of the present invention.

[0024] In the diagram, 1-engine, 2-front exhaust pipe, 3-turbocharger, 4-electric heater, 5-evaporator, 6-bypass pipe, 7-liquid receiving connector, 8-liquid delivery connector, 9-rear exhaust pipe, 10-aftertreatment unit, 11-DOC, 12-DPF, 13-mixer, 14-first SCR carrier module, 15-second SCR carrier module, 16-turbo, 17-condenser, 18-reservoir, 19-water pump, 20-battery, 21-first water supply pipe, 22-first return water pipe, 23-second return water pipe, 24-second water supply pipe, 25-third water supply pipe, 26-first circuit, 27-second circuit, 28-gas supply pipe, 29-reheater. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0026] See Figure 1An integrated engine exhaust energy recovery and aftertreatment purification system includes an engine 1, a front exhaust pipe 2, a turbocharger 3, an EHC (electric heater) 4, an evaporator 5, a bypass pipe 6, a liquid receiving connector 7, and a liquid delivery connector 8. It also includes a first temperature sensor T1, a second temperature sensor T2, a third temperature sensor T3, a fourth temperature sensor T4, a rear exhaust pipe 9, an aftertreatment system 10, which includes a DOC 11, a DPF 12, a first SCR carrier module 14, a second SCR carrier module 15, and a mixer 13. Other components include a first throttle valve P1, a second throttle valve P2, a turbine 16, a condenser 17, a liquid reservoir 18, a pump 19, a battery 20, a first return water pipe 22, a second return water pipe 23, a first water supply pipe 21, a second water supply pipe 24, a third water supply pipe 25, a first circuit 26, a second circuit 27, an air supply pipe 28, and a reheater 29.

[0027] The evaporator 5 at the exhaust treatment path of engine 1 is connected to the front exhaust pipe 2, electric heater 4, and turbocharger 3 at its front end. It is used to receive the exhaust gas delivered from engine 1 and heat the exhaust gas at low temperature. The rear end is connected to the rear exhaust pipe 9 for exhausting the exhaust gas. The rear exhaust pipe 9 is connected to the aftertreatment unit 10. The evaporator 5 is connected in sequence to the turbine 16, condenser 17, liquid reservoir 18, water pump 19, and reheater 29. The front exhaust pipe 2 is equipped with a first temperature sensor T1, and the rear exhaust pipe 9 is equipped with a second temperature sensor T2. A bypass pipe 6 is provided between the front exhaust pipe 2 and the rear exhaust pipe 9. The front end of the bypass pipe 6 is equipped with a first throttle valve P1, and the front end of the evaporator 5 is equipped with a second throttle valve P2.

[0028] The post-processor 10 includes DOC 11, DPF 12, mixer 13, first SCR carrier module 14, second SCR carrier module 15, third temperature sensor T3, and fourth temperature sensor T4.

[0029] The third temperature sensor T3 is located at the front end of the first SCR carrier module 14.

[0030] The fourth temperature sensor T4 is located at the rear end of the second SCR carrier module 15.

[0031] The reheater 29 is connected to the EGR via the gas supply pipe 28.

[0032] The evaporator 5 is provided with a liquid delivery joint 8 and a liquid receiving joint 7, which are connected in sequence to a turbine 16, a condenser 17, a water pump 19, a liquid storage tank 18, and a reheater 29.

[0033] The liquid delivery connector 8 is connected to the condenser 17 through the first water supply pipe 21 and the second water return pipe 23, and the liquid delivery connector 8 is connected to the reheater 29 through the first water return pipe 22.

[0034] The storage tank 18 is connected to the water pump 19 via a second water supply pipe 24, and the water pump 19 is connected to the liquid receiving connector 7 via a third water supply pipe 25.

[0035] The output of turbine 16 is connected to electric heater 4 via first circuit 26, second circuit 27 and battery 20.

[0036] The specific working process of this invention is as follows:

[0037] See Figure 1 and Figure 2 When engine 1 burns and produces exhaust gas, the exhaust gas carries heat through the front exhaust pipe 2. When the temperature of the first temperature sensor T1 is below 200°C, the EHC (electric heater) 4 is activated to help quickly increase the exhaust temperature and improve the aftertreatment conversion efficiency. The second throttle valve P2 is closed, and the first throttle valve P1 is opened. The exhaust bypasses the evaporator 5 and goes directly through the bypass pipe 6 to the aftertreatment unit 10 to treat exhaust pollutants. When the temperature of the first temperature sensor T1 is above 200°C but below 300°C, the EHC (electric heater) 4 is closed, the second throttle valve P2 is closed, and the first throttle valve P1 is opened. The exhaust bypasses the evaporator 5 and goes directly through the bypass pipe 6 to the aftertreatment unit 10 to treat exhaust pollutants. When the temperature of the first temperature sensor T1 is above 300°C, which is much higher than the aftertreatment heating requirement, a large amount of waste heat will be generated. The EHC (electric heater) 4 is closed, the first throttle valve P1 is closed, and the second throttle valve P2 is opened. The exhaust flows through the reheat device to recover waste heat through reheat circulation before going through the aftertreatment unit 10 to treat exhaust pollutants.

[0038] Water pump 19 pressurizes and delivers water from reservoir 18 to evaporator 5. Engine exhaust gas reaches evaporator 5 through front exhaust pipe 2. In evaporator 5, exhaust gas heats water at constant pressure, turning it into steam. The steam in evaporator 5 enters turbine 16 through liquid delivery connector 8, where it expands and performs work. Inside turbine 16, the steam converts heat into electrical energy, which is stored in battery 20 to power EHC (electric heater) 4 at low temperatures. When the steam expands to a certain intermediate pressure inside turbine 16, it exits the turbine and is introduced into reheater 29 to utilize the EGR exhaust gas. The steam is reheated (which can increase the dryness and pressure of the steam) and then enters the turbine 16 to do work. The thermal efficiency of the entire cycle is improved by increasing the steam pressure and temperature, thereby improving the waste heat recovery efficiency. The water vapor after energy conversion enters the condenser 17. The pressure in the condenser 17 is usually very low. The water vapor releases heat at isobaric pressure to become saturated water and then returns to the storage tank 18 through the condenser to complete a reheat cycle. After the reheat cycle, the work done per kilogram of steam increases, the steam consumption rate can be reduced, and the load on the water pump 19 and the condenser 17 can be reduced.

[0039] After waste heat recovery, the exhaust gas enters the aftertreatment unit 10 through exhaust pipe 9. Unburned HC and CO in the exhaust gas are oxidized by DOC 11, and some NO is oxidized to NO2. The second temperature sensor T2 monitors the temperature before DOC. The exhaust gas then enters DPF 12, where particulate matter is filtered. The exhaust gas and NH3 are uniformly mixed in mixer 13. The first SCR carrier module 14 and the second SCR carrier module 15 use NH3 as a reducing agent to catalytically reduce nitrogen oxides. The third temperature sensor T3 and the fourth temperature sensor T4 work together to determine the reaction temperature of the first SCR carrier module 14 and the second SCR carrier module 15.

[0040] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An engine exhaust energy recovery and after-treatment purification system, comprising an engine (1), and further comprising a turbocharger (3), an electric heater (4), an evaporator (5), a turbine (16), a reheater (29), a condenser (17), a water pump (19), a liquid storage tank (18), and an after-treatment system (10), wherein the front end of the evaporator (5) at the exhaust treatment path of the engine (1) is connected to the front exhaust pipe (2) and the electric heater (4) and the turbocharger (3), for receiving exhaust gas delivered from the engine (1) and heating the exhaust gas at low temperature, and the rear end is connected to the rear exhaust pipe (9) for... The exhaust pipe (9) is connected to the after-processor (10) to discharge the exhaust gas; the evaporator (5) is connected in sequence to the turbine (16), condenser (17), liquid storage tank (18), water pump (19) and reheater (29); the front exhaust pipe (2) is provided with a first temperature sensor (T1), the rear exhaust pipe (9) is provided with a second temperature sensor (T2), a bypass pipe (6) is provided between the front exhaust pipe (2) and the rear exhaust pipe (9), the front end of the bypass pipe (6) is provided with a first throttle valve (P1), and the front end of the evaporator (5) is provided with a second throttle valve (P2); It also includes an ECU, which, when the temperature of the first temperature sensor (T1) is below 200°C, turns on the electric heater (4), closes the second throttle valve (P2), opens the first throttle valve (P1), and the exhaust bypasses the evaporator (5) and goes directly through the bypass pipe (6) to the after-processor (10) to treat exhaust pollutants; when the temperature of the first temperature sensor (T1) is above 200°C but below 300°C, turns off the electric heater (4), closes the second throttle valve (P2), opens the first throttle valve (P1), and the exhaust bypasses the evaporator (5) and goes directly through the bypass pipe (6) to the after-processor (10) to treat exhaust pollutants; when the temperature of the first temperature sensor (T1) is above 300°C, turns off the electric heater (4), closes the first throttle valve (P1), opens the second throttle valve (P2), and the exhaust flows through the reheat device to recover waste heat through reheat circulation before going through the after-processor (10) to treat exhaust pollutants. The regenerative device consists of an evaporator (5), a turbine (16), a reheater (29), a condenser (17), a water pump (19), and a storage tank (18); The evaporator (5) is provided with a liquid delivery connector (8) and a liquid receiving connector (7) which are connected in sequence to a turbine (16), a condenser (17), a liquid storage tank (18), a water pump (19) and a reheater (29).

2. The engine exhaust energy recovery and after-treatment purification system according to claim 1, characterized in that: The post-processor (10) includes a DOC (11), a DPF (12), a mixer (13), a first SCR carrier module (14), a second SCR carrier module (15), a third temperature sensor (T3), and a fourth temperature sensor (T4).

3. The engine exhaust energy recovery and after-treatment purification system according to claim 2, characterized in that: The third temperature sensor (T3) is located at the front end of the first SCR carrier module (14).

4. The engine exhaust energy recovery and after-treatment purification system according to claim 2, characterized in that: The fourth temperature sensor (T4) is located at the rear end of the second SCR carrier module (15).

5. The engine exhaust energy recovery and after-treatment purification system according to claim 1, characterized in that: The reheater (29) is connected to the EGR via a gas supply pipe (28).

6. The engine exhaust energy recovery and aftertreatment purification system according to claim 1, characterized in that: The liquid delivery connector (8) is connected to the condenser (17) through the first water supply pipe (21) and the second water return pipe (23), and the liquid delivery connector (8) is connected to the reheater (29) through the first water return pipe (22).

7. The engine exhaust energy recovery and aftertreatment purification system according to claim 1, characterized in that: The storage tank (18) is connected to the water pump (19) via a second water supply pipe (24), and the water pump (19) is connected to the liquid receiving connector (7) via a third water supply pipe (25).

8. The engine exhaust energy recovery and after-treatment purification system according to claim 1, characterized in that: The output of the turbine (16) is connected to the electric heater (4) via the first circuit (26), the second circuit (27) and the battery (20).

9. The control method for an engine exhaust energy recovery and aftertreatment purification system according to claim 1, characterized in that: Includes the following steps: When the temperature of the first temperature sensor (T1) is below 200°C, the electric heater (4) is turned on, the second throttle valve (P2) is closed, and the first throttle valve (P1) is opened. The exhaust bypasses the evaporator (5) and goes directly through the bypass pipe (6) to the after-processor (10) to treat exhaust pollutants. When the temperature of the first temperature sensor (T1) is above 200°C but below 300°C, the electric heater (4) is turned off, the second throttle valve (P2) is closed, and the first throttle valve (P1) is opened. The exhaust bypasses the evaporator (5) and goes through the bypass pipe. (6) The exhaust pollutants are directly processed by the post-processor (10); when the temperature of the first temperature sensor (T1) is higher than 300°C, the electric heater (4) is turned off, the first throttle valve (P1) is closed, and the second throttle valve (P2) is opened. The exhaust flows through the reheat device to recover waste heat through reheat cycle and then passes through the post-processor (10) to process the exhaust pollutants; wherein, the reheat device consists of an evaporator (5), a turbine (16), a reheater (29), a condenser (17), a water pump (19), and a liquid storage tank (18); The water pump (19) pressurizes the water in the storage tank (18) and delivers it to the evaporator (5). The engine exhaust reaches the evaporator (5) through the front exhaust pipe (2). The exhaust gas heats the water in the evaporator (5) at constant pressure to form water vapor. The water vapor in the evaporator (5) enters the turbine (16) through the liquid delivery joint (8) to expand and do work. The water vapor converts heat into electrical energy in the turbine (16) and stores the electrical energy through the battery (20) to supply the electric heater (4) at low temperature. When the water vapor expands to a certain intermediate pressure in the turbine (16), it is withdrawn from the turbine (16) and introduced into the reheater (29) to use the waste heat of the EGR to reheat the steam. Then it enters the turbine (16) to do work. The water vapor after energy conversion enters the condenser (17). The water vapor releases heat at isobaric pressure to become saturated water and then returns to the storage tank (18) through the condenser (17) to complete a reheat cycle.

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