Cold storage power generation system and power generation method thereof

Abstract

The invention discloses a cold storage power generation system and a power generation method thereof, and relates to the technical field of energy utilization, and the key point of the technical scheme is that the cold storage power generation system comprises a phase change cold storage and discharge part and a Rankine cycle expansion acting part; the phase change cold storage and discharge part comprises an LNG (Liquefied Natural Gas) booster pump, a mixed working medium heat exchanger I, a cold storage tank and a mixed working medium heat exchanger II which are connected in sequence; and the Rankine cycle expansion acting part comprises a mixed working medium heat exchanger III, a mixed working medium pressure pump, a mixed working medium seawater heat exchanger, a mixed working medium expansion machine and a generator which are connected in sequence. Effective energy loss caused by frequent starting and stopping of a rear-end power generation device due to change of natural gas consumption by a user can be reduced, so that the cold energy power generation efficiency is improved, meanwhile, through storage of part of liquefied natural gas cold energy in the daytime, Rankine cycle expansion acting power generation is carried out through the cold energy stored in the daytime at night, and the power generation efficiency is improved. And the whole cold storage power generation system can stably and continuously operate.

Description

Technical Field

[0001] The present invention relates to the technical field of energy utilization, and more specifically, to a cold storage power generation system and a power generation method thereof. Background Art

[0002] LNG cold storage power generation system is a technology that uses the large amount of cold energy released during the regasification process of liquefied natural gas (LNG) to generate electricity. Liquefied natural gas (LNG) exists in liquid form at about minus 162°C, and its gasification process releases a large amount of cold energy. This cold energy has great economic and environmental value. The LNG cold storage power generation system can provide a clean energy solution while reducing energy waste by capturing and utilizing this cold energy.

[0003] The working principle of the LNG cold storage power generation system is to recover cold energy mainly by relying on the temperature and pressure difference between LNG and the surrounding environment (such as air, seawater). Refrigerant is used in the LNG gasification process, and the energy contained in LNG is recovered and utilized through the principle of heat transfer. According to the utilization method, it can be divided into two methods: direct utilization and indirect utilization; direct utilization: including cold energy power generation, liquefied air separation, liquid carbon dioxide or dry ice preparation, low-temperature cold storage, seawater desalination, data center cooling, etc.; indirect utilization: mainly through the production of liquid nitrogen or liquid oxygen through LNG cold energy, and then these substances are used for low-temperature crushing, low-temperature bioengineering, sewage treatment and other processes.

[0004] The existing LNG cold storage power generation system has high system complexity in actual application. Changes in natural gas consumption by users cause frequent startup and shutdown of the back-end power generation equipment, resulting in large effective energy loss, low cold energy power generation efficiency, and the entire cold storage power generation system cannot operate stably and continuously. Therefore, the present invention aims to provide a cold storage power generation system and a power generation method thereof to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a cold storage power generation system and a power generation method thereof. The present invention is based on the principles of cold energy storage and cold energy utilization. Under the premise of not increasing the complexity of the system too much, the cold energy of LNG is stored and utilized for power generation through a cold storage device and a Rankine cycle expansion work, thereby reducing the effective energy loss caused by frequent startup and shutdown of the back-end power generation device due to changes in the user's natural gas consumption, thereby improving the efficiency of cold energy power generation. At the same time, by storing part of the cold energy of liquefied natural gas during the day and using the cold energy stored during the day to perform Rankine cycle expansion work for power generation at night, the entire cold storage power generation system can operate stably and continuously.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: a cold storage power generation system and a power generation method thereof, comprising a phase change cold storage and cooling unit and a Rankine cycle expansion unit; the phase change cold storage and cooling unit is used to store the cold energy of liquefied natural gas during the day and release the cold energy of liquefied natural gas at night; the Rankine cycle expansion unit is used to receive the cold energy of liquefied natural gas to generate electricity; the phase change cold storage and cooling unit and the Rankine cycle expansion unit are connected to form a loop;

[0007] The phase-change cold storage and cooling unit comprises an LNG booster pump, a valve 1, a mixed working fluid heat exchanger 1, a cold storage tank and a mixed working fluid heat exchanger 2 which are connected in sequence;

[0008] The Rankine cycle expansion work unit comprises valve 2, mixed working fluid heat exchanger 3, mixed working fluid booster pump, mixed working fluid seawater heat exchanger, mixed working fluid expander, generator and valve 3 which are connected in sequence.

[0009] The present invention also provides a power generation method of a cold storage power generation system, which is characterized by comprising the following steps:

[0010] S1. During the day, the LNG booster pump is used to boost the pressure of the raw liquefied natural gas from the storage tank, so that it passes through the diverter valve 1 and enters the mixed working fluid heat exchanger 1 and the mixed working fluid heat exchanger 3;

[0011] S2, displacing and storing the cold energy of the liquefied natural gas entering the mixed working medium heat exchanger 1 into the cold storage tank;

[0012] S3. The liquefied natural gas entering the mixed working fluid heat exchanger three is heat exchanged with the mixed working fluid heat exchanger three. The liquefied natural gas is pressurized to 2000kPa by a mixed working fluid booster pump and then enters the mixed working fluid seawater heat exchanger through valve two to achieve complete gasification and temperature increase. The liquefied natural gas then enters the mixed working fluid expander and generator in a gas state of 1500kPa to expand and generate power, and then passes through valve three to complete the Rankine cycle expansion and power generation of the entire cold storage power generation system.

[0013] The present invention is further configured as follows: the cold energy stored in the cold storage tank in step S2 is used for the cold storage power generation system to perform Rankine cycle expansion work and generate electricity at night, so as to support the stable and continuous operation of the entire cold storage power generation system.

[0014] In summary, the present invention has the following beneficial effects:

[0015] The present invention is based on the principles of cold energy storage and utilization. Under the premise of not increasing the complexity of the system too much, the cold energy of LNG is stored and utilized for power generation through a cold storage device and a Rankine cycle expansion work, thereby reducing the effective energy loss caused by frequent startup and shutdown of the back-end power generation device due to changes in the user's natural gas consumption, thereby improving the efficiency of cold energy power generation. At the same time, by storing part of the cold energy of liquefied natural gas during the day and using the cold energy stored during the day to perform Rankine cycle expansion work to generate electricity at night, the entire cold storage power generation system can operate stably and continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the process structure of a cold storage power generation system in an embodiment of the present invention.

[0017] In the figure: 1. LNG booster pump; 2. Valve 1; 3. Mixed working fluid heat exchanger 1; 4. Cold storage tank; 5. Mixed working fluid heat exchanger 2; 6. Valve 2; 7. Mixed working fluid booster pump; 8. Mixed working fluid heat exchanger 3; 9. Mixed working fluid seawater heat exchanger; 10. Combined working fluid expander and generator; 11. Valve 3. DETAILED DESCRIPTION

[0018] The following is combined with Figure 1 The present invention is described in further detail.

[0019] Embodiment 1: A cold storage power generation system comprises a phase change cold storage and cooling unit and a Rankine cycle expansion unit; the phase change cold storage and cooling unit is used to store cold energy of liquefied natural gas during the day and release the cold energy of liquefied natural gas at night; the Rankine cycle expansion unit is used to receive the cold energy of liquefied natural gas to generate electricity; the phase change cold storage and cooling unit and the Rankine cycle expansion unit are connected to form a loop;

[0020] The phase-change cold storage and cooling part includes an LNG booster pump 1, a valve 2, a mixed working fluid heat exchanger 1 3, a cold storage tank 4 and a mixed working fluid heat exchanger 2 5 which are connected in sequence;

[0021] The Rankine cycle expansion work unit includes a valve 2 6, a mixed working fluid heat exchanger 3 8, a mixed working fluid booster pump 7, a mixed working fluid seawater heat exchanger 9, a mixed working fluid expander and generator 10 and a valve 3 11 which are connected in sequence.

[0022] In this embodiment, the function of valve 1 2 is to divide the LNG into two parts, one part enters the mixed working fluid heat exchanger 1 3, and is used to replace the cold energy of the LNG to the cold storage tank 4 for use at night, and the other part enters the mixed working fluid heat exchanger 3 8, and is used to use the cold energy for low-temperature Rankine cycle power generation.

[0023] The function of valve 2 6 is to mix the cold energy in the cold storage tank 4 with the cold energy brought by a small amount of LNG at night for use in the rear-end low-temperature power generation.

[0024] The function of valve three 11 is to control the mixed working fluid to enter only the mixed working fluid heat exchanger three 8 during the day, for heat exchange with the cold energy carried by LNG, and to control the mixed working fluid to enter the mixed working fluid heat exchanger two 5 and the mixed working fluid heat exchanger one 3 respectively at night, and can exchange heat with the cold energy in the cold storage tank 4 and the cold energy carried by LNG respectively, and finally be mixed through valve two 6 to enter the rear-end low-temperature power generation cycle.

[0025] Embodiment 2: A method for generating electricity using a cold storage power generation system, comprising the following steps:

[0026] S1. During the day, the LNG booster pump is used to boost the pressure of the raw liquefied natural gas from the storage tank, so that it passes through the diverter valve 2 and enters the mixed working fluid heat exchanger 1 3 and the mixed working fluid heat exchanger 3 8;

[0027] S2, displacing the cold energy of the liquefied natural gas entering the mixed working medium heat exchanger 3 and storing it in the cold storage tank 4;

[0028] S3, the liquefied natural gas entering the mixed working fluid heat exchanger three 8 is heat exchanged with the mixed working fluid heat exchanger three 8, the liquefied natural gas is pressurized to 2000kPa by the mixed working fluid booster pump 7, and then enters the mixed working fluid seawater heat exchanger 9 through the valve two 6 to achieve complete gasification and temperature increase, and then the liquefied natural gas enters the mixed working fluid expander and generator 10 in a gas state of 1500kPa to expand and generate electricity, and then passes through the valve three 11 to complete the Rankine cycle expansion and power generation of the entire cold storage power generation system.

[0029] Preferably, in this embodiment, the cold energy stored in the cold storage tank 4 in step S2 is used for the cold storage power generation system to perform Rankine cycle expansion work and generate electricity at night, so as to support the stable and continuous operation of the entire cold storage power generation system.

[0030] In this embodiment, a specific example is tested. When the LNG input is 5.39×105kg / h, part of the LNG is transferred to the cold storage tank 4 through the mixed working fluid heat exchanger 3 during the day, and the cold energy storage rate is 1.38×108kJ / h. The other part is transferred to the mixed working fluid heat exchanger 3 8 through the stream 4 to exchange heat with the working fluid in the rear Rankine cycle to provide the cold energy required for low-temperature power generation. The mass flow rate of the circulating working fluid is 1.89×105kg / h. At this time, the total output power of low-temperature power generation is 4388kW.

[0031] At night, the cold energy stored during the day is released, and the cold energy in the cold storage tank 4 is replaced by the rear-end low-temperature power generation cycle through the mixed working fluid heat exchanger 2 5, and a small amount of cold energy from the LNG tank is mixed. The temperature of the mixed low-temperature Rankine cycle power generation working fluid is -132.1℃, and the mass flow rate of the circulating working fluid of low-temperature power generation is 1.89×105kg / h. The final total power generation output is 4388kW, and the total power generation output during the day and at night is equal. At this time, the entire cold storage-cold energy utilization system reaches a balanced state.

[0032] Working principle: during the day, the raw liquefied natural gas from the storage tank is pressurized by the LNG booster pump and enters the mixed working fluid heat exchanger 1 3 and the mixed working fluid heat exchanger 3 8 respectively. After entering the mixed working fluid heat exchanger 3 8, the cold energy is replaced into the cold storage tank 4 to be used at night; another part of the liquefied natural gas enters the mixed working fluid heat exchanger 3 8 and exchanges heat with the rear-end Rankine cycle expansion working working fluid. After heat exchange, it is pressurized to 2000kPa by the mixed working fluid pump and then enters the mixed working fluid seawater heat exchanger 9. After being completely gasified and heated, it enters the mixed working fluid expander and generator 10 in a gas state of 1500kPa for expansion. The output work of the mixed working fluid expander and generator 10 is used to drive the generator to produce electricity. Then, the temperature and pressure of the mixed working fluid are reduced and it enters the mixed working fluid heat exchanger 3 8 to continue to exchange heat with the liquefied natural gas; at night, the cold energy stored in the cold storage tank 4 is used for the cold storage power generation system to perform Rankine cycle expansion power generation at night, which can support the stable and continuous operation of the entire cold storage power generation system.

[0033] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A cold storage power generation system and a power generation method thereof, characterized in that: It includes a phase-change cold storage and cooling unit and a Rankine cycle expansion unit; the phase-change cold storage and cooling unit is used to store the cold energy of liquefied natural gas during the day and release the cold energy of liquefied natural gas at night; the Rankine cycle expansion unit is used to receive the cold energy of liquefied natural gas to generate electricity; the phase-change cold storage and cooling unit and the Rankine cycle expansion unit are connected to form a loop; The phase-change cold storage and cooling unit comprises an LNG booster pump (1), a valve one (2), a mixed working fluid heat exchanger one (3), a cold storage tank (4) and a mixed working fluid heat exchanger two (5) which are connected in sequence; The Rankine cycle expansion work unit comprises a valve 2 (6), a mixed working fluid heat exchanger 3 (8), a mixed working fluid booster pump (7), a mixed working fluid seawater heat exchanger (9), a mixed working fluid expander and generator (10) and a valve 3 (11) which are connected in sequence.

2. The power generation method of the cold storage power generation system according to claim 1, characterized in that: The following steps are involved: S1. During the day, the LNG booster pump is used to boost the pressure of the raw liquefied natural gas from the storage tank, so that the raw liquefied natural gas passes through the diverter valve 1 (2) and enters the mixed working fluid heat exchanger 1 (3) and the mixed working fluid heat exchanger 3 (8); S2, displacing and storing the cold energy of the liquefied natural gas entering the mixed working fluid heat exchanger 1 (3) into the cold storage tank (4); S3. The liquefied natural gas entering the mixed working fluid heat exchanger three (8) is heat exchanged with the mixed working fluid heat exchanger three (8). The liquefied natural gas is pressurized to 2000 kPa by the mixed working fluid booster pump (7) and then enters the mixed working fluid seawater heat exchanger (9) through the valve two (6) to achieve complete gasification and temperature increase. The liquefied natural gas then enters the mixed working fluid expander and generator (10) in a gaseous state of 1500 kPa to expand and generate power. Afterwards, the liquefied natural gas passes through the valve three (11) to complete the Rankine cycle expansion and power generation of the entire cold storage power generation system.

3. The power generation method of the cold storage power generation system according to claim 1, characterized in that: The cold energy stored in the cold storage tank (4) in step S2 is used for the cold storage power generation system to perform Rankine cycle expansion work and generate electricity at night, so as to support the stable and continuous operation of the entire cold storage power generation system.

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