Compressed air energy storage and deep cooling air separation coupling energy efficiency improving system and method

Abstract

The invention discloses a compressed air energy storage and deep cooling air separation coupling system energy efficiency improving system and an energy efficiency improving method, the system comprises a compressed air energy storage device and a deep cooling air separation precooling device, a compressed air energy storage process and a deep cooling air separation process are coupled, and exhausted air after expansion power generation is introduced into the lower portion of a newly-added water cooling tower; the circulating water passes through the water cooling tower from bottom to top, dry air in the tower is in direct contact with circulating water introduced from the top of the water cooling tower, and moisture absorption of the dry air is utilized to promote evaporation of water so as to produce cooling water; cooling water enters a water cooling tower of a precooling system of the air separation device through pressure generated by height difference to serve as a water source of the water cooling tower, the cooling water enters a water chilling unit to be further cooled after being cooled to produce chilled water, the chilled water is introduced into the upper portion of the air cooling tower to serve as a cold source to cool raw material air, the comprehensive efficiency of compressed air energy storage is improved, and energy is saved. Cooling water with lower temperature is provided for a water cooling tower of the air separation precooling system, and stable operation of an energy storage side is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of liquefied air energy storage, and in particular to a system and method for improving the energy efficiency of compressed air energy storage and cryogenic air separation coupling. Background Art

[0002] The LAES (liquefied air energy storage, a typical technical solution for compressed air energy storage) system process mainly includes the energy storage stage and the energy release stage; the energy storage stage includes two processes: air liquefaction process and heat storage process; the energy release stage includes two processes: expansion power generation process and cold storage process; the existing technology mainly transfers the compression heat generated in the compressed air energy storage stage to the compressed air coming out of the gas storage through hot water for heating, and then expands and generates electricity, and finally discharges the air after expansion and power generation. The exhaust air after expansion and power generation is dry air. Although the temperature of this part of the exhaust air is very high, the water content is below 1PPm, it has strong hygroscopicity and has refrigeration capacity. After direct discharge, its energy efficiency is not fully utilized, which makes the overall efficiency of the compressed air energy storage device low.

[0003] The patent application with publication number CN118623558A discloses a liquefied air energy storage system and working method, including an air liquefaction subsystem, a cold storage heat regenerator, a liquid air storage tank, and a power generation subsystem. The cold storage heat regenerator is provided with a heat exchange channel, and the liquid air storage tank is provided with a liquefied air inlet, a liquefied air outlet, and a cold air outlet. The air liquefaction subsystem, the heat exchange channel of the cold storage heat regenerator, and the liquefied air inlet of the liquid air storage tank are connected in sequence through a liquefaction pipeline. A throttle valve is provided in front of the liquefied air inlet. The liquefied air outlet of the liquid air storage tank, the heat exchange channel of the cold storage heat regenerator, and the power generation subsystem are connected in sequence through a gasification pipeline; a supercooling subsystem for cooling the air is provided on the liquefaction pipeline between the throttle valve and the heat exchange channel. The present invention also discloses a working method of a liquefied air energy storage system. A supercooling subsystem is added in the invention to provide coldness for the liquefied air to reach a lower temperature. However, the hygroscopic properties of the hot air after expansion are not fully utilized, and its refrigeration capacity is not exerted. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a system and method for improving the energy efficiency of compressed air energy storage and deep cold air separation coupling, which couples the compressed air energy storage process with the deep cold air separation process, and uses the exhaust air after expansion power generation to pass into the lower part of the newly added water cooling tower, and passes through the water cooling tower from bottom to top. The dry air in the tower is in direct contact with the circulating water introduced at the top of the water cooling tower, and the hygroscopicity of the dry air is used to promote the evaporation of water to produce cooling water; the cooling water uses the pressure generated by the height difference to enter the water cooling tower of the precooling system of the air separation device as the water source of the water cooling tower. After the cooling water is cooled, it enters the chiller for further cooling to produce chilled water, and the chilled water is passed into the upper part of the air cooling tower as a cold source to cool the raw air; the water cooling tower of the air separation precooling system is provided with cooling water with a lower temperature to ensure the stable operation of the energy storage side; the comprehensive efficiency of compressed air energy storage is improved and energy is saved.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A system for improving the energy efficiency of a compressed air energy storage and cryogenic air separation coupling system, comprising a multistage heat exchanger group 1, wherein the cold stream inlet end of the first heat exchanger in the multistage heat exchanger group 1 is connected to an external air storage device, the cold stream inlet end of the first heat exchanger in the multistage heat exchanger group 1 is connected to the dry air inlet end of the first expansion generator in the expansion generator group 2, the incoming compressed air is preheated and expanded in the expansion generator group 2 to perform work, the dry air outlet end of the last expansion generator in the expansion generator group 2 is connected to the dry air inlet end at the bottom of the first water cooling tower 3, the chilled water outlet end of the first water cooling tower 3 is connected to the cooling water inlet end above the second water cooling tower 4, the chilled water outlet end of the second water cooling tower 4 is connected to the chilled water inlet end of the upper part of the air cooling tower 6 through a chiller 5, and the chilled water is used as a cold source to cool the raw air.

[0007] The multi-stage heat exchanger group 1 includes n heat exchangers, the expansion generator group 2 includes n expansion generators, the heat exchangers and the expansion generators are connected in series, and n is greater than or equal to 1.

[0008] A method for improving energy efficiency of a compressed air energy storage and cryogenic air separation coupling system, comprising the following steps:

[0009] Step 1: During the discharge phase of the compressed air energy storage device, the compressed air released by the air storage device is preheated by the multi-stage heat exchanger group 1, and then enters the expansion generator group 2 to expand and perform work;

[0010] Step 2, a small amount of dry air from the final expander is exhausted, and the remaining dry air enters the cryogenic air separation precooling device, and enters the first water cooling tower 3 through the dry air inlet at the bottom of the first water cooling tower 3;

[0011] Step 3, after the dry air is heat-exchanged with the cooling water sprayed downward in the first water cooling tower 3, the humidified and heated expanded air flows back to the top of the tower and is released into the atmosphere, and the temperature of the cooling water is reduced;

[0012] In step 4, the chilled water enters the cooling water inlet at the top of the second water cooling tower 4 from the bottom of the first water cooling tower 3, sprays downward as cooling water, exchanges heat with the rising dirty nitrogen gas, and after cooling, enters the top of the air cooling tower 6 through a pipeline and a chiller as chilled water 2.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] When the compressed air energy storage device of the present invention is discharged, the compressed air released by the air storage device is preheated through a multi-stage heat exchanger, and then enters the expander to expand and do work. The comprehensive efficiency of compressed air energy storage is improved. A small amount of dry air from the final expander is emptied, and most of it enters the bottom of the newly built water cooling tower, passing through the water cooling tower from bottom to top. The dry air in the tower is in direct contact with the circulating water (generally 32°C) introduced at the top of the water cooling tower. The hygroscopicity of the dry air is used to promote the evaporation of water to produce cooling water (~26°C), providing cooling water with a lower temperature (originally 32°C, now optimized to 26°C) for the water cooling tower of the air separation precooling system. The cooling water uses the pressure generated by the height difference to enter the water cooling tower of the air separation device precooling system as the water source of the water cooling tower. After the cooling water is cooled, it enters the chiller to further cool down and produce chilled water. The chilled water is introduced into the upper part of the air cooling tower as a cold source to cool the raw air. Energy saving is achieved on the air separation device side.

[0015] The present invention couples the compressed air energy storage process with the deep-cold air separation process, and uses the exhaust air after expansion power generation to pass into the lower part of the newly added water cooling tower, and passes through the water cooling tower from bottom to top. The dry air in the tower is in direct contact with the circulating water introduced at the top of the water cooling tower, and the hygroscopicity of the dry air is used to promote the evaporation of water to produce cooling water; the cooling water uses the pressure generated by the height difference to enter the water cooling tower of the precooling system of the air separation device as the water source of the water cooling tower, and after the cooling water is cooled, it enters the chiller to further cool down and produce chilled water, and the chilled water is passed into the upper part of the air cooling tower as a cold source to cool the raw air; the water cooling tower of the air separation precooling system is provided with cooling water with a lower temperature to ensure the stable operation of the energy storage side; the comprehensive efficiency of compressed air energy storage is improved and energy is saved.

[0016] In summary, the present invention can directly utilize the exhaust gas of the energy storage system expansion generator, making full use of the refrigeration potential of this part of the exhaust gas, thereby achieving energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention.

[0018] Among them, 1. multi-stage heat exchanger group; 2. expansion generator group; 3. first water cooling tower; 4. second water cooling tower; 5. chiller; 6. air cooling tower. DETAILED DESCRIPTION

[0019] The structural principle and working principle of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0020] See also Figure 1 A system for improving the energy efficiency of a coupled system of compressed air energy storage and cryogenic air separation comprises a compressed air energy storage device and a cryogenic air separation precooling device, wherein the compressed air energy storage device comprises a multistage heat exchanger group 1, the cold stream inlet end of the first heat exchanger in the multistage heat exchanger group 1 is externally connected to an air storage device, the cold stream outlet end of the first heat exchanger in the multistage heat exchanger group 1 is connected to the dry air inlet end of the first expansion generator in the expansion generator group 2, the compressed air entering is preheated and expanded in the expansion generator group 2 to perform work, the dry air outlet end of the last expansion generator in the expansion generator group 2 is connected to the dry air inlet end at the bottom of the first water cooling tower 3 of the cryogenic air separation precooling device, the chilled water outlet end of the first water cooling tower 3 is connected to the cooling water inlet end above the second water cooling tower 4, the chilled water outlet end of the second water cooling tower 4 is connected to the chilled water inlet end of the upper part of the air cooling tower 6 through a chiller 5, and the chilled water is used as a cold source to cool the raw air.

[0021] A method for improving energy efficiency by coupling compressed air energy storage with cryogenic air separation comprises the following steps:

[0022] Step 1: During the discharge phase of the compressed air energy storage device, the compressed air released by the air storage device is preheated by the multi-stage heat exchanger group 1, and then enters the expansion generator group 2 for expansion and work;

[0023] Step 2, a small amount of dry air from the final expander is exhausted, and the remaining dry air enters the cryogenic air separation precooling device, and enters the first water cooling tower 3 through the dry air inlet at the bottom of the first water cooling tower 3;

[0024] Step 3, after the dry air A is heat-exchanged with the cooling water sprayed downward in the first water cooling tower 3, the humidified and heated expanded air flows back to the top of the tower and is released into the atmosphere, and the temperature of the cooling water is reduced;

[0025] Step 4, the chilled water enters the cooling water inlet at the top of the second water cooling tower 4 from the bottom of the water cooling tower 3, sprays downward as cooling water, exchanges heat with the rising dirty nitrogen gas, and after cooling, enters the top of the air cooling tower 6 through the pipeline and the chiller as chilled water 2.

[0026] The energy storage side ensures stable operation. The cooling water uses the pressure generated by the height difference to enter the water cooling tower of the air separation unit precooling system as the water source of the water cooling tower (the water source in the conventional process is 32℃ circulating water). After the cooling water is cooled, it enters the chiller to further cool it down and produce chilled water. The chilled water is passed into the upper part of the air cooling tower as a cold source to cool the raw air.

[0027] Example 1

[0028] The precooling system of a 40000Nm3 / h (oxygen / liquid oxygen output) cryogenic air separation unit of a petrochemical enterprise was transformed. Figure 1 The process shown.

[0029] The gas volume of dirty nitrogen in the air separation unit is 56700Nm3 / h, the temperature is 13℃, and the pressure is 1.1bar;

[0030] The expanded dry air volume of the liquefied air energy storage system is 100,000 Nm3 / h, the temperature is 78°C, and the pressure is 1.2 bar;

[0031] The total amount of cooling water is 100,000 kg / h, the temperature is 41°C, and the pressure is 1.5 bar.

[0032] The dry air is passed into the first water cooling tower 3 to cool the cooling water. Aspen software simulation shows that the dry air temperature rises to 50° C., the cooling water temperature drops to 26° C., and the cooling water volume is 100,000 kg / h.

[0033] Through Aspen simulation calculation, it can be obtained that when the first water cooling tower is not used and only the second water cooling tower 4 is used, dirty nitrogen is used to cool the external water supply from the cooling tower 1. At this time, the external water supply is 100,000 kg / h. After being cooled, it enters the air cooling tower through the chiller to cool the air; at this time, the cooling capacity required by the chiller is 2992.37KW.

[0034] When the first water cooling tower 3 and the second water cooling tower 4 are used at the same time, the external water supply of the first water cooling tower 3 is 100000 kg / h, and the second water cooling tower 4 is not supplied with water separately from the outside, and dirty nitrogen is normally introduced; at this time, the cooling capacity required to be supplemented by the chiller is 2303.38 KW.

[0035] The cooling capacity saved by the chiller by using expanded dry air is:

[0036] 2992.37-2303.38=688.99KW

[0037] Taking the chiller model 30HXC as an example, through the relationship between the cooling capacity and power consumption of the chiller, it can be known that when the cooling capacity is 580KW, the motor input power is 118KW, so the power consumption required to produce 688.99KW is:

[0038] 688.99 / 580×118=140.17kW

[0039] The amount of electricity saved per day is

[0040] 140.17KW×8h=1121.39KWh

[0041] The system runs for 330 days, the electricity price is 0.6 yuan / KWh, and the annual electricity saving benefit of the air separation system is:

[0042] 1121.39×350×0.6=235492.03 yuan / year=235,500 yuan / year In this process, the circulating water at 43°C is directly cooled by dry air, which reduces the power consumption of the circulating water station to produce low-temperature circulating water. According to GB-71902008 and other standard documents, the power consumption ratio of the circulating water under this condition is set to 0.05kW / (m3 / h).

[0043] The motor power saved by saving circulating water through the following formula is:

[0044] P=V×0.05kW / (m 3 / h)

[0045] Where V = circulating water volume = 100t / h = 100m 3 / h

[0046] The motor power saved is calculated as:

[0047] P = 100 × 0.05 = 5kW

[0048] Based on 8 hours of discharge per day, the amount of electricity saved in a year is:

[0049] 5KW×8h×350=14000kW·h

[0050] The electricity price is 0.6 yuan / KWh, and the annual electricity cost saved is

[0051] 14000KW·h×0.6 yuan / KW·h=8400 yuan

[0052] The total annual revenue of the renovation project is:

[0053] 23.55+0.84=243,900 yuan

[0054] The investment cost of the renovation project is:

[0055] The equipment cost of the first water cooling tower 3 is RMB 600,000, and the cost of pipelines and construction and installation is RMB 200,000, totaling RMB 800,000.

[0056] The static payback period of the transformed project is 3.28 years.

[0057] Taking into account that the actual working time of this renovation project is mostly during peak power period, the actual annual income will exceed 243,900 yuan, and the static payback period of the project will be within three years.

Claims

1. A system for improving the energy efficiency of a compressed air energy storage and cryogenic air separation coupling system, comprising a multi-stage heat exchanger group (1), characterized in that: The cold stream inlet of the first heat exchanger in the multi-stage heat exchanger group (1) is connected to an external air storage device. The cold stream inlet of the first heat exchanger in the multi-stage heat exchanger group (1) is connected to the dry air inlet of the first expansion generator in the expansion generator group (2). The compressed air entering is preheated and expanded in the expansion generator group (2) to perform work. The dry air outlet of the last expansion generator in the expansion generator group (2) is connected to the dry air inlet at the bottom of the first water cooling tower (3). The chilled water outlet of the first water cooling tower (3) is connected to the cooling water inlet at the top of the second water cooling tower (4). The chilled water outlet of the second water cooling tower (4) is connected to the chilled water inlet at the top of the air cooling tower (6) through the chiller (5). The chilled water is used as a cold source to cool the raw air.

2. According to claim 1, a system for improving the energy efficiency of a compressed air energy storage and cryogenic air separation coupling system, characterized in that: The multi-stage heat exchanger group (1) comprises n heat exchangers, the expansion generator group (2) comprises n expansion generators, the heat exchangers and the expansion generators are connected in series, and n is greater than or equal to 1.

3. A method for improving energy efficiency of a compressed air energy storage and cryogenic air separation coupling system according to claim 1 or 2, characterized in that: The following steps are involved: Step 1, in the discharge stage of the compressed air energy storage device, the compressed air released by the air storage device passes through the multi-stage heat exchanger group (1) for preheating, and then enters the expansion generator group (2) for expansion and work; Step 2, a small amount of dry air from the final expander is exhausted, and the remaining dry air enters the cryogenic air separation precooling device and enters the first water cooling tower (3) through the dry air inlet at the bottom of the first water cooling tower (3); Step 3, after the dry air is heat-exchanged with the cooling water sprayed downward in the first water cooling tower (3), the humidified and heated expanded air flows back to the top of the tower and is released into the atmosphere, and the temperature of the cooling water is lowered; In step 4, chilled water enters the cooling water inlet at the top of the second water cooling tower (4) from the bottom of the first water cooling tower (3), sprays downward as cooling water, exchanges heat with the rising polluted nitrogen gas, and after cooling, enters the top of the air cooling tower (6) through a pipeline and a chiller.

Images