阅读说明：本技术 一种冶金空分系统的余热利用系统及其方法 (Waste heat utilization system and method of metallurgical air separation system ) 是由 漆枫林 欧阳建光 杨巍 于 2020-12-15 设计创作，主要内容包括：本发明属于空分空压机余热回收领域,尤其是一种冶金空分系统的余热利用系统及其方法,针对现有的空分离心式空气压缩机通过使用冷却水的散热系统来给系统降温的过程中,大量的热能就被无端的浪费了,而有色冶炼电解工序中电解液又需要大量饱和蒸汽加热,电解液加热温度也只有63度左右的问题,现提出如下方案,其包括三级热回收系统和四级热回收系统,所述三级热回收系统包括空气过滤器,所述四级热回收系统包括空分空压机,所述空分空压机连接有止回阀,所述止回阀连接有循环泵,本发明充分利用空分空压机所产生的余热,来满足有色冶炼电解液加热的需求,替代低压饱和蒸汽,可使有色企业节能降耗。(The invention belongs to the field of waste heat recovery of air separation air compressors, in particular to a waste heat utilization system of a metallurgical air separation system and a method thereof, aiming at the problems that a large amount of heat energy is wasted endlessly in the process of cooling the system by using a cooling water heat dissipation system of the existing air separation centrifugal air compressor, electrolyte in the nonferrous smelting electrolysis process needs a large amount of saturated steam for heating, and the heating temperature of the electrolyte is only about 63 ℃, the invention provides the following scheme, which comprises a three-stage heat recovery system and a four-stage heat recovery system, wherein the three-stage heat recovery system comprises an air filter, the four-stage heat recovery system comprises an air separation air compressor, the air separation air compressor is connected with a check valve, and the check valve is connected with a circulating pump, the waste heat generated by the air separation air compressor is fully utilized to meet the heating requirement of the nonferrous, the low-pressure saturated steam is replaced, so that the energy conservation and the consumption reduction of colored enterprises can be realized.)

1. A waste heat utilization system of a metallurgical air separation system comprises a three-level heat recovery system and a four-level heat recovery system, wherein the three-level heat recovery system comprises an air filter (1) and is characterized in that the four-level heat recovery system comprises an air separation air compressor, the air separation air compressor is connected with a check valve, the check valve is connected with a circulating pump, the circulating pump is connected with a water supplementing tank and three plate heat exchangers, a softened water supplementing port is arranged on the water supplementing tank, the air filter (1) is connected with a first-level compressor (2), the first-level compressor (2) is connected with a first-level cooler (3), the first-level cooler (3) is connected with a second-level compressor (4), the second-level compressor (4) is connected with a second-level cooler (5), the second-level cooler (5) is connected with a third-level compressor (6, and the waste heat recoverer (9) is connected with a heat recovery water inlet pipe and a heat recovery water outlet pipe.

2. A waste heat utilization system of a metallurgical air separation system according to claim 1, characterized in that a valve (7) is provided between the three-stage compressor (6) and the three-stage cooler (8).

3. A waste heat utilization system of a metallurgical air separation system according to claim 1, characterized in that a compressed air discharge pipe is connected to the tertiary cooler (8).

4. The waste heat utilization system of a metallurgical air separation system according to claim 1, characterized in that the primary cooler (3), the secondary cooler (5) and the tertiary cooler (8) are connected with a cooling water inlet pipe and a cooling water outlet pipe.

5. The heat recovery method for the air compressor of the air separation system as claimed in claims 1 to 4, is characterized by comprising the following steps:

s1: the gas is filtered by an air filter (1), enters a first-stage compressor (2) for compression, is cooled by a first-stage cooler (3), enters a second-stage compressor (4) for compression, is cooled by a second-stage cooler (5), and enters a third-stage compressor (6) for compression;

s2: the compressed gas enters a waste heat recoverer (9), and the waste heat recoverer (9) recovers waste heat in the gas, so that the waste heat is favorable for heating water;

s3: and then the gas is discharged after being cooled by the three-stage cooler (8), so that the energy consumption of a cooling circulating water system is reduced, and hot water heats the electrolyte through the plate heat exchanger to replace low-pressure saturated steam, so that the energy conservation is realized.

Technical Field

The invention relates to the technical field of waste heat utilization of nonferrous metallurgy air separation air compressors, in particular to an air compressor waste heat utilization system and method of an air separation system.

Background

Centrifugal air compressor machine is in operation, generally takes the three to four grades of compression modes, in order to improve compressor efficiency, often sets up intercooler at the intermediate level, uses the heat of cooling water in with high temperature high pressure compressed air to trade out to through the cooling tower fan, with heat effluvium to the atmosphere in, in order to guarantee the safety and stability operation of air compressor machine. In the long-term and continuous operation process of the air compressor, electric energy is converted into mechanical energy, namely the electric energy is converted into high-pressure compressed air energy. The mechanical energy is converted into high-pressure compressed air to generate a large amount of heat, and finally the heat is dissipated in an air cooling or water cooling mode.

At present, the sixth generation of the mainstream external compression air separation process comprises an air compression system, an air purification system, a fluid heat exchange system, an expansion refrigeration system, an air rectification system and other core subsystems. A. An air compression system: the separation of air into its component products is essentially accomplished by energy conversion, and the primary energy input device of the air separation system is the feed air compressor. The air is compressed by a raw material air compressor to obtain the pressure of 0.9-1.0 MPa. B. An air purification system: the air purification system comprises an air precooling system and a molecular sieve purification system. Air compressor's compression causes the air to rise the temperature sharply, though modern air compressor mostly adopts interstage cooling to drop the temperature, still has the heat redundancy. Therefore, an air pre-cooling tower is arranged in the air separation system, the air is further cooled through contact type heat exchange, and the cold energy of the air pre-cooling tower is usually rectified waste nitrogen and a refrigerating machine. The purifier is used for further removing impurities such as moisture, carbon dioxide and the like in the air and preventing the impurities from generating negative influence on the subsequent process. C. The fluid heat exchange system comprises: the normal temperature air and the low temperature nitrogen, oxygen, dirty nitrogen and the like entering the system exchange heat in the heat exchanger, so that most cold energy of the cold fluid is recovered, and the hot fluid also reaches the temperature low enough to prepare for rectification. D. An expansion refrigeration system: the energy of the air separation system is mainly from the expansion machine, and the air pumped from the main heat exchanger is expanded in the turbo expansion machine to reduce the temperature and pressure, so that enough cold energy is provided for the air separation system. E. Air rectification system: the air realizes the separation of components in the fine feed tower, and the fine distillation system is the core system of the air separation. Modern air separation usually adopts a rectification tower with two coupled stages of high pressure and low pressure to realize rectification. Air compressor machine equipment model: 4MSGE + 25/15; exhaust volume: q is 122000m 3/h; exhaust pressure: p is 1.15 Mpa; electric power: 16500KW

During the operation of the above air compressor, the heat carried by the high-temperature and high-pressure gas is approximately 3/4 of the power of the air compressor, and the temperature is usually between 100 ℃ and 130 ℃ and even up to 150 ℃. In the process that the centrifugal air compressor cools the system by using a cooling water heat dissipation system, a large amount of heat energy is wasted without end, a large amount of low-pressure saturated steam is needed for heating nonferrous smelting electrolyte, and the saturated steam is replaced by air separation waste heat, so that the low-pressure saturated steam is saved, and the power consumption of an air separation cooling circulating water system is reduced.

Disclosure of Invention

The invention aims to solve the problems that in the prior art, a centrifugal air compressor is used for cooling a system through a cooling water cooling system, a large amount of heat energy is wasted endlessly, electrolyte in an electrolysis process of nonferrous smelting needs a large amount of saturated steam for heating, and the heating temperature of the electrolyte is only about 63 ℃, so that the system method for heating the electrolyte by using the waste heat of an air compressor of an air separation system is provided.

In order to achieve the purpose, the invention adopts the following technical scheme:

a waste heat utilization system of a metallurgical air separation system, which comprises a three-level heat recovery system and a four-level heat recovery system, the three-stage heat recovery system comprises an air filter, the four-stage heat recovery system comprises an air separation air compressor, the air separation air compressor is connected with a check valve, the check valve is connected with a circulating pump, the circulating pump is connected with a water replenishing tank and three plate heat exchangers, the water replenishing tank is provided with a softened water replenishing port, the air filter is connected with a primary compressor, the primary compressor is connected with a primary cooler, the primary cooler is connected with a secondary compressor, the secondary compressor is connected with a secondary cooler, the secondary cooler is connected with a tertiary compressor, the three-stage compressor is connected with a three-stage cooler and a waste heat recoverer, and the waste heat recoverer is connected with a heat recovery water inlet pipe and a heat recovery water outlet pipe.

Preferably, a valve is arranged between the three-stage compressor and the three-stage cooler.

Preferably, a compressed air discharge pipe is connected to the tertiary cooler.

Preferably, the first-stage cooler, the second-stage cooler and the third-stage cooler are all connected with a cooling water inlet pipe and a cooling water outlet pipe.

The invention also provides a heat recovery method for the air compressor of the air separation system, which comprises the following steps:

s1: the gas is filtered by an air filter and then enters a first-stage compressor for compression, then is cooled by a first-stage cooler and then enters a second-stage compressor for compression, and then the gas is cooled by a second-stage cooler and then enters a third-stage compressor for compression;

s2: the compressed gas enters a waste heat recoverer, and the waste heat recoverer recovers waste heat in the gas, so that the waste heat is favorable for heating water;

s3: and then the gas is discharged after being cooled by the three-stage cooler, the heat in the discharged gas is recovered by the plate heat exchanger, the energy consumption of a cooling circulating water system is reduced, and hot water heats the electrolyte by the plate heat exchanger to replace low-pressure saturated steam, so that the aim of saving energy is fulfilled.

Compared with the prior art, the invention has the beneficial effects that:

the invention fully utilizes the waste heat generated by the air separation air compressor to meet the requirement of heating the electrolyte, and can ensure that enterprises save a large amount of saturated steam.

Drawings

FIG. 1 is a schematic structural diagram of a three-stage heat recovery system of a waste heat utilization system of a metallurgical air separation system according to the present invention;

fig. 2 is a schematic structural diagram of a four-stage heat recovery system of a waste heat utilization system of a metallurgical air separation system provided by the invention.

In the figure: the system comprises an air filter 1, a first-stage compressor 2, a first-stage cooler 3, a second-stage compressor 4, a second-stage cooler 5, a third-stage compressor 6, a valve 7, a third-stage cooler 8 and a waste heat recovery device 9.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.

Example one

Referring to fig. 1-2, a metallurgical air separation system's waste heat utilization system, including tertiary heat recovery system and level four heat recovery system, tertiary heat recovery system includes air cleaner 1, level four heat recovery system includes empty air compressor machine, empty air compressor machine is connected with the check valve, the check valve is connected with the circulating pump, the circulating pump is connected with moisturizing case and three plate heat exchanger, be equipped with the demineralized water moisturizing mouth on the moisturizing case, air cleaner 1 is connected with one-level compressor 2, one-level compressor 2 is connected with one-level cooler 3, one-level cooler 3 is connected with second grade compressor 4, second grade compressor 4 is connected with second grade cooler 5, second grade cooler 5 is connected with tertiary compressor 6, tertiary compressor 6 is connected with tertiary cooler 8 and waste heat recovery ware 9, be connected with heat recovery inlet tube and heat recovery outlet pipe on the waste heat.

In the present invention, a valve 7 is provided between the three-stage compressor 6 and the three-stage cooler 8.

In the present invention, the third stage cooler 8 is connected to a compressed air discharge pipe.

In the invention, the primary cooler 3, the secondary cooler 5 and the tertiary cooler 8 are all connected with a cooling water inlet pipe and a cooling water outlet pipe.

The invention also provides a heat recovery method for the air compressor of the air separation system, which comprises the following steps:

s1: the gas is filtered by an air filter 1, enters a first-stage compressor 2 for compression, is cooled by a first-stage cooler 3, enters a second-stage compressor 4 for compression, is cooled by a second-stage cooler 5, and enters a third-stage compressor 6 for compression;

s2: the compressed gas enters a waste heat recoverer 9, and the waste heat recoverer 9 recovers waste heat in the gas, so that the waste heat is beneficial to heating water;

s3: and then the gas is discharged after being cooled by the three-stage cooler 8, the heat in the discharged gas is recovered by the plate heat exchanger, the energy consumption of a cooling circulating water system is reduced, and the hot water heats the electrolyte by the plate heat exchanger to replace low-pressure saturated steam, so that the energy conservation is realized.

Through the recovery of waste heat of an air compressor, the average gas production rate is 11000m³And h, calculating the fourth stage exhaust temperature of 100 ℃, and installing a fourth stage heat recovery unit to obtain the recovered heat quantity which is C.G.rho.DELTA.T

Wherein C is the specific heat capacity at constant pressure of compressed air and is constant at 1.05KJ/kg DEG C

G is the compressed air volume flow of the air compressor according to the average load, namely 110000Nm³/h。

Rho is the density of the compressed air, and the rho is 1.18kg/Nm by looking up an air parameter table³

And delta T is the temperature difference between the inlet temperature of hot compressed air into the heat exchanger and the temperature of the compressed air after waste heat recovery and utilization in our company. The average value of the temperature of the circulating water tank in operation is 40 ℃, and a heat exchanger is designed according to the end difference of 10 ℃ on the assumption that the temperature of the compressed air after waste heat recovery is calculated according to 50 ℃. The fourth stage exhaust temperature of the centrifugal air compressor is about 100 ℃, and the scheme is calculated according to 100 ℃.

Then delta T-tin-tout-100-50 deg.C

The four-stage heat quantity C · G · ρ ·Δt ═ 1.05 · 120000 · 1.18 · 50 ═ 7434000KJ/h, converted into thermal power, i.e. Q ═ 2065 KW.

Therefore, the total recovered thermal power Q is 2065 KW. The heat quantity is equivalent to 2.95 tons of steam, and the heat recovery of the air compression station can basically meet the low-pressure steam flow requirement of the existing electrolysis. Therefore, the air compressor waste heat recovery is adopted, the normal operation of the air separation air compressor is not influenced, the hot water for maintaining the temperature of the electrolyte can be recovered, the power consumption of the cooling circulating water can be reduced, and the air separation air compressor waste heat recovery can bring various benefits.

Analysis of influence on exhaust pressure after reconstruction

After the improvement, the exhaust pressure of the air separation air compressor is reduced by about 0.008Mpa, namely 8kPa, the pressure loss only accounts for 0.8 percent of the average exhaust pressure, and the pressure loss hardly affects the system according to the existing fluctuation rate.

Energy saving potential analysis

Recovered heat quantity is C.G.rho.DELTA.T

Wherein C is the specific heat capacity at constant pressure of compressed air and is constant at 1.05KJ/kg DEG C

G is the compressed air volume flow of the air compressor according to the average load, namely 110000Nm³/h。

Rho is the density of the compressed air, and the rho is 1.18kg/Nm by looking up an air parameter table³

And delta T is the temperature difference between the inlet temperature of hot compressed air into the heat exchanger and the temperature of the compressed air after waste heat recovery and utilization in our company. The average value of the temperature of the circulating water tank in operation is 40 ℃, and a heat exchanger is designed according to the end difference of 10 ℃ on the assumption that the temperature of the compressed air after waste heat recovery is calculated according to 50 ℃. The fourth stage exhaust temperature of the centrifugal air compressor is about 100 ℃, and the scheme is calculated according to 100 ℃.

Then delta T-tin-tout-100-50 deg.C

The secondary heat quantity, C · G · ρ ·Δt ═ 1.05 × 120000 × 1.18 × 50 ═ 7434000KJ/h, is converted into thermal power, i.e. Q ═ 2065 KW.

Therefore, the total recovered thermal power Q is 2065 KW. The heat is equivalent to 2.95 tons of steam. The air separation air compressor operates for 8200 hours in a year, and the annual recoverable value is 193.52 ten thousand yuan according to the steam price of 80 yuan/ton.

Through optimizing the design of the gas-water heat exchanger, only the pipeline resistance needs to be increased by 0.008Mpa, the safety and stability of the air separation system are not affected, and a starting bypass valve is arranged to switch to the existing operation mode when the accident state occurs.

The waste heat recovery of the centrifugal compressor is determined by the design structure and the working principle of the centrifugal compressor. The working process is that the centrifugal compressor sucks gas and then compresses the gas, so that the pressure of the gas is increased, namely kinetic energy is converted into pressure energy, the motor rotates to drive the gear and the rotor shaft, then the impeller obtains rotational power, external gas is sucked into an inlet of the impeller, then the sucked gas is accelerated and flows to the top end of the impeller due to centrifugal force during operation of the impeller, high-speed gas flows to the diffuser through the impeller, the gas flow speed is reduced and the pressure is increased due to change of area in the diffuser through expansion, and similarly, when the gas flow flows through the volute, the gas flow speed is gradually reduced due to gradual increase of the area of a flow channel, so that the gas pressure is increased.

The centrifugal air compressor is to realize isothermal compression, optimize efficiency, ensure outlet pressure and temperature indexes, arrange intercoolers between each section, namely use cooling water to change the heat of compressed air out, and through cooling tower fan, radiate the heat to the atmosphere, this part heat accounts for more than 70% of compressor total electric power approximately, adopt the air compressor machine compression heat recovery, prepare the required hot water of electrolysis, reduce low pressure steam consumption. And the waste heat recovery equipment is arranged on the rear side of the station room gas transmission pipeline and the rear side of the check valve and on an air pipe before entering the air cooling tower.

The airflow direction is not changed, the follow-up cooling effect and the quality of compressed air are not influenced, and before the compressed air enters the air cooling tower, high-temperature compressed air firstly enters the waste heat recovery equipment, so that the consumption of cooling circulating water can be obviously reduced, the comprehensive energy consumption is reduced, and the actual measurement is smaller than 0.008Mpa value because the air resistance of the heat recovery equipment and a pipe network provided by the scheme is very small, and the gas post-treatment equipment cannot be influenced.

Example two

Referring to fig. 1-2, a metallurgical empty system's waste heat utilization system, including tertiary heat recovery system and level four heat recovery system, tertiary heat recovery system includes air cleaner 1, level four heat recovery system includes empty air compressor machine that divides, empty air compressor machine that divides is connected with the check valve, the check valve is connected with the circulating pump, the circulating pump is connected with moisturizing case and three plate heat exchanger, be equipped with the demineralized water moisturizing mouth on the moisturizing case, air cleaner 1 is connected with one-level compressor 2, one-level compressor 2 is connected with one-level cooler 3, one-level cooler 3 is connected with second compressor 4, second compressor 4 is connected with second grade cooler 5, second grade cooler 5 is connected with tertiary compressor 6, tertiary compressor 6 is connected with tertiary cooler 8 and waste heat recoverer 9, be connected with tertiary cooler 9 on

In the present invention, a valve 7 is provided between the three-stage compressor 6 and the three-stage cooler 8.

In the present invention, the third stage cooler 8 is connected to a compressed air discharge pipe.

In the invention, the primary cooler 3, the secondary cooler 5 and the tertiary cooler 8 are all connected with a cooling water inlet pipe and a cooling water outlet pipe.

In the invention, the four-stage heat recovery system comprises a water replenishing tank, a circulating pump and a plate type heat exchanger.

The invention also provides a heat recovery method for the air compressor of the air separation system, which comprises the following steps:

s1: the gas is filtered by an air filter 1, enters a first-stage compressor 2 for compression, is cooled by a first-stage cooler 3, enters a second-stage compressor 4 for compression, is cooled by a second-stage cooler 5, and enters a third-stage compressor 6 for compression;

s2: the compressed gas enters a waste heat recoverer 9, and the waste heat recoverer 9 recovers waste heat in the gas, so that the waste heat is beneficial to heating water;

s3: and then the gas is cooled by a three-stage cooler 8 and then discharged, and heat in the discharged gas is recovered through a plate heat exchanger.

Through the recovery of waste heat of an air compressor, the average gas production rate is 11000m³And h, calculating the fourth stage exhaust temperature of 100 ℃, and installing a fourth stage heat recovery unit to obtain the recovered heat quantity which is C.G.rho.DELTA.T

Wherein C is the specific heat capacity at constant pressure of compressed air and is constant at 1.05KJ/kg DEG C

G is the compressed air volume flow of the air compressor according to the average load, namely 110000Nm³/h。

Rho is the density of the compressed air, and the rho is 1.18kg/Nm by looking up an air parameter table³

And delta T is the temperature difference between the inlet temperature of hot compressed air into the heat exchanger and the temperature of the compressed air after waste heat recovery and utilization in our company. The average value of the temperature of the circulating water tank in operation is 40 ℃, and a heat exchanger is designed according to the end difference of 10 ℃ on the assumption that the temperature of the compressed air after waste heat recovery is calculated according to 50 ℃. The fourth stage exhaust temperature of the centrifugal air compressor is about 100 ℃, and the scheme is calculated according to 100 ℃.

Then delta T-tin-tout-100-50 deg.C

The four-stage heat quantity C · G · ρ ·Δt ═ 1.05 · 120000 · 1.18 · 50 ═ 7434000KJ/h, converted into thermal power, i.e. Q ═ 2065 KW.

Therefore, the total recovered thermal power Q is 2065 KW. The heat quantity is equivalent to 2.95 tons of steam, and the heat recovery of the air compression station can basically meet the low-pressure steam flow requirement of the existing electrolysis. Therefore, the air compressor waste heat recovery is adopted, the normal operation of the air separation air compressor is not influenced, the hot water for maintaining the temperature of the electrolyte can be recovered, the power consumption of the cooling circulating water can be reduced, and the air separation air compressor waste heat recovery can bring various benefits.

Analysis of influence on exhaust pressure after reconstruction

After the improvement, the exhaust pressure of the air separation air compressor is reduced by about 0.008Mpa, namely 8kPa, the pressure loss only accounts for 0.8 percent of the average exhaust pressure, and the pressure loss hardly affects the system according to the existing fluctuation rate.

Energy saving potential analysis

Recovered heat quantity is C.G.rho.DELTA.T

Wherein C is the specific heat capacity at constant pressure of compressed air and is constant at 1.05KJ/kg DEG C

G is the compressed air volume flow of the air compressor according to the average load, namely 110000Nm³/h。

Rho is the density of the compressed air, and the rho is 1.18kg/Nm by looking up an air parameter table³

And delta T is the temperature difference between the inlet temperature of hot compressed air into the heat exchanger and the temperature of the compressed air after waste heat recovery and utilization in our company. The average value of the temperature of the circulating water tank in operation is 40 ℃, and a heat exchanger is designed according to the end difference of 10 ℃ on the assumption that the temperature of the compressed air after waste heat recovery is calculated according to 50 ℃. The fourth stage exhaust temperature of the centrifugal air compressor is about 100 ℃, and the scheme is calculated according to 100 ℃.

Then delta T-tin-tout-100-50 deg.C

The secondary heat quantity, C · G · ρ ·Δt ═ 1.05 × 120000 × 1.18 × 50 ═ 7434000KJ/h, is converted into thermal power, i.e. Q ═ 2065 KW.

Therefore, the total recovered thermal power Q is 2065 KW. The heat is equivalent to 2.95 tons of steam. The air separation air compressor operates for 8200 hours in a year, and the annual recoverable value is 193.52 ten thousand yuan according to the steam price of 80 yuan/ton.

The present embodiment is different from the first embodiment in that a temperature detector is added, and the temperature of the heat recovery outlet water is detected by the temperature detector.

EXAMPLE III

Referring to fig. 1-2, a waste heat utilization system of a metallurgical air separation system comprises a three-level heat recovery system and a four-level heat recovery system, wherein the three-level heat recovery system comprises an air filter 1, the four-level heat recovery system comprises an air separation air compressor, the air separation air compressor is connected with a check valve, the check valve is connected with a circulating pump, the circulating pump is connected with a water supplementing tank and three plate heat exchangers, the water supplementing tank is provided with a softened water supplementing port, the air filter 1 is connected with a first-level compressor 2, the first-level compressor 2 is connected with a first-level cooler 3, the first-level cooler 3 is connected with a second-level compressor 4, the second-level compressor 4 is connected with a second-level cooler 5, the second-level cooler 5 is connected with a third-level compressor 6, the, the waste heat recoverer 9 is provided with a temperature detector, a flowmeter and a timer, the temperature of the heat recovery water is detected through the temperature detector, the gas flow is detected through the flowmeter, and the time for heating the water to the required temperature is calculated through the timer.

In the present invention, a valve 7 is provided between the three-stage compressor 6 and the three-stage cooler 8.

In the present invention, the third stage cooler 8 is connected to a compressed air discharge pipe.

In the invention, the primary cooler 3, the secondary cooler 5 and the tertiary cooler 8 are all connected with a cooling water inlet pipe and a cooling water outlet pipe.

In the invention, the four-stage heat recovery system comprises a water replenishing tank, a circulating pump and a plate type heat exchanger.

The invention also provides a heat recovery method for the air compressor of the air separation system, which comprises the following steps:

s1: the gas is filtered by an air filter 1, enters a first-stage compressor 2 for compression, is cooled by a first-stage cooler 3, enters a second-stage compressor 4 for compression, is cooled by a second-stage cooler 5, and enters a third-stage compressor 6 for compression;

s2: the compressed gas enters a waste heat recoverer 9, and the waste heat recoverer 9 recovers waste heat in the gas, so that the waste heat is beneficial to heating water;

s3: and then the gas is cooled by a three-stage cooler 8 and then discharged, and heat in the discharged gas is recovered through a plate heat exchanger.

Through the recovery of waste heat of an air compressor, the average gas production rate is 11000m³And h, calculating the fourth stage exhaust temperature of 100 ℃, and installing a fourth stage heat recovery unit to obtain the recovered heat quantity which is C.G.rho.DELTA.T

Wherein C is the specific heat capacity at constant pressure of compressed air and is constant at 1.05KJ/kg DEG C

G is the compressed air volume flow of the air compressor according to the average load, namely 110000Nm³/h。

Rho is the density of the compressed air, and the rho is 1.18kg/Nm by looking up an air parameter table³

And delta T is the temperature difference between the inlet temperature of hot compressed air into the heat exchanger and the temperature of the compressed air after waste heat recovery and utilization in our company. The average value of the temperature of the circulating water tank in operation is 40 ℃, and a heat exchanger is designed according to the end difference of 10 ℃ on the assumption that the temperature of the compressed air after waste heat recovery is calculated according to 50 ℃. The fourth stage exhaust temperature of the centrifugal air compressor is about 100 ℃, and the scheme is calculated according to 100 ℃.

Then delta T-tin-tout-100-50 deg.C

The four-stage heat quantity C · G · ρ ·Δt ═ 1.05 · 120000 · 1.18 · 50 ═ 7434000KJ/h, converted into thermal power, i.e. Q ═ 2065 KW.

Therefore, the total recovered thermal power Q is 2065 KW. The heat quantity is equivalent to 2.95 tons of steam, and the heat recovery of the air compression station can basically meet the low-pressure steam flow requirement of the existing electrolysis. Therefore, the air compressor waste heat recovery is adopted, the normal operation of the air separation air compressor is not influenced, the hot water for maintaining the temperature of the electrolyte can be recovered, the power consumption of the cooling circulating water can be reduced, and the air separation air compressor waste heat recovery can bring various benefits.

Analysis of influence on exhaust pressure after reconstruction

After the improvement, the exhaust pressure of the air separation air compressor is reduced by about 0.008Mpa, namely 8kPa, the pressure loss only accounts for 0.8 percent of the average exhaust pressure, and the pressure loss hardly affects the system according to the existing fluctuation rate.

Energy saving potential analysis

Recovered heat quantity is C.G.rho.DELTA.T

Wherein C is the specific heat capacity at constant pressure of compressed air and is a constant of 1.05 KJ/(kg. DEG C)

G is the compressed air volume flow of the air compressor according to the average load, namely 110000Nm³/h。

Rho is the density of the compressed air, and the rho is 1.18kg/Nm by looking up an air parameter table³

And delta T is the temperature difference between the inlet temperature of hot compressed air into the heat exchanger and the temperature of the compressed air after waste heat recovery and utilization in our company. The average value of the temperature of the circulating water tank in operation is 40 ℃, and a heat exchanger is designed according to the end difference of 10 ℃ on the assumption that the temperature of the compressed air after waste heat recovery is calculated according to 50 ℃. The fourth stage exhaust temperature of the centrifugal air compressor is about 100 ℃, and the scheme is calculated according to 100 ℃.

Then delta T-tin-tout-100-50 deg.C

The secondary heat quantity, C · G · ρ ·Δt ═ 1.05 × 120000 × 1.18 × 50 ═ 7434000KJ/h, is converted into thermal power, i.e. Q ═ 2065 KW.

Therefore, the total recovered thermal power Q is 2065 KW. The heat is equivalent to 2.95 tons of steam. The air separation air compressor operates for 8200 hours in a year, and the annual recoverable value is 193.52 ten thousand yuan according to the steam price of 80 yuan/ton.

The difference between the present embodiment and the second embodiment is that a temperature detector, a flow meter and a timer are added, the temperature of the heat recovery outlet water is detected by the temperature detector, the gas flow rate is detected by the flow meter, the time taken for heating the water to the required temperature is calculated by the timer, and the waste heat recovery efficiency can be calculated.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and equivalent substitutions or changes according to the technical solution and the inventive concept of the present invention should be covered by the scope of the present invention.