Steam exhaust waste heat utilization system based on steam compression and operation method

Abstract

The invention discloses a dead steam waste heat utilization system based on steam compression and an operation method, the dead steam waste heat utilization system is used for recycling waste heat of a waste heat pipeline, the system comprises a control module, and further comprises a softened water supply module, a heat exchange module, a steam compression module and a user output module which communicate in sequence. The number of the waste heat pipelines can be one or more, and the multiple waste heat pipelines are connected in parallel. Each waste heat pipeline can be communicated with one heat exchange module to form a single-stage heat exchange mode; and each waste heat pipeline can also be communicated with a plurality of heat exchange modules in series to form a multi-stage heat exchange mode. The operation mode of the system adopts an automatic control mode to realize automatic start and stop, and automatic adjustment of steam parameters is realized. The scheme has the beneficial effects that waste heat utilization of waste steam heat is realized, the steam recovery efficiency is improved, the utilization cost is reduced, flexible matching design can be realized according to the quality and quantity of waste heat resources, and the scheme has better economical efficiency and popularization value.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat utilization, and in particular to a steam compression-based exhaust steam waste heat utilization system and an operation method. Background Art

[0002] Waste heat is an important available resource, and waste heat utilization is one of the important means of energy conservation and emission reduction. In the production process of industry, food, chemical industry, etc., there is a large amount of waste heat. By recycling and utilizing this waste heat, it can be converted into useful energy, thereby improving the overall efficiency of energy utilization, reducing energy consumption and production costs, reducing greenhouse gas emissions and improving environmental quality, which can provide new impetus for industrial development and promote the development of industry in a more green and sustainable direction.

[0003] Exhaust steam is one of the important ways of utilizing waste heat. For general steam users, they need steam themselves, and a large amount of exhaust steam is also generated during the production process. Traditional exhaust steam utilization mostly adopts the scheme of high-pressure steam injection, which uses high-pressure steam to drive the steam in the exhaust steam to increase its pressure. The amount of steam recovered by this method is relatively limited, and a large amount of high-pressure steam is consumed, and the utilization cost is still relatively high. The present invention proposes a scheme for utilizing the waste heat of exhaust steam based on steam compression. First, the exhaust steam is purified by heat exchange, and then a high-speed centrifugal turbine compressor is used to increase the temperature and pressure to realize the recycling of steam heat. This can greatly improve the utilization rate of energy, reduce the energy cost of the enterprise, and has good economic performance and promotion value. Summary of the invention

[0004] The present invention aims at the deficiencies in the prior art and provides a waste heat utilization system and operation method for exhaust steam based on steam compression. By purifying the waste heat of the exhaust steam through heat exchange and then compressing and boosting the pressure, the waste heat can be effectively recovered, the steam energy cost can be saved, and the system can be intelligentized.

[0005] In order to achieve the above-mentioned object, the present invention provides a steam compression-based exhaust steam waste heat utilization system for recovering and utilizing waste heat from a waste heat pipeline, comprising a control module, a softened water supply module, a heat exchange module, a steam compression module and a user output module connected in sequence; The softened water supply module comprises a softened water tank, a centrifugal pump, and a check valve which are connected in sequence; The heat exchange module includes a diverter valve and a heat exchanger, wherein the diverter valve is connected to the softened water supply module and the cold side inlet of the heat exchanger, and the cold side outlet of the heat exchanger is connected to the steam compression module; the hot side of the heat exchanger is connected to the waste heat pipeline; The waste heat pipeline includes a waste heat pipeline outlet pipe, a waste heat pipeline return pipe, and a fan, the waste heat pipeline outlet pipe is connected to the hot side inlet of the heat exchanger, the hot side outlet of the heat exchanger is connected to the fan, and the fan is connected to the waste heat pipeline return pipe; The steam compression module comprises a buffer tank, a steam compressor, and a desuperheater which are connected in sequence, the cold side outlet of the heat exchanger is connected to the buffer tank inlet, and the desuperheater is connected to the user output module; The steam compression module is provided with an exhaust bypass connected to the waste heat pipeline, the exhaust bypass includes a start-up bypass valve, and the start-up bypass valve is connected to the desuperheater and the outlet pipe of the waste heat pipeline; The steam compression module further includes a stabilizing pipeline, wherein the stabilizing pipeline includes a temperature reducing and pressure reducing device and a bypass valve connected to each other, and connects the inlet and the outlet of the steam compressor; The user output module includes a regulating valve and a steam user, the regulating valve inlet is connected to the desuperheater, and the regulating valve outlet is connected to the steam user.

[0006] Furthermore, the waste heat pipeline is one or more, and the multiple waste heat pipelines are connected in parallel; Each of the waste heat pipelines is connected to one of the heat exchange modules to form a single-stage heat exchange mode, and the heat exchange modules connected to each of the waste heat pipelines are connected to the steam compression module in parallel.

[0007] Furthermore, the waste heat pipeline is one or more, and the multiple waste heat pipelines are connected in parallel; Each of the waste heat pipelines is connected in series with a plurality of the heat exchange modules to form a multi-stage heat exchange mode, and the diverter valves of the plurality of the heat exchange modules are connected in parallel with the softened water supply module; According to the number of the heat exchange modules with the largest number connected in series, the same number of steam compression modules are arranged, and the plurality of steam compression modules are connected in series; The heat exchange modules at the same level of the plurality of waste heat pipelines are connected in parallel and then connected to the steam compression modules at the same level.

[0008] Furthermore, the steam compressor adopts a high-speed centrifugal double-ended cantilever impeller structure, and the motor of the steam compressor adopts a high-speed permanent magnet magnetic bearing motor.

[0009] Furthermore, the softened water supply module is also provided with a reflux circuit, and the reflux circuit includes a reflux valve connecting the inlet and outlet of the centrifugal pump.

[0010] The present invention also provides an operation method of a waste steam waste heat utilization system based on steam compression, comprising the following steps: Step 1: System self-check: Specifically, confirm whether the system has the startup conditions, including checking whether the motor is powered on, whether the control module is powered on, and whether the valve, pump and fan are in normal state; Step 2: Water injection: Specifically, after the system passes the self-check, start the centrifugal pump to inject softened water into the heat exchanger. When the water level reaches a certain level, stop injecting water. Step 3: Open the bypass; specifically, open the start-up bypass valve and close the regulating valve; Step 4: preheating the feed water; specifically, starting the induced draft fan and using the exhaust steam heat from the waste heat pipeline to preheat the feed water through a heat exchanger; Step 5: Start steam compression; specifically, when the heat exchanger feed water temperature and water level meet the conditions, start the steam compressor motor by frequency conversion and keep it running at a low speed; Step 6: Increase the speed; specifically, confirm that the parameters of the motor and steam compressor are normal, gradually increase the motor to the rated speed, and monitor the air concentration at the steam compressor outlet; Step 7: Switch the steam supply mode; when the air concentration at the steam compressor outlet meets the conditions, gradually close the start-up bypass valve, gradually open the regulating valve, and enter the normal steam supply mode; Step 8: Maintain stable operation; specifically, enter normal working state, and put into automatic control mode to maintain stable operation.

[0011] Furthermore, the liquid level automatic control method of the heat exchanger is to calculate the speed signal of the centrifugal pump and the opening signal of the diverter valve through the PID controller according to the measured liquid level signal of the heat exchanger, and transmit them to the corresponding equipment; The automatic steam pressure control method is to calculate the speed signal of the steam compressor motor through the PID controller according to the measured steam pressure signal, and transmit it to the frequency converter of the motor; The automatic temperature control method of steam is to calculate the valve opening signal of the desuperheater through the PID controller according to the measured steam temperature signal, and transmit it to the actuator of the desuperheater valve.

[0012] The beneficial effects of this scheme can be known from the description of the above scheme, and it has the following advantages: (1) No high-pressure steam injection is required to realize the waste heat utilization of exhaust steam, which improves the steam recovery efficiency and reduces the utilization cost, and has good economic and promotion value; (2) According to the quality and quantity of waste heat resources, a variety of utilization methods can be flexibly matched and designed, and a multi-stage arrangement of heat exchange and pressure boost can be carried out to maximize the use of exhaust steam heat within the possible limits of the design conditions, reduce the power consumption of the compressor, and improve the overall energy efficiency level of the system; (3) While the waste heat exchanger realizes heat recovery and utilization, it also uses the heat to heat the softened water on the secondary side to produce clean pure steam, which is equivalent to achieving steam purification and reuse; (4) A buffer tank is set before the input end of the steam compressor. On the one hand, it is used to mix the steam from different heat exchangers. On the other hand, it can play a role in stabilizing the pressure. As a steam storage tank, it stores a certain mass of steam. When the steam production of the heat exchanger decreases, it replenishes part of the steam, and when the steam production is high, it also stores part of the steam. (5) The steam compressor is equipped with a bypass to further increase the operating range of the steam compressor and improve the stability of the steam compressor operation; (6) The steam compressor adopts a high-speed centrifugal double-end cantilever impeller solution, which is driven by a high-speed permanent magnet magnetic bearing motor. It has a compact structure design, small size, oil-free lubrication, can be used for a long time, and is easy to maintain. It is particularly suitable for occasions with high requirements for steam purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the exhaust steam waste heat utilization system based on single-stage steam compression of the present invention; Figure 2 It is a schematic diagram of the exhaust steam waste heat utilization system based on two-stage series-parallel steam compression of the present invention; Figure 3 It is a schematic diagram of the exhaust steam waste heat utilization system based on three-stage series-parallel steam compression of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] A waste steam waste heat utilization system based on steam compression can flexibly match and design a variety of utilization methods according to the quality and quantity of waste heat resources, including single-stage scheme, two-stage series scheme, three-stage series scheme, two-stage parallel scheme, three-stage parallel scheme and series-parallel mixed scheme, etc. When the temperature gradient of the waste steam to be recovered is larger, the number of series stages needs to be increased; when the flow rate of the waste steam to be recovered is larger, the number of parallel stages needs to be increased.

[0016] According to the design and selection of the compressor, taking a single-stage compressor with a compression ratio of 2 as an example, a single-stage compressor is expected to recover exhaust steam heat above 85°C, a two-stage series compressor is expected to recover exhaust steam heat above 70°C, and a three-stage series compressor is expected to recover exhaust steam heat above 50°C. When the exhaust steam volume is large and exceeds the design flow of a single compressor, a larger amount of waste heat resources can be recovered by connecting 2, 3 or even more compressors in parallel. In addition, the effective use of heat can be achieved by combining the compressor and the waste heat exchanger in series and parallel, such as using segmented heat exchange in the exhaust steam section to match the segmented compression of the compressor. The specific series-parallel combination scheme can be designed in a targeted manner based on the waste heat situation. Embodiment 1

[0017] like Figure 1 As shown, a waste steam waste heat utilization system based on single-stage steam compression mainly includes a softened water tank 1, a centrifugal pump 2, a reflux valve 3, a check valve 4, a diverter valve 5, a diverter valve 6, a heat exchanger 7, a heat exchanger 8, a buffer tank 10, a steam compressor 11, a motor 12, a desuperheater 13, a regulating valve 14, a steam user 15, a start-up bypass valve 16, a bypass desuperheater and pressure reducer 17, a bypass valve 18, a waste heat pipeline outlet pipe 21, an induced draft fan 22, a waste heat pipeline return pipe 23, a waste heat pipeline outlet pipe 24, an induced draft fan 25, and a waste heat pipeline return pipe 26.

[0018] The system recycles two waste heat pipelines, of which the waste heat pipeline outlet pipe 21 and the waste heat pipeline outlet pipe 24 represent the two waste heat pipelines respectively. The working fluid of the pipeline is generally a mixture of steam and air. The working fluid temperature varies according to different processes. The higher the temperature, the higher the quality of the waste heat, and the higher the value and economy of the recovery. In this example, the working fluid temperature is taken as 95°C. The two waste heat pipelines transfer heat to the secondary side through heat exchangers 7 and 8 respectively. At the same time, part of the steam in them will condense into water and be collected. The remaining steam and air mixture enters the induced draft fan 22 and the induced draft fan 25 to enter the pressure increase, and then returns to the respective waste heat pipeline return pipes 23 and 26. The temperature of the two exhaust steam after heat recovery is about 85°C.

[0019] The softened water after process treatment is stored in the softened water tank 1. After the water pressure is increased by the centrifugal pump 2, it is divided into two paths through the check valve 4 and enters the secondary side of the heat exchanger 7 and the heat exchanger 8 through the diverter valve 5 and the diverter valve 6 respectively. While the heat exchangers 7 and 8 realize heat recovery, the heat is used to heat the softened water on the secondary side to produce clean pure steam, which is equivalent to steam purification and reuse. After the pure steam produced by the heat exchangers 7 and 8 is mixed in the buffer tank 10, the pressure and flow are balanced and enter the steam compressor 11 together. The steam compressor 11 is driven by the motor 12 to increase the pressure of the steam to the required rated parameters. At the same time as the pressure is increased, according to the principle of gas thermodynamics, the temperature of the steam will also increase. After the steam after pressure and temperature increase passes through the desuperheater 13, it is adjusted to the required steam temperature, and then enters the steam user 15 after the flow is adjusted by the regulating valve 14.

[0020] The buffer tank 10 is used to mix the steam from the heat exchangers 7 and 8 on the one hand, and to stabilize the pressure on the other hand. In some applications, the waste heat parameters also change over time depending on the process, which will cause fluctuations in the steam flow. While stabilizing the pressure, the buffer tank 10 acts as a steam storage tank to store a certain mass of steam, replenishing part of the steam when the steam production of the heat exchangers 7 and 8 decreases, and can also store part of the steam when the steam production is high.

[0021] The steam compressor 11 adopts a high-speed centrifugal double-end cantilever impeller solution with a speed exceeding 20,000 rpm. It is driven by a high-speed permanent magnetic bearing motor. It has a compact structure design, small size, no oil lubrication, can be used for a long time, and is easy to maintain. It is particularly suitable for occasions with high requirements for steam purity. The steam compressor 11 adopts a variable frequency motor, which can be variable speed and frequency control, and utilizes the energy-saving operation of the system.

[0022] The bypass temperature and pressure reducer 17 is used as a bypass of the steam compressor 11 to divert a part of the steam flow under low load conditions, reduce the temperature and pressure, make it consistent with the inlet parameters of the steam compressor 11, and return it to the inlet of the steam compressor 11. The purpose of setting the bypass is to further increase the operating range of the steam compressor 11. When the operating flow is lower than the operating range of the steam compressor 11, by opening the bypass valve 18 and adjusting the bypass temperature and pressure reducer 17, the operating flow of the steam compressor 11 can be increased, and the stability of the operation of the steam compressor 11 can be improved.

[0023] The starting bypass valve 16 is used during the initial startup of the system. When there is a mixture of steam and air in the system loop and some process requirements cannot be directly injected to the user, the starting bypass valve 16 can be used to inject the mixture of steam and air into the exhaust steam side to effectively recover the system heat. When it is detected that the steam quality at the outlet of the steam compressor 11 meets the use requirements, the starting bypass valve 16 is gradually closed, and the regulating valve 14 is gradually opened to enter the normal steam supply mode.

[0024] The system adopts automatic control mode to realize automatic start and stop, which mainly includes the following steps: Step 1: System self-check; confirm whether the system has the startup conditions, including whether the motor is powered on, whether the control system is powered on, and whether the status of valves, pumps, fans, etc. is normal; Step 2: water injection; after the system self-check passes, start the centrifugal pump 2, open the diverter valves 5 and 6, and inject softened water into the heat exchangers 7 and 8. When the water level reaches a certain level, stop water injection; Step 3: Open the bypass; open the starter bypass valve 16 and close the regulating valve 14 to open the bypass exhaust; Step 4: preheating feed water; starting the induced draft fans 22 and 25, using the exhaust steam from the waste heat pipeline outlet pipe 21 and the waste heat pipeline outlet pipe 24 to preheat the feed water in the heat exchanger through the heat exchangers 7 and 8; Step 5: Start steam compression; when the water temperature in the heat exchanger reaches a specified temperature (such as 85°C) and the water level is not lower than 1 / 3 of the water level, start the motor 12 in a variable frequency manner to start the steam compressor 11, and run it at a low speed for 1 minute; Step 6: Increase the speed; confirm that the parameters of the motor 12 and the steam compressor 11 are normal, and then gradually increase the speed of the motor 12 to the rated speed. During this process, monitor the air concentration at the outlet of the steam compressor 11; Step 7: Switch the steam supply mode; when the air concentration is very low, below the lower limit of the measured value, it is considered that the air in the circuit has been completely discharged, and then gradually close the start-up bypass valve 16, gradually open the regulating valve 14, enter the normal steam supply mode, and start supplying steam to the user; Step 8: Maintain stable operation; enter normal working state, and enter automatic control mode to maintain stable operation.

[0025] This system adopts automatic control method to realize automatic adjustment of steam parameters.

[0026] For the liquid level control of heat exchangers 7 and 8, the speed signal of centrifugal pump 2 and the opening signals of diverter valves 5 and 6 are calculated by PID controller according to the measured liquid level signal, and transmitted to the corresponding equipment to complete the liquid level control of closed-loop PID.

[0027] For steam pressure control, the speed signal of the steam compressor 11 is calculated by the PID controller based on the measured steam pressure signal and transmitted to the frequency converter of the motor 12 to complete the steam pressure control of the closed-loop PID.

[0028] For steam temperature control, the valve opening signal of the desuperheater 13 is calculated by the PID controller based on the measured steam temperature signal, and transmitted to the actuator of the valve of the desuperheater 13 to complete the steam temperature control of the closed-loop PID. Embodiment 2

[0029] Double-stage heat exchange + double-stage series steam compression exhaust steam waste heat utilization system Figure 2 As shown, this solution is based on Example 1 and adds major equipment: a secondary diverter valve 5A, a secondary heat exchanger 7A, a secondary buffer tank 10A, a secondary steam compressor 11A, a secondary motor 12A, a secondary desuperheater 13A, a secondary bypass desuperheater and pressure reducer 17A, and a secondary bypass valve 18A.

[0030] The system recycles two waste heat pipelines, of which the waste heat pipeline outlet pipe 21 and the waste heat pipeline outlet pipe 24 represent the two waste heat pipelines respectively. The working fluid of the pipeline is generally a mixture of steam and air. The temperature of the waste heat pipeline outlet pipe 24 is relatively high. Taking 95°C as an example, two-stage heat recovery is adopted. The waste heat pipeline outlet pipe 24 passes through the secondary heat exchanger 7A, the primary heat exchanger 7, and then passes through the induced draft fan 25, and returns to the waste heat pipeline return pipe 26. The temperature of the waste heat pipeline outlet pipe 21 is relatively low. Taking 85°C as an example, a single-stage heat recovery is adopted. The waste heat pipeline outlet pipe 21 passes through the heat exchanger 8, then passes through the induced draft fan 22, and returns to the waste heat pipeline return pipe 23. The temperature of the two exhaust steam after heat recovery is about 70°C.

[0031] The softened water after process treatment is stored in the softened water tank 1. After the water pressure is increased by the centrifugal pump 2, it is divided into three paths through the check valve 4, and enters the secondary side of the primary heat exchanger 7, the secondary heat exchanger 7A, and the heat exchanger 8 through the primary diverter valve 5, the secondary diverter valve 5A and the diverter valve 6 respectively. The steam parameters generated by the primary heat exchanger 7 and the heat exchanger 8 are similar, so the parallel mode is adopted to mix the pure steam generated by the heat exchangers 7 and 8 in the primary buffer tank 10 and enter the primary steam compressor 11 together to increase the pressure. The feed water entering the secondary heat exchanger 7A can produce steam with higher parameters due to heat exchange with the high-temperature section of the exhaust steam. When designed, it matches the steam pressure parameters at the outlet of the primary steam compressor 11. The two steam paths can be mixed in the secondary buffer tank 10A and enter the secondary steam compressor 11A together, and then enter the steam user through the regulating valve 14 after the temperature is adjusted by the secondary desuperheater 13A.

[0032] The series-parallel relationship of the main heat exchange and compression units in this scheme is: the first-stage heat exchanger 7 and the second-stage heat exchanger 7A are connected in series, the first-stage heat exchanger 7 and the heat exchanger 8 are connected in parallel, the second-stage heat exchanger 7A and the first-stage steam compressor 11 are connected in parallel, and the first-stage steam compressor 11 and the second-stage steam compressor 11A are connected in series. Through this series-parallel combination scheme, the heat of the exhaust steam can be utilized to the maximum extent within the possible limit of the design working conditions, the power consumption of the compressor can be reduced, and the overall energy efficiency level of the system can be improved.

[0033] The operation mode of this system adopts automatic control mode to realize automatic start and stop. It is basically the same as the operation mode of Example 1, but it is necessary to focus on the matching start-up mode of the two-stage heat exchanger and the two-stage series compression. When the system is started, the system self-check is first turned on to confirm whether the system has the start-up conditions. After the system self-check passes, the centrifugal pump 2 is started to inject water into the heat exchangers 7, 7A, and 8. When the water level reaches a certain level, the water injection is stopped; the bypass valve 16 is opened, the regulating valve 14 is closed, and the induced draft fans 22 and 25 are started. The exhaust steam of the waste heat pipeline outlet pipe 21 and the waste heat pipeline outlet pipe 24 is used to preheat the feed water in the heat exchanger through the heat exchangers 8 and 7A, 7. When the water temperature reaches the specified temperature of each heat exchanger and the water level is not lower than 1 / 3 of the water level, the motors 12 and 12A are started synchronously by frequency conversion. They are first run at a low speed for 1 minute to confirm that the parameters of the motor and the compressor are normal, and then the motor speed is gradually increased to the rated speed. Embodiment 3

[0034] Three-stage heat exchange + three-stage series steam compression exhaust steam waste heat utilization system Figure 3 As shown, this solution is based on Example 2 and adds major equipment: a three-stage diverter valve 5B, a three-stage heat exchanger 7B, a three-stage buffer tank 10B, a three-stage steam compressor 11B, a three-stage motor 12B, a three-stage desuperheater 13B, a three-stage bypass desuperheater and pressure reducer 17B, and a three-stage bypass valve 18B.

[0035] The system recycles two waste heat pipelines, of which the waste heat pipeline outlet pipe 21 and the waste heat pipeline outlet pipe 24 represent the two waste heat pipelines respectively. The working fluid of the pipeline is generally a mixture of steam and air. The temperature of the waste heat pipeline outlet pipe 24 is relatively high. Taking 95°C as an example, three-stage heat recovery is adopted. The waste heat pipeline outlet pipe 24 passes through the third-stage heat exchanger 7B, the second-stage heat exchanger 7A, the first-stage heat exchanger 7, and then passes through the induced draft fan 25, and returns to the waste heat pipeline return pipe 26. The temperature of the waste heat pipeline outlet pipe 21 is relatively low. Taking 70°C as an example, a single-stage heat recovery is adopted. The waste heat pipeline outlet pipe 21 passes through the heat exchanger 8, and then passes through the induced draft fan 22, and returns to the waste heat pipeline return pipe 23. The temperature of the two exhaust steam after heat recovery is about 50°C.

[0036] The series-parallel relationship of the main heat exchange and compression units in this scheme is: the first-stage heat exchanger 7, the second-stage heat exchanger 7A and the third-stage heat exchanger 7B are connected in series, the first-stage heat exchanger 7 and the heat exchanger 8 are connected in parallel, the second-stage heat exchanger 7A and the first-stage steam compressor 11 are connected in parallel, the third-stage heat exchanger 7B and the second-stage steam compressor 11A are connected in parallel, and the first-stage steam compressor 11, the second-stage steam compressor 11A and the third-stage steam compressor 11B are connected in series. Through this series-parallel combination scheme, the heat of the exhaust steam can be utilized to the maximum extent within the possible limit of the design working conditions, the power consumption of the compressor can be reduced, and the overall energy efficiency level of the system can be improved.

[0037] The operation mode of this system is basically the same as that of Example 2, but the matching startup mode of the three-stage heat exchanger and the three-stage series compression should be considered. When the system is started, the system self-check is first turned on to confirm whether the system has the startup conditions. After the system self-check passes, the centrifugal pump 2 is started to inject water into the heat exchangers 7, 7A, 7B, and 8. When the water level reaches a certain level, the water injection is stopped; the bypass valve 16 is opened, the regulating valve 14 is closed, and the induced draft fans 22 and 25 are started. The exhaust steam from the waste heat pipeline outlet pipe 21 and the waste heat pipeline outlet pipe 24 is used to preheat the feed water in the heat exchanger through the heat exchangers 8 and 7B, 7A, 7. When the water temperature reaches the specified temperature of each heat exchanger and the water level is not lower than 1 / 3 of the water level, the motors 12, 12A, and 12B are started synchronously by frequency conversion. They are first run at a low speed for 1 minute to confirm that the parameters of the motor and the compressor are normal, and then the motor speed is gradually increased to the rated speed.

[0038] Technical features not described in the present invention can be achieved through or by adopting existing technologies and will not be described in detail herein. Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A waste steam waste heat utilization system based on steam compression, used to recover and utilize waste heat from waste heat pipelines, characterized in that: It includes a control module, and also includes a softened water supply module, a heat exchange module, a steam compression module and a user output module which are connected in sequence; The softened water supply module comprises a softened water tank, a centrifugal pump, and a check valve which are connected in sequence; The heat exchange module includes a diverter valve and a heat exchanger, wherein the diverter valve is connected to the softened water supply module and the cold side inlet of the heat exchanger, and the cold side outlet of the heat exchanger is connected to the steam compression module; the hot side of the heat exchanger is connected to the waste heat pipeline; The waste heat pipeline includes a waste heat pipeline outlet pipe, a waste heat pipeline return pipe, and a fan, the waste heat pipeline outlet pipe is connected to the hot side inlet of the heat exchanger, the hot side outlet of the heat exchanger is connected to the fan, and the fan is connected to the waste heat pipeline return pipe; The steam compression module comprises a buffer tank, a steam compressor, and a desuperheater which are connected in sequence, the cold side outlet of the heat exchanger is connected to the buffer tank inlet, and the desuperheater is connected to the user output module; The steam compression module is provided with an exhaust bypass connected to the waste heat pipeline, the exhaust bypass includes a start-up bypass valve, and the start-up bypass valve is connected to the desuperheater and the outlet pipe of the waste heat pipeline; The steam compression module further includes a stabilizing pipeline, wherein the stabilizing pipeline includes a temperature reducing and pressure reducing device and a bypass valve connected to each other, and connects the inlet and the outlet of the steam compressor; The user output module includes a regulating valve and a steam user, the regulating valve inlet is connected to the desuperheater, and the regulating valve outlet is connected to the steam user.

2. The exhaust steam waste heat utilization system based on steam compression according to claim 1 is characterized in that: There is one or more waste heat pipelines, and the multiple waste heat pipelines are connected in parallel; Each of the waste heat pipelines is connected to one of the heat exchange modules to form a single-stage heat exchange mode, and the heat exchange modules connected to each of the waste heat pipelines are connected to the steam compression module in parallel.

3. The exhaust steam waste heat utilization system based on steam compression according to claim 1 is characterized in that: There is one or more waste heat pipelines, and the multiple waste heat pipelines are connected in parallel; Each of the waste heat pipelines is connected in series with a plurality of the heat exchange modules to form a multi-stage heat exchange mode, and the diverter valves of the plurality of the heat exchange modules are connected in parallel with the softened water supply module; According to the number of the heat exchange modules with the largest number connected in series, the same number of steam compression modules are arranged, and the plurality of steam compression modules are connected in series; The heat exchange modules at the same level of the plurality of waste heat pipelines are connected in parallel and then connected to the steam compression modules at the same level.

4. A steam compression-based exhaust steam waste heat utilization system according to any one of claims 1 to 3, characterized in that: The steam compressor adopts a high-speed centrifugal double-end cantilever impeller structure, and the motor of the steam compressor adopts a high-speed permanent magnet magnetic suspension bearing motor.

5. A steam compression-based exhaust steam waste heat utilization system according to any one of claims 1 to 3, characterized in that: The softened water supply module is also provided with a reflux circuit, and the reflux circuit includes a reflux valve connecting the inlet and the outlet of the centrifugal pump.

6. An operating method of a steam compression-based exhaust steam waste heat utilization system according to claims 1-3, characterized in that: The following steps are involved: Step 1: System self-check: Specifically, confirm whether the system has the startup conditions, including checking whether the motor is powered on, whether the control module is powered on, and whether the valve, pump and fan are in normal state; Step 2: Water injection: Specifically, after the system passes the self-check, start the centrifugal pump to inject softened water into the heat exchanger. When the water level reaches a certain level, stop injecting water; Step 3: Open the bypass; specifically, open the start-up bypass valve and close the regulating valve; Step 4: preheating the feed water; specifically, starting the induced draft fan and using the exhaust steam heat from the waste heat pipeline to preheat the feed water through a heat exchanger; Step 5: Start steam compression; specifically, when the heat exchanger feed water temperature and water level meet the conditions, start the steam compressor motor by frequency conversion and keep it running at a low speed; Step 6: Increase the speed; specifically, confirm that the parameters of the motor and steam compressor are normal, gradually increase the motor to the rated speed, and monitor the air concentration at the steam compressor outlet; Step 7: Switch the steam supply mode; when the air concentration at the steam compressor outlet meets the conditions, gradually close the start-up bypass valve, gradually open the regulating valve, and enter the normal steam supply mode; Step 8: Maintain stable operation; specifically, enter normal working state, and put into automatic control mode to maintain stable operation.

7. The operating method of the exhaust steam waste heat utilization system based on steam compression according to claim 6 is characterized in that: The automatic control method of the liquid level of the heat exchanger is to calculate the speed signal of the centrifugal pump and the opening signal of the diverter valve through the PID controller according to the measured liquid level signal of the heat exchanger, and transmit them to the corresponding equipment; The automatic steam pressure control method is to calculate the speed signal of the steam compressor motor through the PID controller according to the measured steam pressure signal, and transmit it to the frequency converter of the motor; The automatic temperature control method of steam is to calculate the valve opening signal of the desuperheater through the PID controller according to the measured steam temperature signal, and transmit it to the actuator of the desuperheater valve.

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