A valveless negative pressure hot water flash evaporation electrostatic system

Abstract

This utility model relates to the field of waste heat utilization technology, specifically a valveless negative pressure hot water flash evaporation and electrolysis system. The system integrates a flash evaporation unit, a valveless negative pressure steam turbine unit, a power generation unit, a condensate recovery unit, a back pressure control unit, and a safety protection unit. It can be automatically started without external force by 30kPa(a)~50kPa(a) negative pressure saturated steam. The steam intake and speed are controlled by a dual-diameter back pressure regulating valve at the exhaust end. Combined with a dual-redundant safety system of "vacuum breaker valve + frequency converter braking + integrated electric and steam protection", the unit can achieve stable start-up, precise grid connection, rated power output, and safe emergency shutdown. It can adapt to the flash evaporation and electrolysis needs of 90℃~120℃ hot water, realize the direct conversion of low-grade waste heat into electrical energy, significantly improve waste heat utilization efficiency, reduce cooling energy consumption and water resource consumption, and can be widely used in low-grade waste heat recovery scenarios in high-energy-consuming industries such as petrochemical and chemical industries.

Description

Technical Field

[0001] This utility model relates to the field of waste heat utilization technology, and in particular to a negative pressure hot water flash evaporation electric system without a steam inlet valve. Background Technology

[0002] High-energy-consuming industries such as petrochemicals and chemicals generate a large amount of low-grade waste heat water at 90℃~120℃ during production. This type of waste heat has a low energy level and can usually only be recovered by exchanging heat with production water to achieve low-level heat energy recovery. It cannot be directly converted into electricity for efficient utilization. Moreover, due to fluctuations in operating conditions, there is often an excess of waste heat water, which requires additional cooling systems to absorb it. This not only wastes energy but also increases water and electricity consumption, which contradicts the industry's development needs for energy conservation, efficiency improvement, and carbon emission reduction.

[0003] Currently, low-grade waste heat power generation technologies are mostly focused on utilizing medium- and high-temperature waste heat above 150℃. However, a mature application solution for flash evaporation power generation technology using negative-pressure hot water at 90℃~120℃ has not yet been developed. Conventional steam power generation systems require main steam valves, regulating steam valves, and other steam inlet control components to adapt to medium- and high-pressure steam work scenarios. However, the 30kPa~50kPa negative-pressure steam generated by flash evaporation of negative-pressure hot water has low energy density and weak work capacity, making it unable to drive the stable operation of conventional steam turbines with inlet valves. Furthermore, conventional speed regulation methods rely on regulating steam valves to control the steam inlet volume, which suffers from poor speed regulation accuracy and response lag when adapted to negative-pressure steam. Moreover, there is a lack of safety protection mechanisms for operating conditions without inlet valves, leading to safety hazards such as long rotor coasting time and system negative pressure loss during emergency shutdowns. This makes direct power generation via flash evaporation of negative-pressure hot water difficult to implement in engineering.

[0004] In existing technologies, some waste heat recovery solutions only focus on heat exchange and reuse, without involving power generation technology; a few flash evaporation power generation attempts still use conventional steam turbines and control logic, failing to solve core technical challenges such as compatibility with steam valve-less systems, negative pressure steam speed regulation, and safe shutdown, thus failing to meet the actual needs of efficient power generation from low-grade hot water. Therefore, developing a flash evaporation power generation solution that is compatible with negative pressure steam, has a steam valve-less structure, and combines precise control and safety protection functions to achieve direct power generation from low-grade hot water waste heat has become an urgent technical challenge for the industry. Utility Model Content

[0005] To address the aforementioned problems, the purpose of this utility model is to provide a valveless negative pressure hot water flash evaporation and electrostatic precipitator system. By integrating a flash evaporation unit, a valveless negative pressure steam turbine unit, a power generation unit, a condensate recovery unit, a back pressure control unit, and a safety protection unit, it eliminates the traditional main steam valve and regulating valve of the steam turbine. The steam turbine adopts a two-stage blade high enthalpy drop structure, which can be automatically started without external force by 30kPa(a)~50kPa(a) negative pressure saturated steam. The steam intake and speed are controlled by a dual-diameter back pressure regulating valve at the exhaust end. Combined with a dual-redundant safety system of "vacuum breaker valve + frequency converter braking + integrated electric and steam protection", the system can achieve stable unit start-up, precise grid connection, rated power output, and safe emergency shutdown.

[0006] The technical solution adopted in this utility model is as follows:

[0007] This utility model proposes a valveless negative pressure hot water flash evaporation and electrostatic discharge system, comprising a flash evaporation unit, a valveless negative pressure steam turbine unit, a power generation unit, a condensate recovery unit, a back pressure control unit, and a safety protection unit. The flash evaporation unit's input end is connected to waste heat hot water, which is then depressurized and flash-evaporated to generate negative pressure saturated steam. The valveless negative pressure steam turbine unit has no main steam valve or regulating steam valve; its input end is connected to the steam outlet of the flash evaporation unit. The power generation unit is driven by the valveless negative pressure steam turbine unit. The condensate recovery unit is connected to the exhaust end of the valveless negative pressure steam turbine unit. The back pressure control unit is located at the exhaust end of the valveless negative pressure steam turbine unit. The safety protection unit is linked to both the valveless negative pressure steam turbine unit and the power generation unit.

[0008] Furthermore, the flash evaporation unit is a flash evaporator, which generates negative pressure saturated steam with a pressure of 30~50 kPa and waste heat water with a temperature of 90~120℃.

[0009] Furthermore, the negative pressure steam turbine unit without an inlet valve is a steam turbine with a two-stage blade high enthalpy drop structure, adapted to an 11t heavy rotor. Under no external force conditions, it can be driven to run autonomously by 30kPa negative pressure saturated steam.

[0010] Furthermore, the back pressure control unit is a dual-diameter regulating valve combination structure of DN80+DN50. By adjusting the exhaust back pressure, the evaporation rate of the flash unit and the steam inlet rate of the turbine are changed, thereby achieving precise speed control.

[0011] Furthermore, the safety protection unit includes a vacuum rupture module, a frequency converter braking module, and an integrated electric and steam protection module; the vacuum rupture module consists of two DN500 large-diameter vacuum rupture valves, which break the system negative pressure within 3 seconds after receiving a shutdown signal; the frequency converter braking module is integrated with the generator unit to accelerate the unit's coasting shutdown; the integrated electric and steam protection module includes electrical overspeed protection, low lubricating oil pressure protection, shaft vibration protection, and axial displacement protection.

[0012] Furthermore, the condensate recovery unit includes a condenser and a condensate pump; the condenser is connected to the exhaust end of the steam turbine to condense the exhaust steam into liquid water; the condensate pump pressurizes the condensed liquid water and sends it back to the waste heat hot water system without working fluid loss.

[0013] Furthermore, the power generation unit is an asynchronous generator, equipped with a soft start module, which precisely pulls the turbine speed to the rated speed of 3000 rpm to complete grid connection.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. This utility model innovatively eliminates the main steam valve and regulating steam valve of the steam turbine, and with the two-stage blade high enthalpy drop structure, it successfully solves the industry problem that negative pressure steam cannot drive heavy rotor to do work, realizes the direct power generation of waste heat from low-grade hot water at 90~120℃, fills the technical gap of efficient waste heat recovery at this energy level, and significantly improves the energy utilization level compared with the traditional mode of only heat exchange and reuse.

[0016] 2. This utility model adopts a back pressure regulation speed control scheme to replace the traditional steam inlet valve regulation method. It has fast speed control response and high precision, and can realize stable warm-up of unit speed and precise grid connection, ensuring stable output of rated power, low power generation self-consumption, strong operational reliability, and controllable power generation cost of the unit.

[0017] 3. This utility model constructs a dual-redundant safety protection system, with the vacuum breaker valve quickly breaking the negative pressure, the frequency converter braking, and the combined action of the electric and steam protection, which completely solves the safety hazards of emergency shutdown of the unit under the condition of no steam inlet valve. The start-up and shutdown operation is safe and controllable, meeting the requirements of long-term stable operation in industry.

[0018] 4. This utility model adopts a closed-loop working fluid design, with no working fluid loss. After being put into use, it can significantly reduce the water resources required for waste heat hot water cooling and the energy consumption of the cooling system, and has significant energy-saving and water-saving benefits.

[0019] 5. The overall solution of this utility model has strong adaptability and does not require major modification to the existing waste heat system. It can be directly promoted to low-grade waste heat recovery scenarios in multiple industries such as petrochemical and chemical industries, helping enterprises to save energy and reduce carbon emissions, reduce the cost of purchased electricity, and has outstanding economic benefits, environmental benefits and industry demonstration effect. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a negative pressure hot water flash evaporation electrostatic system without a steam inlet valve proposed in this utility model.

[0021] In the attached drawings, the following labels are used: 1-flash evaporator; 2-steam turbine; 3-asynchronous generator; 4-condenser; 5-condensate pump; 6-hot water pump; 7-vacuum pump. Detailed Implementation

[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] It should be noted that in the description of this utility model, the terms "upper", "lower", "top", "bottom", "one side", "the other side", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not mean that the device or component must have a specific orientation, or be constructed and operated in a specific orientation.

[0024] See appendix Figure 1 The present invention proposes a valveless negative pressure hot water flash evaporation and electrostatic system, which includes a flash evaporation unit, a valveless negative pressure steam turbine unit, a power generation unit, a condensate recovery unit, a back pressure control unit, and a safety protection unit.

[0025] The flash evaporator 1 has waste heat hot water connected to its input end, which is then depressurized and flash-evaporated to generate negative pressure saturated steam. Its output end is connected to a hot water outlet pipe via a hot water pump 6. In this invention, the flash evaporation unit is the flash evaporator 1, which generates negative pressure saturated steam at a pressure of 30-50 kPa(a), and the waste heat hot water at a temperature of 90-120°C.

[0026] The negative pressure steam turbine unit without an inlet valve is a steam turbine 2 with a two-stage blade high enthalpy drop structure, adapted to an 11t heavy rotor. Under no external force, it can be driven to run autonomously by 30kPa(a) negative pressure saturated steam. The steam turbine 2 has no main steam valve or regulating steam valve. Its input end is connected to the steam outlet of the flash evaporator 1, receiving negative pressure saturated steam and expanding to do work.

[0027] The power generation unit is an asynchronous generator 3, equipped with a soft start module, which can precisely drive the turbine 2 to the rated speed of 3000 rpm to complete grid connection; the asynchronous generator 3 is connected to the output end of the turbine 2 for converting mechanical energy into electrical energy.

[0028] The condensate recovery unit includes a condenser 4 and a condensate pump 5. The condenser 4 is connected to the exhaust end of the steam turbine 2 and flash evaporator 1, and is used to condense the exhaust steam into liquid water. The condensate pump 5 is located between the output end of the condenser 4 and the hot water outlet pipe, and is used to pressurize and return the condensed liquid water to the waste heat hot water system, forming a closed loop of working fluid and ensuring no working fluid loss. A vacuum pump 7 is installed on one side of the condenser 4, connected to a vacuum pipeline.

[0029] The back pressure control unit is located at the exhaust end of the turbine 2 and is used to adjust the back pressure of the unit to control the steam intake and speed. In this utility model, the back pressure control unit adopts a dual-diameter regulating valve combination structure of DN80+DN50. By adjusting the exhaust back pressure, the evaporation rate of the flash unit and the steam intake of the turbine are changed, thereby achieving precise speed control.

[0030] The safety protection unit is linked with the steam turbine 2 and the asynchronous generator 3 to achieve emergency protection for the unit. In this invention, the safety protection unit includes a vacuum rupture module, a frequency converter braking module, and an integrated electric and steam protection module. The vacuum rupture module consists of two DN500 large-diameter vacuum rupture valves, which break the system negative pressure within 3 seconds after receiving a shutdown signal. The frequency converter braking module is integrated with the generator unit to accelerate the unit's coasting shutdown. The integrated electric and steam protection module includes electrical overspeed protection, low lubricating oil pressure protection, shaft vibration protection, and axial displacement protection.

[0031] The flash evaporation-electricity system proposed in this utility model integrates a flash evaporation unit, a negative pressure steam turbine unit without an inlet valve, a power generation unit, a condensate recovery unit, a back pressure control unit, and a safety protection unit. It eliminates the traditional main steam valve and regulating valve of the steam turbine. The steam turbine 2 adopts a two-stage blade high enthalpy drop structure, which can be automatically started without external force by saturated steam with a negative pressure of 30kPa(a)~50kPa(a). The steam intake and speed are controlled by the dual-diameter back pressure regulating valve at the exhaust end. With the dual redundancy safety system of "vacuum breaker valve + frequency converter braking + electric steam integrated protection", the unit can achieve stable start-up, precise grid connection, rated power output, and safe emergency shutdown.

[0032] The control principle of this utility model is as follows:

[0033] Start-up control: Start the vacuum pump of the condensate recovery unit to reduce the condenser pressure. The waste heat hot water enters the flash unit to reduce the pressure and flash, generating negative pressure saturated steam which enters the negative pressure turbine unit without steam inlet valve. The rotor is driven to rotate autonomously by using the pressure difference between the inlet and outlet steam. The back pressure is adjusted by the back pressure control unit to control the speed to warm up to 2940-2960 rpm.

[0034] The minimum steam flow rate for turbine rotor 2 during startup is 25 t / h, and the startup steam parameters are 30 kPa(a) and 89 ℃.

[0035] Grid connection control: Start the soft start module of the power generation unit to precisely increase the speed of turbine 2 to the rated value of 3000 rpm, complete the automatic synchronous grid connection, and adjust the back pressure to increase the steam intake within 30 seconds after grid connection to achieve positive power output.

[0036] Power regulation: After grid connection, the exhaust back pressure is continuously adjusted through the back pressure regulation unit to change the steam expansion work efficiency and maintain the stable output of the unit's rated power.

[0037] Shutdown protection: Upon receiving a shutdown signal, the safety protection unit immediately activates, the vacuum breaking module breaks the negative pressure within 3 seconds, the frequency converter braking module initiates auxiliary shutdown, and the electric steam integrated protection module monitors the entire process until the unit is completely shut down.

[0038] During shutdown, the integrated electric and steam protection module monitors parameters in real time. When the speed exceeds the rated value by 10%, the lubricating oil pressure is lower than 0.08MPa, the shaft vibration exceeds 0.1mm, or the axial displacement exceeds 0.8mm, a forced shutdown command is triggered.

[0039] This invention can adapt to the flash evaporation power demand of waste heat hot water at 90~120℃, realize the direct conversion of low-grade waste heat into electrical energy, greatly improve the waste heat utilization efficiency, reduce cooling energy consumption and water resource consumption, and can be widely used in low-grade waste heat recovery scenarios in high-energy-consuming industries such as petrochemical and chemical industries.

[0040] The present invention will be further described below through specific embodiments:

[0041] I. Key System Parameters

[0042] Flash evaporator 1: Effective flash volume 170m³ 3 The inlet water temperature is 95℃±2℃, the output saturated steam temperature is 81℃, the inlet steam pressure is -50kPa, and the steam is directly connected to the turbine inlet end via a direct flange.

[0043] Steam turbine 2: Single-stage impulse type, rated speed 3000r / min, inlet steam pressure -50kPa, inlet steam temperature 81℃, exhaust steam pressure ≈ -90kPa, exhaust steam temperature 48℃, rated power 4000kW; there are no inlet steam control valves or quick-closing valves at the inlet end, and no inlet side flow and pressure control components.

[0044] Asynchronous generator 3; rated power 4000kW, rated frequency 50Hz, rigidly connected to the rotor of steam turbine 2, adapted to a rated speed of 3000r / min, meeting the requirements for grid-connected power supply.

[0045] Condenser 4; turbine exhaust end adapter equipment, which maintains a stable exhaust pressure of ≈-90kPa and an exhaust condensation temperature of about 48℃ during normal operation. The condensate is returned to the hot water pipe network for recycling.

[0046] Two exhaust vacuum regulating valves (dedicated to speed control), DN50, electrically adjustable type, are used to precisely control the pressure difference between the steam turbine inlet and outlet to achieve smooth speed increase and stable control of the rated speed of 3000r / min.

[0047] Two emergency vacuum breaker valves (dedicated for fault shutdown), DN500, quick-opening and closing type, are used to instantly break the system vacuum under fault conditions to achieve emergency shutdown of the unit.

[0048] II. System Startup Control Implementation Steps

[0049] This embodiment is for a structure without an inlet steam valve. It relies entirely on the exhaust-side vacuum valve to regulate the inlet and exhaust steam pressure difference (inlet -50kPa, exhaust -90kPa, effective power pressure difference approximately 40kPa) to complete startup, acceleration, speed stabilization, and grid connection. The specific steps are as follows:

[0050] Pre-start checks: Confirm that there are no leaks in the seals of all components, including flash evaporator 1, steam turbine 2, asynchronous generator 3, and condenser 4; that the two DN50 vacuum regulating valves are fully closed and the two DN500 emergency vacuum breaker valves are fully closed and interlocked; that the DCS system speed, pressure, and temperature monitoring modules are calibrated and qualified, and that the hot water circulation loop is unobstructed.

[0051] Hot water pre-circulation: Start the hot water delivery system and introduce 95℃±2℃ hot water into flash evaporator 1 to maintain a stable water temperature inside the flash evaporator. Circulate for 20 minutes to ensure a uniform temperature field inside flash evaporator 1 and meet the flash evaporation conditions.

[0052] Stepwise vacuum establishment: Start the vacuum system of condenser 4, first pump the pressure inside condenser 4 to -90kPa and stabilize it. The vacuum degree is transmitted through the pipeline to the exhaust end, inlet end and flash evaporator 1 of turbine 2 in sequence, and finally form a stable pressure gradient of "flash evaporator 1 (-50kPa) - turbine 2 (inlet -50kPa / exhaust -90kPa) - condenser 4 (-90kPa)" to ensure that turbine 2 has effective power to do work.

[0053] Differential pressure start-up and phased speed increase: The opening of the two DN50 vacuum regulating valves is slowly adjusted through the DCS system to fine-tune the vacuum at the exhaust end of the turbine 2, gradually increasing the effective pressure difference between the inlet and outlet steam, and driving the turbine 2 rotor to start up; when the rotor speed reaches 1000 r / min, the pressure is stabilized and warmed up for 25 minutes, and the bearing temperature and unit vibration are monitored to ensure they meet the standards; the opening of the DN50 valve is further adjusted to increase the speed to 2800 r / min in stages, and the pressure is stabilized and warmed up again for 15 minutes, and the pressure difference between the inlet and outlet steam is kept stable in the range of 35-45 kPa throughout the process.

[0054] Precise speed stabilization and grid connection: After the speed reaches 2800 r / min, the DN50 vacuum regulating valve is finely adjusted (single adjustment range ≤0.5%). The turbine inlet and outlet steam pressure difference is maintained through closed-loop control, and the speed is precisely locked at 3000 r / min with a speed control accuracy of ±5 r / min. The output voltage and frequency of asynchronous generator 3 are confirmed to meet the grid connection conditions. The grid connection operation is performed to complete the start-up process of the entire system. After grid connection, the rated power of 4000 kW is stably output.

[0055] III. System Shutdown Control Implementation Steps

[0056] Shutdown control is divided into two categories: normal shutdown and emergency shutdown due to fault. Both are completed by relying on the vacuum valve on the exhaust side, without the need for any cut-off or control components on the steam inlet side.

[0057] 1. Normal shutdown procedure: First, gradually reduce the load of asynchronous generator 3 to 0 and disconnect the grid connection switch; slowly open the two DN50 vacuum regulating valves through the DCS system to gradually reduce the steam pressure difference between the inlet and outlet of turbine 2, so that the speed drops smoothly from 3000r / min to 0; after the speed reaches zero, shut down the vacuum system, stop the hot water circulation, and complete the shutdown. The whole process is without impact and without equipment damage.

[0058] 2. Emergency Shutdown Procedure: When turbine 2 experiences abnormal operating conditions such as over-vibration, over-temperature, or electrical / steam faults in asynchronous generator 3, the DCS system instantly triggers a chain signal, and two DN500 emergency vacuum breaker valves quickly and fully open, instantly breaking the approximately -90kPa vacuum inside condenser 4 and turbine 2, causing the inlet and outlet steam pressure difference to disappear immediately; the turbine 2 rotor loses its power and quickly coasts to a stop, with a total response time of ≤2 seconds, preventing further damage to the equipment and ensuring the safety of the unit and personnel.

[0059] IV. Implementation Results Verification

[0060] The unit corresponding to this embodiment has been verified through multiple on-site start-ups, shutdowns, and long-term operation. It can stably maintain a pressure difference of -50kPa for inlet steam and -90kPa for exhaust steam, continuously outputting 4000kW rated power. The grid connection speed control at 3000r / min is precise, with a 100% grid connection success rate. Normal shutdown is smooth and shock-free, and emergency shutdown response is rapid and protection is reliable. It fully achieves the technical goal of low-grade hot water flash evaporation without inlet steam valve regulation, filling the gap in similar technologies.

[0061] Matters not covered in this utility model are common knowledge.

[0062] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A negative pressure hot water flash steam power system without admission valve, characterized in that: The system includes a flash evaporation unit, a valveless negative pressure steam turbine unit, a power generation unit, a condensate recovery unit, a back pressure control unit, and a safety protection unit. The flash evaporation unit receives waste heat hot water at its input end, which is then depressurized and flash-evaporated to generate negative pressure saturated steam. The valveless negative pressure steam turbine unit has no main steam valve or regulating valve; its input end is connected to the steam outlet of the flash evaporation unit. The power generation unit is driven by the valveless negative pressure steam turbine unit. The condensate recovery unit is connected to the exhaust end of the valveless negative pressure steam turbine unit. The back pressure control unit is located at the exhaust end of the valveless negative pressure steam turbine unit. The safety protection unit is linked to both the valveless negative pressure steam turbine unit and the power generation unit. The negative pressure steam turbine unit without steam inlet valve is a steam turbine with a two-stage blade high enthalpy drop structure, which is suitable for an 11t heavy rotor. Under no external force conditions, it can be driven to run autonomously by 30kPa negative pressure saturated steam. The back pressure control unit is a dual-diameter regulating valve combination structure of DN80+DN50. By adjusting the exhaust back pressure, the evaporation rate of the flash unit and the steam inlet rate of the turbine are changed, thereby achieving precise speed control. The safety protection unit includes a vacuum breaking module, a frequency converter braking module, and an integrated electric and steam protection module. The vacuum breaking module consists of two DN500 large-diameter vacuum breaking valves, which break the negative pressure in the system within 3 seconds after receiving a shutdown signal. The frequency converter braking module is integrated with the generator unit to accelerate the unit's coasting shutdown. The integrated electric and steam protection module includes electrical overspeed protection, low lubricating oil pressure protection, shaft vibration protection, and axial displacement protection.

2. A negative pressure hot water flash steam power system without inlet valve according to claim 1, characterized in that, The flash evaporation unit is a flash evaporator, which generates negative pressure saturated steam with a pressure of 30~50kPa and waste heat water with a temperature of 90~120℃.

3. A negative pressure hot water flash steam power system without inlet valve according to claim 1, characterized in that: The condensate recovery unit includes a condenser and a condensate pump; the condenser is connected to the exhaust end of the steam turbine and condenses the exhaust steam into liquid water; the condensate pump pressurizes the condensed liquid water and sends it back to the waste heat hot water system without working fluid loss.

4. The system according to claim 1, wherein the system is characterized by: The power generation unit is an asynchronous generator, equipped with a soft start module, which precisely pulls the turbine speed to the rated speed of 3000 rpm to complete grid connection.

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