A high-temperature heat pump system

Abstract

The application discloses a high-temperature heat pump system, which comprises a second heat exchanger for heat exchange with waste water, a compressor, a first heat exchanger, a throttling device and the second heat exchanger which are sequentially connected to form a loop, circulating medium flows in the loop, the outlet end of the compressor is further connected with the inlet end of the second heat exchanger through an adjusting valve, and a third heat exchanger is arranged between the adjusting valve and the compressor; a three-way valve is connected to the waste water outlet pipeline of the second heat exchanger, and the third port of the three-way valve is communicated with the water inlet pipeline. The application provides a method capable of realizing stepless energy regulation, meeting long-term stable and reliable operation of the high-temperature heat pump, improving system reliability and realizing stepless energy regulation of the unit.

Description

Technical Field

[0001] This invention relates to high-temperature heat pump systems, specifically a high-temperature heat pump system with stepless quantity adjustment. Background Technology

[0002] High-temperature heat pump technology is a groundbreaking technology that directly recovers low-grade industrial waste heat and converts it into high-grade energy, which can then be reused in other production processes within an enterprise. Under the current national call for energy conservation and emission reduction, it is receiving increasing attention from petrochemical companies.

[0003] In the reboiling unit distillation process of typical petrochemical enterprises, single-stage compression high-temperature heat pump technology can be used. This technology utilizes a heat pump circulating working fluid at approximately 120°C to heat lean amine solution into rich amine solution, while the low-temperature heat source comes from wastewater discharged during production at 60-70°C. This technology and equipment, which uses waste heat to replace the high-temperature heat source, is a typical example of achieving both energy conservation and emission reduction. To meet the continuous production and flexible equipment requirements of petrochemical enterprises, the supporting high-temperature heat pump units are also required to achieve 50-100% capacity regulation. Due to the high operating temperature of high-temperature heat pumps, currently available conventional energy regulation valves cannot meet the reliability requirements for long-term operation at temperatures above 120°C.

[0004] The original system, such as Figure 1 As shown, the high-temperature, high-pressure working fluid discharged from compressor 1 is divided into two paths. One path enters the first heat exchanger 2, where it is condensed and then passes through the throttling device 3. After pressure reduction, it becomes a low-temperature, low-pressure gas-liquid mixture that flows into the second heat exchanger 4. In the second heat exchanger 4, the working fluid absorbs heat from the wastewater and evaporates into a low-temperature, low-pressure gas, which is then drawn into compressor 1 to complete the entire refrigeration cycle. The other path of working fluid discharged from compressor 1 is connected to the inlet of the second heat exchanger 4 through a regulating valve 7. This valve is used to regulate the mass flow rate of the working fluid entering the first heat exchanger 2 and also affects the heat absorbed by the second heat exchanger 4 from the wastewater. The drawback of this system is:

[0005] 1) The exhaust temperature of the compressor's circulating working fluid is around 130℃, which is higher than the general valve component's upper temperature limit requirement of 120℃, which can easily cause valve component seals to fail.

[0006] 2) Under load elastic fluctuations, the heat extracted from the wastewater by the second heat exchanger will also fluctuate, which will cause changes in the working fluid pressure in the second heat exchanger. This may cause the working fluid pressure in the second heat exchanger to exceed the maximum operating pressure allowed by the compressor, resulting in compressor overload protection and the entire system failing to operate. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a high-temperature heat pump system that can operate stably.

[0008] To address the aforementioned problems, this invention provides a high-temperature heat pump system, comprising a second heat exchanger for exchanging heat with wastewater, a compressor, a first heat exchanger, a throttling device, and the second heat exchanger connected in sequence to form a loop, wherein a circulating medium flows within the loop, and the outlet end of the compressor is connected to the inlet end of the second heat exchanger via a regulating valve, wherein a third heat exchanger is provided between the regulating valve and the compressor; a three-way valve is connected to the wastewater outlet pipe of the second heat exchanger, and the third port of the three-way valve is connected to the inlet pipe.

[0009] Preferably, a pressure reducing valve, a third heat exchanger, and a regulating valve are sequentially connected between the inlet end of the second heat exchanger and the outlet end of the compressor.

[0010] Preferably, the second heat exchanger is equipped with a pressure sensor for monitoring the pressure of the circulating medium.

[0011] Preferably, the high-temperature heat pump system further includes a control system for adjusting the three-way valve according to the pressure of a pressure sensor.

[0012] This invention provides a method for achieving stepless energy regulation, which meets the requirements for long-term stable and reliable operation of high-temperature heat pumps, can improve system reliability, and realize stepless energy regulation of the unit. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the original heat pump system;

[0014] Figure 2 A schematic diagram of the high-temperature heat pump system provided by the present invention. Detailed Implementation

[0015] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0016] Example

[0017] like Figure 2 As shown, a high-temperature heat pump system provided by the present invention includes a second heat exchanger 4 for exchanging heat with wastewater. A compressor 1, a first heat exchanger 2, a throttling device 3, and the second heat exchanger 4 are sequentially connected to form a loop, in which a circulating medium flows. A branch line is provided between the outlet end of the compressor 1 and the inlet end of the first heat exchanger 2. This branch line is sequentially connected to a pressure reducing valve 6, a third heat exchanger 5, and a regulating valve 7 before connecting to the inlet end of the second heat exchanger 4. A three-way valve 8 is connected to the wastewater outlet pipe of the second heat exchanger 4, and the third port of the three-way valve 8 is connected to the inlet pipe. A pressure sensor for monitoring the pressure of the circulating medium is installed inside the second heat exchanger 4. The high-temperature heat pump system also includes a control system for adjusting the three-way valve 8 according to the pressure from the pressure sensor.

[0018] The working process of the above system is as follows:

[0019] The high-temperature, high-pressure working fluid discharged from the compressor is divided into two streams. One stream enters the first heat exchanger, where it is condensed and then passes through a throttling device to reduce its pressure, becoming a low-temperature, low-pressure gas-liquid mixture that flows into the second heat exchanger. In the second heat exchanger, the working fluid absorbs heat from the wastewater and evaporates into a low-temperature, low-pressure gas, which is then drawn into the compressor to complete the entire refrigeration cycle. The other stream of working fluid discharged from the compressor first passes through a pressure reducing valve and then through a third heat exchanger to be cooled to below 120°C before being connected to the inlet of the second heat exchanger through a regulating valve.

[0020] The three-way valve added between the wastewater inlet and outlet pipes of the second heat exchanger can adjust the flow rate of wastewater entering the second heat exchanger according to the pressure of the circulating working medium in the second heat exchanger, thereby reducing the heat taken by the working medium from the wastewater and further reducing the pressure of the circulating working medium in the second heat exchanger.

[0021] The advantages of the above system are:

[0022] 1) Since the equipment must first meet the process-side hot water heating temperature requirement of 115℃, the working fluid pressure in the first heat exchanger must be maintained above a certain level. There is a one-to-one positive correlation between the circulating working fluid pressure and temperature; higher working fluid pressure corresponds to a higher saturation temperature. If the high-temperature working fluid cannot be cooled to the reasonable operating temperature range allowed by the valves, the working fluid pressure is reduced after passing through the pressure reducing valve, changing from saturated steam to superheated steam. Then, the working fluid can be cooled to below 120℃ through the third heat exchanger. The flow rate of the working fluid entering the second heat exchanger can then be steplessly adjusted within a certain range through the regulating valve. This satisfies the upper temperature limit requirement of the regulating valve and also regulates the heat output of the entire system. The third heat exchanger can be air-cooled or water-cooled; water cooling is more effective.

[0023] 2) Under load fluctuations, the heat extracted from the wastewater by the second heat exchanger will also fluctuate, causing changes in the working fluid pressure within the second heat exchanger. The three-way valve, based on the working fluid pressure, uses internal PID calculations to adjust the wastewater flow rate through the second heat exchanger. When the working fluid pressure increases, the wastewater flow rate into the second heat exchanger is reduced to prevent excessive pressure from causing compressor overload protection.

Claims

1. A high-temperature heat pump system comprising a second heat exchanger (4) for exchanging heat with waste water, a compressor (1), a first heat exchanger (2), a throttling device (3), the second heat exchanger (4) being connected in series to form a circuit in which a circulating medium flows, the outlet end of the compressor (1) being further connected to the inlet end of the second heat exchanger (4) through a regulating valve (7), characterized in that, The adjusting valve (7) is provided with a third heat exchanger (5) between the compressor (1); the second heat exchanger (4) is connected with a three-way valve (8) on the outlet pipeline of waste water, the third port of the three-way valve (8) is communicated with the inlet pipeline; the inlet end of the second heat exchanger (4) is sequentially connected with a pressure reducing valve (6), a third heat exchanger (5) and an adjusting valve (7) between the outlet end of the compressor (1). ​ 2. The high temperature heat pump system of claim 1, wherein, The second heat exchanger (4) is provided with a pressure sensor for monitoring the pressure of the circulating medium.

3. The high temperature heat pump system of any of claims 1-2, wherein, Further comprising a control system for adjusting the three-way valve (8) according to the pressure of the pressure sensor.

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