A circulating water energy-saving system based on multi-mode regulation

Abstract

The utility model provides a kind of based on the energy-saving system of circulating water multi-mode regulation and control, comprising: circulating water supply main pipe;Circulating water return main pipe;Base load pump group, the outlet of base load pump group is connected to circulating water supply main pipe, and base load pump group includes centrifugal pump, back pressure turbine for driving centrifugal pump and gear box being arranged between centrifugal pump and back pressure turbine;Peak shaving pump group, peak shaving pump group is arranged in parallel with base load pump group, and the outlet of peak shaving pump group is connected to circulating water supply main pipe, and peak shaving pump group includes motor-driven pump, motor for driving motor-driven pump and frequency conversion speed regulating unit electrically connected with motor;Multi-mode regulation and control unit, the output end of multi-mode regulation and control unit is electrically connected with back pressure turbine and frequency conversion speed regulating unit respectively.The utility model solves the problem of energy waste in the full operating condition range caused by excessive design margin in the prior art circulating water system.

Description

Technical Field

[0001] This utility model relates to a circulating water system, specifically a circulating water energy-saving system based on multi-mode regulation, belonging to the field of chemical equipment technology. Background Technology

[0002] In large-scale petrochemical plants such as propane dehydrogenation (PDH) units, the circulating water system is a critical utility unit for ensuring safe and stable production operation. However, during the engineering design phase, due to considerations of operational safety and future expansion, design units typically allow for significant design margins for equipment such as circulating water pumps. This results in the actual operating conditions of the system being far lower than the design conditions after the plant is built and operating stably.

[0003] Therefore, in actual operation, circulating water pumps often operate outside their peak efficiency (BEP) range, resulting in extremely low utilization efficiency of driving energy (such as high-pressure steam or electricity). Furthermore, the production load of chemical plants is not constant, experiencing various operating conditions including start-up, shutdown, full load, and load reduction. Traditional circulating water systems typically employ a crude mode of operation with standby switching, failing to adjust the circulating water supply according to real-time changes in production load. This leads to even more pronounced energy waste during low-load operation. Utility Model Content

[0004] Based on the above background, the purpose of this utility model is to provide a circulating water energy-saving system based on multi-mode regulation, which solves the problem of energy waste in the existing circulating water system due to excessive design margin in the entire operating range.

[0005] To achieve the above-mentioned objectives, this utility model provides the following technical solution:

[0006] A circulating water energy-saving system based on multi-mode regulation includes:

[0007] Main circulating water supply pipe;

[0008] Circulating water return main pipe;

[0009] A base-loaded pump set, the outlet of which is connected to the circulating water supply main pipe, the base-loaded pump set including a centrifugal pump, a back-pressure steam turbine for driving the centrifugal pump, and a gearbox disposed between the centrifugal pump and the back-pressure steam turbine;

[0010] A peak-shaving pump set is provided in parallel with the base-load pump set. The outlet of the peak-shaving pump set is connected to the circulating water supply main pipe. The peak-shaving pump set includes a motor-driven pump, a motor for driving the motor-driven pump, and a variable frequency speed control unit electrically connected to the motor.

[0011] A multi-mode control unit, the output of which is electrically connected to the back-pressure steam turbine and the variable frequency speed control unit respectively.

[0012] By combining base load pumps and peak load pumps in parallel, the base load pumps meet the demand for normal high loads and are driven by steam turbines that are more energy efficient and can utilize low-value steam, thus achieving energy saving under base loads. The peak load pumps, on the other hand, utilize the flexible adjustment characteristics of the variable frequency speed control unit to meet the demand during load fluctuations or low loads, thereby avoiding energy waste.

[0013] Preferably, the input terminal of the multi-mode control unit is used to electrically connect to a feedback signal sensor installed on the circulating water supply main pipe or the circulating water return main pipe.

[0014] Preferably, the feedback signal sensor includes a total flow sensor installed on the circulating water supply main pipe.

[0015] Preferably, the feedback signal sensor includes a water supply pressure sensor installed on the circulating water supply main pipe and / or a return water pressure sensor installed on the circulating water return main pipe.

[0016] Preferably, the feedback signal sensor includes a supply water temperature sensor installed on the circulating water supply main pipe and a return water temperature sensor installed on the circulating water return main pipe.

[0017] Preferably, an outlet check valve and an outlet manual isolation valve are provided on the pipeline connecting the centrifugal pump to the circulating water supply main pipe and on the pipeline connecting the motor-driven pump to the circulating water supply main pipe.

[0018] Preferably, the energy-saving circulating water system based on multi-mode regulation also includes a circulating water tank, and the suction inlets of the centrifugal pump and the motor-driven pump are both connected to the circulating water tank.

[0019] Preferably, the energy-saving circulating water system based on multi-mode regulation also includes a cooling tower, the inlet of which is connected to the circulating water return main pipe, and the outlet of which is connected to the circulating water pool.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This utility model discloses a circulating water energy-saving system based on multi-mode regulation. By combining a base-load pump set and a peak-shaving pump set, it solves the problem that a single type of pump set cannot take into account the efficiency of all operating conditions. Under normal high load, only the centrifugal pump driven by the steam turbine, which is customized for this operating condition, operates, resulting in the lowest energy consumption. During low load or start-up and shutdown, only the motor-driven pump driven by the variable frequency speed control unit operates, providing flow as needed. This combination of modes enables the system to operate in the high-efficiency range under all operating conditions, including 70%-100% load, below 50% load, and peak load.

[0022] The base-mounted pump set of this utility model is driven by a back-pressure steam turbine, which can directly utilize the surplus medium and high pressure steam of the chemical plant and send the low pressure steam after work to the downstream for use, realizing the cascade utilization of energy. The peak-shaving pump set is driven by electricity. The coexistence of pump sets driven by two different energy sources greatly improves the ability of the circulating water system to cope with fluctuations in steam or power supply. Attached Figure Description

[0023] 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 only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a circulating water energy-saving system based on multi-mode control according to this utility model;

[0025] In the diagram: 1. Main circulating water supply pipe; 2. Main circulating water return pipe; 3. Centrifugal pump; 4. Back pressure turbine; 5. Gearbox; 6. Motor-driven pump; 7. Motor; 8. Variable frequency speed control unit; 9. Total flow sensor; 10. Supply water pressure sensor; 11. Return water pressure sensor; 12. Return water temperature sensor; 13. Supply water temperature sensor; 14. Circulating water tank; 15. Cooling tower; 16. Multi-mode control unit. Detailed Implementation

[0026] The technical solution of this utility model will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of this utility model is not limited to the following embodiments, and any modifications and / or alterations made to this utility model will fall within the protection scope of this utility model.

[0027] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the field. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0028] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following detailed description, many specific details are set forth to facilitate explanation and provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.

[0029] like Figure 1 As shown, an embodiment of this utility model discloses a circulating water energy-saving system based on multi-mode control, including a circulating water supply main pipe 1, a circulating water return main pipe 2, a base load pump group, a peak-shaving pump group, and a multi-mode control unit 16.

[0030] The outlet of the base-mounted pump set is connected to the circulating water supply main 1. The base-mounted pump set includes a centrifugal pump 3, a back-pressure steam turbine 4 for driving the centrifugal pump 3, and a gearbox 5 located between the centrifugal pump 3 and the back-pressure steam turbine 4. High-pressure steam of 4.0 MPa enters the back-pressure steam turbine 4 to do work, driving the centrifugal pump 3 to run. The low-pressure steam after doing work is discharged to the downstream low-pressure steam pipeline network or the waste heat generator set 7.

[0031] The peak-shaving pump set is connected in parallel with the base-load pump set, and the outlet of the peak-shaving pump set is connected to the circulating water supply main pipe 1. The peak-shaving pump set includes a motor-driven pump 6, a motor 7 for driving the motor-driven pump 6, and a variable frequency speed control unit 8 electrically connected to the motor 7. The variable frequency speed control unit 8 can smoothly adjust the speed of the motor 7 according to control commands, thereby controlling the output flow and pressure of the motor-driven pump 6.

[0032] The output terminals of the multi-mode control unit 16 are electrically connected to the back-pressure steam turbine 4 and the variable frequency speed control unit 8, respectively. The input terminals of the multi-mode control unit 16 are used to electrically connect to feedback signal sensors installed on the circulating water supply main pipe 1 or the circulating water return main pipe 2. Specifically, the feedback signal sensors include a total flow sensor 9 installed on the circulating water supply main pipe 1, a supply water pressure sensor 10 installed on the circulating water supply main pipe 1, a return water pressure sensor 11 installed on the circulating water return main pipe 2, a supply water temperature sensor 13 installed on the circulating water supply main pipe 1, and a return water temperature sensor 12 installed on the circulating water return main pipe 2.

[0033] Specifically, the multi-mode control unit 16 is an advanced control module in a PLC or DCS. It receives the main production load from the PDH unit DCS as a feedforward signal, as well as feedback signals from the aforementioned multiple sensors. Based on these input signals, the multi-mode control unit 16 issues start / stop control commands to the back-pressure turbine 4 and speed control commands to the variable frequency speed control unit 8 according to preset control logic.

[0034] To protect equipment safety and facilitate maintenance, outlet check valves and manual outlet isolation valves are installed on the pipelines connecting centrifugal pump 3 to the circulating water supply main 1, and on the pipelines connecting motor-driven pump 6 to the circulating water supply main 1. The outlet check valve prevents backflow of water from impacting and causing the pump to stop in reverse during single-pump operation. The manual outlet isolation valve is used to safely physically isolate the pump unit from the main system during equipment maintenance.

[0035] The multi-mode controlled circulating water energy-saving system also includes a circulating water tank 14 and a cooling tower 15. The suction inlets of the centrifugal pump 3 and the motor-driven pump 6 are both connected to the circulating water tank 14. The inlet of the cooling tower 15 is connected to the circulating water return main pipe 2, and the outlet of the cooling tower 15 is connected to the circulating water tank 14. Hot water from the PDH unit user enters the cooling tower 15 for cooling through the circulating water return main pipe 2. The cooled water then enters the circulating water tank 14, and after being pressurized by the base-load pump set and / or peak-shaving pump set, it is sent back to the user through the circulating water supply main pipe 1, thus completing the cycle.

[0036] The workflow of the multi-mode control-based circulating water energy-saving system is described below.

[0037] When the main production load feedforward signal received by the multi-mode control unit 16 is lower than the preset threshold, or during the start-up / shutdown phase of the unit, it is determined to be a low-demand operating condition. At this time, the base load pump group is kept off, and only the peak-shaving pump group is started. At the same time, based on the feedback from the total flow sensor 9 or the pressure sensor, the speed of the motor 7 is adjusted to a lower level through the variable frequency speed control unit 8 to meet the current circulating water demand with minimal power consumption.

[0038] When the main production load signal is in the normal high load range, it is judged as a normal operating condition. The multi-mode control unit 16 issues a command to start the base-load pump set, and the back-pressure steam turbine 4 drives the centrifugal pump 3 to run at a constant speed, so that its operating condition falls in the highest efficiency range, thereby achieving energy saving. At this time, the peak-shaving pump set remains in a shut-down standby state.

[0039] When the production load exceeds 100% or a temporary peak demand occurs, causing the total flow rate or water supply pressure to fall below the set value, it is judged as a peak demand condition. While maintaining the base load pump group at full load, the multi-mode control unit 16 starts the peak-shaving pump group, and adjusts the speed of the motor-driven pump 6 through the variable frequency speed control unit 8 according to the deviation between the pipeline parameters and the target value, so as to supplement the additional flow and pressure to meet the peak demand.

[0040] This article uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principles of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A circulating water energy-saving system based on multi-mode regulation, characterized in that: This energy-saving circulating water system based on multi-mode regulation includes: Circulating water supply main pipe (1); (2) Circulating water return main pipe; The base pump set has its outlet connected to the circulating water supply main pipe (1). The base pump set includes a centrifugal pump (3), a back pressure turbine (4) for driving the centrifugal pump (3), and a gearbox (5) disposed between the centrifugal pump (3) and the back pressure turbine (4). The peak-shaving pump group is arranged in parallel with the base load pump group. The outlet of the peak-shaving pump group is connected to the circulating water supply main pipe (1). The peak-shaving pump group includes a motor-driven pump (6), a motor (7) for driving the motor-driven pump (6), and a variable frequency speed control unit (8) electrically connected to the motor (7). The multi-mode control unit (16) is electrically connected to the back-pressure steam turbine (4) and the variable frequency speed control unit (8).

2. The circulating water energy-saving system based on multi-mode regulation according to claim 1, characterized in that: The input terminal of the multi-mode control unit (16) is used to electrically connect to the feedback signal sensor installed on the circulating water supply main pipe (1) or the circulating water return main pipe (2).

3. The circulating water energy-saving system based on multi-mode regulation according to claim 2, characterized in that: The feedback signal sensor includes a total flow sensor (9) installed on the circulating water supply main pipe (1).

4. The circulating water energy-saving system based on multi-mode regulation according to claim 2, characterized in that: The feedback signal sensors include a water supply pressure sensor (10) installed on the circulating water supply main pipe (1) and / or a return water pressure sensor (11) installed on the circulating water return main pipe (2).

5. A circulating water energy-saving system based on multi-mode regulation according to claim 2, characterized in that: The feedback signal sensors include a water supply temperature sensor (13) installed on the circulating water supply main pipe (1) and a return water temperature sensor (12) installed on the circulating water return main pipe (2).

6. The circulating water energy-saving system based on multi-mode regulation according to claim 1, characterized in that: An outlet check valve and an outlet manual isolation valve are provided on the pipeline connecting the centrifugal pump (3) to the circulating water supply main pipe (1) and on the pipeline connecting the motor-driven pump (6) to the circulating water supply main pipe (1).

7. A circulating water energy-saving system based on multi-mode regulation according to claim 1, characterized in that: The energy-saving circulating water system based on multi-mode regulation also includes a circulating water tank (14), and the suction ports of the centrifugal pump (3) and the motor-driven pump (6) are connected to the circulating water tank (14).

8. A circulating water energy-saving system based on multi-mode regulation according to claim 7, characterized in that: The energy-saving circulating water system based on multi-mode regulation also includes a cooling tower (15), the inlet of which is connected to the circulating water return main pipe (2), and the outlet of which is connected to the circulating water pool (14).

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