Bypass valve control system for back pressure unit of screw expander

Abstract

The utility model discloses a screw expander backpressure unit bypass valve control system which comprises a steam inlet pipe, a bypass pipe, a quick closing valve, a main adjusting valve, a bypass pressure adjusting valve, a screw expander backpressure unit, a steam exhaust pipe and a steam exhaust pressure gauge, the steam inlet pipe and the steam inlet end of the bypass pipe are connected with a steam inlet, and the bypass pressure adjusting valve is installed on the bypass pipe; the generator is connected with a generator active power meter, the tail end of the steam inlet pipe is connected with the screw expander, a steam exhaust port of the screw expander is connected with one end of the steam exhaust pipe, the tail end of the steam exhaust pipe and the tail end of the bypass pipe are connected with a steam delivery pipe network, and the steam exhaust pressure meter is installed on the steam exhaust pipe. The exhaust steam pressure gauge, the generator active power meter, the bypass pressure regulating valve and the main regulating valve are arranged in an interlocking manner; according to the backpressure state, the system judges the control logic of the main regulating valve, the bypass pressure regulating valve and the like, so that steam enters the backpressure screw expander as much as possible, and the maximum efficiency of power generation and backpressure control are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of screw expander back pressure units, in particular to a screw expander back pressure unit bypass valve control system. Background Art

[0002] Screw expanders are designed to optimize thermal energy utilization and improve system efficiency. In a back-pressure screw expander, after steam is generated in the screw expander to generate electricity, it is not discharged directly into the condenser. Instead, it is maintained at a certain pressure and temperature so that it can be used for heating or other industrial purposes. With rising energy costs and increasingly stringent environmental regulations, companies are beginning to seek ways to improve energy efficiency. Back-pressure screw expanders can maximize steam utilization and convert waste heat into effective heat and electricity by maintaining a certain back pressure.

[0003] The original screw expander back pressure unit system has the following disadvantages:

[0004] (1)Reference Figure 1 As shown, in the original system design, the back-pressure screw expander uses the exhaust pressure (PT102) as the only back-pressure control interlock point. During the operation of the back-pressure screw expander, the main steam inlet valve (MV101) is adjusted in real time according to the change of the exhaust pressure, thereby realizing the control of the back pressure. However, the screw expander has a minimum steam consumption, that is, the amount of steam required to maintain the normal operation of the generator to generate electricity. When the system detects that the exhaust pressure is too high, the main regulating valve closes the valve according to the PID closed-loop control. At the same time, because the steam flow entering the back-pressure screw expander is reduced, the pressure is reduced, and the power generation power will also decrease. Finally, the generator enters the reverse power operation state, triggering a protection shutdown, and thus failing to fully utilize the system steam to the maximum efficiency.

[0005] (2) In the original system design, due to the large steam pipeline, the valve diameter is usually greater than DN300. The control accuracy of the main regulating valve is ±0.5%, which also causes large fluctuations in the subsequent back pressure system. It cannot be adjusted quickly and requires repeated adjustments to reach the back pressure set value.

[0006] (3) In the original system design, the bypass pressure regulating valve (PV201) of the system was manually controlled based on the back pressure and the power of the generator. It could not be linked with the main regulating valve, and thus could not achieve the optimal power generation. Utility Model Content

[0007] The utility model aims to provide a bypass valve control system for a back pressure unit of a screw expander.

[0008] The above technical objectives of the present invention are achieved through the following technical solutions:

[0009] A screw expander back pressure unit bypass valve control system, comprising a steam inlet pipe, a bypass pipe, a quick-closing valve, a main regulating valve, a bypass pressure regulating valve, a screw expander back pressure unit, an exhaust pipe and an exhaust pressure gauge, wherein the steam inlet ends of the steam inlet pipe and the bypass pipe are connected to the steam inlet, the quick-closing valve and the main regulating valve are installed on the steam inlet pipe, and the bypass pressure regulating valve is installed on the bypass pipe; the screw expander back pressure unit comprises a screw expander, a reducer and a generator, the generator is connected to the screw expander through the reducer, the generator is connected to a generator active power meter, the end of the steam inlet pipe is connected to the screw expander, the exhaust port of the screw expander is connected to one end of the exhaust pipe, the ends of the exhaust pipe and the bypass pipe are connected to an external steam pipeline network, the exhaust pressure gauge is installed on the exhaust pipe, and the exhaust pressure gauge, the generator active power meter, the bypass pressure regulating valve and the main regulating valve are interlocked.

[0010] Furthermore, a fine-tuning bypass is provided on the steam inlet pipe between the quick-closing valve and the main regulating valve, and a bypass fine-tuning valve is installed on the fine-tuning bypass. The bypass fine-tuning valve is interlocked with the exhaust pressure gauge, the generator active power meter, the bypass pressure regulating valve and the main regulating valve.

[0011] Furthermore, the steam inlet pipe is a DN300 pipe, and the fine-tuning bypass pipe is a DN65 pipe.

[0012] Furthermore, a steam inlet pressure gauge is installed on the steam inlet pipe, and the steam inlet pressure gauge is installed on one end of the steam inlet pipe close to the screw expander.

[0013] In summary, the present invention has the following beneficial effects:

[0014] (1) The utility model interlocks the bypass fine-tuning valve with the exhaust pressure gauge, the generator active power meter, the bypass pressure regulating valve and the main regulating valve. According to the state of the back pressure, the system can determine the control logic of the main regulating valve and the bypass pressure regulating valve, so that steam can enter the back pressure screw expander as much as possible to achieve the maximum efficiency of power generation and the control of back pressure.

[0015] (2) A bypass fine-tuning valve is added to the system design. When the back pressure is too high, the fine-tuning valve is interlocked and controlled first to accurately control the amount of steam entering the back pressure screw compressor, so that the system can reach the system back pressure value faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the original screw expander back pressure unit bypass valve control system diagram;

[0017] Figure 2 This is a diagram of a bypass valve control system for a back pressure unit of a screw expander of the present utility model. DETAILED DESCRIPTION

[0018] The following is a further detailed description of the present invention in conjunction with the accompanying drawings, clearly and completely describing the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] A screw expander back pressure unit bypass valve control system, such as Figure 2 As shown, it includes a steam inlet pipe, a bypass pipe, a quick-closing valve (KV101), a main regulating valve (MV101), a bypass pressure regulating valve (PV201), a screw expander back pressure unit, an exhaust pipe and an exhaust pressure gauge (PT102), wherein the steam inlet ends of the steam inlet pipe and the bypass pipe are connected to the steam inlet, the quick-closing valve (KV101) and the main regulating valve (MV101) are installed on the steam inlet pipe, and the bypass pressure regulating valve (PV201) is installed on the bypass pipe; the screw expander back pressure unit includes a screw expander, a reducer and a generator, The generator is connected to the screw expander via a speed reducer. The generator is connected to a generator active power meter (AP101). The end of the steam inlet pipe is connected to the screw expander. The exhaust port of the screw expander is connected to one end of the exhaust pipe. The ends of the exhaust pipe and the bypass pipe are connected to an external steam transmission network. An exhaust pressure gauge (PT102) is installed on the exhaust pipe. The exhaust pressure gauge (PT102), the generator active power meter (AP101), the bypass pressure regulating valve (PV201), and the main regulating valve (MV101) are interlocked. During system operation, the system determines the control logic of the main regulating valve (MV101) and the bypass pressure regulating valve (PV201) according to the back pressure state, so that steam enters the back pressure screw expander as much as possible to achieve maximum power generation efficiency and back pressure control.

[0020] Furthermore, a fine-tuning bypass is provided on the steam inlet pipe between the quick-closing valve (KV101) and the main regulating valve (MV101), and a bypass fine-tuning valve (MV102) is installed on the fine-tuning bypass. The bypass fine-tuning valve (MV102) is interlocked with the exhaust pressure gauge (PT102), the generator active power meter (AP101), the bypass pressure regulating valve (PV201) and the main regulating valve (MV101).

[0021] Furthermore, the steam inlet pipe is a DN300 pipe, and the fine-tuning bypass pipe is a DN65 pipe. Since the original system design uses the main regulating valve (MV101) as the back pressure interlock control valve, and the steam pipeline is large, the valve control accuracy of ±0.5% will have a greater impact on the back pressure, making it impossible for the screw expander to adjust to the system back pressure value quickly. In the new system design of the utility model, a bypass fine-tuning valve (MV102) is added. When the back pressure is too high, the fine-tuning valve is preferentially interlocked to accurately control the amount of steam entering the back pressure screw machine, so that the system reaches the system back pressure value quickly.

[0022] Furthermore, a steam inlet pressure gauge (PT101) is installed on the steam inlet pipe. The steam inlet pressure gauge (PT101) is installed on one end of the steam inlet pipe close to the screw expander and is used to monitor the pressure on the steam inlet pipe.

[0023] Working principle:

[0024] (1) When the back pressure is detected to be too high, most of the steam enters the back pressure screw expander with high power generation and the bypass pressure regulating valve is in the closed state. Then the main regulating valve is controlled by the optimal interlock to accurately control the amount of steam entering the back pressure screw machine, so that the system reaches the system back pressure value faster.

[0025] (2) When the back pressure is detected to be too low, even if the main regulating valve is fully open and all the steam has entered the back pressure screw expander, it is not possible to adjust the back pressure by simply closing the main regulating valve. Instead, the bypass pressure regulating valve should be opened first and the main regulating valve should be closed at the same time to adjust the back pressure. At the same time, the minimum opening of the main regulating valve should be set according to the power interlock to ensure that the generator is in the power generation state, rather than the reverse power operation state.

[0026] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A screw expander back pressure unit bypass valve control system, comprising a steam inlet pipe, a bypass pipe, a quick-closing valve, a main regulating valve, a bypass pressure regulating valve, a screw expander back pressure unit, an exhaust pipe and an exhaust pressure gauge, wherein the steam inlet ends of the steam inlet pipe and the bypass pipe are connected to the steam inlet, the quick-closing valve and the main regulating valve are installed on the steam inlet pipe, and the bypass pressure regulating valve is installed on the bypass pipe; the screw expander back pressure unit comprises a screw expander, a reducer and a generator, the generator is connected to the screw expander through the reducer, the generator is connected to a generator active power meter, the end of the steam inlet pipe is connected to the screw expander, the exhaust port of the screw expander is connected to one end of the exhaust pipe, the ends of the exhaust pipe and the bypass pipe are connected to an external steam pipeline network, and the exhaust pressure gauge is installed on the exhaust pipe, characterized in that: The exhaust pressure gauge, generator active power meter, bypass pressure regulating valve and main regulating valve are interlocked.

2. A screw expander back pressure unit bypass valve control system according to claim 1, characterized in that: A fine-tuning bypass is provided on the steam inlet pipe between the quick-closing valve and the main regulating valve, and a bypass fine-tuning valve is installed on the fine-tuning bypass. The bypass fine-tuning valve is interlocked with the exhaust pressure gauge, the generator active power meter, the bypass pressure regulating valve and the main regulating valve.

3. A screw expander back pressure unit bypass valve control system according to claim 2, characterized in that: The steam inlet pipe is a DN300 pipe, and the fine-tuning bypass pipe is a DN65 pipe.

4. The screw expander back pressure unit bypass valve control system according to claim 1, characterized in that: The steam inlet pipe is also provided with a steam inlet pressure gauge, which is installed on one end of the steam inlet pipe close to the screw expander.

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