Negative pressure drainage system of screw expander

Abstract

The utility model discloses a screw expander negative pressure drainage system which comprises a screw expander, an evaporative condenser, a drainage flash tank and a vacuum system, a steam exhaust port of the screw expander is connected with the evaporative condenser through a system pipe network, the vacuum system is connected with the condenser, and the drainage flash tank is connected with the condenser. The lowest point of the system pipe network is connected with the drainage flash tank through a drainage pipe, a negative pressure drainage three-way valve is installed on the drainage pipe, one connector of the negative pressure drainage three-way valve is connected with a drainage pump, the drainage flash tank is connected with the vacuum system through a pipeline, and a negative pressure balance valve is installed on the pipeline for connecting the drainage flash tank and the vacuum system. A liquid level meter is mounted on the drain flash tank; the problem of unbalanced pressure is solved. A pipeline is additionally arranged between a vacuumizing pipeline and the drain flash tank, so that gas in the drain flash tank can be vacuumized and pumped away by a vacuum system, and the pressure of the drain flash tank is equal to the pressure in a system pipe network all the time.

Description

Technical Field

[0001] The utility model relates to the technical field of screw expanders, in particular to a negative pressure drain system of a screw expander. Background Art

[0002] When the existing screw expander is used for waste heat recovery, the vented steam is discharged into the atmosphere at a pressure of 0.1MpaA and a temperature of 100℃ after the screw expander does work. The enthalpy value of the steam in the 0.1MpaA section is very high, but the steam in this section is not recovered, so a lot of steam source is wasted. When using condensation vacuum technology to recover the steam in this section, a new problem different from the traditional steam turbine is encountered. The steam turbine uses high-quality superheated steam, which does not contain water. However, the screw expander is used for waste heat recovery, and the quality of the gas source is not guaranteed. Most of it is low-quality saturated steam with a large water content. After the screw expander does work, most of the water is carried into the evaporative cooler along with the steam. There is still a small part of water that cannot be carried away by the steam and remains in the low point of the pipeline between the exhaust port of the screw expander and the evaporative cooler (hereinafter referred to as the system pipeline network). A rope saws through wood and water drips through a stone. Over time, this small part of water that cannot be carried away by steam will accumulate more and more. When it reaches a certain amount, it will hinder the circulation of steam and affect the power generation of the screw expander. In severe cases, it will accumulate at the exhaust port of the screw expander or even inside the screw expander, causing the power of the screw expander to drop sharply, the screw expander to vibrate violently, the speed control cabinet to start the safety protection, the screw expander to shut down, and in severe cases, the screw expander will be damaged.

[0003] As long as the water can be drained out smoothly, this problem can be solved naturally. The biggest difficulty of the problem is that the area where this part of the water is located is under negative pressure. The system pipe network is under negative pressure, and the outside of the system pipe network is under atmospheric pressure. It cannot be solved by simply setting a drain valve at a low point in the system pipe network, because the pressure outside the system pipe network is greater than the pressure inside the system pipe network. Even if the drain valve is opened manually, the water cannot be drained out. Therefore, there must be a technology that can transport the water under negative pressure.

[0004] Existing technologies such as Figure 1 As shown, the system uses two negative pressure steam traps, which have two main disadvantages: (1) if the screw expander is turned on first and then vacuumed during the startup of the screw expander, water will first enter the steam trap expansion tank, and part of the water will remain in the negative pressure steam trap pipeline. At this time, if the vacuum system is turned on again, the water remaining in the pipeline will form a water seal, resulting in pressure imbalance, that is, the steam trap expansion tank is at atmospheric pressure, and the system pipe network is at negative pressure. The pressure in the steam trap expansion tank is greater than the system pipe network pressure, resulting in water not flowing into the negative pressure steam trap expansion tank; (2) The two electric switch valves are costly, complex to control, and troublesome to construct and debug on site. In view of the above situation, the utility model provides a solution. Utility Model Content

[0005] The utility model aims to provide a negative pressure drain system for a screw expander.

[0006] The above technical objectives of the utility model are achieved through the following technical solutions:

[0007] A screw expander negative pressure drain system comprises a screw expander, an evaporative condenser, a drain expansion tank and a vacuum system, wherein the exhaust port of the screw expander is connected to the evaporative condenser through a system pipe network, the vacuum system is connected to the condenser, the lowest point of the system pipe network is connected to the drain expansion tank through a drain pipe, so that the accumulated water in the system pipe network enters the drain expansion tank under the action of its own gravity, a negative pressure drain three-way valve is installed on the drain pipe, a joint of the negative pressure drain three-way valve is connected to a drain pump, the drain expansion tank is connected to the vacuum system through a pipeline, and a negative pressure balancing valve is installed on the pipeline connecting the two, and a liquid level gauge linked to the negative pressure drain three-way valve and the drain pump is installed on the drain expansion tank for monitoring the pressure in the drain expansion tank.

[0008] Furthermore, the hydrophobic expansion container is a sealed water storage container, which plays a medium role in the hydrophobic system and solves the problem that negative pressure water vapor in the system pipe network cannot be directly discharged.

[0009] Furthermore, a pressure transmitter is installed on the hydrophobic expansion tank, which mainly detects the pressure in the hydrophobic expansion tank and works in conjunction with the negative pressure balance valve KV302 and the vacuum system to adjust the pressure in the hydrophobic expansion tank.

[0010] Furthermore, the liquid level meter adopts a magnetic flip plate liquid level meter whose output signal is 4-20MA signal.

[0011] Furthermore, the vacuum system adopts a water ring vacuum pump or a screw vacuum pump. The water ring vacuum pump or the screw vacuum pump is adopted mainly to consider that the vacuum pump can adapt to the water vapor working environment and ensure the reliability of the whole system.

[0012] Furthermore, a valve is installed on the connecting pipe between the hydrophobic expansion tank and the hydrophobic pump, and closing the valve can ensure the airtightness inside the hydrophobic expansion tank; a valve is also installed on the hydrophobic pipe connected to the water outlet of the hydrophobic pump, and the valve is in a closed state when the system is not working.

[0013] Furthermore, the negative pressure drain three-way valve KV301 and the drain pump are both provided with manual and automatic selection switches, so that the drain system can be switched automatically or manually as required.

[0014] In summary, the utility model has the following beneficial effects:

[0015] (1) Solve the problem of pressure imbalance. By installing a pipeline between the vacuum pipeline and the hydrophobic expansion tank, the gas in the hydrophobic expansion tank can be evacuated by the vacuum system, so that the pressure of the hydrophobic expansion tank is always equal to the pressure in the system pipe network;

[0016] (2) Solve the problem of high cost and complex control. Use one electric three-way valve to replace the original two electric valves. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a negative pressure drain system of screw expander in the prior art;

[0018] Figure 2 This is a structural diagram of the negative pressure drain system of the screw expander of the utility model;

[0019] Figure 3 It is a logic diagram of the utility model. DETAILED DESCRIPTION

[0020] The utility model is further described in detail below in conjunction with the accompanying drawings, and the technical solutions in the embodiments of the utility model are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0021] like Figure 2 As shown, a screw expander negative pressure drain system comprises a screw expander, an evaporative condenser, a drain expansion tank and a vacuum system, wherein the exhaust port of the screw expander is connected to the evaporative condenser through a system pipe network, the vacuum system is connected to the condenser, the lowest point of the system pipe network is connected to the drain expansion tank through a drain pipe, a drain pipe is arranged at the lowest point of the system pipe network, and the drain pipe is connected to the drain expansion tank. When there is water accumulation in the system pipe network, the water flows to a lower place due to gravity, and the water will slowly gather in the negative pressure drain. At the front end of the water three-way valve, according to the principle of air pressure balance, as long as the accumulated water is properly controlled, it will flow into the drain expansion tank through the negative pressure drain valve. A negative pressure drain three-way valve is installed on the drain pipe, and a joint of the negative pressure drain three-way valve is connected to the drain pump. The drain expansion tank is connected to the vacuum system through a pipeline, and a negative pressure balance valve is installed on the pipeline connecting the two. A liquid level gauge linked to the negative pressure drain three-way valve and the drain pump is installed on the drain expansion tank to monitor the pressure in the drain expansion tank.

[0022] Furthermore, the hydrophobic expansion container is a sealed water storage container, which plays a medium role in the hydrophobic system and solves the problem that negative pressure water vapor in the system pipe network cannot be directly discharged.

[0023] Furthermore, a pressure transmitter is installed on the hydrophobic expansion tank, which mainly detects the pressure in the hydrophobic expansion tank and works in conjunction with the negative pressure balance valve KV302 and the vacuum system to adjust the pressure in the hydrophobic expansion tank.

[0024] Furthermore, the liquid level meter adopts a magnetic flip plate liquid level meter whose output signal is 4-20MA signal.

[0025] Furthermore, the vacuum system adopts a water ring vacuum pump or a screw vacuum pump. The water ring vacuum pump or the screw vacuum pump is adopted mainly to consider that the vacuum pump can adapt to the water vapor working environment and ensure the reliability of the whole system.

[0026] Furthermore, a valve is installed on the connecting pipe between the hydrophobic expansion tank and the hydrophobic pump, and closing the valve can ensure the airtightness inside the hydrophobic expansion tank; a valve is also installed on the hydrophobic pipe connected to the water outlet of the hydrophobic pump, and the valve is in a closed state when the system is not working.

[0027] Furthermore, the negative pressure drain three-way valve KV301 and the drain pump are both provided with manual and automatic selection switches, so that the drain system can be switched automatically or manually as required.

[0028] Working principle: Reference Figure 3 When the negative pressure drain three-way valve KV301 and the drain pump are both selected to be automatic, the two are linked according to the liquid level of the drain expansion tank. When the program is initialized for the first time, the negative pressure drain three-way valve KV301 opens. When the liquid in the drain expansion tank is lower than the low setting value, the negative pressure drain three-way valve KV301 opens, the system pipe network is connected to the drain expansion tank, and it is not connected to the outside atmosphere. Under the vacuum effect of the vacuum system, the drain expansion tank slowly becomes negative pressure. At this time, the accumulated water in the system pipe network flows into the drain expansion tank; as the water level slowly rises, when the liquid in the drain expansion tank is higher than the high setting value, the negative pressure drain three-way valve KV301 is closed, the system pipe network is not connected to the drain expansion tank, and it is connected to the outside atmosphere. The drain expansion tank slowly changes from absolute pressure to atmospheric pressure, the drain pump motor starts, and the drain expansion tank enters the drain state, until the liquid in the drain expansion tank is lower than the low setting value, KV301 opens, the drain pump motor stops, and the drain expansion tank stops the drain state, and the program logic repeats the cycle in sequence.

[0029] 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 the modifications are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A screw expander negative pressure drain system, characterized in that: The invention comprises a screw expander, an evaporative condenser, a hydrophobic expansion tank and a vacuum system, wherein the exhaust port of the screw expander is connected to the evaporative condenser through a system pipe network, the vacuum system is connected to the condenser, the lowest point of the system pipe network is connected to the hydrophobic expansion tank through a hydrophobic pipe, a negative pressure hydrophobic three-way valve is installed on the hydrophobic pipe, a joint of the negative pressure hydrophobic three-way valve is connected to a hydrophobic pump, the hydrophobic expansion tank is connected to the vacuum system through a pipe, a negative pressure balancing valve is installed on the pipe connecting the two, and a liquid level meter linked to the negative pressure hydrophobic three-way valve and the hydrophobic pump is installed on the hydrophobic expansion tank.

2. A screw expander negative pressure drain system according to claim 1, characterized in that: The hydrophobic expansion container is a sealed water storage container.

3. A screw expander negative pressure drain system according to claim 2, characterized in that: A pressure transmitter is installed on the hydrophobic expansion container.

4. A screw expander negative pressure drain system according to claim 3, characterized in that: The liquid level meter adopts a magnetic flip plate liquid level meter whose output signal is 4-20MA signal.

5. A screw expander negative pressure drain system according to claim 4, characterized in that: The vacuum system adopts a water ring vacuum pump or a screw vacuum pump.

6. A screw expander negative pressure drain system according to claim 1, characterized in that: A valve is installed on the connecting pipeline between the drain expansion container and the drain pump, and a valve is also installed on the drain pipe connected to the water outlet of the drain pump.

7. A screw expander negative pressure drain system according to claim 1, characterized in that: The negative pressure drain three-way valve KV301 and the drain pump are both provided with manual and automatic selection switches.

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