Control system for guaranteeing gas quantity balance of multiple gas holders running in parallel

Abstract

The utility model belongs to the technical field of biogas conveying, and particularly relates to a control system for guaranteeing gas quantity balance of a plurality of gas holders running in parallel, which comprises a biogas main pipeline, gas holders are arranged on each biogas branch of the biogas main pipeline, and Roots blowers are arranged on the biogas main pipeline at the front ends of the gas holders. A gas holder biogas flow meter and a gas holder gas inlet valve are arranged on a biogas branch at the front end of the gas holder, a gas holder liquid level meter is arranged on the gas holder, and a gas holder gas outlet valve is arranged on a biogas branch at the rear end of the gas holder; the control system further comprises a PLC, the gas holder biogas flow meter and the gas holder liquid level meter are connected to the signal input end of the PLC, the control output end of the PLC is connected with a gas holder gas inlet valve, a gas holder gas outlet valve and an intermediate relay coil, and a normally open contact of an intermediate relay is connected in a control loop in series. The gas inlet pressure of the gas holder can be ensured to be stable, the gas inlet amount balance and the gas outlet amount balance of a plurality of gas holders can be ensured, meanwhile, the liquid level of the gas holder is kept balanced, and the utilization of the gas amount of the gas holder is ensured to be maximized.

Description

Technical Field

[0001] The utility model belongs to the technical field of biogas transportation, and in particular relates to a control system for ensuring the gas volume balance of a plurality of gas cabinets running in parallel. Background Art

[0002] At present, as the amount of biogas produced by anaerobic operation increases, it is necessary to configure a corresponding number of gas cabinets at the back end for storage. In particular, for the second phase reconstruction project, due to the gas storage capacity and site issues, it is necessary to build multiple gas cabinets to store and transport biogas. However, when multiple gas cabinets are operated in parallel, there are the following problems: 1. When multiple gas cabinets are operated in parallel, due to the different lengths of the gas inlet pipes of each gas cabinet and the different pressure drops, the short gas inlet pipe has a fast gas inlet and the long gas inlet pipe has a slow gas inlet, resulting in an unbalanced gas intake when different gas cabinets are in operation; 2. When multiple gas cabinets are operated in parallel, due to the different lengths of the gas outlet pipes of multiple gas cabinets and the different pressures in the gas cabinets, the short gas outlet pipe has a fast gas outlet and the long gas outlet pipe has a slow gas outlet, resulting in an unbalanced gas outlet when different gas cabinets are in operation; 3. It is impossible to maximize the utilization rate of multiple gas cabinets when they are in operation. 4. When multiple gas cabinets are operated in parallel to discharge gas, the gas volume indications of each gas cabinet are very different, and it is impossible to balance the gas volume of multiple gas cabinets. When one of the gasholder's air inlet valves or air outlet valves fails, if the personnel do not perform maintenance in time, the gasholder will release gas due to high air inlet pressure, or the gas volume in the gasholder will be low and the gas will be drawn into negative pressure, thus damaging the gasholder. Summary of the invention

[0003] The purpose of the utility model is to provide a control system that ensures the gas volume balance of multiple gas cabinets running in parallel in order to address the above-mentioned problems and shortcomings, which can ensure the stability of the gas cabinet air inlet pressure and the balance of the air intake and outlet volumes of multiple gas cabinets, while achieving the balance of the gas cabinet liquid level and ensuring the maximum utilization of the gas cabinet gas volume.

[0004] To achieve the above purpose, the technical solution adopted is:

[0005] The utility model provides a control system for ensuring the gas volume balance of multiple gas lockers running in parallel, comprising a biogas main pipeline, on which at least two parallel biogas branches are arranged, each biogas branch is arranged with a gas locker, a Roots blower is arranged on the biogas main pipeline at the front end of the gas locker, a gas locker biogas flowmeter and a gas locker air inlet valve are arranged on the biogas branch at the front end of the gas locker, a gas locker liquid level gauge is arranged on the gas locker, and a gas locker air outlet valve is arranged on the biogas branch at the rear end of the gas locker; the control system also comprises a PLC controller, the gas locker biogas flowmeter and the gas locker liquid level gauge are connected to the signal input end of the PLC controller, the control output end of the PLC controller is connected to the coils of the gas locker air inlet valve, the gas locker air outlet valve and the intermediate relay, and the normally open contacts of the intermediate relay are connected in series in the control loop.

[0006] According to the utility model, a control system for ensuring gas volume balance of multiple gas cabinets running in parallel is provided, and further, the number of the Roots blowers is 2 arranged in parallel.

[0007] According to the utility model, a control system is provided for ensuring the gas volume balance of multiple gas cabinets running in parallel. Furthermore, the control system also includes a frequency converter for controlling the outlet air pressure of the Roots blower, and the output terminals of the frequency converter are connected to the Roots blower junction box; a pressure sensor is arranged on the rear end biogas main pipeline of the Roots blower.

[0008] According to the control system of the utility model for ensuring the gas volume balance of multiple gas cabinets running in parallel, further, the PLC controller includes a main controller, a communication module, a switch input module, a switch output module, an analog input module and an analog output module.

[0009] According to the utility model, a control system for ensuring the gas volume balance of multiple gas cabinets running in parallel is provided. Furthermore, analog output signals of the gas cabinet biogas flow meter, gas cabinet liquid level gauge and pressure sensor are connected to the analog input module of the PLC controller through a signal isolator, the switch output module of the PLC controller is connected to the coil of the intermediate relay, the analog input signals of the gas cabinet air inlet valve, gas cabinet air outlet valve and frequency converter are connected to the analog output module of the PLC controller, and the valve opening signals of the gas cabinet air inlet valve and gas cabinet air outlet valve are connected to the analog input module of the PLC controller.

[0010] According to the control system of the utility model for ensuring the gas volume balance of multiple gas cabinets running in parallel, the control system further includes a touch screen, and the touch screen is connected to the switch output module of the PLC controller.

[0011] According to the utility model, a control system is provided for ensuring the gas volume balance of a plurality of gasholders running in parallel. Furthermore, the gasholder liquid level gauge is interlocked with the gasholder air inlet valve. When any liquid level upper limit signal is detected, the gasholder air inlet valve on this branch is closed to stop air supply to the gasholder.

[0012] According to the utility model, a control system is provided to ensure gas volume balance of multiple gas tanks running in parallel. Furthermore, the gas tank liquid level meter is interlocked with the gas tank outlet valve. When any liquid level lower limit signal is detected, the gas tank outlet valve on this branch is closed to stop the gas tank from venting gas.

[0013] The beneficial effects achieved by adopting the above technical solution are:

[0014] The analog signal of the pressure sensor of the utility model is connected to the analog input module of the PLC, and the analog output signal of the PLC is connected to the frequency control input terminal of the frequency converter. After the pressure sensor signal is fed back to the PLC, the frequency converter frequency is controlled by PID regulation, thereby controlling the outlet air pressure of the Roots blower to ensure the stability of the air intake pressure of the gas cabinet. The flow signal of the biogas flow meter of the gas cabinet is connected to the analog input module of the PLC, and the feed flow size of each gas cabinet is set on the touch screen. The analog output signal of the PLC controls the opening of the air intake valve of each gas cabinet. The actual flow of the biogas flow meter of the gas cabinet is compared with the flow set on the touch screen, and the PID controls the opening of the air intake valve, so as to achieve the same air intake pressure and air intake flow of each gas cabinet, and ensure the balance of air intake of multiple gas cabinets.

[0015] The liquid level signal of the gas tank liquid level gauge of the utility model is connected to the PLC analog input module, and the PLC analog output signal controls the opening of each gas tank outlet valve, mainly using the liquid level difference ratio of two gas tanks to control the opening of the gas tank outlet valve, so as to ensure the balance of gas outlet of multiple gas tanks.

[0016] Since the gas volume of the gas cabinet is balanced when the gas is in and out, the utility model realizes the balance of the gas cabinet liquid level. When the liquid level of any gas cabinet is about to reach the lowest level, the interlocking protection lower gas-using unit stops using gas. At the same time, the two gas cabinet liquid level signals are connected in parallel. When the liquid level of one gas cabinet drops to the lowest level, the other one also drops to the lowest level at the same time, ensuring the maximum utilization of the gas cabinet gas volume.

[0017] The utility model has a reasonable design, safe and reliable control, simple and compact structure and high automation level in the control system for ensuring gas volume balance of multiple gas cabinets running in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention are briefly introduced below. The drawings are only used to show some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0019] Figure 1 It is a structural schematic diagram of a control system for ensuring gas volume balance of multiple gas cabinets running in parallel according to an embodiment of the utility model;

[0020] Figure 2 This is an electrical schematic diagram of a PLC controller controlling the start and stop of a Roots blower according to an embodiment of the utility model;

[0021] Figure 3 This is an electrical schematic diagram of a frequency converter controlling a Roots blower according to an embodiment of the utility model;

[0022] Figure 4 It is a connection diagram of the PLC controller and other devices of the embodiment of the utility model;

[0023] Figure 5 It is a wiring diagram of a switch quantity input module and a switch quantity output module of a PLC controller of an embodiment of the utility model;

[0024] Figure 6 It is a wiring diagram of an analog input module of a PLC controller of an embodiment of the utility model;

[0025] Figure 7 It is a wiring diagram of an analog output module of a PLC controller according to an embodiment of the utility model. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings of the specific embodiments of the utility model to clearly and completely describe the exemplary scheme of the utility model. Unless otherwise defined, the technical terms or scientific terms used in the utility model should be the common meanings understood by people with ordinary skills in the relevant field.

[0027] like Figure 1 As shown, this embodiment discloses a control system for ensuring the gas volume balance of multiple gas holders running in parallel, including a biogas main pipeline, on which at least two parallel biogas branches are arranged. This embodiment is illustrated by taking two parallel biogas branches as an example. 1# gas holder and 2# gas holder are arranged on 1# biogas branch and 2# biogas branch, respectively. 1# Roots blower and 2# Roots blower are arranged on the biogas main pipeline at the front end of the two gas holders, and the two blowers are backup for each other, and each blower is controlled by its own frequency converter. The 1# biogas branch at the front end of the 1# gas tank is provided with a 1# gas tank biogas flowmeter and a 1# gas tank air inlet valve, the 2# biogas branch at the front end of the 2# gas tank is provided with a 2# gas tank biogas flowmeter and a 2# gas tank air inlet valve, the 1# gas tank is provided with a 1# gas tank liquid level meter, the 2# gas tank is provided with a 2# gas tank liquid level meter, the 1# biogas branch at the rear end of the 1# gas tank is provided with a 1# gas tank air outlet valve, the 2# biogas branch at the rear end of the 2# gas tank is provided with a 2# gas tank air outlet valve. The control system also includes a PLC controller and a touch screen, the touch screen is used to provide parameter modification and display, the gas tank biogas flowmeter and the gas tank liquid level meter are connected to the signal input end of the PLC controller, and the control output end of the PLC controller is connected to the coils of the gas tank air inlet valve, the gas tank air outlet valve and the intermediate relay, such as Figure 2 As shown, the normally open contacts of the intermediate relay are connected in series in the control circuit. Specifically, the normally open contacts of the intermediate relay for controlling the fan are connected to the contactor coil circuit of the Roots blower, and the start and stop of the motor are controlled by controlling the on and off of the normally open contacts of the contactor; the normally open contacts of the intermediate relay for controlling the valve control the switches of the 1# gas cabinet inlet valve, 1# gas cabinet outlet valve, 2# gas cabinet inlet valve and 2# gas cabinet outlet valve.

[0028] like Figure 4As shown in the figure, the PLC controller includes a main controller, a communication module, an expansion rack, a switch input module, a switch output module, an analog input module and an analog output module. Figure 5 As shown, the switch output module is connected to the coil of the intermediate relay and the touch screen; the field analog input signal is connected to the analog input module, and the analog output module is connected to the valve and control equipment.

[0029] Furthermore, the control system also includes a frequency converter for controlling the outlet air pressure of the Roots blower, such as Figure 3 As shown in the figure, the main contacts of the frequency converter are connected in series in the power supply circuit of the Roots blower. A pressure sensor is installed on the main biogas pipeline at the outlet of the Roots blower. Figure 6 and Figure 7 As shown in the figure, the analog signal of the pressure sensor is connected to the analog input module of the PLC controller through the signal isolator, and the analog input signal of the frequency converter is connected to the analog output module of the PLC controller. The pressure signal is fed back to the PLC controller to set the outlet pressure of the Roots blower. The PLC controls the frequency of the frequency converter through PID regulation, so that the Roots blower works at the set pressure to ensure the stability of the gas cabinet inlet pressure.

[0030] The biogas branch where the 1# gas tank is located is equipped with a biogas flow meter and an air inlet valve for the 1# gas tank; the biogas branch where the 2# gas tank is located is equipped with a biogas flow meter and an air inlet valve for the 2# gas tank. Figure 6 and Figure 7 As shown, the analog output signal of the gas cabinet biogas flowmeter is connected to the analog input module of the PLC controller through the signal isolator, the analog input signal of the gas cabinet air inlet valve is connected to the analog output module of the PLC controller, and the valve opening signal of the gas cabinet air inlet valve is connected to the analog input module of the PLC controller. The air inlet flow of the 1# gas cabinet is fed back to the PLC, the air inlet flow of the 1# gas cabinet is set, and the PID adjustment of the air inlet valve of the 1# gas cabinet is performed according to the flow feedback signal of the biogas flowmeter of the 1# gas cabinet to ensure the stability of the air inlet flow of the 1# gas cabinet. The air inlet flow of the 2# gas cabinet is fed back to the PLC, the air inlet flow of the 2# gas cabinet is set, and the PID adjustment of the air inlet valve of the 2# gas cabinet is performed according to the flow feedback signal of the biogas flowmeter of the 2# gas cabinet to ensure the stability of the air inlet flow of the 2# gas cabinet. This design ensures that the air inlet pressure and air flow of the two gas cabinets are the same, and the air inlet balance of multiple gas cabinets is ensured, which solves the problem of unbalanced gas volume when the gas cabinet is inlet due to different lengths and pressure drops of the air inlet pipelines.

[0031] The 1# gas tank is equipped with a 1# gas tank level gauge and a 1# gas tank outlet valve, and the 2# gas tank is equipped with a 2# gas tank level gauge and a 2# gas tank outlet valve. Figure 6 and Figure 7As shown, the analog output signal of the gas tank level gauge is connected to the analog input module of the PLC controller through the signal isolator, the analog input signal of the gas tank outlet valve is connected to the analog output module of the PLC controller, and the valve opening signal of the gas tank outlet valve is connected to the analog input module of the PLC controller. The 1# gas tank liquid level signal and the 2# gas tank liquid level signal are fed back to the PLC at the same time. The lower liquid level is used as the reference value, and the liquid level difference is calculated and converted into the valve opening ratio. The opening of the 1# gas tank outlet valve and the 2# gas tank outlet valve is adjusted to control the gas volume of the two gas tanks to keep the gas volume balanced when the two gas tanks are discharged.

[0032] The gas tank level gauge is interlocked with the gas tank inlet valve. When any upper limit signal of the liquid level is detected, the gas tank inlet valve on this branch is closed to stop the gas tank from being supplied with gas, so as to prevent the hidden danger of the gas tank being under pressure. The gas tank level gauge is interlocked with the gas tank outlet valve. When any lower limit signal of the liquid level is detected, the gas tank outlet valve on this branch is closed to stop the gas tank from venting gas, so as to prevent the hidden danger of negative pressure in the gas tank. Since the gas volume is balanced during the inlet and outlet, the gas tank liquid level is kept balanced. When the liquid level of any gas tank drops to the lowest level, the interlocking protection lower-level gas-using unit stops using gas. At the same time, the two gas tank liquid level signals are connected in parallel. When the liquid level of one gas tank drops to the lowest level, the other one also drops to the lowest level at almost the same time, so as to ensure the maximum utilization of the gas volume in the gas tank.

[0033] The working principle of the utility model is:

[0034] A pressure sensor is installed on the biogas main pipeline at the rear end of the Roots blower. The PLC controller performs PID control on the inverter of the Roots blower according to the detection value of the pressure sensor to keep the intake pressure stable. A gas cabinet intake valve, a gas cabinet outlet valve, a gas cabinet level meter and a gas cabinet biogas flow meter are installed on each gas cabinet. The gas cabinet level meter is interlocked with the gas cabinet intake valve and the gas cabinet outlet valve. The gas cabinet biogas flow meter and the gas cabinet intake valve PID control maintain the balance of intake flow; the liquid level difference of the gas cabinet level meter and the proportional adjustment control of the gas cabinet outlet valve maintain the balance of outlet flow.

[0035] The detailed working process is as follows:

[0036] (1) Install a pipeline pressure sensor on the biogas main pipeline at the rear end of the Roots blower, and set a pressure value that the pipeline needs to maintain on the touch screen. The pressure signal of the pressure sensor is fed back to the PLC, which performs PID control by comparing the pressure sensor detection value with the set pressure value, and outputs an analog signal to control the frequency of the Roots blower to keep the pipeline pressure at the set pressure. The liquid level of the 1# gas tank and the 2# gas tank is interlocked with the Roots blower. When it is detected that the liquid level of any gas tank is not at the upper limit of the liquid level signal, the Roots blower can be started to supply gas to the gas tank; when it is detected that all gas tanks are at the upper limit of the liquid level signal, the Roots blower is prohibited from starting and stops supplying gas to the gas tank.

[0037] (2) Install a gas inlet valve and a gas inlet gas flow meter at the gas inlet of each gas cabinet. The flow feedback signal of the gas cabinet gas flow meter is fed into the PLC. The gas cabinet feed flow rate is set on the touch screen. The gas cabinet gas flow meter is compared with the actual flow rate to control the opening of the gas cabinet gas inlet valve for PID control. The liquid level of the 1# gas cabinet and the 2# gas cabinet is interlocked with the gas cabinet gas inlet valve. When any liquid level upper limit signal is detected, the gas cabinet gas inlet valve is closed.

[0038] (3) Install a gas tank outlet valve at each gas tank outlet. The liquid level of the 1# gas tank and the liquid level of the 2# gas tank are both fed into the PLC. The PLC calculates the two liquid level differences and converts the liquid level differences into switch signals to control the gas tank outlet valves. If the gas tank liquid level difference is positive, it is converted into an opening signal, and the gas tank outlet valve is opened proportionally according to the opening degree. If the gas tank liquid level difference is negative, it is converted into a closing signal, and the gas tank outlet valve is closed proportionally according to the closing degree. The liquid levels of the 1# gas tank and the 2# gas tank are interlocked with the gas tank outlet valves. When any of the liquid level lower limit signals is detected, the gas tank outlet valve is closed.

[0039] (4) The touch screen is equipped with automatic start-up buttons for each gas cabinet. When one of the gas cabinets is not automatically started (i.e. temporarily not in use), any other gas cabinet can operate freely.

[0040] The preferred embodiments for implementing the present invention have been described in detail above, but it should be understood that the role of these embodiments is only to exemplify, and is not intended to limit the scope, applicability or configuration of the present invention in any way. The protection scope of the present invention is defined by the attached claims and their equivalents. A person of ordinary skill in the art can make many changes to the above embodiments under the guidance of the present invention, and these changes all fall within the protection scope of the present invention.

Claims

1. A control system for ensuring gas volume balance of multiple gas cabinets running in parallel, characterized in that: It comprises a biogas main pipeline, on which at least two parallel biogas branches are arranged, each biogas branch is provided with a gas holder, on the biogas main pipeline at the front end of the gas holder is provided with a Roots blower, on the biogas branch at the front end of the gas holder is provided with a gas holder biogas flow meter and a gas holder air inlet valve, on the gas holder is provided with a gas holder liquid level gauge, and on the biogas branch at the rear end of the gas holder is provided with a gas holder air outlet valve; the control system also comprises a PLC controller, the gas holder biogas flow meter and the gas holder liquid level gauge are connected to the signal input end of the PLC controller, the control output end of the PLC controller is connected to the coils of the gas holder air inlet valve, the gas holder air outlet valve and the intermediate relay, and the normally open contacts of the intermediate relay are connected in series in the control loop.

2. The control system for ensuring gas volume balance of multiple gas cabinets running in parallel according to claim 1 is characterized in that: The number of the Roots blowers is 2 and is arranged in parallel.

3. The control system for ensuring gas volume balance of multiple gas cabinets running in parallel according to claim 1 is characterized in that: The control system also includes a frequency converter for controlling the outlet air pressure of the Roots blower, and the output terminal of the frequency converter is connected to the Roots blower junction box; a pressure sensor is arranged on the rear end biogas main pipeline of the Roots blower.

4. The control system for ensuring gas volume balance of multiple gas cabinets running in parallel according to claim 3 is characterized in that: The PLC controller comprises a main controller, a communication module, a switch quantity input module, a switch quantity output module, an analog quantity input module and an analog quantity output module.

5. The control system for ensuring gas volume balance of multiple gas cabinets running in parallel according to claim 4 is characterized in that: The analog output signals of the gas cabinet biogas flow meter, gas cabinet liquid level gauge and pressure sensor are connected to the analog input module of the PLC controller through a signal isolator, the switch output module of the PLC controller is connected to the coil of the intermediate relay, the analog input signals of the gas cabinet air inlet valve, gas cabinet air outlet valve and frequency converter are connected to the analog output module of the PLC controller, and the valve opening signals of the gas cabinet air inlet valve and gas cabinet air outlet valve are connected to the analog input module of the PLC controller.

6. The control system for ensuring gas volume balance of multiple gas cabinets operating in parallel according to claim 4 is characterized in that: The control system also includes a touch screen, which is connected to the switch output module of the PLC controller.

7. The control system for ensuring gas volume balance of multiple gas cabinets running in parallel according to claim 1 is characterized in that: The gas tank liquid level gauge is interlocked with the gas tank air inlet valve. When any liquid level upper limit signal is detected, the gas tank air inlet valve on this branch is closed to stop the air supply to the gas tank.

8. The control system for ensuring gas volume balance of multiple gas cabinets operating in parallel according to claim 1 is characterized in that: The gas tank liquid level meter is interlocked with the gas tank outlet valve. When any liquid level lower limit signal is detected, the gas tank outlet valve on this branch is closed to stop the gas tank from venting gas out.

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