Liquid caustic soda delivery device and control method thereof

Abstract

The present application relates to a kind of liquid alkali conveying device, including unloading alkali storage tank and liquid alkali storage tank.Unloading alkali storage tank is equipped with feed pipe, liquid alkali circulation pipe, radar liquid level meter I, first liquid alkali self-priming pump;The outlet I of first liquid alkali self-priming pump is equipped with heat exchanger;Liquid alkali circulation pipe is connected with liquid alkali conveying pipe;Liquid alkali circulation pipe is equipped with liquid alkali pump circulation pipe switch valve;The top of liquid alkali storage tank is equipped with radar liquid level meter II;The outlet II of heat exchanger is configured temperature transmitter, and inlet is equipped with steam condensation return water pipe;Steam condensation return water pipe is equipped with steam condensation return water regulating valve;Liquid alkali conveying pipe is equipped with liquid alkali conveying pipe switch valve, purging pipe;Purging pipe is equipped with purging valve;The detection signal of radar liquid level meter I-II, and the execution signal of each valve are all connected to main control and remote monitoring unit.Simultaneously, the present application also provides the control method of the device.The present application can improve the automation level, security, operation stability and operation and maintenance efficiency of liquid alkali conveying system.

Description

Technical Field

[0001] This invention relates to the field of automated control technology for chemical storage and transportation, and in particular to a liquid alkali conveying device and its control method. Background Technology

[0002] Liquid caustic soda is a commonly used bulk raw material in chemical production, widely applied in industries such as papermaking, textiles, printing and dyeing, metallurgy, pharmaceuticals, and food. The transportation of liquid caustic soda typically involves several stages: temporary storage in unloading tanks, pumping transfer, storage in the main tank, and distribution to multiple downstream low-level tanks. Due to the highly corrosive nature of liquid caustic soda and its susceptibility to residual liquid accumulation and crystallization blockage in pipelines under certain operating conditions—especially in northern my country where low winter temperatures significantly increase the risk of crystallization—the transportation process places high demands on pump and valve interlocking, valve function switching, pipeline cleanliness, and cryogenic protection.

[0003] Most existing liquid caustic soda storage and transportation systems employ a combination of decentralized instrumentation and manual operation. The circulation and outlet valves of the liquid caustic soda pumps rely heavily on manual switching or simple interlocking control. Furthermore, existing liquid caustic soda delivery pipelines often require manual purging after shutdown. However, the lack of a unified control logic between manual purging and pump / valve actions easily leads to problems such as untimely or incomplete purging, or misoperation, resulting in crystallization blockage, cleaning difficulties, and abnormal restarts. Moreover, it is labor-intensive. Due to the dispersed data from various monitoring points and actuators, operators find it difficult to achieve centralized monitoring, fault diagnosis, and remote management of the entire process.

[0004] Therefore, there is an urgent need for a liquid alkali delivery device and control method that can realize sequential linkage of pumps and valves, automatic purging, and centralized monitoring. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a highly efficient, safe and highly automated liquid alkali conveying device.

[0006] Another technical problem to be solved by the present invention is to provide a control method for the liquid alkali delivery device.

[0007] To solve the above problems, the present invention provides a liquid alkali conveying device, comprising an unloading alkali storage tank and a liquid alkali storage tank, characterized in that: the top of the unloading alkali storage tank is respectively provided with a feed pipe from the train unloading station, a liquid alkali circulation pipe, and a radar level gauge I, and a first liquid alkali self-priming pump is connected to its side; the outlet I of the first liquid alkali self-priming pump is provided with a heat exchanger; the liquid alkali circulation pipe is connected to a liquid alkali conveying pipe, one end of which is connected to the heat exchanger, and the other end is connected to the liquid alkali storage tank; a liquid alkali pump circulation pipe switch valve is provided on the liquid alkali circulation pipe; the top of the liquid alkali storage tank is provided with... The system includes a radar level gauge II; a temperature transmitter is installed at the outlet II of the heat exchanger, and a steam condensate return water pipe is installed at the inlet; a steam condensate return water regulating valve is installed on the steam condensate return water pipe; a liquid alkali delivery pipeline connected to the liquid alkali storage tank is equipped with a liquid alkali delivery pipeline switch valve and a purge pipeline; a purge valve is installed on the purge pipeline; the detection signals of the radar level gauge I and the radar level gauge II, as well as the execution signals of the liquid alkali pump circulation pipeline switch valve, the steam condensate return water regulating valve, the liquid alkali delivery pipeline switch valve, and the purge valve, are all connected to the main control and remote monitoring unit.

[0008] The main control and remote monitoring unit adopts PLC or DCS and is equipped with a human-machine interface.

[0009] The control method for a liquid alkali conveying device as described above is characterized in that the control method includes three major modules: circulation and conveying, winter antifreeze and temperature control, and safety interlocking and purging.

[0010] The control logic for the circulation and transport includes pump start-up and initial circulation, high-level transport, and low-level switchback circulation; wherein: The pump start-up and initial circulation refer to the starting of the first liquid alkali self-priming pump when the liquid alkali is pumped into the unloading alkali storage tank during unloading and the liquid level is detected to be higher than the first threshold. The high-level conveying refers to the system switching to conveying mode when the liquid level in the alkali unloading storage tank continues to rise to the second threshold. The low liquid level cut-back circulation refers to the process of stopping the supply of liquid alkali to the liquid alkali storage tank and switching back to the circulation mode when the liquid level drops to the first threshold.

[0011] The control logic for winter antifreeze and temperature control includes a normal winter cycle and temperature control, and a summer mode; wherein: The aforementioned winter normalized circulation and temperature control refers to the fact that during winter nights or when there is no unloading task, the first liquid alkali self-priming pump does not stop and remains in a state of constant circulation or liquid alkali delivery; the temperature transmitter of heat exchanger outlet II and the steam condensate return water regulating valve form a PID temperature control loop to control the temperature of heat exchanger outlet II at 18~25℃. The summer mode refers to closing the steam condensate return water regulating valve and disconnecting the PID temperature control circuit.

[0012] The control logic for the safety interlock and purging includes an anti-overflow interlock for the liquid alkali storage tank, a liquid alkali delivery termination determination, and purging; wherein: The anti-overflow interlock of the liquid alkali storage tank refers to the system triggering a high liquid level alarm when the liquid level in the liquid alkali storage tank reaches the third threshold; the system automatically closes the liquid alkali delivery pipeline switch valve, opens the liquid alkali pump circulation pipeline switch valve, keeps the first liquid alkali self-priming pump in circulation state, and notifies the outdoor unloading personnel to stop the operation, forming a safety closed loop; The liquid alkali delivery completion determination and purging refers to the system determining the end of the current liquid alkali delivery task and automatically starting the purging program when the system detects that the liquid levels in both the unloading alkali storage tank and the liquid alkali storage tank remain unchanged for more than the third delay time through background timing. When purging is started, the system closes the liquid alkali delivery pipeline switch valve, opens the purging valve and introduces room temperature compressed air, and automatically closes the purging valve after purging for a fourth delay time.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention integrates liquid level detection, pump start-up and shutdown, valve switching and purging actions into a centralized monitoring unit, realizing fully automated control of the entire process of liquid alkali storage, transportation, temperature control and shutdown maintenance, which can significantly reduce manual operation.

[0014] 2. By setting up high and low liquid level interlocks, monitoring pump operating status, and controlling the sequence of pump and valve actions, this invention helps prevent abnormal situations such as overflow and dry running, thereby improving the safety of system operation.

[0015] 3. By incorporating the purging system into automatic linkage control, the present invention can promptly purge the pipeline after shutdown and idle periods, which helps to reduce liquid alkali residue, crystallization and blockage, and improve the system's long-term stable operation capability.

[0016] 4. By centrally collecting data such as liquid level, flow rate, pressure, temperature and valve position, this invention can realize fault early warning, historical traceability and remote monitoring, which facilitates operation and maintenance management and process optimization. Attached Figure Description

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] Figure 2 This is the control flowchart of the present invention.

[0020] Figure 3 This is the S101 interlocking logic diagram in this invention.

[0021] Figure 4This is the S102 interlocking logic diagram in this invention.

[0022] Figure 5 This is the S103 interlocking logic diagram in this invention.

[0023] In the diagram: 1—Alkali unloading tank; 2—Liquid alkali storage tank; 3—First liquid alkali self-priming pump; 4—Heat exchanger; 5—Radar level gauge I; 6—Liquid alkali pump circulation pipeline switch valve; 7—Radar level gauge II; 8—Temperature transmitter; 9—Steam condensate return water regulating valve; 10—Liquid alkali conveying pipeline switch valve; 11—Purge valve; S101—Circulation and conveying; S102—Winter antifreeze and temperature control; S103—Safety interlock and purging. Detailed Implementation

[0024] like Figure 1 As shown, a liquid alkali conveying device includes an unloading alkali storage tank 1 and a liquid alkali storage tank 2. The top of the unloading alkali storage tank 1 is respectively equipped with a feed pipe from the train unloading station, a liquid alkali circulation pipe, and a radar level gauge I5; a first liquid alkali self-priming pump 3 is connected to its side; a heat exchanger 4 is installed at the outlet I of the first liquid alkali self-priming pump 3; the liquid alkali circulation pipe is connected to a liquid alkali conveying pipe, one end of which is connected to the heat exchanger 4, and the other end is connected to the liquid alkali storage tank 2; a liquid alkali pump circulation pipe switch valve 6 is installed on the liquid alkali circulation pipe; a radar level gauge II 7 is installed on the top of the liquid alkali storage tank 2; a temperature regulator is installed at the outlet II of the heat exchanger 4. The feeder 8 has a steam condensate return water pipe at its inlet; a steam condensate return water regulating valve 9 is installed on the steam condensate return water pipe; a liquid alkali conveying pipeline connected to the liquid alkali storage tank 2 is equipped with a liquid alkali conveying pipeline switch valve 10 and a purging pipeline; a purging valve 11 is installed on the purging pipeline; the detection signals of radar level gauge I5 and radar level gauge II7, as well as the execution signals of liquid alkali pump circulation pipeline switch valve 6, steam condensate return water regulating valve 9, liquid alkali conveying pipeline switch valve 10, and purging valve 11 are all connected to the main control and remote monitoring unit.

[0025] The main control and remote monitoring units adopt PLC or DCS, and are equipped with human-machine interface.

[0026] The liquid alkali pump circulation pipeline switch valve 6, the steam condensate return water regulating valve 9, the liquid alkali conveying pipeline switch valve 10, and the purge valve 11 constitute the pump valve linkage control structure.

[0027] like Figure 2 As shown, a control method for a liquid alkali conveying device includes three main modules: circulation and conveying (S101), winter antifreeze and temperature control (S102), and safety interlock and purging (S103).

[0028] The control logic of the circulation and conveying S101 includes pump start-up and initial circulation, high liquid level conveying, and low liquid level switchback circulation; Figure 3 Here is the interlocking logic diagram for S101, where: Pump start-up and initial circulation refer to the activation of the first liquid caustic soda self-priming pump 3 when liquid caustic soda is pumped into the unloading caustic soda storage tank 1 during unloading, and the liquid level is detected to be higher than the first threshold (which can be changed by the operator with permission settings). Specifically, after the first liquid caustic soda self-priming pump 3 is activated, the system first opens the liquid caustic soda pump circulation pipeline switch valve 6 to perform internal circulation.

[0029] High-level transport refers to the system switching to transport mode when the liquid level in the alkali unloading storage tank 1 continuously rises to the second threshold (which can be changed by the operator with permission settings). Specifically, the liquid alkali transport pipeline switch valve 10 is opened first, and after a first delay time, the liquid alkali pump circulation pipeline switch valve 6 is closed.

[0030] Low-level switching back to circulation means that when the liquid level drops to the first threshold, the delivery of liquid alkali to the storage tank is stopped, and the circulation mode is switched back. Specifically, the liquid alkali pump circulation pipeline switch valve 6 is opened first, and after a second delay time, the liquid alkali delivery pipeline switch valve 10 is closed.

[0031] The control logic of winter antifreeze and temperature control S102 includes winter normal cycle and temperature control, and summer mode; Figure 4 Here is the interlocking logic diagram for S102, where: Winter normalized circulation and temperature control refers to the continuous operation of the first liquid alkali self-priming pump 3 during winter nights or when there is no unloading task, maintaining a state of constant circulation or liquid alkali delivery; the temperature transmitter 8 at the outlet II of heat exchanger 4 and the steam condensate return water regulating valve 9 form a PID (proportional-integral-derivative control algorithm) temperature control loop to control the temperature of outlet II of heat exchanger 4 at 18~25℃.

[0032] Summer mode means closing the steam condensate return water regulating valve 9 and cutting off the PID temperature control circuit.

[0033] The control logic of safety interlock and purging S103 includes anti-overflow interlock for liquid alkali storage tank, liquid alkali delivery termination determination and purging; Figure 5 Here is the interlocking logic diagram for S103, where: The anti-overflow interlock for liquid caustic soda storage tanks refers to the system triggering a high-level alarm when the liquid level in liquid caustic soda storage tank 2 reaches the third threshold. The system automatically closes the liquid caustic soda delivery pipeline switch valve 10, opens the liquid caustic soda pump circulation pipeline switch valve 6, keeps the first liquid caustic soda self-priming pump 3 in circulation mode, and notifies outdoor unloading personnel to stop operations (if any), forming a safety closed loop.

[0034] The liquid alkali delivery completion determination and purging refers to the system determining the end of the current liquid alkali delivery task and automatically initiating the purging procedure when the liquid levels in both the unloading alkali storage tank 1 and the liquid alkali storage tank 2 remain unchanged for more than the third delay time (which can be changed by the operator with permissions) is detected through background timing. When purging is initiated, the system closes the liquid alkali delivery pipeline switch valve 10, opens the purging valve 11 and introduces ambient temperature compressed air. After purging continues for the fourth delay time (which can be changed by the operator with permissions), the purging valve 11 is automatically closed. Example

[0036] Circulation and conveying Pump start-up and initial circulation When the liquid caustic soda is pumped into the unloading caustic soda storage tank 1 during unloading, and the liquid level is >1.0 meter (operator can set permissions to change this), the first liquid caustic soda self-priming pump 3 starts.

[0037] After the pump starts, the system first opens valve 6 of the liquid alkali pump circulation pipeline to perform internal circulation.

[0038] High liquid level transport When the liquid level in the alkali unloading storage tank 1 continues to rise to 1.5 meters to 1.7 meters (operator permissions can be set to change this), the system switches to delivery mode. First, open the liquid alkali delivery pipeline switch valve 10, and after a 5-second delay, close the liquid alkali pump circulation pipeline switch valve 6.

[0039] Low liquid level switch back to circulation When the liquid level drops to 1.0 meter, stop supplying liquid alkali to liquid alkali storage tank 2 and switch back to circulation mode.

[0040] First, open valve 6 of the liquid alkali pump circulation pipeline, delay for 5 seconds, and then close valve 10 of the liquid alkali delivery pipeline.

[0041] Winter frost protection and temperature control Winter normal circulation and temperature control During winter nights or when there is no unloading task, the first liquid caustic soda self-priming pump 3 will not stop running and will continue to circulate or deliver liquid caustic soda.

[0042] Temperature transmitter 8 and steam condensate return water regulating valve 9 form a PID temperature control loop to control the outlet temperature of heat exchanger 4 II at 18~25℃.

[0043] Summer mode Close the steam condensate return water regulating valve 9 and disconnect the PID temperature control circuit.

[0044] Safety interlocks and purging Liquid alkali storage tank overflow prevention interlock In this embodiment, the physical overflow port height of liquid alkali storage tank 2 is 8.5 meters. When the liquid level in the large tank reaches 8.4 meters, the DCS / host computer system will display a high liquid level alarm box.

[0045] The system automatically closes the liquid alkali delivery pipeline switch valve 10, first opens the liquid alkali pump circulation pipeline switch valve 6, delays for 5 seconds, and then closes the liquid alkali delivery pipeline switch valve 10. The first liquid alkali self-priming pump 3 remains in circulation state, and notifies outdoor unloading personnel to stop operations (if any), forming a safety closed loop.

[0046] Liquid alkali delivery termination determination and purging The system uses a background timer. When it detects that the liquid levels of both the alkali unloading tank 1 and the liquid alkali storage tank 2 remain unchanged for more than 30 minutes (operator permissions can be set to change this), it determines that the liquid alkali transportation task for the day (or shift) is over and starts purging.

[0047] Start purging, close the liquid alkali delivery pipeline switch valve 10, open the purging valve 11, introduce room temperature compressed air, purge for 10 minutes (operator permissions can be set to change), and close the liquid alkali delivery pipeline switch valve 10.

Claims

1. A liquid alkali conveying device, comprising an alkali unloading storage tank (1) and a liquid alkali storage tank (2), characterized in that: The top of the alkali unloading storage tank (1) is equipped with a feed pipe from the train unloading station, a liquid alkali circulation pipe, and a radar level gauge I (5), and a first liquid alkali self-priming pump (3) is connected to the side; a heat exchanger (4) is provided at the outlet I of the first liquid alkali self-priming pump (3); the liquid alkali circulation pipe is connected to a liquid alkali conveying pipe, one end of which is connected to the heat exchanger (4), and the other end is connected to the liquid alkali storage tank (2); a liquid alkali pump circulation pipe switch valve (6) is provided on the liquid alkali circulation pipe; a radar level gauge II (7) is provided on the top of the liquid alkali storage tank (2); a temperature transmitter is configured at the outlet II of the heat exchanger (4). The inlet of the device (8) is equipped with a steam condensate return water pipe; the steam condensate return water pipe is equipped with a steam condensate return water regulating valve (9); the liquid alkali conveying pipeline connected to the liquid alkali storage tank (2) is equipped with a liquid alkali conveying pipeline switch valve (10) and a purging pipeline; the purging pipeline is equipped with a purging valve (11); the detection signals of the radar level gauge I (5) and the radar level gauge II (7), as well as the execution signals of the liquid alkali pump circulation pipeline switch valve (6), the steam condensate return water regulating valve (9), the liquid alkali conveying pipeline switch valve (10), and the purging valve (11) are all connected to the main control and remote monitoring unit.

2. The liquid alkali conveying device as described in claim 1, characterized in that: The main control and remote monitoring unit adopts PLC or DCS and is equipped with a human-machine interface.

3. The control method for a liquid alkali conveying device as described in claim 1, characterized in that: The control method includes three main modules: circulation and conveying (S101), winter antifreeze and temperature control (S102), and safety interlock and purging (S103).

4. The control method for a liquid alkali conveying device as described in claim 3, characterized in that: The control logic for the circulation and conveying (S101) includes pump start-up and initial circulation, high-level conveying, and low-level switching back to circulation; wherein: The pump start-up and initial circulation refer to the first liquid alkali self-priming pump (3) starting when the liquid alkali is pumped into the unloading alkali storage tank (1) during unloading and when the liquid level is detected to be higher than the first threshold. The high-level transport refers to the system switching to transport mode when the liquid level of the alkali unloading storage tank (1) continues to rise to the second threshold. The low liquid level cut-back circulation refers to the process of stopping the supply of liquid alkali to the liquid alkali storage tank and switching back to the circulation mode when the liquid level drops to the first threshold.

5. The control method for a liquid alkali conveying device as described in claim 3, characterized in that: The control logic for winter antifreeze and temperature control (S102) includes a normal winter cycle and temperature control, and a summer mode; wherein: The so-called winter normal circulation and temperature control means that during winter nights or when there is no unloading task, the first liquid alkali self-priming pump (3) will not stop and will remain in a state of constant circulation or liquid alkali delivery; the temperature transmitter (8) of outlet II of heat exchanger (4) and the steam condensate return water regulating valve (9) form a PID temperature control loop to control the temperature of outlet II of heat exchanger (4) at 18~25℃. The summer mode refers to closing the steam condensate return water regulating valve (9) and cutting off the PID temperature control circuit.

6. The control method for a liquid alkali conveying device as described in claim 3, characterized in that: The control logic for the safety interlock and purging (S103) includes the anti-overflow interlock for the liquid alkali storage tank, liquid alkali delivery termination determination, and purging; wherein: The anti-overflow interlock of the liquid alkali storage tank refers to the system triggering a high liquid level alarm when the liquid level of the liquid alkali storage tank (2) reaches the third threshold; the system automatically closes the liquid alkali delivery pipeline switch valve (10), opens the liquid alkali pump circulation pipeline switch valve (6), keeps the first liquid alkali self-priming pump (3) in circulation state, and notifies the outdoor unloading personnel to stop the operation, forming a safety closed loop; The liquid alkali delivery end determination and purging refers to the system determining the end of the current liquid alkali delivery task and automatically starting the purging program when the system detects that the liquid level of the unloading alkali storage tank (1) and the liquid level of the liquid alkali storage tank (2) remain unchanged for a period of time exceeding the third delay time through the background timing. When the purging is started, the system closes the liquid alkali delivery pipeline switch valve (10), opens the purging valve (11) and introduces room temperature compressed air. After purging for a fourth delay time, the system automatically closes the purging valve (11).

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