CN114941801A - BOG (boil off gas) emptying control system of LNG (liquefied Natural gas) receiving station - Google Patents
BOG (boil off gas) emptying control system of LNG (liquefied Natural gas) receiving station Download PDFInfo
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- CN114941801A CN114941801A CN202210593035.5A CN202210593035A CN114941801A CN 114941801 A CN114941801 A CN 114941801A CN 202210593035 A CN202210593035 A CN 202210593035A CN 114941801 A CN114941801 A CN 114941801A
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- 239000003949 liquefied natural gas Substances 0.000 title description 33
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- 230000004069 differentiation Effects 0.000 claims 1
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- 230000002159 abnormal effect Effects 0.000 abstract description 7
- 238000005457 optimization Methods 0.000 description 28
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- 238000013022 venting Methods 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- 238000007599 discharging Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 230000008020 evaporation Effects 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
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- 238000012986 modification Methods 0.000 description 3
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000005474 detonation Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000004200 deflagration Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
- F17D1/065—Arrangements for producing propulsion of gases or vapours
- F17D1/07—Arrangements for producing propulsion of gases or vapours by compression
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
- F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/005—Protection or supervision of installations of gas pipelines, e.g. alarm
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- Filling Or Discharging Of Gas Storage Vessels (AREA)
Abstract
The invention discloses a BOG emptying control system of an LNG receiving station, which comprises a BOG main pipe control system and a flare system, wherein an LNG storage tank is connected to a BOG compressor through a BOG main pipe, the BOG compressor outputs BOG gas to a downstream pipe network, the BOG main pipe control system comprises a main control unit, an auxiliary control unit and a gas pressure detector I, the gas pressure detector I is used for detecting gas pressure of the BOG main pipe, the main control unit comprises a main control valve and a PID controller I, the gas pressure detector I is connected with the PID controller I, the PID controller I is connected with the main control valve to open or close the main control valve, the auxiliary control unit comprises an auxiliary control valve and a PID controller II, the gas pressure detector I is connected with the PID controller II, and the PID controller II is connected with the auxiliary control valve to open or close the auxiliary control valve. The invention adopts pressure sectional control, the main control valve and the auxiliary control valve are separately controlled, the main control valve adopts PID control, the auxiliary control valve adopts linear control, the rapid switching on and off of abnormal emptying is ensured, and the stable regulation of the pressure of the BOG main pipe under the condition of normal emptying is also ensured.
Description
Technical Field
The invention relates to the technical field of fuel gas, in particular to a BOG emptying control system of an LNG receiving station.
Background
LNG is vigorously advocated for the nation as clean energy, and will meet the rapid growth of the development of the LNG industry in future petrochemical systems. In the initial stage of the LNG receiving station, because the construction of a downstream gas transmission pipe network is not integrally completed, the gas consumption is relatively small, the normal evaporation gas quantity of the storage tank and the loaded gas phase backflow is temporarily used for supplying gas for downstream users, and therefore the BOG compressor is temporarily used as an external gas transmission compressor. In order to control the LNG tank pressure and the BOG header pressure, the gas is vented at high pressure by adjusting the BOG compressor load and providing a control valve for venting on the BOG header.
At present, BOG house steward pressure comes the aperture of two control valves of simultaneous control to realize BOG house steward pressure control through a PID regulator, lead to BOG house steward excess release very easily when two valves are all under automatic mode, receive PID's regulation effect after excess release, the pressure descends rapidly before the valve leads to two control valves to be fast excessively closed again simultaneously and ensures that LNG storage tank pressure before the valve is unlikely to hang down excessively, so the circulation presents periodic oscillation repeatedly, cause LNG storage tank and BOG house steward pressure to vibrate.
Disclosure of Invention
The invention aims to provide a BOG emptying control system of an LNG receiving station, which solves the problem of repeated periodic oscillation caused by quick opening and closing of the BOG emptying control system based on the separated control of a main control valve and an auxiliary control valve.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a BOG emptying control system of an LNG receiving station comprises a BOG main pipe control system and a flare system, an LNG storage tank is connected to a BOG compressor through a BOG main pipe, the BOG compressor outputs BOG gas to a downstream pipe network, the BOG main pipe control system comprises a main control unit, an auxiliary control unit and a gas pressure detector I, the gas pressure detector I is used for detecting gas pressure of the BOG main pipe, the main control unit comprises a main control valve and a PID controller I, the gas pressure detector I is connected with the PID controller I, the PID controller I is connected with the main control valve to open or close the main control valve, the auxiliary control unit comprises an auxiliary control valve and a PID controller II, the gas pressure detector I is connected with the PID controller II, and the PID controller II is connected with the auxiliary control valve to open or close the auxiliary control valve; the BOG main pipe is divided into a branch and is provided with a main control valve and an auxiliary control valve which are connected in parallel on the main emptying pipe and the main emptying pipe, and the output end of the main emptying pipe is connected to a flare system to burn with a ground flare through the flare system.
As an option, the PID controller I adopts PID control to close or open the main control valve, when the real-time air pressure of the BOG main pipe is greater than the preset value of normal air pressure, the main control valve is controlled to be opened, and the opening I of the main control valve reaches full load when the air pressure difference value is 0.024 Mpa; and the PID controller II adopts linear control to close or open the auxiliary control valve, when the real-time air pressure of the BOG main pipe is greater than the normal air pressure preset value by 0.024Mpa, the auxiliary control valve is controlled to be opened, and the opening II of the auxiliary control valve reaches full load when the air pressure difference value is 0.027 Mpa. So, two PID controllers realize that two valve separation control form owner, assist the collocation, and the main control valve adopts PID control, and the auxiliary control valve adopts linear control, only has the main control valve to stabilize the evacuation under the condition of normal evacuation, and the pressure rises rapidly under the emergency can open the auxiliary control valve rapidly, and when pressure reached 0.027Mpa, two valves of main control valve and auxiliary control valve were opened entirely, effectively guaranteed the quick unloading requirement of torch system.
Wherein, the opening degrees of the main control valve and the auxiliary control valve satisfy the following relation,
when the ground torch is oneWhen the temperature of the water is higher than the set temperature,
when the number of the ground torches is two,
as an option, the BOG main pipe control system further includes a reflux control unit, the reflux control unit includes a reflux valve, a PID controller III, a gas pressure detector II and a temperature detector, the temperature detector and the gas pressure detector II are respectively used for detecting the temperature of gas at the inlet of the BOG compressor and for detecting the gas pressure at the outlet of the BOG compressor, the outlet of the BOG compressor is branched to a branch to be connected to the LNG storage tank through the reflux valve, the temperature detector and the gas pressure detector II are respectively connected with the PID controller III, the PID controller III is connected with the reflux valve, the temperature controller is controlled based on the temperature detector or the gas pressure is controlled based on the gas pressure detector II, so that the reflux valve is closed or opened to the opening III. Therefore, temperature control is adopted firstly to prevent the air pressure from rapidly increasing due to abnormal temperature; and starting air pressure control when the temperature is normal, and controlling the opening of the outlet return valve of the BOG compressor according to the pressure difference change between the high selection value PV of the inlet air pressure of the compressor and the set value SP, so that the inlet air pressure of the compressor is automatically controlled and stabilized at the set normal value according to actual needs.
When the BOG compressor is started, the BOG compressor is controlled by a temperature set value, when the compressor is started to be switched to normal and stable operation, the reflux valve is controlled by the air pressure and the temperature at the inlet of the compressor together, the temperature control is prior to the pressure control, the temperature control is automatically switched to the temperature control under the condition of abnormal temperature, and the undisturbed switching of the pressure control and the temperature control can be realized. The control process of the PID controller III for controlling the return valve is as follows;
firstly, executing a temperature control program after starting up; then judging whether the acquired real-time temperature is normal or not, if so, executing an air pressure control program, and otherwise, executing a temperature control program; finally, repeating the step until the machine is stopped, specifically, after the current air pressure control program or temperature control program is executed for a period of time, judging whether the acquired real-time temperature is normal, if so, executing the air pressure control program, otherwise, executing the temperature control program; wherein a switching program is configured to switch between the temperature control program and the pneumatic control program under the condition of being operated by an operator.
As an option, the torch system includes ground torch and unloading the control unit, unloading the control unit and including PID controller IV, atmospheric pressure detector III, unloading branch road pipe and atmospheric valve, the atmospheric pressure house steward reposition of redundant personnel becomes unloading branch road pipe in order to be connected to ground torch respectively, the atmospheric valve sets up on the unloading branch road pipe, atmospheric pressure detector III is used for detecting the gaseous atmospheric pressure of unloading house steward, atmospheric pressure detector III is connected with PID controller IV, PID controller IV is connected with the atmospheric valve and opens or close the atmospheric valve with control. Therefore, the air pressure detector III detects the real-time air pressure of the gas of the emptying header pipe, the PID controller IV obtains the real-time air pressure value, the real-time air pressure value is compared with the corresponding preset value, then the emptying valve is controlled to be opened, the automatic control of the emptying valve is realized, and the gas is emptied by burning ground torches such as a beacon light of a torch system.
The emptying branch pipe comprises a first branch pipe, a second branch pipe and a third branch pipe, the first branch pipe is directly emptied, the second branch pipe is provided with a second-level emptying valve, the third branch pipe is provided with a third-level emptying valve, a PID controller IV is respectively connected with the second-level emptying valve and the third-level emptying valve, the second-level emptying valve and the third-level emptying valve are directly emptied through the first branch pipe when the air pressure of an emptying header pipe is 0-2Kpa, the second-level emptying valve and the third-level emptying valve are controlled to be opened when the air pressure of the emptying header pipe is 2-6Kpa, the second-level emptying valve and the third-level emptying valve are controlled to be opened when the air pressure of the emptying header pipe is 4-8Kpa, the second-level emptying valve corresponds to the valve with the opening degree of 0-100% when the air pressure of the emptying header pipe is 2-6Kpa, and the third-level emptying valve corresponds to the valve with the opening degree of 0-100% when the air pressure of the emptying header pipe is 4-8 a. Therefore, three-section type emptying control is formed, and meanwhile, the air pressure sections are overlapped, so that the emptying valve can be opened in time for emptying when excess emptying is ensured.
The control process of the PID controller IV for controlling the emptying valve is as follows:
when the air pressure of the emptying header pipe is 0-2Kpa, directly discharging and emptying through a first branch pipe; when the air pressure of the emptying header pipe is more than 2Kpa, the PID controller IV further controls to open the secondary emptying valve, and the air pressure of the emptying header pipe is kept in an open state when 2-6 Kpa; when the air pressure of the emptying header pipe is greater than 4Kpa, the PID controller IV further controls to open the third-stage emptying valve, and the air pressure of the emptying header pipe is 4-8Kpa, so that the second-stage emptying valve and the third-stage emptying valve are kept in an open state. Therefore, three-stage emptying control is formed, and is opened orderly, so that the opening stability of the valve is ensured; meanwhile, the air pressure section is overlapped to ensure that the emptying valve can be opened in time for emptying when excessive emptying is carried out.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
1. in the valve for the BOG main pipe emptying, pressure sectional control is adopted, a main control valve and an auxiliary control valve are separately controlled, main and auxiliary collocation is formed, the main control valve adopts PID control, the auxiliary control valve adopts linear control, abnormal emptying fast switch can be guaranteed, and stable regulation of the pressure of the BOG main pipe can be guaranteed under the normal emptying condition.
2. The control logic is controlled according to the priority level by utilizing an override control principle in the optimization of the BOG compressor, so that the requirement of improving the effective load of the BOG compressor under the normal working condition is met, the automatic switching can be realized according to the temperature alarm set by the compressor, and the compressor is ensured to be always in a safe state.
3. The ground flare system adopts a control mode of dividing pressure into three sections and having cross overlapping, thereby effectively realizing stable emptying, ensuring ordered switching of first-stage, second-stage and third-stage emptying, and timely starting and emptying.
Drawings
FIG. 1 is a block diagram of the control system of the present invention.
Fig. 2 is an example of a compressor control flow of the present invention.
Figure 3 is a pressure daily graph of an LNG storage tank of the present invention.
Fig. 4 is a comparison of the monthly curves of LNG tank pressure before and after the optimization of the present invention.
FIG. 5 is a comparison graph of the open-degree monthly curves of the BOG compressor before and after optimization of the output control valve.
FIG. 6 is a graph of the BOG manifold vent valve optimization of the present invention 18 days later.
FIG. 7 is a graph comparing the pressure cycle curves of the BOG manifold of the present invention.
FIG. 8 is a graph comparing the 10 day fluctuation curves of the optimized pre and post blowdown header pressure of the present invention.
FIG. 9 is a monthly graph of the optimized two and three stage vent valve opening of the present invention.
Detailed Description
The following further describes the embodiments of the present invention with reference to the drawings.
Examples
As shown in fig. 1, a BOG emptying control system for an LNG receiving station includes a BOG header pipe control system and a flare system, an LNG storage tank is connected to a BOG compressor through a BOG header pipe, the BOG compressor outputs BOG gas to a downstream pipe network, the BOG header pipe control system includes a main control unit, an auxiliary control unit, and a gas pressure detector I, the gas pressure detector I is used for detecting gas pressure at P1 of the BOG header pipe, the main control unit includes a main control valve and a PID controller I, the gas pressure detector I is connected to the PID controller I, the PID controller I is connected to the main control valve to open or close the main control valve, the auxiliary control unit includes an auxiliary control valve and a PID controller II, the gas pressure detector I is connected to the PID controller II, and the PID controller II is connected to the auxiliary control valve to open or close the auxiliary control valve; the BOG header is divided into a branch to form a venting header F1, a main control valve and an auxiliary control valve which are connected in parallel are arranged on the venting header, and the output end of the venting header is connected to a flare system to burn through a ground flare of the flare system.
The following will be described with reference to specific examples.
The LNG storage tank has safe operation pressure (air pressure) requirements, and the storage tank pressure is controlled to be 0.5KPa-40 KPa according to design requirements. The BOG main pipe main control valve and the auxiliary control valve control the pressure of the BOG main pipe and the storage tank, the set value of the BOG main control valve and the auxiliary control valve is higher than the vacuum pressure of the LNG storage tank by 0.5KPa and lower than the opening pressure of the safety valve by 40KPa, and the normal control range is 18KPa-26 KPa.
The BOG treatment system is designed to consist of 2 low-temperature reciprocating compressors with the capacity of 8.5t/h, if the flow of BOG is higher than the treatment capacity of the compressors, the pressure of a storage tank and a main pipe is increased, and when the pressure is increased to 0.026MPa, a pressure control valve on the main pipe of the BOG is automatically opened, and part of the evaporation gas exceeding the process requirement is discharged to a flare system.
The design of the flare system comprises two sets of relatively independent closed ground flare systems, the total design handling capacity of the flare system is 90t/h, the flare system is used for safely discharging high-pressure discharged air under the accident condition, and the design handling capacity of each set of ground flare is 45 t/h. Under the normal operation condition, 2 sets of ground torches are operated simultaneously according to 2 sets of ground torches, and 1 set of ground torches cannot be operated by 1 device; under special conditions, when the torch needs to be operated according to 1-in-1 spare, the opening angles of the main control valve and the auxiliary control valve are controlled to be 17%.
The following description will be made of the BOG manifold control system.
As an option, the PID controller I adopts PID control to close or open the main control valve, when the real-time air pressure of the BOG main pipe is greater than the normal air pressure preset value, the main control valve is controlled to be opened, and the opening I of the main control valve reaches full load when the air pressure difference value is 0.024 Mpa; and the PID controller II adopts linear control to close or open the auxiliary control valve, when the real-time air pressure of the BOG main pipe is greater than the normal air pressure preset value by 0.024Mpa, the auxiliary control valve is controlled to be opened, and the opening II of the auxiliary control valve reaches full load when the air pressure difference value is 0.027 Mpa.
A PID controller is added on the basis of the original design, the pressure relief safety range is set to be 0.0240MPA-0.027Mpa according to the process safety pressure requirement, and the opening of the auxiliary control valve is in a direct proportional linear relation with the pressure in the pressure range. So realize two atmospheric valve separation control, newly add the controller simultaneously and adopt linear control guarantee in the condition of emergent evacuation or the unable complete evacuation of single valve, can in time empty fast, guarantee BOG house steward pressure stability. Two controllers form main, assist the collocation, and the main control valve adopts PID control, assists the control valve and adopts linear control, and only the main control valve is stably emptied under the condition of normal emptying, and under the emergency, pressure rises rapidly, and the auxiliary control valve can be opened rapidly, and when pressure reached 0.027Mpa, these two valves were all opened, effectively guaranteed the quick unloading requirement of torch system. TABLE 1, Master and Slave valve position control tables
TABLE 1, Master control valve and auxiliary control valve position control Table
| Function of | Valve actuation | Single torch (limiting valve) | Two torches (Main valve position limitation) | |
| Master control valve | Maintaining tank pressure stable | Smooth and steady regulation | 17％ | 30％ |
| Auxiliary control valve | Emergency evacuation | Quick opening | 17％ | 30％ |
The opening conditions of the auxiliary control valve are as follows:
(1) under an abnormal working condition, the pressure of the BOG main pipe rises rapidly, the main control valve controller cannot be adjusted timely, so that when the pressure exceeds the normal pressure range by 0.024Mpa, the auxiliary control valve is opened, and full-load emptying is achieved when the pressure reaches 0.027 Mpa.
(2) Under normal working conditions, when the pressure exceeds 0.024Mpa due to the fact that the emptying rate exceeds the full-load emptying rate of the main control valve, the auxiliary control valve is opened.
(3) Under normal working conditions, the auxiliary control valve is opened when the pressure exceeds 0.024Mpa due to the dead locking of the main control valve.
The opening degrees of the main control valve and the auxiliary control valve satisfy the following relationship,
when the ground torch is a single torch,
when the ground torches are two torches,
based on the foregoing example, in a preferred embodiment, the PID control program and the linear control program are configured in both the main control valve and the auxiliary control valve, and can be linked with each other or manually switched, so that when the main control valve stops, the auxiliary control valve can be used as the main control valve to realize smooth valve adjustment and maintain stable pressure of the BOG main pipe and the storage tank.
As an option, based on the foregoing example, in a preferred example, the BOG main pipe control system further includes a reflux control unit, the reflux control unit includes a reflux valve, a PID controller III, a gas pressure detector II and a temperature detector, the temperature detector and the gas pressure detector II are respectively used for detecting the temperature of the gas at the inlet Q of the BOG compressor and for detecting the gas pressure at the outlet of the BOG compressor, the outlet of the BOG compressor branches off to be connected to the LNG storage tank through the reflux valve, the temperature detector and the gas pressure detector II are respectively connected to the PID controller III, the PID controller III is connected to the reflux valve, and the reflux valve is closed or opened to the opening III by performing temperature control based on the temperature detector or performing gas pressure control based on the gas pressure detector II.
In order to realize the automatic control of the outlet pressure of the compressor in a DCS system, BOG compressor control logic needs to be optimized, taking the compressor A as an example, a PID control module is added in a DCS program, and the PID module controls the opening of a return valve at the outlet of the compressor A according to the pressure difference change between a high selection value PV of the inlet pressure of the compressor A and a pressure set value SP, so that the outlet pressure of the compressor is automatically controlled and stabilized at the set pressure value according to actual needs, and the problem of low output efficiency of the compressor caused by gas extrusion of a downstream pipe network is effectively solved by utilizing the regulating effect of the return valve. When the compressor A is started, the compressor A is controlled by a temperature set value, when the compressor A is started to be switched to normal and stable operation, the return valve is controlled by the pressure regulation and the temperature regulation of the outlet of the compressor A together, the temperature control is prior to the pressure control, the temperature control is automatically switched to the temperature control under the condition of abnormal temperature, and the undisturbed switching of the pressure control and the temperature control can be realized.
As shown in fig. 2, an example of a compressor control flow is given, and the compressor control process is as follows:
(1) the compressor is preferably controlled by a temperature set point during start-up.
(2) A switching button of temperature control and pressure control is added on a DCS interface, and meanwhile, a pressure control program is added on the basis of the temperature control program, so that an operator can select whether to use the pressure control according to the actual running condition of the compressor.
(3) In order to realize the undisturbed switching between the temperature control mode and the pressure control mode, a switching button is arranged in a program, and an operator can switch the pressure control mode back to the temperature control mode at any time according to actual needs.
Of course, automatic switching control can also be adopted, and the control process of the PID controller III for controlling the return valve is as follows;
firstly, executing a temperature control program after starting up; then judging whether the acquired real-time temperature is normal, if so, executing an air pressure control program, otherwise, executing a temperature control program; finally, repeating the step until the machine is stopped, specifically, after the current air pressure control program or temperature control program is executed for a period of time, judging whether the acquired real-time temperature is normal, if so, executing the air pressure control program, otherwise, executing the temperature control program; wherein a switching program is configured to switch between the temperature control program and the pneumatic control program under the condition of being operated by an operator.
Referring to fig. 3-7, the operation condition test before and after the optimization of the BOG main control system is specifically as follows.
As shown in fig. 3, the pressure day curve of the optimized LNG storage tank is shown. Therefore, after the control optimization of the main control valve, the auxiliary control valve and the compressor is carried out, the pressure oscillation of the LNG storage tank is obviously eliminated, the pressure fluctuation range is basically controlled within 0.5KPa, the evaporation capacity is increased and the BOG capacity at the beginning of loading is increased when the sunlight is strong at noon along with the time change, the valve adjustment is relatively frequent, the curve fluctuation is relatively frequent, the normal evaporation and loading weather backflow conditions of the LNG are met, and the optimization effect of the LNG storage tank pressure control system is good.
As shown in fig. 4, the LNG tank pressure monthly curves before and after optimization are compared; wherein the upper graph is that before optimization, the vibration amplitude is large and the frequency is high; the lower graph shows that after optimization, the amplitude is obviously reduced, and the curve tends to be smooth. Therefore, the pressure control of the LNG storage tank is obviously improved on the date line and the month cycle period, the large-amplitude oscillation condition is basically eliminated, the single-day fluctuation range can be basically controlled within 2KPa, and the optimization requirement is met.
As shown in fig. 5, the opening monthly curves of the before and after optimized output control valves of the BOG compressor are compared, wherein the upper graph is the before optimized temperature control and the lower graph is the after optimized combination control. Therefore, before optimization, the compressor frequently adjusts the load, so that the fluctuation of the opening of the output control valve is obvious, and the opening of the output control valve is mostly about 60%; after optimization, the compressor stably runs under high load, the opening of the control valve is over 99.6 percent, and the output is stable and efficient; the effective load is stably improved, the output efficiency of the compressor is high, the output capacity can achieve the expected purpose of stable output, the influence of BOG compressor load fluctuation on BOG header pipe pressure fluctuation is effectively eliminated, and the optimization effect is met.
FIG. 6 shows the curve for 18 days after optimization of the BOG header vent valve. FIG. 7 shows a comparison of the BOG manifold pressure cycle curves. Therefore, in the daily curve of the BOG main pipe, the sum of the time intervals when the main control valve is at about zero opening is higher than six, the highest opening is less than 8%, and the auxiliary control valve basically keeps zero opening. The fluctuation of the pressure cycle curve of the BOG header pipe is obviously reduced, the pressure cycle curve is effectively controlled within 3KPa, the occurrence of excess emptying is effectively eliminated, the optimization effect is good, and the optimization purpose of reducing emptying loss is achieved.
The flare system will be described below.
As an option, the torch system includes ground torch and unloading the control unit, unloading the control unit and including PID controller IV, atmospheric pressure detector III, unloading branch road pipe and atmospheric valve, atmospheric pressure house steward F shunts into unloading branch road pipe in order to be connected to ground torch respectively, the atmospheric valve sets up on the unloading branch road pipe, atmospheric pressure detector III is used for detecting the gaseous atmospheric pressure of P2 department of unloading house steward, atmospheric pressure detector III is connected with PID controller IV, PID controller IV is connected with the atmospheric valve and opens or close the atmospheric valve with control. Therefore, the air pressure detector III detects the real-time air pressure of the gas of the emptying header pipe, the PID controller IV obtains the real-time air pressure value, the real-time air pressure value is compared with the corresponding preset value, then the emptying valve is controlled to be opened, the automatic control of the emptying valve is realized, and the gas is emptied by burning ground torches such as a beacon light of a torch system.
The emptying branch pipe comprises a first branch pipe F1, a second branch pipe and a third branch pipe, the first branch pipe F1 is directly emptied, the second branch pipe is provided with a second-level emptying valve, the third branch pipe is provided with a third-level emptying valve, a PID controller IV is respectively connected with the second-level emptying valve and the third-level emptying valve, the second-level emptying valve and the third-level emptying valve are directly emptied through the first branch pipe when the air pressure of an emptying header pipe is 0-2Kpa, the second-level emptying valve and the third-level emptying valve are controlled to be opened when the air pressure of the emptying header pipe is 2-6Kpa, the second-level emptying valve and the third-level emptying valve are controlled to be opened when the air pressure of the emptying header pipe is 4-8Kpa, the second-level emptying valve corresponds to a valve with the opening degree of 0-100% when the air pressure of the emptying header pipe is 2-6Kpa, and the emptying valve corresponds to the valve with the opening degree of 0-100% at the air pressure of the emptying header pipe.
So, one-level, second grade, tertiary unloading control mode all are based on unloading house steward pressure control, avoid taking place so that effectively eliminate the switch untimely because of need wait for in the valve back pressure control mode that the preceding one-level valve just can have pressure variation after opening. Setting primary control pressure to be 0-2Kpa, and directly discharging and emptying through a first branch pipe; setting the pressure of the second-stage emptying at 2-6kpa, and controlling the opening of the second-stage emptying valve and the third-stage emptying valve; the pressure of the three-stage emptying is set to be 4-8Kpa, the two-stage emptying valve and the three-stage emptying valve are controlled to be opened, and meanwhile, the pressure section is overlapped to ensure that the three-stage emptying valve can be opened for emptying in time when excess emptying is carried out.
The control process of the PID controller IV for controlling the emptying valve is as follows:
when the air pressure of the emptying header pipe is 0-2Kpa, directly discharging and emptying through a first branch pipe; when the air pressure of the emptying header pipe is more than 2Kpa, the PID controller IV further controls to open the secondary emptying valve, and the air pressure of the emptying header pipe is kept in an open state when 2-6 Kpa; when the air pressure of the emptying header pipe is greater than 4Kpa, the PID controller IV further controls to open the third-stage emptying valve, and the air pressure of the emptying header pipe is 4-8Kpa, so that the second-stage emptying valve and the third-stage emptying valve are kept in an open state. Therefore, three-stage emptying control is formed, and is opened orderly, so that the opening stability of the valve is ensured; meanwhile, the air pressure section is overlapped to ensure that the emptying valve can be opened in time for emptying when excess emptying is carried out.
Referring to fig. 8-9, the pressure oscillations of the flare blow header and the deflagration of the flare system were tested before and after the flare system was optimized as follows.
As shown in FIG. 8, the fluctuation curves of the pre-optimization and post-optimization blow-down header pressure are compared for 10 days, wherein the upper graph is the graph before optimization and after optimization according to the post-pressure control of the pre-stage valve. Therefore, the curve fluctuation of the area in one week of the period before optimization is severe, and the maximum pressure is about 6 pa; after optimization, the pressure fluctuation range of the emptying header is effectively controlled within 3KPa, the vibration frequency is obviously reduced, and the problem of pressure oscillation of the emptying header is eliminated.
As shown in FIG. 9, the opening month curve of the second-level and third-level emptying valves after optimization. Therefore, the opening degree of the second-stage (second-stage) emptying valve is below 60%, the opening duration of each time is short, and the emptying requirement can be met; the three-stage (three-stage) emptying valve is basically not opened and is in a standby state; the optimized venting amount is less, the second section can quickly react and be vented for combustion in time, and the detonation conditions that the high-temperature probe is burnt out and the monitoring camera is burnt out due to overhigh accumulated pressure temperature of the second section flame caused by excessive venting can be avoided.
As described above, the control system is based on the separation control of the main control valve and the auxiliary control valve, and can effectively solve the problem of repeated periodic oscillation caused by quick opening and closing; by utilizing the adjusting function of the reflux valve, the problem of low output efficiency of the compressor caused by the gas extrusion of a downstream pipe network can be effectively solved; and the problem of pressure oscillation of the emptying main pipe is solved by adopting three-stage sectional control. Specifically, as follows, the following description will be given,
1. in the valve for the BOG main pipe emptying, pressure sectional control is adopted, a main control valve and an auxiliary control valve are separately controlled, main and auxiliary collocation is formed, the main control valve adopts PID control, the auxiliary control valve adopts linear control, abnormal emptying fast switch can be guaranteed, and stable regulation of the pressure of the BOG main pipe can be guaranteed under the normal emptying condition.
2. The control logic is controlled according to the priority level by utilizing an override control principle in the optimization of the BOG compressor, so that the requirement of improving the effective load of the BOG compressor under the normal working condition is met, the automatic switching can be realized according to the temperature alarm set by the compressor, and the compressor is ensured to be always in a safe state.
3. The ground flare system adopts a control mode of dividing pressure into three sections and having cross overlapping, thereby effectively realizing stable emptying, ensuring ordered switching of first-stage, second-stage and third-stage emptying, and timely starting and emptying.
4. Economic benefits
The main control valve, the PID controller, the air pressure detector and the like are all the prior art, and are connected and debugged according to the description. The logic optimization process can be realized by background optimization and control logic modification of the existing Siemens control system except for the addition of a small quantity of low-price equipment, and related technical problems of manufacturers can be consulted by telephone if necessary, so that investment can be ignored and not calculated.
According to the statistical data of a measurement and chemical examination center, the average reduction emptying amount per hour of a torch before and after modification is 3000Nm3, the density of liquefied natural gas LNG is 0.42-0.46 ton/cubic meter, the average density is 0.44 ton/cubic meter, the LNG gasification ratio is 1495Nm 3/ton, and the LNG price is calculated according to the market price of 4000 yuan/ton, so that the method comprises the following steps:
5. social benefits
1) The carbon dioxide emission was measured based on the molecular weight, and the average reduction in emissions per hour was 3000Nm3, with more than 99.9% of LNG being methane, the molecular weight being estimated as methane, from which:
2) the optimization control effectively eliminates the periodic detonation problem caused by excess emptying caused by system defects, and eliminates the harm of resonance to artificial islands and auxiliary buildings. As a novel safe torch system, the ground torch system is also the mainstream of future torches due to the characteristics of small safe distance, small noise, low radiation, sufficient combustion and the like.
The above description is intended to be illustrative of the preferred embodiments of the invention, but not to be construed as limiting the scope of the invention as claimed, and all equivalent variations and modifications of the teachings of this invention, which are obvious and suggested by the present disclosure, are intended to be included within the scope thereof.
Claims (8)
1. The utility model provides a LNG receiving station BOG unloading control system, LNG storage tank pass through BOG house steward and are connected to the BOG compressor, and the BOG compressor is gaseous with BOG output to downstream pipe network, its characterized in that: the BOG main pipe control system comprises a main control unit, an auxiliary control unit and a gas pressure detector I, wherein the gas pressure detector I is used for detecting the gas pressure of the BOG main pipe and comprises a main control valve and a PID (proportion integration differentiation) controller I, the gas pressure detector I is connected with the PID controller I, the PID controller I is connected with the main control valve to open or close the main control valve, the auxiliary control unit comprises an auxiliary control valve and a PID controller II, the gas pressure detector I is connected with the PID controller II, and the PID controller II is connected with the auxiliary control valve to open or close the auxiliary control valve; the BOG main pipe is divided into a branch to form a main emptying pipe and the main emptying pipe is provided with a main control valve and an auxiliary control valve which are connected in parallel, and the output end of the main emptying pipe is connected to a torch system to burn with a ground torch through the torch system.
2. The BOG emptying control system of the LNG receiving station as claimed in claim 1, wherein: the PID controller I adopts PID control to close or open the main control valve, when the real-time air pressure of the BOG main pipe is greater than the normal air pressure preset value, the main control valve is controlled to be opened, and the opening I of the main control valve reaches full load when the air pressure difference value is 0.024 Mpa; and the PID controller II adopts linear control to close or open the auxiliary control valve, when the real-time air pressure of the BOG main pipe is greater than the normal air pressure preset value by 0.024Mpa, the auxiliary control valve is controlled to be opened, and the opening II of the auxiliary control valve reaches full load when the air pressure difference value is 0.027 Mpa.
3. The BOG emptying control system of the LNG receiving station as claimed in claim 2, wherein: the opening degrees of the main control valve and the auxiliary control valve satisfy the following relation,
when the ground torch is a single torch,
when the number of the ground torches is two,
4. the BOG emptying control system of the LNG receiving station as claimed in claim 1, wherein: BOG house steward control system still includes the backward flow control unit, the backward flow control unit includes the reflux valve, PID controller III, atmospheric pressure detector II and thermodetector, thermodetector and atmospheric pressure detector II are used for detecting the gaseous temperature of entrance of BOG compressor respectively and are used for detecting the gaseous atmospheric pressure in the exit of BOG compressor, the export of BOG compressor divides a branch road in order to be connected to the LNG storage tank through the reflux valve, thermodetector and atmospheric pressure detector II are connected with PID controller III respectively, PID controller III is connected with the reflux valve, carry out temperature control or carry out atmospheric pressure control based on atmospheric pressure detector II based on thermodetector, so that the reflux valve is closed or is opened to aperture III.
5. The BOG emptying control system of the LNG receiving station as claimed in claim 4, wherein: the control process of the PID controller III for controlling the return valve is as follows;
firstly, executing a temperature control program after starting up; then judging whether the acquired real-time temperature is normal or not, if so, executing an air pressure control program, and otherwise, executing a temperature control program; finally, repeating the step until the machine is stopped, specifically, after the current air pressure control program or temperature control program is executed for a period of time, judging whether the acquired real-time temperature is normal, if so, executing the air pressure control program, otherwise, executing the temperature control program; wherein a switching program is configured to switch between the temperature control program and the pneumatic control program under the condition of being operated by an operator.
6. The BOG emptying control system of the LNG receiving station as claimed in claim 1, wherein: the flare system includes ground torch and unloading the control unit, and unloading the control unit includes PID controller IV, atmospheric pressure detector III, unloading branch road pipe and atmospheric valve, and the atmospheric pressure house steward shunts into the unloading branch road pipe in order to be connected to ground torch respectively, and the atmospheric valve sets up on the unloading branch road pipe, and atmospheric pressure detector III is used for detecting the gaseous atmospheric pressure of unloading house steward, and atmospheric pressure detector III is connected with PID controller IV, and PID controller IV is connected with the atmospheric valve and opens or close the atmospheric valve with control.
7. The BOG emptying control system of the LNG receiving station as claimed in claim 6, wherein: the emptying branch pipe comprises a first branch pipe, a second branch pipe and a third branch pipe, the first branch pipe is directly emptied, the second branch pipe is provided with a second-stage emptying valve, the third branch pipe is provided with a third-stage emptying valve, a PID controller IV is respectively connected with the second-stage emptying valve and the third-stage emptying valve, the second-stage emptying valve is directly emptied through the first branch pipe when the air pressure of the emptying header pipe is 0-2Kpa, the second-stage emptying valve corresponds to 0-100% of opening of a valve when the air pressure of the emptying header pipe is 2-6Kpa, and the third-stage emptying valve corresponds to 0-100% of opening of the valve when the air pressure of the emptying header pipe is 4-8 Kpa.
8. The BOG emptying control system of the LNG receiving station as claimed in claim 7, wherein the control process of the PID controller IV controlling the emptying valve is as follows:
when the air pressure of the emptying header pipe is 0-2Kpa, emptying directly through a first branch pipe; when the air pressure of the emptying header pipe is more than 2Kpa, the PID controller IV further controls to open the secondary emptying valve, and the air pressure of the emptying header pipe is kept in an open state when 2-6 Kpa; when the air pressure of the emptying header pipe is greater than 4Kpa, the PID controller IV further controls to open the third-stage emptying valve, and the air pressure of the emptying header pipe is 4-8Kpa, so that the second-stage emptying valve and the third-stage emptying valve are kept in an open state.
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Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003106498A (en) * | 2001-09-28 | 2003-04-09 | Toho Gas Co Ltd | Bog re-liquefaction and recovery system for lng tank |
| CN202274285U (en) * | 2011-07-06 | 2012-06-13 | 中国寰球工程公司 | Pressure control system of liquefied natural gas storage tank |
| CN104132241A (en) * | 2014-07-29 | 2014-11-05 | 天津安耐吉燃气技术有限公司 | BOG (boil off gas) diffusing recovering apparatus of LNG (liquefied natural gas) storage tank and control method |
| CN104390136A (en) * | 2014-11-11 | 2015-03-04 | 南京工业大学 | BOG recovering method and device |
| KR101670925B1 (en) * | 2015-10-26 | 2016-10-31 | (주)발맥스기술 | Lng boil off gas reliquefaction system and method of the same |
| WO2017092028A1 (en) * | 2015-12-04 | 2017-06-08 | 深圳智慧能源技术有限公司 | Pressure control fixed value adjusting system based on torch operating condition |
| CN107606487A (en) * | 2017-09-14 | 2018-01-19 | 中国寰球工程有限公司 | It is applicable the BOG processing systems and method of LNG storage tank under different designs pressure |
| CN108253518A (en) * | 2017-11-30 | 2018-07-06 | 华能国际电力股份有限公司上海石洞口第电厂 | A kind of thermal power plant heat supply network pressure of steam supply control method |
| CN207990197U (en) * | 2017-12-30 | 2018-10-19 | 大连福佳·大化石油化工有限公司 | A kind of improved spherical tank bleeds off pressure system |
| CN209294807U (en) * | 2018-12-08 | 2019-08-23 | 大连福佳·大化石油化工有限公司 | A kind of improved flare discharge control system |
| CN111174084A (en) * | 2020-03-05 | 2020-05-19 | 新地能源工程技术有限公司 | Method and system for realizing simultaneous loading and unloading of LNG receiving station |
| CN211694344U (en) * | 2020-01-21 | 2020-10-16 | 四川杰瑞恒日天然气工程有限公司 | LNG ration loading system |
| CN215636521U (en) * | 2021-03-22 | 2022-01-25 | 厚普清洁能源股份有限公司 | LNG filling system that no BOG discharged |
-
2022
- 2022-05-27 CN CN202210593035.5A patent/CN114941801B/en active Active
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003106498A (en) * | 2001-09-28 | 2003-04-09 | Toho Gas Co Ltd | Bog re-liquefaction and recovery system for lng tank |
| CN202274285U (en) * | 2011-07-06 | 2012-06-13 | 中国寰球工程公司 | Pressure control system of liquefied natural gas storage tank |
| CN104132241A (en) * | 2014-07-29 | 2014-11-05 | 天津安耐吉燃气技术有限公司 | BOG (boil off gas) diffusing recovering apparatus of LNG (liquefied natural gas) storage tank and control method |
| CN104390136A (en) * | 2014-11-11 | 2015-03-04 | 南京工业大学 | BOG recovering method and device |
| KR101670925B1 (en) * | 2015-10-26 | 2016-10-31 | (주)발맥스기술 | Lng boil off gas reliquefaction system and method of the same |
| WO2017092028A1 (en) * | 2015-12-04 | 2017-06-08 | 深圳智慧能源技术有限公司 | Pressure control fixed value adjusting system based on torch operating condition |
| CN107606487A (en) * | 2017-09-14 | 2018-01-19 | 中国寰球工程有限公司 | It is applicable the BOG processing systems and method of LNG storage tank under different designs pressure |
| CN108253518A (en) * | 2017-11-30 | 2018-07-06 | 华能国际电力股份有限公司上海石洞口第电厂 | A kind of thermal power plant heat supply network pressure of steam supply control method |
| CN207990197U (en) * | 2017-12-30 | 2018-10-19 | 大连福佳·大化石油化工有限公司 | A kind of improved spherical tank bleeds off pressure system |
| CN209294807U (en) * | 2018-12-08 | 2019-08-23 | 大连福佳·大化石油化工有限公司 | A kind of improved flare discharge control system |
| CN211694344U (en) * | 2020-01-21 | 2020-10-16 | 四川杰瑞恒日天然气工程有限公司 | LNG ration loading system |
| CN111174084A (en) * | 2020-03-05 | 2020-05-19 | 新地能源工程技术有限公司 | Method and system for realizing simultaneous loading and unloading of LNG receiving station |
| CN215636521U (en) * | 2021-03-22 | 2022-01-25 | 厚普清洁能源股份有限公司 | LNG filling system that no BOG discharged |
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|---|---|
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