A liquid ethane pipeline intermediate pump station discharge medium safety treatment system and treatment method

Abstract

The present invention discloses a liquid ethane pipeline intermediate pump station discharge medium safety treatment system and treatment method, the liquid ethane is transported through a liquid ethane pipeline, the liquid ethane pipeline is provided with an inlet shut-off valve, an outlet shut-off valve and a booster pump, and the safety treatment system includes an unplanned discharge treatment system, a planned venting system, a recovery system and a control system. Based on the operating characteristics of the liquid ethane long-distance pipeline pump station, combined with the safety protection concept of the conventional oil pipeline intermediate pump station, the present invention adopts the strategy of direct combustion of unplanned discharge medium and efficient recovery of planned venting medium in view of the characteristics of good economic value of ethane recovery and low temperature after discharge, and establishes two independent discharge medium treatment modes, thereby avoiding the construction of high-pressure storage tanks to receive unplanned discharge mediums, and also realizing efficient recovery of trunk pipeline storage mediums.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid ethane transportation, and in particular relates to a liquid ethane pipeline intermediate pump station discharge medium safety treatment system and treatment method. Background Art

[0002] With the development of natural gas processing technology and the development of natural gas efficient utilization technology, the recovery efficiency of ethane in natural gas has been continuously improved, and its long-distance transportation technology needs to be vigorously developed to expand the scope of application. As a type of natural gas ancillary product with a lighter molar mass, ethane products have a higher saturated vapor pressure, a critical temperature of about 32°C, and a critical pressure of about 4.5MPa. Therefore, it is possible to transport them in a single phase in gas or liquid state. Compared with the gaseous ethane pipeline transportation method, liquid transportation has the significant characteristics of small pipe diameter and high transportation efficiency, which is suitable for large-scale and networked transportation of ethane products.

[0003] During the operation of long-distance pipelines, intermediate pumping stations are permanent booster stations. Compared with other stations, pumping stations have relatively more pressure protection points and can also cover the safety protection functions of other types of stations. For typical liquid transportation pipelines, it is necessary to set up storage tanks for water hammer relief and overpressure protection after the pump at the pump station to prevent the internal pressure of the pipeline from exceeding the design pressure. For example, for crude oil or refined oil pipelines, since the medium basically achieves normal pressure stability before entering the pipeline for transportation, the storage tank is designed according to normal pressure, and the discharge and receiving functions can be achieved by meeting the expected discharge volume.

[0004] In contrast, liquid ethane is a pressurized transmission medium, and the general transmission pressure is higher than 5MPa to maintain the liquid phase. During the discharge process, liquid ethane is affected by the discharge back pressure (close to normal pressure), which may produce extremely low temperatures (when adiabatically released to atmospheric pressure, the medium temperature is about -90°C). At the same time, the critical pressure of liquid ethane is only 32°C. If the temperature exceeds this value, the medium will enter the supercritical region or gas phase region, causing a significant decrease in density, which also poses a safety hazard to the safe storage of the tank. In addition, in addition to the aforementioned water hammer overpressure relief and post-pump overpressure relief, liquid ethane pumping stations also need to consider issues such as overpressure relief during shutdown of open pipelines and emptying of upstream and downstream trunk lines for maintenance.

[0005] Since ethane has high economic value, a reasonable discharge medium treatment plan should be proposed based on full consideration of medium characteristics.

[0006] At present, there is no comprehensive report on the safe treatment of liquid ethane pump station medium release. The relevant patent 201911098154.8 proposed the idea of ​​online recovery of pipeline ethane release, that is, real-time heating and recovery of the released medium. Since the ethane reserves in the pipeline are generally large, the construction investment required for selecting a high-pressure gas tank to store gaseous ethane is relatively high; on the other hand, the scheme of using a compressor to pressurize gaseous ethane for high-pressure medium recovery in tank trucks may involve certain transportation risks. Summary of the invention

[0007] The purpose of the present invention is to provide a liquid ethane pipeline intermediate pump station discharge medium safety treatment system and treatment method in order to further promote the development of liquid ethane pipeline transportation technology and ensure operation safety in view of the above-mentioned problems.

[0008] The main technical idea of ​​the present invention is to set up an unplanned discharge treatment system, a planned venting system, a mobile recovery system and a control system based on the operating characteristics of the liquid ethane long-distance pipeline pump station and the safety protection concept of the conventional oil pipeline intermediate pump station. Through the above settings, according to the operating characteristics and safety priority levels of planned venting and unplanned discharge, combined with economic considerations, a more reasonable and reliable liquid ethane intermediate pump station discharge medium safety treatment system and method is formed, thereby satisfying the liquid ethane medium safety discharge in the intermediate pump station, and effectively improving the medium recovery efficiency during pipeline maintenance, and reducing the recovery energy consumption compared to the existing technology.

[0009] The technical solution adopted by the present invention is: a liquid ethane pipeline intermediate pump station discharge medium safety treatment system, the liquid ethane is transported through a liquid ethane pipeline, the liquid ethane pipeline is provided with an inlet shut-off valve, an outlet shut-off valve and a booster pump, characterized in that: the safety treatment system includes an unplanned discharge treatment system, a planned venting system, a recovery system and a control system;

[0010] The unplanned discharge treatment system includes a pipeline discharge unit upstream of the station shut-off valve, an open-air pipeline discharge unit, and a pipeline discharge unit downstream of the booster pump; the pipeline discharge unit upstream of the station shut-off valve is used to safely discharge the overpressure medium under the water hammer overpressure condition of the pipeline upstream of the station shut-off valve, and directly discharge it into the flare system for combustion treatment; the open-air pipeline discharge unit is used to discharge the overpressure caused by the expansion of the medium in the open-air pipeline due to the temperature increase when the station is shut down, and directly discharge it into the flare system for combustion treatment; the pipeline discharge unit downstream of the booster pump is used for overpressure protection of the downstream pipeline of the booster pump and the discharge of the overpressure medium, and directly discharges it into the flare system for combustion treatment;

[0011] The planned venting system includes a venting unit upstream of the inlet block valve and a venting unit downstream of the outlet block valve. The planned venting system is used to safely vent the ethane medium stored in the planned pipeline. The planned venting system is connected to the recovery system; the control system is used to monitor the working status of the pipeline and equipment in real time.

[0012] The liquid ethane pipeline intermediate pump station discharge medium safety treatment system of the present invention, wherein the upstream pipeline discharge unit of the station inlet cut-off valve comprises a water hammer discharge valve arranged upstream of the station inlet cut-off valve and an upstream discharge branch connected to the liquid ethane pipeline;

[0013] The open-air pipeline discharge unit includes a thermal discharge valve arranged on the open-air pipeline in the station and an in-station pipeline discharge branch connected to the liquid ethane pipeline;

[0014] The booster pump downstream pipeline discharge unit comprises a post-pump discharge valve arranged downstream of the booster pump and a post-pump discharge branch connected to the liquid ethane pipeline;

[0015] The upstream discharge branch, the station pipeline discharge branch and the post-pump discharge branch are all connected to the flare system. The media discharged by the pipeline discharge unit upstream of the station shut-off valve, the open air pipeline discharge unit and the pipeline discharge unit downstream of the booster pump under unplanned conditions are directly discharged into the flare system for combustion treatment.

[0016] The liquid ethane pipeline intermediate pump station discharge medium safety treatment system described in the present invention, wherein the upstream discharge branch, the station pipeline discharge branch and the post-pump discharge branch are respectively connected to the pressure relief branch pipe, and the pressure relief branch pipe is connected to the flare system through the vent main pipe, and the pressure relief branch pipe is used to collect the discharge media from each route and send them to the vent main pipe.

[0017] The liquid ethane pipeline intermediate pump station discharge medium safety treatment system of the present invention, wherein the station inlet shutoff valve upstream venting unit comprises an upstream regulating venting valve arranged upstream of the station inlet shutoff valve and an upstream venting pipeline connected to the liquid ethane pipeline;

[0018] The downstream venting unit of the outbound shutoff valve comprises a downstream regulating venting valve arranged downstream of the outbound shutoff valve and a downstream venting pipeline connected to the liquid ethane pipeline;

[0019] The upstream vent pipeline and the downstream vent pipeline are both connected to the recovery system through an adjustable vent main pipe. The vent unit upstream of the inlet block valve and the vent unit downstream of the outlet block valve safely vent the medium stored in the pipeline under planned conditions, and the vented medium goes to the recovery system.

[0020] The liquid ethane pipeline intermediate pump station discharge medium safety treatment system of the present invention comprises a control system including a pressure transmitter and a temperature transmitter arranged on the regulating and venting main pipe.

[0021] The liquid ethane pipeline intermediate pump station discharge medium safety treatment system of the present invention, wherein the recovery system comprises a buffer pressure regulating tank, a refrigeration system, a pump system and a low temperature storage system;

[0022] The buffer pressure regulating tank is used to provide a predetermined back pressure for upstream planned venting, and control the temperature range of liquid ethane when it is discharged to the rated back pressure; the refrigeration system is used to reliquefy the recovered gaseous ethane; the pump system is used to provide power for the reliquefied ethane to enter the cryogenic storage system; the cryogenic storage system is used to receive and store the reliquefied cryogenic atmospheric pressure ethane.

[0023] The liquid ethane pipeline intermediate pump station discharge medium safety treatment system described in the present invention comprises a buffer pressure regulating tank, a refrigeration system, a pump system and a low-temperature storage system which are skidded into a mobile integral structure.

[0024] A method for safely handling discharged medium in an intermediate pump station of a liquid ethane pipeline, characterized in that: the discharged medium of the liquid ethane in the intermediate pump station adopts the discharge mode of unplanned emptying and planned emptying;

[0025] The unplanned venting includes the release of water hammer overpressure in the upstream pipeline of the station cut-off valve, the release of thermal overpressure in the exposed pipeline in the station, and the release of overpressure after the pipeline downstream of the booster pump. The unplanned venting medium is directly sent to the flare system for combustion treatment;

[0026] The planned venting includes venting upstream of the inlet block valve and venting downstream of the outlet block valve. The medium of the planned venting is sent to a mobile recovery system for processing and storage.

[0027] The method for safely treating the discharged medium of the liquid ethane pipeline intermediate pump station of the present invention comprises the following steps: an unplanned discharge treatment system, a planned venting system, a mobile recovery system and a control system are arranged in the liquid ethane intermediate pump station; when the pump station and the pipeline are operating normally, the regulating venting valve in the planned venting system is kept closed, and the water hammer relief valve, the thermal relief valve and the safety valve in the unplanned discharge treatment system are kept online and ready for use;

[0028] The unplanned venting methods specifically include:

[0029] When the inlet block valve is accidentally closed or the pump is stopped, if water hammer overpressure occurs in the upstream pipeline, the water hammer relief valve will automatically open, and the flare system will start the ignition procedure to ensure safe combustion of the medium;

[0030] When the outbound shut-off valve is accidentally closed or the downstream pipeline valve is accidentally closed, if the pressure after the pump exceeds the design pressure of the downstream pipeline, the discharge valve after the pump will automatically open and continue to send a pump stop alarm to the control room. At the same time, the flare system starts the ignition procedure to ensure safe combustion of the medium;

[0031] After the pipeline is shut down, if the internal pressure of the pipeline in the station increases due to the heat of the pipeline and exceeds the set pressure of the thermal relief valve, the thermal relief valve will automatically open and the flare system will start the ignition program to ensure the safe combustion of the medium;

[0032] The planned venting method is: when the upstream trunk line or downstream trunk line of the liquid ethane pipeline needs to be shut down for maintenance, the mobile recovery system is transported to the pump station, assembled and debugged, and the ethane medium stored in the pipeline is safely vented, and the vented medium goes to the mobile recovery system.

[0033] The method for safely treating the discharged medium of the liquid ethane pipeline intermediate pump station of the present invention, and the method for treating the movable recovery system thereof are specifically as follows:

[0034] First, pre-charge the buffer pressure regulating tank with ethane gas, and control the pressure at 1.5-1.8 MPa.g. Open the upstream regulating vent valve and the downstream regulating vent valve, and depressurize the ethane stored in the trunk line and charge it into the buffer pressure regulating tank to form a pressure balance.

[0035] Then, the refrigeration system and the cryogenic storage system are started, and the ethane in the buffer pressure regulating tank enters the refrigeration system and is further cooled after the pressure is adjusted to the gravity pressure, and then the ethane-ethylene refrigerant heat exchange is completed, and the liquefied ethane directly passes through the pump system and enters the cryogenic storage system;

[0036] Finally, when the upstream pipeline pressure drops to the ethane gravity pressure, start the pump system to pressurize the low-temperature liquid ethane flowing out of the refrigeration system to ensure that it enters the low-temperature storage system. The pipeline ethane venting rate in this step should be adjusted by the temperature indicated by the temperature transmitter installed on the trunk pipeline. When the trunk pipeline pressure is close to normal pressure, stop this step.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention is based on the operating characteristics of the liquid ethane long-distance pipeline pump station, combined with the safety protection concept of the conventional oil pipeline intermediate pump station, and takes into account the characteristics of ethane recovery, such as good economic value and low temperature after discharge. It adopts the strategy of direct combustion of unplanned discharge medium and efficient recovery of planned venting medium, and establishes two independent discharge medium processing modes, thereby avoiding the construction of high-pressure storage tanks to receive unplanned discharge medium, and also realizing efficient recovery of trunk pipeline storage medium. Furthermore, a movable recovery system is set up to reduce the daily operation risk of the station, and also improve the economic performance through device reuse. In addition, the ethane pressure in the pipe is reasonably used to provide recovery pre-cooling capacity, which optimizes the system energy consumption.

[0039] The specific manifestations are:

[0040] (1) Scientific setting

[0041] This system focuses on the characteristics of liquid ethane pump station discharge and venting, and sets up two independent discharge medium treatment modes. For unplanned discharge, the idea of ​​direct flare treatment after pressure relief and gasification is preferred, which meets the requirements for safe medium discharge under emergency conditions and effectively reduces the construction investment, operating costs and safety risks of station storage tanks. For planned venting, the venting medium buffering and pressure reduction pre-cooling recovery mode under back pressure control is preferred, which effectively reduces the material requirements of ethane at low pressure and low temperature for station pipelines and buffer pressure regulating tanks, and also tries to use the residual pressure gasification followed by pre-cooling and ethylene circulation refrigeration to achieve ethane atmospheric re-liquefaction, and finally transport it out for recovery by tank trucks.

[0042] (2) Economical

[0043] Based on the characteristics of pressure relief conditions, this system aims to reduce infrastructure investment and efficiently recover ethane. It directly burns the medium discharged from water hammer relief and pump-back relief with large instantaneous storage requirements, reducing the construction and investment costs of high-pressure liquid storage tanks; it reliquefies and recovers ethane stored in trunk pipelines with large reserves and slightly loose venting time requirements, avoiding direct combustion waste. Furthermore, a mobile recovery system is set up to improve the efficiency of equipment use and reduce the total investment of the project. In addition, the original pressure and pressure reduction cooling capacity of ethane venting are fully utilized to reduce the energy consumption of reliquefaction recovery.

[0044] (3) Promoting technological development

[0045] Considering that the development of liquid ethane pipelines in my country is still in its infancy, the present invention will contribute to the further development of liquid ethane station medium release safety recovery technology, and will also contribute to the promotion of the concept of mobile processing systems in special medium pipeline transportation projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be described by way of specific embodiments with reference to the accompanying drawings, in which

[0047] Figure 1 It is a schematic diagram of the process flow of the present invention.

[0048] Markings in the figure: 1 is the liquid ethane pipeline, 2 is the inlet shut-off valve, 3 is the outlet shut-off valve, 4 is the booster pump, 5 is the flare system, 6 is the water hammer relief valve, 7 is the upstream relief branch, 8 is the thermal relief valve, 9 is the pipeline relief branch in the station, 10 is the post-pump relief valve, 11 is the post-pump relief branch, 12 is the pressure relief branch, 13 is the vent main pipe, 14 is the upstream regulating vent valve, 15 is the upstream vent pipeline, 16 is the downstream regulating vent valve, 17 is the downstream vent pipeline, 18 is the regulating vent main pipe, 19 is the pressure transmitter, 20 is the temperature transmitter, 21 is the buffer pressure regulating tank, 22 is the refrigeration system, 23 is the pump system, and 24 is the low-temperature storage system. DETAILED DESCRIPTION

[0049] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0050] Any feature disclosed in this specification (including any additional claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0051] like Figure 1 As shown, a liquid ethane pipeline intermediate pump station discharge medium safety treatment system, the liquid ethane is transported through a liquid ethane pipeline 1, the liquid ethane pipeline 1 is provided with an inlet shut-off valve 2, an outlet shut-off valve 3 and a booster pump 4, the safety treatment system includes an unplanned discharge treatment system, a planned venting system, a recovery system and a control system.

[0052] Among them, the unplanned discharge processing system includes a pipeline discharge unit upstream of the station shut-off valve, an open pipeline discharge unit and a pipeline discharge unit downstream of the booster pump; the pipeline discharge unit upstream of the station shut-off valve is used to safely discharge the overpressure medium under the water hammer overpressure condition of the pipeline upstream of the station shut-off valve 2, and directly discharge it into the flare system 5 for combustion treatment; the open pipeline discharge unit is used to discharge the overpressure caused by the expansion of the medium in the open pipeline due to the increase in temperature when the station is shut down, and directly discharge it into the flare system 5 for combustion treatment; the pipeline discharge unit downstream of the booster pump is used for overpressure protection of the downstream pipeline of the booster pump 4 and the discharge of overpressure medium, and directly discharges it into the flare system 5 for combustion treatment.

[0053] The planned venting system includes a venting unit upstream of the inlet shut-off valve and a venting unit downstream of the outlet shut-off valve. The planned venting system is used to safely vent the ethane medium stored in the planned pipeline. The planned venting system is connected to a recovery system, such as safely venting the stored ethane medium in the buried pipelines upstream and downstream of the pump station before maintenance. The vented medium goes to a movable recovery system. The recovery system is used to regulate the pressure, liquefy, store and recover the ethane discharged from the planned venting system; the control system is used to monitor the working status of the pipeline and equipment in real time and upload data.

[0054] In this embodiment, the upstream pipeline discharge unit of the inlet shut-off valve includes a water hammer discharge valve 6 arranged upstream of the inlet shut-off valve 2 and an upstream discharge branch 7 connected to the liquid ethane pipeline 1; specifically, the upstream discharge branch opens and leads out upstream of the inlet shut-off valve, is made of carbon steel, and has a pipe diameter of preferably DN100. The water hammer discharge valve is connected to the upstream discharge branch, is a two-phase medium discharge valve, and is used for discharging the medium under water hammer overpressure conditions in the upstream pipeline, and is made of stainless steel.

[0055] The open-air pipeline discharge unit includes a thermal discharge valve 8 arranged on the open-air pipeline in the station and an in-station pipeline discharge branch 9 connected to the liquid ethane pipeline 1; specifically, the in-station pipeline discharge branch opens on the internal trunk pipeline and leads out, and is made of carbon steel with a pipe diameter of preferably DN50. The thermal discharge valve is connected to the in-station pipeline discharge branch and is a two-phase medium discharge valve, which is used for discharging overpressure caused by medium heating after the in-station pipeline is stopped, and is made of stainless steel.

[0056] The booster pump downstream pipeline discharge unit includes a post-pump discharge valve 10 arranged downstream of the booster pump 4 and a post-pump discharge branch 11 connected to the liquid ethane pipeline 1; specifically, the post-pump discharge branch opens and leads out on the post-pump main line, is made of carbon steel, and has a pipe diameter not less than 75% of the main line diameter; the post-pump discharge valve is connected to the post-pump discharge branch, is a two-phase medium discharge valve, is used for full discharge of overpressure medium after the pump, and is made of stainless steel.

[0057] The upstream discharge branch 7, the in-station pipeline discharge branch 9 and the post-pump discharge branch 11 are respectively connected to the pressure relief branch pipe 12, the pressure relief branch pipe is made of stainless steel and has a pressure rating of Class 150. The pressure relief branch pipe 12 is connected to the flare system 5 through the vent main pipe 13, the vent main pipe is made of stainless steel and has a pressure rating of Class 150. The pressure relief branch pipe 12 is used to collect the discharged media from various routes and send them to the vent main pipe 13. The media discharged by the pipeline discharge unit upstream of the station shut-off valve, the exposed pipeline discharge unit and the pipeline discharge unit downstream of the booster pump under unplanned conditions are directly discharged into the flare system 5 for combustion treatment.

[0058] Among them, the upstream vent unit of the inlet shut-off valve includes an upstream regulating vent valve 14 arranged upstream of the inlet shut-off valve 2 and an upstream vent pipeline 15 connected to the liquid ethane pipeline 1; specifically, the upstream regulating vent valve is made of carbon steel, installed on a branch of the upstream discharge branch, and opened when the upstream trunk pipeline needs to be vented. The upstream vent pipeline is connected to the upstream regulating vent valve, which is made of carbon steel and has an operating temperature of not less than -20°C.

[0059] The downstream venting unit of the outlet shut-off valve includes a downstream regulating venting valve 16 arranged downstream of the outlet shut-off valve 3 and a downstream venting pipeline 17 connected to the liquid ethane pipeline 1; specifically, the downstream regulating venting valve is made of carbon steel, installed on the downstream discharge branch, and opened when the downstream trunk pipeline needs to be vented. The downstream venting pipeline is connected to the downstream regulating venting valve, is made of carbon steel, and has an operating temperature of not less than -20°C.

[0060] The upstream vent pipeline 15 and the downstream vent pipeline 17 are both connected to the recovery system through the regulating vent main pipe 18. The operating temperature of the regulating vent main pipe is not lower than -20°C. The control system includes a pressure transmitter 19 and a temperature transmitter 20 arranged on the regulating vent main pipe 18. The pressure transmitter and the temperature transmitter are sequentially installed on the regulating vent main pipe to indicate the medium temperature and pressure at the end of the vent main pipe of the planned venting system respectively. The upstream vent unit of the inlet shut-off valve and the downstream vent unit of the outlet shut-off valve are used for the safe venting of the medium in the upstream and downstream buried pipelines of the pumping station before maintenance in the planned state, and the vented medium goes to the recovery system.

[0061] The recovery system includes a skid-mounted buffer pressure regulating tank 21, a refrigeration system 22, a pump system 23 and a low-temperature storage system 24 to form a mobile integral structure, namely a mobile recovery system, which is used to regulate the pressure, liquefy and store and recover the ethane discharged from the planned venting system.

[0062] The buffer pressure regulating tank 21 is used to provide a predetermined back pressure for the upstream planned venting, and control the temperature range of liquid ethane when it is discharged to the rated back pressure. On the one hand, it avoids the temperature from being too low, and on the other hand, it also provides a favorable pre-cooling effect, and is also used to provide medium buffering for downstream operations; specifically, the buffer pressure regulating tank is a steel vertical storage tank equipped with an interface valve, an interface pipeline, and an outlet pipeline. The material is carbon steel, and the operating pressure is not less than 1.5MPa.g. It is used for pre-pressurization after connecting to the planned venting system to form a back pressure of not less than 1.5MPa.g for the planned venting system, so that the liquid ethane in the trunk pipeline is vented to this pressure, and its medium temperature is higher than -15°C, and it is also used for stable supply of the downstream refrigeration system.

[0063] The refrigeration system 22 is a small-scale ethylene refrigeration, ethylene-methane heat exchange and supporting compression system, which is used to reliquefy the recovered gaseous ethane; specifically, the refrigeration system includes skid-mounted feed secondary regulation, refrigerant pressurization, refrigerant air cooling, refrigerant expansion refrigeration, ethane-refrigerant heat exchange and other subsystems, and the refrigerant is preferably ethylene; feed secondary regulation is used to further regulate the pressure and control the flow of ethane at the outlet of the buffer pressure regulating tank, preferably to 0.1MPa.g, and use secondary pressure regulation to generate low temperature as pre-cooling for ethane reliquefaction recovery; refrigerant pressurization, refrigerant air cooling, refrigerant expansion refrigeration, ethane-refrigerant heat exchange and other systems are used to circulate pressurization-expansion refrigeration of the refrigerant, providing the main cold source required for liquefaction of ethane under slightly positive pressure, and the system power is powered by the power generation equipment brought by the movable recovery system.

[0064] The pump system 23 is a cryogenic centrifugal pump system, which is used to provide power for the reliquefied ethane to enter the cryogenic storage system 24; specifically, the pump system is a cryogenic centrifugal pump and supporting pipes, which will not be started before the outlet pressure of the refrigeration system is higher than 0.1MPa, and the liquid ethane can enter the cryogenic storage system using the residual pressure. It will be started after the outlet pressure of the refrigeration system is lower than 0.1MPa to inject the liquid ethane into the cryogenic storage system.

[0065] The cryogenic storage system 24 is a storage device for reliquefied ethane, which is used to receive and store reliquefied low-temperature atmospheric pressure ethane and transport it safely; specifically, the cryogenic storage system is a vehicle-mounted fully refrigerated atmospheric pressure horizontal tank, which can provide a refrigeration temperature of -100°C to ensure the phase stability of liquid ethane at atmospheric pressure, and the filling coefficient shall not be higher than 0.85.

[0066] The working principle and working process of this system are as follows:

[0067] (1) When liquid ethane is transported normally, the pump station provides a main flow channel and boosting power.

[0068] (2) When the shut-off valve at the pump station is closed, the pump body stops running, or the valve downstream of the pump is closed, unplanned overpressure conditions such as water hammer overpressure, overpressure behind the pump, or overpressure due to heat in the closed pipeline may occur. Considering the gasification and low temperature problems after the liquid ethane is released, the unplanned release treatment system is preferably / set up to quickly introduce the overpressured liquid ethane into the flare system through the release valve for combustion, control the system pressure, and safely handle the released medium.

[0069] (3) When the upstream and downstream trunk pipelines of the pump station need to be vented for maintenance, make full use of the time planning characteristics of the maintenance venting, deploy a mobile recovery system in advance, connect it to the planned venting system, and recover ethane with higher economic value. Since ethane is transported in a liquid state in the pipeline, the pressure is generally above 6MPa.g. When ethane is vented, the pressure in the trunk line drops rapidly to 3.8MPa.g (leaving the liquid phase area and entering the gas-liquid two-phase area), and then slowly drops to 2.2MPa.g (leaving the gas-liquid two-phase area and entering the gas phase area), until it drops to normal pressure (gas phase area). During adiabatic discharge, when ethane in the liquid phase or gas-liquid two-phase state is depressurized to normal pressure, the temperature can be as low as -90℃; due to the continuous decrease in pressure, the ethane in the trunk line will also experience a significant temperature drop. Therefore, first use the buffer pressure regulating tank to pre-charge ethane to increase the pressure of the buffer pressure regulating tank and the upstream vent pipeline (or downstream vent pipeline) to above 1.5MPa.g; then open the upstream regulating vent valve (or downstream vent pipeline). At this time, the pressures of the trunk line, vent pipeline and buffer pressure regulating tank are balanced, and ethane enters the gas-liquid two-phase region. During the connection process, since the back pressure is greater than 1.5MPa.g, the lowest medium temperature in the buffer pressure regulating tank will not be lower than -20℃. Subsequently, the refrigeration system and the cryogenic storage system are started, and the ethane in the buffer pressure regulating tank is slowly discharged and enters the refrigeration system, and the back pressure of the secondary pressure regulation is controlled to be 0.1MPa.g (the back pressure is obtained by pre-charging the cryogenic storage system). After the secondary pressure regulation, the temperature of ethane is further reduced to obtain the pre-cooling capacity. At the same time, the refrigeration system adopts ethylene circulation refrigeration, which can provide a cooling temperature as low as -100℃ and exchange heat with ethane until the ethane temperature is cooled to about -90℃ and completely liquefied; the liquefied ethane enters the cryogenic storage system using the residual pressure; as the ethane pressure in the buffer pressure regulating tank gradually decreases, the ethane pre-cooling capacity obtained by the secondary pressure regulation is reduced, and the ethane temperature needs to be monitored in time to adjust the ethylene circulation capacity and the ethane discharge rate. When the liquefied ethane cannot flow into the cryogenic storage system by itself, the pump system is turned on to provide lifting power. During the venting process, the temperature transmitter near the trunk line should be monitored, and the ethane venting speed should be fully controlled to fully exchange heat between the medium in the trunk line and the surrounding environment, and keep the trunk medium temperature above -20℃. When the main line pressure is lower than 0.05MPa.g, ethane recovery is stopped and the remaining gaseous ethane is discharged from the main line by displacement.

[0070] like Figure 1 As shown, a method for safely handling the discharged medium of an intermediate pump station of a liquid ethane pipeline is provided, wherein the discharged medium of the liquid ethane in the intermediate pump station is discharged by unplanned discharge and planned discharge.

[0071] Among them, the unplanned venting includes the release of water hammer overpressure in the pipeline upstream of the station shut-off valve, the release of thermal overpressure in the exposed pipeline in the station, and the release of overpressure after the pipeline downstream of the booster pump. The media of the unplanned venting are directly sent to the flare system for combustion treatment; the planned venting includes the venting upstream of the station shut-off valve and the venting downstream of the station shut-off valve. The media of the planned venting are sent to the mobile recovery system for treatment and storage.

[0072] Specifically, an unplanned release processing system, a planned venting system, a mobile recovery system and a control system are set up in the liquid ethane intermediate pumping station. When the pumping station and the pipeline are operating normally, the regulating venting valve in the planned venting system is kept closed, and the water hammer relief valve, thermal relief valve and safety valve in the unplanned release processing system are kept online and ready for use.

[0073] The unplanned venting methods specifically include:

[0074] When the inlet shut-off valve is accidentally closed or the pump is stopped, if water hammer overpressure occurs in the upstream pipeline, the water hammer relief valve will automatically open and the flare system will start the ignition procedure to ensure safe combustion of the medium.

[0075] When the outbound shut-off valve is accidentally closed or the downstream pipeline valve is accidentally closed, if the pressure after the pump exceeds the design pressure of the downstream pipeline, the discharge valve after the pump will automatically open and continue to send a pump stop alarm to the control room. At the same time, the flare system starts the ignition procedure to ensure safe combustion of the medium.

[0076] After the pipeline stops transporting, if the internal pressure of the pipeline in the station increases due to heating and exceeds the set pressure of the thermal relief valve, the thermal relief valve will automatically open and the flare system will start the ignition program to ensure safe combustion of the medium.

[0077] The planned venting method is: when the upstream trunk line or downstream trunk line of the liquid ethane pipeline needs to be shut down for maintenance, the mobile recovery system is transported to the pump station, assembled and debugged, and the ethane medium stored in the pipeline is safely vented, and the vented medium goes to the mobile recovery system.

[0078] In this embodiment, the processing method of the movable recycling system is specifically as follows:

[0079] First, pre-charge the buffer pressure regulating tank with ethane gas (this part of ethane gas is brought by the recovery system, not the pipeline system), control the pressure at 1.5-1.8MPa.g, preferably 1.5MPa.g, open the upstream regulating vent valve and the downstream regulating vent valve, reduce the pressure of ethane stored in the trunk line and charge it into the buffer pressure regulating tank to form a pressure balance.

[0080] Then, the refrigeration system and the cryogenic storage system are started. The ethane in the buffer pressure regulating tank enters the refrigeration system and is pressured to the gravity pressure (satisfying the pressure at which the ethane flows into the loading tank by gravity after liquefaction) to obtain further cold energy. The ethane-ethylene refrigerant heat exchange is then completed and the temperature drops to -100°C. The liquefied ethane directly bypasses the pump system and enters the cryogenic storage system.

[0081] Finally, when the upstream pipeline pressure drops to 0.1MPa (i.e., the ethane gravity pressure), start the pump system to pressurize the low-temperature liquid ethane flowing out of the refrigeration system to ensure that it enters the low-temperature storage system. The pipeline ethane venting rate in this step should be adjusted by the temperature indicated by the temperature transmitter installed on the trunk pipeline to avoid the trunk ethane venting rate being too fast, affecting the heat exchange between the trunk pipeline and the surrounding environment, causing the temperature in the trunk pipeline to be lower than the operating temperature of the steel. When the trunk pipeline pressure is close to normal pressure, stop this step.

[0082] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A liquid ethane pipeline intermediate pump station discharge medium safety treatment system, wherein the liquid ethane is transported through a liquid ethane pipeline (1), and the liquid ethane pipeline (1) is provided with an inlet shutoff valve (2), an outlet shutoff valve (3) and a booster pump (4), characterized in that: The safety treatment system includes an unplanned release treatment system, a planned venting system, a recovery system and a control system; The unplanned discharge treatment system comprises a pipeline discharge unit upstream of the station shut-off valve, an open-air pipeline discharge unit and a pipeline discharge unit downstream of the booster pump; the pipeline discharge unit upstream of the station shut-off valve is used to safely discharge the overpressure medium under the water hammer overpressure condition of the pipeline upstream of the station shut-off valve (2), and directly discharge it into the flare system (5) for combustion treatment; the open-air pipeline discharge unit is used to discharge the overpressure caused by the expansion of the medium in the open-air pipeline due to the temperature increase when the station is shut down, and directly discharge it into the flare system (5) for combustion treatment; the pipeline discharge unit downstream of the booster pump is used to protect the overpressure of the pipeline downstream of the booster pump (4) and to discharge the overpressure medium, and directly discharge it into the flare system (5) for combustion treatment; The planned venting system includes a venting unit upstream of the inlet block valve and a venting unit downstream of the outlet block valve. The planned venting system is used to safely vent the ethane medium stored in the planned pipeline. The planned venting system is connected to the recovery system. The control system is used to monitor the working status of the pipeline and equipment in real time. The upstream pipeline discharge unit of the station inlet block valve comprises a water hammer discharge valve (6) arranged upstream of the station inlet block valve (2) and an upstream discharge branch (7) connected to the liquid ethane pipeline (1); The open-air pipeline discharge unit comprises a thermal discharge valve (8) arranged on the open-air pipeline in the station and an in-station pipeline discharge branch (9) connected to the liquid ethane pipeline (1); The booster pump downstream pipeline discharge unit comprises a post-pump discharge valve (10) arranged downstream of the booster pump (4) and a post-pump discharge branch (11) connected to the liquid ethane pipeline (1); The upstream discharge branch (7), the station pipeline discharge branch (9) and the post-pump discharge branch (11) are all connected to the flare system (5), and the medium discharged by the pipeline discharge unit upstream of the station shut-off valve, the open air pipeline discharge unit and the pipeline discharge unit downstream of the booster pump in an unplanned state is directly discharged into the flare system (5) for combustion treatment; The station inlet shutoff valve upstream venting unit comprises an upstream regulating venting valve (14) arranged upstream of the station inlet shutoff valve (2) and an upstream venting pipeline (15) connected to the liquid ethane pipeline (1); The outlet block valve downstream venting unit comprises a downstream regulating venting valve (16) arranged downstream of the outlet block valve (3) and a downstream venting pipeline (17) connected to the liquid ethane pipeline (1); The upstream venting pipeline (15) and the downstream venting pipeline (17) are both connected to the recovery system via the regulating venting main pipe (18). The venting unit upstream of the inlet block valve and the venting unit downstream of the outlet block valve safely vent the medium stored in the pipeline under the planned state, and the vented medium goes to the recovery system.

2. The liquid ethane pipeline intermediate pump station discharge medium safety treatment system according to claim 1 is characterized by: The upstream discharge branch (7), the station pipeline discharge branch (9) and the post-pump discharge branch (11) are respectively connected to the pressure relief branch pipe (12), and the pressure relief branch pipe (12) is connected to the flare system (5) through the venting main pipe (13). The pressure relief branch pipe (12) is used to collect the discharge media from each path and send them to the venting main pipe (13).

3. The liquid ethane pipeline intermediate pump station discharge medium safety treatment system according to claim 1 is characterized by: The control system comprises a pressure transmitter (19) and a temperature transmitter (20) which are arranged on the regulating venting main pipe (18).

4. The liquid ethane pipeline intermediate pump station discharge medium safety treatment system according to any one of claims 1 to 3, characterized in that: The recovery system comprises a buffer pressure regulating tank (21), a refrigeration system (22), a pump system (23) and a low-temperature storage system (24); The buffer pressure regulating tank (21) is used to provide a predetermined back pressure for upstream planned venting, and control the temperature range of liquid ethane when it is discharged to the rated back pressure; the refrigeration system (22) is used to reliquefy the recovered gaseous ethane; the pump system (23) is used to provide power for the reliquefied ethane to enter the cryogenic storage system (24); the cryogenic storage system (24) is used to receive and store the reliquefied low-temperature atmospheric pressure ethane.

5. The liquid ethane pipeline intermediate pump station discharge medium safety treatment system according to claim 4 is characterized by: The buffer pressure regulating tank (21), the refrigeration system (22), the pump system (23) and the low-temperature storage system (24) are skidded into a movable integral structure.

6. A method for safely handling discharged medium at an intermediate pump station of a liquid ethane pipeline, using a system for safely handling discharged medium at an intermediate pump station of a liquid ethane pipeline as claimed in claim 1, characterized in that: The release medium of the liquid ethane at the intermediate pump station adopts the release mode of unplanned release and planned release; The unplanned venting includes the release of water hammer overpressure in the upstream pipeline of the station cut-off valve, the release of thermal overpressure in the exposed pipeline in the station, and the release of overpressure after the pipeline downstream of the booster pump. The unplanned venting medium is directly sent to the flare system for combustion treatment; The planned venting includes venting upstream of the inlet block valve and venting downstream of the outlet block valve. The medium of the planned venting is sent to a mobile recovery system for processing and storage.

7. The method for safely handling discharged medium from an intermediate pump station of a liquid ethane pipeline according to claim 6, characterized in that: An unplanned release treatment system, a planned venting system, a mobile recovery system and a control system are installed at the liquid ethane intermediate pump station. When the pump station and pipeline are operating normally, the regulating venting valve in the planned venting system is kept closed, and the water hammer relief valve, thermal relief valve and safety valve in the unplanned release treatment system are kept online and ready for use; The unplanned venting methods specifically include: When the inlet block valve is accidentally closed or the pump is stopped, if water hammer overpressure occurs in the upstream pipeline, the water hammer relief valve will automatically open, and the flare system will start the ignition procedure to ensure safe combustion of the medium; When the outbound shut-off valve is accidentally closed or the downstream pipeline valve is accidentally closed, if the pressure after the pump exceeds the design pressure of the downstream pipeline, the discharge valve after the pump will automatically open and continue to send a pump stop alarm to the control room. At the same time, the flare system starts the ignition procedure to ensure safe combustion of the medium; After the pipeline is shut down, if the internal pressure of the pipeline in the station increases due to the heat of the pipeline and exceeds the set pressure of the thermal relief valve, the thermal relief valve will automatically open and the flare system will start the ignition program to ensure the safe combustion of the medium; The planned venting method is: when the upstream trunk line or downstream trunk line of the liquid ethane pipeline needs to be shut down for maintenance, the mobile recovery system is transported to the pump station, assembled and debugged, and the ethane medium stored in the pipeline is safely vented, and the vented medium goes to the mobile recovery system.

8. The method for safely handling discharged medium from an intermediate pump station of a liquid ethane pipeline according to claim 7, characterized in that: The processing method of the movable recycling system is specifically as follows: First, pre-charge the buffer pressure regulating tank with ethane gas, and control the pressure at 1.5-1.8 MPa.g. Open the upstream regulating vent valve and the downstream regulating vent valve, and depressurize the ethane stored in the trunk line and charge it into the buffer pressure regulating tank to form a pressure balance. Then, the refrigeration system and the cryogenic storage system are started, and the ethane in the buffer pressure regulating tank enters the refrigeration system and is further cooled after the pressure is adjusted to the gravity pressure, and then the ethane-ethylene refrigerant heat exchange is completed, and the liquefied ethane directly passes through the pump system and enters the cryogenic storage system; Finally, when the upstream pipeline pressure drops to the ethane gravity pressure, start the pump system to pressurize the low-temperature liquid ethane flowing out of the refrigeration system to ensure that it enters the low-temperature storage system. The pipeline ethane venting rate in this step should be adjusted by the temperature indicated by the temperature transmitter installed on the trunk pipeline. When the trunk pipeline pressure is close to normal pressure, stop this step.

Images