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Preface: Here, BLOWDOWN refers only to the emergency release of the liquid phase in the system, while the emergency release of the gas phase is referred to as DEPRESSURING. Question: When a certain system in the unit is isolated from the entire unit due to a fire, and if there is a liquid phase in that system, how should one determine whether it is necessary to install a BLOWDOWN (VALVE & DISCHARGE RECEIVER) and how should it be installed? Everyone is welcome to speak up actively (prizes for participation: lol)!
The main sewage pipe inside the device is used to collect sewage from various equipment or pipes, which then flows into this pipe.
Thank you for your participation, but this is primarily designed for emergency release in case of a fire. I guess the place where the gas is released should be a flare, as the system contains hydrocarbons. Also, if flashing occurs when the liquid phase is discharged from high pressure to a lower-pressure flare header, is it then not necessary to install a BLOWDOWN system, and can a DEPRESSURING system alone be used? (Note: This is a foreign project): handshake
The liquid phase discharged to the flare buffer tank can be recovered in that tank
BLOWDOWN is designed for fire scenarios; taking an olefin plant as an example: 1. Light components at C2& above vaporize at room temperature, thus causing DEPRESSURE. 2. C3/C4 has a relatively high vaporization rate at certain temperatures, and it also has a high calorific value; after vaporizing on the ground, what remains in the device is a residue that needs to be removed through a BLOWDOWN process. 3. There are dedicated BLOWDOWN switch valves, fire-resistant clothing is required, and the design is based on withstanding 1500 degrees for half an hour. 4. There is a BLOWDOWN time/capacity calculation sheet, including the column and reflux tank. This kind of design has only been encountered in joint ventures.
The key is how much of it can be vaporized? ? Generally, a liquid phase will be present, so it can be collected in one drain drum; in foreign projects, these drums are buried underground. This tank functions as a means for gas-liquid separation: the liquid phase is retained within the tank, while the gas phase is directed to an appropriate discharge path based on pressure and gas content.
That’s right; it’s actually an LNG project. In China, BLOWDOWN operations have never been carried out before, nor has there been as many ISOLATION SECTIONS built. It is the BLOWDOWN of the components at C3 and above (that is, the liquid phase in the ISOLATION SECTION) that needs to be taken into consideration. Can I find information on how to set this up and perform the calculations in API 521?
It seems that both the DEPRESSURING and BLOWDOWN processes for this project are routed to the flare. :)
Has anyone used HYSYS to calculate blowdown or depressurization? Should the pressure relief of storage tanks or pipelines that contain a liquid phase be done using blow down?
The liquid phase from BLOWDOWN is sent to the accident tank; before reaching the flare, it first passes through a liquid separation tank. The liquid phase retained in the separation tank can be recycled, while the gas phase goes to the flare.