Gas-liquid separator calculation

Regarding the droplet size issue in the gas-liquid separation after propane depressurization, it is recommended to consider the following aspects: According to the HGT 20570 standard, a value of 100–200 μm is usually used as a design benchmark, but for light hydrocarbons like propane, it is advisable to use a lower value (80–150 μm), as their low surface tension makes them prone to breaking into smaller droplets. In practical operations, it is recommended to consider the following: the pressure drop after the pressure relief valve (the greater the pressure drop, the smaller the droplets); the flow rate in the upstream pipeline (the higher the flow rate, the greater the shear force); and whether there are any sources of disturbance such as swirls. If possible, it is best to observe the actual separation effect through pilot tests or consult the operating data of similar systems. We have previously built similar propane separators, and actual measurements showed that the droplet size was around 120μm. These are merely for reference; the specific design recommendations should be based on the process package data or professional calculations~

When designing a propane gas-liquid separator in accordance with the HGT 20570 standard, special attention must indeed be paid to the issue of droplet size. Under reduced-pressure conditions: Propane tends to form small liquid droplets during reduced-pressure flashing; it is advisable to design for a size range of 80–120 μm as a safer option. The actual measurement data from our facility also falls within this range. It is crucial to control the flow rate in the inlet pipeline (it is recommended to keep it at ≤15 m/s) as well as the degree of pressure reduction, as a sudden drop in pressure can cause the liquid droplets to become further atomized. One can use HYSYS or PROII to simulate the flashing process, determine the gas phase carryover rate, and then infer the size distribution of the liquid droplets