During September, the SPE Separations Technology Technical Section hosted “Flow Conditioning Impact on Separations,” presented by Cris Heijckers, managing director of Kranji Solutions.
Heijckers discussed the importance of the distribution of fluid flows in separation vessels. The flow distributions are affected by the vessel, the configuration of its internals, and the layout of the upstream piping connecting to the vessel’s inlet nozzle.
He explained the effects of inlet piping layouts on the flow distribution as it enters the vessel, comparing simulation results of gas-phase computational fluid dynamics (CFD) for various piping layouts. Using multiphase CFD simulations, liquid behavior was illustrated.
Pipe fittings, such as valves, affect the performance of separation vessels. A pressure drop across a valve creates a shearing effect on droplets, making them smaller and more difficult to separate. By optimizing the configuration and location of the vessel’s inlet piping, droplet coalescence can be promoted, which is beneficial to the performance of the separator.
Heijckers concluded with the following guidelines:
- Although CFD analysis investigates the effects of inlet piping layouts and fittings, adequate CFD expertise and separation know-how are required to interpret and understand the simulations to avoid a “nonsense in, nonsense out” outcome.
- When planning the inlet piping configuration, avoid horizontal positioning of the last pipe bend before the vessel inlet. Generally, the farther upstream of the vessel bends in the pipe occur (in the same vertical plane), the better the separation performance.
- An increase in a pipe’s straight length, defined as the distance between the pipe’s last bend and the vessel’s inlet nozzle, affects gas distribution; however, it has more effect on liquid inflow distribution.
- Because pressure drops across valves cause droplet shearing and severe gas maldistribution in the vessel, it is recommended that valves be located as far upstream of the vessel as possible.
- Inlet pipe bends and pipe fittings can cause swirling flow in piping, leading to maldistribution of flow in the vessel.
- For nonideal piping layouts and critical applications, CFD analysis is recommended.
- The configurations of vessel internals and their effects on flow distribution require consideration during the design of the separation process.