2 replies to this topic

[Flyou]

Hi all,

 

I work as a process design engineer in the petroleum field. I design high pressure units (50 to 200 bar) such as hydrotreaters (HDS) and hydrocrackers (HCK).

Sometimes, to recover the pressure energy of a HP liquid stream, i specify Hydraulic Power Recovery Turbines (HPRTs) between HP separator drum and LP separator drum instead of using a control valve. 

Those HPRTs can either drive a pump partially or be equipped with an alternator so as to recover electric energy.

 

My question is about the level conrol of the HP separator drum. 2 types of control can be applied: 

a/ Level control is done with a level control valve on 

[Flyou]

a line by passing the HPRT (representing 10 to 15% of the total flow from the HP drum). In this case there is a flowcontrol valve at the inlet of the HPRT that maintain the flow constant to the turbine. In this case the power recovered is constant, no variation is expected.

 

b/ The level control valve is on the full flow just before the turbine. In this case, the flow to the turbine is not fixed and vary. Consequently, the power recovered at the HPRT also vary.

 

Which control is better? Does anybody has an idea?

In my opinion, in case the HPRT drives partially a pump, as the motor of the pump will have to furnish the other part of the power, case a/ might be better to avoid the variation of power of the motor. Nevertheless, in case the HPRT is connected to an alternator, case b/ might be better since the power recovered is on the total flow and not on 85/90% of the flow.

 

Thx for your help!

[Zubair Exclaim]

Turbines are designed to deliver a maximum efficiency at a certain flow if you select option 1 you can designate that flow on turbine for max efficiency and by pass rest besides its always better to perate a turbine at a constant flow for better performance