LSR Merox treater

What are the 2 cases in which the LSR treater can run?

Case 1:

Can be routed to the treater directly

Case 2:

Bypassed around the LSR treater and first passed through the NHIN for hydrotreating. The LSR then returns to the treater and passes through the unit like normal

Which mode of operation do we run in normally Case 1 or Case 2?

• Case 2 because the NHIN has a better treater that can do a better job at scrubbing H2S from the LSR

Aside from the initial scrubbing what is the other major difference between Case 1 and Case 2?

Case 2 doesn’t have air addition or merox reagent addition in this mode of operation

How does the LSR treater work step By step assuming air is still on and running?

• LSR from Debut bottoms flows through FV-971 or is lumped by 1BP-156 booster pumps to the NHIN for treating, after which it enters the caustic prewash countercurrent to caustic to scrub any H2S

• The LSR then enters the bottom of the Merox mixer unit mixed with air (from FV-969) upstream of the mixer. (Controlled by FYC-969 ratio controller for proper ratio of hydrocarbon to air)

• Merox mixer has a low flow shudown FXSL-977 that will shutdown the air solenoid to the LSR stream

• Off the top of the mixer the LSR enters the caustic settler flowed by the sand filter to settle out any remaining caustic before leaving as caustic scrubbed NHIN LSR to tank

Caustic/Merox flows:

• Off the bottom of the settler the caustic is pumped by 1BP-155/s back into the mixer by flow controller FV-970

*PIC-956 is a back pressure controller downstroke of the sand filter which keeps sufficient pressure on the unit the keep the required air in solution

What is the catalyst used in this treater?

Same as C3/C4

What is the purpose of caustic?

It’s two-fold:

• Transfer mercaptan or sulphur part of mercaptan into the aqueous phase and supply the alkaline environment needed for reaction to proceed in desired direction

What Baume Caustic is considered optimal for liquid-liquid sweetening and why?

• 10 Baume

• Because caustics ability to extract impurities in addition to mercaptan increases above 10 Baume

At what pressure drop across the merox mixer is the degree of mixing considered most optimum?

• a total pressure drop of about 22 psi across the mixer (15 psi not factoring stating head)

What operating temperature is acceptable for this unit and why?

• 80-120F because it’s a compromise between the improved solubility of mercaptans at low temps and increase conversion to disulphide at high temps

What % caustic/ is kept in the recycle stream from the settler and why?

• 5-50% because it ensures some hydrocarbon is recycled with the caustic

• This ensure the settler interface containing settled catalyst is recycled