Two Phase Vertical Separator - Design Procedure [PDF]

Zitiervorschau

Two Phase Separator Vertical Type Design Procedure By: Ali Farrokhzad

Jan 2017

1395‫آبان‬

Balances the drag force:

Net Gravity Force:

Liquid droplets will settle at a constant terminal velocity, UT :

FD=FG

As long as Uv < UT

The liquid droplets will settle out. (Uv: Allowable vertical velocity)

Typically Uv =0.75×UT ~UT

Where:

Coalescing Devices (Mesh Pad, Mist Eliminator , etc.)

:Separator K values determination methods 1. York Mist Eliminator 0.1821  0.0029 P  0.0460 Ln( P )  K  0.35 0.430  0.023 Ln( P ) 

, 1  P  15 , 15  P  40 , 40  P  5500

P in psia

, 0  P  1500

P in psig

2. GPSA K  0.35  0.0001 ( P  100)

:Separator K values determination methods 3. Theoretical (no mist eliminator) K

K

4 gDP 3CD

in

ft / s

C D  eY Y  8.411  2.243X  0.273 X 2  1.865  10 2 X 3  5.201 10 4 X 4  0.95 108  v DP3 (  L   v )   X  Ln 2 v   DP : droplet size in foot (1micron  3.2808410 5 ft )

 : density

in lb / ft 3 ,

 : vis cos ity in cP

:Notes If there is no mist eliminator, it is recommended to use one half of the above values. GPSA Recommendations: • Most vapors under vacuum K= 0.20. • For Glycol and Amine solutions. Multiply K by 0.6-0.8. • For vertical vessels without mist eliminators, divide K by 2. • For compressor suction scrubbers, mole sieve scrubbers and expander inlet separators multiply K by 0.7-0.8

Vessel on Operation :Holdup & Surge Volumes

Surge Volume/Slug Holdup Volume

Holdup Volume

:Holdup & Surge Volumes :Holdup Holdup is defined as the time it takes to reduce the liquid level from normal (NLL ) to empty (LLL ) while maintaining a normal outlet now without feed makeup. i.e. : Deadline to feeding downstream during upstream maintenance/failure. :Surge Surge time is defined as the time it takes for the liquid level to rise from normal (NLL ) to maximum (HLL ) while maintaining a normal feed with out any outlet flow . i.e. : Deadline to receiving feed while downstream maintenance or max. volume of extra liquid to be handled via upstream pulse.

Vertical Separator Design For vertical separators . the vapor disengagement area is the entire cross-sectional area of the vessel so that vapor disengagement diameter call be calculated

For a two-phase vertical separator, the total height can he broken into sections, as shown in Figure. The separator height is then calculated by adding the heights of these sections: HT=HLLL+HH+HS+HLIN+HD

:Definitions Quality: Mass fraction of vapor in the inlet feed.

:Example Size a vertical separator with a mist eliminator pad to separate the following mixture .

q=mV/ mF mF = mL + mV

The operating pressure is 975 psig and the holdup and surge are to be 10 min and 5 min respectively. Use a design temperature of 650°F .

:Design Procedure

:Example K York_mist=0.2714 K GPSA=0.2625 Ktheo (μ=0.01cP, Dp=300 micron)=0.2766 K = min {Ki}=0.2625 Note: There is a mesh pad, so Kfinal = K.

UT = 0.77 ft/s Uv = 0.75 UT = 0.58 ft/s

:Design Procedure

:Example Qv = 10.09 ft3/s

DVD = 4.70 ft = 56.4 in There is a mesh pad, so add 3~6 inch for support ring and round to the next 6 inch. Therefore: D = 60 in = 5 ft

:Design Procedure

:Example 4) QL = 19.8 ft3/min

5) VH = 10×19.8 = 198 ft3

6) VS = 5×19.8 = 99 ft3

:Design Procedure

:Example 7) Vertical vessel with D=5 ft. & P>300 Pisa HLLL= 6 in.

:Design Procedure

:Example 8) HH= Max {10.1 , 1} = 10.1 ft.

9) HS= Max {5.0 , 0.5} = 5.0 ft.

:Design Procedure

:Example 10) With inlet diverter λ = 0.0317 m = 5.11 lb/ft3 Qm = 10.4 ft3/s  dN ≥ 0.71 ft (8.5 in.)  10” Selected  HLIN = 12 in. + 0.7 ft. = 22 in.

:Design Procedure

:Example 11) With mist eliminator:  HD = min {0.5×60 , 24+ ×10} = min {30 , 29} = 29 in.

 HD = min {0.5Dv , 36+ dN}

 HD = min {0.5Dv , 24+ dN}

:Design Procedure

:Example 12) With mist eliminator: HME = 6 in. + 1 ft. = 1.5 ft.

13) HT=6 in.+10.1 ft.+5 ft.+22 in.+29 in.+1.5ft. HT = 0.5+10.1+5+1.83+2.42+1.5=21.35 ft HT = 21.35 ft.

:Design Procedure

:Example 12) HT/D = 21.35 / 5.0 = 4.27 P=960.5 psig > 500 psig L/D: 4~6 HT/D is in range. So design procedure is completed. Design Summary: D= 5 ft. L=21.35 ft.

Nozzle Sizing:

:Example

 Inlet Nozzle:

 Inlet Nozzle:

7~13 m/s or

Q=QL+QV

1. Based on CEP method: 8.5”