Two Phase Separator

Horizontal Type Design Procedure

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Ali Farrokhzad پاییز 1395

Jan 2017

Size a Horizontal separator with a mist eliminator pad to separate the following mixture .

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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 .

Example:

Design Procedure:

Example:

Design Procedure:

Example:

Design Procedure:

Example:

7)

H_LLL = 0.5×5+7

= 9.5 in.

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8)

x = H_LLL/D =0.158

From Eq. → y = 0.102 → A_LLL/A_T = 0.102

→ A_LLL =0.102×19.63 = 2 ft².

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7.

Design Procedure:

Example:

Liquid Inventory Length:

Av

A_{(holdup+surge)}

+

A_LLL

A_T

Liquid Inventory Length (L) vs Separation Length (L_MIN)

Liquid Inventory Length (L) vs Separation Length (L_MIN)

Design Procedure:

Example:

Design Procedure:

Example:

L > 1.2 ×L_MIN → L >> L_MIN

Type:

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Calculation of thickness of Head & Shell

Design Pressure & Design Temperature:

Reference: RULES OF THUMB: SUMMARY , Walas Click to see contents:

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1. Design temperature between -20°F and 650°F is 50°F above operating temperature; higher safety margins are used outside the given temperature range.

If -20 ^oF <OT < 650 ^oF → DT=OT + 50 ^oF

�2. The design pressure is 10% or 10-25 psi over the maximum operating pressure, whichever is greater.

The maximum operating pressure, in turn, is taken as 25 psi above the normal operation.

MOP= NOP+25 psi DP=max.{1.1×MOP , MOP+10~25 psi}

�3. Design pressures of vessels operating at 0-10 psig and 600-1000°F are 40 psig.

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Calculation of thickness of Head & Shell

P, design pressure, psig

Typically,

operating pressure+(15-30) psi or 10-15%, whichever greater.

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T, design temperature , ^oF

Typically,

if T_op > 200°F, DT=operating temperature +25-50°F.

If T_op < 200°F, DT=250°F

�• under 650°Fdoesnot reduce wall thickness�• if overpressure caused by boiling, should be T_BP .

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Allowable Stress of Alloy

Pressure Vessel Handbook-Megyesy

Evaluate Design Temperature for the selected alloy and then read S from the Table.

Design Procedure:

Example:

DT = 650 ^oF

NOP=975 psig

→ MOP=975+25=1000 psig

→ DP=max{1000+25, 1.1×1000}=1100 psig

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Alloy: SA 516 70 Carbon Steel

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• From Table: 17.5 → S= 17500 psi

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Let C.A. t_C= 1/16 = 0.06 in. & Joint Efficiency (E) = 0.85

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Head Type:

D < 15 ft. & P > 100 psig → 2:1 Elliptical

Tips:

According to Walas Rules of Thumbs for Pressure Vessels

Corrosion allowance:

0.35 in. for known corrosive conditions,

0.15 in. for non-corrosive streams, and

0.06 in. for steam drums and air receivers.

Design Procedure:

Example:

15)

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Head Thickness & Area:

Shell Thickness & Area:

Alloy plate thickness:

16)

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17)

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Design Procedure:

Example:

Nozzles Orientation:

Nozzle Sizing:

Example:

→D_V=6”

Vapor Outlet:

U=15~30 m/s or ρU² = 3750 Pa.

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Liquid Outlet:

U=1~4 m/s (min 2”).

Home Work:

Design a Horizontal flash drum by considering below conditions.

Feed enters at 5 barg & 40 ^oC.

Vapor density is 8 kg/m³ & liquid density is 780 kg/m³.

Flow rate of feed is 12,000 kg/hr.

Feed is non corrosive, use your own assumption during sizing.

Report required data as much as possible.

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Assume previous (Vertical H.W.) assumptions and compare the both design cases.

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1) Unit Feed Drum with q=40% , with Mesh pad.

2) Flare K.O. Drum with q=0 , without Mesh pad

3) Unit Feed Drum with q=40% and without mesh pad.

4) Unit Feed Drum with q=80%, with mesh pad.

5) Unit Feed Drum with q=100%, with mesh pad.

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Extra Example:

Slug catcher with q=20% and 40 m³ slug volume as unit feed drum.

References: