You must log in to edit PetroWiki. Help with editing

Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. More information


Coalescers: Difference between revisions

PetroWiki
Jump to navigation Jump to search
mNo edit summary
No edit summary
 
(11 intermediate revisions by 4 users not shown)
Line 1: Line 1:
Liquid-liquid coalecers are also widely used in oil refining industry to remove traces of contaminants.
Liquid-liquid coalecers are also widely used in oil refining industry to remove traces of contaminants.


==Use in separators==
== Use in separators ==
For liquid/liquid coalescence in three-phase separators and other separators in which it is desired to have separate liquid outlets for oil/water, plate packs can enhance separation performance by improving the local flow condition and reducing the distance over which drops have to travel to settle. Plate packs also have been installed to promote gas/liquid separation for degassing application.


Laminar flow is indicated by the flow Reynolds number, which is defined as
For liquid/liquid coalescence in three-phase separators and other separators in which it is desired to separate liquid outlets for oil/water, plate packs can enhance separation performance by improving the local flow condition and reducing the distance over which drops have to travel to settle. Plate packs also have been installed to promote gas/liquid separation for degassing application.


[[File:Vol3_page_024_eq_001.PNG]] ................(1)
The Reynolds number of fluid flow in a plate pack can be defined as


where
[[File:Vol3 page 024 eq 001.PNG|RTENOTITLE]] ................(1)


ρ<sub>c</sub> = continuous phase density, kg/m<sup>3</sup>
where ρ<sub>c</sub> = density of the continuous phase, kg/m<sup>3</sup>; μ<sub>c</sub> = dynamic viscosity of the continuous phase, kg/(m∙s) or N∙s/m<sup>2</sup>; V<sub>c</sub> = mean velocity of the continuous phase, m/s; and d<sub>h</sub> = equivelent diameter of the flow channel.
μ<sub>c</sub> = continuous phase dynamic viscosity, kg/(m∙s) or N∙s/m<sup>2</sup>
V<sub>c</sub> = continuous phase velocity, m/s


and
For a plate pack with a perpendicular gap spacing of d<sub>pp</sub>, the hydraulic diameter is approximately equal to 2 d<sub>pp</sub>. Transition to turbulent flow occurs in the Re range of 1,000 to 1,500.


d<sub>h</sub> = hydraulic diameter.  
To determine the drop size that can be removed, consider the schematic in '''Fig. 8''' of an oil droplet rising in a waterflow between plates. The distance a drop has to settle is d<sub>pp</sub>/cos(α), where d<sub>pp</sub> is the perpendicular spacing of the plate, and α is the inclination angle. For liquids with “nonsticky” solids, the plate spacing and the angle of inclination can be increased to mitigate plugging.


For a plate pack with a perpendicular gap spacing of d<sub>pp</sub>, the hydraulic diameter is approximately equal to 2 d<sub>pp</sub>. Transition to turbulent flow occurs in the Re range of 1,000 to 1,500.
<gallery widths="300px" heights="200px">
 
To determine the drop size that can be removed, consider the schematic in '''Fig. 8''' of an oil droplet rising in a waterflow between plates. The distance a drop has to settle is d<sub>pp</sub>/cos(α), where d<sub>pp</sub> is the perpendicular spacing of the plate, and α is the inclination angle. For liquids with “nonsticky” solids, the plate spacing and the angle of inclination can be increased to mitigate plugging.
 
<gallery widths=300px heights=200px>
File:Vol3 Page 024 Image 0001.png|'''Fig. 8—Depiction of droplet rising between parallel plates (courtesy of CDS Separation Technologies Inc.).'''
File:Vol3 Page 024 Image 0001.png|'''Fig. 8—Depiction of droplet rising between parallel plates (courtesy of CDS Separation Technologies Inc.).'''
</gallery>
</gallery>
<br>
For the plate pack to be effective, the drop must reach the plate before exiting the pack. A ballistic model of the drop results in


[[File:Vol3_page_025_eq_001.PNG]] ................(2)
For the plate pack to be effective, the drop must reach the plate before exiting the pack. A ballistic model of the drop results in


where
[[File:Vol3 page 025 eq 001.PNG|RTENOTITLE]] ................(2)


V<sub>r</sub> = drop/rise velocity, m/s
where V<sub>r</sub> = drop/rise velocity, m/s; V<sub>h</sub> = horizontal water velocity, m/s; L = plate-pack length, m; and d<sub>pp</sub> = plate-pack perpendicular gap spacing, m.
V<sub>h</sub> = horizontal water velocity, m/s
L = plate-pack length, m


and
For a low-drop Reynolds number, the drop/rise velocity is given by Stokes’ law, which is written as


d<sub>pp</sub> = plate-pack perpendicular gas spacing, m.  
[[File:Vol3 page 025 eq 002.PNG|RTENOTITLE]] ................(3)


For a low-drop Reynolds number, the drop/rise velocity is given by Stokes’ law, which is written as
where ρ<sub>w</sub> = water density, kg/m<sup>3</sup>; ρ<sub>o</sub> = oil density, kg/m<sup>3</sup>; μ<sub>w</sub> = water dynamic viscosity, kg/(m∙s) or N∙s/m<sup>2</sup>; g = gravitational acceleration, 9.81 m/s<sup>2</sup>;


[[File:Vol3_page_025_eq_002.PNG]] ................(3)
and


where
D<sub>o</sub> = drop diameter, m.


ρ<sub>w</sub> = water density, kg/m<sup>3</sup>
For a higher-drop Reynolds number, a more general form of '''Eq. 3''' can be used. For a given plate-pack geometry and fluid conditions, the minimum drop that can be removed by the plate pack is obtained from '''Eqs. 2''' and '''3'''.
ρ<sub>o</sub> = oil density, kg/m<sup>3</sup>
μ<sub>w</sub> = water dynamic viscosity, kg/(m∙s) or N∙s/m<sup>2</sup>
g = gravitational acceleration, 9.81 m/s<sup>2</sup>


and
[[File:Vol3 page 025 eq 003.PNG|RTENOTITLE]] ................(4)


D<sub>o</sub> = drop diameter, cm.  
For water drops in oil, the water viscosity in '''Eq. 4''' is replaced with the oil viscosity, and the horizontal velocity is that of the oil phase. Typical design drop size removal in plate packs is approximately 50 μm.


For a higher-drop Reynolds number, a more general form of '''Eq. 3''' can be used. For a given plate-pack geometry and fluid conditions, the minimum drop that can be removed by the plate pack is obtained from '''Eqs. 2''' and '''3'''.
Other designs use mesh and matrix packing for liquid/liquid coalescing. However, plugging issues should be addressed when selecting the coalescer. In general, if solids are present in significant quantities, no coalescing internals are installed.
 
[[File:Vol3_page_025_eq_003.PNG]] ................(4)
<br>
 
For water drops in oil, the water viscosity in '''Eq. 4''' is replaced with the oil viscosity, and the horizontal velocity is that of the oil phase. Typical design drop size removal in plate packs is approximately 50 μm.
 
Other designs use mesh and matrix packing for liquid/liquid coalescing. However, plugging issues should be addressed when selecting the coalescer. In general, if solids are present in significant quantities, no coalescing internals are installed.  
 
 
==Nomenclature==


== Nomenclature ==
{|
{|
|ρc
|=
|continuous phase density, kg/m3
|-
|-
|μc
| ρc
|=  
| =
|continuous phase dynamic viscosity, kg/(m∙s) or N∙s/m2
| continuous phase density, kg/m3
|-
|-
|Vc
| μc
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|continuous phase velocity, m/s
| <span style="line-height: 8.02469062805176px;">continuous phase dynamic viscosity, kg/(m∙s) or N∙s/m2</span>
|-
|-
|dh
| <span style="line-height: 8.02469062805176px;">Vc</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|hydraulic diameter
| <span style="line-height: 8.02469062805176px;">continuous phase velocity, m/s</span>
|-
|-
|Vr
| <span style="line-height: 8.02469062805176px;">dh</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|drop/rise velocity, m/s
| <span style="line-height: 8.02469062805176px;">hydraulic diameter</span>
|-
|-
|Vh
| <span style="line-height: 8.02469062805176px;">Vr</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|horizontal water velocity, m/s  
| <span style="line-height: 8.02469062805176px;">drop/rise velocity, m/s</span>
|-
|-
|L
| <span style="line-height: 8.02469062805176px;">Vh</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|plate-pack length, m
| <span style="line-height: 8.02469062805176px;">horizontal water velocity, m/s</span>
|-
|-
|dpp
| <span style="line-height: 8.02469062805176px;">L</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|plate-pack perpendicular gas spacing, m
| <span style="line-height: 8.02469062805176px;">plate-pack length, m</span>
|-
|-
|ρw
| <span style="line-height: 8.02469062805176px;">dpp</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|water density, kg/m3
| <span style="line-height: 8.02469062805176px;">plate-pack perpendicular gas spacing, m</span>
|-
|-
|ρo
| <span style="line-height: 8.02469062805176px;">ρw</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|oil density, kg/m3  
| <span style="line-height: 8.02469062805176px;">water density, kg/m3</span>
|-
|-
|μw
| <span style="line-height: 8.02469062805176px;">ρo</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|water dynamic viscosity, kg/(m∙s) or N∙s/m2
| <span style="line-height: 8.02469062805176px;">oil density, kg/m3</span>
|-
|-
|g
| <span style="line-height: 8.02469062805176px;">μw</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|gravitational acceleration, 9.81 m/s2
| <span style="line-height: 8.02469062805176px;">water dynamic viscosity, kg/(m∙s) or N∙s/m2</span>
|-
|-
|Do  
| <span style="line-height: 8.02469062805176px;">g</span>
|=  
| <span style="line-height: 8.02469062805176px;">=</span>
|drop diameter, cm
| <span style="line-height: 8.02469062805176px;">gravitational acceleration, 9.81 m/s2</span>
|-
| <span style="line-height: 8.02469062805176px;">Do</span>
| <span style="line-height: 8.02469062805176px;">=</span>
| <span style="line-height: 8.02469062805176px;">drop diameter, m </span>
 
|}
|}


==References==
== References ==
Use this section for citation of items referenced in the text to show your sources. [The sources should be available to the reader, i.e., not an internal company document.]


==Noteworthy papers in OnePetro==
== Noteworthy papers in OnePetro ==


Al-Qahtani, A.A. 2012. Vessel Internal Electrostatic Coalescer technology (VIEC). SPE-156087-MS presented at the SPE International Production and Operations Conference & Exhibition, Doha, Qatar, 14-16 May. http://dx.doi.org/10.2118/156087-MS.
Al-Qahtani, A.A. 2012. Vessel Internal Electrostatic Coalescer technology (VIEC). SPE-156087-MS presented at the SPE International Production and Operations Conference & Exhibition, Doha, Qatar, 14-16 May. http://dx.doi.org/10.2118/156087-MS.


==External links==
== External links ==
 
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro


==See also==
== See also ==
[[Oil and gas separators]]
 
[[Oil_and_gas_separators|Oil and gas separators]]
 
[[PEH:Oil_and_Gas_Separators]]


[[PEH:Oil and Gas Separators]]
==Category==
[[Category:4.1.5 Processing equipment]] [[Category:NR]]

Latest revision as of 11:09, 6 July 2015

Liquid-liquid coalecers are also widely used in oil refining industry to remove traces of contaminants.

Use in separators

For liquid/liquid coalescence in three-phase separators and other separators in which it is desired to separate liquid outlets for oil/water, plate packs can enhance separation performance by improving the local flow condition and reducing the distance over which drops have to travel to settle. Plate packs also have been installed to promote gas/liquid separation for degassing application.

The Reynolds number of fluid flow in a plate pack can be defined as

RTENOTITLE ................(1)

where ρc = density of the continuous phase, kg/m3; μc = dynamic viscosity of the continuous phase, kg/(m∙s) or N∙s/m2; Vc = mean velocity of the continuous phase, m/s; and dh = equivelent diameter of the flow channel.

For a plate pack with a perpendicular gap spacing of dpp, the hydraulic diameter is approximately equal to 2 dpp. Transition to turbulent flow occurs in the Re range of 1,000 to 1,500.

To determine the drop size that can be removed, consider the schematic in Fig. 8 of an oil droplet rising in a waterflow between plates. The distance a drop has to settle is dpp/cos(α), where dpp is the perpendicular spacing of the plate, and α is the inclination angle. For liquids with “nonsticky” solids, the plate spacing and the angle of inclination can be increased to mitigate plugging.

For the plate pack to be effective, the drop must reach the plate before exiting the pack. A ballistic model of the drop results in

RTENOTITLE ................(2)

where Vr = drop/rise velocity, m/s; Vh = horizontal water velocity, m/s; L = plate-pack length, m; and dpp = plate-pack perpendicular gap spacing, m.

For a low-drop Reynolds number, the drop/rise velocity is given by Stokes’ law, which is written as

RTENOTITLE ................(3)

where ρw = water density, kg/m3; ρo = oil density, kg/m3; μw = water dynamic viscosity, kg/(m∙s) or N∙s/m2; g = gravitational acceleration, 9.81 m/s2;

and

Do = drop diameter, m.

For a higher-drop Reynolds number, a more general form of Eq. 3 can be used. For a given plate-pack geometry and fluid conditions, the minimum drop that can be removed by the plate pack is obtained from Eqs. 2 and 3.

RTENOTITLE ................(4)

For water drops in oil, the water viscosity in Eq. 4 is replaced with the oil viscosity, and the horizontal velocity is that of the oil phase. Typical design drop size removal in plate packs is approximately 50 μm.

Other designs use mesh and matrix packing for liquid/liquid coalescing. However, plugging issues should be addressed when selecting the coalescer. In general, if solids are present in significant quantities, no coalescing internals are installed.

Nomenclature

ρc = continuous phase density, kg/m3
μc = continuous phase dynamic viscosity, kg/(m∙s) or N∙s/m2
Vc = continuous phase velocity, m/s
dh = hydraulic diameter
Vr = drop/rise velocity, m/s
Vh = horizontal water velocity, m/s
L = plate-pack length, m
dpp = plate-pack perpendicular gas spacing, m
ρw = water density, kg/m3
ρo = oil density, kg/m3
μw = water dynamic viscosity, kg/(m∙s) or N∙s/m2
g = gravitational acceleration, 9.81 m/s2
Do = drop diameter, m

References

Noteworthy papers in OnePetro

Al-Qahtani, A.A. 2012. Vessel Internal Electrostatic Coalescer technology (VIEC). SPE-156087-MS presented at the SPE International Production and Operations Conference & Exhibition, Doha, Qatar, 14-16 May. http://dx.doi.org/10.2118/156087-MS.

External links

Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro

See also

Oil and gas separators

PEH:Oil_and_Gas_Separators

Category