the retention time of oil in Buffer tank? 4

[ProEngr]

Hi all,
I am fresh chemical engineer, I need help to determine the retention time of oil in buffer tank, because I have a buffer tank (oil & water), and I have all information about this tank.
please can you tell me the procedure? And which API# can I use?
thanks

 

[djack77494]

You'll need to be more specific in your question. Are you trying to provide sufficient residence time to allow water droplets to "fall" out of the oil phase? Time to allow oil droplets to rise out of the aqueous phase? Residence time for control purposes, etc.? We need to know in order to provide an intelligable response.
Doug

 

[ProEngr]

Sorry,
I trying to provide sufficient residence time to allow oil droplets to rise out of the aqueous phase.

 

[ProEngr]

sorry,
I have all feed doc., I have flowrate in & out, size, all information. what I need is the procedure to calculate the residence time of buffer tank, to check? etc.

 

[BigInch]

Google "Stokes flow"

http://scienceworld.wolfram.com/physics/Navier-StokesEquations.html

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[ollie1972]

Coulson Richardson Vol 2 should do it.
Would leave navier-stokes to the cfd packages...

 

[env21tech]

(1) assume droplets are 100 microns = droplet rise velocity of 0.10 cm/sec = 0.003 ft/sec
(2) 0.003 ft/sec = 0.003 cf/sf-sec = 1.2 gpm/sf =1600 gpd/sf
(3) Provide minimum of 0.8 sf of water surface area for every 1600 gpd of flow
(4) Use 2.0 sf/gpd to allow for turbulence and poor flow distribution
(5) Increase area if you need to size for smaller droplets.
(6) Put a beaker of the water on your desk, observe how well a 3" layer clarifies in one minute. Estimate the rise rate from this test. 70% clarification = rise rate of 2"/min = 0.003 ft/sec.

 

[25362]

As I understand the vessel is already there, so are known flow rates, temperatures, densities, viscosities, interfacial tension, etc.

The (non-identified) oil's hold time will depend on:

(a) as indicated above, the "separation" zone holdup volume but also on

(b) the volume of the supernatant oil phase between its high and low levels (alarms?), i.e. the expected operating surge volume range, which will depend on the processing purpose of the buffer tank.

I suggest you consult books on liquid-liquid separation to estimate (a), and tell us something about (b) to enable contributing some thoughts.

 

[25362]

You may find interest in this link:

http://www.clarkson.edu/~wilcox/Design/coalesc.pdf

 

[ProEngr]

thanks