2 replies to this topic

[sanganipratik]

Hi Friends,

 

I have to evaluate the Desalters manufcaturing data/mass balance provided in its offer.

 

I calculated the required dilution water, but it turns out to be only 20% of what is given by the supplier.

 

The supplier has given two values for dilution water flowrate considring Crude oil of API 16 & API 14.

 

1. Does different API result in different values of dilution water flowrate, kindly explain.

 

2. Can someone pls provide me with the solution/spreadsheet to calculate the dilution water flowrate & other paramters for Two stage desalter.

 

3. The parameter are listed below:-

     Dry Crude Flowrate - 104.9 cu.m per hr

     Water content - 25% (v/v)

     Salt content in water/feed - 153000 mg/l

     Mixing Efficiency for each stage is 60% (as per supplier)

     Water content at outlet of 1 & 2 stage is 0.5% (v/v)

     Salt content in dilution water - 500 mg/l

     Max PTB at crude outlet for API- 14 is 44 & API - 16 is 50

     API - 14 density - 888.1 kg/m3, visc -21 cP & API-16 desnity - 906.3 kg/m3, visc - 29.6 cP

 

Thanks in advance.

 

 

   

    

[shan]

Crude densities do not have impact on the desalter water usage. 

 

Assume:

W:  Fresh Dilution Water Flow, cu. m per hour

C1:  1st Stage Outlet Salt Content , mg/l 

 

1st Stage Salt Mass Balance:  104.9 * 25% * 153000 + W * 500 = (104.9*25%+W) * C1

2nd Stage Salt Mass Balance: 104.9 * 0.5% * C1 = (104.9*0.5%+W) * 500

[ahmadikh]

 sanganipratik,

 

I tried to quickly calculate the required wash water flow based on the spreadsheet that I use.

 

1) Does different API result in different values of dilution water flowrate, kindly explain: No...your required dilution water flowrate depends upon the inlet BS&W, PTB and your threshold for outlet BS&W and PTB, also on the salinity of the wash water itself and of course the mixing efficiency... The density (or °API) of the crude along with its viscosity are of the most important parameters which determine the size of your desalters as well as the required electrical power to generate electrical field.

 

2) The wash water flowrate for °API 14 crude oil would be about 4.5 m³/hr (~4.5% of the dry crude oil) assuming 60% mixing efficiency of the mixing valves (is this in the range with the number provided by your Vendor?)... The mixing efficiency could be increased if some other things such as "static mixers" are used, however they all end up in more pressure drop which increase your wash water pump(s) head...Also, how much pressure drop are they providing across their mixing valves? Is it less than 1 Bar? And what is the valve type?

 

Hope this helps...

 

Best,

Milad

Edited by ahmadikh, 25 November 2014 - 01:37 PM.