Q & A > Question Details
I am a Shift supeintendent of the CDU unit.
We could not stabilize the Brine treatment package - Hydrocyclones to separate the oil and sludge from the Brine of the Desalter outlet.
If anybody have the experience regarding the operations of Hydrocyclones (Brine treatment package) in the Brine system, please share with me.
If I can get the optimum dela pressure across, it will be helpful; I could not follow the vendor operational guidelines as it is not performing good.
10/08/2010 A: Christopher Turner, Snamprogetti Ltd, chris.turner@snampro.co.uk
Are you running the cyclones at high or low flows. Cyclones run best at high flows (higher velocity in the cyclone gives more g-force). If you are running near to the minimum flow for the cyclones, install blank cyclones to increase the flow per cyclone.
30/11/2009 A: Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
It is not uncommon to hear that hydrocyclones are not performing well in this duty as you describe. Hydrocylones work best when the process is steady state with no upsets. We are also seeing a trend towards heavier crudes and as the density difference between water / crude lessens, this makes the crude / brine separation in the desalter more difficult. To make matters worse, higher sulphur crudes are becoming more common so the use of H2S scavengers and corrosion inhibitors is increasingly common which also can have a detrimental effect on the stability of the emulsion generated in the desalter. It is also often the case that customers have had capacity creep of their CDUs over time and additional throughput above the nameplate design capacity will also make life difficult for brine underflow system because of reduced residence time in the desalter resulting in an increased crude carryunder to waste water treatment plant via the brine underflow. (can also result in increased brine carryover to CDU as well which is also undesirable).
The main issue we see with hydrocyclones on brine underflow stream that we see is related to high solids content especially during or after mudbusting which often leads to hydrocyclone fouling which will lead to hydrocyclone performance issues. (i.e. crude carryunder to WWTP and possible WWTP upsets there which may result in emissions above licence limits.). The second issue we see is that hydrocyclones are not particularly effective at removing small droplets and as emulsions are becoming more stable and the separations more difficult, hydrocyclones are struggling to maintain a satisfactory level of performance.
Pall Corporation has recently developed a separation device called LUCID (TM) precisely for this application. The PALL Lucid (TM) device is a separator which can tolerate the high solids loading present during mudbusting. Can also tolerate high levels of crude in brine underflow. Extensive laboratory & field trials have been performed to validate the Lucid (TM) performance. Pilot test units are located around the world and are available for demonstration purposes and to conduct sizing confirmation trials to validate sizing and Lucid (TM) system pricing for your particular crude/brine diet. We would be happy to assist with proposing a solution to your issues if you want to discuss an alternative to your existing hydrocyclones with us further.
30/11/2009 A: keith bowers, B and B Consulting, kebowers47@gmail.com
Hydroclones require a difference in specific gravity AT THE OPERATING TEMPERATURE to work. They use the principle of centripetal force developed by rapid rotation of the fluids within the conical device, increasing the separating force by many times. This requires energy input of course, measured by pressure drop across the device. The pressure drop (and separation energy) is a strong function of flow rate. Too low a flow rate will result in poor separation.
It is quite possible the 'sludge' has a specific gravity too close to that of the brine. That can be resolved two ways--raising the temperature of the fluid going into the cyclones (hydrocarbons expand much more than brine as the temperature is raised, increasing the difference) , or by adding a light, easily removed diluent (kerosene?) to the sludge/brine mix to decrease the specific gravity of the hydrocarbon phase.