Talk:Drag reducing agent
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| Thread title | Replies | Last modified |
|---|---|---|
| Do you have experience with DRA (Drag Reducing Agent) in pipeline? | 1 | 08:01, 17 December 2013 |
What has been your experience with DRA in pipeline? The functionality and required dosing rate? The parameters might affect on its performance?
Tom Sifferman
Fluids Specialist at ETTP Consulting
Dosing rate depends in part on the solubility of the DRA in the crude (assuming hydrocarbon system, not water based) and the desired amount of drag reduction desired. Other important parameters are flow rate (actually Reynolds number), temperature, pipe roughness, pipe diameter, etc. Conoco (now ConocoPhillips) has been a big supplier for many years of their CDR called Liquid Power.
Kenneth Chrisman
Sr. Hydraulics Engineer at Chevron Pipeline Co.
To add to Tom Sifferman's comments, The more viscous the stream the less effective DRA is. DRA sets up an interconnected matrix that hinders the eddies that would roll out against the pipe wall to produce drag. The interconnections in the matrix are weakened or broken as a result of shear. So shear in the form of pumps, check valves, slack line and just distance traveled degrades the effectiveness of DRA. It is assumed that DRA is 100% sheared when it passes through a pump. However if a portion of the DRA has not dissolved it can pass through a pump and still provide drag reduction downstream. Check valves roughly produce a 3% reduction in DRA effectiveness on large lines. Slack line, depending on the length, can degrade the DRA completely. And though the DRA manufacturers may tell you otherwise, DRA is degraded with distance traveled. It is not rally distance traveled but accumulated shear from arresting the eddies at the pipe wall. It does the same throughout the mixture resulting in concentric cylinder flow that has a flow profile similar to laminar flow.
To determine how much to inject, I would contact one of the suppliers and ask for their input. Baker and Conoco both have proprietary equations and will provide coefficients that will work with different fluids. The basic equation is shown below:
DR = 1/(A+B/ppm) if you want to ignore degradation with distance
DR = 1/(A+B/eppm) if you want to take distance traveled into account
eppm = ppm*e^(k*x)
where:
DR = Drag Reduction
A,B & k are constants
ppm = concentration in parts per million
eppm = effective concentration in parts per million
x = distance in miles
Gel DRA is typically 1 part active ingredient to 9 parts kerosene.
It is an extremely viscous mixture that is extremely difficult to deal with.
Slurry DRA is typically 1 part active ingredient to 2 parts (alcohol, water, glycol ...)
Slurry is a suspension that has to be stirred. Special equipment is needed to ensure that all passage ways are larger than the particulate. An example of what could happen, if the flow rate is too slow check valve openings can be smaller than the particulate basically filtering it out. This will result in the line being packed solid with active ingredient.
Prof. Dr. Hans-Jörg Oschmann
Prof. II Colloid and polymer chemistry at NTNU
The performance also strongly depends on the Reynolds number (If you plot Drag reducer performance vs Reynolds number you get a curved plot with a maximum depending on the polymer chemistry and molecular weight as primary parameters)
My team will present at the RSC conference in Manchester on this topic (Performance Assessment of drag reducing polymers utilizing a turbulent flow rheometer.) in case you should be attending. The respective paper will be included in the proceedings as well.
As Peter highlighted DRAs are effective in water, oil and multiphase systems though their chemistry needs to be tailored to the application. Water DRAs are commonly surfactants or polyacrylamides, Oil soluble DRAs are based on polyalphaolefins, polyisobutylene etc. Multiphase DRAs are complex formulations.
Isabelle Henaut
research engineer at IFP
Just a breif comment. DRA performance may be altered by dispersed phase such as water droplets , waxy crystals, or precipitated asphaltenes.
