Sour Oil & Gas Advanced Technology (SOGAT) 2016

The Sour Oil & Gas Advanced Technology (SOGAT) conference was held in Abu Dhabi on March 20-24, 2016.  This gathering, which is focused on the gas conditioning issues that must be addressed to deliver sweetened gas for industrial development and infrastructure needs, has become the most prestigious meeting on this topic in the Middle East.

This conference can be considered the counterpart to the Laurence Reid Gas Conditioning (LRGC) conference held each year at the University of Oklahoma in the United States.

At SOGAT, Michael Porter, P.E. delivered a paper introducing a new analysis framework developed by PMI for the analysis and design of thermal reactors for sulfur recovery units.  This new framework represents an entirely new paradigm in the use of CFD to analyze combined thermo/acoustic phenomena.   Prior to PMI’s work in this area, these types of problems were only considered in research or specialized computational environments.  In his presentation and the accompanying paper (linked with this post), Mr. Porter demonstrated that PMI’s techniques can reduce the computing time necessary to obtain valid solutions by several orders of magnitude over techniques currently used to study these phenomena.  With this reduction in the resources required to perform these analyses, this category of coupled thermo/acoustic problems can now be undertaken for refineries and other industrial applications.

Link To Paper

Links to videos:

High-Rate Vibrating Flame

High-Rate Flame in Can

High-Rate Without Choke Ring

Turndown Rate With Choke Ring

Damping Evaluation

In engineering, the damping ratio (ζ) is a dimensionless measure describing how oscillations in a system decay after a disturbance.  One way to evaluate the damping ratio is to excite the system and then use what is called the log decrement method to evaluate the damping.  Figure 1 illustrates the log decrement method.

Fig_1

Unfortunately, real systems don’t always behave in a way that allows clear use of the log decrement.  Figure 2 illustrates the motion of a tall (~80 m) exhaust stack that is excited and then allowed to vibrate freely.

Fig2

The vibration signal has been filtered to remove all but the natural frequency (~0.54 Hz) of the stack.  If the stack was viscously damped, we would expect to see an exponential decay in the motion and the log decrement method could be used to evaluate the damping ratio.  If coulomb (friction) damping controlled, we would expect to see a linear decay in the motion with time.  Looking at Figure 2, neither type of decay is evident.

In order to get a clearer measure of the damping, it is often useful to use a technique that is often used in the acoustical world.  If the vibration amplitude is plotted on a logarithmic scale, it can be shown that:

ζ = 0.183/n                  Equation 1

Where:  n = number of cycles required for the amplitude to drop by 10 dB (a factor of approximately 3.16).

The motion data in Figure 2 has been potted with a logarithmic scale in Figure 3.

fig3

There are two distinct regions of decay in this portion of the signal.  A straight line passing through the first decay segment indicates that the signal would take approximately 12 cycles to decay by 10 dB.  A line passing through the second decay segment indicates that the signal would take approximately 20 cycles to decay 10 dB.  Using the Equation 1, the respective damping values would be 0.015 and 0.009.  The decreasing damping ratio as a function of amplitude is a strong indication that the damping in the stack is coulomb or frictional rather than viscous.

By: Mike Porter

Menu Title