You are currently viewing: Literature



PackView™ - quantitative analysis of packing mal-distribution

The last issue of Tracerco Insight (Vol 6 Ed 1) featured our patent pending FrothView™ technology illustrating how using Tracerco’s new measurement detector technology and analysis of gamma scan data provides quantitative information about the useful capacity of trayed towers. In this article you will learn how applying this technology to packed towers can determine the % liquid fraction providing a measure of the maximum useful capacity of the packing.

Enhanced quantitative analysis of Tracerco Diagnostics™ Scan results
Once beyond questions concerning damage to internals and flooding within a packed tower, the next big concern is the state of liquid distribution through the beds. Historically gamma scan analysis has relied upon performing two sets of parallel scanlines (given the tower diameter is sufficiently large) through the packing as shown in Figure 1, commonly referred to as a grid scan.

The reasoning goes that all scan parameters being constant, particularly the length or path of radiation through the column, uniform liquid distribution can be confirmed by all four scans detecting identical radiation. Figure 2 is a typical example of grid scan results showing all four scanlines matching, implying good liquid distribution.

On the other hand, Figure 3 represents a grid scan where the lines do not seem to match very well but is this liquid mal-distribution? If so, what is the quantity of liquid mal-distribution? Up until now the available qualitative analysis of a gamma scan is not able to answer this very well.

Tracerco has developed an enhancement in detection capability and data presentation that is termed a liquid retention scale. Figure 4 shows typical scan results through a bed of packing. Overlaid on the data is a density scale.

The density scale begins at the density of the dry or non-operating packing. To derive this value it is necessary to know the packing type to reference its dry bulk density. The density scale to the left of the dry packing density is the calculated density of the liquid retained in the bed of packing. As with the normal gamma scan analysis, if the four scanlines have matching liquid retention densities then the implication is the liquid distribution is good. However, if there is a difference between the scanlines, the retention density gives a numerical comparison from which to gauge the extent or severity of any liquid mal-distribution.

Back to Figure 3 – how “bad” is this liquid mal-distribution? Figure 5 shows the scan results from Figure 3 with the liquid retention scale in place. The spread in density from the lightest density, 104 kg/m3, scanline (blue) to the heaviest density, 136 kg/m3, scanline (black) is 32 kg/m3. Scans of dry towers (tower is not operating so presumably no liquid mal-distribution!) have shown that we naturally get a variation of radiation readings corresponding to a 16-32 kg/m3 difference. Based on this guideline a 32 kg/m3 difference among scanlines would hardly seem to be a significant operational problem.

Figure 6 is an example of liquid mal-distribution seemingly becoming a bigger concern. As seen from the liquid retention scale in Figure 6 the spread in density from the lightest density, 24-32 kg/m3, scanline (blue) to the heaviest density, 120 kg/m3, scanline (black) is 88-96 kg/m3. This is a relatively large difference in liquid density so would represent significant liquid mal-distribution.

Other Literature

Moving gamma scanning forward – quantitative analysis of tray capacity

Improving process operating margins can include maximising production of higher value products and/or minimising production costs. Process plants depend heavily on fractionation towers to produce products meeting customer specifications. Tower gamma scanning is well established in the process industries ...


FCC stripper - distribution studies

A Tracerco Diagnostics™ Distribution study can be performed to identify catalyst and vapor distribution in the stripper. Uniform distribution of catalyst and steam in the stripper is critical to achieve high stripping efficiency (less carry-down of the hydrocarbon products from reactor to regenerator). ...


Exchanger leak testing - chemical tracers

Tracerco has been at the forefront of the development of online leak detection for the last 40 years. The method allows the detection of leaks as small as 0.5%. However, customer demands to measure smaller leaks affecting product quality, has prompted extensive research to develop alternative online ...


Tracerco Diagnostics™

Providing real time measurement technologies to assist with critical decision making. Tracerco Scanning Services TRU-SCAN® Application. Do you have problems with the operation of your stripper/absorber or fractionation tower? Is this limiting production? Do you want to reduce your operating costs? ...


Tracerco Diagnostics™ FCCU Study

The Fluidized Catalytic Cracking Unit (FCCU) is the economic heart of a modern refinery. Even small increases in its yield can bring about significant overall gains in productivity and revenue. Tracerco is a world leading industrial technology company providing unique and specialized detection, diagnostic ...


Measurement instruments and servicing

Our Measurement Instruments business designs and manufactures a range of bespoke, low maintenance, high reliability instruments providing operators with real time measurements and in-situ visualisation. Our experienced team technically supports an extensive range of nucleonic measurement instruments ...


Making desalter vessels transparent to optimise crude processing

Making Desalter Vessels Transparent to Optimise Crude Processing... whatever the blend. To improve margins, refiners continuously look to optimise feedstock blends. Variability can bring significant operational challenges during the refining process that must be overcome. One critical need is the efficient ...


PackView™ - quantitative analysis of packing mal-distribution

The last issue of Tracerco Insight (Vol 6 Ed 1) featured our patent pending FrothView™ technology illustrating how using Tracerco’s new measurement detector technology and analysis of gamma scan data provides quantitative information about the useful capacity of trayed towers. In this article ...


Making the invisible visible

In FCC Units (Fluidised Catalyst Cracking Units) the atmospheric residue from the distillation is cracked to LPG, naptha and other components. This sometimes leads to “invisible” deposits inside the Riser. This article features Tracerco’s ThruVision™ scans to illustrate how the ...


Tracerco Profiler™ HMI

A Windows based application offering dynamic displays, diagnostics, trending, control and historical logging. The Profiler™HMI, is a ready-made graphical user interface that provides clear insight into your separation process while enabling efficient operation and control of the Profiler™GPS ...