Petroleum consists of organic compounds and complex hydrocarbons.
These hydrocarbons consist of long chains of carbon and hydrogen molecules which, once refined, break down into a variety of products such as gasoline, diesel, kerosene and fuel oil, but also solvents, fertilisers, pesticides and plastics.
Other products, such as asphalt, can also be cracked by modern refineries into more valuable products.
Cracking is a process whereby complex organic molecules are broken down into simpler molecules by the shattering of carbon-carbon bonds.
In fluid catalytic cracking, the long-chain molecules of highboiling hydrocarbon liquids are turned into much shorter molecular chains at elevated temperature by means of a fluidised powdered catalyst.
This powdered catalyst usually consists of small ceramic balls, or beads, about one-to-two microns in diameter.
These beads, packed in columns, draw out impurities from crude oil as it passes through.
During this process, the beads wear down and by doing so lose their properties as catalysts.
Clemex was provided with four vials containing ceramic beads.
The purpose of the analysis was to see if the software could classify a group of beads by degree of wear.
The vials were numbered: vial number one contained pristine beads; vial number two contained slightly worn beads; vial number three contained worn beads; and vial number four contained fragmented beads.
The beads were randomly placed onto a sticky surface to prevent them from moving around.
If a large number of samples were to be analysed, the use of a grid to hold the samples in place should be considered.
The motorised stage's movement would thus always be the same.
Given the size of the beads (+/- 2mm), a low-power objective must be used to keep them entirely within the visible area (as much as possible).
Nevertheless, the magnification must be sufficiently high to resolve the texture of the ball's surface.
A magnification of 50X was found to be the best compromise for this analysis.
Considering the shape of the beads and the magnification used, it is only possible to focus on small sections of an object at the same time.
The Multi-Layer Grab instruction is thus vital in reconstructing the complete image from the several images taken at different Z positions, each containing only a small area in focus.
The Z displacement of the motorised stage was doubled to increase the speed of the Multi-Layer Grab instruction.
It was found that reflected light and a black background are the conditions that allow for the best contrast of surface details, and thus to obtain the greatest variation in grey levels from one category to another.
Using the analyser, a number of different factors were measured on beads belonging to each of the four categories.
The results obtained were compared using graphs and those that showed a clear-cut variation between categories were retained for use.
These factors are size, grey intensity and texture.
Although none of these three factors alone are enough to categorise the beads according to the four wear-levels, their combined use enables classification.
For a group of beads, the Clemex Vision PE image analysis system can automatically calculate the percentage of each of the four categories to which they belong.
From there, the final classification is easily performed.
