Frequently Asked Questions on PGNAA/PFTNA

What are the benefits of PGNAA relative to alternative techniques for elemental analysis such as XRF?

PGNAA is highly complementary to XRF for many industries with two crucial advantages.

Firstly, because of the highly penetrating nature of neutrons, PGNAA measures the entire volume of a sample or process stream, rather than just the surface. This is a value-defining attribute when it comes to applications such as bulk-ore sorting that rely on the representative measurement of highly heterogeneous streams for success.

Secondly, PGNAA is suitable for lighter elements, specifically those with an atomic number of 18 or less, that are ill-served by XRF; lighter elements emit less energetic X-rays that are prone to attenuation by air. Industrially important elements that lie in this region include sodium, silicon, magnesium, aluminum, sulfur, potassium, and chlorine.

Similarly for detector design, how does design and configuration impact performance and how can it be optimized?

While the source determines signal strength, detector design and configuration determine the extent and efficiency with which gamma rays are captured, and by extension the ability of the system to robustly detect different elements. We use high efficiency sodium iodide detectors for speed, resolution, and stability, specifying between one and four per system depending on application requirements. As with the source(s), detectors are critical to measurement precision, accuracy, and viability and by extension system value. Source and detector should be appropriately matched for optimal performance with options to refine configuration for either repeatability or uniformity depending on requirements.

Can you provide any guidance on how to justify an investment in PGNAA?

A good starting point is to ask the question: What will I do with the data, if the analyzer performs as expected?

This is a key question for a bulk ore sorting project, because while robust, real-time elemental analysis lies at the heart of the process, implementation involves significant investment in the infrastructure of the mine, due to the need to route/reroute streams appropriately. The cost of the analyzer will, in truth, be a very small part of such a project but even so it is crucial to robustly assess what differences in performance might mean. Look for evidence of the level of false acceptance and false rejection the analyzer can deliver (we can certainly help you with this) and do the maths to see what that means in terms of lost revenues since this can be the difference between success and failure. There’s an example of this type of calculation in our copper ebook.

For a process, a cement plant for example, investing in PGNAA may be the key to better and/or automated control. Real-time analyzers allow process operators to a) reduce variability and b) develop the confidence to push harder towards operational limits. Look at what gains in either area might mean since both impacts are likely to deliver economic return. Be sure to factor any capacity to automate into your calculations, including how improvements might drive-up workforce productivity, since there is no doubt that automation is the best way to capitalize on the benefits of real-time analysis. There are good examples of the range of benefits that cement manufacturers have seen, and their value, in our cement ebook. 

How do commercially available systems differ from one another and what features are especially valuable?

The hardware is important since it defines system performance. Alongside source and detector design, as discussed, configurability, ease-of-installation and overall system design are all key.

Which brings us to the other issues beyond the hardware that boost value, the first being expertise. PGNAA has been used for decades but not by all providers. Companies with a track record of success reduce risk and are especially important when it comes to large CAPEX projects. The other critical factor is software. Data usage is defined by accessibility so industry and application specific packages that make it easy to measure, present and use relevant metrics are crucial. Our solutions include Thermo Scientific RAMOS (Raw Mix Optimization Software), Thermo Scientific COBOS (Coal Blend Optimization System) and Thermo Scientific PREBOS (Pre-blending Optimization Software).  

Which industries are the biggest users of PGNAA and why?

The cement and iron ore sintering industries are both big users of PGNAA because it enables real-time kiln and sinter feed chemistry control, thereby helping to reduce fuel consumption and extend kiln life while at the same time improving product quality.  

More generally both the cement and coal industry use PGNAA for stockpile control. By responsively measuring the composition of raw materials it becomes easier to make optimized blends, as cost-efficiently as possible. Investing in PGNAA technology is helping producers to be more agile with respect to using for example, low grade coals and alternative cement ingredients such as fly ash and blast furnace slag, to simultaneously improve economics and environmental impact.

The third major user is the minerals processing industry. Here the role for PGNAA extends from bulk ore sorting – which can transform the profitability of mine operations, especially for low grade ores - through to the more efficient operation of froth flotation circuits where the technique can be used to responsively control reagent dosage in response to incoming mineral composition.