The Benefits Of Real Time Particle Size Analysis

Interview conducted by G.P. ThomasJan 14 2014

AZoM talks to Rob Norris, Divisional Global Account Manager at Malvern Panalytical, about real time particle size analysis within the process environment, using laser diffraction, and the associated benefits.

Could you provide a brief introduction to the Malvern Panalytical process team and how it got started?

The process team at Malvern Panalytical focuses on the installation of analyzers within the process environment. What we mean by this is within the manufacturing plant itself. So typically we’re dealing with continuous measurement, on- or in-line. Particle size analysis is our primary focus, most especially using the technique of laser diffraction, but we have other technologies too. Frequent measurement, to the point of real-time monitoring, is usually the goal, often with the endpoint of automated process control.

In 1996 Malvern Panalytical purchased the rights to the technology of a company called Insitec, who manufactured a laser diffraction particle sizer for process use – and this was how the process team began. Malvern Panalytical has a long and distinguished history in laser diffraction particle size analysis but before 1996 we sold only laboratory systems. Some of these went into some fairly dirty environments to support manufacture but they were not physically integrated with the process equipment in the way that Insitec systems are.

The Insitec system was developed from the beginning as a process analyzer, with no intention of laboratory use. This made it the perfect complement to our established Mastersizer laboratory systems. Buying Insitec enabled us to offer customers a complete ‘lab-to-line’ solution that supported the transfer of specifications developed in the lab, in R&D, out into commercial manufacture to control the process.

Insitec Dry particle size analyzer. Image credit: Malvern Panalytical

What types of industries do you tend to work with?

Some marked trends have helped to define our markets over the last decade or so and today our two most substantial customer groups can be categorized as bulk commodity, high tonnage manufacturers or speciality, high value producers with a specific production issue to address.

As recently as 15 years ago bulk minerals processors and cement manufacturers relied predominantly on manual methods for particle sizing, taking measurements periodically. These included sieving and Blaine measurement, a permeability technique where results can be operator dependent. These industries are characterized by huge throughputs and high energy consumption. Competition for global supply and customer demand for a consistent global product specification, along with rising energy prices has resulted in a sustained focus on efficiency and variable cost, creating an appetite for analytical methods and systems that can help. In these industries our technology is helping to drive down costs and reduce energy usage to an absolute minimum while providing direct output consistency.

The other area where automated, on-line systems can be extremely helpful is for those who don’t want to rely on manual analysis because of the associated Health, Safety and Environmental risks. In speciality chemicals production, for example, those manufacturing pigments, active phamaceutical ingredients (API) and explosives, for example, need to measure toxic or explosive materials. Here the automation we offer eliminates the need for manual contact with hazardous materials.

Do you have machines in the field or are they mainly used in processing plants?

As a company we do provide analytical instruments for use in the field. Particle size analyzers for drilling mud analysis on oil rigs would be a perfect example. However, our Insitec systems are usually installed in processing plants.

Examples of the types of processes that Insitec is used to monitor include: milling; blending/homogenization; spray drying; granulation; emulsification; sedimentation and filtration. It’s usual to find our instruments on the streams of materials which are the output from these specific operations – the outlet line from a mill, for example, or on the overflow of a sedimentation tank. The data gathered can then be used to learn about the process dynamics and how best to control the plant, either manually or automatically, to optimize the process.

Schematic of a milling circuit, with vertical roller mill, for the production of marble powders. Image credit: Malvern Panalytical

Could you go into more detail with respect to the dynamics of the process and what the benefits are?

When we talk about process dynamics we’re really talking about how quickly a process changes. Some processes, those where the material stays in individual pieces of equipment for just a few minutes, for example, can change rapidly and frequently. Others move from one condition to another far more slowly because of inherent lags in the system.

When it comes to monitoring a process it’s vital to match the frequency of measurement with the process dynamics. If the process changes every minute then measuring every half an hour is less than ideal. On the other hand if the process only changes slowly then less frequent measurement can be a pragmatic choice, especially if it helps to reduce analytical spend.

That said it’s not just process dynamics that are important. Even if a process changes relatively slowly, the ability to instantly detect a process upset, an abnormal occurrence, can be crucial, and you only get this with real-time measurement. We’ve worked on a project with a leading global mining and metals company, on their iron ore processing plant that perfectly illustrates this point. Here the implications of a problem with their hydro-cyclone separation plant, which separates out the valuable ore from impurities, are so significant that the cost of real-time particle sizing is recouped through the prevention of just a single incident. This is a problem that can’t be effectively tackled with manual measurement and an example of an application where real-time measurement really comes into its own.

What are the major economic benefits of real time analysis?

The specific economic benefits that stem from an investment in process analysis are unique to every application. In general the financial return accrues from: savings in energy consumption; reductions in waste and re-work; and increased plant throughput. More fundamentally, in certain industries it is now becoming impossible to compete in terms of product quality without access to real-time monitoring.

A case study in the cement industry with Rockwell industries in the US provides a powerful example of what can be achieved. Here a switch to on-line particle sizing on the finished cement grinding circuit, in combination the implementation of automated control, delivered a 15% reduction in energy consumption. A benefit of this scale rapidly pays back the initial investment in new equipment. Payback times for Insitec analyzers are typically very short – less than a year.

So would you say there are any environmental benefits to switching to real time analysis?

Of course energy savings are a major aspect of environmental improvement but there other potential gains too. For example, in minerals processing real-time analysis of the overflow from the final thickener or sedimentation process, used to clean up water for return to the environment, provides constant monitoring of the water quality. By closely controlling particulate levels in the overflow and ensuring that any problems are instantly detected, real-time analysis enables safe water recycling. This is especially important in countries where water is a scarce resource.

Furthermore, the close control that real-time measurement supports can deliver an overall reduction in environmental impact. Again turning to minerals processing, one of our customers found that because of ineffective process control they were putting high grade ore into the waste treatment area. Tighter control enabled the plant to be operated so as extract more valuable material from each tonne of ore, delivering an important overall gain for long-term sustainability.

Could you also just touch on the health and safety aspect of this?

When it comes to HSE benefits these may arise in a number of ways. A well-controlled grinding process may, for example, produce less dust, decreasing the risk of exposure for employees. However, one of the most important HSE benefits we can deliver is to remove the need for human input into sampling and analysis entirely.

One area where we just starting to work, with on-line zeta potential, a relatively new on-line technology, is in the water treatment industry. Here there is a move to unmanned operation at most drinking water plants, with automated in situ monitoring and telemetry to a central control system. Sampling points at water plants can be tricky to access and there is a substantial risk of exposure to chlorine. Moving to unmanned operation is therefore attractive, as well as being economically beneficial, but it requires the development and application of suitable technology.

We’re working on the application of on-line zeta potential measurement to help with control of the amount of chemicals used to ensure the successful flocculation and sedimentation of contaminants. This technology offers considerable scope for automated monitoring, and ultimately automated control. Trials in the US have been very promising with on-line measurements delivering a 15% reduction in the quantity of additives required to maintain water quality, as well as reducing the need for manual analysis.

Drilling companies are also looking for options for remote monitoring, for drilling muds, for example. These muds maintain the safety and efficacy of the well, with particle size measurement one of the measures used to ensure they are fit for purpose. We’ve been working on a system that will allow one person to monitor the quality of the muds at 5-10 different sites, remotely, avoiding the need for dedicated personnel on the rig, a major plus.

In terms of the regulations, have these become tighter over the last few years as well? Is there more of a demand for a more specific particle distribution?

If I take the second part of this question first, then the answer is definitely yes. The demand for particle size distribution data is growing. However when it comes to the product I would highlight the need for quality, rather than new regulation, that is driving this trend. Customers for many products, toners and cement for example, are becoming more discerning and more demanding of the assurance of quality provided by relevant analytical data.

Consider a construction company building a skyscraper. Clearly the cement needs to be meet building requirements and quickly develop the strength to support subsequent floors. At some sites cement is used while it is still warm from manufacture so having a well-defined specification that delivers the required strength, and consistently checking that the product meets this specification, is essential. Detecting a problem when you are three floors higher up the building is not helpful!

However, there are areas where regulation, standards and expert guidance are shaping usage. Drilling muds exemplifies this trend. Here the API is working on standards for the application of laser diffraction to ensure consistency in quality control, because of the potential impact this can have on drill safety.

So are your particle size analyzers used in more high-end applications?

Yes but not exclusively. Our analyzers are used anywhere from food analysis to cooling cow sheds! This latter is a great application from the US where the Insitec is being used to control the atomization of water droplets to maintain an optimal environment for cow health.

Our applications are really diverse. We sample and measure streams from the gram to the tonne scale, both batch and continuous processes. We do this for industries that range from those handling the least expensive of materials to, for example, pharmaceuticals where an active ingredient can be worth thousands of dollars per kilo.

Are there any other case studies at the moment that you want to particularly highlight?

There are a many different applications that have been successfully tackled using the Insitec systems, with different benefits delivered in each case. I think what unites these successful project though is that the customer has had, or developed with our help, a really clear idea of how to productively use the data that the analyzer produces.

It may be that a system is purchased to understand and improve the process, or as a foundation for automated control, or simply to move QC on-line and remove the need for a lab test. These are all valid reasons to switch to in- or on-line analysis but they do create a different set of requirements for the installation. It’s important to establish intentions and deliverables up front to ensure a robust economic evaluation of any investment and to create a realistic view of what will be achieved.

How are you currently involved in Pharmaceutical industry?

The Pharmaceutical industry is currently our second biggest industrial market. We’ve certainly seen an increase in interest in real-time measurement as a result of the Process Analytical Technology (PAT) initiative which is designed to promote an innovative approach to process monitoring and control. However, there is still some way to go in the pharmaceutical industry with regard to fully integrated automated process control at the commercial scale. Our systems are predominantly still used at the pilot stage where they really help to accelerate information gathering and process optimization.

In this area we’re also working with companies developing continuous manufacturing processes, such as GEA Pharma and Glatt. The pharmaceutical industry’s drive to continuous rather than batch processing increases to focus on in-situ analyzers. Here the use of Insitec helps with the optimization and control of, for example, continuous milling/tabletting processes. In addition, we have alternative, highly efficient technology – the Parsum probe - for measuring particle size within a high shear or fluidized bed granulator. Granulation is an important process within the pharmaceutical industry and with Insitec and Parsum we can tackle all associated applications.

Parsum IPP 70-SE particle sizing probe. Image credit: Malvern Panalytical

How sensitive are the machines, and are there any limitations?

There are a number of factors implicit in the term sensitivity. One aspect is repeatability, an area where laser diffraction in general scores very highly. In most laser diffraction applications sampling is now the major source of error and this can be substantially reduced with on-line measurement. As part of any project the process interface requires some careful thought, to ensure reproducible sampling over the long term. The measurement accuracy indicated within the laser diffraction particle size standard ISO13320 is the minimum expected and many projects will exceed these targets, frequently better than +/- 2 % on a Dv50 for the majority of applications

However, when it comes to process analysis sensitivity also implies something about how quickly and easily an analyzer can detect a problem. On a large mineral processing plant an Insitec might gather data every quarter of a second, but a rolling average of these results over a 5 or 10 minutes timeframe is used for control . Using this rolling average overcomes sampling statistics or minor fluctuations to give smoother control. This approach provides the sensitivity to essentially track a grade or set point change in real-time, and equally importantly will almost instantaneously detect a process upset.

Lastly, how do you see the field progressing? Do you see it being implemented in more diverse applications, or do you see more expansion into the areas you’re already in?

Traditionally Malvern Panalytical has developed and sold the Insitec analyzer within a fully integrated set-up. This usually includes the process interface – the hardware to install the analyzer in a line or vessel – and the software and hardware required for control. The result is a turnkey solution with a price tag to match.

There was sound reasoning for this approach which developed in response to customers wanting a fully engineered solution to reduce the risk associated with, what was, relatively new technology. However the turnkey approach made the technology a relatively big investment for certain applications.

If you are a powder coatings company, for example, you may have a single laboratory doing the QC for 8 or 10 different production lines, each making a differently colored product. Where there is a risk of contamination, color contamination in this instance, then sampling different lines through a single optical set-up, a single analyzer, is not advisable. Geographical layout can also be problematic when it comes to sharing an analyzer across lines. However, it is unrealistic to think that 8 to 10 fully integrated on-line systems will be purchased to replace a single lab system, especially if each is a fully integrated system.

Now that the technology is more mature we’re finding that customers have greater confidence in its application, and that they are willing to bring more aspects of a process analysis project in-house. This isn’t just a trend in on-line particle sizing. Process analysis and automation in general are becoming more commonplace and integrating a new sensor within an existing control system is now a relatively routine task.

So we’re now starting to sell sensors only, although turnkey solutions are still available for those who need them. A sensor only purchase is more accessible and so we’re expecting to see the use of the Insitec technology spread in the coming years, away from the innovators and early-adopters to becoming main stream.

The other continuing challenge is to help people understand how to optimize their use of continuous data. Insitec provides new information every few minutes, compared to once a day or every four hours. People like the data and comment on how good it is to have it, but are not always so clear on how to use it! This is where a partnership approach can be really helpful. We know what on-line particle sizing can do but our customers know their processes best. We need to pool our knowledge to create value and maximize the economic return for those companies who choose to invest in this powerful technology.

About Rob Norris

Rob Norris joined Malvern Panalytical in 1994 as Commercial Manager for the UK, responsible for both sales and customer support functions. During this time he championed the development of a Global Key Account program with the aim of ensuring the maximum benefit from their investments with Malvern Panalytical and continuity of support throughout their organizations.

Currently he is a member of the senior management team at Malvern Panalytical and has direct responsibility for the development of the global Process systems business.

He is responsible for a dedicated Process Engineering team,, providing specialist application support to secure and deploy the best Process solutions to a wide variety of industries and ensure full optimization of the project deliverables.