Securing cement quality and sustainability with precise sulfur compound control

Sulfur is under the microscope in cement production, and for good reason. Not only are sulfur emissions tightly regulated in the cement industry – for instance, through the European Union’s Industrial Emissions Directive – but its compounds, such as sulfides and sulfates, also have a big role to play in the quality and characteristics of your cement product.

For example, excess sulfates can make cement harder to handle and finish. Meanwhile, excess sulfides can corrode steel reinforcements in concrete and even damage your kiln lining and equipment.

Fast and precise sulfur characterization is the key. Here’s how it can transform your cement production processes – and why wavelength-dispersive x-ray fluorescence (WDXRF) is the right technique for the job.

Precise analysis enables at-the-line decision-making

Accurately gauging the sulfur compounds present in your cement mix gives process engineers, product managers, and quality control experts the information they need to optimize their processes in real time.

For example, high levels of sulfate in your cement mixture could cause issues with cement durability, particularly for cement that is designed for application in marine or high-moisture environments. Detecting high sulfate levels early enables your staff to:

• Adjust the proportions of the materials in your raw mix or change the fuels used in the kiln to control the chemical reactions
• Introduce mineral additives such as fly ash or slag to balance the composition
• Fine-tune the grinding process to counteract some of the issues associated with high sulfate levels

High levels of sulfide in your mix can be even more problematic, increasing your sulfur dioxide emissions when burning clinker and even corroding your plant equipment. Fast analysis gives you the materials insights you need to protect the environment and your plant’s uptime, for example, by:

• Switching to lower-sulfur fuels or raw materials
• Controlling the temperature of your kiln to prevent sulfates from reducing to sulfides in extreme temperatures
• Optimizing your desulfurization processes to reduce emissions
• Introducing additives to neutralize the threat of excess sulfides

Traditional analysis can’t meet current requirements

In the past, tests to deliver this kind of information have been carried out with wet chemical methods; however, these analytical techniques don’t meet modern requirements. Firstly, they often lack the precision needed to properly fine-tune your cement composition, especially when dealing with lighter compounds like sulfates and sulfides.

Wet chemistry is also unable to deliver the speed necessary to optimize your processes, often taking several days to return results. Titration and gravimetric methods, for example, include complex sample preparation, precipitation, and filtering, all of which are time-consuming and require qualified operators.

Health and safety risks are also a prominent concern with wet chemical analysis. Digesting samples in hazardous chemicals such as hydrochloric acid puts technicians at risk of burns and, particularly when working with sulfur compounds, exposure to toxic gases such as hydrogen sulfide.

With today’s cement manufacturers under constant pressure to increase efficiency, reduce emissions, and cut costs, the labor- and resource-intensity of wet chemical methods make them ill-suited to sulfur compound monitoring. And, in the interests of operator safety, cement producers are looking for methods that pose less of a risk.

WDXRF is the answer to these dilemmas.

WDXRF: Your secret weapon for sulfur speciation

Wavelength-dispersive X-ray fluorescence, or WDXRF, is a non-destructive analysis method in which an X-ray tube is used to irradiate a sample, and the resulting X-rays – each of which has unique radiation characteristics depending on the element it originates from – are separated based on their wavelengths using crystals. This radiation is then analyzed to produce high-resolution data about the elemental makeup of your materials.

One of the key advantages of WDXRF in cement production is that it offers low detection limits and high-resolution results, especially for lighter elements. This is particularly important when monitoring sulfur compounds, as less sensitive instruments may struggle to accurately separate and quantify sulfates and sulfides in the results – negatively impacting your decision-making abilities.

By contrast, Malvern Panalytical’s Zetium instrument offers high resolution and sensitivity, especially for S-KA peaks. This enables you to precisely quantify the sulfur compounds in your mix, even when both sulfates and sulfides are present.

The Zetium also offers short measurement times of just a few minutes per sample, guaranteeing fast responses to production control systems. The Cement edition of Zetium can easily be integrated into automated sample preparation and analysis systems to reduce operator workload, and it is capable of analyzing all major and minor compounds across the cement production line, including raw materials, raw meal, kiln feed, clinker, and cement.

By minimizing the use of wet chemistry in your workflows with WDXRF, you reduce the amount of hazardous waste you produce and your operators’ exposure to dangerous chemicals. And with its low energy consumption and low cost of operation, WDXRF also presents itself as a more sustainable solution to safeguard your emissions targets and your plant costs.

To find out more about the Zetium’s precision in measuring the sulfate and sulfide content of cement materials, download our application note.