Technology to trust for process gas analysis

In November 2020, Heidelberg Materials’ subsidiary Ciments Calcia presented drafted terms of a large-scale investment and reorganisation programme for several of its production sites in France. The €400 million investment programme was in line with Heidelberg Materials’s strategy to create a sustainable low-carbon and high-performance business throughout the group and even included a new 4000 tpd clinker production line at its Airvault cement plant for further fuel handling and efficiency upgrades, as well as process improvements at its cement production sites in Couvrot and Bussac-Forêt.

The cement industry is one of the most energy-intensive industries in the world, with energy accounting for up to 40% of production costs. As a result, the industry has been actively seeking alternative fuels to reduce its reliance on fossil fuels, which are not only costly but also contribute to greenhouse gas emissions. One of the most popular alternative fuels in the cement industry is waste-derived fuel, which includes materials such as shredded wood, waste paper, plastics, tyres, and waste oil. These materials can be used to replace a large portion of fossil fuels in the production process, reducing costs and fostering decarbonisation at the same time. Overall, the trend towards alternative fuels in the cement industry is driven by a need to reduce costs and emissions while remaining competitive in the global market.

Adapting to alternative fuels

Throughout the industry, it is well known that a large share of alternative fuels increases the risk for possible cyclone blockages, ring formation, and corrosion issues, which will consequently lead to a pressure loss, increased wear of the kiln sealing, incomplete combustion, and a rise in sulfur and chlorine volatilisation. Furthermore, the restriction of the kiln diameter can lead to poorly granulated clinker and an increase in gas velocities, which can elevate dust formation and even cause local hot spots inside the pyroprocess, damaging the refractory material and outer kiln shell. The usual associated effects are frequent kiln stops, reduced kiln availability, diminished productivity, and reduced clinker quality caused by the periodic breakaway of deposits. This phenomenon, however, can be avoided by monitoring the gas composition inside the pyroprocess and feeding the information into a closed loop control system to maintain stable and optimised process conditions. Right from the project’s start, the managers at Calcia attached high importance to choosing the correct process gas analysis system for the future growing requirements for process control at upgraded and future plants. Having good experiences with a large installed base of SICK kiln inlet process gas analyser systems not only in France but in many other production sites belonging to the Heidelberg Materials group and following the recommendation of plant operators in various countries, Calcia decided to request SICK to provide its Cement Probe System, SCPS 3300, for the projects to be executed in France.

The main tasks of kiln inlet process gas analysers in cement plants are:

• Measuring the process gas composition in the rotating part of the kiln.
• Monitoring the excess air rate (O₂) at the kiln inlet.
• Checking for carbon monoxide concentration (CO) and completeness of combustion.
• Monitoring NO and NO₂ concentrations for emission and temperature control.
• Monitoring of sulfur volatiles (SO₂).
• Controlling the measurement values mentioned by providing information for burner controls, fuel and raw material mixture adaption, and flue gas cleaning system controls.

In addition to these functionalities, other customers have benefitted from the capability of the analyser system to give an indication about the internal chlorine cycle by measuring the process gas concentration of hydrogen chloride (HCl), helping plant operators to reduce blockage issues caused by high chlorine volatility. Furthermore, this information can help to limit the bypass gas volume flow and keep HCl emissions at a low level.

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Read the article online at: https://www.worldcement.com/special-reports/23102023/technology-to-trust-for-process-gas-analysis/