Sunil Kumar Gupta, Chief Project Officer, Star Cement, discusses how evolving refractory technologies and smarter pyro-processing strategies are redefining performance, durability and cost efficiency.

In recent years, increase in use of alternative fuels, volatile operating conditions and tighter thermal-efficiency targets have reshaped how kilns and preheater lines are designed, lined and monitored. In this interview, Sunil Kumar Gupta shares with how these innovations are strengthening uptime, clinker quality and the future-readiness of India’s pyro-processing systems.

How have refractory demands changed in your kiln and pyro-processing line over the last five years?
Over the past five years, the operational demands on kiln and pyro-processing refractories have intensified, driven by higher kiln throughput and more impact on volume requirements, more stringent thermal-efficiency targets, and the accelerated adoption of alternative fuels (AFR) and mine life- day by day it’s a big challenge.
These factors have necessitated a shift away from conventional alumina-based brick systems toward engineered basic refractories, spinel-forming linings, and high-performance monolithic materials capable of withstanding greater thermal fluctuation, mechanical stress, and chemical attack.

What is the biggest refractory-related challenges you face in preheater, calciner and cooler zones?
Every zone has its own challenges:
A. Preheater
B. Calciner
C. Cooler

A. Preheater

• Fluctuating feed chemistry increases coating instability and causes lining erosion.
• High-speed gas streams and dust-laden environments accelerate abrasion, especially around bends and risers.

B. Calciner

• AFR combustion introduces reducing conditions and alkali–sulphur interactions, which attack conventional refractories.
• Localised hotspots form due to fuel injection patterns, leading to thermal shock and micro-cracking.

C. Cooler

• Clinker breakage patterns cause heavy mechanical wear near the bull nose and in the tertiary
  air duct.
• Modern coolers operate with rapid thermal cycles, which stresses monolithics and metallic anchors.
  The overarching challenge is selecting materials that balance chemical resistance, thermal shock capability, and mechanical strength under constantly changing process conditions.
  With the kiln, we are facing the problem of frequent breakdowns of the kiln bricks, specifically in the burning zone. So far, we were using high alumina but now we are planning to go with basic bricks to have more reliability and the longer operation duration of the kiln.

How do you evaluate and select refractory partners for long-term performance and life-cycle cost?
We evaluate the refractive suppliers based on the following four aspects:
A. Technical Capability
B. Engineering and Design Support
C. Life-Cycle Economics
D. Partner Support and Collaboration
Selecting a refractory partner is not simply a materials purchase, it’s a strategic procurement decision that directly affects plant uptime, process stability, and long-term operating cost. An effective evaluation approach should consider below pillars:

A. Technical Capability
The refractory supplier must demonstrate strong materials performance backed by reliable laboratory testing and consistent production quality. Key technical criteria include:

• Cold Crushing Strength (CCS), abrasion and erosion resistance-Indicates mechanical durability against clinker dust, gas flow, and material movement.
• Chemical resistance and corrosion testing-Confirms the refractory’s ability to withstand alkali attack, clinker phases, alkali sulphates/chlorides, and reducing/oxidizing atmospheres.
• Thermal shock resistance and spalling index-Evaluates resistance to rapid temperature changes and cycling—critical in cement kilns, coolers, risers, and cyclones.
• Density and porosity consistency across batches-Ensures uniform behavior in service and
  reduces the risk of localized weaknesses or premature failures.
• PCE (Pyrometric Cone Equivalent) testing-Measures refractoriness—the temperature at which the refractory begins to soften under its own weight—ensuring suitability for high-temperature zones.

B. Engineering and Design Support
A strong partner provides engineering expertise that prevents failures before they occur.
This includes:

• Proper lining design and zoning
• Thermal calculations, heat loss modeling, and expansion joint design
• Wear-profile analysis and historical performance audits and installation specifications

Engineering support directly influences service life, coating stability, and thermal efficiency.

C. Life-Cycle Economics
Assess the total cost of ownership rather than just initial material costs. This includes installation expenses, refractory maintenance frequency, downtime costs during replacement or repair, and energy efficiency improvements. Refractory partners who provide detailed life cycle cost analysis and emphasise value over initial price help optimise long-term operational costs. Transparent communication about the refractory’s expected service life and maintenance needs is crucial for selecting partners focused on minimizing life-cycle cost.

D. Partner Support and Collaboration
Select refractory partners who offer technical support, expert consultation, and a collaborative approach to tailor solutions. Partners committed to understanding your specific operational conditions, providing training, and proactively addressing performance issues tend to enhance overall refractory service life and reliability.

Can you share a recent instance where improved refractory selection enhanced uptime or clinker quality?
We recently deployed magnesium–iron spindle bricks, which perform exceptionally well across burning, pre-burning and post-burning zones. Their coating-friendly behaviour in the burning zone improves brick life, while their high density in other zones allows stable operation with minimal coating.
By combining coating bricks in the burning zone with non-coating bricks elsewhere, we avoided issues like excessive coating near the tyre area, which can push the kiln into reduction conditions and affect clinker quality. Modern burners with short, hot flames and lower primary air have also helped stabilise coating and heat distribution.
Overall, optimised brick selection paired with the right burner design has improved uptime, reduced wear and delivered more consistent clinker quality.

Use of advanced spinel bricks in kiln linings:

• One 2025 case study described how a cement plant replaced its conventional magnesia-chrome refractory lining in a large dry-process rotary kiln with Magnesium Iron Spinel Brick (and in some cases synthetic magnesium-iron-aluminum spinel) for the kiln’s hot zones.
• After the switch, the plant saw its kiln-lining life extended by over 20 to 30% compared to previous linings — raising lining life from the typical ~8 to 9 months to ~12 to 15+ months without relining.
• This led to a significant reduction in unplanned shutdowns (fewer relining, fewer maintenance events), improving overall operational uptime.
• Because the refractory was more chemically and thermally stable under high temperature and corrosive conditions, the kiln could maintain a more stable thermal profile, which supports consistent clinker formation and improved clinker quality (more uniform mineralogy, less variation due to thermal or chemical stress).

How is the increased use of alternative fuels impacting refractory behaviour in your pyro-line?
Usage of alternative fuels has adverse effect on refractory behaviour in the pyro-line:

A. Higher chemical attack
Alternative fuels (RDF/SRF, biomass, sludge, waste oils) introduce more alkalis, chlorides, and sulphur, cause corrosion of basic bricks, softening of castable, and loss of lining in kiln inlet, riser, and calciner and leads to unstable coating and accelerated wear.

B. More aggressive ash chemistry
AF ash often contains reactive SiO2, Fe2O3, CaO, metals, increases abrasion in kiln inlet and preheater and Generates slag and fluxing reactions that weaken MgO-based bricks.

C. Higher thermal instability
AFs vary in moisture and calorific value, as a result it results in less predictable combustion, produces temperature swings, spalling, microcracks and falling rings and creates hot spots due to irregular flame shape.

D. Changed coating behaviour
AF-related chemistry modifies coating growth and stability. More volatile coating exposes burning zone bricks and overcoating or build-ups in inlet and riser resulting in mechanical damage and choking.

What are plants doing to counter it:

• Switching to MgO–spinel bricks and alkali-/chloride-resistant castables.
• Adding SiC or abrasion-resistant linings in high-velocity or high-ash zones.
• Improving burner control, AF dosing, and raw mix balancing.
• Using sacrificial layers, redesigned anchors, and better insulation to protect main linings.What role does digital monitoring or thermal profiling play in your refractory maintenance strategy?
  Thermal profiling and digital monitoring have become essential predictive-maintenance tools for managing kiln and preheater performance. Online shell scanners now provide continuous thermography from inlet to outlet, helping teams assess coating behaviour and refractory health. Drone-based thermography is gaining popularity because it captures hotspots in areas manual checks cannot reach, especially inside cyclones and the calciner during shutdowns. Alongside kiln and cooler cameras, emerging instruments such as cooler-bed thickness sensors further optimise operation. Together, these technologies deliver better KPIs, more stable coating and improved refractory life.

  A. Kiln Shell Temperature Monitoring (IR scanners and cameras)
  Continuous kiln shell scanning identifies:

• Hot spots signaling refractory thinning or brick loss
• Misalignment, ovality, and ring formation through temperature pattern changes
• Overloaded or under-performing burners by observing flame/heat profile
• This allows maintenance teams to plan brick patching or section repairs before a shell deformation or blowout occurs.

B. Cooler Monitoring (grate cooler and tertiary air duct)
Thermal sensors and camera systems help:

• Spot grate cooler hot spots that indicate coating issues or refractory wear
• Track TA duct temperatures to avoid thermal shock or lining scouring
• Maintain proper heat recovery efficiency, which directly impacts refractory life
• Digital data ensures that refractory life is maximised by maintaining stable thermal conditions.

How do you balance cost, durability and installation speed when planning refractory shutdowns?
Balancing cost, durability and installation speed in cement plant refractory shutdowns is challenging because each section of the process line has different wear mechanisms, temperature profiles and maintenance needs. The strategy below is designed specifically for cement kilns, preheaters, calciners, coolers, riser ducts and cyclones:

A. Kiln burning zone: Prioritise durability—use premium basic bricks. They are more expensive and slower to install, but failures here are extremely costly.
B. Transition zone, calciner and riser ducts: Prioritise speed and cost—use gunning castable and lower-grade bricks. These provide fast installation, are economical, and offer adequate durability for these areas.
C. Cyclones and high-wear areas: Use low-cement castable combined with precast blocks to achieve a balance of durability and installation efficiency.
D. Cooler: Use precast shapes in the hot zones and abrasion-resistant castable elsewhere. The bottom (impact) area is especially critical and requires high-wear-resistant castable.
Use precast blocks to save time as and when justified and use conventional castable in areas
where cost and installation time are lower priorities. Always base decisions on life-cycle cost, not just material price.

Which refractory or pyroprocessing innovations will transform Indian cement operations?
The refractory and pyroprocessing landscape for cement plants in India (and globally) is evolving — and several innovations are taking shape that could significantly transform how cement operations are run: improving durability, lowering energy usage, cutting downtime, and boosting sustainability. Here are the key innovations likely to shape the future of cement-plant refractories and pyro-processing — along with what they mean for Indian operations.
A. Advanced refractory materials: Nano-engineered, spinel-rich, alkali-resistant bricks and ULCC/LCC castable for longer life and fewer shutdowns.
B. Precast and fast-install solutions: Precast blocks, engineered shapes, and fast-dry castable to reduce shutdown time and improve reliability.
C. Digitalisation and predictive monitoring: Kiln shell scanners, thermal imaging, IoT sensors, digital twins and AI-based kiln control for early detection and optimised operation.
D. Refractory recycling and low-carbon materials: Circular-economy reuse of spent refractories and development of low-CO2 refractory mixes.
E. Fuel-flexible and sustainable pyro-processing: Refractories and kiln designs adapted for alternative fuels (RDF, biomass), higher AF substitution, and eventually hybrid/electric kiln concepts.

Together, these innovations will help Indian plants achieve higher thermal efficiency, lower CO2 intensity, and more stable running conditions.