Ashok Kumar Dembla, President and Managing Director, Humboldt Wedag, discusses the integration of AFR and digital twins technology to upgrade cement plants to CCUS readiness.

Technology providers are now playing a decisive role in helping manufacturers reduce emissions while safeguarding efficiency and competitiveness. In this in-depth interview, Ashok Kumar Dembla, President and Managing Director, Humboldt Wedag, outlines how the company’s philosophy is being translated into practical solutions for Indian cement plants.

‘Cement Beyond Carbon’ is a strong strategic statement. How are you adapting this philosophy for Indian cement plants?
‘Cement Beyond Carbon’ is our campaign because we firmly believe that carbon dioxide is extremely harmful to human health. This belief led us to initiate this campaign around four to five years ago, backed by focused technological innovation.
At the first level, it involves relatively straightforward solutions such as maximising the use of alternative fuels and raw materials (AFR), implementing waste heat recovery (WHR) systems, and increasing the use of blended cements.
Beyond these, we are working on advanced technologies such as oxy-fuel combustion, kiln electrification, digitisation, and automation. We are also actively developing carbon capture and utilisation technologies, exploring how captured CO2 can be reused in downstream processes such as urea manufacturing or even innovative products like
protein synthesis.
The idea of ‘beyond carbon’ is not just about achieving net-zero emissions, but about thinking further. How innovation can reduce the cement industry’s contribution, which currently accounts for about 7–8 per cent of global CO2 emissions. This campaign reflects our long-term commitment to fundamentally changing how cement is produced.

You recently executed large 10,000 TPD cement plants. What key learnings from these projects would you like to share?
In India today, due to strong demand growth, inquiries for 10,000 TPD plants have increased significantly, and we have been a major contributor in this segment. We have built plants for UltraTech, are executing projects for Dalmia Cement and My Home, and several of these large-scale units have already been commissioned.
When designing such large plants, special precautions are essential. Cyclone sizes increase significantly, often exceeding 10 metres, so careful design is required to prevent material drop in ducts. NOx control becomes critical, and we address this through our Pyro-Redox technology, which allows NOx reduction without secondary steps such as urea injection. We have successfully implemented this technology in operating plants.
Another important factor is AFR usage.
To accommodate higher AFR volumes without disturbing process stability, the calciner size must be carefully planned. We also rely heavily on simulation tools during the design stage and during operation, we use CFD analysis to troubleshoot and
optimise performance.
Fortunately, these plants are performing extremely well. For example, at My Home Cement, the plant is operating at less than 40 kWh per tonne up to the pyro process, with thermal energy consumption of around 765 kcal/kg. We continue to optimise these parameters further.

How are cement plants benefiting from your PROMAX process control and digitalisation platform?
PROMAX is our core digital platform that integrates multiple modules for process optimisation. It follows a modular approach, meaning systems such as kiln expert control and mill expert control are now implemented using digital twin technology supported by artificial intelligence (AI).
We continuously enhance PROMAX by adding modules such as refractory control, inventory management, and advanced cooler control, which requires extensive sensor integration. The platform has already been implemented in China, and we are now actively promoting PROMAX in India. We are engaging with major cement groups such as UltraTech, Dalmia and Chettinad to deploy this system across their plants.
PROMAX enables an additional 2–3 per cent optimisation in both thermal and electrical energy consumption, which directly contributes to CO2 reduction. It also improves operational stability, reliability, and long-term performance of
cement plants.

How are you supporting the industry’s shift towards calcined clay and lower clinker factors?
India is in a relatively strong position because most of its fly ash production is already utilised in blended cements, but in some cases, this is not techno-economically viable. Calcined clay provides an effective alternative SCM, and under current regulations, LC3 cement allows 25–35 per cent calcined clay content.
A good example is Jaisalmer, where many new cement plants are being established despite the absence of nearby thermal power plants. In such cases, producing calcined clay locally makes strong economic and logistical sense. We are working with companies like Wonder Cement and JK Cement on calcined clay projects.
However, calcined clay requires very specific quality parameters. The kaolinite content must meet certain thresholds, and other clay components must also fall within defined ranges. To support this, we have established a pilot testing facility at our Cologne office in Germany, where we evaluate clay samples. The colour of the calcined clay and its impact on cement strength are critical. One major advantage is that calcined clay requires only about 400 kcal per kg to produce, making it a highly energy-efficient substitute for fly ash and slag.

What role does KHD play in enabling higher AFR substitution at cement plants?
Our AFR solutions cover the entire spectrum, from very low substitution rates to extremely high levels, approaching 90 per cent of calciner fuel. At a basic level, we modify the calciner design by increasing residence time, diameter, and related parameters, allowing up to 40 per cent fuel replacement, provided the RDF particle size is limited to around 25–50 mm.
For higher substitution rates, we offer the PyroRotor system, which can handle larger fuel sizes of 200 mm or more with minimal processing. This material is fired in a separate vessel connected to the calciner. Using this approach, we can replace up to 85–90 per cent of calciner fuel, with around 60 per cent fired through the PyroRotor and fed into the Pyroclon. Whether a client targets 10, 40 or 90 per cent AFR substitution, we have tailored solutions to meet
those goals.

With rising carbon regulations and increasing competition, how are you helping cement producers maintain competitiveness?
Carbon reduction is now non-negotiable. While oxy-fuel technology will eventually play a role, its high capital cost means it will take time to be widely adopted in India. For now, we focus on all feasible measures to reduce CO2 emissions.
In one plant, for example, we supplied roller presses for raw material grinding, finish grinding, and cement grinding. As a result, electrical energy consumption dropped to around 38.5 kWh per tonne up to the pyro process, while blended cement grinding consumes only about 16.5 kWh per tonne.
This plant is also operating with 20 per cent AFR, including hazardous waste, with thermal energy consumption around 685 kcal/kg. We know that every 1 per cent AFR addition typically increases thermal energy consumption by 1–1.5 kcal/kg, so without AFR, consumption would be closer to 683 kcal/kg clinker. Given tightening carbon regulations, we are designing plants to operate with the lowest possible carbon footprint even without carbon
capture technologies.

How do technologies such as CCUS and digital twins help transform cement plant operations?
These technologies significantly reduce manual intervention while improving automation and reliability. In existing plants, the main challenge lies in data integration. Legacy systems often require upgrades to ensure data compatibility and seamless cloud connectivity. Platforms like PROMAX rely on cloud-based infrastructure to create accurate digital twins.
Using simulations and AI-driven optimisation, plants can achieve the next level of efficiency. While initial investment for new plants may increase by 10–15 per cent, the long-term benefits are substantial. Plants typically gain around 3 per cent improvement in both thermal and electrical energy efficiency, along with better manpower utilisation, remote plant control through handheld devices, improved inventory management and higher overall reliability. Currently, many plants operate around 330–345 days per year. With digitalisation and automation, it is possible to improve availability by another 10 days annually—an enormous operational advantage.