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Clinker grinding technology in cement manufacturing

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Clinker grinding technology is the most energy-intensive process in cement manufacturing. Traditionally, it was treated as "low on technology" and "high on energy" as grinding circuits use more than 60 per cent of total energy consumed and account for most of the manufacturing cost.

Since the increasing energy cost started burning the benefits significantly, the grinding technology came under radar of innovation and technology transformation. Focus shifted to being energy efficient and cost reduction. Population of traditional stand-alone two chamber and three chamber ball mills started slowing down getting replaced by vertical roller mills, high pressure grinding rolls (HPGR), pre-grinders, HoroMills along with high-efficiency dynamic separators, static separator (V-sep) with various innovative process combinations. Technology providers used this opportunity to create a business edge. As a result, substantial reduction in energy consumption levels was achieved successful.

Transformation in product portfolio emerged as blessing in disguise to the energy scenario. Change of traditional OPC into PPC, PSC and composite cement was a game changer. PPC captured widespread market giving breather to grinding energy situation as composition bears 35 per cent of fly ash whose grindability is much lower than clinker. This became profitable proposition not only for volume increase but also for reduced energy. Similarly, PSC proved profitable for the plants having resource logistic advantage. PSC manufacturing technology, varied from inter grinding to separate grinding, gave cost advantage due to clinker factor utilisation. The production of composite cements has been increasing for reasons concerned with process economics, energy reduction, ecology (mostly reduction of CO2 emission), conservation of resources and product quality/diversity. The most important properties of cement, such as strength and workability, are affected by its specific surface and by the fineness and width of the particle-size distribution. These can be modified to some extent by the equipment used in the grinding circuit, including its configuration and control.

Ball mill grinding
Evolution of ball mills was the starting point in communition theory adopted widely in cement manufacturing. Size reduction process of bulk solids acquires major part of cement process. This started from wet grinding in three chambers mills to latest mono chamber semi finished ball mills.

Most used systems are two chamber ball mills in finished mode. Grinding in these mills occur due to the effect of cataracting and cascading motion of grinding balls. Crucial factors that influence the grinding efficiency are:

  • Liner design
  • Circumferential velocity of the mill
  • Shape, size and weight of the grinding media
  • Friction between the lining and the grinding media
  • Friction within the mill charge itself

Technology innovation made use of above factors; however results obtained were successful to the limited extent. Liners design advanced from Lorian liners to step liners to double wave to supplier customised patterns having less weight. Similarly classifiers changed from traditional deep wave, conveying pattern to thin design and bolt less, low weight liners. Wear rate of liners and grinding media is the most cost affecting factor. Improvements in wear rates and cost savings seen from Mn-steel to Hichrome to controlled metallurgy.

Higher the percentage chrome, better the wear resistance, however lowers the hardness normally. Hence, in order to make this system cost competitive and efficient, above factors must be used and leveraged for system selection and optimisation.

Vertical roller mill technology
Vertical Roller Mill (VRM) has been the most preferred technology over ball mill grinding in terms of various efficiency factors. VRM functions four main processes of grinding technology which are: drinding, drying, separation and transportation. Grinding efficiency is the energy utilised to create specific surface of material having same chemical/mineralogical composition. This can be expressed as: Eu = (Specific surface created/specific energy used). Energy utilisation in VRM grinding is better than ball mill technology. Theo power cons of VRM = (Sp. grinding press x roller area x No. of rollers x grinding track speed x friction factor). Friction factor differs from mill to mill and material to material.

Advancements in mill capacities and technology changing fast making VRM is most versatile and efficient. For the volume sensitive market, VRM started offering higher capacities, meeting expanding market requirements with single mill. At the same time, maintenance flexibilities proved this technology the most preferred choice. Various mill OEMs have their unique design features, offering advancements in technical features.

HPGR technology
High-pressure grinding rolls (HPGRs), with key process equipment as roller press in cement industry, have struggled and conquered for acceptance as finished mode operation in raw grinding and even as pregrinder in clinker grinding technology. Many of the issues that didn’t favour their widespread use have now been gradually gaining grounds. But still, it will remain subdued in selection arguments with VRM technology. Answer for this is again follows the similar requirement of customers, high capacity systems, low cost, high reliability, ease of operation and better wear resistance factors.

Most prevailing issue in the HPGR system is "high pressure" as the name suggests. High pressure has direct benefit on grinding efficiency however, it also has got immense impact on with standablity of grinding components, metallurgy of grinding profiles, mechanical stresses on drive components, etc.

In contemplating an answer to issue of the HPGR, the status of other accepted technologies like VRM must be examined. As an example, the latest and advanced VRM technology can be considered. When a plant operation / design is being considered, every well-equipped engineer will be able to turn to numerous rules of thumb associated with these factors:

Particle size distribution will be consistent in feed
Centralised and circumferentially distributed feed is required to extract the best performance.
Profile and condition of the HPGR is critical to deliver the best performance These issues prevail in VRM also. However VRM technology is well established to handle the variety of feed PSDs. A comparison between RP and VRM on some of the merits and demerits are as given:

Roller Press Parameters
Roller Press roller diameters typically vary from 0.5 m to 2.8 m, depending on the supplies, and roll widths vary from 0.2 m to 1.8 m. The aspect ratio of the rolls also varies as a function of manufacturer. Typical HPGR throughput rates range from 20 to 3,000 tph at different applications, with installed motor power as high as 3,000 kW per roll. The roller profile is the key deciding parameter on withstanding the high pressure and giving much needed life. This has been one of the significant characteristics of rollers / Roller Presses. but solutions are now in place for adequate life of the profiles. When operating an HPGR, the two most important operating parameters are:

Operating pressure
Roll speed

The two key operating parameters are inherently linked to the following:
RP throughput
Specific pressing force
Maximum pressure between the rolls
Specific energy input
RP Throughput: The throughput can also be calculated from the continuity equation as follows:
M = L x s x u x ?c x 3.6 (EQ 2) where
s = operating gap (mm)
?c = density of the product cake (t/m3)

Specific Pressing Force
The specific pressing force is defined as the grinding force applied to the rolls (kN), divided by the diameter (m) and width (m) of the rolls. The specific pressing force has the unit of N/mm2.Fsp = F/(1,000 x D x L) where,
Fsp = specific pressing force (N/mm2)
F = applied grinding force (kN)
D = roll diameter (m)
L = roll width (m)
Maximum achievable roller force must be at least
5500 kN/m2 for raw material
6000 kN/m2 for clinker and slag

Roller press design & operation
Similar to the VRM, there are few Roller Press Technology providers with different designs and principles. Mainly, they are: KHD, Koppern, Polysius. KHD has considerable roller press population for various applications. Their standard configurations are as below:

Stud lining roller is typical and popular solution for high life usage that KHD offers for. There are many advanced versions above this.

Similarly, Koppern roller press has got latest design features catering to the clinker grinding application. The roller profile is different than the other technology and offers high life hours of operation. Standard design feature and parameters that Koppern offers is as below:

POLYCOM is the established technology in roller press supplied by Thyssenkrupp Industries. Population spread across various application for clinker grinding, raw grinding and also in combi mode and finish mode.

Conclusion
Technology evolution has given user various options and alternatives. These options help user to focus on priorities. Volume is the main criteria. Mill capacities, especially in cement grinding are changing the scenario. There were no high capacity mills in the past for clinker grinding. Advanced VRM technology started offering higher capacity levels so that capex decisions became easy for the user.

At the same time, business expansion became visible in terms of stand-alone grinding station with high capacity mills. This is playing a major role in capturing various market demands and hence cement industry growth.

Design features of Gebr Pfeiffer
Design

  • Roller and grinding bed inclined, concave grinding path
  • Rollers suspended at a pressure frame
  • Hydraulic actuated at a pressure frame
  • Pull rods inclined to absorb torque, mill housing not affected with horizontal forces
  • Swing lift device for retraction & servicing of roller
  • High-efficiency separator type SLS

Operation

  • Start-up with auxiliary drive, rollers statically on grinding table
  • Normally large size mill casing and low pressure losses of gas flow

Design features of Loesche
Design

  • Airlock in general for feeding
  • High-efficiency separator, LDC
  • Conical rollers 2, 3 according to mill capacity with S roller concept
  • Rocker arm with hydraulic cylinders to exert the roller pressure
  • Hydraulic cylinders with nitrogen accumulators
  • Modular design; hydro pneumatic units can be combined with various mill sizes according to throughput or drying needs

Operation

  • Rollers can be lifted from grinding track for low torque start-up of the mill
  • Grinding pressure and counter pressures can be adjusted to maintain smooth operation

Design features of OK
Design

  • Hydro pneumatic system for pressure exertion
  • Multiple rollers, based on capacity
  • Unique grooved roller profile
  • Curved table profile
  • Roller repositioning after wear

Operation

  • Rollers will be lifter position during start up
  • 2,4 rollers can be unloaded for partial capacity operation of special operating conditions
  • Recirculation of hot exit gas to the Mill inlet

Design features of Ploysius Quadropol
Design

  • 4 individual grinding rollers
  • Cambered geometry of roller with better wear resistance
  • Rollers can be swung out for maintenance
  • Bearing assembly located outside the grinding chamber
  • Ring craneway for maintenance works

Operation
Rollers can be unloaded for partial capacity operation of special operating conditions
Nozzle velocities can be adjusted during partial operations
High efficiency SEPOL separator
RP
Few applications in cement
grinding as semi finished mode
– Limited size?not beyond ~120 bar
+ Superior wear solutions
+ lower SEEC for dry and hard
material (Lower than VRM if in finished mode)
+ Market acceptance & early strength of cement
-Sensitive to feed variations
-More equipments & lay out space

VRM:
+ Proven solution, many applications
+ Large single units available
-Reliability of planetary reducer
+ Lower SEEC in compare with ball mill
+ Stable operation easy to achieve…
-… but often requiring water injection
-Support roller technology not successful

Feed chute placed above fixed roller, shut off gate and vertical flow control gate
Feature:

  • Easy operation Only few moving parts
  • Ensures stable operation even for high product fineness
  • Easy start up procedure in
  • combination with ROLCOX
  • Roller profile is called Hexadur. It offers increased life of profile in compare with solid weld rollers.

About the authors:
Shreekant Hulgi Managing Partner, SPV Engineers
Vijaykumar Vemuri Managing Partner, SPV Engineers

Founded in October 2018, SPV Engineers is a partnership firm specialising in process safety (risk) assessments and solutions, plant performance improvement for productivity through "Mill & Kiln Modules", energy cost reduction through electrical and thermal energy optimisation, refractory design, selection and installation services, capex projects through process engineering, plant capacity debottlenecking and feasibility studies, fuel cost reduction through AFR projects and optimisation. SPV Engineers is a sales partner for latest and advanced SpectraFlow online analyser for minute-by-minute analysis and control. SpectraFlow is an analyser with no radiation risk and no statutory safety requirements. SpectraFlow works on unique principle of NIR (Near Infra Red) technology, which is first in the industry with minimum OPEX and cost of ownership.

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Concrete

We consistently push the boundaries of technology

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Swapnil Jadhav, Director, SIDSA Environmental, discusses transforming waste into valuable resources through cutting-edge technology and innovative process solutions.

SIDSA Environmental brings decades of experience and expertise to the important niche of waste treatment and process technologies. As a global leader that is at the forefront of sustainable waste management, the company excels in recycling, waste-to-energy solutions and alternative fuel production. In this conversation, Swapnil Jadhav, Director, SIDSA Environmental, shares insights into their advanced shredding technology, its role in RDF production for the cement industry and emerging trends in waste-to-energy solutions.

Can you give us an overview of SIDSA Environmental’s role in waste treatment and process technologies?
SIDSA is a leading innovator in the field of waste treatment and process technologies, dedicated to delivering sustainable solutions that address the growing challenges of waste management.
SIDSA is a more than 52-year-old organisation with worldwide presence and has successfully realised over 1100 projects.
Our expertise is in the engineering and development of cutting-edge systems that enable the conversion of waste materials into valuable resources. This includes recycling technologies, waste-to-energy (W2E) systems, and advanced methods for producing alternative fuels such as refuse derived fuel (RDF). The organisation prioritises environmental stewardship by integrating energy-efficient processes and technologies, supporting industrial sectors—including the cement industry—in reducing their carbon footprint. Through our comprehensive approach, we aim to promote a circular economy where waste is no longer a burden but a resource to be harnessed.

How does SIDSA Environmental’s shredding technology contribute to the cement industry, especially in the production of RDF?
SIDSA’s shredding technology is pivotal in transforming diverse waste streams into high-quality RDF. Cement kilns require fuel with specific calorific values and uniform composition to ensure efficient combustion and operational stability, and this is where our shredding systems excel. In India, we are segment leaders with more than 30 projects including over 50 equipment of varied capacity successfully realised. Some of the solutions were supplied as complete turnkey plants for high capacity AFR processing. Our esteemed client list comprises reputed cement manufacturers and chemical industries. Our technology processes various types of waste—such as plastics, textiles and industrial residues—breaking them down into consistent particles suitable for energy recovery.

Key features include:

  • High efficiency: Ensures optimal throughput for large volumes of waste.
  • Adaptability: Handles mixed and heterogeneous waste streams, including contaminated or complex materials.
  • Reliability: Reduces the likelihood of operational disruptions in RDF production. By standardising RDF properties, our shredding technology enables cement plants to achieve greater energy efficiency while adhering to environmental regulations.

What are the key benefits of using alternative fuels like RDF in cement kilns?
The adoption of RDF and other alternative fuels offers significant advantages across environmental, economic and social dimensions:

  • Environmental benefits: Cement kilns using RDF emit fewer greenhouse gases compared to those reliant on fossil fuels like coal or petroleum coke. RDF also helps mitigate the issue of overflowing landfills by diverting waste toward energy recovery.
  • Economic savings: Alternative fuels are often more cost-effective than traditional energy sources, allowing cement plants to reduce operational expenses.
  • Sustainability and resource efficiency: RDF facilitates the circular economy by repurposing waste materials into energy, conserving finite natural resources.
  • Operational flexibility: Cement kilns designed to use RDF can seamlessly switch between different fuel types, enhancing adaptability to market conditions.

What innovations have been introduced in waste-to-energy (W2E) and recycling solutions?
SIDSA’s machinery is meticulously engineered to handle the complex requirements of processing hazardous and bulky waste.

This includes:

  • Robust construction: Our equipment is designed to manage heavy loads and challenging waste streams, such as industrial debris, tires and large furniture.
  • Advanced safety features: Intelligent sensors and automated controls ensure safe operation when dealing with potentially harmful materials, such as chemical waste.
  • Compliance with standards: Machinery is built to adhere to international environmental and safety regulations, guaranteeing reliability under stringent conditions.
  • Modular design: Allows for customisation and scalability to meet the unique needs of various waste management facilities.

How does your organisation customised solutions help cement plants improve sustainability and efficiency?
We consistently push the boundaries of technology to enhance waste management outcomes.
General innovations and new product development focus on:

  • Energy-efficient shredders: These machines consume less power while maintaining high throughput, contributing to lower operational costs.
  • AI-powered sorting systems: Utilise advanced algorithms to automate waste classification, increasing material recovery rates and minimising errors.
  • Advanced gasification technologies: Convert waste into syngas (a clean energy source) while minimising emissions and residue.
  • Closed-loop recycling solutions: Enable the extraction and repurposing of materials from waste streams, maximising resource use while reducing environmental impact.

What future trends do you foresee in waste management and alternative fuel usage in the cement sector?
Looking ahead, several trends are likely to shape the future of waste management and alternative fuels in the cement industry:

  • AI integration: AI-driven technologies will enhance waste sorting and optimise RDF production, enabling greater efficiency.
  • Bio-based fuels: Increased use of biofuels derived from organic waste as a renewable and low-carbon energy source.
  • Collaborative approaches: Strengthened partnerships between governments, private industries and technology providers will facilitate large-scale implementation of sustainable practices.
  • Circular economy expansion: The cement sector will increasingly adopt closed-loop systems, reducing waste and maximising resource reuse.
  • Regulatory evolution: More stringent environmental laws and incentives for using alternative fuels will accelerate the transition toward sustainable energy solutions.

(Communication by the management of the company)

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Concrete

FORNNAX Technology lays foundation for a 23-acre facility in Gujarat

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FORNNAX Technology, a leading manufacturer of recycling equipment in India, has marked a major milestone with the Groundbreaking (Bhoomi Pujan) ceremony for its expansive 23-acre manufacturing facility in Gujarat. Specialising in high-capacity shredders and granulators, FORNNAX is strategically positioning itself as a global leader in the recycling industry. The new plant aims to produce 250 machinery units annually by 2030, making it one of the largest manufacturing facilities in the world.
The foundation stone for this ambitious project was laid by Jignesh Kundaria, CEO and Director, alongside Kaushik Kundaria, Director. The ceremony was attended by key leadership members and company staff, signifying a new chapter for FORNNAX as it meets the growing demand for reliable recycling solutions. Speaking on the occasion, Jignesh Kundaria stated, “This marks a historic moment for the recycling sector. Our high-quality equipment will address various waste categories, including tyre, municipal solid waste (msw), cables, e-waste, aluminium, and ferrous metals. this facility will strengthen our global presence while contributing to India’s Net Zero emissions goal by 2070.”
FORNNAX is actively expanding its footprint in critical markets such as Australia, Europe and the GCC, forging stronger sales and service partnerships. The facility will house an advanced Production Department to ensure seamless manufacturing.

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Concrete

Decarbonisation is a focus for our R&D effort

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Dyanesh Wanjale, Managing Director, Gebr. Pfeiffer discusses the need to innovate grinding technologies to make the manufacturing process more efficient and less fuel consuming.

Gebr. Pfeiffer stands at the forefront of grinding technology, delivering energy-efficient and customised solutions for cement manufacturers worldwide. From pioneering vertical roller mills to integrating AI-driven optimisation, the company is committed to enhancing efficiency and sustainability. In this interview, we explore how their cutting-edge technology is shaping the future of cement production.

Can you tell us about the grinding technology your company offers and its role in the cement industry?
We are pioneers in grinding technology, with our company being based in Germany and having a rich history of over 160 years, a milestone we will celebrate in 2024. We are widely recognised as one of the most efficient grinding technology suppliers globally. Our MBR mills are designed with energy efficiency at their core, and for the past five years, we have been focused on continuous improvements in power consumption and reducing the CO2 footprint. Innovation is an ongoing process for us, as we strive to enhance efficiency while supporting the cement industry’s sustainability goals. Our technology plays a critical role in helping manufacturers reduce their environmental impact while improving productivity.

The use of alternative fuels and raw materials (AFR) is an ever-evolving area in cement production. How does your technology adapt to these changes?
Our vertical roller mills are specifically designed to adapt to the use of alternative fuels and raw materials. These mills are energy-efficient, which is a key advantage when working with AFR since alternative fuels often generate less energy. By consuming less power, our technology helps bridge this gap effectively. Our solutions ensure that the use of AFR does not compromise the operational efficiency or productivity of cement plants. This adaptability positions our technology as a vital asset in the industry’s journey toward sustainability.

What are some of the challenges your company faces, both in the Indian and global cement industries?
One of the major challenges we face is the demand for expedited deliveries. While customers often take time to decide on placing orders, once the decision is made, they expect quick deliveries. However, our industry deals with heavy and highly customised machinery that cannot be produced off the shelf. Each piece of equipment is made-to-order based on the client’s unique requirements, which inherently requires time for manufacturing.
Another significant challenge comes from competition with Chinese suppliers. While the Indian cement industry traditionally favoured our technology over Chinese alternatives, a few customers have started exploring Chinese vertical roller mills. This is concerning because our German technology offers unmatched quality and longevity. For example, our mills are designed to last over 30 years, providing a long-term solution for customers. In contrast, Chinese equipment often does not offer the same durability or reliability. Despite the cost pressures, we firmly believe that our technology provides superior value in the long run.

You mentioned that your machinery is made-to-order. Can you elaborate on how you customise equipment to meet the specific requirements of different cement plants?
Absolutely. Every piece of machinery we produce is tailored to the specific needs of the customer. While we have standard mill sizes to cater to different capacity requirements, the components and configurations are customised based on the client’s operational parameters and budget. This process ensures that our solutions deliver optimal performance and cost efficiency. Since these are heavy and expensive items, maintaining an inventory of pre-made equipment is neither practical nor economical. By adopting a made-to-order approach, we ensure that our customers receive machinery that precisely meets their needs.

The cement industry is focusing not only on increasing production but also on decarbonising operations. How does your company contribute to this dual objective, and how do you see this evolving in the future?
Decarbonisation is a key focus for our research and development efforts. We are continuously working on innovative solutions to reduce CO2 emissions and improve overall sustainability. For example, we have significantly reduced water consumption in our processes, which was previously used extensively for stabilisation. Additionally, we are leveraging artificial intelligence to optimise mill operations. AI enables us to monitor the process in real-time, analyse feedback, and make adjustments to achieve optimal results within the given parameters.
Our commitment to innovation ensures that we are not only helping the industry decarbonise but also making operations more efficient. As the cement industry moves toward stricter sustainability goals, we are confident that our technology will play a pivotal role in achieving them.

Can you provide more details about the use of digitalisation and artificial intelligence in your processes? How does this improve your operations and benefit your customers?
Digitalisation and AI are integral to our operations, enabling us to offer advanced monitoring and optimisation solutions. We have developed three distinct models that allow customers to monitor mill performance through their computer systems. Additionally, our technology enables real-time feedback from our German headquarters to the customer. This feedback highlights any inefficiencies, such as when a parameter is outside the optimal range,
and provides actionable recommendations to address them.
By continuously monitoring every parameter in real time, our AI-driven systems ensure that mills operate at peak efficiency. This not only enhances production but also minimises downtime. I am proud to say that our mills have the lowest shutdown rates compared to other manufacturers. This reliability, combined with the insights provided by our digital solutions, ensures that customers achieve consistent and efficient operations. It’s a game-changer for reducing costs and enhancing overall productivity.

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