Cement Industry

About the Cement Industry

Cement, a critical component of concrete, serves as the backbone of modern infrastructure. Its production, however, is one of the most carbon-intensive industrial processes, contributing approximately 7% of global carbon dioxide (CO₂) emissions. To mitigate this environmental impact, the cement industry is exploring alternative fuels and innovative technologies that balance production efficiency with sustainability, while maintaining the chemical integrity required for high-quality cement.

The Cement Manufacturing Process

The production of cement involves several intricate steps, each contributing to its functionality as a binding agent. The process begins with the selection of raw materials, typically limestone (CaCO₃), clay (Al₂Si₂O₅(OH)₄), and silica (SiO₂). These are combined and fed into a rotating kiln, where they are heated to temperatures exceeding 1400°C.

This intense heat initiates a series of endothermic and exothermic reactions. The decomposition of limestone releases calcium oxide (CaO) and carbon dioxide (CO₂) through calcination:

CaCO3 →heat → CaO+CO2

Simultaneously, the clay undergoes dehydration and structural changes, contributing silicon (Si) and aluminum (Al) oxides to the mix. These oxides react with calcium oxide to form tricalcium silicate (Ca₃SiO₅) and dicalcium silicate (Ca₂SiO₄), the primary compounds in cement clinker. Once cooled, the clinker is ground into a fine powder and mixed with gypsum (CaSO₄·2H₂O) to control setting time.

The Carbon Footprint of Cement Production

The emissions associated with cement manufacturing can be divided into two primary sources:

1. Fuel Emissions: Approximately 40% of CO₂ emissions come from the combustion of fuels—typically coal (C), petroleum coke, or natural gas (CH₄)—required to achieve the necessary kiln temperatures. These fuels release significant amounts of carbon dioxide (CO₂) and other greenhouse gases during combustion.

2. Process Emissions: The remaining 60% of emissions are inherent to the calcination reaction, where CaCO₃ decomposes into CaO and CO₂. These emissions are unavoidable without fundamental changes to the chemical 1 process.

Alternative Fuels: Reducing Emissions in Kiln Operation

To address fuel-related emissions, the cement industry is increasingly incorporating alternative fuels, such as:

● Biomass: Organic materials like wood chips, agricultural waste, or algae-derived biofuels, which are rich in carbon (C) but are considered carbon-neutral since they recycle atmospheric CO₂ absorbed during growth.

● Refuse-Derived Fuels (RDF): Combustible components of municipal solid waste, including plastics (C₂H₄) and paper, that reduce landfill use and provide high calorific value.

● Hydrogen (H₂): A clean-burning fuel that produces only water (H₂O) as a byproduct, potentially replacing traditional carbon-based fuels entirely. These alternatives not only reduce fossil fuel consumption but also align with circular economy principles by utilizing waste products effectively.

Innovations in Low-Carbon Cement:

LC3 Limestone Calcined Clay Cement (LC3) represents a breakthrough in reducing process-related emissions. By replacing a portion of clinker with calcined clay (CaAl₂O₅) and finely ground limestone, LC3 achieves significant CO₂ reductions. The calcination of clay occurs at lower temperatures (800-900°C) than traditional clinker production, minimizing energy demand and associated emissions. Moreover, the synergistic reaction between calcined clay and limestone improves cement reactivity, allowing for the production of high-performance materials with a smaller environmental footprint.

Carbon Capture and Storage (CCS)

A longer-term solution to process emissions lies in the implementation of carbon capture and storage (CCS) technologies. Post-combustion systems capture CO₂ from kiln flue gases using amine-based solvents or solid adsorbents. The captured CO₂ can then be compressed and sequestered in geological formations or utilized in other industrial processes, such as producing synthetic fuels or carbonates.

A Sustainable Future for Cement

The integration of alternative fuels, the adoption of LC3, and advancements in CCS position the cement industry as a pivotal player in global decarbonization efforts. By combining cutting-edge chemistry, process innovation, and sustainable practices, the 2 industry can continue to meet the demands of infrastructure development while significantly reducing its environmental impact. This balance of productivity and sustainability underscores the transformative potential of science and technology in reshaping one of the world’s most essential industries.

Concrete Production: A Scientific and Sustainable Perspective

Concrete, one of the most widely used construction materials in the world, is a composite substance formed from several carefully balanced ingredients. Cement, a critical binding agent, comprises only 7% to 15% of the total mix. The majority of the concrete recipe consists of sand, gravel (both fine and coarse aggregates), and water, with optional additives to enhance its properties.

The Composition of Concrete

Concrete’s formulation begins with its primary components:

Cement: The binding agent, derived from calcium oxide (CaO) and silicon dioxide (SiO₂), plays a crucial role in the hardening process through hydration reactions.
Aggregates: Fine sand (SiO₂) and coarse gravel contribute to the bulk and mechanical strength of the material.
Water (H₂O): Initiates the chemical reactions that form hydrated cement compounds, such as calcium silicate hydrate (C-S-H), which gives concrete its structural integrity.

In modern concrete production, the inclusion of admixtures and supplementary cementing materials (SCMs) is becoming increasingly common.

Admixtures: Enhancing Concrete Performance

Admixtures are specialized chemicals added to the concrete mix to modify its behavior during and after the setting process. These include:

Air-entraining agents: Introduce micro air bubbles, enhancing freeze-thaw resistance.
Superplasticizers: Improve flowability and reduce water content without compromising strength.
Viscosity modifiers: Control the spread and cohesion of the mix for precision in applications.
Set retarders or accelerators: Adjust the curing time to match project requirements.

By tailoring these properties, concrete can be optimized for specific construction needs, from high-rise buildings to underwater structures.

Supplementary Cementing Materials (SCMs): A Circular Economy Approach

SCMs, such as fly ash (rich in silicon (Si) and aluminum (Al) oxides), slag from steel production (calcium silicate, CaSiO₃), and silica fume (amorphous SiO₂), are industrial by-products incorporated into the concrete mix. These materials replace a portion of cement, reducing overall CO₂ emissions associated with its production.

The benefits of using SCMs include:

Diverting industrial waste from landfills, minimizing environmental impacts.
Enhancing durability: SCMs contribute to denser concrete with improved resistance to chemical attacks.
Lowering costs by repurposing readily available by-products. This practice aligns with circular economy principles, maximizing the lifecycle value of industrial waste streams.

Raw Materials: Abundant and Essential

The foundational ingredients for cement and concrete—limestone, clay, sand, and water—are among Earth’s most abundant natural resources. Limestone (CaCO₃), the primary source of calcium in cement, is quarried from vast geological deposits. Clay (Al₂Si₂O₅(OH)₄) contributes aluminum and silicon oxides essential for clinker formation. Aggregates such as sand (SiO₂) and gravel provide volume and mechanical strength, while water is crucial for the chemical reactions that drive cement hydration.

Despite their abundance, sustainable sourcing practices are essential to minimize ecological disruption, conserve biodiversity, and maintain resource availability for future generations. In addition, a purposeful and efficient manufacturing process is key to the betterment of the cement industry. At WTW Americas, we are committed to serving our clients with the most reliable, sustainable, and efficient equipment to ensure optimal performance in your production.

WTW Americas Industry Experience

WTW Americas has extensive experience and installations in the cement industry. Some of our references include National Cement, Lehigh Cement, St. Mary’s Cement, Holcim LaFarge, Giant Cement, Tanga Cement, Lagan Cement, Titan Cement, among many others. With a global presence and installations across cement facilities worldwide, our equipment discharges to provide mass flow and consistent material delivery, optimizing process efficiency and reducing operational interruptions.

At WTW Americas, we specialize in sticky, wet, abrasive materials, and are committed to providing robust solutions to our clientele, which ensure seamless material handling and flow throughout the entire production process.

Material Receival

At the beginning of the cement process, WTW Americas Truck Discharge Machine (TDM) serves as the ideal machine to receive raw materials such as Clay, Limestone, Sand, Clinker, Bauxite, Gypsum, Silica, Shale, Iron, and more. The TDM is specifically engineered to speed the unloading of materials into a processing facility, without the need for costly excavation, requiring minimal civil work. The complete unloading facility can receive bulk material from trucks, front-end loaders, barges, and railcars. The TDM will accept a full truck load of material and can be discharged from 0 to 1,200 t/h at constant or variable rates. Our Truck Discharge Machine may also receive Alternative Fuels, Municipal Solid Waste, Refuse Derived Fuel, and Stockpiled Coal among all other bulk materials.

Dust-Tight Conveying, Discharging, Feeding and Distribution

Depending on the type of material received at the beginning of a process, there are multiple pieces of WTW Americas equipment which serve to feed the next step in your process.

In the instance of receiving Clay, Limestone, and other quarried materials, WTW’s Silo Discharge Machine (SDM) and Bunker Discharge Machine (BDM) are both suitable options to store bulk materials.

WTW’s Silo Discharge Machine (SDM) is the most versatile and flexible discharge system. Available in sizes from 1.5 to 6 meters in diameter and capacities up to 1,000 t/h, WTW’s SDM is our most requested installations. The central discharge unit can extract wet, hot, cohesive, sluggish, bulk material stored or buffered in bins or silos and may be directly fed from our Truck Discharge Machine. The rotating discharge arm conveys the bulk material toward the opening in the center of the floor and discharges it 5 through this opening. To prevent the bulk material from flowing out in an uncontrolled manner, the discharge opening is covered by an inner cone. The discharge arm passes underneath the inner cone and activates the entire silo bottom during the discharge operation.

One revolution of this specially curved and profiled arm extracts a uniform disc of material from the silo. This keeps the bulk material column in motion and maintains its flow ability, preventing solidification of the bulk material over time and the risk of bridge formation and ratholing inside the silo.

WTW’s Bunker Discharge Machine (BDM) is another mechanism for releasing tough to manage bulk materials from silos, bunkers, hoppers, bins, stockpiles, and dome type storages. The Bunker Discharge Machine can travel to reclaim from long stockpiles or hoppers and expel it along the bunker shelf onto a gathering conveyor. It is frequently employed in transporting limestone, FGD gypsum, clinker, iron ore, additives, cement, or wastes. When discharging, the BDM moves on rails with its rotating discharge wheel in alternating direction over the bunker shelf and conveys the bulk material out of the bunker into a conveying system placed below the BDM. While usually a belt conveyor, chain conveyors have also been used below the BDM. With reclaim rates from 10 to 2,500 t/h, WTW’s Bunker Discharge Machine has the capability to reclaim materials from massive stockpiles, extreme large silo diameters, free-range and longitudinal bunkers.

Both our SDM and BDM are the ideal choice to discharge, store, and distribute throughout the cement manufacturing process.

Conveying Throughout a Cement Process

When conveying throughout the cement process, one of the most importation risks to be aware of is concrete segregation, which occurs when individual components of concrete begin to separate. Fires, explosions, and cement dust exposure are also high risk in the industry. WTW Americas TKF Chain Conveyors mitigates separation, fire, dust exposure and explosion risk with out dust-tight, explosion-proof, and water-tight conveyors. They are used to distribute, discharge, and transport material in nearly every direction and orientation, frequently employed to move products that would not normally convey on belt conveyors.

Standard or specifically designed, WTW Americas TKF Chain Conveyors are self-cleaning, can run horizontal, inclined, and even vertical with widths from 0.25 to 2 6 meters. Our Chain Conveyor solutions have been rigorously tested to ensure success once installed in the field.

The combination of the chain material, the method of manufacturing the links, the yield strength, hardening of the chain as well as the material of the fastening equipment such as bolts, pins and the tolerances transform our chain into a long-lasting trouble-free system. All connectors and pins are made of high-quality alloy steel that is subjected to special treatments to enhance their duration and resistance to wear and tear.

Sticky, hot (up to 750 ºC), abrasive materials such as synthetic gypsum, sludge, or clinker are easily conveyed from 0 to 1,000 t/h. Our single strand and double strand German engineered chain conveyors are a reliable means of transporting and distributing material from one or more stages of a process to the next.

Finished Product Loading

By integrating WTW Americas’ advanced conveyor, discharge, and handling systems, cement producers can achieve a high level of process reliability, ensuring uninterrupted production and contributing to overall energy efficiency in the highly demanding cement manufacturing process. All our equipment can be modified to meet specific industry needs.

For more information about our equipment, please visit our equipment page.

Learn More

To learn more about WTW Americas equipment and experience in the Cement Industry email info@wtwamericas.com or call +1705-749-3544.

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