Connect with us

Technology

Technology trends in cement pyro system for pollution control

Published

on

Shares

On the backdrop of changes announced by the Ministry of Environment, Jayant Saha, a consultant takes stock of the situation and explains how the industry can prepare itself to face the challenge.

While using wastes from various sources, mainly as fuel, and also its inherent process requirements, cement plants face much adversity including environment pollution. This leads cement plants to undergo continuous technological advancements.

Most of the emissions are in the form of particulate matters, CO2, SOx, NOx and toxic matters containing mercury and other heavy metals and persistent organic pollutants. Almost all of chemical pollutants are generated in pyro section.

CO2 is produced through combustion, calcination, electrical energy consumption and indirectly through vehicles used by plant and plant personnel. To control CO2 generation BEE has introduced PAT scheme. These measures helped industry in reducing CO2 emission from 1.12 (in 1996) to 0.72 t of CO2 per t of cement. Some countries have taken mercury emission seriously and have started controlling it. Most mercury is present in gaseous phase as elemental or oxidized mercury – HgCl2. The common practice to reduce mercury is to increase the oxidized fraction by increasing chlorine content of fuel. Removal of oxidized mercury (typically 95 per cent) is easily done in wet FGD, SDA and CDS scrubbers. Removal of ~90 per cent of total mercury is possible by Br-PAC (Brominated Powdered Activated Carbon) injection added to the removal of oxidized Hg. PAC is injected into flue gas upstream of main filter. Mercury is absorbed on to the carbon and removed in a separate bag house to prevent recycling.

Recently, (August 25, 2014), the Ministry of Environment and Forests (MoEF) in India has introduced restriction on SOx (100 mg/Nm3) and NOx (600 mg/Nm3 for new plant – applicable from 01-06-2015 and 800 mg/Nm3 for old plants – applicable from 01-01-2016) emission. Monitored values are to be corrected to 10 per cent O2 and on dry basis. This led the need for special focus on cement pyro section technology/retrofit.

SOx Emission Control Technology
Emissions of SO2 are prominent in long kilns rather than energy efficient, dry process kiln systems.

Pyritic or organic sulphur gets burnt in the preheater upper cyclones at around 400-600oC forming SO2. Most of SO2 that escapes the preheater with dust is effectively collected if the gases are used in VRM and is re-introduced to the preheater with the kiln feed. Internal recirculation occurs when liberated SO2 gas in the kiln passes through the preheater and combines with the calcined raw meal and also alkalis in the lower cyclone stages, forming CaSO4 and alkali sulfates. Alkalis in excess of chloride combine with sulphur to form more stable alkali sulfates. Sulphur in excess of alkalis forms CaSO4 which has a higher evaporation factor. Optimum molecular ratio between sulphur and alkalis in the kiln system can be expressed as (SO3 / Alk)Optimum = (SO3/ 80)/((K2O/94) + 0.5 * (Na2O/62)) If the ratio exceeds 1.1 "excess" sulphur (E. S.) is available to combine with CaO. E. S. is expressed in grams SO3 per 100 kg clinker and calculated as:

E. S. = 1000 * SO3 GCo 850 * K2O – 650 * Na2O
For easy and hard burning raw mix, this figure should not exceed 600 and 250 gm SO3/100 kg clinker respectively to maintain smooth kiln operation.

The dissociation of alkali sulphate compounds can best be described as AlkGCoSO4 + heat = AlkGCoO + SO2 + ?O2

The equilibrium shifts to the left favouring the formation of Alk-SO4 with increasing O2 and SO2 partial pressure. For increasing oxygen content up to approximately 2 per cent, volatility of sulphur is progressively reduced while increasing the oxygen beyond 2 per cent has a limited effect.

CaSO4 starts to decompose slowly at temperatures above 1220oC.
CaSO4 + heat = CaO + SO2 + ?O2
In a reducing atmosphere (presence of C and CO), both alkali and calcium sulphates decompose releasing SO2.

Generated SO2 travels back to the preheater. With higher sulphur recirculation the plugging problems in the preheater increase significantly. The location of spreader box on kiln riser plays critical importance. If it is possible to place the spreader on the smoke chamber shoulder, the introduced hot meal will absorb the SO2 before it sticks to the riser wall. Thus a higher SO2 content in the smoke gas is allowable, which means that kiln can run with higher excess sulphur, sometimes up to more than 1000 gm/100 kg clinker; however, with consequences of increasing tendency to form dusty clinker.

The introduced sulphur ends up in the clinker if not removed elsewhere. Typically, the limit for sulphur in clinker is 1.6 per cent, as SO3, to assure good quality.

Removal of Sulphur Dioxide

  • There are methods to remove and prevent the formation of SO2 by modifying or controlling conditions in the cement pyro-processing systems.
  • Sufficient oxygen level can be maintained in exhaust gases to stabilise alkali and calcium sulphate compounds formed in the process.
  • The burning zone flame shape can be modified to reduce the possibility of forming localised reducing conditions.
  • Raw materials can be altered to affect the alkali/sulphur molar ratio and also to affect absence of sulphide sulphur, organic sulphide or carbon, may reduce SO2 emissions. Increasing alkali input may not be possible because of product quality limits on total alkali concentration in the cement.
  • Addition of lime in kiln feed helps in absorbing released SO2 to form CaSO4 and gets back to the system.
  • Installation of SOx reduction cyclone directs naturally occurring CaO present in the pyro system, especially in the calciner, to the upper stages. The dust laden gas from the calciner (near the outlet) is withdrawn and passed through an LP cyclone located towards the top of the preheater. The separated dust, rich in CaO, is fed to cyclone 1 or 2. The gas from this cyclone goes to stage two or three cyclone inlet.
  • Scrubber technologies that capture SO2 after the kiln system can be divided into four classes, dry reagent injection, hot meal injection, lime/limestone spray dryer absorber, and wet scrubbers.

NOx Emission Control Technology
NOx (NO and NO2) is formed in cement pyro system by following mechanisms.

Thermal NOx Formation
Thermal NOx is formed at a temperature greater than about 1200?C by direct oxidation of atmospheric nitrogen. Since the flame temperature in cement rotary kiln is about 2000?C, considerable amount of thermal NO is generated.

The thermal reaction between oxygen and nitrogen to form NO takes place as per Zeldovic reaction:

O. + N2 ? NO + N.
N. + O2 ? NO + O.

NO formation increases exponentially with temperature and in the presence of excess oxygen. Factors affecting the concentration of NO in the kiln gases are:

  • Maximum theoretical (adiabatic) flame temperature
  • Flame shape (burner type)
  • Excess air rate
  • Maximum necessary material temperature
  • Material retention time in burning zone
  • Gas retention time in burning zone
  • Kiln loading (TPD/ m3) Lower secondary air temperatures and presence of dust increases NOx formation. Dust reduces radiation from the flame which in turn reduces heat transfer to material.

Fuel NOx Formation
NOx also results from the oxidation of nitrogen compounds present in fuel, other than gaseous. The reaction normally takes place at relatively lower temperature, less than 1200?C.

Fuel NOx formation normally depends on:

  • Nitrogen content in the fuel
  • Volatile content in the (solid) fuel
  • Oxygen level in the combustion zone
  • Initial NO concentration in the combustion gas
  • Temperature in the secondary combustion zone

A higher volatile content in the fuel reduces fuel nitrogen conversion to NO. At temperatures between 800 -?C and 1100 -?C, the following reactions may take place:

N + O ? NO (1)
N + NO ? N2 + O (2)
Since the rate of reaction 2 increases more rapidly than the rate of reaction 1 as the temperature increases, higher temperatures (between 800?C and 1100?C) may reduce NOx emissions in secondary combustion zones.

Prompt NOx Formation
Prompt NOx is formed by fuel-derived radicals, such as CH and CH2, reacting with N2 in hydrocarbon flames. The overall contribution of prompt NOx to total NO is relatively small.

In rotary kiln, thermal NOx generation is dominant whereas in the calciner and in the secondary combustion zone where combustion temperature is up to 1200 -?C fuel NOx is major contributor.

Influence of Kiln System on NOx Emission
Kiln system in cement plant is normally one of the following.
-Pre-heater kiln with grate or planetary cooler
-In-Line Calciner (ILC) kiln
-Separate Line Calciner (SLC) kiln.

In pre-heater kiln the NOx emission is determined exclusively by the condition in the kiln burning zone.

In ILC kiln system the kiln exit gases having NO pass through the calciner. CH radicals and nitrogen from the calciner fuel reacts with kiln NOx to reduce it to free nitrogen. Balance nitrogen compound in calciner fuel during combustion forms NOx. The result may be a net production as well as net reduction of NO in calciner.

In SLC kiln system the combustion in calciner takes place in pure air. When using solid fuel like coal up to 50 per cent of nitrogen compounds in the fuel may get converted into NO. Thermal NO from kiln leaves kiln string without any opportunity to reduce/reburn and gets added to NOx from calciner string. SLC kilns therefore, have higher NOx emissions from stack compared to ILC kiln system.

Control Techniques for NOx Reduction
Typical NOx emission in older technologies can be as high as 1800 – 2000 mg/Nm3, while average emission value in modern plants is around 1200 mg/Nm3.

The reduction of NOx emissions from cement pyro system can be done in two ways.

Primary NOx Reduction Measures
In primary reduction measures existing process is modified to reduce the formation of NOx, The following ways are very common.

  • Optimisation of clinker burning process.
  • Automatic kiln control system or Expert system.
  • Use of Low NOx burner to allow low primary air and to control flame flow pattern.
  • Addition of water to the flame or fuel of the main burner.
  • Staged Combustion in Precalciner.

In calciner staged combustion, fuel is first burned under reducing conditions to reduce NOx and then remaining fuel burns under oxidising conditions to complete the combustion. Introduction of raw meal allows control of calciner temperature. Through these mechanisms, both fuel NOx and thermal NOx are controlled.

The reaction: 2CO+ 2NO ? 2CO2 + N2
Primary reduction measures can reduce NOx level up to 20 per cent.

Secondary NOx Reduction Measures (SNCR)
In Secondary reduction measure a separate gas cleaning unit is added. Selective Non Catalytic Reduction of NO with NH3 was developed by Exxon Research & Engineering Co., USA. The reagent, typically NH3 or urea, is injected into the kiln system at a location with an appropriate temperature window (870?C to 1100?C). The temperature is critical, at higher temperatures the reagents will form additional NOx whereas at lower temperatures the reactions proceed slowly and substantial amounts of unreacted ammonia will escape.

Ammonia and Urea Dissociation and Reduction Pathways have been shown in the Figure 1.

The performance of SNCR system depends on
-Residence time available at optimum temperature.
-Degree of mixing between injected reagent and combustion gases
-Uncontrolled NOx concentration and oxygen level.
-Molar ratio of injected reagent to uncontrolled NOx.

The performance also depends on the efficiency of installed injection system. ERC Chemtrol is one of the leading De-NOx system suppliers and claims a very high efficiency of their system.

SNCR system can easily be installed in pyro system and should be installed after taking primary reduction measures. This can reduce NOx up to 80 per cent.

Authored by Jayanta Saha, Cement Process Consultant (Freelancer) based in Navi Mumbai

Continue Reading
Click to comment

Leave a Reply

Your email address will not be published. Required fields are marked *

Economy & Market

SEW-EURODRIVE India Opens Drive Technology Centre in Chennai

Published

on

By

Shares

The new facility strengthens SEW-EURODRIVE India’s manufacturing, assembly and service capabilities

SEW-EURODRIVE India has inaugurated a new Drive Technology Centre (DTC) in Chennai, marking a significant expansion of its manufacturing and service infrastructure in South India. The facility is positioned to enhance the company’s responsiveness and long-term support capabilities for customers across southern and eastern regions of the country.

Built across 12.27 acres, the facility includes a 21,350-square-metre assembly and service setup designed to support future industrial growth, evolving application requirements and capacity expansion. The centre reflects the company’s long-term strategy in India, combining global engineering practices with local manufacturing and service capabilities.

The new facility has been developed in line with green building standards and incorporates sustainable features such as natural daylight utilisation, solar power generation and rainwater harvesting systems. The company has also implemented energy-efficient construction and advanced climate control systems that help reduce shopfloor temperatures by up to 3°C, improving production stability, product quality and working conditions.

A key highlight of the centre is the 15,000-square-metre assembly shop, which features digitisation-ready assembly cells based on a single-piece flow manufacturing concept. The facility also houses SEW-EURODRIVE India’s first semi-automated painting booth, aimed at ensuring uniform surface finish and improving production throughput.

With the commissioning of the Chennai Drive Technology Centre, SEW-EURODRIVE India continues to strengthen its manufacturing footprint and reinforces its long-term commitment to supporting industrial growth and automation development in India.

Continue Reading

Economy & Market

RAHSTA Roundtable Sets Agenda for Smarter, Safer Highways

Published

on

By

Shares

Roundtable discussions focus on innovation for safer highways.

Held on 12 March 2026 at Courtyard by Marriott, Mumbai, alongside the Infrastructure Today Airport Conclave, the RAHSTA Roundtable brought together stakeholders from across the highways and infrastructure ecosystem to shape the agenda for the 16th RAHSTA 2026, scheduled for 8–9 July 2026 at the Jio Convention Centre, Mumbai. The session focused on key industry themes including road construction, technology, safety and long-term sustainability.

Opening the discussion, Pratap Padode, Founder, FIRST Construction Council, said the roundtable marked the beginning of a broader consultative process leading up to the July event. The aim, he noted, is to bring together industry stakeholders to refine the agenda for discussions on the future of roads, bridges, tunnels and allied infrastructure.

Padode noted that while central road project awards have slowed in recent years, states are increasingly driving the next phase of infrastructure growth. Maharashtra, with its long-term road development plans and agencies such as MSRDC and MSIDC, is expected to play a significant role in this expansion.

RAHSTA Expo 2026 as a specialised platform dedicated to road infrastructure, covering highways, tunnels, bridges and flyovers along with construction technologies, safety systems and maintenance solutions. He also highlighted the growing importance of rural connectivity and said the organisers are engaging with government bodies to highlight rural road development initiatives.

Tanveer Padode, CIO, ASAPP Info Group, presented insights from IMPACCT, the group’s infrastructure intelligence platform. He pointed to a strong project pipeline despite slower highway awards earlier in the year, noting that states such as Maharashtra, Odisha and Arunachal Pradesh are emerging as key drivers of new projects. The data also revealed that only a small group of contractors participates in large-value infrastructure bids.

Lt Gen Rajeev Chaudhary, former Director General, Border Roads Organisation and Chairman of the RAHSTA Expo Committee, emphasised the need for stronger collaboration across the ecosystem, including policymakers, contractors, technology providers and financiers. He also called for addressing systemic issues within the sector and encouraged greater participation of women in infrastructure leadership.

The discussion also explored the evolving economics of road development. Phani Prasad Mandalaparthy, Associate Director, CRISIL Intelligence, noted that the slowdown in project awards reflects a shift towards higher-value logistics corridors rather than simple road widening projects. However, private participation through BOT and TOT models remains limited.

From the contractors’ perspective, Sudhir Hoshing, Whole-Time Director, Ceigall, said companies are becoming more selective in bidding, favouring projects with clearer payment mechanisms and efficient processes. While NHAI continues to offer greater operational clarity, states such as Uttar Pradesh and Bihar were cited as relatively supportive environments for project execution.

Durability and sustainability also emerged as key themes. Himanshu Agarwal, COO – Road & Infrastructure, Zydex Group India, highlighted the need to prioritise lifecycle performance and resilient pavements, while participants discussed the potential of alternative materials such as plastic waste, steel slag and industrial by-products in road construction.

Dr LR Manjunatha, Vice President, JSW Cement, emphasised that India has abundant fly ash, slag and other industrial materials that can improve durability and sustainability if integrated into specifications and policy frameworks.

Technology and equipment challenges were also discussed. Dr Lakshmana Rao Mantri, Dy General Manager, Afcons Infrastructure, highlighted the shortage of tunnel boring machines (TBMs), which is delaying several underground infrastructure projects. Participants agreed that developing domestic TBM manufacturing capabilities will be critical for future infrastructure expansion.

The future of concrete pavements was another area of discussion. Dr V Ramachandra, President, Indian Concrete Institute, stressed that the debate should focus on lifecycle performance rather than material choice alone, noting that evolving design standards are improving the feasibility of concrete roads.

Prof Dharamveer Singh of IIT Bombay added that while India has made significant progress in infrastructure development, stronger capacity building and better execution practices are essential to ensure consistent road quality.

The discussion also touched upon technology adoption in the sector. Rushabh Mamania, Partner & CBO, Roadvision, highlighted the growing role of AI in road infrastructure, noting that AI-driven monitoring systems are already being deployed across large stretches of national highways.

Overall, the roundtable underscored that the future of highway infrastructure will depend not only on the pace of construction but also on durability, safety, technology integration and sustainable materials. The discussions offered valuable insights that will help shape the agenda for RAHSTA 2026 and guide future collaboration within the industry.

Continue Reading

Economy & Market

CTS Roundtable Charts Tech-Led Roadmap for Construction

Published

on

By

Shares

CTS Roundtable Maps Technology Roadmap for Construction

Ahead of the Construction Technology Show (Con Tech Show) 2026, industry leaders, technology innovators and academia came together in Mumbai to deliberate on how digitalisation, automation and industrialised construction can reshape the sector. The discussion made one thing clear: construction can no longer afford to treat technology as optional.

Held on 12 March 2026 at Courtyard by Marriott, Mumbai, alongside the Infrastructure Today Airport Conclave, the CTS Roundtable served as a precursor to the Construction Technology Show 2026, scheduled for 19–20 August 2026 at NESCO, Mumbai.

A platform to move from discussion to deployment

Opening the session, Pratap Padode, Founder and Editor-in-Chief, ASAPP Info Global Group, said construction technology has long remained close to his heart, especially given the sector’s traditionally slow pace of technology adoption. He noted that over the years, the Construction Technology Summit had steadily built interest, and the next step was now to expand it into a larger, more meaningful platform that could bring together technology providers, users, startups and innovators under one roof.

Padode said the vision for CTS is not limited to software alone. The platform aims to embrace all forms of technology that can improve construction efficiency, quality and execution—from digital tools and project management systems to lean construction, off-site fabrication and startup-led innovation. He also highlighted plans to deepen startup participation and create space for young companies to showcase emerging construction solutions.

Industry at a turning point

Moderating the roundtable, Naushad Panjwani, Chairman, Mandarus Partners, set the context by pointing out that the global construction industry, despite being a multi-trillion-dollar sector, continues to lag in productivity. He noted that while manufacturing has consistently improved efficiency, construction has remained slow to modernise.

Referring to both global and Indian trends, Panjwani underlined that the industry is now at a decisive moment. India, he said, is entering a major build cycle, and delivering the next phase of infrastructure and real estate growth through traditional methods alone is no longer viable. The goal of the roundtable, therefore, was not to debate technology in isolation, but to identify the most critical conversations that would bridge the gap between innovation and implementation.

His central message was clear: CTS 2026 must be shaped around themes that make CEOs, CIOs and CTOs feel they cannot afford to miss the event.

From BIM to AI, data to governance

A major theme that emerged through the discussion was the need for better data, better visibility and better decision-making. Dr Venkata Santosh Kumar of IIT Bombay echoed this, saying that the underlying data infrastructure itself needs attention. Construction projects, particularly remote ones, often face issues around connectivity, data collection and data use. Without this foundation, more advanced technologies cannot deliver their full value.

Chandra Vasireddy, CEO & Co-founder, Inncircles, expanded the discussion to governance, arguing that technology must help connect the many moving parts of a construction business. For him, the real value of digital transformation lies in creating better governance, clearer visibility and stronger business outcomes.

Tejas Vara of Inncircles stressed the importance of timely site data for leadership teams, especially in large and remote projects where decisions on materials, machinery and manpower often get delayed because information does not reach headquarters in time.

The role of AI also featured prominently. Rushabh Mamania, Partner and CBO, Roadvision said that while AI and machine learning are now common terms, vision intelligence and language intelligence have still not deeply penetrated the construction sector. He emphasised that startups in India are building relevant AI-led solutions and are already attracting international interest, showing that innovation need not be imported—it can be built locally and scaled globally.

Industrialised construction gains ground

The roundtable also placed strong emphasis on industrialised construction methods. Kalyan Vaidyanathan, CTO – Construction & R&D, Tvasta, called for greater focus on off-site fabrication and the broader industrialisation of construction. Bhargav Jog, General Manager, Dextra, highlighted precast technology and alternative sustainable materials as areas with immediate relevance.

Several participants agreed that modular, precast and pre-engineered approaches are no longer niche ideas. They are increasingly becoming practical responses to the sector’s challenges around labour shortage, timelines, quality control and predictability.

Anup Mathew, Sr VP & Business Head, Godrej, argued that the industry needs a fully integrated approach—from design and procurement to execution and asset management. Unless these are connected, technology adoption will remain fragmented and sub-optimal. He pointed to pre-engineered and modular systems as examples of how industrial thinking can compress timelines, improve quality and reduce dependence on difficult on-site conditions.

Adoption remains the biggest hurdle

While there was broad agreement on the promise of technology, the discussion repeatedly returned to one fundamental challenge: adoption.

Abhishek Kumar, COO, LivSYT, observed that the market is crowded with solutions, but many buyers still struggle to evaluate which technology suits which use case. According to him, the industry needs clearer frameworks to help users select, compare and adopt solutions, rather than expecting a single platform to solve every problem.

Dr Tenepalli JaiSai, Associate Professor, School of Construction(SoC), NICMAR University, noted that isolated technologies will not solve the productivity problem by themselves. What is required is an integrated Construction 4.0 approach, where digital, physical and cyber-physical systems work together rather than in silos.

That concern around silos was reinforced by Subodh Dixit, former Director, Shapoorji Pallonji, who said the issue is not just that technologies are disconnected, but that stakeholders are as well. Clients, consultants, contractors and partners often operate with different priorities. Unless these silos are broken, technology will struggle to percolate across the full project value chain.

Harleen Oberoi, Project Management, Tata Realty shared a practical perspective from the client side, saying that successful BIM implementation requires investment across the ecosystem, not just within one organisation. Trade partners, vendors and other stakeholders must also be trained and aligned if the technology is to deliver its intended results.

Beyond buzzwords

A notable takeaway from the session was that the industry is moving past the phase of treating technology as a buzzword. Participants repeatedly stressed that the real question is not whether technology should be used, but where it creates measurable value and how that value can be scaled.

The conversation also expanded beyond mainstream themes to include repairs and rehabilitation, construction and demolition waste, sustainability, circular economy, green sourcing, carbon measurement, design interoperability, generative design, robotics, and the role of horticulture and greener built environments.

Setting the agenda for CTS 2026

By the close of the session, the roundtable had surfaced a strong set of themes for the upcoming show: BIM and digital twins, AI and data platforms, industrialised construction, startup innovation, governance-led technology adoption, robotics, sustainable materials, and integrated project delivery.

More importantly, the session established CTS 2026 as more than an exhibition. It is shaping up to be a serious industry platform where users, technology providers, researchers and policymakers can collectively define the future of construction.

As Padode noted in his closing remarks, the conversation will continue through further consultations and possibly webinars in the run-up to the show. If the roundtable is any indication, CTS 2026 will aim not merely to showcase technology, but to push the industry towards meaningful adoption at scale.

Continue Reading

Video Thumbnail
â–¶

    SIGN-UP FOR OUR GENERAL NEWSLETTER


    Trending News

    SUBSCRIBE TO THE NEWSLETTER

     

    Don't miss out on valuable insights and opportunities to connect with like minded professionals.

     


      This will close in 0 seconds