Technology
Importance of ACR in design of PJBH/RABH
Published
4 years agoon
By
admin
The single most important criteria of performance for a PJBH/RABH is its air- to- cloth ratio (ACR), writes Rajendra Yadav.
Cement manufacturing involves several processes where the raw materials like limestone, coal, gypsum, fly ash, slag and other materials are transported, ground, weighed, burnt and calcined. These processes use air for moving/burning the materials. After the purpose is accomplished, air is to be removed from the circuit. Several pieces of equipment like cyclones, multi-cyclones, electrostatic precipitators, ventury scrubbers, etc, are used for separating the process dust/ particulate from the gas/air. But one equipment that has caught the fancy of the plant owners for the separation of dust particles from air/fumes, is the bag house. Be it pulse jet or reverse air, a physical filtration device ensures almost one hundred per cent filtration efficiency without being affected by the input conditions.
The pulse jet bag house (PJBH) / reverse air bag house (RABH) are preferred equipment in a cement plant. Their installations have increased year after year and today more than a hundred units are installed in a modern cement plant. However, the awareness about the equipment and its usage has remained limited to a few people. A cement plant process/maintenance engineer is keener in learning the nuances of production equipment like the kiln, cooler, raw mill, cement mill, coal mill, and simply ignores the PJBH/RABH, depending on external agencies for its operation and maintenance.
Unavailability of pertinent literature has also contributed to this comparatively lower awareness. Today, the situation is improving and many cement plants are appointing separate environment engineers who are responsible for the running and upkeep of the equipment. With growing awareness about emission and its ill effects, and the commitment of cement industry to become a green industry with minimum discharge of harmful materials into the environment, the situation will be very different.
What is air- to -cloth ratio?
It is the ratio of gas volume/air flow to the filtration area provided in the PJBH/RABH.
ACR = Gas Volume / Filtration Area
Where,
ACR = m/min
Gas Volume = m3/min
Filtration Area = m2
Normally, it is the application engineer who is designing the PJBH/RABH who decides on what shall be the ACR for a particular PJBH/RABH. However, at several times, the plant owner´s consultant also specifies the ACR to be considered for designing the PJBH/RABH. Who decides what should be ACR is not an important issue here, how to decide ACR is of critical importance. ACR determines the size of the equipment. If you become too conservative then your equipment costs rise very high, whereas if you are too aggressive and design equipment with high ACR, there may be performance issues. Therefore, it is of critical importance that a proper balance is kept while choosing the ACR.
The various aspects to be considered for choosing the right ACR are as follows:
Criticality of application: Is the PJBH/RABH is going to be used as a production and/or product recovery equipment? If yes, then a sufficient design margin must be incorporated and a lot of information should be obtained before deciding the ACR. Operating temperature: The higher the operating temperature, the more critical the filtration. The media used for high temperature filtration are generally very expensive and therefore, sufficient margins must be considered.
Chemical composition of dust: If you are filtering a chemically active dust which is likely to react with any of the components of the flue gas or the filter material, a bigger size filter will help.
Chemical composition of flue gases: If the flue gases carrying the dust to be filtered are corrosive in nature, choosing a conservative ACR will enhance filter life and life of other components. Chemistry coupled with temperature makes it a very critical application.
Presence of moisture: If the flue gases contain water vapour or any other vapour, then having a little more filtration area will only help.
Particle size analysis: Most of the PJBH/RABH are used in industries. The processes generate different particle sizes of the dust. If more than 20 per cent of particles are between 1-5 microns, it is considered fine dust. Filtering fine dust is difficult.
Inlet dust load: If the dust load at inlet to PJBH/RABH is high (> 100 gm/NM3) then using a pre-collector is advisable.
Large particles: If the process is going to have a large part (more than 50 per cent) of the particles above 100 micron in size, then installing a pre-collector can be very useful. If a pre-collector is not installed, abrasion of the filters and casing/hopper is possible.
Cost of product collected: Cost of the product collected is of critical importance. Sometimes, a few days or months` operation can pay for the entire equipment. As a general rule of thumb, a conservative (low) ACR will give better collection efficiency. Therefore, if the bag filter is being installed to collect precious dust, then a lower ACR will pay back very quickly.
Location of the plant: The public awareness about emissions has gone up in recent years and every industry wants a good relationship with its neighbouring community. Therefore, if the plant is close to a city/village and any stoppage of the APC unit even for a few hours, is going to make a big impact on this relationship, then choose the ACR carefully. Equipment with lower ACRs have a tendency to give good life to filters and need fewer replacements.
PJBH/RABH designed using optimum ACR will give the following benefits: Less frequent cleaning: Filters requiring lesser clearing cycles last longer. Each cleaning cycle damages them.
Lower compressed air consumption: Compressors are low efficiency equipment. Usually, they have 30-50 per cent efficiency. PJBH uses compressed air for reverse cleaning of filter bags/cartridges. More cleaning cycles consume higher compressed air and operating costs go Up.
Lower operating pressure drop: PJBH/RABHs designed using optimum ACR yield lower operating pressure drop and thus saves on fan power without sacrificing the filtration efficiency or emission levels.
Useful filter life: It is observed that RABH/PJBH filters with conservative ACR results in long filter life and fewer change of filters over its useful life. This reduces the downtime of equipment, saves the associated parts which are damaged during filter changes and saves the expense on manpower for change of filters, too. I have witnessed more than ten years of filter life for RABH bags and more than six years of filter life for PJBH in process filters where a conservative ACR was used.
The air- to- cloth ratio plays a major role in the performance of PJBH/RABH and it is of utmost importance to specify the ACR you want for your PJBH/RABH. Often, the plants unnecessarily draw more air though the PJBH/RABH due to unavailability of devices for controlling the air flow. Be aware of the flow for which the RABH/PJBH is designed and control it to the designed value, to obtain best performance.
Power saving methods to keep ACR in control
Use on demand cleaning: Use a DP switch to measure the differential pressure drop across the PJBH/RABH and adjust your cleaning cycle accordingly. Maintaining operation within a close range of DP across the plant will lead to stable operating and lower cost of power as well as efficiency.
Use dryer for compressed air: The moisture present in atmospheric air condenses when the air is allowed to expand inside the bag filter. This may make the filter wet at the neck and up to a certain length which then reduces the useful filter area and increases ACR. Therefore, use a dryer for compressed air. The compressed air going into the filter must not have oil/moisture more than 10 ppm.
Use dampers at fan inlet: Process variations results in variation in vent volumes. If there are no dampers to control the flow, the centrifugal fan may draw excess air and push the ACR to very high levels. Dampers are used to create an artificial pressure drop and maintain flow within limits.
Use variable frequency drives: Use variable frequency drives if the process varies frequently. VFDs regulate fan speed and reduce air flow through the unit when it is not desirable to draw large gas volumes. They save energy as well as keeps the ACR within limits.
PJBH/RABHs are positive filtration devices and when designed properly, give you perfect solutions for product recovery/ air pollution control. By specifying or knowing the designed ACR for a particular unit and maintaining the same, you can reap great benefits and derive optimum performance from these units. Insist on knowing these values and have measuring devices in the plant so you can ensure that the operating ACR is as per design. This will help you assess if there are any problems in your process and can also help you save precious energy.
If you become too conservative then your equipment costs rise very high, whereas if you are too aggressive and design equipment with high ACR, there may be performance issues.
Rajendra Kumar Yadav,
Managing Director, Gulmohar Filtech.
rajendra.yadav@gulmohargroup.com
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Economy & Market
RAHSTA Roundtable Sets Agenda for Smarter, Safer Highways
Published
11 hours agoon
March 16, 2026By
admin
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.
Economy & Market
CTS Roundtable Charts Tech-Led Roadmap for Construction
Published
11 hours agoon
March 16, 2026By
admin
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.
Ponnusamy Sampathkumar, Consultant – Process Optimisation and Training, discusses the role of skilled operators as the decisive link between advanced additives, digital control and world-class mill performance.
The industry always tries to reduce the number of operators in the Centre Control Room. (CCR) Though the concept was succeeded to certain extent, still we need a skilled person in the CCR.
In an era where artificial intelligence (AI) grinding aids, performance enhancers, and digital optimisation tools are becoming increasingly sophisticated, it’s tempting to believe that chemistry alone can solve the challenges of mill efficiency. Yet plants that consistently outperform their peers share one common trait: highly skilled operators who understand the mill as a living system, not just a machine.
Additives can improve flowability, reduce agglomeration, and enhance separator efficiency, but they cannot replace the nuanced judgement that comes from experience. Grinding is a dynamic process influenced by raw material variability, moisture, liner wear, ball charge distribution, ventilation, and separator loading. No additive can fully compensate for poor control of these fundamentals.
Operators see what additives cannot
When I joined the cement industry in 1981, not much modernisation was available then. Mostly the equipment was run from the local panel. Once I was visiting the cement mills section. The cement mills were water sprayed over the shell to reduce the temperature to avoid the gypsum disintegration.
The operator stopped the feeding for one of the mills. When I asked the reason, he replied that mill was getting jammed, and he added that he could understand the mill condition by its sound. I also learned that and it was useful throughout my career. In another plant I saw the ‘Electronic Ear,’ which checked the sound of the mill and the signal was looped with feed control!
Whatever modernisation we achieve, it is from the human factor that the development starts.
Additives respond to conditions; operators interpret them.
A skilled operator can detect subtle shifts, like a change in mill sound, a slight variation in circulating load, or a drift in separator cut point. It’s long before instrumentation flags a problem. These micro-observations often prevent major efficiency losses.
Additives work best when the process is stable
I would like to share one real time incident. The mill was running on auto mode looped with the mill outlet bucket elevator kilowatt. (KW)There was a decrease in the KW, and the mill feed was increased by the auto control (PID). After a while, the operator stopped both the feed and the mill. He asked the local operator to check the airslide between mill outlet and the elevator. They found the airslide was jammed and no material flow to the elevator!
The operator deduced the abnormality by his experience by seeing the conditions and the rate of increase of the feed by the auto control.
It’s always the human factor that adds value to the optimisation.
Grinding aids are multipliers,
not magicians.
They deliver maximum benefit only when:
• Mill ventilation is correct
• Ball charge is balanced
• Feed moisture is controlled
• Separator speed and loading are improved
• Blaine targets are realistic
Without these fundamentals, even advanced additives may become costly investments. The operator is responsible for ensuring process stability, whether using a ball mill or a vertical mill. After ensuring the system is stable, the operator observes it briefly before transitioning to automatic control. If there is any anomaly in the system the operator at once takes control of the system, stabilises and bring back to auto control.
Skilled operators adapt in real time
It will be interesting to note that the operators who operate from local panel start to operate from DCS also. They have the experience and the ability to adapt the changes. Operator checks each parameter deeply. Any meagre change in the parameters is also visible to him.
Raw materials change. Weather changes. Wear patterns change.
A skilled operator adjusts:
• Feed rate
• Water injection
• Separator speed
• Grinding pressure (in VRMs)
• Mill load distribution.
These adjustments require intuition built from years of experience, something no additive can replicate.
Human insight prevents over reliance on additives
Plants sometimes increase additive dosage to mask deeper issues like:
• Poor clinker quality
• Inadequate drying capacity
• Incorrect ball gradation
• High residue due to worn separator internals.
A knowledgeable operator finds root causes instead of chasing temporary chemical fixes.
The real optimisation sweet spot is reached when:
• Operators understand how additives interact with their specific mill.
• Additive suppliers collaborate with plant teams.
• Process data is interpreted by humans who know the mill’s behaviour.
This constructive collaboration consistently delivers:
• Lower kWh/t
• Higher throughput
• Better product consistency
• Optimum standard deviation.
Advanced additives are powerful tools, but they are not substitutes for human ability. Grinding optimisation is ultimately a human driven discipline, where skilled operators make the difference between average performance and world class efficiency. Additives enhance the process but operators
control it.
About the author:
Ponnusamy Sampathkumar, Consultant – Process Optimisation and Training, is a seasoned cement process consultant with 43+ years of global experience in plant operations, process optimisation, refractory management, safety systems and training multicultural teams across international cement plants.
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