Large capacity VRMs with multi drives will be the preferred option
Large capacity VRMs with multi drives will be the preferred option

Large capacity VRMs with multi drives will be the preferred option

YV Satyamurthy, Consultant
As a consultant for cement, lime and mineral industry, YV Satyamurthy believes that the statutory requirement of reporting of SOx & NOx along with SPM compels the industry to install CEMS for all the stacks.

What have been the noticeable technological advancements in cement manufacturing that have taken place in the last decade?
Over the last one decade, no major technological breakthroughs have taken place. However, as the plants have to be operated more energy efficiently while complying with stringent regulatory norms for emission control and safety, the technology suppliers have come out with 'Innovations' for improvements on this front. Further, competitive in the market place, the technology development was driven by incorporation of automation systems for better process control, reduction in manpower and reliability of plants for continuous operation.

One more challenge for the technology suppliers was to come with technologies, which are in sized for higher capacities but when the plants have to be operated at lower capacities (due to market conditions), while maintaining higher efficiency parameters.

Some of the major technological innovations made during this decade are:

  • Plants are designed and operated at capacities as high as 14,000 TPD Clinker production
  • ILC technology with 'Low Pressure' drop for six stage 'Pre Heaters' continues to be most preferred option for pyro-processing, irrespective of capacity of plant
  • Multi-drive systems for vertical roller mills (e.g. MVR of Pfieffer or QMS-RD of Polysius) have become a major feature, which eliminated the risk with failure of high HP gearboxes for VRMs. This has made designing the VRMs for very high capacity cement grinding systems (one mill of capacity 3 MTPA)
  • Developments of technologies for AFR processing and firing inside the kilns/calciners
  • Robo-labs for in process quality control
  • Online sampling and analytical systems for in process quality control (like free lime analysers at Cooler inlet, online sampling and analysis by XRF)
  • Traffic management in packing plants with RF tagging of vehicles for optimising the packer outputs
  • Wagon tipplers for unloading capacities of approximately 2,000 TPH as against approxi­mately 1,000 tonnes
  • Design for energy efficient grinding of pet coke
  • Modular design grinding plants for production of (capacity up to 300,000 TPH) by End users at construction sites
  • Online condition monitoring systems for high capacity VRMs
  • Online emission monitoring systems (CEMS)
  • Prefabricated sheds for storage areas
  • Installation of reliable construction lifts for regular operation and maintenance in kiln/silos areas
  • Online particle size analysers are also installed in many of the installation abroad and few plants in India for process control in grinding systems

What is the progress done to reduce overall energy consumption in manufacturing?
Implementation of PAT scheme has made the industry to focus on energy consumption and implement projects of retrofitting/replacement and upgradations to reduce the energy consumption to derive the benefits of this scheme. Taking into account various technological advances made in mechanical conveying systems made the industry to eliminate/minimise the use of pneumatic conveying systems. Many of the old plants have upgraded their process control systems during the period to latest configurations to have sustained kiln operations.

Are you satisfied with the research done on use of low grade limestone and use of ash coal?
A number of initiatives by R&D centres/technology suppliers are required on this topic. Especially, more reliable systems (wobblers), which can work for higher moisture content of limestone are required for removal of clay/siliceous materials from ROM limestone. Research needs to be done for utilisation of High Cl content Lime Stone (Gujarat (Kutch area)/Rajasthan) and its implications on bypass systems and utilisation over burden Bypass ESP dust.

What are the recent developments in pyro processing?

  • Increase of top stage of PH system by distribution rotating disc
  • Separate combustion chamber (e.g. hot disc/step combustor) before pre-calciner for firing RDF (refuse derived fuel)/AFR for better combustion efficiency with clean air entry at high temperature
  • High flame momentum burners (up to 11N/MW)
  • Technology development for prevention/solutions of operational problem such as Snowmen (e.g. Air blast cooler), coating on fan blades, pet coke/AFR grinding/firing systems.
  • Waste Heat recovery by power generation has become a standard industrial practice for greenfield plants
  • Bag house instead of ESPs for cooler exit gases
  • Online free lime sampling at cooler inlet and testing systems for process control
  • Online measurement of production rate on Product conveyors to clinker silo
  • Reliable online measurement of kiln inlet gas analyser for O2 and CO
  • Roller crusher at cooler discharge has become a standard solution for cooler designs

What are your views on the use of fuzz logic and expert systems in kiln and mill operations?
The expert systems and fuzz logic systems for kiln and mill operation have become a standard design feature in all the technology suppliers. However, as the technology suppliers are keeping a very high price for supply of such systems, except for plants, which are above 6,000 TPD capacity, the cement companies are not keen on buying the systems.

How about the use of pet coke on the backdrop of recent ban in Delhi NCR region?
World over, pet coke has been utilised (up to 100 per cent) in cement kilns and cement producers are able to keep the SOx emissions within prescribed limits. However, considering the high Sulphur content in Pet coke supplied by Indian companies, it may be needed to install SOx control systems for Kiln exit gases.

What are the changes you can point out in grinding process?

  • Ball mill systems: Except for small capacity plants, ball mill systems are not preferred for any projects. However, to start with ball mill and later on upgrading with Roller Press for energy efficiency is how cement projects are designed
  • Vertical roller mills or roll press (in finish grinding/semi-finish grinding) is the most preferred choice across all types of cement grinding
  • Large capacity vertical roller mills with multi drives are going to be most preferred option by industry in future
  • Only in areas where water shortage is there for spraying into VRMS (especially for PPC production), roller press systems with ball mill can be a preferred option
  • VRM suppliers have also now come out with designs utilising water spray only for starting the mill for PPC grinding. However, these designs are yet to proven for different Clinker granulometry/hardness

What is your take on continuous emission monitoring system (CEMS)?
The statutory requirement of reporting of SOx and NOx along with SPM compels the industry to install CEMS for all the stacks. As the suppliers of CEMS are already established, proven designs in Europe, there is no problem of choosing a reliable system by the industry.

What are the measures taken to reduce gaseous and dust pollution?
SNCR systems using Ammonia for control of NOx will become a compulsory requirement for the industry and already many of the major cement companies are installing these systems. The designs of bag filters/houses available for achieving < than 10 mg/NM3 is sufficiently adequate to operate the plants below prescribed limits in future. Many plants have already operating at below prescribed limits. Cooler exhaust dedusting through bag houses instead of ESP have to adapted by all the cement producers to meet the prescribed limits. SOx emission control systems only for High S (>5 per cent) petcoke have to be adopted by industry after mapping the present SOx levels for different quality of pet coke. Though all process Stack emissions by the industry are in general, below the present prescribed norms, the fugitive dust emissions and proper design/maintenance of auxiliary bag filters is continue to be a major concern in industry. For plants located in water shortage areas and for opening unloading/storage areas, one option is to go for dry fog systems.

How far has been the penetration of robotic labs for quality control? Comment specifically on sample collection and real time analysis.
The penetration of Robo-lab system is not very encouraging in the Indian cement industry. Wherever these systems are installed, the unresolved issues of maintenance and procurement of spares have become a major concern for reliable operation of the system. Industry is not interested in installation Robo-lab systems due to high CAPEX and negative feedback from clients. However, mechanised sample collection and conveying systems are becoming more and more acceptable, as they reduce the sampling bias and transportation time. Few plants have also installed online analysers (Neutron/Gamma Ray) systems and also online sampling with in-situ XRF/Free lime analysers. Considering CAPEX and reliability view point, it appears these systems are more attractive. On-line Particle size analysers are also installed in many of the installation abroad and few plants in India for process control in grinding systems and this is one the developments.

What about the automation done in the physical testing of cement?
Automation done in the physical testing of cement in modern plants is quite sophisticated. The test results are directly recorded without manual interface and the data goes to MIS system through SAP for review by the top management. Hence there is no chance for bias in reporting. However, this needs a good calibration procedure for the testing machine, duly witnessed and verified at 2-3 levels in the organisation.

What technological gaps you see in plants in India and that in Europe?
As far as major process technology absorption is concerned, the Indian cement industry has state-of-the-art technologies implemented in latest plants of large capacities. However, few gaps do exist in old plants, for which there is a need for absorption of technologies through upgradation or replacements. AFR utilisation technologies are more developed in Europe and some of the plants even achieving 100 per cent; whereas in India, it is in nascent stage.

What are the steps taken to reduce dust and mitigation of CO2 emission per unit of cement in the present system or by way of development of a new product?
As on date, no carbon capturing technology is developed by industry with respect to capturing CO2 through an absorption process. However, a large reduction in clinker factor in cement is achieved through production of more percentage of blended cement and higher levels of absorption of slag and fly ash absorption in cement. A long pending issue of BIS standard for Portland Limestone Cement, where in it is possible to use more than 10 per cent of Limestone in cement is overdue, which can substantially reduced CO2/T of cement. "Carbon Cure, Canada" & "Solidia, US" are two of the major CO2 capturing technologies, which have already completed pilot studies and plan commercialise the technologies.

Is use of simulation based learning for skill upgradation happening in cement?
As in the case of expert system implementation in cement plants, though the simulation based learning is much talked about by industry, it is not fully adopted by the Indian industry. Though vendors offer simulator-based training to end-users, it is very expensive. As manpower costs in packing/bagging and loading are going up, many of the cement plants are revamping the existing systems with semi-automatic and automatic bag loading systems. Proven technological solutions are available and industry is very much focussed in this area.

YV Satyamurthy has an experience of 35 years in functional areas, viz project management for cement and mineral projects, cement plant operations, process and quality Control, EPC contracts, energy management, overseas consultancy services and technical training development.

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