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Energy conservation through energy efficient tech

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The article deals with the energy conservation achieved by adapting various energy-efficient technologies and incorporating energy-efficient operation.

Energy is one of the major inputs for the economic development of our country, more so with depleting fuel reserves. Energy consumption in industrial sector is accounting for about 50 per cent of the commercial energy available in our country. Among the industrial sector, nine sectors have been identified as highly energy-intensive. These include: power, fertilizer, iron and steel, cement, pulp and paper, aluminium, chlor-alkali, textile and railways.

In this scenario of energy shortage, increasing energy demands and price, particularly for developing countries like India, it may be difficult to pursue the present rate of development and will be forced to retard its development/industrialisation programmes for want of sufficient energy reserves, unless focused measures are taken. In this background, the imperative need for every citizen and the industry in particular is to contribute towards energy conservation and environmental sustainability.

This paper deals with the energy conservation achieved by adapting various energy-efficient technologies and incorporating energy-efficient operation. Various activities implemented to reduce power consumption are as enumerated below:

  • Compressor power optimisation
  • Pressure drop reduction in cyclone
  • Single raw meal silo operation instead of two
  • Star feeder instead of 3KS system
  • SPRS for process mil fans
  • Operated Turbo blowers instead of PD blowers
  • Optimisation of air conditioner consumption
  • Provided VFDs to potential equipment
  • Installation of occupancy sensors in load centres
  • Cogged belts in place of V belts & FRP blades in place of aluminium/CI blades
  • Monitoring of special power on a daily basis and controlling of idle power consumption

Lets see the above energy conservative activities in more details:

Energy conservation activity – 1 – Compressor power optimisation
An air compressor is a device that converts power in to potential energy, stored in pressurised vessel. Compressor plays a major role in utility power consumption, Various energy efficient technologies adopted in our unit to optimise compressor power are as below:

Upgradation of old with energy efficient compressor
Background:
In line 2 Pyro section, 1 No of 965CFM, Double stage, water cooled screw compressor, rated shaft power of 132kW (SF – 1.2) was in operation (24×7) for past 14 years, at an operating efficiency of 76 per cent and it consumes around 143 to 145 KW/hour as input power to deliver the specified volume at an pressure of 5.2 to 5.7 bar.

Action taken: Upgradation with latest energy efficient model (925CFM, air cooled, oil flooded double stage screw compressor of shaft power 110KW (SF – 1.1)

Benefits and savings:

  • Power consumption reduced (17 KW/Hr)
  • As this is an air cooled compressor, intangible benefit of reduction in cooling tower operation for 240 LPM (5 KW/Hr)

Installation of VFD in compressor
Background:
For our packing plant operation, double stage air cooled, 535CFM screw compressor was in operation and it consumes around 0.32 to 0.35 units/tonne of cement packing. The loading and unloading pattern of compressor is not uniform. Since the inward movement of cement truck is at different timing and to maintain the truck TAT compressor need to operate on continuous basis, hence ideal running is more.

Action taken: Operating this compressor through VFD, which enabled speed variation of the motor according the pressure setting and constant pressure is maintained in line and ideal running avoided.

Benefits: Compressor power consumption reduced to 0.24 units/tonne of cement packing and for 0.1 units/tonne reduction in cement.

Total savings (units/tonne)Power cost (Rs/unit)Packing in line -2 FY (18-19)Annual savings, (Rs lakh/year) 0.14.8516192587.85

Installation of additional receiver tanks
Background: The compressor air generated in compressor room is directly fed to the receiver tank of CVRM-2 Building, fourth floor. Due to line layout and cement bag house operation, line header pressure is reduced by 0.8 bar and frequent loading/unloading is happening.

Action taken: One more buffer tank of 6,000 liter capacity is installed nearer to the compressor station at ground floor.

Benefits:

Pressure drop in common header line reduced around 0.5 bar
Generation pressure reduced from 6.2 to 5.7 bar

Savings:
Power savings – 0.1 units/tonne of cement grinding
Total savings (units/tonne)Power cost (Rs/unit) Cement grinding in CVRM-2 FY (18-19)Annual savings,
(Rs lakh)Investment cost (Rs lakh)ROI (months)v 0.14.8516152937.830.50.77

Optimisation of pressure settings and vigilant monitoring
Background:
Compressors required for plant operation are connected in common header and tappings are taken from common header irrespective of pressure requirements. Also the pressure drop between the compressor end and load end is on higher side because of various piping sizes. Hence generation pressure setting is maintained more.

Action taken:
Higher volume requirement are taken from common header
High pressure and lower volume requirements at load end are compensated through booster
Operation of standby 950 CFM compressor during peak demand is compensated with smaller capacity compressors connected in the header and pressure settings are optimised
Also by vigilant monitoring and reviewing of compressor consumption on a daily
basis, leakages are arrested and minimised in the initial stage itself

Benefits:
Pressure drop reduced around 0.4 bar
Generation pressure reduced from 6 to 5.5 bar

Energy Conservation Activity – 2
Cyclones in modern cement plant: Modern cement production relies on conservation and efficient use of natural resources viz., raw materials and fuels. Kiln gases are used efficiently to preheat and dry raw materials before they enter the kiln. During design of cement plant pre heater, stages are added to the tower to reduce the pre heater exist temperature, as more heat is transferred to the fresh raw meal. Background: In our line-2 preheater system, it was observed that pressure drop across cyclone 1 was on higher side (i.e., around 250 mmwc instead of recommended range 90-120 mmwc), which affected the heat transfer in the system.

Action taken: For reducing pressure drop, it was decided to widen the gas inlet area. In first phase, the inlet area opening was increased to 250 mm and pressure drop got reduced to 220 mmwc. In second phase, it was further increased to 400 mm and the pressure drop got reduced to 180 mmwc

Benefits:

  • Pressure drop across cyclone-1 reduced from 250 to 180 mmwc (i.e., 70 mmwc)
  • PH fan power consumption reduced around 50 units/hour
  • Improvement of flow in PH cyclones
  • Collection efficiency improvement in PH cyclones

Savings: PH fan power consumption reduced around 150 units/hour
Total Savings (Units /Hr)Power Cost (Rs. / Unit)Running Hrs in FY (18-19)
Annual Savings, (Rs. Lakhs/year)Investment Cost (Rs. Lakhs)ROI (Months)
504.856560.215.912.31.73

Energy conservation activity – 3
Optimisation of raw meal silo operation – blending and extraction: In a cement plant, raw meal silo is meant for storing of raw-meal powder and for homogeneous process for better quality of cement. In Line 1 – 2 numbers of raw meal silo?s are there for this application.

Background: Our L1 kiln is producing clinker for all special cements like OWC, SLS , SRPC, etc. for OWC production, single silo is used, whereas for OPC clinker production two silos are simultaneously operated during feeding and extraction.

Due to this:

  • Auxiliary power consumption was higher
  • All the drives in the circuit were running and standby equipment are not available for operation during failure
  • Hence, planned to optimise raw meal silo operation to save energy

Action taken: For OPC production, single silo operation logic was implemented without affecting product quality.

Benefits:

  • Six drives were stopped in the circuit
  • Ready standby circuit available to avoid breakdowns
  • Reduction in spares and maintenance cost

Savings:
By stopping these equipment, power consumption reduction – 40 kW/hour

Total savings (Units/hour)Power cost (Rs/unit)Running hours in FY (18-19)Annual savings, (Rs Lakh/year)Investment cost (Rs lakh)
404.85592111.49Nil

Energy Conservation Activity – 4

Star feeder instead of 3KS system in cement mill feed: 3KS is an hydraulic system with three flaps, one flap gets open at a time and balance two flaps remains closed in-order to restrict false air entry inside the mill. Star feeder is a rotating feeder consisting of a horizontal shaft fitted with radial blades running within a close-fitting cylindrical chamber provided with an inlet and an outlet.

Background: CVRM-1 Mill – Materials fed through 3KS system and its drawbacks are:

  • 40Frequent gate struck-up due to foreign materials entry
  • Side liner worn out and leads to false air entry (around 23 per cent in CVRM-1 mill circuit)
  • Periodic flap jamming due to moisture in materials

Action taken: For reducing the false air entry and other nuisance – 3KS upgraded with star feeder. In this activity, we eliminated one feeding belt (531BC3) from the circuit and its feeding belt 531-BC2 is extended to fed the mill through star feeder. Star feeder motor capacity and hydraulic pump motor capacities are same.

Benefits:

  • Maintenance cost is reduced on account of one belt conveyor is eliminated
  • False air is reduced to 13 per cent across the mill
  • Elimination of 3KS hydraulic system maintenance

Savings:
Reduction in mill fan power consumption – 70 units/hour
Total savings (KW/hour)Power cost (Rs/ unit)Running hours in FY (18-19)
Annual savings, (Rs lakh)Investment cost (Rs lakh)ROI (Months)
704.855614.519.061710.70

Energy Conservation Activity – 5
SPRS for process mill fans: Slip energy recovery is one of the methods of controlling the speed of an slip ring induction motor. This method is also known as Static Scherbius Drive. In the rotor resistance control method, the slip power in the rotor circuit is wasted as I2R losses during the low-speed operation. The efficiency is also reduced. The slip power from the rotor circuit can be recovered and fed back to the AC source so as to utilise it outside the motor. Thus, the overall efficiency of the drive system can be increased. In a wound-field induction motor the slip rings allow easy recovery of the slip power, which can be electronically controlled to control the speed of the motor. The oldest and simplest technique to invoke this slip power recovery induction motor speed control is to mechanically vary the rotor resistance.

Background: The old SPRS system for CVRM-1 mill fan was installed in 1996 and it was served around 22 years. This SPRS system was outdated, spares are obsolete in the market and due to aging the reliability of this SPRS system is very poor. In last FY around eight months, it was not in operation because of non availability of spares. The speed range is 70 to 99 per cent.

Action taken: New SPRS system installed with wide speed range of 60 to 99 per cent. Also in the new system, the auto transformer is eliminated.

Savings:

  • Operating speed range is wider (i.e. 60 to 99 per cent)
  • Reliability of this new system is very high
  • Spare available in market and maintenance cost is very cheap
  • Auto transformer (575 to 1641 KVA) is eliminated in new system and the rating of recovery transformer also optimised to 450KVA from 837KVA. Hence transformer losses are reduced.
  • Because of reliable system the recovery power/hour is around 150 units.

Total savings (units/hour)Power cost (Rs/ unit)Running hours in FY (18-19)Annual savings (Rs lakh/year)Investment cost (Rs lakh)ROI (Months)
1504.855614.540.854212.3

Energy Conservation Activity – 6
Operated turbo blowers instead of PD blowers: The PD blower is also known as positive displacement blower and it is used to move gas or air for a variety of applications. To be precise, these devices utilise positive displacement technology by trapping a certain volume of air then discharging or forcing it out against the system pressure. The air is usually forced in to some type of pipe or hose to propel materials or gas to a destination. PD blower efficiency will be around 45 to 65 per cent. Turbo blower is the latest technology – energy efficient blower and its efficiency will be around 82 per cent.

Background: PD blowers are used for PC and kiln coal pumping application and it consumes more power for pumping. It occupies more space and generates more heat and noise (requires big silencers) during operation. Also it needs more maintenance. Efficiency of PD blower is very low.

Action taken: Because of efficiency, turbo blowers are operated instead of PD blower for kiln and PC coal pumping application. It occupies less space, operation is very quiet. It has few moving parts hence low maintenance is required and no complex oil cooling system is required for turbo blowers.

Savings: Energy efficient blower and operating at an efficiency of > 82 per cent
Power saving – 95 units/hour (by operating turbo blower for kiln coal pumping – 40 units/hour and by operating turbo blower for PC coal pumping – 55 units/hour)

Energy Conservation Activity – 7
Optimisation of air conditioner power consumption: In line 2 around 222.5 TR of package ACs are installed and operated for maintaining the temperature in PLC, MVAC and VFD rooms, training centre and CCR as listed below:
Sr. NoLocationCapacity (TR)
1Load center 159.5
2Load center 251
3Bag House Load center34
4CVRM Load center22
5RTC22
6CCR34
Total222.5

In CCR & VFD -Load Center the AC’s are operated by 24×7 and in training centre based on need basis. Various energy-efficient technologies were adopted to optimise.

Air conditioner power as below:
Water cooled condenser in place of air cooled condenser Depending on the type of the cooling system the packaged air conditioners are divided as water cooled and air cooled condensers. In water cooled packaged air conditions, the condenser is cooled by the water. The condenser is of shell and tube type, with refrigerant flowing along the tube side and the cooling water flowing along the shell side. The water has to be supplied continuously in these systems to maintain functioning of the air conditioning system. In air cooled packaged air conditioners, the condenser of the refrigeration system is cooled by the atmospheric air. The packaged AC with the air cooled condensers are used more commonly than the ones with water cooled condensers since air is freely available

Background: In L 2, all the package ACs are deigned as air cooled and after five years of use full lifecycle, the cooling efficiency is not effective because of lesser heat transfer in condenser coils. (The thin aluminum fins in coils are choked completely, air is not passing through the fins and getting damaged during cleaning within five years of lifecycle). Hence to maintain the temperature additional AC?s were operated continuously in addition to the regular units.

Action taken: Replaced the air cooled condenser coils with water cooled condensers in phased manner and without operating separate water pumps for water supply, tappings taken from water tanks feed lines and return water line laid to cooling tower.

Benefits:

  • Thus cooling efficiency of package AC’s improved
  • Operation of additional units stopped and standby unit available in all locations to meet the demand during breakdowns
  • Power saving achieved
  • Maintenance reduced

Savings:
Power savings around – 90 units/hour
LocationPower consumption (units/hour) before installation of WC condenser
Power consumption (units/hour) after installation of WC condenser
Load center 15740
Load center 24832
Bag House Load center3216
CVRM Load center2613
RTC2613
CCR3216
Total221130

Optimisation of air condition space
By optimising the room space, air conditioner power consumption reduced and room temperature maintained effectively.

Background: In bag house, the room size is larger and drive panels are accommodated within 3/4th of the room. Similarly in CVRM 2 Load center, the the false ceiling height is on higher elevated level and cooling duct is passing above 2 meters height over the panels. Hence cooling of more areas in done unnecessarily in both load the centers leads to power wastage and requires additional unit operation for effective cooling.

Action taken: In bag house, the cooling area partition modified along with the cooling duct modification to the required space and all other opening outside the new partition were closed. Similarly in CVRM-2 load centre, false ceiling and duct height reduced in such a way that the duct passes at 0.5 meter height over the panels. Thus effective cooling of load centres and panels ensured and additional unit operation is completely stopped.

Benefits:
Standby unit available in both locations to meet the demand during breakdowns
Power saving achieved

AC plant operation based on room temperature instead of return air Background: Package AC’s operation and cutoff is based on return air temperature. Due to leakage/improper flow of return air to the machine room, the AC unit is operated continuously and the room temperature is below the set point. This leads to unnecessary more cooling of load centres, CCR and wastage of power.

Action taken: Temperature controllers installed in all load centres, CCR and interlocked the control circuit of package AC’s with temperature controllers. Nowadays based on room temperature package AC’s are getting one or off. Thus power saving achieved.

Benefits: Power saving achieved. Other projects In addition to the above, various other Encon measures implemented as required, including VFDs for all process cooler fans and key auxilliary bag filter fans, occupancy sensors for the load centres and office building, cogged V belts in-place of V belt for blower and AHU’s. Further, for sustenance and continual improvements, daily energy monitoring of the specific power consumption is done through a structured format, capturing the drive wise power along with key operational parameters and accordingly brainstorming done, corrective actions taken and power optimised.

ABOUT THE AUTHOR: The article is authored by R. Rajamohan, Sr. General Manager( IE, Environment, PH) from Dalmia Cement Bharat Ltd., Dalmiapurum, Trichy.

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Rajasthan gets a water harvesting project

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Prince Pipes and Fittings Limited, in partnership with Ambuja Foundation, has launched a comprehensive water harvesting project in Chomu district of Rajasthan as part of its CSR initiative. The project aims to address water scarcity and enhance community resilience against water-related challenges. Ambuja Foundation will focus on setting up over 50 rooftop rain rainwater harvesting systems to provide a reliable source of water for 250 people. Additionally, efforts will be made to revive 2 village ponds, creating 10,000 cubic meters of water storage capacity, and to rejuvenate groundwater by implementing check dams, farm ponds and farm bunding. The project also includes educating the local community on water conservation techniques and promoting conscious water usage. This initiative seeks to support farmers through the government’s subsidies to install sprinkle irrigation systems at a minimal cost, while also contributing to livestock strengthening and promoting community ownership.

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Innovations in Sustainability

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Dr SB Hegde, Professor, Jain University, Bangalore, and Visiting Professor, Pennsylvania State University, USA, discusses how the cement sector is battling substantial carbon emissions and resource depletion, and embracing advanced technologies to mitigate its environmental impact.

In the relentless pursuit of urbanisation and infrastructure development, the cement industry finds itself at a pivotal intersection of ambition and responsibility. This foundational sector has long been synonymous with progress and growth, providing the bedrock for modern cities and industries. Yet, beneath its seemingly unyielding fa̤ade lies a profound challenge Рthe environmental footprint it leaves behind. Cement production, for its high carbon emissions and resource consumption, is now compelled to rewrite its narrative. The cement industry needs to become more sustainable using advanced technology. In this article, we will explore the world of cement production and discover new solutions that can change its future.

Considering traditional cement production is a major emitter of CO2, accounting for around 8 per cent of global greenhouse gas emissions. It consumes a vast amount of limestone, a finite resource, and contributes to deforestation and habitat destruction in limestone-rich regions.

Supplementary cement materials (SCMs) and creative ideas like Calcined Clay Clinker (LC3) are making a big difference. These different materials are transforming the way things are done. For example, in India, where the cement industry is one of the largest carbon emitters, LC3 technology, which incorporates calcined clays into cement, has been demonstrated to reduce CO2 emissions by up to 30 per cent and substantially decrease energy consumption during the clinker production process. By 2050, it is estimated that the implementation of such alternative materials could help the cement sector reduce its global CO2 emissions by up to 16 per cent.

The cement industry because of its energy-intensive processes, consuming approximately 5 per cent of the world’s total energy and contributing significantly to greenhouse gas emissions.

Waste heat recovery systems, a pivotal technology, are setting an example for sustainability. A case study from a cement plant in Germany showed that waste Innovations in Sustainability Dr SB Hegde, Professor, Jain University, Bangalore, and Visiting Professor, Pennsylvania State University, USA, discusses how the cement sector is battling substantial carbon emissions and resource depletion, and embracing advanced technologies to mitigate its environmental impact. heat recovery reduced energy consumption by approximately 20 per cent and cut CO2 emissions by 1.6 million tons annually. This not only demonstrates the environmental benefits but also underscores the economic advantages of such innovations.

Furthermore, the industry is adopting alternative fuels, often derived from waste materials. Lafarge Holcim, one of the world’s largest cement producers now utilizes alternative fuels in 37 per cent of its cement plants. This has resulted in an estimated reduction of 2.2 million tonnes of CO2 emissions annually, showcasing the transformative potential of sustainable fuel sources.

The electrification of kiln systems is a transformative step towards sustainability. While the shift to electrification is in its nascent stages, there are promising examples. Heidelberg Cement, a global leader in building materials, has set ambitious targets to electrify its cement production processes. By leveraging renewable energy sources, such as wind and solar, the company aims to reduce CO2 emissions by 30 per cent within the next decade. These concrete numbers underscore the industry’s commitment to low-carbon electrification.

Hybrid and flash calcination technologies offer compelling statistics as well. For instance, a pilot project using flash calcination technology in the Netherlands yielded a 25 per cent reduction in CO2 emissions compared to traditional rotary kilns. These numbers highlight the potential of disruptive technologies to reshape the cement industry.

This article is like a clear road map with real examples, explaining how the cement industry is becoming greener and more sustainable. By using technology, the cement industry wants to find a balance between moving forward and taking care of the environment. It’s showing how an industry can change to become more sustainable, strong and responsible for the future.

CURRENT TECHNOLOGIES


1. Alternative raw materials: The cement industry’s traditional reliance on limestone as a raw material is undergoing a transformation. The incorporation of alternative materials like fly ash, slag or pozzolans is a sustainable approach. For example, the use of fly ash in cement production can reduce CO2 emissions by up to 50 per cent compared to traditional Portland cement.

2. Energy efficiency: Improving energy efficiency is crucial. Waste heat recovery systems can significantly reduce energy consumption. For instance, waste heat recovery in cement plants can lead to a 20-30 per cent reduction in energy consumption.

3. Carbon Capture and Storage (CCS): CCS is a promising technology. In Norway, the Norcem Brevik cement plant has successfully demonstrated the capture of CO2 emissions, which are then transported and stored offshore. This technology can capture up to 400,000 tonnes of CO2 annually.

4. Use of alternative fuels: The shift towards alternative fuels can significantly reduce carbon emissions. For example, the use of alternative fuels in the European cement industry results in an average substitution rate of about 40 per cent of conventional fuels.

5. Blended cements: Blended cements, combining clinker with supplementary cementitious materials, can lead to lower emissions. For example, the use of slag and fly ash can reduce CO2 emissions by up to 40 per cent.

INNOVATION FOR THE FUTURE
1. Carbon Capture and Utilisation (CCU): CCU technology is still emerging, but it shows great potential. Innovations like carbon mineralisation can convert CO2 into stable mineral forms. Carbon Engineering, a Canadian company, is working on a direct air capture system that can capture one million tons of CO2 annually.

Feasible CCS technologies for the cement industry include:

a. Post-combustion capture: Capturing CO2 emissions after combustion during clinker production using solvents or adsorbents.
b. Pre-combustion capture: Capturing CO2 before combustion, often used with alternative fuels.
c. Oxy-fuel combustion: Burning fuel in an oxygenrich environment to facilitate CO2 capture.
d. Chemical looping combustion: Using metal oxides to capture CO2 during the calcination process.
e. Carbonation of alkaline residues: Capturing CO2 using alkaline residues from other industrial processes.
f. Integrated Carbon Capture and Storage (ICCS): Directly capturing CO2 from the cement production process.
g. Underground storage: Transporting and storing CO2 underground in geological formations.
h. Enhanced Oil Recovery (EOR): Injecting captured CO2 into depleted oil reservoirs.
i. Mineralisation: Converting CO2 into stable mineral forms for potential use or storage.

The cement industry can reduce emissions by adopting these technologies, but cost, energy, and infrastructure challenges must be addressed for widespread implementation. Collaboration among stakeholders is crucial for successful CCS integration.
2. Biomimicry in cement design: Researchers are exploring biomimetic materials inspired by nature. For example, a company called BioMason uses microorganisms to grow cement-like building materials, reducing energy use and emissions.
3. 3D printing of cement: 3D printing technology offers precise and efficient construction, reducing material waste. In a study, 3D-printed concrete structures used 40-70 per cent less material compared to traditional construction methods.
4. Blockchain for supply chain transparency: Blockchain technology ensures transparency and traceability. It is already being used in supply chains for various industries, including cement. By tracing the origin of raw materials and tracking production processes, it ensures sustainability compliance.

EVALUATING AND IMPLEMENTING SUSTAINABLE TECHNOLOGIES
1. Life Cycle Assessment (LCA): LCAs assess environmental impacts. For instance, a comparative LCA study found that geopolymer concrete (an alternative to traditional concrete) had 36 per cent lower carbon emissions compared to Portland cement.
2. Cost-benefit analysis: Considerations of initial investments and ongoing operational costs are paramount. Studies show that the implementation of waste heat recovery systems can pay back their initial costs in as little as two years, leading to long-term savings.
3. Regulatory compliance: Stricter emissions standards are being enforced globally. The European Union, for instance, has set ambitious emissions targets for the cement industry, mandating a 55 per cent reduction in CO2 emissions by 2030
4. Scalability: The scalability of technologies is critical for industry-wide adoption. Technologies like blended cements and waste heat recovery systems are already scalable, with global cement companies actively implementing them.
5. Stakeholder engagement: Engaging stakeholders is essential. For example, Holcim, a leading cement manufacturer, has partnered with NGOs and local communities to ensure sustainable practices and community involvement in their projects.

In conclusion, the cement industry is on a transformative path towards sustainability, driven by technological innovations. By embracing alternative raw materials, enhancing energy efficiency, and exploring cutting-edge solutions like carbon capture and utilization, the industry is reducing its environmental impact. The future holds even more promise, with biomimetic materials, 3D printing and blockchain enhancing sustainability.

Evaluating and implementing these technologies necessitates comprehensive assessments, cost-benefit analyses, regulatory compliance, scalability and stakeholder engagement. The industry’s commitment to sustainability not only addresses environmental concerns but also aligns with societal values and expectations, setting the stage for a greener and more responsible future for cement production.

REFERENCES:
1. NIST. (National Institute of Standards and Technology) Role of NIST in Sustainable Cements.
2. International Energy Agency. Cement Technology Roadmap 2018.
3. Gassnova. Longship – CO2 Capture, Transport, and Storage.
4. European Cement Association. Cembureau.
5. CSI. (Cement Sustainability Initiative) Slag Cement and Concrete.
6. Carbon Engineering. Direct Air Capture and Air To Fuels.
7. The University of New South Wales. Alternative Cement Discovery Set to Reduce Carbon Emissions.
8. BioMason. BioMason Technology.
9. NCCR Digital Fabrication. DFAB House Project.
10. IBM Blockchain. IBM Blockchain Solutions for Supply Chain.
11. ScienceDirect. Life Cycle Assessment of Geopolymer Concrete.
12. Energy.gov. Heat Recovery Technologies.
13. EU Climate Action. EU Climate Action: Climate Targets for Cement Industry.

ABOUT THE AUTHOR:


Dr SB Hegde is an industrial leader with expertise in cement plant operation and optimisation, plant commissioning, new cement plant establishment, etc. His industry knowledge cover manufacturing, product development, concrete technology and technical services.

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Stud technology has proven to be a boon for the industry

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Ashok Kumar Dembla, President and Managing Director, KHD Humboldt Wedag India, discusses the advancements in grinding solutions that focus on low energy consumption, dust free circuits and low maintenance.

Tell us about the role of your grinding solutions in the cement industry?
We all know that grinding constitutes about 65-70 per cent of electrical energy consumption of cement manufacturing. Any saving in grinding energy can be good for operating cost reduction. Also, energy cost is increasing with time, therefore cement manufacturing companies are looking for new technologies for low electrical energy consumption. In the past few years, KHD has worked extensively in the field of grinding to reduce electrical energy consumption in the cement industry, which also helps in reduction in carbon footprints. We at KHD provide all kinds of grinding solutions be it raw material grinding, cement grinding or slag grinding.

How do you customise your grinding solutions to fit the requirements of distinct cement plants?
Based on the cement manufacturers requirement, we offer customised solutions for various grinding circuits. Every cement plant has specific requirements. Like some focus on low-cost solutions, some focus on energy efficiency whereas some focus on operational excellence. The input material hardness, moisture, abrasively, feed size and product requirement decide what solution is to be offered for achieving a cost effective and energy efficient solution. We have various sizes of roller presses, various types of roller surfaces, types of rollers and arrangement of roller presses in the circuit like roller press in semi-finish mode, roller press in finish mode, size of ball mill in semi-finish mode, location of static separator in process circuit, etc. So, based on all the factors, we decide what is to be offered.

How do your grinding solutions help cement plants achieve energy efficiency?
Latest developments related to raw material grinding in finish grinding in roller press have paid dividends even for soft and medium to hard material. Hard raw materials are giving higher bonus factor in finish grinding roller press systems and cement manufacturers are getting 2-4 Kwh/t saving in electrical energy in raw material grinding itself by using this technology as compared to vertical mill technology. Typical circuit offered by KHD for raw materials grinding in ComFlex Grinding circuit has advantages to process raw materials with high moistures with incorporation of V-Separator below the roller press and use of hot gases to dry the raw materials.
With the focus of the industry towards WHR systems, roller press grinding has further received acceptance as it uses no water for bed stabilisation and uses minimum hot gases as compared to other contemporary technologies.
In case of cement grinding, two technologies are being accepted, either vertical roller mill or roller press in semi-finish or finish grinding. Roller press in finish grinding has the advantage of further saving of 3-4 Kwh/t as compared to semi-finish grinding and vertical mill technology. With more acceptance of blended cements like PPC, PSC and composite cements, roller press in finish grinding is accepted as advanced technology in cement grinding. Typical finish and semi-finish grinding circuits offered by KHD are very popular in the cement industry. which includes use of roller press alone or in combination of roller press and ball mill respectively.
In the case of slag grinding, acceptance of roller press in finish grinding is well recognised. It offers a distinct advantage of saving of about 6-7 Kwh/t as compared to the vertical roller mill at 4200 Blaine. The advantage comes due to the hardness of slag and pressure grinding in roller press instead of attrition and low pressure in vertical roller press. Moisture issue is also tackled with the problem of coating by incorporating a V-separator below the roller press.

Tell us about the role of separators in the grinding process? How do they help achieve cost efficiency?
The basic role of a separator is to separate the feed material entering into it after grinding into two products i.e., coarse and fine. While fine is normally the final product in case of dynamic separator and is intermediate product in case of V-Separator. Dynamic separators have also gone through various technological developments, and we are offering 4th generation high efficiency separators now-a-days. These separators offer sharp cut point and minimum bypass (particle below 3 microns). This leads to less recirculation of fines thus improving the availability of the system and in turn efficiency of the system. V-separator is an excellent pre-separator cum dryer (in case of wet material) which is used for pre-separating the roller press throughput before the second separation in a dynamic separator. Two stage separation in the roller press circuit makes it energy efficient and ensures proper product quality.

Materials used for the manufacturing of cement are evolving every day. How does your machinery adapt to this change at the cement plants?
With the trends more on low clinker to cement ratio, today the Indian cement industry is moving very fast toward this aspect. PSC, PPC, composite cements are going up the curve. The cement industry is well versed with the utilisation and manufacturing of blended cement. KHD is one of the key suppliers for providing energy efficient technologies viz roller press grinding for the production of blended cement.
It is estimated that decreasing the clinker ratio in production of cement contributes to nearly 37 per cent of targeted CO2 reduction. By promoting PPC and PSC cement in India, more than 85 per cent cement is produced as blended cement or composite cement (which has come into existence during the last 3-5 years). PPC allows 35 per cent fly-ash usage at present, whereas PSC allows 55 per cent to 65 per cent granulated slag in clinker. Increase of Pozzolana (fly-ash) usage in PPC, up to 45 per cent can reduce the carbon footprint further which has a permissible limit of up to 55 per cent in some European countries. Our roller presses are well versed to take care of all these materials smoothly.

What role does technology play in designing and executing your grinding circuit at the cement plants?
It’s mainly the technology that has promoted the roller press circuits for grinding over VRM technology. Our technology takes into consideration the lowest energy consumption, dust free circuits, nil water consumption, lower maintenance and more in terms of availability and reliability. So, all the systems are based on technology to address all these points. For example, roller press surface plays an important role regarding maintenance requirements. Stud surface of roller press can provide continuous availability of roller press for 4-5 years without any welding requirement. Welded surfaces also have less than half the requirement of welding as compared to VRM, which has the attrition principle of grinding in addition to pressure grinding.

What are the major challenges in curating and executing grinding solutions?
Over the years we have done intensive work in the field of grinding solutions. We don’t foresee any major challenge now as we have already achieved lower power consumption, dust free circuits, more reliability, environmentally friendly grinding. However, we are on the track of continuous improvements to even achieve better because we believe that nothing is impossible, and we are always bound to reach new heights. With use of blended cements and LC3 Cement in coming future in India we are expecting higher blain requirement in final product which may see some technological advances in secondary grinding i.e., ball mills may be replaced by special mills however roller press shall continue in semi-finish and finish grinding applications.

Tell us about the innovations by your organisation in the near future that the cement industry can look forward to.
At present, the focus is to use roller press in finish grinding to get maximum energy advantage as compared to ball mill grinding especially for blended cement. Apart from electrical energy, the focus is also on roller press surfaces, which has minimum wear and offers trouble and maintenance free operation. Stud technology has proven to be a boon for the industry. Tungsten Carbide Studs are fixed on the roller surface by pressing in pre-drilled rollers, which offers autogenous grinding and minimum wear. Life expected out of these roller surfaces varies from 25,000-40,000 hours of operations without any surface maintenance.
Apart from this, developments are focussed on optimising the process circuit for energy efficient and pollution free operation. Developments in actuated dosing gate for feeding material to roller press and online monitoring of roller press surface are also worth noticing. There shall also be developments related to use of digital technology to monitor the performance of these grinding systems, which can contribute towards optimised production and increased availability due to timely signals regarding maintenance requirements.

-Kanika Mathur

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