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Optimising Heat Utilisation

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With Waste Heat Recovery as a viable alternative for the power needs of cement plants, Triveni Turbines presents case studies to support their findings on the role of thermal renewable fuels in aiding the cement sector inch closer to its goal of a sustainable future.

The cement industry is an energy-intensive industry. On an average, the energy cost is around 40 per cent of the cost of production for cement manufacturing. The heat generated in cement processes is generally lost up to 30 to 40 per cent.
Cement plants in India have Captive Power Plants (CPP), which are fired using fossil fuel (coal). These are in operation for several decades. Nowadays, the CPPs installed in cement plants use heat through Waste Heat Recovery (WHR) to generate power. Typically 20 to 30 per cent of the power requirement for cement plants can be fulfilled using waste heat for power generation.
Globally, WHR based plants installed in the cement industry are based on three processes, namely

  • Steam Rankine Cycle System (SRC)
  • Organic Rankine Cycle System (ORC)
  • Kalina Based System

The function of the WHR is to recover the heat from the hot stream using Heat Recovery Steam Generators (HRSG) or Waste Heat Recovery Boiler (WHRB) to generate superheated steam. It can be used in the process (for co-generation) or to drive a steam turbine (combined cycle). 
The WHR based power plants installed in cement processing plants use the heat generated through rotary kiln preheater (PH) and after quenching cooler (AQC) exhaust hot gases for power generation. 
In India, the customer prefers SRC for WHR power generation in Cement Plants. Technically, in SRC, the exhaust gases from the rotary kiln pass through PH and go to the PH boiler. Similarly, mid-tapping from AQC gives hot gases to the AQC boiler. One cement kiln line requires 2 PH boilers and 1 AQC boiler. Based on the heat source, these boilers generate low-pressure steam of 12 ata to 18 ata at a temperature of 350 to 450 degree Celsius. and Low Pressure (LP)steam 2 ata to 3 ata pressure and temperature of 175 to 195 degree Celsius.
WHR-based power plants also exist in the sectors like sponge iron, steel and chemicals, which came into existence from the year 2000 onwards in the Indian market. Initially in India, the major cement manufacturers installed cement WHR plants made in China while over the last decade or so, Indian boiler and Turbine OEMs offered products indigenously designed and manufactured catering to the market dynamics, demand requirements and providing sustained long-term aftermarket services.

Steam turbines for a Waste Heat Recovery based power plants in an overseas location.

Cement WHR
Triveni Turbines is associated with cement WHR for many years now and has executed numerous prestigious projects with leading cement manufacturers in India and abroad. The requirement for cement WHR depends on the cement kiln capacity, heat utilisation, and plant efficiency.
Triveni is currently in the process of installing many cement WHR projects and is also working on multiple projects that are either in the enquiry or in the order finalisation stage.
Triveni has developed efficient injection condensing turbines that use medium pressure steam as turbine inlet and low pressure as injection steam. With the addition of 7th generation turbine blades developed by Triveni, power generation output is more for input steam parameters or gas parameters.


Salient features of Triveni’s steam turbines in the cement industry are as follows:

  • Integral Lube Oil tank: Triveni offers an Integral Lube Oil tank for Power House Layout and civil cost optimisations of TG House. The benefits include a reduction in the civil cost of the project.
  • Mechanical Run Test (MRT): Live steam mechanical run test at Triveni’s manufacturing facility for the steam turbines. The Turbine is tested with live steam from boilers at Bengaluru works with job-mounted turbo supervisory systems, Woodward governor, and gearbox.
  • In-house Manufacturing: Turbine components like blades, rotors, and casing are manufactured and assembled at Triveni’s facility.
  • Vacuum Tunnel: High-speed balancing of turbine rotor on ‘Schenk’ Vacuum Tunnel 
  • Gear Box (Triveni Power Transmission) assembly is done along with the Turbine on the same base plate and converts into a single product. A separate foundation of the gearbox is not required.
  • Inlet Valve: Triveni supplies a customised inlet governing valve is designed in-house to overcome the varied load fluctuations in the cement industry
  • Injection Control Valve: Triveni supplies a specially designed globe control valve to maintain the minimum differential pressure to avoid the energy loss which results in the indirect losses in the final output.

Best practices on steam turbine design solution
Large cement companies are primarily considering WHR power plants for their Greenfield projects. Dependency on the Chinese turbines has now declined in the Indian market as the Indian OEM’s adapted to injection condensing turbines technology with a dominant leadership. Triveni has a firm reference of injection condensing turbines supplied to cement WHR plants across India. 
Specific design consideration is vital in the injection and admission zone. The rotor designed by Triveni has the higher stability to offset the excitation due to fluctuating injection steam loads. To meet customer requirements for various mid-pressure and low-pressure steam combinations, an injection condensing turbine was developed by Triveni and is successfully working in the Indian Cement Industry. Design and engineering teams carried out Computational Fluid Dynamic (CFD) analysis and creep-fatigue analysis to address this issue. This design philosophy is a value-addition for Triveni for its robust and efficient cement
WHR solution.

Environmental concerns and the solutions offered
According to industry sources, cement manufacturing accounts for an estimated 4 to 8 per cent of the world’s carbon dioxide (CO2) emission, making it a significant contributor to global warming. Increasing the energy efficiency of cement plants by replacing fossil fuels with thermal renewable fuels (such as waste heat) and capturing and storing the CO2 to contain greenhouse gas (GHG) emissions are some of the solutions common to the cement industry and other industrial sectors.

WHR power potential
There is a vast potential for power generation from waste heat across the world. The installation of cement WHR based power plants in China is over 80 per cent, much ahead of India. Similarly, Europe, the USA, and Latin America plan to implement WHR in their cement plants. It is observed that waste heat recovery-based power plants are emerging as an excellent value addition to the existing captive power plants. Other than reducing energy costs significantly, it can also be a reliable source of power. 

Case studies of Triveni                                                                                                      
a. Waste Heat Recovery based Power plant in Madhya Pradesh, India
Driven by Triveni 1*22.5 MWe Injection Condensing steam turbines with an inlet steam parameter of 12 Bar and 425 degree Celsius with 0.2 Bar Exhaust

Specific design consideration is vital in the injection and admission zone.

Customer challenge                                                                                                       
The steam flow in this project was from multiple sources (i.e., multiple boilers). Steam generation depends on the waste heat generated from hot gas temperature from the preheating process and AQC process. There is a variation in the steam inlet at Medium Pressure (MP) and Low Pressure (LP) side and load variation in load or power output.

Solution                                                                                                                        
The steam turbine we proposed is an Injection condensing turbine that receives MP steam as an inlet and LP steam as an injection in the middle steam path. The steam collected was from 4 No’s of Preheater (PH) boilers and 2 No’s of After Quenching Cooler (AQC) Boilers from the two cement kilns of 7,000 TPD and 8,000 TPD capacity.                                  
The steam turbine generator (STG) is suitable for an air-cooled condenser with a new generation blade design and reaction stages. Despite various challenges, the commissioning of the Turbine was executed with quick delivery of eight months, which set a benchmark for Triveni in the cement industry.

Benefits                                                                                                                             
The company does not have a captive power plant installed, and this WHR plant has offered many benefits. The waste gas generated at around
400 degree Celsius is cooled to 130 degree Celsius, thus safeguarding the environment and simultaneously utilising the waste heat to generate almost free power.     
b. Waste Heat Recovery based Power plant installed overseas
Driven by Triveni 1*30 MWe Bleed condensing steam turbines with an inlet steam pressure of
65 Bar and 505 degree Celsius with 0.1 Bar
Exhaust pressure

Customer challenge                                                                                                                                     
The customer proposed installing a power plant and expanding the company’s manufacturing capacity and was on the lookout for a steam turbine solution provider. The customer wanted to generate the necessary power by banking on their captive power capacities and to ensure a steady supply for critical processes.

Solution                                                                                                                                     
Triveni offered the best solution to meet the plant efficiency by utilising the waste heat recovered from the existing blast furnace for power generation.

Benefits                                                                                                                                                   The company entrusted Triveni’s expertise in manufacturing robust and highly reliable products. It awarded us with the supply contract of a steam turbine that benefits from improving the plant’s energy efficiency, reducing the energy cost, and transmitting surplus electricity to the grid.
To complement the above new product portfolio, Triveni’s refurbishment arm Triveni REFURB steps up to provide an aftermarket solution for the complete range of rotating equipment across the globe. From steam turbines, compressors to the gas turbine range, we have adapted ourselves to ensure that customers find a one stop solution.
Over a period of time, the existing turbines degrade thereby reducing the efficiency of the turbines by consuming more steam. The Triveni REFURB team provides solutions to enhance the efficiency of turbines of ‘Any make, Any age’ by only replacing the critical components of the turbine i.e., rotor, guide blade carriers and bearings, which ensures the efficiency is restored and thereby reducing the carbon footprint.
Triveni REFURB converts the existing turbine into injection mode turbine. The turbines are then re-engineered to allow additional steam to be injected into the turbine and improve the efficiency of the plant.
a. Conversion of Bleed Condensing Turbine to Injection Condensing
A Chinese Turbine 1*25MWe Bleed Condensing Turbine with 84 Bar 515 degree Celsius inlet conditions and 0.176 Bar Exhaust pressure

Customer challenge                                                                                                                                     
A major cement Industry customer wanted to convert their existing Chinese make turbine from a 3 bleed condensing to injection condensing turbine. The pressure at the inlet was reduced to 13 Bar 425 degree Celsius as against 84 bar 515 degree Celsius. The injection parameters are 2.25 Bar 185 degree Celsius.

Solution                                                                                                                                     
Due to the steep drop in inlet pressure the volumetric expansion was almost three times the original condition. We had proposed to modify the Inlet valve of the turbine and the first stage nozzles to accommodate this expansion. Two bleed ports were closed and the injection would be taken from the third bleed port. Complete re-engineering of the turbine was undertaken to adopt the upgraded steam flow path.

Benefits                                                                                                                                                   By keeping the existing casing and civil foundation, customers benefited by lower expenditure and improved efficiency. This would enable the customer to get a faster Return on Investment (within 2 years) and enhanced life of the turbine.

Author: Arun Mote, Executive Director, Triveni Turbine Limited

Concrete

Shree Cement Expands Bangur Concrete Network with Patna Plant

New facility takes the company’s national RMC network to 36 plants

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Shree Cement has inaugurated a 60 m³/hour ready-mix concrete plant in Patna, Bihar, under its Bangur Concrete brand. The facility takes the company’s ready-mix concrete (RMC) network to 36 plants across India and strengthens its presence in eastern markets.

The plant was inaugurated by Neeraj Akhoury, managing director of Shree Cement, in the presence of senior company officials and other guests. It has been established to serve demand for ready-mix concrete in Patna and neighbouring areas, where infrastructure development, urban expansion and real estate activity are supporting construction growth.

The facility is designed to supply construction projects across Patna and surrounding markets. Its installed capacity of 60 m³/hour will enable Bangur Concrete to serve customers across the region while improving distribution and supply capabilities in eastern India.

The expansion is intended to improve customer service, strengthen the company’s market presence and support development activity in Bihar. The plant incorporates modern batching technology, material handling systems and quality control processes aimed at maintaining consistency in production and improving operational efficiency.

With the addition of the Patna facility, Bangur Concrete now operates 36 RMC plants across India. The business is expanding its footprint in key construction markets to improve customer access to ready-mix concrete, which is increasingly used in infrastructure, commercial and residential projects because it supports controlled production, consistent quality and more efficient material management at construction sites.

The facility will also follow environmentally responsible operating practices, in line with Shree Cement’s focus on sustainable construction solutions. The latest addition adds capacity to the company’s RMC operations and supports its efforts to serve regional construction markets as development activity continues across Bihar.

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Concrete

Ambuja Plans 2.9 MTPA Godda Cement Unit

Proposed unit forms part of Ambuja Cements’ Rs. 145 bn expansion

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Ambuja Cements has proposed a 2.9 mn tonnes per annum (MTPA) cement grinding unit in Godda district, Jharkhand, as part of a Rs. 145 bn expansion programme. The plan is intended to lift the company’s overall cement capacity to 155 MTPA by financial year 2029-30 (FY30), from its current 113.5 MTPA.

The proposal forms part of the Adani Group company’s wider manufacturing expansion across eastern and northeastern India, according to a company statement issued on Monday. The Godda unit would add grinding capacity to Ambuja Cements’ network and is intended to help serve demand in Jharkhand and neighbouring states.

Locating production closer to these markets is expected to reduce transportation costs and delivery times, while the project could support employment in plant operations, maintenance, logistics and administration. The company also linked the facility to indirect activity in transportation, contract services, construction, warehousing and local supply chains.

The expansion plan includes a 2.9 MTPA grinding unit each in Assam and Bihar, as well as additional clinker capacity in Assam. Together, the projects are designed to distribute manufacturing capacity more widely and improve the connection between clinker production and grinding operations, Ambuja Cements’ cement-business chief executive Vinod Bahety said.

Clinker is the intermediate material produced before it is ground and blended to make cement, making the Godda proposal part of a broader materials and logistics network rather than an isolated facility. Ambuja Cements has not provided a commissioning timeline, a Godda-specific investment breakdown, land details or a detailed employment estimate in the supplied announcement.

The project’s impact will depend on implementation of the plant, associated transport links and local supply chains. The announcement sets out the capacity objective but does not specify the project’s construction schedule or operational start date.

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Concrete

Beyond Automation: Building AI-driven Cement Plants

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Prerak Manisha Shah, Founder and CTO, Cogniify.ai, draws a sharp distinction between automation and self-optimisation, and the need for a workforce that understands both the capabilities and the limits of the intelligence they are working with.

The cement production process uses a lot of energy, involving various steps such as processing of raw materials, use of kilns and running machinery. There are numerous factors that should be kept in balance in order to make the process effective. It is possible to save production costs, quality and environment performance. In spite of the fact that traditional automation has allowed to achieve consistency in working and reduce the level of human interference, it is not always possible to monitor changing conditions and solve issues in advance.
Artificial Intelligence (AI) is the latest approach that has transformed cement production. By analysing up-to-date data and supporting companies in search for the correct solution, it is possible to turn the production process into one of continuous optimisation and advancements.

Difference between automation and self-optimisation
Automation and self-optimisation may seem synonymous, but they play different roles. Automated systems obey predefined rules. For instance, a conveyor belt comes to a halt when a sensor senses something blocking it; kilns will have their fuel input adjusted by temperature regulators when the temperature readings go out of range. Self-optimisation takes it a step further. The system is capable of obtaining historical data, as well as current operational data, and then using it to understand what is going on in the plant and how to improve operational efficiency.
Thus, instead of sticking to a certain temperature, an AI-based system evaluates how the composition of raw materials, fuel properties, feed rates, and air distribution can influence kiln performance. It also creates recommendations about what to change in order to ensure the quality of clinker with minimum fuel costs. With a proper set of controls and safety features, some adjustments can be performed automatically.
The distinction is significant: automation is about executing commands, while self-optimisation is connected to making better decisions based on available data. In any case, human supervision is required, particularly with regard to the decisions that could affect safety, product quality and stability of operations.

Turning the kiln into an intelligent, predictive system
The rotary kiln is the main equipment in the cement manufacturing process. It is important to keep the kiln operating appropriately to get the desired quality of clinker, which is an intermediate material for cement production. That said, the kiln’s performance depends on many factors that are extensively interconnected. Any change in one of them would influence the rest. Traditionally, the operators would make use of their experience and laboratory results combined with information from the control room, reacting to those changes.
Nevertheless, AI can assist them in the process of handling changes that occur within the operating kiln. For example, predictive models would estimate what will happen if raw material composition or fuel quality is changed. It would give the operators a chance to optimise the operational conditions beforehand. AI can also help to discover unstable conditions within the kiln, which would suggest forthcoming problems. It is also worth mentioning, however, that these advantages depend widely on the accuracy of data received from sensors used in the production premises as well as the availability of models and their connection with the process.

Predictive maintenance
When unexpected breakdowns happen in manufacturing, it can produce a vast amount of disruption in manufacturing. For example, equipment such as kiln drives, gearboxes, fans, and conveyors can lead to decreased production without counting the increased expense in repairs and altered time of deliveries. Traditional preventive maintenance reduces the chances of errors because it helps plan inspections and maintenance of the machines, but in certain cases it appears unnecessary.
With predictive maintenance, AI programmes use data about vibration, temperature of bearings, electric current of the motor and operating time of the equipment in order to determine when the machine is likely to break. For instance, decisions about making preventive maintenance of the gearbox in your cement mill may be made only with the help of the changing pattern of vibrations. The moment the AI recognises that the vibration of the machine has changed, the engineers will be able to check the machine before it breaks down. In that way, the engineers would be able to examine its parts and bring them to ordering spare parts and plan maintenance works.

Energy optimisation
In cement production, energy is one of the highest operational costs since kilns require a lot of thermal energy while raw mills, cement mills, fans, and other equipment need a lot of energy. Thus, increased efficiency has a direct influence on the operational costs and emissions when it comes to cement manufacturing. Since machines operate in different conditions, AI could help improve productivity through energy use optimisation based on how parameters and working conditions affect fuel and electricity consumption.
AI can help determine optimal parameters such as kiln charge, combustion, mill charge, airflow, and equipment operation to find all the possibilities for maximising the efficiency of the process. AI can help distinguish conditions that include high specific energy consumption so that the operators can adapt their processes without risking the quality of their products. An important contribution of AI includes the development of algorithms that optimise processes, taking into account the need to minimise fuel costs, production, and the quality of clinker. Applying AI technology allows automating processes where one would be unable to optimise energy consumption properly. This helps to reduce costs related to a plant’s operation without making high-level changes in
its operation.

Making sustainability a real-time operational goal
In the concrete industry, sustainability creates a strong connection to efficiency in performance and operations. The process of making concrete involves a combustion process as well as the process of converting limestone into cement, which generates emissions of carbon dioxide. The electricity that is consumed and the fuel types that are used also contribute to overall emissions of the plant. Analytics involved with AI technologies can contribute to the reduction of emissions by enabling continuous monitoring of processes associated with fuel and energy use. Analytics allows assessing the emitters in real time based on data related to the fuel burnt, heating processes, and emissions, as well as deviations from the norm that have occurred. AI gives the chance to evaluate these deviations and take actions in order to keep stable conditions in the kiln. It also provides businesses with chances to optimize the level of air used and make processing much more efficient.
When good measurement methods are used, AI can provide actual monitoring of emissions intensity. However, the application of AI technologies alone will not help eliminate the emissions connected with limestone chemistry.

Connecting the entire plant through a digital twin
Cement manufacturing entails various activities that are interrelated to each other. A modification in raw mill will have an impact on kiln feeding and also the performance of the kiln in turn will influence the quality of clinker produced and demand for energy that is needed for grinding cement. If every machine is optimised independently, it may lead to the loss of chances to improve overall efficiency of the cement production. A digital twin is an outstanding technology that allows overcoming this problem.
A digital twin is a technology that allows creating a representation of concrete equipment or process based on the data received from equipment or process operation. Depending on the characteristics, it can allow simulation of work conditions and test
various decisions. When combined with AI, this technology can test various scenarios and make coordinated decisions by departments. In particular, engineers can evaluate various potential improvements before real implementation. A digital twin is not equal to a complete copy of a physical plant or equipment.

From data collection to decisions
The optimisation of AI technology needs a good digital foundation that aggregates valid data from sensors, labs, maintenance history, meters, and production software. Otherwise, isolated systems make it hard to combine important pieces of information. For example, while the maintenance department knows about continuous malfunctions with a fan, at the same time, the production group has information about changing operational conditions. Thus, it would be impossible to understand what a specific piece of data means. A good digital foundation incorporates good definitions of data used, proper communication between systems followed by a good data storage process, and clear identification of the one who owns this particular data. Furthermore, cybersecurity, access control, and protection of crucial technologies must be given serious consideration.
Data quality is very important, as wrong data from sensors, missing values or misnamed historical records can result in misleading outputs from AI. Therefore, factories must develop technology to ensure correct data, monitor the quality of models used and train them with respect to changes in devices or operational conditions. The goal is to turn collected data into useful suggestions for action.

The human factor
The change to self-optimising actions is not just a technology-related task; it’s also a change in how people do their business. Workers, maintenance specialists, and professionals have field knowledge that can’t be replaced by AI technology. Teams should be able to trust recommendations provided by AI or other systems, which means understanding the suggestions, the reasons behind those suggestions, and expectations in regard to the effects of the offer.
An algorithm that generates alerts without explanations or makes absurd recommendations will have difficulty becoming a part of daily operations. Therefore, the cement industry has to make sure that staff is involved in the identification of issues where AI can be used, as well as in testing and outcome evaluation processes. Training should educate personnel to interpret AI results, understand limitations, and know when to stop AI recommendations.
The establishment of limitations for automated operations is of utmost importance, as well as making sure that there are procedures created to react to sensor malfunctions, communication loss, or abnormal behaviour of the model. All that needs to be done for employees to perceive AI as an assistant improving their experience and expertise.
The future of cement production relies on transitioning from being an isolated automated industry to a connected, data-led and more self-optimising. The application of artificial intelligence permits the plants to predict equipment failure, improve stability of kilns, reduce energy use and put a higher focus on sustainability. Digital twins and data integration enable the producers to understand the influence of adjustments that come at different stages throughout the production process as far as the entire production line is concerned.
At the same time, technology cannot achieve results by itself. The success of the plant relies on the use of accurate data; verified models, information security measures, efficient process management and knowledgeable personnel. Moreover, it should be taken into account that cement plants do not need to shop today, as the result has to be reached stage by stage.

About the author:
Prerak Manisha Shah, Founder and CTO, Cogniify.ai, is an AI and data engineering expert with experience at Meta and Harvard Medical School. He specialises in machine learning, predictive analytics and enterprise AI, applying data-driven solutions to improve operational efficiency and business outcomes.

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