Industrial waste heat is the energy that is generated in processes which is not put into any practical use and is lost, wasted and dumped into the environment. Recovering the waste heat (WHR) can be conducted through various waste heat recovery technologies to provide valuable energy sources. An interview with Triveni Turbine's Arun Mote.

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  Q1. Provide us a brief introduction of your company and its products and services.
A1. Triveni Turbine Ltd. is the largest manufacturer of industrial steam turbines in terms of unit volume in the sub 30 MW range globally. With more than 1 billion operating hours of turbine fleet, the company has installed over 4,000 steam turbines (total 13 GW power generation capacities) across 20 industries. Triveni is present in over 70 countries around the world. Triveni manufactures turbines at its world-class manufacturing facilities located in Bengaluru, India. Triveni Turbines offers steam turbine solutions for Industrial Captive and Renewable Power. Our steam turbines are used in diverse industries, ranging from steel, cement, sugar, textiles, chemical, pulp and paper, petrochemicals, fertilisers, solvent extraction, metals, palm oil to food processing, oil and gas, waste to energy (WtE). Many of the leading cement companies use the steam turbines made by Triveni for recovery of the waste heat.

The company’s product portfolio comprises a large range of back-pressure and condensing steam turbines that are easily customized to suit sector-specific and customer-specific needs. Equipped with a choice of impulse and reaction technology, these turbines can work across a wide range of pressure and flow applications.

The Aftermarket business of the Company, Triveni REFURB, works globally across all brands of rotating equipment leaving a positive footprint on repair, spares, overhauling, efficiency improvements etc upto 300MW including the C-WHR sector.

Q2. Tell us about the progress being made on renewable energy in our country. Where do we stand in comparison to developed economics and what is our goal?
A2. In India, existence of renewable energy began in the early 2000s. With the initiative from the Central and State Governments and implementation of Indian Electricity Act of 2002, certain drive and incentives were given to renewable energy segment like biomass IPP’s, Wind Energy, Solar Energy, WtE, and bagasse based sugar cogeneration.

Renewable energy capacity addition in India for FY20 stands at 9.4 GW, out of which solar power alone contributes 6.4 GW. Wind energy is the second major contributor. Solar and wind energy constitute the utility power generation and are Independent Power Producers ( IPP ) that generates the power to utilities and large users while the non-IPP’s are generating the power for the industrial consumption. Waste heat recovery power plants in the sectors like Sponge Iron, Steel and Cement came into existence from the year 2000 onwards in the Indian market. Earlier in India, cement giants installed cement WHR plants made in China. Over the last decade, Indian boiler and turbine OEM’s offered the products that were indigenously designed and manufactured catering to the ever-changing market demand along with providing sustained long-term aftermarket services. These plants are able to deliver the design outputs consistently.

India is one of the countries with a strong presence of cement WHR power plants. Countries with developed economies like USA, Europe and Japan that have surplus power have not invested in the cement WHR technology.

Q3.Size wise which is the largest Waste Heat Recovery (WHR) project you had executed? What were the challenges?
A3. Cement WHR depends on cement kiln capacity, heat utilization and plant efficiency. Accordingly, potential WHR power generation varies from 4-25 MW. More than 20 MW power generation is quite uncommon.

Triveni provided 22.5MW steam turbine to Prism Johnson Cement WHR plant through the EPC company - ThyssenKrupp Industries. This 22.5 MW steam turbine is an Injection condensing turbine which receives Medium Pressure (MP) steam as inlet and Low Pressure (LP) steam as injection in mid steam path. Steam is collected from 4 No’s of Preheater (PH) boilers and 2 No’s After Quenching Cooler (AQC) Boilers from the two cement kilns of 7000 TPD and 8000 TPD capacity.

It was challenging to take up this project as the steam flow was across multiple sources (i.e. multiple boilers). Steam generation depends on the waste heat generated from hot gas temperature from preheating process and AQC. Due to this there is variation in steam inlet at MP and LP side and load variation in load or power output.

However, commissioning of the turbine was successfully completed despite the challenges that we faced with the quick turbine delivery of 8 months. This sets a benchmark for Triveni in the Cement industry.

Prism Johnson Cement does not have Captive power plant installed and this WHR plant has offered many benefits to them.

On the other hand, Triveni REFURB, is working on providing solution to customers having existing “Turbines without Injection”. These Turbines are re-engineered to allow the additional steam to be injected into the Turbine and improve the efficiency of the plant.

Q4.Throw light on three waste heat power recovery systems. Which has been popular in among cement plants?
A4.Globally there are three processes by which WHR plants are installed in a Cement Industry.

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

In India, Steam Rankine Cycle (SRC) is widely used for WHR power generation across cement plants.

In SRC, exhaust gases from rotary kiln pass through preheaters (PH) to the preheater boiler. Similarly mid tapping from AQC induces hot gases to AQC boiler. One line of cement kiln can give waste heat for 2 PH boiler and 1 AQC boiler for steam generation. These boilers, based on heat source, generate medium pressure (MP) steam of 11 Ata-18 Ata at temperature 300-465 Deg C and low pressure (LP) steam of 2 Ata - 3.5 Ata pressure at temperature 180-205 Deg C.

Injection condensing turbines are widely used for such applications. These turbines use the Medium Pressure (MP) steam as inlet to turbine and inject the LP steam to the LP side of turbine, later this combined steam is expanded at LP/exhaust side to 0.1 Ata or 0.2 Ata based on water cooled condenser or air cooled condenser options.

Generating steam from hot gases is a significant technology in the cement industry. Leading Indian boiler OEM’s have developed expertise in steam generation under various conditions. Similarly, the Injection condensing turbine developed by Triveni for different MP and LP steam combinations are successfully working across the Indian cement sector. These indigenized steam turbines and boilers helps in eliminating the dependency on Chinese boilers and Chinese turbines which were earlier being used in WHR plants till the year 2012-14.

Dependency on Chinese turbines has now declined in the Indian market as the Indian OEM’s adapted to Injection condensing turbines technology with a dominant leadership. As per recent industry estimates, close to 50-60% of cement plants in India have installed WHR based power plants so far and the rest are in the process of setting up the plants in the next 3 to 4 years’ time period.

Large cement companies are mostly considering WHR power plants for their Greenfield projects.

Below table demonstrates the technical parameters benchmarked for available heat per ton of clinker in cement plants that are considered for WHR power generation.

WHR FLOW DIAGRAM

Triveni has a strong reference of Injection condensing turbines supplied to cement WHR plants across India. Specific design consideration is important in injection and admission zone. The rotor designed by Triveni has the higher stability to offset the excitation due to fluctuating injection steam loads. Turbine mid-section and low pressure section is subjected to cyclic fatigue loads induced by thermal cycle and flow variations. To address this issue design and engineering teams carry out CFD analysis and creep fatigue analysis. This design philosophy is a feather in the cap for Triveni for its robust and efficient cement WHR solution.

Typical Admission/Injection cross section of a Triveni Turbine

Thermo-Structural Transient Analysis: Turbine Steam Path

Q5. Which are the sections of Cement Plants from where you recover the heat and which are the sections where there is potential but one cannot recover the heat?
A5. As mentioned, Preheaters which collects hot gases from cement kiln and AQC (After Quenching Chambers/Coolers) are the primary source of heat. Hot gases from these when passed through steam generators/boilers produces medium pressure steam of 11 Ata,300 Deg C to 18 Ata,465 Deg C and LP steam(injection steam) at 2 -3.5 Ata and 180-205 Deg C.

Presently these are sources of heat in cement plants. Heat from the raw mill section or exhaust gases from boilers are unutilized as the heat is of low quality and cannot be used in present form.

To increase the power output in new plants, fire heaters are used where the temperature of hot gases are increased by burning pet coke or low-grade coal. Gas temperature and finally MP steam temperature is increased to 465 -470 deg C. one of the leading cement manufacturer has used this concept in their new cement plants.

Q6. Typically what is payback period of the WHR project? Has it changed over period of time?
A6. Capex investment for WHR projects is Rs.10 Crore per MW power generation. But its Opex cost is very low. No main fuel cost or supplementary fuel is required. Due to the availability of free heat in the form of waste gases from cement manufacturing process, power generation cost is significantly low as compared to CPP power generation or grid power cost. WHR power plants are installed in existing cement plant and new cement plant. The land and other infrastructure are readily available at these sites. There is continuous focus to reduce Capex cost.

In the Aftermarket segment, the re-engineered/efficiency enhanced Turbine offers a payback of 2 years as there will be no modifications on the civil foundation and the existing balance of plant will mostly remain the same.

Q7.What are the offerings of Triveni Turbines for C- WHR power plants.
A7.Triveni has developed efficient Injection condensing turbines which take medium pressure steam as turbine inlet and LP steam as injection steam after certain stages. With addition of 7 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 Integral Lube Oil tank for Power House
  

          Layout and civil cost optimizations of TG House.
          Benefit - Reduction in civil cost of the project.

• MRT – Live steam mechanical run test at Triveni’s manufacturing facility for the steam turbines. Turbine is tested with live steam from boilers at Bengaluru works with job mounted turbo supervisory systems, Woodward governor and gear box.
• In-house Manufacturing- Turbine components like blades, rotor, and casing are manufactured and assembled at Triveni’s facility.
• Vacuum Tunnel – High speed balancing of turbine rotor on “Schenk” Vaccum Tunnel
• Triveni Gear Box- Gear Box (Triveni Power Transmission) assembly is done along with the turbine on the same base plate and converts into a single product. Separate foundation of gear box is not required.

Q8.What is Triveni Turbines contribution to Cement WHR? How it sees road ahead.
A8.Triveni is associated with C-WHR since many years and executed numerous prestigious projects with the leading cement manufacturers.

Following is list of some of key projects successfully executed by Triveni
Turbines in C-WHR sector:
Ultratech Cement – 70MW
Dalmia Cement – 40 MW
Nuvoco Vistas – 20MW
Penna Cement – 30MW
Prism Johnson Cement – 23MW
We are currently working on multiple projects which are in the enquiry and -finalisation stage.
Way forward to cement WHR is the implementation of such projects over the coming years.

Q9.Can WHR energy be treated as renewable energy? What has been approach in our country?
A9.Technically Cement WHR (C WHR) can be treated as renewable energy as the fossil fuels like coal, pet coke are not used. Here combustion of natural resources do not take place. It helps in preserving earth’s diminishing natural resources like coal. It also helps in reducing carbon emission. But in India it is seen as an Industrial consumption or in-house consumption and not for utility. Hence incentives, policy guidelines or the drive from the governments does not exist. Cement sectors have opted the WHR technology and are saving precious resources as coal.

Q10.Do you think bringing WHR under renewable gets more traction? What is the situation in other countries?
A10. Presently 50-60% of cement manufacturing plants have already implemented WHR technology in their cement plants. Big cement manufacturers in India have already installed CWHR in their plants and planning to install in the other plants also. However a few other manufacturers, having one or two manufacturing plants and limited geographical presence are not opting for WHR due to the need for major Capex Investment and financial constraints. If C- WHR is treated as renewable energy source and incentives are offered it will get more traction for WHR power plants.

This will reduce load on the grid power and also helps in saving coal reserves for future generation. The industry associations and sector specific associations can play role in bringing Central Government and State Government ministry’s or Electricity regulators on a single platform. This forum can decide the long and short term policies to promote and implement C- WHR in all plants in India. China is much ahead of us in C-WHR and had over 80% of plants installed C-WHR. Europe, USA and Latin America are planning to implement C-WHR in their cement plants and some International tenders are already under discussions and advance stage of finalization.

A greater push is required for C-WHR in the Indian context and in the upcoming years, Triveni will play a significant role in installing C-WHR 100% across the cement manufacturing plants in India.

About Arun Mote: Arun graduated from I I T Bombay further with a Master’s degree in Mechanical Engineering. Obtained his MBA from Jamnalal Bajaj Institute of Management Studies, Bombay University. Joined Larsen & Toubro Limited as a Management Trainee looking after Caterpillar product line. Subsequently, he changed over to SKF Bearings Limited and was looking after automation and electrical segments. Subsequent he worked with a Central Air Conditioning Company of Blue Star Limited. For last 20 years he is with Triveni Turbine looking after turbine business. Under his leadership, the turbine business has turned around and has grown many times and established leadership in Industrial Turbines in domestic and also in overseas market.