• Thermal power generation: challenges ahead

    Jun 2019 / by P K. Chanda

    Indian power sector is undergoing a rapid change in the form of more attention being given in the generation of non-conventional and renewable energy sources. However, this only contributes around 30% while fossil power generation is contributing 70% for which the country will be very much dependent in the coming years too. The concentration of carbon dioxide is one of the major GHGs in the Earth’s atmosphere. It has crossed the historic level of 415 ppm for the first time since the dawn of the humanity. While the use of the super critical technology boilers would curtail the emissions of greenhouse gases from the power sector, it has to be given much preferred option for the installation of the thermal power projects in India in future and it is in the face of climate change issue and the age old sub-critical boilers which are to be phased out. The Paris Agreement aims at limiting the temperature to well below two degree Celsius. In order to achieve this, the world thermal power plants are to reduce carbon dioxide emissions by at least 50 per cent of 2017 levels by the year 2030; it is according to the IPCC report released late in 2018. It is to be noted that the National Integrated Energy Policy of India adopted in 2006 has called for increase coal use efficiency in thermal power sector to nearly 40% with proportionate use of greenhouse gas emmisions, water use and cost of carbon capture and gradually maturing to achieve higher thermal energy conversion efficiency.

    CFD based performance optimization of steam turbines

    Jun 2019 / by R. Sarath

    The design of steam turbines for power plant applications is to aim for higher efficiencies and to improve the heat rate. A major contribution to this aim is expected from reduction of flow losses. The present paper deals with the performance optimization of the steam turbines using Computational Fluid Dynamics (CFD) methodologies. The CFD study includes flow path design and optimization of the LP blade profiles, prediction of pressure recovery of diffuser in exhaust hood, flow pattern in steam turbine components like casing, valves, exhaust hood, bearings etc., and estimation of loss coefficients. The numerical CFD simulations are performed using commercial software Ansys CFX and flow path design using AxStream. The methodologies within the CFD study including conjugate heat transfer analysis (CHT) and flownoise simulations (flow acoustics) are described in detail in this paper. The fluid along with the solid is modelled for conjugate heat transfer analysis to establish the wall heat transfer coefficients, which are used as inputs for further thermal structural analysis. The flow acoustics studies are carried out to establish the flow noise and to optimize the turbine design by reducing the noise levels. The applications of CFD in the design of steam turbine control valves, pressure drop in steam strainer are described in this paper. The strategies described are used to optimize the performance for wider ratings of steam turbines for power plant and industrial applications.
    Keywords: CFD, steam turbine; exhaust hood; loss coefficient; pressure recovery

    Performance evaluation of steam relieving capacity of safety valves of 300 MW power boiler within coal switching limits – a case study

    Jun 2019 / by Chittatosh Bhattacharya

    Sizing of safety valves and adequacy in their steam relieving capacity have enormous importance in achieving maximum steaming capacity of single or multi-fuel fired power generating boilers ensuring operational safety. With a change in worst/best design fuel parametric limits, the boiler steaming capacity is affected, thereby causing the variation in demand of safe steam relieving capacity. Beside that, aging of pressure parts limits the operating pressure thereby increases steam generation demand to maintain boiler maximum continuous steaming rate. All these factors, in turn, affect the performance capability of the precommissioned safety valves. In this paper, the effect of variation of available coal to best design coal is investigated in the context of maximum steam generating capability and therby to identify the adequacy of steam relieving capacity of various safety valves of a 300 MW pulverised coal fired boiler of a thermal power plant running with corner firing, radiant furnace, superheaters, and reheaters and operated with Rankine steam cycle in subcritical regime.

    Operation of supercritical boiler – an overview

    Jun 2019 / by A. Dhavaselvam

    The present energy situation alerts a focused approach towards environmental preservation and cost-effectiveness. Increase in cycle efficiency by adapting supercritical technology is an important step in the reduction of fuel burnt and the greenhouse gas emission. The boiler that operates on critical pressure or above that is known as supercritical boiler. The supercritical boiler is spontaneously converting water into steam but in subcritical it has more circulation to convert the same.

    Different designs of CFBC boilers

    Jun 2019 / by K. Santhanaraj

    Options for generating energy, steam, and heat with the aid of boiler and firing system are greater than ever – as is the demand for relevant know-how in order to make the best possible use of these options. Options for environment-friendly technologies include wind power, solar power, hydro thermal tidal energy, ocean thermal, fluidized bed combustion technologies etc. The first 84 MW thermal output industrial CFBC based power plant in Lunen Germany went on line in the year 1982; it was demonstrated by Lurgi. As on today, over 80 CFBC units rated above 200 MWe operate worldwide. In China alone, total number of CFB boilers in operation by the end of 2007 was 2637 units with total installed capacity of about 40,000MWe; among the total 40,000 MWe CFB boilers, unit capacity between 100-200 MWe was over 100 units and unit capacity of 300 MWe was 8 units in operation.

    Advances in instrumentation and control – an innovative approach to improve power plant efficiency

    Jun 2019 / by K. Ganesan

    Power plants installed in India in the past three decades realized the automation techniques using the conventional control and instrumentation (C&I) technologies existing at that time. In due course of time the availability and reliability the conventional control and instrumentation system could not be ensured due to frequent failure of electronic modules/false signaling in some part of C&I systems at times. R&M of existing C&I systems with the stateof- the-art DCS is the solution for all the problems. The design of distributed control system (DCS) for R&M works in a typical power plant starts with the environmental requirements such as dedicated Precision Air Conditioners, Construction of Remote Input/Output rooms to connect the existing signals etc.

    The space requirements for new cabinets and the methodology of changeover from existing to new system; process parameters measurements and command interface to field retaining the field sensors and devices with new DCS are to be analyzed and engineered to meet the new requirements. The design of system configuration, hardware, software, input output subsystem, automation subsystem, communication subsystem are the main considerations in R&M works. All these design requirements are elaborated.

    The speed of response of DCS, redundancy, advanced controls are designed to meet the specific needs of the existing plant. The design of time synchronization with GPS clock and within the system is also elaborated. The electrical desk interface depicting the complete operation and monitoring of unit and station electrics to facilitate 100% screen based operation necessitates interface logic schemes design. The benefits derived from the R&M works in a typical installation is summarized.

    Profitability prediction in thermal power enterprise based on the improved system dynamics model

    Jun 2019 / by Shuliang Liu and Yijing Liang

    This paper improved the system dynamics model, established the model of the thermal power enterprise profitability. Using Newton interpolation method to optimize the nonlinear function, MATLAB to fitting equation and data analysis. And through the VENSIM to present a simulation. The model is dissertative and validated by some thermal power enterprise’s financial data. This model can provide enterprises with management decision-making reference.
    Keywords: Improved system dynamics model, thermal power enterprises, profitability, prediction

    Environmental issues and challaenges of flue gas desulfurization plants in India

    May 2019 / by P. Rajan and G. Natarajan

    International awareness of environmental concerns has been increasing in recent years as economists forecast explosive growth around the world. Such predictions highlight the importance of minimizing the impact of increased air, water, and solid waste pollutants. One area that has received a considerable amount of attention is the concern about the potential for acid rain that results from the generation of sulfur dioxide (SO2) and nitrogen oxides (NOx) during the combustion of fossil fuels. Particularly notable are the programmes on flue gas desulfurization (FGD) technologies that have been ongoing in a number of countries for several years. Seeking to improve the effectiveness of SO2 emission control, FGD research and development has progressed to the point that an array of processes are available to cover a broad range of site-specific, technical, and economic considerations.

    Indian power sector – challenges and way forward

    May 2019 / by Subhendu Podder and Amar Nath Bhadra

    India is one of the fastest growing economies in the world and is moving ahead with developmental path, and process. Sustaining a fast-paced growth rate and driving a comprehensive development requires addition of major infrastructures like power, road, communication, and transportation. To ensure inclusive growth infrastructure should also grow side by side but to ensure the sustainability that growth shall be in the green path. Historically, the proportion of coal-based thermal power in India is higher that needs correction to ensure sustainability. Greenhouse gases (GHGs) that emit from coal-based combustions, vehicle exhaust, and irresponsible use of pesticides is causing a significant damage in the quality of atmosphere. India recognises the need for sourcing the additional energy requirement mostly from the renewable sources like solar and wind but that has created a new debate on the challenges of thermal power station even with Advanced Ultra Super Critical Technology (AUSCT). The obvious fall-out of the above has increased the business opportunity in renewables in one hand and obsolescence of existing coal-based thermal power generating plants on the other. This paper is aimed at analyzing the real issues and suggesting way forward for long-term sustainability.
    Keywords: Make in India, GHG, challenges, future

    Future of coal-based thermal power plants in India

    May 2019 / by Shaikh Shamser Ali, Ruchi Tyagi, Nidhi M J and Atul Agarwal

    Coal-based power plants in India has played its part significantly and contributed hugely to the economic growth of India. With the passage of time, technological advancement, environmental concerns and economic viability, it may not be advisable to continue anymore with fossil fuel based, mainly coal-based, power plants in India. Low plant load factor, water shortage, additional infrastructural burden, falling generation cost of renewable energy and huge maintenance cost of ageing and old existing power plants add to that ooze making the coal-based power plants less attractive. Existing known fossil fuel reserves can cater us for the next 150 years. Therefore, there is a need for identifying and shifting to other sources of energy in future times.
    Keywords: Fossil fuel, coal-based power plants, thermal energy, power generation, power consumption, renewable energy

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