Power Plants In India Research Articles

Natural radionuclides from coal fired thermal power plants – estimation of atmospheric release and inhalation risk

Coal, bottom ash and fly ash samples were collected from three different coal-fired thermal power plants in India and subjected to gamma spectrometry analysis for natural radioactivity contents. The results of present study show that fly ash and bottom ash contains two to five times more natural radionuclides than feed coal. None of the fly-ash and bottom ash samples had radium equivalent activities and external hazard index values more than 370Bq kg -1 and unity respectively. However the absorbed dose rate at 1m above the ash pond was 79.19nGyh -1 (average of 3 plants) higher than the global average value of 55nGyh -1 . The corresponding annual external effective dose is estimated to be 0.68mSvy -1 , which is also more than that (0.46mSvy -1 ) in areas of natural background radiation. The 5th percentile, 95th percentile and mean values for total inhalation risk arising from radionuclides (Ra 226 ,T h 228 ,P b 210 and Nat-U) were found to be 3.83 × 10 −9 , 6.50 × 10 −8 and 2.08 × 10 −8 respectively. In India, the rapid increase in thermal generation capacity and at the same time a deterioration of the quality of coal with increased ash content resulted in huge quantity of fly ash and bottom ash of varying properties. The coal contains naturally occurring primordial radionuclide thus the use of coal as a heat source for electric power generation will result in the emission of a variety of natural radioactive elements into the environment. The trace elements in coal that are naturally radioactive are uranium (U), thorium (Th), and their decay products, including radium (Ra) and radon (Rn). Thus coal fired power plant is a major contributor towards the Technologically Enhanced Natural Radiation (TENR) as it results in generation of huge amounts of fly ash and bottom ash containing natural radionuclides. Indian coal used in power plants generally has high ash content and is of lower quality (Mathur et. al., 2003). Presently about 110 million tonnes of coal-ash is generated in India from more than 70 thermal power plants (Sarkar et. al., 2005). By the year 2012 this is predicted to increase to 170 million tonnes per annum (Rajamane, 2003). Thus, fly ash and bottom ash are significant sources of exposure to the naturally occurring radionuclides that affect especially the population in the vicinity of industrial areas. In India, the major portion of fly ash produced goes for disposal in ash ponds and landfills; and a small fraction of it is utilized in construction material (taking advantage of its cementitious or binding characteristic) or as soil amendment (mainly because of its high alkalinity). The openly dumped fly ash poses radiation hazard due to the leachability of radionuclides into the ground water stream ultimately contaminating the drinking waters. The disposal and even the utilization in construction work also leads to exposure to radiation doses to the personals in vicinity. Therefore it is necessary to characterize and quantify the natural radioactivity content in fly ash and bottom ash for subsequent evaluation of the associated environmental and biological risks. The feed coal used in power plants contains various elements, minerals and organic constituents. Upon burn up the elements tend to get enriched in the ashes. Radionuclides which are normally found in the coals get enriched into the ashes after burn up. The concentration of most radioactive elements in

Hot Corrosion & Erosion Problems in Coal Based Power Plants in India and Possible Solutions – A Review

Hot corrosion and erosion are recognized as serious problems in coal based power generation plants in India. The coal used in Indian power stations has large amounts of ash (about 50%) which contain abrasive mineral species such as hard quartz (up to 15%) which increase the erosion propensity of coal. Hot corrosion and erosion in boilers and related components are responsible for huge losses, both direct and indirect, in power generation. An understanding of these problems and thus to develop suitable protective system is essential for maximizing the utilization of such components. These problems can be prevented by either changing the material or altering the environment or by separating the component surface from the environment. Corrosion prevention by the use of coatings for separating material from the environment is gaining importance in surface engineering.

Influence of Chemical Reagents on Rheological Properties of Fly Ash-Water Slurry at Varying Temperature Environment

About 70% of total electrical energy is generated from thermal power plants in India which in turn release about 160 Mt of fly ash as solid waste annually. Transportation and disposal of such a huge amount of fly ash is a major problem faced by the power plants. Presently fly ash is transported as lean slurry in pipe lines requiring about 80 to 85% of water with high energy input. A major impediment in high volume transportation of fly ash is its high specific gravity as compared to that of water. The objective of the present study was to evaluate the rheological characteristics of high concentration fly ash slurry with and without a chemical reagent at varying temperature environment to facilitate smooth flow of materials in the pipelines. Six different composition of fly ash slurry samples were considered for investigation. The main constituents of the slurry were fly ash, water, a cationic surfactant, and a counter-ion. Detailed rheological properties were determined using a cylindrical coaxial rotational rheometer at shear rates varying from 25s to 1000s for 40% solid concentration (by weight). Temperature was varied from 20uC to 40uC for all the shear rates investigated. Test results showed that all the slurries exhibited shearthinning behaviour in the presence of the surfactant. The influence of cationic tenside on drag reduction of fly ash slurry was also studied. The distinctive reduction of surface tension on colloidal dispersion characteristics of the fly ash slurry was observed in the presence of the tenside. It revealed that the slurry developed in the above manner has a potential to be transported through pipelines with minimal energy consumption. f 2011 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 2 September 2011; Received in revised form 5 October 2011; Accepted 8 November 2011

Merchant power plants in India: risk analysis using simulation

PurposeThe purpose of this paper is to understand the risk‐return profile of merchant power plants (MPPs) as compared to power plants with off‐take agreements in the Indian context.Design/methodology/approachInformation from the literature was analyzed to identify major risks associated with MPPs. Literature pertaining to risk analysis of capital investments and simulation technique to analyze risks was studied. Financial models for a power plant with off‐take agreements and that for an MPP were developed and risks have been analyzed by incorporating uncertainties. The risk analysis was performed with the application of stochastic simulations using the Monte Carlo technique.FindingsThe results indicate that risk‐return profile differs significantly for a MPP as compared to a power plant with off‐take agreements. The model indicates that equity internal rate of return (IRR) for MPP ranges between 49.33 and 0.43 per cent with mean IRR values ranging between 28.86 and 13.53 per cent for different scenarios. The mean equity IRR for a comparative power plant with off‐take agreements is 14.83 per cent.Research limitations/implicationsThe project financial models are developed using typical values for the Indian context. The robustness of the results can be improved by considering project‐specific variables in the financial model. Owing to limited availability of past data, power price fluctuation scenarios have been generated based on expert opinion. When additional data on power price become available, these could be incorporated in the simulation analysis.Originality/valueMPP is a new concept for India. There is very little research in this area. This paper makes an attempt to understand the financial risk and return from MPPs in more detail.

Simulation of dust loaded V-I characteristics of a commercial thermal power plant precipitator

A new approach based on finite difference method, is proposed for the simulation of electrical conditions in a dc energized wire-duct electrostatic precipitator with and without dust loading. Simulated voltage-current characteristics with and without dust loading were compared with the measured characteristics for analyzing the performance of a precipitator. The simple finite difference method gives sufficiently accurate results with reduced mesh size. The results for dust free simulation were validated with published experimental data. Further measurements were conducted at a thermal power plant in India and the results compares well with the measured ones.

Characterization of High Carbon Ash from Thermal Power Station Using Pulverized Fuel Combustor

Fly ash collected from a local captive power plant has been fully characterized in respect of its physico-chemical, morphological, and mineralogical features. The high carbon ash consists of large unburnt, irregular carbonaceous particles, which appear to be porous. The non-magnetic particles are more irregular in shape as compared to their magnetic counterpart. Fe bearing crystallites appear in a variety of geometrical patterns on the surfaces of magnetic components. Some of the coarser fractions of the ash have high calorific value and may be used as domestic fuel. The causes for inefficient combustion of the feed coal used have been identified and possible remedies suggested. The presently reported work is expected to be a good beginning for proper management of high carbon ash—generated by several captive power plants in India.

Assessment of scale of hazards due to pool fire for a fossil fired power plant in India

Hazards for a fossil fired power plant located at coastal Gujarat in India have been assessed. The trajectory and spread of the plume from tanks of fossil fired power plant were predicted using existing models named Carter, Mills, Briggs and Zonato during winter and summer seasons with low and high wind speeds observed in day and night hours. Results show that wide areas of habitation and human settlement to the northeast of the site may be potentially under hazards due to southwesterly and southerly winds during summer. Plume heights and widths are found high in the morning hours or late night when wind speeds are low. As wind speed increases around noon, low plume heights and widths are obtained. Length scales become low at low wind speeds and vice-versa. Lethal doses of thermal radiation beyond radial distance of 70 m are within the tolerable limit under hazardous condition.

Flow accelerated corrosion and its control measures for the secondary circuit pipelines in Indian nuclear power plants

A plain carbon steel feeder pipeline in the secondary circuit failed downstream of a flow measurement device (orifice meter) during operation at nuclear power plant. A detailed failure analysis done on the failed pipeline is described in this paper. The results established the fine surface pattern of ‘Horseshoe pits’ at the affected regions. X-ray diffraction analysis on the samples far from the failed regions showed presence of magnetite but on the sample from the failed region showed peaks due to base metal only, indicating dissolution of the oxide. Thickness profiling of the pipeline indicated reduction of thickness from the design 7.62 mm to a minimum of 0.4–1.4 mm at the location of the failure. These observations are characteristic of single phase flow accelerated corrosion. This paper details the extent of flow accelerated corrosion in various Indian power plants and the remedial measures for replacement and possible design and water chemistry changes to combat it.

Sliding wear performance of high-velocity oxy-fuel spray Al2O3/TiO2 and Cr2O3 coatings

High-velocity oxy-fuel (HVOF) spray ceramic oxide coatings have immense potential in industrial applications. However, they are not widely used yet due to the lack of an adequate scientific database created after testing these coatings for specific industrial applications. Two such ceramic coating powders, Al2O3+(40%)TiO2 and Cr2O3, were deposited on AISI 309 SS stainless steel by the HVOF spray technique, in order to enhance its wear resistance. This stainless steel is used in many components of thermal power plants in India, where it suffers one or more types of wear. The as-sprayed coatings were characterized by XRD and SEM analyses. Subsequently, the sliding wear behaviours of the uncoated, HVOF spray Al2O3+(40%)TiO2 and Cr2O3 coated AISI 309 SS were investigated according to ASTM standard G99-03 on a pin-on-disc wear test rig. Cumulative wear rate and coefficient of friction (μ) were calculated for the coated as well as the uncoated specimens for 30, 50, and 70 N normal loads at a constant sliding velocity of 1 m/s. Some of the worn-out surfaces were characterized by SEM analysis. Both the as-sprayed coatings exhibited typical splat morphology of a thermal spray process. The XRD analysis indicated the formation of Al2O3 and TiO2 phases for the Al2O3+(40%)TiO2 coating, and Cr2O3 phase for the Cr2O3 coating. It has been concluded that HVOF spray Al2O3+(40%)TiO2 and Cr2O3 coatings can be useful in minimizing the wear problem of AISI 309 SS. These coatings were found to be successful in retaining their surface contact with the substrate after the wear tests. The HVOF spray Cr2O3 coating can be recommended as a slightly better choice to reduce the wear of AISI 309 SS in comparison with the Al2O3+(40%)TiO2 coating.

Assessment of atmospheric PAHs profile through Calotropis gigantea R.Br. leaves in the vicinity of an Indian coal-fired power plant

Biomonitoring of polycyclic aromatic hydrocarbons (PAHs) in the leaves of Calotropis gigantea R.Br. were performed at seven sites in the surrounding areas of a Thermal Power Plant (TPP), using the gas chromatography and mass spectrometry technique. The primary objective of the study was to monitor the degree of PAHs load in the nearby sites around TPP compared to distant sites. Total PAH (SigmaPAH) concentrations in the leaves ranged from 372.18 (at control site 7) to 4362.35 ng g(-1) d.w. (at highest polluted site 4). The concentration factors ranged from 2.65 to 11.72 for the sites located at 1 km to the point source and 1.0 to 7.08 for distant sites. The share of carcinogenic PAHs to the total PAHs differed with the site, ranging from 10.76% to 26.92%. The sites located closer to TPP have shown higher concentrations of medium and high molecular weight PAHs, which decreased gradually with the distance from the source. The total PAH burden at control site was dominated by the low and medium molecular weight PAHs compounds viz., naphthalene, acenaphthylene, acenaphthene, phenanthrene, fluoranthene, pyrene, chrysene, coronene., whilst at other sites medium and high PAHs viz., fluoranthene, pyrene, benzo (a) anthracene, chrysene, benzo (b) fluoranthene, benzo (e) pyrene and coronene showed the highest values. These results support the biomonitoring ability of Calotropis gigantea R.Br. leaves to monitor PAHs contamination.

Safety in nuclear power plants in India

Safety in nuclear power plants (NPPs) in India is a very important topic and it is necessary to dissipate correct information to all the readers and the public at large. In this article, I have briefly described how the safety in our NPPs is maintained. Safety is accorded overriding priority in all the activities. NPPs in India are not only safe but are also well regulated, have proper radiological protection of workers and the public, regular surveillance, dosimetry, approved standard operating and maintenance procedures, a well-defined waste management methodology, proper well documented and periodically rehearsed emergency preparedness and disaster management plans. The NPPs have occupational health policies covering periodic medical examinations, dosimetry and bioassay and are backed-up by fully equipped Personnel Decontamination Centers manned by doctors qualified in Occupational and Industrial Health. All the operating plants are ISO 14001 and IS 18001 certified plants. The Nuclear Power Corporation of India Limited today has 17 operating plants and five plants under construction, and our scientists and engineers are fully geared to take up many more in order to meet the national requirements.

Composition and size distribution of particules emissions from a coal-fired power plant in India

Particulate matter in fly ash from ESP inlet and outlet of a coal fired power plant in India was measured for five units of 120MW and 210MW of the power plant. Samples of the pulverised coal and bottom and fly ashes were also collected. The size distribution and chemical composition of particulate matter were determined using a laser particle analyser, an ion chromatograph (IC) and an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The observed particle mass concentration at the ESP inlet was 5443–21483mgNm−3 whereas the outlet concentration was found as 12–315mgNm−3 thereby giving total removal efficiency of 95.7–99.8%. A fine particle mode appeared at the particle size of 0.4–0.9μm and coarse particle mode appeared at the particle size greater than 1μm. Magnesium and iron remained in bottom ash and showed high concentrations 99 and 2154μgg−1 (ppmw) respectively, while other elements such as lead, chromium and zinc were observed in higher concentration in ESP inlet flue gas. Relative enrichment of trace elements (except Fe) in fly ash was observed higher than that in bottom ash.

Optimal time for investment to regulate emissions of particulate matter in Indian thermal power plants

ABSTRACTThis study aims to find the optimal switching point for the Indian coal-based power plants to switch to a cost-effective technology and reduce particulate emissions. Regulation in the form of an emission standard, an emissions tax, an ash tax, or a coal tax provides an incentive for the power plants to abate. We have taken a period of 40 years to show the pattern of abatement in a sample of 40 power plants. Linear programming using GAMS has been used for the analysis to determine when the plants will shift to cost-efficient technology. We have first done the analysis on a firm-to-firm basis and then we have aggregated to show the variability of our results.

Measurement of CO 2, CO, SO 2, and NO emissions from coal-based thermal power plants in India

Measurements of CO 2 (direct GHG) and CO, SO 2, NO (indirect GHGs) were conducted on-line at some of the coal-based thermal power plants in India. The objective of the study was three-fold: to quantify the measured emissions in terms of emission coefficient per kg of coal and per kWh of electricity, to calculate the total possible emission from Indian thermal power plants, and subsequently to compare them with some previous studies. Instrument IMR 2800P Flue Gas Analyzer was used on-line to measure the emission rates of CO 2, CO, SO 2, and NO at 11 numbers of generating units of different ratings. Certain quality assurance (QA) and quality control (QC) techniques were also adopted to gather the data so as to avoid any ambiguity in subsequent data interpretation. For the betterment of data interpretation, the requisite statistical parameters (standard deviation and arithmetic mean) for the measured emissions have been also calculated. The emission coefficients determined for CO 2, CO, SO 2, and NO have been compared with their corresponding values as obtained in the studies conducted by other groups. The total emissions of CO 2, CO, SO 2, and NO calculated on the basis of the emission coefficients for the year 2003–2004 have been found to be 465.667, 1.583, 4.058, and 1.129 Tg, respectively.

A Novel tool for assessing slagging propensity of coals in PF boilers

Over the years, wide ranges of testing and evaluating procedures have been developed to predict plant performance. Some of the conventional test results and empirical ratios generated out of it offer poorer predictive capability for slagging behaviour experienced in power plants. For better understanding of the coal properties related to slagging problems, a new coal characterization index based on thermo-mechanical analysis (TMA) has been developed in Research and Development Laboratory, BHEL, Tiruchirapalli. A new sampling set up has been designed to carry out shrinkage measurements using TMA. Coal samples collected from various Indian power plants are evaluated. The shrinkage profile of the ash specimen was recorded and characteristic data from the profile were taken for further calculations. Based on proximate analysis, calorific value of the fuels and the shrinkage data of the ash, a new slagging propensity index was proposed. The new index offers better correlation with field observation and hence the new index proposed, offer better predictive capability for understanding the field slagging observations than the conventional indices. The new empirical index can be used as guidelines for relative assessment of coals with respect to slagging, while designing the boiler and tuning the operational parameters.

Measuring environmental efficiency of industry: a case study of thermal power generation in India

Technical and environmental efficiency of some coal-fired thermal power plants in India is estimated using a methodology that accounts for firm’s efforts to increase the production of good output and reduce pollution with the given resources and technology. The methodology used is directional output distance function. Estimates of firm-specific shadow prices of pollutants (bad outputs), and elasticity of substitution between good and bad outputs are also obtained. The technical and environmental inefficiency of a representative firm is estimated as 0.06 implying that the thermal power generating industry in Andhra Pradesh state of India could increase production of electricity by 6/ while decreasing generation of pollution by 6%. This result shows that there are incentives or win–win opportunities for the firms to voluntarily comply with the environmental regulation. It is found that there is a significant variation in marginal cost of pollution abatement or shadow prices of bad outputs across the firms and an increasing marginal cost of pollution abatement with respect to pollution reduction by the firms. This result calls for the use of economic instruments like pollution taxes instead of command and control regulation used currently in India to reduce air pollution.

An assessment of soil contamination due to heavy metals around a coal-fired thermal power plant in India

Combustion of coals in thermal power plants is one of the major sources of environmental pollution due to generation of huge amounts of ashes, which are disposed off in large ponds in the vicinity of the thermal power plants. This problem is of particular significance in India, which utilizes coals of very high ash content (∼55 wt%). Since the thermal power plants and the ash ponds are located in densely populated areas, there is potential chance for contamination of soil and groundwater of the surrounding areas from the toxic trace elements in the ash. An attempt has been made to study the extent of soil contamination around one of the largest thermal power plants of India located at Kolaghat, West Bengal India. Chemical analysis of the top soils and the soils collected from the different depth profiles surrounding the ash ponds, show that the top soils are enriched in the trace elements Mo, As, Cr, Mn, Cu, Ni, Co, Pb, Be, V, Zn, which show maximum enrichment (2–5) in the top soils collected from all the soil profiles. These elements are also enriched in the pond ash. Since there are no other sources of industrial effluents, it can be said that the enrichment of the trace elements (Mn, Co, Mo, Cr, Cu, Pb, Zn, As, Ni, Be, V) is attributed to their input from ash from the disposal pond. The study has been further strengthened by log-normal distribution pattern of the elements.

Analysis of fly ash heavy metal content and disposal in three thermal power plants in India

The study investigates the heavy metal content of fly ash and bottom ash from three major power plants in North India, using flame atomic absorption spectrometry. It also studies the prevalent disposal methods used at these sites. The ashes were analysed for the presence of Cr, Mn, Pb, Zn, Cu, Ni and Co and detectable levels of all were found in both fly ash and bottom ash. The concentrations of Cr and Zn were highest while Co concentration was less. The wet disposal method is used in two of the power plants (site 1 and site 3). Neither of the sites uses ash pond lining in the construction of the ash ponds, hence leaching of the heavy metals is possible. Site 2 has adopted 100% dry disposal system which allows better utilization but incurs additional costs. Better management practices, increased utilization and proper disposal practices need to be undertaken to minimize the adverse environmental impact.

Regulatory practices for nuclear power plants in India

Atomic Energy Regulatory Board (AERB) is the national authority to ensure that the use of ionizing radiation and nuclear energy in India does not cause undue risk to the health of workers and members of the public, and the environment. AERB fulfills its mission by stipulating and enforcing rules and regulations concerned with nuclear and radiological safety. This paper describes the regulatory authorization process of AERB as applicable to nuclear power plants (NPPs) during their construction as well as operating phases. The safety review process during construction is presented as case studies. Some current issues related to operating plants are also described. Two typical examples of safety upgradations made in old generation nuclear plants are given. The regulatory process in India is continuously evolving to cater to the new developments. Some of the recent initiatives taken by AERB in that direction are briefly described. Today AERB faces new challenges like simultaneous review of a large number of new projects of diverse designs, a fast growing nuclear power program and functioning of operating plants in a competitive environment. This paper delineates how AERB is gearing up itself to meet these challenges in an effective manner.

Regulation of suspended particulate matter (SPM) in Indian coal-based thermal power plants: A static approach

This study aims to find the best policy, which would induce the Indian coal-based power plants to abate particulate emissions in the most cost effective way. The empirical analysis of the power plants suggests that replacing the age-old boilers is of utmost importance along with switching to low-ash albeit expensive coal is cost effective. Installation of pollution control equipment in the form of an ESP or a baghouse depends on the target emission level. In the Indian scenario an ash tax can be considered the best policy instrument along with an emission tax to induce the power plants to adopt the cost efficient technology.