VARIATION OF BOILER EFFICIENCY WITH RESPECT TO BOILER LOADS BY INCREASING OF EXCESS AIR

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2 Int. J. Engg. Res. & Sci. & Tech Arunesh Kumar et al., 2014 Research Paper ISSN Vol. 3, No. 4, November IJERST. All Rights Reserved VARIATION OF BOILER EFFICIENCY WITH RESPECT TO BOILER LOADS BY INCREASING OF EXCESS AIR Arunesh Kumar 1 *, Abhishek Arya 2 and Rahul Kumar Singh 3 *Corresponding Author: Arunesh Kumar arunesh.mechanical@gmail.com The main motive of this study is to identify maximum energy loss areas in any thermal power stations and generate a plan to reduce them using energy and exergy analysis as the tools. The energy sources are decreasing down day by day around the world due to the growing demand and sometimes due to ageing of machinery. Most of the power plants are designed by the energetic performance criteria based not only on the first law of thermodynamics, but the real useful energy loss cannot be justified by the fist law of thermodynamics, because it does not differentiate between the quality and quantity of energy. The main objective of this paper is to survey the technical options for waste heat capture and consider in greater depth of Waste heat capture method through the use of real life examples. Present study deals with the comparison of energy and exergy analysis of thermal power plants stimulated by coal. Our national electricity requirement is about 2100 MW against 1615 MW supply; this is evident of about 21% deficit in terms of power requirements. In view of this situation, greater need of efficiency improvement of a thermal power plants Keywords: Energy, Exergy, Heat balance sheet, Thermal Power Station, Fuel INTRODUCTION Power plant is assembly of systems or subsystems to generate electricity. Power plant generates the electricity result of combustion of fuel into mechanical work and is thermal energy. The availability of electricity and its per capita consumption shows index of national standard of living in the present day and flourishing power generation. The role of efficiency monitoring lies in maximizing generation from power plants. It enhances energy efficiency of the power plant. In order to keep maximum output from a given input, the units must run at the maximum possible efficiency. Power sector is one of the key sectors contributing significantly to the growth of country s economy. Power sector needs a more useful role 1 M.Tech Scholar (Thermal Engineering), Department of Mechanical Engineering, SCOPE Engineering College, Bhopal, India. 2 Assistant Professor, Scholar, Department of Mechanical Engineering, SCOPE Engineering College, Bhopal, India. 3 M.Tech Scholar, Department of Mechanical Engineering, SCOPE Engineering College, Bhopal, India. 307

3 to be played in defining, formulating and implementing the research projects with close involvement of all utilities like solar energy and other various non conventional sources. The increase in energy consumption, particularly in the past several decades, has raised fears of exhausting the globes reserves of coal, petroleum and other resources in the future. The huge consumption of fossil fuels has caused visible damage to the environment in various forms. Every year human activity dumps roughly 8 billion metric tons of carbon into the atmosphere, 6.5 billion tons from fossil fuels and 1.5 billion from deforestation At present India is sixth largest country in the world in electricity generation, having aggregate capacity of 177 GWs out of which 65% is from thermal, 21% from hydro, 3% from nuclear and the rest about 11% is from renewable energy sources. Although over the years, Indian power sector has experienced a fivetime increased in its installed capacity a jump from 30,000 MW in 1981 to over 176, MW by 30 June 2014 but still there is a huge gap in generation and demand in India hence need to be establish more generation plants preferably to be come f rom renewable sources by governmental as well as various private participation. Process of Thermal Power Plants The whole process comprises of generating heat energy in the boiler and then converting heat energy generated in the boiler into mechanical energy in the turbine and further converting this mechanical energy generated in the turbine into electrical energy in the alternator. Coal will be used as fuel in the boiler. The combustion of the fuel generates the heat energy in the boiler. The heat energy transfer to heat transfer area provided in the different area like (bed coils, water wall, steam drawn /mud drum economizer super heater, pre heater. This will be transferred to the water which will pass through and steam is generated and this steam will be further superheated in the super heater so that dry superheated steam will be generated. This steam will be fed into the turbine and this steam expands in the turbine and generates mechanical energy will be converted in to electrical energy. The whole process is comprises in Figure 1. Figure 1: General Layout of Thermal Power 308

4 Aim The main analysis of the study is to find out those areas where energy losses are occurring maximum and modified them for efficient and effective improvement in thermal power station. Objectives The object to satisfy this are To conduct energy calculation of the overall plant and determine the efficiencies and energy losses of all the major components on the power station. Select and modified the areas where energy losses are being experienced. Determine the costs and payback periods for the new technologies suggested for efficiency improvements. Types of Fuel Used in Boiler There are many type of fuel used in boiler to generate necessary heat (Table 1). of the it s thermal energy is converted into mechanical energy which is further used for generation electric power. The steam coming out of the steam turbine is condensed in the condenser and condensate is supplied back to the boiler with the help of the feed pump and cycle is repeated. The function of the boiler is to generate the steam.the function of condenser is to condense the steam coming out of steam turbine at low pressure. The function of the steam turbine is to convert part of heat energy of steam into mechanical energy. The function of feed pump is to raise the pressure of the condensate from the condenser pressure (0.015 bar ) to boiler pressure (200 bar). The other components like economizer, super heater and steam feed heaters are used in the primary circuit to increase the overall efficiency of the thermal power plant. Figure 2: working of Thermal Power Plant Table 1: Various Types of Fuels Used in Boiler Fuel GCV(Kcal/kg) Coal a) Bituminous 4,500 to 6,500 b) Anthracite 6,500 to 7,700 c) Lignite 3,500 to 4500 Furnace oil 10,500 to 11,700 Natural Gas 8,200 to 8,600 KCal/Nm 3 Agro fuels 3,100 to 4,500 Kerosene 11,100 11,100 LPG 11,600 to 11,700 KCal/Kg Working of Thermal Power Plant Steam is generated in the boiler of the thermal power plant using the heat of the fuel burned in the combustion chamber. The steam generated is passed through steam turbine where the part HISTORICAL PROSPECTIVE The scenario of energy in thermal power plant are discussed that fossil fuels contribute 80%, renewable Energy resources contribute 14% and nuclear 6% of world annual energy use. These numbers will soon change as the world s population grows, energy demand rises, inexpensive oil and gas deplete, global warming. Effects continue to rise and urban pollution worsens the living conditions. The development 309

5 Table 2: Heat Balance Sheet Steam Gross S.No. Bioler Generation Calorific Boiler Fuel Load TPH Value Efficiency Consumption Kcal/kg. kg/s Theoretical Requirement Excess 0% Total Table 3: Standard Values Table 4: Efficiency Of Boiler With Different Boiler Loads And 0% Excess Air Grass calorific value of coal Feed water temperature 3300 kcal/kg 180 o c % of oxygen in flue gases 5.5 % of co 2 in flue gases 11 Flue gas temperature C % Hydrogen in fuel 1.2 Ambient temperature Humidity of Theoretical required for boiler Actual mass of supplied Specific heat of superheated steam Boiler pressure Steam temperature Enthalpy of steam Enthalpy of feed water temperature 35 0 C kg/kg of dry 4.58 kg/kg of coal 5.95 kg/kg of coal 0.45k cal/kg,k 96 bar c 3060 kj/kg kj/kg Table 5: Efficiency of Boiler With Different Boiler Loads and 20% Excess Air Steam Gross S.No. Bioler Generation Calorific Boiler Fuel Load TPH Value Efficiency Consumption Kcal/kg. kg/s Theoretical Requirement Excess req.@ 0% Total req.@0%

6 Table 6: Efficiency of Boiler With Different Boiler Loads and 30% Excess Air Steam Gross S.No. Bioler Generation Calorific Boiler Fuel Load TPH Value Efficiency Consumption Kcal/kg. kg/s Theoretical Requirement Excess 0% Total Table 7: Efficiency of Boiler With Different Boiler Loads and 40% Excess Air Steam Gross S.No. Bioler Generation Calorific Boiler Fuel Load TPH Value Efficiency Consumption Kcal/kg. kg/s Theoretical Requirement Excess req.@ 0% Total req.@0% of alternative energy sources and devices will emerge more rapidly to address the world s energy and Environmental situation. Thus, the establishment of a sustainable energy Is one of the most pressing tasks of humanity? With the exhaustion of Fossil resources, the energy economy will change to a chemical and an Electrical base. Mahindra Lalwani and Mool Singh revealed that, India consumes 7% of coal of the world where as China, US, Japan and Rest of the world consumes 43%, 9%, 4% and 20%, respectively. 68% of World s consumption of coal for the generation of electricity. Coal-fired Generation increases by an annual average of 2.3%, making coal the second fastest-growing source for electricity generation. METHODOLOGY AND FORMULAE USED Performance of Steam Generator Evaporation Rate The quantity of water evaporated into steam per hour is called the evaporation rate. It is expressed as kg of steam/h, or kg of steam/h/m 2 of heating surface, or kg of steam/h/m 3 of furnace volume, or kg of steam/kg of fuel fired. Equivalent Evaporation It is the equivalent of the evaporation of 1 kg of water at 100 o C to steam at 100 o C, it requires kj = 2260 kj. Factor of Evaporation The ratio of actual heat absorption above feed water temperature for transformation to steam (wet, dry, or superheated), to the latent heat of steam at atmospheric pressure ( bar) is known as factor of evaporation. Then equivalent evaporation = Actual evaporation Factor of evaporation where m e = [ (h 1 h f ) / h fg ] m s = F m s 311

7 Heat Losses in a Boiler Plant 1. Heat used to generate steam, Q= m s (h 1 h f ) 2. Heat lost to flue gases. The flue gases contain dry products of combustion and the steam generated due to the combustion of hydrogen in the fuel. Heat lost to dry flue gases, Q 1 = m g c pg (T g T a ) m g = Mass of gases formed per kg of fuel c pg = Specific heat of gases T g = Temperature of gases, o C T a = Temperature of entering the combustion chamber of the boiler, o C 3. Heat carried by steam in flue gases- Q 2 = m s1 (h s1 h f1 ) m s1 = Mass of steam formed per kg of fuel due to combustion of H 2 in fuel h f1 = Enthalpy of water at boiler house temperature h s1 = Enthalpy of steam at the gas temperature and at the partial pressure of the vapor in the flue gas 4. Heat loss due to incomplete combustion If carbon burns to CO instead of CO 2 then it is known as incomplete combustion. 1 kg of C releases 10,200 kj/kg of heat if it burns to CO whereas it releases 35,000 kj/kg if it burns to CO 2. if the percentages of CO and CO 2 in flue gases by volume are known, then CO C Mass of C burnt to CO CO CO CO, CO2 = % by volume of CO and CO 2 in flue gases 2 C = fraction of carbon in 1 kg of fuel Heat lost due to incomplete combustion of carbon per kg of fuel, CO C 35, , 200 Q3 CO CO 2 Q 3 CO C CO CO 5. Heat lost due to unburnt fuel Q 4 = m f1 C.V 2 24,800 ki / kg of fuel m f1 = Mass of unburnt fuel per kg of fuel burnt 6. Heat unaccounted Q 6 = Q (Q 1 +Q 2 +Q 3 +Q 4 +Q 5 ) Q = m f C.V = Heat released per kg of fuel Boiler Trial and Heat Balance Sheet There are three purposes of conducting the boiler trial. 1. To determine and check the specified generating capacity. Of the boiler when working at full load conditions. 2. To determine the thermal efficiency of the plant. 3. To draw up the heat balance sheet so that suitable corrective measures may be taken to improve the efficiency. The following measurements should be observed during the boiler trial. 1. The fuel supplied and its analysis. 2. Steam generated and its quality or superheat. 3. Flue gases formed from exhaust analysis. 4. Air inlet temperature and gases exhaust temperature. 312

8 5. Volumetric analysis of exhaust gases. Figure 4: Efficiency Vesus Excess Air 6. Mass of fuel left unburnt in ash. 7. Feed water temperature. The Heat balance sheet is a symmetric representation of heat released from burning of fuel and heat distribution on minute, hour or per kg of fuel basis. RESULTS AND DISCUSSION Vardhman Group is a leading textile conglomerate in India having a turnover of $1009 mn. Spanning over 25 manufacturing facilities in five states across India, the Group business portfolio includes Yarn, Greige and Processed Fabric, Sewing Thread, Acrylic Fiber and Alloy Steel. Vardhman has evolved through history from a small beginning in 1965 into a modern textile major under the dynamic leadership of its chman, S P Oswal. His vision and insight has given Vardhman an enviable position in the textile industry. Under his leadership, Vardhman is efficiently using resources to innovate, diversify, integrate and build its diverse operations into a dynamic modern enterprise. Figure 3: Efficiency Versus Excess Air Figure 5: Efficiency Vesus Excess Air Figure 6: Efficiency Vesus Excess Air 313

9 Figure 7: Efficiency Vesus Excess Air steam generation also varies at different boiler loads. 4. In this study show the variation of with fuel consumption and basically 40% use to reduce the loses and improve boiler efficiency 5. In this study the calculation of efficiency based on 20%, 30%, 40% which gives the excellent variation in boiler efficiency. CONCLUSION The following conclusions have been drawn from the experimental results: This paper show the enervative ideas to reduce losses of boiler and improve boiler efficiency by using the variation of boiler load and also percentage of We conclude the following point which points show in paper and by using of heat balance sheet clearly indicate unnecessary loss of heat. Give some ideas to reduce unnecessary loses and improve boiler efficiency. 1. This study shows the working process of thermal power plants and indicates the performance of boiler which can be improving by using load variation. 2. This study show the performance of Vardhman Yarns, Satlapur, Mandideep in which steam generation has been done at a boiler pressure of 96 bars and temperature approximately 380 degree Celsius. 3. In this study show the variation of fuel consumption for various boiler loads and also 6. In this study we see that at minimum boiler load the efficiency of boiler is minimum in range which is show in graph and with the variation of boiler load efficiency of boiler range also vary which is clearly show in graph. 7. Boiler load and variation help to show the variation in the boiler efficiency. In graph 1.1 we are see that at 0% the boiler efficiency range is maximum and at 40% the boiler efficiency range is minimum REFERENCES 1. Bejan (2002), Fundamentals of Exergy Analysis, Entropy Generation Minimization, and the Generation of Flow Architecture, International Journal of Energy Research, Vol. 26, No. 7, pp Jin H, Ishida M, Kobayashi M and Nunokawa M (1997), Exergy Evaluation of Two Current Advanced Power Plants: Supercritical Steam Turbine and Combined Cycle, Trans. of ASME, Vol. 119, pp Naterer G F, Regulagadda P and Dincer I (2010), Exergy analysis of a thermal power plant with measured boiler and turbine Losses, Applied Thermal Engineering, Vol. 30, pp

10 4. Tekin T and Bayramoglu M (1998), Exergy Analysis of the Sugar Production Process from Sugar Beets, Int. J. of Energy Research, Vol. 22, pp W iser W endell H (2000), Energy Resources: Occurrence, Production, Conversion, Use, ISBM (Alk.Paper). 315

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