ENERGETIC AND EXERGETIC ANALYSIS OF BAGASSE & COAL FIRED BOILER USE IN TEXTILE PROCESS PLANT

Transcription

1 ENERGETIC AND EXERGETIC ANAYSIS OF BAGASSE & COA FIRED BOIER USE IN TEXTIE PROCESS PANT Ketan. T. Patel 1, Ketan. R. Chaudhari 2 and Dharmesh B. Patel 3 1,2,3 Mechanical Engg. Department, Government Polytechnic, Waghai Abstract in this study, energetic and exergetic analysis of steam generation device which is use in 25 MW capacities Textile Process and also in captive power plants. To analyze the boiler detailed in energetic and exergetic losses has been presented. Due to economically and reduce environmental pollution by mixing of fuel is best for steam generation plant. Energy analysis give only quantities result while energy analysis presents qualitative result about actual energy consumption. Exergy is maximum theoretical useful work at dead state that may be received from energy in a system of ideal machines. Take all data from T. M. Patel Dying Industries PVT. TD., Kadodra - Surat. So here, energetic & exergetic analysis, exergetic destruction by mixing of bagasse and coal used in boiler to analyze energetic and exergetic analysis done and select best for (4% B+ 6% ) used to produce economical for steam generation. Keywords Boiler Plant, Fuel and its combustion, Energetic & Exergetic analysis, Efficiency calculation, exergetic destruction. I. INTRODUCTION Now a current scenario world energy crisis, which is bound to become more critical, makes it imperative to look for new sources of energy and strive for a more efficient use of existing fuels. Energy demand is more and more now increases and at the same fuel which is use day by day is reduces. Energy sector is one of the important areas in the economic development of any country. Vigorous efforts are being made in almost all the developing and developed countries of the world to find alternative sources of energy. India is second largest country to produce bagasse in the world approximately 14%. In India presently there are more than 571 sugar mills in operation and they produce 2.2 million tons of sugar. Bagasse is the fibrous residue of the sugar cane stalk coming from the mill after crushing and extraction of juice. So there is largest raw material like a fuel is used for Boiler to economical compare to other fuel and produce low pollution. The main problem is to present moisture contents in Bagasse is reduce the performance. So Fuels like ignite coal and Bagasse is mixing with different percentage and analysis of Boiler Direct and Indirect Method and analysis is done on basis of 1 st and 2 nd law, after completing the result which is economic fuel and best suitable for power generation. The objective of this paper is to study the process plant components using the first and second laws of thermodynamics. The concepts of energy and exergy destruction enable us to evaluate the efficiency with which the available energy is consumed. Exergetic analysis provides the tool for a clear distinction between energy losses to the enviornment and internal ireeversibilites in the process. Exergy analysis is a methodology for the evaluation of the performance of devices and processes, and involves examining the exergy at different points in a series of energy conversion steps. The analysis shows that the first law efficiency of Boiler Plant with different fuels like Bagasse and ignite coal and also to use different percentage of them mixing respectively % for (4% B+6% ) is best & as well as exergetic rational efficiency of Boiler Plant is 35.3 %. A. FUES, IT S COMBUSTION & BOIER PANT: - A.1 FUE: - Fuel is, technically speaking, a substance which can chemically react with oxygen and produce heat energy [1]. It can be found in large quantities in nature, it can be transported and stored, it has an acceptable price, and the products of its chemical processes pollute the environment within DOI: /IJMTER FVHB2 17

2 reasonable limits. Its natural substances are of organic origin with more or less combustible parts. The knowledge of the fuel properties helps in selecting the right fuel for the right purpose and efficient use of the fuel. A.2 COMBUSTION: - Combustion involves a chemical reaction during which the interatomic bonds of the molecules of fuel and oxygen are broken and there is rearrangement of atoms in new molecular combination. The new compounds have less energy, and the energy released during combustion equals the difference in the energy of reactants of that of products formed: Fuel + Oxygen CO 2 + H 2 O + N = Heat Products Reactants Fig. 1 Simplified view of solid fuel Combustion is obviously an exothermic reaction; during combustion energy is released to the surroundings in the form of heat which can be used economically for industrial and domestic purposes. Combustion refers to the rapid oxidation of fuel accompanied by the production of heat, or heat and light. Complete combustion of a fuel is possible only in the presence of an adequate supply of oxygen[2]. Nitrogen reduces combustion efficiency by absorbing heat from the combustion of fuels and diluting the flue gases. This reduces the heat available for transfer through the heat exchange surfaces. The objective of good combustion is to release all of the heat in the fuel. This is accomplished by controlling the 3T s of combustion which are: Temp. High enough to ignite & maintain ignition of fuel, Turbulence or intimate mixing of the fuel and oxygen, and Time sufficient for complete combustion. A.3 OVERVIEW OF BOIER PANT: - A boiler is an enclosed vessel that provides a means for combustion heat to be transferred into water until it becomes heated water or steam. Water is a useful and cheap medium for transferring heat to a process. When water is boiled into steam its volume increases about 1,6 times, producing a force that is almost as explosive as gunpowder. This causes the boiler to be extremely dangerous equipment that must be treated with utmost care [3]. The Indian Boilers Act was enacted to consolidate and amend the law relating to steam boilers. Indian Boilers Regulation (IBR) was created in exercise of the powers conferred by section 28 & 29 of the Indian Boilers Act. IBR Steam Boilers means any closed vessel exceeding liters in capacity and which is used expressively for generating steam under pressure and includes any mounting or other fitting attached to such vessel, which is wholly, or partly under pressure when the steam is shut off. II. ITERATUE REVIEW The present reviews the work carried out by various investigators on energy and exergy analysis. Steam and Gas Turbine Plant, Co Generation Plants and chemical and process Industries. More emphasis is given on the power generation industries as it is the aim of the present study. There seems to have less number of studies or reports on the energy and Exergy analyses of bagasse based systems because of using bagasse for producing power and process heat is relatively new technology compared to the conventional coal fired power All rights Reserved 18

3 [1] SR N O AUTHOR (YEAR) 1 Chin W. W. & El Masri arson E.D Si-Doek Oh Hyo-Sun Pang alwnai N PJ Prasad Rao RD Patel CP Panchal Patel K. T. 29 International Journal of Modern Trends in Engineering and Research (IJMTER) TABE 1 SUMMERY OF ITEARTURE REVIEW TITE Exergy analysis of combined cycle Part-2. Bio-mass Gasifier gas turbine co-generation in the pulps and paper industries. Exergy analysis for a gas turbine co-generation system. Exergy analysis for a captive power plant. Exergy Analysis for a gas turbine co-generation plant Energy & exergy analysis for a captive power plant. Energy and exergy analysis of a combined cycle power plant. Energy and exergy analysis of boiler with different fuels like indian, imported coal & SHS oil III. ANAYSIS METHODOOGY Following assumptions are made for present analysis Combustion products are treated as ideal gas. Combustion process in combustion chamber is complete. Kinetic & potential components of exergy are negligible. osses in various pumping devices are not considered. WORK CARRIED OUT Exergy balance analysis of steam bottoming cycle shows the selection of the two pressures evaporator cycles results in improvement in efficiency. Bio-mass Gasifier gas turbine is a technology for bio-mass electricity generation and reduces co 2 emissions at turbine exhaust. Analysis of co-generation system at part load and full load condition & influence of inlet air temp. and relative humidity of inlet air on the performance of the system. Exergy studies and parametric studies to analyze the effect of various parameters on the performance of the plant. Analysis of co-generation system at part load and full load condition. Exergy audit of the plant & comparison of 1 st law and 2 nd law efficiency of the plant. Exergy analysis of the combined cycle power plant with Grassman and Sankey Diagram, with computer programme. 1 st law of efficiency of boiler theoretical is more but 2 nd law exergy efficiency is more reduce and losses of various system identified. Mixing with different fuels to procduced power economical and environmental aspect required. B. 1 ENERGY ANAYSIS Basically Boiler efficiency can be tested by Direct & Indirect method. Direct is old method which is simple and easy but losses are not identified at various stages of boiler system and it is not use now a days. Indirect method is also called as heat loss method. We can idenfified losses of various system and prevent them and increses the efficiency by decresses the losses. The efficiency can be arrived at, by subtracting the heat loss fractions from All rights Reserved 19

4 B.2 EXERGY ANAYSIS The exergy analysis of boiler plant is carried out in order to find out the lost work. i.e. the difference in exergy supplied and exergy output is the lost work of the system or component. The basic Exergy equation for one kg substance in flowing open systems, disregarding kinetic and potential exergy terms is as follows: Ex = (H H ) T (S S ).(1) Hence from T. J. Kotas [4] for dry organic substance contained in solid fuels consisting of C, H, O, and N, with a mass ratio of oxygen to carbon less than.667, the following expression was obtained in terms of mass ratios. Φ dry = x (h/c) +.61 x (o/c)+.44 x (n/c).(2) For the fossil fuels with the mass ratio 2.67 > o/c >.667, which in particular, includes wood x (h/c) [ x (h/c) x (n/c)] Φ dry = x (o/c).(3) Now Chemical Exergy is given as, ε = [C.V x (Moisture)] x Φ x S.(4) Here different sub regions are as follows, Sub Region I Combustion Chamber Sub Region II Heat Transfer to Water Sub Region III Flue gas mixing with atmosphere Exergy balance in the sub region I gives, I 1 = Ex 1 - Ex 2 Ex 2 = n p2 x ε h p2 + Σ n ε p Σ n ε h p = (θ 2 - θ ) Σ n Cp ε And, Ex 1 = m Fuel x ε Fuel.(5).(6).(7).(8) Fig.2 Simplified view of Boiler All rights Reserved 11

5 So, the 2 nd law efficiency of region I is nd η 2 law = (Ex 2 / Ex 1 ) x 1% I 2 = (Ex 2 - Ex 3 ) (Ex S - Ex FW ) nd η 2 law = [(Ex S - Ex FW ) / Ex 2 ] x 1% So, Irreversibility I 3 = Ex 3 Hence the rational efficiency of the boiler is ψ = [(Ex S - Ex FW ) / Ex 1 ] x 1%.(9).(1).(11).(12) A short calculation of flue gas exergy will be provided based upon certain assumptions. Fuel used in calculation is Bagsse with standard composition which is given in Data. Combustion is complete with 5% of air excess and outgoing flue gas temperature is 151 C. Chemical composition as per data Stoichiometric air to fuel ratio: λ = 5.59 : 1 (Total mass of air supplied = 5.59 which is calculated in Energy analysis) Flue gas temperature: θ fg = 151 C ower heating value:.(13) Stoichiometric air quantity:.(14) Flue gas composition: n fg = n CO2 + n H2O + n SO2 + n N2 + n O2.(15) Flue gas mole mass and mole heat capacity: [C mp fg ] 151 = n CO2 [C mpco2 ] n H2O [C mph2o ] n SO2 [C mpso2 ] n N2 [C mpn2 ] n O2 [C mpo2 ] Fuel mass flow rate: q mf = [m s (h S h W )] / [ h (n fg [C mp fg ] 151 θ fg )] n fg.(16).(17) TABE 2 ANAYSIS DATA FOR BOIER Steam generation rate = 5kg/s Steam pressure = 98 bar Steam temperature = 783 K Feed water temperature = 459 K %CO2 in Flue gas = 14 %CO in flue gas =.55 Ambient temperature = 34 K Surface temperature of boiler = 348 K Wind velocity around the boiler = 3.8 m/s Bagasse Fuel Analysis (in All rights Reserved 111

6 Ash content = 1.5 Moisture = 49.2 Carbon content = 9 Hydrogen content = 3.6 Nitrogen content =.6 Oxygen content = 44.5 GCV = 181 kj/kg IV. RESUT AND DISCUSSION Energetic efficiency of the Boiler is calculated after finding out the various losses, which take place in a Boiler. First law analysis shows the efficiency of Bagasse amd igmite coal fired Boiler is gives the energy distribution and losses of various thermodynamic states of Boiler with various fuels used as below table. TABE 3 Energetic Efficiency of fuel used in Boiler SR NO FUE TOTA OSS EFFICIENCY 1 Bagasse ignite coal % B + 8 % % B + 6 % % B + 5 % % B + 4 % % B + 2 % Fig.3 Energetic efficiency & Total oss vs Fuel Exergetic analysis the rational efficiency of this plant takes into account destruction includes the physical and chemical exergy during combustion of fuel in presence of air. In the 2 nd law analysis the maximum loss of exergy is while converting the chemical energy of fuel to that in to heat energy. This is due to the high production of entropy during the process of All rights Reserved 112

7 TABE 4 Exergetic Efficiency of fuel used in Boiler Sr N o Fuel 1 Bagasse ignite coal % B + 8 % % B + 6 % % B + 5 % % B + 4 % % B + 2 % 72.8 I Sub Region III (Rationa II l efficienc y) V. CONCUSION Fig. 4 Exergetic Efficiency of Region I, II & III vs Fuel Here mixing fuel of Bagasse and ignite coal with different percentage (4% B + 6% ) is the best for economical and environment aspect performance of the boiler for the generation of steam. Here huge difference between first and second law efficiency of the boiler such as 7.55% and 35.3% respectively. Maximum saving the annually fuel and financial for using this composition of fuel in the industries process plant. After completion of combustion process of bagasse, ash is mostly use for the raw material of the Brick and Cement manufacturing so pollution is also reduce and complete the cycle of environment. This is due to large amount of energy degradation. This degradation of energy increases the entropy and hence a decrease in the exergy or second law efficiency. REFERENCES [1] Fundamentals for analysis and calculation of energy performance by Z. K. Morvay, D. D. Gvozdenac [2] Energy efficiency in Thermal Utilities by B.E.E. (Bureau of Energy Efficiency), [3] Energy & Exergy analysis of a boiler with different fuels like Indian coal, Imported coal &.S.H. S. oil, M.E. Thesis, MSU Baroda-29 and 1 st National TFMS-212 CKPECT SURAT by Ketan T. Patel. [4] Kotas, T. J. : The energy method of Thermal Plant Analysis, Butter Worths, ondon, [5] Panchal C. P. : Energy and Exergy of A Combined Cycle Power Plant, M. E. Thesis, S.V.N.I.T., Surat, India, 23. Manual for Boiler operation and All rights Reserved 113