EXERGY AND ENERGY ANALYSIS OF 250 MW COAL BASED THERMAL POWER PLANT AT DIFFERENT LOADS

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1 EXERGY AND ENERGY ANALYSIS OF 250 MW COAL BASED THERMAL POWER PLANT AT DIFFERENT LOADS Vibhanshu Vishesh 1, Neel Kanth Grover 2 1 Assistant Proessor, Department o Mechanical Engeerg, BSAITM, Harayana (India) 2 Associate Proessor, Department o Mechanical Engeerg, SBSSTC, Punjab (India) ABSTRACT Power generation plays a most important role the development o country and the livg standards. Ab 80% o electricity produced rom ossil uels and 20% rom renewable resources but now a day we are acg a problem o lackg o ossil uels or long time as per demand generatg. So we need to customize its use and enhance the put eiciency o power plant. Thereore this paper to d the real distribution o energy loss and weak lks electricity production, a 250 MW thermal power plant is taken or example, major equipments o plant under related condition 50%, 80% and 100% loads we present how to improve the eiciencies and whether a urther spection required o 250 MW coal based power plant. So Energy and Exergy analysis have been carried order to evaluate the energetic and exergetic eiciencies o the plant and its components at dierent loadg condition and most o the power plants are designed on the basis o energetic perormance and is based on the First Law o Thermodynamics only. The real useul energy loss cannot be justiied by the First Law o Thermodynamics because it does not dierentiate between the quality and quantity o energy. Energy analysis presents only quantity based result while Exergy analysis presents quality along with quantity based results o the power plant. This paper presents the Exergy analysis is more useul as Energy analysis o coal ired thermal power plants. Key Words: Energy analysis, Exergy analysis, Flow system o power plant, Exergy destruction, Energy and Exergy eiciency, Mass energy and exergy balance equation, Second Law o Thermodynamics. I. INTRODUCTION Energy consumption plays an important role the development o any country and the livg standards o human beg [1]. So the energy supply needs to improve the utilization o energy resource. Thereore, the complexity o power generatg units has creased and this requires thermodynamic calculations with high accuracy. Thereore Energy and Exergy analysis has creasgly attracted the terest or the achievement o the goal. Generally, we evaluate the perormance o thermal power plants through energy analysis criteria which is based on the prciple o First Law o Thermodynamics. But currently we use Exergy analysis which is based on the prciple o Second Law o Thermodynamics has ound a useul method the design process, evaluation, optimization and improvement o thermal power plants. The exergetic perormance analysis does not determe 212 P a g e

2 only magnitudes, location and causes o irreversibility the power plant but also provides more meangul assessment o plant dividual component eiciency. Thereore it can be said that utilizg exergetic and energetic analysis together can give a complete analysis o the power plant system. Energy is always conserved every device or process while Exergy does not conserved but it destroyed. The Second Law analysis o a power cycle gives us to identiy the major sources o loss and shows avenues or urther perormance improvement [2]. With the help o exergy analysis we are able to identiy the location o degradation o energy and rank them terms o their signiicance. The exergy consumption durg a process is proportional to entropy creation due to irreversibility. Exergy consumption or order o destruction is the orm o environmental damage. By preservg Exergy we can crease the eiciency and can be reduce the environmental damage up to limit [3]. 1.1 Energy and Exergy Total energy creates with the sum o available energy plus unavailable energy. Total energy is simply called Energy and available energy is called Exergy. Exergy lows to and rom components however do not balance dicatg a disappearance or consumption o exergy. This disappearance is really a conversion rom available energy to unavailable energy. Consumption shows the amount o loss o available energy. Components consume exergy by virtue o the eectiveness o their ability to transer available energy. In order to compare on basis o quality levels o various energy carriers [4], e.g. uels, it is necessary to determe the equivalents o each energy quantity at a particular grade level. This can be done by usg exergy concept because which overcomes the limitations o the irst law o thermodynamics. An exergy analysis is a useul concept o ecology and sustaability because it can use at a common measure o resource quality along with quantity [5]. In order to perorm the exergy analysis o the plant, the detail steam properties, mass, energy and exergy balances or the unit were conducted. The exergy values o each component are calculated by assumg that the component is an open system and there are only physical exergy associated with the material streams. II.POWER PLANT CONFIGURATION The power plant has three turbes; High, Intermediate and Low pressure turbe (HP, IP and LP) and is connected to the generator. It has also seven heaters which our are low pressure heaters and three are high pressure heaters. 3 CV 1 A STM.C L 1 B 5 K FL T R L DF CO CV 2 I E D BOI S AI P 1 1 H M G. 4 2 W CV 3 1 CO H 1 W 7 Z B A HT 2 G. HT HT HT HT HT Y Figure -1: Flow system o coal ired power plant 213 P a g e

3 2.1 Overall Energy Eiciency Rate o Energy enterg the control volume 3 with uel is: t En m * LHV And, Total energy low rate enterg the control volume 3 is written as [6] En En En 13 The composition o coal which has been considered or the analysis are as: 82.5% C, 5.09% H2, 9.2% O2, 1.66% N2, Ash 12.2%, H2O 10% Now, Energy low rate leavg the control volume 3 with lue gas is expressed as En g g g j j m h And, Total energy low rate leavg the control volume 3 cludg that with circulatg water g En En En 14 The net power put rom the control volume 3 is calculated as: P G P net aux Thereore, the energy eiciency (The First Law eiciency) o the control volume 3 is written as ollows 1 En 2.2 Overall Exergy Eiciency Pnet En Rate o Exergy enterg the control volume 3 with uel [7]: Ex e mnc M c And, Total Exergy low rate enterg the control volume 3 is Ex Ex Ex 13 Now, Exergy low rate leavg the control volume 3 with lue gas is Ex g g g j j m e And, Total Exergy low rate leavg the control volume 3 cludg that with circulatg water g Ex Ex Ex 14 Thereore, the net power put rom the control volume 3 is P G P net aux The Exergy eiciency (The Second Law eiciency) o the control volume 3 is evaluated by usg the ollowg Equation, 214 P a g e

4 2 Ex Pnet Ex III. RESULT PARAMETERS The design data o the plant components o 250 MW coal based thermal power plant have been used or the present energy and exergy analysis to calculate the energy low and exergy low at dierent stages. The energy and exergy eiciencies o the components have been determe usg the equations [8]. Energy and exergy lows rate or the complete power cycle are computed rom the plant design data at 50%, 80% and 100% loadg condition and the results are tabulated as: Table-1: Energy and Exergy eiciency o plant and its component at dierent loads Component Energy Eiciency Exergy Eiciency 50% 80% 100% 50% 80% 100% Overall plant Boiler Turbe Cycle Condenser Condensate extension pump HTR HTR HTR HTR HTR5 (Deaerator) HTR HTR The analysis shows that crease overall energy eiciency and decrease exergy eiciency at 100 percentage o loadg condition. The decrease exergy eiency is shows that the loss o exergy the steam generation unit (Boiler) and turbe. There is strikg dierence the composition o the represented energy and exergy balances. It is noted that the exergy analysis has been utilized or process eiciencies detail and compared to the energy analysis. 215 P a g e

5 Chart-1: Percentage o Energy loss From chart it can be seen that the maximum energy loss occurred condenser. So The First law analysis directs to make our attention towards the condenser improvement and or the plant perormance improvement. Ab 40% o the total plant energy losses occur condenser only and these losses are useless or the generation o electric power. Thus the analysis o the plant based only on the First Law prciples may mislead to the pot that the chances o improvg the electric power put o the plant. Hence the First Law analysis cannot be used to p pot prospective areas or improvg the eiciency o the electric power generation. Chart-2: Percentage o Exergy loss Here chart 2 we can easily seen that how the exergy beg losses the components o the plant and overall plant. It can be observed that the maximum exergy loss occurs the Boiler component and that may be due to the irreversibility o the combustion process the boiler. On another side the exergy destruction rate o the condenser is only 12%.So the real losses the boiler where entropy was created. Hence Exergy analysis 216 P a g e

6 (Second law o Thermodynamics) shows that the boiler section has need to urther spection or the improvement o perormance o power plant not the condenser. The calculated exergy eiciency o the overall power cycle is 28% at 100% load. It means that we have a improvement chance ab 72% i.e. are available or improvement [9]. IV. CONCLUSIONS Energy and Exergy analysis here concluded that, this study proves more useul because it easily shows that which analysis is more eicient or the improvement o power plant and where the urther spection required through the steam generation. It gives a logical and practical solution to achieve the goal o more eicient put. From the data considered and the requent analysis gives the ollowg conclusions: From the analysis it is ound that exergy eiciency is lower than energy eiciency. It has been observed that 27% exergy loss occur boiler which shows boiler is not ully adiabatic and the combustion may not be complete properly. This large exergy loss ocurrs due to the combustion reaction and the large temperature dierence durg heat transer between gas and steam. When we compare it with overall plant put, we ound more exergy loss ocurss boiler. The maximum energy destruction occurs the condenser which guides to eicient heat transer between hot stream and cold stream. Poor load energy eiciency is aspects to higher relative energy rejection. On the other hand, bad poor load exergy eiciency is not due to higher relative exergy rejection but caused by higher relative exergy consumption. Results show that a little deviation perormance o HP heaters will have greater impact on cycle eiciency because HP heaters deals with higher temperature dierence between eed water and extraction steam consume i.e larger quantity o exergy. When First Law o Thermodynamics analysis does not dicate perormance deterioration while exergy analysis ppots eiciencies and dicate avenues or improvement. Energy analysis results lead to erroneous conclusion that major loss is associated with the heat rejection at the condenser, while exergy analysis quantitatively demonstrates that only a very small amount o work potential is lost the condenser (sce the heat is rejected nearly at the ambient temperature). Operation and matenance decisions based on exergy analysis o the power plants proved more eective. Exergy based approach o perormance monitorg operatg power plants helps better management o energy resources and environment. REFERENCES [1]. Hasan, HE., Ali, VA., Burhanett, Ahmet, D., Suleyman, HS., Bahri, S., Ismail, T., Cengiz, G., Selcuk, A., Comparative energetic and exergetic perormance analysis or coal-ired thermal power plants Turkey, International Journal o Thermal Sciences 48: ,2009. [2]. Kotas, TJ., The Exergy Method o Thermal Plant Analysis, Butterworths: London, P a g e

7 [3]. Rosen, MA., Dcer I., "Thermoeconomic analysis o power plants: an application to the coal ired electrical generatg station, "Energy Conversion and Management 44 (2003) [4]. Sachdeva, K.B. and Karun, Perormance Optimization o Steam Power Plant through Energy and Exergy Analysis, International Journal o Current Engeerg and Technology, Vol.2, No.3, Sept, [5]. Kaushika, S.C., Reddya, V.S., and Tyagib, S.K., Energy and exergy analysis o thermal power plants: A review, Renewable and Sustaable Energy Reviews 15, , [6] Bejan, A., Fundamentals o Exergy Analysis, Entropy Generation Mimization, and the Generation o Flow Architecture, International Journal o Energy Research, Vol. 26, No. 7, pp , [7] M.J., Moran MJ, H.N., Shapiro. Fundamentals o engeerg thermodynamics. NewYork :John Wiley; [8] Rudra, S., Shim, H.M. and Kim, H.T., Exergetic analysis o coal ired thermal power plants based advance steam parameters, 4 th BSME-ASME International Conerence on Thermal Engeerg, December, [9] Jayamaha, Lal, In: Energy Eicient Buildg Systems, Hard book. McgrawHill education, Europe, 2008 BIOGRAPHIES Er. Vibhanshu Vishesh, Assistant Proessor (Mechanical Engeerg), BSAITM, FBD, India Dr. Neel Kanth Grover, Associate Proessor (Mechanical Engeerg), SBSSTC, FZR, India 218 P a g e