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Investigation of particulate control in thermal power plant using


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Investigation of particulate control in thermal power plant using

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME149INVESTIGATION OF PARTICULATE CONTROL IN THERMALPOWER PLANT USING ELECTROSTATIC PRECIPITATORSanjay paliwal1, H.Chandra21Research Scholar, Singhania University Jhunjhunu, Rajasthan, India2Department of Mechanical Engineering, Bhilai Institute of Technology, Durg (CG) IndiaABSTRACTAnalysis of particulate control in thermal power plant using electrostatic precipitatorhas been carried out by using standard mathematical models supplemented by the relevantdata collected from Korba East Phase (Ph)-III thermal power plant, under Chhattisgarh StateElectricity Board (CSEB) operating at Korba, Chhattisgarh, India. The mathematical modelshave been used to predict the emission level for different parameters of ESP. In this paperfocuses on the Indian power scenario in view of Coal based thermal power generation.Several types of pollutants emitted from power plant are considered but the main focus of thispaper is air pollutants emitted from thermal power plants. It is shown that significantimprovement in thermal efficiency and environment advantages may be obtained for a coalbased thermal power plant.1 INTRODUCTIONOut of different air pollutants ash is mineral matter present in the fuel. For apulverized coal unit 60-80 % of ash leaves as fly ash with the flue gases. Though there areseveral devices for collection of fly ash, the two efficient (≥ 99 % collection efficiency)emission control devices are fabric filters and Electrostatic Precipitator (ESPs). Fabric filtershas low installation cost but high maintenance cost; and large pressure drop, which reducesthe plant efficiency. The ESP is one of the most widely used devices for controllingparticulate matter especially fly ash. Although they often demand higher capital investment incomparison with gas cleaning methods, the low operating cost and maintenance costs, thehigh collection efficiency (> 99%) & the ability to face severe operating conditions makeESPs suitable in the pollution problems characterizing many process installations such ascoal-based thermal power plants, cement plants, iron industries and glass manufacture [1],[2], [9], [10], [11], [12].INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERINGAND TECHNOLOGY (IJMET)ISSN 0976 – 6340 (Print)ISSN 0976 – 6359 (Online)Volume 4, Issue 3, May - June (2013), pp. 149-154© IAEME: Impact Factor (2013): 5.7731 (Calculated by GISI)www.jifactor.comIJMET© I A E M E
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME150The ESP once designed for a set of parameters to provide certain efficiency willdefinitely not function to the desired level if the designed parameters are changed. Certainlythe design can accommodate a little variance in the parameter but one should not expectmiracle from an ESP. It is costly to replace the old ESPs, however after proper investigations,they can be made function quite efficiently by replacing/ upgrading of some of thecomponents adopting better operational methods [3],[11].Upgrading or designing mostly means taking account of stricter inlet and outletrequirements resulting from the latest emission limits set by public authorities. For this reasona comparison of the original and new rating specifications is imperative. In doing this it isimportant to look at as many as possible previously taken measurement readings, especiallythe measurement made in the course of acceptance tests, and to compare and evaluate themwith reference to the required future performance [5].In this paper analysis has been carried to predict emission levels achieved based onthe dimensional and migration velocity obtained during operation of ESPs selected in KorbaEast Ph-III power plant of CSEB. New parameters of ESPs have been obtained for meetingimproved emission standards.2 SPECIFICATION OF PLANTAs per the requirement of different data for the coal analysis, coal is taken intoaccount from Manikpur coalmines (open cast mines) at Korba district of Chhattisgarh. Theash content has been taken on the basis of collection of five years data of “analysis of coal asreceived from the Manikpur coalmines”. Three cases of ash are analyzed, which are:(i) Minimum ash case: A=38.6%, M=5.5%, V.M=21.6%, F.C=33%(ii) Average ash case: A=42%, M=5.1%, V.M=20.5%, F.C=32.4%(iii) Maximum ash case: A=43.1%, M=5.1%, V.M=19.7%, F.C=32.1%Where A, M, V.M, F.C are ash, moisture, volatile matter, and fixed carbon respectively.The data for the ultimate analysis of the Manikpur coal, on as received basis inpercent is taken from the Central Power Research Institute (CPRI) –materials technologydivision, C.S.E.B, Korba (east) dated 21-02-2012. It is shown as below:Carbon (C) =37.9%, Hydrogen (H) =3.38%, Nitrogen (N) = 0.69%, Sulfur (S) = 0.43%.Now the technical specification of the ESP (used for fly ash collection frompulverized coal fired boiler flue gas) at Korba East Phase (Ph)-III thermal power plant (2×120MW), as provided by [4] is given below:(1) Design conditions: gas flow rate = 215 m3/s, temperature = 1410C, dust concentration(inlet) = 90 gm/Nm3.(2) Type of precipitator: FAA-4*45-2*72-140(3) Number of ESP/boiler = 2(4) Number of gas path/ boiler = 1
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME151(5) Number of fields in series/ gas path = 4(6) Guaranteed collection efficiency for design condition = 99.83 %(7) Treatment time = 33.75 seconds(8) Collection electrodes: total number of collecting plates/ boiler = 2352, nominal heightof collecting plate = 14 m, nominal length of collecting plate = 750 mm(9) Emitting electrodes: type = spiral, number of electrodes/ESP = 10368, spacing (mm) =200/ 300(10) Dust hoppers: number of hoppers/boilers = 16, capacity = 1936 kg(11) Rectifier: rating = 70 kV (peak) 800 mA, number = 8/ESP, type = semiconductordiodes full wave, location = ESP roof(12) Migration velocity = 0.028 m/s(13) Total collection area = 48388 m2(14) Area per gas path = 24193.95 m23 METHODOLOGIES3.1 SamplingFeed coal and electrostatic precipitator (ESP) fly ashes were at Korba East Phase(Ph)-III thermal power plant. The contents of the coal samples have been collected and thepercentages of oxygen (O).For the investigation of particulate matter, using ESPs in thermalpower plant, standard mathematical models are used. To get the collection efficiency of ESPit is required to know the inlet dust concentration to ESP. For this some parameters arerequired and are given below.3.2 AnalysisThe contents of the coal samples have been collected and the percentage of oxygen(O) in the coal is calculated by using following formula [6] taking coal as 100 %:O = 100 – (C+H+N+S+A+M) (1.1)Where, O, C, H, N, S, A, and M are percentage of oxygen, carbon, hydrogen, nitrogen,sulfur, ash and moisture in coal sample.Now the theoretical air-fuel ratio (A/F) is calculated by [7].(A/F)th, m, d = (2.66 C + 7.94 H2 +0.998 S – O2)/ 0.232 kg of air/ kg of fuel (1.2)where, A/F is air-fuel ratio, ‘th’ is for theoretical, ‘m’ is for gravimetric (mass), ‘d’ isfor dry, and C, H2, S, & O2 are percentage of carbon, hydrogen, sulfur, & oxygen in coalsample.(F/A)th, m, d = 1/{(A/F)th, m, d} kg of fuel/ kg of air (1.3)Volume of air = Vair = V1 = mass of air (mair)/ density of air (ρair) m3/ kg of fuel (1.4)
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME152Where, mair = (A/F)th, m, d kg of air/ kg of fuel, and ρair = density of air at 1410C (designcondition temperature of ESP) is 2.556 kg/ m3.Let volume, temperature and pressure of air at Normal Temperature and Pressure(NTP) is V2, T2, and P2 respectively, then:(P1V1)/T1 = (P2V2)/T2 (1.5)Where, P1, V1, and T1 are pressure, volume, and temperature of air ate design condition ofESP. If P1 = P2, T1 = (141+273) = 414 K and T2 = 273 K, then:V2 = (V1T2)/ T1 Nm3/ kg of fuel (1.6)V3 = (V2)/ 1000 Nm3/ gm of fuel (1.7)Inlet dust concentration (m1) = {(F/A)th,m,d ×A×FA}/{EA × V3} gm/Nm3(1.8)Where, A, FA and EA are percentage ash, fly ash (taking as 80%, 85%, and 90%) andexcess air (105%).After getting value of m1 we can perform design analysis of ESP. The collectionefficiency of ESP (η) is given as:η = 1- (m2/m1) (1.9)Where, m2 = outlet dust concentration (gm/Nm3) which has maximum value of 0.150gm/Nm3according to CPCB. The collection efficiency of ESP (η) is also given by Deutsch-Anderson equation [2], [8].η = 1- exp {(-wA)/Q} (1.10)Where, w = migration velocity (m/s), A = total collection area of plates (m2) and Q=volume flow rate of gas stream (m3/s) = 215 m3/s.4 RESULTS AND DISCUSSIONSBy using above mathematical model we will take results for percent change in totalcollection area (as the original total collection area is 48388 m2); for two cases: (i) changingmigration velocity (from 0.028 to 0.04 m/s) & keeping other variables constant, (ii) keepingmigration velocity constant and changing other variables. All the calculation is done for thecases, minimum ash, average ash & maximum ash. When the migration velocity is changingthen results are drawn for each specific outlet dust emissions of 0.150, 0.125, 0.100, 0.075, &0.05 g/Nm3by varying inlet dust concentration (Fig. 1).
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME153Fig.1 Manikpur coal, minimum ash, outlet emission = 0.150 gm / Nm3Also when migration velocity is changing then results are drawn for constant inlet dustconcentration & varying outlet emissions (Fig.2).Fig.2 Manikpur coal, inlet dust concentration = 46.5 gm/Nm3Similarly, when keeping migration velocity constant then results are obtained by varying inletdust concentration (Fig. 3).Fig. 3 Manikpur coal, migration velocity = 0.028 m/s-39-32-25-18-11-4346 48 50 52%ChangeInTotalCollectionAreaInlet Dust Concentration(gm/Nm3)w-0.028w=0.03w=0.035w=0.04Linear (w-0.028)Linear (w=0.03)Linear (w=0.035)Linear (w=0.04)-43-36-29-22-15-8-1613200.04 0.08 0.12 0.16%ChangeInTotalCollectionAreaOutlet Emissions(gm/Nm3)w=0.028w=0.030w=0.035w=0.04Linear (w=0.028)Linear (w=0.030)Linear (w=0.035)Linear (w=0.04)-43-36-29-22-15-8-1613200.04 0.08 0.12 0.16%ChangeInTotalCollectionAreaOutlet Emissions(gm/Nm3)w=0.028w=0.030w=0.035w=0.04Linear (w=0.028)Linear (w=0.030)Linear (w=0.035)Linear (w=0.04)
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 3, May - June (2013) © IAEME154The results reveal that for a constant outlet emission and fly ash percentage, the totalcollection area decreases with the increase in migration velocity. For constant migration velocityand outlet emission, the total collection area increases with the increase in the fly ash percent. Forconstant migration velocity and outlet emission, the total collection area increases with the ashcontent in the coal. i.e. from minimum ash to maximum ash. As far as the efficiency is concerned,it increases with the fly ash percent and the inlet dust concentration while, it also increases withthe ash content but it decreases with the outlet emission at constant migration velocity, fly ashand ash content.5 CONCLUSIONSThe investigation shows in order to meet the better emission standards the size of ESPsshould be increased which is costly affair. A cheaper option is to adapt micro processor controllercharging system which will enhance the migration velocity and hence met the emission standards.The cost of such device will be much cheaper as compared to increase the size of ESP.REFERENCES[1] Gautam Pankaj, “Energy Saving and Efficiency Improvement of ESP”, Dissertation of Energy and Environmental management, Centre for Energy Studies, December 2001.[2] Masters Gilbert M., 2000, Introduction to Environmental Engineering and Science, PrenticeHall of India, New Delhi.[3] Chandra A., and Vanchipurackal Ison V., 14 – 17thMay, 2001, Performance Upgradation ofESP using Difficult Coal, Eighth International Conference on Electrostatic Precipitator, SeriesB-3, Brimingham, Alabana, USA.[4] Flakt, “Installation Operation and Maintenance of ESP Manual”, CSEB, 1990.[5] Frank, Werner J., 18th– 21stJune, 1996, Aspects of ESP Upgrading, Sixth InternationalConference on Electrostatic Precipitator, Budapest, Hungary, pp. 203-208.[6] Sarkar, Samir, 1998, Fuels and Combustion, Orient Longman, Mumbai, pp. 217-256.[7] Culp, Archie W.: Principles of Energy Conversion. 2nd ed., Singapore, Mc Graw-Hill BookCompany, 1984, pp. 100-103.[8] Peavy Howard S., Rowe Donald R. and Tchobanoglous George, 1985 EnvironmentalEngineering, New Delhi, Mc Graw-Hill Book Company, pp. 536-539.[9] White, J.H., 1963, Industrial Electrostatic Precipitation. International Society of ElectrostaticPrecipitation.[10] Srinivas, D.S.R.K., 1996, Status of Electrostatic Precipitator Technology Usage in India, TERIInformation Monitor on Environmental Science, Vol. 1, No. 1, pp. 1-12[11] Ray, T. K., 1990, Parameters Affecting Fly Ash Precipitator Performance, Journal of Institute ofEngineers, Vol. 71, pp. 22-30.[12] Chandra A., Sabberwal S. P., and Mukerjee, A.K., 18th – 21st June, 1996, PerformanceEvaluation of an ESP Using Low Grade coal, Sixth International Conference on ElectrostaticPrecipitator, Budapest, Hungary, pp. 209-214.[13] Vivek singh, Dr. A.C. Tiwari, “Performance Analysis of Electrostatic Precipitator in ThermalPower Plant”, International Journal of Mechanical Engineering & Technology (IJMET),Volume 3, Issue 2, 2012, pp. 431 - 436, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.[14] Manjinder Bajwa and Piyush Gulati, “Comparing the Thermal Power Plant Performance atVarious Output Loads by Energy Auditing (A Statistical Analyzing Tool)”, InternationalJournal of Mechanical Engineering & Technology (IJMET), Volume 2, Issue 2, 2011,pp. 111 - 125, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.