REDUCTION OF PARTICULATE MATTER EMISSION AFTER ELECTROSTATIC PRECIPITATORS RECONSTRUCTION AT UNIT A5 OF THE TPP KOLUBARA

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1 REDUCTION OF PARTICULATE MATTER EMISSION AFTER ELECTROSTATIC PRECIPITATORS RECONSTRUCTION AT UNIT A5 OF THE TPP KOLUBARA M. Erić, A. Erić, P. Škobalj, D. Cvetinović, P. Stefanović Institute of Nuclear Sciences Vinča, Laboratory for Thermal Engineering and Energy P.O.Box 522, Belgrade, Serbia, tel , Long term plan of environmental modernization for Economic Assosiation TPP Nikola Tesla has been prepared in year 2002, which subsidiary is Thermal Power Plant Kolubara. Priority is given to reduction of emission of particulate matters fly ash from the stacks as sources of pollution. Reconstruction of electrostatic precipitators of Thermal Power Plant Kolubara A5 unit have been performed from to Suppliers of electrostatic precipitators guaranteed the outlet concentration of particulate matter in the amount of 50 mg/m 3, which was also confirmed by the guarantee investigation. Reduction of the outlet concentration of particulate matter was achieved by increasing of height and number of collecting electrodes by adding one additional field of electrodes and enhancement of current and voltage characteristics of electrostatic precipitator sections. Guarantee tests were performed by Institute of Nuclear Sciences Vinča, Laboratory for Thermal Engineering and Energy during July 2010, in accordance with standard ISO 9096 (2003). In this paper will be present results of particulate matter emission before and after electrostatic precipitators reconstruction, which will be compared and analized in relation to particulate matter emission limit, which suppliers of electrostatic precipitators guaranteed. Key words: particulate matter, emission, electrostatic precipitator, reconstruction, modernization. 1. INTRODUCTION As one of the biggest polluters thermal power plants invest great amount od money into new facilities for reduction of particulate matter, sulfur and nitrogen oxides. Electrostatic precipitators in Serbian power plants have been in operation for 20 to 35 years or more. The work analyses detemined that performaces are worse than proected values. PE Electric Power Industry of Serbia has adopted a long-term plan of modernization for pollution reduction. Reconstruction of existing electrostatic precipitators in TPP Nikola Tesla (units A1,A2, A4 and A5)

2 and TPP Kostolac (units A1 and A2) has been carried out to dimnish emission of particulate matter below the referent value of 50 mg/nm 3. [1,2]. Tests for particulate matter emissions, before reconstruction of electrostatic precipitators, has shown that the emissions of particulate matter at unit A5 were 259 mg/m 3 in 2006 th and 425 mg/m 3 in 2008 th [3,4]. At unit A5 TPP Kolubara electrostatic precipitators were reconstructed and modernized in the period from to th.. 2. BASIC DATA OF UNIT A5 Unit A5, nominal rate 110 MW became operational 1979 th. The steam boiler produced in the SES, Slovakia has pulverized coal combustion system, natural circulation, drum and reheated steam system. The basic design characteristics of the boiler plant are given in Table 1 [5]. Table 1. Basic design characteristics of the boiler plant at unit A5 Parameter Unit of measure Value Nominal steam production t/h 380 Pressure of superheated steam bar 136 Feeding water temperature 0 C 246 Temperature of superheated / reheated steam 0 C 540/540 Pressure of reheated steam bar 35 Exit flue gas temperature 0 C 180 Characteristics of the lignite from surface coal mining field Kolubara are given in Table [5]. Table 2. Characteristics of the lignite from surface coal mining field Kolubara Parameter Unit of measure Value Net Calorific Value kj/kg 6280 Moisture content % 49 Ash content % 20 Combustible matter % BASIC DATA OF ELECTROSTATIC PRECIPITATORS Manufacturer ZVVZ-Milevsko, Czech Republic has built two electrostatic precipitators at unit А5 ТPP "Kolubara", Veliki Crljeni. Precipitators have been reconstructed and modernized by the company from Poland ELWO and companies from Serbia Energoprojekt-Oprema i Energoprojekt-Entel. Reconstruction was performed in the period from to th.. Electrostatic precipitators are shown in Figures 1-3.

3 Figure 1. Left electrostatic precipitator side view Figure 2. Right electrostatic precipitator rear view

4 Figure 3. Flue gas flow through electrostatic precipitator Gas cleaning system consist of a two one-line electrostatic precipitators (ESP), with three consecutive gas cleaning zones per line (placing 1x3 zones together). First zone of each electrostatic precipitators is additionaly divided by two sub-zones. The precipitator is made of a steel plated chamber ensoconced above the ground level on a rigid supporting structure. Each chamber is topped with a two layer roof covering supporting insulators and electrical equipment. Each filter is bottomed with six ash collecting hoppers pyramidal type (two hoppers per zone), placed along the flue gas flow direction. Connection flanges of bothimlet and outlet nozzles (one inlet and one outlet nozzle) are prepared for horizontal gas duct before and after filter. Internal equipment of

5 electrostatic precipitator consist of collecting plate electrodes and disharge electrodes with appropriate suspension elements and rapping mechanism. Additionaly, the electrostatic precipitator is rigged with a set of necessary platforms, ladders and stairs for comfortable maintenance and service. Electrostatic precipitator inlet nozzle is jonted with sall part of inlet duct: from compensator s flange at outside wall of boiler house. Electrostatic outlet part is jointed with small part of outlet duct to compesator at fan s flange. The basic technical characteristics of the electrostatic precipitator are given in Table 3. Table 3. Technical characteristics of the electrostatic precipitator Tehnical characterisrics of one ESP Before reconstruction After reconstruction Unit A5 Year of unit operational start /reconstruction ESP Flue gas flow (standard conditions, wet gas) Inlet mass concentration of particulate matter (g/m 3 ) Guaranteed elestrostatic precipitator eficiency (%) 98,5 99,9 Number of fields - sections 4 4 Active ESP length (m) 10,2 13,5 Active high of electric field (m) 10,5 14,6 Number of gas passages Width of a gas passage (mm) Primary voltage (V) Primary current (А) - zone 1: 2x210 zone 2: 3: 368 Secondary voltage-peak value without load (kv) Secondary current-average value of field (ma) 1250 section 1 and section 3 and Installed capacity (kva) - section 1 and 2 84 section 3 and Electrostatic precipitator s weight (t) TEST RESULTS Electrostatic precipitators manufacturer guarantees: Particulate matter concentracion at electric precipitator outlet : 50 mg/nm 3 (dry gas, O 2 =6%), only if gases are dedusting from electrostatic precipitator under these conditions: Fuel Type: lignite * net calorific value: 6280 kj/kg * ash content: 20% * moisture content: 59%

6 Inlet flue gas at electrostatic precipitator * flue gas flow Nm 3 /h, dry flue gas ( m 3 /h, wet flue gas with 20% H 2 O) * flue gas temperature o C (номинална 180 o C) * inlet particulate matter concentracion 40 46,6 g/m 3, O 2 =6%, dry flue gas * content H 2 O 17-21% * content O 2 6% Guarantee tests were performed in the July 2010 year by the Institute of Nuclear Sciences''VINČA'', Laboratory for Thermal Engineering and Energy, in accordance with the program performance test, which is in accordance with ISO Six test have been performed at 100 % nominal unit power for both precipitators at the same time. Totally, 12 tests have been performed. Test results of particulate matter emission for both electrostatic precipitators at unit A5 are shown in Figures 3-6. Particulate matter emission [mg/m 3 ] working conditions guaranteed conditions limit value 1L 1R 2L 2R 3L 3R 4L 4R 5L 5R 6L 6R Test number (L-left ESP / R-right ESP) Figure 3. Particulate matter emission test results of ESP at unit A5

7 Electrtrostatic precipitator efficiency [%] 100,0 99,9 99,8 99,7 99,6 99,5 99,4 99,3 99,2 99,1 99,0 guaranteed value 1L 1R 2L 2R 3L 3R 4L 4R 5L 5R 6L 6R Test number (L-left ESP / R-right ESP) Figure 4. Electrostatic percipitator effiency for guaranteed conditions Particulate matter emission [kg/h] 7,0 6,5 6,0 5,5 5,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0,0 1L 1R 2L 2R 3L 3R 4L 4R 5L 5R 6L 6R Test number (L-left ESP / R-right ESP) Figure 5. Particulate matter emission test results in kg/h for guaranteed conditions

8 Particulate matter emission [kg/mwh] 0,07 0,06 0,05 0,04 0,03 0,02 0,01 0,00 1L 1R 2L 2R 3L 3R 4L 4R 5L 5R 6L 6R Test number (L-left ESP / R-right ESP) Figure 6. Particulate matter emission test results in kg/mwh for guaranteed conditions 5. CONCLUSION Tests of 12 electrostatic precipitators have been performed According to the Programme performance at unit A5 of TPP Kolubara. Tests were performed at the same time on the left and the right precipitator. Measured values of particulate matter concentration on electrostatic precipitator exit for guaranteed conditions of the boiler and precipitators are lower than guarantee value of 50 mg/nm 3. The highest single measured value is 26.7 mg/nm 3. Conclusion, based on the measurements, analyzed results, and performed chemical analysis, is that the reconstructed and modernized electrostatic precipitators at unit A5 of TPP KOLUBARA fulfilled guaranteed value in term of particulate matter concentration at the exit of electrostatic precipitators. REFERENCES [1] Erić, M., Stefanović, P., Kisić, D., Reduction Verification of the Particulate Matter Emission after Electrostatic Precipitators Reconstruction at Units A1, A2 and A4 of the TPP Nikola Tesla, TERMOTEHNIKA, 2010, XXXVI, 1, [2] Kisić, D., Žbogar Z., Milić, M., Ćeran, N., Strugar, G., Stefanović, P.,. Erić, M., Reduction of Particulate Matter Emission after Electrostatic Precipitators Reconstruction at the TPP Nikola Tesla A, Proceedins, International Symposium Power Plants 2008, Vrnjačka Banja,2008. [3] ***, State of environment in PE Electric Power Industry of Serbia for 2006, PE Electric Power Industry of Serbia, Belgrade, maj 2007 [4] Gavrić, M., Vlajčić, A., Čeperković, B., The Green Book of Electric Power Industry of

9 Serbia, PE Electric Power Industry of Serbia, Belgrade, june [5] Erić, M., Erić, A., Spasojević, V., Škobalj, P., Stefanović, P., Guaranteed tests of Electrostatic Precipitators at Unit A5 of the TPP Kolubara Veliki Crljeni, Report NIV LTE 455, Institute of Nuclear Sciences Vinča, Vinča, 2010.