Investigation of Particulate Emission from a Malaysian Power Plant Firing Australian Coal

A New Plant, Tanjung Bin Power Station, in Jahor, Malaysia reported high opacity readings from the stack when firing an Australian Coal. This paper reports the results of an investigation by a team assembled by Peter Tait, Process Essential, to determine if the properties of the coal contributed to the emissions. We formulated hypotheses of what could cause increased opacity at Tamjun Bin Power Station. These were: 1. miss calibration of the opacity meter, 2. Small particles, 3. electrical properties of the particles and ESP layers, 4.. slippage of particles past the ESP. Tanjung Bin Power Station had two of three 700 MWe units commissioned in at the time of this investigation, January 2008. We took and analyzed samples at 4 location through the electrostatic precipator (ESP), a pulverized coal sample from the conveyor belt feeding the boiler, and the fly ash slipping through the ESP. These samples were analyzed for partile size distribution (PSD), the images were recorded using Scanning Electron Microscope (SEM), and the samples evaluated for elemental analyses. The pulverized coal samples were also analyzed for mineral matter distribution (excluded, included, organically attached mineral matter) The analyses showed: 1. the fly ash from the ESP showed no fine particles. 2. The fly ash from each progressively zone of the ESP showed a natural progression in size. 3. The slippage fly ash contains large particles indicating that sneakage (flue gas by-passing the collection fields) is normal. 4. The quantity of fly ash collected is one order of magnitude lower than predicted by the opacity reading, indicating possible miss calibration of the opacity meter. 6. The resistivity of fly ash is normal and should not result in excess particle emissions. 7. Elements including Ca are not high in the fly ash slippage, indicating elements are not adversely contributing to slippage. 8. Greater slippage of the fine particles past the electric fields in the ESP is considered normal. 9. The resistivity of the fly ash may be causing collection problems.

Investigation of Particulate Emission from a Malaysian Power Plant Firing Australian Coal By John H. Pohl*, Energy International, Laguna Woods, CA, 92637 USA Peter Tait, Process Essentials Pty Ltd, Fortunde Valley( Brisbane), QLD 4006, Australia Southwood, Scott, Ensham Coal Sales Pty Ltd, Brisbane, QLD, 4064, Australia ABSTRACT A New Plant, Tanjung Bin Power Station, in Jahor, Malaysia reported high opacity readings from the stack when firing an Australian Coal. This paper reports the results of an investigation by a team assembled by Peter Tait, Process Essential, to determine if the properties of the coal contributed to the emissions. We formulated hypotheses of what could cause increased opacity at Tamjun Bin Power Station. These were: 1. miss calibration of the opacity meter, 2. Small particles, 3. electrical properties of the particles and ESP layers, 4.. slippage of particles past the ESP. Tanjung Bin Power Station had two of three 700 MWe units commissioned in at the time of this investigation, January 2008. We took and analyzed samples at 4 location through the electrostatic precipator (ESP), a pulverized coal sample from the conveyor belt feeding the boiler, and the fly ash slipping through the ESP. These samples were analyzed for partile size distribution (PSD), the images were recorded using Scanning Electron Microscope (SEM), and the samples evaluated for elemental analyses. The pulverized coal samples were also analyzed for mineral matter distribution (excluded, included, organically attached mineral matter) The analyses showed: 1. the fly ash from the ESP showed no fine particles. 2. The fly ash from each progressively zone of the ESP showed a natural progression in size. 3. The slippage fly ash contains large particles indicating that sneakage (flue gas by-passing the collection fields) is normal. 4. The quantity of fly ash collected is one order of magnitude lower than predicted by the opacity reading, indicating possible miss calibration of the opacity meter. * Author to whom question should be directed at [e-mail] 6. The resistivity of fly ash is normal and should not result in excess particle emissions. 7. Elements including Ca are not high in the fly ash slippage, indicating elements are not adversely contributing to slippage. 8. Greater slippage of the fine particles past the electric fields in the ESP is considered normal. 9. The resistivity of the fly ash may be causing collection problems. BOILER PROBLEM Tanjung Bin had two of the three 700 MWe boilers commissioned at the time of this investigation, January 2008. The plant reported high opacity readings when firing either the subject Australian Coal or a South Africa Coal (Forzando). The meter had been calibrated using a low ash Indonesian Coal with high moisture content. The opacity meter reading is low when burning the Indonesian coals, low when burning the Australian test coal at low loads, but is high at full loads. Fine particles could be the cause of the indicated high emission from the plant. SAMPLES A program to identify the cause of the problem and a solution, if possible, were formulated. The program involved taking ash samples from 4 positions along the ESP, slippage through the ESP, and a coal sample from the conveyor belt feeding the boiler. Figure 1. shows the sample system used. The sample system used is an industrial vacuum cleaner that draws from the duct. The sample is quenched by drawing a controlled amount of air. The amount of air is controlled by tape over the holes to control the flow. ANALYSES These samples were analyzed for: 1. Particle size Distribution (PSD) (performed by Australian Coal Industry Research Laboratory, ACIRL, and Herman Research Laboratory, HRL. 2. Elemental analyses 3. Mineral matter distribution (excluded, included, inherent mineral matter) 4. Resistivity measurement Figure 2. shows the stack for the three boilers. The left hand plume is burning a coal/oil mixture. The right hand plume is burning the test Australian Coal. The picture was taken at 1029 on 19 April 2007. The plume from the test coal is recognizable less opaque than the coal/oil plume. Figure 2. Tanjang Bin Boiler. PARTICLE SIZE DISTRIBUTION (PSD) Particle size under 50 um has the expected progression along the ESP. The number of fine particles increases from zone 1 to 4. The ESP slippage contained unexpected course material. This indicates a possibility of by-pass of course particle past the ESP field (sneakage) Alternatively, this could be a result of agglomeration. However, the size distributions were measured using a Malvern scattering technique. In this technique, sonic vibration is used to separate easily separated particles. Figure 3. shows the PSD of particles less than 50 um. Figure 3. Size Distriabution Data for 50 um Particles. FINE PARTICLE DUE TO CALCIUM The Ca concentration is reasonable uniform along the ESP. Table 1. Shows the concentration of calcium at different zones in the ESP. The slippage is normalized. The amount of slippage ash is only 84.3 % so the slippage was normalized. TABLE 1. Zone 1. CaO-8.80% Zone 2. CaO-8.40% Zone 3. CaO-6.70% Zone 4. CaO-5.60% 0.90%Z1+0.1%Z4-8.76% SLIPPAGE NORMALIZED-8.30% There is little change in the concentration of CaO through the ESP and no change with particle size. Tait(2008), Kadykova and Hibbert (2007) and Lowen (2008). Figure 3. shows the concentration of several elements with particle size. Ca for instant increases from about 2% in particles less than 0.5 um to about 5 % for particles 5-10 um. However in general there is little change in composition with particle size. Figure 3. Calcium Composition of Different Sized Ash Particles. Figure 4. shows the distribution composition for particles less than 20 um. For particle < 20 um no collection issues should develop. Elements are fairly evenly distributed. The concentration of Ca is less in small particles which is the opposite of the hypothesis. Figure 4. Composition Particle Size Distribution RESISITIVITY Resistivity can adversely affect ESP performance. When the resistivity of the ash layer builds up the potential of the field become large and the ash layer ionizes and reverses direction back into the ESP. Figure 5. illustrates ESP performance. Normal Resistitivy is between 10(8) and 10(12) ohm-M. When the resistivity of the ash layer becomes higher or lower than these values ESP collection efficiency begins to fall off. Figure 6. shows the resistivity of fly ash from a number of coals tested by ACRIL. Figure 5. ESP Collection. Figure 7. compares the resistivity of the test coal ash with other coals tested by ACIRL. The results show that the ash of the test coal is quite normal at 10(9)=10(10) ohm-M. Figure 6. Resistivity of Coal Ash Layers. Figure 7. Resistivity of Test Coal Compared to Other Coals Tested by ACIRL. V-I CURVES V-I curve are another way to be sure the ESP is operating with high collection efficiency. Figure 8. Shows the V+I curves collected at the Power Station for peak, average, and minimum voltage. When operating normally the V-I curves should show an increase of V when increases. The minimum voltage for the test coal shows a slight decrease with increasing current. This is a mild indication of back Corona which can lead to poor collection efficiency. Figure 8. V-I Curves for Test Coal in the Tanjung Bin Boiler. OPACITY METER An opacity meter is commonly used to monitor particulate emission. This device measures the obscuring of light. The light is obscured by absorption, reflection, and scattering. The values depend on the particle sizze, projected area, and optical properties of the particles. We measured the mass of particles and found that the mass was about one order of magnitude less than indicated by the opacity meter reading. This has been independently confirmed by an independent investigator that the meter indicated too high emissions. CONCLUSION Formulation of small particle does not seem to be the cause high particle emission. Niether does the resistivity of the ash seem to be a problem. The high calcium does not seem to contribute to emission. The most likely cause of high emission is caused by improper calibration of the opacity meter REFERENCES Tait, Peter, "Final Report: Investigation of Stack Opacity at Tanjung Bin Power Station, Jahor, Malaysia, Process Essential, Brisbane, QLD., Australia, April 2008. Kosasi, Johan and Don Holcombe, "Process Essentials: Interim Report: Analysis and Testing of Pulverized Coal and Fly Ash', Australian Industry Research Laboratory (ACIRL), Booval, QLD., Australia, 7 April 2007. Kadykova, Goulnara and Denny Hibbert, 'Particle Size Distribution of One Sample of Fly Ash", HRL Technology Pty. Ltd., Mulgrave, Victoria, Australia, 27 June 2007. Wilkins, John, "Tanjung Bin Power Station ESP Operating Characteristic and Performance Improvement Options, Indigo, Milton, Qld. Australia, 26 June 2007. Lowen, E., " Elemental Ash Analyses by Particle Size Range", JK-Tech, Indoorpilly, Qld., Australia, April 2008.