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Real time size distribution monitoring of power plant particle emissions
J. Aerosol Sci., Vol. 26. Suppl 1, pp. $675-$676, 1995 Elsevier Science Ltd Printed in Great Britain 0021-8502/95 $9.50 + 0.00
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REAL TIME SIZE DISTRIBUTION MONITORING OF POWER PLANT PARTICLE EMISSIONS Mikko Moisio, Marko Marjam&ki and Jorma Keskinen, Tampere University of Technology, Department of Physics, P.O.Box 692 FIN 33101 Tampere, Finland Tuomas Valmari and Esko I. Kauppinen Technical Research Centerof Finland (VTT), Laboratoryof Heating and Ventilation Aerosol Technology Group, P.O.Box 204, FIN-02151 Espoo, Finland
Keyword$ -- real-time monitoring: particle size distribution: rapping emissions: ESP: ELPI: TEOM INTRODUCTION As the collection efficiency of particulate control devices is increased, the penetration of fine fly ash particles becomes more important. Also the effect of short time scale events, such as rapping of the electrostatic precipitator (ESP) collecting and emitting electrodes, boiler soot blowing and changes of boiler and ESP operation parameters on particulate emissions must be considered (e.g. Matts, 1987) in order to minimize the emissions level. Advanced control of power plant emissions has thus created a need for measuring particle size distributions in near real-time. EXPERIMENTAL A system for measuring particle size distribution and mass concentration in near real-time was used, based on two measurement devices. The Electrical Low Pressure Impactor (ELPI) developed at Tampere University of Technology (Keskinen et al., 1992 and 1993) was used for size distribution measurement and the Tapered Element Oscillating Microbalance (TEOM, Rupprecht & Patashnick Co., Inc.; Valmari et al., 1993) was used for mass concentration measurement. Sampling from the power plant stack was carried out using a sampling system with an isokinetic nozzle, a precut cyclone (cut size of 3 mm) and two ejector-based diluters (Yl&talo et al., 1992; Koch et al., 1988) having 100 as the total nominal dilution ratio. Sampling ports were located downstream the ESP. Comparison measurements were made with ordinary low pressure impactor (LPI). The measurement system was used for monitoring emissions from a full scale peat fired power plant and for determining ESP rappings of a pulverized coal power plant. In both experiments, both short time-scale distribution/concentration changes as well as longer time period (plant power output) trends were recorded. For comparison, total mass concentration was calculated as a function of time for both devices. From the ELPI raw data, the mass concentration was calculated by summing up the concentrations in each size fraction. The integration time of the ELPI was varied from 1 s to 3 min. RESULTS AND DISCUSSION The time resolution of ELPI was found to be adequate for clearly identifying ESP rapping emission peaks. Both of the instruments generally agreed on concentration changes/levels in different operation situations; soot blowing emissions and load level changes of both boilers were easily tracked. Concentrations varied from approximately 1 mg/m3 to 100 mg/m3. The system was found to be suitable for fast monitoring of both particle size distribution and mass $675
$676
M. Molslo et al.
concentration. The ELPI and the TEOM agreed relatively well considering their very different measuring principles. At very low concentrations the ELPI could be operated with shorter integration time, due to the somewhat better sensitivity. Figure 1 shows the mass concentration outputs of the devices during very low concentration operation. The right hand side figure shows the mass size distribution difference between soot blowing and normal operation. Note that the distribution was measured during the higher concentration level.
10. 1000 it
Base
Soot blowing ¢ >
TEOM
[
ELPI
m
E
100
level
....... Soot blow
....,*.~.
1o
3"
1
2 1 0 23:00
o.1 0.01
I
I
0:00
1:00 Time
I
2:00
0.01
0.1
1
10
Particle diem ete r [pro ]
(hh~11m)
Fig. 1. Peat fired power plant: mass concentration and size distribution of different soot blowing emissions of peat power plant. ACKNOWLEDGMENTS: This study has been funded by the Finnish Ministry of Trade and Industry and Tampella Power via environmental engineering research program $1HTI-2. We thank the power plants operating staff for their contribution to the field measurements. REFERENCES Keskinen J., Pietarinen K., Lehtim&ki M.(1992): J.Aerosol Science, Vol23., No. 4, pp.353-360. Keskinen, J., Moisio, M., Hautanen, J., Pietarinen, K., Kauppinen, E.I., Joutsensaari, J., Yl&talo, S. and Valmari, T. (1993) 12th Annual Meeting of the American Association for Aerosol Research. October 11-15, 1993, Oak Brook, Illinois. Koch, W., LSdding, H., MOlter, W. and Munzinger, F. (1988) Staub-Reinhaltung der Luft 48, 341-344. Matts, S. (1987) Proc. The Third Int. Conference on Electrostatic precipitation, October 1987.Abano-Padova, Italy. p. 103. Yl&talo S., Kauppinen E., Hautanen J., Joutsesaari J., Ahonen P., Lind T., Jokiniemi J. and Kilpel&inen M. (1992). European Aerosol Conference, Oxford. J. Aerosol Science, 23, Suppl. 1, pp. 795-798. Valmari S. T., Ahonen P.P, Joutsensaari J., Kauppinen E.I. and Jokiniemi J.K (1993) J. Aerosol Science, 24, Suppl. 1, pp. 303-304.
~,DOl'-amon l
REAL TIME SIZE DISTRIBUTION MONITORING OF POWER PLANT PARTICLE EMISSIONS Mikko Moisio, Marko Marjam&ki and Jorma Keskinen, Tampere University of Technology, Department of Physics, P.O.Box 692 FIN 33101 Tampere, Finland Tuomas Valmari and Esko I. Kauppinen Technical Research Centerof Finland (VTT), Laboratoryof Heating and Ventilation Aerosol Technology Group, P.O.Box 204, FIN-02151 Espoo, Finland
Keyword$ -- real-time monitoring: particle size distribution: rapping emissions: ESP: ELPI: TEOM INTRODUCTION As the collection efficiency of particulate control devices is increased, the penetration of fine fly ash particles becomes more important. Also the effect of short time scale events, such as rapping of the electrostatic precipitator (ESP) collecting and emitting electrodes, boiler soot blowing and changes of boiler and ESP operation parameters on particulate emissions must be considered (e.g. Matts, 1987) in order to minimize the emissions level. Advanced control of power plant emissions has thus created a need for measuring particle size distributions in near real-time. EXPERIMENTAL A system for measuring particle size distribution and mass concentration in near real-time was used, based on two measurement devices. The Electrical Low Pressure Impactor (ELPI) developed at Tampere University of Technology (Keskinen et al., 1992 and 1993) was used for size distribution measurement and the Tapered Element Oscillating Microbalance (TEOM, Rupprecht & Patashnick Co., Inc.; Valmari et al., 1993) was used for mass concentration measurement. Sampling from the power plant stack was carried out using a sampling system with an isokinetic nozzle, a precut cyclone (cut size of 3 mm) and two ejector-based diluters (Yl&talo et al., 1992; Koch et al., 1988) having 100 as the total nominal dilution ratio. Sampling ports were located downstream the ESP. Comparison measurements were made with ordinary low pressure impactor (LPI). The measurement system was used for monitoring emissions from a full scale peat fired power plant and for determining ESP rappings of a pulverized coal power plant. In both experiments, both short time-scale distribution/concentration changes as well as longer time period (plant power output) trends were recorded. For comparison, total mass concentration was calculated as a function of time for both devices. From the ELPI raw data, the mass concentration was calculated by summing up the concentrations in each size fraction. The integration time of the ELPI was varied from 1 s to 3 min. RESULTS AND DISCUSSION The time resolution of ELPI was found to be adequate for clearly identifying ESP rapping emission peaks. Both of the instruments generally agreed on concentration changes/levels in different operation situations; soot blowing emissions and load level changes of both boilers were easily tracked. Concentrations varied from approximately 1 mg/m3 to 100 mg/m3. The system was found to be suitable for fast monitoring of both particle size distribution and mass $675
$676
M. Molslo et al.
concentration. The ELPI and the TEOM agreed relatively well considering their very different measuring principles. At very low concentrations the ELPI could be operated with shorter integration time, due to the somewhat better sensitivity. Figure 1 shows the mass concentration outputs of the devices during very low concentration operation. The right hand side figure shows the mass size distribution difference between soot blowing and normal operation. Note that the distribution was measured during the higher concentration level.
10. 1000 it
Base
Soot blowing ¢ >
TEOM
[
ELPI
m
E
100
level
....... Soot blow
....,*.~.
1o
3"
1
2 1 0 23:00
o.1 0.01
I
I
0:00
1:00 Time
I
2:00
0.01
0.1
1
10
Particle diem ete r [pro ]
(hh~11m)
Fig. 1. Peat fired power plant: mass concentration and size distribution of different soot blowing emissions of peat power plant. ACKNOWLEDGMENTS: This study has been funded by the Finnish Ministry of Trade and Industry and Tampella Power via environmental engineering research program $1HTI-2. We thank the power plants operating staff for their contribution to the field measurements. REFERENCES Keskinen J., Pietarinen K., Lehtim&ki M.(1992): J.Aerosol Science, Vol23., No. 4, pp.353-360. Keskinen, J., Moisio, M., Hautanen, J., Pietarinen, K., Kauppinen, E.I., Joutsensaari, J., Yl&talo, S. and Valmari, T. (1993) 12th Annual Meeting of the American Association for Aerosol Research. October 11-15, 1993, Oak Brook, Illinois. Koch, W., LSdding, H., MOlter, W. and Munzinger, F. (1988) Staub-Reinhaltung der Luft 48, 341-344. Matts, S. (1987) Proc. The Third Int. Conference on Electrostatic precipitation, October 1987.Abano-Padova, Italy. p. 103. Yl&talo S., Kauppinen E., Hautanen J., Joutsesaari J., Ahonen P., Lind T., Jokiniemi J. and Kilpel&inen M. (1992). European Aerosol Conference, Oxford. J. Aerosol Science, 23, Suppl. 1, pp. 795-798. Valmari S. T., Ahonen P.P, Joutsensaari J., Kauppinen E.I. and Jokiniemi J.K (1993) J. Aerosol Science, 24, Suppl. 1, pp. 303-304.