|ICESP X CONFERENCE PAPER ABSTRACTS 3A SERIES
Held in Cairns,
Conference on Electrostatic Precipitation (ICESP)
is the official conference of the International Society for Electrostatic
PRADIP KUMAR MANDAL AND TANUJ KUMAR
Coal used in Indian thermal power stations is of inferior grade having low heat value andhigh ash content due to drift origin. However, Indian power coal ash is specially known by its refractory in nature and low sulphur (below 0.5%) and alkalis (less than 1.5%) contents. Due to presence of low sulphur and alkalis and consequently having very high ash resistivity (1012 – 1014 O cm) it is difficult to achieve good E.S.P. performance. Majority of Indian thermal power stations have E.S.P. for ash collection.
In the present paper various attempts have been made to analyze the causes of problems in terms of the chemical constituents of ash, resistivity, conductivity, etc. A special emphasis was given to correlate the different forms of sulphur (organic, pyretic and sulphate sulphur) on E.S.P. performance. The total sulphur can not predict the E.S.P. performance; it is the forms of sulphur that decides the performance. Organic sulphur in coal mainly improves the ash resistivity through SO3 adsorption from flue gas whereas pyretic sulphur is responsible for slag and clinker formation in the boiler and evacuated through bottom hoper as bottom ash in dry bottom furnace.
The electrostatic precipitator (ESP) performance is sensitive to fly ash properties. The ESP sizeand design for a new installation has to be carefully selected based on coal and coal ash data together with operating conditions. Experiences from similar installations are utilized as base for new ESP sizes and for upgrading of existing ESP's.
Chinese coals are now often seen in specifications for new plants together with other export coals from e.g. Australia, South Africa and Indonesia. In China new ESP's are built and existing ESP's are upgraded to encounter an increased power demand and comply with more stringent emission requirements. Knowledge about the properties of fly ashes from Chinese coals is necessary to provide a good basis for ESP performance predictions. Mineral analyses and laboratory combustion studies were made for selected Chinese coals to provide deeper knowledge about ash properties, which are of importance for the ESP operation.
Some Chinese coals are
characterized by high aluminum contents in the ash compared to other
commonly used coals. These coals often
generate back-corona conditions in the ESP. A high content
of aluminum in comparison with silica indicates high contents of
minerals like kaolinite and aluminosilicate,
which often have fine mineral size distributions in the coals. Sodium
and iron are generally known to be
beneficial for the ESP operation. In some Chinese coals more sodium
and iron are associated with
aluminosilicates than for non-Chinese coals. The influence of sodium
and iron on ESP performance is
certainly dependent on in which form sodium and iron occur in the
RONGHUA WANG AND KEPING YAN
This paper describes a
new three-phase T/R power source together with its automatic voltage
controller. Since May 2005, the power sources have been applied in
two Chinese 125 MW coal fired power plants. Six months industrial
demonstrations indicated that in contrast to conventional single
phase T/R, the three-phase T/R can significantly increase the corona
current. The voltage ripple is around 3-5% only. Meanwhile, its
power factor is around 0.9. By using the new AVC, upto 60% of
electricity consumption can be saved.
Last updated: May 10, 2009.
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