Abstract
Superheater is for generating superheated steam from the saturated steam
from the evaporator outlet. In the case of pulverized coal fired boiler, a
relatively small amount of ash causes problems with ash fouling on the
heating surfaces, including the superheaters. In the convection pass of
the boiler, the flue gas temperature is lower and ash deposits can be
loose or sintered. Ash fouling not only reduces heat transfer from the
flue gas to the steam, but also is the cause of a higher pressure drop on
the flue gas flow path. In the case the pressure drop is greater than the
power consumed by the fan increases. If the superheater surfaces are
covered with ash than the steam temperature at the outlet of the
superheater stages falls, and the flow rates of the water injected into
attemperator should be reduced. There is also an increase in flue gas
temperature after the different stages of the superheater. Consequently,
this leads to a reduction in boiler efficiency. The paper presents the
results of computational fluid dynamics simulations of the first stage
superheater of both the boiler OP-210M using the commercial software. The
temperature distributions of the steam and flue gas along the way they
flow together with temperature of the tube walls and temperature of the
ash deposits will be determined. The calculated steam temperature is
compared with measurement results. Knowledge of these temperatures is of
great practical importance because it allows to choose the grade of steel
for a given superheater stage. Using the developed model of the
superheater to determine its degree of ash fouling in the on-line mode one
can control the activation frequency of steam sootblowers.
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