FIELD OF INVENTION
The present invention relates to a process for prevention of slagging on
Boiler water wall by blowing boundary air jet along the Boiler water wall.
This boundary air jet blowing system reduces ash melting temperature
near to Boiler water wall in an Indian coal fired Boiler.
BACKGROUND OF THE INVENTION
Slagging is the formation of molten or partially fused deposits of ash on
furnace walls or convection surfaces exposed to radiant heat.
Slag is formed when molten or soft ash particles are not cooled down to
solid state when they reach the hot surface. Typical ash deformation
temperatures (or so called "ash fusion" temperatures) are 1150 to 1250°C.
When furnace gas temperatures is in excess of 1400°C, a semi-molten ash
that may stick to the relatively cooler water walls. Most ash tends to be
re-solidified due to the relatively lower temperature at the tube surface
and the particles fractures on impact and partially bounce back into the
gas stream. However, if the furnace is too small, the exit gas temperature
is too high or the melting point of ash is relatively low, molten ash may
not have enough time to be re-solidified when they hit the heat surface,

therefore they are easy to stick to the surface and cause the accumulation
of deposits leading to slagging.
Depending on the strength and physical characteristic of the deposit,
steam or air soot blower may be able to remove most of them. However,
the base deposit generally remains attached to the tube, allowing
subsequent deposits to accumulate much more rapidly particularly below
the burner zone.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a process to
prevent the slagging and ash deposition by blowing boundary air jet which
eliminates the disadvantages of existing state of art.
An another object of the invention is to propose a process to prevent the
slagging and ash deposition by blowing boundary air jet which enhances
the heat transfer rate by preventing slag in Boiler water wall.
A further object of the invention is to propose a process to prevent the
slagging and ash deposition by blowing boundary air jet which increases
the life of the Boiler water wall.

SUMMARY OF THE INVENTION
The boundary air jet system is placed on bottom of the burner area of the
furnace and it is used for Indian coal fired boilers. This boundary air jet is
flowing over the Boiler water wall. The boundary air jet is preventing slag
formation for Boiler water wall and this boundary air jet (excess air) is also
used for combustion at the top of the furnace zone. The ash melting
temperature is low at near the burn zone of the Boiler water wall when
the boundary air jet is flowing over the Boiler water wall. So the heat
distribution/absorption will be developed evenly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1- Shows an embodiment of the typical Boiler water wall
arrangement with slagging formation.
Figure 2- Shows an embodiment of the "Using boundary air jet to prevent
slagging for Boiler water wall".

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Fig. 1 shows the typical water wall (1) arrangement with slagging (2)
formation for Indian coal fired Boiler. When the ash melting temperature
exceeds the furnace operating temperature, the Slag (2) will be formed on
Boiler water wall (1). So, even heat distribution is affected for formation of
Slagging.
Introduction of high pressure boundary air jet emits from a lancing pipe
inside the boiler prevents the slagging formation for Boiler water wall as
shown in Fig. 2 and this boundary air jet (3) (excess air) is also used to
combustion at the top of the furnace zone. The boundary air jet (3) flow
direction is shown in Fig. 2. This excess air (3) is utilized to combust the
flue gas un-burnt carbon particle. The ash melting temperature will be
reduced when the boundary air jet (3) is flowing over the Boiler water
wall.

WE CLAIM
1. A process to prevent slagging for Indian coal fired boiler by blowing
air comprising:
- a high pressure air jet emits through a lancing pipe is blown
on the slag deposit zone inside the boiler;
characterized in that boundary air reduces the temperature along
the boundary wall of the boiler which prevents the formation of
nucleus and subsequent growth of slag on the wall enabling the
boiler to run with high heat efficiency.

The present invention relates to a process to prevent slagging for Indian
coal fired boiler by blowing air comprising a high pressure air jet emits
through a lance pipe is blown on the slag deposit zone inside the boiler
characterized in that boundary air reduces the temperature along the
boundary wall of the boiler which prevents the formation of nucleus and
subsequent growth of slag on the wall enabling the boiler to run with high
heat efficiency.