Note: Descriptions are shown in the official language in which they were submitted.
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1
Description
Title of Invention: A BURNER
[1] The present invention relates to a burner for introducing solid
particulate fuel to a
burning zone of a kiln such as a rotary kiln for manufacturing cement clinker
or
similar, said burner comprising a centrally located duct for conducting solid
fuel to an
inlet opening and at least one duct for conducting primary air to one or more
annular
nozzles surrounding the inlet opening of the centrally located duct.
[2] Burners of the aforementioned kind are well-known. Normally, the central
duct for
conveying solid fuel in these known burners is configured as one single piece
of a long
pipe, the extent of which typically runs parallel and concentric to the
longitudinal axis
of the burner so that the fuel is introduced to the burning zone in a
direction parallel to
the longitudinal axis of the burner and consequently also to the surrounding
primary
air. Experiments conducted by the applicant of this patent application with
different
types of solid fuel with different particle sizes, forms and densities proved
that the
optimum fuel burnout will not always take place when using parallel
introduction.
Thus it transpired that fine-grained fuels such as coal meal achieve the best
burnout
when introduced parallel to the longitudinal axis of the burner, whilst coarse-
grained
fuels such as various types of alternative fuel, including e.g. plastics,
paper, rubber and
wood chips, achieve the best burnout when entered at an upward angle to the
lon-
gitudinal axis of the burner. Attempts have been made to meet the various re-
quirements of the range of solid fuels as regards i.a. the direction of
introduction by
configuring the burner with more ducts for the introduction of various solid
fuel types,
see e.g. WO 2008-065554 owned by the applicant of this patent application, the
content of which patent is hereby claimed to be included herein. The
disadvantage of a
burner with several ducts for the introduction of solid fuels is the fact that
the quantity
of transport air is increased as the number of ducts increase, and the
quantity of
transport air is therefore relatively large, which is undesirable as it
increases both fuel
requirements and the cost of the burner as the number of ducts increase.
Therefore
none of the known burners are configured optimally as regards the operational
as well
as the financial aspects when they are intended for the introduction of
various types of
solid particulate fuels.
[3] It is the objective of the present invention to provide a burner by means
of which the
aforementioned disadvantages are reduced.
[4] According to the invention, this is achieved by a burner of the kind
mentioned in the
introduction and characterized in that the centrally located duct for
conducting solid
fuel is arranged so that the direction of introduction of the fuel relative to
the lon-
gitudinal axis of the burner and consequently the direction of introduction of
the
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primary air may be adjusted continuously during operation of the burner.
[5] Hereby is obtained a burner with which different types of solid
particulate fuels and
mixtures thereof may be introduced via one and the same duct to the burning
zone of a
kiln so that the quantity of transport air and the cost of the burner are
reduced. This is
because the direction of introduction of the solid fuel relative to the
longitudinal axis of
the burner and consequently the direction of introduction of the primary air
may be
adjusted to the optimal direction for the solid fuels introduced at any time
notwith-
standing the type or mixing ratio of these so as to avoid burnout of the
burner lining
and at the same time achieving a longer introduction path for the fuel.
[6] In principle, the centrally located duct for conducting solid fuels may be
designed in
any way which enables the continuous adjustment of the direction of
introduction of
the fuel relative to the longitudinal axis of the burner during its operation.
E.g. the duct
may be configured as a long pipe which at a point along its length is
pivotally
suspended from a hinge, and which is connected to a mechanism for rotating the
pipe
suspended from the hinge up and down in a vertical plane. As mentioned in the
in-
troduction, the solid fuel duct or pipe is surrounded by at least one annular
duct, the
inner pipe of which defines a pressurised chamber, which by at least one plate
is
blanked off at the inlet end of the burner, said plate being provided with an
opening for
the leading through of the solid fuel duct. For the purposes of limiting the
size of the
opening and thus the gap between the solid fuel duct and the opening as much
as
possible, it is preferred that the solid fuel duct is pivotally suspended from
a hinge,
which is placed immediately next to the opening. If necessary, the gap may be
sealed
using appropriate flexible sealants. In a variation of the burner according to
the
invention, the pressurised chamber mentioned above is not demarcated from the
inner
duct for the injection of primary air, but forms a part thereof.
[7] Burners of the aforementioned type are usually approximately ten metres
long, and
the achievable change to the direction of introduction of the solid fuel would
therefore
be limited to a very narrow interval if the solid fuel duct consists of a
long, non-
flexible pipe. It is therefore preferred that the solid fuel duct is
configured of at least
two parts being connected to each other by means of a flexible connection,
such as a
resilient hose made of, for instance, reinforced rubber, a ball joint or
similar. The
connection between the two parts of the duct does not need to be air-tight as
it is
preferred to maintain the pressure outside the duct at a higher level than the
pressure in
the solid fuel duct. The shorter the part of the duct closest to the inlet end
of the burner
is, the greater is the achievable change to the direction of introduction of
the solid fuel,
which should be possible to be varied within a range between 0 to 30 ,
preferably
between 0 and 15 and most preferably between 0 and 10 relative to the
longitudinal
axis of the burner.
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[8] Alternatively, the duct may be formed in full or in part of a flexible
hose, such as a
reinforced rubber hose, which may be moved using a suitable mechanism between
the
two extreme positions as regards adjustment of the direction of fuel
introduction.
[9] According to the invention, the burner may include additional ducts for
the in-
troduction of other types of fuel, such as oil and gas.
[10] The invention will now be described in further details with reference to
the drawing,
being diagrammatical, and where
[11] Figure la shows a cross-section of the inlet end of a burner according to
the
invention, which is set for the introduction of coarse-grained solid fuel, and
[12] Figure lb shows the same burner set for the introduction of fine-grained
solid fuel.
[13] Figures la and lb depict a burner meant for the introduction of various
types of solid
particulate fuels to the burning zone of a kiln. The burner comprises a
centrally located
duct 1 for conducting solid fuel to an inlet opening 16 and two annular,
concentric
ducts 3, 4 for conducting primary air to an annular nozzle 17, which ducts 3,
4 and
nozzle 17 surround the central fuel duct 1 and the inlet opening 16
respectively. The
solid fuel duct 1 is surrounded by the annular duct 3, the inner pipe 2 of
which defines
a pressurised chamber 15, which at the inlet end of the burner is blanked off
by two
plates 13, which are provided with an opening 14 for the leading through of
the solid
fuel duct 1.
[14] In order to be able to introduce various types of solid fuels with
different particle
sizes, forms and densities as well as combinations thereof in an optimum
manner via
one and the same duct 1 to the burning zone of a kiln so that the quantity of
transport
air and the cost of the burner may be reduced, the duct 1 for conducting solid
fuels is
arranged so that the direction 5 of introduction of the fuel relative to the
longitudinal
axis 6 of the burner and consequently the direction of introduction of the
primary air
may be adjusted continuously during operation of the burner.
[15] Thus the burner may be set to take into account the fact that fine-
grained fuels, such
as coal meal, achieve the best burnout when introduced parallel to the
longitudinal axis
of the burner, as shown in Figure lb, whilst coarse-grained fuels, such as
various types
of alternative fuel, including i.a. plastics, paper, rubber and wood chips,
achieve the
best burnout when introduced at an upward angle to the longitudinal axis of
the burner,
as shown in Figure Ia. In other words, the direction 5 of introduction of the
solid fuel
relative to the longitudinal axis 6 of the burner and consequently the
direction 7 of in-
troduction of the primary air may be adjusted to the optimum direction for the
solid
fuels introduced at any time notwithstanding the type or mixing ratio of
these.
[16] In the illustrated burner, the solid fuel duct 1 comprises two duct parts
8 and 9 which
are connected to each other by means of a suitable connection 10, such as a
flexible
hose or a ball joint. The duct part 9 is pivotally suspended from a hinge 11
placed im-
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mediately next to the opening 14 and may be rotated vertically up and down via
a
mechanism 12 connected to the duct part 8 in the current version, consequently
altering
the direction 5 of introduction of the fuel. The shorter the duct part 9
closest to the inlet
end of the burner is, the greater is the achievable change to the direction 5
of in-
troduction of the solid fuel, which should preferably range between 0 and 10
relative
to the longitudinal axis of the burner.
