CLEANABLE CIRCUMFERENTIALLY FINNED HEAT EXCHANGER

ECHANGEUR DE CHALEUR A AILETTES INTERNES DECRASSABLES

English Abstract

CLEANABLE CIRCUMFERENTIALLY FINNED HEAT EXCHANGER

Abstract of the Disclosure
A heat exchanger for use in a particle laden gas stream and
employing a plurality of circumferentially finned tubes. The tubes
are arranged in line with respect to gas flow, and a soot blower uses
an elongated tubular element with nozzles projecting steam downwardly
between the in-line finned tubes. The soot blower is movable to
traverse the heat exchanger. And the blowing medium may be
interrupted when the soot blower is in line with the tubes.




C790160

Claims

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CLAIMS
1. A heat exchanger arrangement for transferring heat
from the flow of particle laden hot gases to a flow of fluid com-
prising: a duct for confining the flow of gases; a plurality of
circumferentially finned tubes located within said duct, with the
axis of said tubes perpendicular to the flow of gases, said tubes
arranged in a plurality of rows transverse to the gas flow, the tubes
of each row being in line with respect to gas flow; means for passing
the flow of fluid through said finned tubes; a soot blower comprising
a tubular blowing element having its axis parallel to said finned
tubes and having nozzle openings directed parallel to the flow of
gases and toward said circumferentially-finned tubes; means for
traversing said tubular blowing element across said duct in a direc-
tion perpendicular to the axis of said element; and means for passing
a flow of blowing medium through said blowing element.
2. A heat exchanger arrangement as in Claim 1 having also:
means for interrupting the flow of flowing medium when the nozzles of
said element are in alignment with said finned tubes.

Description

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i CLEANABLE CIRCUMFERENTIALLY FINNED HEAT EXCHANGER

Backaround of the Invention
The invention relates to a heat exchanger arrangement and,
in particular, to an arrangement for use in a particular laden gas
stream.
With the present day trend moving towards coal firing, with
; the development moving in the direction of gasification systems
handling charred-ash laden gases, the need for inexpensive, compact
heat exchangers to hold down design cost has grown in importance.
10Spiral-finned surface affords one oF the best opportunities
to affect the desired economy since it produces a material, space and
cost saving. Moreover~ it is a form of extended surface that can be
efficiently produced.
Although this surface has been applied with economy for gas-
and oil-fired units, and for some coal-fired units, it is not possible
to design spiral-finned heat exchangers for particulate-laden gases
with assurance that surface failing will not be a problem. This di~fi-
; culty ar;ses because there is no effective way to clean these surfaces
as they are arranged. Rotating soot blowers are ineffective because
of the staggered-lame tubing disposition and because of the presence
of fins

Summary of the Invention
The invention comprises a heat exchanger arrangement using
circumferentially finned tubing located within a gas flow duct with
the tubes arranged in in-line relationship. A soot blower includes

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a tubular blowing elernent located adjacent the tube bank with the
element arranged parallel to the tubes and ~ith nozzles in the
element arranged to blow between the in-line tubes in a direction
parallel to the gas flow. The soot blowing element traverses the
width cf the duct so that it blows between each line of tubes in
turn. The blowing medium may be interrupted when the nozzles are
in line with the tubes of the tube bank.

Brief Description of the Draw~
Figure 1 is a sectional side elevation illustrating the
heat exchange arrangement;
Figure 2 is a sectional view taken through 7ine 2-2 of
Figure 1, and
Figure 3 is a detail view taken in the area of the center
of the soot blowing element as indicated by section 3-3 of Figure 2.

Description of the Preferred Embodiment
A gas duct 10 confines a -flow 12 of particle laden hot gas.
Such gas may be from a coal-fired furnace or a coal gasifier. A
plurality of tubes 14 are circumferentially finned to supply ex-
tended heating surface such as by the use of spiral fins. Such
finning increases the effective heating surface of the tubes but is
subject to plugging in a dust laden atmosphere.
A plurality of these tubes are connected in series flow
relationship with a flow of fluid such as water forced through the
tubes by means of pump 16. This may be a feedwater pump for a steam
~enerator or it may be a recirculating pump -for a gas-to-gas heat
exchanger system with a fluid loop.
The axis of the tubes 14 is perpendicular to the flow of
gases, and the tubes are arranged in a plurality of rows 18, 20, 22
transverse to the gas flow. The tubes of each row such as tubes 24,
26, 28 and 22 are in line with respect to gas flow. The tubing as
arranged has a one-inch space between the edges of fins o-f adjacent
tubes in ~he horizontal plane and one-half inch clear between fins


in a vertical plane.
A soot blower 30 includes a tubular blowing element 32
having its axis parallel to -the finned tubes 14. It includes nozzle
openings 34 on the bottom and top sides of the element arranged to
direct the flow of fluid flowing through the element upwardly and
downwardly parallel to the direction of the flowing gases.
A blowinq medium such as steam or air is passed through
supply line 36 through control box 38 and thence through a tube 40
to the blowing element. In the location shown it can be seen that
; 10 a stream of blowing mediurn can be projected upwardly and/or down-wardly between the rows of tubes thereby achieving effective pene-
tration and cleaning of the finned surfaces.
Control box 38 also includes means for supporting the soot
blower assembly from support member 42. It also inc1udes means for
traversing the element 32 across the width of the duct in a direction
perpendicular to the axis of the element. Accordingly in traversing
the duct the jet stream is blown through each of the series of open-
ings between the in-line tubes.
The control box 38 also includes means to interrupt the
flow of the blowing medium at those locations where the element 32
is in line with a row of tubes such as 18 20 or 22 thereby avoiding
direct impingement on the tubing at close range. The blowing element
32 may be arranged to blow in both directions as illustrated or it
may be arranged to blow only downwardly or upwardly depending on the
arrangement of the tubing adjacent thereto.
.