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Патент USA US3066667

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Dec. 4, 1962
|_. E. GRIFFITH
3,066,657
CONTROL OF SUPERHEAT
Filed A'pril 6, 1960
2 Sheets-Sheet 1
INVENTOR.
Lou/s E. GRIFFITH
Dec. 4, 1962
|_. E. GRIFFITH
3,066,657
CONTROL OF‘ SUPERHEAT
Filed April 6, 1960
2 Sheets-Sheet 2
INVENTOR.
Lou/s E . GRIFFITH
»
BY
'i 4.112!
United States Patent O?lice
3,056,?57
Patented Dec. 4, 1962
2
3,{i‘d6,657
tlilhi'f‘ii?h UF SUPERHEAT
Louis
M.
Griffith, Worcester, Mass, assignor to Riley
Stoker (Iorporation, Worcester, Mass, a corporation of
Massachusetts
Filed
6, 19643, Ser. No. 20,4‘99
6 Claims. (til. 122-479?)
tion and the manner of its organization, may be better
understood by referring to the following description taken
in connection with the accompanying drawings forming
a part thereof in which:
FIG. 1 is a longitudinal sectional view of a steam gen
erating unit embodying the principles of the present inven
tion;
FIG. 2 is a somewhat enlarged view of a portion of the
This invention relates to control of superheat and, more
apparatus shown in FIG. 1 taken on the lines II—II of
particularly, to a method and apparatus arranged to main 10 FIG. 1;
tain the temperature of superheated steam produced by a
FIG. 3 is a sectional view taken on the lines III-III of
steam generating unit at a constant, preselected value.
FIG. 2; and
This is a continuation-in-part of patent application Serial
FIG. 4 is a sectional view taken on the lines IV—lV of
Number 584,121, ?led May 10, 1956, now abandoned.
FIG. 2.
In the past, there have been many concepts used in con 15
For the purposes of this speci?cation the expression
nection with steam generating units to maintain the tem
“longitudinal” refers to a direction from the front to the
perature of the superheated steam at a ?xed value irre
rear of the steam generating unit, i.e., in the plane of
spective of changes in ioad on the unit. For instance, the
FIG. 1, while the expression “transverse” refers to a direc
flow of gases over the superheater elements has been con
tion from side to side of the furance, or at right angles to
trolled by the use of dampers; this practice has the disad 20 the plane of FIG. 1.
vantage of being relatively insensitive and producing rela
tively high exit gas temperatures at certain loads so that
the overall efficiency of the unit is decreased. superheat
Referring ?rst to FIG. 1, wherein is best shown the
general principles of the present invention, a steam gen
erating unit, designated generally by the reference nu
temperature has also been controlled by desuperheaters
meral it), is shown as comprising a furnace 11 and a
wherein the steam generating unit produces superheated 25 boiler 12 supported in a structural steel framework 13.
steam at the highest temperature necessary at a reduced
load and the steam is cooled to produce the desired steam
The furnace 11 comprises a front wall 14, a rear wall 15,
and side walls 16, serving to de?ne a combustion cham
temperature at highest loads; this has the disadvantage of
ber 17. The boiler 12 consists of a steam and water drum
requiring extremely large superheater elements to take
18 having downcomers 19 connecting it to a lower header
care of adverse conditions. superheat has been con 30 21 which serves water wall tubes 22 extending upwardly
trolled by recirculating a portion of the gases from the
along the walls of the furnace 11. The header 21 and the
back passes of the unit to the furnace proper; this has the
water walls 22 serve to form a hopper 23 located in the
disadvantage of producing high dust loading of the fur
lower part of the combustion chamber 17 constructed in
nace gases with resultant cutting and deterioration of the
the manner shown and described in the patent to Balmer
boiler tubes and increase of power requirements. An 35 No. 2,503,148. The boiler also comprises a primary
other method of controlling superheat that has been pro
superheater 24 and a secondary superheater 25. The
posed is the use of a so-called “tilting” burner in which
water wall tubes which extend along the rear wall 15
case the ?ame in the furnace is directed upwardly or
of the furnace 11 extend across the top of the combus
downwardly depending on what is necessary to maintain
tion chamber 17 to form a slag screen 26. The secondary
the superheated steam at a constant value; the burners 40 superheater 25 consists of a ?rst portion. 27, situated im
required for this practice are extremely complicated and
mediately above the combustion chamber 17, and a sec
expensive to build and maintain. Other methods and ap_
ond section 28 which is placed rearwardly of the rear
paratus for controlling superheat have been suggested
wall 15 of the furnace, which second section is subject
which are of lesser importance than those described above
only to convection heat transfer. The ?rst section of
but there is no practice which could be said to be perfect 45 the secondary superheater 25 is subject to both radiation
since all previously-mown methods of controlling super
from the combustion chamber 17 and convection heat
heat suifer from di?iculties which render them less than
transfer from the gases passing upwardly and rearwardly
ideal. These de?ciencies in the prior art have been ob
of the furnace at the upper portion thereof.
viated by the present invention in a novel manner.
A series 29 of burners is mounted in the front Wall 14
it is therefore an outstanding object of the present in
in the furnace 11, while a series 31 is situated in the rear
vention to provide a method and apparatus for the con
wall 15. Certain of the burners in the series 29 are con
nected by a conduit 32 to a conduit 33, While certain of
the method is simple and effective and the apparatus is
the burners in the series 31 are connected by a conduit
inexpensive to manufacture and maintain.
34 to the conduit 33. The remainder of the burners in
Another object of the invention is the provision of an 55 the series 29 is connected by a conduit 35 to a conduit 36
apparatus for the control of superheat whose operation
while certain of the burners in the series 31 are connected
is not detrimental to the efficiency of the steam generating
by a conduit 37 to the conduit 36. The conduits 33 and
unit.
36 are connected through a vertical conduit 38 to a fuel
Another object of the invention is the provision of a
supply, not shown. The conduit 38 is connected with
method and apparatus for the control of superheat which 60 the conduits 37 and 33 by a Y-shaped ?xture with the
can be used for initial adjustments of superheat mad-e nec
conduits 36 and 33 extending at substantial angles to
essary by inaccuracies in design and construction and is
the centerline of the conduit 38. A dividing vane 39 is
also extremely sensitive in maintaining superheat at con
situated at the junction of conduits 36 and 33 to conduit
trol of superheat in a steam generating unit in which
stant temperature irrespective of changes in load.
38, and is connected to the fixture by hige pin 41 which
A still further object of the instant invention is the pro 65 permits the vane completely to shut off conduit 36 or con
vision of a method and apparatus for the control of super
duit 33 alternatively, or to occupy any intermediate posi
heat in which the mass flow of the steam generating unit is
tion. A crank arm 42 is keyed to the pivot pin 4-1 for the
not increased.
actuation of the vane. The outer end of the crank arm 42
Although the novel features which are believed to be
is connected to the piston rod 43 of a hydraulic linear
characteristic of this invention were particularly pointed 70 actuator 44 which is connected by hydraulic lines 45 and
out in the claims appended hereto, the invention itself,
46 to a master control 47. The control 47 isconnected
as to its objects and advantages, the mode of its opera
by a line 48 to a thermocouple 49 situated in the super
access’?
A.
heated steam header 51 of the boiler. In the conduit 38
somewhat above the connections to the conduits 33 and
36 is situated a flow control valve 52 mounted on a hori
zontal pivot 53 passing through the center of the conduits.
The valve 52 is movable about the hinge pin 53 to either
Let us assume that the present apparatus has been
tested for operation at 100% load. During the initial op
eration of the apparatus, the vanes in the burners have
been adjusted to give the exact temperature desired in
the superheated steam header 5i and then the vanes have
been ?xed in that position. it will be understood that the
flame which originates in the upwardly tilted vane burners,
such as burners 63 and ‘65 of the series 29 residing in the
shut off the conduit 38 completely or to open it substan
tially. Keyed to the pivot pin 53 is a crank arm 54, the
outer end of which is connected by hydraulic lines 57 and
58 to a controller 59. The controller is connected by a
front wall of the furnace, will be tilted upwwdly and the
line 61 to a pressure bulb 62 located in the superheated 10 gas resulting from these upwardly-tilting burners will
steam header 51 of the boiler.
reach the superheater at a higher temperature because it
FIG. 2 is an elevational view of the series 29 burners
has had less opportunity to give off its heat by radiation
as they appear from inside the combustion chamber 17.
to the water wall of the furnace. On the other hand, the
The series consists of four burners 63, 64, 65 and d6.
burners such as burners
and
which have their vanes
Each of these burners is of the intertube type shown in 15 tilted downwardly, will produce flame which is directed
the patent application of Craig, Serial No. 299,888, ?led
toward the bottom of the furnace and the gases leaving
July 19, 1952, now Patent No. 2,759,469. For instance,
these burners and entering the upper parts of the furnace
the burner 63, as shown in FIG. 3 consists of a plurality
to pass over the superheater, will be relatively cool, since
of vanes ‘67 mounted on pivot pins 68 which pivot pins
they have traveled along a longer path through the com
in turn are mounted in blocks 69 clamped to the water wall 20 bustion chamber 17 and have had an opportunity to cool
boiler tubes 22. The tubes act as supports for the vanes
by radiation of heat to the water walls of the furnace.
and a great deal of bending of tubes is avoided by this
Now, when the turbine load drops to a lower level, it will
construction. It will be observed from FIG. 3 that
be necessary to permit a smaller amount of steam to pass
the tubes 22 are bent rearwardly in rows of three to
into the turbine and this is accomplished by a valve in the
form openings for the passage of fuel and air. After 25 conduit passing from the header 51 to the turbine. When
initial adjustment, the vanes in burner v6% are directed
this valve is closed down for a low load on the turbine,
downwardly and this is true of burner 65 also. 9n the
the pressure in the header 5!. rises and this change is felt
other hand from FIG. 4 it can be observed that the vanes
by the gas bulb 62 which lies in that header so that a
of burner 64 are directed upwardly and this is also true
signal indicative of that rise passes through the line 61 to
of burner 66. ‘Burner boxes '71, 72, ‘73 and 7d are
the controller 59. The controller immediately sends the
provided for the burners 63, d4, 65 and 66 respectively.
signal through the hydraulic lines 5’? and 52-} to the linear
The burner box 71 is connected by a conduit 7% to the
actuator 56 which acts upon the cranl; arm 54 to turn the
conduit 35 while the burner box 73 is connected by con
valve 52 to a position in which less fuel will be permitted
duit ‘76 to the same conduit 35. The burner boxes 72
to enter the conduit
A smaller amount of fuel enter
and 74 are connected by conduits '77 and 78 respectively, 35 ing the conduit 3% means that less fuel will be burned in
to the conduit 32. As is evident in PEG. 2 the vane 39 is
the combustion chamber 17, less steam generated, and
curved to ?t the walls of the conduit with which it engages
the pressure will drop to the desired value. However, in
on occasion. Furthermore the valve 52 is circular in
order that it may completely close off the conduits 38 on
reducing the amount of combustion taking place in the
combustion chamber the amount of gases ?owing over the
occasion. The operation of the invention will be readily 40 superheater elements have also been reduced. This means
understood in view of the above description. Fuel, which
that the superheated steam entering the header 51 will
may be pulverized coal or gas, passes downwardly past
the valve 52 through the conduit 38 and past the vane
39 into the conduits 33 and 36 from which it is distrib
uted to the burners in the series 29 and 31. Air is
admitted with the fuel and burns within the combustion
chamber 17. The products of combustion pass upwardly
through the screen 26 over the superheater 25 and steam is
enter it at a lower temperature. This lower temperature
is immediately felt by the thermocouple 1&9 and a signal
passes through the line 48 to the controller 47. The con
troller 4'7 sends a signal through the conduits 4-5 and 46
to the linear actuator 44 so that it reacts through its pis
ton rod 43 and the crank arm 42 to move the vane 39 to
another position. The vane will be moved to a position
generated in the tubes 22. The steam generated in the
boiler is released in the steam and water drum T8 and
such that the fuel entering the conduit 36 is increased
be maintained at constant values irrespective of other con
creased so that the tempcrature of the superheated steam
entering the header 511 will be increased, thus to com
conduit
proportionately
36 is connected
over thatthrough
enteringthetheconduits
conduit37 and 35
passes into the primary superheater 24 and from there
to the secondary superheater 25, where it is superheated
and the conduits 75, ‘i6 and the like, to the upwardly di
in the ?rst portion 27 and the second portion 28. Both
rected burners of the series 29 and 3:1. The fuel pass
parts of the secondary superheater are subjected to con
ing through the conduit 33 and the conduits 32 and 31%,
vective heat transfer and, in addition, the ?rst portion 27 55 which are connected to the downwardly directed burners,
is also subjected to radiation from the combustion cham
will be reduced. This means that the amount of gas
ber 17. After passing through the superheater the steam
leaving the burners which are directed upwardly will be
is discharged into the superheated steam header, 51 and
increased, while the amount of gas in the flame leaving
from there to the turbine, not shown, whereby electrical
the burners which are directed downwardly will be de
energy is produced. It is important that the pressure and 60 creased. The net eifect is that the temperature of the
temperature of the superheated steam in the header 51
gases passing over the superheater elements will be in
ditions in the furnace, particularly changes in load. This
is because the turbine is very sensitive to changes in pres
pensate for the drop in superheat due to the drop in load.
sure and temperature. Furthermore, if the temperature 65 This is the correction which it was desired to make. it
in the superheater elements is allowed to go too high,
will be understood, of course, that the valve 52 will be ad
there is a strong likelihood of tube failure. In present
justed to occupy a position permitting the proper amount
day boiler design it is necessary, because of the demand
of fuel to enter the system at any load, the proper amount
for very high superheated steam temperatures, to use su
of fuel being allowed to enter the system in any instance
perheated steam temperatures that are very close to the 70 being su?icient to maintain the pressure of steam in the
temperature of failure of the alloy metals used in the
header 51 at a constant value. At the same time the
superheater tubes. Without close control of the super
vanes 39 will divide the fuel between the upwardly di
heated steam temperature it is possible that the tempera
rected burners and the downwardly directed burners in
ture of failure of the superheater tubes may be exceeded
such a way as to maintain the temperature of the steam
and a disaster may result.
75 in header 51 at a constant value.
5
3,066,657
6
It will be readily understood that the present method
and apparatus for the control of superheat suffers from
of fuel and air in the second stream increasing with in
none of tho de?ciencies which are found in prior art
crease of load to maintain the temperature of the super
heated stream at a preselected value.
practice. For instance, all of the gas originating in the
combustion chamber passes over any heat saving devices,
heated stream in a steam generating unit having a ver
3. A method of controlling the temperature of super
such as economizers and air heaters, which are used
with the steam generating unit. There is no complicated
apparatus that may become fouled with tenacious and
tically-elongated furnace with walls which are lined
throughout their heights with steam generating tubes and
with a gas exit at the upper end, the unit having a sub
corrosive materials which are to be found in a steam gen
stantial convection superheater, comprising the steps of
erating unit since the only moving elements in the system 10 increasing and decreasing the total amount of fuel intro
are the valve 52 and the vane 39 which are elements of a
type long recognized in the art and which have been im
proved until they no longer give trouble in this type of
application. Since it is not necessary to desuperheat from
a higher temperature, the sizes of the superheaters may 15
be reduced to a minimum and there is no necessity for
‘duced into the unit in response to decreases and increases
respectively in the load on the unit to maintain the steam
pressure constant, causing a division of the total fuel
into at least a ?rst and a second stream, mixing the streams
of fuel with air, introducing the ?rst stream of fuel
and air into the unit ‘at an intermediate part of the fur
the use of extremely large amounts of expensive high
nace in the form of a plurality of third streams in a ?xed
alloy steel.
direction, introducing the second stream of fuel and air
While certain novel features of the invention have been
into the unit at an intermediate part of the furnace in
shown and described, and are pointed out in the annexed 20 the form of a plurality of fourth streams in a ?xed direc
claims, it will be understood that various omissions, sub
tion which lies at a substantial vertical angle to and
stitutions and changes in the forms and details of the de
downwardly from the direction of the ?rst stream, the
vice illustrated, and in its operation, may be made by
third and fourth streams being alternately arranged, caus
those skilled in the art without departing from the spirit
ing the gases in the third and fourth streams to pass over
of the invention.
25 the superheater, and the total fuel passing into the said
The invention having been thus described, what is
?rst stream increasing and decreasing in response to de
claimed as new and desired to secure by Letters Patent is:
creases and increases respectively in the temperature of
the steam at the steam outlet of the unit to maintain the
temperature at a constant preselected value.
1. A method of controlling the temperature of super
heated steam in a steam generating unit having ‘a sub
stantial convection superheater and having a vertically 30
elongated combustion chamber with walls which are
lined throughout their heights with steam generating tubes,
comprising the steps of adjusting the total amount of fuel
4. Apparatus for controlling superheat in a steam gen
erating unit having a substantial convection superheater
and having a vertically-elongated combustion chamber
with walls which are lined throughout their heights with
steam generating tubes, comprising a series of ?rst burn
introduced into the unit in response to the load on the
unit, causing a division of the total fuel into at least a 35 ers located at an intermediate portion of the combustion
?rst and a second stream, introducing the ?rst stream of
chamber and each adapted to direct a ?ame downwardly
fuel into the unit at an intermediate portion of the com
of the unit, a series of second burners located at an inter
bustion chamber in the form of a plurality of third streams
mediate portion of the combustion chamber and each
in a ?xed direction, introducing the second stream of
adapted to direct a ?ame upwardly of the unit, the ?rst
fuel into the unit at an intermediate portion of the com 40 and second burners being alternately arranged, a gas
bustion chamber in the form of a plurality of fourth
passage into which the gases from the burners are di
streams in a ?xed direction which lies at a substantial
rected and in which the superheater resides, means in
vertical angle to the direction of and extending down
creasing and decreasing the total amount of fuel passing
wardly from the direction of the third stream, causing
through the burners in response to decrease and increase
the gases resulting from the third and fourth streams to 45 respectively in the pressure at the steam outlet of the
pass over the superheater, the third and fourth streams
unit, and means responsive to the temperature of the
being alternately arranged, and adjusting the proportions
steam at the steam outlet of the unit to divide the total
of the total fuel divided into the ?rst and second streams
amount of the fuel between the two series of burners,
in response to the temperature of the steam at the steam
the amount of fuel received by the series of second burn
outlet of the unit, the proportion of fuel in the second 50 ers increasing and decreasing with an increase or decrease
stream increasing with increase in load to maintain the
respectively in the load on the unit to maintain the tem
temperature of the superheated steam at a preselected
perature of the superheated steam at a preselected value.
value.
5. Apparatus for controlling superheat in a steam gen
2. A method of controlling the temperature of super
heated steam in a steam generating unit having a sub
stantial convective superheater and having a vertically
elongated combustion chamber with walls which are
lined throughout their heights with steam generating tubes,
comprising the steps of adjusting the total amount of fuel
erating unit having a vertically-elongated furnace with
55 walls which are lined throughout their heights with steam
generating tubes and with a gas exit at the upper end, the
unit having a substantial convection superheater, com~
prising -a series of ?rst burners located at an intermediate
portion of the furnace and each adapted to direct the
introduced into the unit in response to the pressure at 60
?ame in a ?xed direction, a series of second burners lo
the steam outlet of the unit, causing a division of the
cated at an intermediate portion of the furnace and each
total fuel into at least a ?rst and a second stream, mix
adapted to direct the ?ame in a direction lying at a sub—
ing the streams of fuel with air, introducing the ?rst
stantial
vertical angle to the direction of the ?ame from
stream of fuel and air into the unit at an intermediate
the ?rst burners, the ?rst and second burners being alter
portion of the combustion chamber in the form of a
plurality of third streams at a ?xed upwardly-directed 65 natively arranged, a gas passage into which the gases
from the burners are directed and in which the super
angle, introducing the second stream of fuel and air into
heater resides, means increasing and decreasing the total
the unit at an intermediate portion of the combustion
chamber in the form of a plurality of fourth streams at
amount of fuel passing through the burners in response
a ?xed downwardly-directed angle, the third and fourth
to
increase or decrease respectively in the load, and means
streams being alternately arranged, causing the gases in 70 responsive to the temperature of the steam at the steam
the third and fourth streams to pass over the superheater,
outlet of the unit to divide the total amount of fuel
and adjusting the proportions of the total fuel divided into
between the two series of burners to maintain the steam
the ?rst and second streams in response to the temperature
temperature at a constant preselected value, the amount
of the steam at the steam outlet of the unit, the proportion 75 of fuel received by the series of second burners increas
3,066,657
7
ing and decreasing with an increase or decrease respec
tively in load on the unit.
6. Apparatus for controlling superheat in a steam gen
erating unit having a vertically-‘elongated furnace with
front, rear, and side walls which are lined throughout
their heights with steam generating tubes and with a gas
exit at the upper end, the unit having a substantial con
5%
and second burners being alternately arranged, a gas
vpassage into which the gases from the burners are di
rected and in which the superheater resides, means in
creasing and decreasing the total amount of fuel passing
through the burners in response to increase or decrease
respectively in the load, and means responsive to the tem
perature of the steam at the steam outlet of the unit to
divide the total amount of fuel between the two series
vection superheater, comprising a series of ?rst intertube
of burners to maintain the steam temperature at a con
burners located in opposed relationship at an interme
diate portion of the front and rear walls of the furnace 10 stant preselected value, the amount of fuel received by
and each having a set of vanes adapted to direct the ?ame
the series of second burners increasing and decreasing with
at a ?xed angle to the horizontal, a series of second inter
an increase or decrease respectively in load on the unit.
tube burners located in opposed relationship at an inter
mediate portion of the front and rear Walls of the furnace
References Cited in the file of this patent
and each having a set of vanes adapted to direct the ?ame 15
UNITED STATES PATENTS
in a direction lying at a substantial vertical angle to the
2,832,323
Craig ________________ __ Apr. 29, 1958
direction of the ?ame from the ?rst burners, the ?rst
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