Background Of The Invention
[0001] This invention relates to improved air-cooled vacuum steam condensers serving steam
turbine power cycles or the like and, more particularly, to improved apparatus for
condensing steam or other vapors and draining the condensate over a wide range of
loads, pressures and ambient air temperatures and also completely removing the steam-transported,
undesirable, non-condensible gasses that migrate and collect at the end of the steam
condensing system.
Description Of The Background Art
[0002] One technique for generating mechanical energy is the use of a turbine, boiler and
an array of coupling conduits. Water is first converted to steam in the boiler. The
steam is then conveyed to the turbine wherein the steam is expanded in its passage
through rotating blades thereby generating shaft power. An array of conduits couple
the turbine and the boiler and also define a working fluid return path from the turbine
back to the boiler through steam condenser mechanisms in a continuing cycle of operation.
[0003] Steam condenser mechanisms include air-cooled vacuum steam condensers which may
be considered as being comprised of four basic elements or systems: the steam condensing
system, the air moving system, the condensate drain system and the non-condensible
gas removal system.
[0004] The main problems plaguing the industry today are in the condensate drain and non-condensible
gas removal systems that result in condensate freezing followed by the rupturing of
bundle drains and heat exchanger tubes. The reasons for their failures can be traced
to faulty condensate-drain hydraulic-design, the trapping of non-condensible gasses
in the rear headers of the heat exchanger bundles and inadequate freeze protection.
The problems are aggravated further by the wide range of plant operating conditions
imposed upon the equipment and by low ambient air temperatures coupled with high winds.
[0005] Various approaches are disclosed in the patent literature to improve the efficiency
hydraulics, freeze protection and control of air-cooled vacuum steam condensers and
related devices. By way of example, note U.S. Patents Numbers 2,217,410 to Howard
and 3,289,742 to Niemann. These patents disclose early versions of heat exchangers
for use in turbine systems. Other patents relating to improving air-cooled system
steam condensers include U.S. Patents Numbers 2,247,056 to Howard and 3,429,371 to
Palmer. These patents are directed to control apparatus for accommodating pressure
variations. In addition, U.S. Patent Number 4,585,054 to Koprunner is directed to
a condensate draining system. The linear arrangement of tubes in A-frame steam condensers
is disclosed in U.S. Patents Numbers 4,177,859 to Gatti and 4,168,742 to Kluppel while
U-shaped tubes are disclosed in U.S. Patents Numbers 3,705,621 and 3,887,002 to Schoonman.
In addition, applicant Larinoff describes a wide variety of improvements in air-cooled
heat exchangers in his prior U.S. Patents Numbers 3,968,836; 4,129,180; 4,240,502
and 4,518,035. Such improvements relate to condensate removal, air removal, tube construction,
cooling controls and the like. Lastly, various improvements in mechanisms for non-
analogous technologies are disclosed in U.S. Patents Numbers 2,924,438 to Malkoff;
3,922,880 to Morris and 4,220,121 to Maggiorana.
[0006] As illustrated by the great number of prior patents and commercial devices, efforts
are continuously being made in an attempt to improve air-cooled vacuum steam condensers
having particular utility in systems configuration with steam turbine cycles. Such
efforts are being made to render condensers more efficient, reliable, inexpensive
and convenient to use, particularly over a wider range of thermal operating conditions.
None of these previous efforts, however, provides the benefits attendant with the
present invention. Additionally, the prior patents and commercial devices do not suggest
the present inventive combination of component elements arranged and configured as
disclosed and claimed herein. The present invention achieves its intended purposes,
objects and advantages over known devices through a new, useful and unobvious combination
of component elements, with the use of a minimum number of functioning parts, at a
reasonable or lower cost to manufacture, and by employing only readily available materials.
[0007] Therefore, it is an object of this invention to provide an improved turbine for converting
steam energy into mechanical energy upon expansion of steam therein, a boiler for
generating steam to be fed to the turbine, and a conduit arrangement coupling the
boiler to the turbine and then recoupling the turbine exhaust to the boiler through
steam condensing mechanisms, the condensing mechanisms include a plurality of finned
tubes through which the expanded exhaust steam flows and is condensed; a plurality
of bundle front headers at the lower ends of the condensing tubes for receiving exhaust
steam from the turbine; a plurality of bundle rear headers at the output ends of the
condensing tubes for receiving condensate and non-condensible gasses; and means in
the rear headers to remove non-condensible gasses from the rear headers.
[0008] It is yet another object of this invention to properly and completely drain condensate
from air-cooled steam condenser systems and protect them from freezing.
[0009] Lastly it is a further object of the present invention to completely remove undesired
gasses from the terminal points of a steam condensing system which are the cause of
freezing problems and tube corrosion.
[0010] The foregoing has outlined some of the more pertinent objects of the invention. These
objects should be construed to be merely illustrative of some of the more prominent
features and applications of the intended invention. Many other beneficial results
can be attained by applying the disclosed invention in a different manner or by modifying
the invention within the scope of the disclosure. Accordingly, other objects and a
fuller understanding of the invention may be had by referring to the summary of the
invention and the detailed description of the preferred embodiment in addition to
the scope of the invention defined by the claims taken in conjunction with the accompanying
drawings.
SUMMARY OF THE INVENTION
[0011] The invention is defined by the appended claims with the specific embodiment shown
in the attached drawings. For the purpose of summarizing the invention, the invention
may be incorporated into an improved steam powered system comprising a turbine for
converting steam energy into mechanical energy upon expansion of steam therein, a
boiler for generating steam to be fed to the turbine, and a conduit arrangement coupling
the boiler to the turbine and then recoupling the turbine exhaust to the boiler through
steam condensing mechanisms, the condensing mechanisms including a plurality of finned
tubes through which the expanded exhaust steam flows and is condensed; a plurality
of bundle front headers at the lower ends of the condensing tubes for receiving exhaust
steam from the turbine; a plurality of bundle rear headers at the higher ends of the
condensing tubes for receiving non-condensible gasses; and means in the rear headers
to remove non-condensible gasses from the rear headers. The last mentioned means includes
a suction sparger extending the length of each rear header with a plurality of orifices
spaced along the length of the sparger. The draining condensate inside the tubes flows
downwardly against the upward flow of the steam in a scrubbing manner for reheating
purposes. The system further includes condensate reheating means in the front headers
positioned in the path of the falling condensate to bring the condensate back to saturation
temperature.
[0012] The invention may also be incorporated into a condensing and draining mechanism for
use in a steam condenser comprising a plurality of condensing tubes through which
steam may flow for being condensed into water and continually drained therefrom; a
plurality of front headers at the lower ends of the condensing tubes for receiving
steam to be condensed; a plurality of rear headers at the upper ends of the condensing
tubes for receiving non-condensible gasses from the condensing tubes; and heat transfer
fins on the condensing tubes to facilitate steam condensing within the tubes, such
fins extending downwardly from the rear headers toward the front headers and in the
area below the pre-condensers the fins are of varying predetermined lengths to control
air temperature enveloping the pre-condenser tubes.
[0013] The invention may also be incorporated into a mechanism to remove non-condensible
gasses in a steam condenser comprising a plurality of condensing tubes through which
exhaust steam may flow for being condensed into water and non-condensible gasses to
be removed; a plurality of lower headers at the input end of the condensing tubes
for receiving exhaust steam to be condensed; a plurality of rear headers at the output
ends of the condensing tubes for receiving non-condensible gasses from the condensing
tubes; suction sparger with orifices installed within each of the rear headers to
receive non-condensible gas mixtures; and connecting piping extending downwardly from
each suction sparger toward the front headers to couple to each pre-condenser tube
for the removal of the non-condensible gasses. The plurality of condensing tubes are
arranged in bundles with a plurality of rows of condensing tubes in each bundle and
with each row of each bundle terminating in a separate rear header and with a separate
suction sparger installed in each rear header. The mechanism further includes an air-cooled
pre-condenser tube set in a select and predetermined air temperature zone of the main
condenser coupling a preselected suction sparger from each tube row of each bundle.
The mechanism further includes a fist-stage steam jet air ejector for each pre-condenser
tube row. The mechanism further includes a second-stage ejector, an inter-condenser
and an after-condenser coupled to the output of the first-stage steam jet air ejector.
The orifices in the suction sparger are of varying diameters for equalizing the mass
flow of non-condensible gas mixtures (i) along the length of the rear headers and
from the (ii) various bundles as located throughout the tower structure. The mechanism
further includes a windshield covering the condensing tubes with connecting piping
extending downwardly from the rear headers a predetermined distance as a function
of the extent of temperature control desired.
[0014] The invention may also be incorporated into a device for condensing steam and for
removing the non-condensible gasses therefrom, an improved conduit arrangement defining
a gas/vapor path extending from a lower header to an upper header with condensing
tubes extending therebetween for steam as it moves from the first header toward the
second header, a sparger located in operative association with the second header for
receiving the non-condensible gasses freed from the steam during its condensation
and for the removing of such non-condensible gasses from the system.
[0015] Lastly, the invention may also be incorporated into apparatus for removing non-condensible
gasses from steam being condensed as it moves upwardly through tubes from a front
header toward a rear header, means located in the rear header for the receipt of the
non-condensible gasses generated from the steam being condensed, the means having
a plurality of orifices along its length and adapted to be coupled to a first stage
ejector.
[0016] The foregoing has outlined rather broadly the more pertinent and important features
of the present invention in order that the detailed description of the invention that
follows may be better understood so that the present contribution to the art can be
more fully appreciated. Additional features of the invention will be described hereinafter
which form the subject of the claims of the invention. It should be appreciated by
those skilled in the art that the conception and the disclosed specific embodiment
may be readily utilized as a basis for modifying or designing other structures for
carrying out the same purposes of the present invention. It should also be realized
by those skilled in the art that such equivalent constructions do not depart from
the spirit and scope of the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For a fuller understanding of the nature and objects of the invention, reference
should be had to the following detailed description taken in conjunction with the
accompanying drawings in which:
Figure 1 is a simplified version of a steam power cycle that is a partially schematic
and a partially diagrammatic illustration of a boiler, turbine, pumps, coupling conduits
and an air-cooled steam condenser. The condenser shown is an "A" frame design with
steam flowing upward in the finned tubes while condensate drains downward to the steam
supply duct in a counter-flow manner. It is mechanical forced draft with condensate
drain to a storage tank and a two stage steam operated air removal system.
Figures 2 and 3 are elevational drawings with vertical sections through the bundles
and with a forced draft fan in the middle serving both banks;
Figure 4 is a view of the front header showing its tube holes where the exhaust steam
enters to be condensed.
Figure 5 is a sectional view through the bundle showing finned tubes attached four
rows deep. It also shows the evacuation piping placed inside the bundle channel frame.
Figure 6 is a sectional view across a bundle showing the air-cooled pre-condenser
set on top of the frame with piping leading to the rear headers.
Figure 7 is a view looking into the rear header end of the bundle. It shows the vent
manifolds inside each of the four rear manifolds.
Figure 8 is a sectional view of a rear header showing the placement of the vent manifold
and its orifices.
Figure 9 is a flow diagram of the gas removal vacuum system. It shows the pre-condenser
resting on top of the bundles close to the steam supply duct.
Figure 10A, 10B, 10C and 10C are simplified versions of bundle gas removal designs
that have been used in the past and compared to the proposed system.
[0018] Similar referenced characters refer to similar parts throughout the several Figures.
DETAILED DESCRIPTION OF THE INVENTION
Overview
[0019] With reference to Figure 1, there is shown a power system 10 for converting thermal
energy into mechanical energy. The system includes a boiler 12 for generating steam
and a turbine 14 which expands the high pressure steam thereby converting its energy
into shaft power. The waste steam exhausted from the turbine is condensed in an air-cooled
steam condenser 18 and the condensate is returned to the power cycle via conduits
16 and auxiliaries. The steam condensing mechanism 18 consists of sub-systems which
may be considered as including a steam condensing system 22, an air moving system
24, a condensate drain system 26 and a gas removal vacuum system 28.
Steam Condensing System
[0020] The steam condensing mechanism employed in the preferred embodiment of the present
invention consists of a main steam duct 33 feeding a steam supply duct 35 to which
the steam condensing bundles 56 are attached at the front header 34. The exhaust steam
flows upward through a plurality of parallel finned tubes 32 where it is condensed
and the condensate runs downward in the same tubes in counter-flow manner back into
the steam supply duct 35. In the disclosed preferred embodiment, the bundles 56 are
arranged in two banks 46 and 48 in an A-frame configuration with the front header
34 on the bottom and the rear headers 36, 38, 40 and 42 on the top. The tubes 32 are
provided with fins 52 to facilitate and promote more efficient heat transfer. The
heat transfer involves the flow of ambient air 50 over the finned tubes for cooling
purposes to condense the steam into water. The condenser tubes of each bank are separated
into a plurality of bundles 56 as shown in Figures 1 and 9. Within each bundle, the
tubes are arranged in a plurality of rows 60, 62, 64 and 66, four in the disclosed
preferred embodiment as shown in Figure 5. The four parallel rows are symmetrically
positioned in the bundle with the cold ambient air striking row 60 first while the
heated air leaving row 66 is discharged back into the atmosphere.
[0021] Each row of tubes has its own rear header 36, 38, 40 and 42 which are the terminal
points of the steam condensing system and therefore the gathering points for all the
non-condensible gasses released by the condensing steam. While the steam moves upward
through the tubes, the condensate flows downward by gravity in the same tubes and
drains into the steam supply duct 35.
[0022] The steam condensing system employed in this invention may be considered as consisting
of a single-pass, multi-row, extended surface, air-cooled, heat exchanger bundles
with a separate rear header for each row. The tubes are in a single pass arrangement
in relation to the air flow on the outside and the steam flows counter to its condensate
inside the tubes. The bundle arrangement must be inclined toward the front header
34 sufficiently so that the condensate can drain by gravity back into the steam supply
duct 35. From that minimum position it can be tilted upward until it is completely
vertical to meet design/installation requirements.
[0023] The important advantages of this new steam condensing system can be set forth as
follows. A. This design does not require additional devices for the withdrawal of
condensate from the bundles. B. The counter-flow movement of steam and condensate
inside the same tubes produces a condensate temperature close to the saturation temperature
of the steam. C. Final condensate saturation temperature can be achieved by the use
of a separate reheating element installed in the steam supply duct. D. Most importantly,
this design has a low internal steam pressure drop because of its short steam-condensing
path length. This means the condenser can operate with a lower turbine exhaust pressure
during cold weather which is very desirable from a plant thermal efficiency aspect.
Air Moving System
[0024] The air moving system 24 employed in the disclosed preferred embodiments of this
invention is the conventional industry type shown in the patent literature. It preferably
employs either mechanical draft fans 86, natural draft or some combination of both.
The fan arrangements can be either of the induced or forced draft type. In all cases
the forced air flow across the outside of the finned tubes is the cooling medium that
condenses the steam inside the tubes.
[0025] It should be noted here that, although the bundles employed in this invention show
four rows, all the disclosures in this patent apply to bundles of one or more rows.
Condensate Drain System
[0026] The condensate drain system starts at the point where the condensate flows out of
the finned condensing tubes 32 into the steam supply duct 35 by gravity as shown in
Figure 2. Its vertical fall is intercepted by a condensate reheating element 166.
During cold weather the condensate is subcooled by its contact with the metal walls
of tube 32 but it can be readily reheated to the steam saturation temperature by breaking
it up into droplets and thin films and delaying its fall. The condensate reheating
element 166 can do this with an interwoven mesh material or some other such device
that is at saturation temperature being suspended in this steam atmosphere. The reheating
element can also be constructed of trays and baffles similar to designs presently
employed in commercial heaters. This element provides the added contact surface area
and time delay that is necessary to bring the condensate back up to the desired saturation
temperature.
[0027] Returning to Figure 1, condensate flow from steam supply duct 35 is via pipe manifold
82 into drain pipe 83 and then into tank 84. The steam pressure inside tank 84 is
the same as that in supply duct 35 because of piping connection 100. The condensate
flow from supply duct 35 to storage tank 84 is entirely by gravity. Condensate pumps
88 take suction from the storage tank and return the condensate back to the power
cycle to repeat the process.
Gas Removal Vacuum System
[0028] One of the most important aspects of the present invention is the gas removal vacuum
system. It is the subject of another U.S. Patent Application Serial Number (Attorney
Docket Number L043/1), filed on the same date herewith by the same inventor. The difference
between these two systems is the manner in which the condensate is drained from the
pre-condensers. In the companion invention, the steam which is condensed in the pre-condensers
flows back into the bundle rear headers by gravity where it mixes with the bulk of
the condensate and is withdrawn from the system by means of water legs. In this present
invention the steam which is condensed in connecting piping (121, 123, 125 and 127)
and in the pre-condensers flows by gravity directly into the condensate storage tank
84 via a fluid separating connection 128.
[0029] For a better understanding of what is being proposed in this invention as regards
the removal of non-condensible gasses from air-cooled steam condensers, a short review
of past arrangements and problems is helpful.
[0030] First, to answer the question as to what are these non-condensible mixed gasses in
the exhaust steam of power cycles. These inert gasses are the result of boiler water
treating chemicals that are continually injected into the boiler feed water system.
They vaporize in the boiler drum but do not condense when cooled down. They also are
the result of air leakage around shaft seals such as the turbine, condensate pumps
and valve stems. Air leakage also occurs at the welded joints of the steam condensing
system which includes steam ducts, manholes, bundles, tanks, condensate piping, etc.
There could be a large presence of inert gasses in the turbine exhaust steam.
[0031] The second question that arises is why are they important in the design consideration
of steam condensers. These inert gasses can cause tube corrosion, but more importantly,
tube failures resulting from freezing. These gasses are frequently trapped in stagnant
pockets in rear headers which then grow in size and progress down into the condensing
tubes. If there is condensate present, it can freeze because the stagnant gas pockets
become cold, having displaced the steam. Frozen condensate can rupture tubes and pipes
that will shut down the power generating unit. During the summer these same gas pockets
will blanket finned-tube heat-transfer surfaces thereby degrading the plant's thermal
performance.
[0032] Knowing what these inert gasses are and what they do, we can now examine how they
have been handled in the past and compare that with what is now being proposed. Figures
10A, 10B, 10C and 10D present the various design attempts in removing the undesirable
gasses from the condenser. The IDEAL gas removal design shown in Figure 10A would
be a cone-shaped bundle where steam (S) enters the cavity and is condensed leaving
the gasses behind. As more steam enters and condenses, the gasses are pushed further
and further ahead until finally they reach the tip of the cone where there is practically
no steam and all gas. The first-stage ejector then "sucks" out nearly pure gas and
discharges it from the system. There are no stagnant pockets in the IDEAL design because
of its cone shape, however, this bundle cannot be built and remains only as an ideal
concept.
[0033] Scheme A, Figure 10B, shows past attempts by industry at solving this problem. The
total steam condensing surface is built in two sections or zones. They could be separate
bundles as shown or they could be incorporated in the same bundle. The attempt here
is to try to concentrate the inert gasses before they are withdrawn at point Y. The
two sections could have the same heat transfer capacity or the second section could
be as small five per cent of the heat transfer surface area of the first section.
The rear header 36 of the first section may or may not be the cavity which serves
as the front header 34 for the second section. There are many design variations on
this connection. The patent literature shows the following names for the first section:
Main Condenser, Primary Condenser, First Condensing Zone and First Plurality Tubes.
The second section names have been shown as: Dephlegmator, Vent Condenser, Secondary
Condenser, After Condenser, After-cooler Section, Second Condensing Zone, Second
Plurality of Tubes and Reflux Condenser.
[0034] Regardless of the bundle size, shape, tube passes, tube arrangement, configuration,
etc., the design aim is always to drive the gasses toward the terminal end (E) of
the condenser and then remove them with an ejector system. A typical rear header length,
which is the bundle width (W), could be as large as ten feet. There could be fifty
finned tubes in this width all discharging gasses into the rear header. However, the
gas quantities entrapped in the steam are minute by comparison to the total mass of
steam being condensed. Typically in a small condensing system for every 1,000 lbs/hr
of steam entering a bundle with a fifty tube row there is less than 1.0 lbs/hr of
gas vapor mixture that is sucked out of the rear header at point Y by the first stage
ejector. Considering the internal volume of a rear header that is ten feet long, a
1.0 lb/hr flow withdrawal rate toward the one pipe connection (Y) is very, very small.
[0035] With this arrangement where there is but one pipe connection from the rear header
to the ejector, it is quite obvious that there will be stagnant pockets of inert gasses
in the rear header as shown in Figure 10B. In fact, the real danger is that these
pockets will extend down into the finned tubes along both sides of the bundle where
freeze damage then occurs. The vapor/gas fluid being withdrawn by the ejector is that
which comes mainly from the finned tubes in the immediate vicinity of the suction
opening (Y). These few tubes opposite opening (Y) bring in a continual supply of additional
steam and gas into the withdrawal area where all the action takes place. The remaining
tubes, which are the majority, merely stagnate with gas movement created mainly by
molecular diffusion and small eddies rather than pressure gradients. The inert gasses
keep accumulating and concentrating inside the tubes along the sides of the bundle
with very slow movement toward the suction opening (Y). That is the nature of fluid
movements with the type of containment and withdrawal arrangements presently practiced.
[0036] Scheme B, Figure 10C, has a main condenser where each bundle rear header 36 has a
vent tube or tubes. This vent tube 170 is finned similar to the main condenser. It
is in essence a pre-condenser to the first stage ejector which is built into the same
bundle as the main condenser. This scheme does a better scavenging job of the rear
header than does Scheme A. The mass volume of gas/vapor mixture leaving the bundle
at (Y) and entering the ejector at (Z) is the same for both Scheme A and B. The mass
volume of gas/vapor leaving the rear header of Scheme B at point (X) is considerably
larger than that leaving at point (Y), Scheme A, due to the condensation of steam
vapor in the vent tube. Since the mass volume flow at point (X), Scheme B, is larger,
the flow volumes and velocities around suction opening (X) are higher. However, this
design has the same basic flaw that Scheme A has in that the flow into suction opening
(X) comes mostly from tubes in the immediate vicinity of the opening. The rest of
the rear header and the tubes along the sides to the bundle stagnate.
[0037] Scheme C, shown in figure 10D, is the new invention with its suction sparger that
shows how it proposes to scavenge the rear header by the vary nature of its construction.
[0038] The purpose of this system is to remove all of the non-condensible gasses from the
bundle rear headers 36, 38, 40 and 42. These non-condensible gasses are part of the
normal steam cycle vapor system and become the gas residue when the vapors are condensed.
A flow diagram of the gas removal vacuum system 28 of the present invention is shown
in Figures 1 and 9. The gas removal starts with the suction sparger 116 installed
in all rear headers; then piping 121, 123, 125 and 127 connecting the suction spargers
to pre-condensers 120, 122, 124 and 126; then additional piping connects the pre-condensers
to a liquid/vapor separator 128 where the liquid flows to the condensate storage tank
84 by gravity while the gasses and vapors flow to the first-stage ejectors; then the
gasses and vapors enter the steam jet air ejector package 130 where the gasses are
further concentrated and then ejected from the system into the atmosphere at point
134 while the condensate from the steam vapors is returned to the cycle. A more detailed
explanation of each of these gas removal steps follows.
[0039] As was stated earlier, the inert gasses all end up in the rear headers 36, 38, 40
and 42. To remove them from the rear headers, it is necessary to create a higher vacuum
which is a lower absolute pressure than that which exists in the rear headers. This
is accomplished by the first-stage ejectors 144 and completed by the remainder of
the steam jet air ejector package 130. The suction sparger 116 is the starting point
for the gas removal process. Each rear header, of which there are four per bundle,
has its own suction sparger running the full length of the rear header as shown in
Figure 7. The spargers have orifices 114 drilled along the entire length through which
the gasses and vapors enter. Any condensate which enters the sparger either flows
out of a single small drain hole 136 shown in Figure 8 and located at the closed end,
or it flows into connecting piping 121, 123, 125 and 127 and then drains into the
pre-condenser. The vapor/gas flow from the rear header through the orifices is induced
by the action of the steam jet ejectors. The orifices are positioned such that they
face a calm area 138 as shown in Figure 8 and are located midway between two adjacent
tubes 32. The other side of the sparger pipe faces the heat exchanger tube 32 openings
which is the turbulent zone or area 140. It is turbulent because there is some steam
flow in the rear header between tubes in the same row. This steam interchange amongst
tubes 32 occurs as a result of uneven cooling air velocities across the face of the
bundle. Locating the suction orifices in the calm zone of the rear headers insures
a more effective scavenging job. Since each condensing tube 32 discharges some gas,
the multiplicity of suction orifices 114 means that the gasses have only to travel
a few inches in the rear header before they enter an orifice in the suction sparger
116. This is unlike the usual steam condenser bundle rear header which has but one
suction pipe connection where the gasses must travel from a minimum of a few inches
to a maximum of five to ten feet, depending on the suction pipe location.
[0040] The orifices 114 are of different diameters along the length of the suction sparger
114 and also vary from bundle to bundle depending on the bundle location in the tower
structure. These orifices are sized to perform several important flow-equalizig functions.
The national steam condenser code specifies the required evacuation capacity (lbs/hr)
of the steam jet air ejector package 130 based on the size of steam condenser, i.e.,
mass quantity of steam condensed (lbs/hr). Hence, the orifices are sized to flow the
code mandated capacity plus the steam vapor capacity condensed in a pre-condenser,
if used. In this first calculation step an orifice diameter is found knowing total
flow quantities, total bundles and total orifices. Now since the bundles close to
the first-stage ejectors will have less piping pressure drops, they would normally
flow a larger amount of gas/vapors than the bundles located at the end of the tower.
Hence, the first adjustment to the orifice diameters is to equalize the flows irrespective
of the bundle location in the tower structure. That means that bundles located close
to the first-stage ejectors will have smaller orifices than the bundles located at
the end of the tower. With this adjustment all bundles will now deliver the same mass
quantity of gas/vapor to the evacuation system. There is a second adjustment to be
made to the orifice diameters which concerns operations inside the rear headers. Flow
through the sparger orifices must be equalized along its entire length. This will
insure that each increment of length along the rear headers is being evacuated evenly
since each finned tube 32 is discharging very nearly the same quantity of gas. The
orifice 114 openings near the front end of the sparger 116 will be slightly smaller
than the orifices near the closed end which are further away and therefore have a
larger piping pressure drop.
[0041] The rear header evacuation piping 121, 123, 125 and 127 is run inside the bundle
channel frame 148 as shown in Figures 3, 5, 6 and 7 and then brought outside with
piping 30 running on top of the bundle frames near the steam supply duct 35 as shown
in Figures 1, 2, 3, 6 and 9. By installing fins 53 on pipes 30, low-cost air-cooled
pre-condensers 120, 122, 124 and 126 can be made to serve the first-stage ejectors
144. Such a pre-condenser increases the scavenging rate of the rear headers by the
amount of steam vapor it condenses. In the process of doing that, it provides a more
concentrated inert gas mixture to the ejectors which makes them more efficient.
[0042] The steam vapor condensing capability of this air-cooled pre-condenser is dependent
upon, amongst other things, the temperature of the cooling air 50 passing through
its fins 53 as it lies on top of the main steam condensing tubes 32. This air temperature
in turn is controlled by the number of fins 52 installed on tubes 32 located directly
below the pre-condensers. As the fins are stripped back along the tubes as shown in
Figure 2 the temperature of the air reaching the pre-condensers drops and then more
steam vapor is condensed. Figure 2 shows the top row fins stripped to a distance L
while the bottom row is left intact; rows 2 and 3 are stripped varying amounts. This
control of the number of heat dissipating fins built into the path of this small segment
of cooling air gives the designer flexibility to maximize the steam vapor condensing
capability of the pre-condenser and minimize the potential for freezing.
[0043] The air-cooled pre-condenser is installed in the warm air stream of the bundle air
discharge to protect it from freezing. The vapor/gas mixture flowing in the pre-condenser
tubes 30 does not carry much steam so that it does not have the self protection features
as does the regular steam condensing tube 32. Although the pre-condenser is protected
by being surrounded with heated air, it is still subject to freezing if it is not
protected from cold blasting winds. In cold climate installations a removable, sheet-metal,
protective wind shield 162, would be installed to partially cover the pre-condenser.
[0044] The pre-condenser is shown installed on the bottom of the bundles 56 near the steam
supply duct 35 to achieve greatest freeze protection. In warmer climate installations
the pre-condenser could be installed near the to of the bundles just below rear header
42. This would save piping costs for items 121, 123, 125 and 127.
[0045] Steam vapors condensed in connecting piping 121, 123, 125 and 127 and in pre-condensers
120, 122, 124 and 126 all drain by gravity toward the fluid separating connection
128. This is a "T" pipe connection installed in a vertical position as shown in Figures
1 and 9. The condensate flows downward through pipes 71, 73, 75 and 77 by gravity
into the condensate storage tank 84, while the vapors and gasses flow upward through
the tees toward the first-stage ejector 144. The condensate pipes 71, 73, 75 and 77
terminate below the water level in the tank because they also serve as water-leg seals.
Condensate levels in these water legs are above the water level in the tank and each
is at a different height because they all have different internal vapor pressures.
In cold climate installations, the small condensate pipes 71, 73, 75 and 77 are fastened
to the much larger and warmer pipe 83 and then all five pipes are wrapped with heat
insulation as a single line.
[0046] The vapors and gasses leaving the fluid separator 128 enter the first-stage ejectors
144 of which there are four; one for each bundle row because they all have different
pressures and cannot be tied together. The use of multiple first-stage ejectors discharging
into a common inter-condenser is generally known in the existing art in the process,
petrochemical, pharmaceutical and related industries. The process cycles generally
have several points, at different pressures, which must be evacuated with their own
first- stage ejectors which then discharge into the shell of a common condenser.
As shown in Figures 1 and 9, the first-stage ejectors then discharge their mixture
into inter-condenser 150 and the second-stage ejector 154 withdraws that shell mixture
and discharges it to the after-condenser 152. The after-condenser condenses the remaining
steam vapor and discharges the residue of inert gasses into the atmosphere via vent
134. This air ejection package 130 is a conventional two-stage steam ejector unit
with inter and after-condensers. Motor driven vacuum pumps with or without air ejectors
could be readily substituted for the steam operated device shown.
[0047] The low-cost pre-condenser 120, 122, 124 and 126 would be installed when operating
conditions indicated the need for additional scavenging of the rear headers. If they
were not needed, then there would be some cost savings by eliminating the fins 53
on piping 30, the fluid separating connection 128 and the four condensate drain lines
71, 73, 75 and 77 and running the extraction piping 30 in the cavity below bundle
air seal 164 Figures 2 and 3.
[0048] The invention may thus be considered as apparatus for condensing steam and for removing
the non-condensible gasses therefrom. The apparatus includes an improved conduit
arrangement defining a gas/vapor path extending from a lower first header to an upper
second or last header with condensing tubes extending therebetween for steam as it
moves upwardly through the condensing tubes from the first header toward the second
header. A sparger is located in operative association with the second header and is
formed with a plurality of orifices along its length for receiving the non-condensible
gasses freed from the steam during its condensation and for the removing of such non-condensible
gasses from the system. The sparger is then coupled to a first stage ejector.
[0049] Although the preferred arrangement as illustrated in the drawings of this invention
shows four rows of tubes, all of the disclosure in this invention apply to bundles
constructed with one or more rows. Similarly, each row may have a different finned
tube diameter such as, the first row could be one and one-half inch in diameter, the
second row one and one-forth inch in diameter and the third row one inch in diameter.
[0050] The present disclosure includes that contained in the appended claims as well as
that of the foregoing description. Although this invention has been described in its
preferred forms with a certain degree of particularity, it is understood that the
present disclosure of the preferred form has been made only by way of example and
numerous changes in the details of construction and combination and arrangement of
parts may be resorted to without departing from the spirit and scope of the invention.
1. A steam powered system comprising a turbine for converting steam energy into mechanical
energy upon expansion of steam therein, a boiler for generating steam to be fed to
the turbine, and a conduit arrangement coupling the boiler to the turbine and then
recoupling the turbine exhaust to the boiler through steam condensing mechanisms,
the condensing mechanisms including:
a plurality of finned tubes through which the expanded exhaust steam flows and is
condensed;
a plurality of bundle front headers at the lower ends of the condensing tubes for
receiving exhaust steam from the turbine;
a plurality of bundle rear headers at the higher ends of the condensing tubes for
receiving non-condensible gasses; and
means in the rear headers to remove non-condensible gasses from the rear headers.
2. The system as set forth in Claim 1 wherein the last mentioned means includes a
suction sparger extending the length of each rear header with a plurality of orifices
spaced along the length of the sparger.
3. The system as set forth in Claim 1 wherein the draining condensate inside the tubes
flows downwardly against the upward flow of the steam in a scrubbing manner for reheating
purposes.
4. The system as set forth in Claim 3 and further including condensate reheating means
in the front headers positioned in the path of the falling condensate to bring the
condensate back to saturation temperature.
5. For use in a steam condenser, a condensing and draining mechanism comprising:
a plurality of condensing tubes through which steam may flow for being condensed into
water and continually drained therefrom;
a plurality of front headers at the lower ends of the condensing tubes for receiving
steam to be condensed;
a plurality of rear headers at the upper ends of the condensing tubes for receiving
non-condensible gasses from the condensing tubes; and
heat transfer fins on the condensing tubes to facilitate steam condensing within the
tubes, such fins extending downwardly from the rear headers toward the front headers
and in the area below the pre-condensers the fins are of varying predetermined lengths
to control air temperature enveloping the pre-condenser tubes.
6. For use in a steam condenser, mechanism to remove non-condensible gasses comprising:
a plurality of condensing tubes through which exhaust steam may flow for being condensed
into water and non-condensible gasses to be removed;
a plurality of lower headers at the input end of the condensing tubes for receiving
exhaust steam to be condensed;
a plurality of rear headers at the output ends of the condensing tubes for receiving
non-condensible gasses from the condensing tubes;
a suction sparger with orifices installed within each of the rear headers to receive
non-condensible gas mixtures; and
connecting piping extending downwardly from each suction sparger toward the front
headers to couple to each pre-condenser tube for the removal of the non-condensible
gasses.
7. The mechanism as set forth in Claim 6 wherein the plurality of condensing tubes
are arranged in bundles with a plurality of rows of condensing tubes in each bundle
and with each row of each bundle terminating in a separate rear header and with a
separate suction sparger installed in each rear header.
8. The mechanism as set forth in Claim 7 and further including an air-cooled pre-condenser
tube set in a select and predetermined air temperature zone of the main condenser
coupling a preselected suction sparger from each tube row of each bundle.
9. The mechanism as set forth in Claim 8 and further including a fist-stage steam
jet air ejector for each pre-condenser tube row.
10. The mechanism as set forth in Claim 9 and further including a second-stage ejector,
an inter-condenser and an after-condenser coupled to the output of the first-stage
steam jet air ejector.
11. The mechanism as set forth in Claim 7 wherein the orifices in the suction sparger
are of varying diameters for equalizing the mass flow of non-condensible gas mixtures
(i along the length of the rear headers and from the (ii) various bundles as located
throughout the tower structure.
12. The mechanism as set forth in Claim 6 and further including a windshield covering
the condensing tubes with connecting piping extending downwardly from the rear headers
a predetermined distance as a function of the extent of temperature control desired.
13. In a device for condensing steam and for removing the non-condensible gasses therefrom,
an improved conduit arrangement defining a gas/vapor path extending from a lower header
to an upper header with condensing tubes extending therebetween for steam as it moves
from the first header toward the second header, a sparger located in operative association
with the second header for receiving the non-condensible gasses freed from the steam
during its condensation and for the removing of such non-condensible gasses from the
system.
14. Apparatus for removing non-condensible gasses from steam being condensed as it
moves upwardly through tubes from a front header toward a rear header, means located
in the rear header for the receipt of the non-condensible gasses generated from the
steam being condensed, the means having a plurality of orifices along its length and
adapted to be coupled to a first stage ejector.