Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02405397 2002-09-27
STEAM PRESSURE REDUCING AND CONDITIONING SYSTEM
TECHNICAL FIELD OF THE INVENTION
The present invention concerns a steam pressure reducing and
conditioning system.
BACKGROUND OF THE INVENTION
Referring to Prior Art Figure 3, it has been known to have a steam
pressure reducing and conditioning system comprising a steam source 24 (such
as boiler) for generating superheated steam S, a pressure reducing and
conditioning valve 21 for depressurizing and desuperheating steam S generated
by this steam source 24, and a discharge pipe 23 connected to an outlet of
steam pressure reducing and conditioning valve 21, and connected to a steam
work section 22, downstream of valve 21.
As illustrated in Prior Art Figure 3, steam pressure and conditioning valve
21 receives superheated and pressurized steam S inflowing in inlet 21 a. Steam
S is desuperheated and depressurized by passing steam S valve 21 and
injecting subcooled water mist W (not shown) from one or more nozzles 25 in
the
lower portion of valve 21.
The desuperheated and depressurized steam S,, discharged from the
valve 21 and the subcooled water mist W injected in valve 21, flow into the
discharge pipe 23 and are conveyed to the steam work section 22. A portion of
discharge pipe 23 is arranged horizontally 23a. Some of the subcooled water
mist W condenses and clings to the discharge pipe at 23a and flows along the
bottom of the horizontal section. Steam S, flows past these areas of
condensation creating temperature differentials in the interior surface of the
pipe
23.
Consequently, the pipe 23 deforms (bends upward) and possibly breaks
due to expansion and stress due to the temperature difference in horizontal
section of pipe 23, and moreover, the condensed moisture Wl, flowing at the
bottom of the pipe 23 is enrolled up by the high speed flow of steam S,
(jumping
phenomenon). The jumping phenomenon erroneous temperature
1
CA 02405397 2008-08-27
measurements in temperature sensors in the pipe 23 for detecting the heat of
the steam S1.
It is an object of the present invention to provide a steam pressure
reducing and conditioning system that can solve the aforementioned
problems.
In one particular embodiment there is provided a steam conditioning
system having: a steam conditioning valve for depressurizing and
desuperheating superheated steam by supplying moisture thereto said valve
oriented wherein flow is discharged from the valve through a lower discharge
1() end of said valve in a downward substantially vertical direction; a
discharge
pipe connected to the lower discharge end of the steam conditioning valve,
the discharge pipe comprising: a substantially horizontal section being
provided with a moisture drain in proximity to the bottom of the horizontal
section; a substantially vertical section between the lower discharge end of
the steam conditioning valve and the horizontal section; a nozzle for
injecting
a water mist into the lower discharge end of the steam conditioning valve
wherein the nozzle has a discharge opening exiting into an annular reduction
in the longitudinal cross-section of the lower discharge end of said valve;
and
a conduit for connecting said nozzle to said moisture drain for transporting
condensed water to said nozzle, wherein moisture is drawn from said
moisture drain of the discharge pipe through the transport conduit and out the
nozzle discharge opening into the lower discharge portion of the conditioning
valve due to Venturi effect in the annular reduction of the discharge portion
of
the valve.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosed invention will be described with reference to the
accompanying drawings, which show important sample embodiments of the
invention and which are incorporated in the specification hereof by reference.
A
more complete understanding of the present invention may be had by
reference to the following Detailed Description when taken in conjunction with
the accompanying drawings, wherein:
2
CA 02405397 2008-08-27
Fig. 1 is a partial side view with schematic elements illustrating the
operation of the steam pressure reducing and conditioning system of the
present invention;
Fig. 2 is a partial cross-section view illustrating a portion of the
pressure reducing and conditioning valve used in the system of the present
invention of Fig. 1; and
Fig. 3 is a partial side view with schematic elements illustrating the
operation of a prior art steam pressure reducing and conditioning system.
SUMMARY OF THE INVENTION
Reference is now made to the Drawings wherein like reference characters
denote like or similar parts throughout the Figures.
The present invention concerns a steam pressure reducing and
conditioning system comprising a steam reducing and conditioning valve 1 for
desuperheating and depressurizing superheated steam S by injecting subcooled
water mist W in the lower portion of valve 1. A discharge pipe 3 is connected
at
its proximal end to the exit of valve 1. A steam work section 2 is connected
at the
distal end of pipe 3. The discharge pipe 3 has a horizontal portion 3a, and
said horizontal portion 3a is provided with a moisture drain 4 at the bottom
2a
CA 02405397 2002-09-27
portion or at a portion near the bottom of the horizontal portion 3a of pipe
3.
Condensed subcooled water mist ("moisture") W, is extracted from discharge
pipe 23 by drain 4 and is recycled and reinjected as moisture W to be supplied
to
the vapor S in said conditioning valve 1. Moisture drain 4 is connected by a
moisture transport conduit 5 to the conditioning valve 1.
The steam conditioning valve 1 further includes a reduced annular section
9 with a nozzle 5a disposed therein for injecting subcooled water mist W into
the
reduced annular section 9 of conditioning valve 1. Moisture W is drawn into
steam flow S due to the Venturi effect caused by the pressure drop through the
reduced annular section.
METHOD OF OPERATION
A superheated steam S is desuperheated by supplying subcooled water
mist ("moisture") W to steam conditioning valve 1. The desuperheated steam S,
flowing out from the conditioning valve 1 and the moisture W used for cooling
in
discharge valve 1 flows into discharge pipe 3, and is introduced in the steam
work section 2 connected to the downstream area of the discharge pipe 3.
In the present invention, when the moisture W discharged from the
conditioning valve 1 flows through the horizontal section 3a of the discharge
pipe
3, the condensed moisture W1 is drained from a moisture drain 4 disposed at
the
bottom portion 3a of this pipe 3, and the moisture W, extracted from the
moisture
drain 4 is recycled as part of moisture W to be supplied to the steam S in the
steam conditioning valve 1.
Consequently, moisture W, can be removed from the horizontal section
3a of the pipe 3, preventing the moisture W, from stagnating at the bottom of
the
pipe, solving the aforementioned problem of the prior art discussed in the
background section, and further, the recycling of moisture W1 used for cooling
the vapor S again in the conditioning valve 1 saves energy.
DETAILED DESCRIPTION
The attached drawings show an embodiment of the present invention,
which will be described below.
3
CA 02405397 2002-09-27
This embodiment of the present invention comprises, as shown in Figs. 1
and 2, a steam desuperheating and conditioning valve 1 wherein a superheated
and pressurized steam S generated in a steam generation source 8 (for
instance, boiler) flows into a first port 1 a of conditioning valve I. Steam S
is
desuperheated and depressurized by passing through a small hole section 6
(diffuser) having scattered small holes 6a, and the steam S, is discharged
from a
second port lb of conditioning valve 1. Steam S, is desuperheated by injecting
a subcooled water mist "moisture" W from one or more nozzles 7. A discharge
pipe 3 is connected at its proximal end to the exit of conditioning valve 1,
and at
its distal end to a steam work section 2 (for instance, condenser for a
nuclear
reactor).
Also, in this embodiment, the discharge pipe 3 is provided with a
horizontal section 3a extending from the conditioning valve 1 and disposed
horizontally with an elbow section 3b (bent section). The discharge pipe 3 is
so
composed that the condensed moisture W, flowing in this horizontal section 3a
is part of the moisture W to be supplied to the vapor S in the conditioning
valve
1.
To be more specific, as shown in Fig. 1, said discharge pipe 3 is provided
with a moisture drain 4 having a drain hole 4a at or near the bottom portion
of
the horizontal section 3a, said moisture drain 4 is provided with a moisture
transport conduit 5 for conveying moisture W, extracted from the moisture
drain
4 to the vapor cooler 1.
This moisture transport conduit 5 is a tubular element having a
predetermined diameter, and connected to a reduced annular area 9 constituting
a predetermined area of the conditioning valve 1, where a steam S1 flowing in
the conduit will flow faster than the steam flowing in the larger diameter
discharge pipe 3.
Referring to Figure 2, an annular reduced diameter section 9 is disposed
in the lower portion of conditioning valve I at a position near the jet nozzle
7 of
the conditioning valve 1. A nozzle 5a of the moisture conduit 5 exits into
this
reduced diameter section 9, and it is so configured that the moisture W, in
the
4
CA 02405397 2002-09-27
moisture conduit 5 is injected into depressurized steam S, path, in this
reduced
diameter section 9.
This reduced diameter section 9 obtains improved cooling effect by
maintaining the steam S, flow rate immediately passing through the reduced
diameter section 9 faster than the vapor S, passing through the discharge pipe
3, thereby reducing the pressure at the position of the reduced diameter
section
9 below the pressure in the discharge pipe 3. This pressure drop in a reduced
diameter section 9 is due to the increased velocity of a constant flow volume.
Such an effect is well known in the art and is referred to as a Venturi
effect.
Consequently, this embodiment of the present invention allows return of the
moisture W, from the discharge pipe 3 to the conditioning valve 1 by
connecting
the nozzle 5a of moisture transport conduit 5 to this reduced diameter section
9,
and drawing the moisture W, from the nozzle 5a into the conditioning valve 1
using the differential pressure generated by the Venturi negative pressure
phenomenon.
Considering the optimal conditions for the circulation method using this
differential pressure, it is preferable to set this level difference to 10
meters or
less, in the case where the moisture drain 4 is placed lower than the nozzle
5a
(no limitation in the case where the moisture drain section 4 is placed higher
than the nozzle 5a).
In this embodiment, the vapor S, differential pressure is used as
mentioned before, as a means for recycling the moisture W, flowing from the
conditioning valve 1 back to the conditioning valve 1. The system also permits
connecting the moisture transport conduit 5 to a desired position of the
conditioning valve 1 by disposing a forced delivery apparatus (for instance a
pump or the like), in the middle section of the moisture transport conduit 5.
Composed as described above, this embodiment desuperheats the steam
S in the conditioning valve 1, and the desuperheated and depressurized steam
S, is discharged from the conditioning valve 1 together with moisture W into
the
discharge pipe 3. The steam S, flowing through discharge pipe 3 is introduced
into the steam work section 2 connected to the distal end of the discharge
pipe
3. The moisture W, flowing at the bottom of the discharge pipe 3 is extracted
by
5
CA 02405397 2002-09-27
the moisture drain 4, transferred by the moisture transport conduit 5 and
recycled as moisture W for cooling in the steam conditioning valve 1.
Therefore, this embodiment provides for an energy efficient removal of the
moisture W, from the horizontal section 3a of the discharge pipe 3, thereby
preventing the moisture W, from stagnating at the bottom of the discharge pipe
3, avoiding as much as possible the pipe 3 deformation (damage) and the
detrimental effect to the temperature detection sensor and other problems of
the
prior art. Additionally, the present invention provides for recycling the
moisture
W, used for cooling the vapor S, in the conditioning valve 1 providing for
energy
efficient cooling.
6
