U.S. patent application number 11/909668 was filed with the patent office on 2008-12-11 for use of fluidic pumps.
Invention is credited to Anthony Banford, Emmanuel Gaubert, Philip Hopkins.
Application Number | 20080304977 11/909668 |
Document ID | / |
Family ID | 34566741 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080304977 |
Kind Code |
A1 |
Gaubert; Emmanuel ; et
al. |
December 11, 2008 |
Use of Fluidic Pumps
Abstract
The invention provides a method for the transportation of at
least one material in a molten state from a first location to a
second location, the method comprising the use of transfer means
comprising a fluidic pump to effect the transportation of said at
least one material. The preferred type of fluidic pump is the
Reverse Flow Diverter (RFD) Pump. Preferably, the at least one
material in a molten state comprises at least one molten inorganic
salt or molten metal, preferably alkali metal halides such as
potassium chloride or lithium chloride, or eutectic mixtures
thereof. The materials are in a molten state, at a temperature
which is usually in excess of 200.degree. C. A preferred gas for
use according to the method of the invention is dry argon. In a
particularly preferred embodiment, the method of the present
invention is applied to the transportation of molten salts in dry
conditions in various applications in the nuclear industry.
Inventors: |
Gaubert; Emmanuel;
(Rochechouart, FR) ; Hopkins; Philip; (Manchester,
GB) ; Banford; Anthony; (Cheshire, GB) |
Correspondence
Address: |
WARD AND SMITH, P.A.
1001 COLLEGE COURT, P.O. BOX 867
NEW BERN
NC
28563-0867
US
|
Family ID: |
34566741 |
Appl. No.: |
11/909668 |
Filed: |
March 29, 2006 |
PCT Filed: |
March 29, 2006 |
PCT NO: |
PCT/GB2006/001157 |
371 Date: |
July 15, 2008 |
Current U.S.
Class: |
417/86 |
Current CPC
Class: |
F04F 5/54 20130101; F04B
15/04 20130101; F04D 7/06 20130101; F04F 5/24 20130101 |
Class at
Publication: |
417/86 |
International
Class: |
F04B 23/14 20060101
F04B023/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2005 |
GB |
0506511.5 |
Claims
1. A method for the transportation of at least one material in a
molten state from a first location to a second location, said
method comprising the use of transfer means comprising a fluidic
pump to effect the transportation of said at least one material,
wherein said material has a melting point at a temperature which is
in excess of 150.degree. C.
2. A method as claimed in claim 1 wherein said fluidic pump
comprises a Diode Pump or a Reverse Flow Diverter Pump.
3. (canceled)
4. A method as claimed in claim 2 wherein said Reverse Flow
Diverter Pump comprises gas control means, a charge vessel, a
reverse flow diverter and discharge pipework, said gas control
means facilitating the repeated supply of pressurised gas to the
charge vessel in two phases, said phases comprising a drive phase
and a refill phase.
5. A method as claimed in claim 4 wherein, during the refill phase,
a partial vacuum is applied to the charge vessel via the gas
control means to augment the filling rate.
6. A method as claimed in claim 2 wherein said Reverse Flow
Diverter Pump is located inside a feed vessel.
7. A method as claimed in claim 2 wherein said Reverse Flow
Diverter Pump is installed externally to a feed vessel, with
penetration into the lower part of the supply tank.
8. A method as claimed in claim 2 wherein said Reverse Flow
Diverter Pump comprises an Immersion Reverse Flow Diverter.
9. A method as claimed in claim 2 wherein said gas control means
comprises at least two jet pumps, comprising at least one drive jet
pump and at least one suction jet pump, or the availability of
vacuum and pressurised gas.
10. A method as claimed in claim 9 which additionally comprises the
provision of a gas leg between the charge vessel and each of said
at least two jet pumps.
11. (canceled)
12. A method as claimed in claim 1 wherein the material for
construction of said fluidic pump comprises carbon steel, a
Hastelloy, or a silicon carbide ceramic.
13. (canceled)
14. A method as claimed in claim 1 wherein said transfer means is
adapted to allow for the dilation of pipework with temperature.
15. A method as claimed in claim 14 wherein said transfer means
comprises sections of bent pipes.
16. A method as claimed in claim 1 wherein said temperature is in
excess of 200.degree. C.
17. A method as claimed in claim 1 wherein said transportation of
said at least one material in a molten state from said first
location to said second location occurs in dry conditions which are
free from aqueous contamination.
18. A method as claimed in any claim 4 wherein said pressurised gas
comprises a dry and/or inert gas.
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
23. A method as claimed in claim 4 wherein said pressurised gas
comprises dry argon.
24. A method as claimed in claim 4 wherein said pressurised gas is
heated to substantially the same temperature as the melt prior to
use.
25. A method as claimed in claim 4 wherein the pathway through
which the gas is introduced into the apparatus containing the
molten material is heated to ensure that the gas remains at
elevated temperature prior to contact with the molten material.
26. A method as claimed in claim 1 wherein said at least one
material in a molten state comprises at least one molten inorganic
salt or molten metal, a chemical compound or mixture having a
melting point in the range 200.degree. to 1200.degree. C., or a
polymer having a melting point in excess of 200.degree. C.
27. (canceled)
28. (cancelled)
29. A method as claimed in claim 26 wherein said at least one
molten inorganic salt comprises potassium chloride or lithium
chloride, or eutectic mixtures thereof.
30. A method as claimed in claim 26 wherein said molten inorganic
salt is contaminated with species showing radioactivity.
31. (canceled)
32. A method as claimed in claim 26 wherein said at least one
molten metal comprises at least one of sodium, zirconium, aluminum,
titanium, cadmium, uranium or other actinide, or a molten alloy
such as generally used in the foundry or steel-making industry.
33. (canceled)
34. (canceled)
35. A method as claimed in claim 26 wherein said mixture comprises
NaOH/sodium carbonate eutectic.
36. (canceled)
37. A method as claimed in claim 1 wherein the viscosity of the at
least one material in a molten state does not exceed 20 cp.
38. (canceled)
39. A method as claimed in claim 1 wherein the rate of
transportation of said at least one molten material is in the range
between 0.1 and 10 l/s.
40. (canceled)
41. (canceled)
42. (canceled)
43. (canceled)
44. (canceled)
45. (canceled)
46. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the transportation of
materials, more particularly the transportation of molten
materials. Most specifically, the invention is concerned with the
transportation of materials in the molten state, and provides a
simple, dependable method for this purpose.
BACKGROUND TO THE INVENTION
[0002] There is a frequent requirement in industry for the use of
molten materials, both as solvents and as reaction media.
Naturally, there are occasions when the use of such materials
requires the use of a plurality of vessels and, therefore,
necessitates the transportation of the materials between locations.
Technically, this can cause problems, since it is generally the
case that elevated temperatures have to be maintained throughout
the operations which are being performed, in order that the molten
materials remain in a molten state. Thus, it is necessary that
methods of transportation which are employed should not at any
point give rise to a fall in temperature which might lead to
solidification of the material.
[0003] Furthermore, it is often the case that chemical reactions
are required to be carried out in an inert atmosphere from which
air--more specifically, the moisture associated with the
atmosphere--are excluded, in order that unwanted side reactions and
hydrolysis may be avoided which, in extreme circumstances, may
completely prevent a desired reaction from being achieved. In
addition, moisture-sensitive components have to be protected from
contact with the atmosphere at all times in order that problems
associated with hydrolysis and/or degradation may be avoided.
[0004] Such difficulties are frequently encountered on a laboratory
scale, but may be fairly easily overcome in such circumstances by
the provision of an inert blanket of, typically, nitrogen gas using
standard laboratory procedures. When moisture-sensitive materials
require to be handled on a commercial scale, however, the potential
difficulties are exacerbated, and carefully devised procedures have
to be implemented in order that serious problems do not occur. This
is particularly true when such materials have to be transported
though industrial scale apparatus and plant machinery, where damage
to the apparatus could occur, as well as loss of the material.
[0005] In this context, the present inventors have specifically
addressed the difficulties which are associated with the handling
of so-called molten salts on a plant scale. These materials find
widespread use, for example, in the reprocessing/waste conditioning
of irradiated nuclear fuel by means of the Argonne National
Laboratory electrometallurgical treatment process (ANL--EMT) and
the Dimitrovgrad SSC--RIAR process, which both use molten salts at
high temperatures (773 and 1000 K, respectively). Molten salts have
also been proposed for use in the reprocessing of irradiated fuels
from Light Water Reactors (LWRs). A further major interest in
molten salts has centred on their potential use in molten salt
reactors, which would produce electricity, as well as burning
actinides and long-lived fission products.
[0006] These molten salts are typically mixtures of salts which are
liquid only at high temperatures. Traditionally molten salts melt
above 150.degree. C., and more frequently at much higher
temperatures than this, and such salts are usually composed of
inorganic cations. Thus, it can be seen from a consideration of the
prior art that the use of molten salts in industrial applications
is widespread, and there is frequently a requirement for the
handling and transportation of such materials on an industrial
scale.
[0007] Specific examples of the requirement for the handling of
molten salts include the transfer of molten salts with a pump, most
particularly a centrifugal pump, at solar power stations, wherein a
mixture comprising sodium and potassium hydroxides and nitrites,
melting at 146.degree. C., is typically employed, and wherein there
is a requirement for the molten salt to be handled at temperatures
of up to 500.degree. C. Alternatively, simple mixtures of sodium
and potassium hydroxides, melting at 225.degree. C. and showing
increased stability at higher temperatures, may be utilised.
[0008] It will be apparent, therefore, that there are certain key
requirements for the satisfactory handling of molten salts in
industrial applications. Primarily, of course, it is necessary that
there should be provided a heating system capable of heating and
melting salts above the melting point of the salts, and desirably
at a suitably higher temperature, preferably in the range of
500.degree. to 550.degree. C., so to make the melt less viscous.
Furthermore, the apparatus should incorporate suitable insulation
around vessels and pipes, to reduce heat losses and to ensure that
no cold spot develops, which could result in freezing of the
salts.
[0009] In the event that some freezing of the molten salt does
occur, however, it is essential that the apparatus should be able
to withstand a subsequent re-melting operation without suffering
damage, and it is important that the design of the apparatus should
take such considerations into account.
[0010] It is also generally found that the volume of salts
increases by 20% when changing from the solid to the molten state,
so that a zoned heating system is essential to prevent bursting of
pipes or vessel deformation during melting of the salts. As an
alternative to the zoned-heating of vessels to avoid deformation,
it is possible to provide vessels having modified designs, such as
conical vessels, although this is inevitably a more expensive
option.
[0011] In view of the hygroscopic nature of molten salts, it is
also vital to ensure that a dry environment exists in order to
prevent the salts from absorbing moisture, since this would lead to
the release of hydrogen chloride gas and, as a consequence, would
promote very rapid corrosion of the rig, especially at high
temperatures. Thus, it is essential that an inert atmosphere is
provided within the apparatus and, hence, an inerting system,
preferably using an inert gas or a mixture of inert gases, is
incorporated in the apparatus. Typically, said inert gas comprises
argon, especially in nuclear applications where uranium metal is
being handled, since nitrogen has the potential to react with
uranium metal to form uranium nitride.
[0012] Desirably, a system for the handling of molten salts should
also be adapted to incorporate various other additional features
which would facilitate the safe and efficient handling of the said
materials. Included among these features would be the following:
[0013] pressure and vacuum relief system; [0014] gas analyser to
detect concentrations of O.sub.2 and H.sub.2O in the ppm range, in
order to monitor the quality of the inerting system; [0015]
corrosion-resistant and heat resistant metallic parts; [0016]
heat-resistant gaskets, for example graphite-containing gaskets;
[0017] design which accounts for the dilation of pipe with
temperature, for example by the insertion of sections of bent pipes
in order to minimise stresses on pipes and prevent damage or
rupture; and [0018] supervisory control and data acquisition system
(SCADA) to provide interlocks, thereby preventing maloperation and
ensuring sequenced heating--thus, for example, preventing a user
from activating any pump if the salts temperatures in various
places in the rig are not above a given threshold value, i.e. above
the melting point temperature, or ensuring that the correct heating
sequence is adhered to by eliminating the possibility that, for
example, a bottom wrap might be heated as the first step.
[0019] In the light of the above requirements, the present
inventors have sought to provide an apparatus and method which may
be used for the safe and efficient handling and transportation of
molten salts and which may find more general application in the
industrial handling and transportation of molten materials.
[0020] The use of fluidic pumps is known in a large number of
industrial applications for the transfer of various liquids.
Specifically, in the nuclear industry, such pumps have found
application in the transfer of fluidic radioactive materials at
ambient temperatures and has, for example, facilitated complete
containment of the fluids during maintenance procedures, due to the
fact that such pumps have no moving parts in contact with the
fluids and the said procedures are, consequently, all carried out
on external parts of the pumps. This is a vital consideration in
the case of radioactive fluids due to the highly toxic nature of
the materials concerned. Examples of such applications are
disclosed in GB-A-2070699, GB-A-2122262, GB-A-2220709 and
GB-A-2283065.
[0021] Several types of fluidic pump are available, particular
examples being Diode Pumps and Reverse Flow Diverter Pumps. The
common feature of all these pumps is that they use a compressed
gas, such as air or nitrogen, as the power source, and are driven
by means of a cyclic gas pressure pulse. However, the use of such
pumps for the transportation of fluids at very high temperatures
has not been reported and, most particularly, their application to
the transportation of molten materials under such conditions is not
documented.
[0022] Thus, the present inventors have sought to provide a new
method for the transportation of molten materials. More
particularly, the present invention seeks to provide a method for
the transportation of molten salts, which are generally hygroscopic
inorganic salts with melting points in excess of 150.degree. C.,
and more commonly above 200.degree. C., with particular emphasis
being given to the transportation of molten salts utilised in the
nuclear reprocessing industry.
STATEMENTS OF INVENTION
[0023] Thus, according to the present invention, there is provided
a method for the transportation of at least one material in a
molten state from a first location to a second location, said
method comprising the use of transfer means comprising a fluidic
pump to effect the transportation of said at least one
material.
[0024] Typically, said at least one material in a molten state
comprises at least one molten inorganic salt or molten metal.
Preferred molten inorganic salts comprise inorganic halides, most
preferably alkali metal halides such as potassium chloride or
lithium chloride, or eutectic mixtures thereof. Said materials are
in a molten state, at a temperature which is generally in excess of
150.degree. C., and more usually in excess of 200.degree. C.
Optionally, said at least one material in a molten state may
additionally comprise sludge, fines, or other suspended
material.
[0025] Said method comprises the provision of a fluidic pump in the
apparatus in which said at least one molten material is contained
in order to move, lift, transport, transfer or pump said material
from said first location to said second location.
[0026] It is frequently the case that the at least one material
which is to be transported is sensitive to moisture and/or oxygen.
This is certainly true in the case of hygroscopic materials such as
molten salts and, in such cases, it is necessary to maintain dry
conditions and a dry atmosphere throughout processing. Thus, a
preferred embodiment of the invention envisages a non-aqueous
system, wherein there is provided a method according to the
invention for the transportation of at least one material in a
molten state from a first location to a second location in dry
conditions, free from aqueous contamination or any aqueous
materials.
[0027] In the case of oxygen sensitive materials it is, of course,
a requirement that an inert atmosphere should be provided. As
previously noted, the common feature of these fluidic pumps is that
they use a compressed gas, such as air or nitrogen, as the power
source, and are driven by means of a cyclic gas pressure pulse. In
necessary instances, therefore, the pressurised gas may comprise a
dry or an inert gas, or a gas which is both dry and inert. Said gas
may comprise a mixture of gases and, in cases where oxygen
sensitivity does not have to be considered, compressed air,
preferably dry compressed air, provides a suitable gas. A preferred
inert gas is argon; dry argon is suitable for virtually all
applications.
[0028] Optionally, the gas may be heated to substantially the same
temperature as the melt prior to use in order to avoid the
possibility that some solidification of the molten material may
occur on contact with the gas, or during transportation. The
pathway through which the gas is introduced into the apparatus
containing the molten material may also be heated, in order to
ensure that the gas remains at elevated temperature prior to
contact with the molten material. However, in many applications it
is not found to be necessary for either the gas or the pathway to
be heated, since no solidification of the molten material occurs in
the absence of such heating.
DESCRIPTION OF THE INVENTION
[0029] The simplest type of pump is the Reverse Flow Diverter (RFD)
Pump and this is particularly suited to the present application.
The RFD pump comprises a gas controller, a charge vessel, a reverse
flow diverter and discharge pipework. The operation of the pump
relies on the repeated supply of compressed gas to the charge
vessel in two phases, the drive phase and the refill phase.
[0030] During the drive phase compressed gas is passed through the
gas controller to the charge vessel and this forces the molten
material through the RFD, where an increase in flow velocity occurs
in a region of reduced cross-section, leading to a fall in pressure
in that region which causes more molten material to be sucked from
a connected supply tank and, thereby, on to delivery through the
discharge pipework. This phase continues until the charge vessel is
empty, whereupon the pump enters the refill phase when molten
material passes from the supply tank, through the RFD, to refill
the charge vessel. When necessary, a partial vacuum may optionally
be applied to the charge vessel, via the gas controller, to augment
the filling rate. Once the charge vessel is full, the pump
re-enters the drive phase and the phases are repeated in this way
in order to produce a cyclic pumping action.
[0031] An RFD pump may be installed either externally to the supply
tank, with penetration into the lower part of the supply tank or,
where space and lid penetrations allow, the pump may be located
inside the tank. An alternative form of RFD pump comprises the
Immersion RFD, which utilises an RFD mounted within a gas piston,
and thereby minimises the maximum lid penetration required; such
form of pump is of particular use when space or tank lower
penetrations are limited, since it is possible to insert the pump
into a supply tank via an inspection port.
[0032] Suitable materials for construction of fluidic pumps are
determined largely by the nature of the products with which they
are to come in contact. Clearly, it is essential that the materials
should be resistant to attack by these products. In the case of
molten salts, for example, it has been found that carbon steel is
generally satisfactory, although with some molten salts at
particularly high temperatures or pressures, the increased fluid
flow experienced in the region of reduced cross-section within the
RFD can result in some corrosion occurring under certain
conditions. In such cases, the situation may be remedied by
employing a more resistant material in the manufacture of the RFD,
suitable examples including a Hastelloy or a silicon carbide
ceramic.
[0033] When handling the transfer of molten salts, fluidic pumps
have the advantage that there are no moving parts in direct contact
with the salts, thereby minimising the wear and corrosion problems
so frequently encountered with conventional pumps.
[0034] In operation, the design and choice of a suitable RFD pump
for a given melt density is essential to achieve flow when the
suction drive cycle is applied repeatedly. Furthermore, suitable
heating of the charge vessel and RFD device is essential in order
to maintain the material in a molten state. Operation of the RFD
device is dependent on the provision of at least two jet pumps,
comprising at least one drive jet pump and at least one suction jet
pump, or the availability of vacuum and pressurised gas.
[0035] Preferably, the fluidic pump comprises a controller, adapted
to time the drive and suction phases so as to achieve a
satisfactory flow, and to avoid overblow or aspiration, and the
creation of a spray of molten material at the delivery end of the
pipe. Clearly, as pressurised gas is supplied to an apparatus, the
pressure in the apparatus will increase and, therefore, adjusting
the controller so as to set the drive and suction times in
accordance with these requirements is an operation most
satisfactorily carried out by a skilled person, since it is
important that undesirable pressure fluctuations should be avoided
whilst performing the method of the invention.
[0036] Another preferred feature of a fluidic pump for use
according to the method of the invention envisages the provision of
a gas leg, between the charge vessel and each of said at least two
jet pumps, in order to avoid the possibility that the melt could
reach the jet pump, in the event that the melt was over-aspired.
Preferably, each of said gas legs has a height of at least 8 m.
[0037] It is also preferred that, during operation, a pressure
relief adjustment should be carried out to ensure that the pressure
is 40 mbarg or less, so that overfilling of the charge vessel may
be avoided. Self-filling of the charge vessel occurs due to the
positive pressure in the main vessel. It is also desirable that a
facility should be available to allow for a decrease in the suction
time, so as to accommodate the self-filling of the charge
vessel.
[0038] The method of the invention is applicable to the
transportation of a range of molten materials. Particular mention
may be made of molten salts or combination of molten salts, having
melting points in the range of 200.degree. to 1200.degree. C.
However, the molten material may also comprise at least one of the
following: [0039] a metal in a molten state, typically sodium,
zirconium, aluminium, titanium, cadmium, uranium or other actinide;
[0040] a molten alloy, for example as generally used in the foundry
or steel-making industry; [0041] a chemical compound or mixture
having a melting point in the range 200.degree. to 1200.degree. C.,
for example LiCl/KCl eutectic, or NaOH/sodium carbonate eutectic,
the latter having m.p. 284.degree. C. and finding use in
pyrochemistry and for the treatment or destruction of wastes;
[0042] a polymer having a melting point in excess of 200.degree.
C.
[0043] Successful application of the method of the invention
requires that the material to be transported should be sufficiently
mobile in its molten state to allow it to flow through a given
apparatus from a first location to a second location. Consequently,
it is necessary that the viscosity of the material should not
exceed certain limits. In general it is found that optimum results
are achieved when the viscosity does not exceed 20 cp, and
preferably, it will not exceed 15 cp. In such circumstances,
transportation of a range of molten materials may be achieved at
rates in the range between 0.1 to 10 l/s, with the exact rate
frequently being dependent on parameters such as the diameter of
pipes and the efficiency of the fluidic pump which can, of course,
place limitations on the upper end of this range.
[0044] It will be understood from the foregoing that it is often
preferred that the gas which is supplied should be dry and/or
inert, in order that the gas will not react with, or be absorbed
by, the molten material. However, circumstances may be envisaged
wherein it might be acceptable, or even desirable, that the gas
should react with, or be absorbed by, the said materials. Thus, the
invention is not limited to the use of non-reacting gases, since it
may be required to react or saturate a molten material with a
particular gas.
[0045] The method of the invention provides a simple, reliable and
repeatable means for the transportation of molten materials, and
does not require the provision of additional moving parts. In
operation, no further heating of the molten material occurs, as is
the case with the increasing temperature observed as a consequence
of the mechanical energy delivered by a centrifugal pump, for
example.
[0046] In a particularly preferred embodiment, the method of the
present invention may be successfully applied to the transportation
of molten salts at high temperatures, and particularly to the
transportation of molten inorganic halides, such as lithium
chloride, potassium chloride and eutectic mixtures thereof. The
method is of particular value in the transportation of such molten
salts in various applications in the nuclear industry, especially
in nuclear fuel reprocessing, when the molten salts may be
contaminated with numerous species showing radioactivity,
including, for example, various lanthanide and actinide metals and
their compounds, or assorted fission products, and provides a safe
and convenient means for the transportation of the said
materials.
DESCRIPTION OF THE DRAWINGS
[0047] The method of the present invention will now be further
illustrated, though without in any way limiting its scope, by
reference to the accompanying figures, wherein
[0048] FIG. 1 shows a schematic diagram of a Reverse Flow Diverter
Fluidic Pump in an internally mounted arrangement for use in the
transportation of molten salts according to the method of the
invention; and
[0049] FIG. 2 shows a graphical representation of the results
achieved by the application of the method of the invention to the
transportation of molten salts.
[0050] Looking firstly at FIG. 1, there is shown a simplified
schematic diagram of a Reverse Flow Diverter Pump in an internally
mounted arrangement, suitable for use in a molten salts dynamic
rig. The apparatus comprises a feed vessel (1), inside which are
located a charge vessel (2) and a Reverse Flow Diverter (3). The
feed vessel and charge vessel contain molten salt (4). The Reverse
Flow Diverter (3) is connected to the charge vessel (2) by means of
a pipeline (5), and a further pipeline (6) exits the feed vessel
(1) from the Reverse Flow Diverter (3). Pipeline (7) connects the
charge vessel (2) to drive jet pump (8), which, in turn, is linked
to suction jet pump (9) and first control valve (10). The suction
jet pump (9) is connected to a second control valve (11) and, via
pipeline (12), to vent (13). Pipeline (12) is also linked to the
feed vessel (1) by means of pressure relief valve (14). Valve (14)
serves to protect feed vessel (1) from overpressure; a vacuum
relief valve (not shown) is also fitted to feed vessel (1) as an
additional means of protection against overpressure. The apparatus
of FIG. 1 also includes an argon supply, a suitable control unit,
and other control valves which are not specifically
illustrated.
[0051] In operation, argon, supplied under pressure, is passed
through first control valve (10) and drive jet pump (8) to the
charge vessel (2), thereby forcing the fluid through the pipeline
(5) to the Reverse Flow Diverter (3) and causing more fluid to be
sucked from the feed vessel (1). The fluid is then delivered
through the pipeline (6) and transported to a different location.
This part of the cycle comprises the drive phase and continues
until the charge vessel is empty, which typically is for a period
of around 15 seconds.
[0052] Thereafter, in the refill phase, fluid passes from the feed
vessel (1) through the Reverse Flow Diverter (3) to refill the
charge vessel (2). Preferably, a partial vacuum is applied to the
charge vessel (2) by means of the suction jet pump (9), via
pipeline (12), in order to augment the rate of filling. This part
of the cycle is generally complete in around 45 seconds, so that
the full cycle takes in the order of 1 minute to complete, and is
then repeated as many times as necessary to complete the transfer
of molten material.
[0053] Turning now to FIG. 2, there is illustrated the results of
extended trials of a Reverse Flow Diverter with molten salts,
showing plots of (a) salt level and (b) rig pressure against time.
The labels 1 to 5 on the plot correspond to various rest times
between each drive-suction cycle. By comparison of the observed
change in salt level with the rig pressure at the same time in the
operation, it may be deduced that the molten material was pumped by
the RFD.
[0054] Thus, for example, at the end of the series indicated by
labels 3 and 4, once the RFD pump is stopped, the level in the
pumping tank (V2002) increases as the holdup of melt decreases in
the receipt vessel and pipes, that is as the melt drains back into
the pumping tank. Conversely, at the start of the series indicated
by label 2, once the RFD pump is started, the level in the main
tank decreases whilst the holdup of melt increases in pipes, i.e.
the main tank is partially emptied. More generally, in a closed
loop system between two vessels, the melt level in the pumping tank
will vary primarily as a function of the flow rate of the melt.
However, these variations are frequently more complex than the
shutdown and startup examples explained herein, as will be apparent
to the skilled person from a detailed analysis of FIG. 2.
* * * * *