Title: Method and plant for cooling fluids by direct contact with liquefied gases
Abstract: A method and apparatus for cooling a fluid in the liquid state, possibly also containing solid elements, comprising feeding said fluid into a containing member for said fluid and also feeding into said member a cooling fluid in the liquid state, such as a liquefied gas; said fluids are brought into direct contact within said containing member so that by absorbing heat, the cooling fluid passes into the gaseous state and cools the fluid to be cooled, these fluids then being extracted directly from said member by separate conduits.
Patent Number: 6,968,705 Issued on 11/29/2005 to Frati
| Inventors:
|
Frati; Maurizio (Milan, IT)
|
| Assignee:
|
L'Air Liquide, Société Anonyme à Directoire et Conseil de Surveillance (Paris, FR)
|
| Appl. No.:
|
774287 |
| Filed:
|
February 6, 2004 |
Foreign Application Priority Data
| Dec 03, 2003[IT] | MI2003A2367 |
| Current U.S. Class: |
62/64; 62/121; 62/50.2 |
| Intern'l Class: |
F25D 017/02 |
| Field of Search: |
62/64,502,98,121,373
|
References Cited [Referenced By]
U.S. Patent Documents
| 3878683 | Apr., 1975 | Imai.
| |
| 4141224 | Feb., 1979 | Alger et al.
| |
| 4237695 | Dec., 1980 | Oberpriller et al.
| |
| 4329850 | May., 1982 | Drummond.
| |
| 4330307 | May., 1982 | Coury.
| |
| 4348867 | Sep., 1982 | Musschoot.
| |
| 4438633 | Mar., 1984 | Hiser.
| |
| 4667418 | May., 1987 | White.
| |
| 5106400 | Apr., 1992 | Tick.
| |
| 5478584 | Dec., 1995 | Donohue et al.
| |
| 5802858 | Sep., 1998 | Cheng et al.
| |
| 6837613 | Jan., 2005 | Terentiev.
| |
| Foreign Patent Documents |
| 356055798 | May., 1981 | JP.
| |
| 356080600 | Jul., 1981 | JP.
| |
| 401167565 | Jul., 1989 | JP.
| |
Primary Examiner: Doerrler; William
Assistant Examiner: Ali; Mohammad M.
Attorney, Agent or Firm: Russell; Linda K., Haynes; Elwood
Claims
1. A method for the controlled continuous cooling of a subject fluid by using
a cooling fluid comprising:
a) introducing said subject fluid into a containing member, wherein said subject
fluid is in the liquid state, said containing member further comprising an upper
end and a lower end,
b) providing a cooling fluid to a tank, wherein said tank is fluidly connected
to said containing member by at least one conduit,
c) introducing said cooling fluid into said containing member,
d) directly contacting said cooling fluid with said subject fluid in said containing member,
e) cooling said subject fluid, wherein said cooling fluid enters the vapor phase,
f) removing said cooling fluid in the vapor state and said subject fluid from
said containing member.
2. The method according to claim 1, wherein said subject fluid is a consumable goods.
3. The method of claim 1, wherein said subject fluid is a food product.
4. The method of claim 1, wherein said subject fluid is single-phase.
5. The method of claim 1, wherein said subject fluid is multi-phase.
6. The method of claim 5, wherein said subject fluid contains solid bodies.
7. The method according to claim 1, wherein the contact between the cooling fluid
and the subject fluid takes place at a pressure greater than atmospheric.
8. The method according to claim 7, wherein the cooling fluid fed to the containing
member is pressurized.
9. The method according to claim 7, wherein the pressure in the containing member
is used to evacuate the subject fluid from said containing member.
10. The method according to claim 7, wherein the pressure in the containing member
is regulated by the pressure drop through a valve positioned in a discharge conduit
for said cooling fluid in vapor state.
11. The method according to claim 7, wherein the pressure in the containing member
is regulated on the basis of the level of the subject fluid in said containing member.
12. The method according to claim 1, wherein the cooling fluid is selected from
the group consisting of N2, CO2 and Ar.
13. The method according to claim 1, wherein said subject fluid is removed at
the lower end of said containing member, and said cooling fluid in vapor state
are removed from the upper end of said containing member.
14. The method according to claim 13, wherein said vapor is inserted into the
containing member to facilitate mixing between the subject fluid and the cooling fluid.
15. The method according to claim 14, wherein the inserted vapor is chemically
identical to the cooling fluid.
16. The method according to claim 14, wherein the inserted vapor is chemically
different from the cooling fluid.
17. The method according to claim 1, wherein one or more of the temperature,
the pressure and the level of the fluid in the containing member is continuously controlled.
18. The method according to claim 14, wherein the vapor is inserted into the
containing member in accordance with the physical characteristics of the subject
fluid which is present in said containing member.
19. An apparatus for the controlled continuous cooling of a subject fluid by
using a cooling fluid comprising:
a) a tank of cooling fluid, said cooling fluid comprising a liquefied gas,
b) a containing member,
c) said tank being connected to said containing member by a cooling fluid conduit,
d) said containing member comprising a subject fluid conduit,
e) said containing member comprising at least one internal chamber to which said
cooling fluid conduit and said subject fluid conduit are connected and within which
said subject fluid is placed into direct contact with said cooling fluid,
f) said containing member comprising cooling gas discharge conduit and cooled
subject fluid discharge conduit through which cooling fluid in vapor phase and
cooled subject fluid are separately extracted after their mutual direct contact.
20. The apparatus according to claim 19, wherein cooling fluid conduit is connected
to the containing member via an injector with an orifice sized for the entry of
said cooling fluid into said containing member.
21. The apparatus according to claim 19, wherein said cooling fluid conduit is
connected to the containing member by a pipe provided with a flow control valve.
22. The apparatus according to claim 20, wherein a vapor conduit is connected
to the liquefied gas conduit, said vapor conduit feeding said vapor to said injector
when the flow of liquefied gas to the containing member through said cooling fluid
conduit ceases.
23. The apparatus according to claim 20, wherein said cooling gas discharge conduit
is connected to a circuit unit, said circuit unit comprising recycle conduits and
said injector, wherein said circuit unit withdraws part of said vapor from said
cooling gas discharge conduit and injects it into said containing member in order
to facilitate mixing of said cooling fluid with said subject liquid.
24. The apparatus according to claim 23, wherein said circuit unit is connected
to a feed conduit for powering fluid.
25. The apparatus according to claim 23, wherein an auxiliary gas conduit is
connected to a lower part of said containing member in order to feed gas or vapor
into said containing member to facilitate mixing of the cooling fluid with the
subject fluid.
26. The apparatus according to claim 19, wherein said cooling gas discharge conduit
comprises a valve member enabling the pressure in the interior of said member to
be regulated.
27. The apparatus according to claim 19, further comprising plant control means
connected to measurement means for measuring one or more of the temperature, the
pressure, or the level of the fluids within said containing member.
Description
This application claims the benefit of priority under 35 U.S.C. § 119 (a)
and (b) 1 to Italian Application No. MI2003A002367, filed Dec. 3, 2003, the entire
contents of which are incorporated herein by reference.
The present invention relates to a method and plant for cooling a fluid in accordance
with the introduction to the corresponding independent claims.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention provides a method and plant for cooling fluids in the liquid state,
possibly also containing solid elements, by means of a cooling fluid consisting
of a liquefied gas such as N2, CO2, Ar or a mixture thereof, the cooling fluid
passing into the gaseous or vapour state following the heat transfer.
2. Related Art
As is widely known, to cool a liquid, apparatus or plants are usually used having
surfaces of separation between the cooling fluid and the fluid to be cooled. However,
this solution necessarily implies a low overall heat transfer coefficient and a
mechanical action on the fluids due to the friction between these and the separation
surfaces. This mechanical action limits the use of this type of apparatus if this
phenomenon can degrade the organoleptic characteristics of the fluid to be cooled,
such as in the case of pressed grape pulp.
A method for cooling fluids using liquefied gases is already known from a previous
patent of the same applicant. That patent (IT1313938) describes a method for cooling
a liquid in a controlled manner using liquefied gases as coolants, said liquid
possibly also containing solid bodies. The method consists of feeding said liquid
to be cooled into a containing member, also feeding into said member a suitable
quantity of liquefied gas such that this latter comes into direct contact with
said liquid, this contact leading to the transformation of the liquefied gas into
a gaseous phase and to the cooling of the liquid, said gas or vapour and said cooled
liquid then being extracted from the containing member.
In this prior patent a conduit is provided to transfer the cooled fluid and the
gas or vapour, generated during heat transfer by the apparatus in which the heat
transfer takes place, to the apparatus in which the two fluids are separated, this
conduit being traversed by the fluids at high velocity so that both the cooled
liquid, or two-phase solid-liquid mixture, and the cooling fluid in the gas or
vapour state are transferred simultaneously.
OBJECTS OF THE INVENTION
If the characteristics of the liquid to be cooled are such as to enable it, any
contained solid parts may undergo damage within this conduit because of their high
velocity, a non-limiting example being damage to the grapes in the case of pressed
grape pulp.
BRIEF DESCRIPTION OF THE DRAWINGS
For a further understanding of the nature and objects for the present invention,
reference should be made to the following detailed description, taken in conjunction
with the accompanying drawings, in which like elements are given the same or analogous
reference numbers and wherein:
An object of the present invention is to provide a method and plant for cooling
a liquid, possibly also containing solid elements, which represent an improvement
over similar known methods and plants.
Another object is to provide a plant which uses compact apparatus and simplified
operative modalities compared with similar known plants.
These and further objects which will be apparent to the expert of the art are
attained by a method and plant in accordance with the accompanying claims.
The present invention will be more apparent from the accompanying drawing, which
is provided by way of non-limiting example, and in which:
DESCRIPTION OF PREFERRED EMBODIMENTS
- Conduit 3 is the Subject Fluid Conduit.
- Conduit 6 is the Cooling Fluid Conduit.
- Conduit 9 is the Vapor Conduit.
- Conduit 14 is the Cooled Subject Fluid Discharge Conduit.
- Conduit 18 is the Cooling Gas Discharge Conduit.
- Conduit 20 is the Auxiliary gas Conduit.
- Conduits 22, 26 are the Recycle Conduits.
- Conduit 24 is the Feed Conduit.
FIG. 1 is a schematic view of a plant according to the invention;
FIG. 2 shows a liquefied gas injector of the plant of FIG. 1;
FIGS. 3,
4 and
5 show three variants of the feed line for the
liquefied cooling gas and the gas or vapour used in the plant of FIG. 1.
With reference to the said figures, a line
1 is shown comprising a pump
2 drawing a liquid to be cooled (contained in its own tank or present in
a transfer line, not shown). From the pump there extends a pipe
3 provided
with a valve
3a through which the liquid to be cooled is fed to a
containing and heat transfer member (or cooler)
4 where it comes into direct
contact with a liquefied gas taken from its own storage tank
5 via one or
more lines
6 (of which only one is shown in the figures) provided with a
three-way valve
8 and injector
7 which feeds the liquefied gas into
the cooler
4. The injector
7, shown in FIG. 2, is sized to enable
definite quantities of liquefied gas to pass through a sized hole
7a
after the liquefied gas, originating from the pipe
6, has passed through
the portion
7c.
Gas or vapour is fed in the aforedescribed manner to prevent the injector
7
filling with cooling liquid along the portion
7c when liquefied gas
feed via the injector is not required, with the risk that on again connecting the
injector
7 associated with the line
6, contact takes place between
the liquefied gas and the liquid to be cooled, with possible freezing of this latter
because of the low temperature attained, and consequent obstruction of the injector
7, so preventing its correct operation.
If the pressure in the tank
5 is insufficient for injecting the liquefied
gas into the cooler
4, a pump with suitable characteristics for supplying
the necessary pressure is connected into the line
6, said pump not being
shown in the figures.
By way of example, the cooling fluid is a liquefied gas such as N2, CO2 or Ar.
A gas or vapour pipe
9 provided with a valve
10 is connected to
the
valve
8, of known three-way type, the gas or vapour being injected, by the
injector
7, into the cooler
4 instead of the liquefied gas when the
valve
8 shuts off liquefied gas passage along the pipe
6.
Gas or vapour is fed in the aforedecribed manner to prevent the injector
7
filling with cooling liquid along the portion
7c when liquefied gas
feed via the injector is not required, with the risk that on again connecting the
injector
7 associated with the line
6, contact takes place between
the liquefied gas and the liquid to be cooled, with possible freezing of this latter
because of the low temperature attained, and consequent obstruction of the injector
7, so preventing its correct operation.
FIGS. 3 and 4 show two alternative solutions for injecting gas or vapour into
the injector
7 when this latter is not traversed by the liquefied gas.
Specifically, in the solution shown in FIG. 3 the three-way valve is
replaced by two one-way valves, one connected into the pipe
6 and one into
the pipe
9; with this solution, when liquefied gas is to be injected the
valve
8a is opened and the valve
10 is closed and, vice versa,
when gas is to be injected the valve
10 is closed and the valve
8a
is opened.
The solution shown in FIG. 4 is usable when the pressure of the gas or vapour
present in the pipe
9 is less than that of the liquefied gas present in
the pipe
6 and greater than that present in the cooler
4, and consists
of replacing the valve
10, shown in FIGS. 1 and 3, with a unidirectional
non-return valve
10a which allows gas or vapour to pass when the
valve
8 is closed.
From the aforestated it follows that the injector
7 is always traversed
by a liquefied gas or by a gas or vapour, so preventing the presence in the portion
7c of liquid to be cooled.
FIG. 5 shows a solution which does not use the injector
7 with the sized
hole
7a, but uses only a control valve
8b to dispense
the liquefied gas.
In the cooler
4 the direct contact between liquefied gas and the liquid
to be cooled takes place at higher than atmospheric pressure. Known components
are installed in the cooler to measure the process parameters such as one or more
temperature indicators
13, level indicators
12 and pressure indicators
11.
A discharge pipe
18 with relative valve
19 is installed in the
top
of the cooler
4 to evacuate the gas or vapour generated by the liquefied
gas which is developed within the cooler
4 as a result of heat transfer.
By suitably regulating the opening of the valve
19, the pressure within
the container member
4 can be regulated, as will be described, this pressure
being used to push the cooled liquid out of the container member
4 via the
line
14.
A part of the gas or vapour developed within the cooler
4 can be withdrawn
from the pipe
18 by a pipe
22, this gas or vapour part being fed,
using a powering fluid originating from the line
24 (connected to a suitable
tank or to a distributor line thereof) provided with a valve
25, and aided
by a known injector
23, into the bottom of the cooler
4 to adequately
mix the liquid to be cooled and the liquefied gas present therein. For example,
the injector
23 is an expansion-compression conduit known as a Venturi tube,
but can be any other machine which draws in and compresses the vapour drawn from
the cooler
4 using electromechanical energy without the aid of a powering fluid.
The said control unit (not shown) receives the values of the measured parameters
such as temperatures from the indicator
13, the level from the indicator
12, and the pressure from the indicator
11, and processes the determined
values in accordance with known algorithms with which the system is provided. The
result of processing the said algorithms is the definition of the state (such as
valve positions, i.e. open/closed/partially open, etc.) of the said components
during operation, this state being achieved by the system with the aid of known
controlled electropneumatic components connected to the movable parts of the plant
(for example valves).
This expedient means that because of this mixing action, when the flow of cooled
liquid is to continue, the friction which the pressure in the cooler
4 has
to overcome is of dynamic instead of static type, it being well known that dynamic
friction is less than static friction so that the pressure required to reactivate
the flow is less in this case than without mixing the liquid, the initial flow
reactivation rate consequently being less than without fluidification, so more
slowly modifying the operating conditions and hence limiting the system oscillations
about hydrodynamic equilibrium.
In the bottom of the cooler
4 there is also installed a pipe
20
with relative valve
21 for possible addition of gas or vapour for the purpose
of adequately mixing together the liquid to be cooled and the cooling gas, within
the cooler.
To control the cooling process, the invention comprises a control unit (not shown,
comprising for example an electronic processor and/or a programmable unit or PC)
and other known electromechanical components, the purpose of which is to position
the plant components (such as the valves
8,
10,
15,
17,
19,
21,
25 and the pump
2) as required for proper operation
of the plant and in accordance with the logic described hereinafter.
The said control unit (not shown) receives the values of the measured parameters
such as temperatures from the indicator
13, the level from the indicator
12, and the pressure from the indicator
11, and processes the determined
values in accordance with known algorithms with which the system is provided. The
result of processing the said algorithms is the definition of the state (such as
valve; positions, i.e. open/closed/partially open etc.) of the said components
during operation, this state being achieved by the system with the aid of known
controlled electropneumatic components connected to the movable parts of the plant
(for example valves).
A possible method of operating the invention will now be described by way of
non-limiting illustration.
The liquid to be cooled is forced through the plant
3 and into the cooler
4 where its level is determined by the indicator
12 and its temperature
by the probe
13. The level indicator
12 is linked by algorithmic
correlation to a valve
19 connected into the pipe
18, this algorithmic
correlation associating a determined degree of opening of the valve
19 with
the level of the fluid present in the cooler
4, determined by the indicator
12. Specifically, various correlation algorithms can be used but all have
the following characteristics:
- lesser opening of the valve 19 corresponds to greater level,
- total closure of the valve 19 corresponds to a level chosen as
the maximum allowable for operation.
The temperature indicator
13 continuously determines the temperature of
the mixture of fluids, i.e. the liquid to be cooled, the liquefied gas and liquefied
gas vapour, present in the cooler
4 and if this is greater than the required
set value, the control unit feeds liquefied gas into the cooler
4 via one
or more lines
6 connected to one or more injectors
7.
Those injectors
7 which at a given time are not traversed by liquefied
gas are traversed instead by gas or vapour via the pipes
9 connected to
the injectors by correctly positioning the three-way valve and opening the valve
10; alternatively, if the three-way valve
3 is not present but instead
one of the expedients indicated in FIGS. 3 and 4 is provided, these connections
are made by closing the valve
8a and opening the valve
10
if the expedient adopted is that indicated in FIG. 3, or by closing only the valve
8a if the expedient adopted is that of FIG. 4.
At the commencement of the cooling process, the liquid to be cooled, forced into
the cooler
4 by the pump
2, begins to fill the cooler, and when its
level reaches a minimum threshold, definable at any particular time by the control
unit, this latter opens the valve
15 and possibly the valve
17 connected
into the pipe
16, to enable the cooled liquid contained in
4, if
the internal pressure allows it, to emerge for feeding to the required destination.
The valve
17 is opened mainly when the cooled liquid has a high viscosity,
hence presenting a considerable resistance to movement and therefore requiring
a high pressure within the cooler
4.
As the feed of liquid to be cooled continues, its level within the cooler
4
continues to increase. By virtue of the correlation between the level and the degree
of opening of the valve
19 and consequently of the pressure drop that this
generates in the vapour leaving the pipe
18, at a certain point a pressure
is attained in the cooler which is sufficient to overcome the pressure drop through
the transfer line
14. On attaining this pressure, the cooled liquid begins
to leave the cooler through the pipe
14.
For a better understanding of the aforestated, it should be noted that the said
sufficient pressure is attained because if cooled liquid is not emerging or emerging
at a lower rate than the entry rate, the fluid level within the cooler increases,
then by virtue of the algorithmic correlation between the measured level and the
opening of the valve
19 connected into the discharge pipe
18 for
the gas or vapour generated by heat transfer between the liquefied gas and the
liquid to be cooled, the valve
19 tends to close, to offer a resistance
to gas or vapour exit and hence generate within the cooler
4 a pressure
necessary and sufficient to eject the cooled liquid.
The pressure stabilizes at a value such as to enable an exit flow rate of cooled
liquid to be achieved equal to the entry flow rate, this signifying a constant
level and hence, if in the meantime there have been no variations in the flow of
gas or vapour generated by the refrigerant fluid to be disposed of, a constant
degree of opening of the valve
19, so attaining a hydrodynamic equilibrium
situation within the cooler.
The value of the parameters involved in the hydrodynamic equilibrium position,
such as internal pressure and fluid level and/or opening of the valve
19,
can vary with time depending on the hydrodynamic characteristics of the fluids
concerned, the liquefied gas and the liquid to be cooled, their flow rates and
the pressure drops which the cooled liquid has to overcome to reach its next destination,
downstream of the pipe
14.
The invention, structured in this manner, operates continuously by injecting
that quantity of liquefied gas necessary and sufficient for the required cooling
of the liquid transiting through the cooler
4.
If the liquid to be cooled has a viscosity and/or density such that its mixing
by the gas or vapour developed by the liquefied gas and passing through the fluid
mass contained in the cooler
4 is insufficient for uniform cooling, the
required mixing can be achieved by feeding into it a quantity of gas or vapour
sufficient for the purpose via the pipe
20 and valve
21.
Another way of achieving sufficient mixing, while limiting the gas or vapour
quantity to be added, is to use the pipes
22,
24,
26, the
injector
23 and the valve
25 in the following manner.
By opening the valve
25 to a defined extent, a determined quantity of
gas
or liquid enters the injector
23 via the line
24, to act as a powering
fluid which, by creating a vacuum in the pipe
22, draws the gas or vapour
from the line
18 and mixes it with the powering gas or vapour which, via
the pipe
26 is fed to the bottom of the cooler
4 to hence achieve
an adequate degree of mixing.
On termination of the cooling process, the cooler can be emptied of its contents
by simply not feeding the liquid to be closed, closing the valve
3a and
the valve
19 and feeding gas, vapour or liquefied gas into the cooler until
this produces a pressure sufficient to expel all the cooled liquid contained in
the cooler.
It will be understood that many additional changes in the details, materials,
steps and arrangement of parts, which have been herein described in order to explain
the nature of the invention, may be made by those skilled in the art within the
principle and scope of the invention as expressed in the appended claims. Thus,
the present invention is not intended to be limited to the specific embodiments
in the examples given above.
*
