Hydrogen fluoride supply unit
The present invention which claims priority to European patent application
N° 10177188.9 filed September 16, 2010 the whole content of this application
being incorporated herein by reference for all purposes relates to a hydrogen
fluoride supply unit, a chemical plant comprising such unit and a method of
hydrogen fluoride supply.
Hydrogen fluoride is useful notably as feed material for chemical
manufacturing processes such as manufacture by electrolysis of molecular
fluorine (F ), useful for example as chamber cleaning gas in the semiconductor
industry, and the manufacture of other fluorinated chemicals such as fluorinated
hydrocarbons.
In reference WO 2004/009873, an apparatus and a method for the
generation of fluorine by the electrolysis of hydrogen fluoride are described.
The apparatus comprises: a plurality of individual fluorine generating cassettes;
said individual fluorine generating cassettes being operably connected to a
fluorine gas distribution system for the remote use and consumption of said
fluorine gas; said fluorine generating cassettes being individually isolatable from
said gas distribution system and removable from the apparatus for remote
maintenance. In line 32 on page24 it is mentioned that a supply of liquid
hydrogen fluoride is held in a tank. A hydrogen fluoride vaporizer vaporizes
liquid hydrogen fluoride from the tank and supplies it to the cassettes to maintain
a constant concentration of electrolyte.
The invention now makes available a hydrogen fluoride supply unit which
allows for stable and economic supply of HF while minimizing safety risks.
The invention concerns in consequence a hydrogen fluoride supply unit
which comprises a plurality of transportable hydrogen fluoride storage
containers (1) connected to a hydrogen fluoride supply line (2) wherein at least
one of the hydrogen fluoride storage containers has a capacity of equal to or
greater than 500 1. Preferably, all of the hydrogen fluoride storage containers
have a capacity of equal to or greater than 500 1.
Short description of the drawing
Figure 1 shows a hydrogen fluoride supply unit of the present invention
comprising storage containers (1), a hydrogen fluoride supply line (2), a
manifold (3) and remotely controlled valve (4). Figure 1 provides an
embodiment wherein the HF withdrawn from the storage containers (1) is
forwarded to an HF electrolysis cell (7) wherein F is produced.
Detailed description of the invention
"Hydrogen fluoride" (HF) is understood to denote in particular anhydrous
hydrogen fluoride. When included in a storage container, the hydrogen fluoride
is generally liquid. Preferably, no sorbent is contained in the hydrogen fluoride
storage containers. Preferably, the anhydrous HF essentially consists of HF.
The hydrogen fluoride supply unit according to the invention generally
comprises from 2 to 20, preferably from 3 to 10, more preferably 4, 5 or 6
storage containers.
In a particular embodiment, the hydrogen fluoride supply unit further
comprises, preferably permanently, at least one hydrogen fluoride emergency
container. Such hydrogen fluoride emergency container is preferably an empty
hydrogen fluoride storage container as described herein, which is preferably
connected to the hydrogen fluoride supply line. The hydrogen fluoride
emergency container is suitably kept under pressure of an inert gas or under
vacuum. The hydrogen fluoride emergency container is generally operable to
receive HF from a leaking hydrogen fluoride storage container.
Means for transferring HF from a leaking HF storage container to the
hydrogen fluoride emergency container include, for example, inert gas pressure
or a pump.
In the hydrogen fluoride supply unit according to the invention, the
hydrogen fluoride storage containers are generally hollow bodies which can
optionally be mounted on wheels or which can be transported e.g. by a forklift.
The hydrogen fluoride storage generally has at least a liquid line and a gas line.
In that case, the liquid line can be connected, if appropriate to the hydrogen
fluoride supply line, for example by means of a flange connection. The gas line
can additionally be connected to an inert gas (e.g anhydrous air or nitrogen)
supply line which allows to pressurize the hydrogen fluoride storage container.
In the hydrogen fluoride supply unit according to the invention, preferably
each hydrogen fluoride storage container has generally a capacity of from 500
to 5000 1more preferably, 5001 to 4000 1, and especially preferably from 1000 to
3000 1. Particular examples of hydrogen fluoride storage containers are tanks
approved by RID/ADR - IMDG - of UN T22 or, preferably, UN T20 type. Such
tanks are commercially available.
In the hydrogen fluoride supply unit according to the invention, each
storage container can be suitably connected to the hydrogen fluoride supply line
through a manifold (3).
In the hydrogen fluoride supply unit according to the invention, each
storage container is preferably individually isolatable from the hydrogen fluoride
supply line.
In the hydrogen fluoride supply unit according to the invention, the storage
containers (1) can generally be isolated from the hydrogen fluoride supply
line (2) by a remotely controlled device (4), preferably a remotely controlled
valve. More preferably, each storage container is equipped with a remotely
controlled device (4), preferably a remotely controlled valve, allowing to isolate
that container from the hydrogen fluoride supply line.
When remotely controlled valves are present, manual valves are suitably
installed in addition. The remotely controlled valves allow for example to
operate the HF storage containers from a remote control-room.
In a preferred embodiment, the HF storage containers comprise an
automatic HF level sensor. In particular the HF storage containers can be
installed on weighing scales. In this preferred embodiment, preferably, a process
control system, in particular an automatic process control system is operable to
close the remotely controlled valve of a first, empty HF container and to open the
remotely controlled valve of another second HF-containing hydrogen fluoride
storage container. This embodiment is particularly effective to avoid manual
handling of HF valves and to ensure a continuous HF supply.
In a preferred aspect, the valves are operable to close automatically in case
of anomal operation state, such as for example a process interruption in a process
equipment connected to the HF supply line.
In another preferred aspect, the valves are operable to close automatically
in case of an HF leakage in the hydrogen fluoride supply unit according to the
invention. Such HF leakage can for example be caused by a leakage of optional
flange connections inside the HF storage container. This avoids in particular the
necessity to approach the hydrogen fluoride supply unit in this case.
More preferably the storage containers can be isolated from the HF supply
line by double isolation valves having a closed isolation space. In that case, the
hydrogen fluoride supply unit according to the invention suitably further
comprises at least one interspace vent valve in connection with one or more
closed isolation space. The interspace vent valve is generally operable to remove
optionally present hydrogen fluoride from the closed isolation space. Removal
can be carried out, for example, by applying vacuum. In another aspect, removal
can be carried out, for example, by flushing the closed isolation space with an
inert gas and/or a pressurized purging gas such as for example anhydrous air or,
preferably, nitrogen. In one aspect, the removal is carried continuously.
Preferably, the removal is carried out discontinuously, in particular when an HF
storage container is connected to and/or disconnected from the supply line. If
appropriate, gases recovered from the closed isolation space are suitably vented
to an HF destruction unit, for example a scrubber.
In a preferred aspect of the hydrogen fluoride supply unit according to the
invention, the hydrogen fluoride storage containers (1) are contained in an
enclosed space (5) having at least a closeable door (6) allowing for entering into
or removing from the enclosed space a hydrogen fluoride storage container. In
one embodiment of this aspect the enclosed space contains the hydrogen fluoride
storage containers and the connections to the hydrogen fluoride supply line. In
another embodiment, the enclosed space contains in addition an evaporator for
evaporation of liquid HF. In this preferred aspect and its embodiments, the
enclosed space suitably comprises an HF sensor capable to trigger connection of
the enclosed space to an HF destruction system (10). Suitably, the enclosed
space is connected to the HF destruction system through a suction line (9)
connected to a fan which is operable to transport gas from the enclosed space to
the HF destruction system. The HF destruction system is preferably a scrubber.
The scrubber suitably contains an aqueous alkaline solution, for example a KOH
solution.
The invention also concerns a chemical plant comprising the hydrogen
fluoride supply unit according to the invention. In a particularly preferred aspect
the chemical plant according to the invention is used for the manufacture of
fluorine by electrolysis of HF. In that case the hydrogen fluoride supply line (2)
is generally connected to an electrolysis cell (7) for producing fluorine by HF
electrolysis of a molten salt electrolyte.
In this particularly preferred aspect, it is advantageous that the plant
comprise a common destruction system for F and HF. Such common
destruction system can for example be a scrubber containing an aqueous KOHsolution
and optionally Na2S203 or K2S2O3.
In the chemical plant according to the invention, the aggregate capacity of
the hydrogen fluoride storage containers in the hydrogen fluoride supply unit
generally corresponds to 5 to 60 days, preferably from 15 to 30 days of HF
requirement of the chemical plant to produce the chemical, e.g. F2, at its full
capacity.
Figure 1 shows, without intended limitation, a particular embodiment of a
fluorine plant according to the invention:
A plurality of transportable hydrogen fluoride storage containers (1) is
connected to a hydrogen fluoride supply line (2) through a manifold (3). Each
storage container (1) can be individually isolated from the hydrogen fluoride
supply line (2) by a remotely controlled valve (4). Hydrogen fluoride storage
containers (1), manifold and remotely controlled valves are contained in an
enclosed space (5) having a closeable door (6) allowing for entering into or
removing from the enclosed space a hydrogen fluoride storage container (1).
The enclosed space further comprises an HF sensor capable to trigger connection
of the enclosed space to HF destruction system (10). The enclosed space is
connected to the HF destruction system through a suction line (9) connected to a
fan (not shown) which is operable to transport gas from the enclosed space to the
HF destruction system. The hydrogen fluoride supply line (2) enters into an HF
evaporator (8) operable to vaporize liquid HF, which is connected to electrolysis
cell (7) in which HF can be electrolyzed to produce molecular fluorine (F2) .
In a particular aspect, the chemical plant according to the invention has
several, for example 1,2,3,4,5,6,7, or 8 production lines for the manufacture of
fluorine by electrolysis of HF having a corresponding number of hydrogen
fluoride supply units according to the invention.
In another particular aspect, the chemical plant according to the invention
may have several, for example 1,2,3,4,5,6,7, or 8 production lines, e.g. for the
manufacture of fluorine by electrolysis of HF and a lower number, e.g. ,2,3 or 4
of hydrogen fluoride supply units according to the invention.
The invention also relates to a process for the manufacture of a chemical,
in particular fluorine, comprising use of the chemical plant according to the
invention.
The invention also relates to a method for the supply of hydrogen fluoride
to a chemical plant, which comprises (a) filling at least one transportable
hydrogen fluoride storage container with hydrogen fluoride, (b) transporting the
hydrogen fluoride storage container to the hydrogen fluoride supply unit, (c)
connecting the hydrogen fluoride storage container to the hydrogen fluoride
supply line and (d) supplying hydrogen fluoride from the hydrogen fluoride
storage container to the hydrogen fluoride supply line.
In the method according to the invention, the filling can be preferably
carried out at an HF production site, where HF is produced for example by
reaction of fluorspar with sulfuric acid.
In the method according to the invention, transporting the hydrogen
fluoride storage container to the hydrogen fluoride supply unit generally
comprises transportation by a vehicle such as ship, railway or, preferably, truck.
Usually, the hydrogen fluoride storage container is loaded on and/or unloaded
from the second container by suitable devices such as for example a crane or a
forklift.
In a preferred embodiment of the method according to the invention more
than one hydrogen fluoride storage containers are transported in a second
container, preferably an ISO container. In that case the number of hydrogen
fluoride storage containers in said second container is preferably lower than the
number of hydrogen fluoride storage containers in the hydrogen fluoride supply
unit.
In a particular example, 3 identical hydrogen fluoride storage containers
having each a capacity of 2000-30001, preferably about 25001, for example UN T
20 type containers, are loaded into 1 ISO container and transported to a hydrogen
fluoride supply unit according to the invention. The latter hydrogen fluoride
supply unit preferably comprises 4 identical containers as described here before.
In the method according to the invention, the connecting is generally
carried out with a periodicity of more than 12 days, often equal to or more than
15 days or 18 days, preferably the periodicity is more than 20 days.
A suitable method for supplying liquid HF from a hydrogen fluoride
storage container to the HF supply line is to pressurize the container with an inert
gas such as N2 .
In a preferred aspect of the method according to the invention the
supplying comprises supplying hydrogen fluoride to the hydrogen fluoride
supply line successively from different hydrogen fluoride storage containers. In
that case, generally only one hydrogen fluoride storage container has an open
connection to the hydrogen fluoride supply line. A particular successive supply
scheme comprises successively supplying hydrogen fluoride from all but one
hydrogen fluoride storage container.
It has been found that the fluorine supply unit according to the invention,
the chemical plant according to the invention and the method according to the
invention allow for reduced number of servicing and connecting operations thus
minimizing hazard risk in connection with HF.
Should the disclosure of any of the patents, patent applications, and
publications that are incorporated herein by reference be in conflict with the
present description to the extent that it might render a term unclear, the present
description shall take precedence.
The example here after is understood to illustrate the invention without
however limiting it.
Example
In an HF manufacturing plant 3 UN T 20 type containers are each filled
with 25001 of anhydrous HF and loaded with a crane into an ISO container which
is loaded onto a truck. The truck transports the ISO container to a fluorine
manufacturing plant, where the UN T 20 type containers are unloaded by a
forklift and transported through a door into a HF storage room made of polymer
coated steel having the dimensions of a sea container 3 empty UN T 20 type
containers are removed from the room and loaded into the ISO container. The 3
HF containing containers are connected by an operator through standard
connections to a manifold equipped with remote control valves having a further
HF containing UN T 20 type container connected thereto. After connecting the
operator leaves the room and shuts the door. From a control room an automatic
system shuts and opens the remote control valves to have one HF containing
UN T 20 type deliver HF to an HF supply line which passes through an
evaporator. HF storage containers are installed on weighing scales, so that when
a HF container is empty, a process control system closes the isolation valves of
the empty containers and opens the valves of another container containing HF,
without manual handling and without disruption of the HF supply. Gaseous HF
is fed into an electrolysis cell producing F by electrolysis of HF in Fx2HF
containing molten electrolyte. The F capacity of the plant is 150 t/year. After
about 15 days of full capacity F2 production, 3 full UN T 20 type HF containers
are supplied and exchanged for the empty ones as described above.
C L A I M S
1. A hydrogen fluoride supply unit which comprises a plurality of
transportable hydrogen fluoride storage containers (1) connected to a hydrogen
fluoride supply line (2) wherein at least one of the hydrogen fluoride storage
containers has a capacity of equal to or greater than 500 1.
2. The hydrogen fluoride supply unit according to claim 1, which
comprises from 2 to 20, preferably from 3 to 10, more preferably from 4 to 6
storage containers.
3. The hydrogen fluoride supply unit according to claim 1 or 2, wherein
each storage container is connected to the hydrogen fluoride supply line through
a manifold (3).
4. The hydrogen fluoride supply unit according to anyone of claims 1
to 3, wherein each storage container is individually isolatable from the hydrogen
fluoride supply line.
5. The hydrogen fluoride supply unit according to claim 4, wherein the
storage containers (1) can be isolated from the hydrogen fluoride supply line (2)
by a remotely controlled device (4), preferably a remotely controlled valve.
6. The hydrogen fluoride supply unit according to anyone of claims 1
to 5, wherein the hydrogen fluoride storage containers (1) are contained in an
enclosed space (5) having at least a closeable gate (6) allowing for entering into
or removing from the enclosed space a hydrogen fluoride storage container.
7. The hydrogen fluoride supply unit according to anyone of claims 1
to 6 wherein each hydrogen fluoride storage container has a capacity of from 500
to 5000 1, often from 500 to 4000 1preferably from 1000 to 3000 1.
8. The hydrogen fluoride supply unit according to anyone of claims 1
to 7 further comprising, preferably permanently, at least one hydrogen fluoride
emergency container which is preferably an at least partially empty hydrogen
fluoride storage container connected to the hydrogen fluoride supply line.
9. A chemical plant comprising the hydrogen fluoride supply unit
according to anyone of claims 1 to 8.
10. The chemical plant according to claim 9, for the manufacture of
fluorine, wherein the hydrogen fluoride supply line (2) is connected to an
electrolysis cell (7) for producing fluorine by HF electrolysis of a molten salt
electrolyte.
11. The chemical plant according to claim 9 or 10, wherein the aggregate
capacity of the hydrogen fluoride storage containers corresponds to 15 to 60
days, preferably from 15 to 30 days of HF requirement of the chemical plant to
produce the chemical at full capacity.
12. A process for the manufacture of a chemical comprising use of the
chemical plant according to anyone of claims 9 to 11.
13. A method for supply of hydrogen fluoride to a chemical plant, which
comprises (a) filling at least one transportable hydrogen fluoride storage
container with hydrogen fluoride, (b) transporting the hydrogen fluoride storage
container to the hydrogen fluoride supply unit (c) connecting the hydrogen
fluoride storage container to the hydrogen fluoride supply line and (d) supplying
hydrogen fluoride from the hydrogen fluoride storage container to the hydrogen
fluoride supply line.
14. The method according to claim 13, wherein more than one hydrogen
fluoride storage containers are transported in a second container, preferably an
ISO container and the number of hydrogen fluoride storage containers in said
second container is lower than the number of hydrogen fluoride storage
containers in the hydrogen fluoride supply unit.
15. The method according to claim 13 or 14, wherein said connecting is
carried out with a periodicity of more than 12 days, preferably more than
15 days.