PROCEDE POUR L'ELIMINATION DE HALONS OU DE FLUOROCARBURES OU CHLOROFLUOROCARBURES EN CONTENANT

PROCESS FOR THE DISPOSAL OF HALONS OR HALON-CONTAINING FLUOROCARBONS OR CHLOROFLUOROCARBONS

Abrégé anglais

-1-
Abstract of the Disclosure
Process for the disposal of halons or halon-containing
fluorocarbons or chlorofluorocarbons
The invention relates to a process for the disposal of
halons or halon-containing FCs or CFCs, wherein the
latter are thermally or photochemically decomposed in the
presence of a hydrogen source, the gas produced,
containing HF, HBr, CO2, water and, if appropriate, HCl,
is cooled, the hydrogen halides are absorbed in a
scrubbing liquid in a gas scrubber column and neutralized
with a base, and any elemental bromine or chlorine
contained in the gas is reduced to the corresponding
salts with a reducing agent.

Revendications

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Patent claims:
1. A process for the disposal of halons (bromo-
fluorocarbons or bromochlorofluorocarbons) or mixtures
thereof with fluorocarbons (FCB) or chlorofluorocarbons
(CFCs), wherein
a) the halons or mixtures thereof with FCs or CFCs are
thermally or photochemically decomposed in the
presence of a hydrogen source,
b) the gas produced in step a), containing HF, HBr,
CO2, water and, if appropriate, HCl, is cooled to
5 - 50°C, and
c) in a gas scrubber column, the hydrogen halides are
absorbed in a scrubbing liquid from the gas obtained
in step b), and neutralized with a base, and any
elemental bromine or chlorine contained in the gas
is reduced to the corresponding salts with a redu-
cing agent, the scrubbing liquid and the gas being
fed in at the middle of the gas scrubber column and
the base and, if appropriate, the reducing agent
being introduced at the top of the gas scrubber
column, and a gas free of hydrogen halides being
withdrawn at the top of the gas scrubber column and
a brine solution being withdrawn at the bottom of
the gas scrubber column.
2. The process as claimed in claim 1, wherein the
halons have 1 to 3 carbon atoms.
3. The process as claimed in claim 1 or 2, wherein
the FCs or CFCs have 1 to 6 carbon atoms.
4. The process as claimed in one of claims 1 to 3,
wherein the gas scrubber column used in step c) is
operated adiabatically.
5. The process as claimed in one of claims 1 to 4,

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wherein the gas scrubber column used in step c) is
operated so that the brine solution leaving at the bottom
of the first stage has a pH of 5 - 8.4.
6. The process as claimed in one of claims 1 to 4,
wherein the gas scrubber column used in step c) is
operated so that the bring solution leaving at the bottom
of the first stage has a salt content of 30 - 40% by
weight.
7. The process as claimed in one of claims 1 to 6,
wherein the gas scrubber column used in step c) is a two-
stage column and the scrubbing liquid and the gas
produced in step a) are fed in at the top of the first
stage and the base and, if appropriate, the reducing
agent are introduced at the top of the second stage.

Description

HOECHST AKTIENGESELLSCHAFT HOE 93/F 213 Dr. MA
De~cription
Process for the disposal of halons or halon-containing
fluorocarbons or chlorofluorocarbons
The invention relate~ to a process for the di~po~al of
bromofluorocarbons or bromochlorofluorocarbons (called
halons hereafter) or mixtures thereof with fluorocarbons
(FCs) or chlorofluorocarbons (CFCs).
The object of the invention is to dispo~e of halons and
at the ~ame time to obtain reusable products, for ~xample
a concentrated brine solution containing bromine, from
which elemental bromine, potassium fluoride and potassium
chloride can then be recovered. Although the producer~ of
halon-containing fire-extinguishing agents are faced with
a dispo~al emergency, no proces~ has yet been di closed
which meets these requirements and solveQ the problem of
separating from one another the extremely corrosive
products formed e.g. in the thermal decomposition o~
halons.
:
It has now been found, aurprisingly, that the above
object is achieved by thermally decomposing halons,
halon-containing FCs or halon-containing CFCs, for
example by mean~ of an oxyhydrogen flame, cooling the gas
stream formed, absorbing the HF and ~Br produced by the
decomposition and any HCl produced (when using bromo-
chlorofluorocarbon~ or halons mixed with chlorofluoro-
carbona) from the gas stre~m in a gas scrubber column and
neutralizing the acid~ formed with a base. If necessary,
a reducing agent is also added to reduce any el~mental
chlorine or bromine produced by the thermal deco~position
to the corresponding salts.
The invention accordingly provide a proceas for the
disposal of halons (bromofluorocarbon~ or bromochloro-
fluorocarbon~) or mixtures thereof with fluorocarbon~
(FCs) or chlorofluorocarbon~ (CFCs), wherein

~ 2.8'85~
2 -
a) the halonE or ~ixtures thereof with FCs or CFCB are
thermally or photochamically docompo~ed ln the
presence of a hydrogen cour~e,
b) the ga~ produced in ~t~p a), conta~nin~ ~F, HBr,
C2~ water and, 1~ approprinte, ~Cl, i8 cooled to
5 50C and
c) in a gas ~crubber column, the hydrogen halides are
ab~or~ed in a scrubbing liguid from the ga~ obtained
in step b), and n~utralized w~th a ba~e, and any
elemental bromine or chlorino contained ~n the gac
is reducod to th~ correcponding ~alts with a redu-
cing agent, tho scrubbing llguid and tho gao b~ing
fed in ~t tho middle of the gas ~crubber column and
the base and, if appropriato, the reducing agent
being $ntroducod at the top of the ga~ ecrubber
column, and a ga~ free of hydrogen halide~ boing
withdrawn at the top of the gas ~crubber column and
a brine solution being withdrawn at the bottom of
the gas scrub~er ~olumn.
The halon~ (bromo~luorocarbon~ or bro~ochlorofluorocar~
bons) disposed of according to the lnvention g~nerally
have 1 to 3 ~arbon atom~. They can be ~om~letely or
partially halogenated.
The halons can be pre~ent individu~lly, mixed with one
another or m~xed with FCe or CFC~ or both. The FCs ~d
CFCs generally havo 1 to 6 carbon atom~ and can b~
completely or parti~lly halogenated.
The hydrogen source used in ~top ~ preferably hydro-
gen itself or a hydroc~rbon. The thermRl decomposition i~
prefernbly carried out in a ~r~cking reactor auch a~ that
described in EP-A-0 212 410.
In Btop b), the ga~ produced in ~tep a), ~ontaining ~F,
HBr, C02 and w~ter (~nd also HCl when u~ing chloro$1uoro-

~ ~ 2 S ~i ~
carbons or bromochlorofluorocarbons), is cooled to5 - 50C, preferably 5 - 30C.
The gas scrubber column used in ~tep c) ie preferably a
two-~tage column, the scrubbing liquid and the gas
produced in step a) being fed in at the top of the first
stage and the base and, if appropriate, the reducing
agent being introduced at the top of the second stage.
The gas scrubber column can be operated isothermally or
adiabatically under normal, reduced or exces~ pre~eure.
Thepreferredoperatingprocedure i8 adiabatic, especially
at normal pressure.
The gas scrubber column i~ preferably operated 50 that
the brine solution leaving at the bottom has a pH of
5 - 8.4, preferably 6 - 6.5, and the ~alt content is
20 - 50% by weight, pre~erably 30 - 40% by wei~ht.
The scrubbing liquid used in step c) can be water, a
dilute solution of alkali metal hydroxide, alkaline earth
metal hydroxide, alkali metal carbonate, alkaline earth
metal carbonate, alkali metal hydrogencarbonate or
alkaline earth metal hydrogencarbonate, or a dilute brine
solution having a similar compoRition to that of the
brine solution leaving at the bottom of the gas scrubber
column.
Suitable reducing agenta are agueou~ solutions o~ alkali
metal ~ormate, alkali metal hydrogen~ulfite, hydrazine or
~ulfur dioxide gaQ, preferably aqueou~ solution~ of
sodium or potassium formate. It i8 only necessary to add
a reducing agent when the gas produced in ~tep a)
actually contains Br2 and/or Cl2, which can easily be
e~tabli~hed by analysi~.
Ba~es which can be used are an alkali metal or alkaline
earth metal hydroxide or an alkali metal or alkaline
earth metal carbonate or hydrogencarbonate, preferably
eodium or pota~sium hydroxide or carbonate.

~, 2 ~ t~i 5 9
-- 4
The invention will be illustrated in greater detail by
the following Example and Figure 1.
Example 1
The decompo~it~on according to step a) wa~ carried out ~n
a Diabon tube (l) (length - 800 mm, diameter = 48 mm)
equipped at the upper end with an electrically ignited
burner jet (2). 100 g/h of halon/CFC mixture ~40% by
weight of dichlorodifluoromethane, R 12, 50% by weight of
trichlorofluoromethano, R 11, 10% by weight of trifluoro-
bromomethane, halon 13B1) were decompo~ed by mean~ ofoxyhydrogen (35 l/h of H2, 10.5 l/h of l). Attached to
the lower end of the Diabon tube (1) was a Diabon plat~
heat exchanger (3) (length = 400 mm) in which the hot
decomposition gaee~ were cooled to room temperature. The
cooled ga~es were then pa~sed through the line (4) into
the top of the column (5) (length = 400 mm; diameter =
100 mm; PTF~ ned steel column with lateral feed pipo
and 4 mm PP Raschig rings a~ packing), which ~erved as
the first stage of a two-~tage scrubber. At the beginning
of the experiment, water wa~ circulated (ca. 2000 ml/h)
via the line (6) with a pump (7). Attached to the column
(5) was a second column (8) (length = 1000 mm: diametor
- 50 mm; PTFE- lined ~teel coll~n with lateral feed pipe
and 4 mm PP Raschig rings as packing) as the ~econd
stage. 30% by weight agu~ous ROH (ca. 300 ml/h) was
metered into the top of the column (8) from the storage
ve~sel (9) via the line (10) and 10% by weight aqueous
potassium formate ~olution (ca. 30 ml/h) was metered in
from the storage ve~sel (11) via the lines (12) and (10).
The metering process was controlled by the pH and the
electrical potential (measurement at the outlet of the
colum~ (8)). When 100 g of halon/CFC mixture had been
pa~sed through, the oontinuous discharge of part (ca.
330 ml/h) of the bottom of the column (5) into th~
~torage vessel (1~) via the line (13) was started. The
e$fluent brine ~olution had a salt content of ca.

~ 3
-- 5 --
30 - 35% by weight. Elemental bromine and chlorine and
hypobromit e, hypochlorite, bromate and chlorate were
undetectable by analysi~. The proportion of carbonate and
hydrogen-carbonate wa~ b610w 0.1% by weight at a pH of
the brine solution of 6.5. C02 escaped at the top of the
column (8) via the line (15).

Dessin représentatif