Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICE FOR CARRYING OUT GAS REACTIONS, USE OF THE DEVICE
AND PROCESS FOR OPERATING THE DEVICE
Description
This invention relates to an apparatus for carrying out gas
reactions, comprising a reaction space which is closed at the
bottom by a container filled with water and at the top by a
fume hood, where a first gas stream is introduced through
nozzles into the reaction space and a second gas stream is
introduced through nozzles into the water, where the reaction
space has a constriction in whose vicinity the nozzles dis-
posed in the reaction space are provided, and where the gase-
ous reaction products are discharged from the fume hood. Each
gas stream may consist of one or several gaseous substances.
This invention furthermore relates to the use of the appara-
tus and to a method of operating the apparatus.
An apparatus as described above is known from the publication
by Kummel and Wiese, Chemie-Anlagen + Verfahren, 1977, issue
7, pages 56 to 57 and 66. The publication proposes to use the
known apparatus for the combustion of exhaust gases which
contain noxious substances and/or together with air form an
explosive mixture. It has turned out that the operational
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safety of the known apparatus requires improvement, as the
combustion reactions performed in the known apparatus do not
always take a quantitative course, and furthermore the inlet
nozzles for the combustion air, which are disposed in the re-
action space, are attacked by corrosion.
It is the object underlying the invention to improve and de-
fine the known apparatus as well as the conditions for oper-
ating the same such that the gas reactions taking place
within the same take a quantitative course, and that the noz-
zles disposed in the reaction space are protected against
corrosion.
The object underlying the invention is solved in that the
nozzles disposed in the reaction space are inclined towards
the water surface and have an angle of inclination of 12 to
16° with respect to the horizontal, that the diameter of the
reaction space in the vicinity of the constriction is reduced
by 20 to 30 %, and that the constriction in the reaction
space is disposed such that 20 to 30 0 of the height of the
reaction space lie between water surface and constriction,
and 80 to 70 0 of the height of the reaction space lie be-
tween constriction and fume hood.
By means of this combination of features it is advantageously
achieved that the gas streams are mixed thoroughly, so that
the reactions taking place between them take a quantitative
course. Since the nozzles of the reaction space are inclined
in the direction of the water surface, the reactions between
the individual gaseous substances start directly above the
water surface. The constriction of the reaction space effects
a very good vortexing of the gaseous reactants, where the re-
duction of the diameter of the reaction space by 20 to 30 %,
which is caused by the constriction, on the one hand effects
a good vortexing of the reactants and on the other hand only
a comparatively small increase of the flow rate of the gase-
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ous reactants, so that the reaction space on the whole has
optimum flow and mixing conditions. Due to the fact that be-
tween the constriction and the fume hood the major part of
the volume of the reaction space is disposed, the quantita-
tive course of the gas reactions is ensured, as the part of
the reaction space disposed above the constriction ensures a
dwell time of the reactants which is necessary and sufficient
for the quantitative course of the reaction. Even in the fume
hood disposed above the reaction space there still takes
place a secondary, although minor, reaction of the gaseous
reactants.
In particular when using the apparatus for the combustion of
exhaust gases containing noxious substances, which exhaust
gases have a comparatively low calorific value and a variable
content of noxious substances, it has turned out to be advan-
tageous in accordance with the invention that in the reaction
space and/or in the container filled with water fuel nozzles
are provided, through which a gaseous auxiliary fuel is blown
into the reaction space and/or into the water. Hence it is
possible to always maintain a high enough combustion tempera-
ture in the apparatus and to prevent the combustion reaction
from coming to an end. As gaseous auxiliary fuel natural gas
is preferably used. By blowing the auxiliary fuel into the
water, a high enough combustion temperature is adjusted di-
rectly above the water surface, which promotes the quantita-
tive course of the reaction.
Although the nozzles disposed in the reaction space consist
of the usual heat- and corrosion-resistant materials, corro-
sion problems are nevertheless frequently observed. The cor-
rosion problems occurring at the nozzles disposed in the re-
action space for introducing the first gas stream and at the
fuel nozzles can, however, advantageously be avoided in ac-
cordance with the invention in that the nozzles disposed in
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the reaction space consist of titanium or an alloy having a
high titanium content.
In accordance with the invention it is provided that the ap-
paratus is used for the combustion of gases and exhaust gases
which contain gaseous as well as dust-like noxious substances
and/or together with air form an explosive mixture. The com-
bustion air or the combustion air enriched with oxygen is in-
troduced as first gas stream through nozzles into the reac-
tion space, and the gas or exhaust gas is introduced as sec-
ond gas stream through nozzles into the water. When the gases
and exhaust gases have a low calorific value, an auxiliary
fuel, preferably natural gas, is blown into the reaction
space and/or into the water through fuel nozzles. It was sur-
prisingly found out that dust contained in the gases and ex-
haust gases does not impede the combustion process, as it is
washed out by the water. To prevent the dust from being en-
riched in the water, it must be separated from the water con-
tinuously or discontinuously by means of filtration. The
gases and exhaust gases burnt in the apparatus may contain
CO, hydrocarbons, halogenated hydrocarbons, H2S, CS2, COS,
hydrogen and/or minor amounts of chlorine as gaseous noxious
substances. It was observed that the combustion of the gases
and exhaust gases takes a quantitative course, which means
that the combustion gases leaving the fume hood do no longer
contain the gaseous noxious substances contained in the gases
and exhaust gases, and that the auxiliary fuel has been con-
verted into water and COZ for 100 %. The amount of the com-
bustion air is chosen such that with respect to all oxidizing
compounds there is a surplus of oxygen of 0.2 to 0.4. The
lower part of the inventive apparatus designed as water bed
reliably protects the nozzles disposed below the water sur-
face against a flashback, which in the known combustion
plants must be prevented by means of additional measures
(flame guard) in particular when small amounts of gas and/or
highly explosive gasoues substances are burnt in the plants.
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For the case that the gases and exhaust gases supplied to the
combustion contain noxious substances that react with water,
such as HC1, S03 or NH3, it is possible that these noxious
substances adsorbed in water are continuously or discontinu-
ously separated from the water; for instance, S03 may be pre-
cipitated as calcium sulfate, HC1 may be neutralized, and NH3
may be removed by distillation.
In accordance with the invention it is furthermore provided
that the apparatus is used for carrying out chemical gas re-
actions. It was surprisingly found out that due to the inven-
tive combination of features the apparatus can also be used
as chemical reactor; for instance, hydrogen sulfide can be
reacted with air to form sulfur dioxide. In the apparatus,
there can also be effected the addition of chlorine or bro-
mine to lower olefins in the gas phase with a very good
yield. In particular when the apparatus in accordance with
the invention is used for carrying out chemical reactions,
the materials of the inner walls and the inlet nozzles must
be adapted to the conditions of the chemical process taking
place in the apparatus. In so far, corrosion problems should
be observed, which are caused by the used gaseous substances
or the reaction products.
The object underlying the invention is finally solved by a
method of operating the apparatus, where the mean dwell time
of the gaseous substances in the reaction space as well as in
the fume hood is 1 to 5 s, and the mean gas velocity in the
reaction space is 2 to 6 m/s, where the nozzles disposed in
the reaction space are operated with an excess pressure of 35
to 45 mbar, and the nozzles disposed below the water surface
are operated with an excess pressure of 45 to 55 mbar. It was
found out that the reactions carried out in the apparatus
take a quantitative and trouble-free course under the inven-
tive operating conditions. Even possibly occurring deflagra-
tions do not jeopardize the operational safety of the appara-
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tus when the inventive operating conditions are maintained.
The excess pressure to be maintained during the operation of
the nozzles refers to the gas pressure in the reaction space
and to the pressure exerted by the water column, and in the
case of possible deflagrations it also prevents the flashback
of gases, reaction products and water into the nozzles and
the supply systems for the individual gas streams connected
with the nozzles.
The subject-matter of the invention will subsequently be ex-
plained in detail with reference to the drawing, which shows
V
the longitudinal section of the apparatus in accordance with
the invention.
The apparatus in accordance with the invention consists of
the reaction space 1 with the diameter dR and the height hR.
The reaction space 1 has a heat-resistant and corrosion-
resistant inner wall, whose material is selected according to
the conditions existing in the reaction space 1. For in-
stance, the temperature in the reaction space 1 during the
combustion of gases and exhaust gases is 800 to 1000 °C with
a surplus of oxygen in the gaseous reaction mixture. The re-
action space 1 is closed at the top by the fume hood 3 from
which the hot, gaseous reaction products 16 are discharged
through the exhaust gas line 4. The inner wall of the fume
hood 3 and the exhaust gas line 4 is designed corresponding
to the inner wall of the reaction space 1. The heat content
of the hot, gaseous reaction products 26 is utilized in an
expedient way, which may be effected in a recuperator or in a
waste heat boiler and is not represented in the drawing. The
reaction space 1 is closed at the bottom by the container 2,
which is filled with water.
The reaction space 1 has a constriction 8, which reduces the
diameter dR of the reaction space 1 by 20 to 30 %. In the vi-
cinity of the constriction 8 the diameter dE thus amounts to
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80 to 70 0 of the diameter dR of the reaction space 1. The
constriction 8 should expediently have surfaces inclined with
respect to the horizontal, as this is schematically illus-
trated in the drawing. The constriction 8 divides the reac-
tion space 1 into two parts, and it is arranged such that 20
to 30 0 of the height hR of the reaction space 1 lie between
the water surface 9 and the constriction 8, and 80 to 70 a of
the height hR of the reaction space 1 lie between the con-
striction 8 and the fume hood 3.
The container 2, which may have a flat or funnel-shaped bot-
tom 17, is filled with water. When the water takes up dust or
gaseous noxious substances from the second gas stream, part
of the water is discharged from the container 2 through line
15 and purified by corresponding processes, which is not rep-
resented in the drawing. At the height of the water level 9,
fresh water or purified water is supplied to the container 2
through line 14, so that a constant water level can always be
maintained in the container 2. The supply of water is regu-
lated according to the principle of communicating vessels, so
that even variations in the water content of the container 2
are safely compensated. As the gaseous substances supplied by
means of the water take up water and discharge the same from
the container 2, a completion of the water content of the
container 2 is necessary in any case.
In the container 2, gas inlet nozzles are provided, which are
preferably designed as nozzle tubes 11, and to which the sec-
ond gas stream is supplied through line 10. As second gas
stream, gases and exhaust gases are used, which are burnt
with the first gas stream or reacted. The~second gas stream
is distributed in the water by means of the nozzle tubes ll,
rises in the water and through the water surface 9 enters
into the reaction space 1. In the vicinity of the constric-
tion 8 nozzles 7 are provided, to which the first gas stream
is supplied through line 6, and through which the first gas
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stream is introduced into the reaction space 1. The nozzles 7
are inclined towards the water surface 9 and have an angle of
inclination of 12 to 16° with respect to the horizontal, so
that the gas jet emerging from the nozzles 7 is directed onto
the water surface 9. The nozzles 7 preferably consist of an
alloy with a high titanium content.
In particular when exhaust gases and gases of low calorific
value should be burnt in the inventive apparatus, it is nec-
essary to supply a gaseous auxiliary fuel, preferably natural
gas, to the apparatus, in order to maintain the required com-
bustion temperature and ensure a quantitative combustion of
all noxious substances contained in the gases and exhaust
gases. The gaseous auxiliary fuel may be introduced both into
the reaction space 1 and into the container 2 filled with wa-
ter, where the introduction of the auxiliary fuel into the
container 2 turned out to be particularly advantageous. In
the container 2 fuel nozzles are provided, which are prefera-
bly designed as nozzle tubes 13, and to which the auxiliary
fuel is supplied through line 12. Mixing the auxiliary fuel
with the second gas.stream is already effected in the water,
and through the water surface 9 the gas mixture enters the
reaction space 1, where close to the water surface 9 it al-
ready gets in contact with the first gas stream. Furthermore,
the auxiliary fuel may be introduced into the reaction space
1 wholly or in part through the nozzles 18, which are dis-
posed above the constriction 8, and to which the auxiliary
fuel is supplied through line 15.
In the apparatus in accordance with the invention exhaust
gases were burnt on a technical scale, which contained the
hydrocarbons and chlorinated hydrocarbons in small amounts.
These noxious substances could be converted into C02, H20 and
HC1 for 100 %. The combustion was effected at 800 to 900°C,
where the apparatus was constantly provided with natural gas
as auxiliary fuel. In the inventive apparatus there was also
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burnt the exhaust gas obtained in the production of titanium
tetrachloride from Tio2, C12 and carbon. There was utilized
the Deacon equilibrium, where HC1 is formed from chlorine and
water.
The operation of the apparatus is performed such that the
mean dwell time of the gaseous substances in the reaction
space 1 and the fume hood 3 is about 3 to 4 s. In addition, a
mean gas velocity of 3 to 5 m/s is maintained in the reaction
space 1. The first gas stream is introduced into the reaction
space 1 through the nozzles 7 with an excess pressure of
about 40 mbar. The second gas stream is blown into the water
through the nozzles 11 with an excess pressure of about 50
mbar. The auxiliary fuel is supplied with a corresponding ex-
cess pressure.
