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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a method for fire extinguishment on a
liquid chlorosilane compound or, more particularly, relates to a method of
fire extinguishment on a chlorosilane compound by sprinkling an inert
powdery material over the surface.
As is well known, chlorosilane compounds, such as trichlorosilane, dimethyl
chlorosilane and the like, are very useful chemical starting materials in
various modern industries such as manufacture of semiconductor silicon,
synthetic quartz, silicone polymers and the like and the consumption of
these materials in industries are rapidly increasing year by year. A very
serious problem in these industries is the accident of fire on the
chlorosilane compound which is usually a very inflammable liquid because
chlorosilane compounds are generally very unstable in air having a
relatively low flash point. Moreover, burning chlorosilane compounds
produce a large volume of toxic gases and the fire on a burning
chlorosilane compound can be extinguished only with great difficulties.
Various kinds of fire-extinguishing agents of course have been proposed in
the prior art for fire extinguishment on such a chlorosilane compound but
few of them are quite effective, if not ineffective. Even worse, the
ingredients of some of conventional fire-extinguishing agents in a powdery
form may react with the chlorosilane compound to promote formation of
toxic or inflammable gases. Fire-extinguishing agents in a gaseous or
liquid form, such as carbon dioxide gas and certain highly halogenated
hydrocarbon compounds, are also not effective for fire extinguishment on
chlorosilane compounds. In place of these manufactured fire-extinguishing
agents, dry sand and water as natural materials can also be used for the
purpose without noticeable effect of fire extinguishment. For example,
fire on a chlorosilane compound can be extinguished only by sprinkling a
large volume of sand thereover. When natural sand is used as such,
impurity materials contained in the sand may eventually react with the
chlorosilane compound to produce toxic gases. The effectiveness of water
as a fire-extinguishing agent of chlorosilane compounds is relatively low.
Moreover, violent reactions disadvantageously take place between water and
the chlorosilane compound to produce toxic gases such as hydrogen chloride
and to cause formation of a large amount of a gel-like material. Certain
chlorosilane compounds, when reacted with water, may produce hydrogen gas
which itself is inflammable or explosive in an oxidizing atmosphere
resulting in a secondary hazard.
Accordingly, it is an urgent technical problem in industries to establish
an efficient and safe method for fire extinguishment on a chlorosilane
compound without the above described disadvantages and problems in the
prior art methods.
SUMMARY OF THE INVENTION
Accordingly, the present invention, which has been completed as a result of
the extensive investigations undertaken with an object to solve the above
described problems, provides a method for fire extinguishment on a
combustible liquid chlorosilane compound which comprises sprinkling porous
particles of an inert material over the surface of the chlorosilane
compound. The amount of the porous inert powder sprinkled over the surface
of a burning chlorosilane compound should be at least 100 kg per cubic
meter of the chlorosilane compound.
In particular, the particles of the inert powdery material should be porous
siliceous particles mainly composed of silica or silica-alumina havng a
porosity in the range from 45 to 85% and a pore diameter in the range from
0.1 to 100 .mu.m and having a particle diameter in the range from 5 .mu.m
to 5 mm, the contents of silica and silica-alumina in the siliceous
particles being at least 80% by weight and at least 90% by weight,
respectively.
The above described method of the invention is of course quite effective in
most cases to extinguish fire on a chlorosilane compound. There are some
cases, however, that the above described method is still insufficient to
rapidly extinguish the fire on certain kinds of the chlorosilane
compounds, especially, with extreme violence of fire. The invention also
provides a method for efficiently extinguishing fire in such a case, which
comprises, following the above mentioned sprinkling of a porous inert
powdery material over the fire, spraying water or a highly halogenated
liquid hydrocarbon compound over the fire in an amount of, for example, at
least 10% by volume of the chlorosilane compound.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The chlorosilane compound as the objective material of the inventive
fire-extinguishing method includes various kinds of chlorosilane compound
used in the manufacture of semiconductor silicon, synthetic quartz,
silicone polymers and the like and represented by the general formula
R.sub.u SiH.sub.v Cl.sub.w, (I)
in which R is a monovalent hydrocarbon group exemplified by alkyl groups,
e.g., methyl and ethyl groups, alkenyl groups, e.g. vinyl group, and aryl
groups, e.g., phenyl group, the subscript u is zero, 1, 2 or 3, the
subscript v is zero, 1, 2 or 3 and the subscript w is 1, 2 or 3 with the
proviso that u+v+w=4. Typical examples of the chlorosilane compound
include trichlorosilane of the formula SiHCl.sub.3, trimethyl chlorosilane
of the formula (CH.sub.3).sub.3 SiCl, methyl dichlorosilane of the formula
CH.sub.3 SiHCl.sub.2, dimethyl dichlorosilane of the formula
(CH.sub.3).sub.2 SiCl.sub.2, methyl trichlorosilane of the formula
CH.sub.3 SiCl.sub.3, phenyl trichlorosilane of the formula C.sub.6 H.sub.5
SiCl.sub.3 and diphenyl dichlorosilane of the formula (C.sub.6
H.sub.5).sub.2 SiCl.sub.2 and the like. Each of these chlorosilane
compounds is a very inflammable liquid having a relatively low flash point
and, once it is set on fire, the fire can be extinguished only with great
difficulties. In particular, extinguishment of fire is extremely difficult
when the fire is on trichlorosilane, trimethyl chlorosilane or methyl
dichlorosilane. Combustion of these chlorosilane compounds unavoidably
produces toxic hydrogen chloride gas and, in some cases, even more toxic
chlorine gas.
The fire-extinguishing material to be sprinkled over a burning chlorosilane
compound is a porous inert powdery material which should preferably be a
siliceous powder composed of at least 80% by weight of silica (SiO.sub.2)
or at least 90% by weight of silicaalumina (SiO.sub.2 +Al.sub.2 O.sub.3).
The powder should contain an as little as possible amount of impurities
responsible for the formation of toxic gases by reacting with the
chlorosilane compound and the particles thereof should have a porosity in
the range from 45 to 85%. Several natural materials meet the requirements
after a treatment with an acid, drying, calcination and the like
pretreatment depending on the nature of the material occurring in nature.
Such a natural product more or less contains various impurities including
iron oxide Fe.sub.2 O.sub.3, calcium oxide CaO, magnesium oxide MgO,
potassium oxide K.sub.2 O, sodium silicate xNa.sub.2 O.multidot.ySiO.sub.2
and the like, of which the impurities of alkali and alkaline earth oxides
are particularly undesirable because these impurities may react directly
with the chlorosilane compound to produce toxic gases such as hydrogen
chloride or inflammable gases such as hydrogen. It is of course that the
moisture more or less contained in the fire-extinguishing material reacts
with the chlorosilane compound to hydrolyze the same so that the material
should be dried to minimize the moisture content therein.
The siliceous powdery material should have a particle size distribution in
the range from 5 .mu.m to 5 mm. When the powder contains a substantial
amount of particles having a particle diameter smaller than 5 .mu.m, such
fine particles may readily be blown away by the flame violently rising up
on the burning chlorosilane so that the content of such fine particles
should be as small as possible. This requirement of the particle size
distribution in the inventive method should be compared with that in the
conventional powdery fire-extinguishing agents which should have a
particle diamater not exceeding 177 .mu.m according to the industrial
standard and actually have a particle diameter of around 10 .mu.m as an
optimum condition. When the porous siliceous powder is used as a filling
of a fire extinguisher and ejected from the nozzle, in particular, the
powder should have a particle size distribution preferably in the range
from 5 to 200 .mu.m.
As is mentioned above, the particles of the powdery material should be
porous. Preferably, the particles should have a pore diameter in the range
from 0.1 to 100 .mu.m and a porosity in the range from 45 to 85%. This
requirement means that conventional porous siliceous materials such as
silica gels and silica-alumina gels are not suitable for the object of the
inventive method because most of the pores in these materials are smaller
than 0.1 .mu.m in diameter. When the pore diameter is too small with a
consequently very large effective surface area, a considerable amount of
heat of adsorption may be generated by the adsorption of the chlorosilane
compound on the effective surface of the porous particles in contact
therewith to cause undesirable increase in the temperature of the
chlorosilane compound by the heat of adsorption.
One of the suitable porous siliceous materials to meet the above described
requirements is a natural amorphous silica sand as a kind of geyserite and
sold under a tradename of Silton 3S which should be calcined and refined
prior to use. The powdery siliceous material thus obtained typically
contains 89.1% by weight of silica and a porosity of 70% with a true
density of 2.3 g/cm.sup.3. When a silica-alumina based porous powdery
material is desired in view of the somewhat larger true density, the above
mentioned Silton 3S is uniformly blended with kaolin together with water
and the blend is dried, calcined, pulverized and finally classified
relative to the particle size using a sieve. The thus prepared porous
silica-alumina powdery material typically contains 68% by weight of silica
and 23% by weight of alumina when the blending ratio of Silton 3S and
kaolin is 1:1 by weight and have a porosity of 80% with a true density of
2.5 g/cm.sup.3.
The amount of the sprinkled porous siliceous powder is of course important
in order to efficiently extinguish the fire on a chlorosilane compound.
The method of the invention can be efficiently practiced usually
sprinkling the powder in an amount of at least 100 kg per cubic meter of
the burning chlorosilane compound.
Sprinkling of the above described porous siliceous powder over the burning
chlorosilane compound may be not fully effective, as is sometimes the case
when trichlorosilane, methyl dichlorosilane and the like having hydrogen
atoms directly bonded to the silicon atoms and a relatively low boiling
point are set on fire. In this case, the ambient temperature often
approaches the boiling point of the chlorosilane compound. To overcome
such a difficulty, sprinkling of the porous siliceous powder should be
followed by spraying of water or a highly halogenated liquid hydrocarbon
compound over the burning chlorosilane compound. The highly halogenated
liquid hydrocarbon compound is represented by the general formula
C.sub.p H.sub.q X.sub.r, (II)
in which X is an atom of halogen selected from the group consisting of
fluorine, chlorine and bromine, the subscript p is 1 or 2, the subscript q
is zero, 1 or 2 and the subscript r is 2p+2-q. Typical examples of such
highly halogenated hydrocarbon compounds include monobromo monochloro
methane, carbon tetrachloride and dibromo tetrafluoroethane sold under
tradenames of Halon 1011, Halon 1040 and Halon 2402, respectively, of
which monobromo monochloromethane is preferred in the inventive method.
Tetrafluoro dibromoethane is less effective since it has a relatively low
boiling point and the latent heat of vaporization thereof is about a half
of that of monochloro monobromomethane or carbon tetrachloride. Carbon
tetrachloride is a traditional fire-extinguishing agent effective in the
fire accident of various combustible materials. This material, however,
may react with water or steam in the flame to produce very toxic phosgene
COCl.sub.2 so that it is not approved by the regulation of laws in many
countries as a generalpurpose fire-extinguishing agent. Notwithstanding
this problem, even carbon tetrachloride can be used as the spraying liquid
in the inventive method. This is because, in the inventive method,
spraying of carbon tetrachloride is always preceded by sprinkling of the
porous siliceous powder over the burning chlorosilane compound to suppress
or control the flame. The method of spraying water or the highly
halogenated hydrocarbon liquid is not particularly limitative but it is
desirable that the liquid is sprayed in as fine as possible droplets and
should be sprayed uniformly all over the layer of the already sprinkled
porous siliceous powder. The amount of sprayed water or highly halogenated
hydrocarbon compound should be at least 10% by volume of the burning
chlorosilane compound.
Caution should be given that spraying of the highly halogenated hydrocarbon
compound must be preceded by all means by sprinkling of a sufficient
amount of the porous siliceous powder all over the surface of the burning
chlorosilane compound since otherwise no fire-extinguishing or suppressing
effect can be obtained rather with an effect of increasing the violence of
the fire if not to mention formation of toxic gases such as phospgene,
hydrogen chloride, hydrogen bromide, hydrogen fluoride and the like.
According to the theoretical consideration for the mechanisms of
fire-extinguishment, at least one of the following four conditions must be
satisfied including:
(1) removing effect, i.e. to remove the combustible material away from the
burning area;
(2) suffocating effect, i.e. to shield the burning area from supply of
oxygen;
(3) cooling effect, i.e. to suppress burning of the combustible material by
absorbing the heat of combustion and cooling the burning material below
the ignition temperature of the material; and
(4) suppressing effect, i.e. to retard the reaction of the combustible
material with oxygen.
In many cases, the efficiency of fire-extinguishment can be synergistically
increased by satisfying two or more of these conditions simultaneously in
comparison with the efficiency when only one of them is satisfied.
When the porous siliceous powder is sprinkled over the burning chlorosilane
compound according to the inventive method, the powder undergoes
absolutely no chemical changes since the powder has no reactivity with the
chlorosilane compound and it is itself incombustible and thermally stable.
By virtue of the porosity of the powder, the sprinkled powder first
absorbs the chlorosilane compound as the combustible material to exhibit
the above mentioned removing effect. Further, the suffocating effect can
be obtained by sprinkling the powder in such a sufficiently large volume
that the open surface of the burning chlorosilane compound is entirely
covered therewith to shield the surface from the atmospheric oxygen.
As is mentioned before, sprinkling of the porous siliceous powder over the
burning chlorosilane compound may not always be fully effective to rapidly
extinguish the fire, especially, when a chlorosilane having hydrogen atoms
directly bonded to the silicon atoms and having a relatively low boiling
point, such as trichlorosilane and methyl dichlorosilane, has been set on
fire at a relatively high ambient temperature. When water or a highly
halogenated hydrocarbon compound, each being a liquid at room temperature,
is sprayed over the surface of the porous siliceous powder covering the
surface of the chlorosilane compound, the sprayed liquid is absorbed by
the porous powder to enhance the suffocating effect to more fully shield
the surface of the burning chlorosilane compound and, in addition, the
absorbed liquid is then vaporized by the heat of combustion to absorb a
large quantity of the latent heat for vaporization so that the cooling
effect is obtained to exhibit a synergistic effect with suffocation thus
to extinguish the fire very rapidly and efficiently. The above described
mechanisms well explain the unexpectedly high efficiency for the rapid and
reliable extinguishment of fire on any burning chlorosilane compound
according to the inventive method including spraying of water or a highly
halogenated liquid hydrocarbon compound.
To summarize, the method of the present invention is very effective for
fire extinguishment on a hardly extinguishable chlorosilane compound such
as trichlorosilane, methyl dichlorosilane, trimethyl chlorosilane and the
like by sprinkling the specific porous inert powder over the surface of
the burning chlorosilane compound, if necesary, followed by spraying of a
liquid which may be water or a highly halogenated hydrocarbon compound.
The advantages obtained by this fire-extinguishing method include that:
(1) any violent fire on a hardly extinguishable chlorosilane compound can
be extinguished rapidly and efficiently;
(2) the fire-extinguishing work can be performed with a minimum volume of
toxic gases produced by the reaction of the chlorosilane compound and the
fire-extinguishing agent;
(3) no secondary hazard may take place during and after the
fire-extinguishing works;
(4) the cost for the fire-extinguishing agent is low because the porous
siliceous powder is an inexpensive material and a small amount thereof is
effective for the purpose; and
(5) contamination of the environment is insignificant because the fire can
be extinguished by merely sprinkling the porous siliceous powder over the
surface followed, if necessary, by spraying water or a halogenated
hydrocarbon liquid.
In the following, the method of the invention for extinguishment of fire on
a chlorosilane compound is described in more detail by way of examples
making comparison with conventional methods. In the following
fire-extinguishing tests, the result of each test for a particular
combination of the inflammable chlorosilane compound and the
fire-extinguishing method was evaluated in four ratings of A, B, C and D,
the notation A corresponding to a very high fire-extinguishing efficiency,
D corresponding to a poor fire-extinguishing efficiency to be avoided for
the purpose and B and C corresponding to intermediate efficiencies between
A and D.
EXAMPLE 1
Fire-extinguishment test was undertaken using trichlorosilane, which is a
notoriously dangerous material with extreme difficulties of fire
extinguishment thereon, as a burning liquid. Thus, 50 ml of
trichlorosilane were taken in a stainless steel-made vessel having a
diameter of 10 cm and a depth of 6 cm and ignited. When the flame had
spread all over the liquid surface, 33 g of a porous siliceous powder were
sprinkled so that the fire could immediately be extinguished without
evolution of any toxic gas or white fume (fire-extinguishing efficiency
A).
The porous siliceous powder used here was Silton 3S after calcination and
acid-leaching to remove alkaline material followed by washing with water
having a particle diameter in the range from 10 to 500 .mu.m, a pore
diameter in the range from 0.2 to 10 .mu.m and porosity of 70%.
For comparison, similar fire-extinguishment tests were undertaken by
replacing 33 g of the porous siliceous powder with 1025 g of dry sand, 500
g of water or 88 g of a conventional fire-extinguishing agent composed of
50% by weight of sodium hydrogencarbonate, 22% by weight of alumina, 15%
by weight of silica gel and 13% by weight of other ingredients. The
results of these comparative tests were that the use of dry sand was not
practically feasible due to the so large amount of the sand required for
complete extinguishment of fire (fire-extinguishing efficiency C) while
sprinkling of water produced large volumes of toxic gases and white fume
(fire-extinguishing efficiency D) and the conventional fire-extinguishing
agent immediately reacted with the chlorosilane compound to produce large
volumes of toxic gases and white fume although the amount thereof required
for extinguishment of the fire was relatively small in comparison with dry
sand and water (fire-extinguishing efficiency C).
EXAMPLE 2
Fire-extinguishment test was undertaken using 500 ml of trichlorosilane
taken in an iron-made vessel of 2500 ml capacity having a diameter of 18
cm and a depth of 10 cm and igniting the silane to allow it burning for 30
seconds prior to the start of the fire-extinguishing work. Thereafter, 500
g of the same porous siliceous powder as used in Example 1 were sprinkled
over the surface of the burning silane so that the fire was immediately
extinguished without being followed by evolution of white fume
(fire-extinguishing efficiency A).
For comparison, similar fire-extinguishment tests were undertaken by
sprinkling or spraying, in place of 500 g of the porous siliceous powder
according to the invention, 4200 g of dry sand, 3200 g of water, 1500 g of
a so-called BC fire-extinguishing agent mainly composed of sodium
hydrogencarbonate or 1500 g of a fire-extinguishing agent for
chlorosilanes specifically formulated with sodium hydrogencarbonate,
alumina and silica gel for fire extinguishment on chlorosilanes. The
results were as follows. Thus, sprinkling of dry sand was quite
ineffective and the fire could not be extinguished at all despite the so
large amount of the sprinkled sand (fire-extinguishing efficiency D).
Spraying of water was effective in extinguishment of the fire but a large
volume of white fume, which was presumably composed of silica and hydrogen
chloride, was produced during the period before and after extinguishment
of the fire (fire-extinguishing efficiency C). The BC fire extinguishing
agent was also effective to suppress the violence of the fire within a
relatively short time but a large number of bubbles of, presumably, the
gasified silane compound were noticed rising in the liquid
(fire-extinguishing efficiency C). The last mentioned fire extinguishing
agent for chlorosilanes was also effective to suppress the violence of the
fire within a relatively short time but this fire-extinguishing agent
could not be evaluated as suitable for practical purposes because the
remaining volume of the silane compound was heated up to a boiling
condition along with production of toxic gases in a high concentration
(fire-extinguishing efficiency D).
The results of the above described comparative tests indicate that,
although some of the conventional methods may be effective in fire
extinguishment on trichlorosilane, it is a serious common problem in using
these conventional fire-extinguishing agents that a large volume of toxic
gases and white fume is unavoidably produced in the course of sprinkling
of the fire-extinguishing agent if not to mention the disadvantage that
the amount thereof required for complete fire extinguishment is quite
large in comparison with the porous siliceous powder according to the
invention.
On the contrary, the method of the present invention is outstandingly
advantageous because not only the fire on a chlorosilane compound can
readily and rapidly be extinguished by sprinkling a small amount of the
porous siliceous powder but also only a very small volume of toxic gases
is produced in the course of the powder sprinkling and absolutely no white
fume was produced after extinguishment of the fire.
EXAMPLE 3
Fire-extinguishment tests were undertaken for four kinds of chlorosilanes
including trimethyl chlorosilane, methyl dichlorosilane, dimethyl
dichlorosilane and methyl trichlorosilane. The experimental procedure was
substantially the same as in Example 1 using 50 ml of each of the
chlorosilane compounds and the same porous siliceous powder. For
comparison, similar tests were undertaken using dry sand as the
fire-extinguishing agent. The results of these tests were as follows.
Trimethyl chlorosilane
The fire on the silane compound could be extinguished by sprinkling 150 g
of the porous siliceous powder over the silane compound according to the
invention absolutely without production of toxic gases and white fume
(fire-extinguishing efficiency B) while 430 g of dry sand were required
for extinguishing the fire after the liquid was heated to boiling with
evolution of toxic gases even after extinguishment of the fire
(fire-extinguishing efficiency C).
Methyl dichlorosilane
The fire on the silane compound could be extinguished by sprinkling 150 g
of the porous siliceous powder over the silane compound according to the
invention absolutely without production of toxic gases and white fume
(fire-efficiency B) while sprinkling of 500 g of dry sand was ineffective
in extinguishing the fire (fire-extinguishing efficiency D).
Dimethyl dichlorosilane
The fire on the silane compound could be duly extinguished by sprinkling 75
g of the porous siliceous powder over the silane compound according to the
invention absolutely without production of toxic gases and white fume
after extinguishment of the fire (fire-extinguishing efficiency A). The
fire also could be extinguished by sprinkling 340 g of dry sand over the
silane compound. In this case, however, the silane liquid was heated to
boiling along with evolution of a large volume of toxic gases which lasted
even after extinguishment of the fire (fire-extinguishing efficiency C).
Methyl trichlorosilane
The fire could be easily extinguished by sprinkling only 15 g of the porous
siliceous powder without gas evolution even after extinguishment of the
fire (fire-extinguishing efficiency A). The fire could also be
extinguished by sprinkling 250 g of dry sand (fire-extinguishing
efficiency B).
As is understood from the above given results of the fire extinguishment
tests, the method of the present invention is very effective for fire
extinguishment of on dimethyl dichlorosilane and methyl trichlorosilane
and fully practicable for the fire on trimethyl chlorosilane and methyl
dichlorosilane.
EXAMPLE 4
Fire-extinguishment tests were undertaken using trichlorosilane, methyl
dichlorosilane and trimethyl chlorosilane as the inflammable liquids at an
ambient temperature of 30.degree. C. in an atmosphere of 90% relative
humidity. These chlorosilane compounds are notorious in respect of the
difficulty of fire extinguishment thereon. Thus, each a 50 ml portion of
the silane compound was taken in a stainless steel-made vessel having a
diameter of 10 cm and a depth of 6 cm and ignited to be allowed burning
for 20 seconds before the start of the fire extinguishing work and
thereafter 50 g or 70 g of the same porous siliceous powder as used in
Example 1 were sprinkled over the surface of the burning silane compound.
Separately, further tests were undertaken in which sprinkling of 50 g or
70 g of the porous siliceous powder was followed by spraying of monobromo
monochloromethane, carbon tetrachloride or water. The results of these
tests were as follows.
Trichlorosilane
Sprinkling of 50 g of the powder was not fully effective in extinguishing
the fire though with suppression of fuming (fire-extinguishing efficiency
C). When sprinkling of 50 g of the powder was followed by spraying of 5 g
of monobromo monochloromethane, the fire could readily be extinguished
within 15 seconds (fire-extinguishing efficiency A). Spraying of 6 g of
carbon tetrachloride after the powder sprinkling was also effective to
extinguish the fire within 20 seconds (fire-extinguishing efficiency B).
Spraying of 10 g of water was also effective to extinguish the fire though
with evolution of a small volume of toxic gases (fire-extinguishing
efficiency B).
Methyl dichlorosilane
Sprinkling of 70 g of the powder was not sufficient to extinguish the fire
although the violence of the fire could be somewhat subdued with
indication of boiling by the noise within the liquid (fire-extinguishing
efficiency D). Spraying of 10 g of monobromo monochloromethane following
sprinkling of 70 g of the powder was effective to extinguish the fire
within 30 seconds (fire-extinguishing efficiency B). Spraying of 10 g of
water following sprinkling of 70 g of the powder was effective to
extinguish the fire within 20 seconds (fire-extinguishing efficiency A).
Trimethyl chlorosilane
Sprinkling of 50 g of the powder was not sufficient to extinguish the fire
although the violence of the fire could be somewhat subdued
(fire-extinguishing efficiency C). Spraying of 5 g of monobromo
monochloromethane following sprinkling of 50 g of the powder was effective
readily to extinguish the fire within 15 seconds (fire-extinguishing
efficiency A). Spraying of 10 g of water following sprinkling of 50 g of
the powder was effective to extinguish the fire within 20 seconds
(fire-extinguishing efficiency B).
The above described results of the fire extinguishment tests indicate that
the effect of spraying of the highly halogenated hydrocarbon compound or
water is very remarkable when complete extinguishment cannot be obtained
by sprinkling the porous siliceous powder.
EXAMPLE 5
The procedure of the fire extinguishment tests using trichlorosilane,
methyl dichlorosilane and trimethyl chlorosilane was substantially the
same as in Example 4 except that the porous silica-based powder in Example
4 was replaced with a silicaalumina-based porous powder prepared from
Silton 3S and a kaolin by blending in a 1:1 by weight ratio and kneading
them with water, calcining the blend at 1000.degree. C. and acid-leaching
of the calcined material in hydrochloric acid followed by washing with
water, dehydration and drying at 105.degree. C. The thus obtained porous
siliceous powder contained 68% by weight of silica SiO.sub.2 and 25% by
weight of alumina Al.sub.2 O.sub.3 and had a particle diameter in the
range from 40 to 500 .mu.m with a pore diameter distributing in the range
from 0.1 to 50 .mu.m and a porosity of 80%. In each of the fire
extinguishment tests carried out at an ambient temperature of 25.degree.
C., sprinkling of 70 g or 90 g of the powder was always followed by
spraying of monobromo monochloromethane or water. The results of the fire
extinguishment tests were as follows.
Trichlorosilane
Sprinkling of 70 g of the powder was effective in reducing the volume of
the fume and the fire could be extinguished with 40 seconds by subsequent
spraying of 10 g of monobromo monochloromethane (fire-extinguishing
efficiency B). Replacement of 10 g of monobromo monochloromethane with 15
g of water was also effective in extinguishing the fire within 45 seconds
(fire-extinguishing efficiency B).
Methyl dichlorosilane
Sprinkling of 90 g of the powder was effective in subdueing the violence of
fire and the fire could be extinguished with 45 seconds by subsequent
spraying of 10 g of monobromo monochloromethane (fire-extinguishing
efficiency B). Replacement of monobromo monochloromethane with the same
amount of water was also effective in extinguishing the fire within 45
seconds (fire-extinguishing efficiency B).
Trimethyl chlorosilane
Sprinkling of 70 g of the powder was effective in subdueing the violence of
fire and the fire could be extinguished with 40 seconds by subsequent
spraying of 10 g of monobromo monochloromethane (fire-extinguishing
efficiency B). Replacement of 10 g of monobromo monochloromethane with 15
g of water was also effective in extinguishing the fire within 30 seconds
(fire-extinguishing efficiency A).
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