Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to chemical engineering
and more particularly to chemical compression reactors, and may
be used in chemical industries for carrying out a wide range of
yas-phase chemical reactions at high pressures and temperature
More specifically it may be used for effecting rapid gas-phase
reactions which proceed intensively under the pulse effect of
temperature and pressure when the reaction mixture is under
such temperature and pressure conditions which are maximal for
the given compression cycle, for a period that does not exceed
one millisecond.
me prior art teaches different versions of chemical
compression reactors intended for carrying out reactions in a
gas phase. Free-piston compression reactors belong to a separa-
te group. Such reactors compriqe a housing with a cylindrical
reaction chamber closed at the ends, wherein the reactants are
compresqed by a free-piston, i.e. a piston which has no mecha-
nical linking whatsoever. In the prior art are known reactors
which have several quch housings, as well as reactors wherein
one reaction chamber is provided with several pistons. In the
latter case the motion of the pistons is synchronized by special
means.
For example, the prior art teaches a chemical free-
piston compression reactor comprising a housing secured on a
base and having a cylindrical reaction chamber with a horizontal
longitudinal axis. Inside the chamber there is disposed a reci-
procating free-piston consisting of two halves interconnected
by a rod and dividing the reaction chamber in two working spaces.
Each working space has at its ends a port for feeding
in the charge which is closed by a poppet valve. In addition,
the end of each working space is provided with an additional
port which is also closed by a poppet valve. This additional
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port serves for feeding in a gas under a high pressure. All the
va:Lves are opened by solenoids which are controlled by contacts
actuated by the rod connecting the two halves of the piston.
The valveq are provided with springs which act on them and close
them when the qolenoids are de-energized. The contacts cut-in
the solenoids for opening the respective valves at the end of
the expansion stroke in the respective working spaces.
Each working space is provided with ports for exhaust
of the reaction products. mese ports are disposed so that they
are open when in a given working space the piston is at the end
of the expansion stroke. At this time the other end of the pis-
ton in the other working space completes the compression stroke.
When the piston is oscillating the gas fed into the
working space is compressed while the piston moves in one direc-
tion and expands while the latter moves in the opposite direc-
tion. In the other working space such processes take place in
the opposite phase. ~uring the expansion of the gas the scaveng-
ing operation takes place - the next portion of the reagent and
said high-pressure gas is fed through the ports for feeding in
reagents at the ends of the reaction chamber, and the reaction
products exhaust through the ports in the side wall of the
reaction chamber.
However, in all the prior art models of chemical com-
pression free-piston reactors the forces of friction between the
piston and the reaction chamber walls are great and, consequent-
ly, so are energy losses due to friction. This disadvantage is
critical for a chemical free-piston compression reactor. The
theory of oscillations teaches that the energy stored by an os-
cillating system, a piston in this case, is directly associated
with the extent of the losses in the oscillating system during
the resonance excitation: the greater the losses, the lower the
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energy of the system, i.e. of the piston, the lower the pressure
and the temperature of compression by the piston of the reagents
in the chemicaL free-piston compression reactor, the lower the
conversion ratio in it, as well as the product output (the pro-
ductivity) of the reactor.
Moreover, no provision is made in the prior art models
of the reactors for preventing the intermixing of the charge
fed into the reactor and the reaction products leaving the re-
action chamber. Because of this the product output of the re-
actor becomes lower and the selectivity of the process deterio-
rates if the product is unstable (the selectivity with regard
to the target product is determined here as the ratio of the
yield of the target product of the reaction expressed in per-
centage to the total yield of all the reaction products). ~his
is mainly due to the fact that in the prior art models no pro-
vision is made for complete exhaust from the reactor of the
reaction products. me rating of exhaust may be defined as the
ratio of the amount of the reaction products which have not been
evacuated during one piston stroke to the volume of the reagents
subjected to compression. me exhaust of the reaction products
from the reactor can be improved by means of raising the sca-
venging ratio, i.e. the ratio of the volume of gas leaving the
reactor between two compression strokes to the volume of the
working space. However, such a technique results in dilution of
the reaction products with the starting charge which is tanta-
mount to lower conversion of the charge and, consequently, im-
pairs the characteristics of all the subsequent technological
operations aimed at isolation of the target product, and re-
cycling the unreacted raw material is increased.
It is an object of the present invention to provide a
chemical free-piston compression reactor wherein a high product
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output would be ensured.
It is another object of the invention to provide a
chemical reactor wherein the selectivity of the process is
ensured.
This is achieved by that in a chemical free-piston com-
pression reactor comprising a housing secured on a base and hav-
ing a cylindrical reaction chamber with a reciprocating free-
piston housed therein and dividing the reaction chamber into two
working spaces, ports for feeding in reagents, provided in the
end faces of the reaction chamber and closed by controlled val-
ves, and ports for the exhaust of reaction products provided in
its side wall, according to the invention, the axis of the re-
action chamber i~ disposed vertically and the ports for the ex-
haust of reaction products are spaced at a distance from the
ports for feeding reactants into the same working space equal
to 2.5 to 10 times the bore of the reaction chamber.
A relatively large distance between the input and ex-
haust ports increases both the product output of the reactor
and the selectivity of the process.
An increase in the distance between the ports for feed-
ing in and exhaust requires an increase in the total length of
the housing of the chemical compression reactor and this can
be achieved only when the axis of the reaction chamber is dis-
posed vertically.
Ihe ports for the exhaust of reaction products may be
provided with controlled valves, which makes it possible to
close the valves at the moments when the starting mixture and
not the reaction products is near them. ~his increases even
~urther the productivity of the reactor with regard to the pro-
duct and the selectivity.
In the end faces of the reaction chamber there may be
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several ports for feeding reactants, which are arranged symme-
trically to the axis of the reaction chamber. It has been ex-
perimental,ly shown that this measure additionally contributes
to an increase in the productivity of the reactor and the selec-
t~vity of the processes carried out in it. me ports for feed-
ing in reagent~ may also be made in the form of annular slits
concentric to the axis of the reaction chamber. Such a design
makes it possible to effectively attain between results as re-
gards the productivity and the selectivity.
In addition, irrespective of the number and the design
of the valves, they may be made as normally free, i.e. free
when the control is cut off. This ensures their opening at a
minimal pressure drop and also leads to an increase in the pro-
ductivity of the reactor and reduces the degree of intermixing
of the reagentq and reaction products.
The invention will be better understood from a consi-
deration of a detailed description of specific embodiments
thereof with reference to the accompanying drawings, wherein:
Fig. 1 shows a longitudinal section of a chemical free-
piston compression reaction vessel according to the invention,
Fig. 2 is a section along the line II-II in Fig. l,
Fig. 3 shows an embodiment of ports for feeding in re-
agents, in a longitudinal section, accordin~ to the invention,
Fig. 4 is a section taken along the line IV-IV in Fig.
3.
~ he herein-proposed chemical compression reactor com-
prises a housing l (Fig. l) secured on a base 2. In the housing
1 there is provided a cylindrical reaction chamber 3 whose axis
is disposed vertically. A reciprocating free-piston 4 divides
the reaction chamber 3 into two working spaces - an upper work-
ing space 5 and a lower working space 6 and can perform vertical
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reciprocating motion.
Four ports 7(Figs. 1 and 2) and four ports 8 (Fig. 1)
for feeding reagents into the working spaces 6 and 5 respective-
ly are made in the end faces of the reaction chamber 3 symme-
trically in relation to its axis. The ports 7 are closed by
poppet valves 9 controlled by a solenoid 10 and the ports 8 are
closed by poppet valves 11 controlled by a solenoid 12.
me valves 9 and 11 of the ports 7 and 8 for feeding
in reagents must be preferably normally free. Generally the
ports 7 and 8 may be in any number, but preferably from 3 to
12, and they must be disposed symmetrically with regard to the
axis of the reaction chamber 3, which makes it possible to uni-
formly distribute the stream of the reagent being fed through-
out the entire section of the reaction chamber 3. The ports
for feeding in reagents may also be made in the form of an annu-
lar slit 13 (Fig. 3) concentric relative to the axis of the
reaction chamber 3.
me annular slit 13 is closed by a controlled valve 14
(Figs. 3 and 4) of an appropriate shape.
In the side walls of the reaction chamber 3 ports 15
are made (Fig. 1) for the exhaust of the reaction products from
the lower working space 6, and ports 16 for the exhaust of the
reaction products from the upper working space 5. All the ports
15 communicate with a circular collector means 17 the outlet
from which is closed by a valve 18 controlled by a solenoid 19.
Similarly the ports 16 communicate with a collector means 20
whose outlet is closed by a valve 21 controlled by solenoid 22.
m e distance "1" from the ports 8 for feeding reagents
into the working space 5 to the ports 16 for the exhaust of the
reaction products from the same working space 5 (as well as the
distance from the ports 7 to the ports 15) is equal to three
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times the bore "d" of the reaction chamber 3 but may vary from
2.5 d to 10 d.
The ports 15 and 16 for the exhaust of the reaction pro-
ducts in some cases may not be closed by valves (not shown in
the drawings). However, in such cases to prevent unreacted
reagents ~rom passing through, it is necessary to maintain cer-
tain ratios between the length of the piston stroke, the length
of the piston and the distance between the ports for feeding in
reagents and the ports for the exhaust of the reaction products.
To start the chemical compression reactor it is neces-
sary to supply gaseous reagents at a pressure of 10 to 20 at-
mospheres to the valves 9 and 11 which close the ports 7 and 8.
A portion of gaseous reagents is fed into the lower working spa-
ce 6 by controlling the valves 9. Meanwhile the valves 11 and 21
must be closed and the valve 18 opened. Under the action of
gaseous reagents the piston 4 rises, compressing the gas in the
upper working space 5. In the lower working space 6 the gas ex-
pands and partly flows out through the ports 15, therefore the
pressure in the lower working space 6 becomes lower than that in
the upper working space 5, the piston 4 stops and then starts
going down. A portion of gaseous reagents which, while expand-
ing, provide an additional impulse to the piston 4 should be fed
at this moment in to the upper working space 5 through the open-
ings 8. During the downward movement of the piston 4 the valves
18 and 9 should be closed and the valve 21 opened. During this
stroke the piston 4 compresses the gas in the lower working
space 6 and the gas acquires a higher potential energy than
during the previous stroke of the piston 4 in the upper working
space 5.
During the downward movement of the piston 4 a portion
of gas from the upper working space 5 flows out through the
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ports 16 since the valve 21 will be opened. Thus, the amount
of gas in the working spaces 5 and 6 does not increase from
~troke to stroke of the piston 4, but during every stroke of
th~ piston 4 a certain amount of energy is supplied to it due to
the supply of a next portion of gaseous reagents. Therefore,
with every stroke the piston 4 in the reaction chamber 3 moves
faster and respectively compresses gaseous reagents to ever
higher pressures and temperatures.
The speed of movement of the piston 4 and the frequency
of its oscillations increase until the energy brought to the
pi~ton 4 at every stroke is equali2ed with the energy losses.
Under the stationary working conditions the proposed
reactor operates in the following manner.
The piston 4 from the lower dead centre moves upward
under the efect of reagents compreqsed thereunder, the pressure
in the lower working space 6 dropping, and at the moment when it
becomes lower than that in the supply manifold, the valves 9
open due to the pressure gradient, and fresh charge is fed into
the reactor. me solenoid 10 closes the valves 9 in about 0.01
second after the charge starts coming in. When the lower end of
the rising piston 4 reaches the ports 15 or somewhat later, the
valve 18 opens via the solenoid 19. E`rom this moment on and
till the return of the lower end of the piston 4 to the level of
the ports 15 the outflow of gas from the lower working space 6
is taking place if the valve 18 is not closed by a command. At
this time the compression has taken place in the upper working
space 5 so that the return of the piston 4 occurs due to the ef-
fect of the gases compressed in the upper working space 5. In
its further downward movement the piston 4 reaches the lower
dead centre from which we began the description of its movement.
All the processes in the upper working space 5 are identical
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with those taking place in the lower working space 6 but they
occur in the opposite phase.
The increased distance between the ports 7 for feeding
in reagents and the ports 15 for the exhaust of the reaction
products (the ports 8 and the ports 16 respectively), a great
number of the ports 7 and 8 for feeding in reagents arranged
symmetrically relative to the axis of the reaction chamber 3
~or one or two ports in the form of an annular slit 13 shown
in Figs. 3 and 4), the presence of controlled valves 1~ and 21
(Fig. 1) as well as the vertical disposition of the housing 1
on the base 2 considerably increase the productivity of the
compression reactor and improve the selectivity of the process
as it has been shown by means of directed experiments with va-
rious embodiments of designs within the scope of the present in-
vention.
It has been found that an increase in the distance bet-
ween the ports for feeding in reagents and the ports for the ex-
haust of reaction products from 1.5 times the bore of the reac-
tion chamber 3 (as it was done in the prior art construction)
to 10 times the bore with a simultaneous increase in the number
of the ports for feeding in from one to twelve results in a ten-
fold increase of the rating of exhaust of the reaction products,
with the scavenging ratio equal to unity. This is accompanied
by a respective growth of the productivity o-f the reactor (cal-
culated on product).
Likewise, it has been found that for the case of reac-
tion of hydrodealkylation of xylenes in a mixture with hydrogen
wherein toluene is an intermediate product the selectivity at-
tained in the reactor of the new design is much higher than the
selectivity obtained for the construction taught by the prior
art.
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If the ratio y = (C7H8~ x 100%: [(C7H8) + (C6H6)],
wherein the values in brackets are volume concentrations of the
respective substances i~ taken as the measure of selectivity (y~
then in the prior art reactor having one port for feeding in re-
agents in each working space and the distance between the port
for feeding in reactants and the port for the exhaust of
reaction products equal to 1.5 times the bore of the working
chamber, the value y does not exceed 12% with the scavenging
ratio equal to unity.
In the new construction wherein the distance between
the ports for feeding in reagents and the ports for the exhaust
of reaction products is equal to 10 times the bore of the
working chamber and the number of ports for feeding in reac-
tants equal to 12 the selectivity y reaches 70%. Thus, the new
embodiments of the compression reactor bring about an unexpected
effect - an increase in the selectivity of chemical conversion.
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