Note: Descriptions are shown in the official language in which they were submitted.
1053780
BACKGROUND OF THE INVENTION
This invention relates to apparatus and methods for
the controlled high pressure polymerization of ethylene into
polyethylene and to similar types of processes in which temper-
ature control is essential for assuring good quality as wellas efficient and effective production.
While the invention relatesgenerally to the control-
ling of processes in accordance with a critical peak temperature
which may shift position back and forth in a reactor during
the process, the invention will be best understood in terms of
a preferred embodiment which is concerned with the polymeriza-
tion of high pressure ethylene to produce polyethylene.
As set forth in U.S. Patent 2,852,501 of September
16, 1958 (W.R. Richard, Jr., et al), polyethylene is an excep-
tionally important material of commerce suitable for use inmolding and also having substantial use in film form. Poly-
ethylene is most effectively produced by subjecting ethylene
to the polymerizing action of elevated temperatures while the
ethylene is confined within a high pressure tubular reactor or
the like. The polymerization reaction is comparatively slow
and it is known to employ an initiator solution which is intro-
duced into the reactor to speed up the reaction. The solution
includes catalysts such as, for example, benzoyl peroxide or
other free-radical promoting catalysts. As will be seen, tem-
perature peaks occur in reactors downstream of the positions atwhich the initiator solution is introduced.
As further stated in Patent 2,852,501, to obtain
practical reaction rates and production yields, the ethylene/
catalyst mixtures can be passed continually through a tubular
reactor. Since the polymerization of ethylene is highly exo-
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i~S3780
thermic, conditions of temperature control are important and
particularly peak temperatures which are reached within the
reactor are of extreme importance. If too high a peak tempera-
ture occurs within the reactor, degradation of the product will
result, this ranging in severity from discoloration of the
polymer product to substantially complete carbonization of
ethylene and polymer. For this reason it was sometimes be-
lieved preferable in the past to reduce various operational
parameters to a lower value than would achieve an optimum yield
in order to achieve a better quality of product. However, op-
erating at milder reaction conditions does not necessarily as-
sure trouble-free operation and sometimes degradation of the
product can occur even at these reduced temperatures.
Pressure fluctuations occurring in reactors employed
for the production of polyethylene result in temperature changes
which also make the temperature difficult to monitor and :~-
control. Some of these pressure changes are incidental to reac-
tions taking place during polymerization, but other pressure
changes are purposefully employed to prevent the accumulation
of polymer on the interior walls, these purposeful changes
being known as "bump-cycles" and being effected by the opera-
tion of "let-down" valves at the exit end of the reactor. This
bump cycle may, for example, cause the reduction of pressure
within~arreactor from 40,000 psi to 35,000 psi, this being a
drop of 5,000 psi which causes a shifting of the temperature
profiles throughout the reactor thus contributing to the diffi-
culties experienced in monitoring critical peak temperatures
and controlling the associated process in accordance therewith.
Temperature profiles as mentioned hereinafter are
discussed by way of example in U.S. Patent 3,299,033 of January
~05;~780
17, 1967 (R.M. Douglas). In this patent is discussed a method
for continuously injecting a controlled volume of ini~iator
solution through a line into a polymerization zone maintained
at operating pressures in excess of 7,500 psi and in which zone
the pressure is subjected to periodic variations. The technique
disclosed in this patent comprises applying and maintaining a
pressure on the initiator solution in the line which is greater
than the operating pressure existing in the reaction zone, con-
tinuously sensing the periodic pressure variations occurring in
this zone, and continuously controlling the volume of initiator
solution injected into this zone in response to the periodic
pressure variations.
In U.S. Patent 3,079,372 of February 26, 1963 (R.P.
Fulknier et al.) is disc]osed a system in which thermocouples
are arranged at spaced intervals within a tubular reactor in
temperature sensing contact with the contents of the rea~tor.
Also provided is a product diversion valve which diverts pro-
duct from a product collector. A valve actuator is provided
which is responsive to the thermocouples to divert product
when the temperature at any point in the reactor exceeds a pre-
determined level. A collector is disposed to receive the di-
verted product.
As will be seen hereinafter, the instant invention
detects a peak temperature in a reactor despite the positional
shifting of the same and processes the signal to generate a
basic signal to control the amount of initiator solution intro-
duced into the reactor. This technique is of course wholly
different from that disclosed in U.S. Patents 3,079,372 or
2,852,501.
,l.o5:~780
DESCRIPTION t~F TEIIS IN~7ENTION
It is an object of the invention to provide improved
high pressure apparatus for the polymerization of ethylene and
more generally to provide improved apparatus for controlling
critical temperatures which may occur during operation of such
polymerization apparatus.
Another object of the invention is to provide im-
proved methods for controlling the introduction of catalysts
into materials undergoing polymerization in order to control
operational parameters such as temperatures in such polymeriz-
ing materials.
Yet another object of the invention is to provide im-
proved electronic circuits capable of distinguishing between a
plurality of electrical signals representing the temperatures
at various points within a reactor to select the critical peak
signal therefrom and to use such peak signal in controlling the
magnitude of the associated critical temperatures.
A further object of the invention is to provide im-
proved methods and apparatus for improving the quality and
yield of products such as polymers by controlling the introduc-
tion of catalysts used in the production thereof.
To achieve the above and other objects of the inven-
tion, there is provided an apparatus comprising a source of
materials and an elongated reaction system coupled thereto in
which a process involving these materials takes place. Where,
for example, the polymerization of high pressure ethylene is
involved, the high pressure ethylene will be fed into a tubular
reactor and at one or more zones of the reactor there will be
introduced catalysts which promote the polymerization and
affect the quantity and quality of the polyethylene produced.
1053780
With reference to the general type of apparatus con-
templated in accordance with the invention, peak or other such
critical temperatures will occur within the reactor and may
for various reasons, shift back and forth positionally along
the reactor. In accordance with the invention, there are pro-
vided circuits which detect the critical temperature despite
the movement of the same within the reactor and which employ
this critical temperature to generate a corrective signal to
adjust conditions which affect the magnitude of this tempera-
ture.
In the case of polymerization of high pressure ethy-
lene, the corrective signal is employed to adjust the quantity
of catalyst injected into the high pressure reactor. In accor-
dance with one embodiment of the invention, this is accomplished
by converting the difference signal generated by a comparator,
which compares the peak temperature signal with a preset re-
ference signal representative of the magnitude of the desired
peak temperature, into a pressure signal, which is used to
control a catalyst intensifier pump.
Thus, in accordance with the present teachings, an
improvement is provided in elongated apparatus for conducting
chemical reactions which includes feed means for introducing the
reactant materials thereto. The improvement includes a plurality
of thermocouples which are spaced along a portion of the apparatus
downstream of the point of introduction of a key reactant material.
A plurality of matching electrical amplifiers which are coupled to
each of the thermocouples amplifies the temperature responsive
electrical signals emitted therefrom. A gating circuit is provided
coupled electrically with the amplifiers in such a way that only
t~le peak signal from among the amplifiers is transmitted. Means
are provided for applying the peak signal to controls on the feed
means in order to adjust the rate of introduction of the key
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reactant material in response to the relative strength of the
peak signal.
In accordance wi~h a further teaching, an improvement is
provided in the process for carrying out a chemical reaction on a
S substained basis wherein at least one key reactant is gradually
introduced as the positive flow delivery system into an elongated
reaction zone over a considerable period of time. The improvement
comprises electrically sensing the temperature at a plurality
of stations in the reaction zone spaced apart through a portion
of the zone just downstream from the point of introduction of the
key reactant. The resultant plurality of separate electrical
signals are passed simultaneously through matching amplification
circuits and the amplified signals are converged into a gatin~ -
circuit which transmits only the peak signal while cutting off
all of the rest. The peak signal if transmitted back to control
responsively the diriving element of the positive flow delivery
stream and thus the rate of introduction of the key reactant.
According to a further feature of the invention,
temperatures are measured at positions, spaced along a tubular
reactor, by thermocouples which generate signals which are fed
into a gating circuit which selectes the critical peak signal
therefrom. This peak signal is then fed into a comparator
which yields a difference signal which is representative of
the extent of departure from the desired peak temperature in
the reactor. This difference signal is fed to a transducer
which converts the same into a pressure signal controlling a
valve which in turn controls the speed of a pump supplying
one or more materials to the tubular reactor. According to a
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further feature of the invention, the peak or critical tem-
perature is also fed to a recording and display device so that
an operator can monitor trends in the operation.
Materials can be injected into reactor apparatus of
the invention at a plurality of positions in which event the
critical temperature in each reactor zone relating to each
such position can be monitored in accordance with the invention.
Other objects and features of the invention, as well
as advantages thereof will appear from the detailed description
which follows hereinafter as illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 diagrammatically illustrates a polyethlene
reactor including the improvements of the invention;
Figure 2 illustrates a detail of the reactor of Fig.
1 with respect to the mounting of one of the thermocouples in
the reactor;
Figure 3 is a chart illustrative of possible tempera-
ture profiles in the reactor of Fig. l;
Figure 4 is a partially block, and partially schema-
tic, diagram of electrical circuits constituting the tempera-
ture measuring and reactor control elements associated with
the reactor of Fig. l; and
Figure 5 is a diagram of one of the peak temperature
picker or selection circuits included in the circuitry of Fig.
4.
DETAILED DESCRIPTION
The apparatus illustrated in Fig. 1 represents the
essential sections of a polyethylene tubular reactor. Th~rein,
~0537~30
for example, the pressure can vary up to 60,000 psi and greater
and the temperatures can vary from about 225F up to 700F
and possibly greater. The usual operating pressure in the pre-
ferred embodiment of the invention will, however, generally be
in the order of 30,000 + 10,000 psi, whereas the temperature
may vary between about 500 and about 650F and preferably
within a range of from 550-600F.
More particularly, the apparatus of Fig. 1 comprises
a source 10 of high pressure ethylene feeding into a tubular
reaator consisting of a plurality of tubular sections 12a to
12z. These tubular sections are connected in series relation
by connecting blocks such as the block 42 between sections 12d
and 12e.
As is well known, the tubular sections usually have
water jackets (not shown) operatively associated therewith.
These tubular jackets are supplied with hot water via a line
16 and cold water via a line 18, there being provisions made
for water return via a line 20. The blocks such as 42 consti-
tute discontinuities in the water jackets and are bypassed as
indicated by line 22. Valves such as indicated at 24 are dis-
tributed throughout the water jacket system to provide for
varying the flow of hot and cold water, these valves serving
to a limited extent to control temperature within the reactor.
According to known techniques, an initiator solution
including, for example, a peroxide initiator in a solvent, is
introduced into the reactor system to promote polymerization
and improve and control the quality and quantity of the poly-
ethylene produced therein. This initiator solution in the
illustrated reactor is introduced into the block indicated at
26 and at the block indicated at 28. The source of the initia-
1053780
tor solution is the intensifier pump 30 with respect to the
block 26 and the intensifier pump 32 with respect to the block
28. The intensifier construction may be as indicated in U.S.
Patent 3,234,882, which issued February 15, 1966 ~R.M. Douglas
et al).
As will be described in greater detail hereunder,
the introduction of initiator solution into the system at posi-
tions corresponding to the blocks 26 and 28 will result in
peak temperatures which may occur at varying positions within
two zones downstream of said respective blocks. To measure
temperatures within these zones, thermocouples are installed
in the blocks in the first zone indicated at 38, 40, 42, 44
and 46 and in the second zone in the blocks indicated at 48,
50, 52, 54 and 56. Additional thermocouples may be installed
in the remaining blocks but will not be discussed in connec-
tion with th~s embodiment of the invention.
The thermocouples in the first zone are coupled to
an automatic control system 58 connected via line 60 to in-
tensifier pump 30. The thermocouples in the second zone are
coupled to an automatic control 62 connected via line 64 to
intensifier pump 32. The details and operation of these two
automatic control systems will be described in greater detail
hereinafter.
The upstream end of the tubular reactor is consti-
tuted by the block 26. The downstream end of the tubularreactor is indicated at 66. The downstream end discharges in-
to a separator 68 which functions to separate the ethylene and
polyethylene. The functions of the separator are described in
U.S. Patent 2,852,501, previously mentioned herein. Valve 70
is a high pressure letdown valve functioning to reduce the
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1053780
pressure in the tubular reactor periodically to cause pres-
sure pulses therein for minimizing the accumulation of poly-
mer within the reactor. For example, with a pressure of
40,000 psi employed within the reactor, valve 70 will provide
for a 5,000 psi reduction every thirty seconds to a pressure
of 35,000 psi. This "bump cycle" is a known technique and is
not within the scope of the present invention, except for the
fact that it contributes to peak temperature displacements
within the reactor with which the present invention is con-
lm~ cerned. Valve 70 is shown as coupled via line 72 to source lO
sinee it is a back-pressure controller.
As has been indicated above, an essential part of
the apparatus illustrated in Fig. 1 is constituted by the
thermocouples which are spaced downstream of the positions at
which initiator solution is introduced into the reactor system.
These thermocouples are mounted, as shown by way of example in
Fig. 2 wherein is seen block 38 connecting tubular sections
12b and 12c. .
Tubular section 12b comprises a flange 74 connected
to block 38 by means of bolts 76 and 78. Tubular section 12c
comprises flange 80 connected to block 38 by bolts 82 and 84.
Within block 38 is defined recess 85 through which is extended
tip 86 of thermocouple elements well known in the art.
A complete thermocouple structure is illustrated with
respect to tip 86. This tip is a part of sheathed thermo-
couple 87 which at end 88 is connected to braided lead wire
90 terminating in a connect-disconnect type plug 92. Plug 92
leads the signal generated in the thermocouple to a circuit
arrangement which will be described hereinafter. Sheathed
~hermoeouple 87is mounted within plug 94. The oombined
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1053780
thermocouple 87 and plug 94 are mounted within fitting 96 for
accommodation within recess 85 by means of threads 98. The
thermocouples may be of various types mounted in any suitable
manner, the locations rather than the details of the thermo-
couples being significant in the invention.
Fig. 3 is a chart illustrating temperature profiles
in a typical tubular reactor of the type described hereinabove
wherein are included thirty-six blocks within selected of
which may be installed one or more thermocouples in the manner
indicated, for example, in Fig. 2.
The abscissa 102 in Fig. 3 indicates the block number
commencing with the upstream end 104 and terminating with the
downstream end 106 of the tubular reactor. The ordinate 108
indicates temperature of increasing degree. Curve 110 indi-
cates, by way of example, a peak occurring at block number 4and a second peak occurring at block number 22. These peaks
are substantially immediately adjacent and downstream of block
numbers 1 and 19 to which intensifier pumps connect. Curve 112
illustrates the profile at a subse~uent time period of the pro-
cess. This curve illustrates that the peaks have shifted andnow occur at block numbers 7 and 23.
Reasons for the shifting of the peaks include the
bump cycle referred to hereinabove as well as changing condi-
tions within the reactor such as, for example, adherence to
the interior wall of the reactor of polymer which is generated
and so forth. Experience has shown, however, that the peaks
will move to a limited exten~ only and that the temperature
peaks can be monitored by thermocouples arranged in two groups
of about five blocks each, defining first and second zones lo-
cated respectively downstream of the two blocks through which
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105;~780
initiator solution is introduced into the reactor. For thenormal velocities of material through the reactor, i.e. about
5 to 100 feet per second, the peak temperature will occur some-
where within less than five blocks. The distance between
blocks can be varied from about 5 to 60 feet depending on the
diameter of the reactor and the v~locity of material through
the reactor. The distance is chosen such that once the peak
temperature has been determined as disclosed herein, the tem-
perature in the adjacentdownstreamthermocouple will usually
be a few degrees lower than the peak temperature and no more
than about 10F lower.
In Fig. 4 are illustrated thermocouple groups 114 and
116 associated with each of the two zones indicated above.
Thermocouple group 114 is connected to peak picker 118, where-
as thermocouple group 116 is coupled to peak picker 120. The
details of these peak pickers will be described in more detail
hereinafter in conjunction with Fig. 5. It is sufficient at
this point merely to understand that each peak picker operates
to pass through one of the five thermocouple signals received,
said one signal being the peak temperature in the associated
zone. Power for peak picker 118 is controlled by switch 122,
whereas power for peak picker 120 is controlled by switch 124.
Power sources are indicated generally at 126 and 128.
Two comparators 130 and 132 are included in the cir-
cuit of Fig. 4. Comparator 130 receives power from source
126 whereas comparator 132 receives power from source 128.
Comparator 130 is connected to peak picker 118 via line 134
and comparator 132 is connected to peak picker 120 via line
136.
A recorder and display unit 138 is also included in
1053780
the circuit of Fig. 4. It is connected to peak picker 118
via line 140 and with peak picker 120 via line 142. Recorder
138 is connected with comparator 130 via line 144 and with
comparator 132 via line 146. Recorder 139 and comparators
130 and 132 are connected in a loop circuit with peak pickers
118 and 120 and form load circuits therefor.
The function of recorder 138 is to record the peak
voltages or temperatures for each of the two zones in the reac-
tor downstream of the positons at which the initiator solu-
tions are introduced and to display the same so that an opera-
tor can follow and analyze trends in the process if so desired.
For this purpose there may be employed a two-pen recorder
which traces temperature and/or voltage recordings on a paper
strip.
The purpose and function of comparators 130 and 132
are to receive peak indicating signals from peak pickers 118
and 120 and to compare these signals with operator-selected
reference signals indicative of the peak temperatures which
are desired in the respective zones in the reactor of Fig. 1.
Comparators 130 and 132 generate difference signals which re-
present the -differences between the magnitudes of the peak
temperatures in said zones and the respective values desired
therefor. These difference signals are transmitted onto lines
148 and 150.
The signals on lines 148 and 150 are transmitted
to transducers 152 and 154. In these transducers, the electri-
cal signals received from comparators 130 and 132 are converted
into pneumatic signals which are transmitted onto lines 156
and 158. Transducers 152 and 154 may be any type of trans-
ducer suitable for converting a signal of, for example, 10-50
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105;~780
milliamps to a pneumatic pressure signal of, for example, 3
to 15 psig. One such transducer which has been satisfactorily
employed is the ~ype 546 Electropneumatic Transducer manufac-
tured by the Fisher Governor Company of Marshalltown, Iowa.
Intensifier pumps which are adapted to be controlled
by the signals on lines 156 and 158 have associated therewith
control valves 160, 162, 164 and 166 indicative of the provi-
sion of four such pumps. While only two pumps are actually
necessary (i.e., one for each of the aforesaid æones) four
pumps are provided which may be selectively coupled to the in-
dicated blocks by the use of switches 168, 170, 172 and 174.
This permits holding one or more pumps in reserve to accomo-
date possible breakdowns. More particularly, lines 156 and
1~8 are connected to solenoids 176, 178, 180, 182, 184, 186, 188
and 190 which selectively feed valves 160, 162, 164 and 166,
selection being controlled by selector switches 168, 170,
172 and 174.
Connected between solenoids 176 and 178 and valve
160 is a booster 192. Connected between solenoids 180 and 182
and valve 162 is a booster 194. A booster 196 is connected
between solenoids 184 and 186, on the one hand, and valve 164
on the other hand. A booster 198 is connected between valve
166 and solenoids 188 and 190.
The function of the boosters 192, 194, 196 and 198
is to improve the stroking speed and frequency response of the
intensifier pumps coupled to valves 160, 162, 164 and 166.
Such boosters are well known and commercially available.
Fig. 5 illustrates schematically how a peak picker
circuit (118 or 120 in Fig. 4) operates to select and pass
only the strongest signal rQm the five thermocouples in a
~053780
given zone of the tubular reactor shown in Fig. 1. Thus,
thermocouples 202, 204, 206, 208 and 210 from the given zone
are each connected to identical power driven D.C. amplifiers
212, 214, 216, 218 and 220. In these D.C. amplifiers, the
very low voltage level thermocouple signals are magnified and
then fed to separate but identical isolation circuits 222,
224, 226, 228 and 230. In these isolation circuits each signal
is first chopped by an oscillator input into 60 cycle per
second A.C. and then transformed to a higher power level.
The respective signals, now in 60 cycle A.C. current,
are further amplified by means of A.C. amplifiers 232, 234,
236, 238 and 240. The initial outputs from said A.C. ampli-
fiers are taken off to low temperature selector circuit 244
which is biased to respond to an excessively low signal to
pass a signal to alarm circuit 252 which can activate a warning
light 256 and/or ring a bell (not shown), Just beyond the
low temperature selection point, each output signal from said
A.C. amplifiers is connected to the anode of identical recti-
fier diodes 231, 233, 235, 237 and 239. Since the cathodes
of each of said diodes are connected to a common junction or
terminal 241, a gating circuit is formed which cuts off all
diode outputs except the strongest and thus passes only the
peak signal into high selector circuit 242. This high tempera-
ture signal from circuit 242 can be used for several purposes,
e.g., to trigger alarm and/or safety shutdown devices 246 and/
or 248 and to operate record~r 138 of Fig. 4.
In accordance with the present invention, however,
the most vital feedback contro~ function performed by the high
temperature signal is indicated by current output branch cir-
cuit 250 which leads to comparator 130 from which a difference
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signal can be obtained as previously explained. This differ-
ence output 254 would then be sent through line 148 of Fig.
4 to control the speed of the intensifier pump feeding the
initiator solution to the reaction zone in question.
With reference to the circuits and apparatus described
above, polymerization of high pressure ethylene takes place as
follows:
High pressure ethylene is introduced into the reactor
from source 10. Initiator solution is introduced into the
reactor from intensifier pumps 30 and 32. Temperature peaks
occur in respective zones downstream of the positions at which
the initiator solution is introduced. During the polymeriza-
tion of the high pressure ethylene, pressure in the reactor is
periodically reduced by operation of valve 70. This, as stated
above, assists in preventing accumulation of polyethylene on
interior walls within the system. Due to this bump cycle and
for other reasons, the peak temperatures occurring in the zones
referred to above do not have fixed positions, but instead are
displaced within their respective zones. These zones are, how-
ever, limited and by no means constitute the entire extent of
the reactor. In each of the zones, the associated groups of
thermocouples bracket the distance through which peak tempera-
tures can be displaced during normal operation. The tempera-
tures sensed by these two groups of thermocouples are converted
into voltages which are fed to peak pickers 118 and 120 respec-
tively. In these peak pickers, the voltages are amplified by
D.C. amplifiers 212-220, chopped by circuits 222-230 and fed
to A.C. power amplifiers 232-240 to provide stronger output
signals.
The gating circuit formed by connection of diodes
231-239 to the common terminal 241 of high selector circuit
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242 permits only the peak signal to be passed. The peak sig-
nal for each of the two zones is fed to comparator 130 or 132
respectively. The peak signals are also fed to recorder 138
whereat they are traced, according to known procedures, on
paper strips for display purposes so that an operator can
follow the trends of the peaks in each zone, irrespective of
the positional shifting thereof.
Preset reference signals having a strength represen-
tative of the peak temperatures desired in the respective zones
are entered by an operator into comparators 130 and 132 which
compare same with respective peak signals coming from peak
pickers 118 and 120. Difference signals of the order of 10-50
milliamps are transmitted to transducers 152 and 154 which pro-
duce corresponding pneumatic signals which are transmitting
via lines 156 and 158 and selected of solenoids 176-190 to
valves 160-166. Selection is made by switches 168-174.
Boosters 192-198 minimize the delay in responding to the sig-
nals produced on lines 156 and 158.
The pumps selected by switches 168-174 correspond
to intensifiers 30 and 32 (Fig. 1). The valves 160-166 cor-
respond to the valves which control the speed of operation of
these pumps in the manner set forth in U.S. Patent 3,234,882
(see for example valve 14 in said patent). The outputs of
the intensifiers are fed through valves 34 and 36 into the
reactor system.
From what has been stated hereinabove, it is seen
that the peak voltage in each of the two zones in the reactor
system is used to control the rate of introduction of initiator
solution at positions ~pstream of such zones. Despite the fact
that the peak temperature may shift position somewhat from
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1053780
time to time due to a variety of reasons, the peak tempera-
ture is always maintained under close control. It is to be
understood that some slight deviation is permissible such as,
for example, might occur due to the presence of a peak inter-
mediate the thermocouples. This, however, has not been foundto be of significance in view of the speed of flow of materials
through the reactor system. In such processes, where the
possibility of peaks occurring intermediate adjacent thermo-
couples might be of importance, it would of course be possible
to position additional thermocouples between the blocks thereby
to minimize the importance of this problem.
From what has been stated hereinabove, it will be
seen that the invention relates generally to an apparatus ~
wherein an elongated reaction system receives raw materials in
such a manner that a critical or peak temperature occurs in
the system and is displaceable therein, the invention providing
for monitoring the critical peak temperature despite displace-
ment of the same and for controlling the supply of at least
one of the aforesaid materials to the reaction system based on
said critical or peak temperature.
Generally, the method of the invention involves con-
trolling a reaction which is taking place in an elongated
reaction system in which there is a shifting temperature pro-
file. From what has been stated herein, it will now be under-
stood that the method involves establishing a temperature cri-
terion such as, for example, a desired peak temperature, and
sensing temperatures at a plurality of stations spaced along
the aforenoted system whereafter the reaction is controlled
accordingly to maintain a peak temperature which corresponds
most closely to the temperature criterion.
lOS3780
According to the method of the invention, control
of the reaction is preferably effected by controlling one of
the materials introduced into the reactor. From the preferred
embodiment described above, it is seen that, where the reaction
is the polymerization of high pressure ethylene in which
ethylene and initiator solution are supplied to the reaction
syst~m, control is best effected by adjusting the rate at
which the initiator solution is supplied.
Finally, it has been seen that the method of the in-
vention preferably involves continuously displaying the peak
temperature, this being effected, for example, by a recorder
tracing one or more lines indicative of peak temperat~res in
the reactor system.
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