DE2237983B2 - ARRANGEMENT FOR REGULATING THE ACID STRENGTH IN AN ISOPARAFFIN-OLEFINAL KYLING PLANT - Google Patents

Description

Description of the drawings

F i g. 1 is a block diagram of the inventive arrangement for controlling the acid strength in FIG an alkylation plant, shown partially in schematic form;

= .; F i g. 2 is a diagrammatic representation of signals; as shown during a typical operating cycle of the η of FIG. 1 system shown occur;

Figures 3 through 5 are detailed block diagrams of the the programming device shown in FIG. 1, Setpoint signal device and acid strength signal device;

F i g. 6A through 6B, when merged at line AA , show a detailed block diagram of the diagram shown in FIG. 1 olefin signal device shown.

Description of the invention

In FIG. 1 shows part of an alkylation plant in which an olefin _{reacts with isoparaffin in catalyst against warx, such as H 2} SO ₄ or HF, to form an isoparaffin of higher molecular weight. For purposes of illustration, the acid in the description below is intended to be H ₂ SO ₄ . The olefin can be butene, propene, or a mixture of butene and propene, while the isoparaffin can be isobutane. The in the F i g. The control system shown in Fig. 1 controls the acid strength in the course of the reaction by determining the current acid strength and comparing the current acid strength with a required acid strength. The control system also anticipates changes in acid strength due to changes in the amounts of acid consuming components from the starting olefin in order to control the acid strength so as to expedite the control process. Olefin and isoparaffin enter a contactor 4 through line 6, in which olefin and isoparaffin with acid flowing through line? is introduced, come into contact. Contactor 4 delivers an acid-hydrocarbon mixture through line 8 to acid settler 12. Settler 12 separates the hydrocarbon product from the acid and the hydrocarbon product is withdrawn through line 14 while acid is removed through line 16. The acid settler 12 may be the only one in the plant, or it can be the last of a group of acid settlers. Fresh acid is added to line 16 through line 17 as needed to maintain a required acid strength. Part of the acid in line 7 is passed through line 2! removed. The acid removed can be made available for another alkylation plant or disposed of.

An acid strength analyzer 22 periodically draws acid samples from the line 16 and supplies the signals E ₁ to E ₄ . As the acid strength analyzer 22, an ordinary device can be used. The acid sample is analyzed by titrating with alkali from 24 introduced through line 25 at a constant rate. The start of each sampling cycle from the line 16 is controlled by the reset _{signal E 6} from a programming device 27.

The signal E ₁ , shown in FIG. 2, of the analyzer 22 appears at the point in time at which the titration begins, while the signal E ₂ , in FIG. 2, occurs by the time the titration is complete. The occurrence of the pulse signal E ₃ indicates that the amplitude of the signal E ₄ corresponds to the density of the acid sample. The signals E ₁ and E _{2 of} the analyzer 22 are sent to the programming device 27, while the signals E ₃ and E _{4 are sent} to the Acid strength signal device 35 can be given.

The programming device 27 controls the control sequence of the development of the setpoint _{pulse series E 10} and the signal Ej ₁ which is supplied by the setpoint signal device 28. £, “and E ₁₁ are used to control the setpoint of a conventional quantity regulating device30. This operates a valve 32 to reduce the throughput of the through line 21

To control the removed acid in accordance with the signal E ₁₂ from a conventional measuring sensor 33, which corresponds to the flow rate of the escaping acid in the line 21 and its setpoints. Since the acid system is a closed circuit, the acid flowing through line 21 corresponds to the fresh acid flowing through line 17, so that the proportion of fresh acid added to the system is actually caused by the control of the acid removed through line 16.

The programming device 27 supplies a signal E ₇ , which corresponds to the titration time I T of the acid sample and the pulse signals E _A to E _{c of} the acid strength signal device 35. The acid strength signal device 35 is controlled by the pulse signals E _A to E _c , providing a signal E ₁₄ which is the average acid strength in accordance with the signal E _{4 of} the analyzer 22 and the direct current voltages K ₁ to K ₄ and K ₂₄ originating from a direct current voltage source 37 is equivalent to. Signal E ₁₄ is applied to the setpoint signal _{device 28, which also receives a signal E 15} corresponding to an anticipated required acid strength from the olefin signal device 36, as determined from olefin and isoparaffin. The setpoint signal device 28 is controlled by pulse signals E _B and E ₀ to E _n from the programming device 27, providing a series of pulses E ₁₀ and the signal E ₁₁ door, the quantity control device 30 in accordance with the signals E ₁₄ and E ₁₅ and the direct current voltages K ₅ to K ₉ from the direct current voltage source 37. The setpoint signal _{device 28 also supplies a signal E 16} to the programming device 27. Each pulse of the pulse series E ₁₀ changes the setpoint of the controller 30, while signal E ₁₁ controls the direction of the change in the setpoint. The pulse series E ₁₀ has no pulses if the target value for the acid strength should not be changed.
If the amount of acid emerging from line 21 is changed, the acid level in the settler changes accordingly. A level sensor 40 provides a signal corresponding to the acid level to a conventional level recording controller 42. The controller 42 provides a signal to a valve 45 in FIG

Line 17 corresponding to the difference between the level signal from the sensor 40 and the position of the setpoint in 42, which is a predetermined acid level of the settler 12 corresponds. The valve 45 controls the fresh acid throughput in the line 17 to the acid level in the stacker 12 to restore it to its specified height.

If the acid strength is increased by changing the setpoint of the quantity control device 30, the amount of acid to be dispensed increases.

The controller 42 operates the valve 45 to increase the amount of fresh acid and thereby an increase bring about the acid in the settler 12 to a predetermined acid level. The increase in fresh

amount of acid leads to an increase in acid strength in the system.

If the acid strength is reduced, the amount of acid to be dispensed decreases, which in turn reduces the acid level in the stacker 12 increases. The increase in acid level causes the amount of fresh acid to decrease by the Reduce acid in settler 12 to a predetermined acid level. The decrease in the amount of fresh acid reduces the acidity in the system.

The olefin signal device 36 supplies the signal E ₁₅ to the setpoint signal device 28 in accordance with a signal E ₁₇ from the chromalography device 38, which corresponds to the constituents of the starting olefin, in accordance with a signal E ₁₈ from a conventional sensor 40 which is the amount of the starting olefin in corresponds to the line 6, in accordance with the direct current _{voltages F 10} to K ₁₅ , K ₂₅ and K ₂₆ from the direct current voltage source 37 and in accordance with the pulse signals E ₈ , E ₁ to E ₁ from the programming device 27.

The chromatography device 38 also supplies a pulse train E ₁₇₁₄ to the programming device 27. The pulses in the pulse train E _{17 / (} coincide with those of the signal E ₁₇ .

In FIG. 3 shows the programming device 27 with an “on / off” switch 101 which _{receives a direct current voltage K 16} from the direct current voltage source 37. The switch 101 controls the operation of the control system. If it is in operation, 101 applies the voltage K ₁₆ to the inverter 103 and to the AND gate 106. The inverter 103 reverses the voltage Kj _{6 in} order to reset a flip-flop 104 to an erased state. _{The erasing pulse E 6} that occurs at the end of each working cycle controls the flip-flop 104 in a set state, in which it remains until it is reset by closing the switch 101. When changing from the deleted to the set state, a (J output of the flip-flop 104 controls a monostable multivibrator 105. The activated multivibrator 105 delivers a pulse signal E ₁ -.

The pulse train E _{17-4 of} the chromatography device 38 is applied to the AND gate 106, which controls the pulse signals E ₁ to E _R. The AND gate 106 is made operational by the voltage K ₁₆ as a function of the logic decoder 108. During operation, the pulse series E ₁₇ ″ passes the AND gate 106 to a conventional counter 110, which counts the pulses in the signal E _{17 A} according to the various peaks in the signal E _n . The logic decoder 108 decodes the counting of the counter 110 providing a plurality of outputs for the monostable multivibrators 114. The logic decoder 108 may be a device _S5 which includes AND gates associated with each stage of the counter 110 in the manner that each AND gate provides an output for a different count indication in counter 110. After 10 counts have been reached, the DC output supplied by the logic decoder 10 to the AND gate 106 goes to a low level, as a result of which the AND gate is switched off and the pulse series E _{n A} is blocked to prevent further counting in the counter 110.

The monostable multivibrators 114 represent a multiplicity of monostable multivibrators. Each monostable multivibrator is linked to a different AND gate in the decoder 108 and is controlled by its output by providing a pulse signal. The monostable multivibrators 114 supply a multiplicity of pulse signals E ₁ to E _R which coincide with the peaks of the signal E ₁₇ , which corresponds to the various constituents of the starting olefin, as is determined in the chromatography device 38. The F i g. 2 shows the pulse E, and FIG. 2 the pulse E _R. Only one interruption is shown for the pulse £ _R. This is because E ₁ E _{R precedes E R in} time, and in this particular case the pulse E _{K is used} to start the control sequence and is therefore with the others in FIG. 2 pulse series shown in a temporal relationship.

The pulse signal E _{R of} the monostable multivibrators 114 controls a further monostable multivibrator 116, which serves as a sound delay and supplies a pulse for the flip-flop 117. The trailing edge of the pulse from the multivibrator 116 controls the flip-flop 117 in its set state. The Q and Q outputs of a flip-flop are high and low DC voltages when the flip-flop is in a set state. The Q and (J output levels are reversed when the flip-flop is in an erased state. The flip-flop 117 provides its Q output as signal E ₄ , see FIG. 2; to the acid strength signal device 35 and 35 an AND gate 118, and makes the AND gate 118 partially operational. The end of the titration signal E ₂ drives a flip-flop 132 to a set state and causes 132 to provide a high DC output to the AND gate 118 and thereby make 118 operational The AND gate 118 controls the development of the pulse signals E _B , E _D , E _£ , E _F , E ₁₁ , E _s and E ₁₁ so that these occur only after the acid strength and starting olefin analysis has been completed.

When fully operational, the AND gate 118 passes time pulses from the clock 120 to a conventional counter 124. A logic decoder 125 decodes the counting in the counter 124, providing a large number of trigger inputs for a large number of monostable multivibrators, which are reproduced as monostable multivibrators 127. The decoder is arranged in such a way that a time differential is provided between the penultimate and the last counting process. The monostable multivibrators 127 supply the in FIG. Signals E _D , E _s , E ₁ ,, £ _E , £ _F , E ₁₁ and E _{B shown in FIG} . The time differential occurs between the signals E 1 and E ₈ and should be of sufficient length to allow the setpoint value in the quantity control device 30 to pass through its entire range, although this is normally not necessary.

After the end of the pulse series E ₁₀ , the setpoint signal device 28 ran a signal E ₁₆ ar a flip-flop 134 un <i controls it into its set state. The Q output of the flip-flop 134 makes the AND gate 135 operational when the flip-flop 134 is in the cleared state and turns off the AND gate 135 when the flip-flop 134 is in its set state. When ready for operation, the AND gate 135 time pulses from the clock 137 as signal E ₀ and the time pulses are blocked when the AND gate 135 state is switched off. The pulse signal E _{H of} the multivibrators 12 ″ controls the flip-flop 1341 - an erased state

t>

so that the Q ~ output of flip-flop 134 is the AND gate 135 brings it into operation.

That ! T signal E ₇ is developed by a flip-flop 140, a clock 141, an AND gate 142, monostable multivibrators 144 and 145, a counter 148, a memory cell 150 and a digital-to-analog converter 151. The beginning of the titration signal E, from the acid strength analyzer 22 controls the flip-flop 140 in a set state. The Q output of flip-flop 140 renders AND gate 142 operational and causes 142 timing pulses to pass to counter 148. The counter 148 counts the time pulses that have passed through the AND gate 142. The end of the titration signal E ₁ controls the flip-flop 140 in a cleared state and causes the Q output to switch the AND gate 142 off. When the AND gate 142 is switched off, it blocks the line pulses from the clock 141 so that the counting process in the counter 148 corresponds to the time interval between the signals E ₁ and E ₂ , which is the tilralion time I T.

The change in the (7 output of flip-flop 140 as a result of controlling flip-flop 140 to the cleared state with the aid of signal E ₂ controls switching delay multivibrator 144 and causes 144 to provide a pulse. Pulses controls the multivibrator 145 so that the multivibrator 145 delivers a pulse after the counter 148 has finished a counting process. The pulse from the multivibrator 145 controls the memory cell 150 in order to receive and store the counting of counter 148 in 150. The digital- Analog converter 151 converts the stored counting process in 150 into signal E ₇ .

The pulse signal E _{B of} the monostable multivibrator 127 also controls a monostable delay multivibrator 155, which supplies a pulse to a further monostable multivibrator 156, the trailing edge of which controls the monostable multivibrator 156 and causes 156 a cancellation pulse E ₆ (see Fig. 2). supplies. The cancellation pulse E ₆ is supplied to the chromatography device 38, the setpoint signal device 28, the counters 110, 124 and 148, the memory cell 150 and the flip-flops 117, 104 and 132, the flip-flops 117 and 132 being reset to the deleted state to return the control mode.

In FIG. 4 shows in detail the setpoint signal device 28, which combines the signal E ₁₄ , which corresponds to the feedback information relating to the acid strength, with the signal E ₁₅ , which corresponds to the anticipated, required acid strength, while providing a pulse series E ₁₀ and a signal E _n for changing the set point of the flow record controller 30 if needed. The pulse train E ₁₀ and the signal E ₁₁ are provided in the manner specified in claim 1.

A sampling and storage circuit 201 is controlled by the pulse signal E _{0 of} the programming device 27 for storing the direct current voltage V ₅ , which corresponds to a required acid strength. The subtracter 204 subtracts the acid strength _{signal E 14 of} the signal device 35 from the output of the sampling and storage circuit 201 while providing an error signal for a further sampling and storage circuit 205. The sampling and storage circuit 205 is controlled by the pulse E _{E of} the programming device 27 and supplies one corresponding output.

The circuit 207 supplies a signal corresponding to the absolute value of the output F _{n of} the sampling and storage circuit 205. The circuit 207 may be a squaring circuit which squares the output of the sampling and storage circuit 205 or a square root circuit which the square root of the output of the squaring circuit

ίο forming the absolute value! F _n | pulls. The absolute value _{signal F n} I is multiplied by the signal from the sampling and storage circuit 205 in the multiplier 209. The product signal of the multiplier 209 is multiplied by the direct current voltage K ₆ in the multiplier 210.

The output of another sampling and storage circuit 206 is multiplied by a DC voltage K ₇ in multiplier 214. The sampling and storage circuit 206 is controlled by the pulse signal E _{B to store the F n} signal from the sampling and storage circuit 205 so that it can be used as the F n ^ ₁ signal during the next cycle.
A multiplier 217 multiplies the F n signal of the sampling and storage circuit 205 by a direct current voltage K ₈ . The summer 218 sums the product signals of the multipliers 210, 214 and 217 to form a sum signal for a further multiplier 220.

The multiplier 220 multiplies the sum signal by a DC voltage signal K ₉ to form one of the expression

G ₃ IF _n IF _n )

corresponding output.

The summer 225 sums the output of the multiplier 220 with a signal which corresponds to the term SP _n _] from a further sampling and storage circuit 226 and a signal of a multiplier 227 which corresponds to the term SP _n _ _t [U _n ) ( see equation 5). The summer 225 supplies a sum signal, which _{corresponds to the term SP n} , to the further sampling and storage circuit 230, which is controlled by the pulse signal E _{F of} the programming device 27.

The SP _n _, and SP n outputs of the circuits 226 and 230 are compared in the comparator 244 with the formation of the signal E _11. If the output of the sampling and storage circuit 226 is greater than the output of the sampling and storage circuit 230, then the setpoint is shifted in one direction. If the output of the sampling and storage circuit 226 is equal to or smaller than the output of the sampling and storage circuit 230, then the setpoint value of the quantity control device 30 is changed in the opposite direction.

The subtracter 245 subtracts the SF _n _, output of the sampling and storage circuit 226 from the SF n output provided by the sampling and storage circuit 230 while providing an error signal which indicates the change in setpoint value

for an analog-to-digital converter 248 which converts the error signal into a digital signal. The pulse signal E ₁₁ from the programming device 27 controls a conventional counter 250 to the digital

509 584/475

Input signal from transducer 248. Counting pulses E ₀ from programming device 27 enter counter 250. The counting pulses E ₀ are also provided as a pulse series E ₁₀ . After a certain counting sequence has been reached, a logic decoder 251 sends a signal E ₁₆ to the programming device 27, which ends the counting pulses E ₀ so that the number of _{pulses in signal E 10} corresponds to the appropriate change in the setpoint value.

The sampling and storage circuit 226 is controlled by the pulse signal E _{8 of} the programming device 27 in order to receive the SP "signal of the sampling and storage circuit 230 so that it is available as an SP _n _ _r signal for the next cycle. The SP _n ^ ₁ signal from the sampling and storage circuit 226 is multiplied in the multiplier 227 by the signal E _{15 of} the olefin signal device 36 to form the SP _n _i (1 / “) signal (cf. equation 5).

In FIG. 5 shows the acid strength signal device, consisting essentially of two analog computers. An analog computer provides a signal that corresponds to the acid strength, AS , in accordance with the following equations:

(D

where VOL _{C is} the volume of the base required for the titration of the acid sample , N _{c is} the normality, _{MÄQ A is} the milliequivalent weights of acid and W _{A is} the acid weight. Equation 1 can also be written as:

AS =

(\ T) (FR _C ) ( N _C ) (MÄQ _A (D _A ) (VOL ₃ )

(2)

where IT is the titration time, FR _{C is} the base flow rate, D _{A is} the acid density and VOL _{5 is} the volume of the acid sample.

The analog computer for solving equation 2 consists of a sampling and storage circuit 300, multipliers 304 to 304C, a divider 306 and an electronic switch 308. The signal E ₃ from the analyzer 22 occurs when the signal E _{4 has} the density D _A of Acid sample and controls the sampling and storage circuit 300 to receive the signal E ₄ at that time. The output of the sampling and storage circuit 300 is applied to the multiplier 304 where it is multiplied by a direct current voltage V ₁ which corresponds to the volume VOL _{8 of} the acid sample. The multiplier 304 supplies a signal corresponding to the denominator of equation 2.

The multiplier 304/4 multiplies the IT signal E ₇ from the programmer 27 by the base flow rate signal V ₂₄ . from the DC voltage source 37 with the provision of a product signal corresponding to the term Δ T FR _C. The product signal of the multiplier 304 A is multiplied by the DC voltage V ₂ , which corresponds to the base normality, for example it may be 0.2 meq / ml, in order to provide a product signal to the multiplier 304 C, in which it is multiplied by the DC voltage V ₃ . The direct current voltage F ₃ corresponds to the milliequivalent weight MEQ _{A of} the acid, the acid for industrial purposes being H ₂ SO ₄ with a milliequivalent weight of 0.04904 grams / meq. The product signal from multiplier 304C corresponds to the numerator in equation 2. Divider 306 divides the numerator signal from multiplier 304C by the denominator signal from multiplier 304 to provide a signal corresponding to the term AS of equation 2 to electronic switch 308. The electronic Switch 308 is controlled by the pulse signal E _{A in} such a way that the acid strength signal AS from the divider 306 passes once per cycle.

The second analog computer in the acid strength signal device 35 supplies a signal in accordance with

Is calculated with Equation 3 below and includes a subtracter 315, sampling and storage circuitry 318 and 318/1, a summer 320 and a multiplier 325:

AS _n = ^ S .., + C, (/ 1S "- AS" .i). (3)

wherein AS _n avg ittliche acid strength during a current cycle, AS _n _, the acid strength during an immediately preceding cycle, -4S _n an instantaneous acid strength which is obtained during a current cycle, and C ₁ is a constant having the value 0.75 means. The subtracter 315 subtracts an output of the sampling and storage circuit 318, which corresponds to the term AS _n ^ ₁ in Equation 4, from the acid strength signal passed through the switch 308, providing one of the expressions / IS ,, -. ^, , ^) corresponding signal. A multiplier 325 multiplies the signal of the subtracter 315 by a direct current voltage V ₄ , which corresponds to the constant C ₁ with the value 0.75. The output of the multiplier 325 is given to the summer 320 together with the output of the sampling and storage circuit 318, providing a signal which corresponds to the average acid strength AS _n for the sampling and storage circuit 318 A. The pulse signal E _D controls the sampling and memory circuit 318/4 to receive the / 4S "signal to form signal E ₁₄ . The sampling and latch circuit 318 is controlled by pulse signal E ₁ of the programming device 27 to the / lS store _n signal of the sampling and SpeI chersch al tung · 318/1 for use as AS _n _ _r Si gnal during the next cycle .

In FIGS. 6A and 6B, the peaks of the signal E ₁₇ correspond to the chromatography device 3}

the various Ausgangsolefinbestandteüen dei in line 6. The sampling and Speicherschaltun gen 400-4007 are controlled by the pulse signals E to E _R to accommodate the various peaks de signal E _17th The following table

relates a single sampling and storage circuit to the corresponding component

circuit

Bcstandtfil

400

400/4

Ethane
propane

D I

continuation component circuit Isobutane 400 β η-butane 400C Isopentane 400D n-pentane 400 pounds Propene 400F Butene 400G Pents 400Η all connections 400 / with 6 and more Carbon atoms

_{The output of the sampling and storage circuits 400 to 400 / is fed} to the multipliers 403 to 403 / and multiplied here by the voltages K ₁₀ to V 10h which correspond to the various counting factors of the individual components of the chromatography device 38. For example, the voltages K ₁₀ to F ₁₀ , 0.02; 0.2; 1.0; 0.2; 0.15; 0.02; 0.2; 0.10; 0.02 and 0.10 volts. The product signals of the multipliers 403 to 403 / are stored by the circuits 405 to 405 / in response to the pulse signal ' E ₀ from the programming device 27. The sampling and storage circuits 405 to 405 / are used in the sense that their outputs correspond to the various Components of the starting olefin correspond to the totalizer 406 can be entered at the same time. The summer 406 provides a normalized signal.

The acid strength is not influenced by all components of the starting olefin. It has been found that propene, butene, pentene and some compounds with 6 or more carbon atoms influence the acid strength. Therefore, the signals of the sampling and storage circuits 403 F to 403 /, which correspond to these components, are operated while providing the signal Ei ₅ .

The dividers 410 to 410C divide the signals from the sampling and storage circuits 405 F to 405 / corresponding to the four components by the normalized signal from the summer 406. The signals of the dividers 410 to 410C are passed through the sampling and storage circuits 412 to 412 C collected for each period and stored in response to the pulse signal E _{s from} the programming device 27.

The multipliers 415 to 415 C, the adders 416 and 425, the multipliers 418, 422 and 423, the sampling and memory circuits 420 to 420B and the divider 474 are in an analog computer available to solve the following equations:

A = KR (C _x Q ₁ + C ₂ Q ₂ + C ₃ Q ₃ + C ₄ &), (4)

where A is the load value of the acid system, K is a constant with the value 1.0, R is the olefin throughput, C ₁ to C ₄ constants, which correspond to the ratio of kilograms of acid consumed per liter of acid-consuming olefin constituents, and Q ₁ to

Q ₄ mean the percentages of acid-consuming constituents in the starting olefin.

U =

_ A

(P, A _n + P ₂ A "_ _y ),

where U _{n is} the anticipated required acid strength during a current cycle, A _{0 is} the initial stress value of the acid system, A _n and A _n ^ ₁

to mean the load values for the current cycle and the cycle immediately preceding it, and P ₁ , P ₂ , P ₃ mean constants with the values 1.0, -1.0 and 1.0.

The multipliers 415 to 415 C multiply the outputs of the sampling and storage circuits 412 to 412C by the DC voltages K ₁₂ to K ₁₂₀ which correspond to the constants C ₁ to C ₄ of equation 4. The summer 416 sums the outputs of the multipliers 415 to 415C to provide a sum signal which is multiplied in the multiplier 418 with the olefin flow rate signal E ₁₈ from the sensor 40 to provide a signal to the multiplier 419. The multiplier 419 multiplies the signal from the multiplier 418 by the voltage K ₂₅ , which corresponds to the term K in the equation 4, to provide a signal corresponding to the term A of the equation 4.

The sampling and latch circuit 420 is the pulse signal E ₇ -. Controlled by the programming device 2 ", where E _T occurs early in the process to the signal from the multiplier as X save ₀ signal The divider 424 divides the DC voltage K _14, which the Term P ₃ corresponds to equation ί through the output of the sampling and storage circuit 420 providing a signal corresponding to the term P ₃ IA _0.

The sampling and storage circuit 420 A is controlled in each cycle by the pulse signal E _{1 of} the programming device 27 in order to collect and store the output of the multiplier 419 while providing a signal which corresponds to the term A of equation 5 for the multiplier 421 The multiplier 421 multiplies the signal from the circuit 420 A by the DC voltage K ₂₆ which corresponds to the constant P ₁ in equation 6, providing a signal for the summing 425. The sampling and storage circuit 420 B. is from the pulse signal E _{B of} the Programming device 27 controlled at the end of each cycle in order to collect and store the output of the multiplier 419 while providing a signal corresponding to the term A _n .ι for the next cycle. The signal from the sampling and storage circuit 420 B is _{multiplied by the direct current voltage K 15} , which corresponds to the term P _2. Summer 425 sums the output of "multiplier 421" with the product signal of multiplier 422, providing one of the parentheses

Part of the signal corresponding to equation 6, which is multiplied in the multiplier 423 by the signal from the divider 424 to provide a signal E ₁₅ .

Although the system according to the invention is

Using analog computers, a digital computer can also be used. The setpoint signal device 28, the acid strength signal device 35 and the olefin signal device 36 may

2

then replaced by a digital computer, conventional analog-to-digital conversion techniques are used in conjunction with sampling and storage circuits. Some of the sampling and storage circuits are controlled by the programming device 27 /. To store the peaks of the signal E ₁₇ , as was done with the analog computers. Another sampling and storage circuit is controlled by the signal E _{2 of} the acid strength analyzer 22 in order to store _{the density signal E 4.} The output of the sampling and storage circuits and the signals E ₅ and E ₁₈ are converted into digital signals.
The described system according to the invention provides

a responsive control system for controlling acid strength in an alkylation plant. acid Starch measurements are made with measurements of olefin composition and olefin flow rate combined with providing a control signal for controlling the acid strength in an alkyl system. The arrangement described provides eii of the acid strength en'spre in the alkylation plant corresponding signal and delivers a further signal which; an anticipated required acid strength as determined, corresponds to, in accordance with the amount of acid consuming components from the olefin entering the Alkylierunesanlaae.

In addition 7 sheets of drawings

Claims (3)

Patent claims: .. = -> *: 1. Arrangement for controlling the acid strength in ■ my isoparaffin-olefin alkylation plant, consisting of nus an analyzer to cut the strength of each circulatory acid, a flow regulator for Determine the amount of acid withdrawn from the process and an analyzer zar Determination of the composition and quantity of the starting hydrocarbons introduced into the reactor, characterized in that one uses the determined signals for calculation the setpoint for the acid used to be discharged from the system according to the formula SP _n = SP _n ^ ₁ + G ₄ (G ₁ F _n + G ₁ F _n ., + G ₃ | F _n | F _n ) SP _n ., A (P ₁ A _{n +} P ₂ linked, in which F _{n is} the difference between a required acid strength and the average acid strength for the current cycle, F _n _j the difference between the required and the average acid strength of the previous cycle, IF _n I the absolute value of F _n , A ₀ the to expected acid consumption, A _{n is} the measured acid consumption during the current cycle, A _n _ _{t is} the measured acid consumption during the previous cycle, and G ₁ , G ₂ , G ₃ , G ₄ and P ₁ , P ₂ , P _{3 are} constants. 2. Arrangement according to claim 1, characterized in that one is the difference between a required acid strength and the average acid strength for the current cycle following formula JTFR _C N _C MÄQ _A ^AS - determined, where J T is the titration time, FR _{C is} the flow rate of the base entering the acid strength analyzer , N _{c is} the normality of the base, _{MÄQ A is} the milliequivalent weight of the acid, VOL _{S is} the volume of the acid sample and D _{A is} the acid density. 3. Arrangement according to claim 1, characterized in that the respective acid consumption according to the formula A = KR (C ₁ Q ₁ + C ₂ Q ₂ + CiQ ₃ + C ₄ QJ determined, where Q ₁ , Q ₂ , Q ₃ and Q _{4 are} the ratios of the individual olefinic constituents to the total olefin, C ₁ , C ₂ , C ₃ and C ₄ the amount of acid (kg) per volume (liter) of each olefin constituent, R den Indicates olefin flow and K is a constant. The present invention relates to an arrangement for controlling the acid strength in an isoparaffin-olefin alkylation plant, from an analyzer to determine the strength of the circulatory acid, a Flow controller to determine the amount of acid withdrawn from the process and an analyzer to determine the composition and quantity of the starting hydrocarbons introduced into the reactor consists In systems of this type, it is known both the olefin content of the feedstock and the starch to measure the circulating acid in order to maintain an optimal acid concentration. After "American Petroleum Refining, New York, 1959 ', the optimum acid concentration is found in an alkylation plant adjusted by controlling the addition of fresh acid. The optimum is based on the operating costs and thus the acid consumption is determined. Furthermore, optimization systems for technical purposes are whole generally known that with an input variable in the sense of an advance signal and a feedback signal by means of a mathematical model and an optimization algorithm a control variable for a to be controlled. Create an object (see »Automation and automatic control, Berlin, 1970 «). The object of the present invention is to find the target value for the acid strength in an isoparaffin-olefin alkylation plant to adapt to the fluctuations in the olefin feed. The setpoint is in the sense to constantly monitor economic operation of the plant and the fluctuations in the Olefineinspeisuig adapt. The invention relates to the arrangement shown in the preceding claims Control of acid strength in an isoparaffin-olefin alkylation plant. The solution according to the invention is based on the special type of linkage of the measured signals which are formed from the acid concentration, the olefin composition, the amount of starting hydrocarbons fed in and the amount of acid withdrawn. The link is made by forming the difference between a required acid strength or an expected acid consumption and the corresponding actual values of the previous measuring cycle.
The advantage of this arrangement for regulating the acid strength consists in a shortening of the regulation time when concentration fluctuations occur in the olefin feed and in the more precise adaptation of the acid concentration to an economical optimum value. The target value generation and optimization takes place automatically during the operation of the alkylation system and guarantees a high degree of accuracy through constant control with a feedback signal from an acid strength analyzer. A particular advantage of the arrangement according to the invention is the processing of the feedback signal. This is done by averaging a large number of measured concentration values. This means that the control system is highly sensitive to parameter fluctuations a stable control behavior is always guaranteed.