SU1123026A1 - Method of automatic control of periodic process of producing cellulose acetates - Google Patents

Abstract

THE METHOD OF AUTOMATIC CONTROL OF THE PERIODIFICATION PROCESS FOR THE TREATMENT OF CELLULAR ACETATES by cellulose processing with an activating agent, partial dosing of the components of the acetylating mixture and subsequent two-stage hydrolysis) successively at elevated and atmospheric pressure with stirring, including regularization of the reaction temperature in the reactor, in order to increase the accuracy of maintaining the desired filtration value of the target; , determine the temperature of the reaction mixture after treatment with an activating agent, after the supply of the first portion of adethylating mixture and the time The maximum temperature and its value after the last feed has been applied. the acetylating mixture determines the time to reach the maximum temperature, its value, the time to reach the specified viscosity value of the reaction mixture and its temperature, and the tegsheterography at the stage of hydrolysis at atmospheric pressure is adjusted depending on the desired value of the filterability index and the measured time and temperature values.

Description

The invention relates to the field of automation of production processes, in particular to automation and management in the production of cellulose derivatives.

The closest to the invention is a method for automatically controlling the periodic process of obtaining cellulose acetates by treating cellulose with an activating agent, dosing the acetyl mixture components in portions and after two-stage hydrolysis sequentially at elevated and atmospheric pressure while moving, including adjusting the temperature of the acid stream and adjusting the amount of catalyst , discrete on the preparation of the last portion of the acetylating mixture, depending imosti from the rate of change in zkosti--. the mixture in the processing of pulp with the penultimate portion of the acetylating mixture 1J.

The disadvantage of this method is that the process does not take into account the effect of the hydrolysis stage on the quality indicator of cellulose acetate acetate-filterability, which leads to its unstable value.

The magnitude of the filterability index of cellulose acetate is formed during the stages of acetylation and hydrolysis of the resulting cellulose triacetate. It depends on the quality of the raw materials used, the time of acetylations and hydrolysis ,. as well as on the technological parameters of these stages, in particular, on the temperature at the moment of the start of hydrolysis, and

this relationship is not taken into account, which leads to an unstable filterability index of cellulose acetate ..

The purpose of the invention is to improve the accuracy of maintaining a given filterability value of the finished cellulose acetate product.

The goal is achieved by the fact that according to the method of automatic control; batch process of acetylation of cellulose by treating cellulose with an activating agent, partial dosing. components of acetylating mixture and subsequent two-stage hydrolysis sequentially at elevated and atmospheric pressure with stirring, including -control of the temperature of the reaction mixture in the reactor, determine the temperature of the reaction mixture after treatment with an activating agent, after the first portion of acetylating mixture is fed and the time to reach the maximum temperature and its value After the last portion of the acetylating mixture has been supplied, the time to reach the maximum temperature is determined, its value, time to reach izheni predetermined value of viscosity of the reaction mixture and its tomper.aturu and tempera.turu hydrolysis step .If atmospheric davl.eiii adjusted depending on the desired receptacle Achen filterability index and measured values of time and temperature.

- The method is as follows. way ..

Acetic acid activated cellulose is additionally treated with acetic anhydride c. for 11.5 hours at 18-28 ° C, and then alternately with two portions of the acetylating mixture. After adding the second portion of acetylide mixture to the mixture after a certain time in the reactor, the mixture passes into a pasty state, and at this moment the drive of the stirrer; and the reactor reaches the maximum current value. After the completion of the acetylation process, determined by the frequency of the field of the mixture and the real mixture has reached the specified viscosity of 120 s, hydrolysis is carried out in two stages: first under pressure for 2-3 hours, the second is at atmospheric pressure 89 hours. -,

I-. The drawing shows a block diagram of a control system implementing the proposed method,

In the reactor 1, equipped with the jacket 2, for: load the cellulose, process it with acetic anhydride and successively prepared portions of the acetylating mixture. The contents of the reactor are continuously stirred. Simultaneously with the loading of the pulp into the jacket 2, a coolant is supplied, the sensor 3 continuously measures the temperature in the reactor 1 and supports it by means of a regulating unit. 4, I will act on the refrigerant supply valve 5. The amount of acetic anhydride supplied to reactor 1 is measured by the counter biv, the moment of equality of the cake and the specified amount of acetic anhydride by the regulating unit 7 causes the signal 8 to stop the supply of acetic anhydride. At the same time, the block 7 generates a signal, the starting time of the master block 9 (electronic clock). After a predetermined period of time (2 hours) block 9, a signal is sent to block 10 for inputting the tegsheratura value measured by sensor 3 into the computing unit t1, and that: also the signal for loading into the reactor 1 the first portion of acetylating mixture. The amount of acetylating mixture is measured by liquid meter 12 and, at the time of equalizing and setting the number of the first portion of the acetylizing mixture of controls, block 13 issues a signal to stop the supply of the first acetylating mixture to valve V4. At the same time give a signal to. the timing of the driver unit 9, which is set to the zero position and starts the timing of the time since the end of the supply of the first portion of acetyl mixture mixture,. to unit 10 for inputting the temperature i, the sensor being measured. 3 in | this moment, in the calculating unit block and also the signal for switching on the differentiating block 15; At the moment when the maximum temperature value is reached, the block 15 signals the blocks 9 and 10 to enter the computation block 11 1 time to reach the maximum temperature 1 maximum temperature and also turns on the block 16, which sets the temperature reference value to control unit 4, equal to Hoetl (), At the moment of equality of the current and for the given Values of temperature, measured by the sensor 3, the control unit 4 causes the second signal to flow. portions of the acetylating mixture. The amount of acetylating mixture is measured with a counter 17 and at the moment of equality of the current and specified values

15T5.58b

r, M2-Q ,,

where ij is the temperature at the beginning of the hydrolysis stage at atmospheric pressure, s,

g.1gcha1 f «v, i.mOK 4

iyg is the temperature of the cellulose processing radium by the indicated anhydride to acylation, ° C ,. The quantity of the second portion of the acetylating mixture is controlled; the second unit 18 gives a signal to the valve 19 to stop the supply of the second portion of the acetylating mixture. At the same time, signals are sent to the time set by block 9, which is set to the zero position and start. From the time the second portion of the acetylating mixture is supplied and to the differentiating block 15 to determine the maximum temperature measured by sensor 3. At the time of .belowing the maximum temperature value, the block 15 causes the signal to the blocks 9 and 10 to enter the computed block 11 value, the time to reach the maximum temperature. ) start the maximum temperature tJJ, and also includes a block 20, which compares the current viscosity value of the reaction mixture measured by sensor 21 with the specified value .... At the moment of equality of the current AND set viscosity value of -20 activates the signal time set by blocks 9 and 10 to the input of the time value of reaching the specified viscosity and temperature value tg at this moment in the calculating block 11. At the same time, the block 20 draws a signal to the valve 22 dl. supply of hydrolysis water. -Block 11 calculates the optimal temperature value at the moment of the beginning of the hydrolysis stage at atmospheric pressure tj and through: block 16 sets this value as a reference to the regulating block 4 ,. which influences the refrigerant supply valve 5, maintains the temperature in the reactor as measured by sensor 3. The duration of the initial stage of hydrolysis at atmospheric pressure is 45-90 minutes. The temperature at the final stage of this hydrolysis is 60i5C. The basis of the computing unit; put sledukitsa. statistical dependence: -, the maximum temperature value during processing by the acetylization mixture, ° C {ü. - the initial temperature value during the processing of the 1st portion. acetylating mixture, CV. mctf t. - the maximum temperature value when processing the second nopiJtHeft acetylating mixture. c - value of temperature at the moment of comprehension of a given viscosity value, C,, -, mot - time to reach a temperature value tj, h, time to reach the maximum ftnaf th temperature value,, Zg - time to reach a given viscosity value of the reaction mixture b} , h J7 required filterability of cellulose acetate. This statistical dependency is obtained from the results of a passive experiment for the following intervals of variation of regime parameters: - AgiiTJ tSS, 5 15tt "i39 4.25., 25 0, 75 364tj 46 ,, 75 Examples of the implementation of the proposed method for controlling the periodic process of cellulose acetate production are presented in the table. Due to the introduction of an additional control effect - maintaining the required temperature at the beginning of the hydrolysis stage, cellulose acetate has batch by batch of more stable and high values of filterability index 9.9-15.8 g / cm compared to 5.5-10.2 g / cm known This leads to an improvement in the quality of cellulose acetate, a reduction in the labor intensity of its further processing, and allows an increase in the output of higher-grade products according to OST 6-05451-80 by 5% compared with the lime method.

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Claims (1)

METHOD FOR AUTOMATIC CONTROL batch process P0 ~ radiation cellulose acetate, by treating the cellulose with an activating agent portsialnogo dispensing components acetylating mixture and the subsequent two-stage gidroliza1 sequentially under elevated atmospheric pressure while stirring SRI comprising the reaction temperature control in the reactor, characterized in that ^"in order ^to improve the accuracy of maintaining a given filterability value of the target product, determine the temperature of the reaction mixture After treatment with an activating agent, after the first portion of the acetylating mixture has been supplied and the time to reach the maximum temperature and its value, after the last portion of the acetylating mixture has been fed, the time to reach the maximum temperature, its value, the time to reach the set value of the viscosity of the reaction mixture and its temperature, and the hydrolysis stage at atmospheric pressure is regulated depending on the set value of the filterability index and the measured values of time and temperature.