SU1660726A1 - A method of automatic control of potentially hazardous chemical engineering - Google Patents

Abstract

The invention relates to the field of automatic control of potentially dangerous exothermic processes in pre-emergency conditions, can be used in the chemical and other related sectors of the industry and reduces product losses by reducing the number of process outages. The method involves supplying the refrigerant through the jacket of the reactor, inert to the reaction mass of the coolant, directly into the reactor and stopping the supply of the source reactant to the reactor when the temperature or rate of growth of the temperature of the reaction mass exceeds the specified value, and the coolant is supplied conditions. When the growth rate of the temperature difference between the reaction mass and the refrigerant is greater than zero, the second time derivative of the temperature of the reaction mass is greater than zero, and pressure in the reactor is less than or equal to the limit value. 1 il.

Description

This invention relates to the automatic control of potentially dangerous exothermic processes in pre-emergency conditions and can be used in the chemical, petrochemical and other related industries.

The aim of the invention is to reduce product losses by reducing the number of emergency shutdowns of the process.

The drawing shows a functional diagram of the method.

A potentially hazardous process is carried out on an installation that consists of a jacketed reactor 1 and a stirrer 2 equipped with a manhole (not shown) and an actuator for supplying the reaction ingredients, a remotely controlled valve 3, a valve 4 for cooling the reactor with a flow of hard refrigerant and a valve 5 for heating the contents of the reactor by the flow of coolant through the inlet 6, the jacket of the reactor and the outlet 7. The lid of the reactor is connected by pipeline to valve 8, which is connected by pipeline to reverse refrigeration com having a bond with the atmosphere (not shown). The cooled, inert with respect to the reaction mass substance, if necessary, is fed into the reactor through the pipeline dispenser 9, which implements the analog-frequency principle

ABOUT

oh oh

h |

go

feed regulation with converter 10.

The dispenser is mounted on the pipeline connecting the tank 11 for storing the cooled inert cooler with the reactor cavity. On the bottom of the reactor mounted actuating device 12 (valve) for resetting the reaction mass. The control part of the automatic reactor protection system consists of the first temperature sensor 13 (for example, a double thermocouple) that monitors the state of the hazardous process variable connected to it by the communication line of the sensor signal to signal converter 14, convenient 15 for further use; a second temperature sensor 15, which is differentially connected to the first temperature sensor in order to measure the temperature difference between the reaction mass and the coolant 20 connected to the first and second temperature sensors, a DC amplifier 16 with a standard output; computing unit 17; a pressure transducer 18, the output of which is connected to the 25 input of the position regulator 19 and to the second input of the logic unit 20, which functions as a position regulator. The pipeline connecting the reactor cover to the valve 8 is provided with a device 30 (separator) 21 for separating the liquid and gaseous phases. The valve 8 is connected to the reflux condenser 22, the outlet of which is connected to the container 11. A pipeline with a bursting 35 membrane 23 is also mounted on the lid.

Example 1. The process for the nitration of 2-methylimidazole (2-MI) is carried out as follows. In the reactor 1 with a capacity of 10 liters through the hatch, not 40 shown in the diagram, 4.5 liters of 80–82% ferric acid are placed and 1.5 kg of 2 MI are added to it while stirring and cooling through the same hatch. One of the original ones the reaction ingredients are fed to the reactor 1 45 gradually along the process through the valve

3 with remote control. When powdering 2-MI using an automatic control system, the temperature is stabilized at a level of 25 - 40 ° C. Upon completion of the dissolution of 2-MI in acid, the solution is heated by changing the setting of the automatic temperature control system to 105 ± 2 ° C. With this valve

4 is closed, and the valve 5, on the contrary, is closed. After the preset temperature is established in the solution, 2.5 l of nitric acid is fed through the valve

3 with a flow rate of 0.8 - 1 l / h. In case the automatic control system

so crap given 3 ° C fast

Mas Klyu Shalo (azo

at the beginning of the 6, a decree of 9 s and a turn on (at present, (about the same time, 110 ° day of the day, the price of the problem is about technology d (T

by that

footprints

cars on the go

 those.

temperature will exhaust its cooling resources, for example, when the set temperature of the reaction mass rises by 3 ° C (110 ° C) or when the temperature rises

mass - P 0,5 ° C / min, there is a disconnection from the reactor 1 with the jacket and the stirrer 2 supply lines of the source reagent (nitric acid) using valve 3.

At the same time, valve 4 opens the flow of hard refrigerant through pipe 6, jacket of the reactor and pipe 7. At the same time, if the pressure in the reactor is not too high and the following thermal conditions do not occur, the metering device 9 with the analog-frequency converter 10 switches from the tank 11, into the reactor (at its bottom) of a cooled inert cooler, trifluoroacetic acid, having a lower boiling point (Boiling point 74 ° C) than the regulated process temperature, valve 8 opens at the same time, linking The reactor cavity with reflux condenser 22. At the same time, by boiling out trifluoroacetic acid, powerful low-inertial heat removal is maintained and the desired temperature is maintained at 105–110 ° C. over 0.5 RR, where Rpr is the pressure response of the safety membrane, the supply of inert condensate is stopped, it is not produced either, if during the chemical process it produces with a planned heating of the reaction mass, i.e. d (Tr m THL)

dt the temperature of the reaction mass falls,

 0, and if the growth rate

d2 Tp m dt

0

those.

The signal from the second output of the computing unit 17 is equal to zero. The input signals to the automatic control system according to the parameters predicting the onset of a pre-emergency situation: the temperature and thermal power of the reaction process come from sensors 13 (double thermocouple) and 15 (thermocouple) through the converter 14 and the DC amplifier 16.

Thus, an increase in the temperature in the reactor above the predetermined premaximal value or a similar increase in its derivative causes an automatic control protective

impact of the first stage, stopping the process by cutting off the supply of the source reagent, simultaneously enhancing the supply of refrigerant to the jacket of the reactor and (with the above facilities) supplying the cooled inert coolant, trifluoroacetic acid, to the reaction mixture at the bottom of the reactor. As these control actions, there are signals from the computing unit 17 to the valves 4 and 5 on the one hand and to the dispenser 9 and valve 8 on the other.

The signal from the computing unit 17 to the metering device 9 passes through the analog-frequency converter 10 only if the pressure in the reactor measured by the converter 18 does not exceed a predetermined value. The ablation of the foaming reaction mass during violent evaporation and bubbling is eliminated by means of a liquid separator 21 and a gaseous medium. In the event that the protective effect of the first stage is insufficient, an increase in pressure over the maximum value specified by the regulation causes the controlling effect of the second stage, which eliminates the process by discharging the reaction mass through valve 12 into the emergency container. The control signal of the regulator 19 is used as a control action of the second stage.

Example 2, Po removes the possibility of using the proposed method in a process with a different chemistry.

In the reactor 1 with a capacity of 10 liters of the installation described above (in the first example), 5 ± 0.5 liters of 20% oleum are placed and, at 95 ± 5 ° C, a pre-prepared solution of 1 kg of methanitrobenzoic acid in 2.5 liters of concentrated nitric acid. Temperature control in the pre-emergency mode is carried out in the same way as in the first example using the supply of cooled trifluoroacetic acid to the reaction mass at the bottom of the reactor.

PRI me R 3. The possibility of using cooled inert condensate (e.g., liquid nitrogen) to implement the proposed method is removed.

A suspension of 240.3 g of pyridone and 10.8 g of urea in 735 ml of acetic anhydride is placed in a 1.2-liter reactor 1, mounted instead of a ten-liter reactor. Then to this suspension, heated to 40 ° C, 100 ml of 98% nitric acid are dosed for one hour. In the course of the dosage, they are simulated by the failures of the dosing system, expressed in an increase in the consumption of nitric acid. At normal dosing, maintaining the temperature in the reactor at the prescribed level (40 - 45 ° C) is carried out only by changing the temperature of the water in the jacket and coil of the reactor. During the imitation of failures of the dosing system (with an increase in the planned consumption by 2 times), the traditional temperature stabilization system, carrying out heat removal through the walls of the jacket and the coil, cannot perform its function; the temperature rises above 50 ° C and, as in the first example, a cooler, in this case liquid nitrogen, having a temperature of 195.8 ° C, is fed into the reactor. The filing of the latter is strictly regulated by the control system described above, which implements the algorithm presented in the claims. As a result of supplying a cooler to the reaction mass (at the bottom of the reactor), the temperature of the latter returns to the prescribed limits of 40 - 45 ° C, and nitrogen vapor is bubbled and released into the atmosphere.

The proposed technical solution makes it possible to increase the reliability of control, since it reduces the probability of pre-emergency modes going into emergency mode and increases the efficiency of the process by reducing the number of emergency stops at which there is a loss of the reaction product and an increase in unproductive labor costs.

The use of the proposed method also makes it possible to intensify a number of processes (to increase their productivity by 10–15%) by increasing the first setpoint of the hazardous parameter and the corresponding approximation of the routine to the instability limit.

The use of the proposed method makes it possible to carry out fast processes in reactors with agitators, which are not possible to be realized at all by conventional methods.

Claims (1)

Invention Formula Method for automatic control of a potentially hazardous chemical process in a pre-emergency mode by supplying refrigerant through the jacket of the reactor, a cooler directly to the reaction mixture and stopping the supply of the initial reagent to the reactor when the temperature rises or rises in the temperature of the reaction mass of the reactor and the refrigerant temperature characterized in that, in order to reduce product losses by reducing the number of accidental process shutdowns; a liquid inert with respect to the reaction mass is used as a coolant; the coolant is supplied for periods of time that satisfy the conditions d (Tr. - Thl) Q. cr. Tr. Q, . d t dt  0.5 RP, where Tr.m., Thl is the temperature of the reaction mass and the refrigerant; P, Ppr is the pressure in the reactor and the maximum allowable pressure in the reactor. //