SU771225A1 - System for combined control of pressure and temperature in periodic pulp digesters - Google Patents

Description

pulp pulping, where the solid line shows the graph at the initial temperature of the boiler, and the dotted one at 50-80 ° C,

The system contains a control object 1, the output of which is set to date 1 and 2 of temperature, an electronic bridge 3 containing two pneumatic converters, pressure and temperature controllers 4 and 5, a software setpoint 6 of temperature, an actuator 7 installed on the steam supply line to the cooking boiler of object 1 , comparison element 8, made in the form of a five-membrane pneumatic relay, pneumo-electric transducer 9, which is a membrane chamber connected by a rod with a microswitch, Final sensors 10 and 11 Cooking time and duration, made in the form of variable resistances with a linear characteristic, computing device 12, calculating the required rate of temperature rise, unit 13 for changing the frequency of the pulses, associated with the generator 14 of pulses, and control device 15.

At the same time, the outputs of the pneumatic converters of the electronic bridge 3 are connected to the inputs of the regulators 4 and 5 of pressure and temperature, and the second input of the regulator 5 of the temperature is connected to the output of the program setpoint 6 of temperature. Moreover, one of the outputs of the control device 15 is connected to the input of the software setting device 6, the output of which is connected to the first input element 8 of the comparison, the second input of which is connected to the output of the electronic bridge 3, and the output through the pneumo-electric converter 9 is connected to one of the inputs of the control device 15, the other the input of which is connected to the output of the generator 14 of pulses and the output to one of the inputs of the unit 13 for changing the frequency of the pulses, the second input of which is connected to the output of the computing device 12 ,. The inputs of which are connected to the setting devices 10 and 11 of the final temperature and duration of cooking and to the current output of the electronic bridge 3. In addition, the microswitch of the pneumatic converter 9 is installed in the control device 15.

The signal from the temperature sensor 2 is fed to the 5 {throne bridge 3, where it is converted into pneumatic signals. From the output of the electronic bridge .3, the pneumatic signal from the first converter, which is proportional to the pressure of saturated liquor vapor at a given real temperature, goes to pressure regulator 4, and from the second to temperature regulator 5. The task to the temperature controller 5 comes from the program setting device 6. The temperature controller 5 controls the actuating mechanism 7. The automatic setting of the software setting device 6 to the zero position, depending on the initial temperature of the boiler, i.e. the automatic output of the setpoint generator 6 to the beginning of the thermal graph themes is performed by inputting the comparison element 8 to the positive chamber of a pneumatic signal from an electropneumatic transducer of the electronic bridge 3, and to the negative one from the programming point 6. The signal from the output of the comparison element 8 is fed to the input pnevmoelektroprё5 educator 9.

. Automatic change of the angle of inclination of the temperature rise graph (see Fig. 2) in order to reach the specified final cooking temperature

Q is a constant predetermined time: depending on the initial temperature of the boiler, and the manual setting of the technological mode of cooking is carried out using a computing device 12, which, using the setpoint adjusters 10 and 11 of the final temperature and duration of the cooking time and the current output of the electronic bridge, calculates the required speed temperature rise (i.e., the slope of the temperature graph

0 cooking from time to time according to the formula

TO:

HAE

where K is the rate of rise of temperature

 set final cooking temperature;

TH is the initial temperature of the boiler; Bbo predetermined cooking time.

The signal from the output of the computing device 12 is fed to the input of the pulse frequency changing unit 13, which, in proportion to the calculated signal, changes the duration of the pauses or pulses of the pulse generator 14.

After setting the required pulse frequency to the pulse generator 14, the pulse frequency changing unit 13 is commanded by the control device 15 to turn off until the next cycle, and the pulse generator 14 through the control device 15 with a predetermined frequency and pulse duration affects the programming unit 6 until the boiler temperature reaches the final set value value.

in the initial position in the digester, there is an initial (residual) temperature T ". When you turn the system into operation, the program temperature setpoint 6 automatically triggers, which moves the driver until the output signal of the program setpoint generator

is not compared with the initial temperature signal in the boiler T, coming from the electronic bridge 3. Simultaneously, the pulse frequency changing unit 13 is turned on and the pulse frequency calculated by the computing device 1 is automatically set on the generator 14.

When the task becomes equal to the parameter value (i.e., the initial temperature in the boiler TC), the comparison element issues a signal to the pneumatic electric converter 9, the KOTOPOI contact switches on the second operating mode of the setting device 6, i.e. software upgrade task. The unit 13 for changing the frequency of the pulses in this moment is disconnected from the generator 14 of the pulses until the next cycle. The regulator 5 processes the temperature in the boiler, respectively, 3 times.

When the temperature in the boiler 1720c reaches, a signaling contact in bridge 3 closes, which switches on the third mode of operation of the setpoint b, mode of returning of the setpoint: to its initial position (172 ° C is the limit of the cooking temperature).

When the task becomes zero, the contact of the software master 7 is opened and the system is turned off.

The program for raising the task is provided with the help of the software setting unit 6 and the generator of 14 pulses. At the same time, the software setting device 6 provides the linearity of the temperature graph versus time, and the generator - its angle of inclination.

The use of the proposed system will improve the performance of the digester, reduce the specific steam consumption for cooking by increasing the accuracy of maintaining the temperature graph by 56%.

Claims (1)

1. Copyright Certificate CCCF 299742, cl. R 21 S 7/12, 1970.