SU858858A1 - Method of automatic controlling of several parallely operating apparatus - Google Patents

Description

(54) METHOD FOR AUTOMATIC CONTROL OF THE BLOCK OF PARALLEL-OPERATING MACHINES

one

The invention relates to the automatic control of a unit in parallel with operating apparatuses and can be applied in the oil refining, petrochemical, chemical and other industries.

There is a known method of automatically controlling successively operating distillation and distillation columns by changing the feedstock feed depending on the algebraic sum of target and intermediate production flow rate signals and the level in the distillation column in the first case, and in the second case by adjusting the feedstock feed by impurity concentration feed stock and bottoms 1.

However, the known method is unacceptable in cases where the consumption of feedstock for a unit of successively operating distillation and distillation columns is predetermined by the productivity and operating conditions of previous apparatuses, i.e., when the consumption of feedstock is predetermined. These methods of automatic control are inoperative.

The closest to the technical essence of the present invention is a method of automatic control of a unit of parallel operating devices by changing the consumption of raw materials for each device depending on the value of the total load on the block while simultaneously adjusting the ratio of the costs of material flows to each device with correction for the composition of the raw material, arriving at block 2.

However, the known method does not minimize the losses of the target product, since the distribution of loads is performed without taking into account the operating efficiency of each apparatus.

The purpose of the invention is to reduce losses, j of the target product.

This goal is achieved in that the supply of the feedstock is carried out depending on the level in the raw material tank of temperature, level and pressure in each apparatus.

The drawing shows the principle of the automatic control circuit.

The scheme contains an intermediate tank 1, distillation columns 2 and 3,

level 4 and 5 sensors, pressure sensors 6 and 7, temperature sensors 8 and 9, flow sensors 10 and 11, regulators 12 and 13, level controller 14, flow regulators 15 and 16, level sensor 17, functional blocks 18 and nineteen.

The method is carried out as follows.

In the production of phenol and acetone, phenol is fed to intermediate tank 1, from which two parallel distillation columns 2 and 3 are fed, where the separation of phenol and phenol resin takes place. The quality of separation on each column is different and depends on the state of the heat exchangers and the plates of the columns. The deposition of dirt on the walls of the condenser tubes, the resinification of the boiler tubes leads to a deterioration of heat transfer and a change in pressure and temperature in the columns, which ultimately leads to a deterioration in the quality of separation.

Experimentally found the dependence between the concentration of the target product (phenol) in the bottom of the liquid from the process parameters in the form of a linear polynomial

C ao + a, H - agT + ajP + (1)

where H is the level in the cube of the column;

T is the temperature in the cube of the column; p is the pressure in the cube of the column; G - feed consumption per column.

In the presence of apparatus operating in parallel, there is a form of equations (1) that differ in the magnitude of the coefficients.

Under normal conditions, the parameters H, T and P are supported by the corresponding control systems at a given level and the magnitude of the loss C depends only on the load. If any parameter deviates, for example, the temperature due to the contamination of the heat exchange surface of the boiler, maintaining the loss of the target product at the same level can be achieved only by changing the load.

Thus, to maintain the loss of the desired product with the bottom liquid, the required loading level of the column can not be used as an effective control variable.

If there are n apparatuses (in this example, a block of two parallel distillation columns), the load on the block, which is strictly specified by the performance of the previous node, must be distributed between the apparatuses so that the losses of the target product on each apparatus are the same.

Changes in the level, temperature and pressure in each column are recorded with appropriate sensors. Signals proportional to these changes, from sensors 4-9, are fed to the corresponding functional blocks 18 and 19. This is where the power comes from; the level 14 controller. The output signals of the functional blocks 18 and 19, which are the result of the algebraic addition of the input signals multiplied by constant coefficients, are sent as a task to the corresponding flow controllers 15 and 16.

In the steady state, these regulators maintain a certain flow rate.

In the event that at least one parameter entered in the functional block changes, the consumption of raw materials for this column will be adjusted.

When the performance of the previous node changes, the level in intermediate tank 1 begins to change.

A signal proportional to this level change is transmitted from level sensor 17 to controller 14, the output of which is input to both functional blocks 18 and 19, which form the reference signal for the respective flow controllers 15 and 16.

Regulators change the cost of each column of the block so that the total change in flow per block is equal to the change in performance of the previous node. When this occurs, the redistribution of the flow rate of the original mixture on

each column in accordance with the values of temperature, level and pressure, characterizing the quality of separation in each column.

The economic effect from the introduction of the proposed method will be about 20 thousand.

rub. in year. Economy is achieved by reducing the acetone concentration in the phenolic fox by 0.1 abs.% And the phenol in the phenol resin by 1.2 abs.%.

Claims (2)

1. USSR author's certificate number 509279, cl. B 01 D 3/42, 1974. 2. USSR author's certificate number 538733, cl. B 01 J 1/22, 1975.