SU1593677A1 - Method of controlling evaporation of lye - Google Patents

Abstract

The invention relates to methods for controlling liquor evaporation processes in multi-unit vacuum evaporation plants used in pulp and paper production, and improves their efficiency by reducing heat losses and contamination of secondary steam. The method consists in regulating the heating steam pressure, measuring scale formation, regulating the pressure difference between the heating steam of the first building and the juice of the latter, the heating steam consumption in the first building and water into the steam condenser with correction of the pressure regulators of the heating and juice steam, measuring the flow and the concentration of one stripped off liquor and the concentration of sulfur-containing substances in the condensate of the juice vapor, the magnitude of which corrects the settings for the heating steam regulators of the first building, the pressure The last-steam juice case and heating steam condensate levels in the first case and the steam steam in the remaining station buildings. 1 il.

Description

This invention relates to methods for controlling liquor evaporation processes in continuous evaporation plants and can be used in the pulp and paper industry.

The aim of the invention is to increase the efficiency of the process of evaporation of liquor by reducing heat losses and contamination of the condensate of the juice vapor.

The drawing shows a diagram of a control system implementing the method.

The evaporation plant consists of surface type evaporators 1-3 and a water-cooled steam condenser 4.

The flow rates of condensate removed from the first evaporator 1, and the temperature difference between it and the secondary steam are fed to the input of the computing unit 5, the output signal of which is fed to the functional unit 6. The input from the unit 6 also receives a signal from the computing unit 7, which takes into account the flow and the concentration of black liquor fed to the evaporation.

The task produced by the functional unit 6 is fed to the input of the differential pressure controller 8, to which the signal of the current value of the differential pressure from the sensor 9 is supplied. The output signal of the regulator

CJ

about

Xi

a 8 is the task to the regulators 10 and 11, respectively, of the pressure of the heating steam supplied to the first evaporator and the juice vapor in the last evaporator connected to the steam condenser 4.

The output signal of the regulator 8 is fed to the computing device 12, the input of which receives signals from the output of the functional unit 6, from the output of the block 13, which calculates the consumption of absolutely dry matter of the black liquor evaporated in the evaporator of black liquor using the value of its concentration, from the flow sensor and the condensate concentration sensor juice steam discharged into the sewer. Computing device 12 generates an output signal used as references to regulators 10 and 11, respectively, of heating steam pressure and secondary steam, and regulators 14-17, respectively, of pure condensate levels, steam condensate in evaporators, and steam condensate condensate in steam condensers 4.

When changing (reducing) the concentration of black liquor supplied to the evaporation station by the functional unit 6 in accordance with the signal of the computing unit 7, a task is generated to the controller 8 for a corresponding increase in the pressure differential by simultaneously changing the tasks to the pressure regulators 10 and 11. Thereby, an increase in the flows of heating steam and cooling water is produced, which provides an increase in the pressure differential (temperature pressure). The latter contributes to the increase in the efficiency of the process of evaporation of black liquor in evaporators 1--3, which can be recorded by flow sensors and the density of the evaporated black liquor in the block. 13, determining the amount of absolutely dry matter in the evaporated black liquor.

The signal from the sensor of the concentration of sulfur-containing substances in the condensate of the juice vapor is fed to the computing device 12 to correct the pressure drop and the flow of absolutely dry black liquor at the inlet and outlet of the evaporator station. The output signal of the computing device 12 adjusts the differential pressure. Research institutes between the heating steam of the first evaporator unit 1 and the juice vapor of the last evaporator unit 3, as well as the level of pure condensate in the device .1 and

juice condensate levels in apparatus 2 and 3.

Thus, the computing device 12 calculates the settings for the regulators 10 and 11, respectively, of the heating steam pressure in the first evaporator and the vapor pressure in the last evaporator and the regulator 14-17, respectively, of the pure condensate and juice condensate according to the following dependencies:

U 3fl n U 3fl n-1 + ki {AX4 n-DHtek n} + + k2 {AX3fl n-1} -AXTeK n-1};

AX akj-sgDnSANN 5. . LA „asv

+ Okm (А G55) -Ь Gkkn- 5 As (AS), where zd is the task for the regulators, I 10,11,14,15,16,17;

ki and k2 are the coefficients of the static onQ of the computing device 12;

AH is the signal characterizing the state of the evaporation process;

Ok, czkm, “kn - the tune- ki;

, 5 Scores - signals proportional to the deviations of the measured parameters of the evaporation process;

And - the signals corresponding to differences,;

This increases the efficiency of the black liquor evaporation process by reducing heat losses and contaminating juice steam condensate.

Claims (1)

Invention Formula 5 A method of controlling the process of evaporation of liquor in a multi-unit vacuum evaporation station by adjusting the pressure of the heating steam and measuring the scale formation, adjusting 0 pressure difference between the heating steam of the first case and the steam flow of the last one, the consumption of heating steam in the first case and water into the steam condenser with the correction of tasks to the pressure regulators of the heating and 5 of steam vapor, characterized in that, in order to increase efficiency by reducing heat losses and contamination of the juice vapor condensate, the flow rate and concentration are additionally measured 50 evaporated liquor and the concentration of sulfur-containing substances in the juice steam condensate, according to the values of which adjust the settings for the heating steam regulators of the first building, the pressure of the juice vapor of the last building and the levels of condensate, the heating steam in the first building, and the juice steam in the remaining buildings of the station. .  zacyz black crack