SU1501008A1 - Method of automatic control of treatment of wood chips in soaking unit - Google Patents

Abstract

The invention relates to the automatic control of the process of preparing chips in the production of chemical-mechanical and chemical-thermomechanical pulp and can be used in automated control systems for technological processes in the pulp and paper industry. The purpose of the invention is to improve the quality of the target product due to the stabilization of the thermal regime of impregnation of chips and the stabilization of residual alkalinity in recycle. In contrast to the known method, which measures the current flow rates of caustic soda and monosulphite solutions entering the apparatus, the temperature of the impregnating solution downstream of the heater and the level in the impregnation apparatus and changes the consumption of caustic soda, monosulphite, water, recirculated and steam into the heater. , the rotational speed and load 7 of the feed screw, the flow rate and vapor pressure, the concentration of caustic soda, monosulfite and residual alkalinity, recycle temperature, and the temperature in the lower part of the apparatus are additionally measured. The measured parameters calculate the specific consumption of caustic soda, monosulfite, heat coming from the steam, the rate of change of the level, are compared with the given values of these parameters, determine the magnitude of the mismatch and the sign of the mismatch, and calculate the values of the corrections correcting the given values, and entering the corrective corrections depending on the combination of mismatch signs between measured and specified values. 1 il.

Description

The invention relates to automatic control of the process of preparation of chips in the production of chemical-mechanical (HMM) and chemical-thermomechanical (CTHM) pulp and can be used in automated process control systems of technological technology.

pulp and paper industry, construction materials industry and wood processing industry.

The purpose of the invention is to improve the quality of the target product by stabilizing the thermal regime of impregnating the chips and stabilizing the residual alkalinity in the recycle.

The drawing shows a block diagram of a system that implements a method for automatically controlling the processing of wood chips.

The control object is the impregnating apparatus 1, at the entrance to which the substrate is placed; 1 the impregnating solution checker 2, which is a mixture of caustic soda, monosulfite and water. There is a recycle pipe. The impregnating solution is heated by steam, which enters the impregnating apparatus. After washing, the chips are fed into the apparatus with a screw feeder.

The automatic control system includes sets of automatic flow meters 3-5, an aqueous solution of caustic soda, monosulfite and recirculation, respectively, rotational speed sensor 6, auger feeding chips into the impregnating apparatus, feed screw drive current sensor 7, set of automatic flow meter 8 the steam entering the impregnating unit consisting of a DTC diaphragm, a condensation vessel of the SKM-100-1 type and a Sapphire-22DTs differential meter, a set of an automatic vapor pressure gauge 9, from a condensation vessel of the type CKI I-100-1 and a manometer of the Sapfyr-22DI type, a set of automatic meter 10 level in the impregnating device, including a separating vessel of the СРС-63-1 type and a manometer of the Sapphire-22da type, sensors P - 13 of the temperature, respectively, of the impregnating the solution behind the preheater, recirculated oil and in the lower part of the impregnating device, sensors-devices 14 - 16, respectively, the concentration of caustic soda (caustic soda), monosulfite solution and recirculated nta, block 7 for calculating the flow rate of air-dry chips entering the prop Totally, blocks 18, 19, the calculation of the specific consumption of chemicals - caustic soda and monosulfite, respectively, 84

block 20 for calculating the heat content (enthalpy) of steam; block 21 for calculating the specific consumption of heat supplied from steam to the impregnating unit.

The system also contains setting controls: 22 temperatures in the lower part of the impregnating device} 23 maximum permissible value of the rate of change of the level in the impregnating device; 24 values of the partial derivative of the enthalpy of steam over its pressure; 25 constant term. In the expression for determining the enthalpy of steam; 26

specific consumption of caustic soda; 27 specific consumption of monosulfite; Level 28 in the impregnator; 29 residual alkalinity concentrations in pe1D1rkul nte; 30 recycle temperature and 31 maximum allowable specific consumption of caustic soda. In the system, there is also a block 32 for calculating the mismatch between the maximum allowable and calculated values of the modulus of the rate of change of the measured level in the impregnating device, block 33 for calculating the mismatch between the set and measured values of the concentration of residual alkalinity in recirculation, a block 34 for calculating the mismatch between the maximum allowable and calculated values of specific consumption of caustic soda. Mismatch calculation units are associated with control units 35 - 42, respectively, the specific consumption of caustic soda, the specific consumption of monosulfite, the temperature in the lower part of the impregnating apparatus,

recycle temperature, impregnation solution temperature behind preheater 2, specific heat consumption with steam, level in the apparatus and recirculation flow rate. A level sensor 10 is connected to a block 43 for calculating the rate of change of this level, connected to block 44 for determining the modulus of this speed and block 45 for determining the sign of the rate of change of level in an impregnating apparatus. In block 46, the sign of the mismatch between the maximum allowable and calculated values of the modulus of the rate of change of the level is determined, in block 47 the sign of the discrepancy between the specified and measured

the concentration of residual alkalinity in the recirculation, in block 48 - the sign of the mismatch between the maximum allowable and the calculated

values of specific consumption of sodium hydroxide. The system contains blocks 49-51 (52) of calculating corrective actions on the change of set points, respectively, the specific consumption of caustic soda, recirculated temperature at various operating modes and temperature in the lower part of the impregnating apparatus; the setpoint value calculation unit 53 is recirculated; logic blocks 54, 55; logic blocks 56, 57; And type blocks; 58, 59 logic units. OR type, electropneumatic converters 60-66, regulator sets 67–72 with pneumatic actuators of the PSP-1 type for changing the flow rates, respectively, of the steam entering the preheater and the impregnating device, the redirculator entering the monosulfite tank, recirculation nta in the heater, water, solutions of monosulfite and caustic soda entering the impregnating apparatus through the heater. All elements of the control system, with the exception of automatic gauges, transducer sensors and sets of regulating bodies with actuators, are implemented using a Remikont R-120 regulating microprocessor controller.

The method for automatically controlling the processing of wood chips is carried out as follows.

The signals from sensors 6, 7 are received at block 17, in which the flow rate (t / day) of air-dry pressure MaOM / VaOH is calculated.

 NoOH

SG

: NctiSO}

- kg / t (2) 1.44

, kg / t (3

ten

yes mvon. ,, 50j- costs solutions

chemicals5 l / min;

NoOH, so7 concentrations of chemical solutions, g / l.

The control units 35 and 36 receive signals from the blocks 18, 19 and 15 sensors 26 and 27 of the specific consumption of caustic soda and monosulfite. The control signals from the output of the regulating units 35 and 36 through the corresponding transducers 65 and 64 are fed to sets of 73 and 72 regulating bodies with exhaust mechanisms installed on the supply lines of the caustic soda and monosulfite solutions to the impregnating device. This is how the specific consumption of chemicals is regulated, which in turn contributes to the stability of residual alkalinity in recirculating gas. The signal from the output of block 17 goes to block 53, in which the set value of the recirculated consumption is calculated by the following formula:

20

25

thirty

ъ l / min

(four)

„Where Kg is the coefficient proportional to l / min

THE STAINS;;,

t / day

Py entering the apparatus for impregnation, according to the following formula:

G

 1C

 ,

 W

(one)

The signals from the set of the automatic meter 5 of the recirculated flow rate 40 and the block 53 are fed to the regulating unit 42, which generates a control signal received through the converter 66 to the set 70 of the regulator, - the regulator with the actuator, g., 3 - rotation frequency The power supply is mounted on the screw auger 1 / s and the current is 4E 7 tj where there is recirculation.

In this way, the consumption of recycle gas is controlled, which leads to an increased stability 50 of residual alkalinity in it. Signal

electric screw auger loads. BUT;

K - coefficient of proportionality per day, - (77s) L

Signals from sets of automatic flow meters of caustic soda and monosulfite solutions, sensors 14, 5 concentrations and a signal from

from the temperature sensor 13 in the lower part of the apparatus enters the regulating unit 37. The input of the unit 37 also receives the signal of the specified unit 17 and receives, respectively, 55 temperatures from the setting unit 22. The units 18 and 19, in which the equal signal from the unit 37 is calculated through

Converter 60 is supplied to the regulator's set with full-time costs q - caustic soda and q f 505 monosulita using the following formulas:

68, installed by MaOM / VaOH

SG

: NctiSO}

- kg / t (2) 1.44

, kg / t (3)

yes mvon. ,, 50j- costs solutions

chemicals5 l / min;

NoOH, so7 concentrations of chemical solutions, g / l.

Regulatory units 35 and 36 receive signals from units 18, 19 and sensors 26 and 27 of specific consumption of caustic soda and monosulfite. The control signals from the output of the regulating units 35 and 36 through the corresponding transducers 65 and 64 are fed to sets of 73 and 72 regulating bodies with exhaust mechanisms installed on the supply lines of the caustic soda and monosulfite solutions to the impregnating device. This is how the specific consumption of chemicals is controlled, which in turn contributes to the stability of the residual alkalinity in recirculating gas.

ъ l / min

(four)

„Where Kg is the coefficient proportional to l / min

THE STAINS;;,

t / day

from the temperature sensor 13 in the lower part of the apparatus enters the regulating unit 37. To the input of the unit 37 also receives the signal specified by the value mechanism 68 installed on the pipeline of steam entering the impregnating apparatus.

The signal from the temperature sensor 12 is recirculated to the input of the regulating unit 38. The input of the unit 38 also receives a signal of the setpoint temperature from the setting unit 30. The control signal from the unit 38 is fed to the unit 32, which is the given temperature of the impregnating solution behind the heater. The signal from the temperature sensor I1 for the heater also enters the block 39.

A control signal from block 39 is generated by digitally modifying the following analog algorithm:

 Cr (0 / - bz) i () cJt, u .0

from (5)

where is the nominal value of the control signal, i.e. temperature setting after heater, C (from block 38);

03.03 set (from block 30) and measured (from block 12) temperature values of recirculated nta, C.

The signal from the code of the block 39 enters the input of the regulating block 40, being the specified value of the specific heat consumption coming from the steam to the impregnating unit.

The control signal of block 39 is generated by a digital modification of the following algorithm:

q3, q3a, .K, (wu, (6)

where q

, 0

s 18

-p - - m is the nominal value of the control signal, i.e. task on the specific heat consumption with steam; the given (c 39) and measured (c i) temperature values of the impregnating solution downstream of the preheater, c. The signals from the vapor pressure gauge kit 9, as well as from the setting units 24 and 25, are fed to block 20, in which the heat content (enthalpy) of the steam is calculated using the following formula:

 .

YR „

(- € 1l) ap, -

00 P

(ii)

 a,

n (7)

(RP -.RP) 55 s;

0

five

where „is the initial enthalpy of the pair,

kJ / kg;

Pp, Pn - initial and measured vapor pressure, KPa.

The signal from the outputs of the blocks 20, 17 and the set of the automatic meter 8 consumption: the steam to the impregnating unit I is fed to the block 21, in which the specific heat consumption coming from the steam to the impregnating unit is calculated, according to the following formula:. in-Gn-24 kJ

n G; - -; - 0

(eight)

where steam consumption, kg / h

The signal from the output of the block 21 is fed to the regulating block 40, which generates a control signal, which in turn comes through the converter 62 to the kit 67 of the regulator with the actuator installed on the steam supply line to the heater 2.

Direct control of residual alkalinity in the recycle is carried out as follows.

The signals from the residual alkalinity concentration sensor in the recirculation and from the setpoint generator 29, which forms the specified value of the residual alkalinity concentration in the recirculation, are sent to block 33, in which the error is calculated using the following formula:

five

0

LS

31

 ,

g / l

(9)

Where

s - s

bj L

I

a 31

- given (from block 29) and measured (from block 16) values of the concentration of residual alkalinity, g / l.

five

Further, the error signal Ann from block 33 goes to blocks 49 - 52, in which, respectively, corrective actions are formed according to the following formulas:

(KC, -K /. "

and h

gd NoOH

0 -Nkg

t

/.d

-hl- 3.e NaOH

(ten)

) d

5 s;

Cji

 VNaO "9j qli ;-) 4f," oH

s d9n

ef

. -.iCsLо

 "Sytl /:

0u1Cj

C; (12) C (13)

de. g / l / kg / t;

e ,, Kt,

/ l / ° C; K, g / l / OS - coefficients

the following regression equations obtained by the method of least squares according to the JQ statistical data of operation of the impregnating apparatus; ic

. .- ,, 93 li

LUD, - changes in the set temperature values of the recirculated nta and in the lower part 20 of the apparatus;

, - setpoint temperature of the impregnating solution .25 in the lower part of the apparatus, C;

Sz, S ,, s-Kv.bz 4N-OM% -OK V

с ,, с;, „- (15) 30

m

g v o

-mo

where, in turn, C; Cj, and C 3.0 are the free terms of the regression equations.

Due to the fact that an increase in the specific consumption of caustic soda leads to a deterioration in the dewatering capacity of the pulp obtained by grinding the impregnated and then pressed wood chips, a restriction on the specific consumption of caustic soda has been introduced into the system.

The input from block 34, which calculates the mismatch between the maximum allowable and calculated values of specific consumption of caustic soda, receives signals from blocks 31 and 18.

The mismatch is determined by the following error:

& H

No he (, en

- g

Ch / aon Yamaon

.kg / t

(17)

 Pmoon is the maximum allowable (from block 31) and the calculated value of specific consumption of caustic soda, g / l. In block 48, the sign of the mismatch is determined, and in block 47 1501008

ten

Jq ic

li

20

. 25

thirty

35

Q ds

Q

55

mismatch sign from block 33. Signals from block 47 and 48 are sent to logical control block 55, which controls the AND 56, 57 and OR 58 and 59 logic blocks. With a positive mismatch sign (from block 48) and any mismatch sign from block 47 or with negative signs of both mismatches, block 55 outputs a control signal. As a result, logical blocks AND 56, 57 skip corrective actions from the outputs of blocks 49 and 50. Logical blocks OR 58, 59 in this case do not miss corrective actions from blocks 51 and 52. With a negative error sign, q jlJ (jH block 48) and a positive mismatch sign from block 47, the opposite connection of corrective actions takes place, i.e. blocks 58 and 59 operate. The level in the impregnating apparatus influences the degree of impregnation of the chips, and consequently, the concentration of residual alkalinity in the recirculation, indirectly characterizing the degree of impregnation of the chips, will change with the level.

To improve the accuracy of stabilization of residual alkalinity in the recirculation, it is necessary to improve the accuracy of level control in the impregnating apparatus. This is done as follows. The signal from the set of the automatic level meter 10 goes to the regulating unit 41. Here the signal (set to 41) receives the setpoint signal from the sensor 28. The control signal from the output of the block 41 through the converter 63 goes to the regulator set with the actuator 71 installed on the water pipeline. The signal from set 10 also enters block 43, in which the rate of change of the level is calculated. The signal from the output of block 43 is supplied to blocks 44 and 45, in which the module M and the sign of the rate of change of the level are determined respectively. A signal proportional to the velocity modulus and a signal of the maximum allowable speed from the setpoint 23 arrive at block 32, in which their mismatch is calculated. The output of block 32 enters block 46, in which the sign of this error is determined. The signs of the aforementioned mismatch and the level change speed enter the logic control unit 54, the output of which through the converter 61 enters the regulator kit with the actuator 69 mounted on the recycle pipeline to the monosulfite tank.

If the sign from the error block 46 is positive for any sign from the speed block 45 or negative for a negative speed sign from block 45, the control valve 69 on the recirculation dump into the monosulfite tank is closed. With a negative sign from the mismatch block 46 and a positive one from the block 45 of speed and the control valve 69 opens the recirculation valve to the monosulfite tank.

The presence of a lot of tourist control of the thermal mode of the impregnating unit 1 provides an increase in the accuracy of stabilization of the thermal mode of impregnation in various zones and gives a reduction in steam consumption. The presence of corrective actions (from block 49) on changes of the specified values of specific steam consumption, temperature (from blocks 50, 51) recirculation and temperature (from block 52) in the lower part of the boiler according to concentration deviation (from block 16) residual alkalinity in recycling, taking into account the magnitude and sign of the rate of change in the level (from sensor 10) to regulate it ensures the stabilization of the residual alkalinity when the physicochemical properties of the incoming chips change, which, in turn, ensures the requirements of the impregnation schedule and further and grinding .schepy - defined indicators pulp at umenschenii energy consumption.

The possibility of switching (blocks 55–59) of corrective actions, depending on the specific consumption of caustic soda, increases the dewatering capacity of wood pulp, which in turn ensures the required moisture of cardboard on CMM and reduces the consumption of caustic soda.

Claims (1)

Invention Formula A method for automatically controlling the processing of wood chips in an impregnating apparatus by changing the flow rate of caustic soda and monosulfite entering the apparatus, measuring the temperature of the impregnating solution after the preheater, changing the steam flow rate to the preheater, adjusting the flow rate of recirculated nta depending on the amount of mismatch between the specified and measured values flow rate and level control in the impregnating apparatus, depending on the magnitude of the mismatch between the set and measured values, changes the consumption of water entering the apparatus and the consumption of recirculated gas coming into the monosulfite tank, —o t is due to the fact that, in order to increase the quality of the target product due to the stabilization of the thermal regime and residual alkalinity in the recirculator, measure the rotational speed and load of the feed screw of the apparatus, which determines the flow rate of air-dry chips, the flow rate and pressure of steam at the inlet of the injection unit, the temperature of the recycle, the temperature of the impregnating solution in the lower part of the apparatus, the concentration solutions of caustic soda and mono sulfite at the entrance to the apparatus and 0 the concentration of residual alkalinity in recirculation, calculate the specific consumption of monosulfite according to its consumption, concentration and consumption of air-dry wood chips and according to the value of the mismatch between the calculated and specified values regulate the consumption of monosulfite solution into the apparatus, calculate the specific consumption of caustic soda according to its the consumption, concentration and consumption of air-dry chips, determine the magnitude and sign of the mismatch between the maximum allowable and calculated specific consumption, calculate the specific heat consumption for the air flow rate 5 The amount of chips and the steam flow rate and its pressure determine the magnitude and sign of the mismatch between the target and the measured. The measured values of residual alkalinity in the recirculation, 0 calculate the rate of change of the level in the apparatus, the sign of this speed and the value of its module, which is compared with the set value of the module, determine the sign of the error and the negative sign of the error of the module and a positive sign the rate of change of the level in the apparatus is used to discharge the recirculated nta into the monosulfite tank, and the control of the consumption of the recir the crop is carried out according to the magnitude of the mismatch between the measured flow rate and the setpoint, for which a value proportional to the calculated flow rate of air-dry chips is used, while the flowrate of the caustic soda solution is controlled by the mismatch of the current value of the specific flowrate of caustic soda and value, corrected by the magnitude of the mismatch of the concentration of residual alkalinity, the negative sign of this mismatch and any sign of the mismatch of The specific consumption of caustic soda, the regulation of the consumption of steam in the preheater is carried out depending on the magnitude of the mismatch of the current value of the specific heat consumption and a given one proportional to the temperature of the impregnating solution behind the preheater. five d 5 20 the value of the mismatch of the temperature of the recirculation ntaj corrected by the magnitude of the mismatch of the concentration of residual alkalinity, the negative sign of this discrepancy and any sign of the mismatch between the specified and current values of the specific caustic soda, and the magnitude of the mismatch between the current and the specified values of the concentration of residual alkalinity in the recirculation of the residual alkali the sign of the mismatch of this concentration and the negative sign of the mismatch of the specific consumption of caustic soda I regulate t steam consumption in the heater and adjust the set value of the temperature of the impregnating solution in the lower part of the apparatus, which is compared with the current value of this temperature, and the flow rate of steam in the impregnating apparatus is adjusted according to the amount of mismatch. steam