RU2027765C1 - Adaptive system for controlling the process of preparation of slaked lime - Google Patents

Abstract

FIELD: chemical, construction, food-processing and other branches of industry. SUBSTANCE: system has temperature sensors for sensing temperature of gas-vapor mixture and slaked lime, regulator with filter, first, second, third and fourth summators, first, second and third multipliers for multiplying by fixed coefficient, devices generating average predetermined values of temperatures of gas-vapor mixture and slaked lime, devices generating average and maximum values of concentration of calcium hydroxide in slaked lime, actuating mechanism and regulating member. The members of adaptive system are connected so that increase in precision of stabilization of predetermined value of concentration of calcium hydroxide in slaked lime is provided. EFFECT: increased efficiency of adaptive system by increased precision of concentration of calcium hydroxide in slaked lime. 1 dwg

Description

 The invention relates to devices for automatically controlling the process of preparation of milk of lime in extinguishing apparatuses and may find application in chemical, construction, food and other industries.

 The hydration process of the calcined lump of lime is carried out, as a rule, in rotating drum absorbers. Calcined lime and liquid are fed to the apparatus inlet in the amounts required for the reaction of calcium oxide contained in lime with water.

 The product of this highly exothermic reaction is calcium hydroxide. It is poorly soluble in water, and with increasing temperature, the solubility becomes even less.

 Depending on the amount of reagents supplied to the hydrator, either dry powder is obtained at its output — a product of dry hydration (when water is supplied in an amount close to that required by stoichiometry), or a lime suspension is a product of wet hydration (when water is supplied with two to three times excess versus required by stoichiometry). The dissolution of hydroxide in water is accompanied by heat in an amount corresponding to the concentration of the resulting solution.

 The viscosity of the lime suspension decreases with increasing temperature. This property is used in industry to produce calcium hydroxide-concentrated suspensions.

 The use for the hydration of industrial liquids instead of pure water can increase the concentration of calcium hydroxide in the lime suspension without increasing its viscosity. This, in turn, makes it possible to transport such a suspension through pipelines to other production departments.

 An indirect parameter characterizing the quality of the target product is the density of the lime suspension. However, its use in creating systems for regulating the hydration process is complicated by the inconsistency of the content of impurities in the composition of calcined lime, which, in turn, affects the density and leads to ambiguous results at a constant concentration of lime suspension of calcium hydroxide.

 The parameters listed above: the costs of the reagents, the temperatures of the incoming and outgoing flows, their viscosity and density are somehow used in known devices and systems for automatically controlling the hydration process.

 A known system in which, depending on the magnitude of the torque characterizing the viscosity, is dosed the flow rate of the quenching fluid (see US patent N 2904401). A significant delay in the control channel, as well as a low correlation of the viscosity with the content of calcium hydroxide in the lime suspension, lead to the inefficiency of such a control system.

 A device for regulating the process of extinguishing lime in continuously operating extinguishing devices, which provides a system for changing (patent GDR N 97589) the water supply to the quenching depending on the moisture content of the material at the beginning and at the end of the apparatus (see patent GDR N 97589). However, the use of such a device is limited to the dry hydration process.

 A large inertia of the system along the channel and the amount of unextinguished lime (liquid flow) is possessed by a device for automatically controlling the process of preparing milk of lime, including a system for changing the flow rate of liquid entering the extinguishing apparatus, depending on the temperature of the milk of lime with correction for the amount of heat introduced into the apparatus by the liquid and quicklime (1).

 A known system of automatic control of the process of preparation of milk of lime, which implements a method of controlling the process by changing the flow rate of the liquid into the extinguishing apparatus depending on the temperature of the reaction mixture at its outlet (see ed. St. USSR N 1502618, class C 13 D).

 The disadvantage of this system is the low accuracy of stabilization of a given value of calcium hydroxide concentration in milk of lime due to a significant delay in the control system.

 The same drawback is inherent in the automatic control system for the preparation of milk of lime by changing the flow rate of the liquid entering the extinguishing apparatus, depending on the temperature of the steam-gas mixture at its outlet (2), since there is a weak correlation of this parameter and the concentration of calcium hydroxide in the milk of lime. Moreover, due to the low inertia of the temperature signal of the gas-vapor mixture, random changes in its value lead to undesirable disturbances introduced into the control system, which, in turn, affects the quality of stabilization of the content of calcium hydroxide in the product.

 Closest to the technical nature of the proposed one is a system for regulating the process of preparing milk of lime, which implements a process control method (3). The system includes a steam-gas mixture temperature sensor, a regulator, an actuator, and a regulator installed on the liquid supply line to the extinguishing apparatus. In this system, the temperature signal of the gas-vapor mixture is additionally adjusted by the vacuum in the exhaust pipe at the outlet of the apparatus and then goes to control the flow of liquid into the damper. However, the noted drawbacks are eliminated only partially by this system, leaving the accuracy of stabilization of the concentration of calcium hydroxide in lime suspension at a low level.

 The purpose of the invention is to increase the accuracy of stabilization of a given value of the concentration of calcium hydroxide in milk of lime.

 The goal is achieved in an adaptive system for controlling the process of preparing milk of lime, including a temperature sensor for the gas-vapor mixture, a regulator, an actuator and a regulating body installed on the liquid supply line to the extinguishing apparatus, and a temperature sensor for the milk of lime at the outlet of the extinguishing apparatus. The controller contains a filter, first, second, third and fourth adders, first, second and third multiplication devices, and the output of the temperature sensor of the gas-vapor mixture through the filter is connected to the first input of the first adder, the second input of which is connected to the output of the device forming the specified average value of the gas-vapor temperature mixture, and the output of the temperature sensor of the milk of lime is connected to the first input of the second adder, the second input of which is connected to the output of the device, forming a predetermined average temperature milk of milk. The outputs of the first and second adders through the first and second devices multiplying by a constant coefficient are connected respectively with the first and second inputs of the third adder, the other two inputs of which are connected with the outputs of the devices forming the average and maximum values of the concentration of calcium hydroxide in milk of lime. The output of the third adder through the third multiplier by a constant coefficient is connected to the first input of the fourth adder, the second input of which is connected to the output of the correction device, and the output is connected to the actuator.

 Distinctive features of the system are the additional introduction of a temperature sensor for milk of lime at the outlet of the quencher, as well as the fact that the controller contains a filter, first, second, third, fourth adders, the first, second and third devices multiplying by a constant coefficient, a device that generates a given average value the temperature of the vapor-gas mixture, a device forming a predetermined average temperature value of milk of lime, a device forming an average value of the concentration of calcium hydroxide in lime vom milk, means forming a maximum value of concentration of calcium hydroxide in lime milk. Moreover, the output of the temperature sensor of the gas-vapor mixture through the filter is connected to the first input of the first adder, the second input of which is connected to the output of the device forming the specified average temperature of the gas-vapor mixture, and the output of the temperature sensor of milk of lime is connected to the first input of the second adder, the second input of which is connected to the output a device forming a predetermined average temperature value of the milk of lime. The outputs of the first and second adders through the first and second devices multiplying by a constant coefficient are connected to the first and second inputs of the third adder, the other two inputs of which are connected to the outputs of the devices forming the average and maximum values of the concentration of calcium hydroxide in the milk of lime. The output of the third adder through the third multiplier by a constant coefficient is connected to the first input of the fourth adder, the second input of which is connected to the output of the correction device, and the output is connected to the actuator.

 These differences make it possible to increase the stabilization accuracy of a given value of calcium hydroxide concentration in milk of lime due to the use of temperature signals measured by temperature sensors that most adequately characterize the stabilized concentration, high dynamics of the temperature signal, gas-vapor mixture, and a high degree of correlation of the temperature signal of milk of lime with the concentration of calcium hydroxide , applying a filter to reduce errors introduced into the system in case of random changes aloinertsionnogo temperature signal vapor-gas mixture, increasing the sensitivity by use of a system totalizer signals generated as a difference between their current values and srednezadannymi, introducing an additional correction device in accordance with situational process changes.

 The drawing shows a diagram of an adaptive control system for the preparation of milk of lime in a rotating extinguishing apparatus.

 The system comprises a technological apparatus 1, a temperature sensor 2 for a steam-gas mixture, a regulator 3, a filter 4, an adder 5, a device 6 forming a predetermined average temperature value of a gas-vapor mixture, a milk milk temperature sensor 7, an adder 8, a device 9 forming a predetermined average temperature value of a lime milk, devices 10 and 11 multiplying by a constant coefficient, adder 12, devices 13 and 14, forming the average and maximum values of the concentration of calcium hydroxide in milk of lime, device 15 multiplication and a constant coefficient, adder 16, correction device 17, actuator 18. The vapor-gas mixture temperature sensor 2 is connected by its output to a filter 4, the output of which is connected to the first input of the adder 5, and the second input is connected to the output of the device 6, which forms a given average temperature gas-vapor mixture. The sensor 7 of the temperature of the milk of lime is connected by its output to the first input of the adder 8, and the second input is connected to the output of the device 9, forming a predetermined average temperature of the milk of lime. Adders 5 and 8 are connected by their outputs to devices 10 and 11 multiplied by a constant coefficient, respectively. The adder 12 is connected to the output of the multiplication devices 10 and 11 by a constant coefficient, as well as to the outputs of the devices 13 and 14, which form the average and maximum values of the concentration of calcium hydroxide in the milk of lime. The adder 12 is connected by its output to the device 15 multiplying by a constant coefficient. The inputs of the adder 16 are connected to the outputs of the device 15 multiplying by a constant coefficient and the correction device 17, and the output is connected to the input of the actuator 18.

C_макс-

+K₁(t_пгс-

)+K₂(t_им-

)

, где Y - величина управляющего воздействия, %;
Y_p - расчетное значение управляющего воздействия, %;
Y_к - корректирующий сигнал, %;
С_макс,

- максимальное и среднее значения концентрации гидроксида кальция в известковом молоке, н.д. ("нормальное давление" соответствует 1/20 г-эвк. вещества в 1 л раствора);
t_пгс,

- текущее и заданное среднее значение температуры парогазовой смеси, ^оС;
t_им,

- текущее и заданное среднее значение температуры известкового молока, ^оС;
К₁, К₂, К₃ - постоянные коэффициенты.The system functioning algorithm can be represented as:
Y = Y _p + Y _k ;
Y _p = K

C _max -

+ K ₁ (t _pgs -

) + K ₂ (t _them -

)

where Y is the magnitude of the control action,%;
Y _p is the calculated value of the control action,%;
Y _to - correction signal,%;
With _max

- maximum and average concentration of calcium hydroxide in milk of lime, n.d. ("normal pressure" corresponds to 1/20 g-euc. substances in 1 liter of solution);
t _pgs

- current and predetermined average temperature of the vapor-gas mixture, ^о С;
t _them

- current and predetermined average temperature of the milk of lime, ^о С;
K ₁ , K ₂ , K ₃ are constant coefficients.

 The system works as follows.

 In the extinguishing apparatus 1 serves simultaneously lime and liquid, which, entering into a reaction, form a milk of lime at the outlet of the apparatus. At the same time, a significant amount of heat is generated with the formation of a vapor-gas mixture directed to the atmosphere.

 The temperature of the gas-vapor mixture is measured by a sensor 2, the signal of which is supplied to a regulator 3, including a filter 4, which reduces (smoothes) the oscillations of this parameter. The output signal of the filter goes to the first adder 5, where the signal equivalent to the average temperature of the steam-gas mixture generated by the device 6 is subtracted from it. The temperature of the milk of lime is measured by the sensor 7, the signal of which goes to the second adder 8, where the signal equivalent to the average is subtracted the set value of the temperature of the milk of lime, formed by the device 9. The output signals of the first and second devices are multiplied in devices 10 and 11 by constant coefficients. Moreover, the multiplication coefficient of the device 10 is significantly (several times) less than the multiplication coefficient of the device 11, which allows calculating the current value of the concentration of calcium hydroxide in the milk of lime at the exit of the quencher with higher accuracy, since the degree of correlation of the latter with the temperature of the milk of lime is higher than with the temperature of the vapor-gas mixture.

 The output signals of the multiplication devices are fed to the inputs of the third adder 12. In addition, signals equivalent to the average and maximum values of the concentration of calcium hydroxide in the milk of lime, generated in devices 13 and 14, are supplied to the other two inputs of the adder. The summing device generates a signal proportional to the difference between the maximum and current calcium hydroxide concentration values. This signal is multiplied by a constant coefficient by the third multiplication device 15 and fed to the input of the fourth adder 16, where it is added to the correction signal generated by the device 17. The correction signal is generated by the process personnel taking into account the specific technological situation and adapts the system to maintain a stable optimum value of calcium hydroxide content in milk of lime.

 Formed in this way, the control signal of the controller is supplied to the actuator 18.

; t_им* =

; на выходе сумматоров 5 и 8 нулевые сигналы. Выходной сигнал Y_p = const и имеет величину соответствующую условиям стационарности процесса (Y_p*). Величина сигнала, управляющего положением исполнительного механизма Y, скорректированная исходя из технологической ситуации в отделении гашения (сигнал Y_к) будет равна:
Y = Y_p* + Y_к.In the steady state operating mode, the current and average setpoints of the temperature of the gas-vapor mixture and milk of lime correspond to each other, i.e.:
t _pgs * =

; t _them * =

; at the output of adders 5 and 8, zero signals. The output signal is Y _p = const and has a value corresponding to the stationary conditions of the process (Y _p *). The value of the signal that controls the position of the actuator Y, adjusted based on the technological situation in the blanking compartment (signal Y _to ) will be equal to:
Y = Y _p * + Y _k .

In transient conditions that occur during operation during fluctuations in the content of calcium oxide in calcined lime, etc., the output signals of the temperature sensors 2 and 7 of the gas-vapor mixture and milk of lime change their value. In this case, the output signals of the adders 5, 8, 12 will change, and at the same time, the value of the calculated control signal Y _p , and therefore the signal Y supplied to the actuator 18. Changing the position of the actuator brings the fluid flow into the apparatus in accordance with the new oxide content calcium in lime. The current temperature values of the gas-vapor mixture and milk of lime take steady-state values. The system comes back to a stationary mode of operation.

 The implementation of the inventive system can significantly increase the accuracy of stabilization of a given value of the concentration of calcium hydroxide in milk of lime.

For example, a system implemented by the prototype, provides the maintenance of the specified parameter within: C _back. ± 10 n.a., and the system according to the invention: C _back. ± 5 n.a. Thus, the stabilization accuracy C _ass. according to the invention increases by 2 times.

Claims (1)

 ADAPTIVE SYSTEM OF MANAGEMENT OF THE PROCESS OF LIQUID MILK PREPARATION, including a steam-gas mixture temperature sensor, a regulator, an actuator and a regulating body installed on the liquid supply line to the extinguishing apparatus, characterized in that, in order to improve the accuracy of stabilization of the set value of calcium hydroxide concentration in the milk of lime, it is equipped with a temperature sensor for milk of lime, installed at the exit of the extinguishing apparatus, units for the formation of average and maximum the centering of calcium hydroxide in the milk of lime, the units for forming a predetermined average value of the temperature of the vapor-gas mixture and the temperature of the milk of lime and a correction unit, and the controller contains a filter, four adders and three multiplication units, the output of the temperature sensor of the vapor-gas mixture through the filter connected to the first input of the first adder, the second input of which is connected to the output of the unit for forming a predetermined average temperature of the gas mixture, and the output of the temperature sensor of the milk of lime is connected the first input of the second adder, the second input of which is connected to the output of the unit for setting the specified average temperature value of the milk of lime, while the outputs of the first and second adders through the first and second multiplication units are respectively connected to the first and second inputs of the third adder, the other two inputs of which are connected to the outputs blocks of formation of the average and maximum values of the concentration of calcium hydroxide in milk of lime and the output of the third adder through the third multiplication unit is connected to the first input a fourth adder, the second input of which is connected to the output correction unit, and the output of this adder is connected to an actuator.

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