RU2449215C1 - Temperature control method of steam-air mixture in scalding chamber at manufacture of round and ring-shaped cracknels - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: to scalding chamber with moving round and ring-shaped cracknels there supplied is steam-air mixture from electric steam generator; temperature of mixture is measured in scalding chamber; deviation from the specified temperature is determined and depending on difference and difference sign of temperature there increased or decreased is water supply to steam generator; at that, electric steam generator is used with three electrodes installed inside it, to which three-phase alternating current voltage is supplied; at that, there set in advance is relationship between current flowing through electrodes and steam generator water level, using it for control of amount of supplied water to steam generator during steam formation.

EFFECT: enlarging functional capabilities and improving reliability of temperature control system of steam-air mixture.

5 cl, 3 dwg

Description

The proposed method for controlling the temperature of the steam-air mixture in the scalding chamber relates to the field of automation of production processes of products, the food industry, is intended to maintain the steam temperature within the specified limits in the scalding chamber in the manufacture of ram-and-dried products and can be used in other areas and, in particular, in technological processes in which moving products are dried using hot air and steam-air mixtures.

Known methods for controlling the temperature of the vapor-air mixture when drying capillary-porous materials, for example, methods of drying pasta when they move at a constant speed and a rigid stepwise change in temperature over time by changing the fuel supply to the steam generator (Italian company "Bryanti" and "Pavan", a Swiss company “Buhler”) and methods of drying pasta by changing the speed of movement of products depending on the temperature of the drying agent (RU patent for invention No. 2186500, issued August 10, 2002. Bull. No. 22). These methods gradually bring the product to a predetermined humidity, for example from 30 to 12 percent.

A significant drawback of the first of these methods is that during the drying process it is not possible to directly measure the humidity of the product, and express control after leaving the drying unit requires a lot of time, therefore, for a real process, it becomes impossible to adjust the drying time for the mass of products in the drying unit or already out of it, that is, this mass is actually a marriage. The second of these methods is not applicable for in-line production, since it is necessary to adjust the speed of movement of products not only in the drying unit, but also in the entire production chain, which is unacceptable due to loss of productivity.

In the scalding chamber during the production of ram-dried products before baking, a slight moisture removal (drying) is required, which is carried out by hot steam at a given temperature, which is maintained by regulating the water level in the steam generators and regulating the amount of supplied fuel (gas or electricity as the most common). The specifics of the operation is such that the steam does not return to the steam generator from the chamber, but is removed to the atmosphere, that is, the system is open.

A known method of controlling the output power of an electrode steam generator as part of a heated condensate return system (closed system), implemented in patent RU No. 2140609, IPC F22B 1/30, F24H 1/20, publ. 10/27/1999, however, it lacks control of the temperature of the steam in the system and the water level in the steam generator itself, that is, the control functions are limited.

Closest to the proposed method is a method with an electric electrode steam generator, the main implementation of which is described in patent RU No. 90167 for utility model (published on 12/27/2009. Bull. No. 36). It can be taken as a prototype.

The essence of the method for controlling the output parameter of the electric electrode steam generator when using it with a scalding chamber is that the upper level of the water is controlled by a rod-sensor, upon closing of which the water supply electromagnetic valve and the electric pump unit are de-energized through water to the housing, and they are turned on after the time set by the time relay.

The specified method in relation to the scalding chamber in the manufacture of sheep-dried products has the following disadvantages:

- since the water vapor contains various salt and other chemical components, the sensor rod is overgrown with a corresponding coating, which causes its electrical resistance to change, which leads to untimely shutdown of the pump and the electromagnetic valve, and over time this leads to the loss of the functioning of the upper level control system water in the steam generator and to stop its operation to replace the sensor rod with a new one, that is, such a method is not sufficiently reliable during operation;

- when the electric circuit "rod-sensor - water - housing" is opened, the time relay is turned on, after which the set operating time has elapsed, the pump and the electromagnetic valve are turned on and water is pumped, i.e. in fact, the lower water level is not controlled. At this point in time, the lower water level may not have been reached or has already been passed, but in both cases, this leads to a deviation of the steam pressure at the outlet of the boiler from the set one, which is unacceptable in some applications, that is, the functionality of the steam generation method is limited;

- when adjusting the temperature of the steam-air mixture in the scalding chamber during the production of ram-and-dried products in this way, stop production every two weeks, disassemble the system, replace the water level sensors in the steam generator and restart the system. Such stops, firstly, reduce the performance of the entire process and, secondly, require additional costs for the re-equipment of the system;

- a gradual exit of the regulator from the water supply control zone during this period leads to a mismatch of the measured steam temperature in the scalding chamber with a given water level in the steam generator, which leads to the rejection of products in the subsequent operation of their baking and to an additional cost overrun of material and fuel and energy resources.

The technical problem solved by the invention is to expand the functionality and increase the reliability of the temperature control system of the steam-air mixture, to reduce the marriage of ram-dried products, to reduce the time of repair and maintenance work at a given performance.

The solution to the technical problem lies in the fact that in the method of controlling the temperature of the steam-air mixture in the scalding chamber in the production of the ram-dried products, which consists in the fact that the vapor-air mixture from the electric electrode steam generator is fed into the scalding chamber with the moving ram-drying products, the temperature of the mixture is measured in the scalding chamber, determine the deviation from the set temperature and depending on the difference and the sign of the temperature difference increase or decrease the water supply to the steam generator torus, an electric steam generator is used as a steam generator with three electrodes installed inside it, to which an alternating three-phase current voltage is applied, the relationship between the current flowing through the electrodes and the water level in the steam generator is preliminarily set, the obtained current values are stored in the form of settings and used for regulation of the amount of incoming water to the steam generator in the process of vaporization, and the choice of one or another setting at the appropriate time m, depending on the difference and the sign of the difference between the measured and preset temperatures of steam-air mixture in the scalding chamber.

The relationship between the current flowing through the electrodes and the water level in the steam generator is determined from the expression:

where U is the value of the AC voltage supplied to the electrodes;

R _e - electrical resistance of the electrodes;

L is the distance between the electrodes of the steam generator;

l is the width of the electrode;

h _n , h _in - the values of the water level, respectively, at the lower and upper boundaries of the level relative to the lower ends of the electrodes;

ρ _about - electrical resistivity of water;

I _n - the value of the current through the electrodes for the lower water level in the corresponding setting;

I _в - current value through electrodes for the upper water level in the corresponding setting.

The water supply to the steam generator is regulated cyclically by turning on the electromagnetic water supply valve when the current measured in the electrodes reaches the current set for the lower water level in the corresponding setting, and turning off the water supply electromagnetic valve when the current measured in the electrodes reaches the current set for the upper water level in the corresponding set point.

The choice of a particular setting with the corresponding currents for the upper and lower water levels during the process of vaporization is carried out depending on the magnitude and sign of the temperature deviation in the scalding chamber in accordance with the expression:

Where

Y (t) - current setting with its upper and lower current values;

Y (t) ⁺ - new setpoint with higher upper and lower current values;

Y (t) ^- - new setting with lower upper and lower current values;

T _to , T _z , ΔT, ΔT _z - respectively, the measured temperature value in the scalding chamber, the set temperature value, the difference between them and the set difference value;

sign (ΔT) - sign of the difference between the measured value of the temperature of the vapor-air mixture in the scalding chamber and the set value.

The electrodes are made in the form of rectangular plates and they are placed in radial planes relative to the central axis of the steam generator housing, while the planes are placed at an angle of 120 angular degrees relative to each other.

The essence of the proposed method for controlling the temperature of the steam-air mixture in the scalding chamber is illustrated by drawings (Fig. 1, Fig. 2, Fig. 3), while Fig. 1 is a structural diagram of a control system, Fig. 2 is a section BB of a steam generator 1 on figure 1, figure 3 is a structural diagram of an algorithm for controlling the temperature of the vapor-air mixture in the control system of figure 1.

The following notation is used in the figures:

1 - the case of the steam generator with a sealed lid;

2 - water;

3 - electrodes;

4 - current meter;

5 - electromagnetic voltage starter;

6 - scalding chamber;

7 - controller for controlling the pump and the solenoid valve;

8 - pump;

9 - the electromagnetic valve;

10, 11 - power circuits, respectively, of the pump and the solenoid valve;

12 - safety valve;

13 - pressure switch with electrical contact mn;

14 - valve for the release of steam;

15 - drain valve;

16 - check valve; h _in , h _n , h _zn - respectively, the upper, lower and predetermined initial water levels in the boiler;

17 - sensor for measuring the temperature in the scalding chamber;

Y ₁ , Y ₂ , ... Y _N - current settings with their lower In ₁ , In ₂ , ... In _N and upper I ₁ , I ₂ , ... In _N current values;

I _i is the current measured in the electrodes of the steam generator;

T _to , T _z , ΔT _z - respectively, the measured temperature in the scalding chamber, the set value and the set value of the difference between them;

E ₁ , E ₂ , E ₃ - electrodes of the electrode steam generator (figure 2);

L is the distance between the electrodes;

α = 120 ° - the angle between the electrodes;

l, l ₀ - width and thickness of the electrodes, respectively;

r ₀ is the radius of the base of the cylindrical column of water bounded by the inner ends of the electrodes;

r ₁ is the radius of the base of the cylindrical column of water bounded by the outer ends of the electrodes;

r ₂ is the radius of the base of the cylindrical body of the steam generator;

R _in - the area of the flow of electric current in water;

And ₁ -A ₁₂ - operations in the algorithm for controlling the temperature of the vapor-air mixture in the scalding chamber (Fig.3), implemented in the controller 7 of the control system of Fig.1;

And ₁ - entering into the controller a group of current settings with its lower and upper values of the currents I _n , I _in and the values of the set temperatures T _s and ΔT _s ;

And ₂ - selection of the current setting Y (t) with its upper and lower current values;

And ₃ - inclusion of the pump and the electromagnetic valve of water supply;

A ₄ is a comparison of the current value of the current I _i through the electrodes with the upper value of the current I _{in the} current setting, if they are equal, then operation A ₅ ;

A ₅ - turn off the pump and the solenoid valve for water supply;

And ₆ - the expectation of the equality of the measured current I _i with the lower current value I _{n the} current setting, if they are equal, then operation A ₇ is performed;

A ₇ - measurement of the temperature of the steam T _ko in the scalding chamber;

A ₈ - calculation of the difference ΔT = T _to -T _s ;

A ₉ is a comparison of the calculated difference with a given ΔT _s , if | ΔT | ≤ΔT _s , then go to step A ₃ , if not, then step A ₁₀ is performed;

A ₁₀ - determination of the sign of the temperature difference sign (ΔT); if it is negative, then operation A ₁₁ is performed, otherwise operation A ₁₂ and return to operation A ₃ ;

A ₁₁ - selection of the setpoint Y (t) ⁺ one more than the current;

And ₁₂ - selection of the setting Y (t) ^- one less than the current.

The essence of the method is as follows. Before starting work, the initial data is entered into the controller 7 (Fig. 1): current settings Y ₁ , Y ₂ , ... Y _n with their values of currents I _n , I _c and temperatures T ₃ , ΔT _s (operation A ₁ in Fig. 3 ) Then turn on the voltage ~ 380 V, which through the electromagnetic starter 5 and block 4 is supplied to the electrodes 3 installed in the case of the steam generator 1. The controller 7 selects the current setting (for example, Y (t _i )) with its current values I _ni and I _bi (operation A ₂ in FIG. 3), turns on the pump 8 through the power circuit 10 and opens the electromagnetic valve for supplying water 9 through the control circuit 11. Water begins to flow into the case of the steam generator 1 through the check valve 16, which causes the water level to change in the h direction _c , increasing the current flowing through cutting electrodes 3. During this period, the current in the meter 4 is measured and compared with a given I _vi in the set point (operation A ₄ in FIG. 3). Upon reaching the current I _bi , which means reaching the level h _bi , the controller 7 turns off the pump 8 and the electromagnetic valve for supplying water 9 (operation A ₅ in figure 3). Due to the flow of electric current through the electrodes in the region of conductive water R _in (figure 2), the water heats up and evaporates, decreasing in volume in the direction h _n , which reduces the current passing through the electrodes. During this period, the current in meter 4 is also measured, and in controller 7, a comparison is made with the given I _ni in this setting (operation A ₆ in FIG. 3). Upon reaching the current I _HI, which means achievement level h _HI, measured chamber temperature sensor 17 scalding 6 (A ₇ step 3), and the controller 7 computes a difference between the predetermined and measured T _of a scalding chamber and _to a temperature T compared with a given value of this difference ΔT _s modulo (operation A ₈ in figure 3). If the difference is within the specified tolerance (operation A ₉ in FIG. 3), then the controller 7 again turns on the pump 8 and the electromagnetic valve for supplying water 9 and operations A ₃ -A _{6 are} repeated. If the temperature difference is out of tolerance, then using the controller 7 the sign of the difference is determined (operation A ₁₀ in FIG. 3), and if the sign is negative, then a new setpoint is selected with a number one greater than Y (t) ⁺ , if the sign is positive, then select the setting with the number one less than Y (t) ^- (operation A ₁₁ , A ₁₂ in figure 3). After selecting a new setpoint, operations A ₃ -A ₆ are periodically performed, but with new values of I _n and I _c , and therefore with new values of the water level h _n and h _c .

Operations A ₈ -A ₁₂ are performed by the controller 7 in accordance with the expression:

The numerical values of the settings with currents I _n and I _in for a steam generator with specific dimensions are determined in advance using the expressions:

In this case, the current through the electrodes of the boiler and water flows only in the region R _in (shaded in figure 2). The diameter of the steam generator casing (r ₂ in FIG. 2) affects only the time period of the water supply and evaporation cycles (operation A ₃ -A ₆ in FIG. 3). The electrode planes are shifted relative to each other at an angle of 120 °, thereby ensuring uniform distribution of currents through the electrodes, i.e. uniform vaporization from the entire surface of the water.

Measurement of the current flowing through the electrodes of the steam generator with specific design parameters, and the use of its value to control the pump and the electromagnetic water supply valve, allows for self-regulation of the water level in the steam generator and dispense with any level sensors, thereby increasing the reliability of the entire temperature control system in the chamber scalding, increased time between repair and maintenance work.

Establishing the relationship between the specific steam temperature in the scalding chamber and the flowing current in the electrodes of a specific electric steam generator allows controlling the steam temperature through pre-calculated current settings by maintaining a given level of water supplied to the steam generator, which extends the functionality of the control system for various applications of the electric steam generator, in in particular for scalding chambers in the production of various types of sheep-dried products.

This method is implemented and implemented on a production line for the production of lamb and dried products at the enterprise Voploschenie LLC (Orel) to control the temperature of the steam in the scalding chamber with dimensions of 2700 * 2000 * 2050 mm and a cylindrical electric electrode steam generator with a diameter of 300 mm and a height 700 mm with three electrodes measuring 300 * 40 * 10 mm. During the operation during the year, not a single preventive repair was required, there was no violation of any technological regulations due to the fault of this complex, and the error in the temperature of the steam in the scalding chamber did not exceed 0.1 degrees Celsius from the set value.

Thus, in the method the technical tasks are solved, significant differences are determined, which indicates the presence of the novelty criterion and the patentability criterion of the invention.

Claims (5)

1. The method of controlling the temperature of the steam-air mixture in the scalding chamber in the production of the ram-dried products, which consists in the fact that the steam-air mixture from the electric electrode steam generator is fed into the scalding chamber with the moving ram-drying products, the temperature of the mixture in the scalding chamber is measured, and the deviation from the set value is determined temperature and depending on the difference and the sign of the temperature difference increase or decrease the water supply to the steam generator, characterized in that as the steam generator and they use an electric electrode steam generator with three electrodes installed inside it, to which an alternating three-phase current voltage is applied, the relationship between the current flowing through the electrodes and the water level in the steam generator is preliminarily established, the obtained current values are stored in the form of settings and used to control the amount of incoming water into the steam generator in the process of vaporization, and the choice of a particular setting at the appropriate time is carried out depending m difference and sign of the difference between the measured and preset temperatures of steam-air mixture in the scalding chamber. 2. The method according to claim 1, characterized in that the relationship between the current flowing through the electrodes and the water level in the steam generator is determined from the expression:

,
where U is the value of the AC voltage supplied to the electrodes;
R _e - electrical resistance of the electrodes;
L is the distance between the electrodes of the steam generator;
l is the width of the electrode;
h _n , h _in - the values of the water level, respectively, at the lower and upper boundaries of the level relative to the lower ends of the electrodes;
ρ _about - electrical resistivity of water;
I _n - the value of the current through the electrodes for the lower water level in the corresponding setting;
I _в - current value through electrodes for the upper water level in the corresponding setting. 3. The method according to claim 1, characterized in that the regulation of the water supply to the steam generator is carried out cyclically by turning on the electromagnetic valve of the water supply and the pump when the measured current in the electrodes reaches the current set for the lower water level in the appropriate setting, and turning off the electromagnetic valve of the water supply and pump when the measured current in the electrodes reaches the current set for the upper water level in the appropriate setting. 4. The method according to claim 1, characterized in that the choice of one or another setting with the corresponding currents for the upper and lower water levels during vaporization is carried out depending on the magnitude and sign of the temperature deviation in the scalding chamber in accordance with the expression:

where - Y (t) current setting with its upper and lower current values;
Y (t) ⁺ - new setpoint with higher upper and lower current values;
Y (t) ^- - new setting with lower upper and lower current values;
T _to , T _z , ΔT, ΔT _z - respectively, the measured temperature value in the scalding chamber, the set temperature value, the difference between them and the set difference value;
sign (ΔT) - sign of the difference between the measured value of the temperature of the vapor-air mixture in the scalding chamber and the set value. 5. The method according to claim 1, characterized in that the electrodes are made in the form of rectangular plates and arrange them in radial planes relative to the central axis of the steam generator housing, while the planes are arranged at an angle of 120 ° relative to each other.

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