RU2350866C1 - Technique of automatic control over process of dispersion materials drying in active hydrodynamics devices with heat medium recirculation - Google Patents

Abstract

FIELD: heating, drying.

SUBSTANCE: invention relates to drying machinery immediately dealing with techniques of automatic control over the process of dispersion materials drying in active thermodynamics devices with heat medium recirculation; it is to be implemented in such spheres as food and chemical industries as well as other economy branches allied thereto. The proposed technique of automatic control over the process of dispersion materials drying in active thermodynamics devices with heat medium recirculation envisages the dispersion material(s) pre-drying and drying and measurement of the following parameters: feed material flow rate, moisture content and temperature, ready dried material flow rate and moisture content, flow rate, moisture content and temperature of the heat medium supplied and moisture content of the heat medium discharged. Data retrieved by the sensors performing measurement of the feed material flow rate, moisture content and temperature, ready dried material flow rate and moisture content, flow rate, moisture content and temperature of the heat medium supplied and moisture content of the heat medium discharged is transmitted to a microprocessor unit. The latter, using an embedded algorithm, specifies the optimum thermal regime and heat medium delivery regime depending on the content of moisture and heat in the feed material and material to have undergone drying treatment and operates the executive mechanisms of the calorifiers and the blower fans to provide for establishment of the optimum regime (mode) aforesaid with a view of ensuring reliable maintenance of the preset parameters of the material being treated. The above process additionally envisages deployment of sensors registering wattage consumption with the calorifiers and the blower fans with the information thus retrieved transmitted to the microprocessor unit that performs continuous calculation of total power consumption per weight unit of the material being treated. In case of a power consumption increase or decrease registered the microprocessor unit generates a command to accordingly decrease or increase the heat medium temperature and flow rate. Optimum feed material flow rate value is taken to be determined by minimisation of the power consumption cost function. In addition to that the drying process control regime is initially adjusted with tangentially delivered fluxes of heat medium whose temperature and flow rate are modulated based on deviation of the currently actual quantity of moisture being evaporated within the suspension-and-swirl layer dryer zones from the values preset. After that if modulation of temperature and flow rate of the tangentially delivered fluxes of heat medium fails to ensure maintenance of the required value of moisture content in the material to have undergone treatment, temperature and flow rate of the heat medium axial flux are modulated. The innovation consists in one of the rapid dryer sections being pre-dried with the heat medium discharged and in drying with the suspension-and-swirl layer dryer being performed within the discharged heat medium recirculation system. Depending on the moisture content in the discharged heat medium within each of the three sections the discharged heat medium may either be mixed with or give up heat to the atmospheric air delivered in auxiliary calorifiers. The auxiliary valves the heat medium delivery system is equipped with enable direction of the atmospheric air supplied into the auxiliary calorifiers (when the discharged heat medium due to its high moisture content is delivered for heat exchange into the auxiliary calorifiers on a command issued by the microprocessor unit). If the content of moisture in the discharged heat medium is insignificant the microprocessor unit commands to deliver it for mixture with the atmospheric air supplied with the valves directing the atmospheric air supplied to bypass the auxiliary calorifiers which finally results in reduction of resistance in the heat medium delivery system. Additionally control is exercised over entrainment of the material being treated with the help of sensors of feed material flow rate and feed material and ready-dried material moisture content; based on their readings the microprocessor unit calculates the amount of the ready-dried material without allowance for entrainment. The actual amount of the ready-dried material is registered by the ready-dried material flow rate sensor. Based on the data retrieved the microprocessor unit calculates the amount of the ready-dried material entrainment by the discharged heat medium and, depending on the currently applicable requirements to the drying process, generates a command to modulate operation of the blower fans executive mechanisms to provide for the heat medium delivery rate reduction.

EFFECT: improved quality of the material to have undergone treatment; environmental impact minimisation; specific energy consumption decrease; reduction of material entrainment during drying.

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Description

The invention relates to a drying technique, and in particular to methods for automatically controlling the drying processes of dispersed materials with recirculation of the coolant in devices with active hydrodynamics and can be used in food, chemical and related industries.

Closest to the proposed technical essence and the achieved result is a method for automatically controlling the drying of dispersed materials in an active hydrodynamic mode, comprising drying due to the heat of the spent heat carrier and drying the material and consisting in measuring the flow rate, humidity and temperature of the starting material entering the dryer, flow rate and humidity of the dried material, moisture content, temperature and flow rate of the coolant entering the dryer, moisture content of the coolant eating after drying, while the information from the sensors measuring the flow rate, humidity and temperature of the starting material entering the dryer, flow rate and humidity of the dried material, moisture content, temperature and flow rate of the heat transfer agent entering the dryer, the moisture content of the heat transfer agent after drying is supplied to the microprocessor, which the algorithm incorporated in it, depending on the amount of moisture and heat contained in the source and dried material, sets the temperature regime and the mode of supply of the coolant at the inlet to the dryer by means of actuators of heaters and fans in order to ensure the specified parameters of the material to be dried, in addition, sensors are used that measure the power consumption of fans and heaters, the information from which is fed to the microprocessor, which continuously determines the total energy costs per unit mass of the material to be dried, and if they increase , then reduces the temperature and flow rate of the coolant, if they decrease, it increases, and the optimal flow rate of the source material and it is determined by minimizing the function of the cost of energy costs, in addition, the correction of the control mode of the drying process is carried out at two levels, while at the first level, when the current value of the amount of moisture evaporated in any zone of the dryer deviates from the set one, they affect the temperature and flow rate of the tangentially supplied coolant flow, and at the second level, if the change in temperature and flow rate of the tangentially supplied coolant flow does not provide the required moisture content of the dried material, affect the flow rate and temperature of the axial flow of the coolant [Patent RU No. 2290583, F26В 25/22, 12/27/2006]. The known method has several significant disadvantages:

- insufficiently high quality of the finished material;

- lack of a control system for the drying process with recirculation of waste coolant;

- lack of an effective heat recovery system for waste heat carrier;

- the inability to control the entrainment of material with waste coolant;

- loss of dried material during the drying process.

An object of the invention is to improve the quality of the finished material, reduce the negative impact of waste heat carrier on the environment, reduce specific energy consumption, reduce material losses during the drying process.

The object of the invention is achieved by the fact that in the proposed method for automatically controlling the drying process with recirculation of the coolant in devices with active hydrodynamics, which provides for the drying and drying of dispersed materials and consists in measuring the flow rate, humidity and temperature of the starting material, flow rate and humidity of the dried material, moisture content, temperature and flow rate of the coolant entering the dryer, moisture content of the coolant after drying, the information from the sensors, and measuring the flow rate, humidity and temperature of the starting material, flow rate and humidity of the dried material, moisture content, temperature and flow rate of the heat carrier entering the dryer, the moisture content of the heat transfer medium after drying is supplied to the microprocessor, which according to the algorithm laid down in it, depending on the amount of moisture and heat contained in source and dried material, sets the temperature regime and the mode of supply of the coolant for drying by means of actuators of heaters and fans in order to ensure I set the parameters of the material to be dried, while additionally using sensors that measure the power consumption of fans and heaters, the information from which is fed to the microprocessor, which continuously determines the total energy costs per unit mass of the material to be dried, and if they increase, it reduces the temperature and flow rate of the coolant, if they decrease, it increases, the optimal consumption of the starting material is determined by minimizing the function of the cost of energy costs, in addition, The drying process control mode is first carried out by tangentially supplied coolant flows, the temperature and flow rate of which are influenced by the deviation of the current value of the amount of evaporated moisture in the sections of the dryer with a weighted-swirl layer from the set one, and then, if the temperature and flow rate of the tangentially supplied coolant flows change does not provide the required humidity of the dried material, affect the flow rate and temperature of the axial flow of the coolant, new is that in a vortex the dryer is dried by the spent heat carrier of one of the sections of the dryer, and in the dryer with a weighted-swirling layer, drying is carried out in the waste heat carrier recirculation system, while depending on the humidity of the spent heat carrier of each of the three sections, it can be mixed with atmospheric air supplied to the dryer or given heat entering the drying air into the air in additional heaters, additional valves installed in the coolant supply system can direct the flow ambient air to additional heaters, if the exhaust heat carrier has a high humidity and is sent by the microprocessor to heat transfer to additional heaters, if the exhaust heat medium has a low humidity, it is sent by the microprocessor to mix with the air entering the dryer, and the valves direct incoming air, bypassing additional heaters, thereby reducing the resistance of the coolant supply system to the dryer, while controlling the entrainment m of dried material using flow sensors of the source material, as well as humidity sensors of the source and dried material, according to the readings of which the microprocessor determines the amount of dried material, provided that it is non-toxic according to the formula:

- количество высушенного материала получаемого при сушке, при условии его безуносности, кг/ч;Where

- the amount of dried material obtained by drying, subject to its non-tolerance, kg / h;

Q ₁ - the amount of initial wet material fed to the drying, kg / h;

w ₁ - relative humidity of the starting material,%;

w ₂ - relative humidity of the dried material,%,

The actual amount of dried material is determined using the flow sensor of the dried material. The microprocessor determines the ablation of material with waste heat carrier by the formula:

where U is the amount of material carried away with waste coolant, kg / h;

Q ₂ - the actual amount of dried material obtained, kg / h

If the value of U is greater than the permissible U _add specified in the microprocessor depending on the requirements for the drying process, the microprocessor generates a signal proportional to the value of UU _add , which affects the actuators of the fans, reducing the flow of coolant.

The technical result consists in improving the quality of the dried material, reducing the negative impact on the environment, reducing specific energy consumption, reducing material losses during the drying process.

Figure 1 presents a diagram that implements the proposed method for automatically controlling the drying process.

The scheme contains a vortex dryer 1 for drying the feedstock, a dispenser 2, a dryer with a weighted-swirling layer 3, consisting of three sections I, II, III; cyclones 4 for cleaning the spent coolant from dried material, fans 5 for supplying coolant; heaters 6, 7 for heating the coolant, a collection of dried material 8; lines: supply of the initial wet material 9, supply of atmospheric air 10, supply of the tangential flow of the coolant to section I 11, supply of the tangential flow of the coolant to section II 12, supply of the tangential flow of the coolant to section III 13, supply of the axial flow of the coolant 14, removal of the dried material from I section 17, removal of dried material from II section 16, removal of dried material from III section 15, removal of spent coolant from I section 18, removal of spent coolant from II section 19, removal th coolant III of section 20; sensors: flow rate 21, temperature 22 and humidity 23 of the starting material, humidity 24 and temperature 25 of the air supplied to the heating, flow rate 26, temperature 27 and humidity 28 of the tangential flow of the coolant entering the first section of the dryer, flow rate 29, temperature 30 and humidity 31 tangential flow of coolant entering the second section of the dryer, flow rate 32, temperature 33 and humidity 34 tangential flow of coolant entering the third section of the dryer, flow rate 35, temperature 36 and humidity 37 of the axial flow spruce entering the dryer, humidity 38 and temperature 39 of dried material obtained in the first section of the dryer, humidity 40 and temperature 41 of dried material obtained in the second section of the dryer, humidity 42 and temperature 43 of dried material obtained in the third section of the dryer, humidity 44 and temperature 45 of the waste fluid from the first section of the dryer, humidity 46 and temperature 47 of the waste fluid from the second section of the dryer, humidity 48 and temperature 49 of the waste fluid from the third section of the dryer; actuators 50-59; (a, b, c, d, d, f, f, s, u, and, k, l, m, n, o, p, p, s, t, y, f, x, t, h, w , u, e, u, i - input control channels, d, f, g, h, i, j, k, l, q, r, s, t, v, w, Y, z - output control channels), flow sensor of dried material 60, microprocessor 61.

The drying method is as follows.

The initial wet dispersed material is first supplied to the vortex dryer 1, where it is dried by the heat of the spent heat carrier, then the dispenser 2 is fed into the I, II and III sections of the dryer 3 with a weighted-swirl layer. Information on the flow, temperature and humidity of the dried material in line 9 is transmitted using sensors 21, 22, 23 to the microprocessor 61, which, according to the algorithm laid down in it, depending on the amount of moisture and heat contained in the initial wet material fed to the drying, sets temperature and supply mode of the coolant at the inlet to the dryer by means of fans 5, heaters 6, 7.

During the drying process of the dispersed material in a suspended-swirl layer using current information from the moisture sensors of the starting material 23 and dried 38, 40, 42, the current moisture value of the starting material and the dried material in each of the three sections is measured, according to which the control mode is adjusted the drying process in each section of the dryer. Due to this, the quality of the dried material is significantly improved.

If the current value of the moisture flow evaporated in the first section of the dryer deviates from the set value, the microprocessor 61 calculates the required temperature change of the tangentially supplied coolant flow to the first section and corrects it using the air heater 6 installed in line 11. If the required humidity is not reached, the microprocessor 61 calculates the necessary change in the flow rate of the tangentially supplied coolant flow to the I section and carries out its correction by means of a fan 5 installed in line 11.

If the current value of the moisture flow evaporated in the II section of the dryer deviates from the given one, the microprocessor 61 calculates the necessary temperature change of the tangentially supplied coolant flow to the II section and corrects it by means of the air heater 6 installed in line 12. If the desired humidity is not reached, the microprocessor 61 calculates the necessary change in the flow rate of the tangentially supplied coolant flow to the II section and carries out its correction by means of a fan 5 installed in line 12.

If the current value of the moisture flow evaporated in the III section of the dryer deviates from the given one, the microprocessor 61 calculates the required temperature change of the tangentially supplied coolant flow to the III section and corrects it by means of the air heater 6 installed in section 13. If the required humidity is not achieved, the microprocessor 61 calculates the necessary change in the flow rate of the tangentially supplied coolant flow to the III section and carries out its correction by means of a fan 5 installed in line 13.

If the change in temperature and flow rate of the tangentially supplied coolant flow does not provide the required moisture content of the dried material, then the control mode is adjusted by adjusting the temperature and flow rate of the axial coolant flow. The microprocessor 61 calculates the required change in the temperature of the axial flow of the coolant and carries out its correction by means of the air heater 6 installed in line 14. If the desired humidity is not achieved, the microprocessor 61 calculates the necessary change in the flow rate of the axial flow of the coolant and carries out its correction through the fan 5 installed in line 14.

The dried material together with the spent coolant are removed from each section of the dryer and fed to the corresponding cyclones 4 for cleaning, where they are separated. The dried material obtained in each of the three sections along lines 15, 16 and 17 enters the collection 8, while using the sensors 38, 40 and 42, the microprocessor 61 receives current information about the moisture content of the dried material, and using the sensors 39, 41 and 43 obtains current temperature information of the dried material.

Using sensors 44, 46 and 48, the microprocessor 61 receives current information about the humidity of the spent coolant flows coming from sections I, II, and III of the dryer, respectively, and using sensors 45, 47, and 49, the microprocessor 61 receives current information about the temperature of the spent coolant flows, coming from sections I, II and III of the dryer, respectively.

Using actuators 50, 51 and 52, the microprocessor 61 directs the flow of waste coolant with minimal humidity to the vortex dryer.

The microprocessor 61, depending on their humidity and temperature, directs the remaining two flows of the spent heat carrier using the actuators 53, 54, 55, 56, 57, and 58, either to mix it with atmospheric air supplied to the drying line 10 or to heat the air supplied for drying into heaters 7.

Using the flow sensors of the source material 21, as well as humidity sensors of the source and dried material, the microprocessor 61 determines the amount of dried material (subject to its non-balance) by the formula:

- количество высушенного материала, получаемого при сушке, при условии его бузуносности, кг/ч;Where

- the amount of dried material obtained by drying, subject to its blanching, kg / h;

Q ₁ - the amount of initial wet material fed to the drying, kg / h;

w ₁ - relative humidity of the starting material,%;

w ₂ - relative humidity of the dried material,%.

The actual amount of dried material is determined using the flow rate sensor of the dried material 61. Microprocessor 61 determines the ablation of material with waste heat carrier by the formula:

where U is the amount of material carried away with waste coolant, kg / h;

Q ₂ - the actual amount of dried material obtained, kg / h If the value of U is greater than the allowable U _add specified in the microprocessor depending on the requirements for the drying process, the microprocessor generates a signal proportional to the value of UU _add , which affects the actuators of the fans 5, reducing the flow of coolant. Thus, the proposed automatic control scheme allows you to control the ablation of the material together with the spent coolant.

The proposed method can be implemented when drying dispersed materials in an experimental setup designed and manufactured at the Voronezh State Technological Academy [Patent No. 2272230 Russia, IPC7 F26B 17/10. A dryer with active hydrodynamics and after-treatment material [Text] / Antipov S.T., Pribytkov A.V., Zhuravlev A.V. Voronezh, state technol. Acad. - No. 2004130341; declared 10/15/2004; publ. 03/20/2006, Bull. 8.].

Thus, the proposed method for automatically controlling the drying process of dispersed material in a suspension-swirl layer allows you to:

- to obtain dried material of higher quality due to independent control of the drying process in each of the three sections;

- carry out automatic control of the drying process of dispersed materials with a system for recycling waste heat carrier;

to carry out efficient heat recovery of waste heat carrier;

- to carry out automatic control of material entrainment during drying.

Claims (1)

A method for automatically controlling the drying process with recirculation of the coolant in devices with active hydrodynamics, which includes drying and drying of dispersed materials, which consists in measuring the flow rate, humidity and temperature of the starting material, flow rate and humidity of the dried material, moisture content, temperature and flow rate of the coolant supplied to the drying, moisture content of the coolant after drying, while information from sensors measuring the flow rate, humidity and temperature of the starting material, flow rate and humidity of dried material, moisture content, temperature and flow rate of the heat transfer agent to be dried, the moisture content of the heat transfer agent after drying is supplied to the microprocessor, which, according to the algorithm laid down in it, depending on the amount of moisture and heat contained in the source and dried material, sets the temperature and flow mode for drying by means of actuators of heaters and fans in order to ensure the specified parameters of the dried material, while additionally using sensors that measure the power consumption of fans and heaters, the information from which is fed to a microprocessor, which continuously determines the total energy costs per unit mass of the dried material, and if they increase, it reduces the temperature and flow rate of the coolant, if it decreases, it increases the optimal consumption of the source material is determined by minimizing the function of the cost of energy costs, in addition, the correction of the control mode of the drying process is carried out first tangentially under with the same coolant flows, the temperature and flow rate of which are influenced by the deviation of the current value of the amount of evaporated moisture, in the zones of the dryer with a suspended-swirl layer from the specified one, and then, if the change in temperature and flow rate of the tangentially supplied coolant flows does not provide the required moisture content of the dried material, the flow rate and temperature of the axial flow of the coolant, characterized in that in the vortex dryer carry out the drying of the waste coolant of one of the sections of the dryer with a weighted-swirling layer, and in a dryer with a weighted-swirling layer, drying is carried out in the exhaust coolant recirculation system, while depending on the humidity of the spent heat-transfer medium in each of the three sections, it can be mixed with the atmospheric air supplied to the dryer or give off heat to the dryer ambient air in additional air heaters, additional valves installed in the coolant supply system can direct incoming air into the additional air heater if the waste heat carrier has a high humidity and is sent by the microprocessor to heat transfer to additional heaters, if the waste heat carrier has a low humidity, it is sent by the microprocessor to mix with the atmospheric air entering the dryer, and the valves direct incoming air, bypassing the additional heaters, thereby reducing resistance of the coolant supply system to the dryer, while controlling the entrainment of the dried material using flow sensors the source material, as well as humidity sensors of the source and dried material, according to the readings of which the microprocessor determines the amount of dried material, provided that it is non-balanced by the formula

Where

- the amount of dried material obtained by drying, subject to its non-tolerance, kg / h;
Q ₁ - the amount of initial wet material fed to the drying, kg / h;
w ₁ - relative humidity of the starting material,%;
w ₂ - relative humidity of the dried material,%,
the actual amount of dried material is determined using the flow rate sensor of the dried material, the microprocessor determines the ablation of material with waste heat carrier by the formula

,
where U is the amount of material carried away with waste coolant, kg / h;
Q ₂ - the actual amount of dried material obtained, kg / h, if the value of U is greater than the permissible U _add specified in the microprocessor depending on the requirements for the drying process, the microprocessor generates a signal proportional to the value of UU _add , which affects the actuators of the fans, reducing the flow of coolant.