Constant-temperature drying control method for direct-fired dryer

Abstract

The invention discloses a control method for constant-temperature drying of a direct-fired dryer, which comprises the following steps: (1) when drying operation needs to be carried out, ignition is firstly carried out, and the flame of a combustor is turned to the maximum, so that problems in a combustion bin are quickly lifted up; (2) when the temperature of the air inlet reaches the set PID adjustment value of the air inlet, PID adjustment of the air inlet is started; (3) when the temperature of the air outlet reaches the set PID adjustment value of the air outlet, PID adjustment of the air outlet is started; and (4) when the drying temperature reaches the discharging set value monitored by the sensor and the drying humidity reaches the discharging set value monitored by the sensor, flame is turned off for cooling, and then discharging is conducted. The heating value of the combustor can be accurately adjusted, the problems of long drying time and frequent ignition possibly occurring in the traditional drying process are solved, the drying time is effectively shortened, meanwhile, the problem that the service life is shortened due to frequent ignition is solved, and therefore energy waste is reduced, and energy efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of direct-fired dryers, and in particular to a control method for constant-temperature drying of a direct-fired dryer. Background Art

[0002] Currently, many dryers on the market are steam heat exchange dryers, which obtain water vapor through boilers. The heat exchanger then converts the heat energy of the water vapor into the air, and the heat energy is brought to the inside of the dryer through the circulating fan, thereby achieving the purpose of drying the material. However, in this series of energy conversions, there will be a lot of energy loss, and the boiler is a special equipment that requires annual inspection every year. The direct-fired dryer just solves this problem. It heats the air by directly burning natural gas, avoiding a lot of energy loss.

[0003] Direct-fired dryers mainly rely on advanced burner devices and are combined with PID control algorithms. The system has a self-tuning function and can also set appropriate proportional, integral, differential gain, and differential time coefficients. Set the target value, the PLC collects the system temperature in real time, and uses the real-time temperature less than the over-limit temperature as a safety condition for the burner ignition start. After the burner is ignited, the time required for ignition to complete is passed, and the burner damper position angle is calculated. This process is the completion of ignition calibration, which is used as an enabling condition for PID operation.

[0004] The angle per unit time is obtained by dividing the maximum angle of the burner damper by the time required to open to the maximum angle. The time for the burner flame to increase or decrease, multiplied by the angle per unit time, can be converted into the damper position angle (percentage). The PID operation output value is compared with the damper position angle value. If the operation output value is less than the damper position angle (percentage), the burner flame increases. If the operation output value is greater than the damper position angle (percentage), the burner flame decreases.

[0005] However, the existing direct-fired dryers may have problems such as long drying time and frequent ignition during the drying process, which not only reduces the working efficiency, but also shortens the service life and increases energy consumption. Therefore, the above problems need to be solved urgently. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a control method for constant temperature drying of a direct-fired dryer, which can accurately adjust the heating value of the burner, avoid the problems of long drying time and frequent ignition that may occur in the traditional drying process, effectively shorten the drying time, and also prevent the problem of shortened service life caused by frequent ignition, thereby reducing energy waste and improving energy efficiency.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solution: A control method for constant temperature drying of a direct-fired dryer of the present invention has the following innovative features: (1) When drying is required, first ignite the burner and turn the burner flame to the maximum to quickly raise the temperature in the combustion chamber; (2) When the air inlet temperature reaches the set air inlet PID adjustment value, the air inlet PID adjustment is started; (3) When the air outlet temperature reaches the set air outlet PID adjustment value, the air outlet PID adjustment is started; (4) When the drying temperature reaches the discharge setting value monitored by the sensor, and the drying humidity reaches the discharge setting value monitored by the sensor, the flame is turned off and the machine enters cooling mode before discharging the material.

[0008] Preferably, in the above step (1), after the burner is started, the burner burns with a maximum flame and its opening rate must be set to 100%.

[0009] Preferably, in the above step (2), if the air inlet temperature is suddenly too high and exceeds the set maximum value, a setting is performed to limit the flame size and automatically adjust the flame size of the burner; when the flame size changes from small to large, the flame size decreases according to the amplitude of the temperature exceeding the limit; when the temperature slowly decreases, the flame size is restored according to the amplitude of the temperature exceeding the limit.

[0010] Preferably, in the above step (2), the air inlet PID adjustment value is set to 210 degrees.

[0011] Preferably, in the above step (3), if the outlet temperature is suddenly too high and exceeds the set maximum value, a setting is made to limit the flame size and automatically adjust the flame size of the burner; when the flame size is increasing from small to large, the flame size decreases according to the amplitude of the temperature exceeding the limit; when the temperature slowly decreases, the flame size is restored according to the amplitude of the temperature exceeding the limit.

[0012] Preferably, in the above step (3), the air outlet PID adjustment value is set to 105 degrees.

[0013] Preferably, in the above step (4), the discharge setting value of the drying humidity is set to 91 percent, at which time the burner stops heating and enters cooling.

[0014] The beneficial effects of the present invention are as follows: the present invention can accurately adjust the heat generation of the burner, avoiding the problems of long drying time and frequent ignition that may occur in the traditional drying process, effectively shortening the drying time, and also preventing the problem of shortened service life caused by frequent ignition, thereby reducing energy waste and improving energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 The present invention is a schematic diagram of a control method for constant temperature drying of a direct-fired dryer. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be clearly and completely described below through specific implementation methods.

[0018] The present invention provides a control method for constant temperature drying of a direct-fired dryer. The core of the method is to accurately adjust the heat of the burner through a control signal, thereby avoiding the problems of long drying time and frequent ignition that may occur in the traditional drying process, effectively shortening the drying time, and also preventing the problem of shortened service life caused by frequent ignition, thereby reducing energy waste and improving energy efficiency. Figure 1 As shown, the following steps are included: (1) When drying is required, first ignite the burner and turn the burner flame to the maximum to quickly raise the temperature in the combustion chamber; In the above steps, after the burner is started, the burner burns with the maximum flame and it is necessary to ensure that its opening rate is set to 100%.

[0019] (2) When the air inlet temperature reaches the set air inlet PID adjustment value, the air inlet PID adjustment is started; In the above steps, if the air inlet temperature is suddenly too high and exceeds the set maximum value, the flame size limit is set to automatically adjust the flame size of the burner; when the flame size changes from small to large, the flame size decreases according to the degree of temperature excess; when the temperature slowly drops, the flame size is restored according to the degree of temperature excess, thereby ensuring that the flame size does not exceed the set maximum value by a large amount.

[0020] In the above steps, the air inlet PID adjustment value is set to 210 degrees, that is, when the air inlet temperature reaches 210 degrees, the burner will be adjusted according to the air inlet PID control.

[0021] (3) When the air outlet temperature reaches the set air outlet PID adjustment value, the air outlet PID adjustment is started; In the above steps, if the outlet temperature is suddenly too high and exceeds the set maximum value, the flame size limit is set to automatically adjust the flame size of the burner; when the flame size changes from small to large, the flame size decreases according to the degree of temperature excess; when the temperature slowly drops, the flame size is restored according to the degree of temperature excess, thereby ensuring that the flame size does not exceed the set maximum value by a large amount.

[0022] In the above steps, the set air outlet PID adjustment value is 105 degrees, that is, when the air outlet temperature reaches 105 degrees, the burner will be adjusted according to the air outlet PID control.

[0023] (4) When the drying temperature reaches the discharge setting value monitored by the sensor, and the drying humidity reaches the discharge setting value monitored by the sensor, turn off the flame and enter cooling, and then discharge; In the above steps, the discharge setting value of the drying humidity is set to 91 percent, and when the discharge setting value of the drying humidity is reached, the burner stops heating and enters cooling.

[0024] The beneficial effects of the present invention are as follows: the present invention can accurately adjust the heat generation of the burner, avoiding the problems of long drying time and frequent ignition that may occur in the traditional drying process, effectively shortening the drying time, and also preventing the problem of shortened service life caused by frequent ignition, thereby reducing energy waste and improving energy efficiency.

[0025] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in the field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the technical requirements.

Claims

1. A control method for constant temperature drying of a direct-fired dryer, characterized in that The following steps are involved: (1) When drying is required, first ignite the burner and turn the burner flame to the maximum to quickly raise the temperature in the combustion chamber; (2) When the air inlet temperature reaches the set air inlet PID adjustment value, the air inlet PID adjustment is started; (3) When the air outlet temperature reaches the set air outlet PID adjustment value, the air outlet PID adjustment is started; (4) When the drying temperature reaches the discharge setting value monitored by the sensor, and the drying humidity reaches the discharge setting value monitored by the sensor, the flame is turned off and the machine enters cooling mode before discharging the material.

2. A control method for constant temperature drying of a direct-fired dryer according to claim 1, characterized in that: In the above step (1), after the burner is started, the burner burns at the maximum flame and its opening rate must be set to 100%.

3. A control method for constant temperature drying of a direct-fired dryer according to claim 1, characterized in that: In the above step (2), if the air inlet temperature suddenly becomes too high and exceeds the set maximum value, the flame size limit is set to automatically adjust the flame size of the burner; when the flame size is increasing from small to large, the flame size decreases according to the degree of temperature exceeding the limit; when the temperature slowly decreases, the flame size is restored according to the degree of temperature exceeding the limit.

4. A control method for constant temperature drying of a direct-fired dryer according to claim 3, characterized in that: In the above step (2), the air inlet PID adjustment value is set to 210 degrees.

5. A control method for constant temperature drying of a direct-fired dryer according to claim 1, characterized in that: In the above step (3), if the outlet temperature suddenly becomes too high and exceeds the set maximum value, the flame size limit is set to automatically adjust the flame size of the burner; when the flame size is increasing from small to large, the flame size decreases according to the degree of temperature exceeding the limit; when the temperature slowly decreases, the flame size is restored according to the degree of temperature exceeding the limit.

6. A control method for constant temperature drying of a direct-fired dryer according to claim 5, characterized in that: In the above step (3), the air outlet PID adjustment value is set to 105 degrees.

7. A control method for constant temperature drying of a direct-fired dryer according to claim 1, characterized in that: In the above step (4), the discharge setting value of the drying humidity is set to 91%, at which time the burner stops heating and enters cooling.

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