Heating control device and method for paper-making reconstituted tobacco drying box
阅读说明：本技术 一种造纸法再造烟叶干燥箱的加热控制装置及方法 (Heating control device and method for paper-making reconstituted tobacco drying box ) 是由 张书云 郭文敏 孙宇 曹铭 苏刚 畅浩 刘彦龙 于 2019-10-09 设计创作，主要内容包括：本发明公开了一种造纸法再造烟叶干燥箱的加热控制装置及方法,包括热交换器、蒸汽阀门、压力仪表、热风干燥箱、温度仪表、蒸汽管路和热风管道。控制系统接收现场压力仪表和温度仪表的检测信号,同时读取生产系统工作车速,自动计算出蒸汽预设压力值,经压力仪表和蒸汽阀门组成的PID连锁控制回路后,输出蒸汽阀门的开度。在生产预热阶段,通过控制蒸汽阀门的开度上升斜率以防止产生水击,造成对热交换设备的机械损坏,在生产运行阶段,通过控制压力预设参数的上升、下降斜率,以防止出现压力大幅度波动,导致热交换器内相态变化,影响换热质量,以保证控制的平稳性,确保被加热纸页质量的稳定性。(The invention discloses a heating control device and method for a paper-making reconstituted tobacco drying box. The control system receives detection signals of the field pressure instrument and the temperature instrument, simultaneously reads the working speed of the production system, automatically calculates the preset pressure value of the steam, and outputs the opening degree of the steam valve after passing through a PID (proportion integration differentiation) interlocking control loop formed by the pressure instrument and the steam valve. In the production preheating stage, the rising slope of the opening degree of the steam valve is controlled to prevent water hammer from generating and causing mechanical damage to heat exchange equipment, and in the production running stage, the rising slope and the falling slope of preset pressure parameters are controlled to prevent phase change in the heat exchanger and influence heat exchange quality due to large-amplitude fluctuation of pressure, so that the control stability is ensured, and the quality stability of the heated paper is ensured.)
1. A heating control device of a paper-making reconstituted tobacco drying box is characterized by comprising a heat exchanger, a steam valve, a pressure instrument, a hot air drying box and a temperature instrument;
the steam pipeline is connected with the heating side inlet of the heat exchanger, and the heating side outlet of the heat exchanger is connected with the steam condensate water recovery pipeline;
the heated side of the heat exchanger is respectively connected with an air inlet and an air outlet of the hot air drying box through a circulating ventilation pipeline;
a steam valve and a pressure instrument are arranged on the steam pipeline;
a temperature instrument is arranged on a circulating ventilation pipeline between the heat exchanger and an air inlet of the hot air drying box;
the steam valve, the pressure instrument and the temperature instrument are all connected with a control system through electric signals.
2. The heating control device of the paper-making process reconstituted tobacco drying box according to claim 1, wherein the temperature instrument is used for displaying hot air temperature in real time and referring to the hot air temperature without directly participating in control, the speed of the paper machine is used as a reading parameter of a control system and participates in linkage adjustment, the system automatically calculates and presets a required corresponding steam pressure value according to current operating conditions, the preset steam pressure value is connected to a PID linkage control loop formed by the pressure instrument and a steam valve, and the control loop outputs a signal for automatically adjusting the opening degree of the steam valve.
3. A heating control method of a paper-making reconstituted tobacco drying oven, characterized in that the heating control device of claim 1 or 2 is used, and comprises the following steps:
1) the control system detects the current production state, if the current production state is judged to be a preheating stage, the input steam pressure is the heating pipe pressure, the control system obtains a preset pressure value under the heating pipe condition through table lookup and calculation, and transmits the preset pressure value to the PID interlocking loop to adjust the steam valve;
if the current stage is judged to be the non-preheating stage, entering the step 2);
2) the control system judges whether the steam valve is in a normal production state, if the steam valve is in the normal production state, the step 3) is carried out, if the steam valve is in an abnormal production state, the control system judges whether the production is finished, and if the steam valve is judged to be finished, the control system controls the steam valve to be closed;
if judging that the non-production is finished, the control system returns to the step 1);
3) the control system reads the current production work vehicle speed data, obtains a corresponding hot air temperature value in a table look-up mode, calculates a preset pressure value under the condition, judges whether the preset pressure value is more than 20% of the total range of the pressure instrument, and if so, takes the preset pressure value as an input parameter to be switched into a slope control subprogram;
if not, judging whether the PID interlocking loop is automatically/manually switched, and if the loop is switched to a manual state, automatically tracking an opening signal before switching by the opening of the steam valve; if the switching is not performed, PID interlock loop control is performed.
4. The heating control method of the paper-making reconstituted tobacco drying oven according to claim 3, characterized in that the PID interlocking loop is a PID interlocking loop composed of a pressure instrument and a steam valve.
5. The heating control method of the paper-making reconstituted tobacco drying oven according to claim 3, characterized in that in the step 1), in order to prevent the output fluctuation of the PID interlocking loop, the control system takes the output value of the PID interlocking loop as the input parameter of a slope control subprogram, the control system switches to the slope control subprogram to perform the ascending slope control of the steam valve opening, and the return value of the slope control subprogram is used for the steam valve again.
6. The heating control method of the paper-making reconstituted tobacco drying box according to claim 3, characterized in that in the step 3), the PID interlocking loop is indirect PID interlocking control between a preset pressure value and the opening of a steam valve.
7. The heating control method of the paper-making reconstituted tobacco drying oven according to claim 3 or 6, characterized in that the preset pressure value firstly passes through an ascending/descending slope control subroutine, and the pressure return parameter after slope control enters a conventional PID interlocking loop to adjust the opening degree of the steam valve.
8. The heating control method of the paper-making reconstituted tobacco drying oven according to claim 3, wherein the control method of the slope control subroutine comprises the following steps:
1) comparing the preset pressure value with the last pressure output value, judging whether the difference value is greater than zero, and entering the step 2 if the difference value is not greater than zero);
if the difference is greater than zero, judging whether the difference is greater than a set ascending gradient value, if so, determining that the current pressure output value is the last pressure output value plus the ascending gradient value, entering a step 3), and if not, determining that the current pressure output value is the last pressure output value, and entering the step 3);
2) judging whether the absolute value of the difference is larger than the set descending gradient value or not, if not, the current pressure output value is equal to a preset pressure value, and entering the step 3); if yes, the current pressure output value is equal to the last pressure output value-descending gradient value, and the process goes to step 3);
3) the routine returns.
Technical Field
The invention belongs to the technical field of paper making of reconstituted tobacco, and particularly relates to a heating control device and method for a paper-making reconstituted tobacco drying box.
Background
The drying box equipment of the paper-making reconstituted tobacco production line is used for slowly baking the coated wet paper in a circulating hot air heating mode to obtain a soft and dry reconstituted tobacco finished product. The hot air in the drying box is heated by circulating air through a heat exchanger, the heating medium of the heat exchanger is steam, and the amount of the steam is adjusted through a steam valve arranged on a steam pipeline to control the temperature of the hot air.
In the production process of the paper-making reconstituted tobacco, the hot air temperature of the drying box plays a crucial role in the stability of the product quality, and the accurate and stable hot air temperature can effectively ensure the softness and the sensory quality of the product. The hot air temperature is too high, the wet paper after coating is accelerated to solidify the dip coating liquid, the coating liquid has poor penetration effect, the white core phenomenon of the product is easily caused, and the hot air temperature is too low, so that the wet paper cannot be effectively dried, and the sticking phenomenon of the product is easily caused.
Because the heat exchanger of the heating equipment usually adopts saturated steam to heat air, the stable and effective control of the steam quantity is not only the key of the hot air temperature control, but also the effective guarantee of the safe operation of the subsequent equipment. When the equipment is just started, the steam pipeline and the rear-stage heat exchanger are both cold, and if a large amount of steam is introduced instantly, water is easily generated in the pipeline to sag, so that a water hammer phenomenon is caused, great impact is brought to the pipeline and the heat exchange equipment, and the pipeline and the heat exchange equipment can be damaged in serious conditions. During the operation of the equipment, the phase change in the heat exchanger is easily caused by the large fluctuation of the introduced steam flow, the heat exchange quality is influenced, and the fluctuation of the hot air temperature is caused.
In order to avoid the fluctuation of the hot air temperature, in the prior art, for example, in chinese patent publication No. CN103383182A, a PID interlocking control mode of the hot air temperature and the steam valve is adopted, and since the temperature detecting instrument is installed on the circulating air duct, the influence of the adjustment of the steam valve on the temperature is delayed in this way, and the system control is prone to the repeated fluctuation phenomenon. And the temperature instrument installed in the air duct is easily influenced by hot air flow impact and product paper dust deposition, so that the detection data is deviated, vicious circle is controlled, and the product quality is seriously influenced.
In the publication No. CN103383182A, a traditional PID control algorithm is adopted for control, the control is simple, the fluctuation of the PID loop output under special conditions is not considered, when the output changes greatly, the opening of the steam valve changes greatly, which is likely to cause unstable temperature control, or water hammer phenomenon is generated to cause damage to related equipment, and the control method adopted in the patent is complicated in operation, and different hot air temperature values need to be set according to different process requirements (such as the change of the production speed).
Disclosure of Invention
The invention aims to provide a heating control device and a heating control method for a paper-making reconstituted tobacco drying box, and solves the problems that the control is not stable in the temperature control mode of the existing hot air drying box, so that the product quality control is not stable, and the operation of steam pipeline accessories and post-stage equipment is not safe.
The invention is realized by the following technical scheme:
a heating control device of a paper-making reconstituted tobacco drying box comprises a heat exchanger, a steam valve, a pressure instrument, a hot air drying box and a temperature instrument;
the steam pipeline is connected with the heating side inlet of the heat exchanger, and the heating side outlet of the heat exchanger is connected with the steam condensate water recovery pipeline;
the heated side of the heat exchanger is respectively connected with an air inlet and an air outlet of the hot air drying box through a circulating ventilation pipeline;
a steam valve and a pressure instrument are arranged on the steam pipeline;
a temperature instrument is arranged on a circulating ventilation pipeline between the heat exchanger and an air inlet of the hot air drying box;
the steam valve, the pressure instrument and the temperature instrument are all connected with a control system through electric signals.
The temperature instrument is used for displaying the hot air temperature in real time and referring to the hot air temperature without directly participating in control, the paper machine speed is used as a reading parameter of a control system and participates in linkage adjustment, the system automatically calculates and presets a required corresponding steam pressure value according to the current operating condition, the preset steam pressure value is connected into a PID linkage control loop formed by the pressure instrument and a steam valve, and the control loop outputs a signal for automatically adjusting the opening degree of the steam valve.
Use of the heating control device of
1) the control system detects the current production state, if the current production state is judged to be a preheating stage, the input steam pressure is the heating pipe pressure, the control system obtains a preset pressure value under the heating pipe condition through table lookup and calculation, and transmits the preset pressure value to the PID interlocking loop to adjust the steam valve;
if the current stage is judged to be the non-preheating stage, entering the step 2);
2) the control system judges whether the steam valve is in a normal production state, if the steam valve is in the normal production state, the step 3) is carried out, if the steam valve is in an abnormal production state, the control system judges whether the production is finished, and if the steam valve is judged to be finished, the control system controls the steam valve to be closed;
if judging that the non-production is finished, the control system returns to the step 1);
3) the control system reads the current production work vehicle speed data, obtains a corresponding hot air temperature value in a table look-up mode, calculates a preset pressure value under the condition, judges whether the preset pressure value is more than 20% of the total range of the pressure instrument, and if so, takes the preset pressure value as an input parameter to be switched into a slope control subprogram;
if not, judging whether the PID interlocking loop is automatically/manually switched, and if the loop is switched to a manual state, automatically tracking an opening signal before switching by the opening of the steam valve; if the switching is not performed, PID interlock loop control is performed.
The PID interlocking loop is a PID interlocking loop consisting of a pressure instrument and a steam valve.
In the step 1), in order to prevent output fluctuation of the PID interlocking loop, the control system takes the output value of the PID interlocking loop as an input parameter of a slope control subprogram, the slope control subprogram is switched to carry out ascending slope control on the opening of the steam valve, and the return value of the slope control subprogram is used for the steam valve again.
In the step 3), the PID interlocking loop is indirect PID interlocking control between a preset pressure value and the opening of the steam valve.
The preset pressure value firstly passes through an ascending/descending slope control subprogram, and the pressure return parameter after slope control enters a conventional PID interlocking loop to adjust the opening of the steam valve.
The control method of the slope control subroutine comprises the following steps:
1) comparing the preset pressure value with the last pressure output value, judging whether the difference value is greater than zero, and entering the
if the difference is greater than zero, judging whether the difference is greater than a set ascending gradient value, if so, determining that the current pressure output value is the last pressure output value plus the ascending gradient value, entering a step 3), and if not, determining that the current pressure output value is the last pressure output value, and entering the step 3);
2) judging whether the absolute value of the difference is larger than the set descending gradient value or not, if not, the current pressure output value is equal to a preset pressure value, and entering the step 3); if yes, the current pressure output value is equal to the last pressure output value-descending gradient value, and the process goes to step 3);
3) the routine returns.
The invention has the beneficial effects that:
because the hot air temperature measurement has certain error or instability, the control system only takes the hot air temperature value as a control reference to reflect the change state of the hot air. The system automatically matches the required actual temperature control value according to the current working speed of the equipment, the corresponding steam pressure values in different states are calculated and preset according to the temperature values, and the preset pressure values are connected into the PID control loop, so that on one hand, a large amount of manual operation can be saved, and the operation error is reduced, on the other hand, steam pressure is adopted to participate in PID interlocking control, the phenomena of long response time and control lag caused by direct participation of hot air temperature in control can be effectively avoided, and the phenomena of control error and instability caused by the influence of hot air flow and dust accumulated on product paper on temperature detection can be effectively avoided.
The rising slope control of the valve opening degree is adopted in the production preheating stage, steam can be slowly introduced, the steam pipe warming time is ensured, the water hammer phenomenon generated in the steam pipeline is avoided, and the cracking and the leakage of the rear-stage heat exchanger can be possibly caused in serious conditions.
In the production operation stage: in order to avoid the rapid change of the opening of the steam valve, the change slope control is adopted when the fluctuation of the preset value of the steam pressure is large, and the automatic tracking control is adopted when the PID linkage input is switched by mistake, so that the rapid fluctuation of the ventilation temperature is reduced, and the quality stability of the product is ensured.
Drawings
FIG. 1 is a flow chart of a heating control apparatus according to the present invention;
FIG. 2 is a logic diagram of the control method of the present invention;
FIG. 3 is a logic diagram of the control method of the slope control subroutine of the present invention.
Description of the reference numerals
1 steam valve, 2 pressure instrument, 3 temperature instrument, 4 heat exchangers, 5 hot air drying box, 6
Detailed Description
The technical solutions of the present invention are described in detail below by examples, and the following examples are only exemplary and can be used only for explaining and explaining the technical solutions of the present invention, but not construed as limiting the technical solutions of the present invention.
As shown in figure 1, the heating control device of the paper-making process reconstituted tobacco drying box provided by the application comprises a heat exchanger 4, a
According to the heating control method of the paper-making reconstituted tobacco drying box, the temperature instrument is used for displaying the air temperature of the drying box, the speed of the paper machine is used as the reading data of the system and directly participates in linkage adjustment, different working speeds correspond to different hot air temperatures according to process requirements, the automatic control system searches for corresponding temperature values according to current operating parameters, and further corresponding steam pressure values are automatically calculated and preset.
The pressure instrument and the steam valve are subjected to PID interlocking control, the control system performs comparison operation according to an automatically preset pressure value and a real-time read pressure value, the opening of the steam valve is controlled according to an output result, when the steam pressure value is far smaller than a preset value, the opening of the steam valve is increased, and when the steam pressure value is close to the preset value, the steam valve is closed.
The control system automatically detects the production running state, and adopts different control measures including a production preheating stage and a production running stage according to different production running states.
A production preheating stage: after the preset pressure value is connected into the PID loop, the output of the loop does not directly act on the steam valve, but the output of the PID loop is used as an intermediate value and is controlled according to a certain rising slope, and the result after slope control acts on the steam valve to automatically control the opening of the valve.
And (3) production operation stage: when the control system detects that the fluctuation amount of the preset pressure value and the last preset value is more than 20% of the measuring range of the pressure instrument, the change slope control of the preset value is carried out, and the value after the slope control is used as the input parameter of the PID loop to be controlled. When the control system detects that the PID loop has mode (automatic input/release) switching, the system automatically tracks, the PID loop output value before mode switching is used as direct output to act on a steam valve, and the control output is carried out according to the normal PID loop under other normal states.
The specific control method comprises the following steps:
a heating control method of a paper-making reconstituted tobacco drying oven uses any one of the heating control devices, and comprises the following steps:
before control, circulating hot air temperature values corresponding to different production working speeds are required to form a temperature corresponding table and stored in a control system for the control system to call, and meanwhile, the control system also stores an empirical calculation formula of the hot air temperature values and corresponding steam pressure values, so that the steam preset pressure required under different conditions can be calculated in real time conveniently. Therefore, the preset steam pressure value can be obtained by looking up the table and calculating according to the production working speed.
1) The control system detects the current production state, if the current production state is judged to be a preheating stage, the production is in a standby state at the moment, the effective working speed is 0, the input steam pressure is the heating pipe pressure at the moment, the control system obtains a preset pressure value under the heating pipe condition through table lookup and calculation, and transmits the preset pressure value to a PID (proportion integration differentiation) interlocking loop to adjust a steam valve; when the actual pressure value is far smaller than the preset value, the opening of the valve is increased, when the actual pressure value is close to the preset value, the opening of the valve is reduced, in order to prevent the PID interlocking loop from outputting fluctuation to cause that the steam valve is opened too much instantly, the PID interlocking loop output value is used as an input parameter of a slope control subprogram in the control, the subprogram is switched in to carry out the ascending slope control of the opening of the valve, and the return value of the subprogram is used for the steam valve again, so that the steam valve is changed linearly and slowly.
If the current stage is judged to be the non-preheating stage, entering the step 2);
2) the control system judges whether the production is in a normal production state, if the production is in a normal production state, the step 3) is carried out, if the production is in an abnormal production state, the control system judges whether the production is finished, and if the production is finished, the control system controls the steam valve to be closed.
If judging that the non-production is finished, the control system returns to the step 1);
3) the control system reads the current production work vehicle speed data, obtains a corresponding hot air temperature value in a table look-up mode, calculates a preset pressure value under the condition, judges whether the preset pressure value is more than 20% of the total range of the pressure instrument, and if so, transfers the preset pressure value as an input parameter into a slope control subprogram; in order to prevent the repeated fluctuation of a preset pressure value caused by the too fast change of the vehicle speed and finally cause the repeated change of the phase state of steam in the heat exchanger to influence the heat exchange quality, the preset steam pressure parameter and the opening of a steam valve are subjected to indirect PID interlocking control. The preset pressure value firstly passes through an ascending/descending slope control subprogram, and the pressure return parameter after slope control enters a conventional PID control loop to adjust the steam valve.
If not, judging whether the PID interlocking loop is automatically/manually switched, and if the loop is switched to a manual state, automatically tracking the opening signal before switching by the opening of the steam valve; if the switching is not performed, PID interlock loop control is performed.
The PID interlocking loop is a PID interlocking loop consisting of a pressure instrument and a steam valve.
In the step 1), in order to prevent the output fluctuation of the PID interlocking loop, the control system takes the output value of the PID interlocking loop as the input parameter of a slope control subprogram, the slope control subprogram is switched to carry out the ascending slope control of the opening of the steam valve, and the return value of the slope control subprogram is used for the steam valve again.
In the step 3), the PID interlocking loop is indirect PID interlocking control between a preset pressure value and the opening of the steam valve.
The preset pressure value firstly passes through an ascending/descending slope control subprogram, and the pressure return parameter after slope control enters a conventional PID interlocking loop to adjust the opening of the steam valve.
The control method of the slope control subprogram comprises the following steps:
the input parameter of the subroutine is the pressure set value, and the slope control parameter is 20/100 (maximum value of the pressure meter engineering-minimum value of the pressure meter engineering), i.e. 20% of the total measuring range of the pressure meter.
1) Comparing the preset pressure value with the last pressure output value, judging whether the difference value is greater than zero, and entering the
if the difference is greater than zero, judging whether the difference is greater than a set ascending gradient value, if so, determining that the current pressure output value is the last pressure output value plus the ascending gradient value, entering a step 3), and if not, determining that the current pressure output value is the last pressure output value, and entering the step 3);
2) judging whether the absolute value of the difference is larger than the set descending gradient value or not, if not, the current pressure output value is equal to a preset pressure value, and entering the step 3); if yes, the current pressure output value is equal to the last pressure output value-descending gradient value, and the process goes to step 3);
3) the routine returns.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
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