Cane sugar can be generally divided into caramel, glycol, triose and the like. Carbohydrates, also commonly known as white sugar, are in the form of granules. According to the national standard GB317-1998, the equivalent diameter of the formazan crystal is generally 0.28~2.5mm. The final step in the production of sugar is to separate the crystals from the massecuite using a centrifuge. The separation equipment used is numerous, complex and varied in performance.
1 Types of commonly used white sugar centrifuges
Commonly used white sugar separation equipment is divided into continuous type and intermittent type. There are various types of domestic or imported automatic, semi-automatic and manual. Generally, the above-mentioned suspended batch centrifuge is widely used. There are a variety of models for the upper suspension centrifuge. According to the shape of the drum, it can be divided into two types: flat bottom and cone bottom. According to the unloading method, it can be divided into three types: gravity unloading, manual unloading, and mechanical scraping. Can be divided into multi-speed motors, DC motors, variable frequency speed control, resistance shifting and many other; operating control methods are also electrical, gas-liquid, mechanical and other methods. Suitable for the separation of medium particle solids suspensions such as sugar, monosodium glutamate, glucose, salt and polyvinyl chloride resins.
Guangxi is a sugar-producing province of sugar cane in China. It has a large number of white sugar producers. The centrifuges currently used are: Imported models: Broadbent fully automatic overhangs imported from the UK. These models are computer controlled, pneumatically driven, and scraped, with high reliability and productivity, but at a relatively high price. At present, domestic manufacturers have cooperated with British Broadbent to develop similar products, such as TBS fully automatic suspension batch centrifuge.
Domestic models: There are fully automatic, semi-automatic and manual-type over-suspension batch centrifuges in domestic models. The automatic type has XJZ, XZ, XR and other types, and most of them use multi-speed motor, AC frequency conversion speed control and other drag forms. For historical reasons, the manual type upper suspension centrifuge has a large possession in Guangxi sugar production enterprises, and the ZL-1200 type is one of the typical models. The ZL-1200 model is taken as an example to introduce the structure and use characteristics of the manual type upper suspension centrifuge, and to upgrade the automation technology of this type of machine in order to reduce labor intensity, improve product quality, improve machine reliability and production efficiency. Happening.
2 Manual type upper suspension centrifuge structure and use characteristics
The ZL-1200 over-suspension centrifuge is a manual-operated vertical batch centrifuge with a conical bottom, gravity unloading, multi-speed motor tow drive, and pneumatic actuator. The working part of the centrifuge is a hanging blue, which is driven by a multi-speed motor to achieve speed switching of multiple gears (including 4 gears in neutral).
The working process of the machine is: manually turn on the motor to the first speed, clean the screen with a flushing pipe, and then open the feeding switch. The pneumatic sugar paste gate is opened to realize the feeding. After the feeding is enough, the feeding switch is manually closed. Honey, after a period of time, switch to the second speed and continue to divide the honey and wash the water manually (water temperature 70~80 °C). In the process of completing the production cycle, the centrifuge needs to collect two different sugar-containing honey juices. The water is separated from the raw honey with higher sugar content, and the honey-water separation mechanism is set by the cylinder to be “original honeyâ€. State, when washing water, the honey water separation mechanism needs to be switched from "original honey" to "washing honey" state [1]. Observe the length of the washing water by observing the color of the white sugar, then manually switch to the third speed, and manually open the steam valve, steam wash with high temperature steam, continuously separate for several minutes after the steam washing is completed, and then step back to the first step by step. The speed of the gear is braked, the discharge switch is opened, the cylinder lifts the blue cover, and the caramel is discharged under gravity to the vibrating screen at the lower part of the centrifuge to complete the entire cycle. Generally, about 500 kg of sugar paste is fed each time, and an operation cycle takes about 3.5 to 5 minutes.
In the production process, the process of rinsing the filter screen, feeding, steam washing, separation, etc., including the motor speed gear position adjustment are all manually controlled. The length of operation is generally judged according to the operator's experience, due to the cutting into different speed gears. The motor is constantly accelerating or decelerating, and the operator also needs to control the operating moments of some actions according to different speeds. Since the manual model control system does not need to detect the motion state of the actuator itself, the accuracy of the actuator manufacturing requirements is relatively low (such as a large pin gap), so the equipment is simple in structure and low in price. However, due to the low precision of the motion of the mechanism, the swing is large and continuous monitoring is required, resulting in high labor intensity, unstable production speed and product quality.
3 manual type upper suspension centrifuge automation technology upgrade
According to the structure and use characteristics and deficiencies of the ZL-1200 type supersuspension centrifuge, in order to improve the degree of automation, improve reliability and productivity, it can be upgraded with automation technology. Technical transformation strives for low cost, retains and perfects manual operation without changing the main structure of the machine, increases the automatic operation mode, can be converted manually and automatically and can modify the operating parameters online. The main points of automation transformation are:
1) Manufacture of automatic controller: It is required to set the time of each process online on the operation display screen, and can display the real-time working state of each process, and realize the fully automatic cycle operation of the combined control of electric, pneumatic and mechanical control of the whole machine.
The working condition of the white sugar separator is relatively harsh. The use of water washing and steam washing causes the working environment temperature and humidity to be large; the viscosity and corrosiveness of the honey water in the sugar paste easily cause the control element to fail; the frequent change of the drag motor Blocking, shifting, causing serious electromagnetic interference and so on. A fully enclosed, integrated form of controller can be used. When retrofitting, the PLC of Japan Matsushita Co., Ltd. is used as the core control device. The manual, automatic switch and knob are set on the operation panel of the automatic controller, and the touch buttons for inputting/modifying the operating parameters are set. The liquid crystal display is used to display the operating state parameters such as the speed and time of the centrifuge.
2) Drag mode: keep the multi-speed motor drag drive mode of the centrifuge unchanged, and control the speed gear switch by the PLC control system.
3) Processing of the actuator: Most of the actuators of the original machine use cylinders as the driving device, such as feed gate mechanism, brake mechanism, unloading mechanism, honey water separation mechanism, etc., a small amount of direct manual action, such as anti-drip bucket, washing Steam washing valve, etc. In the actual transformation, for the original pneumatic actuator, the electrical signal of the original control pneumatic valve can be switched to the PLC output port. Some models use a 220 volt AC double solenoid valve to directly match the PLC and reduce The number of output ports was changed to a two-position four-way spring return type 24 volt DC single electromagnet valve.
Increase the automatic washing circuit: When adjusting the washing position and time by manual washing, during the actual transformation, a large number of tests were made to make a washing water pipe with 5 high-pressure atomizing nozzles, and the water washing valve was directly controlled by PLC.
Increase the anti-drip door mechanism: Due to the viscosity of the sugar paste, after the feed door is closed, the residual sugar paste in the introduction slot after the feed gate will continuously drop into the hanging blue, causing the value of the color sugar value to exceed the standard. Generally, a tray is used for manual operation, and a pneumatic anti-drip door mechanism is added during the transformation. In the process of separating the sugar paste, the anti-drip bucket is used to catch the residual sugar paste, and the anti-drip bucket is driven by the cylinder during the feeding, and the residual sugar will be caught. Pour the paste into the hanging blue.
4) Add various detection and sensing devices: In order to realize the coordination of each action, position sensors are needed to detect the state of each actuator. Because the manual type has the characteristics of low precision of the actuator and low motion accuracy, to prevent The sensor is faulty and leaking, and the setting of the sensor is very important. It must be set at a position where the motion relationship is relatively determined and reproducible according to the action characteristics of the specific mechanism.
Detection of the loading amount of the confectionery: When manually operated, the amount of the confectionery into the hanging blue is controlled by manual observation, and automatic measurement is required in the automatic mode. It is generally possible to design a sugar paste measuring device using the principle of electrode detection resistance change and direct mechanical triggering. The electrode type measuring device is liable to cause malfunction due to the influence of the fluctuation of the conductivity of the sugar paste; the mechanical type has high reliability because the position of the confectionery is directly detected. Figure 1 is a schematic diagram of the installation of a mechanical sugar paste measuring instrument [2] designed during the technical upgrade process. The measuring instrument is mounted on the centrifuge casing 5, and the detecting plate 3 is close to the inner wall of the hanging blue 4, and the hanging blue with the shaft 1 Rotate, so that the incoming massecuite is evenly distributed in the hanging blue due to the centrifugal force. As the feeding increases, the sugar paste is thickened, the sugar paste line is continuously moved outward, and finally the probe plate is contacted, and the detecting plate is rotated around the rotating shaft to drive the sensing block movement. The proximity switch 2 is triggered to generate a full signal, the PLC outputs a closing signal, and the feed gate is closed under the driving of the cylinder. Adjusting the distance between the detector plate and the inner wall of the sling can control the amount of sugar that enters the sling. The meter's detection status is set and reset by the internal small cylinder drive.
Motor speed detection: Motor speed is an important parameter in the control process. In the automatic mode operation, it is necessary to control the speed gear position and process switching according to the motor speed. It can be measured by the method of pulse counting. Two iron sensing blocks rotating with the rotating shaft are installed at the top rotating shaft of the multi-speed motor, and the proximity switch sends an induction signal, and the PLC calculates the motor rotation speed according to the input pulse.
Brake detection: Discharge must be guaranteed after a reliable brake. Whether the reliable brake is detected is that after the brake cylinder action signal is output, if the measured value of the speed measuring device within 10 seconds (adjustable) is not zero, the system determines that the brake has failed.
The controller is connected to external input components (sensors) and output components (such as air valves, water valves, steam valve coils) through shielded cables.
After the electrical control and mechanical parts have been modified, the test machine can be carried out. The process and control process of the caramel separation in the automatic mode of the centrifuge is shown in Figure 2.
At the beginning of the cycle, the PLC accepts the signals sent by the field master signal, speed detection unit, position sensor, etc., and then logically judges, then issues instructions according to the programmed process to control the motor speed and the actuators. Among them, the length of the washing time is adjusted according to the blockage of the screen; when the washing valve is energized, the PLC simultaneously outputs a signal to the valve of the honey water separating mechanism, and the mechanism is switched from the "original honey" to the "washing honey" state; According to the speed, the switching timing of the motor downshift gear is controlled to avoid overheating of the motor. The operation is generally advanced. Manual operation, after the machine is running normally, the automatic mode is cut into the line in one cycle, and the automatic cycle operation is performed.
1 Types of commonly used white sugar centrifuges
Commonly used white sugar separation equipment is divided into continuous type and intermittent type. There are various types of domestic or imported automatic, semi-automatic and manual. Generally, the above-mentioned suspended batch centrifuge is widely used. There are a variety of models for the upper suspension centrifuge. According to the shape of the drum, it can be divided into two types: flat bottom and cone bottom. According to the unloading method, it can be divided into three types: gravity unloading, manual unloading, and mechanical scraping. Can be divided into multi-speed motors, DC motors, variable frequency speed control, resistance shifting and many other; operating control methods are also electrical, gas-liquid, mechanical and other methods. Suitable for the separation of medium particle solids suspensions such as sugar, monosodium glutamate, glucose, salt and polyvinyl chloride resins.
Guangxi is a sugar-producing province of sugar cane in China. It has a large number of white sugar producers. The centrifuges currently used are: Imported models: Broadbent fully automatic overhangs imported from the UK. These models are computer controlled, pneumatically driven, and scraped, with high reliability and productivity, but at a relatively high price. At present, domestic manufacturers have cooperated with British Broadbent to develop similar products, such as TBS fully automatic suspension batch centrifuge.
Domestic models: There are fully automatic, semi-automatic and manual-type over-suspension batch centrifuges in domestic models. The automatic type has XJZ, XZ, XR and other types, and most of them use multi-speed motor, AC frequency conversion speed control and other drag forms. For historical reasons, the manual type upper suspension centrifuge has a large possession in Guangxi sugar production enterprises, and the ZL-1200 type is one of the typical models. The ZL-1200 model is taken as an example to introduce the structure and use characteristics of the manual type upper suspension centrifuge, and to upgrade the automation technology of this type of machine in order to reduce labor intensity, improve product quality, improve machine reliability and production efficiency. Happening.
2 Manual type upper suspension centrifuge structure and use characteristics
The ZL-1200 over-suspension centrifuge is a manual-operated vertical batch centrifuge with a conical bottom, gravity unloading, multi-speed motor tow drive, and pneumatic actuator. The working part of the centrifuge is a hanging blue, which is driven by a multi-speed motor to achieve speed switching of multiple gears (including 4 gears in neutral).
The working process of the machine is: manually turn on the motor to the first speed, clean the screen with a flushing pipe, and then open the feeding switch. The pneumatic sugar paste gate is opened to realize the feeding. After the feeding is enough, the feeding switch is manually closed. Honey, after a period of time, switch to the second speed and continue to divide the honey and wash the water manually (water temperature 70~80 °C). In the process of completing the production cycle, the centrifuge needs to collect two different sugar-containing honey juices. The water is separated from the raw honey with higher sugar content, and the honey-water separation mechanism is set by the cylinder to be “original honeyâ€. State, when washing water, the honey water separation mechanism needs to be switched from "original honey" to "washing honey" state [1]. Observe the length of the washing water by observing the color of the white sugar, then manually switch to the third speed, and manually open the steam valve, steam wash with high temperature steam, continuously separate for several minutes after the steam washing is completed, and then step back to the first step by step. The speed of the gear is braked, the discharge switch is opened, the cylinder lifts the blue cover, and the caramel is discharged under gravity to the vibrating screen at the lower part of the centrifuge to complete the entire cycle. Generally, about 500 kg of sugar paste is fed each time, and an operation cycle takes about 3.5 to 5 minutes.
In the production process, the process of rinsing the filter screen, feeding, steam washing, separation, etc., including the motor speed gear position adjustment are all manually controlled. The length of operation is generally judged according to the operator's experience, due to the cutting into different speed gears. The motor is constantly accelerating or decelerating, and the operator also needs to control the operating moments of some actions according to different speeds. Since the manual model control system does not need to detect the motion state of the actuator itself, the accuracy of the actuator manufacturing requirements is relatively low (such as a large pin gap), so the equipment is simple in structure and low in price. However, due to the low precision of the motion of the mechanism, the swing is large and continuous monitoring is required, resulting in high labor intensity, unstable production speed and product quality.
3 manual type upper suspension centrifuge automation technology upgrade
According to the structure and use characteristics and deficiencies of the ZL-1200 type supersuspension centrifuge, in order to improve the degree of automation, improve reliability and productivity, it can be upgraded with automation technology. Technical transformation strives for low cost, retains and perfects manual operation without changing the main structure of the machine, increases the automatic operation mode, can be converted manually and automatically and can modify the operating parameters online. The main points of automation transformation are:
1) Manufacture of automatic controller: It is required to set the time of each process online on the operation display screen, and can display the real-time working state of each process, and realize the fully automatic cycle operation of the combined control of electric, pneumatic and mechanical control of the whole machine.
The working condition of the white sugar separator is relatively harsh. The use of water washing and steam washing causes the working environment temperature and humidity to be large; the viscosity and corrosiveness of the honey water in the sugar paste easily cause the control element to fail; the frequent change of the drag motor Blocking, shifting, causing serious electromagnetic interference and so on. A fully enclosed, integrated form of controller can be used. When retrofitting, the PLC of Japan Matsushita Co., Ltd. is used as the core control device. The manual, automatic switch and knob are set on the operation panel of the automatic controller, and the touch buttons for inputting/modifying the operating parameters are set. The liquid crystal display is used to display the operating state parameters such as the speed and time of the centrifuge.
2) Drag mode: keep the multi-speed motor drag drive mode of the centrifuge unchanged, and control the speed gear switch by the PLC control system.
3) Processing of the actuator: Most of the actuators of the original machine use cylinders as the driving device, such as feed gate mechanism, brake mechanism, unloading mechanism, honey water separation mechanism, etc., a small amount of direct manual action, such as anti-drip bucket, washing Steam washing valve, etc. In the actual transformation, for the original pneumatic actuator, the electrical signal of the original control pneumatic valve can be switched to the PLC output port. Some models use a 220 volt AC double solenoid valve to directly match the PLC and reduce The number of output ports was changed to a two-position four-way spring return type 24 volt DC single electromagnet valve.
Increase the automatic washing circuit: When adjusting the washing position and time by manual washing, during the actual transformation, a large number of tests were made to make a washing water pipe with 5 high-pressure atomizing nozzles, and the water washing valve was directly controlled by PLC.
Increase the anti-drip door mechanism: Due to the viscosity of the sugar paste, after the feed door is closed, the residual sugar paste in the introduction slot after the feed gate will continuously drop into the hanging blue, causing the value of the color sugar value to exceed the standard. Generally, a tray is used for manual operation, and a pneumatic anti-drip door mechanism is added during the transformation. In the process of separating the sugar paste, the anti-drip bucket is used to catch the residual sugar paste, and the anti-drip bucket is driven by the cylinder during the feeding, and the residual sugar will be caught. Pour the paste into the hanging blue.
4) Add various detection and sensing devices: In order to realize the coordination of each action, position sensors are needed to detect the state of each actuator. Because the manual type has the characteristics of low precision of the actuator and low motion accuracy, to prevent The sensor is faulty and leaking, and the setting of the sensor is very important. It must be set at a position where the motion relationship is relatively determined and reproducible according to the action characteristics of the specific mechanism.
Detection of the loading amount of the confectionery: When manually operated, the amount of the confectionery into the hanging blue is controlled by manual observation, and automatic measurement is required in the automatic mode. It is generally possible to design a sugar paste measuring device using the principle of electrode detection resistance change and direct mechanical triggering. The electrode type measuring device is liable to cause malfunction due to the influence of the fluctuation of the conductivity of the sugar paste; the mechanical type has high reliability because the position of the confectionery is directly detected. Figure 1 is a schematic diagram of the installation of a mechanical sugar paste measuring instrument [2] designed during the technical upgrade process. The measuring instrument is mounted on the centrifuge casing 5, and the detecting plate 3 is close to the inner wall of the hanging blue 4, and the hanging blue with the shaft 1 Rotate, so that the incoming massecuite is evenly distributed in the hanging blue due to the centrifugal force. As the feeding increases, the sugar paste is thickened, the sugar paste line is continuously moved outward, and finally the probe plate is contacted, and the detecting plate is rotated around the rotating shaft to drive the sensing block movement. The proximity switch 2 is triggered to generate a full signal, the PLC outputs a closing signal, and the feed gate is closed under the driving of the cylinder. Adjusting the distance between the detector plate and the inner wall of the sling can control the amount of sugar that enters the sling. The meter's detection status is set and reset by the internal small cylinder drive.
Motor speed detection: Motor speed is an important parameter in the control process. In the automatic mode operation, it is necessary to control the speed gear position and process switching according to the motor speed. It can be measured by the method of pulse counting. Two iron sensing blocks rotating with the rotating shaft are installed at the top rotating shaft of the multi-speed motor, and the proximity switch sends an induction signal, and the PLC calculates the motor rotation speed according to the input pulse.
Brake detection: Discharge must be guaranteed after a reliable brake. Whether the reliable brake is detected is that after the brake cylinder action signal is output, if the measured value of the speed measuring device within 10 seconds (adjustable) is not zero, the system determines that the brake has failed.
The controller is connected to external input components (sensors) and output components (such as air valves, water valves, steam valve coils) through shielded cables.
After the electrical control and mechanical parts have been modified, the test machine can be carried out. The process and control process of the caramel separation in the automatic mode of the centrifuge is shown in Figure 2.
At the beginning of the cycle, the PLC accepts the signals sent by the field master signal, speed detection unit, position sensor, etc., and then logically judges, then issues instructions according to the programmed process to control the motor speed and the actuators. Among them, the length of the washing time is adjusted according to the blockage of the screen; when the washing valve is energized, the PLC simultaneously outputs a signal to the valve of the honey water separating mechanism, and the mechanism is switched from the "original honey" to the "washing honey" state; According to the speed, the switching timing of the motor downshift gear is controlled to avoid overheating of the motor. The operation is generally advanced. Manual operation, after the machine is running normally, the automatic mode is cut into the line in one cycle, and the automatic cycle operation is performed.
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