The computer management system of cotton processing mainly consists of two parts: the process monitoring system and the cotton processing automatic control system.
(1) Ginning process monitoring system
Characteristics of the monitoring system used in ginning plants:
(1) The main control user can manage multiple signals at the same time; one channel or one channel can be observed at the same time through the screen splitter Multiplex screen.
(2) Through the control keyboard, many variable lenses can be controlled to stretch, focus and other actions to achieve close-up and panoramic observation of the monitored objects.
(3) The horizontal and pitch rotation of the machine can be controlled through the control keyboard, making it easier to find the object to be observed.
(4) Use hard disk recording to save historical images.
(5) The image quality reaches TV level or VCD effect.
The digital video surveillance system of the ginning plant is shown in Figure 6-11.
(2) Cotton processing automatic control system
The cotton processing automatic control system currently mainly includes online control of sub-cotton drying, online control of lint humidification and online testing devices for cotton bale moisture regain.
Online control of cotton drying and lint humidification uses an infrared moisture tester to detect the moisture content of cotton online. The test results are transmitted to the console in the control room. The automation equipment in the console automatically adjusts the drying of cotton based on the moisture content. Machine or lint humidifier can keep the moisture content of lint at 7% to 8% (can be adjusted based on experience). At the same time, the console can also issue instructions to control the speed of the gin to achieve the best processing effect.
The cotton bale moisture regain online testing device is an intelligent product specially developed to adapt to the reform requirements of the cotton quality inspection system and to automatically detect the moisture regain of cotton bales online for cotton processing plants. It can be used with barcode systems, IC card code single systems, and drying systems. Integrate dry systems. The test device is designed using the relationship between cotton moisture regain and its resistance. There are two types of sensing heads: ring type and pin type, but their design principles and circuit structures are exactly the same, and the software processes are slightly different.
(3) Design principles of online moisture testing and control devices
The relatively mature technology for online testing of cotton and lint moisture and online testing devices for moisture regain of cotton bales is infrared moisture measurement technology. The design principles and circuit structures of the two are exactly the same, but the software processes are slightly different.
1. Electrical conductivity of cotton fiber
The electrical conductivity of fiber is generally expressed by mass specific resistance ρ m. When the relative air humidity is 30% to 90%, the mass specific resistance ρm and the moisture regain W have the following approximate relationship:
Where: t——temperature, ℃.
2. The effect of temperature on the conductive properties of cotton fiber
The resistance of water-containing cotton fiber decreases as the temperature increases, where the rate of change of lgρ to temperature varies with the moisture regain rate and temperature. The moisture regain of cotton fiber The greater the moisture regain rate of cotton fiber, the greater the influence of temperature on it. The lower the moisture regain rate of cotton fiber, the smaller the influence of temperature on it.
Years of experience show that the moisture regain is above 7%. Taking 20℃ as the benchmark, for every 1℃ increase in cotton fiber temperature t, the moisture regain is corrected by -0.1%, and for every 1℃ decrease in cotton fiber temperature, the moisture regain is corrected by +0.1 %, correction value C=0.1×(20-t)
In the formula: C————Cotton fiber moisture regain correction coefficient;
t——Temperature, ℃.
When the moisture regain is below 7%, in an environment lower than 20℃, temperature compensation shall be carried out according to the moisture regain temperature compensation table. In an environment higher than 20℃, the temperature compensation shall still be carried out according to the above formula.
3. Testing principle
Each molecular bond can absorb near-infrared light energy of a certain fixed wavelength. For example, O—H bonds in water molecules, C—H bonds in oils and organic matter, N—H bonds in proteins, etc. The degree of absorption of near-infrared light energy of a certain fixed wavelength by an object reflects the proportion of the corresponding component in the object. The probe continuously emits a series of beams through the infrared filter, part of which is absorbed by the object under test, and the remaining unabsorbed beams are reflected. These reflected infrared rays can be focused on the detector. Electronic components within the probe shape the light beam collected by the detector into a value that indicates the proportion of a certain component.
In short, first measure the moisture regain of cotton bales, and then make temperature corrections to get the final correct moisture regain.
4. Technical requirements
(1) Measuring range: The reading measured by the device is the moisture regain of the cotton bale. The measuring range is 4% to 7% in the middle layer and 7% to 13% in the lower layer.
(2) DC working voltage: 90V±2V for the middle layer test circuit and 45V±2V for the lower layer test circuit.
(3) Cotton bale density: Cotton bale density should comply with the requirements of GB/T19820-2005 standard.
(4) Measurement accuracy: Use calibration resistors to verify, and the accuracy should meet the following requirements:
(5) Temperature test range: -30～40℃.
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