Design of control system in HDT tobacco dryer based on constant dehydration amount

In order to alleviate the fluctuation of moisture content in cut tobacco out of HDT dryer and stabilize processing hot air temperature, a control system based on constant dehydration amount was proposed. The throughput regulation of cut tobacco was linked to the moisture contents in input and output tobacco in a cascade way to keep the actual dehydration amount identical with the set amount. When the moisture content in input tobacco fluctuated, the system regulated the input rate of cut tobacco accordingly on the basis of the moisture content deviation to keep a constant dehydration amount of the dryer and stabilize the moisture content in output tobacco. The cut tobacco for manufacturing cigarettes of brand "Yun Yan (Purple)" was tested in Qujing Cigarette Factory, the results showed that the standard deviation of moisture content in output tobacco decreased from 0.25% to 0.073%, that of processing hot air temperature decreased from 1.73 to 0.35℃; the consumption of natural gas reduced from 85.65 to 79.34 m³/batch, and 25 RMB yuans production cost were saved per batch. This method provides a technical support for improving the control precision of moisture content in output tobacco and reducing energy consumption.