Advanced optimization control application for milk powder concentration and drying
Category:
Intelligent control system
Information description:
In the production of milk powder, the dry process and the wet process, the concentrated and dry process in the wet process is the key process of the milk powder production process. The working principle of concentration is to use the indirect steam heating method under the vacuum of 20~80 kPa under negative pressure to heat the milk, so that the water is continuously vaporized and discharged, and the dry matter content in the milk is increased from 12% to 50%. To achieve the purpose of concentration. The working principle of drying is that the hot air sent to the drying chamber is in contact with the concentrated atomized droplets, and after a short heat exchange process, the moisture of the droplets is instantaneously evaporated. The droplets are dried to a milk powder with a water content of 3% to 5%, and the water vapor is taken away by hot air. The milk powder concentration process control generally adopts the PLC/DCS automatic control system, which is monitored and controlled by the operator. In this process, the dry matter content of the concentrated discharge will be affected by many factors such as the dry matter content of the milk, the steam temperature and flow rate, and the degree of vacuum. The process is complicated.
These factors and the level of the operator in the production process will affect the control of the concentration of concentrated dry matter. Univariate PID control does not completely eliminate the effects of these disturbances. APC can provide the factory with more control methods such as feedforward control, decoupling control, and model prediction. Help the plant to increase the stability of concentrated dry matter content through the APC controller. The fluctuation of dry matter content is reduced, the factory can increase the target value of concentrated dry matter content, increase the heat exchange efficiency of the concentrated evaporator, and save energy. In addition, the total output of the dryer can be increased. For example, if the concentration of dry matter in the evaporator is increased by 0.5%, the output of the dryer can be increased by 2%.
During the drying process, the moisture content of the finished milk powder is affected by factors such as dry matter content of the concentrated material, lactose content, hot air temperature, humidity, and pressure. The APC controller can help improve the stability of the water content of the milk powder. The factory can increase the average moisture content of the milk powder in the standard range, and pursue the quality stability, the production edge and the best benefit. A 50,000-ton/year milk powder production line, with an increase in moisture of 0.2-0.3% milk powder, has an economic benefit of several million yuan/year.
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