| Generally, the production process of electrolytic aluminium is divided into three stages: baking electrolyzer, setting up and regular production in present electrolytic aluminium industry. In these three stages, the first stage, which lasts about 3~4 days, is shorter than the other two stages, but it influences the life-span of electrolyzer directly, and accordingly influnces the economic benefits of electrolytic aluminium factory. At present, three main ways are employed to bake electrolyzer in our country: baking with melted aluminium, baking with coke-ash and baking with graphite. As a matter of fact, the previous ways belong to resistance-heated method. Because of uneven heating and some other causes, these methods have a great harm to the life-span of electrolyzer.In this paper, the shortcomings of these three methods were analyzed at first, and then a new method, which was called fuel-direct-baking method, and its control system was put forward, in combination with the research situation in this field home and abroad. The whole system has been applied in the No. 1 Branch electrolytic aluminium factory of Shanxi Xiezhou Guanlu Co.Ltd and good results have been obtained. The main research contents and results are shown as follows:(1) In order to meet the actural need of this research project, the general ways to bake electrolyzer, which include Aluminium-liquor- baking method, coke-ash-baking method and graphite-powder-baking method, are introduced in details. Their shortcomings and effects on the life-span of electrolyzer are also analyzed.(2) On the basis of the actural condition of the electrolytic factory, Fuel-direct-baking method is put forward, and its mechanism and advantages are analyzed as well.(3) According to the characteristics such as great difficulties in data acquisition on spot, severe environment, and many interfering factors, a new control system with high reliability and high anti-jamming capacity has been designed.(4) Hardware composition of the control system is presented according to the whole project. The following aspects such as the configuration of PLC's hardware, memory organization, PLC's running principle, and wiring terminals of frequency converter of fan-machine and oil pump are emphasized. In addition, the whole system's wiring chart is explained at the last part of this paper.(5) Due to the limitation of traditional PID algorithm, expert PID control algorithmis employed. The principle of expert system is introduced at first, and then the realization of expert controller is presented.(6) The fulfillment of software of fuel-direct-baking method is introduced in details.The OMRON PLC's instruction system and the programs realized with this instruction system are also set forth. |
