Intelligent Control System Of Electro-fused Magnesia Furnace

Electric fused magnesium is a kind of refractory materials with the characteristics of high melting point, corrosion resistance, good insulation and good slag resistance. Electrical Fused magnesium is widely used in metallurgical industry, glass industry, cement industry, nonferrous metal smelting industries and so on. The most simply and directly method of producing electrical fused magnesium is electric melting. Electric fused magnesium furnace is the core equipments to produce electric fused magnesium and is a kind of high energy-consuming quipments. Energy consumption per production refers to the consumption of electric energy to produce one ton of qualified fused magnesia and is a production index to character energy-consuming for producing qualified fused magnesia.Therefore, decreasing energy consumption per production is important to realize reducing energy consumption of electric fused magnesium furnace production process and improving production efficiency.Energy consumption per production index of electric fused magnesium furnace production process is influenced by maximum power demand, electrode melting current, electrode diameter, electrode circle diameter, particle size of raw material, quality of furnace body and so on. The strong nonlinear relation exists between energy consumption per production index and electrode melting current. It is difficult to describe the relation with mathematic model. The index cann’t be measured on-line and change with perpoties of raw materials and furnace condition. The strong nonlinear relation exists between melting current and the position of electrode. Between of the three-phase electrode melting current is strong coupled. The production dynamic characteristics changes with adding materials, exhausting, normal melting and abnormal melting furnace condition. It is difficult to use the existing control method to realize the automatic control of melting current. The melting current setting and control are still in the manual control mode. When furnace condition changes, it is difficult for operator to adjust electrode positon timly and accuatly. Melting current is volatile. Sometimes, melting current exceeds the maximum power demand and the maximum melting current equipment capacity allowed and causes the damage of the equipment and interruption of production process. It is impossible to decrease energy consumption per production index.In the paper, the research for a specialized intelligent control system for electric fused magnesium furnace is made with the support of "National Support Project (2007BAE25B01)" and relying on the platform of technology innovation "985project" on process industry integrated automation. The target of the specialized intelligent control system of electric fused magnesium furnace is to decrease energy consumption per production index on the condition of production quality guarantee. Intelligent control method for electric fused magnesium furnace targeting to decrease energy consumption per production index is poposed; intelligent control software is programed on the basis of above Intelligent control method for electric fused magnesium furnace; specialized intelligent control system for electric fused magnesium furnace composing of intelligent control software, PLC, operation panel, melting current transformers, electric transducers and electrode regulating device is built; industry experience is perfomed. The specific works are as follows:1. Intelligent control method for electric fused magnesium furnace targeting decreasing energy consumption per production index is proposed. The method is composed of funace condition identification, melting current setting model and melting current switching controller.(1) According to three-phase melting current fluction trend, funace condition including adding materials, exhausting, normal and abnormal can be determined based on the rule-based reason technology.(2) Melting current setting model is composed of melting current presetting computational model and melting current setting compensation model. Melting current target value range including melting current maximum value, minimum value and melting current preset value can be achieved by melting current presetting computational model. The melting current presetting value can be compemsated by melting current setting compensation model based on case-base reason technology. According to the furnace condition identified by furnace condition identification model, melting current setting compensation model get the compensation value.(3) Melting current switching controller is composed of normal smelting condition controller, adding materials controller, exhausting controller, abnormal smelting condition controller and switching mechanism. Switching mechanism can switch working controller according to the furnace condition identified by furnace condition identification model. The normal smelting condition controller is alse called three-phase coordinating controller which decides the adjustment sequence among three-phase electrode according to diffence between the melting current measurement and set value and the decoupling rule among three-phase electrode. When making decision, three-phase coordinating controller applys the rule-base reason technology. According to the difference between the melting current measurement and set value, Single-phase melting current controller gets the time and direction for electrode adjustment based on the rule-base reason technology. The electrode position can be adjusted and melting current changes accordingly. So, the melting current set value can be traced by measurement to decrease energy consumption per production index.2. Based on above mentioned intelligent control method, the intelligent control software composed of melting current intelligent setting module, melting current intelligent control module and monitoring module is developed.3. Specialized intelligent control system for electric fused magnesium furnace is developed. The system is composed of intelligent control software, PLC, operation panel, melting current transformers, electric transducers and electrode regulating device.4. The specialized intelligent control system is applied on the electric fused magnesium furnace of a magnesia-based refractories materials producing plant. The on-site installation, commissioning and industrial experiment are performed and put into operation. The result of industrial experiments shows that melting current fluctuation range is reduced evidently, current fluctuation range is reduced by56.6%in normal smelting condition; the proposed electric fused magnesia furnace intelligence control method can identify furnace condition timely and make compensation according to the identified furnace condition; when melting current setpoints changes, the new setpoints can be traced timely. Based on the statistical analysis for the production index, compared with the manual control, energy consumption per production index is dropped2.9%, the finished product rate index increased by1.1%. The specialized intelligent control system is generalized. The results of operating for a long time shows that energy consumption per production index is dropped5.12%.