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August 11th, 2010 saw roomful guests of honour and warm atmosphere at the meeting room of Gong Yi Hotel in Henan province. Here was the Appraisal Meeting for the 13 scientific & technological achievements including the Development and Commercial Application of 400kA-family High Energy Efficiency Aluminum Reduction Cell Technology, etc. that were jointly completed by NEUI, Henan Zhongfu Industrial Co., Ltd, Zhengzhou Zhonshi Cell Technology Co., Ltd and Northeastern University, etc .
Organized by China Nonferrous Metals Industry Association (“CNIA”), the Appraisal Meeting was chaired by CNIA deputy secretary-general, Mr. Zhang Hongguo. CNIA chairman, Mr. Kang Yi, presented the meeting and gave an important speech. The Director of the Appraisal Committee was acted by Mr. Niu Yinjian, vice chairman of Nonferrous Metals Industry Society of China. Vice Directors of the Appraisal Committee were acted by academician Qiu Dingfan from Beijing General Research Institute of Mining & Metallurgy, academician Zhang Guocheng and professor Yang Runhuai from the General Research Institute for Nonferrous Metals, and professor Liu Fengqin from Zhengzhou Research Institute of CHALCO. Members of the Appraisal Committee include the technical experts and leaders of the aluminum industry from China International Engineering Consulting Corporation, Institute of Electrical Engineering, Chinese Academy of Sciences, North China University of Technology, Henan Nonferrous Metals Industry Association, Nanshan Group, China Power Investment Cooperation and Inner Mongolia HMHJ Aluminum Electricity Co., Ltd, etc.
The appraisal results of the 8 scientific & technological achievements that NEUI engaged mainly and participated are briefed as follows:
1. Development and Commercial Application of 400kA-family High Energy Efficiency Aluminum Reduction Cell Technology
(1) The 400kA-family High Energy Efficiency Aluminum Reduction Potline and the Production Technology has firstly been developed by using the digital simulation technology and combined with the experiences from developing high amperage aluminum reduction cells, and has been put into commercial application.
(2) The busbar device of the 400kA-family high energy efficiency aluminum reduction cell, which is developed by applying the aluminum reduction cell electromagnetic field coupling simulation software and MHD-NEUI aluminum reduction cell magnetic fluid simulation & analysis software, has achieved high stability of the magnetic fluid, which ensures the high efficiency and stable operation of the aluminum reduction cells under the low voltage.
(3) The Low Temperature Difference Baking Technology, the Technology of Pot Start-up with Rapid Voltage Step-down, and Process Technology for Stable Production under Lowe Voltage, which have been developed based on the characteristics of the high amperage aluminum reduction cells, have ensured excellent technical-economical indices.
(4) The first created Pipe Truss Superstructure, Elastic Pot Shell Structure, and Sub-section Gas Collection Technology have optimized the whole steel structure of an aluminum reduction cell, reduced largely the investment for aluminum reduction cells, prolonged the service life of the reduction cells, and increased the pot hooding efficiency.
Through over two years’ operation, the Project has achieved excellent technical-economical indices such as the average pot voltage of the whole potline of 3.85V, DC current consumption of12328kW/t, and anode effect frequency of 0.015 AE/pot•day. The technology has reached the international top level.
2. Research on MHD Stability Technology and Busbar Device for High Amperage Reduction Cells
(1) Comprehensively analyzed the factors that affect the accuracy of the reduction cell’s magnetic fluid calculation. After tests and research, the boundary conditions for the calculation of the magnetic field of high amperage reduction cells have been optimized, which has improved the accuracy of the numerical simulation.
(2) The busbar arrangement of Asymmetric Strong Compensation at Both Ends, Multi-point Weak Compensation at the Bottom is firstly invented.
(3) The busbar device is designed with coupling of the power balance simulation and magnetic field simulation. Its anode and cathode current distribution is uniform, which has improved the safety and economy of reduction cells’ operation. The busbar device researched and developed by this Project has been applied in the 400kA-family high energy efficiency potlines of Henan Zhongfu Industry Co., Ltd. The actual measured results have shown that the main technical indicators accord with the simulating results, and obvious economic benefits and social benefits have been achieved. The technology has reached world advanced level.
3. Development and Research of the Pipe Truss Superstructure for High Amperage Aluminum Reduction Cells
(1) The Pipe Truss Superstructure for High Amperage Aluminum Reduction Cells belongs to the first in the world, and has the advantages of high strength and less materials.
(2) The new type crust breaker, the rod sealing device, and the submerged anode lift installation methods, etc. are all developed based on the pipe truss structure and are firstly used, which ensures the integrity and tightness of the cell superstructures.
The Pipe Truss Superstructure developed by the project has been used by Henan Zhongfu Industry Co., Ltd. on its 400kA-family high energy efficiency aluminum reduction cells. Comparing with the reduction cells not installed with the Pipe truss superstructure, its steel consumption for per unit current is reduced by 13%, and has achieved obvious economic benefits. The technology has reached world leading level.
4. Development of the Negative Pressure Balance Technology for the Gas Collection System of High Amperage Aluminum Reduction Cells
(1) The CFD numerical simulation calculation technology has been, for the first time, applied in the design of the gas collection system for high amperage aluminum reduction cells;
(2) The sub-section gas collection structure has been used for the gas collection system of the aluminum reduction cells, which has realized the even distribution of the negative pressure in the reduction cells. Thus, the hooding efficiency is improved.
(3) The dual-duct gas exhausting system has firstly been used, which has achieved the efficient gas collection and reduced the fugitive emissions. Compared with traditional gas collection structure, the resistance of this new structure is reduced by approximately 80Pa, the gas emission volume for per ton aluminum production is reduced by approximately 20% and the power consumption of the gas scrubbing system is reduced by approximately 100kWh/t.
The technology has been successfully applied in the 400kA-family high energy efficiency aluminum reduction potlines of Zhengzhou Zhongfu Industry Co., Ltd., and has achieved environmental protection indices including the hooding efficiency of more than 99%, the total fluoride emission of no more than 0.6kg/t and dust emission of no more than 1.0kg/t. It has achieved notable economic and social benefits. The technology has reached world leading level.
5. Parallel Symmetric Type Rectification & Power Supply System for Super High Amperage Aluminum Reduction Cells
(1) The separate arrangement of the positive & negative busbars and large components on the Parallel Symmetric Type Rectification & Power Supply System have effectively reduced the electric motive force of the rectification system, enhanced the explosion prevention ability and reduced the electromagnetic noise of the system.
(2) Large components matched with double quick fuse are used for the rectification system, with components being axially press-fitted and negative and positive bridge arms being separated, which improves the short circuit resistance capability and safety of the system. The rectifier transformer and the rectifier device are connected by the straight bus bar in parallel, which makes the inductance and the resistance of each sub-circuit the same, and the harmonic wave content being reduced. Thus, the rectification efficiency has been improved to over 98.29%.
(3) 6-hole aluminium alloy busbars are used for the rectification device, which has solved the problems including press-fit, busbar stress, component cooling and electrocorrosion to the busbar, etc. occurring to components over 4 inches. Comparing with the traditional rectification & power supply system which is of co-phase counter parallel connection, this system can prevent rectifiers from potential risks caused by the high amperage single potline, and have yielded significant economic and social benefits.
The parallel symmetric type rectification and power supply system for the high amperage aluminium reduction potlines developed by this project belongs to the first in the world, and the entire equipment technology level is up to the world leading level.
6 Intrinsic Value Intelligent Control System for Aluminum Reduction Cells
(1) The neural network has been used to trace the inherent characteristics of the reduction cells, and the genetic algorithm has been used to accelerate the tracing speed, through which the intrinsic value of process parameters including alumina concentration, anode and cathode distance（ACD）, and temperature of the reduction cell are obtained.
(2) The control of the reduction cell is individualized based on the intrinsic value of the reduction cell. This control technology has been applied in the 400kA aluminum reduction cells in Zhongfu Industry Co., Ltd. Under low pot voltage conditions, the accuracy of the voltage has been controlled within 10mV, the alumina concentration has been controlled within the range of 1.5~2.5%wt; and anode effect frequency has been controlled to less than 0.015 AE/pot•day. The control technology is of good effect, and has achieved notable economic and social benefits.
The control strategy of the intrinsic value intelligent control system for aluminum reduction cells has reached world leading level.
7. Development of Comprehensive Production Energy-saving Technologies for High Amperage Reduction Cells
(1) The digital technology and the network technology have firstly been used on the development of the current stablizing power supply technology and device for aluminium reduction potlines. The technology of pot stop or re-start up and pot welding without power blackout has helped realize the stable constant current operation of the high amperage aluminium reduction potlines.
(2) The Compressible Lining Structure, High-effective Impervious Brick and Even-current Cathode Conductor Structure for aluminium reduction cells are firstly invented, and the Constant Temperature Solidifying Titanium Boride is used for the aluminum reduction cells, which has greatly prolonged the service life of reduction cells and improved production stability.
(3) The Grid Type Aluminium Busbar Surface Compression-fitting Method & Busbar Installation Technology, the Low Resistance Cathode Collector Bar Ramming Technology, as well as the Collector Bar-Anode Contact Resistance Control Technology have effectively reduced the reactive power consumption of the aluminium reduction cells.
(4) Successfully developed the baking gas control technology and associated equipment package for the anode baking furnace. The use of this technology and equipment have reduced the energy consumption during baking operation and obviously improved the anode quality.
The Project has been applied on 6 test pots of 320kA of Henan Zhongfu Industry Co., Ltd. Through 4 years of whole potline operation, it shows that the operation is stable and the overhauling wastes and PFC emissions have been greatly reduced. The technology has reached the world leading level.
8. Development of Production Technologies for 400kA-family Aluminum Reduction Cells
(1) The Low Temperature Difference Baking Technology is firstly invented. The optimized tar fraction proportioning has reduced the impulse voltage, cathode cracks in the baking area, as well as the power consumption during the baking period.
(2) The Technology of Pot Start-up with Rapid Voltage Step-down has been developed. The technical conditions, such as low molten aluminium level and high heat insulation material level, have reduced the pot voltage and temperature during pot start-up, so the power consumption during the start-up period is reduced.
(3) Developed the Low Voltage Aluminium Reduction Technology, enabling a stable operation under low voltage condition;
The nearly 2 years’ operation of the 400kA-family HEE Aluminium Reduction cells in the 230kt/a potline of Zhongfu Industry shows very good technical & economic indices:
The average pot voltage: 3.85V;
DC consumption: 12328kWh/t.Al
Anode effect frequency: 0.015AE/pot﹒day.
The technology is up to the world leading level.
Among the 13 achievements, 9 of them are up to the world leading level, and 1 is up to China leading level.
So powerful expert team attending the meeting and so many achievements being appraised during the meeting were unprecedented for all previous appraisal meetings on aluminium reduction industry technologies, which marks that what have been appraised during the meeting is rewriting a new technological innovation chapter for China’s aluminum reduction industry. It also indicates that these scientific & technological achievements will impel China’s aluminum reduction industry and overall equipment & technology level to achieve a new leap.
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