High Temperature Flue Gas Roasting for Aluminum Electrolytic Cells

 Ⅰ. Introduction

 High Temperature Flue Gas Roasting Technology for Aluminum Reduction Cells and JW-6 type serial calciner are jointly developed by Zhengzhou Jingwei Technology and University of Chongqing. The calciner composed of burner, ignition controller, and air fuel regulating system, oxygen analyzer, PLC control system, fuel truck and so on. Natural gas, liquid gas and coal gas can be used as fuel.

 The technology and equipment are applicable to the roasting startup of ordinary cells and new-type cathodic electrolytic cells and can be rapidly installed in the electrolytic cells to be started to realize the roasting startup of new cells and the secondary roasting startup of scheduled cell shutting and accidental cell shutting.

 Applied to the roasting startup of electrolytic cells, the technology and device can effectively improve the roasting quality and reduce electricity consumption. When they are applied to the roasting of the secondary start-up cells, dadoing operation is not needed, which can save a large number of manpower and electricity consumption, reduce the risk of missing any cell and improve service life of the cells.

 Table of Comparison between Coke Granule Roasting Cost and Fuel Gas Roasting Cost (Single cell)

 Note: 1. Before the roasting startup, the cells shall be baked to about 950℃ and then started by filling electrolyte; 2. Electricity price shall be accounted by 0.51Yuan/kwh; 3. Natural gas shall be taken as fuel and accounted by 4RMB Yuan/Nm3; if producer gas is adopted, the fuel gas cost is about 50% of natural gas cost.

 Ⅱ. Features

 1. Save electricity and reduce roasting cost: Making roasting startup by adopting this technology can substantially reduce the electricity consumption and reduce the overall roasting startup cost. Take 300kA electrolytic as an example, when start by filling electrolyte, more than 30 thousand RMB Yuan can be saved for each single cell.

 2. Solve the oxidation problem: A reasonable air-fuel ratio regulatory process is built into this device. The sufficient combustion of fuel in the burner will inject the high-temperature flue gas to the cavity between cathode and anode. Naked fire cannot contact the cathode and anode carbon blocks which are not oxidated during the roasting process.

 3. The rate of temperature rise can be regulated and controlled: The device has such a function that the user can define the heating curve during the roasting and allow making online adjustment according to the on-site roasting conditions. The system can control the roasting and heating processes and keep the roasting evenly in accordance with the heating curve and heat insulation curve, which is propitious to prolong the service life of the cells while improving the startup quality.

 4. Roasting temperature is uniform and can prolong the service life of the cells: Automatically control the heating insulating process during the roasting and evenly arrange the burner nozzle. The cavity of the electrolytic cell is filled with high-temperature flue gas, with even temperature, and the extended legs at ends and sides can be baked fully at first attempt. The temperature in cell cavity varies little to reduce the thermal stress impact and causing cathode flaw, which is propitious to keep stable production in electrolytic cell and prolong the service life of the cell.

 5. Reduce the workload of roasting startup: adopting this technology for roasting startup can avoid the work of laying and salving coke granules reduce labor strength and improve roasting quality.