1 Introduction At present, many aluminum plants in China have roasting and anode open roasting furnaces, and most of the oven heating curves adopt a 48-hour flame moving cycle, and the operating furnace chamber is 6 furnace chambers or 7 furnace chambers, which is quite satisfactory. Oven effect. However, this method has certain defects. After baking the calciner, it is necessary to convert the oven curve with a flame shift period of 48 hours into a normal production curve with a flame shift period of 36 hours, and also to the oven 6 The room or 7-room operation is converted into a 5-room operation for normal production. The commonly used transformation methods are a transition curve method and a hysteresis shift method. The conversion time is long and the process is complicated.
We have studied the experience of open-type roasters at home and abroad. Based on the advantages of our imported SETARAM company's advanced combustion heating control equipment and the only domestic fuel gas used as a calcining furnace, we have boldly proposed a roaster. The oven uses a 36-hour flame shift cycle and a new process of 8-chamber operation. Not only can it meet the requirements of the heating rate of the oven, but also make the conversion of the oven curve to the normal production curve after the furnace is more convenient and simple.
2 Oven The oven for the specific operation of the roaster is a load-bearing oven. The oven uses two flame systems, a 36-hour flame shift cycle, and eight chambers. In the No. 23 furnace chamber, the ignition started, and three furnace chambers were connected in series at the beginning. After the three flame moving cycles, the fourth furnace chamber was added as the temperature increased, and then one furnace chamber was added after each flame moving period. Until the system has enough 8 furnace chambers. Previously, each time the furnace was moved, only the exhaust frame was moved forward (the direction of flame movement) to a furnace chamber. After heating through eight flame shift cycles, the first heated furnace chamber (the furnace chamber where HR2 is located) begins to enter the cooling phase. The flame moving pattern cooling stage is divided into a natural cooling stage and a forced cooling stage.
The 21 oven oven uses a 288-hour heating curve. The flame movement period is the temperature rise interval. The temperature used for the duration of the temperature rise is 36 hours, and the cooling time is 432 hours.
3 oven process analysis (1) to control the negative pressure at the nozzle when the oven is ignited. After the flame is burned normally and stabilized, the negative pressure at the zero pressure frame is controlled, and the side fire path is required to be large, and the middle fire passage is appropriately smaller. (2) The oven curve is not well controlled in the 800 heat preservation section. After the actual measurement, the heating rate of the fire channel temperature from 790823 is (3) the temperature difference between the upper and the lower of the fire channel during the load oven, and the difference in the room temperature of the medium temperature furnace is about 10090. The low temperature furnace has a small room temperature difference of about 5060, which is directly related to the amount of flue gas in the furnace chamber. Generally, the negative pressure is large, the amount of smoke is large, and the temperature difference between the upper and lower sides is small.
4 oven results (1) After 12 days of heating and 18 days of cooling, the furnace chamber was observed, the fire wall was almost unchanged, and there was no bulging, concave, mud falling off, etc. 1, 7 side bin and outer furnace wall slightly outside the drum and the cross wall between the 15cm vertical joint, and the large wall is still integrated. On the No. 9 furnace chamber 6, the top cover arch was 23 cm. The reference height of the 23 furnace chamber before and after the oven was measured to check the sinking of the furnace body. The measurement results show that the furnace body basically conforms to the thermal expansion law of the refractory material, and no sinking of the furnace body is found.
(2) This oven uses natural gas as fuel.
(3) Taking advantage of natural gas as a fuel, the first trial production uses a 3-hour operating oven curve with a 36-hour flame shift cycle. Before the ignition starts, there are two closed furnace chambers filled with filler materials, and then the anode carbon blocks are loaded from the furnace chamber. With load-bearing oven, the negative pressure loss is small, the furnace wall is not easy to be deformed, and the oven and production can be carried out at the same time, which greatly saves energy. After baking the furnace, due to the 36-hour flame shift cycle of 288 hours of oven heating curve, the process of converting to a normal production 36-hour flame-moving cycle 180 hours heating curve is very short, one furnace chamber is lost for every two flame moving cycles. Eight furnace chambers were converted into five furnace chambers after only six flame shift cycles (9 days). During the conversion process, the temperature rise is relatively stable, and the quality of the baked anode carbon block is not affected.
(4) Component density Low calorific value furnace chamber number ash pseudo-specific gravity specific specific gravity resistance strength reactive furnace chamber first layer carbon block third layer carbon block furnace chamber sixth layer carbon block third layer carbon block.
5 Conclusions (1) The oven was operated with a 36-hour flame shift cycle of 288 hours, and the operation was simple. The conversion between the oven curve and the normal production curve was simple and stable. Does not affect the quality of the anode carbon block produced by the load oven.
(2) With the load oven, the oven and the production are carried out at the same time, which not only improves the quality of the oven but also saves energy.
(3) The heating rate of the open roaster oven is controlled within 8/h, which will not affect the furnace body.
(4) The physical and chemical properties of the anode carbon block produced by the trial production of the load oven are basically qualified, and are all used for the start of electrolytic baking.
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