4. Boiling roaster roasting fine ore is heated in a boiling state - the reduction process, with coal or coal gas as the reducing agent. The boiling furnace has a simple structure, and the process flow is shown in Fig. 5. It consists of a furnace body, a bottom bellows and an air distribution plate. The shell of the furnace body is made of steel plate, the interior is made of fire brick, and the top of the furnace is made of silicate refractory concrete.
The bubbling bed is the main place for ore roasting, and a conical bed (23° full taper angle) is used, so that the material in the bed can be fully “boiling†and the fine powder can be carried away by the airflow. In addition to satisfying the necessary roasting time of the fine powder during the current-carrying process, the middle portion of the furnace can also return some of the fine powder to the boiling bed. The bellows is an excessive component of the air entering the furnace. It has the function of reducing the air pressure head, so that the air is uniformly introduced into the furnace through the distribution plate. Since the air has been preheated before entering the furnace, the wind box is insulated. The distribution plate consists of a flower board and a hood. The hood is a tapered side hole type, and the slab is filled with refractory material below the side hole of the hood to protect the flower board from being burned out.
Manganese ore eighty-one test furnace built in 1977 industrial process 100t / a ore, manganese oxide ore to roasting of manganese ores, ore crushed to 5mm or less after the infeed screw feeder boiling furnace, the coal is reduced with screw pump Compressed air is delivered from the bottom of the boiling furnace into the furnace. The air required for boiling as a boiling medium and pulverized coal is preheated by the exhaust gas and uniformly distributed into the furnace through a distribution plate.
The pulverized coal is sprayed into the ebullating bed, and is burned under the condition of insufficient air to generate a high-temperature reducing gas, and the ore is heated to a desired temperature and the reduction reaction is completed.
The calcined product is composed of overflowing coarse-grain roasting ore and collecting dust to recover fine powder, and enters the slurry pool through the water quenching tank. The techniques for boiling roasting manganese ore are listed in Table 3.
Although the structure of the boiling furnace is simple, the heat consumption is high and the smoke is large. Therefore, it has not been applied in the production of manganese ore industry in China. [next]
(2) Neutral roasting Neutral roasting manganese ore is aimed at decomposing manganese carbonate ore, releasing carbon dioxide, volatile matter and crystal water, thereby improving manganese grade. This process has been widely used in China's manganese carbonate mine.
The roasting process of manganese carbonate ore is an endothermic reaction. Since the manganese carbonate ore is also mixed with other carbonate minerals, their decomposition pressures are different, so the decomposition temperatures required are not the same, and their decomposition temperatures are shown in the table. 4.
Table 4 Â Carbonate mineral decomposition temperature | ||||
Carbonate mineral | MnCO 3 | FeCO 3 | MgCO 3 | CaCO 3 |
Decomposition temperature / °C | 642 | 459 | 681 | 1157 |
In order to fully decompose the manganese carbonate mineral, the calcination temperature must reach 800~1000 °C, but the calcination temperature is too high, the heat consumption is large, and at the same time, some mineral surfaces are softened and bonded, resulting in production obstacles.
The roasting of manganese carbonate ore is mostly carried out by using a round kiln, and the purpose of roasting is achieved by the convenience of the manganese ore sintering process.
The Xiangtan manganese mine was the first to use a round kiln to roast manganese carbonate lump ore. The structure of the round kiln is very simple. There are two kinds of specifications at present: the diameter of the upper kiln of Xiang-manganese type is 6.6m, the diameter of the bottom is 6m, it is horn type, the height of the inner space is 4m, and five 0.5m wide ventilation kiln and kiln are arranged at the bottom. The external fan is connected, the volume is 115m 3 , the mine can be loaded with 250t, the production cycle is 15 days, and the annual output of roasting ore is 2880t, which is manual loading and unloading, and the labor intensity is large. The diameter of the top of the peach-manganese round kiln is 5.8m, the bottom diameter is 5.2m, the net height is 4.5m, and the bottom discharge is used. Therefore, the total discharge capacity is 105m 3 , the ore can be loaded 220t, the production cycle is 8 days, and the annual roasting ore is 2300t. .
Daxin manganese ore also has a round kiln for neutral roasting of manganese carbonate ore. The diameter of the upper kiln is 6m, the bottom diameter is 5.5m, the net height is 6.5m, the total volume is 180m 3 , the filling can be 500t, and the production cycle is 8 days. Annual processing of roasting ore 20000t.
In the early 1970s, the Xiangtan manganese ore was subjected to a roasting test of manganese carbonate ore using a furnace similar to a shaft furnace. The ore particle size was 5 to 200 mm, and the blast furnace gas was used as a heat source. The calcination temperature was 850-900 ° C, and the interval was 20 min. It can carry out continuous production and reduce the physical labor intensity, but the baking temperature is not easy to control, and it is easy to knot the kiln, which needs further improvement.
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