Soft manganese ore suspension reduction roasting process technology

First, the test materials

The ore used in this test was provided by Guangxi Xinzhen Manganese Industry Group Co., Ltd. Tables 1 and 2 are the composition analysis and particle size composition of the ore, respectively.

Table 1 Multi-element analysis results of Xinzheng manganese ore / (wt,%)

Table 2 New vibration manganese ore particle size analysis / (wt,%)

The block and the powder sample were separately ground into a light sheet and a sheet, and the mineral composition of the ore was observed and analyzed. According to the structural structure of the block-like ore, manganese ore can be classified into two types: breccia-like manganese ore and strip-shaped manganese ore.

Brecciated manganese ore: a dark brown brown ore, brecciated structure, clay minerals, silica and manganese composed breccia is hematite (limonite) cemented.

Manganese ore (manganese rehydration): complex fine particles manganite, opaque, and fine quartz, sericite (illite) intertwined within the angular distribution of gravel. The aggregate of irregular manganese minerals is generally 6 to 31 μm and the smallest is 1 to 2 μm. There may be a small amount of other manganese minerals that are not easily distinguishable under the microscope.

Gangue mineral: Hematite (limonite): distributed in the form of a network of veins, in the form of cement or agglomerates, cemented together with breccia composed of manganese minerals, quartz, clay minerals, etc. The mesh width is 15 to 48 μm, and the agglomerate shape can reach 103 μm.

Strip-shaped manganese ore: The ore is brownish black, dyed, fine-grained, and banded. The strips are shown in different shades of light, and the strips vary in width and width, mainly due to the different opaque mineral content. The darker bands are rich in manganese minerals and red limonite, and the shallower parts are rich in gangue minerals such as quartz and sericite (illite).

Manganese mineral: It is mainly identified as a rehydrated manganese ore according to the following probes and microscopic identification. Manganese minerals are intertwined with clay minerals (kaolinite, illite, etc.) and quartz. The particles are generally 10 to 34 μm and the smallest is 1 to 2 μm.

Gangue minerals: mainly quartz, red limonite, sericite, clay minerals, etc., characterized by gangue in the breccia ore.

According to microscopic observation, chemical analysis, XRD diffraction analysis and probe analysis, the average mineral content of the original ore is: rehydration manganese ore 40%; quartz 25%; sericite (illite) 5%; clay mineral 10%; calcite 5%; feldspar 3%; hematite (limonite) 10%; other 2%.

Mineral technology studies on manganese ore have shown that manganese ore can be classified into two categories: breccia-type manganese ore and strip-shaped manganese ore. The average ore of the original ore is mainly 10% of reclaimed manganese ore, quartz, hematite (limonite); the secondary mineral is 5% of sericite (illite), clay minerals, calcite, feldspar, etc. A small amount of manganese minerals are present in the monomer, and 85% of the manganese minerals are intertwined with the gangue minerals.

The solid fuel for test - pulverized coal is the common coal for Wugang Wulongquan Mine Cement Plant. The main indicators are shown in Table 3.

Table 3 Industrial pulverized coal analysis results /%

Second, muffle furnace roasting test

For the reduction roasting process, the main process parameters affecting the reduction efficiency are: 1 the amount of reducing agent; 2 temperature, 3 reaction time. To this end, the ore roasting conditions were tested for different process parameters, and the roasting products were subjected to magnetic separation and iron removal tests using magnetic separation tubes.

In order to study the suspension state roasting effect and process conditions of manganese oxide ore, the reduction roasting was first carried out in a muffle furnace. The calcination was carried out in a high-temperature box type electric resistance furnace (12 kW), and the ore loading amount was 50 g each time, and the roasting effect was examined by adjusting the temperature, the roasting time, and the ratio of the coal to coal. The calcined product is directly cooled into water, and then subjected to dehydration drying, shrinkage, grinding, and magnetic separation. The weak magnetic separation test was carried out using the XCGS-73 type magnetic separation tube produced by Tianjin Mining Instrument Factory. The weak magnetic separation test of the magnetic separation tube has an excitation current of 1.5 A and a magnetic field strength of 119.4 kA/m.

(1) Calcination temperature test

The test conditions of the muffle furnace roasting temperature are as follows: the amount of coal powder is 10%, the roasting time is 50 min, and the test results are shown in Table 4. When the temperature is above 800 ° C, the conversion of M0 ₂ to MO is above 90%, and the reduction reaction is relatively sufficient. When the temperature reached 900 ° C, Mn0 _{2 was} all converted to MnO. The reaction temperature was selected from 800 to 850 ° C as the optimum temperature condition for the muffle furnace roasting.

Table 4 Roasting temperature test results

 Temperature / °C 

(2) Roasting time and magnetic separation test

The purpose of the calcination time test and the magnetic separation test is mainly to investigate the effect of calcination time on reduction conversion rate and magnetic separation and iron removal. Considering the energy consumption problem, the manganese ore reduction temperature is about 750 ° C, the test temperature is selected as 750 ° C, and the coal powder is 10%. The test results are shown in Table 5.

Table 5 Muffle furnace roasting time test results /%

Table 5 shows that, in the firing time 30 ~ 50min, both conversion and MnO ₂ reduction effect of magnetic iron were stable, the amount of iron metal can lose about 30% of the gold, but not more than grade iron is reduced, and therefore, It is reasonable to determine that the muffle furnace roasting time is 50 min.

The test conditions and results of coal powder consumption are shown in Table 6. It can be seen from Table 6 that at a temperature of 850 to 900 ° C, the amount of pulverized coal is in the range of 5% to 15%, and the reduction conversion ratio of MnO ₂ can reach 90% or more. Therefore, it is determined that the appropriate amount of reducing agent is 10% of the amount of coal powder.

Table 6 Muff furnace roasting pulverized coal consumption test

 900 

The above tests show that the manganese ore of Guangxi Xinzheng Manganese Industry Group Co., Ltd. can be calcined in a muffle furnace, and the manganese oxide conversion rate can be greater than 90% and the ore reduction reduction roasting is weak in the temperature range of 800-950 °C. The magnetic separation rate of iron removal reaches 30%, and the loss rate of Mn and Mn0 is less than 3%. Therefore, the use of reduction roasting is an effective way to achieve the utilization of such manganese oxide ore resources. However, due to the long time required for conventional roasting and low production efficiency, more in-depth research is needed to truly realize the utilization of the ore. Developed a new method and apparatus for roasting, simplifying the process and shortening the roasting time.

Third, semi-industrial experimental study of suspension state reduction roasting

Based on the results of laboratory-type suspension reduction roasting test, a semi-industrial test device for multi-stage suspension reduction roasting reaction was designed, which consisted of preheater, multi-stage suspension reactor, air duct and hot blast stove. For the new process of “multi-stage suspension reduction roasting reaction-magnetic separation”, the main process parameters affecting the rapid reduction of MnO ₂ to Mn0 in the case of gas-solid flow field are: CO concentration, temperature, solid-gas ratio, ore particle size . To this end, ore calcination conditions and continuous tests were carried out in the semi-industrial test apparatus shown in Fig. 1 for different process parameters.

Figure 1 Semi-industrial test flow chart of multi-stage suspension reduction roasting

The material is dispersed and suspended in the gas stream. The time required for the gas stream to transfer heat to the material is short, and the actual heat transfer rate is high. The heat transfer coefficient between gas and solid phase is more than that of the traditional rotary kiln, the heat transfer coefficient is increased by more than 3000 times, and the gas-solid contact area is increased by tens of thousands of times. The multi-stage suspension reduction roasting test uses suspension preheating and reaction furnace technology. The material is preheated in the suspension preheater and reacted in the reaction furnace. Some of the fine fractions have a rapid reduction roasting reaction in the third stage cyclone. Sampling analysis of the three-stage cans showed that the conversion rate of manganese oxide (MnO2·n H ₂ o) to Mn0 was about 70%.

The multi-stage suspension reduction roasting system is composed of a four-stage cyclone cylinder and a first-stage reaction furnace. In order to improve the thermal efficiency and dust collection efficiency (gas-solid separation efficiency), the running material and material loss (short circuit) are greatly reduced. First, the cold state test is carried out to find the process parameters of the pressure air volume which avoids the minimum of running materials and material loss (short circuit). Provide data for determining the design parameters and process parameters of the hot mold device.

According to the results of the pilot test, the semi-industrial multi-stage suspension roasting test changes the atmospheric conditions, and other conditions are selected to vary within a small range. The temperature of the multi-stage suspension reactor is in the range of 1000 to 1050 ° C, and the treatment amount is about 500 kg / h. Conditions and results are shown in Table 7.

Table 7 Semi-industrial test results of suspended manganese roasting

The atmosphere condition test results show that the temperature of the reactor is about 1050 °C, the upper temperature reaches 958-972 °C, when the CO content is above 3.5%, the conversion of Mn02 reaches over 99%, and the effect is ideal. However, due to the fine grain size of the original ore powder, the current semi-industrial experimental furnace has to be improved in the design of the dust collection rate when processing such materials.

Analysis of energy consumption of manganese oxide suspension reduction roasting

In order to determine the technical and economic indicators of the manganese oxide suspension reduction roasting process, the continuous heat test is used as an example to analyze the thermal equilibrium energy consumption of the system (Table 8). The basic raw data are as follows:

Table 8 Semi-industrial test heat balance table of manganese oxide suspension reduction roasting

The specific heat of manganese ore powder is 1.22kj/kg·°C; the calorific value of CO is 1.18MJ/kg, and the consumption is calculated as 3% of the volume of gas; the specific heat of exhaust gas is 1.424kJ/m ³ ·°C; the calorie loss is 260kj. /kg, manganese ore burned 12.43%.

The heat balance calculated according to the semi-industrial test roasting production unit is shown in Table 8.

Reaction MnO ₂ +CO Mn0+C0 ₂ thermal effect: 15.123 kj/mol (exothermic), 4.54kj/kg;

Return air volume: 50%; cylinder heat dissipation: 10%; treatment capacity: 500 kg / h; solid-gas ratio: 0. 5kg / standard m ³ ; finished product temperature: 800 ° C; exhaust gas discharge temperature: 150 ° C.

According to the calculation of the heat balance table, the heat consumption required for roasting 1t ore is: 1.432×106kJ/t (original ore), equivalent to standard coal, manganese oxide suspension reduction, semi-industrial test energy consumption: 48.94kg (standard coal)/t (original ore) ).

V. Conclusion

(1) The soft manganese ore is subjected to reduction and calcination in a stacked state. In the temperature range of 800-950 ° C, the conversion rate of the soft manganese ore (manganese dioxide is converted to manganese monoxide) is greater than 90%, and the ore reduction reduction roasting weak magnetic separation iron removal rate When it reaches 30%, the loss rate of Mn and Mn0 is less than 3%.

(2) The semi-industrial experimental study of multi-stage suspension reduction roasting with a processing capacity of 500kg/h, the residence time of the material in the system is only a few seconds. According to the continuous test results, the new operating manganese ore is suspended reduction roasting, the suitable operating parameters are: multi-stage suspension reactor temperature 1050 ~ 950 ° C, in the semi-industrial test, multi-stage suspension reactor population gas CO concentration 4.5% ~ 7.5 %, the solid-gas ratio in the multi-stage suspension reactor is 0.5-0.8 kg/Nm ³ , and the conversion rate of manganese dioxide is over 90%.

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